| Research background:Inflammatory bowel disease(IBD)is a chronic recurrent disease characterized by intestinal inflammation.The exact cause of IBD is not clear,but it is believed that genetic susceptibility and persistent inflammation and immune response are strongly associated with the occurrence of IBD.Ulcerative colitis(UC)is one of the main diseases of IBD,which occurs in the mucous membrane and submucosa of the colon and causes superficial damage to the intestinal wall.Patients with long-term or severe ulcerative colitis are more likely to develop colorectal cancer(CRC)than the general population,and the mortality rate of patients with UC-related colorectal cancer is also higher than that of patients with common colorectal cancer.Clinically,there are a variety of treatments,including drug therapy,antibody therapy and surgical treatment,which can alleviate colitis.However,there is a large gap in the therapeutic effect and different degrees of side effects for different individuals.Therefore,elucidating the regulatory mechanism of UC and exploring and developing more effective treatments are of positive clinical significance for the cure of colitis.Photobiological regulation(Photobiomodulation,PBM)is a low-intensity laser(or light)therapy,which controls tissue regeneration by exposing biological tissue to weak laser or light-emitting diodes and regulating cell proliferation and migration.Studies have shown that PBM therapy can reduce the expression of inflammatory mediators,relieve pain and edema,and accelerate collagen remodeling.However,whether PBM therapy plays a significant role in improving colitis has not been reported.Therefore,the present study is mainly focuses on two scientific questions:(1)Whether PBM play a role in regulating the development of colitis as a new treatment?(2)How does PBM improve colitis?To explore these two questions will be helpful to promote the development of photobiological regulation in the treatment of ulcerative colitis.Research Purposes:The animal model of experimental colitis induced by sodium dextran sulfate(Dextran sulphate sodium,DSS)was used to clarify the effect of monochromatic light produced by light-emitting diodes on colitis in mice and explore its possible mechanism,so as to provide theoretical value and animal experimental data for the research and development of new therapeutic methods for colitis,and provide new ideas for the prevention and treatment of colitis.Research methods:This study explored the intervention effect and regulatory mechanism of monochromatic light on colitis at animal,cellular and molecular levels.Firstly,animal experiments were used to determine whether monochromatic light has the effect of improving intestinal inflammation.C57BL/6J mice were treated with monochromatic light during the colitis model induced by DSS.FITC-Dextran nanoparticles and H&E staining were used to analyze the damage of colon barrier.The changes of cytokine gene,intestinal tight junction protein and rhythm gene were detected by real-time fluorescence quantitative polymerase chain reaction(Real-time fluorescence quantitative polymerase chain reaction,Q-PCR)and Western blot.The changes of T cells and macrophages were analyzed by flow cytometry and immunofluorescence.Secondly,the in vitro experiment was used to explore the mechanism of monochromatic light improving inflammation at the cellular and molecular level.The effect of rhythm gene Bmall(Brain and Muscle ARNT-Like 1)on the expression of inflammatory cytokines was investigated by transfection of overexpression plasmid and small interference RNA in vitro.The protein levels of cytokines in the supernatant of cell culture were detected by Elisa(Enzyme-linked immunosorbent assay).Results:The results of animal experiments showed that the improvement effect of blue light on colitis induced by DSS was significantly better than that of red light and green light in terms of colon length,intestinal structure,barrier function and expression of inflammatory cytokines,and the high intensity of blue light showed more significant effect than that of low intensity of blue light.Further analysis showed that the proportion of CD4+T cells,M1 macrophages and CD169+macrophages in the colon of mice treated with blue light decreased significantly,while the proportion of CD8+T cells and M2 macrophages increased.Moreover,the decreased level of BMAL1 in colon from colitic mice was rescued by blue light treatment.Cell experiments showed that Bmall was closely related to the production of IL-6,IL-10,IL-1β and TNF-α.Conclusions:This study confirmed that high intensity blue light treatment has a significant inhibitory effect on experimental colitis in mice.On the one hand,blue light changed the proportion of CD4+and CD8+T cells in the intestinal tract of mice,increased the proportion of anti-inflammatory macrophages and decreased the proportion of pro-inflammatory macrophages.On the other hand,blue light prevented the decrease of rhythmic gene expression caused by colitis,promoted the recovery of rhythmic gene Bmall,and played a role in relieving colitis.And over-expression of Bmall could promote the production of IL-10 and inhibit the expression of IL-6,IL-1β and TNF-α,and IL-10 is closely related to the polarization of M2 macrophages.Therefore,high-intensity blue light can be used as a means to treat colitis.However,the mechanism of blue light regulating the occurrence and development of colitis still needs to be further studied. |
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