Papers by Nitish Mahapatra
Chromogranin A (CHGA), a 48 kDa secretory pro-hormone, is the major protein co-stored and co-rele... more Chromogranin A (CHGA), a 48 kDa secretory pro-hormone, is the major protein co-stored and co-released with catecholamines from secretory vesicles in adrenal medulla and postganglionic sympathetic axons. CHGA is over-expressed in essential hypertension, a complex trait with genetic predisposition. Conversely, the plasma concentration of the catestatin fragment of CHGA is diminished both in established hypertension and in patients’ still-normotensive offspring at genetic risk of developing the disease. These human findings suggest a mechanism whereby diminished catestatin might increase the risk for hypertension. We generated Chga null (Chga-/-) and “humanized” CHGA mice to probe CHGA and catestatin in vivo. Telemetric and tail-cuff studies on blood pressure (BP), transthoracic echocardiography, and hemodynamic studies reveal extreme cardiovascular changes in Chga-/mice: (i) Elevated systolic and diastolic BP (by up to 43.7 mmHg); (ii) Loss of diurnal BP variation; (iv) Increased left...
Molecular and Cellular Biology
Hypercholesterolemia is a strong predictor of cardiovascular diseases. 3-Hydroxy-3-methylglutaryl... more Hypercholesterolemia is a strong predictor of cardiovascular diseases. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase gene (Hmgcr) coding for the rate-limiting enzyme in the cholesterol biosynthesis pathway is a crucial regulator of plasma cholesterol levels. However, the post-transcriptional regulation of Hmgcr remains poorly understood. The main objective of this study was to explore the role of miRNAs in the regulation of Hmgcr expression. Systematic in silico predictions and experimental analyses reveal that miR-27a specifically interacts with the Hmgcr 3′-untranslated region in murine and human hepatocytes. Moreover, our data shows that Hmgcr expression is inversely correlated with miR-27a levels in various cultured cell lines, human and rodent tissues. Actinomycin D chase assays and relevant experiments demonstrate that miR-27a regulates Hmgcr by translational attenuation followed by mRNA degradation. Early Growth Response 1 (Egr1) regulates miR-27a expression under basal and...
Molecular and Cellular Biochemistry
Journal of Molecular Biology
MMP7 (Matrilysin), a potent extracellular matrix degrading enzyme with wide substrate specificity... more MMP7 (Matrilysin), a potent extracellular matrix degrading enzyme with wide substrate specificity, is emerging as a new regulator of cardiovascular diseases including coronary artery disease and atherosclerosis. However, potential contributions of MMP7 genetic variations to hypertension remain unknown. In this study, we first probed for the association of a tag single nucleotide polymorphism (SNP) in the MMP7 gene promoter (-181A/G; rs11568818) with hypertension in an urban south Indian population (n=1517). The heterozygous A/G genotype showed a strong association with hypertension as compared to the A/A wild-type genotype (OR=1.641, 95% CI=1.276-2.109; p=1x10-4); AG genotype carriers also displayed significantly higher diastolic blood pressure and mean arterial pressure than AA genotype subjects. The study was replicated in a north Indian population (n=977) as well (OR=1.520, 95% CI =1.106-2.090; p=0.01). Transient transfection experiments using MMP7 promoter-luciferase reporter co...
Current Medicinal Chemistry
Background: Cardiovascular disease (CVD), the most common cause of death globally, accounts for ~... more Background: Cardiovascular disease (CVD), the most common cause of death globally, accounts for ~30% of all deaths worldwide. Hypertension is a common contributor to morbidity and mortality from CVD. Methods and Results: The plasma concentration of chromogranin A (CgA) is elevated in patients with CVD as well as patients with established human essential hypertension and heart failure (HF). In contrast, the plasma level of the CgA-derived peptide catestatin (CST) is diminished in human essential hypertension. Low conversion of CgA-to-CST has been associated with increased mortality in patients hospitalized with acute HF. Consistent with human findings, the lack of CST in CgA knockout (Chga-KO) mice eventuates in the development of hypertension and supplementation of CST to Chga-KO mice restores blood pressure, implicating CST as a key player in regulating hypertension. In the peripheral system, CST decreases blood pressure by stimulating histamine release, inhibiting catecholamine se...
The Journal of biological chemistry, Aug 30, 2017
The acidic glycoprotein chromogranin A (CHGA) is co-stored/co-secreted with catecholamines and cr... more The acidic glycoprotein chromogranin A (CHGA) is co-stored/co-secreted with catecholamines and crucial for secretory vesicles biogenesis in neuronal/neuroendocrine cells. CHGA is dysregulated in several cardiovascular diseases, but the underlying mechanisms are not well established. Here, we sought to identify common polymorphisms in the CHGA promoter and to explore the mechanistic basis of their plausible contribution to regulating CHGA protein levels in circulation. Resequencing of the CHGA promoter in an Indian population (n=769) yielded nine SNPs: G-1106A, A-1018T, T-1014C, T-988G, G-513A, G-462A, T-415C, C-89A and C-57T. Linkage disequilibrium (LD) analysis indicated strong LD among SNPs at the -1106, -1014, -988 and -89 bp positions and between the -1018 and -57 bp positions. Haplotype analysis predicted five major promoter haplotypes that displayed differential promoter activities in neuronal cells; specifically, haplotype 2 (containing variant T alleles at -1018 and -57 bp) ...
Cell and tissue research, Jun 20, 2017
Chromogranin A (CgA) is a prohormone and a granulogenic factor that regulates secretory pathways ... more Chromogranin A (CgA) is a prohormone and a granulogenic factor that regulates secretory pathways in neuroendocrine tissues. In β-cells of the endocrine pancreas, CgA is a major cargo in insulin secretory vesicles. The impact of CgA deficiency on the formation and exocytosis of insulin vesicles is yet to be investigated. In addition, no literature exists on the impact of CgA on mitochondrial function in β-cells. Using three different antibodies, we demonstrate that CgA is processed to vasostatin- and catestatin-containing fragments in pancreatic islet cells. CgA deficiency in Chga-KO islets leads to compensatory overexpression of chromogranin B, secretogranin II, SNARE proteins and insulin genes, as well as increased insulin protein content. Ultrastructural studies of pancreatic islets revealed that Chga-KO β-cells contain fewer immature secretory granules than wild-type (WT) control but increased numbers of mature secretory granules and plasma membrane-docked vesicles. Compared to W...
Journal of Molecular and Cellular Cardiology, 2017
Despite the well-known role of cystathionine γ-lyase (Cth) in cardiovascular pathophysiology, tra... more Despite the well-known role of cystathionine γ-lyase (Cth) in cardiovascular pathophysiology, transcriptional regulation of Cth remains incompletely understood. Sequencing of the Cth promoter region in mouse models of genetic/essential hypertension (viz. Blood Pressure High [BPH], Blood Pressure Low [BPL] and Blood Pressure Normal [BPN] mice) identified several genetic variations. Transient transfections of BPH/BPL-Cth promoter-reporter plasmids into various cell types revealed higher promoter activity of BPL-Cth than that of BPH-Cth. Corroboratively, endogenous Cth mRNA levels in kidney and liver tissues were also elevated in BPL mice. Computational analysis of the polymorphic Cth promoter region predicted differential binding affinity of c-Rel, HOXA3 and IRF1 with BPL/BPH-Cth promoter domains. Over-expression of c-Rel/HOXA3/IRF1 modulated BPL/BPH-Cth promoter activities in a consistent manner. Gel shift assays using BPH/BPL-Cth-promoter oligonucleotides with/without binding sites for c-Rel/HOXA3/IRF1 displayed formation of specific complexes with c-Rel/HOXA3/IRF1; addition of antibodies to reaction mixtures resulted in supershifts/inhibition of Cth promoter-transcription factor complexes. Furthermore, chromatin immunoprecipitation (ChIP) assays proved differential binding of c-Rel, HOXA3 and IRF1 with the polymorphic promoter region of BPL/BPH-Cth. Tumor necrosis factor-α (TNF-α) reduced the activities of BPL/BPH-Cth promoters to different extents that were further declined by ectopic expression of IRF1; on the other hand, siRNA-mediated down-regulation of IRF1 rescued the TNF-α-mediated suppression of the BPL/BPH-Cth promoter activities. In corroboration, ChIP analysis revealed enhanced binding of IRF1 with BPH/BPL-Cth promoter following TNF-α treatment. BPL/BPH-Cth promoter activity was diminished upon exposure of hepatocytes and cardiomyoblasts to ischemia-like pathological condition due to reduced binding of c-Rel with BPL/BPH-Cth-promoter. Taken together, this study reveals the molecular basis for the differential expression of Cth in mouse models of essential hypertension under basal and pathophysiological conditions.
Cellular and Molecular Life Sciences, 2010
Chromogranin A (CHGA) is ubiquitously expressed in secretory cells of the endocrine, neuroendocri... more Chromogranin A (CHGA) is ubiquitously expressed in secretory cells of the endocrine, neuroendocrine, and neuronal tissues. Although this protein has long been known as a marker for neuroendocrine tumors, its role in cardiovascular disease states including essential hypertension (EH) has only recently been recognized. It acts as a prohormone giving rise to bioactive peptides such as vasostatin-I (human CHGA 1-76) and catestatin (human CHGA 352-372) that exhibit several cardiovascular regulatory functions. CHGA is over-expressed but catestatin is diminished in EH. Moreover, genetic variants in the promoter, catestatin, and 3 0-untranslated regions of the human CHGA gene alter autonomic activity and blood pressure. Consistent with these findings, targeted ablation of this gene causes severe arterial hypertension and ventricular hypertrophy in mice. Transgenic expression of the human CHGA gene or exogenous administration of catestatin restores blood pressure in these mice. Thus, the accumulated evidence establishes CHGA as a novel susceptibility gene for EH.
Hypertension, 2016
C hromogranin A (CHGA) is a ≈50-kDa soluble, acidic glycoprotein that plays an essential role in ... more C hromogranin A (CHGA) is a ≈50-kDa soluble, acidic glycoprotein that plays an essential role in the formation of catecholamine secretory vesicles in neuronal, endocrine, and neuroendocrine tissues. 1 Expression levels of CHGA have been found to be elevated in rodent models of both genetic 2 and acquired forms of hypertension. 3 Elevated plasma CHGA levels are associated with clinical severity and serve as independent prognostic indicators in patients with complicated myocardial infarction, 4 acute coronary syndromes, 5 and chronic heart failure. 6 CHGA also acts as a prohormone and gets cleaved to give rise to several bioactive peptides, 7 including vasostatin (human CHGA 1-76 , a vasodilator and suppressor of inotropy/lusitropy), 8 pancreastatin (human CHGA 250-301 , a dysglycemic hormone), 9 Abstract-Catestatin (CST), an endogenous antihypertensive/antiadrenergic peptide, is a novel regulator of cardiovascular physiology. Here, we report case-control studies in 2 geographically/ethnically distinct Indian populations (n≈4000) that showed association of the naturally-occurring human CST-Gly364Ser variant with increased risk for hypertension (ageadjusted odds ratios: 1.483; P=0.009 and 2.951; P=0.005). Consistently, 364Ser allele carriers displayed elevated systolic (up to ≈8 mm Hg; P=0.004) and diastolic (up to ≈6 mm Hg; P=0.001) blood pressure. The variant allele was also found to be in linkage disequilibrium with other functional single-nucleotide polymorphisms in the CHGA promoter and nearby coding region. Functional characterization of the Gly364Ser variant was performed using cellular/molecular biological experiments (viz peptide-receptor binding assays, nitric oxide [NO], phosphorylated extracellular regulated kinase, and phosphorylated endothelial NO synthase estimations) and computational approaches (molecular dynamics simulations for structural analysis of wild-type [CST-WT] and variant [CST-364Ser] peptides and docking of peptide/ligand with βadrenergic receptors [ADRB1/2]). CST-WT and CST-364Ser peptides differed profoundly in their secondary structures and showed differential interactions with ADRB2; although CST-WT displaced the ligand bound to ADRB2, CST-364Ser failed to do the same. Furthermore, CST-WT significantly inhibited ADRB2-stimulated extracellular regulated kinase activation, suggesting an antagonistic role towards ADRB2 unlike CST-364Ser. Consequently, CST-WT was more potent in NO production in human umbilical vein endothelial cells as compared with CST-364Ser. This NO-producing ability of CST-WT was abrogated by ADRB2 antagonist ICI 118551. In conclusion, CST-364Ser allele enhanced the risk for hypertension in human populations, possibly via diminished endothelial NO production because of altered interactions of CST-364Ser peptide with ADRB2 as compared with CST-WT.
Journal of Molecular Biology, 2015
Renalase, a recently identified oxidoreductase, is emerging as a novel regulator of cardiovascula... more Renalase, a recently identified oxidoreductase, is emerging as a novel regulator of cardiovascular and metabolic disease states. The mechanism of regulation of renalase gene, especially at the post-transcriptional level, is completely unknown. We set out to investigate the possible role of microRNAs in regulation of renalase gene in this study. Computational predictions using multiple algorithms coupled with systematic functional analysis revealed specific interactions of miR-29a/b/c and miR-146a/b with mouse and human renalase 3'-UTR in cultured cells. Next, we estimated miR-29b and miR-146a as well as renalase expression in genetically hypertensive blood pressure high (BPH) and genetically hypotensive blood pressure low (BPL) mice. BPH kidney tissues showed diminished (~1.6-1.8 fold) renalase mRNA/protein levels and elevated (~2.2 fold) miR-29b levels as compared to BPL. A common single nucleotide polymorphism (SNP) in human renalase 3'-UTR (C/T; rs10749571) creates binding site for miR-146a; consistently, miR-146a down-regulated human renalase 3'-UTR/luciferase activity in the case of T allele suggesting its potential role in regulation of renalase in humans. Indeed, genome-wide association studies revealed directionally concordant association of rs10749571 with diastolic blood pressure, glucose and triglyceride levels in large human populations (n≈58,000 to 96,000 subjects). This study provides evidence for post-transcriptional regulation of renalase gene by miR-29 and miR-146 and has implications for inter-individual variations on cardio-metabolic traits.
The Journal of biological chemistry, Jan 6, 2015
Elevated expression of matrix metalloproteinase7 (MMP7) has been demonstrated to play a pivotal r... more Elevated expression of matrix metalloproteinase7 (MMP7) has been demonstrated to play a pivotal role in cancer invasion. The -181A/G (rs11568818) polymorphism in MMP7 promoter modulates gene expression and plausibly affects cancer progression. Here, we evaluated the impact of -181A/G polymorphism in MMP7 promoter activity and its association with gastric cancer risk in eastern Indian case-control cohorts (n=520). The GG genotype as compared to the AA genotype was predisposed (p=0.02; OR=1.9, 95% CI=1.1-3.3) to gastric cancer risk. Stratification analysis showed that tobacco addiction enhanced gastric cancer risk in GG in comparison to AA genotype (p=0.03, OR=2.46, 95% CI=1.07-5.68). Meta-analysis revealed that tobacco enhanced the risk for cancer more pronouncedly in AG and GG carriers. Activity and expression of MMP7 were significantly higher in the GG than AA carriers. In support, MMP7 promoter-reporter assays showed greater transcriptional activity towards A to G transition under...
Journal of Neurochemistry, 2015
Monoamine oxidase A (MAOA) plays important roles in the pathogenesis of several neurological and ... more Monoamine oxidase A (MAOA) plays important roles in the pathogenesis of several neurological and cardiovascular disorders. The mechanism of transcriptional regulation of MAOA under basal and pathological conditions, however, remains incompletely understood. Here, we report systematic identification and characterization of cis elements and transcription factors that govern the expression of MAOA gene. Extensive computational analysis of MAOA promoter, followed by 5'-promoter deletion/reporter assays, revealed that the -71/-40 bp domain was sufficient for its basal transcription. Gel-shift and chromatin immunoprecipitation assays provided evidence of interactions of the transcription factors GATA2, Sp1 and TBP with this proximal promoter region. Consistently, over-expression of GATA2, Sp1 and TBP augmented MAOA promoter activity in a coordinated manner. In corroboration, siRNA-mediated down-regulation of GATA2/Sp1/TBP repressed the endogenous MAOA expression as well as transfected MAOA promoter activity. Tumor necrosis factor-alpha (TNF-α) and forskolin activated MAOA transcription that was reversed by Sp1 siRNA; in support, TNF-α- and forskolin- induced activities were enhanced by ectopic over-expression of Sp1. On the other hand, MAOA transcription was diminished upon exposure of neuroblasts or cardiac myoblasts to ischemia-like conditions due to reduced binding of GATA2/Sp1/TBP with MAOA promoter. In conclusion, this study revealed previously unknown roles of GATA2, Sp1 and TBP in modulating MAOA expression under basal as well as pathophysiological conditions such as inflammation and ischemia, thus providing new insights into the molecular basis of aberrant MAOA expression in neuronal/cardiovascular disease states. This article is protected by copyright. All rights reserved.
Applied and environmental microbiology, 1997
Acidophilic heterotrophic strain GS19h of the genus Acidocella exhibited extremely high resistanc... more Acidophilic heterotrophic strain GS19h of the genus Acidocella exhibited extremely high resistance to CdSO4 and ZnSO4, with a MIC of 1 M for each. The respective MICs for an Acidocella aminolytica strain were 400 and 600 mM. The MICs of NiSO4 for the above strains were 200 and 175 mM, respectively. These strains were also resistant to CuSO4, the MICs being 20 and 40 mM, respectively. An Acidocella facilis strain showed resistance only to ZnSO4, with a MIC of 150 mM. The metal salts, in general, extended the lag period, log period, and generation time, with decreases in growth rate and optimum growth. A. aminolytica and strain GS19h each contain more than one plasmid, while A. facilis contains none. After transformation by electroporation with the plasmid preparation from strain GS19h, an Acidiphilium multivorum strain became highly resistant to cadmium and zinc, and the plasmid profile of the transformed cells was found to differ from that of the original Acidiphilium multivorum str...
Current Medicinal Chemistry-Immunology, Endocrine & Metabolic Agents, 2004
ABSTRACT
American Journal of Hypertension, 2005
Genetic studies of essential hypertension, a complex, polygenic, and age-dependent disorder, have... more Genetic studies of essential hypertension, a complex, polygenic, and age-dependent disorder, have not been able to completely elucidate the genes responsible for development of the trait. We used a novel strategy to compare gene expression in the adrenal gland of two independent rodent models of human essential hypertension (the spontaneously hypertensive rat, SHR, and the blood pressure high mouse, BPH), with the goal of uncovering shared, common genetic mechanisms of hypertension across mammalian species that might, therefore, be pertinent to human hypertension. We deliberately studied young, 4-to 5-week-old, "prehypertensive" SHR and BPH that had not yet developed complete elevations in blood pressure (BP), so that we could minimize the impact of chronic, sustained BP elevation, age, and other confounding factors on gene expression, therefore increasing the likelihood that differential expression reflects relatively early pathogenic mechanisms in hypertension, rather than later responses to, or compensations for BP elevation. We compared transcript expression patterns of genes orthologous between the rat and the mouse, and presented candidate genes for hypertension that are differentially expressed in the same direction in SHR and BPH (ie, overexpressed in both SHR and BPH, or underexpressed in both SHR and BPH). Then we used a systems biology approach to analyze expression patterns in biochemical pathways and networks to isolate systems involved in hypertension pathology in both SHR and BPH. We found transcript pattern evidence for involvement of several systems in the pathology of hypertension in SHR and BPH: adrenal catecholamines and sympathetic function; steroid hormone synthesis, catabolism, and its contribution to enhanced glucocorticoid sensitivity in SHR; oxidative stress and its role as a common mechanism of vascular and end-organ injury; and intermediary metabolism with global but mechanistically different perturbations in SHR and BPH. Approximately 10% of the differentially expressed orthologous genes we studied shared a common direction of expression in the two hypertensive rodent strains, suggesting fundamental transcriptional mechanisms in common whereby mammals can elevate BP or respond to such elevation; even these shared orthologs spanned a diverse set of biological processes, reinforcing the multifactorial and complex nature of hypertension.
Physiological Genomics, 2010
A-null model of hypertension: transcriptomic Global metabolic consequences of the chromogranin Yo... more A-null model of hypertension: transcriptomic Global metabolic consequences of the chromogranin You might find this additional info useful...
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Papers by Nitish Mahapatra