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Results for “Phenotypic modulation”

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PubMed1993

Relationship between functional Na+ pumps and mitogenesis in cultured coronary artery smooth muscle cells.

An increase in functional sarcolemmal Na(+)-K(+)-ATPase (Na+ pump) precedes proliferation in vascular smooth muscle cells (VSMCs) seeded in 10% fetal bovine serum (FBS), but its role in mitogenesis is unresolved. Enzymatically dispersed canine coronary artery VSMCs were seeded in FBS and studied through confluence. Before a shift in cell cycle (G1-->S, G2 + M) and appearance of the nonmuscle isoform of myosin (MHCnm), intracellular Na+ content (Na+i) and cell volume (CV) increased (day 0 through day 3). Na+ pump number ([3H]-ouabain binding) increased at day 4 followed by a decrease in Na+i and CV. When Na+ pumps were inhibited by the addition of ouabain to FBS, VSMCs were arrested in G1, and MHCnm was not upregulated. Na+i increased similarly to that in FBS but failed to correct to day 0 levels. Withdrawal of ouabain at day 4 in culture led to an increase in Na+ pump number, a decrease in Na+i, entry of cells into S and G2 + M, and upregulation of MHCnm. These data suggest that Na+i, phenotypic modulation, and entry of cells into the cell cycle are temporally related, with Na+ pump-mediated correction of increased Na+i as a key event in the VSMC mitogenic process.

Animals↗

PubMed1997

Endothelial cell-conditioned medium downregulates smooth muscle contractile protein expression.

Smooth muscle cells (SMC) within atherosclerotic lesions proliferate and exhibit phenotypic modulation, but the contribution of vascular endothelium to this process is poorly understood. Our aim was to examine the effects of endothelial cell-conditioned medium (ECCM) on vascular SMC growth and differentiation. Rat aortic ECCM stimulated a ninefold increase in [3H]thymidine incorporation and downregulated smooth muscle-specific myosin heavy chain and alpha-actin synthesis in rat aortic SMC. These effects were not inhibited by antibodies to platelet-derived growth factor (PDGF)-BB or PDGF-AB or with a PDGF beta-receptor subunit. Treatment with PDGF-BB (at a concentration found in ECCM), PDGF-AA, basic fibroblast growth factor, endothelin-1, or transforming growth factor-beta did not reproduce these effects. The ECCM activities were sensitive to heat and trypsinization, were >30 kDa in molecular mass, and bound weakly to heparin-Sepharose. Our data indicate that cultured endothelial cells produce a factor(s) that downregulates contractile protein expression in SMC, which may contribute to SMC dedifferentiation and proliferation.

Actins↗

PubMed1995

ATP raises [Ca2+]i via different P2-receptor subtypes in freshly isolated and cultured aortic myocytes.

In vascular smooth muscle, extracellular ATP induces an increase in intracellular [Ca2+] ([Ca2+]i). Various agonists have been used to characterize P2-purinoceptor subtypes involved in the ATP-induced [Ca2+]i rise, measured by indo 1 fluorescence, in both freshly isolated and cultured rat aortic smooth muscle cells. alpha, beta-Methylene-ATP increased [Ca2+]i via Ca2+ entry through P2x-receptor channels in freshly isolated but not in cultured cells. 2-Methylthio-ATP and ADP failed to release Ca2+ via P2y-receptor activation in freshly isolated cells, whereas such a response was obtained in cultured cells. UTP, by stimulating P2u receptors, released Ca2+ from intracellular stores in both freshly isolated and cultured cells. These results suggest that, in the course of the culture process, P2x-receptor activation-induced responses were lost, whereas P2y-receptor activation-induced [Ca2+]i rise appeared, these two phenomena being independent. Responses to P2x-receptor agonist were lost in all culture conditions, whereas functional P2y receptors appeared only in cells that were stimulated with serum to induce cell cycle progression. The phenotypic modulation of vascular myocytes was therefore associated with a change in the functional P2-purinoceptor subtypes.

Adenosine Triphosphate↗

PubMed2001

Aging, oxidative responses, and proliferative capacity in cultured mouse aortic smooth muscle cells.

The cellular mechanisms that contribute to the acceleration of atherosclerosis in aging populations are poorly understood, although it is hypothesized that changes in the proliferative capacity of vascular smooth muscle cells is contributory. We addressed the relationship among aging, generation of reactive oxygen species (ROS), and proliferation in primary culture smooth muscle cells (SMC) derived from the aortas of young (4 mo old) and aged (16 mo old) mice to understand the phenotypic modulation of these cells as aging occurs. SMC from aged mice had decreased proliferative capacity in response to alpha-thrombin stimulation, yet generated higher levels of ROS and had constitutively increased mitogen-activated protein kinase activity, in comparison with cells from younger mice. These effects may be explained by dysregulation of cell cycle-associated proteins such as cyclin D1 and p27Kip1 in SMC from aged mice. Increased ROS generation was associated with decreased endogenous antioxidant activity, increased lipid peroxidation, and mitochondrial DNA damage. Accrual of oxidant-induced damage and decreased proliferative capacity in SMC may explain, in part, the age-associated transition to plaque instability in humans with atherosclerosis.

Aging↗

PubMed2006

Role of the adventitia in pulmonary vascular remodeling.

An increasing volume of experimental data indicates that the adventitial fibroblast, in both the pulmonary and systemic circulations, is a critical regulator of vascular wall function in health and disease. A rapidly emerging concept is that the vascular adventitia acts as biological processing center for the retrieval, integration, storage, and release of key regulators of vessel wall function. In response to stress or injury, resident adventitial cells can be activated and reprogrammed to exhibit different functional and structural behaviors. In fact, under certain conditions, the adventitial compartment may be considered the principal injury-sensing tissue of the vessel wall. In response to vascular stresses such as overdistension and hypoxia, the adventitial fibroblast is activated and undergoes phenotypic changes, which include proliferation, differentiation, upregulation of contractile and extracellular matrix proteins, and release of factors that directly affect medial smooth muscle cell tone and growth and that stimulate recruitment of inflammatory and progenitor cells to the vessel wall. Each of these changes in fibroblast phenotype modulates either directly or indirectly changes in overall vascular function and structure. The purpose of this review is to present the current evidence demonstrating that the adventitial fibroblast acts as a key regulator of pulmonary vascular function and structure from the "outside-in."

Animals↗

PubMed2005

Identification, structural, and functional characterization of a new early gene (6A3-5, 7 kb): implication in the proliferation and differentiation of smooth muscle cells.

Arterial smooth muscle cells (SMCs) play a major role in atherosclerosis and restenosis. Differential display was used to compare transcription profiles of synthetic SMCs to proliferating rat cultured SMC line. An isolated cDNA band (6A3-5) was shown by northern (7 kb) to be upregulated in the proliferating cell line. A rat tissue northern showed differential expression of this gene in different tissues. Using 5' RACE and screening of a rat brain library, part of the cDNA was cloned and sequenced (5.4 kb). Sequence searches showed important similarities with a new family of transcription factors, bearing ARID motifs. A polyclonal antibody was raised and showed a protein band of 175 kd, which is localized intracellularly. We also showed that 6A3-5 is upregulated in dedifferentiated SMC (P9) in comparison to contractile SMC ex vivo (P0). This work describes cloning, structural, and functional characterization of a new early gene involved in SMC phenotype modulation.

Journal Article↗

PubMedDate not supplied

Atorvastatin treatment prevents alterations in coronary smooth muscle nuclear Ca2+ signaling in diabetic dyslipidemia.

Atorvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, alters bulk myoplasmic Ca2+ regulation and inhibits phenotypic modulation and proliferation of vascular smooth muscle in culture. Nuclear Ca2+ (Ca(n)) signaling is tightly coupled to transcriptional events and cell growth. Therefore, we hypothesized that in vivo treatment with atorvastatin would attenuate alterations in mitogen-induced Ca(n) signaling associated with coronary atherosclerosis. Three groups of male Yucatan pigs were treated for 20 weeks: controls, alloxan-induced diabetics fed an atherogenic diet and diabetics fed an atherogenic diet plus atorvastatin (80 mg/day). Right coronary artery single-cell cytosolic Ca2+ (Ca(c)) and Ca(n) responses to the mitogen endothelin-1 (5 x 10(-8) M) were measured by laser confocal microscopy using the calcium indicator Fluo-4. We observed a 39% increase in Ca(c) and a 52% increase in Ca(n) responses to endothelin-1 in cells from diabetic dyslipidemic arteries compared to control. These alterations were prevented in animals treated with atorvastatin. We show that during proliferation, the nucleus of a smooth muscle cell becomes rounded and loses the characteristic multilobular shape, clefts and invaginations. Consistent with this, a redistribution of Ca2+ stores from a transnuclear morphology in controls to a more perinuclear morphology occurred in cells from diabetic dyslipidemic arteries and was prevented by atorvastatin. In addition, the peak Ca(n) responses to endothelin-1 were inversely correlated (r = 0.712) with the extent of the transnuclear distribution of Ca2+ stores and directly correlated (r = 0.874) with the extent of atherosclerosis, as assessed in vivo by intravascular ultrasound. These findings indicate that chronic treatment with atorvastatin directly decreases mitogen-induced Ca(n) mobilization, which we suggest is related to the spatial localization of Ca(n) stores.

Alloxan↗

PubMedDate not supplied

Angiotensin-II-and endothelin-induced protein phosphorylation in cultured vascular smooth muscle cells.

In cultured vascular smooth muscle cells, angiotensin II and endothelin stimulate a variety of intracellular signals, including generation of inositol trisphosphate and diacylglycerol, mobilization of intracellular calcium, and activation of protein kinase C. These latter two events have been shown to mediate the phosphorylation of numerous proteins, but these substrates and the specific pathways mediating their phosphorylation have not been identified in vascular smooth muscle. Angiotensin II (100 nM, 10 min) induced a characteristic pattern of protein phosphorylation, which included the phosphorylation of many proteins, ranging in molecular mass from 20 to 76 kD. Three of these proteins have been identified as vimentin (M(r) 57,000), a specific protein kinase C substrate (M(r) 76,000) and the myosin light chain (M(r) 20,000). The 76-kD protein was one of the most highly phosphorylated proteins after agonist treatment. Endothelin-1 produced an identical pattern of phosphorylation. Five of these substrates were also phosphorylated by phorbol-12-myristate-13-acetate, and 5 were also phosphorylated after treatment with ionomycin. In general, the protein-kinase-C-dependent phosphorylations were sustained, while those mediated by calcium were rapid. Since these experiments were performed in cultured, phenotypically modulated cells stimulated with agents that promote cellular hypertrophy or hyperplasia, this pattern of phosphorylation may be representative of that seen during the growth response.

Angiotensin II↗

PubMed2005

HERP1 inhibits myocardin-induced vascular smooth muscle cell differentiation by interfering with SRF binding to CArG box.

OBJECTIVE: Myocardin is a coactivator of serum response factor (SRF) required for vascular smooth muscle cell (VSMC) differentiation. HERP1 is a transcriptional repressor, which is abundantly expressed in vascular system and is known to function as a target gene of Notch. However, the role of HERP1 in the pathogenesis of vascular lesions remains unknown. The present study characterizes the expression of HERP1 in normal and diseased vessels, and tests the hypothesis that HERP1 inhibits SRF/myocardin-dependent SMC gene expression. METHODS AND RESULTS: Immunohistochemistry revealed that HERP1 and myocardin expression was localized to SMC in the neointima of balloon-injured rat aorta and in human coronary atherosclerotic lesions. Expression of both HERP1 and myocardin was elevated in cultured VSMCs compared with medial SMC. Overexpressed HERP1 inhibited the myocardin-induced SMC marker gene expression in 10T1/2 cells. HERP1 protein interfered with the SRF/CArG-box interaction in vivo and in vitro. Immunoprecipitation assays showed that HERP1 physically interacts with SRF. CONCLUSIONS: HERP1 expression was associated with the SMC proliferation and dedifferentiation in vitro and in vivo. HERP1 may play a role in promoting the phenotypic modulation of VSMCs during vascular injury and atherosclerotic process by interfering with SRF binding to CArG-box through physical association between HERP1 and SRF.

Adult↗

PubMed2002

Synthesis of collagen is dysregulated in cultured fibroblasts derived from skin of subjects with varicose veins as it is in venous smooth muscle cells.

BACKGROUND: The dilatation and tortuosity observed in varicose veins provide evidence for progressive venous wall remodeling associated with abnormalities of smooth muscle cells and extracellular matrix. The present study was designed to examine if the phenotypic modulations observed in the venous smooth muscle cells of patients with varicose veins were also present in their dermal fibroblasts. METHODS AND RESULTS: Collagen type I (collagen I), type III (collagen III), and type V (collagen V) were compared in dermal fibroblasts derived from the skin of control subjects and patients with varicose veins. The synthesis of collagen I, the release of its metabolites, and the expression of its mRNA were increased in fibroblasts from patients with varicose veins, whereas the synthesis of collagen III was decreased but not correlated with a decrease in mRNA expression and in metabolite release. Matrix metalloproteinases (MMP1, 2, 7, 8, 9, and 13) and their inhibitors (TIMP1 and 2) were quantified in both cell types; only the production of proMMP2 was increased in cells derived from patients with varicose veins. CONCLUSIONS: These findings suggest that the synthesis of collagen I and III is dysregulated in dermal fibroblasts derived from patients with varicose veins. These results are comparable with those observed in smooth muscle cells derived from varicose veins, thus suggesting a systemic alteration of tissue remodeling in subjects with varicose veins.

Aged↗

PubMed2003

Epiregulin as a major autocrine/paracrine factor released from ERK- and p38MAPK-activated vascular smooth muscle cells.

BACKGROUND: The coordinated activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) is critical for the induction of vascular and visceral smooth muscle cell (SMC) dedifferentiation. We previously reported that on the forced activation of both MAPKs, visceral SMCs secrete a non-heparin-binding protein factor(s) that is involved in the dedifferentiation of neighboring SMCs. In this study, we sought to identify the dedifferentiation factor(s) derived from vascular SMCs (VSMCs). METHODS AND RESULTS: We fractionated the VSMC dedifferentiation factor(s) in the conditioned medium obtained from differentiated VSMCs in which both ERK and p38MAPK were forcedly activated and identified epiregulin as a major autocrine/paracrine factor for VSMC dedifferentiation. The epiregulin-induced VSMC dedifferentiation was mediated through the coordinated activation of ERK and p38MAPK. Unsaturated lysophosphatidic acid and platelet-derived growth factor-BB, which are potent VSMC dedifferentiation factors, rapidly upregulated epiregulin mRNA expression in an ERK- and p38MAPK-dependent manner. Reverse transcriptase-polymerase chain reaction and/or immunohistological analyses revealed the restricted expression of epiregulin in human atherosclerotic and balloon-injured rat arteries, in which the phenotypic modulation of medial VSMCs occurred in vivo. CONCLUSIONS: Epiregulin is released from VSMCs primed by atherogenic factors and acts as a major autocrine/paracrine factor for VSMC dedifferentiation. It may be involved in the progression of vascular remodeling such as atherosclerosis.

Animals↗

PubMed2001

Cell cycle in vasculoproliferative diseases: potential interventions and routes of delivery.

Atherosclerosis and restenosis of epicardial vessels are among the greatest challenges facing the clinical cardiologist, and phenotypic modulation and proliferation of smooth muscle cells are major components of the vasculoproliferative response. Proliferation is regulated by the interplay of regulatory proteins at checkpoints in the cell cycle that alter cellular growth. Activation of the cell cycle and the genetic control of its progression are final common pathways in this process. Investigators have postulated that cell-cycle inhibition using drugs and genetic or physical methods has the potential to reverse or prevent the vasculoproliferative process. The current challenge is to translate in vitro data demonstrating the efficacy of cell-cycle inhibition to clinical trials. At present, the steps that must be taken to meet this goal are (1) to design methods of delivery of these agents to specific sites, (2) to identify appropriate cellular targets to elicit cell-cycle arrest, and (3) to improve the therapeutic ratio by minimizing potential side effects. This review discusses current concepts of the cell cycle, target-regulating mechanisms, and possible interventions in vasculoproliferative diseases. We also discuss ongoing clinical trials that use antiproliferative agents in the hope of limiting the course of these diseases, as well as the promise that antiproliferative therapy holds in the coming decade.

Animals↗

PubMed1994

Direct in vivo gene transfer into porcine myocardium using replication-deficient adenoviral vectors.

BACKGROUND: Efficient methods of introducing genes into myocardial cells must be developed before local somatic cell gene therapy can be implemented against myocardial disease. Although adenoviral (Ad5) vectors have been used to target rodent hearts and plasmid DNA has been directly injected into the myocardium of rats and dogs, the amounts of recombinant protein produced by these procedures have not been reported, and adenoviral vectors have not been used in large mammalian hearts. METHODS AND RESULTS: Replication-deficient recombinant adenoviral vectors carrying either the luciferase or lacZ reporter genes were injected directly into the ventricular myocardium of adult domestic swine for evaluation of reporter gene expression. This procedure did not affect regional myocardial function as assessed by systolic wall thickening using ultrasonic crystals. Luciferase activity was detected 3 days after injection, increased markedly at 7 days, and then declined progressively at 14 and 21 days. Luciferase production was comparable in the right and left ventricular walls and increased with increasing amounts of virus, reaching 61 +/- 21 ng at the highest dose examined (3.6 x 10(9) plaque-forming units). The injection of 200 micrograms of plasmid DNA (pRSVL) produced levels of luciferase comparable to 1.8 x 10(8) plaque-forming units of recombinant Ad5; however, when normalized to the number of genes injected, the adenovirus was 140,000 times more efficient than plasmid DNA. Histochemical analysis of beta-galactosidase activity produced by a second Ad5 vector demonstrated that nearly all (> 95%) of the stained cells were cardiomyocytes and that the percentage of cardiomyocytes infected by the virus could be quite high in microscopic regions adjacent to the needle track (up to 75% in fields of 60 to 70 cells); however, Ad5-infected cells were rarely observed farther than 5 mm from the injection site. Furthermore, the Ad5 vector induced pronounced leukocytic infiltration that was far in excess of that seen after injection of vehicle alone. CONCLUSIONS: This study demonstrates for the first time that direct intramyocardial injection of replication-deficient adenovirus can program recombinant gene expression in the cardiomyocytes of a large animal species with relevance to human physiology. The efficiency of adenovirus-mediated gene transfer is far superior to that of plasmid DNA injection, and this method appears to be capable of producing more recombinant protein. However, the cell-mediated immune response to the Ad5 vector and the limited distribution of reporter gene expression suggest that less immunogenic recombinant vectors and more homogeneous administration methods will be required before Ad5 vectors can be successfully used for phenotypic modulation.

Adenoviridae↗

PubMed1996

Nonmuscle and smooth muscle myosin heavy chain expression in rejected cardiac allografts. A study in rat and monkey models.

BACKGROUND: Diagnosis of acute rejection and graft arteriosclerosis (chronic rejection) is critical to the success of cardiac transplantation, but accurate diagnosis is often difficult. We have reported that there are three types of vascular myosin heavy chain (MHC) isoforms: SM1, SM2, and SMemb. SM2 is specifically expressed in differentiated smooth muscle cells (SMCs). SMemb is a nonmuscle-type MHC abundantly expressed in SMCs of fetal aorta. METHODS AND RESULTS: To evaluate the usefulness of MHC expression for diagnosis and analysis of acute and chronic rejection, heterotopic cardiac transplantation was performed in rats and monkeys. Immunohistochemistry, electron microscopy, and Northern blot assay were performed to evaluate MHC expression. SMemb was expressed in spindle-shaped cells located in acutely rejected myocardium in the rats and monkeys. These cells were also observed in areas lacking cellular infiltration. These SMemb-positive cells were activated fibroblasts or myofibroblasts. SMemb mRNA was enhanced parallel to the progression of acute rejection. In the coronary arteries of chronically rejected allografts, enhanced SMemb and reduced SM2 expression was observed in both thickened intima and media. The reduced medial SM2 expression was observed before the intimal thickening occurred. These cells were phenotypically modulated SMCs. CONCLUSIONS: Altered expression of MHC isoforms is a sensitive indicator in the diagnosis of acute and chronic cardiac rejection. The pathophysiology of this alteration in MHC isoform expression should be studied further to elucidate the pathogenesis of cardiac rejection.

Animals↗

PubMed1996

Adventitial myofibroblasts contribute to neointimal formation in injured porcine coronary arteries.

BACKGROUND: The adventitia undergoes remodeling changes after a deep medial coronary injury. Because this process is associated with the formation of adventitial myofibroblasts, which resemble medial smooth muscle (SM) cells, we have examined myofibroblast involvement in the development of neointima. METHODS AND RESULTS: In a porcine model, severe endoluminal coronary injury resulted in fibroblast proliferation and adventitial remodeling. Significant adventitial responses were associated with increased neointimal formation (P < .01). To examine the contribution of adventitial cells to the development of neointima, proliferating cells were labeled with bromodeoxyuridine (BrdU) at 12 and 24 hours after injury, and their subsequent localization was determined by immunohistochemistry (n = 24). At 2 to 3 days after severe injury, the adventitia contained numerous BrdU-labeled cells (37 +/- 4%), whereas the media demonstrated infrequent labeled cells (4 +/- 1%). Adventitial cells lacked alpha-SM actin and desmin, which distinguished them from medial SM cells. At 7 to 8 days, some labeled cells acquired characteristics of myofibroblasts expressing alpha-SM actin. They were found to translocate to the gap between dissected media and contributed to the formation of neointima (76 +/- 19%). At 18 to 35 days, labeled cells were abundant in the neointima (86 +/- 5%). They showed uniform immunostaining for alpha-SM actin but not for desmin, thereby differing from medial SM cells and blood-borne cells. CONCLUSIONS: This study demonstrates translocation of adventitial fibroblasts to neointima, their phenotypic modulation to myofibroblasts, and distinct characteristics of myofibroblasts within neointima after severe endoluminal coronary injury. These findings suggest the significance of vascular fibroblasts in the process of arterial repair.

Animals↗

PubMed1990

Changes in angiotensinogen messenger RNA in differentiating 3T3-F442A adipocytes.

Angiotensinogen messenger RNA (mRNA) has been identified in both brown and white adipose tissue. Recently we have shown that when 3T3-L1 cells were treated with isobutylmethylxanthine (IBMX) to accelerate differentiation, angiotensinogen mRNA increased markedly in adipocytes as compared with preadipocytes. To determine if a correlation existed between the regulatory events associated with the differentiation process, we compared the change in angiotensinogen mRNA in spontaneously differentiating 3T3-F442A cells with two established parameters of differentiation in adipocyte cell lines. Differentiation was assessed by visual examination of cells for lipid droplets, fluorescent staining of the F-actin fibers, and increases in glycerol phosphate dehydrogenase mRNA. F-actin fibers were highly structured in preadipocytes, becoming disassembled and very disorganized as cells differentiated into adipocytes. The quantity of angiotensinogen mRNA increased as the number of lipid-containing cells increased within a culture. Glycerol phosphate dehydrogenase mRNA accumulated in differentiated adipocytes to about the same extent as angiotensinogen mRNA. Thus, increases in angiotensinogen mRNA were associated with the morphological and biochemical changes that occur during the phenotypic modulation of 3T3-F442A cells.

Actins↗

PubMed1997

Alterations in calcium stores in aortic myocytes from spontaneously hypertensive rats.

The aim of the present work was to further characterize intracellular calcium stores released by angiotensin II (Ang II) in spontaneously hypertensive rat (SHR) and Wistar-Kyoto rat (WKY) vascular smooth muscle cells (VSMCs) and to study their alterations associated with proliferation. Intracellular Ca2+ concentration was monitored by image analysis in aortic myocytes loaded with fura 2. In the presence of extracellular Ca2+, sensitivity to Ang II in proliferating VSMCs was not different in the two strains, but it increased 10-fold in confluent VSMCs from SHR-compared with those from WKY. In Ca(2)+-free medium, Ca2+ release induced by thapsigargin (10 mumol/L) was significantly greater (about twofold) in SHR than WKY, in both proliferating and confluent cultures, with responses during proliferation being 0.7-fold smaller. Responses to Ang II were abolished after exposure of the cells to thapsigargin. In proliferating cultures, ryanodine (10 mumol/L) did not modify the rises in intracellular Ca2+ concentration induced by Ang II in VSMCs from both strains. Conversely, in confluent cultures, ryanodine reduced Ang II (100 nmol/L)-induced Ca2+ release to the same level as in proliferating cultures, and it suppressed the difference between SHR and WKY. These results show that the ryanodine-sensitive Ca2+ release induced by Ang II is enhanced in VSMCs from SHR at confluence and is impaired during proliferation. Thus, they suggest that differences in Ca2+(-)induced Ca2+ release from the sarcoplasmic reticulum may participate in increased responsiveness of VSMCs to Ang II in SHR and in phenotypic modulation of vascular myocytes during proliferation.

Angiotensin II↗

PubMed2002

Angiotensin II induces myocyte enhancer factor 2- and calcineurin/nuclear factor of activated T cell-dependent transcriptional activation in vascular myocytes.

It is well known that angiotensin II (Ang II) is implicated in the phenotypic modulation and hypertrophy of vascular smooth muscle cells (VSMCs). To study the mechanisms by which Ang II contributes to the pathological changes of VSMCs, we examined whether Ang II stimulated myocyte enhancer factor 2 (MEF2)- and calcineurin/nuclear factor of activated T cell (NFAT)-dependent transcriptional activation of genes in VSMCs. Ang II increased the DNA binding activity of MEF2A and its expression at the protein level. Ang II induced c-jun promoter activity, and this increase was inhibited by dominant-negative mutants of MEF2A and mitogen-activated protein kinase kinase 6 but not by calcineurin inhibitors. Ang II stimulated NFAT DNA binding activity and NFAT-dependent gene transcription, and these effects of Ang II were inhibited by calcineurin inhibitors. Furthermore, Ang II induced the promoter activity of the nonmuscle-type myosin heavy chain B gene, which we used as a marker of the dedifferentiated state of VSMCs, and this increase was inhibited by calcineurin inhibitors but not by the dominant-negative mutants of MEF2A or mitogen-activated protein kinase kinase 6. Finally, Ang II increased protein synthesis, and this increase was inhibited by infection with an adenovirus construct that expresses the dominant-negative mutant of MEF2A but not by calcineurin inhibitors. These results suggest that Ang II stimulates the MEF2- and calcineurin/NFAT-dependent pathways and that these pathways have distinct roles in VSMCs.

Angiotensin II↗