Gastric tissue selenium levels in healthy persons, cancer and non-cancer patients with different kinds of mucosal damage

Mechanistic research: Selenium regulates virulence factors, reducing adhesion ability and inflammatory damage of Helicobacter pylori

BACKGROUND

The pathogenicity of Helicobacter pylori is dependent on factors including the environment and the host. Although selenium is closely related to pathogenicity as an environmental factor, the specific correlation between them remains unclear.

AIM

To investigate how selenium acts on virulence factors and reduces their toxicity.

METHODS

H. pylori strains were induced by sodium selenite. The expression of cytotoxin-associated protein A (CagA) and vacuolating cytotoxin gene A (VacA) was determined by quantitative PCR and Western blotting. Transcriptomics was used to analyze CagA, CagM, CagE, Cag1, Cag3, and CagT. C57BL/6A mice were infected with the attenuated strains subjected to sodium selenite induction, and H. pylori colonization, inflammatory reactions, and the cell adhesion ability of H. pylori were assessed.

RESULTS

CagA and VacA expression was upregulated at first and then downregulated in the H. pylori strains after sodium selenite treatment. Their expression was significantly and steadily downregulated after the 5th cycle (10 d). Transcriptome analysis revealed that sodium selenite altered the levels affect H. pylori virulence factors such as CagA, CagM, CagE, Cag1, Cag3, and CagT. Of these factors, CagM and CagE expression was continuously downregulated and further downregulated after 2 h of induction with sodium selenite. Moreover, CagT expression was upregulated before the 3rd cycle (6 d) and significantly downregulated after the 5th cycle. Cag1 and Cag3 expression was upregulated and downregulated, respectively, but no significant change was observed by the 5th cycle. C57BL/6A mice were infected with the attenuated strains subjected to sodium selenite induction. The extent of H. pylori colonization in the stomach increased; however, sodium selenite also induced a mild inflammatory reaction in the gastric mucosa of H. pylori-infected mice, and the cell adhesion ability of H. pylori was significantly weakened.

CONCLUSION

These results demonstrate that H. pylori displayed virulence attenuation after the 10th d of sodium selenite treatment. Sodium selenite is a low toxicity compound with strong stability that can reduce the cell adhesion ability of H. pylori, thus mitigating the inflammatory damage to the gastric mucosa.

Modulation of protein tyrosine phosphorylation in gastric mucosa during re-epithelization processes

AIM: To investigate the role of protein tyrosine phosphorylation in gastric wound formation and repair following ulceration.

METHODS: Gastric lesions were induced in rats using restraint cold stress. To investigate the effect of oxidative and nitrosative cell stress on tyrosine phosphorylation during wound repair, total activity of protein tyrosine kinase (PTK), protein tyrosine phosphatase (PTP), antioxidant enzymes, nitric oxide synthase (NOS), 2’,5’-oligoadenylate synthetase, hydroxyl radical and zinc levels were assayed in parallel.

RESULTS: Ulcer provocation induced an immediate decrease in tyrosine kinase (40% in plasma membranes and 56% in cytosol, P < 0.05) and phosphatase activity (threefold in plasma membranes and 3.3-fold in cytosol), followed by 2.3-2.4-fold decrease (P < 0.05) in protein phosphotyrosine content in the gastric mucosa. Ulceration induced no immediate change in superoxide dismutase (SOD) activity, 30% increase (P < 0.05) in catalase activity, 2.3-fold inhibition (P < 0.05) of glutathione peroxidase, 3.3-fold increase (P < 0.05) in hydroxyl radical content, and 2.3-fold decrease (P < 0.05) in zinc level in gastric mucosa. NOS activity was three times higher in gastric mucosa cells after cold stress. Following ulceration, PTK activity increased in plasma membranes and reached a maximum on day 4 after stress (twofold increase, P < 0.05), but remained inhibited (1.6-3-fold decrease on days 3, 4 and 5, P < 0.05) in the cytosol. Tyrosine phosphatases remained inhibited both in membranes and cytosol (1.5-2.4-fold, P < 0.05). NOS activity remained increased on days 1, 2 and 3 (3.8-, 2.6-, 2.2-fold, respectively, P < 0.05). Activity of SOD increased 1.6 times (P < 0.05) days 4 and 5 after stress. Catalase activity normalized after day 2. Glutathione peroxidase activity and zinc level decreased (3.3- and 2-fold, respectively, P < 0.05) on the last day. Activity of 2’,5’-oligoadenylate synthethase increased 2.8-fold (P < 0.05) at the beginning, and 1.6-2.3-fold (P < 0.05) during ulcer recuperation, and normalized on day 5, consistent with slowing of inflammation processes.

CONCLUSION: These studies show diverse changes in total tyrosine kinase activity in gastric mucosa during the recovery process. Oxidative and nitrosative stress during lesion formation might lead to the observed reduction in tyrosine phosphorylation during ulceration.

Selenium in serum and neoplastic tissue in breast cancer: correlation with CEA

Trace element selenium (Se) is regarded to be a breast cancer preventive factor involved in multiple protective pathways. In all, 80 women with breast cancer who underwent a radical mastectomy were enrolled in the study. Serum Se and carcinoembryonic antigen levels were measured using a fluorometric and IRMA assay, respectively. Se tissue concentration was determined by a tissue extracting fluorometric assay. For statistical analysis purposes t-test was used and P-values <0.001 were regarded as statistically significant. Serum Se was 42.5±7.5 μg l⁻¹ in breast cancer patients and 67.6±5.36 μg l⁻¹ in the age-matched control group of healthy individuals. Serum carcinoembryonic antigen in patients was 10±1.7 U ml⁻¹ (normal <2.5 U ml⁻¹ in nonsmokers/<3.5 U ml⁻¹ in smokers). A statistically significant difference was found for both serum Se and CEA between two groups studied (P<0.001). Neoplastic tissue Se concentration was 2660±210 mg g⁻¹ tissue; its concentration in the adjacent non-neoplastic tissue was 680±110 mg g⁻¹ tissue (P<0.001). An inverse relationship between Se and CEA serum levels was found in the two groups studied (r=−0.794). There was no correlation between serum/tissue Se concentration and stage of the disease. The decrease in serum Se concentration as well as its increased concentration in the neoplastic breast tissue is of great significance. These alterations may reflect part of the defence mechanisms against the carcinogenetic process.

Severe gastritis in the Peruvian Andes

OBJECTIVE

To compare the Helicobacter pylori-associated pathology in gastric biopsies taken from patients living at sea level with those taken from patients living at high altitude.

METHODS AND RESULTS

We included 38 patients from a hospital in the Andean city of La Oroya, Peru, located at 3700 m in altitude, and 40 control patients taken from Comas Clinic located in the city of Lima at sea level. Fibrepanendoscopy and multiple biopsies were performed in all the patients followed by histopathological examination. In the antrum, patients from the Andean town had a higher prevalence of glandular lymphoid adherence lesions, active germinal centres, moderate to severe chronic atrophic gastritis, intestinal metaplasia and moderate to severe total deep gland loss, than did patients from the coastal town. Furthermore, the severity of the histological lesions seen in the gastric body and cardia was significantly greater in the high-altitude patients than in those from sea level.

CONCLUSION

This study suggests that the severity of H. pylori-associated gastric lesions seen on histopathological examination is greater in patients living at high altitude, the cause of which is most probably multifactorial but nonetheless principally altitude related.

Plasma and gastric tissue selenium levels in patients with Helicobacter pylori infection

GOALS

We investigated plasma and gastric mucosal selenium levels in patients with Helicobacter pylori (HP)-associated histopathologic findings in their gastric antral mucosa.

STUDY

Before and after a successful HP eradication therapy, we quantitated the plasma and antral selenium levels in patients with HP-associated chronic antral gastritis using atomic absorption flame emission spectrometry. The same measurements were done in patients with dyspeptic complaints who had normal antral histology and negative urease test.

RESULTS

Thirty-four patients were studied, of whom 24 had HP-associated chronic antral gastritis confirmed by histology and positive urease test; the control group included 10 healthy patients. There was no difference between the groups with regard to age, gender, and number of smokers. All patients with HP infection were diagnosed with diffuse antral gastritis. Histopathology showed that 11 (49%) had some degree of atrophy. Of the 11 patients, 7 were classified as having chronic atrophic gastritis (CAG) without intestinal metaplasia (IM), 4 had IM, and none had dysplasia. The plasma concentrations of selenium were found to be very similar in controls and HP-infected subjects (68.0 +/- 25.97 microg/L and 71 +/- 32.9 microg/L, respectively; p > 0.05). The antral biopsy samples of the patients with HP-associated gastritis contained significantly higher levels of tissue selenium than the controls (20.17 +/- 19.74 microg/g and 2.83 +/- 1.42 microg/g, respectively; p < 0.05). Also, it was shown that antral tissue selenium levels decrease after successful HP eradication therapy (20.17 +/- 19.4 microg/g and 7.4 +/- 4.56 microg/g, respectively; t < 0.05). The patients with HP gastritis were assigned to mild, moderate, and severe gastritis groups, according to the histopathologic degree of inflammation present. The antral gastric selenium levels were significantly higher in patients with moderate and severe HP gastritis (21.13 +/- 22.5 microg/g and 22.81 +/- 17.35 microg/g, respectively) than in patients with mild gastric inflammation (9.53 +/- 10.3 microg/g; p < 0.05). The selenium concentrations in the biopsies of patients with CAG were significantly lower than in those with HP gastritis who did not have CAG (9.45 +/- 6.44 microg/g vs. 19.13 +/- 22.48 microg/g, respectively; p < 0.05).

CONCLUSIONS

Selenium accumulates in gastric tissue when it is needed, as is the case in HP-related antral inflammation. This reactive increase in gastric mucosal selenium seems to disappear in the presence of precancerous gastric lesions in the setting of HP-associated gastritis.

Serum and tissue selenium contents related to renal disease and colon cancer as determined by electrothermal atomic absorption spectrometry

Microwave digestion with nitric acid and hydrogen peroxide was applied to the determination of selenium in biological tissues by Electrothermal Atomic Absorption Spectrometry (ETAAS). Validation of this method is presented in terms of adequate recovery of selenium from standard reference materials and the method is applied to carcinogen human colon tissue. Ultramicrofiltration was used to study selenium protein binding and its fractionation and speciation in blood serum. These studies showed that 95% of the total selenium in serum seems to be bonded to high-molecular-weight proteins. Experiments with renal failure patients showed lower selenium levels than in the health population (0.57 +/- 0.23 mM versus 0.81 +/- 0.11 mM). A wider distribution pattern of total serum selenium concentration (from 0.1 to 1 mM) was clearly observed in renal failure patients. However, the ultramicrofiltrable selenium fraction was always constant, even in the presence of desferrioxamine (DFO).