Paradoxical effects of a selective cyclooxygenase-2 inhibitor, etodolac, on proliferative changes of forestomach in alloxan-induced diabetic rats

Acetaminophen-Induced Forestomach Lesion in Normal Rats Following Intravenous Exposure

Four groups of ten male and ten female rats each were treated intravenously with saline, 400 mg/kg/day of a commercially available injectable acetaminophen formulation, or 400 mg/kg/day of a new injectable acetaminophen formulation with (aged) or without (fresh) impurities daily for fourteen days. Gross observations of the mucosal surface of the stomachs from treated rats included multifocal to diffuse pale, elevated foci confined to the nonglandular region of the stomach. Treatment-related histologic observations consisted of epithelial hyperplasia and hyperkeratosis of the nonglandular mucosa of the stomach. The epithelial hyperplasia was characterized by a thickened epithelium, frequently accompanied by the development of undulations at the basement membrane zone, resulting in the formation of rete ridgelike structures protruding into the underlying tissue. The submucosa was usually expanded by edema and occasionally contained an infiltrate of neutrophils, eosinophils, and macrophages. The hyperplasia was usually accompanied by hyperkeratosis resulting in thickening of the stratum corneum. The incidence and severity of the gastric changes were similar across all treatment regimens. Although considered clinically irrelevant since humans do not have a forestomach equivalent, these results are significant in that this appears to be the first report of forestomach hyperplasia and hyperkeratosis following intravenous exposure to acetaminophen.

Enhanced tumorigenesis of forestomach tumors induced by N-Methyl-N'-nitro-N-nitrosoguanidine in rats with hypoinsulinemic diabetes

Hyperinsulinemia and hyperglycemia in prediabetic and diabetic patients are thought to increase the risk of developing neoplasms because insulin is a growth factor with pre-eminent metabolic but also mitogenic effects. To determine the effect of hypoinsulinemic diabetic conditions on carcinogenesis, we examined N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced forestomach carcinogenesis in hypoinsulinemic diabetic WBN/Kob rats aged about 45 weeks (DM) compared with non-diabetic younger WBN/Kob rats (C1), non-diabetic Wistar rats age-matched to DM (C2), and non-diabetic Wistar rats age-matched to C1 (C3). All rats were treated with MNNG by gavage and were killed at 40 weeks after dosing. Various-sized tumors were disseminated throughout the forestomach of all rats, and the ratio of the area of tumors to the whole forestomach area was 23.3% in the DM group and was higher than in the C1-3 (4.2-14.3%) groups. The incidence of carcinoma was much higher in the DM group (36.8%) than in the C1-3 (7.1-16.7%) groups, and the incidence of papilloma was also significantly higher in the DM group (84.2%) than in the C1-3 (28.5-50.0%) groups. The average thickness of the squamous epithelium in the non-neoplastic mucosa was significantly greater in the DM group (50.8 mum) than in the C1-3 (29.6-37.9 microm) groups. Immunohistochemically, the Ki-67-positive index in the non-tumorous mucosa of the DM group (42.0%) was significantly higher than that of the C1-3 groups (18.8-33.3%). These results suggest that prolonged hyperglycemic conditions without hyperinsulinemia enhance tumorigenesis of MNNG-induced tumors by enhanced proliferative activity of the squamous epithelium in the rat forestomach.

Effects of the antifungal agent itraconazole on proliferative changes of the forestomach mucosa in alloxan-induced diabetic rats

Alloxan-induced diabetic rats frequently exhibit proliferative lesions of squamous hyperplasia accompanied by chronic inflammation and Candida albicans infection in the forestomach, and some lesions progress to squamous cell carcinoma (SCC). Candida infection causes not only hyperplastic changes with inflammation but might also lead to SCC in human oral mucosa. Thus, the present study was conducted to examine the effects of the antifungal agent itraconazole (ITCZ) on proliferative and inflammatory changes of the forestomach in alloxan-induced diabetic WBN/Kob rats. Diabetes was induced by alloxan at fifteen weeks of age. Rats were allocated to three groups at forty-five weeks of age and were given ITCZ by gavage 0 (vehicle control), 5, and 10 mg/kg/day for four weeks, and they were sacrificed at the sixty-fifth week of age. Mucosal hyperplastic changes were consistently accompanied by inflammation and Candida infections in the 0 mg/kg group. These lesions were reduced by ITCZ (0 mg/kg; 100%, 5 mg/kg; 53.5%, 10 mg/kg; 61.5%). Squamous cell carcinoma was detected in three rats from the 0 mg/kg, but only one rat from the 10 mg/kg dose groups in this study. Itraconazole reduced the degree of mucosal hyperplasia, inflammatory changes, and Candida infection. Therefore, C. albicans infection was an important factor in pathogenesis of mucosal proliferation and inflammation.