ABSTRACT
Myocarditis is a kind of myocardial inflammatory infiltration disease. Many interventions are not effective in the treatment of myocarditis because the mechanism of myocarditis has not been elucidated. Previous studies have found that interleukin-17 (IL-17) could stimulate the expression of monocyte chemokine protein 1 (MCP-1) and mediate myocardial inflammatory infiltration. This study aimed to explore the role of Act1/TRAF6/TAK1 cascade in IL-17-induced MCP-1 expression based on a well-designed experimental autoimmune myocarditis (EAM) model. It was found that IL-17 could stimulate the expression of MCP-1 by activating Act1/TRAF6/TAK1 cascade in EAM. The expression of Act1, TRAF6 and TAK1 followed downregulation by the application of IL-17 antibody. Additionally, myocardial inflammatory cell infiltration was observably alleviated by interfering TAK1 with TAK1 siRNA, and both MCP-1 mRNA and protein expression followed downregulation. This study suggested that IL-17 could activate the Act1/TRAF6/TAK1 pathway to upregulate MCP-1 expression in the EAM, and will offer a new perspective for the study on the mechanism of myocarditis.
Subject(s)
Autoimmune Diseases , Myocarditis , Autoimmune Diseases/genetics , Chemokines/metabolism , Connexin 43/metabolism , Humans , Interleukin-17/metabolism , MAP Kinase Kinase Kinases/metabolism , Monocytes/metabolism , Myocarditis/genetics , Peptide Fragments/metabolism , TNF Receptor-Associated Factor 6/metabolismABSTRACT
IL-17 participates in the development of many autoimmune diseases by promoting the expression of some chemokines. Chemokine C-C motif ligand 2 (CCL2) is an important factor at the infiltration of mononuclear cells in the myocardial tissue of viral myocarditis (VMC). It was found that IL-17 could aggravate myocardial injury by upregulating CCL2. But the underlying mechanism involved in CCL2 secretion induced by IL-17 in cardiac myocytes remains unclear. This study investigated the role of transcription factor AP-1 in IL-17 induced CCL2 expression. The results showed that IL-17 mediated the activation of Act1, TRAF6, p38MAPK and c-Jun/AP-1 not Wnt or PI3K signalling pathway to upregulate CCL2 expression in cardiac myocytes. After blocking Act1/TRAF6/p38MAPK cascade and interfering AP-1 with Curcumin or c-Jun siRNA, CCL2 expression induced by IL-17 was significantly attenuated at both mRNA and protein levels. Furthermore, the phosphorylation of c-Jun was suppressed when cardiac myocytes were treated with Act1 siRNA, TRAF6 siRNA, SB203580 (p38MAPK inhibitor) or SP600125 (JNK inhibitor) in cardiac myocytes. In conclusion, IL-17 could stimulate the expression of CCL2 in cardiac myocytes via Act1/TRAF6/p38MAPK-dependent AP-1 activation, which may provide a new target for the diagnosis and treatment of VMC.
Subject(s)
Chemokine CCL2/genetics , Gene Expression Regulation , Interleukin-17/metabolism , Myocytes, Cardiac/metabolism , TNF Receptor-Associated Factor 6/metabolism , Transcription Factor AP-1/metabolism , p38 Mitogen-Activated Protein Kinases/metabolism , Animals , Animals, Newborn , Chemokine CCL2/metabolism , Interleukin-17/pharmacology , Mice , Myocytes, Cardiac/drug effects , Phosphorylation , Signal Transduction/drug effectsABSTRACT
IL-17 plays a key role in a variety of autoimmune diseases. MCP-1 is involved in the infiltration of mononuclear cells of myocardium in VMC. However, the relationship between IL-17 and MCP-1 in myocardial injury remains unclear. In this study, expression of MCP-1 mRNA and protein in cardiac myocytes was detected with qRT-PCR and ELISA, respectively. It was found that IL-17A induced MCP-1 expression in a dose- and time-dependent manner in cardiac myocytes, which could be blocked by IL-17A and IL-17RA neutralizing antibodies. NF-κB p65 and p-p65 protein expression in cardiac myocytes was studied with western blotting. Rates of p-p65 in whole lysates and in nuclear lysates all increased in the first 15 min. Meanwhile, the amount of NF-κB p65 in whole lysates did not change, but the amount of NF-κB p65 in nuclear lysates increased in the first 15 min. Then the optimal sequence and concentration of NF-κB p65 siRNAs was selected. After transfection of 10 nM siRNA-2 of NF-κB p65 into cardiac myocytes before stimulation by IL-17A, expression of MCP-1 mRNA and protein obviously decreased. In conclusion, expression of MCP-1 induced by IL-17 requires NF-κB through the phosphorylation of p65 in cardiac myocytes, which is meaningful to study the onset of chronic viral myocarditis and will provide a new target for the treatment of viral myocarditis.