Dual role of eugenol on chronic gastric ulcer in rats: Low-dose healing efficacy and the worsening gastric lesion in high doses

This study evaluated the gastric healing activity of eugenol, the main bioactive compound from clove (Syzygium aromaticun) essential oil. Five groups of female Wistar rats were submitted to acetic acid-induced ulcer model and treated with Vehicle (1 mL/kg, p.o.), eugenol (1, 10 or 100 mg/kg, p.o) or omeprazole (20 mg/kg, p.o), twice a day, by seven or fourteen days. Macroscopic, microscopic and biochemical analyses were performed in the ulcerated site. Eugenol (1 mg/kg, p.o) administered by 7 or 14 days accelerated the gastric healing process by 33% and 52%, respectively. The healing actions of eugenol were accompanied by the rescue on the histological architecture and the normalization of the superoxide dismutase and catalase activity. Moreover, eugenol (1 mg/kg, p.o) reduced the gastric mucosal myeloperoxidase activity and increased the mucin secretion. In contrast, eugenol at a dose of 100 mg/kg administered by 7 days enhanced 49% the ulcerated area, but at 10 mg/kg did not change the ulcer area after 7 or 14 days of treatment. Thus, despite the undesirable results due to the worsening of the gastric lesion with the use of eugenol in high doses, the antiulcer potential of this compound is evident and manageable in an adequate dose.

Maytenus robusta Reissek, a medicinal plant popularly used to treat digestive diseases, promotes ameliorative effects in colon and liver of mice exposed to dextran sulfate sodium

ETHNOPHARMACOLOGICAL RELEVANCE

Maytenus robusta Reissek (Celesteraceae), popularly named as cafezinho do mato or coração de bugre, is employed to treat inflammatory digestive diseases in the south of Brazil. However, despite popular usage, the effects of this species on an experimental model of ulcerative colitis are unknown.

AIM OF THE STUDY

To evaluate the effects of M. robusta extract (HEMR) on colon and liver from mice with colitis induced by dextran sulfate sodium (DSS).

MATERIALS AND METHODS

Firstly, the cytotoxicity of HEMR and its effects on ROS and nitrite production in IEC-6 cells were evaluated. The experimental colitis was established by adding 3% DSS on drinking water of mice and the effects of HEMR (1-100 mg/kg, p.o, once a day by 7 days) in colonic and hepatic tissues were analyzed.

RESULTS

The HEMR (1-100 μg/mL) did not alter the cell viability but reduced nitrite production of IEC-6 stimulated by LPS. Moreover, HEMR (100 mg/Kg) attenuates macro and microscopic alterations in the colon from mice exposed to DSS, as evidenced by a reduction of the colon shortening, attenuation of the epithelial erosion, submucosal edema and preservation of the Goblet cells integrity, as well as the restoration of mucin depletion. The treatment with HEMR increased GSH amount, reduced LOOH levels and normalizes CAT activity in the colon. The group treated with HEMR showed increased GST activity, reduced MPO activity and decreased inflammatory cytokines secretion (TNF and IL-6) in the colonic tissue. In the liver, HEMR increased GST activity, decreased the GPx activity and reduced IL-6 levels. Furthermore, the HEMR treatment reduced AST and ALT serum levels in mice exposed to DSS. Finally, the HEMR was able to reduce intestinal transit.

CONCLUSIONS

HEMR treatment minimizes inflammation of the colon and maintaining the antioxidant homeostasis. In addition, HEMR may be a potential tool to prevent hepatic injury secondary to ulcerative colitis.

Role of the antioxidant properties in the gastroprotective and gastric healing activity promoted by Brazilian green propolis and the healing efficacy of Artepillin C

Green propolis is a resinous substance used in folk medicine given its anti-inflammatory, antibacterial, and anti-ulcer effects. Our research group has already confirmed the gastroprotective activity of hydroalcoholic extract from green propolis (HEGP), as well as of its main isolated compounds. In continuity, this study evaluated the antioxidant mode of action involved in the preventive effect induced by HEGP, and its therapeutic gastric healing potential on installed ulcers. In addition, the healing effect of its main compound Artepillin C was also investigated. Acute and chronic ulcers were induced in rats by given ethanol or acetic acid, respectively. In acute model, the rats were orally pre-treated with vehicle (water plus 1% Tween, 1 mL/kg), HEGP (30-300 mg/kg), or carbenoxolone (200 mg/kg) 1 h prior the ulcer induction. In the chronic ulcer protocol, the rats received vehicle (water plus 1% Tween, 1 mL/kg), HEGP (300 mg/kg), or omeprazole (20 mg/kg) twice a day by 7 days, whereas groups of mice received vehicle (water plus 1% Tween, 1 mL/kg), Artepillin C (18 mg/kg), or ranitidine (20 mg/kg) twice a day by 4 days. Ulcerated tissue was collected for histological, histochemical, immunostaining, oxidative, and inflammatory analyses. The in vitro scavenger activity of HEGP was also verified using the DPPH assay. The oral pre-treatment with HEGP (100 and 300 mg/kg) prevented the gastric epithelial damage promoted by ethanol. Besides, HEGP (100 and 300 mg/kg) reduced SOD activity about 11% and 26%, respectively, and increased the activity of GST around 20% and CAT in 80%. HEGP (300 mg/kg) also reduced the production of reactive oxygen species, as well as lipoperoxidation levels in the ethanol-ulcerated tissue. In the acetic acid-induced chronic ulcer, the daily treatment with HEGP (300 mg/kg) accelerates the healing process by 71%. In this model, HEGP normalized SOD and CAT activity and increased GST activity by 109% when compared to non-ulcerated rats. In both models, the extract administration increased the mucin PAS staining and reduced the myeloperoxidase activity at the ulcer site. Moreover, the treatment with HEGP enhanced the PCNA immunostaining, but did not alter the concentration of collagen in the acetic acid-ulcerated tissue. The extract had a direct DPPH radical-scavenging ability (LogIC₅₀: 0.56). Besides, as expected, HPLC analysis showed Artepillin C as a major compound and its administration at 18 mg/kg also accelerated the gastric healing ulcer process in mice. Our findings confirm that HEGP displays both gastroprotective and gastric healing properties, contributing to the validation of its popular use as preventive and therapeutic approaches. These actions occur through the increase in mucin production and the reestablishment of the oxidative balance due to a reduction in gastric inflammation.

Hydroalcoholic extract of Tagetes erecta L. flowers, rich in the carotenoid lutein, attenuates inflammatory cytokine secretion and improves the oxidative stress in an animal model of ulcerative colitis

Given the role of oxidative stress in ulcerative colitis (UC) etiology, and the amount of lutein (a carotenoid with antioxidant properties) in the dry hydroalcoholic extract of Tagetes erecta flowers (DHETE), this study investigated the intestinal anti-inflammatory properties of DHETE in an animal model of UC. The amount of lutein in the extract was determined by ¹H-nuclear magnetic resonance spectroscopy, and total phenols, radical scavenger capability, cytotoxicity, and effects on reactive oxygen species and nitric oxide production were evaluated in vitro. Experimental UC was established by adding 5% dextran sulfate sodium (DSS) to drinking water, with the effects of DHETE (30-300 mg/kg, once a day for 7 days) on the morphological (colon length and weight), clinical (disease activity index and body weight loss), microscopic (histological score and mucin levels), and biochemical parameters analyzed. The lutein concentration found in DHETE was 8.2%, and DHETE scavenged 2,2-diphenyl-1-picrylhydrazyl radicals at 1000 μg/mL The exposure of intestinal epithelial cells to DHETE did not change its viability but reduced reactive oxygen species and nitric oxide production after lipopolysaccharide stimulation. In vivo, DHETE (300 mg/kg) attenuated weight loss, disease activity index, colon shortening, and histopathological changes promoted by DSS intake. Moreover, DHETE increased mucin colonic staining. The treatment with DHETE decreased myeloperoxidase activity as well as tumor necrosis factor and interleukin-6 levels. The extract also increased reduced glutathione levels and catalase activity and normalized superoxide dismutase and glutathione-S-transferase activities. In conclusion, DHETE reduced colitis severity by attenuating inflammatory cytokine secretion and improved the endogenous antioxidant defense in DSS-induced UC in mice.