Renal protection in chronic kidney disease: hypoxia-inducible factor activation vs. angiotensin II blockade

Abstract

The 5/6thnephrectomy or ablation/infarction (A/I) preparation has been used as a classic model of chronic kidney disease (CKD). We observed increased kidney oxygen consumption (QO2) and altered renal hemodynamics in the A/I kidney that were normalized after combined angiotensin II (ANG II) blockade. Studies suggest hypoxia inducible factor as a protective influence in A/I. We induced hypoxia-inducible factor (HIF) and HIF target proteins by two different methods, cobalt chloride (CoCl2) and dimethyloxalyglycine (DMOG), for the first week after creation of A/I and compared the metabolic and renal hemodynamic outcomes to combined ANG II blockade. We also examined the HIF target proteins expressed by using Western blots and real-time PCR. Treatment with DMOG, CoCl2, and ANG II blockade normalized kidney oxygen consumption factored by Na reabsorption and increased both renal blood flow and glomerular filtration rate. At 1 wk, CoCl2and DMOG increased kidney expression of HIF by Western blot. In the untreated A/I kidney, VEGF, heme oxygenase-1, and GLUT1 were all modestly increased. Both ANG II blockade and CoCl2therapy increased VEGF and GLUT1 but the cobalt markedly so. ANG II blockade decreased heme oxygenase-1 expression while CoCl2increased it. By real-time PCR, erythropoietin and GLUT1 were only increased by CoCl2therapy. Cell proliferation was modestly increased by ANG II blockade but markedly after cobalt therapy. Metabolic and hemodynamic abnormalities were corrected equally by ANG II blockade and HIF therapies. However, the molecular patterns differed significantly between ANG II blockade and cobalt therapy. HIF induction may prove to be protective in this model of CKD.