Catestatin Gly 364 Ser Variant Alters Systemic Blood Pressure and the Risk for Hypertension in Human Populations via Endothelial Nitric Oxide Pathway

Chromogranin 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. Expression levels of CHGA have been found to be elevated in rodent models of both genetic and acquired forms of hypertension. Elevated plasma CHGA levels are associated with clinical severity and serve as independent prognostic indicators in patients with complicated myocardial infarction, acute coronary syndromes, and chronic heart failure. CHGA also acts as a prohormone and gets cleaved to give rise to several bioactive peptides, including vasostatin (human CHGA 1–76 , a vasodilator and suppressor of inotropy/lusitropy), pancreastatin (human CHGA 250–301 , a dysglycemic hormone), 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. (Hypertension. 2016;68:334-347. DOI: 10.1161/ HYPERTENSIONAHA.116.06568.) • Online Data Supplement