Cytosolic Phospholipase A2 modulates Tryglycerides acummulation in Renal Cells Under Osmotic Stress Through Arachidonic Acid-PPARg Axis

PARRA, LEANDRO G.; ZERPA, ANDREA; ERJAVEC, LUCIANA C.; SETTON-AVRUJ, PATRICIA C.; FERNÁNDEZ TOME, MARÍA C.

CABA

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

SAIB (Sociedad Argentina de Investigación Bioquímica y en Biología Molecular)

Hyperosmolarity is a key controversial signal for renal cells. Under physiological conditions, it induces renal cell differentiationand maturation of the urine concentrating system. However, abrupt changes in environmental osmolarity may also induce cell stressthat can lead to cell death. To adapt and survive in such adverse conditions, renal cells implement different osmoprotectivemechanisms that include both the upregulation of cyclooxygenase-2 (COX-2) expression and prostaglandins (PGs) synthesis fromarachidonic acid (AA), and a coordinated increase in phospholipids (GP) and triacylglycerides (TG) biosynthesis. In this work weevaluated whether hyperosmolarity modulates AA metabolism in MDCK cells under osmotic stress and the role of thephospholipase A2 (PLA2)-AA-PPARγ axis 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) andtreated in the presence or not of different PLA2 subtypes, COX and PPARγ inhibitors or a PPARγ agonist. RT-qPCR and WBstudies showed that hyperosmolarity increased cPLA2 expression at 24 and 48 h in a time-dependent manner. Moreover, cellstreated with hyperosmolar media showed changes in cPLA2 intracellular distribution. Inhibition of cPLA2 but not iPLA2 norsPLA2 prevented hyperosmolarity-induced TG synthesis and lipid droplets accumulation.It is worth to point out that prostaglandin synthesis inhibition with Indomethacin (Indo) not only failed to prevent hyperosmolarityinduced TG synthesis and accumulation but also exacerbated it. Similar results were obtained when cells were treated with PPARγagonist Rosiglitazone (Rosi) under hyperosmotic conditions.In addition to this, hyperosmolarity increased free intracellular AA levels which was even higher when AA conversion intoprostaglandin was blocked with Indo. Furthermore, inhibition of PPARγ with GW-9662 not only prevented the effects of Indo andRosi on TG synthesis but also reduced TG synthesis stimulated by hyperosmolarity.Our results suggest that hyperosmolarity induces AA release from GP by cPLA2 activity and that AA stimulates TG synthesis andLD formation through PPARγ activation. Therefore, this work highlights the role of cPLA2 as an osmoprotective gene.