Hypertonicity induces opposite regulation of PPAR GAMMAand Cyclooxygenase 2 expression in renal cells

CASALI, CECILIA IRENE; WEBER, KAREN; MIKKELSEN, EVELYN; FERNANDEZ TOME, MARIA DEL CARMEN

PUERTO MADRYN

Congreso; 46 REUNÍON ANUAL DE LA SOCIEDAD ARGENTINA DE BIOQUIMICA Y BIOLOGIA MOLECULAR; 2010

SAIB

Hypertonicity induces opposite regulation of PPARg and Cyclooxygenase 2 expression in renal cells Cecilia I. Casali, Karen Weber, Evelyn Mikkelsen, Mar¨ªa C. Fern¨¢ndez Tome C¨¢tedra Biolog¨ªa Celular y Molecular. Facultad de Farmacia y Bioqu¨ªmica, UBA. IQUIFIB-CONICET Peroxisome proliferator-activated receptors (PPARs) regulate the transcription of lipid metabolism related-genes including cyclooxygenase (COX2) which is considered an osmoprotective molecule in renal cells. Although PPAR¦Ã was demonstrated to be present in renal cells, the relationship between both proteins has not been established. The present work explores whether PPAR¦Ã regulates COX2 expression in renal epithelial cells in isotonic and hypertonic conditions. MDCK cell cultures were grown in isotonic (298 mOsm/Kg H2O) and NaCl-hypertonic (500 mOsm/Kg H2O) media in the absence or presence of PPAR¦Ã agonists, rosiglitazone (Rosi) and 15-deoxy-¦¤12,14-PGJ2 (PGJ2), or antagonist, GW9662 (GW). After 24 h, treated cells were collected and submitted to westernblot analysis for PPAR¦Ã and COX2 In parallel experiments, immunofluorescence microscopy was performed. In isotonicity, Rosi and PGJ2 decreased COX2 expression, but they did not affect PPAR¦Ã protein. Therefore, the activation of PPAR¦Ã represses COX2 expression. In hypertonicity, the NaCl-induced increase of COX2 level was not prevented by GW, suggesting that PPAR¦Ã is not involved. But, when PPAR¦Ã was evaluated, the active form of PPAR¦Ã2 was withdrawn. Taken together these results suggest that the up-regulation of the osmoprotective gene COX2 in cells submitted to high-NaCl medium only occurs after the down-regulation of PPAR¦Ã2.