Induction of Zf9 in the kidney following early ischemia/reperfusion

Induction of Zf9 in the kidney following early ischemia/reperfusion.BackgroundAn improved understanding of the early cell injury mechanisms is critical for effective therapy of acute renal failure (ARF).MethodsWe utilized cDNA microarrays to identify renal genes that are induced very early after renal ischemia in a mouse model, whose protein products might provide novel information regarding the pathogenesis of ARF. The findings were confirmed by downstream mRNA and protein expression studies, as well as knockdown analysis with antisense primers.ResultsThe maximally induced gene (21-fold at 3 hours of reflow) was Zf9, a Kruppel-like transcription factor involved in the regulation of transforming growth factor-β1 (TGF-β1). The rapid induction of Zf9 mRNA was confirmed by Northern analysis (14.5-fold at 3 hours of reflow) and that of Zf9 protein by Western analysis (10.5-fold at 3 hours of reflow). Zf9 protein was induced in both proximal and distal tubule cells in a cytoplasmic as well as nuclear distribution. TGF-β1 protein was also up-regulated in a pattern parallel to that of Zf9. In cultured human proximal tubule cells, induction of ischemia by partial adenosine triphosphate (ATP) depletion resulted in a rapid up-regulation of both Zf9 and of TGF-β1 proteins. Antisense oligonucleotides to Zf9 markedly blunted the induction of Zf9 and TGF-β1, and significantly inhibited the apoptotic response to ATP depletion.ConclusionInduction of Zf9 and its transactivating factor TGF-β1 may play a critical and hitherto unrecognized role in the early apoptotic response to ischemic renal injury