Cell Membrane Biogenesis: A Matter of Survival. Its Role in Renal Epithelia Restitution After Calcium Oxalate Injury.

Abstract

Calcium oxalate (CaOx) is the main component of kidney stones. These stones interact with the surface of renal epithelial cells and initiate injury. In differentiated renal epithelial cells (DREC), we demonstrated that oxalate (Oxa) injures monolayers, which undergo a type II epithelial-mesenchymal transition during the first 24 h (the damage period). Thereafter, cells gradually recover their morphology, restituting the monolayer between 48 and 72 h (the restitution period). Since Oxa induces lipid peroxidation (LPO), which disrupts membrane homeostasis, we hypothesize that epithelial restitution occurs after the activation of lipid metabolism and the restoration of cellular membrane integrity. The goal of this study was to determine the role of glycerolipid (GL) metabolism in DREC monolayer survival and restitution after Oxa injury. DREC monolayers were incubated with 1.5 mM Oxa during the damage and the restitution periods. After the damage period, we found alterations in the DREC monolayer and a decrease in cell number. Moreover, Oxa-induced LPO changes membrane composition and properties. These changes were accompanied by the activation of glycerophospholipid (GP) and triacylglyceride (TG) synthesis and by an increase in the number of lipid droplets (LD), but a decrease in their size. The inhibition of lipin activity impaired GP and TG synthesis, completely preventing DREC monolayer restitution. Collectively, these results demonstrate that Oxa-induced LPO disrupts DREC membrane properties, changing their biophysics and composition, which affects cell physiology. To restore cell homeostasis, GL synthesis and LD biogenesis are activated, allowing the gradual recovery of the DREC monolayer phenotype, and highlighting the importance of membrane structure maintenance in cell survival.