Effects Of Mycophenolate Mofetil On The Expression Of Intestinal Gamma Delta T Cells And Plasma IL-6 And TNF-alpha In Mice

Background and purpose:Mycophenolate mofetil（MMF）is an immunosuppressive agent widely used in solid organ transplantation.After oral administration,it is rapidly hydrolyzed into the active drug moiety mycophenolic acid（MPA）in the stomach^[1],which selectively inhibits T/B lymphocyte proliferation by inhibiting the activity of inosine-5′-monophosphate dehydrogenase through non-competitive inhibition.MPA inhibits organ rejection and maintains the function of transplanted organs^[2].Mycophenolate mofetil is generally tolerated by patients,main adverse reactions include gastrointestinal adverse reactions,bone marrow suppression and opportunistic infections^[3].The pathogenesis of MMF-associated enteritis is still unclear,most clinical organ transplantation experts and related researchers believe that MPA or its metabolites are related to local toxicity^[4],however,the effect of MPA on intestinal lymphocyte proliferation has not been reported.The intestine is not only a functional organ of the digestive system,but also an important immune organ.Intestinal interepithelial lymphocyte（IEL）is located between epithelial cells and basement membrane.As the first barrier against external microorganisms,IEL plays an important role in the maintenance of intestinal function,immune surveillance and the maintenance of intestinal ecological balance^[5].Among them,gamma-delta T lymphocyte plays an important role in intestinal immunity,accounting for 10%-37%IELs in human intestinal mucosa and up to 40%in mouse intestine^[6].It is known that in inflammatory bowel disease（IBD）,intestinal barrier function is impaired due to deterioration of epithelial tight junction（TJ）structure.Cell culture studies have shown that some pro-inflammatory cytokines,such as TNF-alpha,IFN-gamma and IL-13,weaken barrier function by reducing the expression of tight junction（TJ）,stimulating cytoskeleton contraction and inducing epithelial cell apoptosis^[7].This experiment was designed:1)to establish a mouse model of MMF-associated enteritis by injecting mycophenolate mofetil suspension into mice;2)to investigate the effect of mycophenolate mofetil on the changes of intestinal gamma delta cells and the secretion and expression of plasma IL-6 and TNF-alpha;3)to explore the possible mechanism of MMF on intestinal inflammation;4).to provide ideas for prevention and treatment of mycophenolate mofetil related enteritis.Methods:Adult male C57BL/6（C57）mice were randomly divided into two groups:saline（NS）group and mycophenolate mofetil（MMF）group.Mice in group MMF were given intragastric administration of mycophenolate mofetil suspension 500mg/kg.D once a day.The mice in group NS were given the same volume of saline containing the same dose of Twain-80 and benzyl alcohol suspension for 15 days.The weight and defecation of mice were monitored every day.The changes of gamma delta T cells in each intestinal segment of the mice were detected by flow cytometry.The concentrations of plasma IL-6 and TNF-alpha were detected by Elisa,and the intestinal segments of mice were examined by HE.Results:After 15 days of continuous infusion of mycophenolate mofetil suspension,the MMF-related enteritis model was established in mice.The results showed that the fecal water content increased and the weight of mice decreased.Compared with the control group,the weight of mice in MMF group decreased gradually,while the weight of mice in NC group did not change significantly.Starting from the 11th day,the body weight of MMF group mice was significantly different from that of the first day（P<0.05）,while that of NC group mice did not change significantly during the experiment（P>0.05）.The body weight of the two groups was significantly different（P<0.05）.The fecal water content of MMF mice increased significantly from the 11th day.Compared with NS group,the proportion of gamma-delta T cells in intestinal epithelial intercellular lymphocyte（IEL）of mice in MMF group decreased,while the concentration of IL-6 and TNF-alpha in plasma increased（P<0.05）.Immunohistochemistry showed that the intestinal epithelial cells in MMF group secreted a large amount of IL-6.Intestinal pathology showed edema and hyperemia of intestinal villi and mucosa,infiltration of inflammatory cells,increase of apoptotic cells in crypts,and partial loss of villi.Conclusion:Mycophenolate mofetil could decrease the ratio of gamma delta T cells in intestinal IEL and increase the secretion of pro-inflammatory factors IL-6 and TNF-alpha in plasma.