INCREASED EXPRESSION OF HEAT-SHOCK-PROTEIN-70 PROTECTS A549 CELLS AGAINST HYPEROXIA

Acute and chronic lung injury secondary to hyperoxia remains an import ant complication in critically ill patients, and, consequently, there is interest in developing strategies to protect the lung against hyper oxia. Heat shock proteins (HSPs) confer protection against a broad arr ay of cytotoxic agents, In this study, we tested the hypothesis that i ncreased expression of the 70-kDa HSP (HSP70) would protect cultured h uman respiratory epithelium against hyperoxia. Recombinant A549 cells were generated in which human HSP70 was increased by stable transfecti on with a plasmid containing human HSP70 cDNA under central of the cyt omegalovirus promoter (A549-HSP70 cells). A549-HSP70 cells exposed to hyperoxia had greater acute survival rates and clonogenic capacity com pared with wild-type A549 cells and with control cells stably transfec ted with the empty expression plasmid. Hyperoxia-mediated lipid peroxi dation and ATP depletion were also attenuated in A549-HSP70 cells expo sed to hyperoxia. Increased expression of HSP70 did not detectably alt er mRNA levels of the intracellular antioxidants manganese superoxide dismutase, catalase, and glutathione peroxidase. Collectively, these d ata demonstrate a specific in vitro protective role for HSP70 against hyperoxia and suggest that potential mechanisms of protection involve attenuation of hyperoxia-mediated lipid peroxidation and ATP depletion .