The ameliorative effect of Heme Oxygenase System on early Diabetic Nephropathy in Streptozotocin-Induced Diabetic Rats

Background: Diabetic nephropathy (DN) is one of the most common and severe microvascular complications of diabetes mellitus (DM) and the leading cause of end-stage renal disease. Although hemoxygenase (HO) is cytoprotective, the potential renoprotective mechanisms of HO-1 induction remain to be explored. Aim: The aim of this study is to evaluate the possible protective effect of HO induction on streptozotocin (STZ)-induced early DN and various mechanisms underlie this effect in rats. Materials & methods: Single intraperitoneal (i.p.) injection of STZ(60mg/kg) was administered to induce early DN in rats. Four weeks after STZ injection, the diabetic rats were divided into four groups (10 rats each), namely, STZ -diabetic, Hemin treated diabetic, Hemin and chromium-mesoporphyrin (CrMP) treated diabetic and CrMP treated diabetic group. The normal rats were chosen as control group .The diabetic rats received either hemin(15 mg/kg,ip) or CrMP(4 μmol/kg ,ip) alone or combined treatment of both , twice weekly for 4 weeks.DN was assessed, eight weeks of STZ injection, by measuring plasma adiponectin, serum insulin, glucose and creatinine levels, renal hemoxygenase -1(HO-1)concentration , monocyte chemoattractant protein – 1(MCP-1),intercellular adhesion molecule -1(ICAM-1), nuclear factor - Kappa beta(NF-κB), tumor necrosis factor - alpha (TNF-α),hydroxyprolin, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and urinaryalbumin , collagen, creatinine and 8- isoprostane and8- hydroxyguanosine (8-OHDG) levels.Results: Hemin – induced HO upregulation, in STZ -diabetic rats suppressed the hyperglycemiawith increased adiponectin and insulinotropic effect. Correspondingly, hemin reduced themarkers of kidney dysfunction including albuminuria, collagen and creatinine excretion togetherwith reduced serum creatinine level, suggesting improved kidney function. Similarly, hemin,suppressed renal proinflammatory chemokines, MCP-1, ICAM-1with parallel reduction in renalproinflammatory cytokine TNF-α and the inflammatory/oxidative transcription factor, NF-κB, inSTZ-diabetic rats. Moreover hemin therapy was associated with marked reduction in STZinduced elevation in renal fibrotic marker, hydroxyprolin. Furthermore, hemin significantlydecreased the enhanced renal NADPH oxidase with parallel reduction of urinary 8- isoprostaneand 8-OHDG, surrogate urinary markers of oxidative stress. Contrarily, coadministering the HOinhibitor, CrMP with the HO-inducer, hemin nullified the antidiabetic and renoprotective effects,whereas administering CrMP alone abrogated HO level, aggravated hyperglycemia, furtherincreased renal MCP-1, ICAM-1, NF-κB, TNF-α, hydroxyprolin with deterioration of oxidativestress markers and exacerbating renal dysfunction in diabetic animals.CONCLUSION: These findings suggest that the reduction of renal injury in diabetic rats uponinduction of HO-1 was associated with decreased renal oxidative stress, fibrosis andinflammation, implicating the role of HO-1 induction as a future treatment of DN.