Cathelicidin stimulates colonic mucus synthesis by up-regulating MUC1 and MUC2 expression through a mitogen-activated protein kinase pathway

Objective Mucus forms the physical barrier along the gastrointestinal(GI)tract.It plays an important role to prevent mucosal damage and inflammation.Our previous finding showed that antibacterial peptide 'cathelicidin' increased mucus thickness and prevented inflammation in the colon.In the current study,we examined the protective mechanisms by which the peptide increased mucus synthesis in vitro.Methods Human colonic cell line(HT-29)was used to assess the stimulatory action of cathelicidin on mucus synthesis which was measured by the D-[6-3H] glucosamine incorporation assay.Results Human cathelicidin(LL-37)dose-dependently(10-40 μg·mL-1)and significantly stimulated mucus synthesis.Real-time PCR data showed that addition of LL-37 induced more than 50% increase in MUC1 and MUC2 mRNA levels.Treatment with MUC1 and MUC2 siRNAs normalized the stimulatory action of LL-37 on mucus synthesis.LL-37 also activated the phosphorylation of mitogen-activated protein(MAP)kinase in the cells.A specific inhibitor of the MAP kinase pathway,U0126,completely blocked the increase of MUC1 and MUC2 expression as well as mucus synthesis by LL-37.Conclusions Taken together LL-37 stimulates mucus synthesis through the activation of MUC1 and MUC2 expression and the MAP kinase pathway in human colonic cells.

Evaluation and SAR analysis of the cytotoxicity of tanshinones in colon cancer cells

AIM:This study was designed to evaluate the anti-cancer actions of tanshinone I and tanshinone IIA,and six derivatives of tanshinone IIA on normal and cancerous colon cells.Structure activity relationship(SAR) analysis was conducted to delineate the significance of the structural modifications of tanshinones for improved anti-cancer action.METHOD:Tanshinone derivatives were designed and synthesized according to the literature.The cytotoxicity of different compounds on colon cancer cells was determined by the MTT assay.Apoptotic activity of the tanshinones was measured by flow cytometry(FCM).RESULTS:Tanshinone I and tanshinone IIA both exhibited significant cytotoxicity on colon cancer cells.They are more effective in p53+/+ colon cancer cell line.It was also noted that the anti-cancer activity of tanshinone I was more potent and selective.Two of the derivatives of tanshinone IIA(N1 and N2) also exhibited cytotoxicity on colon cancer cells.CONCLUSIONS:The anti-colon cancer activity of tanshinone I was more potent and selective than tanshinone IIA,and is p53 dependent.The derivatives obtained by structural modifications of tanshinone IIA exhibited lower cytotoxicity on both normal and colon cancer cells.From steric and electronic characteristics point of view,it was concluded that structural modifications of ring A and furan or dihydrofuran ring D on the basic structure of tanshinones influences the activity.An increase of the delocalization of the A and B rings could enhance the cytotoxicity of such compounds,while a non-planar and small sized D ring region would provide improved anti-cancer activity.