Role of NF-kB in COX2 expression in renal cells under hypertonic stress.

CASALI, CECILIA IRENE; WEBER, KAREN; FAGGIONATO, DANIELA; MESSINGER, DAIANA; FERNANDEZ , MARIA DEL CARMEN

Mendoza

Congreso; Reunion de la Sociedad Argentina de Bioquimica y biología molecular; 2012

SAIB

Renal medullary cells are exposed to variable and high concentrations of NaCl as part of the urinary concentrating system. In such hypertonic conditions, renal cells still survive and function by activating the transcription of various osmoprotective genes, among them, cyclooxygenase 2 (COX2). It was demonstrated that NF-kB transcription factor is involved in COX2 expression in different cell types but not in renal cells. The present work evaluates whether NF-kB regulates COX2 expression in renal epithelial cells under hypertonicity. MDCK cell cultures were grown during 1.5, 3, 6, 12 and 24 h in isotonic (298 mOsm/Kg H2O) and NaCl-hypertonic (520 mOsm/Kg H2O) media in the absence or presence of NF-kB inhibitors, PDTC and parthenolide. RT-PCR and westernblot (WB) analysis showed the increase in the expression of COX2 and NF-kB after hypertonic challenge. Cellular fractionation followed by WB, and microscopy showed the translocation of NF-kB from the cytosol to the nucleus suggesting the activation of the transcription factor. The NaCl-induced of COX2 mRNA and protein was prevented by PDTC and parthenolide, showing that NF-kB is involved in COX2 expression. Taken together these results suggest that the up-regulation of the osmoprotective gene COX2 in cells submitted to high-NaCl medium occurs due to the NF-kB activation.