Antioxidant effects of unpolished Sung-Yod sticky rice on prevention of ethylene glycol-induced renal pathology in rats

Abstract

Background : Kidney stone is a chronic disease that is found worldwide. The high prevalence of the kidney stone in Thailand observed in the northeastern part which was about 16.9%. The pathogenesis of calcium oxalate stone formation originated from crystallization of calcium and oxalate ions in renal tubular fluid, overgrowth, aggregation and adhesion to renal epithelial cells. The adhesion of CaOx crystals to renal tubular cell is a critical step of kidney stone formation. It can cause increased oxidative stress and result in the renal tubular cells damage. Studying in natural products may be an alternative way to prevent the pathogenesis of stone formation.

Objective : To study the antioxidant potential of Sung Yod sticky rice extract on the prevention of ethylene glycol-induced renal tissue damage in rats.

Methods Unpolished Sung-Yod sticky rice was extracted. The total anthocyanin and phenolic contents were determined by pH differential method and Follin Ciocalteu reagent assay, respectively. The percentage of antioxidant activity was assessed by DPPH scavenging assay compared with the standard serial concentrations of ascorbic acid. In in vivo experiment, rats were divided into two groups: ethylene glycol control (EGC) group received normal drinking water for two weeks and SY treated group was daily fed SY at the dose of 200 mg/kg by gastric intubation for two weeks. After two weeks, 0.5% ethylene glycol was administered in all groups, and 1% ammonium chloride was fed by gastric intubation for one week.
At the end of the experiment, the kidney tissues were collected for histological study. Oxidative stress, 8 hydroxyguanosine (8-OHG), was determined by immunoperoxidase whereas antioxidant biomarkers including superoxide dismutase (SOD) and catalase were observed by Western immunoblotting.

Results : The mean total anthocyanin and total phenolic compounds were 19.566g/g dry weights and 0.295 mg/g dry weight, respectively. The half maximal inhibitory concentration of the Sung-Yod sticky rice extract was significantly increased at the fifth teen folded compared with ascorbic acid (P < 0.05). Pathological changes of the kidney including tubular dilation, shrinkage of glomerulus and the flattened renal tubular cells in rat were reduced by treatment with Sung Yod sticky rice extract. The number of 8-OHG -positive cells decreased in the SY treated group. The expression of SOD and catalase significantly increased in the SY treated group, as compared with EGC group.

Conclusion These findings demonstrate that the Sung-Yod sticky rice extract has a protective effect on the ethylene glycol-induced renal pathology. This extract might be beneficial in preventing the cause of kidney stone.