The immunosuppression of macrophages underlies the cardioprotective effects of catestatin (CST)

Abstract

38Objective: Hypertension (HTN) is a global pandemic, affecting more than one billion people. 39Although catestatin (CST), a chromogranin A (CgA)-derived peptide, decreases blood pressure 40 (BP) in rodent models of HTN, the mechanisms underlying its hypotensive action is yet to be 41 established. Here we generated CST knockout (CST-KO) mice to pinpoint the mechanism of the 42 hypotensive action of CST. 44Methods and Results: CST-KO mice were hypertensive; their serum cytokines were elevated, 45 anti-inflammatory genes were downregulated, and their hearts showed marked infiltration with 46 macrophages. CST replenishment reversed all these phenotypes -it normalized BP, reduced 47 serum cytokines, upregulated anti-inflammatory genes, and reduced the cardiac infiltrates by 48 ~30%, as determined by FACS. Pre-conditioning-induced cardioprotection was also abolished in 49 CST-KO mice. We hypothesize that CST's anti-hypertensive and cardioprotective effects may be 50 caused by suppressed trafficking of macrophages to the heart and reduced inflammation. Such 51 cause-and-effect relationship is supported by the fact that CST-KO mice became normotensive 52 when they were depleted of macrophages using chlodronate, or when they received bone marrow 53 transplant from wild-type littermates. Mechanistically, cardiac tissue transcriptomes revealed 54 multiple altered gene expression programs in CST-KO mice that are commonly encountered in 55 human cardiomyopathies. Among others, a prominent reduction of Glo1 gene was seen in CST-56 KO mice; supplementation with CST increased it expression by >7-fold. Because Glo1 in 57 macrophages metabolizes methylglyoxal, an inflammatory agent whose accumulation promotes 58 vascular damage in HTN and T2DM, this could be one of the means by which CST attenuates 59 inflammation and improves cardiovascular health. Repletion of CST also improved glucose 60 metabolism and increased the surface area of mitochondrial cristae and decreased the secretion 61 of catecholamines; the latter explains the anti-hypertensive actions of CST. 63Conclusions: We conclude that the anti-hypertensive effects of CST is mediated at least in part 64 via CST's anti-inflammatory actions; in the absence of CST, macrophages are more reactive, they 65 infiltrate the heart and alter the ultrastructure, physiologic and molecular makeup of the 66 myocardium. These studies implicate CST as a key mediator of the observed crosstalk between 67 systemic and cardiac inflammation in HTN.68 69 70 71 3 Abbreviations 72 2DG: 2-deoxy-glucose 73 Actc1: cardiac muscle actin alpha 74 Atp5j: mitochondrial ATP synthase subunit F6 75 BRS: baroreflex sensitivity 76 Cd36: cluster of differentiation 36 77 Cers2: ceramide synthase 2 78 CgA: chromogranin A 79 CST: catestatin 80 CST-KO: CST knockout Introduction 122 123 Hypertension (HTN) is an important risk factor for cardiovascular disease (CVD) and mortality 1 .124 The burden of HTN and the estimated HTN-associated deaths have increased substantially over 125 the past 25 years 2 .126 The role o...

The anti-inflammatory peptide Catestatin blocks chemotaxis

“…In a colitis model, CST also reduced granulocyte infiltration in the colon (8). In line with this, the adrenal gland, heart, and gut of CST knockout mice display increased macrophage infiltration (4,7,12). In this study, we show that while CST itself is weakly chemotactic, it blocks the extravasation and migration of phagocytes both in vitro and in vivo.…”

“…S1). Thus, both our in vivo and in vitro migration assays show that CST is weakly chemotactic, raising the question how CST can reduce monocyte and granulocyte infiltration in inflamed tissues such as the liver (diet induced obese mice), intestine (colitis model), heart (hypertension model) and atheromatous plaques (atherosclerosis model) (4,7,8,12,13).…”

“…Being an anti-inflammatory peptide, CST reduces inflammation in cardiac and chronic inflammatory diseases (3,(7)(8)(9). Despite the chemotactic effects of CST (7,10,11), administration of exogenous CST reduces monocyte and macrophage infiltration in the liver, heart and gut in mouse models of type II diabetes, hypertension, atherosclerosis and colitis (4,7,8,12,13). In a colitis model, CST also reduced granulocyte infiltration in the colon (8).…”

Chromogranin A regulates gut permeabilityviathe antagonistic actions of its proteolytic peptides

“…CgA is extensively processed to CST. To study the role of CgA and its peptides in the regulation of the gut barrier, we used systemic CgA-KO (deletion of exon 1 and ~1.5 kbp proximal promoter, thereby completely inactivating the Chga allele) 34 and CST-KO mice (the 63 bp CST domain of CgA was deleted from Exon VII of the Chga gene) 35 . We analyzed the function and morphology of the gut barrier in CST-KO mice.…”

Catestatin regulates the colonic mucus layer in inflammatory bowel disease

“…We also characterized the thickness of the mucus layer in CST-KO and wildtype (WT) mice. Since we recently showed that macrophages (and possibly other bonemarrow derived immune cells) are major producers of CST 18,19 , we determined the effect of bonemarrow transfer from WT mice into CST-KO mice on the colonic mucus layer.…”