Ethnopharmacological relevance

Li-Zhong-Tang (LZT) is a well-known Chinese herbal formulation first described in one of traditional Chinese medicine (TCM) scriptures, Treatise on Febrile Diseases. LZT has been commonly prescribed for the treatment of various gastrointestinal diseases for over 1800 years, and has demonstrated pronounced therapeutic effects on patients with gastric ulcers.

Aim of the study

The present study aimed to scientifically evaluate protective effects of LZT on indomethacin (IND)-induced gastric injury in rats and to elucidate whether LZT exerts its gastro-protective effects via enhancing mucosal immunity by regulating TLR-2/MyD88 signaling pathway.

Material and methods

Gastric ulcers were induced in male Sprague-Dawley (SD) rats with a single oral dose of 150 mg/kg IND. Ulcer index (UI) and curative index (CI) were evaluated. Histopathological examinations were performed and microscopic score (MS) was macroscopically calculated. The volume of gastric juice, free acidity, total acidity, and gastric pH was measured. The gastroprotective and inflammatory biomarkers including levels of nitric oxide (NO), tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂), and malondialdehyde (MDA) were determined. Expression levels of TLR-2 and MyD88 mRNA were assessed by qRT-PCR. The expression, distribution, and co-localization of TLR-2 and MyD88 protein were determined by Western blot, immunohistochemistry, and immunofluorescence, respectively.

Results

Induction of gastric ulcers in rats resulted in very significantly increased UI and elevated volume and acidity of gastric juice, which were markedly attenuated by LZT treatment. Microscopic examinations of the IND-induced gastric ulcers revealed severe gastric hemorrhagic necrosis, submucosal edema, and destruction of epithelial cells, which were significantly attenuated in LZT-treated rats. Moreover, treatment with LZT remarkably increased gastric mucosal levels of PGE₂ and NO, and lowered highly elevated levels of TNF-α and MDA in gastric ulcerative rats. Mechanistically, LZT inhibited mRNA and protein expression of TLR-2 and MyD88 and enhanced immune function in gastric mucosa. Immunohistochemical analyses and immunofluorescent detection further confirmed a markedly decreased co-localization of TLR-2 and MyD88 protein in the gastric mucosa of LZT-treated rats as compared to that of gastric ulcerative rats.

Conclusions

These findings indicate that LZT alleviates serious gastric mucosal ulcerations induced by IND. Protective effects of LZT on gastric ulcers are believed to be associated with the intensification of the anti-oxidative defense system, mitigation of proinflammatory cytokines, stimulation of the production of cytoprotective mediators, and improvement of the mucosal immunity through TLR-2/MyD88 signaling pathway.