Protective Effects of Dioscorea batatas Flesh and Peel Extracts against Ethanol-Induced Gastric Ulcer in Mice

Abstract

Gastric ulcer is a major digestive disorder and provoked by multifactorial etiologies, including excessive alcohol consumption. In this study, we examined the gastroprotective effect of aqueous and ethanolic extracts of Dioscorea batatas Decne (DBD; commonly called Chinese yam) flesh or peel against acidified ethanol-induced acute gastric damage in mice. Our findings demonstrated that oral supplementation of aqueous or ethanolic extracts of DBD flesh or peel before ulcer induction was significantly effective in macroscopically and histologically alleviating ethanol-induced pathological lesions in gastric mucosa, decreasing the plasma levels of inflammatory mediators, such as nitric oxide and interleukin-6, attenuating the gastric expression of cyclooxygenase-2, and increasing the gastric content of prostaglandin E₂. In particular, pretreatment with the flesh extract prepared in 60% ethanol prominently decreased the expression of biomarkers of oxidative stress, including the plasma levels of 8-hydroxy-2-guanosine and malondialdehyde, and restored heme oxygenase-1 expression and superoxide dismutase activity in the stomach. Overall, these findings suggest that the oral supplementation with DBD extract, especially flesh ethanol extract, prior to excessive alcohol consumption, may exert a protective effect against ethanol-induced gastric mucosal damage in vivo, presumably through the activation of the antioxidant system and suppression of the inflammatory response.

Keywords: Dioscorea batatas Decne; antioxidant; ethanol-induced damage; gastric ulcer; inflammation.

Figure 1

Dioscorea batatas Decne (DBD) flesh and peel extracts improved the macroscopic morphology of gastric damage induced by HCl/ethanol in mice. ICR mice were randomly assigned to 15 different groups (8 mice per group). The water or ethanol extracts of flesh or peel were orally and singly administered, at a designated dose, 3 h prior to an intragastric infusion of ethanol, to induce acute gastric ulceration. After 1 h, mice were sacrificed. (A) Representative photos of the dissected stomach. (B) Score for macroscopic gastric damage. The data obtained from individual animal samples per group were averaged (n = 8); values represent mean ± standard deviation (SD). OMEP, omeprazole used as a positive control. WE, water extract; EE-60, ethanol extract in 60% ethanol; EE-95, ethanol extract in 95% ethanol. Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).

Figure 2

DBD flesh and peel extracts alleviated HCl/ethanol-induced gastric epithelial damage. The dissected stomach tissue was fixed in formalin solution, embedded in paraffin, sectioned using a microtome, and stained with hematoxylin and eosin (H&E) for histological analysis. (A) Representative photomicrographs of gastric mucosal surface (magnification, 40×). (B) Score for gastric mucosal damage. Values represent mean ± SD (n = 8). OMEP, omeprazole used as a positive control. WE, water extract; EE-60, ethanol extract in 60% ethanol; EE-95, ethanol extract in 95% ethanol. Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).

Figure 3

DBD flesh and peel extracts reduced HCl/ethanol-induced oxidative stress. The levels of 8-OHdG in the serum (A) and malondialdehyde (MDA) in the stomach homogenate (B) were elevated by ulcer induction and lowered by pretreatment with the extracts. Values represent mean ± SD (n = 8). Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).

Figure 4

Effect of pretreatment with DBD flesh and peel extracts on catalase (CAT) and superoxide dismutase (SOD) activities in stomach homogenate. (A,B) HCl/ethanol treatment resulted in significant reduction in the activities CAT and SOD. Pretreatment with WE or EE restored the enzyme activities, but not significantly at the 0.05 level. Values represent mean ± SD (n = 8). Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).

Figure 5

DBD flesh and peel extracts decreased HCl/ethanol-induced production of inflammatory factors. The serum samples were collected after sacrificing HCl/ethanol-treated mice. The plasma levels of NO and proinflammatory cytokines (IL-6 and TNFα) were measured by ELISAs. The increased levels of plasma NO (A) and IL-6 (B) by gastric ulcer induction were significantly decreased by pretreatment with both WE and EE. However, TNFα levels (C) in the experimental groups were considerably reduced by pretreatment with flesh or peel EE, but not with WE. Values represent mean ± SD (n = 8). Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).

Figure 6

DBD flesh and peel extracts influenced the expressions of the inflammatory marker COX-2 and the antioxidant enzyme HO-1 in gastric mucosa. Stomach homogenates were used for the analysis of protein expression of COX-2 (A) and HO-1 (B). Both WE and EE of flesh and EE of peel reduced the increased expression of COX-2 in HCl/ethanol-treated stomach. However, HO-1 protein level increased only by pretreatment with flesh extracts; in particular, EE was more potent than WE. Peel extracts showed no significant influence on HO-1 expression. Values represent mean ± SD (n = 8). Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).

Figure 7

DBD flesh and peel extracts increased the HCl/ethanol-lowered level of PGE₂ level in stomach homogenate. The gastric PGE₂ level was prominently decreased by ulcer induction, but the oral administration of the extracts resulted in changes in PGE₂ level. In particular, pretreatment with flesh WE and peel EE-95 significantly restored PGE₂ level. Values represent mean ± SD (n = 8). Bars not sharing common letter represent statistically significant difference from each other (p < 0.05).