Santos Kivia B S, de Castro Fonseca Matheus, Teixeira Gabriel H M, Sanches Bruno, Guatimosim Silvia, Rossi Leonardo, Verly Pablo W, Pereira Elisa Santiago, Cavalcante Walter, Birbrair Alexander, Bloise Enrrico, Tapia Juan C, Guatimosim Cristina
Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Brazil.
Department of Biology and Biological Engineering, California Institute of Technology, USA.
Neurochem Int. 2025 Aug 26;190:106040. doi: 10.1016/j.neuint.2025.106040.
Increasing evidence suggests that the sympathetic nervous system profoundly interacts with skeletal muscle, influencing both muscle fiber function and composition. β-ARs, the predominant adrenergic receptor subtype in muscle fibers, have been shown to enhance protein synthesis, reduce protein degradation, facilitate muscle contraction and relaxation, and improve neuromuscular junction (NMJ) transmission upon activation. In this study, we investigated the effects of Formoterol, a highly selective β-adrenoceptors (β-AR) agonist, on the presynaptic terminal of motor neurons. We used myography, FM1-43 fluorescent dye assays, and transmission electron microscopy (TEM) to evaluate the NMJ following β-AR activation. We demonstrated that β-AR activation by Formoterol enhances muscle contractility and both spontaneous and evoked exocytosis of acetylcholine (ACh)-containing synaptic vesicles at the mouse diaphragm NMJ. Formoterol-induced morphological changes in diaphragmatic NMJs were consistent with increased exo-endocytic activity. Notably, Formoterol-evoked exocytosis displayed sexual dimorphism, with females showing a significantly milder response compared to males. In females, Formoterol-induced synaptic vesicles exocytosis was mediated solely by P/Q-type voltage-activated Ca channels, whereas in males, it involved both P/Q-type channels, transient receptor potential channel of the vanilloid subtype (TRPV) 1 calcium channels, and an additional, yet unidentified, component. Orchiectomized males exhibited responses to Formoterol similar to the females, whereas ovariectomy did not modify female drug responses, indicating that male hormonal environment orchestrates the sex-differences herein described. These findings not only highlight the importance of sex-specific mechanisms but also reveal a novel effect of β-AR activation directly on presynaptic terminals by Formoterol, enhancing exocytosis at the NMJ and thereby increasing neuromuscular transmission.
越来越多的证据表明，交感神经系统与骨骼肌存在着深刻的相互作用，影响着肌纤维的功能和组成。β-肾上腺素能受体（β-ARs）是肌纤维中主要的肾上腺素能受体亚型，已被证明在激活后可增强蛋白质合成、减少蛋白质降解、促进肌肉收缩和舒张，并改善神经肌肉接头（NMJ）传递。在本研究中，我们研究了高选择性β-肾上腺素能受体（β-AR）激动剂福莫特罗对运动神经元突触前终末的影响。我们使用肌动描记法、FM1-43荧光染料检测和透射电子显微镜（TEM）来评估β-AR激活后的神经肌肉接头。我们证明，福莫特罗激活β-AR可增强小鼠膈肌神经肌肉接头处的肌肉收缩力以及含乙酰胆碱（ACh）的突触小泡的自发和诱发胞吐作用。福莫特罗引起的膈肌神经肌肉接头形态变化与胞吞胞吐活性增加一致。值得注意的是，福莫特罗诱发的胞吐作用表现出性别差异，与雄性相比，雌性的反应明显较轻。在雌性中，福莫特罗诱导的突触小泡胞吐作用仅由P/Q型电压激活钙通道介导，而在雄性中，它涉及P/Q型通道、香草酸亚型瞬时受体电位通道（TRPV）1钙通道以及另一种尚未确定的成分。去势雄性对福莫特罗的反应与雌性相似，而卵巢切除并未改变雌性对药物的反应，表明雄性激素环境决定了本文所述的性别差异。这些发现不仅突出了性别特异性机制的重要性，还揭示了福莫特罗直接对突触前终末激活β-AR的新作用，增强了神经肌肉接头处的胞吐作用，从而增加了神经肌肉传递。
