Exogenous administration of heme oxygenase-1 by gene transfer provides protection against hyperoxia-induced lung injury

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Abstract

Heme oxygenase-1 (HO-1) confers protection against a variety of oxidant-induced cell and tissue injury. In this study, we examined whether exogenous administration of HO-1 by gene transfer could also confer protection. We first demonstrated the feasibility of overexpressing HO-1 in the lung by gene transfer. A fragment of the rat HO-1 cDNA clone containing the entire coding region was cloned into plasmid pAC-CMVpLpA, and recombinant adenoviruses containing the rat HO-1 cDNA fragment Ad5-HO-1 were generated by homologous recombination. Intratracheal administration of Ad5-HO-1 resulted in a time-dependent increase in expression of HO-1 mRNA and protein in the rat lungs. Increased HO-1 protein expression was detected diffusely in the bronchiolar epithelium of rats receiving Ad5-HO-1, as assessed by immunohistochemical studies. We then examined whether ectopic expression of HO-1 could confer protection against hyperoxia-induced lung injury. Rats receiving Ad5-HO-1, but not AdV-βGal, a recombinant adenovirus expressing Escherichia coli β-galactosidase, before exposure to hyperoxia (>99% O2) exhibited marked reduction in lung injury, as assessed by volume of pleural effusion and histological analyses (significant reduction of edema, hemorrhage, and inflammation). In addition, rats receiving Ad5-HO-1 also exhibited increased survivability against hyperoxic stress when compared with rats receiving AdV-βGal. Expression of the antioxidant enzymes manganese superoxide dismutase (Mn-SOD) and copper-zinc superoxide dismutase (CuZn-SOD) and of L-ferritin and H-ferritin was not affected by Ad5-HO-1 administration. Furthermore, rats treated with Ad5-HO-1 exhibited attenuation of hyperoxia-induced neutrophil inflammation and apoptosis. Taken together, these data suggest the feasibility of high-level HO-1 expression in the rat lung by gene delivery. To our knowledge, we have demonstrated for the first time that HO-1 can provide protection against hyperoxia-induced lung injury in vivo by modulation of neutrophil inflammation and lung apoptosis.

Authors

Leo E. Otterbein, Jay K. Kolls, Lin L. Mantell, Julia L. Cook, Jawed Alam, Augustine M.K. Choi