Lupeol alleviates coxsackievirus B3-induced viral myocarditis in mice via downregulating toll-like receptor 4

Objectives To investigate the effect of lupeol in a mouse model of viral myocarditis induced by coxsackie virus B3 (CVB3). Methods Mice were separated into controls (DMEM, n = 20) and CVB3 infected groups (i.e., untreated CVB3 [n = 40]; CVB3 + lupeol 50 mg/kg [n = 40]; CVB3 + lupeol 100 mg/kg [n = 40]; CVB3 + small interfering RNA (siRNA)- toll-like receptor 4 (TLR4) [n = 20]; siRNA + EXP-H mice [n = 20]). Reverse transcription polymerase chain reaction (RT-PCR), western-blot assay, immunohistochemistry, enzyme-linked immunosorbent (ELISA) assay and histopathology were performed to investigate the cardioprotective role of lupeol. Results The elevated pro-inflammatory cytokines in CVB3-infected mice (i.e., interleukin-1 beta [IL-1 beta]; interleukin-6 [IL-6]; tumour necrosis factor-alpha [TNF-alpha]) were significantly reduced by lupeol 50 or 100 mg/kg. Interestingly, the mRNA level and protein level of toll-like receptor 4 (TLR4) were inhibited by lupeol. Conclusions Lupeol alleviates CVB3-induced viral myocarditis and myocardial damage in mice. The underlying mechanism may due to downregulation of TLR4.