Adenoviral vector-mediated transfer of human heme oxygenase in rats decreases renal heme-dependent arachidonic acid epoxygenase activity

Intravenous administration of an adenovirus human heme oxygenase (HO)-1 gen e construct to rats resulted in functional expression of human HO-1 in brai n, heart, lung, liver, and kidney. Because accurate assessment of human HO- 1 mRNA in various tissues by Northern analysis is not sufficiently sensitiv e, we developed a method for quantifying human HO-1 mRNA copies with quanti tative reverse transcription-polymerase chain reaction techniques; this all owed us to use the same primers for both the sample and internal standard. Administration of the adenovirus human HO-1 gene resulted in the detection of human HO-1 mRNA in various tissues with the highest levels seen in the k idney followed, in order, by lung. liver. brain. heart. Human HO-1 was dete ctable for up to 4 weeks in all tissues studied. Administration of adenovir us human HO-1 resulted in maximal increase of HO activity after 1 to 2 week s in rats. The increase in HO activity due to gene transfer also was associ ated with a parallel decrease (similar to 25%) in cytochrome P-450 (CYP) co ntent and in CYP-dependant arachidonic acid metabolism. In addition, we inv estigated the possibility that the human HO-1 gene altered the expression o f the endogenous rat enzyme after administration of cobalt chloride s.c.. C obalt chloride administration resulted in increased HO activity in all tiss ues examined in rats transduced with the human HO-1 gene to the same degree as in nontransduced rats. The metal was a more potent inducer of renal HO activity than was the adenoviral-mediated human HO-1 vector. The increase i n HO activity after adenoviral-mediated human HO-1 transfer was associated with a decrease in microsomal heme-CYP and CYP activity. The increase in HO -1 activity after adenovirus-mediated human HO-1 gene transfer may prove us eful as a means of selectively increasing enzyme activity in a specific org an and regulating homeostasis by modulation of vasoactive molecules such as carbon monoxide and bilirubin and, in addition, providing a means of deliv ering the human HO-1 gene for experimental purposes.