Magnolol and Honokiol Attenuate Apoptosis of Enterotoxigenic Escherichia Coli-Induced Intestinal Epithelium by Maintaining Secretion and Absorption Homeostasis and Protecting Mucosal Integrity

Abstract

BACKGROUND The cortex of Magnolia officinalis has long been used as an element of traditional Chinese medicine for the treatment of anxiety, chronic bronchitis, and gastrointestinal dysfunction. This study aimed to elucidate the underlying mechanism of its functional ingredients (magnolol and honokiol) in modifying the secretion and absorption homeostasis and protecting mucosal integrity in an Enterotoxigenic Escherichia coli (ETEC)-induced diarrhea mouse model. MATERIAL AND METHODS This study established a diarrhea mouse model infected by ETEC at a dosage of 0.02 ml/g live body weight (BW) in vivo. Magnolol or honokiol was followed by an intraperitoneal administration at dosages of 100, 300, and 500 mg/kg BW according to a 3×3 factorial arrangement. The useful biomarkers for evaluating the integrity of intestinal tract and histologic injury were analyzed and morphological development (including villus height, crypt depth, and ratio of villus height to crypt depth) and the expressions of inflammatory cytokines were determined by real-time PCR. RESULTS The results showed that magnolol and honokiol (500 mg/kg BW) reduced the concentrations of NO, DAO, and DLA, and iNOS activity, and the mRNA expressions of the interferon gamma (IFN-γ) and interleukin 10 (IL-10), and inhibited intestinal epithelial cell apoptosis. Magnolol and honokiol (300 mg/kg BW) elongated the villus height and crypt depth and decreased the number of goblet cells and the ratio of villus height to crypt depth. CONCLUSIONS The current results indicate that magnolol and honokiol enhance the intestinal anti-inflammatory capacities, elongate the villus height and crypt depth, and reduce goblet cell numbers to inhibit the intestinal epithelium apoptosis and effectively protect the intestinal mucosa. These results show that magnolol and honokiol protect the intestinal mucosal integrity and regulate gastrointestinal dysfunction.

Figure 1

Effects of magnolol and honokiol on ETEC-induced changes in histopathology of the ileal tissue in mice of different experimental groups (n=5, ×250). The lengths of 30 villi were measured by the distance in μm from the crypt neck to the villus tip, the depths of 30 crypts were determined, and the goblet cells in each 30 oriented villi were counted. The mice were first infected by ETEC suspensions and then treated by loperamide hydrochloride or magnolol and honokiol. (A) Shows the normal appearance of normal control mice. (B) Shows the appearance of ETEC-induced mice. (C) Shows the appearance of loperamide hydrochloride-treated ETEC-induced mice. (D–L) Shows the appearance of 100 mg magnolol/kg BW (M100) ×100 mg honokiol/kg BW (H100) administration, M100×H300, M100×H500, M300×H100, M300×H300, M300×H500, M500×H100, M500×H300, and M500×H500 treated ETEC-induced mice.

Figure 2

The apoptosis appearance of ETEC-induced ileum tissues treated by magnolol and honokiol in mice of different experimental groups (n=5, ×400). DNA fragmentation was examined by terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling staining. (A) Shows the apoptosis appearance of the normal control mice. (B) Shows the apoptosis appearance of ETEC-induced mice. (C) Shows the apoptosis appearance of loperamide hydrochloride-treated ETEC-induced mice. (D–L) Shows the apoptosis appearance of magnolol and honokiol administration at 100 mg/kg BW (M100) ×100 mg/kg BW (H100), M100×H300, M100×H500, M300×H100, M300×H300, M300×H500, M500×H100, M500×H300, and M500×H500 treated ETEC-induced mice.