AHR Is Involved In Regulating The Immunomodulatory Function Of Mesenchymal Stem Cells

Background:Mesenchymal cells(MSCs)have self-renewal,multidirectional differentiation,and immune regulatory functions.The immune regulatory ability of MSCs is the main pharmacodynamic mechanism for their clinical application in the treatment of immune system related diseases.Studies suggest that one of the mechanisms by which MSCs exert immune regulatory effects is the secretion of soluble factors,such as indoleamine 2,3-dioxygenase(IDO),which has been extensively studied.In tryptophan metabolism,IDO1 and interleukin-4 inducible gene 1(IL4I1)convert tryptophan(Trp)into kynurenine(Kyn),and play an immunomodulatory role by activating the metabolic pathway of kynurenine-aryl hydrocarbon receptor(Kyn-AHR).Objective:To explore the effect of aryl hydrocarbon receptors on the immune regulatory function of mesenchymal stem cells.Methods:RT-qPCR and IF were used to detect the expression levels of IDO1,IL4I1,and aryl hydrocarbon receptors in MSCs before and after stimulation with inflammatory cytokines;lipofectamine 3000 transfected si-Ctrl,si-IDO1,si-IL4I1,and si-AHR into MSCs,blocking the Kyn-AHR signaling pathway;PMA induced human monocytic leukemia cells(THP-1)into macrophages;conditioned medium from MSCs was co-cultured with THP-1 induced macrophages,RT-qPCR and ELISA were performed to detect the macrophage inflammatory factors IL-6,IL-1β,TNF-α expression levels.Results:MSCs have immunosuppressive effects.MSCs that are not stimulated by cytokines can inhibit the secretion of inflammatory factors by macrophages,with high expression of AHR and almost no expression of IDO and IL4I1 proteins;After stimulation with different cytokines,the immune regulatory function of MSCs was enhanced,and the metabolic enzymes IDO1,IL4I1,and AHR were upregulated at different time periods;Through IFN-γ treatment,the expression of tryptophan metabolizing enzymes IDO1 and IL4I1 in MSCs was most significantly upregulated,with an increase in AHR entering the nucleus;Downregulation of AHR expression can inhibit the immunomodulatory effect of unstimulated MSCs.Conclusion:Aryl hydrocarbon receptors are involved in regulating the immune function of MSCs,and downregulation of AHR can inhibit the immune regulation of MSCs.