Effect of N-Methyl-N-Nitrosourea on Helicobacter-induced Gastric Carcinogenesis in C57BL/6 Mice

Effects of Helicobacter pylori and Moluodan on the Wnt/β-catenin signaling pathway in mice with precancerous gastric cancer lesions

BACKGROUND

Helicobacter pylori (H. pylori) is the primary risk factor for gastric cancer (GC), the Wnt/β-Catenin signaling pathway is closely linked to tumourigenesis. GC has a high mortality rate and treatment cost, and there are no drugs to prevent the progression of gastric precancerous lesions to GC. Therefore, it is necessary to find a novel drug that is inexpensive and preventive to against GC.

AIM

To explore the effects of H. pylori and Moluodan on the Wnt/β-Catenin signaling pathway and precancerous lesions of GC (PLGC).

METHODS

Mice were divided into the control, N-methyl-N-nitrosourea (MNU), H. pylori + MNU, and Moluodan groups. We first created an H. pylori infection model in the H. pylori + MNU and Moluodan groups. A PLGC model was created in the remaining three groups except for the control group. Moluodan was fed to mice in the Moloudan group ad libitum. The general condition of mice were observed during the whole experiment period. Gastric tissues of mice were grossly and microscopically examined. Through quantitative real-time PCR (qRT-PCR) and Western blotting analysis, the expression of relevant genes were detected.

RESULTS

Mice in the H. pylori + MNU group showed the worst performance in general condition, gastric tissue visual and microscopic observation, followed by the MNU group, Moluodan group and the control group. QRT-PCR and Western blotting analysis were used to detect the expression of relevant genes, the results showed that the H. pylori + MNU group had the highest expression, followed by the MNU group, Moluodan group and the control group.

CONCLUSION

H. pylori can activate the Wnt/β-catenin signaling pathway, thereby facilitating the development and progression of PLGC. Moluodan suppressed the activation of the Wnt/β-catenin signaling pathway, thereby decreasing the progression of PLGC.

Protective Effect of Salvianolic Acid A against N-Methyl-N-Nitrosourea-Induced Retinal Degeneration

Objective

Retinal degeneration (RD) is a serious, irreversible, and blinding eye disease, which seriously affects the visual function and quality of life of patients. At present, there is no effective method to treat RD. The final outcome of its development is photoreceptor cell oxidation and apoptosis. Therefore, looking for safe, convenient, and effective antioxidant therapy is still the key research field of Rd. In this study, the mice model of RD was induced by N-methyl-N-nitrosourea (MNU) in vivo to explore the therapeutic effect and mechanism of salvianolic acids (Sal A) on RD. In vitro, the protective effect of Sal A on MNU injured 661 W cell line of mouse retina photoreceptor cone cells was investigated preliminarily.

Methods

Male C57BL/6 mice (7–8 weeks old) received a single intraperitoneal injection (ip) of 60 mg/kg MNU or vehicle control. Treatment groups then received Sal-A 0.5 mg/kg and 1.0 mg/kg via daily intravenous injections. On day 7, functional and morphological examinations were performed, including photopic and scotopic electroretinography (ERG) and hematological analyses to observe functional changes and damage to the outer nuclear layer (ONL). On the 3rd and 7th days, the levels of superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were determined. The expression of retinal Bax, Bcl-2, and caspase-3 was quantified by Western blot and RT-PCR assays. 661 W strain of mice retinal photoreceptor cone cells were cultured in vitro and treated with 1 µm MNU. The cells in the treatment group were given 50 μM Sal A as an intervention. The growth of 661 W cells was observed and recorded under an inverted light microscope, and the activity of cells was detected by the MTT method.

Results

Sal A treatment was effective against MNU-induced RD in mice at both 0.5 mg/kg/d and 1.0 mg/kg/d doses, and the protective effect was dose-dependent. Sal A can alleviate MNU-mediated alterations to retinal ERG activity and can support maintenance of the thickness of the ONL layer. Sal A treatment increases the expression of retinal SOD and reduces the lipid peroxidation product MDA, suggesting that its protective effect is related to the oxidation resistance. It can offset changes to the expression of apoptotic factors in the retina caused by MNU treatment. Sal A mitigates MNU-mediated damage to cultured mice photoreceptor cone cells 661 W in vitro.

Conclusion

Sal A alleviates the damage caused by MNU to retinal photoreceptor cells in vivo and in vivo, and its protective effect is related to its antioxidant and antiapoptotic activities.

Gastric Leptin and Tumorigenesis: Beyond Obesity

Leptin, an adipocyte-derived hormone and its receptor (ObR) expressed in the hypothalamus are well known as an essential regulator of appetite and energy expenditure. Obesity induces abundant leptin production, however, reduced sensitivity to leptin leads to the development of metabolic disorders, so called leptin resistance. The stomach has been identified as an organ that simultaneously expresses leptin and ObR. Accumulating evidence has shown gastric leptin to perform diverse functions, such as those in nutrient absorption and carcinogenesis in the gastrointestinal system, independent of its well-known role in appetite regulation and obesity. Overexpression of leptin and phosphorylated ObR is implicated in gastric cancer in humans and in murine model, and diet-induced obesity causes precancerous lesions in the stomach in mice. While the underlying pathomechanisms remain unclear, leptin signaling can affect gastric mucosal milieu. In this review, we focus on the significant role of the gastric leptin signaling in neoplasia and tumorigenesis in stomach in the context of hereditary and diet-induced obesity.

Preventive effect of Oenothera rosea on N-methyl-N-nitrosourea-(NMU) induced gastric cancer in rats

Background

Currently, gastric cancer (GC) is considered a public health problem worldwide. Using medicinal plants for the prevention of chronic diseases such as cancer constitutes new alternatives in traditional medicine. Oenothera rosea (OR) could be an option, but it needs to be evaluated.

Aim

The main objective of this study was to evaluate the protective effect of OR extract on N-methyl-N-nitrosourea (NMU)-induced GC in rats.

Methods

In total, 80 male Holtzman rats were randomized into five groups. Group A received the saline solution (5mL/kg), group B received NMU 500 μg/kg (cancer inductor) by oral administration for 16 weeks, and groups C, D, and E were treated with OR extract (100, 200, and 300 mg/kg, respectively) and NMU in order to evaluate the preventive effect on cancer induced by NMU for 16 weeks. Blood and histological samples of stomachs were collected to determine histopathological, biochemical, and hematological parameters between different experimental groups.

Results

Groups C, D, and E presented less histopathological changes such as anaplastic and hyperplastic cells, compared with group B. Hematological and biochemical parameters were recorded, and superoxide dismutase, malondialdehyde, and nitric oxide levels were statistically less than those of NMU group (P<0.05, P<0.01, and P<0.01).

Conclusion

Considering the histopathological signs and the antioxidant activity in vivo as well as hematological and biochemical parameters of ethanolic extract of OR, we concluded that its administration in rats has a protective effect on GC, which is induced experimentally. This species could be studied in clinical trials for patients with GC in the future.