OBJECTIVETo determine the expression of TREM-1 (triggering receptor expressed on myeloid cells-1) in macrophages after coxsackievirus B3 (CVB3) infection and the cardiomyocytes viability after culturing with supernatant of macrophages in the absence and presence of TREM-1 inhibitor LP-17 to explore if TREM-1 is involved in the pathogenesis of CVB3 infection induced inflammation and cardiomyocytes injury.

METHODSTREM-1 mRNA and TREM-1 and DAP-12 protein expression in macrophages were detected by Real-time PCR at 0, 1, 4, 8 and 12 h and by Western blot at 0, 16, 24 and 48 h post CVB3 infection. TNF-α secretion of macrophages was measure by ELISA, vitality and the apoptosis degree of cardiomyocytes was assessed by CCK8 and Annexin V-FITC after the cardiomyocytes were cultured with the supernatant of macrophages in normal control group, CVB3 infection group and LP-17 pretreated CVB3 infection group.

RESULTSTREM-1 mRNA expression was significantly upregulated at 4, 8, and 12 h (peaked at 8 h) and TREM-1 protein expression was significantly upregulated at 16 and 24 h and returned to baseline level at 48 h after CVB3 infection. The protein expression of DAP-12, a direct downstream signaling molecule of TREM-1, also significantly increased at 24 and 48 h post CVB3 infection (P < 0.01). Level of macrophages secreted TNF-α post CVB3 infection was significantly reduced in LP-17 pretreated cells (P < 0.01), LP-17 pretreatment also significantly improved viability and significantly reduced apoptosis of cardiomyocytes cultured with supernatant of CVB3 infected macrophages (P < 0.01).

CONCLUSIONTREM-1 might be an important mediator post CVB3 infection and a major player on inducing excess macrophages-related inflammation and resulting in an indirect injury to cardiomyocytes.