The Role Of IRKA-M In Inflammatory Regulation Of Myocardial Ly6C^low Cell Subset After Myocardial Infarction And On The Effect Of Collagen Synthesis Of Fibroblasts

Background:Cardiac remodeling impedes long-term survival in patients after acute myocardial infarction(MI).Extended inflammatory response after MI contributes to remodeling process.Post-infarction inflammation and repair involve the transformation of monocytes/macrophages subsets-from proinflammatory subsets(Ly6Chigh)to inhibitory subsets(Ly6Clow).IRAK-M is an important inhibitor regulating the inflammatory signaling pathway through toll-like receptor(TLR)in mononuclear cells.Objective:This study was designed to explore the role of IRAK-M on the inflammatory effect and regulation of myocardial Ly6Clow mononuclear cell subset after MI,and on the effect of collagen-synthesis of fibroblasts.Methods:In this study,the myocardial infarction model of IRAK-M gene knockout(IRAK-M-/-)mice and wild type(WT)mice was established.By using immune magnetic beads separation and flow cytometry,the ly6C monocyte/macrophage subsets in myocardium after myocardial infarction were obtained.The mRNA expression levels of multiple proinflammatory,anti-inflammatory factors and TLR pathway-associated signaling molecules were detected by RT-PCR.High IRAK-M expression monocytes was established and used in co-culture experiment with fibroblasts in vitro,and RT-PCR was used to detect the mRNA expression of a-SMA and type Ⅰ/Ⅲ collagen in fibroblasts.Fibroblast-mediated collagen pads were made to test contractive capacity.Results:(1)IRAK-M-/-did not affect the ly6C monocytes subsets in myocardium in mice after 7 days of MI;(2)on the 7th day after MI,Ly6Clow/int cells of IRAK-M-/-mice expressed lower IL1β,TGFβ,MMP2 and higher TNFα,MCP-1,IL-10 than those in the WT mice;(3)compared to WT mice,Ly6Clow/int cells of IRAK-M-/-mice expressed lower levels of IRAK-1,IRAK-4,TRAF6,IKK-γ,ERK,NF-κB,p38,and higher level of IκBα;(4)compared to fibroblasts co-cultured with WT THP-1 cells in vitro,fibroblasts co-cultured with IRAK-M over-expression monocytes/macrophages expressed higher levels of α-SMA,Ⅰ/Ⅲ type collagen significantly;(5)compared to WT THP-1 cells,co-culturing with IRAK-M over-expression THP-1 cells did not affect fibroblasts collagen pad contraction.Conclusion:IRAK-M deficiency affected the inflammatory characteristics of Ly6Clow subset during MI repair.High expression of IRAK-M in monocytes/macrophages may affect the activation and collagen expression of fibroblasts.