Inhibition of heat-shock protein 70 induction in intestinal cells overexpressing cyclooxygenase 2

Background & Aims: The cyclooxygenase (COX) enzymes catalyze the initial st ep of prostaglandin formation; the inducible form, COX-2, plays a role in i nflammation, Heat-shock protein 70 (hsp70) is a stress-responsive gene impo rtant for cell survival; induction of hsp70 appears to be mediated, in part , by the prostaglandin pathway, We determined the effect of COX-2 overexpre ssion on hsp70 induction in rat intestinal epithelial (RIE) cells, Methods: RIE cells transfected with COX-2 complementary DNA oriented in the sense ( RIE-S) or antisense (RIE-AS) direction were subjected to a heat shock; RNA and protein were harvested and analyzed by Northern and Western blots, resp ectively, Gel shift assays were performed to assess DNA binding, Results: B oth hsp70 messenger RNA and HSP70 protein levels were increased in the RIE- AS cells, whereas induction was markedly inhibited in the RIE-S cells after heat shock. Inhibition of heat-shock factor binding was noted in RIE-S cel ls, suggesting that heat-shock transcription factor regulation may explain the inhibition of hsp70. The COX-2 selective inhibitor, NS-398, reversed th e effects of COX-2 overexpression. Conclusions: The results support a funct ional role for the prostaglandin/COX pathway in the induction of hsp70. The findings underscore a potential regulatory mechanism involving an inverse relationship between COX-2 expression and hsp70 induction.