Salidroside mitigates skeletal muscle atrophy in rats with cigarette smoke-induced COPD by up-regulating myogenin and down-regulating myostatin expression

Abstract

Objectives: The present study aimed at investigating the therapeutic effect of Salidroside on skeletal muscle atrophy in a rat model of cigarette smoking-induced chronic obstructive pulmonary disease (COPD) and its potential mechanisms.

Methods: Male Wistar rats were randomized, and treated intraperitoneally (IP) with vehicle (injectable water) or a low, medium or high dose of Salidroside, followed by exposure to cigarette smoking daily for 16 weeks. A healthy control received vehicle injection and air exposure. Their lung function, body weights and gastrocnemius (GN) weights, grip strength and cross-section area (CSA) of individual muscular fibers in the GN were measured. The levels of TNF-α, IL-6, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) in serum and GN tissues as well as myostatin and myogenin expression in GN tissues were measured.

Results: In comparison with that in the healthy control, long-term cigarette smoking induced emphysema, significantly impaired lung function, reduced body and GN weights and CSA values in rats, accompanied by significantly increased levels of TNF-α, IL-6 and MDA, but decreased levels of SOD and GSH in serum and GN tissues. Furthermore, cigarette smoking significantly up-regulated myostatin expression, but down-regulated myogenin expression in GN tissues. Salidroside treatment decreased emphysema, significantly ameliorated lung function, increased antioxidant, but reduced MDA, IL-6 and TNF-α levels in serum and GN tissues of rats, accompanied by decreased myostain, but increased myogenin expression in GN tissues.

Conclusion: Salidroside mitigates the long-term cigarette smoking-induced emphysema and skeletal muscle atrophy in rats by inhibiting oxidative stress and inflammatory responses and regulating muscle-specific transcription factor expression.

Keywords: Muscle dystrophy; Muscle-specific transcription factors; Salidroside; chronic obstructive pulmonary disease.

Figure 1. Salidroside alleviates emphysema and lung function in rats with cigarette smoking-induced COPD

(A) Histological changes in lung tissues. Scale bars = 50 μm. (B,C) Lung functional measurements. (D,E) Lung histological measurements. Data are representative images (magnification ×400) or the mean ± SD of each group (n=8 rats per group). **P<0.01, ***P<0.001 vs. the control group, ^#P<0.05, ^##P<0.01, ^###P<0.001 vs. the COPD group.

Figure 2. Salidroside treatment mitigates the COPD-mediated skeletal muscle atrophy in rats

Rats were subjected to air or cigarette smoking and treated with the different doses of Salidroside daily for 16 weeks, and their grip strengths (A) and body weights (B) were measured. The left GN weights (C) and CSAs (D,E) were measured. Scale bars = 50 μm. Data are representative images (magnification ×400) or the mean ± SD of each group (n=8 rats per group). ***P<0.001 vs. the control group, ^#P<0.05, ^##P<0.01, ^###P<0.001 vs. the COPD group.

Figure 3. Salidroside treatment reduces the oxidative stress-related pro-inflammatory cytokine production in rats

(A–C) The levels of MDA, SOD and GSH in serum and GN tissue homogenates of individual rats were measured. (D,E) The levels of TNT-α and IL-6 in serum and GN tissue homogenates of individual rats. Data are presented as the mean ± SD of each group (n=8 rats per group) from three independent assays. ***P<0.001 vs. the control group, ^#P<0.05, ^##P<0.01, ^###P<0.001 vs. the COPD group.

Figure 4. Salidrosides reduce the myostatin expression and enhance the myogenin expression in GN tissues of rats

(A,B) Western blot analysis of the relative levels of myostatin and myogenin to β-actin expression in the GN tissues of individual groups of rats. (C) Quantitative RT-PCR analysis for the relative levels of myostatin and myogenin mRNA transcripts in the GN tissues of individual rats. (D–F) Immunohistochemistry analysis of myostatin expression and the percentages of nuclear myogenin cells in the GN tissues of individual rats. Scale bars = 50 μm. Data are representative images (magnification ×400) or present as the mean ± SD of each group (n=8) from three separate experiments. *P<0.05, **P<0.01, ***P<0.001 vs. the control group, ^#P<0.05, ^##P<0.01, ^###P<0.001, vs. the COPD group.