MODULATIION OF GENTAMICIN-AND CISPLATIN-INDUCED NEPHROTOXICITY AND ACUTE RENAL FAILURE BY METHANOLIC EXTRACTS OF SOYABEAN (GLYCINE MAX (L.) MERR.) IN RATS

Abstract

Cisplatin and gentamicin are potent chemotherapeutic agents whose clinical efficacies have been demonstrated in many human malignancies and life-threatening bacterial infections respectively. Nephrotoxicity, however, limits the full clinical utility of these drugs. This study investigated the protective effect of methanolic extract of soybean (MESB) against this adverse effect and the mechanisms for protection. Nephrotoxicity was induced by the administration of gentamicin (80 mg/kg/day subcutaneously for 12 days) and cisplatin (2 mg/kg/day intraperitoneally for 5 days) one-hour after oral administration of 250-1000 mg/kg/day MESB in rats. In vitro, the antioxidant activity of MESB was investigated in the trolox equivalent antioxidant capacity (TEAC) [using 2,2-azinobis[3-ethylbenzothiazoline-6-sulfonate] (ABTS)], ferric reducing antioxidant power (FRAP) and reducing power (RP) assays, as well as in Fe³+/ascorbate- and 2,2,-azobis (2-amidinoproparie) hydrochloride (AAPH)-induced lipid peroxidation (LPO) models. The radical scavenging activity (RSA) of MESB on hydroxyl (OH), superoxide (O₂), nitric oxide (NO) and 1,1-dipheny-2-picrylhydrazyl (DPPH) radicals was also evaluated. MESB was fractionated by column chromatography over silica gel60 and sephadex LH-20. Separated fractions were subjected to thin-layer chromatography. Data were analyzed by ANOVA. Cisplatin-associated increase in Blood Urea Nitrogen (BUN) was significantly (p<0.05) decreased by 49.8%, 59.0%. 21.1% and creatinine by 34.7%. 62.1%, 24.6% following 250, 500 and 1000 mg/kg MESB administration respectively. Elevation in BUN caused by gentamicin was significantly (p<0.05) decreased by 76.5%, 76.6% and creatinine by 78.6%, 77.7% following treatment with 500 and 1000 mg/kg MESB respectively. Doses of MESB at 250, 500 and 1000 mg/kg increased significantly (p<0.05) cisplatin-associated decreases in activities of superoxide dismutase (SOD) by 103.9%, 219.5%, 28.6%, catalase (CAT) by 11.6%, 27.8%, 8.4% and glutathione-s-transferase (GST) by 103.0%, 110.4%, 53.7% respectively. Decrease in glutathione (GSH) level induced by cisplatin also increased significantly (p<0.05) by 184.6% and 161.5% at 500 and 1000mg/kg doses respectively. Also, MESB prevented gentamicin associated decreases in renal activities of Y-glutamyltransferase by 33.8% and 84.7% and aspartate aminotransferase by 11.9% and 13.5%. Furthermore, MESB prevented cisplatin-associated increases in urinary N-acetyl-B-D-glucosaminidase excretion by 37.7%, 49.2%, 14.6%, serum NO production by 35.5%, 36.4%, 33.8%, LPO by 46.4%, 54.6%, 41.6% and activities of myeloperoxidase and xanthine oxidase by 26.8%, 40.6%, 7.4% and 0%, 2.2%, 17.9% respectively in the rats. In vitro, the antioxidant activity of MESB ranged from 24.8±5.6 to 228.0±13.61µmol trolox equivalent in the TEAC assay at 125-500µg and also demonstrated marked RP Fe³+ascorbate- and AAPH-induced LPO were significantly (p<0.001) inhibited by 46.3% and 40.0% at 800µg respectively. MESB exhibited maximum RSA of 24.1% (50µg), 68.2% (50µg), 55.6% (1mg), and 11.6% (50µg) on NO'', O₂, OH and DPPH radicals respectively (p<0.05). Phytochemical analysis revealed the presence of antioxidant phenolics with dihydroxy and trihydroxy groups. Methanolic extract of soybean protected against cisplatin- and gentamicin-associated renal dysfunction and injury probably, by antioxidant, free radical scavenging and anti-inflammatory activities attributable to the presence of phenolic compounds.