Retrovirus-mediated HO gene transfer into endothelial cells protects against oxidant-induced injury

Heme oxygenase (HO)-1 is a stress protein that has been implicated in defen se mechanisms against agents that may induce oxidative injury, such as endo toxins, heme, and cytokines. Overexpression of HO-1 in cells might, therefo re, protect against oxidative stress produced by certain agents, specifical ly heme, by catalyzing its degradation to bilirubin, which by itself has an tioxidant properties. We report for the first time the successful transduct ion of human HO-1 gene into rat lung microvessel endothelium using replicat ion-defective retroviral vector. Cells transduced with human HO-1 gene exhi bited a 2.1-fold increase in HO-1 protein level, which was associated with a 2.3-fold elevation in enzyme activity compared with that in nontransduced cells. The cGMP content in transduced endothelial cells was increased by 2 .9-fold relative to that in nontransduced cells. Moreover, human HO-1 gene- transduced endothelial cells acquired substantial resistance to toxicity pr oduced by exposure to heme and H2O2 compared with that in nontransduced cel ls. The protective effect of enhancement of HO-1 activity against heme and H2O2 was reversed by pretreatment with stannic mesoporphyrin, a competitive inhibitor of HO. These data demonstrate that the induction of HO-1 in resp onse to injurious stimuli represents an important mechanism for moderating the severity of cell damage. Regulation of HO activity in this manner may h ave clinical applications.