Smooth muscle contraction–related pathways

Smooth muscle contraction is a fundamental physiological process that regulates the diameter of hollow organs, such as blood vessels, airways, and the gastrointestinal tract (StatPearls, 2023). The process is primarily driven by an increase in cytosolic calcium, which binds to calmodulin and activates myosin light chain kinase (MLCK), leading to the phosphorylation of the 20-kDa myosin light chain (MLC20) and subsequent cross-bridge cycling (PubMed, PMC6016530). Beyond calcium-dependent mechanisms, the RhoA/Rho-kinase (ROCK) pathway plays a critical role in "calcium sensitization" by inhibiting myosin light chain phosphatase (MLCP), thereby maintaining contraction even at low calcium levels (NCBI, NBK554425). Dysregulation of these signaling pathways is a hallmark of various clinical conditions, including hypertension, asthma, and gastrointestinal motility disorders (PubMed, 28838933). Therapeutic agents, including calcium channel blockers, beta-2 adrenergic agonists, and phosphodiesterase inhibitors, target specific components of these pathways, such as L-type calcium channels (e.g., amlodipine), beta-2 adrenergic receptors (e.g., salbutamol), or phosphodiesterase enzymes (e.g., sildenafil), to modulate muscle tone and restore physiological function (NCBI, NBK542176).

Other names

Vascular smooth muscle contractionSmooth muscle signalingMyogenic responseCalcium-dependent smooth muscle contraction

Drugs modulate smooth muscle tone by altering intracellular calcium levels, inhibiting myosin light chain kinase (MLCK), activating myosin light chain phosphatase (MLCP), or inhibiting Rho-associated protein kinase (ROCK) to regulate the phosphorylation state of myosin light chains (StatPearls, 2023; NCBI, NBK542176).