Gastric mucosal defensive factors: the therapeutic strategy

Cell proliferation in ventromedial hypothalamic lesioned rats inhibits acute gastric mucosal lesions

AIM

The role of mucosal layer thickness on prevention of acute gastric mucosal lesions (AGMLs) was examined in ventromedial hypothalamic (VMH)-lesioned rats.

MATERIALS AND METHODS

The incidence of AGMLs after 48-h fasting and 60% ethanol injection into the stomach after 24-h fasting, aggressive factors (gastric acid and serum gastrin) and defensive factors [hexosamine, gastric mucosal blood flow (GMBF), serum thiobarbituric acid reacting substances (TBARS), and thickness of the gastric mucosal layer] were evaluated in VMH-lesioned rats. The effects of cell proliferation on the gastric mucosal layer of these rats were evaluated by H-E staining and immunostaining with proliferating cell nuclear antigen (PCNA).

RESULTS

After 48-h fasting, no AGMLs were observed in VMH-lesioned and sham VMH-lesioned rats (controls). With 60% ethanol administration after 24-h fasting, the numbers of AGMLs were similar in the two groups, but the ulcer index, a marker of ulcer formation, was lower in VMH-lesioned rats compared to that in sham VMH-lesioned rats. VMH-lesioned rats showed increased gastric acid secretion and serum gastrin compared to sham VMH-lesioned rats, indicating an increase in aggressive factors in VMH-lesioned rats. The two groups had similar levels of gastric mucosal hexosamine, GMBF, and gastric mucosal TBARS, but VMH-lesioned rats had an increased thickness of the mucosal cell layer, indicating an increase in defensive factors in these rats. Histologically, VMH-lesioned rats had an increased total mucosal cell layer, especially for the surface epithelial cell layer, and an increased PCNA-labeling index, a marker of cell proliferation, especially in the proliferative zones of gastric mucosa, indicating increased cell proliferation in the proliferative zone of the gastric mucosa.

CONCLUSION

VMH-lesioned rats are resistant to AGML formation due to increased cell proliferation in gastric mucosa through elevating the levels of defensive factors over those of aggressive factors.

Effects of gastric vagotomy on visceral cell proliferation induced by ventromedial hypothalamic lesions: role of vagal hyperactivity

In rats, ventromedial hypothalamic (VMH) lesions induce cell proliferation in the visceral organs (stomach, small intestine, liver, and pancreas) due to hyperactivity of the vagus nerve. To investigate the effects of selective gastric vagotomy on VMH lesion-induced cell proliferation and secretion of gastric acid, we assessed the mitotic index (the number of proliferating cell nuclear antigen (PCNA)-immunopositive cells per 1,000 cells in the gastric mucosal cell layer) and measured the volume of secreted basal gastric acid. Furthermore, to explore whether or not ethanol-induced acute gastric mucosal lesions (AGML) lead to ulcer formation in VMH-lesioned rats, we assessed the ulcer index of both sham-operated and VMH-lesioned rats after administration of ethanol. VMH lesions resulted in an increased mitotic index and thickness of the gastric mucosal cell layer and gave rise to the hypersecretion of gastric acid. Selective gastric vagotomy restored these parameters to normal without affecting cell proliferation in other visceral organs. Ethanol-induced AGML caused ulcers in sham VMH-lesioned rats, whereas VMH-lesioned rats were less likely to exhibit such ulcers. These results suggest that VMH lesion-induced vagally mediated cell proliferation in the visceral organs is associated with hyperfunction in these organs, and VMH lesion-induced resistance to ethanol may be due to thickening of the gastric mucosal cell layer resulting from cell proliferation in the gastric mucosa-this in turn is due to hyperactivity of the vagus nerve.

Expression of HSP72 in the gastric mucosa is regulated by gastric acid in rats-correlation of HSP72 expression with mucosal protection

BACKGROUND AND AIM

The real mechanism of adaptive cytoprotection in the gastric mucosa is not well established. In the present study, we investigated the effect of acid suppressing agents on a 72-kDa heat shock protein (HSP72) expression, which is known as endogenous cytoprotective factor, in the gastric mucosa. Also, the association of gastric mucosal protective function against HCl-challenge was compared between HSP72-induced and -reduced group.

MATERIALS AND METHODS

Expression of HSP72 was measured by Western blotting in the gastric mucosa before and after administration of famotidine or omeprazole. The gastric mucosal protective function against 0.6 N HCl was compared between control group and HSP72-reduced group. Also, the effect of increased expression of gastric HSP72 by additional administration of zinc sulfate or zinc L-carnosine, which is known as HSP72-inducer, on mucosal protective function was studied.

RESULTS

HSP72 expression in the gastric mucosa was reduced by acid suppressing agents. The lowest expression level of HSP72 was observed 12 h (famotidine, H2-receptor antagonist) or 48 h (omeprazole, proton pump inhibitor) after administration. The gastric mucosal protective ability against 0.6 N HCl was also reduced when HSP72 expression was decreased by famotidine or omeprazole. This phenomenon was reversed by HSP72 induction by additional administration of zinc derivatives.

CONCLUSION

Our results might indicate that the expression of HSP72 in the gastric mucosa is physiologically regulated by gastric acid, and that HSP72 induction could be important in view of mucosal protection especially when HSP72 expression is reduced by administration of acid suppressing agents such as proton pump inhibitor or H2 receptor antagonist.