Regulation of Pulmonary Vasoconstriction by Agonists and Caveolae

Abstract

Sustained pulmonary vasoconstriction contributes to the elevated pulmonary vascular resistance observed in pulmonary arterial hypertension. A rise in cytosolic Ca 2+ in pulmonary artery smooth muscle cells (PASMCs) is major trigger for pulmonary vasoconstriction. One family of drugs currently being pursued as a potential treatment for pulmonary hypertension are the statins, which act by depleting cholesterol and reducing the number of caveolae. This study aimed at investigating the role of caveolae, membrane receptors, and ion channels (that are potentially located in the caveolae) in agonist-mediated pulmonary vasoconstriction in order to gain a greater understanding of the signaling mechanisms involved in the regulation of pulmonary vascular tone. Chronic treatment of PASMCs with the cholesterol-depleting agent, methyl-β-cyclodextrin (MβCD), significantly reduced the number of cholesterol rich caveolae regions in the membrane. This disruption of cholesterol in caveolae significantly inhibited pharmacomechanical (induced by phenylephrine), but not electromechanical (induced by elevated extracellular potassium concentration), rat pulmonary artery contraction. These results indicate that receptors may Address correspondence to Jason X.J. Yuan, MD, PhD, Division of Pulmonary and Critical Care Medicine, Department of Medicine, MC 0725, University of California, San Diego, 9100 Gilman Drive, LaJolla, CA 92093-0725, USA. xiyuan@ucsd.edu. The current address of Christian Schach is Clinic for Internal Medicine II, University of Regensburg, Regensburg, Germany. In pulmonary vascular smooth muscle and endothelial cells, caveo-lae and the signaling cascades localized in the caveolae may have differential effects on pulmonary vascular tone. In this study, we investigated the role of caveolae in electromechanical and pharmacomechanical coupling mechanisms involved in regulating pulmonary vasoconstriction and vasodilation. HHS Public Access Methods and Materials Tension Measurement in Isolated Pulmonary Artery RingsPulmonary arteries, 2nd to 3rd divisions with an internal diameter of ∼400 μm, were isolated from male Sprague-Dawley rats (100 to 250 g) in accordance with the animal use protocol approved by the Institutional Animal Care and Use Committee of the University of California, San Diego. Adipose and connective tissues were carefully removed, and the remaining arteries were cut into 1 to 2 mm long rings and mounted on stainless steel wire (100 μm in diameter) to a force transducer (Harvard Apparatus, Holliston, MA) in an organ bath (the volume is approximately 0.75 mL). Isometric tension was continuously monitored and recorded using DATAQ data acquisition software (DATAQInstruments). Isolated PA rings were superfused (2 to 2.5 mL/min) with modified Krebs solution (MKS; at 37°C) consisting of (in mM): 138 NaCl, 1.8 CaCl 2 , 4.7 KCl, 1.2 MgSO 4 , 1.2 NaH 2 PO 4 , 5 HEPES, and 10 glucose (pH 7.4, with 2 M NaOH). For Ca 2+ -free (0 Ca) MKS, CaCl 2 was replaced by equimolar MgCl 2 and 1 mM EGTA was added to chelate ...

Increase in caveolae and caveolin-1 expression modulates agonist-induced contraction and store- and receptor-operated Ca2+ entry in pulmonary arteries of pulmonary hypertensive rats

“…Furthermore, application of exogenous CSD peptide as the surrogate of Cav-1 enhanced both SOCE and ROCE in PASMCs, further suggests specific involvement of the caveolar protein. These results are consistent with a previous study showing that incubation of PAs with MβCD reduced the number of cholesterol rich caveolae and inhibited phenylephrine-induced contraction, but had no effect on contraction activated by KCl [64]. Our results are also congruent with reports that SOCE activity in PASMCs is dependent on the expression of Cav-1 [31,65].…”

Bone marrow‐derived CX3CR1 progenitors contribute to neointimal smooth muscle cellsviafractalkine CX3CR1 interaction

“…SMCs perform a pivotal physiological role in vivo, underpinning vessel wall structural integrity (19 -21), maintain-ing vasomotor tone, and initiating contractile responses to pulsatile flow (22)(23)(24) and vascular agonists (25,26). In pathophysiologic states such as atherosclerosis and restenosis after angioplasty, SMCs contribute to cellular components of the plaque fibrocellular cap (27,28) and the neointimal repair response (29,30) within the injured vessel segment.…”

Sarcolemmal cholesterol and caveolin-3 dependence of cardiac function, ischemic tolerance, and opioidergic cardioprotection

“…In coronary and other vascular smooth muscles, M␤CD treatment modifies ion channel function (BK Ca and Ca 2ϩ -activated Cl Ϫ currents) and receptordependent control of intracellular Ca 2ϩ concentration and vascular tone (40,47,51). M␤CD also modifies BK Ca currents in nonvascular smooth muscle (50), together with BK Ca activity (43) and agonist-mediated Ca 2ϩ entry (30) in the vascular endothelium.…”