Effects of chronic portal hypertension on agonist-induced actin polymerization in small mesenteric arteries

2006 ◽  
Vol 290 (5) ◽  
pp. H1915-H1921 ◽  
Author(s):  
Xuesong Chen ◽  
Kristin Pavlish ◽  
Hai-Ying Zhang ◽  
Joseph N. Benoit
Keyword(s):  
Smooth Muscle ◽  
Portal Hypertension ◽  
Vascular Smooth Muscle ◽  
Actin Polymerization ◽  
Smooth Muscle Contraction ◽  
Isometric Tension ◽  
Mesenteric Arteries ◽  
Dynamic Regulation ◽  
Force Development

The ability of arterial smooth muscle to respond to vasoconstrictor stimuli is reduced in chronic portal hypertension (PHT). Additional evidence supports the existence of a postreceptor defect in vascular smooth muscle excitation contraction coupling. However, the nature of this defect is unclear. Recent studies have shown that vasoconstrictor stimuli induce actin polymerization in smooth muscle and that the associated increase in F-actin is necessary for force development. In the present study we have tested the hypothesis that impaired actin polymerization contributes to reduced vasoconstrictor function in small mesenteric arteries derived from rats with chronic prehepatic PHT. In vitro studies were conducted on small mesenteric artery vessel rings isolated from normal and PHT rats. Isometric tension responses to incremental concentrations of phenylephrine were significantly reduced in PHT arteries. The ability to polymerize actin in portal hypertensive mesenteric arteries stimulated by phenylephrine was attenuated compared with control. Inhibition of cAMP-dependent protein kinase (PKA) restored agonist-induced actin polymerization of arteries from PHT rats to normal levels. Depolymerization of actin in arteries from normal rats reduced maximal contractile force but not myosin phosphorylation, suggesting a key role for the dynamic regulation of actin polymerization in the maintenance of vascular smooth muscle contraction. We conclude that reductions in agonist-induced maximal force development of PHT vascular smooth muscle is due, in part, to impaired actin polymerization, and prolonged PKA activation may underlie these changes.

scholarly journals Myosin phosphorylation triggers actin polymerization in vascular smooth muscle

2008 ◽  
Vol 295 (5) ◽  
pp. H2172-H2177 ◽  
Author(s):  
Xuesong Chen ◽  
Kristin Pavlish ◽  
Joseph N. Benoit
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Light Chain ◽  
Actin Polymerization ◽  
Smooth Muscle Contraction ◽  
Mesenteric Arteries ◽  
Force Generation ◽  
Actin Binding ◽  
Binding Motif ◽  
Force Development

A variety of contractile stimuli increases actin polymerization, which is essential for smooth muscle contraction. However, the mechanism(s) of actin polymerization associated with smooth muscle contraction is not fully understood. We tested the hypothesis that phosphorylated myosin triggers actin polymerization. The present study was conducted in isolated intact or β-escin-permeabilized rat small mesenteric arteries. Reductions in the 20-kDa myosin regulatory light chain (MLC20) phosphorylation were achieved by inhibiting MLC kinase with ML-7. Increases in MLC20 phosphorylation were achieved by inhibiting myosin light chain phosphatase with microcystin. Isometric force, the degree of actin polymerization as indicated by the F-actin-to-G-actin ratio, and MLC20 phosphorylation were determined. Reductions in MLC20 phosphorylation were associated with a decreased force development and actin polymerization. Increased MLC20 phosphorylation was associated with an increased force generation and actin polymerization. We also found that a heptapeptide that mimics the actin-binding motif of myosin II enhanced microcystin-induced force generation and actin polymerization without affecting MLC20 phosphorylation in β-escin-permeabilized vessels. Collectively, our data demonstrate that MLC20 phosphorylation is capable of triggering actin polymerization. We further suggest that the binding of myosin to actin triggers actin polymerization and enhances the force development in arterial smooth muscle.

scholarly journals Abl activation regulates the dissociation of CAS from cytoskeletal vimentin by modulating CAS phosphorylation in smooth muscle

2010 ◽  
Vol 299 (3) ◽  
pp. C630-C637 ◽  
Author(s):  
Li Jia ◽  
Dale D. Tang
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Actin Polymerization ◽  
Spatial Location ◽  
Smooth Muscle Contraction ◽  
Nonreceptor Tyrosine Kinase ◽  
Force Development ◽  
Muscle Inhibition ◽  
A Cell ◽  
Contractile Activation

Abl is a nonreceptor tyrosine kinase that is required for smooth muscle contraction. However, the mechanism by which Abl regulates smooth muscle contraction is not completely understood. In the present study, Abl underwent phosphorylation at Tyr412 (an index of Abl activation) in smooth muscle in response to contractile activation. Treatment with a cell-permeable decoy peptide, but not the control peptide, attenuated Abl phosphorylation during contractile stimulation. Treatment with the decoy peptide did not affect the association of Abl with the cytoskeletal protein vinculin and the spatial location of vinculin in smooth muscle. Inhibition of Abl phosphorylation by the decoy peptide attenuated the agonist-induced phosphorylation of Crk-associated substrate (CAS), an adapter protein participating in the signaling processes that regulate force development in smooth muscle. Additionally, previous studies have shown that contractile stimulation triggers the dissociation of CAS from the vimentin network, which is important for cytoskeletal signaling and contraction in smooth muscle. In this report, the decrease in the amount of CAS in cytoskeletal vimentin in response to contractile activation was reversed by the Abl inhibition with the decoy peptide. Moreover, force development and the enhancement of F-actin-to-G-actin ratios (an indication of actin polymerization) upon contractile activation were also attenuated by the Abl inhibition. However, myosin phosphorylation induced by contractile activation was not affected by the inhibition of Abl. These results suggest that Abl regulates the dissociation of CAS from the vimentin network, actin polymerization, and contraction by modulating CAS phosphorylation in smooth muscle.

Norepinephrine and endothelin activate diacylglycerol kinases in caveolae/rafts of rat mesenteric arteries: agonist-specific role of PI3-kinase

2007 ◽  
Vol 292 (5) ◽  
pp. H2248-H2256 ◽  
Author(s):  
Christopher J. Clarke ◽  
Vasken Ohanian ◽  
Jacqueline Ohanian
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Contraction ◽  
Smooth Muscle Contraction ◽  
Pi3 Kinase ◽  
Mesenteric Arteries ◽  
Dependent Manner ◽  
Kinase Inhibition ◽  
Small Arteries ◽  
Vascular Smooth Muscle Contraction

The phosphatidylinositol (PI) signaling pathway mediates norepinephrine (NE)- and endothelin-1 (ET-1)-stimulated vascular smooth muscle contraction through an inositol-trisphosphate-induced rise in intracellular calcium and diacylglycerol (DG) activation of protein kinase C (PKC). Subsequent activation of DG kinases (DGKs) metabolizes DG to phosphatidic acid (PA), potentially regulating PKC activity. Because precise regulation and spatial restriction of the PI pathway is necessary for specificity, we have investigated whether this occurs within caveolae/rafts, specialized plasma membrane microdomains implicated in vascular smooth muscle contraction. We show that components of the PI signaling cascade-phosphatidylinositol 4,5-bisphosphate (PIP2), PA, and DGK-θ are present in caveolae/rafts prepared from rat mesenteric small arteries. Stimulation with NE or ET-1 induced [33P]PIP2 hydrolysis solely within caveolae/rafts. NE stimulated an increase in DGK activity in caveolae/rafts alone, whereas ET-1 activated DGK in caveolae/rafts and noncaveolae/rafts; however, [33P]PA increased in all fractions with both agonists. Previously, we reported that NE activated DGK-θ in a phosphatidylinositol 3-kinase (PI3-kinase)-dependent manner; here, we describe PI3-kinase-dependent DGK activation and [33P]PA production in caveolae/rafts in response to NE but not ET-1. Additionally, PKB, a potential activator of DGK-θ, translocated to caveolae/rafts in response to NE but not ET-1, and PI3-kinase inhibition prevented this. Furthermore, PI3-kinase inhibition reduced the sensitivity of contraction to NE but not ET-1. Our study shows that caveolae/rafts are major sites of vasoconstrictor hormone activation of the PI pathway in intact small arteries and suggest a link between lipid signaling events within caveolae/rafts and contraction.

Catecholamine release: mechanism of mercury-induced vascular smooth muscle contraction

1975 ◽  
Vol 229 (1) ◽  
pp. 8-12 ◽  
Author(s):  
HS Solomon ◽  
NK Hollenberg
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Electromagnetic Flowmeter ◽  
Smooth Muscle Contraction ◽  
Release Mechanism ◽  
Adrenergic Blockade ◽  
Mercuric Ion ◽  
Anesthetized Dogs

The mechanism by which mercuric ion (HgCl2) induces contraction of vascular smooth muscle was defined in the kidney of anesthetized dogs and in rabbit aortic strips. In vivo, HgCl2 injected into the renal artery induced a dose-related reduction in renal blood flow (electromagnetic flowmeter) and glomerular filtration rate (creatinine clearance). An intra-arterial infusion of phenoxybenzamine (POB) significantly reduced the vascular response to HgCl2 (P less than 0.001). In vitro, alpha-adrenergic blockade with phentolamine and POB prevented mercury-induced contraction, whereas agents that block serotonin, histamine, acetylcholine, and angiotensin did not do so. Norepinephrine receptor "protection" from phenoxybenzamine blockade sustained the response to HgCl2. Reserpine pretreatment produced a parallel reduction in the response of the aorta to tyramine and mercury. The results are consistent with an indirect action of mercuric ion via release of endogenous catecholamines.

Abstract 509: Essential Role of Vascular Smooth Muscle Bmal1 in Diurnal Variations of Contraction and Blood Pressure

Hypertension ◽  
2012 ◽  
Vol 60 (suppl_1) ◽  
Author(s):  
Wen Su ◽  
Zhongwen Xie ◽  
Zhenheng Guo ◽  
Ming C Gong
Keyword(s):  
Blood Pressure ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Essential Role ◽  
Smooth Muscle Contraction ◽  
Diurnal Variations ◽  
Mesenteric Arteries ◽  
Isometric Contractions ◽  
Vascular Smooth Muscle Contraction

Bmal1 is an obligatory core clock gene that is ubiquitously expressed but has been demonstrated to have tissue specific functions. However, the vascular smooth muscle specific function of bmal1 is unknown. We generated a smooth muscle specific bmal1 knockout mouse model (SM-bmal1-ko) and investigated the role of bmal1 in vascular smooth muscle contraction and blood pressure regulation. Isometric contractions were measured in isolated right renal artery and 2 nd order branch of mesenteric artery helical strips. Blood pressure was monitored in conscious free-moving mice using radiotelemetry. We demonstrated that bmal1 was selectively deleted in smooth muscle enriched tissues like mesenteric arteries. Moreover, the diurnal variations of bmal1 target genes per1/2 were abolished in mesenteric arteries. The isometric contractions in response to alpha1 agonist phenylephrine and to 5-HT were significantly diminished in vascular helical strips isolated from SM-bmal1-ko mice compared to that from control flox mice. The contractile diurnal variations detected in the renal arteries isolated from control flox mice were significantly diminished in samples isolated from SM-bmal1-ko mice. Moreover, in vivo , the diurnal variations in the instantaneous pressor responses to intravenous phenylephrine injection were significantly diminished in SM-bmal1-ko mice compared to control flox mice. Twenty four hour mean arterial blood pressure was significantly decreased under 12:12 light:dark, constant light or constant dark conditions. Importantly, the amplitude of blood pressure diurnal variations was significantly diminished in SM-bmal1-ko mice. Importantly, neither the level nor the diurnal variations of locomotor activity was affected by bmal1 deletion. This indicates that the central SCN clock function is not affected in the SM-bmal1-ko mice and the blood pressure alterations in SM-bmal1-ko mice is not a consequence of changed locomotor activity. Taken together, our results demonstrate an essential role of bmal1 in the diurnal variations of vascular smooth muscle contraction and blood pressure.

scholarly journals Abl knockout differentially affects p130 Crk-associated substrate, vinculin, and paxillin in blood vessels of mice

2009 ◽  
Vol 297 (2) ◽  
pp. H533-H539 ◽  
Author(s):  
Shu Chen ◽  
Ruping Wang ◽  
Qing-Fen Li ◽  
Dale D. Tang
Keyword(s):  
Blood Pressure ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Contraction ◽  
Knockout Mice ◽  
Actin Polymerization ◽  
Fluorescent Microscopy ◽  
Smooth Muscle Contraction ◽  
Cellular Process ◽  
Actin Dynamics

Actin polymerization has recently emerged as an important cellular process that regulates smooth muscle contraction. Abelson tyrosine kinase (Abl) has been implicated in the regulation of actin dynamics and force development in vascular smooth muscle. In the present study, the systolic blood pressure was lower in Abl−/− knockout mice compared with wild-type mice. The knockout of Abl diminished the tyrosine phosphorylation of p130 Crk-associated substrate (CAS, an adapter protein associated with smooth muscle contraction) in resistance arteries upon stimulation with phenylephrine or angiotensin II. The agonist-elicited enhancement of F-actin-to-G-actin ratios in arteries assessed by fluorescent microscopy was also reduced in Abl−/− mice. It has been known that vinculin is a structural protein that links actin filaments to extracellular matrix via transmembrane integrins, whereas paxillin is a signaling protein associated with focal contacts mediating actin cytoskeleton remodeling. The expression of vinculin and paxillin at protein and messenger levels was lower in arterial vessels from Abl knockout mice. However, the agonist-induced increase in myosin phosphorylation was not attenuated in arteries from Abl knockout mice. These results indicate that Abl differentially regulates Crk-associated substrate, vinculin, and paxillin in arterial vessels. The Abl-regulated cellular process and blood pressure are independent of myosin activation in vascular smooth muscle.

Cultured smooth muscle approach in the study of hypertension

1992 ◽  
Vol 70 (4) ◽  
pp. 573-579 ◽  
Author(s):  
Stephen C. Pang ◽  
Shannon L. Venance
Keyword(s):  
Cell Culture ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Spontaneously Hypertensive Rat ◽  
Marked Change ◽  
Culture Technique ◽  
Mesenteric Arteries ◽  
Experimental Hypertension ◽  
In Vitro Techniques

The systemic vasculature is known to undergo marked change in both human and experimental hypertension. The in vitro study of individual cellular components from the blood vessel wall and the regulation of their intracellular biochemical processes will aid in developing an understanding of the pathogenesis of hypertension. Vascular smooth muscle cells derived from the aorta and mesenteric arteries of normotensive and hypertensive rats can be successfully maintained in culture, providing a system free of confounding variables such as blood pressure. To assist in fully understanding the pathophysiology of hypertension, this cell culture model can be used to examine interactions between receptor and ligand, the transduction of an associated signal, characterization of subsequent intracellular responses and ultimately, quantification of a physiological and functional consequence of these events, for example, proliferation. The application of in vitro techniques to hypertension research will continue to contribute new knowledge to increase our understanding of the mechanisms behind the hypertensive disease process.Key words: experimental hypertension, spontaneously hypertensive rat, vascular smooth muscle, aorta, mesenteric arteries, cell culture technique.

scholarly journals Regulation of PKC Autophosphorylation by Calponin in Contractile Vascular Smooth Muscle Tissue

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Hak Rim Kim ◽  
Cynthia Gallant ◽  
Kathleen G. Morgan
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Contraction ◽  
Smooth Muscle Tissue ◽  
Hydrophobic Site ◽  
Regulatory Phosphorylation ◽  
Motif Site ◽  
Key Enzyme

Protein kinase C (PKC) is a key enzyme involved in agonist-induced smooth muscle contraction. In some cases, regulatory phosphorylation of PKC is required for full activation of the enzyme. However, this issue has largely been ignored with respect to PKC-dependent regulation of contractile vascular smooth muscle (VSM) contractility. The first event in PKC regulation is a transphosphorylation by PDK at a conserved threonine in the activation loop of PKC, followed by the subsequent autophosphorylation at the turn motif and hydrophobic motif sites. In the present study, we determined whether phosphorylation of PKC is a regulated process in VSM and also investigated a potential role of calponin in the regulation of PKC. We found that calponin increases the level of in vitro PKCαphosphorylation at the PDK and hydrophobic sites, but not the turn motif site. In vascular tissues, phosphorylation of the PKC hydrophobic site, but not turn motif site, as well as phosphorylation of PDK at S241 increased in response to phenylephrine. Calponin knockdown inhibits autophosphorylation of cellular PKC in response to phenylephrine, confirming results with recombinant PKC. Thus these results show that autophosphorylation of PKC is regulated in dVSM and calponin is necessary for autophosphorylation of PKC in VSM.

Effects of the β-Receptor Antagonists Propranolol, Oxprenolol and Labetalol on Human Vascular Smooth-Muscle Contraction

1978 ◽  
Vol 55 (3) ◽  
pp. 235-240
Author(s):  
R. F. W. Moulds ◽  
R. A. Jauernig ◽  
J. D. Hobson ◽  
J. Shaw
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Barium Chloride ◽  
Smooth Muscle Contraction ◽  
Hypotensive Activity ◽  
Inhibitory Effects ◽  
Vascular Effects ◽  
High Concentrations ◽  
Β Receptor

1. Spiral strips of human digital arteries have been studied in vitro to investigate whether dl-propranolol, d-propranolol, oxprenolol and labetalol have peripheral vascular effects in man. 2. Labetalol was a potent inhibitor of contractile responses to noradrenaline, but had less effect on responses to 5-hydroxytryptamine and barium chloride. 3. dl-and d-propranolol were equally effective inhibitors of responses to barium chloride. They were only weak antagonists of noradrenaline responses, but stronger, non-competitive antagonists of 5-hydroxytryptamine responses. 4. Oxprenolol was only a weak inhibitor of the responses to both noradrenaline and 5-hydroxytryptamine and had little effect on responses to barium chloride. 5. It is concluded that labetalol has specific α-adrenoreceptor-blocking properties, which are probably relevant to its therapeutic action in man. Propranolol has non-specific inhibitory effects on vascular smooth muscle, which might contribute to its hypotensive activity at high concentrations, but oxprenolol has only slight peripheral effects that are probably therapeutically insignificant.

Dual Actions of Halothane on Intracellular Calcium Stores of Vascular Smooth Muscle

1996 ◽  
Vol 84 (3) ◽  
pp. 580-595 ◽  
Author(s):  
Takashi Akata ◽  
Walter A. Boyle
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Intracellular Calcium ◽  
Inhibitory Effect ◽  
Isometric Tension ◽  
Mesenteric Arteries ◽  
Calcium Stores ◽  
Free Solution ◽  
Dependent Inhibition ◽  
Permeabilized Muscle

Background Halothane has been reported to affect the integrity of intracellular Ca2+ stores in a number of tissues including vascular smooth muscle. However, the actions of halothane on intracellular Ca2+ stores are not yet fully understood. Methods Employing the isometric tension recording method, the action of halothane in isolated endothelium-denuded rat mesenteric arteries under either intact or beta-escinmembrane-permeabilized conditions was investigated. Results Halothane (0.125-5%) produced concentration-dependent contractions in Ca2+ free solution in both intact and membrane-permeabilized muscle strips. Ryanodine treatment or repetitive application of phenylephrine eliminated both caffeine-and halothane-induced contractions in the Ca2+ free solution. When either halothane and caffeine, caffeine and halothane, phenylephrine and halothane, or inositol 1,4,5-triphosphate and halothane were applied consecutively in the Ca2+ free solution in either intact or membrane-permeabilized muscle strips, the contraction induced by application of the second agent of the pair was inhibited compared to application of that agent alone. However, when procaine was applied before and during application of the first agent, the contraction induced by the first agent was inhibited and the contraction induced by the second agent was restored. Heparin inhibited the inositol 1,4,5-triphosphate-mediated contraction, but not contractions induced by halothane or caffeine. Halothane (0.125-5%), applied during Ca2+ loading, produced concentration-dependent inhibition of the caffeine contraction (used to estimate the amount of Ca2+ in the store) in both intact and membrane-permeabilized muscle strips. In contrast, halothane applied with procaine during Ca2+ loading produced concentration-dependent enhancement of the caffeine contraction. This enhancement was observed only in the intact but not in the membrane-permeabilized condition. Conclusions Halothane has two distinct actions on the intracellular Ca2+ stores of vascular smooth muscle, a Ca2+ releasing action and a stimulating action on Ca2+ uptake. Halothane releases Ca2+ from the stores that are sensitive to both caffeine/ryanodine and phenylephrine/inositol 1,4,5-triphosphate through a procaine-sensitive mechanism. The observed inhibitory effect on Ca2+ uptake is probably caused by the Ca2+ uptake after blockade of Ca2+ release may be membrane-mediated.

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