We developed a retrovirus-mediated human heme oxygenase-1 (HO-1) gene expression system and assessed the impact of heme on the inducibility of the HO-1 gene in rat lung microvessel (RLMV) endothelial cells and in newborn Sprague-Dawley (SD) rats. Overexpression of the HO-1 gene driven by HO-1 promoter (HOP) resulted in an increase in HO-1 protein and HO activity by 4.8- and 1.3-fold, respectively, compared to the viral LTR promoter. The increased HO-1 gene expression was associated with the enhancement of CO production. In cells transduced by HOP-driven HO-1 gene, there was a decrease in basal cyclooxygenase (COX) activity as measured by PGE(2). The degree of HO-1 expression and, consequently, the levels of cellular heme were directly related to COX activity. Supplementation with heme markedly increased PGE(2) and cGMP synthesis. In all (6/6) of newborn SD rats injected with retrovirus LSN-HOP-HO-1, both HO-1 and neo(r) transcripts were expressed in tissues. We hypothesize that degree of HO-1 gene expression resulted in a differential rate of cellular heme-dependent enzyme gene expression, which may play a vital role in maintaining cellular homeostasis.
Copyright 2002 Wiley-Liss, Inc.