ABSTRACT
Exposure to perinatal hypoxia results in alteration of the adult pulmonary circulation, which is linked among others to alterations in K(+) channels in pulmonary artery (PA) smooth muscle cells. In particular, large conductance Ca(2+)-activated K(+) (BK(Ca)) channels protein expression and activity were increased in adult PA from mice born in hypoxia compared with controls. We evaluated long-term effects of perinatal hypoxia on the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway-mediated activation of BK(Ca) channels, using isoproterenol, forskolin, and dibutyryl-cAMP. Whole-cell outward current was higher in pulmonary artery smooth muscle cells from mice born in hypoxia compared with controls. Spontaneous transient outward currents, representative of BK(Ca) activity, were present in a greater proportion in pulmonary artery smooth muscle cells of mice born in hypoxia than in controls. Agonists induced a greater relaxation in PA of mice born in hypoxia compared with controls, and BK(Ca) channels contributed more to the cAMP/PKA-mediated relaxation in case of perinatal hypoxia. In summary, perinatal hypoxia enhanced cAMP-mediated BK(Ca) channels activation in adult murine PA, suggesting that this pathway could be a potential target for modulating adult pulmonary vascular tone after perinatal hypoxia.
Subject(s)
Cyclic AMP/physiology , Hypoxia/metabolism , Large-Conductance Calcium-Activated Potassium Channel alpha Subunits/metabolism , Muscle, Smooth, Vascular/metabolism , Prenatal Exposure Delayed Effects/metabolism , Pulmonary Artery/metabolism , Age Factors , Animals , Colforsin/pharmacology , Female , Isoproterenol/pharmacology , Male , Mice , Mice, Inbred C57BL , Muscle, Smooth, Vascular/drug effects , Pregnancy , Pulmonary Artery/drug effectsABSTRACT
Perinatal adverse events such as limitation of nutrients or oxygen supply are associated with the occurrence of diseases in adulthood, like cardiovascular diseases and diabetes. We investigated the long-term effects of perinatal hypoxia on the lung circulation, with particular attention to the nitric oxide (NO)/cGMP pathway. Mice were placed under hypoxia in utero 5 days before delivery and for 5 days after birth. Pups were then bred in normoxia until adulthood. Adults born in hypoxia displayed an altered regulation of pulmonary vascular tone with higher right ventricular pressure in normoxia and increased sensitivity to acute hypoxia compared with controls. Perinatal hypoxia dramatically decreased endothelium-dependent relaxation induced by ACh in adult pulmonary arteries (PAs) but did not influence NO-mediated endothelium-independent relaxation. The M(3) muscarinic receptor was implicated in the relaxing action of ACh and M(1) muscarinic receptor (M(1)AChR) in its vasoconstrictive effects. Pirenzepine or telenzepine, two preferential inhibitors of M(1)AChR, abolished the adverse effects of perinatal hypoxia on ACh-induced relaxation. M(1)AChR mRNA expression was increased in lungs and PAs of mice born in hypoxia. The phosphodiesterase 1 (PDE1) inhibitor vinpocetine also reversed the decrease in ACh-induced relaxation following perinatal hypoxia, suggesting that M(1)AChR-mediated alteration of ACh-induced relaxation is due to the activation of calcium-dependent PDE1. Therefore, perinatal hypoxia leads to an altered pulmonary circulation in adulthood with vascular dysfunction characterized by impaired endothelium-dependent relaxation and M(1)AChR plays a predominant role. This raises the possibility that muscarinic receptors could be key determinants in pulmonary vascular diseases in relation to "perinatal imprinting."
Subject(s)
Endothelium, Vascular/metabolism , Hypoxia/metabolism , Lung Diseases/metabolism , Lung/blood supply , Phosphodiesterase I/metabolism , Prenatal Exposure Delayed Effects/metabolism , Receptor, Muscarinic M1/metabolism , Acetylcholine/pharmacology , Animals , Cyclic GMP , Endothelium, Vascular/pathology , Female , Gene Expression Regulation/drug effects , Hypoxia/pathology , Lung/metabolism , Lung/pathology , Lung Diseases/pathology , Male , Mice , Nitric Oxide/metabolism , Pregnancy , Prenatal Exposure Delayed Effects/pathology , Pulmonary Circulation/drug effects , Vasodilation/drug effects , Vasodilator Agents/pharmacologyABSTRACT
The aim of the study was to determine which cholinergic muscarinic receptor subtype is responsible for the endothelium-dependent vasodilatation evoked by acetylcholine (ACh) in mouse arteries. Endothelium-dependent relaxations were evaluated using isometric tension measurement of ring from femoral and aortic artery of M1, M2, and M3 knockout (KO) mice. Rings of femoral and aortic artery from M3 KO mice did not exhibit relaxation at the opposite of rings from M1+M2 KO and wild-type (WT) mice, which were relaxed by ACh. The proportion of endothelial cells responsive to ACh, as manifested by an increase in cytosolic free calcium ([Ca]i), was also observed on the intima of aorta wall in vitro by using laser line confocal microscopy. Of the cells from M3 KO mice and M1+M2 KO mice, 4% and 23%, respectively, responded to ACh in comparison with 20 % in WT mice. These results show that in the endothelium from femoral and aortic artery, the larger proportion of cells that express M3 receptor is responsible for the specificity of the M3 receptor subtype for endothelium-dependent relaxation caused by ACh.
Subject(s)
Endothelium, Vascular/physiology , Receptor, Muscarinic M3/physiology , Vasodilation/physiology , Acetylcholine/pharmacology , Animals , Aorta, Thoracic/drug effects , Aorta, Thoracic/physiology , Endothelium, Vascular/drug effects , Femoral Artery/drug effects , Femoral Artery/physiology , In Vitro Techniques , Mice , Mice, Knockout , Microscopy, Confocal , Receptor, Muscarinic M1/genetics , Receptor, Muscarinic M1/physiology , Receptor, Muscarinic M2/genetics , Receptor, Muscarinic M2/physiology , Receptor, Muscarinic M3/genetics , Vasodilation/drug effects , Vasodilator Agents/pharmacologyABSTRACT
The physiology of smooth muscle and endothelial cells of a particular vascular bed and from different species differs from each other. Acetylcholine causes an endothelium-dependent relaxation of preconstricted pulmonary arteries from the rat. This relaxation is mediated by nitric oxide (NO) plus a yet-unidentified endothelium-derived hyperpolarizing factor, which relaxes the smooth muscles by hyperpolarizing them. Our aim is to test whether these observations could be generalized to the smooth muscle cells from the mouse pulmonary artery. Smooth muscle or endothelial cell membrane potential of strips of murine pulmonary artery were measured simultaneously with the force developed by the strip. Acetylcholine hyperpolarized the endothelial cells. However, acetylcholine did not induce an endothelium-dependent hyperpolarization of the smooth muscle, while it relaxed the strip in an endothelium-dependent manner. This relaxation was abolished by an inhibitor of NO synthesis, nitro-L-arginine. Moreover, nitroglycerin relaxed the strips without changing the membrane potential of the smooth muscle cells. Injection of Lucifer yellow into the endothelial cells and the smooth muscle cells did not show heterocellular dye coupling. Furthermore, electron microscopy did not show gap junction plate at the myoendothelial junctions. We conclude that in the mouse main pulmonary artery, NO alone is responsible for the acetylcholine-induced endothelium-dependent vasodilatation, whereas the phenomenon called endothelium-derived hyperpolizing factor is not present. Therefore, caution should be taken when comparing different animal models to study pulmonary circulation and its reactivity.
