MO459: Characterization of Adrenal Gland Derived Mediators of Vascular Calcification

Abstract

Abstract BACKGROUND AND AIMS Adrenal glands participate in cardiovascular physiology and pathophysiology via the synthesis and secretion of various well-known compounds like mineralocorticoids, amine peptides and glucocorticoids. In this study, a previously unknown systemic function of adrenal glands, that is the regulation of vascular calcification processes was investigated. METHOD The homogenate of the bovine adrenal gland was separated using chromatographic fractionation. The fractions were analysed in aortic smooth muscle cells, aortic rings and vitamin D3 plus nicotine elastocalcinosis rat model for effects on vascular calcification processes. Potential mediators were distinguished by mass spectrometry and comparison with pertinent databases. For ease of therapeutic application, smaller fragments of the identified mediators were analysed to identify the active sites. RESULTS We identified a new 19aa peptide, named ‘calcification blocking factor’ (CBF), which shows a promising protective effect against vascular calcification. CBF is released from the parent protein Chromogranin A, which is released from adrenal glands via enzymatic cleavage by calpain 1 and kallikrein. CBF reduced the calcium content of cells and aortic rings in calcifying cultures. CBF downregulates vascular smooth muscle cell (VSMC) trans-differentiation into osteoblast-like cells within the vascular wall via the sodium-dependent phosphate transporter PIT-1 and by inhibiting the NF-κB activation and the subsequent BMP2/p-SMAD pathway. VDN animals treated with CBF show a significantly decreased pulse pressure as a marker of arterial stiffness. An 8aa peptide was found to have a better effect on reducing vascular calcification when compared to the original peptide. CONCLUSION The adrenal glands participate in cardiovascular (CV) physiology and the pathophysiology of CV diseases through their effects on sodium and water metabolism, vascular tone and cardiac function. In the present study, we identified a previously uncharacterized peptide secreted from the adrenal gland that modulates cardiovascular calcification by regulating osteoblastic differentiation in the context of vascular calcification. We show that CBF reduces calcification via PIT-1/NF-κB/BMP2/p-SMAD pathway. Further, we identified the active site of this peptide (8aa long) which can be used as a therapeutic agent. These findings suggest a novel function of adrenal glands in cardiovascular calcification.