OBJECTIVE Heme oxygenase-1 (HO-1) has been implicated in graft protection because its induction is associated with long-surviving allografts. The aim of this study was to analyze the efficacy of adenovirus-mediated HO-1 overexpression to inhibit graft arteriosclerosis and estimate whether the protective role correlated with nuclear factor kappaB (NF=kappaB) expression and grafts apoptosis. METHODS Aortic transplantation was performed using inbred Brown-Norway (BN) rats (RT1n male) as donors and Lewis rats (RT1l male) as recipients. The experiments were divided into four groups: group A, Lewis-Lewis (n=6), no treatment; group B, BN-Lewis (n=6), no treatment; group C, BN-Lewis (n=6), donor aorta perfused with buffer containing 4x10(10) pfu Ad-Null (the noncoding adenoviral vector); and group D, BN-Lewis (n=6), donor aorta perfused with buffer containing 4x10(10) pfu Ad-HO-1 (adenoviral vector coding for HO-1). All grafts were harvested at 60 days after transplantation. Reverse transcriptase polymerase chain reaction was performed to detect the expression of HO-1 gene. Hematoxylin and eosin staining was used to detect the morphology and cytology of the transplanted vessels. Intimal thickening was detected by Masson staining. Immunohistochemistry was used to detect the localization and expression of HO-1 and NF-kappaB and TUNEL assays to detect the apoptosis of the grafts. RESULTS Gene transfer of HO-1 grafts using an adenoviral vector resulted in the expression of HO-1 protein in endothelium and adventitia. We observed that the intimal thickness in Ad-HO-1-treated aortas (11.11+/-0.92 microm) was significantly thinner compared with untreated (85.20+/-6.90 microm) or Ad-null treated (87.20+/-6.20 microm) aortas (P<.01). Immunohistology showed that treatment with Ad-HO-1 resulted in a significant reduction in leukocyte infiltration and a decreased number of vascular smooth muscle cells in the intima, compared with Ad-null-treated aortas. The levels of NF-kappaB and the number of apoptotic cells in Ad-HO-1-treated aortas showed significantly lower compared with Ad-null-treated arotas (P<.05). CONCLUSIONS HO-1 prevented the development of graft arteriosclerosis in the rat aortic transplant model. The protective role of HO-1 in chronic rejection lesions seemed to correlate with downregulation of the expression of NF-kappaB and inhibition of apoptosis in the grafts.