Redox-dependent MAP kinase signaling by Ang II in vascular smooth muscle cells: role of receptor tyrosine kinase transactivation

2003 ◽  
Vol 81 (2) ◽  
pp. 159-167 ◽  
Author(s):  
Rhian M Touyz ◽  
Montserrat Cruzado ◽  
Fatiha Tabet ◽  
Guoying Yao ◽  
Steven Salomon ◽  
...  

We investigated the role of receptor tyrosine kinases in Ang II-stimulated generation of reactive oxygen species (ROS) and assessed whether MAP kinase signaling by Ang II is mediated via redox-sensitive pathways. Production of ROS and activation of NADPH oxidase were determined by DCFDA (dichlorodihydrofluorescein diacetate; 2 μmol/L) fluorescence and lucigenin (5 μmol/L) chemiluminescence, respectively, in rat vascular smooth muscle cells (VSMC). Phosphorylation of ERK1/2, p38MAP kinase and ERK5 was determined by immunoblotting. The role of insulin-like growth factor-1 receptor (IGF-1R) and epidermal growth factor receptor (EGFR) was assessed with the antagonists AG1024 and AG1478, respectively. ROS bioavailability was manipulated with Tiron (10–5 mol/L), an intra cellular scavanger, and diphenylene iodinium (DPI; 10–6 mol/L), an NADPH oxidase inhibitor. Ang II stimulated NADPH oxidase activity and dose-dependently increased ROS production (p < 0.05). These actions were reduced by AG1024 and AG1478. Ang II-induced ERK1/2 phosphorylation (276% of control) was decreased by AG1478 and AG1024. Neither DPI nor tiron influenced Ang II-stimulated ERK1/2 activity. Ang II increased phosphorylation of p38 MAP kinase (204% of control) and ERK5 (278% of control). These effects were reduced by AG1024 and AG1478 and almost abolished by DPI and tiron. Thus Ang II stimulates production of NADPH-inducible ROS partially through transactivation of IGF-1R and EGFR. Inhibition of receptor tyrosine kinases and reduced ROS bioavaliability attenuated Ang II-induced phosphorylation of p38 MAP kinase and ERK5, but not of ERK1/2. These findings suggest that Ang II activates p38MAP kinase and ERK5 via redox-dependent cascades that are regulated by IGF-1R and EGFR transactivation. ERK1/2 regulation by Ang II is via redox-insensitive pathways.Key words: ERK1/2, p38MAP kinase, EGFR, IGF-1R, signal transduction.

2001 ◽  
Vol 85 (06) ◽  
pp. 1104-1110 ◽  
Author(s):  
C. Viedt ◽  
K. Nguyen ◽  
S. Beer ◽  
J. Kreuzer ◽  
R. Busse ◽  
...  

SummaryActivation of vascular smooth muscle cells (VMSC) by thrombin induces the expression of the chemokine, monocyte chemoattractant protein-1 (MCP-1). We investigated in cultured human and rat VSMC whether reactive oxygen species (ROS) derived from the vascular NADPH oxidase contribute to this effect. Exposure of cultured VSMC to thrombin rapidly increased ROS formation, phosphorylation of p38 MAP kinase as well as the expression of MCP-1. Specific inhibition of the p22phox subunit of the vascular NADPH oxidase using either p22phox neutralizing antibody or p22phox antisense oligonucleotides attenuated thrombin-induced ROS generation. Furthermore, thrombininduced p38 MAP kinase activation as well as MCP-1 expression were impaired by antioxidants as well as by p22phox antisense oligonucleotides. Inhibition of p38 MAP kinase diminished the thrombin-induced expression of MCP-1. Conclusion: Thrombin, by activating a p22phoxcontaining NADPH oxidase, elicits ROS generation and activation of p38 MAP kinase in VSMC. The subsequent induction of MCP-1 expression highligts the crucial role of the p22phox-containing NADPH oxidase in thrombin-induced signal transduction in VSMC.


Endocrinology ◽  
2007 ◽  
Vol 148 (8) ◽  
pp. 4023-4031 ◽  
Author(s):  
Marie-Claude Lauzier ◽  
Elisabeth L. Pagé ◽  
Maude D. Michaud ◽  
Darren E. Richard

Hypoxia-inducible factor-1 (HIF-1) is a decisive element for the transcriptional regulation of many genes expressed in hypoxic conditions. In vascular smooth muscle cells, the vasoactive hormone angiotensin II (Ang II) is a very potent inducer and activator of HIF-1. As opposed to hypoxia, which induces HIF-1α by protein stabilization, Ang II induced HIF-1α through transcriptional and translational mechanisms. Interestingly, a number of intracellular signaling events triggered by Ang II are mediated by the transactivation of receptor tyrosine kinases. The major receptor tyrosine kinases shown to be transactivated by Ang II in vascular smooth muscle cells are the epidermal growth factor receptor and the IGF-I receptor. In this study, we demonstrate that the transactivation of both these receptor tyrosine kinases is involved in HIF-1 complex activation by Ang II. More interestingly, this modulation of HIF-1 is at different degrees and through different pathways. Our results show that transactivation of IGF-I receptor is essential for HIF-1α protein translation through phosphatidylinositol 3-kinase/p70S6 kinase pathway activation, and epidermal growth factor receptor transactivation is implicated in HIF-1 complex activation through the stimulation of the p42/p44 MAPK pathway. Our results therefore show that Ang II-induced receptor tyrosine kinase transactivation is essential in both the induction and activation of HIF-1. These findings identify novel and intricate signaling mechanisms involved in HIF-1 complex activation.


Author(s):  
Ekhtear Hossain ◽  
Yuan Li ◽  
Madhu B Anand-Srivastava

We earlier showed that Ang II- induced overexpression of Giα proteins contributes to the hyperproliferation of vascular smooth muscle cells (VSMC). In addition, the implication of JAK2/STAT3 pathway in Ang II-induced hyperproliferation of VSMC has also been reported. However, the role of JAK2/STAT3 pathway in Ang II-induced overexpression of Giα proteins and hyperproliferation of VSMC remains unexplored. In the present study, we show that inhibition or knockdown of JAK2/STAT3 pathway by a specific inhibitor ‘Cucurbitacin I’ (CuI) or siRNAs attenuated Ang II-induced overexpression of Giα proteins and hyperproliferation of VSMC. In addition, the enhanced expression of cell cycle proteins induced by Ang II was also attenuated by CuI. Furthermore, Ang II-induced enhanced production of superoxide anion (O2-), H2O2, NADPH oxidase activity, as well as the enhanced expression of NADPH oxidase subunits implicated in enhanced expression of Giα proteins and hyperproliferation were also attenuated by inhibition of JAK2/STAT3 pathway. On the other hand, Ang II-induced inhibition/augmentation of the levels of nitric oxide/ peroxynitrite in VSMC were restored to control levels by CuI. In summary, our results demonstrate that Ang II through JAK2/STAT3 pathway increases nitroxidative stress which contributes to the overexpression of Giα proteins, cell cycle proteins and hyperproliferation of VSMC.


1996 ◽  
Vol 271 (2) ◽  
pp. H595-H601 ◽  
Author(s):  
M. Okuda ◽  
Y. Kawahara ◽  
M. Yokoyama

Angiotensin II (ANG II), a potent growth-promoting factor of vascular smooth muscle cells (VSMC), induces activation of mitogen-activated protein (MAP) kinases and subsequent expression of the c-fos protooncogene in VSMC. However, it remains obscure whether ANG II induces activation of the ras protooncogene product (Ras), and if it does, whether Ras is involved in signaling from the ANG II receptor to the MAP kinase pathway in VSMC. In cultured VSMC, ANG II activated Ras comparably to epidermal growth factor. ANG II-induced Ras activation was detectable within 1 min and maximal at 2–5 min. The ANG II type 1 (AT1) receptor antagonist, CV-11974, completely inhibited this reaction. Pertussis toxin treatment of VSMC inhibited ANG II-induced Ras activation by approximately 70% but had no effect on ANG II-induced MAP kinase activation and c-fos expression. These results indicate that ANG II activates Ras via AT1 receptors, which are predominantly linked to a G protein of the Gi subfamily in VSMC1 and suggest that Ras activation may not be a prerequisite for ANG II-induced MAP kinase activation and c-fos expression in this cell type.


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