Studies On The Role Of PDGFRα~+ Cell/SK3 And ICC/ANO1 In Colitis-induced Colonic Transit Disorder Of Mice

Colonic transit refers to the process of advancing the product of digestion from the proximal colon to the distal colon and rectum.Stable and regular colonic motility is one of the important conditions for normal defecation function.Clinically,diseases with colonic transit dysfunction are very common,such as inflammatory bowel disease(IBD)and irritable bowel syndrome(IBS).The latest research shows that in patients with severe IBD and its remission period,the total gastrointestinal transit time and colorectal transmission time are significantly longer than that in healthy people,and the frequency of colon movement is significantly negatively correlated with the transmission time.Experts believe that the high frequency of colon movement in IBD patients may be due to the fact that inflammatory factors stimulate the colon to be in a highly sensitive state and cause colon contraction,but they cannot produce effective transit motility.However,the mechanism of IBD induced colonic transit dysfunction is still not fully understood.Colonic transit requires the joint regulation of smooth muscle and enteric nerve.Studies have shown that mesenchymal cells ICC and PDGFRα~+respectively with smooth muscle cells(SMC)form SIP syncytium by gap junctions,neurotransmitter mediated smooth muscle contraction and relaxation response by SIP syncytium.Nitric oxide(NO)neurotransmitter inhibits ANO1 channel on ICC,resulting in hyperpolarization of smooth muscle.Inhibitory neurotransmitter purine can apply to P2Y1 receptor on PDGFRα~+cells,activate SK3 channel on PDGFRα~+cells,hyperpolarizes smooth muscle by gap junctions.Therefore,the excitatory effect of ICC-ANO1 balanced the inhibitory effect of NO-ICC-ANO1 and purine-PDGFRα~+-SK3,which is the key to the normal colon transit.When this balance is broken,it will cause colon transit disorder.At present,scholars’studies on IBD mainly focus on the high sensitivity of visceral sensation,and rarely discuss the mechanism of colon transit disorder.Therefore,this research mainly includes two parts.First of all,we studied the distributions of ICC and PDGFRα~+cells in the proximal and distal colons.And then we explored the mechanism of ICC-ANO1 and PDGFRα~+-SK3 in IBD colonic transit disorder.Through colonic migrating motor complexes and the isolated smooth muscle contraction experiments,the contraction role of ANO1and SK3 channel were investigated.The role of neurotransmitters in the regulation of ICC and PDGFRα~+cells was described using molecular and electrophysiological intracellular recordings.Our results showed that the distributions of ICC and PDGFRα~+cells were different in the proximal and distal colons of normal mice,that is,the distribution of ICC in the proximal colon was dominated,and the distribution of ICC from the proximal to distal colon was decreasing.While the distribution of PDGFRα~+cells was decreasing from the proximal to distal colon,that is,the distribution of PDGFRα~+cells in the distal colon was dominated.Compared with normal mice,the CMMC in isolated colon of colitis mice was obviously disturbed and the transit speed was obviously slowed down.The expressions of c-KIT,ANO1,PDGFRαand SK3 in colonic smooth muscle layer of colitis mice were significantly down-regulated compared with normal mice.Compared with normal mice,colonic smooth muscle of colitis mice showed significantly reduced response to agonists and blockers of ANO1 and SK3 channels.Compared with normal mice,the amplitudes of s IJP and fIJP induced by colon smooth muscle electric field stimulation were decreased.The above results suggest that:There were more ICCs in the proximal colon and more PDGFRα~+cells in the distal colon.It is the differential distribution of these two types of cells that creates a pressure gradient from the near to the far in the colon,allowing the stool to pass smoothly.The functions of ICC/ANO1 and PDGFRα~+/SK3 were down-regulated in the colonic smooth muscle of colitis mice,which significantly reduced the functional activity of NO-ICC-ANO1-SMC and purine-P2Y1-SK3-SMC signaling pathway,and finally led to colonic transit disorder.The results of this study have important theoretical significance for digestive physiology,and also provide new ideas and new therapeutic targets for the prevention and treatment of colitis.