Cytosolic Phospholipase A2 modulates Triacylglycerides accumulation in renal cells under osmotic stress through Arachidonic Acid-PPARg axis

PARRA, LEANDRO; ZERPA, ANDREA; ERJAVEC, LUCIANA; CASALI, CECILIA; SETTON-AVRUJ, PATRICIA; FERNÁNDEZ TOME, MARIA DEL CARMEN

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2022

SAIB

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. To adapt and survive in such adverse conditions, renal cells implement different osmoprotective mechanisms that include both the upregulation of cyclooxygenase-2 (COX-2) expression and prostaglandins (PGs) synthesis from arachidonic acid (AA), and a coordinated increase in phospholipids (GP) and triacylglycerides (TG) biosynthesis. In this work we evaluated whether hyperosmolarity modulates AA metabolism in MDCK cells under osmotic stress and the role of the phospholipase A2 (PLA2)-AA-PPARγ pathway in TG synthesis activation. MDCK cells were subjected to hyperosmolarity (298-512 mOsm/kg H2O) for different periods of time (0, 12, 24 and 48 h) and treated with different PLA2s, COX and PPARγ inhibitors or a PPARγ agonist. RT-qPCR and WB studies showed that hyperosmolarity increased cPLA2 expression at 24 and 48 h in a time-dependent manner. Moreover, cells treated with hyperosmolar media showed changes in cPLA2 intracellular distribution. Inhibition of cPLA2 but not iPLA2 nor sPLA2 prevented hyperosmolarity-induced TG synthesis and lipid droplets accumulation.Strikingly, prostaglandin synthesis inhibition with Indomethacin (Indo) not only failed preventing hyperosmolarity-induced TG synthesis and accumulation but also exacerbated it. Similar results were obtained when cells were treated with PPARγ agonist Rosiglitazone (Rosi) under hyperosmotic conditions.In addition to this, hyperosmolarity increased free intracellular AA levels and this increment was even higher when AA conversion into prostaglandin was blocked with Indo. Furthermore, inhibition of PPARγ with GW-9662 not only prevented the effects of Indo and Rosi on TG synthesis but also reduced TG synthesis compared to hyperosmolar control.Our results suggest that hyperosmolarity induces AA release from GP by cPLA2 activity and that AA stimulates TG synthesis and LD formation through PPARγ activation. Therefore, this work highlights the role of cPLA2 as an osmoprotective gene.