Mechanisms of endothelin-1-induced contraction in pulmonary arteries from chronically hypoxic rats

Abstract

Endothelin-1 (ET-1), a potent vasoconstrictor, is believed to contribute to the pathogenesis of hypoxic pulmonary hypertension. Previously we demonstrated that contraction induced by ET-1 in intrapulmonary arteries (IPA) from chronically hypoxic (CH) rats occurred independently of changes in intracellular Ca2+ concentration ([Ca2+]i), suggesting that ET-1 increased Ca2+ sensitivity. The mechanisms underlying this effect are unclear but could involve the activation of myosin light chain kinase, Rho kinase, PKC, or tyrosine kinases (TKs), including those from the Src family. In this study, we examined the effect of pharmacological inhibitors of these kinases on maximum tension generated by IPA from CH rats (10% O2 for 21 days) in response to ET-1. Experiments were conducted in the presence of nifedipine, an L-type Ca2+ channel blocker, to isolate the component of contraction that occurred without a change in [Ca2+]i. The mean change in tension caused by ET-1 (10(-8) M) expressed as a percent of the maximum response to KCl was 184.0+/-39.0%. This response was markedly inhibited by the Rho kinase inhibitors Y-27632 and HA-1077 and the TK inhibitors genistein, tyrphostin A23, and PP2. In contrast, staurosporine and GF-109203X, inhibitors of PKC, had no significant inhibitory effect on the tension generated in response to ET-1. We conclude that the component of ET-1-induced contraction that occurs without a change in [Ca2+]i in IPA from CH rats requires activation of Rho kinase and TKs, but not PKC.

Effects of Rho-Kinase Inhibition on Pulmonary Hypertension, Lung Growth, and Structure in Neonatal Rats Chronically Exposed to Hypoxia

“…Therefore, it is not possible, taking the present pharmacological approach, to distinguish indirect consequences of ROCK inhibitor-induced vasodilatation from limiting effects on other ROCK-mediated pathways. Other mechanisms, not explored in this study, by which ROCK inhibitors may have limited vascular remodeling include attenuated vascular production of endothelin-1 (27), inhibited downstream signaling of G-protein-coupled receptor ligands (11,28), and augmented function of the NO/ cyclic GMP pathway (29).…”

“…Recent studies have implicated the RhoA/Rho-kinase (ROCK) pathway as central to the initiation and perpetuation of chronic PHT (5), based largely on the effects of two ROCK-specific kinase inhibitors: Y-27632 and fasudil (6). ROCK inhibitors have been reported to inhibit pulmonary artery myogenic responses in hypoxiaexposed adult rats (7) and fetal sheep (8) and to reverse sustained pulmonary vasoconstriction in response to hypoxia (9,10), bleomycin (10), or the infusion of vasoconstrictors, such as endothelin-1 (11). Systemic administration of ROCK inhibitors, commenced at the onset of injury, has been reported to prevent PHT induced either by hypoxia (9) or monocrotaline (12) in adult rodents.…”

Chronic hypoxia augments depolarization-induced Ca2+sensitization in pulmonary vascular smooth muscle through superoxide-dependent stimulation of RhoA

“…Findings that basal tone is elevated in pulmonary arterial rings from CH rats (34,54) and that vasodilators substantially lower pulmonary vascular resistance in CH rats acutely returned to a normoxic environment (34) provide further evidence that the vasoconstrictor response to CH is multifaceted and a primary determinant of pulmonary hypertension. Consistent with these findings, recent studies from our laboratory and others have identified an effect of CH on induction of myogenic tone in small pulmonary arteries (3) and enhancement of agonist-dependent vasoconstriction through a RhoA/ Rho kinase (ROCK)-mediated myofilament Ca 2ϩ sensitization pathway (14,20,34,54), responses that may contribute to the pathogenesis of pulmonary hypertension in this setting.…”

Effects of Stellate Ganglion Block on the Peri-operative Vasomotor Cytokine Content and Intrapulmonary Shunt in Patients with Esophagus Cancer

“…Some studies demonstrated that acute anoxia could stimulate mRNA expression of vascular ET and its release (Weigand et al, 2006;Li et al, 2013). In the meantime, ET has the functions of promoting the proliferation of vascular smooth muscles and endothelial cells to further induce the changes in ultrastructures of vascular walls.…”