Bronchial smooth muscle contraction pathway (BSMC pathway)

The bronchial smooth muscle contraction pathway is a complex physiological signaling network that regulates the diameter of the airways in the lungs by controlling the tone of smooth muscle cells. Contraction is primarily triggered by the autonomic nervous system through the release of acetylcholine, which activates Gq-coupled Muscarinic M3 receptors, leading to increased intracellular calcium and activation of myosin light chain kinase (MLCK) [StatPearls: Physiology, Smooth Muscle Contraction]. Conversely, relaxation is mediated by the activation of Gs-coupled Beta-2 adrenergic receptors, which increases cyclic AMP (cAMP) levels, inhibits MLCK, and promotes bronchodilation [PubMed: 24633444]. Dysregulation of this pathway is a central feature of obstructive lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), where hyper-responsiveness leads to pathological narrowing of the airways [NIH: Asthma]. Pharmacological management of these conditions involves the use of beta-agonists to induce relaxation and muscarinic antagonists to prevent contraction, thereby maintaining airway patency and improving respiratory function [NCBI: Bronchodilators].

Other names

Airway smooth muscle contraction pathwayBronchoconstriction signaling cascadeASM contraction pathway

Modulation of intracellular cAMP and calcium levels through Beta-2 adrenergic receptor agonism, Muscarinic M3 receptor antagonism, and Phosphodiesterase inhibition.