P0916OLIVE LEAF EXTRACT IMPROVES RENAL ANTIOXIDANT DEFENSE WITHOUT ALTERING THE HEME OXYGENASE-1/BILIVERDIN REDUCTASE PATHWAY IN HYPERTENSIVE RATS WITH FOCAL SEGMENTAL GLOMERULOSCLEROSIS

Abstract

Abstract Background and Aims Oxidative stress is implicated in the pathophysiology of chronic kidney disease. Previously, we showed that adriamycin (anticancer agent, enhances reactive oxygen species production) induced focal segmental glomerular sclerosis (FSGS) with massive proteinuria in spontaneously hypertensive rats (SHR). The heme oxygenase (HO) system plays an important role in regulating oxidative stress and is protective in chronic kidney disease. HO-1 is a cytoprotective enzyme that catalyzes the conversion of highly reactive free heme molecules into biliverdin, carbon monoxide, and iron. Biliverdin is subsequently converted to bilirubin by biliverdin reductase and has potent antioxidant effect. Olive leaf extract (OLE, Olea europaea L.) is rich in phenolic compounds that are known to possess powerful antioxidant properties. Here, we aimed to investigate the effects of OLE, focusing on its modulatory role on oxidative stress and HO-1/BVR pathway in the kidney of SHR with adriamycin-induced FSGS. Method Adult females SHR were divided into three groups. Control rats received vehicle. Two other groups, FSGS and FSGS+OLE, received adriamycin (2 mg/kg body weight i.v.) twice in 3-week-interval. After the second injection, FSGS+OLE group received OLE (80 mg/kg/day) by gavage for 6 weeks. Mean blood pressure (MAP), urine albumin-to-creatinine (Ualb/cr), renal HO-1 and biliverdin reductase protein expressions (Western Blot), protein carbonyl content (PCOs), and antioxidant capacity (ABTS) were analyzed. Results In FSGS group albuminuria was significantly increased in comparison to the level in control. Chronic consumption of OLE markedly, but not significantly decreased Ualb/cr compared to that in control. Analysis of renal PCOs revealed that significant enhancement of protein oxidation in the kidney of model group was reduced after OLE treatment to the level as in control. The ABTS level in kidney homogenates significantly decreased in FSGS group in comparison to the level in control. OLE significantly increased renal antioxidant capacity in FSGS+OLE group compared to that in model group. Western blot analysis of HO-1, and biliverdin reductase in the kidney revealed that protein expressions of both enzymes were significantly decreased in FSGS group compared to that in control. Following OLE treatment in FSGS+OLE group protein expressions of HO-1, and biliverdin reductase remained at similar level as in model group. No change in MAP values were observed between control and model groups. OLE significantly decreased MAP in FSGS+OLE group in comparison to the value of model group, and nearly significant reduction of MAP compared to the value of control. Conclusion Collectively, our results showed that OLE expressed its antioxidant property and improved oxidative status in the kidney of SHR with ADR-induced FSGS, independently of the HO-1/BVR pathway.