We demonstrate for the first time that CgA is produced by human myocardium and exerts negative inotropic and lusitropic effects on mammalian heart. CgA may represent a key player in neuroendocrine regulation of cardiac function and a potential therapeutic target in heart failure.

CgA is a pro-hormone, precursor of several active fragments likely to exert biological effects in chronic heart failure. CgA serum levels are increased in patients with chronic heart failure and are a predictive factor for mortality.

• Circulating chromogranin A and its fragments form a balance of anti-and proangiogenic factors regulated by thrombin-dependent cleavage.• The alteration of this balance could provide a new mechanism for triggering angiogenesis in cancer and other pathophysiologic conditions.Angiogenesis, the formation of blood vessels from pre-existing vasculature, is regulated by a complex interplay of anti and proangiogenic factors. We found that physiologic levels of circulating chromogranin A (CgA), a protein secreted by the neuroendocrine system, can inhibit angiogenesis in various in vitro and in vivo experimental models. Structure-activity studies showed that a functional antiangiogenic site is located in the C-terminal region, whereas a latent anti-angiogenic site, activated by cleavage of Q76-K77 bond, is present in the N-terminal domain. Cleavage of CgA by thrombin abrogated its anti-angiogenic activity and generated fragments (lacking the C-terminal region) endowed of potent proangiogenic activity. Hematologic studies showed that biologically relevant levels of forms of full-length CgA and CgA1-76 (anti-angiogenic) and lower levels of fragments lacking the C-terminal region (proangiogenic) are present in circulation in healthy subjects. Blood coagulation caused, in a thrombin-dependent manner, almost complete conversion of CgA into fragments lacking the C-terminal region. These results suggest that the CgA-related circulating polypeptides form a balance of anti and proangiogenic factors tightlyregulated byproteolysis. Thrombin-induced alteration of this balance could provide a novel mechanism for triggering angiogenesis in pathophysiologic conditions characterized by prothrombin activation. (Blood. 2013;121(2):392-402) IntroductionAngiogenesis, the process of formation of new blood vessels from pre-existing vessels, is tightly regulated by the coordinated action of anti and proangiogenic factors. [1][2][3] When this balance is disturbed, the result is either excessive or insufficient angiogenesis. Altered angiogenesis, causing excessive or insufficient blood vessel growth, is a common denominator underlying many pathologic conditions, including cardiovascular diseases, macular degeneration, skin diseases, diabetic ulcers, stroke, rheumatoid arthritis, cancer, and many others. [1][2][3] A growing body of evidence suggests that angiogenesis can be regulated by peptides derived from proteins released by neurons and neuroendocrine cells. For example, we have previously shown the recombinant fragment 1-78 of human chromogranin A (CgA), a 439-residue long protein stored in the secretory granules of many endocrine cells, neurons, and cardiomyocytes 4-6 can inhibit angiogenesis in experimental models. 7 Other investigators have shown that a synthetic fragment encompassing residues 352-372 (CgA352-372) can promote angiogenesis. 8 Studies on the mechanism of action have shown that CgA1-78 (also called vasostatin-1) can inhibit endothelial cell proliferation, migration, and invasion induced by vascular endothelial growth factor...

Elevated levels of circulating chromogranin A (CgA), a protein stored in the secretory granules of many neuroendocrine cells and neurons, have been detected in the blood of patients with neuroendocrine tumors or heart failure. The pathophysiological role of increased secretion of CgA is unknown. Using mice bearing subcutaneous tumors genetically engineered to secrete CgA in circulation, we have found that increased blood levels of this protein prevent vascular leakage induced by tumor necrosis factor-alpha (TNF) in the liver venous system. Structure-activity studies, carried out with CgA fragments administered to normal mice, showed that an active site is located within residues 7-57 of CgA. Accordingly, an anti-CgA antibody directed to residues 53-57 inhibited the effect of circulating CgA, either endogenously produced or exogenously administered, on liver vessels. Studies of the mechanism of action showed that CgA inhibits TNF-induced VE-cadherin down-regulation and barrier alteration of cultured endothelial cells, in an indirect manner. Other effectors, such as thrombin and vascular endothelial growth factor were partially inhibited by CgA N-terminal fragments in in vitro permeability assays. These findings suggest that circulating CgA could help regulate the endothelial barrier function and to protect vessels against TNF-induced plasma leakage in pathological conditions characterized by increased production of TNF and CgA, such as cancer or heart failure.