MO614: Modified Lipid Metabolism and Cytosolic Phospholipase A2 Activation in Mesangial Cells Under Pro-Inflammatory Conditions

Abstract

Abstract BACKGROUND AND AIMS Diabetic kidney disease (DKD) is thought to be a consequence of hyperglycemia and driven by early glomerular hemodynamic changes and progressive expansion of the mesangium. The molecular mechanism behind the pathophysiological alterations of the mesangium is yet to be elucidated. This study aimed at investigating whether lipid signaling might be the missing link. METHOD Human mesangial cells (HMCs) were stimulated with high glucose, IL-1β or PDGF-BB. Production of IL-1β and PDGF-BB, COX-2 induction and cPLA2 activation and prostaglandin secretion were investigated using a combination of ELISA, western blot, lipidomics, qPCR and activity assays. Inhibition of cPLA2 was evaluated using ELISA, migration and proliferation assays. Validation of data was performed in silico using the Nephroseq database [1] and a recently published glomerular transcriptomic DKD database. [2] RESULTS Stimulation of HMCs with high glucose primed IL-1β secretion through inflammasome NLRP3 signaling. In turn, IL-1β was able to stimulate PDGF-BB release. PDGF-BB increased IL-1β secretion synergistically. Both IL-1β and PDGF-BB stimuli caused lipid metabolism variations and in particular triggered the formation of phosphorylated sphingoid bases (PSBs) and the activation of the enzymes cPLA2 and COX-2. This led to the formation of prostanoids from arachidonic acid produced by cPLA2. As a result, prostaglandins were secreted. Another product of cPLA2 activation was lysophosphatidic acid (LPA), a proliferation effector. Blocking cPLA2-mediated release of arachidonic acid could in fact reduce HMCs’ proliferation and secretion of prostaglandins. CONCLUSION Hyperglycemia primes glomerular inflammatory and proliferative stimuli triggering lipid metabolism modifications in HMCs. The upregulation of cPLA2 was found to be critical in this setting. cPLA2 inhibition with AACOCF3 reduced mesangial secretion of prostaglandins and proliferation, making it a potential target for DKD therapy.