Thrombin receptor activation elicits rapid protein tyrosine phosphorylation and stimulation of the raf-1/MAP kinase pathway preceding delayed mitogenesis in cultured rat aortic smooth muscle cells: evidence for an obligate autocrine mechanism promoting cell proliferation induced by G-protein-coupled receptor agonist.

Molloy, Christopher J.; Pawlowski, John E.; Taylor, David; Turner, Christopher E.; Weber, Holger; Peluso, Marianne

doi:10.1172/jci118531

Cited by 87 publications

(37 citation statements)

References 58 publications

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“…We also observed marginal tyrosine phosphorylation of a =44 kDa protein in thrombin-stimulated cells which was also inhibited by PD98059. This protein may well correspond to p44 mapk which is known to be activated in response to thrombin in other cell types, including smooth muscle [22]; inhibition by PD98059 would be consistent with previous observations that PD98059 totally blocks all measurable in vitro MAP kinase activity in adipocytes [8]. However, unlike the phosphorylation of the 42 kDa protein (p42m~pk), tyrosine phosphorylation of the 44 kDa substrate was not consistently observed in our experiments and, if present, (Fig.…”

Section: Discussionsupporting

confidence: 92%

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI₂ release but has no effect on von Willebrand factor secretion or E‐selectin expression

et al. 1996

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We have examined the potential role of MAP kinase in the regulation of endothelial cell PGI2 synthesis, vWF secretion and E-selectin expression using the specific MEK inhibitor PD98059. PD98059 dose-dependently attenuated the tyrosine phosphorylation and activation of !}42 mapk in response to thrombin or inflammatory cytokines. Inhibition of thrombinmapk induced p42 activation was paralleled by an inhibitory effect of PD98059 on thrombin-driven PGI2 generation but not on vWF secretion or IL-lo0TNF~-induced E-selectin expression. These results provide evidence for a key role for !142 mapk in the acute regulation of PGI2 synthesis in human endothelial cells and suggest that activation of the MAP kinase cascade is not obligatory for cytokine-stimulated E-selectin expression.

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Section: Discussionsupporting

confidence: 92%

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI₂ release but has no effect on von Willebrand factor secretion or E‐selectin expression

et al. 1996

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“…PDGFinduced MAP kinase activation is reported to be biphasic in VSMC as well as in mesangial cells. 21,22 Thus, a rapid increase in activity, maximal at 5 to 10 minutes, is followed by a lower sustained activity at 4 to 6 hours. 22 The second sustained activation of MAP kinase appears to be essential for proliferation.…”

Section: Discussionmentioning

confidence: 99%

Trapidil Inhibits Platelet-Derived Growth Factor–Stimulated Mitogen-Activated Protein Kinase Cascade

Hoshiya

Awazu

1998

Hypertension

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Abstract-Trapidil, an antiplatelet drug, has been shown to reduce restenosis after angioplasty. It exerts its action, at least in part, by inhibiting vascular smooth muscle cell proliferation, antagonizing platelet-derived growth factor (PDGF). We examined its site of action on PDGF cellular signaling. Exposure of cultured rat vascular smooth muscle cells to increasing concentrations of trapidil for 18 hours resulted in a dose-dependent reduction in PDGF-BB-stimulated [ 3 H] thymidine incorporation. Trapidil (400 g/mL) increased PDGF ␤-receptor protein by 28Ϯ8%, whereas PDGF-induced tyrosine phosphorylation of PDGF ␤-receptor remained unchanged. PDGF-induced tyrosine phosphorylation of phospholipase C␥, the p85 regulatory subunit of phosphatidyl-inositol 3 kinase, Ras GTPase-activating protein, and an adaptor molecule Shc were also not altered. On the other hand, trapidil inhibited PDGF-stimulated mitogen-activated protein kinase (MAP kinase) activity by 35Ϯ7% at 10 minutes and by 32Ϯ10% at 6 hours. Activation of Raf-1, an upstream activator of MAP kinase, by PDGF was also attenuated by trapidil. Moreover, protein content of MAP kinase phosphatase-1, which inactivates MAP kinase, was elevated in trapidil-treated cells. These actions of trapidil may be mediated by cAMP. Thus, there was a 1.9-fold increase in cellular cAMP generation in trapidil-treated cells. The present results demonstrate that trapidil antagonizes PDGF-induced mitogenesis and MAP kinase activation in vascular smooth muscle cells, probably through cAMP. (Hypertension. 1998;31:665-671.)

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“…Our laboratory had previously demonstrated that RASM cells treated with the GPCR agonists -thrombin or AII secreted potent mitogenic factors into the cell culture media (Weber et al 1994, Molloy et al 1996. Since previous studies had implicated growth factors such as basic FGF, PDGF, or IGF-I in this mechanism, we attempted to identify the mitogenic components in GPCR agonist-stimulated RASM cell conditioned media using a panel of specific growth factor-neutralizing antibodies.…”

Section: Identification Of Activin a In Conditioned Media Samples Fromentioning

confidence: 99%

“…However, the induction of DNA synthesis in response to AII or -thrombin in vascular SMCs is delayed when compared with mitogens such as platelet-derived growth factor (PDGF), basic fibroblast growth factor (FGF) or fetal bovine serum (Weber et al 1994, Molloy et al 1996. This delay may be due to a requirement for the production of endogenous growth factors in vascular SMCs that mediate the GPCR agonist-mediated responses.…”

Section: Introductionmentioning

confidence: 99%

Novel cardiovascular actions of the activins

Molloy¹,

Taylor²,

Pawlowski³

1999

Journal of Endocrinology

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Proliferation and directed migration of vascular cells are key components in vascular diseases such as atherosclerosis and restenosis following percutaneous transluminal coronary angioplasty. However, the precise cellular and molecular mechanisms involved in the control of vascular cell proliferation or migration at the tissue level remain largely undefined. Molecules contributing to these processes are elaborated by distinct cell types and act in both autocrine and paracrine modes. They include two broad classes, polypeptide growth factors and vasoactive G-protein-coupled receptor (GPCR) agonists. Examples of the former, such as platelet-derived growth factor, bind to and activate cell surface receptor tyrosine kinases, initiating intracellular biochemical signaling pathways associated with cell proliferation or migration. In contrast, recent evidence suggests that vasoactive GPCR agonists (e.g. angiotensin II, endothelin-1, -thrombin) elicit cell growth indirectly by inducing the production of autocrine or paracrine factors in vascular cells. Recent studies have identified activin A as a novel component of conditioned medium obtained from GPCR agonist-stimulated vascular smooth muscle cells (SMCs). Although activin A alone only weakly stimulated rat aortic SMC DNA synthesis, it demonstrated a potent co-mitogenic effect in combination with either epidermal growth factor (EGF) or heparin binding EGF-like growth factor in these cells, increasing DNA synthesis by up to 5-and 4-fold respectively. Furthermore, in a rat carotid-injury model, activin A mRNA was upregulated within 6 h after injury, followed by increases in immunoreactive protein detected in the expanding neointima 7 to 14 days later. Taken together, these results indicate that activin A is a common vascular SMC-derived growth factor induced by vasoactive agonists that may, either alone or in combination with other factors, contribute to fibroproliferative vascular diseases.

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Cited by 87 publications

References 58 publications

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI₂ release but has no effect on von Willebrand factor secretion or E‐selectin expression

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI₂ release but has no effect on von Willebrand factor secretion or E‐selectin expression

Trapidil Inhibits Platelet-Derived Growth Factor–Stimulated Mitogen-Activated Protein Kinase Cascade

Novel cardiovascular actions of the activins

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Cited by 87 publications

References 58 publications

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI2 release but has no effect on von Willebrand factor secretion or E‐selectin expression

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI2 release but has no effect on von Willebrand factor secretion or E‐selectin expression

Trapidil Inhibits Platelet-Derived Growth Factor–Stimulated Mitogen-Activated Protein Kinase Cascade

Novel cardiovascular actions of the activins

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Product

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Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI₂ release but has no effect on von Willebrand factor secretion or E‐selectin expression

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI₂ release but has no effect on von Willebrand factor secretion or E‐selectin expression