It is known that hypoxia causes pulmonary artery constriction normally maintaining optimal ventilation-perfusion matching in the lung but leading to pulmonary hypertension development. The mechanisms of the sustained hypoxic pulmonary vasoconstriction (HPV) remain unclear. The aim of this study was to determine the role of gap junctions (GJs) between smooth muscle cells (SMCs) in the sustained HPV development and involvement of arachidonic acid (AA) metabolites in GJs-mediated signaling. The vascular tone was measured in bovine intrapulmonary arteries (BIPA) using isometric force measurement technique. Expression of contractile proteins was measured using Western blot technique. Mass spectrometry analysis of the tissue bath fluid was done for AA metabolites detection. Values are means±S.D., compared by Student`s T-test. 13-hours chronic hypoxia elicited endothelium-independent sustained HPV in BIPA with amplitude 148±21 % of contraction evoked by 120 mM KCl (n=13). Inhibition of GJs with 18β-glycyrrhetinic acid (18β-GA, 52±17, n=7, P<0.05), heptanol (49±21, n=10, P<0.05) and Gap-27 (44±16, n=5, P<0.05), and inhibition of 15- and 20-hydroxyeicosatetraenoic acid (HETE) synthesis (49±12, n=10, P<0.05 and 51±15, n=10, P<0.05) significantly decreased HPV in deendothelized BIPA. The sustained HPV was not dependent on Ca2+ entry (122±16 %, n=8, P>0.05) and decreased in Ca2+-free solution (131±18 %, n=8, P>0.05), or by Rho-kinase inhibitor Y-27632 (152±14 %, n=8, P>0.05). 15- and 20-HETE evoked constriction of BIPA was inhibited by 18β-GA and Gap-27 (from 98±22 %, n=8, to 42±19 %, and to 43±14 %, n=8, P<0.05, respectively). Inhibition of GJs decreased smooth muscle myosin heavy chain (SM-MHC) expression (from 1.56±0.22 to 0.48±0.11, n=8 normalised by β-actin expression, P<0.05), and myosin light chain phosphorylation (from 0.53±0.15 to 0.18±0.11, n=8, P<0.05) in BIPA. Mass spectrometry also detected 15,20-DiHETE in the presence of 20-HETE in tissue bath fluid. Taken together, our novel findings show that GJs between SMCs are involved in the sustained HPV in BIPA and AA metabolites passing through GJs appear to mediate SM-MHC expression and contribute to the sustained HPV development.
Physiology 2015 (Cardiff, UK) (2015) Proc Physiol Soc 34, PC275
Poster Communications: A potential role for arachidonic acid metabolites in gap junctions-mediated signaling between smooth muscle cells in the sustained hypoxic pulmonary vasoconstriction development
I. Kizub1,2, A. Lakhkar2, V. Dhagia2, S. Joshi2, S. Gupte2
1. Experimental Therapeutics, Institute of Pharmacology and Toxicology of NAMS of Ukraine, Kiev, Ukraine. 2. Pharmacology, New York Medical College, Valhalla, New York, USA Minor Outlying Islands.
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