TRIACYLGLYCERIDE (TAG) METABOLISM REGULATION BY HYPEROSMOTIC ENVIRONMENT IN RENAL EPITHELIAL CELLS.

PARRA, L; WEBER, K; CASALI, CI; FERNÁNDEZ-TOME, MC

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB conference; 2019

SAIB y PABMB

Hyperosmolarity is a key controversial signal for renal cells. Under physiological conditions, it induces renal cell differentiation and maturation of urine concentrating system. However, abrupt changes in environmental osmolarity may also induce cell stress that can lead to death. Both conditions require lipid synthesis either for membrane expansion or for osmoprotection. In Madin-Darby canine kidney (MDCK) cells we showed that hyperosmolarity upregulates phospholipid (PL) as well as triglycerides (TAG) de novo synthesis. We also showed that hyperosmolarity activates SREBP-mediated transcriptional regulation of lipogenic genes such us lipin and diacylglycerol acyltransferase (DGAT) enzymes. In the present work we evaluated which signaling pathway mediates hyperosmolarity upregulation of lipid. MDCK were subjected to hyperosmolality (298-512 mOsm/kg H2O) for 48h, treated with different phospholipases (PLA2, PLD, PLC-PI and PLC-PC) or kinases (PI3K, PKC or MAPKs) inhibitors and labeled using [14C]-Glycerol. After treatments, lipids were extracted, separated by TLC and quantified. Neither MAPKs inhibitors nor PKC and PI3K were mediating TAG, but not PL, synthesis. PLC-PI and PLC-PC inhibitors increased PL and TAG synthesis; PLD activity was also involved in PL and TAG homeostasis. cPLA2 inhibitors prevented hyperosmotic-induced lipid synthesis. Such decrease seemed to be due to a down regulation of lipin2 and DGAT1 and DGAT2 expression which were evaluated by RT-PCR. As PLA2 activity generates arachidonic acid (AA) to form prostaglandins (PGs), we evaluated the effect of PGs synthesis inhibitor in lipid synthesis; either indomethacin or NS398 significantly increased lipid metabolism. Thus, hyperosmolar induced lipid metabolism is modulated by different signaling systems, specially by the axis PLA2 ? COX2.