Melatonin Alleviates Cardiac Function in Sepsis-Caused Myocarditis via Maintenance of Mitochondrial Function

Abstract

Melatonin (N-acetyl-5-methoxytryptamine) has been shown to have a cardioprotective effect against myocarditis. However, the mechanisms underlying the protective role of melatonin (MLT) in sepsis-induced myocarditis are yet to be revealed. In this study, MLT was administrated to mice, 14 days before cecal ligation puncture surgery. Echocardiography results showed that MLT alleviated cardiac dysfunction in sepsis-induced myocarditis. Furthermore, MLT reduced cardiac inflammation by inhibiting the expression of Il-1α, Il-1β, Il-6, and Mcp-1 messenger RNA (mRNA) levels. The RNA sequencing (RNA-seq) assays with heart tissues showed that MLT maintains the mitochondrial function in sepsis-caused myocarditis. Additionally, the production of reactive oxygen species (ROS) in heart tissues was suppressed by MLT. Taken together, in evaluating the therapeutic effect of MLT on sepsis-induced myocarditis, the results showed that MLT alleviated cardiac damage by regulating mitochondrial function and mitochondrial ROS.

Keywords: ROS; cardiac function; melatonin; mitochondria; sepsis-induced myocarditis.

Figure 1

Melatonin alleviates cardiac dysfunction in sepsis-induced myocarditis. Eight-week old mice were treated with melatonin (MLT) (25 μg/ml) dissolved in drinking water for 14 days. (A) Representative echocardiogram of the cardiac function of mice (M-mode) for each condition. (B–D) Quantification of the left ventricular end-systolic diameter (LVIDs, mm), left ventricular ejection fraction (LVEF, %), and left ventricular fractional shortening (LVFS, %). (E) Representative images of the HE staining of the heart tissues (scale bar = 100 μm), the black arrow indicates the inflammatory infiltration area. Values are presented as means ± SD, *vs. sham, p < 0.05; ^#vs. CLP, p < 0.05.

Figure 2

Melatonin relieves cardiac inflammation in sepsis-induced mice. The heart tissue inflammatory cytokines Il-1α (A), Il-1β (B), Il-6 (C), and Mcp-1 (D) mRNA levels were measured using real-time quantitative PCR (RT-qPCR). Values are presented as means ± SD, *vs. sham, p < 0.05; ^#vs. CLP, p < 0.05.

Figure 3

Melatonin ameliorates mitochondrial dysfunction in sepsis-induced myocarditis. (A) Gene ontology (GO) enrichment for the regulated genes between the cecal ligation puncture (CLP) group and CLP + MLT group. The effects of MLT on the cardiac mitochondrial levels of mitochondrial isocitrate dehydrogenase (ICDHm) (B), succinate dehydrogenase (SDH) (C), malate dehydrogenase (MDH) (D), NADH oxidase (NOX) (E), and NADPH-cytochrome C reductase (NCR) (F). Values are presented as means ± SD, *vs. sham, p < 0.05; ^#vs. CLP, p < 0.05.

Figure 4

Melatonin modulates mitochondrial antioxidant status in the heart after CLP. Effects of MLT on the cardiac mitochondrial antioxidant levels of superoxide dismutase (SOD) (A), catalase (CAT) (B), glutathione (GSH) (C), glutathione s-transferase (GST) (D), and glutathione peroxidase (GPx) (E). Values are presented as means ± SD, *vs. sham, p < 0.05; ^#vs. CLP, p < 0.05.

Figure 5

Melatonin reduces reactive oxygen species (ROS) in CLP-induced mice. Nox2 (A) and Sod2 (B) mRNA levels are measured using RT-PCR. (C) Representative images of dihydroethidium (DHE) staining of the heart tissues (scale bar = 50 μm). (D) The ROS production was quantified and presented as the mean fluorescence intensity. Values are presented as means ± SD, *vs. sham, p < 0.05; ^#vs. CLP, p < 0.05.