MO185: Post-Translational Carbamylation of Sortilin is Associated with Cardiovascular Calcification in Chronic Kidney Disease

Abstract

Abstract BACKGROUND AND AIMS Sortilin, an intracellular sorting receptor, has been identified as a cardiovascular (CV) risk factor in the general population. Patients with chronic kidney disease (CKD) are highly susceptible to developing CV complications such as CV calcification. However, specific CKD-induced post-translational protein modifications of sortilin and their link to CV calcification remain unknown. METHODS Circulating sortilin isolated from two independent CKD cohorts was analysed by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/TOF mass spectrometry). The binding partner affinity was analysed by surface plasmon resonance spectroscopy. The effect of carbamylated sortilin on vascular calcification was analysed in vitro using human coronary artery smooth muscle cells. RESULTS In CKD patients, targeted mass spectrometric analyses of circulating sortilin revealed an increase in carbamylated lysine residues with kidney function decline. Carbamylation did not affect dimer formation of sortilin assessed by mass spectrometry. We observed an increased affinity of interleukin 6 to in vitro carbamylated sortilin. Carbamylated sortilin increased SMC calcification in vitro that was accelerated by interleukin 6, while carbamylated albumin and collagen type I did not affect SMC calcification. Mass-spectrometry imaging of human calcified arteries revealed in situ carbamylated sortilin. In CKD patients, sortilin carbamylation was associated with coronary artery calcification volume, independent of age, kidney function and other risk factors. Moreover, patients with carbamylated sortilin displayed significantly faster coronary artery calcification progression than patients without sortilin carbamylation. CONCLUSION Carbamylated sortilin is a risk factor for CV calcification and may contribute to elevated CV complications in patients with CKD.