Department of Health Sciences, University of Rome Foro Italico, Rome, Italy.
Med Sci Sports Exerc. 2011 Dec;43(12):2259-73. doi: 10.1249/MSS.0b013e3182223094.
Salmeterol is a β2-adrenergic receptor agonist widely used for the treatment of asthma and chronic obstructive pulmonary disease. It has been shown that salmeterol is also used at supratherapeutic doses as performance-enhancing substance in sport practice. Although the abuse of β-agonists might determine some adverse effects, the molecular effects of salmeterol on skeletal muscle cells remain unclear.
We evaluated the effects of salmeterol (0.1-10 μM) on both proliferative and differentiated rat L6C5 and mouse C2C12 skeletal muscle cell lines. The metabolic effects were evaluated by glyceraldehyde phosphate dehydrogenase, lactate dehydrogenase, citrate synthase, 3-OH acyl-CoA dehydrogenase, and alanine transglutaminase activities. Cytotoxic and apoptotic effects were analyzed by 3-(4,5-dimethylthiazol-1)-5-(3-carboxymeth-oxyphenyl)-2H-tetrazolium, trypan blue exclusion assay, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, Western blot analysis, and immunofluorescence staining.
We showed that salmeterol reduced the growth rate of proliferating cells in a dose- and time-dependent manner (6-48 h). An increase in oxidative metabolism was found after 6 h in C2C12 and L6C5 myoblasts and in C2C12 myotubes with respect to control cells, while in L6C5 myotubes, anaerobic metabolism prevailed. Exposure of myoblasts and myotubes for 48 and 72 h at high salmeterol concentrations induced apoptosis by the activation of the intrinsic apoptotic pathway, as confirmed by the modulation of the apoptotic proteins Bcl-xL, caspase-9, and poly (ADP-ribose) polymerase and by the cytoplasmic release of Smac/DIABLO.
Altogether, our results demonstrate that short-term supratherapeutic salmeterol exposure increased oxidative metabolic pathways on skeletal muscle cells, whereas prolonged treatment inhibits cell growth and exerts either a cytostatic or a proapoptotic effect in a time- and dose-dependent way.
沙美特罗是一种广泛用于治疗哮喘和慢性阻塞性肺疾病的β2-肾上腺素能受体激动剂。已经表明，沙美特罗也被超治疗剂量使用作为运动实践中的性能增强物质。尽管β-激动剂的滥用可能会导致一些不良反应，但沙美特罗对骨骼肌细胞的分子影响尚不清楚。
我们评估了沙美特罗（0.1-10 μM）对增殖和分化的大鼠 L6C5 和小鼠 C2C12 骨骼肌细胞系的影响。通过甘油醛磷酸脱氢酶、乳酸脱氢酶、柠檬酸合酶、3-OH 酰基辅酶 A 脱氢酶和丙氨酸转谷氨酰胺酶活性评估代谢效应。通过 3-（4,5-二甲基噻唑-1）-5-（3-羧基甲氧基苯基）-2H-四唑、台盼蓝排斥试验、末端脱氧核苷酸转移酶 dUTP 缺口末端标记试验、Western blot 分析和免疫荧光染色分析细胞毒性和细胞凋亡效应。
我们表明，沙美特罗以剂量和时间依赖的方式降低了增殖细胞的生长速度（6-48 小时）。在 C2C12 和 L6C5 成肌细胞中，6 小时后观察到氧化代谢增加，而在 C2C12 肌管中则观察到与对照细胞相比，厌氧代谢占主导地位。在高沙美特罗浓度下，成肌细胞和肌管暴露 48 和 72 小时会通过激活内在凋亡途径诱导细胞凋亡，这通过凋亡蛋白 Bcl-xL、caspase-9 和聚（ADP-核糖）聚合酶的调节以及 Smac/DIABLO 的细胞质释放得到证实。
总之，我们的结果表明，短期超治疗剂量的沙美特罗暴露增加了骨骼肌细胞的氧化代谢途径，而长期治疗则以时间和剂量依赖的方式抑制细胞生长并发挥细胞抑制或促凋亡作用。
