Overexpression of heme oxygenase‐1 (HO‐1) in V79 cells results in increased resistance to hyperbaric oxygen (HBO)‐induced DNA damage

Abstract

Heme oxygenase (HO) catalyzes the rate-limiting step in the oxidative degradation of heme to biliverdin. The isoform HO-1 is inducible by a variety of agents causing oxidative stress and has been suggested to play an important role in cellular protection against oxidant-mediated cell damage. Using treatment of cell cultures with hyperbaric oxygen (HBO) as a model for oxidative stress, we have shown an induction of HO-1 in isolated human lymphocytes after a single HBO exposure and protection of these cells against DNA damage by subsequent oxidative stress. In contrast, V79 Chinese hamster cells showed neither a comparable adaptive protection nor an induction of HO-1 after HBO exposure, which makes this cell line an attractive model system for a further characterization of HO-1-mediated protection. In the present study, we investigated whether overexpression of HO-1 renders V79 cells more resistant to DNA damage induced by HBO. Transient transfection of V79 cells with a full-length human HO-1 cDNA resulted in a 2-3-fold increase in HO-1 protein levels. Comet assay experiments with and without FPG posttreatment for the determination of oxidative DNA base damage showed that HO-1 overexpressing V79 cells were significantly protected against oxidative DNA damage induced by a single HBO exposure. Furthermore, HO-1-transfected cells exhibited a clearly reduced induction of micronuclei after HBO treatment. Since the observed protective effects were abolished by cotreatment with the HO-1 inhibitor tin-mesoporphyrin, our study suggests that a low-level overexpression of HO-1 provides protection against oxidative DNA damage induced by HBO.