Ca2+ signaling in hypoxic pulmonary vasoconstriction: effects of myosin light chain and Rho kinase antagonists.
Antagonists of myosin light chain (MLC) kinase (MLCK) and Rho kinase (ROK) are thought to inhibit hypoxic pulmonary vasoconstriction (HPV) by decreasing the concentration of phosphorylated MLC at any intracellular Ca(2+) concentration ([Ca(2+)](i)) in pulmonary arterial smooth muscle cells (PASMC); however, these antagonists can also decrease [Ca(2+)](i). To determine whether MLCK and ROK antagonists alter Ca(2+) signaling in HPV, we measured the effects of ML-9, ML-7, Y-27632, and HA-1077 on [Ca(2+)](i), Ca(2+) entry, and Ca(2+) release in rat distal PASMC exposed to hypoxia or depolarizing concentrations of KCl. We performed parallel experiments in isolated rat lungs to confirm the inhibitory effects of these agents on pulmonary vasoconstriction. Our results demonstrate that MLCK and ROK antagonists caused concentration-dependent inhibition of hypoxia-induced increases in [Ca(2+)](i) in PASMC and HPV in isolated lungs and suggest that this inhibition was due to blockade of Ca(2+) release from the sarcoplasmic reticulum and Ca(2+) entry through store- and voltage-operated Ca(2+) channels in PASMC. Thus MLCK and ROK antagonists might block HPV by inhibiting Ca(2+) signaling, as well as the actin-myosin interaction, in PASMC. If effects on Ca(2+) signaling were due to decreased phosphorylated myosin light chain concentration, their diversity suggests that MLCK and ROK antagonists may have acted by inhibiting myosin motors and/or altering the cytoskeleton in a manner that prevented achievement of required spatial relationships among the cellular components of the response.
Wang
Jian
J
Division of Pulmonary & Critical Care Medicine, The Johns Hopkins Asthma and Allergy Center, Baltimore, MD 21224, USA.
Weigand
Letitia
L
Foxson
Joshua
J
Shimoda
Larissa A
LA
Sylvester
J T
JT
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D015687:Cell Hypoxia; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors*; D008168:Lung / Q000098:blood supply* / Q000187:drug effects / Q000201:enzymology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011651:Pulmonary Artery / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar; D014661:Vasoconstriction / Q000187:drug effects*; D054460:rho-Associated Kinases
D020746:Calcium Channels, L-Type; D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase