Leishmania is a unicellular protozoan parasite which causes leishmaniasis, a neglected tropical d... more Leishmania is a unicellular protozoan parasite which causes leishmaniasis, a neglected tropical disease. It possess a unique thiol metabolism comprising of several proteins among which, tryparedoxin (cTXN) and tryparedoxin peroxidase (cTXNPx), function in concert as oxidoreductases, utilizing trypanothione as a source of electrons to reduce the hydroperoxides produced by macrophages during infection. This detoxification pathway is unique and essential for the survival of Leishmania. Herein, we report the functional characterization of Leishmania donovani cTXN and its interaction with cTXNPx. The full length recombinant cTXN and cTXNPx proteins were purified in the native state and biochemical analysis showed that the cTXN-cTXNPx coupled system efficiently degraded hydrogen peroxide and tert-butyl hydroperoxide by transferring reducing equivalents from trypanothione. In silico investigation of the potential interaction between cTXN and cTXNPx proteins showed strong interaction of mod...
Patients on dual antiplatelet therapy following percutaneous coronary intervention often have ind... more Patients on dual antiplatelet therapy following percutaneous coronary intervention often have indications for concurrent oral anticoagulation or triple antithrombotic therapy (TT). Although TT may decrease ischemic complications, it may confer increased bleeding risk. We hypothesize that the use of ticagrelor in TT is associated with higher risk of complications; accordingly, we sought to determine predictors of complications in patients on TT. Patients discharged on TT after percutaneous coronary intervention were followed prospectively for 12 months. The primary endpoint was a composite of ischemic (death, myocardial infarction, stroke) and major bleeding complications or net adverse clinical event (NACE). A major secondary endpoint was BARC (Bleeding Academic Research Consortium) types 2, 3, or 5 bleeding. Outcomes were compared between ticagrelor- and clopidogrel-treated patients. Multivariable analyses were performed to elucidate predictors of complications. Twenty-seven of 152...
Leishmania donovani is a unicellular protozoon parasite that causes visceral leishmaniasis (VL), ... more Leishmania donovani is a unicellular protozoon parasite that causes visceral leishmaniasis (VL), which is a fatal disease if left untreated. Certain Fe-S proteins of the TCA cycle and respiratory chain have been found in the Leishmania parasite but the precise mechanisms for their biogenesis and the maturation of Fe-S clusters remains unknown. Fe-S clusters are ubiquitous cofactors of proteins that perform critical cellular functions. The clusters are biosynthesized by the mitochondrial Iron-Sulphur Cluster (ISC) machinery with core protein components that include the catalytic cysteine desulphurase IscS, the scaffold proteins IscU and IscA, and frataxin as an iron carrier/donor. However, no information regarding frataxin, its regulation, or its role in drug resistance is available for the Leishmania parasite. In this study, we characterized Ld-frataxin to investigate its role in the ISC machinery of L. donovani. We expressed and purified the recombinant Ld-frataxin protein and observed its interaction with Ld-IscU by co-purification and pull-down assay. Furthermore, we observed that the cysteine desulphurase activity of the purified Ld-IscS protein was stimulated in the presence of Ld-frataxin and Ld-IscU, particularly in the presence of iron; neither Ld-frataxin nor Ld-IscU alone had significant effects on Ld-IscS activity. Interestingly, RT-PCR and western blotting showed that Ld-frataxin is upregulated in AmpB-resistant isolates compared to sensitive strains, which may support higher Fe-S protein activity in AmpB-resistant L. donovani. Additionally, Ld-frataxin was localized in the mitochondria, as revealed by digitonin fractionation and indirect immunofluorescence. Thus, our results suggest the role of Ld-frataxin as an iron binding/carrier protein for Fe-S cluster biogenesis that physically interacts with other core components of the ISC machinery within the mitochondria.
Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions, Jan 3, 2015
Our objective was to perform an updated systematic review to compare the efficacy and short- and ... more Our objective was to perform an updated systematic review to compare the efficacy and short- and long-term mortality of surgical myectomy (SM) and alcohol septal ablation (ASA) by including most recent and largest cohort studies published in last few years. SM and ASA are the two invasive strategies used to relieve left ventricular outflow tract obstruction (LVOTO) in patients with drug refractory symptomatic hypertrophic cardiomyopathy (HCM). In the absence of a randomized trial, we tried to compare the pros and cons of the two procedures using a systematic review and meta-analysis. A comprehensive search of three major databases was performed. We included original research studies comparing data on ASA and SM. Of 1,143 citations, 10 studies were included in the analysis. A total of 805 patients underwent ASA and 1,019 underwent SM. Patients undergoing SM were younger (MD 6.3, P = 0.0001) and had higher reduction in the LVOT gradient (MD -9.56, P = 0.05). However, there was similar...
Despite the significant amount of experimental data available on trehalose, the molecular mechani... more Despite the significant amount of experimental data available on trehalose, the molecular mechanism responsible for its intracellular stabilising properties has not emerged yet. The repair of cellular homeostasis in many protein-misfolding diseases by trehalose is credited to the disaccharide being an inducer of autophagy, a mechanism by which aggregates of misfolded proteins are cleared by the cell. In this work, we expressed the pathogenic N-terminal fragment of huntingtin in Δnth1 mutant (unable to degrade trehalose) of Saccharomyces cerevisiae BY4742 strain. We show that the presence of trehalose resulted in the partitioning of the mutant huntingtin in the soluble fraction of the cell. This led to reduced oxidative stress and improved cell survival. The beneficial effect was independent of the expression of the major cellular antioxidant enzyme, superoxide dismutase. Additionally, trehalose led to the overexpression of the heat shock protein, Hsp104p, in mutant huntingtin-expressing cells, and resulted in rescue of the endocytotic defect in the yeast cell. We propose that at least in the initial stages of aggregation, trehalose functions as a stabiliser, increasing the level of monomeric mutant huntingtin protein, with its concomitant beneficial effects, in addition to its role as an inducer of autophagy.
In the recently published MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Si... more In the recently published MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX) trial, the use of transradial access (TRA) compared to transfemoral access (TFA) during percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) was associated with a reduction in net adverse cardiovascular events. However, the results of MATRIX must be interpreted with caution due to several limitations including the strong modulating effect of operator/center experience on the relative efficacy of TRA and the inclusion of 2 distinct patient populations (ST-segment elevation and non-ST-segment elevation ACS). Therefore, although important, the results of MATRIX have strong limitations and are not sufficient to definitively identify an approach of choice during PCI for ACS. Further research is needed before strong, evidence-based recommendations regarding the approach of choice during PCI for ACS can be made.
Carvedilol is a poorly water-soluble oral antihypertensive agent, with problems of variable bioav... more Carvedilol is a poorly water-soluble oral antihypertensive agent, with problems of variable bioavailability and bio-inequivalence related to its poor water-solubility. This work investigated the possibility of developing Carvedilol tablets, allowing fast, reproducible, and complete drug ...
ABSTRACT Purpose: In patients with Takotsubo cardiomyopathy (TTC), left ventricular wall motion (... more ABSTRACT Purpose: In patients with Takotsubo cardiomyopathy (TTC), left ventricular wall motion (LVWM) usually recovers rapidly, therefore residual symptoms may be described to depression. However, we have previously shown that inflammatory activation and accentuated BNP release persist for at least 3 months post TTC, and this is associated with impaired global longitudinal strain (GLS). We have now sought to determine (1) the bases for heterogeneity of residual GLS and (2) whether this results either from severe acute inflammation or slow resolution of inflammatory changes. Methods: Data from TTC patients with adequate 2D speckle-tracking echocardiographs were evaluated. Correlations between GLS and (i) severity of acute episode [peak CK, NT-proBNP, metanephrine, high sensitive C-reactive protein (hsCRP), asymmetric dimethylarginine (ADMA) levels, platelet responsiveness to NO, LVWM score index, and myocardial T2 signal intensity on MRI], (ii) residual markers of inflammation were evaluated by univariate and multiple linear regression analyses. Results: In 51 TTC patients aged 66±12 (SD), acute GLS was significantly impaired compared to 3 months (-12±4% vs -18±3%, p=0.0001). GLS at 3 months was significantly correlated with acute elevation of NT-proBNP and metanephrine levels (r=0.34, p=0.02; r=0.4, p=0.009, respectively). Moreover, metanephrine levels represented an independent predictor of poor recovery (β=0.4; p=0.03). Furthermore, residual GLS was significantly correlated with simultaneous NT-proBNP (r=0.47, p=0.003); this association persisted with multiple linear regression (β=0.51; p=0.002).
Cardiac arrest (CA) is relatively rare but lethal complication of takotsubo cardiomyopathy (TTC).... more Cardiac arrest (CA) is relatively rare but lethal complication of takotsubo cardiomyopathy (TTC). In most instances, patients are diagnosed with TTC after CA, making it difficult to distinguish if TTC is the precipitant or the consequence of the index event. In this systematic review, patient-level data were obtained to seek out the characteristics of patients in whom the underlying cause of CA is TTC. A comprehensive search of 4 major databases (Embase, Ovid MEDLINE, PubMed, and Google Scholar) was performed from their inception to the last week of September 2014. Of 186 citations, 62 case studies were included in the analysis, providing patient-level data on 77 patients. In 60 patients (78%), the diagnosis of TTC was made after CA. Patients presenting with CA were younger (mean age 49.5 ± 16 vs 64.9 ± 11 years, p <0.0001) and had relatively shorter corrected QT interval (mean 530 ± 101 vs 616 ± 140 ms) on electrocardiography. TTC-related hypotension was the major cause of CA in...
Leishmania is a unicellular protozoan parasite which causes leishmaniasis, a neglected tropical d... more Leishmania is a unicellular protozoan parasite which causes leishmaniasis, a neglected tropical disease. It possess a unique thiol metabolism comprising of several proteins among which, tryparedoxin (cTXN) and tryparedoxin peroxidase (cTXNPx), function in concert as oxidoreductases, utilizing trypanothione as a source of electrons to reduce the hydroperoxides produced by macrophages during infection. This detoxification pathway is unique and essential for the survival of Leishmania. Herein, we report the functional characterization of Leishmania donovani cTXN and its interaction with cTXNPx. The full length recombinant cTXN and cTXNPx proteins were purified in the native state and biochemical analysis showed that the cTXN-cTXNPx coupled system efficiently degraded hydrogen peroxide and tert-butyl hydroperoxide by transferring reducing equivalents from trypanothione. In silico investigation of the potential interaction between cTXN and cTXNPx proteins showed strong interaction of mod...
Patients on dual antiplatelet therapy following percutaneous coronary intervention often have ind... more Patients on dual antiplatelet therapy following percutaneous coronary intervention often have indications for concurrent oral anticoagulation or triple antithrombotic therapy (TT). Although TT may decrease ischemic complications, it may confer increased bleeding risk. We hypothesize that the use of ticagrelor in TT is associated with higher risk of complications; accordingly, we sought to determine predictors of complications in patients on TT. Patients discharged on TT after percutaneous coronary intervention were followed prospectively for 12 months. The primary endpoint was a composite of ischemic (death, myocardial infarction, stroke) and major bleeding complications or net adverse clinical event (NACE). A major secondary endpoint was BARC (Bleeding Academic Research Consortium) types 2, 3, or 5 bleeding. Outcomes were compared between ticagrelor- and clopidogrel-treated patients. Multivariable analyses were performed to elucidate predictors of complications. Twenty-seven of 152...
Leishmania donovani is a unicellular protozoon parasite that causes visceral leishmaniasis (VL), ... more Leishmania donovani is a unicellular protozoon parasite that causes visceral leishmaniasis (VL), which is a fatal disease if left untreated. Certain Fe-S proteins of the TCA cycle and respiratory chain have been found in the Leishmania parasite but the precise mechanisms for their biogenesis and the maturation of Fe-S clusters remains unknown. Fe-S clusters are ubiquitous cofactors of proteins that perform critical cellular functions. The clusters are biosynthesized by the mitochondrial Iron-Sulphur Cluster (ISC) machinery with core protein components that include the catalytic cysteine desulphurase IscS, the scaffold proteins IscU and IscA, and frataxin as an iron carrier/donor. However, no information regarding frataxin, its regulation, or its role in drug resistance is available for the Leishmania parasite. In this study, we characterized Ld-frataxin to investigate its role in the ISC machinery of L. donovani. We expressed and purified the recombinant Ld-frataxin protein and observed its interaction with Ld-IscU by co-purification and pull-down assay. Furthermore, we observed that the cysteine desulphurase activity of the purified Ld-IscS protein was stimulated in the presence of Ld-frataxin and Ld-IscU, particularly in the presence of iron; neither Ld-frataxin nor Ld-IscU alone had significant effects on Ld-IscS activity. Interestingly, RT-PCR and western blotting showed that Ld-frataxin is upregulated in AmpB-resistant isolates compared to sensitive strains, which may support higher Fe-S protein activity in AmpB-resistant L. donovani. Additionally, Ld-frataxin was localized in the mitochondria, as revealed by digitonin fractionation and indirect immunofluorescence. Thus, our results suggest the role of Ld-frataxin as an iron binding/carrier protein for Fe-S cluster biogenesis that physically interacts with other core components of the ISC machinery within the mitochondria.
Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions, Jan 3, 2015
Our objective was to perform an updated systematic review to compare the efficacy and short- and ... more Our objective was to perform an updated systematic review to compare the efficacy and short- and long-term mortality of surgical myectomy (SM) and alcohol septal ablation (ASA) by including most recent and largest cohort studies published in last few years. SM and ASA are the two invasive strategies used to relieve left ventricular outflow tract obstruction (LVOTO) in patients with drug refractory symptomatic hypertrophic cardiomyopathy (HCM). In the absence of a randomized trial, we tried to compare the pros and cons of the two procedures using a systematic review and meta-analysis. A comprehensive search of three major databases was performed. We included original research studies comparing data on ASA and SM. Of 1,143 citations, 10 studies were included in the analysis. A total of 805 patients underwent ASA and 1,019 underwent SM. Patients undergoing SM were younger (MD 6.3, P = 0.0001) and had higher reduction in the LVOT gradient (MD -9.56, P = 0.05). However, there was similar...
Despite the significant amount of experimental data available on trehalose, the molecular mechani... more Despite the significant amount of experimental data available on trehalose, the molecular mechanism responsible for its intracellular stabilising properties has not emerged yet. The repair of cellular homeostasis in many protein-misfolding diseases by trehalose is credited to the disaccharide being an inducer of autophagy, a mechanism by which aggregates of misfolded proteins are cleared by the cell. In this work, we expressed the pathogenic N-terminal fragment of huntingtin in Δnth1 mutant (unable to degrade trehalose) of Saccharomyces cerevisiae BY4742 strain. We show that the presence of trehalose resulted in the partitioning of the mutant huntingtin in the soluble fraction of the cell. This led to reduced oxidative stress and improved cell survival. The beneficial effect was independent of the expression of the major cellular antioxidant enzyme, superoxide dismutase. Additionally, trehalose led to the overexpression of the heat shock protein, Hsp104p, in mutant huntingtin-expressing cells, and resulted in rescue of the endocytotic defect in the yeast cell. We propose that at least in the initial stages of aggregation, trehalose functions as a stabiliser, increasing the level of monomeric mutant huntingtin protein, with its concomitant beneficial effects, in addition to its role as an inducer of autophagy.
In the recently published MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Si... more In the recently published MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX) trial, the use of transradial access (TRA) compared to transfemoral access (TFA) during percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) was associated with a reduction in net adverse cardiovascular events. However, the results of MATRIX must be interpreted with caution due to several limitations including the strong modulating effect of operator/center experience on the relative efficacy of TRA and the inclusion of 2 distinct patient populations (ST-segment elevation and non-ST-segment elevation ACS). Therefore, although important, the results of MATRIX have strong limitations and are not sufficient to definitively identify an approach of choice during PCI for ACS. Further research is needed before strong, evidence-based recommendations regarding the approach of choice during PCI for ACS can be made.
Carvedilol is a poorly water-soluble oral antihypertensive agent, with problems of variable bioav... more Carvedilol is a poorly water-soluble oral antihypertensive agent, with problems of variable bioavailability and bio-inequivalence related to its poor water-solubility. This work investigated the possibility of developing Carvedilol tablets, allowing fast, reproducible, and complete drug ...
ABSTRACT Purpose: In patients with Takotsubo cardiomyopathy (TTC), left ventricular wall motion (... more ABSTRACT Purpose: In patients with Takotsubo cardiomyopathy (TTC), left ventricular wall motion (LVWM) usually recovers rapidly, therefore residual symptoms may be described to depression. However, we have previously shown that inflammatory activation and accentuated BNP release persist for at least 3 months post TTC, and this is associated with impaired global longitudinal strain (GLS). We have now sought to determine (1) the bases for heterogeneity of residual GLS and (2) whether this results either from severe acute inflammation or slow resolution of inflammatory changes. Methods: Data from TTC patients with adequate 2D speckle-tracking echocardiographs were evaluated. Correlations between GLS and (i) severity of acute episode [peak CK, NT-proBNP, metanephrine, high sensitive C-reactive protein (hsCRP), asymmetric dimethylarginine (ADMA) levels, platelet responsiveness to NO, LVWM score index, and myocardial T2 signal intensity on MRI], (ii) residual markers of inflammation were evaluated by univariate and multiple linear regression analyses. Results: In 51 TTC patients aged 66±12 (SD), acute GLS was significantly impaired compared to 3 months (-12±4% vs -18±3%, p=0.0001). GLS at 3 months was significantly correlated with acute elevation of NT-proBNP and metanephrine levels (r=0.34, p=0.02; r=0.4, p=0.009, respectively). Moreover, metanephrine levels represented an independent predictor of poor recovery (β=0.4; p=0.03). Furthermore, residual GLS was significantly correlated with simultaneous NT-proBNP (r=0.47, p=0.003); this association persisted with multiple linear regression (β=0.51; p=0.002).
Cardiac arrest (CA) is relatively rare but lethal complication of takotsubo cardiomyopathy (TTC).... more Cardiac arrest (CA) is relatively rare but lethal complication of takotsubo cardiomyopathy (TTC). In most instances, patients are diagnosed with TTC after CA, making it difficult to distinguish if TTC is the precipitant or the consequence of the index event. In this systematic review, patient-level data were obtained to seek out the characteristics of patients in whom the underlying cause of CA is TTC. A comprehensive search of 4 major databases (Embase, Ovid MEDLINE, PubMed, and Google Scholar) was performed from their inception to the last week of September 2014. Of 186 citations, 62 case studies were included in the analysis, providing patient-level data on 77 patients. In 60 patients (78%), the diagnosis of TTC was made after CA. Patients presenting with CA were younger (mean age 49.5 ± 16 vs 64.9 ± 11 years, p <0.0001) and had relatively shorter corrected QT interval (mean 530 ± 101 vs 616 ± 140 ms) on electrocardiography. TTC-related hypotension was the major cause of CA in...
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Papers by Kuljit Singh