Although heat preconditioning has been known to be protective in various types of injury, the precise molecular mechanism for this is unclear. Recent observations that indicate that previous heat shock has an anti-inflammatory, antiapoptotic effect led to this investigation of the in vivo effect of heat preconditioning on NF-kappaB activation and inflammation and also on tubular cell injury in ischemic acute renal failure (ARF). Heat preconditioning provided marked functional protection and also reduced histologic evidence of tubular necrosis. Ischemia/reperfusion-induced NF-kappaB activation was suppressed by heat preconditioning with a subsequent decrease in monocyte chemoattractant protein-1 expression and inflammatory cell infiltration. Heat preconditioning also suppressed the accumulation of phosphorylated inhibitory kappaBalpha (IkappaBalpha) with a resultant depletion of cytoplasmic IkappaBalpha, indicating that heat preconditioning blocked the activation of the IkappaB kinase complex. Tubular cell apoptosis, determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, also was decreased by heat preconditioning, and this was accompanied by decreased caspase 3 activation. Among several heat-shock proteins (HSP), HSP-70 was induced primarily by heat preconditioning. Inhibition of HSP-70 by quercetin almost completely reversed the functional protection that was provided by heat preconditioning. These data provide evidence that HSP-70 affords protection via inhibition of NF-kappaB-mediated inflammation and also inhibition of the cell death pathway in ischemic ARF. Further elucidation of the cytoprotective mechanism of stress proteins could facilitate new target or drug development in the treatment of ARF.