Abstract P145: Cathelicidin Antimicrobial Peptide Is Upregulated After Myocarditis and Inhibits Fibroblast Migration via P2x7 Receptor Signaling

Abstract

Rationale _ Experimental autoimmune myocarditis in BALB/c mice is a model of inflammatory heart disease. It is well known that the process of this model exhibits the acute inflammation phase followed by the healing phase. However, the precise mechanisms how the inflammation terminates and the healing proceeds remain to be elucidated. Objective _ To identify the molecule which functions in the healing phase of EAM and investigate its pathophysiological roles on cardiac cells. Methods and Results _ To induce EAM, BALB/c mice were immunized twice with α-myosin heavy chain peptide. The severity of inflammation peaked at 21days after immunization and mitigated at 28days. To analyze the alterations of gene expression profile during healing phase, we performed microarray analyses using mRNA from hearts of 21day and 28day after immunization. Among up-regulated genes, we focused on cathelicidin antimicrobial peptide (CAMP) which has been reported to be involved in anti-inflammatory response and epithelial tissue repair. Histochemical staining using anti-CAMP antibody revealed that CAMP expresses in inflammatory cells in EAM hearts. Treatment with LL37, a human homologue of CAMP, mediated activation of ERK, JNK and p38 in fibroblasts from neonatal rat hearts, whereas it failed to activate those MAP kinases in rat neonatal cardiomyocytes, suggesting CAMP is engaged in healing process by regulating function of fibroblasts. In addition, LL–37 treatment mediated morphological changes of fibroblasts and decreased migration distances assessed by wound healing assay as well (283±43 mm in treated cells vs 183±54 mm in cells treated with 10 mg/ml of LL37, p<0.01). The expression of focal adhesion kinase is decreased in LL37 treated cardiac fibroblasts compared with non-treated cells. Moreover, blockade of P2X7 receptor which is known as a receptor for LL37 restored the migration distances after LL37 treatment, suggesting that LL37 suppresses cardiac fibroblast motility via P2X7 receptor signaling. Conclusion _ Our results indicate that CAMP is up-regulated after myocarditis and inhibits fibroblasts migration via P2X7 receptor signaling. Those results suggest that CAMP could be a useful tool to inhibit fibrotic changes in inflammatory heart disease.