Transcriptome-based identification of pro- and antioxidative gene expression in kidney cortex of nitric oxide-depleted rats

Nitric oxide (NO) depletion in rats induces severe endothelial dysfunction within 4 days. Subsequently, hypertension and renal injury develop, which are ameliorated by α-tocopherol (VitE) cotreatment. The hypothesis of the present study was that NO synthase (NOS) inhibition induces a renal cortical antioxidative transcriptional response and invokes prooxidative and proinflammatory gene expression due to elimination of dampening effects of NO and enhanced oxidative stress. Male Sprague-Dawley rats received NOS inhibitor N^ω-nitro-L-arginine (L-NNA, 500 mg/l water) for 4 (4d-LNNA), 21 (21d-LNNA), or 21 days with VitE in chow (0.7 g/kg body wt/day). Renal cortical RNA was applied to oligonucleotide rat arrays. In 4d-LNNA, 21d-LNNA, and 21d-LNNA+VitE, 120, 320, and 184 genes were differentially expressed, respectively. Genes related to glutathione and bilirubin synthesis were suppressed during 4d and 21d-LNNA and not corrected by VitE. Proteinuria, tubulointerstitial macrophages, and heme-oxygenase-1 (HO-1) expression were strongly correlated. Remarkably, pro-oxidative genes were not induced. Inflammation- and injury-related genes, including kidney injury molecule-1 and osteopontin, were unchanged at day 4, induced at 21d, and partly corrected by VitE. Superimposing HO-1 inhibition on NOS inhibition had no impact on the development of hypertension. To summarize, renal expression of genes involved in synthesis of the antioxidants glutathione and bilirubin seemed directly NO dependent, but there were no direct effects of NO depletion on pro-oxidant systems. This indicates that renal transcriptional regulation of two defense systems, glutathione and bilirubin syntheses, seems to depend upon adequate NO synthesis. Interaction between NO synthesis and heme degradation pathways for blood pressure regulation was not found.