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PubMed1979

Responsiveness to insulin of glucose metabolism in cultured rat and human arterial smooth muscle cells.

Smooth muscle cells growing in the primary culture derived from outgrowths of the intimal-medial explants of both rat and human arteries were used. The 72-hr sequential glucose uptake by the cells of both species in culture dishes was enhanced only slightly with time by the addition of insulin to culture medium, and this enhancement was statistically not significant. The glucose conversions to CO2 and lipids by the rat and human cells dissociated for tracer study were not affected significantly during the 2-hr incubation by the insulin addition in vitro. The smooth muscle cells of both species cultured for a week in medium enriched with insulin and then dissociated revealed the significantly increased glucose conversion to lipids, while the increase in the glucose coversion to CO2 was not significant in these cells. Thus, the smooth muscle cells of both rat and human seem to show significant metabolic response to chronic, but not acute, exposure to insulin. Therefore, it is likely that the persistent change in the insulin level may lead to abnormal metabolic state in the artery.

Animals↗
PubMed2001

Neurotransmission and drug effects in urethral smooth muscle.

Urethral smooth muscle tension is one of the factors contributing to the maintenance of intraurethral pressure and to continence. This tension is controlled by nervous mechanisms involving a complex pattern of efferent and afferent signalling in parasympathetic, sympathetic, and somatic nerves, with resulting release of contraction- and relaxation-producing transmitters and mediators. Sympathetic activity, via release of NA and stimulation of urethral smooth muscle alpha1-ARs, is the main contraction-producing factor. Among the three high affinity alpha1-AR subtypes identified in molecular cloning and functional studies, the alpha1A subtype seems to predominate in both the male and female urethra. The physiological role of the urethral beta-adrenoceptors has not been established, and the importance of muscarinic receptors (and subtypes) for urethral function is presently unclear. Nitric oxide, produced by nitric oxide synthase within cholinergic nerves, seems to be the predominant inhibitory neurotransmitter, but there is good evidence for the existence of other, as yet unidentified, non-adrenergic, non-cholinergic inhibitory messengers. Vasoactive intestinal polypeptide, adenosine 5'-triphosphate, and carbon monoxide (CO) all relax urethral smooth muscle, and are potential candidates for the nonadrenergic, noncholinergic relaxation, but their roles for urethral function remain to be defined.

Humans↗
PubMedDate not supplied

Signalling pathways activated by 5-HT(1B)/5-HT(1D) receptors in native smooth muscle and primary cultures of rabbit renal artery smooth muscle cells.

The potential of primary cultures of rabbit renal artery vascular smooth muscle cells (VSMCs) was assessed as a means to investigate the signalling pathways linked to 5-hydroxytryptamine (5-HT) 5-HT(1B)/5-HT(1D) receptors in native arteries. In renal artery segments denuded of endothelium, incubated with ketanserin and prazosin (each 1 microM), and prestimulated with 20 mM K(+) Krebs buffer, 5-HT and CP 93,129, a 5-HT(1B) receptor agonist, evoked concentration-dependent contractions. GR 127935, a 5-HT(1B)/5-HT(1D) receptor antagonist, significantly antagonised 5-HT-evoked contractions at nanomolar concentrations. Reverse transcription polymerase chain reaction (RT-PCR) of mRNA from smooth muscle cells from the isolated renal artery and from primary cultures of VSMCs from the same artery expressed mRNA transcripts for the 5-HT(1B) receptor and the 5-HT(1D) receptor in both preparations. The sequence of the PCR fragments corresponded to the known sequence for these receptors. Application of 5-HT evoked a concentration-dependent, pertussis toxin (PTx)-sensitive reduction in cyclic AMP in both cultured cells and intact artery (cyclic AMP concentration reduced by 65.53 +/- 3.33 and 52.65 +/- 5.34% from basal with 10 microM 5-HT, respectively). The effect of 10 microM 5-HT on cAMP was increased in the presence of 20 mM K(+) (reduced by 82.50 +/- 2.50 and 87.54 +/- 3.97%, respectively). In intact arteries, contraction through 5-HT(1B)/5-HT(1D) receptors was significantly attenuated by inhibitors of phosphatidylinositol 3-kinase (wortmannin) and activated mitogen-activated protein kinase (MAPK), MEK (U0126). In the cultured VSMCs, activated MAPK was identified by immunocytochemistry and immunoblotting after stimulation with 5-HT, but only if 20 mM K(+) was present at the onset of stimulation. These data provide the first direct evidence that 5-HT(1B)/5-HT(1B) receptors are linked to the activation of MAPK and indicate that primary cultures of renal VSMCs could provide a model system to study further the signalling pathways linked to these receptors.

Androstadienes↗
PubMed1988

Differential pharmacologic sensitivity of cyclic nucleotide phosphodiesterase isozymes isolated from cardiac muscle, arterial and airway smooth muscle.

Phosphodiesterase isozymes were isolated by diethylaminoethyl ether (DEAE) column chromatography from cardiac muscle (canine, guinea pig), vascular (canine and guinea pig aortic) and airway (canine tracheal) smooth muscle. All peak I phosphodiesterases had a low apparent Km (0.29-0.49 microM) for guanosine 3':5' cyclic monophosphate (cGMP) and all peak III phosphodiesterases had a low apparent Km (0.35-0.58 microM) for adenosine 3':5' cyclic monophosphate (cAMP); trachealis peak III also had a high Km for cAMP (32 microM). The potency and selectivity for inhibition of peak I or peak III phosphodiesterase by theophylline and papaverine, the peak I selective inhibitor M + B 22948, and the peak III selective inhibitors amrinone, milrinone, imazodan, CI-930 and piroximone were approximately equal when isozymes isolated from aortic smooth muscle were compared to isozymes isolated from cardiac muscle of both species. Rolipram was relatively potent as a peak III phosphodiesterase inhibitor in canine cardiac muscle, but was impotent in the other cardiovascular peak IIIs. In tracheal smooth muscle, the cardiovascular selective peak III phosphodiesterase selective inhibitors were substantially less potent while rolipram was more potent as a peak III inhibitor. In summary, these studies show that while cardiac and vascular smooth muscle phosphodiesterase isozymes are pharmacologically similar, there is pharmacological and substrate heterogeneity of peak III phosphodiesterase in aortic vs. trachea smooth muscle within the same species.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1983

Studies on isolated smooth muscle cells. VIII. 45Ca-efflux from single smooth muscle cells isolated from taenia coli of guinea pig.

45Ca-loaded single smooth muscle cells were prepared from taenia coli of guinea pig. The cells were perfused continuously with physiological salt solution on membrane filter with pore size of 12 microns and radioactivity in the effluent was determined. The 45Ca-efflux curves consisted of two straight lines in semilogarithmic figure representing loosely and tightly bound calcium compartments with half time of 1.87 +/- 0.27 and 6.78 +/- 0.43 min, respectively. The loosely bound calcium was supposed to be localized on plasma membrane. Size of the tightly bound 45Ca was dependent on period for calcium-depletion of the preparation prior to 45Ca-loading. The efflux was stimulated by acetylcholine and the stimulated efflux returned to the spontaneous efflux level instantly after removal of acetylcholine. This stimulation was abolished by atropine. Repetitive stimulation failed to increase 45Ca-efflux while the rate of the spontaneous 45Ca-efflux did not change significantly. These results suggested that, in taenia coli of guinea pig, at least three calcium compartments existed, loosely bound calcium, tightly bound calcium and more tightly bound calcium which can be released by acetylcholine, in addition to calcium in extracellular fluid. Advantages and disadvantages of using single smooth muscle cells for investigation of calcium movement and some technical improvement for determination of 45Ca-efflux from single cells were described.

Acetylcholine↗
PubMed1996

Expression of the smooth muscle cell calponin gene marks the early cardiac and smooth muscle cell lineages during mouse embryogenesis.

Although several genes are considered markers for vascular smooth muscle cell (SMC) differentiation, few have been rigorously tested for SMC specificity in mammals, particularly during development where considerable overlap exists between different muscle gene programs. Here we describe the temporospatial expression pattern of the SMC calponin gene (formerly h1 or basic calponin) during mouse embryogenesis and in adult mouse tissues and cell lines. Whereas SMC calponin mRNA expression is restricted exclusively to SMCs in adult tissues, during early embryogenesis, SMC calponin transcripts are expressed throughout the developing cardiac tube as well as in differentiating SMCs. Transcription of the SMC calponin gene initiates at two closely juxtaposed sites in the absence of a consensus TATAA or initiator element. Transient transfection assays in cultured SMC demonstrated that high level SMC calponin promoter activity required no more than 549 nucleotides of 5 sequence. In contrast to the strict cell type-specificity of SMC calponin mRNA expression, the SMC calponin promoter showed activity in several cell lines that do not express the endogenous SMC calponin gene. These results demonstrate that SMC calponin responds to cardiac and smooth muscle gene regulatory programs and suggest that the cardiac and smooth muscle cell lineages may share a common gene regulatory program early in embryogenesis, which diverges as the heart matures. The finding that the isolated SMC calponin promoter is active in a wider range of cells than the endogenous SMC calponin gene also suggests that long-range repression or higher order regulatory mechanism(s) are involved in cell-specific regulation of SMC calponin expression.

Animals↗
PubMed1999

Heparin inhibits proliferation of myometrial and leiomyomal smooth muscle cells through the induction of alpha-smooth muscle actin, calponin h1 and p27.

Mast cells are widely distributed in human tissues, including the human uterus. However, the function of mast cells in uterine smooth muscle has not been clearly established. Mast cells possess secretory granules containing such substances as heparin, serotonin, histamine and many cytokines. To help establish the role of mast cells in the human myometrium, the action of heparin was investigated using smooth muscle cells (SMC) from normal myometrium and from leiomyoma. The proliferation of cultured myometrial and leiomyomal SMC was inhibited by heparin treatment. Flow cytometric analysis showed that the population in the G1 phase of the cell cycle increased under heparin treatment. Western blotting analysis showed that markers of SMC differentiation such as alpha-smooth muscle actin (alpha-SMA), calponin h1 and cyclin-dependent kinase inhibitor p27 were induced by heparin, whereas cell-cycle-related gene products from the G1 phase of the cell cycle, such as cyclin E and cdk2, were not changed. Taken together, these results indicate that heparin inhibits the proliferation of myometrial and leiomyomal SMC through the induction of alpha-SMA, calponin h1 and p27. We suggest that heparin from mast cells may induce differentiation in uterine SMC and may influence tissue remodelling and reconstruction during physiological and pathophysiological events.

Actins↗
PubMed2002

Signal transduction and protein phosphorylation in smooth muscle contraction.

Smooth muscles are important constituents of vertebrate organisms that provide for contractile activity of internal organs and blood vessels. Basic molecular mechanism of both smooth and striated muscle contractility is the force-producing ATP-dependent interaction of the major contractile proteins, actin and myosin II molecular motor, activated upon elevation of the free intracellular Ca2+ concentration ([Ca2+](i)). However, whereas striated muscles display a proportionality of generated force to the [Ca2+](i) level, smooth muscles feature molecular mechanisms that modulate sensitivity of contractile machinery to [Ca2+](i). Phosphorylation of proteins that regulate functional activity of actomyosin plays an essential role in these modulatory mechanisms. This provides an ability for smooth muscle to contract and maintain tension within a broad range of [Ca2+](i) and with a low energy cost, unavailable to a striated muscle. Detailed exploration of these mechanisms is required to understand the molecular organization and functioning of vertebrate contractile systems and for development of novel advances for treating cardiovascular and many other disorders. This review summarizes the currently known and hypothetical mechanisms involved in regulation of smooth muscle Ca2+-sensitivity with a special reference to phosphorylation of regulatory proteins of the contractile machinery as a means to modulate their activity.

Actins↗
PubMed2006

Hyperplasia suppressor gene associates with smooth muscle alpha-actin and is involved in the redifferentiation of vascular smooth muscle cells.

Vascular smooth muscle cell (VSMC) differentiation and phenotypic modulation are characterized by changes in gene expression for smooth muscle (SM) marker contractile proteins such as SM alpha-actin and SM22alpha. Hyperplasia suppressor gene (HSG) is a potent VSMC proliferation-inhibiting factor; however, it is not known if HSG is involved in the redifferentiation of VSMCs. Here, the redifferentiation of the dedifferentiated VSMCs was induced by serum withdrawal or all-trans retinoic acid (atRA), HSG gene expression and its role in VSMC phenotypic modulation were studied by reverse transcription - polymerase chain reaction, Western blotting, and cell migration assay. The results indicated that HSG gene expression increased significantly during VSMC redifferentiation induced by serum deprivation or atRA and peaked at 24 h, then was maintained at higher levels. Meanwhile, SM marker contractile proteins SM alpha-actin and SM22alpha were increased by more than 2-fold. Coimmunoprecipitation and immunofluorescent experiments revealed that anti-HSG antibody could precipitate SM alpha-actin, and HSG and SM alpha-actin colocalized within the cytoplasm of differentiated VSMCs. Migration activity of VSMCs was dramatically suppressed after cells were transfected with HSG expression plasmids. These findings suggested that HSG is associated with SM alpha-actin in VSMC cytoplasm, and is involved in VSMC differentiation and migration.

Actins↗
PubMed1995

Carvedilol, a new vasodilating beta-adrenoceptor blocker, inhibits oxidation of low-density lipoproteins by vascular smooth muscle cells and prevents leukocyte adhesion to smooth muscle cells.

The present study was undertaken to assess the effect of carvedilol, a new vasodilating beta-adrenoceptor blocker with antioxidant activity, on the oxidation of low-density lipoproteins (LDL) by rat aortic smooth muscle cells (RASMC). LDL oxidation was assessed as thiobarbituric acid reactive substances (TBARS) formation and increase in electrophoretic mobility. Oxidized (ox) LDL-induced cytotoxicity was assessed as lactate dehydrogenase release (LDH) from cells and ox-LDL-enhanced adhesiveness of the RASMC for leukocytes was also determined. Carvedilol inhibited TBARS formation and LDH release from RASMC with IC50 values of 1.74 and 1.62 microM, respectively. Under the same conditions, the IC50 values of probucol and nicardipine were 2.33 and 5.60 microM, respectively, for inhibition of TBARS and 5.16 and 12.10 microM, respectively, for inhibition of LDH release; propranolol, atenolol, pindolol and labetalol, at concentrations up to 100 microM, had virtually no effect on either variable. RASMC-dependent ox-LDL stimulated the adhesive properties of RASMC for both monocytes and neutrophils in a concentration- and time-dependent manner, which were prevented when the RASMC were treated with carvedilol (IC50 2.07 microM for monocytes and 1.12 microM for neutrophils), whereas other beta blockers, at concentrations up to 30 microM, had only mild effects. The monoclonal antirat intercellular adhesion molecule-1 antibody partially inhibited ox-LDL-induced adhesion of RASMC for monocytes and neutrophils. Northern analysis demonstrated that ox-LDL induced intracellular adhesion molecule-1 messenger RNA expression on RASMC, which was inhibited by carvedilol and probucol via inhibition of LDL oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1998

Pharmacological characterization of muscarinic receptors in rabbit isolated iris sphincter muscle and urinary bladder smooth muscle.

1. The pharmacological characteristics of muscarinic receptors in the rabbit iris sphincter muscle were studied and compared to M3 receptors in rabbit urinary bladder smooth muscle. 2. (+/-)-Cis-dioxolane induced concentration-dependent contractions of the iris sphincter muscle (pEC50 = 6.41+/-0.10, Emax = 181+/-17 mg, n = 38) and urinary bladder smooth muscle (pEC50 = 6.97+/-0.04, Emax = 4.28+/-0.25 g, n = 54). These contractions were competitively antagonized by a range of muscarinic receptor antagonists (pK(B) values are given for the iris sphincter muscle and the bladder smooth muscle, respectively): atropine (9.30+/-0.07 and 9.40+/-0.04), AQ-RA 741 (6.35+/-0.04 and 6.88+/-0.03), darifenacin (9.56+/-0.05 and 9.12+/-0.05), methoctramine (5.75+/-0.07 and 5.81+/-0.06), oxybutynin (8.10+/-0.09 and 8.59+/-0.06), pirenzepine (6.79+/-0.05 and 6.89+/-0.04), secoverine (7.54+/-0.05 and 7.66+/-0.05), p-F-HHSiD (7.55+/-0.09 and 7.50+/-0.05) and zamifenacin (8.69+/-0.10 and 8.36+/-0.06). A significant correlation between the pK(B) values in the bladder and the pK(B) values in the iris was obtained. 3. In both tissues, the pK(B) values correlated most favorably with pKi values for these compounds at human recombinant muscarinic m3 receptors. A reasonable correlation was also noted at human recombinant muscarinic m5 receptors given the poor discriminative ability of ligands between m3 and m5 receptors. 4. Overall, the data from this study suggest that the muscarinic receptors mediating contraction of the rabbit iris sphincter muscle and urinary bladder smooth muscle are similar and equate most closely with the pharmacologically-defined muscarinic M3 receptor.

Animals↗
PubMed1986

Analysis of smooth muscle myosin phosphorylation with native pyrophosphate gels and its application to studies on myosin phosphorylation in contracting smooth muscle.

Gizzard smooth muscle myosin, the 20,000 Mr light chain (L20) of which had been phosphorylated in vitro with a calmodulin-myosin light chain kinase system, was separated into 5 isolated bands in a pyrophosphate polyacrylamide gel. Their mobilities were in the following order: myosin with 2 unphosphorylated L20 (GM) less than myosin with 1 unphosphorylated and 1 mono-phosphorylated L20 (GMP1) less than myosin with 2 mono-phosphorylated L20 (GMP2) less than myosin with 1 mono-phosphorylated and 1 di-phosphorylated L20 (GMP3) less than myosin with 2 di-phosphorylated L20 (GMP4). We used this pyrophosphate polyacrylamide gel electrophoresis to analyze the phosphorylated state of taenia coli smooth muscle during K+-induced contraction. During the initial 2 min contraction, phosphorylated forms corresponding to GMP1 and GMP2 were detected in addition to the unphosphorylated form.

Animals↗
PubMed2000

Diagnostic implications of elevated levels of smooth-muscle myosin heavy-chain protein in acute aortic dissection. The smooth muscle myosin heavy chain study.

BACKGROUND: A rapid 30-minute assay of circulating smooth-muscle myosin heavy-chain protein has been developed as a biochemical diagnostic tool for aortic dissection. OBJECTIVE: To determine the sensitivity and specificity of this assay. DESIGN: Cross-sectional study. SETTING: 8 major cardiovascular centers in Japan. PATIENTS: 95 patients with acute aortic dissection, 48 patients with acute myocardial infarction, and 131 healthy volunteers. MEASUREMENTS: Levels of circulating smooth-muscle myosin heavy-chain protein. RESULTS: Patients with acute aortic dissection who presented within 3 hours after onset had elevated levels of circulating smooth-muscle myosin heavy-chain protein. In these patients, the assay had a sensitivity of 90.9%, a specificity of 98% compared with healthy volunteers, and a specificity of 83% compared with patients who had acute myocardial infarction; the clinical decision limit was 2.5 microgram/L. All patients with proximal lesions had elevated levels of smooth-muscle myosin heavy-chain protein, and only patients with distal lesions had decreased levels (<2.5 microgram/L). CONCLUSIONS: Levels of smooth-muscle myosin heavy-chain protein can be used to diagnose aortic dissection soon after symptom onset. The assay had the greatest diagnostic value in patients with proximal lesions.

Aged↗
PubMed1988

Phosphorylation of two sites on smooth muscle myosin. Effects on contraction of glycerinated vascular smooth muscle.

Contraction of glycerinated porcine carotid artery smooth muscle in response to calcium (20 microM), calmodulin (10 microM), and MgATP was associated with phosphorylation of the 20,000-dalton myosin light chain (LC20) to an average stoichiometry of 1.47 mol of PO4/mol of LC20. Tryptic and chymotryptic phosphopeptide maps of the mono- and diphosphorylated forms of LC20 purified from skinned muscles demonstrated the presence of a single phosphopeptide in all cases. Phosphoamino acid analysis indicated that the monophosphorylated form contained primarily phosphoserine, whereas the diphosphorylated form contained both phosphoserine and phosphothreonine. Thiophosphorylation of LC20 by adenosine 5'-O-(thiotriphosphate) resulted in the incorporation of 1 mol of thiophosphate into phosphoserine. Thiophosphorylated LC20 could be subsequently phosphorylated at a threonine residue to a stoichiometry of 1.7 mol of PO4/mol of LC20 by incubation in the presence of MgATP, calcium, and calmodulin. The extent of multiple site phosphorylation of LC20 was dependent upon both the ionic strength and the free Mg2+ concentration in the muscle bath; increasing either ionic strength (0.07-0.15 M) or [Mg2+] (1-20 mM) resulted in lower stoichiometries of LC20 phosphorylation. The effect of multiple site phosphorylation on contraction was examined in muscles which were seqentially phosphorylated at serine followed by threonine. Full activation (21 degrees C) of both isometric force (1.4 newtons/cm2) and unloaded shortening velocity (0.016 L0/s) was achieved following thiophosphorylation to 1.1 mol of PO4/mol of LC20. No further activation of either isometric force (1.5 newtons/cm2) or unloaded shortening velocity (0.015 L0/s) occurred following phosphorylation to 1.7 mol of PO4/mol of LC20.

Adenosine Triphosphate↗
PubMed2001

The proliferative response of p53 knock-out mouse-derived vascular smooth muscle cell line, P53LMAC01, to PDGF, when compared with human aortic smooth muscle cells.

To develop an in vitro experimental model of vascular smooth muscle cell hyperplasia, a major feature in chronic cardiac rejection, we studied a novel vascular smooth muscle cell line, P53LMAC01 (AC01), which was established from aortic smooth muscles of p53 knock-out mice, to determine its response to a platelet-derived growth factor (PDGF) and to Cyclosporin A (CsA). The responses were compared with those of human aortic smooth muscle cells (AOSMC). The AC01 exhibited a distinct proliferative response to PDGF similar to that of AOSMC under serum-free conditions. 10 ng/ml of PDGF-BB increased by a factor of 4.5 and PDGF-AB doubled the thymidine uptake, but PDGF-AA caused only a slight increase. The proliferation was markedly inhibited by 10(-6) M of CsA but less affected by 10(-7) M. These results indicate that the AC01 cell line could provide a convenient experimental system for investigating chronic rejection in vitro and that the system might work as a screening model of agents for treating transplant-related arteriosclerosis.

Animals↗
PubMed2000

Age-dependent increase in c-fos activity and cyclin A expression in vascular smooth muscle cells. A potential link between aging, smooth muscle cell proliferation and atherosclerosis.

OBJECTIVE: Aging can be defined as a progressive deterioration of biological functions after the organism has attained its maximal reproductive competence, which is usually associated with a decrease in proliferative ability in most cell types. However, in certain pathological situations such as atherosclerosis and restenosis, aging has been shown to be associated with a higher level of vascular smooth muscle cell (VSMC) proliferation and neointimal lesion formation after angioplasty. In the present study, we investigated potential mechanisms involved in the age-dependent increase in VSMC proliferation. METHODS AND RESULTS: Primary cultures of VSMCs were isolated from young (6-8-month-old) and old (4-5-year-old) New Zealand rabbits. Results from cell counting assays and FACS analysis were consistent with a shortening of the cell cycle in old VSMCs. Western blot analysis in serum stimulated cells showed a significant increase in the level of cyclin A and cyclin-dependent kinase 2 proteins in the old vs. young VSMCs. In marked contrast, expression of cyclin E in VSMCs was not influenced by aging. Transient transfection assays showed an age-dependent increase in transcription from the human cyclin A promoter. Parallel studies demonstrated that the expression of the AP1 transcription factor c-fos, which interacts with the cyclin A promoter and stimulates VSMC proliferation, was also increased in old VSMCs. Consistent with this notion, electrophoretic mobility shift assays demonstrated an increase in AP1 DNA-binding activity in old VSMCs. CONCLUSIONS: These studies suggest that age-associated increase in c-fos activity contributes to augmented cyclin A expression and VSMC proliferation in old animals. These mechanisms might contribute to the higher prevalence and severity of atherosclerosis in the elderly.

Aging↗