Project description:Tissue Factor Pathway Inhibitor-2 is Induced by Fluid Shear Stress in Vascular Smooth Muscle Cells and Affects Cell Proliferation and Survival Introduction: Vascular smooth muscle cells (SMCs) are exposed to fluid shear stress (FSS) after interventional procedures such as balloon-angioplasty. Whereas the effects of hemodynamic forces on endothelial cells are explored in detail, the influence of FSS on smooth muscle cell function is poorly characterized. Here, we investigated the effect of FSS on SMC gene expression and function. Methods: Laminar FSS of arterial level (14 dynes/cm2) was applied to SMC cultures for 24 h in a parallel-plate flow chamber. The effect of FSS on gene expression was first screened with microarray technology and the results further verified by real time (RT) PCR and immunoblotting. Protein expression was also studied in the rat carotid artery after balloon-injury and DNA synthesis and apoptosis was examined in SMCs in vitro. Results: Microarrays identified tissue-pathway inhibitor-2 (TFPI-2) as the most differentially expressed gene by FSS in cultured SMCs. The regulatory effect of FSS on the expression of TFPI-2 was confirmed by RT-PCR and immunobloting demonstrating a more than 400-fold increase in TFPI-2 expression in SMCs exposed to FSS compared to static controls and a consistent upregulation at the protein level. Functionally, SMC proliferation was decreased by FSS and recombinant TFPI-2 was found to inhibit SMC proliferation and induce SMC apoptosis as indicated by activation of caspase-3. In vivo, TFPI-2 expression was found to be up-regulated 5, 10 and 20 h after rat carotid balloon-injury and immunohistochemistry demonstrated TFPI-2 protein in luminal SMCs exposed to FSS in rat carotid intimal hyperplasia 10 days after balloon-injury. Conclusion: FSS strongly influence gene expression in cultured SMCs and induce TFPI-2 expression, which is also expressed after rat carotid balloon injury in luminal SMCs exposed to FSS. Functionally, TFPI-2 may play an important role in vessel wall repair by regulating SMC proliferation and survival. Further studies are needed to elucidate the mechanisms by which TFPI-2 control SMC function. 3 x 2 samples from a paired fluid shear stress experiment on smooth muscle cells.
Project description:AimsVascular peroxidase 1 (VPO1) is a newly identified haem-containing peroxidase that catalyses the oxidation of a variety of substrates by hydrogen peroxide (H(2)O(2)). Considering the well-defined effects of H(2)O(2) on the vascular remodelling during hypertension, and that VPO1 can utilize H(2)O(2) generated from co-expressed NADPH oxidases to catalyse peroxidative reactions, the aims of this study were to determine the potential role of VPO1 in vascular remodelling during hypertension.Methods and resultsThe vascular morphology and the expression of VPO1 in arterial tissues of spontaneously hypertensive rats and Wistar-Kyoto rats were assessed. The VPO1 expression was significantly increased concomitantly with definite vascular remodelling assessed by evaluating the media thickness, lumen diameter, media thickness-to-lumen diameter ratio and mean nuclear area in artery media in spontaneously hypertensive rats. In addition, in cultured rat aortic smooth muscle cells we found that the angiotensin II-mediated cell proliferation was inhibited by knockdown of VPO1 using small hairpin RNA. Moreover, the NADPH oxidase inhibitor, apocynin, and the hydrogen peroxide scavenger, catalase, but not the ERK1/2 inhibitor, PD98059, attenuated angiotensin II-mediated up-regulation of VPO1 and generation of hypochlorous acid.ConclusionVPO1 is a novel regulator of vascular smooth muscle cell proliferation via NADPH oxidase-H(2)O(2)-VPO1-hypochlorous acid-ERK1/2 pathways, which may contribute to vascular remodelling in hypertension.
Project description:Vascular smooth muscle cells (VSMCs) are primarily responsible for vasoconstriction and the regulation of blood pressure1. Pyroptosis, a particular form of regulated cell death, is involved in multiple vascular injuries, including hypertensive vascular dysfunction. This pyroptotic cell death is mediated by the pore-forming protein of Gasdermin D (GSDMD). This study was designed to examine the direct effect of GSDMD on smooth muscle cell pyroptosis and vascular remodeling. Findings revealed that GSDMD was activated in Angiotensin (Ang) II- treated aortas. We then showed that genetic deletion of Gsdmd reduced vascular remodeling and aorta pyroptosis induced by Ang II in vivo. Aberrant expression of GSDMD by recombinant AAV9 virus carrying Gsdmd cDNA aggravated the level of pyroptosis in aortas of Ang II mice. Gain- and loss-of- function analysis further confirmed that GSDMD regulated the pyroptosis of murine aortic vascular smooth muscle cells (MOVAS) in an in vitro model of tumor necrosis factor (TNF)-α treatment, which was achieved by transfecting expressing plasmid or siRNA, respectively. Overall, this study provided evidence supporting the active involvement of GSDMD in smooth muscle cell pyroptosis and Ang II-induced mice vascular injury. This finding lends credence to GSDMD as a potential therapeutic target for hypertensive vascular remodeling via inhibiting pyroptosis.
Project description:Hypertension is a disease associated to increased plasma levels of angiotensin II (Ang II). Ang II can regulate proliferation, migration, ROS production and hypertrophy of vascular smooth muscle cells (VSMCs). However, the mechanisms by which Ang II can affect VSMCs remain to be fully elucidated. In this context, autophagy, a process involved in self-digestion of proteins and organelles, has been described to regulate vascular remodeling. Therefore, we sought to investigate if Ang II regulates VSMC hypertrophy through an autophagy-dependent mechanism. To test this, we stimulated A7r5 cell line and primary rat aortic smooth muscle cells with Ang II 100 nM and measured autophagic markers at 24 h by Western blot. Autophagosomes were quantified by visualizing fluorescently labeled LC3 using confocal microscopy. The results showed that treatment with Ang II increases Beclin-1, Vps34, Atg-12-Atg5, Atg4 and Atg7 protein levels, Beclin-1 phosphorylation, as well as the number of autophagic vesicles, suggesting that this peptide induces autophagy by activating phagophore initiation and elongation. These findings were confirmed by the assessment of autophagic flux by co-administering Ang II together with chloroquine (30 μM). Pharmacological antagonism of the angiotensin type 1 receptor (AT1R) with losartan and RhoA/Rho Kinase inhibition prevented Ang II-induced autophagy. Moreover, Ang II-induced A7r5 hypertrophy, evaluated by α-SMA expression and cell size, was prevented upon autophagy inhibition. Taking together, our results suggest that the induction of autophagy by an AT1R/RhoA/Rho Kinase-dependent mechanism contributes to Ang II-induced hypertrophy in VSMC.
Project description:Asymmetrical dimethylarginine inhibits nitric oxide synthase, cationic amino acid transport, and endothelial function. Patients with cardiovascular risk factors often have endothelial dysfunction associated with increased plasma asymmetrical dimethylarginine and markers of reactive oxygen species. We tested the hypothesis that reactive oxygen species, generated by nicotinamide adenine dinucleotide phosphate oxidase, enhance cellular asymmetrical dimethylarginine. Incubation of rat preglomerular vascular smooth muscle cells with angiotensin II doubled the activity of nicotinamide adenine dinucleotide phosphate oxidase but decreased the activities of dimethylarginine dimethylaminohydrolase by 35% and of cationic amino acid transport by 20% and doubled cellular (but not medium) asymmetrical dimethylarginine concentrations (P<0.01). This was blocked by tempol or candesartan. Cells stably transfected with p22(phox) had a 50% decreased protein expression and activity of dimethylarginine dimethylaminohydrolase despite increased promoter activity and mRNA. The decreased DDAH protein expression and the increased asymmetrical dimethylarginine concentration in p22(phox)-transfected cells were prevented by proteosomal inhibition. These cells had enhanced protein arginine methylation, a 2-fold increased expression of protein arginine methyltransferase-3 (P<0.05) and a 30% reduction in cationic amino acid transport activity (P<0.05). Asymmetrical dimethylarginine was increased from 6+/-1 to 16+/-3 micromol/L (P<0.005) in p22(phox)-transfected cells. Thus, angiotensin II increased cellular asymmetrical dimethylarginine via type 1 receptors and reactive oxygen species. Nicotinamide adenine dinucleotide phosphate oxidase increased cellular asymmetrical dimethylarginine by increasing enzymes that generate it, enhancing the degradation of enzymes that metabolize it, and reducing its cellular transport. This could underlie increases in cellular asymmetrical dimethylarginine during oxidative stress.
Project description:ObjectiveThe G protein-coupled receptor (GPCR)-kinase2 interacting protein1 (GIT1) is a scaffold protein involved in angiotensin II (Ang II) signaling. Histone deacetylase-5 (HDAC5) has emerged as an important substrate of calcium/calmodulin-dependent protein kinase II (CamK II) in GPCR signaling. Here we investigated the hypothesis that Ang II-mediated vascular smooth muscle cell (VSMC) gene transcription involves GIT1-CamK II-dependent phosphorylation of HDAC5.Methods and resultsAng II rapidly stimulated phosphorylation of HDAC5 at Ser498 in VSMCs. Knockdown of GIT1 significantly decreased HDAC5 phosphorylation induced by Ang II. The involvement of Src, phospholipase gamma (PLCgamma), and CamK II in GIT1-mediated HDAC5 phosphorylation was demonstrated. The association of GIT1 and CamK II was constitutive but increased after stimulation with Ang II. Moreover, the interaction of GIT1 and CamK II through the ARF GTPase-activating protein (ARF-GAP) and coiled-coil domains of GIT1 was essential for the phosphorylation of HDAC5. Finally, knockdown of GIT1 decreased myocyte enhancer factor 2 transcriptional activity induced by Ang II.ConclusionsThis study identifies a novel function for GIT1 as a mediator of Ang II-induced VSMC gene transcription via a Src-PLCgamma-CamK II-HDAC5 signaling pathway.
Project description:Angiotensin II (Ang II)-induced vascular injury is exacerbated by high-salt diets. This study examined the effects of high-sodium level on Ang II-induced cell proliferation in rat vascular smooth muscle cells (VSMCs). The cells were cultured in a standard medium containing 137.5 mmol l(-1) of sodium. The high-sodium medium (140 mmol l(-1)) contained additional sodium chloride. Extracellular signal-regulated kinase (ERK) 1/2 phosphorylation was determined by western blot analysis. Cell proliferation was evaluated by [(3)H]-thymidine incorporation. Ang II (100 nmol l(-1)) significantly increased ERK 1/2 phosphorylation and cell proliferation in the both medium containing standard sodium and high sodium. High-sodium level augmented Ang II-induced ERK 1/2 phosphorylation and cell proliferation compared with standard sodium. Pre-treatment with candesartan (1 μmol l(-1), Ang II type 1 receptor blocker) or PD98095 (10 μmol l(-1), ERK kinase iinhibitor) abolished the proliferative effect induced by high sodium/Ang II. Pre-treatment with 5-N,N-hexamethylene amiloride (30 μmol l(-1), Na(+)/H(+) exchanger type 1 (NHE-1) inhibitor), but not SN-6 (10 μmol l(-1), Na(+)/Ca(2+) exchanger inhibitor) or ouabain (1 mmol l(-1), Na(+)/K(+)-ATPase inhibitor) attenuated ERK 1/2 phosphorylation or cell proliferation. Osmotic pressure or chloride had no effect on Ang II-induced proliferative changes. High-sodium level did not affect Ang II receptor expression. Ang II increased intracellular pH via NHE-1 activation, and high-sodium level augmented the pH increase induced by Ang II. These data suggest that high-sodium level directly augments Ang II-induced VSMC proliferation through NHE-1- and ERK 1/2-dependent pathways and may offer new insights into the mechanisms of vascular remodeling by high-sodium/Ang II.
Project description:Tissue Factor Pathway Inhibitor-2 is Induced by Fluid Shear Stress in Vascular Smooth Muscle Cells and Affects Cell Proliferation and Survival Introduction: Vascular smooth muscle cells (SMCs) are exposed to fluid shear stress (FSS) after interventional procedures such as balloon-angioplasty. Whereas the effects of hemodynamic forces on endothelial cells are explored in detail, the influence of FSS on smooth muscle cell function is poorly characterized. Here, we investigated the effect of FSS on SMC gene expression and function. Methods: Laminar FSS of arterial level (14 dynes/cm2) was applied to SMC cultures for 24 h in a parallel-plate flow chamber. The effect of FSS on gene expression was first screened with microarray technology and the results further verified by real time (RT) PCR and immunoblotting. Protein expression was also studied in the rat carotid artery after balloon-injury and DNA synthesis and apoptosis was examined in SMCs in vitro. Results: Microarrays identified tissue-pathway inhibitor-2 (TFPI-2) as the most differentially expressed gene by FSS in cultured SMCs. The regulatory effect of FSS on the expression of TFPI-2 was confirmed by RT-PCR and immunobloting demonstrating a more than 400-fold increase in TFPI-2 expression in SMCs exposed to FSS compared to static controls and a consistent upregulation at the protein level. Functionally, SMC proliferation was decreased by FSS and recombinant TFPI-2 was found to inhibit SMC proliferation and induce SMC apoptosis as indicated by activation of caspase-3. In vivo, TFPI-2 expression was found to be up-regulated 5, 10 and 20 h after rat carotid balloon-injury and immunohistochemistry demonstrated TFPI-2 protein in luminal SMCs exposed to FSS in rat carotid intimal hyperplasia 10 days after balloon-injury. Conclusion: FSS strongly influence gene expression in cultured SMCs and induce TFPI-2 expression, which is also expressed after rat carotid balloon injury in luminal SMCs exposed to FSS. Functionally, TFPI-2 may play an important role in vessel wall repair by regulating SMC proliferation and survival. Further studies are needed to elucidate the mechanisms by which TFPI-2 control SMC function.
Project description:ERK5 is involved in proliferation of vascular smooth muscle cells (VSMC). The proliferative actions of insulin and angiotensin-II (A-II) in VSMC are mediated in part by ERK1/2. We hypothesized that insulin and A-II also regulate ERK5 activity in VSMC. Acute treatment (<60min) with insulin or A-II increased phosphorylation of ERK1/2 at 15min and ERK5 at 5min. Chronic treatment (< or = 8h) with insulin increased ERK1/2 phosphorylation by 4h and ERK5 by 8h. A-II-stimulated phosphorylation of ERK1/2 by 8h and ERK5 by 4h. The EC(50) for insulin treatment effecting ERK1/2 and ERK5 phosphorylation was 1.5 and 0.1nM, whereas the EC(50) for A-II was 2nM, each. Insulin plus A-II induced an additive effect only on ERK5 phosphorylation. Inhibition of insulin- and A-II-stimulated phosphorylation of ERK5 and ERK1/2 by PD98059 and Wortmannin exhibited differential and time-dependent effects. Taken together, these data indicate that insulin and A-II regulate the activity of ERK5, but different from that seen for ERK1/2.
Project description:Osteopontin (OPN) is a multifunctional protein found in abundance in atherosclerotic plaques. Angiotensin II (Ang II) promotes atherosclerosis by inducing adhesion and migration of vascular smooth muscle cells (VSMCs). MicroRNAs (miRNAs) are critical regulators of protein expression. However, the relationship between Ang II, miRNAs and OPN has yet to be fully explored.Using cultured VSMCs, we found that Ang II increased cellular OPN protein expression 4 h after treatment by 420 ± 54% (p < 0.03) in a translation dependent manner. Sequence analysis revealed a putative binding site for mir181a and raised the possibility that miR181a is a potential regulatory mechanism for OPN expression. We demonstrated that Ang II decreased miR181a expression by 52 ± 7% (p < 0 .0001) and overexpressing miR181a inhibited Ang II induced increases in OPN protein expression by 69 ± 9% (p < 0.05). Furthermore, we demonstrated that miR181a is functionally important in that overexpression of miR181a inhibited VSMCs adhesion to collagen in response to Ang II as compared to controls by 36 ± 4%. (p < 0.05) CONCLUSIONS: These results demonstrate that miR181a regulates OPN expression and that altering miR181a expression may be a novel therapeutic approach to modulate OPN protein expression.