Early renal ischemia, with or without reperfusion, activates NF kappa B and increases TNF-alpha bioactivity in the kidney

Purpose: Acute tubular necrosis (ATN) and the ensuing renal failure induced by ischemia and reperfusion injury (I/R) remain a major cause of morbidity and mortality among patients in the intensive care unit. Although it is we ll established that exogenous tumor necrosis factor-alpha (TNF) induces ren al injury, it remains unknown whether ischemia and/or reperfusion activates the signaling mechanisms required for renal TNF production. We hypothesize d that ischemia and/or reperfusion would activate the oxidant. sensitive TN F transcription factor, nuclear factor kappa B (NF kappa B), and thereby le ad to renal TNF production. Materials and Methods: Male Sprague-Dawley rats were anesthetized with sodi um pentobarbital, after which various periods of renal ischemia, with or wi thout reperfusion, were induced in fats. At different time intervals, kidne ys were harvested and NF kappa B activation (electrophoretic mobility shift assay), TNF mRNA content (RT-PCR), and TNF bioactivity (WEHI-164 cell clon e cytotoxicity assay) were determined. Results: Results indicate that 15 minutes of ischemia alone activates NF ka ppa B, whereas peak activation occurred at 30 minutes of ischemia alone. NF kappa B remained activated through 60 minutes reperfusion. Thirty minutes of ischemia is required to induce renal TNF mRNA production; however, renal TNF protein expression and bioactivity peaked following 1 hour of ischemia and 2 hours reperfusion. Conclusions: These results are the initial demonstration that renal ischemi a, with or without reperfusion, activates the TNF transcription factor NF k appa B and increases TNF bioactivity in the kidney.