Study Of Protective Effect And Mechanism Of Different Extracts Of Zanthoxylum Bungeanum Pericarp On The Model Of Murine Ulcerative Colitis

Ulcerative colitis(UC),a chronic and relapsing inflammatory disease of the gastrointestinal tract,not only affects millions of patients worldwide,but also increases the risk of colon cancer.Although the etiology and pathogenesis of UC are complicated and remain uncertain,genetic susceptibility of the host,the host immune system,the intestinal microflora,and changed colonic barrier function have been found to be about the developments and course of UC.Currently,most therapeutic drugs have been used to relieve the symptoms of patients with UC,including glucocorticosteroids and immunosuppressive agents.However,most of these agents are not very effective and have severe side effects.Zanthoxylum bungeanum(Z.bungeanum),which belongs to the Zanthoxylum genus of the Rutaceae family,is now wildly distributed in China and some Southeast Asian countries.The pericarp of Z.bungeanum is now wildly used as a kind of spice and as traditional Chinese medicine due to its therapeutic properties.Z.bungeanum has wide variety of biological and pharmacological activities,including anti-inflammation,antioxidant and antibacterial properties.In the study presented here,we examined the protective effects and mechanisms of Z.bungeanum pericarp extract(ZBE)and essential oil of Z.bungeanum pericarp(ZBEO)on dextran sulfate sodium(DSS)-induced UC model mice.The results showed that ZBE and ZBEO treatment relieved loss of body weight,reduced disease activity index(DAI)scores,inhibited myeloperoxidase(MPO)activity and colonic shortening.Histopathological analysis showed that the DSS group existed distortion of crypts,loss of goblet cells,and severe mucosal damage.However,administration of ZBE and ZBEO to DSS-induced UC mice could obviously improve the pathological changes.These findings indicated that ZBE and ZBEO had protective effect on the UC induced by DSS.Therefore,ZBE and ZBEO were further investigated to determine the mechanisms on UC mice.The results showed that ZBE could inhibit the activation of TLR4 and TLR4-related signaling pathways(NF-?B and MAPK)and subsequent pro-inflammatory cytokines,which played an anti-UC role.ZBEO could regulate the activation of NF-?B and PPAR? pathways and subsequent pro-inflammatory cytokines.In addition,ZBEO inhibited NLRP3 inflammasome activation and regulated the expression of tight junction(TJ)molecule ZO-1.Surprisingly,treatment with ZBEO increased levels of the commensal bacteria containing Lactobacillus and Bifidobacteria but reduced Escherichia coli(E.coli)levels in the feces of mice induced by DSS.More interestingly,ZBEO(20 mg/kg)treatment alone could significantly decrease the E.coli level.Then,we investigated the components of ZBEO.The results showed that 20 compounds were identified,and the main constituents were terpinen-4-ol(TER)(25.34%).According to the above achievements,we investigated the effect of TER on UC.The results showed that TER had a role in anti-UC.The mechanisms in vivo and in vitro showed TER inhibited the activation of NF-?B and NLRP3 inflammasome,regulated the expression of TJ molecule ZO-1 and occludin,re-balanced intestinal microflora(E.coli and Lactobacillus)and decreased serum lipopolysaccharide(LPS)concentrations.The DSS-induced mice colitis model was used to further elucidate the key role of NLRP3 inflammasome in TER protective effects by comparing WT mice and NLRP3-/-mice.The results showed that NLRP3-/-mice were significantly protected from DSS-induced colitis.In addition,consistent with the results from colitis experiment in C57BL/6 mice,administration of TER(20 mg/kg)showed a significant improvement on DSS-induced colitis of WT mice.However,TER did not protective effects on DSS-treated colitis in NLRP3-/-mice,suggesting that NLRP3 inflammasome may be involved in the preventive effect of TER on DSS-induced colitis.We further compared the activity of NLRP3 inflammasome in colon samples of WT and NLRP3-/-mice.The results showed that high levels of caspase-1,ASC,and IL-1? were observed in the colon of WT mice receiving DSS,but not in those of NLRP3-/-mice.Furthermore,DSS-increased caspase-1,ASC,and IL-1? levels in the colon were significantly decreased by TER treatment in WT mice,but did not in NLRP3-/-mice.Our findings indicated that the NLRP3 inflammasome may play a critical role on DSS-induced colitis and its inhibition contributes to the anti-inflammatory effect of TER.In conclusion,these results showed that Z.bungeanum(ZBE,ZBEO,TER)protects mice from DSS-induced UC.We wished that our results would provide theoretical guidance and help for the application of Z.bungeanum in clinical and the development of protective drugs for UC and colitis-associated diseases.