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Article
Brain Delivery of Drug and MRI Contrast Agent: Detection and
Quantitative Determination of Brain Deposition of CPT-Glu Using
LC-MS/MS and Gd-DTPA Using Magnetic Resonance Imaging
Kayann Tabanor, Phil Lee, Paul Kiptoo, In-Young Choi, Erica B.
Sherry, Cheyenne Sun Eagle, Todd D Williams, and Teruna J. Siahaan
Mol. Pharmaceutics, Just Accepted Manuscript • DOI: 10.1021/acs.molpharmaceut.5b00607 • Publication Date (Web): 24 Dec 2015
Downloaded from http://pubs.acs.org on January 3, 2016
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Molecular Pharmaceutics
!
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#$ #
!
Kayann Tabanor,1,6 Phil Lee,2, 3 Paul Kiptoo,1 In Young Choi,2,3,4 Erica B. Sherry,2
Cheyenne Sun Eagle,1 Todd D. Williams,5 and Teruna J. Siahaan1,*
1
Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence, KS 66047,
USA; 2Hoglund Brain Imaging Center, 3Department of Molecular & Integrative Physiology, and
4
Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA;
and 5Mass Spectrometry Laboratory, The University of Kansas, Lawrence, KS 66047, USA;
6
Current Address: XenoTech, LLC, Lenexa, KS 66219, USA.
: Enhancing Brain Delivery and Quantitation of Molecules in the Brain
*
: Dr. Teruna J. Siahaan, Department of Pharmaceutical Chemistry,
The University of Kansas, Simons Research Laboratories, 2095 Constant Ave., Lawrence,
Kansas 66047, Phone: 785 864 7327, Fax: 785 864 5736, E mail: siahaan@ku.edu
%&'()
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Successful treatment and diagnosis of neurological diseases depend on reliable
delivery of drugs across the blood brain barrier (BBB), which restricts penetration of
pharmaceutical drugs and diagnostic agents into the brain. Thus, developing new non invasive
strategies to improve drug delivery across the BBB is critically needed. This study was aimed at
evaluating the activity of HAV6 peptide (Ac SHAVSS NH2) in improving brain delivery of
camptothecin glutamate (CPT Glu) conjugate and gadolinium diethylenetriaminepentaacetate
(Gd DTPA) contrast agent in Sprague Dawley rats. Brain delivery of both CPT Glu and Gd
DTPA was evaluated in an
$ ' rat brain perfusion model in the presence and absence of
HAV6 peptide (1.0 mM). Gd DTPA (0.6 mmol/kg) was intravenously (i.v.) administered with
and without HAV6 peptide (0.019 mmol/kg) in rats. The detection and quantification of CPT
Glu and Gd DTPA in the brain were carried out by LC MS/MS and quantitative magnetic
resonance imaging (MRI), respectively. Further, in vivo delivery of Gd DTPA was evaluated
with intravenous Gd DTPA administration with and without HAV6 peptide in rats using T1
weighted MRI. Rats perfused with CPT Glu in combination with HAV6 had significantly higher
deposition of drug in the brain compared to CPT Glu alone. MRI results also showed that
administration of Gd DTPA in the presence of HAV6 peptide led to significant accumulation of
Gd DTPA in various regions of the brain in both the
$ ' rat brain perfusion and
studies. All observations taken together indicate that HAV6 peptide can disrupt the BBB and
enhance delivery of small molecules into the brain.
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Molecular Pharmaceutics
*
) !
)*
Many potential drugs developed for the treatment of diseases of the central nervous system
(CNS) such as Alzheimer’s, Parkinson’s, brain tumors and brain infections have failed due to
challenges in delivering sufficient therapeutic doses into the brain. Difficulty in delivering drugs
is largely attributed to the presence of the blood brain barrier (BBB) and/or unfavorable
physical chemical properties of the drug for penetrating the BBB.1 4 The BBB is comprised of
capillary endothelial cells that act as a highly selective filter between systemic blood circulation
and the brain. The main function of the BBB is to regulate the passage of nutrients into the brain
and provide protection against unwanted invaders such as toxins and pathogens.2 The
transcellular transport of molecules (e.g., drugs or diagnostic agents) is normally limited by their
unfavorable physicochemical and structural properties as substrates for efflux pumps.5, 6 Another
route to the brain is the paracellular passage, in which drugs can permeate through the
intercellular tight junctions of the BBB.1, 7 Tight junctions (TJs), adherens junctions (AJs), and
desmosomes are composed of cell adhesion proteins that act as zippers between cell membranes.
At the TJs, the cell membranes are connected by protein protein binding of occludins and
claudins while the AJs are linked by E and VE cadherins that are joined into the cell cytoplasm
by the scaffolding proteins α , β , and γ catenins.2, 8 Desmocollins and desmogleins are cadherin
family proteins located at desmosomes below the AJs and disruption of TJs and AJs has been
shown to enhance paracellular permeation of molecules.1, 9
HAV (His Ala Val) and ADT (Ala Asp Thr) peptides have been developed to modulate
cadherin cadherin interactions at the intercellular junctions and to increase the transport of
marker molecules through the paracellular pathway of the BBB.10 12 HAV and ADT peptides
derived from the EC1 domain of E cadherin caused increases in paracellular permeation of 14C
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mannitol through Madin Darby canine kidney (MDCK) cell monolayers, and these peptides
caused a drop in transepithelial electrical resistance (TEER) values of the cell monolayers.13, 14
Furthermore, HAV6 peptide (Ac SHAVSS NH2) enhanced the paracellular permeation of the
anticancer drug 3H(G) daunomycin and
14
C mannitol across the BBB in an
perfusion rat model.10 Recently, HAV6 peptide has been shown to enhance
$ ' brain
delivery of
gadolinium diethylenetriaminepentaacetate (Gd DTPA), rhodamine 800 (R800), and IRDye
800cw polyethylene glycol (800cw PEG, 25 kDa).12 Gd DTPA is a magnetic resonance imaging
(MRI) contrast agent while R800 is a near IR dye for fluorescence imaging as well as a substrate
for the efflux pump P glycoprotein (Pgp). HAV6 peptide also enhanced the brain delivery of
large molecules such as 25 kDa 800cw PEG.12
The focus of this work was to evaluate the ability of HAV6 peptide to enhance the brain
delivery of (a) camptothecin glutamate (CPT Glu; +
,) in an
$ ' rat brain perfusion
model and (b) gadolinium diethylenetriaminepentaacetate (Gd DTPA) in an
perfusion model and
$ ' rat brain
in Sprague Dawley rats. This work was also aimed at developing
methods to detect and quantify the amount of molecules delivered to the brain using liquid
chromatography mass spectrometry/mass spectrometry (LC MS/MS) and magnetic resonance
imaging (MRI). CPT Glu is an ester conjugate between an anticancer drug camptothecin (CPT)
and L glutamic acid (L Glu) to improve solubility of CPT. In the
$ ' rat brain perfusion
model, CPT Glu conjugate was delivered in the presence and absence of HAV6 peptide. To
detect the amount of CPT Glu and CPT in the brain, a method to extract CPT Glu and CPT from
the brain was developed. Then, an LC MS/MS method was developed to quantitate the amount
of CPT Glu and CPT in the brain extract. The idea of using LC MS/MS is to directly detect the
compound of interest and its metabolites while eliminating the use of radiolabeled compounds.
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The effect of HAV6 peptide in enhancing the brain delivery of Gd DTPA was evaluated using
$ ' rat brain perfusion and
intravenous (i.v.) delivery in Sprague Dawley rats and the
brain localization and deposition of Gd DTPA was quantified using MRI.
&
"# *
& -) #
The HAV peptide used in this study was synthesized using
solid phase peptide synthesis with Fmoc chemistry as previously reported.10, 14 The peptide was
cleaved from the resin using a standard method, and purified by reversed phase HPLC using a
C18 semi preparative column. The pure fractions were pooled and lyophilized. The purity of the
peptide used was >96% as determined by analytical HPLC using a C18 analytical column. The
identity of the peptide was confirmed by mass spectrometry. Ketamine hydrochloride and
xylazine were purchased from Vedco, Inc. (St. Joseph, MO) and Akorn, Inc. (Decatur, IL),
respectively. Gadolinium diethylenetriaminepentaacetate (Gd DTPA) contrast agent used for
MRI was obtained from Bayer Healthcare (Leverkusen, Germany). All other reagents and
solvents were purchased from Sigma Aldrich Chemical Company (St. Louis, MO).
CPT was conjugated to L Glu via
an ester bond between the alcohol functional group at C20 (20 OH group) on CPT and the alpha
carboxylic acid group of the L glutamic acid (Glu) using previous methods with minor
modifications (+
,).15 A mixture of suspensions of CPT (0.10 g, 0.288 mmol), scandium
triflate (0.085 g, 0.173 mmol), N Boc L Glu(OtBu) OH (0.524 g, 1.728 mmol), and N, N
dimethylaminopyridine (0.11 g, 0.864 mmol) in 5.0 mL anhydrous dimethylformamide (DMF)
was cooled to –8°C in salt water ice bath. Then, 1,3 diisopropylcarbodiimide (0.142 mL, 0.907
mmol) was added slowly into the reaction mixture, stirred at –8°C for 30 min, allowed to warm
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to room temperature, and reacted for 1 h. The reaction mixture was treated with water (50 mL)
and extracted with 100 mL dichloromethane. The organic extract was washed sequentially with
0.1 M HCl (200 mL) and 0.1 M NaHCO3 (200 mL), followed by water extraction. The organic
layer was dried with sodium sulfate followed by evaporation under reduced pressure. The CPT
N Boc L Glu(OtBu) was treated with a solution of dichloromethane trifluoroacetic acid (1:1, 2
mL) and stirred at room temperature for 1 h. The solvent was removed under reduced pressure
and the resulting residue was purified by reverse phased HPLC using a C18 semi preparative
column. The fractions containing the desired product were pooled and concentrated followed by
lyophilization to give 0.90 g of CPT Glu conjugate (Figure 1). The mass spectrometry result
produced a dominant peak at m/z = 478.15, which corresponds to the calculated molecular
weight of CPT Glu. The CPT Glu was dissolved in DMSO d6 and analyzed using the Bruker
Advance AV III 500 NMR spectrometer. 1H NMR (DMSO d6): δ 12.45 (s, 1H), 8.73 (s, 1H),
8.47 (s, 2H), 8.15 (d, 2H), 7.88 (m, 1H), 7.74 (t, 1H), 7.27 (s, 1H), 5.57 (s, 2H), 5.33 (s, 2H),
4.38 – 4.5 (s, 1H), 2.62 (m, 1H), 2.10 – 2.30 (m, 4H), 0.90 (t, 3H).
! "
(!
)
!
! '
$* Stock solutions (1 mg/mL) of CPT, CPT Glu,
and SN 38 were dissolved in dimethyl sulfoxide (DMSO) and stored at –20°C. Working
solutions of CPT and CPT Glu were prepared prior to experiments by diluting the stock solutions
with acetonitrile:water ( " 1:1). Final concentrations of CPT and CPT Glu for calibration
standards were in the range between 5 and 500 ng/mL. SN 38 was used as an internal standard
(IS). Calibration curves for both CPT and CPT Glu were constructed by plotting the ratio of the
peak area of the analyte and IS at each concentration. These standards were used to determine
the total concentration of CPT and CPT Glu delivered to the brain of each rat. Working
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standards used for extraction recovery experiments were prepared by diluting stocks solutions in
DMSO and phosphate buffer, pH 3.0 (1:1 v/v) before spiking in tissue homogenate.
+,
%
(
$$'
#
. Extraction recovery of CPT and CPT
Glu from brain tissue homogenate was determined as the ratio between the amount of analyte
extracted from spiked brain homogenate and the amount of analyte extracted from spiked blank
medium. Each analyte was evaluated at 50, 250, and 500 ng/mL concentrations. The brain of an
untreated rat (blank) was homogenized, and 190 TL aliquots of tissue homogenate were spiked
with 10 TL of working standards for CPT and CPT Glu. Each of the working standards
contained IS at a concentration of 25 ng/mL. Then, the mixture was vortexed for 1 min followed
by addition of a mixture of phosphate buffer at pH 3 and acetonitrile ( " 1:6, 1 mL) into the
homogenate. The homogenate was vigorously vortexed for 1 min followed by centrifugation at
12000 rpm. The supernatant was isolated, transferred to a clean tube, and evaporated to dryness
under nitrogen at 40°C. The dry extract was reconstituted in 300 TL of acetonitrile:water
containing 0.1% formic acid ( " 1:1), vortexed for 30 sec, and centrifuged for 5 min at 12000
rpm to remove additional precipitated proteins.
+,
(
'# (
$$'
(
$ '
('$
* A mixture of phosphate
buffer at pH 3.0 and 0.30 M phosphoric acid ( " 1:1) was added to each whole brain tissue. The
mixture was homogenized using a PowerGen 700 tissue homogenizer. Aliquots (190 TL) from
rat brain homogenate were spiked with 10 µL IS (25 ng/mL) and vortexed. The samples were
then extracted with 1.0 mL of 0.30 M phosphoric acid and acetonitrile ( " 1:6) and vortexed
vigorously for 1 min. Each homogenate was centrifuged at 12000 rpm for 5 min. The resulting
supernatant was isolated and evaporated to dryness under nitrogen at 40°C. The residue was
resuspended in 300 TL of acetonitrile:water with 0.1 % formic acid ( " 1:1). Samples were then
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vortexed and centrifuged (12000 rpm for 5 min) to remove additional precipitated proteins. The
sample (5 TL) was injected into the LC MS/MS.
& $ '
#
!" !* Chromatography of each
$(
sample was performed on an Acquity UPLC system (Water Corp., Milford, MA) with a
temperature controlled autosampler set at 8°C. Separation was performed at room temperature
on a Luna UPLC C18 reversed phase analytical column (2.1 mm × 50 mm, 5 Tm particle size,
100 Å; Phenomenex, Inc., Torrance, CA). A C18 guard cartridge (4 mm × 2 mm ID) was used to
protect the main column. The mobile phases consisted of a binary gradient system composed of
solvent A containing H2O:acetonitrile:formic acid (98.92:1:0.08) and solvent B containing
acetonitrile:H2O:formic acid (98.92:1:0.08). Analytes were eluted using a gradient system of
15% solvent B (initial), 15–30% solvent B (2.5 min), 30–90% solvent B (1 min), 90–15%
solvent B (0.5 min), and 15% solvent B (1 min). The sample injection volume was 5 TL. The
samples were eluted at a flow rate of 0.40 mL/min for a total run time of 5 min.
On line MS detection was performed on a Quattro Ultima triple quadrupole mass analyzer
(Micromass Ltd., Manchester, UK) equipped with an electrospray ionization (ESI) source
coupled to the UPLC system. Data were acquired in multiple reaction monitoring (MRM) mode
to monitor the characteristic pseudomolecular ion [MH]+ of the compounds. Nitrogen was used
as the desolvation gas, and argon gas was used for collision induced dissociation (CID). All
analytes were fragmented with cone voltage and collision energy set at 35V and 28V,
respectively. MRM chromatograms were quantified using MassLynx v 4.1 software (Micromass
UK Ltd) by integration of peaks.
#
$%
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%!
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All protocols involving the use of animals, including
!
&& %
$$$.
$ ' rat brain perfusion studies, were
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approved by the Institutional Animal Care and Use Committees (IACUC) at the University of
Kansas. The
$ ' rat brain perfusion studies were done on adult male Sprague Dawley rats
weighing 250–350 g following similar methods described in previous studies.10 Brain delivery of
CPT Glu was done in the presence and absence of 1.0 mM HAV6 peptide. CPT Glu (0.021
mmol/kg) was perfused in 10 mL of bicarbonate buffer (pH 7.4) containing 4.2 mM KCl, 1.5
mM CaCl2, 0.9 mM MgCl2, 128 mM NaCl, 2.4 mM NaH2PO4, and 24 mM NaHCO3. Prior to the
experiment, the perfusate was supplemented with D glucose (6 mM) followed by filtration and
oxygenation upon incubation under 95% O2 and 5% CO2 at 37°C. The rats were anaesthetized
with a combination of ketamine (100 mg/kg) and xylazine (5 mg/kg) delivered intraperitoneally.
Then, the left common carotid artery (LCCA) was cannulated with a polyethylene catheter (PE
50) containing heparinized saline (100 IU/mL). The left pteryopalatine, occipital, and superior
thyroid arteries were ligated using surgical thread. A heat lamp was used to maintain the
animal’s body temperature during the experiment.
Immediately after performing a heart cut on the anesthetized rat, the LCCA was washed with
saline delivered from a syringe pump (Model 341 B, Sage Instruments) at 5 mL/min for 10 sec.
The brains were then perfused with 10 mL of 1.0 mM HAV6 in HCO3– buffer (pH 7.4) with 0.5
% Tween 20 at 5 mL/min. This was followed by perfusion of 10 mL of HAV6 (1.0 mM) and
CPT Glu (0.021 mmol/kg) in HCO3– buffer (pH 7.4) with 0.5 % Tween 20 at the same flow rate.
Finally, a 10 sec post perfusion wash with saline solution was delivered. The experiment was
terminated by animal decapitation followed removal of the brain tissue. The whole brain was
immediately stored in –80°C until further use. A similar study was done using only CPT Glu as a
control. The brains were first perfused with 10 mL of HCO3– buffer (pH 7.4) with 0.5 % Tween
20 at 5 mL/min. Then, 10 mL of CPT GLU (0.021 mmol/kg) in HCO3– buffer (pH 7.4) with 0.5
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% Tween 20 were subsequently perfused at the same flow rate. The samples were extracted and
analyzed using LC MS/MS as described above.
Similar to
$ ' brain perfusion of CPT Glu, perfusion of Gd DTPA in the presence and
absence of HAV6 peptide was carried out followed by quantification of Gd DTPA brain
deposition using MRI. Briefly, the brains were perfused with 10 mL of 1.0 mM HAV6 in HCO3–
buffer at pH 7.4 with 0.5 % Tween 20 at 5 mL/min. Then, a perfusion of 10 mL 0.6 mmol/kg
Gd DTPA (Magnevist, Berlex labs, NJ) in the presence of 1.0 mM HAV6 peptide in HCO3–
buffer at pH 7.4 with 0.5 % Tween 20 was carried out at a flow rate of 5 mL/min. A 10 sec post
perfusion wash was delivered using saline solution. The amount of Gd DTPA that penetrates
across the BBB was determined from sacrificed animals at room temperature using a quantitative
T1 mapping MRI technique. Ex vivo MRI was performed using a quadrature volume coil in a 9.4
Tesla horizontal bore MR system equipped with a Agilent INOVA console (Agilent, Palo Alto,
CA) and a 12 cm gradient insert (400 mT/m, 250 µs; Magnex Scientific, Abingdon, UK). T1
mapping was performed using a modified Look Locker sequence for multi slice and multiple
phase encodings per inversion pulse (TR/TE = 4/2 ms, FOV = 3 cm, slice thickness = 1 mm,
matrix size = 128 x 128, flip angle = 20o, 22 inversion times from 40 – 5470 ms, 2 phasing
encoding steps per inversion pulse, acquisition time = 8.5 min) and T1 maps were generated
using a program written in IDL (RSI, CO).16 R1 (= 1/T1) values were obtained from regions of
interest (ROI) placed in olfactory bulbs, cortex, striatum, hippocampus, cerebellum, spinal cord,
ventral, deep rostral (mostly hypothalamus and pallidum), and deep caudal (mostly midbrain)
regions. The experiments were performed with n = 4 for each experimental group (control,
vehicle + Gd DTPA, and HAV peptide + Gd DTPA).
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# ' " $%
!
HAV6 peptide in
" %
!
&(
)&'*
%
+
#. The effect of
brain delivery of Gd DTPA was evaluated with * * administration of
Gd DTPA using T1 weighted MRI. Briefly, Sprague Dawley rats were anesthetized using 3%
isoflurane initially followed by 1–2% isoflurane in a gas mixture of air and oxygen at a ratio of
1:1. Two separate * * catheters (Insyte Autogard, 22 GA, 0.9 × 25 mm, Becton Dickinson,
Sparks, MD) were inserted into two separate tail veins and secured with tape. One of the * *
catheters was used for infusion of the Gd DTPA contrast agent and the other was used for
infusion of either the vehicle control or the HAV6 peptide.
The animal was placed in the magnet in a prone position using an acrylic sled with its head
held steady by two ear bars and a bite bar. The animal’s body temperature was maintained at
37°C using a blanket with warm water circulation; its body temperature was monitored using a
rectal temperature sensor (Cole Palmer, Vernon Hills, IL). The animal’s respiratory rate was
monitored using a pneumatic pillow sensor (SA instruments, Stony Brook, NY). A quadrature
RF surface coil with two geometrically decoupled loops was used to transmit/receive MR signals
at 400 MHz. T1 weighted MR images were acquired using multi slice spin echo sequence
(TR/TE = 240/10.5 ms, FOV = 3 cm, slice thickness = 2 mm, matrix size = 192 × 192, number
of averages = 4, scan time per time point = 3 min).
Prior to infusion of the test compounds, baseline MR scans of the brain for the first 6 min (2
time points) were collected for each rat and this allowed each animal to serve as its own control.
After the second time point, the contrast agent, Gd DTPA (0.6 mmol/kg), was administered
intravenously by an initial bolus followed by a slow infusion
the tail vein catheter to establish
a rapid rise and subsequent plateau of plasma Gd DTPA concentration during the study. After
10th time point (~30 min), either HAV6 peptide (0.019 mmol/kg) or vehicle was administered
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intravenously through the second tail vein catheter by a slow infusion for 1.0 min. MR scans
were acquired immediately after the administration of the peptide or vehicle for 45 min. Time
courses of T1 weighted MRI signals were obtained from regions of interest (ROI) placed in
sagittal sinus, muscle, olfactory bulb, deep rostral region (mostly hypothalamus and pallidum),
deep caudal region (mostly midbrain), striatum, cortex, hippocampus, cerebellum, and spinal
cord regions. To compare Gd DTPA delivery to the brain between control and HAV6 peptide
groups, signal intensities of T1 weighted MR images were first normalized using the average
signals of time points 1 and 2 (before contrast agent administration) and again with the averaged
of time points 9 and 10 (prior to peptide infusion). Relative changes of T1 weighted signal
intensities following Gd DTPA administration are proportional to the Gd DTPA concentration in
the ROIs. This normalization scheme removed the effect of variations among animals in
clearance of Gd DTPA. Areas under the curve (AUCs) were calculated by integrating the
normalized time courses over time for each region of interest.
&
. Statistical analysis was done using one way ANOVA with student
Newman Keul post hoc tests to compare the difference in the deposition of total amount of CPT
in the brain when CPT Glu was administered in combination with HAV6 peptide and when
CPT Glu was administered alone. For MRI studies, AUC values obtained from animals receiving
both Gd DTPA and HAV6 peptide were compared to those obtained from the control groups.
Drastic changes in the MRI signal represented significant perturbation of the BBB. A
less than 0.05 was used as a criterion for statistical significance.
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&#!" #
#
.
/
#
0
. The synthesis of CPT Glu involved a
two step reaction in DMF by forming an ester bond between the α COOH of Boc L Glu(OtBu)
OH and the 20 OH of camptothecin (+
,). The carboxylic acid group of Boc L Glu(OtBu)
OH was activated by 1,3 diisopropylcarbodiimide (DIPC) and reacted with CPT in the presence
of DMAP and scandium triflate as catalysts. This conjugation reaction generated about 90%
yield of the desired product; however, this reaction produced isomerization at the α carbon of the
Glu residue, as previously observed.15 The tert butyl ester and Boc protecting groups were
cleaved by 50% TFA in DCM to give the crude CPT Glu. The crude CPT Glu was purified
using a reversed phase C18 column to produce a pure conjugate; mass spectrometry ESI MS and
1
H NMR confirmed the identity of the final pure product.
1
1
#* 23 0 "
#$ #. Standard solutions of
CPT, CPT Glu, and SN 38 (IS) were first analyzed using MS and MS/MS to obtain their
precursor and product ions, respectively. ESI full scan spectra produced dominant peaks of MH+
at m/z 349.1 for CPT, m/z 478.1 for CPT Glu, and m/z 393.1 for SN 38. LC MS/MS collision
induced dissociation of each MH+ ion to produce major fragments at m/z 305.2 for CPT (Figure
2A) and m/z 331.0 for CPT Glu (Figure 2B). Product ions from both CPT and SN 38 were
derived from the loss of CO2 (–44 u) from the lactone ring (Figure 2A).17 The CPT fragment of
CPT Glu was generated via the loss of the Glu residue (–147 u) upon ester bond cleavage
(Figure 2B). The precursor and product ions obtained from MS/MS spectra were used to
generate transitions for their use in MRM. The transition pairs used in MRM detection for each
analyte were
"- 349.1 >> 305.2 for CPT, m/z 478.1 >> 331.0 for CPT Glu, and m/z 393.1 >>
349.1 for SN 38 as IS. Figure 3 represents MRM chromatograms of rat brain tissue before and
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$ ' brain perfusion with CPT Glu. Analysis of brain tissues of untreated rats showed
that there was no endogenous interference at the retention times of CPT, CPT Glu, and SN 38
(data not shown). UPLC chromatography of CPT Glu resulted in the elution of two peaks at 1.93
and 2.04 min (Figure 3A) with the same precursor/product transition, which is interpreted as the
presence of a diastereomer likely generated during the esterification reaction. Both peaks were
summed to represent the total amount of CPT Glu detected. CPT Glu was hydrolyzed by
esterase enzymes to produce CPT in the brain (Figure 3B). The internal standard (IS) spiked into
tissue homogenate after extraction was successfully separated from other analytes (Figure 3C).
&4
&
5 To quantitatively determine the total amount of
CPT delivered into the brain, extraction efficiency was determined for CPT and CPT Glu from
brain homogenates using previously published methods with minor modifications.18 The
extraction recoveries for CPT and CPT Glu were determined by comparing the ratio of a peak
area of extracted analyte previously spiked into brain homogenates to a peak area of analyte
spiked into extracted blank solutions. The recovery values from extracted brain were found to be
86–92% and 95–101% for CPT and CPT Glu, respectively. These values are ideal for recovery
of drugs from tissues where analysis can be hindered due to a high degree of protein drug
binding.
Calibration curves for CPT and CPT Glu were constructed in biological matrices (brain and
plasma) to determine the limit of detection (LOD), limit of quantification (LOQ), linearity, and
range. The standards for CPT and CPT Glu were around 1–500 ng/mL and 50–500 ng/mL,
respectively. The calculated LOD and LOQ for CPT in biological matrices were found to be 2.4
and 7.9 ng/mL, respectively. CPT Glu provided slightly higher values of LOD and LOQ,
approximately 17 and 57 ng/mL, respectively. Both analytes showed good linear response with
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regression values of 0.99. Assay results from quality control samples further demonstrated that
this LC MS/MS method had acceptable precision and accuracy. The coefficients of variation for
inter day and intra day samples were found to be less than 10% as shown in Table 1, suggesting
that the method was robust and could be used for analysis of samples extracted from brain
homogenates.
. #
& .
.
The activity of HAV6 peptide in improving paracellular transport of CPT Glu across the BBB
was evaluated using the
$ ' rat brain perfusion model. The rat brain was first perfused with a
10 mL solution containing 1.0 mM HAV6 peptide and then with a 10 mL solution of a mixture
of CPT Glu (0.021 mmol/kg) and 1.0 mM HAV6 peptide. As a control, the rat brain was
perfused with 10 mL of vehicle followed by a 10 mL solution of CPT Glu (0.021 mmol/kg). A
flow rate of 5 mL/min was chosen because the hydrostatic pressure at this flow rate was high
enough to ensure brain regional flow rates similar to those in physiological conditions without
compromising the integrity of the tight junction.19, 20 The results showed that HAV6 peptide
significantly enhanced brain delivery of CPT Glu compared to control ( < 0.05) (Figure 4).
Because some of the conjugate was converted to CPT by esterase in the brain, both CPT Glu and
CPT were used to calculate the total amount of transported CPT. The total amount of delivered
CPT Glu in the presence of HAV6 was 2058 ± 428 ng of CPT per g of rat brain while the total
amount of delivered CPT Glu in vehicle was 1282 ± 110 ng of CPT per g of rat brain.
The second study was carried out to evaluate the efficacy of HAV6 peptide to enhance brain
delivery of Gd DTPA using the
$ ' rat brain perfusion model, which was analyzed using
MRI. In this case, Gd DTPA (0.6 mmol/kg) and vehicle, Gd DTPA and HAV6 peptide (1.0
mM), or vehicle only (control) was perfused into the brains followed by MRI scanning. The
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quantities of Gd DTPA in different regions of the brain were expressed in R1 values, whose
differences from those without Gd DTPA administration are proportional to the concentration of
Gd DTPA in the brain.21 Compared to vehicle only, rats perfused with Gd DTPA and vehicle
had increased R1 values in cortex, brain ventral, and deep caudal, suggesting small amount
extravasation of Gd DTPA in the brain and/or residual intravascular Gd DTPA in perfusate.
Compared to Gd DTPA and vehicle, rats treated with Gd DTPA in the presence HAV6 showed
more significantly increased R1 values in the olfactory bulb (OB), hippocampus (HPC),
cerebellum (CBLM), brain ventral (BV), deep rostral (DPRST), and deep caudal (DPCDL)
regions (+
7
6).
& .
5 5
5 &
modulation of the BBB using HAV6 peptide was evaluated in Sprague Dawley rats by i.v.
administration of Gd DTPA (0.6 mmol/kg) in combination with vehicle or HAV6 peptide (0.019
mmol/kg). Ideally, Gd DTPA administration should be limited to very low doses as possible.
However, during our method development the contrast to noise ratio at 0.1 mmol/kg was low.
The signal contrast at 0.6 mmol/kg was sufficient to provide visually appreciable MR signal
changes and image contrasts and therefore we chose to increase it to 0.6 mmol/kg. Other studies
have shown that single administration of Gd DTPA at 1.0 mmol/kg in rats was well tolerated
without any organ toxicity.22 Normalized T1 weighted MRI time courses from representative
regions of interest are shown in Figure 6. The time courses from the sagittal sinus area showed
no significant difference in rats receiving Gd DTPA with HAV6 peptide compared to those with
vehicle, indicating similar systemic levels of Gd DTPA (Figure 6B vs. 6E and 6C vs. 6F). In
contrast, rats receiving Gd DTPA + HAV6 peptide showed significantly higher T1 weighted
signal intensities than those receiving Gd DTPA + vehicle. For instance, the MR images of the
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olfactory bulb in Figures 6A and D show that rats receiving Gd DTPA plus HAV6 (Figure 6A)
had significantly higher T1 weighted signal intensities (as seen by more brighter areas) compared
to the control group (Figure 6D); indicating higher accumulation of the contrast agent. T1
weighted signal intensities were used to quantify the accumulation of Gd DTPA in both groups.
The time course profiles in various brain regions indicate a rapid alteration of the BBB following
administration HAV6 peptide, as seen in the sharp increase of Gd DTPA delivery within 3 min
of injection of HAV6 peptide (Figure 7). In contrast, a steady decline without any increase in the
time courses at various regions of the brain without HAV6 peptide reflects gradual clearance of
Gd DTPA from circulation. As shown in the saggital sinus (Figure 7A), the muscle (Figure 7B),
cortex (Figure 7C), the hippocampus (Figure 7D), olfactory bulb (Figure 7E), and deep rostral
(Figure 7F) regions, we observed significantly higher overall accumulation of Gd DTPA among
the Gd DTPA + HAV6 group compared to the control group; indicating enhanced brain delivery
of Gd DTPA in animals receiving HAV6 peptide. The area under the curves (AUCs) of various
regions of the brains (Figure 8) shows significant enhanced accumulation of Gd DTPA in the
muscle (M), olfactory bulb (OB), deep rostral (DPRST), deep caudal (DPCDL), hippocampus
(HPC), and cortex (CTX) regions of brains in animals received Gd DTPA + HAV6 peptide
compared to those received Gd DTPA + vehicle.
# !## )*
The poor BBB penetration property of drugs and diagnostic agents is one of the major challenges
in diagnosing and treating diseases affecting the CNS. One challenge to molecules in reaching
the brain is due to recognition by an active efflux pump. Another concern is physicochemical
properties of delivered molecules such as size, charge, and hydrophilicity, which prevent them
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from partitioning to cell membranes for crossing transcellular pathways of the BBB. In addition,
tight junctions limit the paracellular permeation of molecules through the BBB. There are a few
non invasive strategies to improve brain delivery of drugs, which include the use of high osmotic
mannitol23 25 and bradykinin receptor agonists such as CereportTM.26 One potential drawback of
using a high concentration of mannitol to disrupt the BBB is associated with a long recovery
period that increases the risk of infection, neurotoxicity, and inflammation in the brain.24
Although bradykinin agonists resulted in shorter recovery times, the clinical utility of these
analogs was ineffective.23, 24 Thus, there is a need to find alternative methods to improve the
delivery of drugs to the brain.
Our research focused on the use cadherin derived peptides to increase the permeability of the
BBB by inhibiting protein protein interactions at the intercellular junctions in a more selective
manner. In contrast to the long recovery periods required after the use of hypertonic mannitol
solutions, we anticipate quick recovery and re establishment of the integrity of the BBB
following transient perturbation using cadherin peptides. Previous
studies in Balb/c mice
have shown that the BBB opening produced by HAV6 was limited to less than 1 h;12 indicating
that the BBB integrity returned to normal within an hour. Here, the BBB modulatory activity of
HAV6 was investigated in Sprague Dawley rats to improve the delivery of CPT Glu and Gd
DTPA into rat brains using an
$ ' brain perfusion model as well as
brain delivery of
Gd DTPA via i.v. administration.
CPT is a naturally occurring alkaloid extracted from the
'
plant; it
suppresses cancer proliferation by inhibiting topoisomerase I enzyme activity required for cancer
cell replication and transcription.27 30 CPT has been shown to have a wide spectrum of activities
against human cancer malignancies such as lung, prostate, breast, colon, stomach, and ovarian
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carcinomas.31 Unfortunately, its utility to treat cancers, including brain tumors, has been limited
by its unfavorable physicochemical properties. For example, CPT has very poor aqueous
solubility (2.5 Tg/mL), making it difficult to formulate.30 The lactone group on CPT is stable
below pH 5.5 and undergoes lactone hydrolysis to CPT carboxylate at physiological conditions
(pH 7.4) (Figure 1). CPT carboxylate binds to human serum albumin (HSA), which causes
lowering of the effective concentration of CPT in the bloodstream.27 To solve the solubility
problem, several derivatives of CPT such as topotecan (Hycamtin®) and irinotecan (Campto®)
were developed. These derivatives are currently being used to treat patients with peripheral
cancers such as various forms of ovarian, cervical, and lung cancers.27, 32 However, these current
drugs have not been used to treat brain tumors because of their difficulty in crossing the BBB.
In this study, a CPT Glu conjugate was synthesized to improve CPT solubility, and its brain
delivery was investigated with the help of HAV6 peptide as a BBB modulator. Formation of
CPT Glu enhanced the water solubility more than 400 fold compared to that of CPT.
Unfortunately, the formation of CPT Glu produced diastereomers of GPT Glu with racemization
at the alpha carbon of the Glu residue. However, both GPT Glu diastereomers (Figure 3B) were
successfully delivered into the brain using an
$ ' rat brain perfusion model, and CPT was also
observed in the brain homogenate (Figure 3C). Because HAV6 peptide enhanced the paracellular
transport of molecules, it was reasoned that the diastereomeric structures of CPT Glu did not
influence their penetration through the intercellular junctions of the BBB (Figure 4).
The acidic extraction method developed was efficient in extracting the conjugate (CPT Glu)
along with its hydrolyzed product CPT from brain tissue homogenates. After delivery, some of
CPT Glu molecules were converted to CPT via cleavage of the esterase bond. Ester formation at
the 20 OH group has been shown previously to stabilize the lactone A ring at physiological pH,
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preventing the loss of activity associated with lactone ring opening.29, 33 Conjugation of the 20
OH group with different moieties has been shown to improve the physicochemical properties and
pharmacokinetic profiles of CPT.29, 30, 34, 35 The propionate ester of 20 OH in CPT did not show
any lactone ring hydrolysis when incubated for 4 h in phosphate buffered saline solution
containing 4% human plasma, while CPT alone was rapidly converted to the CPT carboxylate
form in 11 min (Figure 1).36 38 These results support the idea that formation of the ester
increases the stability of the lactone ring in CPT.
The extraction and LC MS/MS detection methods were successfully developed for
quantification of delivered CPT Glu and CPT in the brain. The LC MS/MS method was
developed to detect both CPT Glu and CPT and for validation of the method. It started with the
determination of product ions from CPT Glu and CPT. Full scan spectra of all analytes were
generated using electrospray ionization (ESI) positive ion mode in a solvent system consisting of
50:50 acetonitrile and water with addition of 0.1% formic acid (Figures 2 & 3). CPT, CPT Glu,
and SN 38 produced protonated molecular ion peaks. The SN 38 (IS) was spiked in all matrices
prior to introduction to LC MS/MS as a control for HPLC injection and ionization variability.
When CPT, CPT Glu, and SN 38 were subjected to collision induced dissociation (CID), the
energy applied fragmented the lactone ring, removing the CO2 residue from both CPT and SN 38
molecules and producing a stable abundant product ion at m/z 305.2 and 349.1, respectively.
CPT Glu produced a major product at m/z 331.1 when analyzed under the same conditions
(Figure 2B). This fragment occurred from cleavage of the ester bond at the 20 OH position of the
CPT lactone ring. Comparison of the fragmentation pattern of CPT Glu ( "- 478.1 >> "- 331.1)
to that of CPT ( "- 349.1 >>
"- 305.2) showed that the fragmentation of CPT Glu did not
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involve the lactone ring. This indicates that the addition of the L Glu amino acid residue to CPT
offers some lactone ring stability as previously mentioned with CPT propionate ester.
For method validation, quality control (QC) samples were used to check for accuracy,
precision, sensitivity, linearity of calibration curves, matrix effects, recovery, stability, and
reproducibility according to the FDA guidance for bioanalytical method validation over a
concentration range of 0–500 ng/mL.39 CPT and CPT Glu were quantitatively determined from
peak areas calculated after the SRM scanning (Table 1). CPT Glu had slightly higher LOQ and
LOD of 57 ng/mL and 17 ng/mL, respectivelyAll of our QC samples were highly reproducible
and had coefficients of variation between 0.99% and 14.17%. This indicates that this method is
precise and accurate. Good linearity was observed over the studied concentration range, with R2
= 0.9 or better. The extraction recoveries of CPT and CPT Glu from brain tissue homogenates
were excellent, with more than 86% efficiency over concentrations ranging from 1–500 ng/mL.
Acetonitrile precipitation was used to remove interfering endogenous proteins as well as take
advantage of the high solubility of CPT and CPT Glu in organic solvents. Phosphate buffer, pH
3.0, was added to the extraction procedure to ensure determination of total amount of drug
delivered in lactone form. All of the above indicate that our LC MS/MS method was robust and
suitable for quantification of CPT and CPT Glu after the
Results from the
$ ' brain perfusion.
$ ' rat brain perfusion studies showed a significantly higher brain
deposition of CPT Glu when it was delivered with HAV6 peptide (1.6 fold) compared to
delivery to CPT Glu with vehicle (Figure 4). This was the first result to show that HAV6 peptide
enhanced the delivery of CPT Glu into the brain as detected by mass spectrometry. Besides
detecting CPT Glu, mass spectrometry also detected CPT in the brain, indicating that CPT Glu
was converted to CPT in the brain after delivery. This result confirmed previous
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perfusion studies that HAV6 enhanced brain delivery of
14
C mannitol and [3H(G)]
daunomycin.10 12
Another method to confirm the BBB modulatory activity of HAV6 peptide was to deliver an
MRI contrast agent, Gd DTPA, into rat brains using the
$ ' rat brain perfusion model and
living rats. The advantage of the MRI method is that it can evaluate the delivery efficiency of
Gd DTPA in various parts of the brain and this can also be done in living animals. Although it is
very likely the CPT Glu and Gd DTPA might cross the BBB differently, we anticipate both
molecules would cross the BBB predominantly via the paracellular route. It is widely accepted
that Gd DTPA would cross the BBB
the paracellular route due to its hydrophilic nature.
Similarly, conjugation of CPT to glutamic acid would make it more hydrophilic as demonstrated
by increased solubility in water. In addition to the difficulties encountered by drugs in crossing
the BBB, another major obstacle in the delivery of drugs to the brain is the inability of the drugs
to diffuse and penetrate the brain far away to the target site in pharmacologically relevant
quantities. The pathway taken by the drugs to reach the site of action is highly tortouous and
narrow. Here, we wanted to take advantage of the capabilities of MRI to evaluate the
enhancement in the delivery of Gd DTPA to various regions of the brain following modulation
of the BBB permeability using cadherin peptide. MRI can provide a quantitative assessment of
amount of tracer molecules present in the extracellular space. Contrast agent molecules present
in the extravascular space shorten T1 relaxation time of water signals surrounding the contrast
agent molecules and amplify the detectability of the tracer molecules dramatically and enables
detection of very low levels of tracers. We believe that increased T1weighted MRI signals in
various areas of the brain sufficiently demonstrate the entry of contrast agent molecules into the
extravascular space due to increased BBB permeability via HAV6 peptide perturbation both
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$ ' and
. The data from the
$ ' brain perfusion studies indicated that the depositions of
Gd DTPA were significantly higher in highly vascularized parts of the brain such as olfactory
bulb, hippocampus, cerebellum, brain ventral, deep rostral, and deep caudal regions. MRI studies
in living rats showed the
BBB modulatory activity of the HAV6 peptide to enhance brain
delivery of Gd DTPA in various regions of the brain including muscle, olfactory bulb, deep
rostral, deep caudal, hippocampus, and cortex regions, which consistent with the
$ ' brain
perfusion study. The effect of HAV6 peptide in modulating the BBB to deliver Gd DTPA was
immediate or as soon as 3 minutes. This finding was consistent with previous studies to enhance
brain delivery of Gd DTPA using HAV6 and ADTC5 peptides in Balb/c mice.11, 12
In our previous studies, we observed that increase in BBB permeability did not show any
increase in cerebral blood flow;12 suggesting that the differences in the increase in BBB regional
permeability could be attributed to the differences in vasculature in these regions. Targeting
abnormally highly vascularized regions would be beneficial in the treatment of brain tumors
particularly glioblastomas. In contrast to normal blood vessels, tumor vasculature in
glioblastomas are highly proliferative resulting in extensive vascularization which is critical for
tumor progression and invasion.40 One of the potential limitation of HAV6 peptide is that it also
modulate E cadherins in other organs (i.e., intestinal mucosa, lung and kidney). Thus, we are
currently developing methods to improve selectivity of cadherin peptides to selectively modulate
cadherins in the blood brain barrier over cadherins in to the other organs. In future, we hope to
develop a more sensitive LC MS/MS assay that would estimate regional enhancement of various
molecules following transient BBB disruption and correlate the results with the MRI data. Also,
we hope to evaluate a number of molecules with different physicochemical properties and try to
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understand what properties are important for transport of drug molecules so that they can reach
the target regions in therapeutically relevant quantities.
Cadherin peptides enhanced brain delivery of molecules in a global manner; in other words,
the delivery of molecules was not specific to a certain part(s) of the brain. This is due to the
potential mechanism of action of cadherin peptides in modulating the BBB. Cadherin peptides
create a higher BBB permeability and paracellular transport of molecules because they disrupt
cadherin cadherin interactions in the intercellular junctions of the BBB. Our results showed that
the quantities of brain deposition of Gd DTPA were higher in parts of the brain with higher
vascularization than section with lower vascularization regions (Figures 5 and 8). This is
consistent with data from the in vivo studies in Balb/c mice, where three different cadherin
peptides (i.e., HAV6, cHAVc3, and ADTC5) enhance the deposition of Gd DTPA in the brain
posterior region higher than the midbrain region.11,
12, 41
Furthermore, the deposition of Gd
DTPA in the midbrain region was higher than the anterior region.11, 12, 41 Thus, the quantities of
brain depositions of delivered molecules correspond to the density of vascularization of each
section of the brain. For a small molecule such as Gd DTPA, cyclic cadherin peptides (i.e.,
cHAVc3 and ADTC5) allowed the brain delivery of Gd DTPA when the peptides delivered 2 h
earlier than Gd DTPA.11, 41 However, no enhancement of Gd DTPA brain delivery was observed
when it was delivered 4 h after administration of cadherin cyclic peptides. This result indicates
that cHAVc3 and ADTC5 open the BBB for about 2–4 h. In contrast, linear HAV6 peptide
modulates the BBB in less than 1 h time frame.12 For a large molecule such as IRdye labeled 25
kDa polyethylene glycol (IRdye 800cw PEG), both linear HAV6 and cyclic cHAVc3 peptides
increase its brain delivery when administered together with peptide.12, 41 However, when the
IRdye 800cw PEG was delivered 1 h after administration of linear HAV6 or cyclic cHAVc3
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peptides there was no enhancement of brain delivery.12, 41 In other words, large molecules could
be only be delivered at the early state of the BBB modulation. This result suggests that the BBB
size of opening by cadherin peptides is a time dependent manner and the opening for small
molecules has a longer time window than for large molecules. Our hypothesis is that cadherin
peptides modulate the BBB by immediately generating both large and small openings in the
intercellular junctions of the BBB; however, the large size openings collapse to small size
openings as the time progresses.
The long term opening of the BBB may cause unwanted side effects in the brain because the
BBB opening could allow the penetration of unwanted molecules (i.e., proteins, peptides) and
particles (i.e., cells) from the blood stream into the brain. Although in inflammatory situations
the BBB is also leaky for allowing temporary infiltration of immune cells into the brain, the
long term opening could have unfavorable effect to the brain. The effects of repeated and long
term BBB opening by cadherin peptides have not yet been studied; thus, these effects will be
studied in the future. It is interesting that cadherin peptides induce only a short period of the
BBB opening for large molecules (i.e., IRdye 800cw PEG); therefore, this is an advantage
characteristic of cadherin peptide because it could prevent the delivery of large unnecessary or
toxic molecules (e.g., protein) into the brain.
)* "!# )*#
In conclusion, this study demonstrated that HAV6 enhanced the brain delivery of CPT Glu and
Gd DTPA in an
$ ' rat brain perfusion assay compared to control. The HAV6 peptide also
significantly improved brain deposition of Gd DTPA in the
study. The improved brain
delivery of those molecules was attributed to increased permeability of the BBB upon
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intercellular junction modulation by HAV6 peptide. This modulation occurred in a matter of
minutes after injection of HAV6 peptide. The developed LC MS/MS was very sensitive and
selective to identify and quantify CPT Glu and CPT in the brain. The detection limits can be as
low as 2.4 and 17 ng/mL for CPT and CPT Glu, respectively. As shown from studies using MRI,
the molecules were delivered more efficiently to the vascularized regions. In the future, HAV6
will be used to deliver CPT Glu into the brains of animals (i.e., rat and mouse) with brain tumors
and to deliver large molecules (e.g., peptides, proteins, nucleotides) into the brains of animals
with brain diseases for treatments and diagnostic purposes.
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%*)("&
& &* #
Funding for this research was provided by an R01 NS075374 grant from National Institute of
Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH). CSE was also
supported by a Research Initiative for Scientific Enhancement grant (R25 GM062881) from
National Institute of General Medical Sciences (NIGMS), NIH. The Hoglund Brain Imaging
Center is supported by a generous gift from Forrest and Sally Hoglund and funding from the
National Institutes of Health (P30 HD002528, S10 RR29577, UL1 RR033179, and P30
AG035982).
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! & "& &* #
,5 Structures of camptothecin (CPT), camptothecin glutamate conjugate (CPT Glu), and
SN 38 as an internal standard as well as the synthetic scheme to make CPT Glu. CPT
is stable at pH below 5.5 and the lactone ring CPT carboxylate at the physiological
condition (pH 7.4).
+
85 Mass spectra for the daughter ions and MRM transitions for ( ) CPT
"- 349.1 >>
305.2 and ( ) CPT Glu "- 478.1 >> 331.0.
+
25 UPLC chromatograms of brain tissue homogenates for CPT, CPT Glu, and SN 38.
( ) CPT Glu (1.93 and 2.04 min) extracted from brain tissue extract after
$ ' brain
perfusion, (B) hydrolyzed product CPT (3.59 min) detected in brain homogenate after
perfusion studies, and ( ) internal standard, SN 38 (25 ng/mL), spiked and extracted
from tissue homogenate with retention time of 3.43 min.
+
95 Total amount of equivalent CPT accumulation in the brain after
$ ' brain
perfusion of CPT Glu in the presence and absence of HAV6 peptide. Rat brains were
perfused with CPT Glu (0.021 mmol/kg) in the presence or absence of 1.0 mM
HAV6 peptide at a flow rate of 5 mL/min. Data are represented as mean ± s.d. with
< 0.05.
+
65 The MRI scans of the brain from
$ ' rat brain perfusion studies to compare the R1
= 1/T1 values of the brain regions of rats treated with Gd DTPA (0.5 mmol/kg), Gd
DTPA (0.5 mmol/kg) with HAV6 peptide (1.0 mM), and vehicle. The differences in
R1 values were determined at various parts of the brain, including olfactory bulbs
:) ;, cortex :
<;, striatum :#
;, hippocampus :-
spinal cord :# *;, brain ventral : 7;, deep rostral :
:
;, cerebellum :
" ;,
# ;, and deep caudal
";. Data are represented as mean ± SD. Statistical significance considered at
< 0.05, designated as (*) for vehicle
$* Gd DTPA; (#) for vehicle
DTPA+HAV6, and (†) for Gd DTPA $* Gd DTPA +HAV6.
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+
=5 Representatives of MR images showing Gd DTPA deposition at various brain regions
following intravenous infusion of Gd DTPA (0.6 mmol/kg) and HAV6 peptide (0.021
mmol/kg) or vehicle to induced disruptions of the BBB. Signal intensities of MR
images at time point 16 were normalized with those at time point 1. MR images
show that there was no significant difference in the levels of Gd DTPA in the saggital
sinus region (arrow heads) between Gd DTPA + HAV6 group ( and
) and that of
Gd DTPA alone (& and +). Gd DTPA levels in the olfactory bulb were significantly
higher in ( ) Gd DTPA + HAV6 group compared to ( ) Gd DTPA alone; suggesting
that HAV6 improved the transport of Gd DTPA across the BBB. Gray scale bar
indicates normalized signal intensities ranges of 0–3.0.
+
>5 Amount of Gd DTPA in various regions of the brain over time to show kinetic
deposition of Gd DTPA following intravenous infusion of Gd DTPA and HAV6
peptide or vehicle to induced disruptions of the BBB. At 0–6 min, the brain was
scanned as the baseline. At 6 min, Gd DTPA (0.6 mmol/kg) was delivered i.v.
followed by observation until 10th time point (~30 min). HAV6 peptide (0.021
mmol/kg) or vehicle was injected i.v. immediately after 10th time point and the
depositions of Gd DTPA were monitored up to 45 min. Time courses of T1 weighted
MRI signals were normalized first with those before Gd DTPA administration and
then with those before HAV6 peptide administration. Normalized time courses are
from ( ) sagittal sinus, ( ) muscle, ( ) cortex, ( ) hippocampus, (&) olfactory bulb,
and (+) deep rostral. Data is represented as mean ± SD. (*) indicates significant
differences between Gd DTPA+HAV6 and Gd DTPA+vehicle group with p < 0.05.
+
35 Area under curve (AUC) values showing deposition of Gd DTPA in various regions
of rat brain following intravenous infusion of Gd DTPA+vehicle and Gd
DTPA+HAV6 peptide. SS = sagittal sinus; M = muscle; OB = olfactory bulb; DPRST
= deep rostral; DPCDL = deep caudal; STR = striatum; HPC = hippocampus; CTX =
cortex; CBLM = cerebellum; and SPN = spinal cord. Data are represented as mean ±
SD. (*) indicates significant differences between groups Gd DTPA+HAV6 and Gd
DTPA+vehicle with p < 0.05.
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0 ,
.
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CPT
CPT Glu
Page 30 of 49
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1.
Laksitorini, M.; Prasasty, V. D.; Kiptoo, P. K.; Siahaan, T. J. Pathways and progress in
improving drug delivery through the intestinal mucosa and blood brain barriers.
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'
2.
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function of the blood brain barrier. / '
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$ 8B,B1 01, (1), 13–25.
Reichel, A. Addressing central nervous system (CNS) penetration in drug discovery:
basics and implications of the evolving new concept.
$ 8BBC1 2, (11), 2030–
49.
4.
Pardridge, W. M. Alzheimer's disease drug development and the problem of the blood
brain barrier.
5.
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8BBC1 ., (5), 427–32.
$
McCaffrey, G.; Davis, T. P. Physiology and pathophysiology of the blood brain barrier: P
glycoprotein and occludin trafficking as therapeutic targets to optimize central nervous
system drug delivery. 3 &
6.
8B,81 24, (8), 1131–40.
$ #
Mandery, K.; Glaeser, H.; Fromm, M. F. Interaction of innovative small molecule drugs
used for cancer therapy with drug transporters.
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Gabathuler, R. Approaches to transport therapeutic drugs across the blood brain barrier to
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Wolburg, H.; Lippoldt, A.
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composition and regulation.
$ '
8BB81 06, (6), 323–37.
Wheeler, G. N.; Parker, A. E.; Thomas, P. A.; Ataliotis, P.; Poynter, D.; Arnemann, J.;
Rutman, A. J.; Pidsley, S. C.; Watt, F. M.; Rees, D. A.; Buxton, R. S.; Magee, A. I.
Desmosomal glycoprotein DGI, a component of intercellular desmosome junctions, is
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* ,CC,1 66, 4796–4800.
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Siahaan, T. J.
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Laksitorini, M. D.; Kiptoo, P. K.; On, N. H.; Thliveris, J. A.; Miller, D. W.; Siahaan, T. J.
Modulation of intercellular junctions by cyclic ADT peptides as a method to reversibly
increase blood brain barrier permeability. 3
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On, N. H.; Kiptoo, P.; Siahaan, T. J.; Miller, D. W. Modulation of blood brain barrier
permeability in mice using synthetic E cadherin peptide.
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8B,91 55, (3), 974–81.
Sinaga, E.; Jois, S. D.; Avery, M.; Makagiansar, I. T.; Tambunan, U. S.; Audus, K. L.;
Siahaan, T. J. Increasing paracellular porosity by E cadherin peptides: discovery of bulge
and groove regions in the EC1 domain of E cadherin.
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Makagiansar, I.; Avery, M.; Hu, Y.; Audus, K. L.; Siahaan, T. J. Improving the selectivity
of HAV peptides in modulating E cadherin E cadherin interactions in the intercellular
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Greenwald, R. B.; Pendri, A.; Zhao, H. Stereoselective acylation of 20 (S) camptothecin
with amino acid derivatives using scandium triflate/DMAP.
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Kim, J.; Choi, I. Y.; Michaelis, M. L.; Lee, P. Quantitative in vivo measurement of early
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sensitive LC/MS/MS assay for 7 ethyl 10 hydroxycamptothecin (SN 38) in mouse plasma
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Martins, S. M.; Wendling, T.; Goncalves, V. M.; Sarmento, B.; Ferreira, D. C.
Development and validation of a simple reversed phase HPLC method for the
determination of camptothecin in animal organs following administration in solid lipid
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#
Liu, X.; Tu, M.; Kelly, R. S.; Chen, C.; Smith, B. J. Development of a computational
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'#
$
$ 8BB91 09, (1),
132–9.
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Takasato, Y.; Rapoport, S. I.; Smith, Q. R. An in situ brain perfusion technique to study
cerebrovascular transport in the rat.
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Effects of aging on blood brain barrier and matrix metalloproteases following controlled
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and/or blood tumor barriers. / ' $' #
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Synthesis and in vivo antitumor efficacy of PEGylated poly(l lysine) dendrimer
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20 O acylcamptothecin derivatives: evidence for lactone stabilization. 3 : #
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2., (15), 4601–6.
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