Decreased Serum 5-HT: Clinical Correlates and Regulatory Role in NMJ of MG
Xinru Shen1,2, Jing Zhang1, Xinyue Zhou1,2
1Department of Neuroimmunology, Henan Institute of Medical and Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, China.
Objective:
Although 5-Hydroxytryptamine (5-HT) indirectly stimulates muscle contraction and participates in regulating Acetylcholine receptor (AChR) cluster homeostasis in cellular, animal, and clinical studies, evidence regarding its potential to modulate muscle contraction in myasthenia gravis (MG) remains limited. We aim to determine the levels of 5-HT in MG and investigate its potential role as a regulatory neurotransmitter in promoting muscle contraction.
Methods:
We collected serum from 109 patients with MG and 110 healthy volunteers, and recorded clinical variables, including myasthenia gravis classification (MGFA), quantitative myasthenia gravis score (QMG), and serological examination. The effects of 5-HT on the neuromuscular junction (NMJ) were further identified using cellular and molecular experiments.
Results:
In this study, we observed that serum 5-HT levels decrease in patients with MG (p < 0.0001) compared with disease-free control. The thymoma-associated complications alleviated this reduction (p < 0.0001). Our functional studies showed that 5-HT promotes the development of motor (cholinergic) neuron-like axons and increases intracellular calcium peaks, which is proportional to the amount of neurotransmitter released (p < 0.0001). AChR-autoantibody treatment increases the expression of 5-HT2R mRNA in muscle tube cells (p < 0.001), and the downstream signaling pathway of 5-HT2R is involved in the regulation of AChR cluster homeostasis.
Interpretation:
This first report of clinical characteristics and serum 5-HT levels from a cross-sectional cohort study on MG suggests that 5-HT plays a critical role in maintaining NMJ homeostasis. Additional cross-sectional data on more MG phenotypes and longitudinal monitoring data are needed to explore the role of 5-HT in the pathophysiological mechanisms of MG.
Related Concept Videos
01:15Myasthenia Gravis: Diagnostic Tests
The edrophonium test is a diagnostic tool for myasthenia gravis. It involves...
01:20Myasthenia Gravis: Overview and Treatment
These antibodies interfere with the function of the nicotinic receptors in three ways: by binding to the receptor and disrupting acetylcholine binding; by causing cross-linking of receptors which...
01:26Chemical Synapses
Because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to opening of postsynaptic ion channels. Additionally, this signaling is...
01:26Chemical Synapses
Because chemical synapses depend on the release of neurotransmitter molecules from synaptic vesicles to pass on their signal, there is an approximately one millisecond delay between when the axon potential reaches the presynaptic terminal and when the neurotransmitter leads to opening of postsynaptic ion channels. Additionally, this signaling is...
01:28Disorders of the Skeletal Muscle
Musculoskeletal disorders
Musculoskeletal disorders involve injuries and conditions affecting the skeletal muscles and associated connective tissues. These disorders can arise from acute biomechanical stresses or chronic overuse and can occur across different age groups. Common injuries include sprains, fractures, and muscular strains, often resulting from...
01:30Indirect-Acting Cholinergic Agonists: Pharmacological Actions
At the neuromuscular junction, these agents work by inhibiting the breakdown of acetylcholine, allowing it to remain bound to the receptor and bind to nearby receptors. This process leads to repetitive firing of the endplate, causing muscle...