In non-excitable cells, activation of G-protein-coupled phospholipase C (PLC)-linked receptors ca... more In non-excitable cells, activation of G-protein-coupled phospholipase C (PLC)-linked receptors causes the release of Ca(2+) from intracellular stores, which is followed by transmembrane Ca(2+) entry. This Ca(2+) entry underlies a small and sustained phase of the cellular [Ca(2+)](i) increases and is important for several cellular functions including gene expression, secretion and cell proliferation. This form of transmembrane Ca(2+) entry is supported by agonist-activated Ca(2+)-permeable ion channels that are activated by store depletion and is referred to as store-operated Ca(2+) entry (SOCE) and represents a major pathway for agonist-induced Ca(2+) entry. In excitable cells such as smooth muscle cells, Ca(2+) entry mechanisms responsible for sustained cellular activation are normally considered to be mediated via either voltage-operated or receptor-operated Ca(2+) channels. Although SOCE occurs following agonist activation of smooth muscle, this was thought to be more important in replenishing Ca(2+) stores rather than acting as a source of activator Ca(2+) for the contractile process. This review summarizes our current knowledge of SOCE as a regulator of vascular smooth muscle tone and discusses its possible role in the cardiovascular function and disease. We propose a possible hypothesis for its activation and suggest that SOCE may represent a novel target for pharmacological therapeutic intervention.
ABSTRACT Thyrotoxic periodic paralysis is an uncommon complication of hyperthyroidism. It is char... more ABSTRACT Thyrotoxic periodic paralysis is an uncommon complication of hyperthyroidism. It is characterized by acute attacks of hypokalaemic paralysis in male patients with thyrotoxicosis. It is often a benign condition responsive to therapy and the myopathy usually recovers fully within days (3) . On rare occasions, however, it is fatal due to respiratory muscle paralysis or dysrhythmias. In Hong Kong, TPP accounts for the majority (~80%) of hospital admission with hypokalaemic paralysis. This article is protected by copyright. All rights reserved.
Nitric oxide production is stimulated by an increase of the concentration of cytosolic Ca2+ in va... more Nitric oxide production is stimulated by an increase of the concentration of cytosolic Ca2+ in vascular endothelial cells. Recent evidence suggests that nitric oxide and cGMP might attenuate Ca2+ influx and, at the same time, initiate a Ca2+ removal mechanism, thereby decreasing the intracellular concentration of endothelial Ca2+ in a negative feedback fashion. Such a negative feedback mechanism could serve
Cardiac pacemaking is a complex phenomenon that is not completely understood. Canonical transient... more Cardiac pacemaking is a complex phenomenon that is not completely understood. Canonical transient receptor potential isoform 3 (TRPC3) channel is a cation channel that permeates both Ca(2+) and Na(+). TRPC3 was previously found to express in adult cardiomyocytes. However, its role in cardiac pacemaking is unexplored. Here we used mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) to investigate whether TRPC3 regulates the spontaneous automaticity and the underlying mechanism involved. Immunocytochemistry results showed that TRPC3 is expressed at the T-tubules of mESC-CMs. Whole-cell patch clamping showed that single mESC-CMs contain TRPC3 current. Confocal Ca(2+) imaging showed that the TRPC3-specific blocker Pyr3 decreased Ca(2+) transients and local Ca(2+) release (LCR) of mESC-CMs. Combined current and voltage clamp recordings from the same cell showed that reducing the TRPC3 current, either by Pyr3 or a dominant negative (loss-of-function) construct of TRPC3, decreased ...
We recently identified a new COPI-interacting KXD/E motif in the C-terminal cytosolic tail (CT) o... more We recently identified a new COPI-interacting KXD/E motif in the C-terminal cytosolic tail (CT) of Arabidopsis endomembrane protein 12 (AtEMP12) as being a crucial Golgi retention mechanism for AtEMP12. This KXD/E motif is conserved in CTs of all EMPs found in plants, yeast and humans, and is also present in hundreds of other membrane proteins. By cloning selective EMP isoforms from plants, yeast and mammals, we here studied the localizations of EMPs in different expression systems since there are contradictory reports on the localizations of EMPs. We showed that the N-terminal and C-terminal GFP-tagged EMP fusions were localized to Golgi and post-Golgi compartments respectively in plant, yeast and mammalian cells. In vitro pull-down assay further proved the interaction of the KXD/E motif with COPI coatomer in yeast. COPI loss of function in yeast and plants caused mislocalization of EMPs or KXD/E-motif-containing proteins to vacuole. Ultrastructural studies further showed that RNAi...
Cytosolic Ca2+ ([Ca2+]i) is an important signal that regulates cardiomyocyte differentiation duri... more Cytosolic Ca2+ ([Ca2+]i) is an important signal that regulates cardiomyocyte differentiation during cardiogenesis. TRPV1 is a Ca2+-permeable channel that is expressed in cardiomyocytes. In the present study, we utilized mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) as a model to investigate the functional role of TRPV1 in cardiomyocyte differentiation. Induction of embryonic stem cells into cardiomyocytes was achieved using embryoid body (EB)-based differentiation method. Quantitative PCRs showed an increased TRPV1 expression during the differentiation process. In [Ca2+]i measurement study, application of TRPV1 agonists, capsaicin and camphor, elicited a [Ca2+]i rise in mESC-CMs, the effect of which was abolished by TRPV1-shRNA. In functional study, treatment of EBs with TRPV1 antagonists (capsazepine and SB366791) and TRPV1-shRNA reduced the size of the EBs and decreased the percentage of spontaneously beating EBs. TRPV1 antagonists and TRPV1-shRNA also suppressed the...
Angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) [Ang (1-7)]-Mas constitutes the vaso-p... more Angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) [Ang (1-7)]-Mas constitutes the vaso-protective axis and is demonstrated to antagonize the vascular pathophysiological effects of the classical renin-angiotensin system. We sought to study hypothesis that upregulation of ACE2-Ang (1-7) signaling protects endothelial function through reducing oxidative stress that would result in beneficial outcome in diabetes. Ex vivo treatment with Ang (1-7) enhanced endothelium-dependent relaxation (EDR) in renal arteries from diabetic patients. Both Ang (1-7) infusion via osmotic pump (500 ng/kg/min) for 2 weeks and exogenous ACE2 overexpression mediated by adenoviral ACE2 via tail vein injection (109 pfu/mouse) rescued the impaired EDR and flow-mediated dilatation (FMD) in db/db mice. Diminazene aceturate treatment (15 mg/kg/day) activated ACE2, increased circulating Ang (1-7) level, and augmented EDR and FMD in db/db mouse arteries. In addition, activation of ACE2-Ang (1-7) axis reduced...
Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress ... more Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress and elicit a mechanoelectric transduction cascade that initiates compensatory mechanisms. Mechanosensitive ion channels in the plasma membrane are responsible for transducing the mechanical signals to electrical signals. However, the mechanisms underlying channel activation in response to mechanical stress remain incompletely understood. Transient Receptor Potential (TRP) channels serve essential functions in several sensory modalities. These channels can also participate in mechanotransduction by either being autonomously sensitive to mechanical perturbation or by coupling to other mechanosensory components of the cell. Here, we investigated the response of a TRP family member, TRPC5, to mechanical stress. Hypoosmolarity triggers Ca2+ influx and cationic conductance through TRPC5. Importantly, for the first time we were able to record the stretch-activated TRPC5 current at single-channe...
Current drug targets. Cardiovascular & haematological disorders, 2005
The dried roots of Scutellaria baicalensis (S. baicalensis) Georgi (common name: Huangqin in Chin... more The dried roots of Scutellaria baicalensis (S. baicalensis) Georgi (common name: Huangqin in China) have been widely employed for many centuries in traditional Chinese herbal medicine as popular antibacterial and antiviral agents. They are effective against staphylococci, cholera, dysentery, pneumococci and influenza virus. Baicalein, one of the major flavonoids contained in the dried roots, possesses a multitude of pharmacological activities. The glycoside of baicalein, baicalin is a potent anti-inflammatory and anti-tumor agent. This review describes the biological properties of baicalein (Table 1), which are associated with the prevention and treatment of cardiovascular diseases. Baicalein is a potent free radical scavenger and xanthine oxidase inhibitor, thus improving endothelial function and conferring cardiovascular protective actions against oxidative stress-induced cell injury. Baicalein lowers blood pressure in renin-dependent hypertension and the in vivo hypotensive effec...
Urocortin and other hypothalamus corticotropin-releasing factor (CRF) polypeptides play biologica... more Urocortin and other hypothalamus corticotropin-releasing factor (CRF) polypeptides play biologically diverse roles in the stress, cardiovascular and inflammatory responses by acting on central and peripheral CRF receptors. Urocortin shows a significantly high sequence homology to CRF, and the concurrent expression of type-2 CRF (CRF2) receptors with urocortin in the heart suggests that urocortin may play a physiological role in the cardiac function. Urocortin is thought to be the endogenous agonist producing the cardiovascular actions previously attributed to CRF. This review highlights the current novel findings on the molecular and cellular mechanisms by which urocortin may exert its cardiovascular protective action.
Heme oxygenase-1 (HO-1) exerts vaso-protective effects. Such benefit in diabetic vasculopathy how... more Heme oxygenase-1 (HO-1) exerts vaso-protective effects. Such benefit in diabetic vasculopathy however remains unclear. We hypothesize that bilirubin mediates HO-1-induced vascular benefits in diabetes. Diabetic db/db mice were treated with hemin (HO-1 inducer) for two weeks, and aortas were isolated for functional and molecular assays. Nitric oxide (NO) production was measured in cultured endothelial cells. Hemin treatment augmented endothelium-dependent relaxations (EDRs) and elevated Akt and eNOS phosphorylation in db/db mouse aortas, which were reversed by HO-1 inhibitor SnMP or HO-1 silencing virus. Hemin treatment increased serum bilirubin and ex vivo bilirubin treatment improved relaxations in diabetic mouse aortas, which was reversed by Akt inhibitor. Biliverdin reductase silencing virus attenuated the effect of hemin. Chronic bilirubin treatment improved EDRs in db/db mouse aortas. High glucose-induced reductions in Akt and eNOS phosphorylation, and NO production were revers...
Proceedings of The National Academy of Sciences, 2004
Canonical transient receptor potential (TRPC) channels are Ca2+-permeable nonselective cation cha... more Canonical transient receptor potential (TRPC) channels are Ca2+-permeable nonselective cation channels that are widely expressed in numerous cell types. Seven different members of TRPC channels have been isolated. The activity of these channels is regulated by the filling state of intracellular Ca2+ stores and/or diacylglycerol and/or Ca2+/calmodulin. However, no evidence is available as to whether TRPC channels are regulated by
Pharmacological research : the official journal of the Italian Pharmacological Society, Jan 9, 2015
Chemotherapy targeting anti-angiogenesis in tumors may have insufficient efficacy, but little is ... more Chemotherapy targeting anti-angiogenesis in tumors may have insufficient efficacy, but little is known about the underlying mechanisms. Here, we showed that the Ca(2+)-permeable channel, TrpC5, is highly expressed in human breast cancer after long-term chemotherapy drug-treatment. It mediates downstream hypoxia-inducible factor 1α accumulation in the nucleus, and then activates the transcription of vascular endothelial growth factor which promotes tumor angiogenesis, leading to a poor chemotherapeutic outcome. We verified this mechanism at both the cellular and xenograft levels. Moreover, in samples from patients, high TrpC5 expression was correlated with enhanced tumor vasculature after chemotherapy. Taken together, our research demonstrated the essential role of TrpC5 in tumor angiogenesis when facing the challenge of chemotherapy and presents a new potential target for overcoming the high vasculature of human breast cancer after chemotherapy.
Objective: Urocortin possesses cardioprotective properties against the damaging effects of ischem... more Objective: Urocortin possesses cardioprotective properties against the damaging effects of ischemia / reperfusion injury. Our previous study demonstrated that urocortin can induce both endothelium-dependent and -independent coronary relaxation. However, the mechanisms thereby urocortin triggers endothelium-independent relaxation have not been investigated. The present study aimed to 2 11 examine the role of cyclic AMP and Ca -activated K channels in the
Objectives: Estrogen exerts cardiac protection via multiple cellular mechanisms. Estrogen modifie... more Objectives: Estrogen exerts cardiac protection via multiple cellular mechanisms. Estrogen modifies vasodilatation induced by certain relaxants such as b-adrenoceptor agonists. However, little is known whether low concentrations of b-adrenoceptor agonists would reciprocally influence the acute relaxant response to estrogen. The present study was designed to investigate the synergistic interaction between isoproterenol and 17b-estradiol, and the role of endothelium and cyclic
The International Journal of Biochemistry & Cell Biology, 2009
The severe acute respiratory syndrome-coronavirus (SARS-CoV) caused an outbreak of atypical pneum... more The severe acute respiratory syndrome-coronavirus (SARS-CoV) caused an outbreak of atypical pneumonia in 2003. The SARS-CoV viral genome encodes several proteins which have no homology to proteins in any other coronaviruses, and a number of these proteins have been implicated in viral cytopathies. One such protein is 3a, which is also known as X1, ORF3 and U274. 3a expression is detected in both SARS-CoV infected cultured cells and patients. Among the different functions identified, 3a is a capable of inducing apoptosis. We previously showed that caspase pathways are involved in 3a-induced apoptosis. In this study, we attempted to find out protein domains on 3a that are essential for its pro-apoptotic function. Protein sequence analysis reveals that 3a possesses three major protein signatures, the cysteine-rich, Yxx phi and diacidic domains. We showed that 3a proteins carrying respective mutations in these protein domains exhibit reduced pro-apoptotic activities, indicating the importance of these domains on 3a's pro-apoptotic function. It was previously reported that 3a possesses potassium ion channel activity. We further demonstrated that the blockade of 3a's potassium channel activity abolished caspase-dependent apoptosis. This report provides the first evidence that ion channel activity of 3a is required for its pro-apoptotic function. As ion channel activity has been reported to regulate apoptosis in different pathologic conditions, finding ways to modulate the ion channel activity may offer a new direction toward the inhibition of apoptosis triggered by SARS-CoV.
showed COX-2 expression mainly in the endothelium. Enzyme immunoassay and high-performance liquid... more showed COX-2 expression mainly in the endothelium. Enzyme immunoassay and high-performance liquid chromatog- raphy-coupled mass spectrometry showed release of prostaglandin (PG)F2 and prostacyclin (PGI2) increased by ACh; only PGF2 caused contraction at relevant concentrations. COX-2 expression, ACh-stimulated contractions, and vascular sensitivity to PGF2 were augmented in aortae from aged hamsters. Human renal arteries also showed thromboxane-prostanoid receptor-mediated ACh- or PGF2-induced
This study examined endothelium-derived mediators of acetylcholine-induced relaxation in male rat... more This study examined endothelium-derived mediators of acetylcholine-induced relaxation in male rat femoral arteries. Arterial rings were suspended in a myograph for the measurement of isometric force. The generation of hydrogen peroxide (H2O2) in endothelial cells was detected using the fluorescent probe, 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester. N(G)-nitro-L-arginine methyl ester (L-NAME, NOS inhibitor) and 1H-[1,2,4]oxadiazolo[4,2-alpha]quinoxalin-1-one (ODQ, guanylate cyclase inhibitor) alone or in combination with indomethacin (cycloxygenase inhibitor) diminished acetylcholine-induced endothelium-dependent relaxation to a similar extent. A small relaxation to acetylcholine in 60 mM KCl-constricted rings was abolished by L-NAME. Acetylcholine-induced relaxation was reduced by charybdotoxin plus apamin (intermediate- and small-conductance Ca2+-activated K+ channel blockers, respectively) or by 30 mM KCl. Both ouabain (Na+/K+ ATPase inhibitor) and BaCl2 (K(IR) channel blocker) also inhibited the relaxation albeit to a lesser degree. In the presence of L-NAME, ODQ plus indomethacin, charybdotoxin plus apamin or ouabain plus BaCl2 produced further inhibition. Catalase attenuated acetylcholine-induced relaxations and this attenuation was prevented by 3-amino-1,2,4-triazole (catalase inhibitor). Catalase did not affect acetylcholine-induced relaxations in rings treated with L-NAME or ODQ. Acetylcholine increased the dichlorofluorescein fluorescence intensity in native endothelial cells and this effect was abolished by catalase and by L-NAME. Exogenous H2O2 caused endothelium-independent relaxation that was slightly inhibited by iberiotoxin, ODQ or significantly reduced by elevated KCl, and abolished by catalase. The present results indicate that in addition to nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF, sensitive to charybdotoxin plus apamin, ouabain, and BaCl2), the endothelium of rat femoral artery can release H2O2 in response to acetylcholine, which was sensitive to L-NAME. Thus, the eNOS-dependent H2O2 is likely to be the third mediator of acetylcholine-mediated relaxations in rat femoral arteries.
In non-excitable cells, activation of G-protein-coupled phospholipase C (PLC)-linked receptors ca... more In non-excitable cells, activation of G-protein-coupled phospholipase C (PLC)-linked receptors causes the release of Ca(2+) from intracellular stores, which is followed by transmembrane Ca(2+) entry. This Ca(2+) entry underlies a small and sustained phase of the cellular [Ca(2+)](i) increases and is important for several cellular functions including gene expression, secretion and cell proliferation. This form of transmembrane Ca(2+) entry is supported by agonist-activated Ca(2+)-permeable ion channels that are activated by store depletion and is referred to as store-operated Ca(2+) entry (SOCE) and represents a major pathway for agonist-induced Ca(2+) entry. In excitable cells such as smooth muscle cells, Ca(2+) entry mechanisms responsible for sustained cellular activation are normally considered to be mediated via either voltage-operated or receptor-operated Ca(2+) channels. Although SOCE occurs following agonist activation of smooth muscle, this was thought to be more important in replenishing Ca(2+) stores rather than acting as a source of activator Ca(2+) for the contractile process. This review summarizes our current knowledge of SOCE as a regulator of vascular smooth muscle tone and discusses its possible role in the cardiovascular function and disease. We propose a possible hypothesis for its activation and suggest that SOCE may represent a novel target for pharmacological therapeutic intervention.
ABSTRACT Thyrotoxic periodic paralysis is an uncommon complication of hyperthyroidism. It is char... more ABSTRACT Thyrotoxic periodic paralysis is an uncommon complication of hyperthyroidism. It is characterized by acute attacks of hypokalaemic paralysis in male patients with thyrotoxicosis. It is often a benign condition responsive to therapy and the myopathy usually recovers fully within days (3) . On rare occasions, however, it is fatal due to respiratory muscle paralysis or dysrhythmias. In Hong Kong, TPP accounts for the majority (~80%) of hospital admission with hypokalaemic paralysis. This article is protected by copyright. All rights reserved.
Nitric oxide production is stimulated by an increase of the concentration of cytosolic Ca2+ in va... more Nitric oxide production is stimulated by an increase of the concentration of cytosolic Ca2+ in vascular endothelial cells. Recent evidence suggests that nitric oxide and cGMP might attenuate Ca2+ influx and, at the same time, initiate a Ca2+ removal mechanism, thereby decreasing the intracellular concentration of endothelial Ca2+ in a negative feedback fashion. Such a negative feedback mechanism could serve
Cardiac pacemaking is a complex phenomenon that is not completely understood. Canonical transient... more Cardiac pacemaking is a complex phenomenon that is not completely understood. Canonical transient receptor potential isoform 3 (TRPC3) channel is a cation channel that permeates both Ca(2+) and Na(+). TRPC3 was previously found to express in adult cardiomyocytes. However, its role in cardiac pacemaking is unexplored. Here we used mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) to investigate whether TRPC3 regulates the spontaneous automaticity and the underlying mechanism involved. Immunocytochemistry results showed that TRPC3 is expressed at the T-tubules of mESC-CMs. Whole-cell patch clamping showed that single mESC-CMs contain TRPC3 current. Confocal Ca(2+) imaging showed that the TRPC3-specific blocker Pyr3 decreased Ca(2+) transients and local Ca(2+) release (LCR) of mESC-CMs. Combined current and voltage clamp recordings from the same cell showed that reducing the TRPC3 current, either by Pyr3 or a dominant negative (loss-of-function) construct of TRPC3, decreased ...
We recently identified a new COPI-interacting KXD/E motif in the C-terminal cytosolic tail (CT) o... more We recently identified a new COPI-interacting KXD/E motif in the C-terminal cytosolic tail (CT) of Arabidopsis endomembrane protein 12 (AtEMP12) as being a crucial Golgi retention mechanism for AtEMP12. This KXD/E motif is conserved in CTs of all EMPs found in plants, yeast and humans, and is also present in hundreds of other membrane proteins. By cloning selective EMP isoforms from plants, yeast and mammals, we here studied the localizations of EMPs in different expression systems since there are contradictory reports on the localizations of EMPs. We showed that the N-terminal and C-terminal GFP-tagged EMP fusions were localized to Golgi and post-Golgi compartments respectively in plant, yeast and mammalian cells. In vitro pull-down assay further proved the interaction of the KXD/E motif with COPI coatomer in yeast. COPI loss of function in yeast and plants caused mislocalization of EMPs or KXD/E-motif-containing proteins to vacuole. Ultrastructural studies further showed that RNAi...
Cytosolic Ca2+ ([Ca2+]i) is an important signal that regulates cardiomyocyte differentiation duri... more Cytosolic Ca2+ ([Ca2+]i) is an important signal that regulates cardiomyocyte differentiation during cardiogenesis. TRPV1 is a Ca2+-permeable channel that is expressed in cardiomyocytes. In the present study, we utilized mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) as a model to investigate the functional role of TRPV1 in cardiomyocyte differentiation. Induction of embryonic stem cells into cardiomyocytes was achieved using embryoid body (EB)-based differentiation method. Quantitative PCRs showed an increased TRPV1 expression during the differentiation process. In [Ca2+]i measurement study, application of TRPV1 agonists, capsaicin and camphor, elicited a [Ca2+]i rise in mESC-CMs, the effect of which was abolished by TRPV1-shRNA. In functional study, treatment of EBs with TRPV1 antagonists (capsazepine and SB366791) and TRPV1-shRNA reduced the size of the EBs and decreased the percentage of spontaneously beating EBs. TRPV1 antagonists and TRPV1-shRNA also suppressed the...
Angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) [Ang (1-7)]-Mas constitutes the vaso-p... more Angiotensin-converting enzyme 2 (ACE2) - angiotensin (1-7) [Ang (1-7)]-Mas constitutes the vaso-protective axis and is demonstrated to antagonize the vascular pathophysiological effects of the classical renin-angiotensin system. We sought to study hypothesis that upregulation of ACE2-Ang (1-7) signaling protects endothelial function through reducing oxidative stress that would result in beneficial outcome in diabetes. Ex vivo treatment with Ang (1-7) enhanced endothelium-dependent relaxation (EDR) in renal arteries from diabetic patients. Both Ang (1-7) infusion via osmotic pump (500 ng/kg/min) for 2 weeks and exogenous ACE2 overexpression mediated by adenoviral ACE2 via tail vein injection (109 pfu/mouse) rescued the impaired EDR and flow-mediated dilatation (FMD) in db/db mice. Diminazene aceturate treatment (15 mg/kg/day) activated ACE2, increased circulating Ang (1-7) level, and augmented EDR and FMD in db/db mouse arteries. In addition, activation of ACE2-Ang (1-7) axis reduced...
Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress ... more Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress and elicit a mechanoelectric transduction cascade that initiates compensatory mechanisms. Mechanosensitive ion channels in the plasma membrane are responsible for transducing the mechanical signals to electrical signals. However, the mechanisms underlying channel activation in response to mechanical stress remain incompletely understood. Transient Receptor Potential (TRP) channels serve essential functions in several sensory modalities. These channels can also participate in mechanotransduction by either being autonomously sensitive to mechanical perturbation or by coupling to other mechanosensory components of the cell. Here, we investigated the response of a TRP family member, TRPC5, to mechanical stress. Hypoosmolarity triggers Ca2+ influx and cationic conductance through TRPC5. Importantly, for the first time we were able to record the stretch-activated TRPC5 current at single-channe...
Current drug targets. Cardiovascular & haematological disorders, 2005
The dried roots of Scutellaria baicalensis (S. baicalensis) Georgi (common name: Huangqin in Chin... more The dried roots of Scutellaria baicalensis (S. baicalensis) Georgi (common name: Huangqin in China) have been widely employed for many centuries in traditional Chinese herbal medicine as popular antibacterial and antiviral agents. They are effective against staphylococci, cholera, dysentery, pneumococci and influenza virus. Baicalein, one of the major flavonoids contained in the dried roots, possesses a multitude of pharmacological activities. The glycoside of baicalein, baicalin is a potent anti-inflammatory and anti-tumor agent. This review describes the biological properties of baicalein (Table 1), which are associated with the prevention and treatment of cardiovascular diseases. Baicalein is a potent free radical scavenger and xanthine oxidase inhibitor, thus improving endothelial function and conferring cardiovascular protective actions against oxidative stress-induced cell injury. Baicalein lowers blood pressure in renin-dependent hypertension and the in vivo hypotensive effec...
Urocortin and other hypothalamus corticotropin-releasing factor (CRF) polypeptides play biologica... more Urocortin and other hypothalamus corticotropin-releasing factor (CRF) polypeptides play biologically diverse roles in the stress, cardiovascular and inflammatory responses by acting on central and peripheral CRF receptors. Urocortin shows a significantly high sequence homology to CRF, and the concurrent expression of type-2 CRF (CRF2) receptors with urocortin in the heart suggests that urocortin may play a physiological role in the cardiac function. Urocortin is thought to be the endogenous agonist producing the cardiovascular actions previously attributed to CRF. This review highlights the current novel findings on the molecular and cellular mechanisms by which urocortin may exert its cardiovascular protective action.
Heme oxygenase-1 (HO-1) exerts vaso-protective effects. Such benefit in diabetic vasculopathy how... more Heme oxygenase-1 (HO-1) exerts vaso-protective effects. Such benefit in diabetic vasculopathy however remains unclear. We hypothesize that bilirubin mediates HO-1-induced vascular benefits in diabetes. Diabetic db/db mice were treated with hemin (HO-1 inducer) for two weeks, and aortas were isolated for functional and molecular assays. Nitric oxide (NO) production was measured in cultured endothelial cells. Hemin treatment augmented endothelium-dependent relaxations (EDRs) and elevated Akt and eNOS phosphorylation in db/db mouse aortas, which were reversed by HO-1 inhibitor SnMP or HO-1 silencing virus. Hemin treatment increased serum bilirubin and ex vivo bilirubin treatment improved relaxations in diabetic mouse aortas, which was reversed by Akt inhibitor. Biliverdin reductase silencing virus attenuated the effect of hemin. Chronic bilirubin treatment improved EDRs in db/db mouse aortas. High glucose-induced reductions in Akt and eNOS phosphorylation, and NO production were revers...
Proceedings of The National Academy of Sciences, 2004
Canonical transient receptor potential (TRPC) channels are Ca2+-permeable nonselective cation cha... more Canonical transient receptor potential (TRPC) channels are Ca2+-permeable nonselective cation channels that are widely expressed in numerous cell types. Seven different members of TRPC channels have been isolated. The activity of these channels is regulated by the filling state of intracellular Ca2+ stores and/or diacylglycerol and/or Ca2+/calmodulin. However, no evidence is available as to whether TRPC channels are regulated by
Pharmacological research : the official journal of the Italian Pharmacological Society, Jan 9, 2015
Chemotherapy targeting anti-angiogenesis in tumors may have insufficient efficacy, but little is ... more Chemotherapy targeting anti-angiogenesis in tumors may have insufficient efficacy, but little is known about the underlying mechanisms. Here, we showed that the Ca(2+)-permeable channel, TrpC5, is highly expressed in human breast cancer after long-term chemotherapy drug-treatment. It mediates downstream hypoxia-inducible factor 1α accumulation in the nucleus, and then activates the transcription of vascular endothelial growth factor which promotes tumor angiogenesis, leading to a poor chemotherapeutic outcome. We verified this mechanism at both the cellular and xenograft levels. Moreover, in samples from patients, high TrpC5 expression was correlated with enhanced tumor vasculature after chemotherapy. Taken together, our research demonstrated the essential role of TrpC5 in tumor angiogenesis when facing the challenge of chemotherapy and presents a new potential target for overcoming the high vasculature of human breast cancer after chemotherapy.
Objective: Urocortin possesses cardioprotective properties against the damaging effects of ischem... more Objective: Urocortin possesses cardioprotective properties against the damaging effects of ischemia / reperfusion injury. Our previous study demonstrated that urocortin can induce both endothelium-dependent and -independent coronary relaxation. However, the mechanisms thereby urocortin triggers endothelium-independent relaxation have not been investigated. The present study aimed to 2 11 examine the role of cyclic AMP and Ca -activated K channels in the
Objectives: Estrogen exerts cardiac protection via multiple cellular mechanisms. Estrogen modifie... more Objectives: Estrogen exerts cardiac protection via multiple cellular mechanisms. Estrogen modifies vasodilatation induced by certain relaxants such as b-adrenoceptor agonists. However, little is known whether low concentrations of b-adrenoceptor agonists would reciprocally influence the acute relaxant response to estrogen. The present study was designed to investigate the synergistic interaction between isoproterenol and 17b-estradiol, and the role of endothelium and cyclic
The International Journal of Biochemistry & Cell Biology, 2009
The severe acute respiratory syndrome-coronavirus (SARS-CoV) caused an outbreak of atypical pneum... more The severe acute respiratory syndrome-coronavirus (SARS-CoV) caused an outbreak of atypical pneumonia in 2003. The SARS-CoV viral genome encodes several proteins which have no homology to proteins in any other coronaviruses, and a number of these proteins have been implicated in viral cytopathies. One such protein is 3a, which is also known as X1, ORF3 and U274. 3a expression is detected in both SARS-CoV infected cultured cells and patients. Among the different functions identified, 3a is a capable of inducing apoptosis. We previously showed that caspase pathways are involved in 3a-induced apoptosis. In this study, we attempted to find out protein domains on 3a that are essential for its pro-apoptotic function. Protein sequence analysis reveals that 3a possesses three major protein signatures, the cysteine-rich, Yxx phi and diacidic domains. We showed that 3a proteins carrying respective mutations in these protein domains exhibit reduced pro-apoptotic activities, indicating the importance of these domains on 3a's pro-apoptotic function. It was previously reported that 3a possesses potassium ion channel activity. We further demonstrated that the blockade of 3a's potassium channel activity abolished caspase-dependent apoptosis. This report provides the first evidence that ion channel activity of 3a is required for its pro-apoptotic function. As ion channel activity has been reported to regulate apoptosis in different pathologic conditions, finding ways to modulate the ion channel activity may offer a new direction toward the inhibition of apoptosis triggered by SARS-CoV.
showed COX-2 expression mainly in the endothelium. Enzyme immunoassay and high-performance liquid... more showed COX-2 expression mainly in the endothelium. Enzyme immunoassay and high-performance liquid chromatog- raphy-coupled mass spectrometry showed release of prostaglandin (PG)F2 and prostacyclin (PGI2) increased by ACh; only PGF2 caused contraction at relevant concentrations. COX-2 expression, ACh-stimulated contractions, and vascular sensitivity to PGF2 were augmented in aortae from aged hamsters. Human renal arteries also showed thromboxane-prostanoid receptor-mediated ACh- or PGF2-induced
This study examined endothelium-derived mediators of acetylcholine-induced relaxation in male rat... more This study examined endothelium-derived mediators of acetylcholine-induced relaxation in male rat femoral arteries. Arterial rings were suspended in a myograph for the measurement of isometric force. The generation of hydrogen peroxide (H2O2) in endothelial cells was detected using the fluorescent probe, 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester. N(G)-nitro-L-arginine methyl ester (L-NAME, NOS inhibitor) and 1H-[1,2,4]oxadiazolo[4,2-alpha]quinoxalin-1-one (ODQ, guanylate cyclase inhibitor) alone or in combination with indomethacin (cycloxygenase inhibitor) diminished acetylcholine-induced endothelium-dependent relaxation to a similar extent. A small relaxation to acetylcholine in 60 mM KCl-constricted rings was abolished by L-NAME. Acetylcholine-induced relaxation was reduced by charybdotoxin plus apamin (intermediate- and small-conductance Ca2+-activated K+ channel blockers, respectively) or by 30 mM KCl. Both ouabain (Na+/K+ ATPase inhibitor) and BaCl2 (K(IR) channel blocker) also inhibited the relaxation albeit to a lesser degree. In the presence of L-NAME, ODQ plus indomethacin, charybdotoxin plus apamin or ouabain plus BaCl2 produced further inhibition. Catalase attenuated acetylcholine-induced relaxations and this attenuation was prevented by 3-amino-1,2,4-triazole (catalase inhibitor). Catalase did not affect acetylcholine-induced relaxations in rings treated with L-NAME or ODQ. Acetylcholine increased the dichlorofluorescein fluorescence intensity in native endothelial cells and this effect was abolished by catalase and by L-NAME. Exogenous H2O2 caused endothelium-independent relaxation that was slightly inhibited by iberiotoxin, ODQ or significantly reduced by elevated KCl, and abolished by catalase. The present results indicate that in addition to nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF, sensitive to charybdotoxin plus apamin, ouabain, and BaCl2), the endothelium of rat femoral artery can release H2O2 in response to acetylcholine, which was sensitive to L-NAME. Thus, the eNOS-dependent H2O2 is likely to be the third mediator of acetylcholine-mediated relaxations in rat femoral arteries.
It is well established that the accumulation of high levels of reactive oxygen species (ROS), due... more It is well established that the accumulation of high levels of reactive oxygen species (ROS), due to excessive generation of ROS and/or impaired antioxidant capacity of cells, can result in oxidative stress and cause oxidative damage to cells and their functions [...]
Atherosclerosis is a chronic inflammatory arterial disease characterized by build-up of atheromat... more Atherosclerosis is a chronic inflammatory arterial disease characterized by build-up of atheromatous plaque, which narrows the lumen of arteries. Hypercholesterolemia and excessive oxidative stress in arterial walls are among the main causative factors of atherosclerosis. Transient receptor potential channel M2 (TRPM2) is a Ca2+-permeable cation channel activated by oxidative stress. However, the role of TRPM2 in atherosclerosis in animal models is not well studied. In the present study, with the use of adeno-associated virus (AAV)-PCSK9 and TRPM2 knockout (TRPM2−/−) mice, we determined the role of TRPM2 in hypercholesterolemia-induced atherosclerosis. Our results demonstrated that TRPM2 knockout reduced atherosclerotic plaque area in analysis of En face Oil Red O staining of both whole aortas and aortic-root thin sections. Furthermore, TRPM2 knockout reduced the expression of CD68, α-SMA, and PCNA in the plaque region, suggesting a role of TRPM2 in promoting macrophage infiltration...
BackgroundBiological pacemakers consisting of pluripotent stem cell-derived cardiomyocytes are po... more BackgroundBiological pacemakers consisting of pluripotent stem cell-derived cardiomyocytes are potentially useful for treating bradycardia. However, tachyarrhythmia caused by derived cardiomyocytes themselves is one of main barriers hampering their clinical translation. An in-depth understanding of the mechanisms underlying the spontaneous action potential (a.k.a. automaticity) might provide potential approaches to solve this problem. The aim of this project is to study the role of canonical transient receptor potential isoform 7 (TRPC7) channels in regulating the automaticity of embryonic stem cell-derived cardiomyocytes (ESC-CMs).Methods and resultsBy Western blotting, the expression of TRPC7 was found to be increased during the differentiation of mouse ESC-CMs (mESC-CMs). Adenovirus-mediated TRPC7 knockdown decreased while overexpression increased the frequency of Ca2+transients (CaTs), local Ca2+releases (LCRs), and action potentials (APs) as detected by confocal microscopy and ...
: Resveratrol is well known to exhibit vascular relaxant and antihypertensive effects. In this st... more : Resveratrol is well known to exhibit vascular relaxant and antihypertensive effects. In this study, we determined the effects of resveratrol on the modulation of cytosolic [Ca2+] level and adenosine 5′-triphosphate–induced Ca2+ release from the sarcoplasmic reticulum (SR) in rat aortic smooth muscle cells (ASMCs) and explored its underlying mechanisms. In this article, cytosolic [Ca2+] and SR [Ca2+] in ASMCs were determined by Fluo-4/acetoxymethyl and Mag-Fluo-4/acetoxymethyl respectively. Resveratrol (20, 50, and 100 µM) caused a rapid and substantial reduction in cytosolic [Ca2+] in ASMCs bathed in normal Hank's Balanced Salt Solution or Ca2+-free Hank's Balanced Salt Solution. Pretreatment with resveratrol reduced adenosine 5′-triphosphate–induced SR Ca2+ release and SR Ca2+ content. In the cells bathed in Na+-free physiological saline, which favors the reverse mode of the Na+–Ca2+ exchanger (NCX), resveratrol induced an increase in cytosolic [Ca2+] and SR [Ca2+]. However, its effect on cytosolic [Ca2+] was inhibited by the selective NCX inhibitor, SEA0400. Our findings suggest that resveratrol reduces cytosolic [Ca2+] and SR [Ca2+] in ASMCs in normal physiological saline, which might be, at least in part, mediated by the NCX.
BackgroundTRPP2 (Polycystin-2) is a Ca2+ permeable nonselective cationic channel essential for ma... more BackgroundTRPP2 (Polycystin-2) is a Ca2+ permeable nonselective cationic channel essential for maintaining physiological function in live cells. Stromal interaction molecule 1 (STIM1) is an important Ca2+ sensor in store-operated Ca2+ entry (SOCE). Both TRPP2 and STIM1 are expressed in endoplasmic reticular membrane and participate in Ca2+ signaling, suggesting a physical interaction and functional synergism.MethodsWe performed co-localization, co-immunoprecipitation, and fluorescence resonance energy transfer assay to identify the interactions of TRPP2 and STIM1 in transfected HEK293 cells and native vascular smooth muscle cells (VSMCs). The function of the TRPP2-STIM1 complex in TG or ATP-induced SOCE was explored using specific siRNA. Further, we created TRPP2 CKO mouse to investigate the functional role of TRPP2 in agonist-induced vessel contraction.ResultsTRPP2 and STIM1 form a complex in transfected HEK293 cells and native VSMCs. Genetic manipulations with TRPP2 siRNA, dominan...
MicroRNAs (miRNAs) are crucial for the post-transcriptional control of protein-encoding genes, an... more MicroRNAs (miRNAs) are crucial for the post-transcriptional control of protein-encoding genes, and together with transcription factors (TFs) regulate gene expression; however, the regulatory activities of miRNAs during cardiac development are only partially understood. In this study, we tested the hypothesis that integrative computational approaches could identify miRNAs that experimentally could be shown to regulate cardiomyogenesis. We integrated expression profiles with bioinformatics analyses of miRNA and TF regulatory programs to identify candidate miRNAs involved with cardiac development. Expression profiling showed that miR-200c, which is not normally detected in adult heart, is progressively down-regulated during cardiac development and during in vitro differentiation of human embryonic stem cells (hESCs) to cardiomyocytes (CMs). We employed computational methodologies to predict target genes of both miR-200c and five key cardiac TFs to identify co-regulated gene networks. T...
Inhibition of microRNA-92a (miR-92a) is reported to suppress endothelial inflammation and delay a... more Inhibition of microRNA-92a (miR-92a) is reported to suppress endothelial inflammation and delay atherogenesis. We hypothesize that miR-92a inhibition protects endothelial function through suppressing oxidative stress in diabetic db/db mice. In this study, we found elevated expression of miR-92a in aortic endothelium from db/db mice and in renal arteries from diabetic subjects. Endothelial cells (ECs) exposed to advanced glycation end products (AGEs) and oxidized LDL (oxLDL) express higher level of miR-92a. Overexpression of miR-92a impairs endothelium-dependent relaxations (EDRs) in C57BL/6 mouse aortas. Overexpression of miR-92a suppresses expression of heme oxygenase-1 (HO-1), a critical cytoprotective enzyme, whereas inhibition of miR-92a increases HO-1 expression in human umbilical vein ECs (HUVECs) and db/db mouse aortas. Importantly, miR-92a inhibition by Ad-anti-miR-92a improved EDRs and reduced reactive oxygen species (ROS) production in db/db mouse aortas. HO-1 inhibition b...
TRPV4-C1 heteromeric channels contribute to store-operated Ca(2+) entry in vascular endothelial c... more TRPV4-C1 heteromeric channels contribute to store-operated Ca(2+) entry in vascular endothelial cells. However, the negative regulation of these channels is not fully understood. This study was conducted to investigate the inhibitory effect of PKG1α on TRPV4-C1 heteromeric channels. Immuno-fluorescence resonance energy transfer (FRET) was used to explore the spatial proximity of PKG1α and TRPC1. Phosphorylation of endogenous TRPC1 was tested by phosphorylation assay. [Ca(2+)]i transients and cation current in MAECs were assessed with Fura-2 fluorescence and whole-cell recording, respectively. In addition, rat mesenteric arteries segments were prepared, and vascular relaxation was examined with wire myography. In immuno-FRET experiments, after exposure of these cells to 8-Br-cGMP, more PKG1α was observed in the plasma membrane, and PKG1α and TRPC1 were observed to be in closer proximity. TAT-TRPC1(S172) and TAT-TRPC1(T313) peptide fragments, which contain the PKG targeted residues Se...
Arteriosclerosis, thrombosis, and vascular biology, Jan 14, 2016
Bone morphogenic protein 4 (BMP4) is an important mediator of endothelial dysfunction in cardio-m... more Bone morphogenic protein 4 (BMP4) is an important mediator of endothelial dysfunction in cardio-metabolic diseases, whereas platelet-derived growth factors (PDGFs) are major angiogenic and proinflammatory mediator, although the functional link between these 2 factors is unknown. The present study investigated whether PDGF mediates BMP4-induced endothelial dysfunction in diabetes mellitus. We generated Ad-Bmp4 to overexpress Bmp4 and Ad-Pdgfa-shRNA to knockdown Pdgfa in mice through tail intravenous injection. SMAD4-shRNA lentivirus, SMAD1-shRNA, and SMAD5 shRNA adenovirus were used for knockdown in human endothelial cells. We found that PDGF-AA impaired endothelium-dependent vasodilation in aorta and mesenteric resistance arteries. BMP4 upregulated PDGF-AA in human and mouse endothelial cells, which was abolished by BMP4 antagonist noggin or knockdown of SMAD1/5 or SMAD4. BMP4-impared relaxation in mouse aorta was also ameliorated by PDGF-AA neutralizing antibody. Tail injection of ...
In living cell membranes, K(+) permeability is higher than that of other ions such as Na(+) and C... more In living cell membranes, K(+) permeability is higher than that of other ions such as Na(+) and Cl(-) owing to abundantly expressed K(+) channels. Polarized membrane potential is mainly established by K(+) outward flow because the K(+) concentration in the intracellular side is much higher than that in the extracellular side. We have found that the small synthetic molecule 1 is capable of self-assembling into selective K(+) channels, enhancing K(+) permeability and hyperpolarizing liposome membrane potential. Interestingly, molecule 1 also functions as K(+) channel hyperpolarizing living cell membrane potential and relaxing agonist-induced blood vessel contraction. Therefore, it may have the potential to become a lead compound for the treatment of human diseases associated with K(+) channel dysfunction.
Rationale: Bone morphogenic protein (BMP)4 can stimulate superoxide production and exert proinfla... more Rationale: Bone morphogenic protein (BMP)4 can stimulate superoxide production and exert proinflammatory effects on the endothelium. The underlying mechanisms of how BMP4 mediates endothelial dysfunction and hypertension remain elusive. Objective: To elucidate the cellular pathways by which BMP4-induced endothelial dysfunction is mediated through oxidative stress–dependent upregulation of cyclooxygenase (COX)-2. Methods and Results: Impaired endothelium-dependent relaxations, exaggerated endothelium-dependent contractions, and reactive oxygen species (ROS) production were observed in BMP4-treated mouse aortae, which were prevented by the BMP4 antagonist noggin. Pharmacological inhibition with thromboxane prostanoid receptor antagonist or COX-2 but not COX-1 inhibitor prevented BMP4-induced endothelial dysfunction, which was further confirmed with the use of COX-1 −/− or COX-2 −/− mice. Noggin and knockdown of BMP receptor 1A abolished endothelium-dependent contractions and COX-2 upr...
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TRPC1 by Xiaoqiang Yao