Betulinic acid reduces inflammation in rats with sepsis-induced myocardial dysfunction by inhibiting TLR4/MyD88/NF-B signaling pathway

In this study, we aimed to investigate the effect and underlying mechanism of betulinic acid (BA) on myocardial dysfunction in septic rats. Twenty-four male Sprague-Dawley rats were randomly allocated into four groups (n = 6 rats/group): the sham operation (Control) group, the cecal ligation and puncture (CLP) group, the BA 10 mg/kg group, and the BA 50 mg/kg group. The septic rat model was induced through cecal ligation and puncture in the CLP and BA groups, except for the Control group. Then, cardiac function parameters were assessed using echocardiography, myocardial injury markers were quantified via biochemical assays, and myocardial histopathological injuries were observed through H&E staining. Inflammatory factors in the serum were measured using ELISA assays, immunohistochemistry and qRT-PCR were performed to determine macrophage numbers and the expression of iNOS, CD86, Arg-1, and Mrc1 in myocardial tissue. The protein expression levels of TLR4, Myd88, and NF-kappa B in myocardial tissue were assessed through western blot analysis. The results showed that BA significantly improved cardiac function, reduced myocardial injury, and attenuated inflammation in CLP rats. Specifically, BA decreased LVEDD and LVESD while increasing LVEF and LVFS. Furthermore, BA upregulated the levels of BNP, cTnT, CK-MB, LDH, IL-6, IL-1 beta, and TNF-alpha in CLP rat serum. Additionally, BA reduced macrophage infiltration, inhibited M1/M2 gene expression, and downregulated TLR4, Myd88 and NF-kappa B protein expression in CLP rats myocardial tissues. In conclusion, BA can inhibit myocardial inflammation and prevent sepsis-induced myocardial dysfunction by inhibiting TLR4/MyD88/NF-kappa B signaling, thereby promoting M2 macrophage polarization in myocardial tissues.