Hypericumsampsonii attenuates inflammation in mice with ulcerative colitis via regulation of PDE4/PKA/CREB signaling pathway

Abstract

Ethnopharmacological relevanceHypericum sampsonii Hance (Yuanbaocao), a traditional herbal medicine with various pharmacological properties, is traditionally used to treat diarrhea and enteritis in China for hundreds of years. Investigations have uncovered its anti-inflammatory effects and corresponding bioactive constituents in H. sampsonii, however, the mechanisms of action for the treatment of enteritis are still unclear. Aims of the studyThis study aims to investigate the therapeutic effects and molecular mechanisms of H. sampsonii in a dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mice model. Materials and methodsThe major ingredients of the ethyl acetate extract (HS) in H. sampsonii were analyzed by UPLC-QTOF-MS. The inflammatory state of UC mice was caused by 3% DSS once daily for seven days. During DSS treatment, the mice in the positive drug group and the other three groups were orally administered 5-ASA (positive control) or HS daily. After treatment with HS or 5-ASA for a week, colonic pathological observation and the molecular biological index were performed for therapeutic evaluation, including visual inspection in the length and weight of colons and spleens, pathological morphology by hematoxylin and eosin (HE) staining, determination of oxidative markers, inflammatory cytokines and tumor necrosis factor-alpha (TNF-α) levels in colonic tissues as well as spleen index. Gene expression levels of inflammatory cytokines, antioxidant enzymes and PDE4 were detected using kits and PCR, while the expression of colonic tight junction proteins and relative signals of PKA/CREB signaling pathway were analyzed by Western blot. ResultsThe main components in HS were found to be polycyclic polyprenylated acylphloroglucinols (PPAPs). HS distinctly alleviated DSS-stimulated UC-like lesions symptoms as evidenced by a significant recovery from body weight, colon lengths, and histological injuries of colons. HS reduced the accumulation of pro-inflammatory cytokines and improved the mRNA level of IL-10. Simultaneously, the colonic mRNA expression levels of IL-1β, IL-17, iNOS and COX-2 were all significantly suppressed by HS in a dose-dependent manner. Furthermore, HS restored the protein expression of tight junction-associated protein (ZO-1 and occluding). Besides, HS significantly inhibited the protein level of PDE4 and decreased the expressions of PKA and phosphorylated CREB. ConclusionThis is the first work about main composition and anti-UC effect of Hypericum sampsonii Hance. For the first time, this study reveals HS is not toxic in a single dose and exert significantly protective effect in DSS-colitis mice. The underlying mechanisms may involve the improvement to inflammatory status, the protection for intestinal barrier function, the inhibition of PDE4, and the activation of PKA/CREB signaling pathway. This study provided an experimental basis for the traditional application of H. sampsonii Hance in the treatment of diarrhea and dysentery.