Heat shock induces IκB-α and prevents stress-induced endothelial cell apoptosis. Discussion

Objective: To determine whether prior heat shock would attenuate endothelial cell apoptosis and whether any effect of preemptive heat shock is mediated through a nuclear factor kappa B and inhibitor kappa B α mechanism. Design: A randomized, controlled in vitro study. Setting: A laboratory in a large, academic medical center. Interventions: Cultured primary porcine endothelial cells were treated with increasing doses of sodium arsenite (40-160 μmol/L), after which the interval until subsequent apoptotic (lipopolysaccharide-arsenite) challenge was varied (4-16 hours). The degree of cell death and apoptosis were determined using neutral red uptake and staining with annexin V and propidium iodide, respectively. Inducible heat shock protein 70 and inhibitor kappa B α levels in treated cells were determined by Western blot analysis. Lipopolysaccharide-induced nuclear factor kappa B activity was assessed using an electrophoretic mobility shift assay. Results: Prior arsenite treatment decreased cell death by apoptosis in a time- and dose-dependent manner. Specifically, a higher sodium arsenite concentration and shorter intervals afforded better protection (P=.01, 160 μmol/L at 4 hours). Protection against apoptosis correlated with increased heat shock protein 70 and inhibitor kappa B α levels and decreased nuclear factor kappa B binding activity. Conclusions: Arsenite, an inducer of the heat shock response, decreased stress-induced endothelial cell apoptosis. The mechanism of this protection may include decreased nuclear factor kappa B activity or increased inducible heat shock protein 70 levels. Heat shock protein 70 may serve as a molecular marker to determine not only the phenotypic state of the cell but also the durability of protection afforded by heat shock. These data support the hypothesis that stress-induced changes in transcription factor activity and protein expression can regulate the induction of apoptosis.