Functional expression of human heme oxygenase-1 gene in renal structure of spontaneously hypertensive rats

Heme oxygenase (HO), by catabolizing heme to bile pigments, regulates the levels and activity of cellular hemoprotein and HO activity. We examined the effect of delivery of the human HO-1 gene on cellular heme in renal tissue using a retroviral vector. We used a single intracardiac injection of the concentrated infectious viral particles in 5-day-old spontaneously hypertensive rats; 25 were transduced with empty vector and 25 were transduced with the human HO-1 gene. Functional expression of human and rat HO-1 was measured after 2 and 4 weeks. Reverse transcription polymerase chain reaction showed that human HO-1 mRNA was expressed as early as 2 weeks, with the highest levels in the kidney. Western blot analysis showed distribution of human HO-1 protein in rat kidney structures, predominantly in the thick ascending limb of the loop of Henle as well as in proximal tubules and preglomerular arterioles. These areas also demonstrated higher HO activity as measured by in- creased conversion of heme to bilirubin and carbon monoxide. Functional expression of the human HO-1 gene was associated with a decrease in blood pressure in 4- and 8-week-old spontaneously hypertensive rats. Compared with nontransduced rats, human HO-1 gene overexpression in transduced rats was associated with a 35% decrease in urinary 20-hydroxyeicosatetraenoic acid, a potent vasoconstrictor and an inhibitor of tubular Na+ transport, which may be related to the decrease in blood pressure.