Vascular oxidant stress early after balloon injury: evidence for increased NAD(P)H oxidoreductase activity

Oxidative stress generated by polycyclic aromatic hydrocarbons from ambient particulate matter enhance vascular smooth muscle cell migration through MMP upregulation and actin reorganization

Background

Epidemiological studies have suggested that elevated concentrations of particulate matter (PM) are strongly associated with the incidence of atherosclerosis, however, the underlying cellular and molecular mechanisms of atherosclerosis by PM exposure and the components that are mainly responsible for this adverse effect remain to be established. In this investigation, we evaluated the effects of ambient PM on vascular smooth muscle cell (VSMC) behavior. Furthermore, the effects of polycyclic aromatic hydrocarbons (PAHs), major components of PM, on VSMC migration and the underlying mechanisms were examined.

Results

VSMC migration was significantly increased by treatment with organic matters extracted from ambient PM. The total amount of PAHs contained in WPM was higher than that in SPM, leading to higher ROS generation and VSMC migration. The increased migration was successfully inhibited by treatment with the anti-oxidant, N-acetyl-cysteine (NAC). The levels of matrix metalloproteinase (MMP) 2 and 9 were significantly increased in ambient PM-treated VSMCs, with MMP9 levels being significantly higher in WPM-treated VSMCs than in those treated with SPM. As expected, migration was significantly increased in all tested PAHs (anthracene, ANT; benz(a)anthracene, BaA) and their oxygenated derivatives (9,10-Anthraquinone, AQ; 7,12-benz(a)anthraquinone, BAQ, respectively). The phosphorylated levels of focal adhesion kinase (FAK) and formation of the focal adhesion complex were significantly increased in ambient PM or PAH-treated VSMCs, and these effects were blocked by administration of NAC or α-NF, an inhibitor of AhR, the receptor that allows PAH uptake. Subsequently, the levels of phosphorylated Src and NRF, the downstream targets of FAK, were altered with a pattern similar to that of p-FAK.

Conclusions

PAHs, including oxy-PAHs, in ambient PM may have dual effects that lead to an increase in VSMC migration. One is the generation of oxidative stress followed by MMP upregulation, and the other is actin reorganization that results from the activation of the focal adhesion complex.

Induction of apoptosis and autosis in cardiomyocytes by the combination of homocysteine and copper via NOX-mediated p62 expression

High levels of homocysteine (Hcy) associated with cardiovascular events are accompanied by increased copper (Cu) concentrations in the blood. Hcy has been shown to promote endothelial dysfunction, whereas the effect of Hcy on cardiomyocytes and the role of Cu in the pathogenesis remain less understood. In the present study, it is demonstrated that the combination of Hcy and Cu²⁺-induced apoptosis and autosis of cardiomyocytes simultaneously, and thus led to cardiac dysfunction in hyperhomocysteinemic rats. These effects were associated with p22^phox activation and NADPH oxidase (NOX)-mediated p62 upregulation. Inhibition of the expression of p22^phox or p62 in cardiomyocytes significantly attenuated Hcy and Cu²⁺-mediated reactive oxygen species (ROS) generation and cell death. Furthermore, interrupting the NOX-p62 axis prevented diastolic dysfunction in hyperhomocysteinemic rats (HcyR). These findings establish that the induction of apoptosis and autosis of cardiomyocytes through stimulating the NOX-p62-signaling pathway constitutes a novel mechanism of Hcy and Cu-induced cardiac dysfunction.

Redox-sensitive enzyme SENP3 mediates vascular remodeling via de-SUMOylation of β-catenin and regulation of its stability

Background

Oxidative stress plays critical pathophysiological roles in vascular remodeling-related cardiovascular diseases, including hypertension, atherosclerosis, and restenosis. Previous studies demonstrate that SENP3, a redox-sensitive SUMO2/3-specific protease, is strongly implicated in cancer development and progression. However, the role of SENP3 in vascular remodeling remains unknown.

Methods

We generated three mouse models of vascular remodeling due to low shear stress, hypertension, and atherosclerosis. The expression of SENP3 was determined by western blotting and/or immunofluorescence staining in cultured vascular smooth muscle cells (VSMCs), animal models, and human samples. The biological function of SENP3 in proliferation and migration of VSMC and vascular remodeling was further investigated in vitro and in vivo models.

Findings

SENP3 was highly expressed in VSMCs of remodeled arteries, accompanied by elevated reactive oxygen species (ROS) levels. In cultured VSMCs, SENP3 protein levels were enhanced by oxidized low-density lipoprotein and Angiotensin II in a ROS-dependent manner. SENP3 overexpression significantly promoted and sh-RNA-mediated knockdown markedly inhibited VSMCs proliferation and migration. Immunofluorescence staining showed that SENP3 expression was correlated with intimal area in remodeled arteries. Furthermore, we demonstrated that SENP3 interacted with β-catenin and inhibited its proteasome-dependent degradation via de-SUMOylation of β-catenin. Most importantly, SENP3^+/− mice exhibited alleviated vascular remodeling.

Interpretation

Our results highlight the important function of SENP3 as a redox sensor and mediator in vascular remodeling.

The SGLT2 inhibitor Empagliflozin attenuates interleukin-17A-induced human aortic smooth muscle cell proliferation and migration by targeting TRAF3IP2/ROS/NLRP3/Caspase-1-dependent IL-1β and IL-18 secretion

Chronic inflammation and persistent oxidative stress contribute to the development and progression of vascular proliferative diseases. We hypothesized that the proinflammatory cytokine interleukin (IL)-17A induces oxidative stress and amplifies inflammatory signaling in human aortic smooth muscle cells (SMC) via TRAF3IP2-mediated NLRP3/caspase-1-dependent mitogenic and migratory proinflammatory cytokines IL-1β and IL-18. Further, we hypothesized that these maladaptive changes are prevented by empagliflozin (EMPA), an SGLT2 (Sodium/Glucose Cotransporter 2) inhibitor. Supporting our hypotheses, exposure of cultured SMC to IL-17A promoted proliferation and migration via TRAF3IP2, TRAF3IP2-dependent superoxide and hydrogen peroxide production, NLRP3 expression, caspase-1 activation, and IL-1β and IL-18 secretion. Furthermore, NLRP3 knockdown, caspase-1 inhibition, and pretreatment with IL-1β and IL-18 neutralizing antibodies and IL-18BP, each attenuated IL-17A-induced SMC migration and proliferation. Importantly, SMC express SGLT2, and pre-treatment with EMPA attenuated IL-17A/TRAF3IP2-dependent oxidative stress, NLRP3 expression, caspase-1 activation, IL-1β and IL-18 secretion, and SMC proliferation and migration. Importantly, silencing SGLT2 attenuated EMPA-mediated inhibition of IL-17A-induced cytokine secretion and SMC proliferation and migration. EMPA exerted these beneficial antioxidant, anti-inflammatory, anti-mitogenic and anti-migratory effects under normal glucose conditions and without inducing cell death. These results suggest the therapeutic potential of EMPA in vascular proliferative diseases.

Reactive Oxygen Species: Modulators of Phenotypic Switch of Vascular Smooth Muscle Cells

Reactive oxygen species (ROS) are natural byproducts of oxygen metabolism in the cell. At physiological levels, they play a vital role in cell signaling. However, high ROS levels cause oxidative stress, which is implicated in cardiovascular diseases (CVD) such as atherosclerosis, hypertension, and restenosis after angioplasty. Despite the great amount of research conducted to identify the role of ROS in CVD, the image is still far from being complete. A common event in CVD pathophysiology is the switch of vascular smooth muscle cells (VSMCs) from a contractile to a synthetic phenotype. Interestingly, oxidative stress is a major contributor to this phenotypic switch. In this review, we focus on the effect of ROS on the hallmarks of VSMC phenotypic switch, particularly proliferation and migration. In addition, we speculate on the underlying molecular mechanisms of these cellular events. Along these lines, the impact of ROS on the expression of contractile markers of VSMCs is discussed in depth. We conclude by commenting on the efficiency of antioxidants as CVD therapies.

Reperfusion injury as a target for diminishing infarct size

Therapies for preventing reperfusion injury (RI) have been widely studied. However, the attempts to transfer cardioprotective therapies for reducing RI from experiments into clinical practice have been so far unsuccessful. Pathophysiological mechanisms of RI are complicated and compose of many pathways e.g. hypercontracture-mediated sarcolemma rupture, mitochondrial permeability transition pore persistent opening, reactive oxygen species formation, inflammation and no-reflow phenomenon. Based on research, it cannot be determined which mechanism dominates, probably they cooperate with a domination of one or another in different clinical circumstances. Our hypothesis is, that only intervention that at the same time interferes with different (all?) pathways of RI may turn out to be effective in decreasing the final area of infarction.

Redox Activation of Nox1 (NADPH Oxidase 1) Involves an Intermolecular Disulfide Bond Between Protein Disulfide Isomerase and p47phox in Vascular Smooth Muscle Cells

Objective- PDI (protein disulfide isomerase A1) was reported to support Nox1 (NADPH oxidase) activation mediated by growth factors in vascular smooth muscle cells. Our aim was to investigate the molecular mechanism by which PDI activates Nox1 and the functional implications of PDI in Nox1 activation in vascular disease. Approach and Results- Using recombinant proteins, we identified a redox interaction between PDI and the cytosolic subunit p47^phox in vitro. Mass spectrometry of crosslinked peptides confirmed redox-dependent disulfide bonds between cysteines of p47^phox and PDI and an intramolecular bond between Cys 196 and 378 in p47^phox. PDI catalytic Cys 400 and p47^phox Cys 196 were essential for the activation of Nox1 by PDI in vascular smooth muscle cells. Transfection of PDI resulted in the rapid oxidation of a redox-sensitive protein linked to p47^phox, whereas PDI mutant did not promote this effect. Mutation of p47^phox Cys 196, or the redox active cysteines of PDI, prevented Nox1 complex assembly and vascular smooth muscle cell migration. Proximity ligation assay confirmed the interaction of PDI and p47^phox in murine carotid arteries after wire injury. Moreover, in human atheroma plaques, a positive correlation between the expression of PDI and p47^phox occurred only in PDI family members with the a' redox active site. Conclusions- PDI redox cysteines facilitate Nox1 complex assembly, thus identifying a new mechanism through which PDI regulates Nox activity in vascular disease.

Periadventitial local drug delivery to target restenosis

The adventitia functions as a dynamic compartment for cell trafficking into and out of the artery wall, and communicates with medial and intimal cells. The resident cells in the tunica adventitia play an integral role in the regulation of vessel wall structure, repair, tone, and remodeling. Following injury to the vascular wall, adventitial fibroblasts are activated, which proliferate and differentiate into migratory myofibroblasts, and initiate inflammation through the secretion of soluble factors such as chemokines, cytokines, and adhesion molecules. The secreted factors subsequently promote leukocyte recruitment and extravasation into the media and intima. The adventitia generates reactive oxygen species and growth factors that participate in cell proliferation, migration, and hypertrophy, resulting in intimal thickening. The adventitial vasa vasorum undergoes neovascularization and serves as a port of entry for the delivery of inflammatory cells and resident stem/progenitor cells into the intima, and thus facilitates vascular remodeling. This review highlights the contribution of multilineage cells in the adventitia along with de-differentiated smooth muscle-like cells to the formation of neointimal hyperplasia, and discusses the potential of periadventitial local drug delivery for the prevention of vascular restenosis.

Astaxanthin-antioxidant impact on excessive Reactive Oxygen Species generation induced by ischemia and reperfusion injury

Oxidative stress induced by Reactive Oxygen Species (ROS) was shown to be involved in the pathogenesis of chronic diseases such as cardiovascular pathologies. Particularly, oxidative stress has proved to mediate abnormal platelet function and dysfunctional endothelium-dependent vasodilatation representing a key factor in the progression of ischemic injuries. Antioxidants like carotenoids have been suggested to contribute in their prevention and treatment. Astaxanthin, a xanthophyll carotenoid produced naturally and synthetically, shows interesting antioxidant and anti-inflammatory properties. In vivo studies applying different models of induced ischemia and reperfusion (I/R) injury confirm astaxanthin's protective action after oral or intravenous administration. However, some studies have shown some limitations after oral administration such as low stability, bioavailability and bioefficacy, revealing a need for the implementation of new biomaterials to act as astaxanthin vehicles in vivo. Here, a brief overview of the chemical characteristics of astaxanthin, the carrier systems developed for overcoming its delivery drawbacks and the animal studies showing its potential effect to treat I/R injury are presented.

Limiting Injury During Saphenous Vein Graft Preparation For Coronary Arterial Bypass Prevents Metabolic Decompensation

Standard harvest and preparation of human saphenous vein (HSV) for autologous coronary and peripheral arterial bypass procedures is associated with injury and increased oxidative stress that negatively affect graft performance. In this study we investigated the global metabolomic profiles of HSV before (unprepared; UP) and after standard vein graft preparation (AP). AP-HSV showed impaired vasomotor function that was associated with increased oxidative stress, phospholipid hydrolysis and energy depletion that are characteristic of mechanical and chemical injury. A porcine model (PSV) was utilized to validate these metabolomic changes in HSV and to determine the efficacy of an improved preparation technique (OP) using pressure-regulated distension, a non-toxic vein marker, and graft storage in buffered PlasmaLyte solution in limiting metabolic decompensation due to graft preparation. Deficits in vasomotor function and metabolic signature observed in AP-PSV could be largely mitigated with the OP procedure. These findings suggest that simple strategies aimed at reducing injury during graft harvest and preparation represents a straightforward and viable strategy to preserve conduit function and possibly improve graft patency.

Vascular remodeling: A redox-modulated mechanism of vessel caliber regulation

Vascular remodeling, i.e. whole-vessel structural reshaping, determines lumen caliber in (patho)physiology. Here we review mechanisms underlying vessel remodeling, with emphasis in redox regulation. First, we discuss confusing terminology and focus on strictu sensu remodeling. Second, we propose a mechanobiological remodeling paradigm based on the concept of tensional homeostasis as a setpoint regulator. We first focus on shear-mediated models as prototypes of remodeling closely dominated by highly redox-sensitive endothelial function. More detailed discussions focus on mechanosensors, integrins, extracellular matrix, cytoskeleton and inflammatory pathways as potential of mechanisms potentially coupling tensional homeostasis to redox regulation. Further discussion of remodeling associated with atherosclerosis and injury repair highlights important aspects of redox vascular responses. While neointima formation has not shown consistent responsiveness to antioxidants, vessel remodeling has been more clearly responsive, indicating that despite the multilevel redox signaling pathways, there is a coordinated response of the whole vessel. Among mechanisms that may orchestrate redox pathways, we discuss roles of superoxide dismutase activity and extracellular protein disulfide isomerase. We then discuss redox modulation of aneurysms, a special case of expansive remodeling. We propose that the redox modulation of vascular remodeling may reflect (1) remodeling pathophysiology is dominated by a particularly redox-sensitive cell type, e.g., endothelial cells (2) redox pathways are temporospatially coordinated at an organ level across distinct cellular and acellular structures or (3) the tensional homeostasis setpoint is closely connected to redox signaling. The mechanobiological/redox model discussed here can be a basis for improved understanding of remodeling and helps clarifying mechanisms underlying prevalent hard-to-treat diseases.

Altered AP-1/Ref-1 redox pathway and reduced proliferative response in iNOS-deficient vascular smooth muscle cells

We previously reported that injury-induced medial vascular smooth muscle cell (VSMC) proliferation and neointima formation in carotid arteries of inducible nitric oxide synthase knockout (iNOS KO) mice were significantly reduced compared with wild type (WT). However, the molecular pathway underlying such differences is not known. In this in vitro study, we discovered that the AP-1/Ref-1/thioredoxin signaling pathway is altered in aortic VSMC from iNOS KO mice, which leads to reduced growth response when compared with aortic VSMC from WT mice. After equal initial seeding, the cell number after 7 days in serum medium was less in iNOS KO cells compared with WT VSMC (1.2-0.6-105 vs 3.2-1.1-105; p < 0.05). Significantly more iNOS KO cells remained in the G0/G1 phase compared with WT cells after 24-h serum treatment (82.6-13.7% vs 62.3-14.6%; p < 0.05) by cell-cycle analysis. Nuclear PCNA expression was also less in the iNOS KO cells, which was not affected by exogenous NO or superoxide. Superoxide generation after 24-h serum stimulation was less in the iNOS KO cells compared with WT cells. After 30-min serum stimulation, AP-1 DNA binding was reduced and a lack of increase in nuclear c-Jun protein was observed in iNOS KO VSMC. RT-PCR analysis confirmed a lack of inducible c-Jun mRNA after serum stimulation in the KO cells. In addition, KO cells had less nuclear reducing factor-1 (Ref-1) and serum-inducible thioredoxin protein expression. Reduced proliferative response of iNOS KO VSMC to serum treatment is associated with altered AP-1/Ref-1/thioredoxin pathway activation.

Salusin-β Promotes Vascular Smooth Muscle Cell Migration and Intimal Hyperplasia After Vascular Injury via ROS/NFκB/MMP-9 Pathway

AIMS

Media-to-intima migration of vascular smooth muscle cells (VSMCs) is critical to intimal thickening in atherosclerosis and restenosis after coronary angioplasty. The aim of this study is to determine the effects of salusin-β on VSMC migration and intimal hyperplasia after vascular injury and the underlying mechanism.

RESULTS

In vitro, salusin-β promoted VSMC migration, which was attenuated by matrix metalloproteinase (MMP)-9 inhibition. Inhibition or knockdown of p65-nuclear factor kappa beta (NFκB) in VSMCs suppressed salusin-β-induced MMP-9 expression and VSMC migration. Salusin-β increased NADPH oxidase 2 (NOX2) expression and reactive oxygen species (ROS) production, which were prevented by NOX2-small interfering RNA (siRNA) transfection. Salusin-β-induced p65-NFκB translocation, MMP-9 expression, and VSMC migration were inhibited by ROS scavenger, NADPH oxidase inhibitor, or NOX2-siRNA. In vivo, carotid artery ligation-induced vascular injury resulted in intimal hyperplasia in injured artery in rats. Salusin-β was upregulated in the injured carotid arteries of rats, which was attributed to reduced miR-133a-3p expression. Knockdown of salusin-β with siRNA attenuated the vascular injury-induced intimal thickening, p65-NFκB nuclear translocation, and NOX2 and MMP-9 expressions in rats.

INNOVATION

Salusin-β is a critical modulator in VSMC migration and neointima formation in response to vascular injury.

CONCLUSIONS

Salusin-β promotes VSMC migration and vascular injury-induced intimal hyperplasia via MMP-9 accumulation due to NOX2 activation, followed by ROS production, IκBα phosphorylation and degradation, and p65-NFκB translocation. We propose that salusin-β may be important in the VSMC migration and neointima of some vascular diseases. Antioxid. Redox Signal. 24, 1045-1057.

Nrf2/Keap1 system regulates vascular smooth muscle cell apoptosis for vascular homeostasis: role in neointimal formation after vascular injury

Abnormal increases in vascular smooth muscle cells (VSMCs) in the intimal region after a vascular injury is a key event in developing neointimal hyperplasia. To maintain vascular function, proliferation and apoptosis of VSMCs is tightly controlled during vascular remodeling. NF-E2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1) system, a key component of the oxidative stress response that acts in maintaining homeostasis, plays an important role in neointimal hyperplasia after a vascular injury; however, the role of Nrf2/Keap1 in VSMC apoptosis has not been clarified. Here we report that 14 days after arterial injury in mice, TUNEL-positive VSMCs are detected in both the neointimal and medial layers. These layers contain cells expressing high levels of Nrf2 but low Keap1 expression. In VSMCs, Keap1 depletion induces features of apoptosis, such as positive TUNEL staining and annexin V binding. These changes are associated with an increased expression of nuclear Nrf2. Simultaneous Nrf2 depletion inhibits Keap1 depletion-induced apoptosis. At 14 days after the vascular injury, Nrf2-deficient mice demonstrated fewer TUNEL-positive cells and increased neointimal formation in the neointimal and medial areas. The results suggest that the Nrf2/Keap1 system regulates VSMC apoptosis during neointimal formation, thereby inhibiting neointimal hyperplasia after a vascular injury.

The orphan nuclear receptor Nur77 inhibits low shear stress-induced carotid artery remodeling in mice

Shear stress, particularly low and oscillatory shear stress, plays a critical pathophysiological role in vascular remodeling-related cardiovascular diseases. Growing evidence suggests that the orphan nuclear receptor Nur77 [also known as TR3 or nuclear receptor subfamily 4, group A, member 1 (NR4A1)] is expressed in diseased human vascular tissue and plays an important role in vascular physiology and pathology. In the present study, we used a mouse model of flow-dependent remodeling by partial ligation of the left common carotid artery (LCCA) to define the exact role of Nur77 in vascular remodeling induced by low shear stress. Following vascular remodeling, Nur77 was highly expressed in neointimal vascular smooth muscle cells (VSMCs) in the ligated carotid arteries. The reactive oxygen species (ROS) levels were elevated in the remodeled arteries in vivo and in primary rat VSMCs in vitro following stimulation with platelet-derived growth factor (PDGF). Further in vitro experiments revealed that Nur77 expression was rapidly increased in the VSMCs following stimulation with PDGF and H₂O₂, whereas treatment with N-acetyl cysteine (NAC, a ROS scavenger) reversed the increase in the protein level of Nur77 induced by H₂O₂. Moreover, Nur77 overexpression markedly inhibited the proliferation and migration of VSMCs, induced by PDGF. Finally, to determine the in vivo role of Nur77 in low shear stress-induced vascular remodeling, wild-type (WT) and Nur77-deficient mice were subjected to partial ligation of the LCCA. Four weeks following surgery, in the LCCAs of the Nur77-deficient mice, a significant increase in the intima-media area and carotid intima-media thickness was noted, as well as more severe elastin disruption and collagen deposition compared to the WT mice. Immunofluorescence staining revealed an increase in VSMC proliferation [determined by the expression of proliferating cell nuclear antigen (PCNA)] and matrix metalloproteinase 9 (MMP-9) production in the Nur77-deficient mice. There was no difference in the number of intimal apoptotic cells between the groups. Taken together, our results indicate that Nur77 may be a sensor of oxidative stress and an inhibitor of vascular remodeling induced by low shear stress. Nur77, as well as its downstream cell signals, may thus be a potential therapeutic target for the suppression of vascular remodeling.

Smooth muscle specific overexpression of p22phox potentiates carotid artery wall thickening in response to injury

We hypothesized that transgenic mice overexpressing the p22^phox subunit of the NADPH oxidase selectively in smooth muscle (Tg^p22smc) would exhibit an exacerbated response to transluminal carotid injury compared to wild-type mice. To examine the role of reactive oxygen species (ROS) as a mediator of vascular injury, the injury response was quantified by measuring wall thickness (WT) and cross-sectional wall area (CSWA) of the injured and noninjured arteries in both Tg^p22smc and wild-type animals at days 3, 7, and 14 after injury. Akt, p38 MAPK, and Src activation were evaluated at the same time points using Western blotting. WT and CSWA following injury were significantly greater in Tg^p22smc mice at both 7 and 14 days after injury while noninjured contralateral carotids were similar between groups. Apocynin treatment attenuated the injury response in both groups and rendered the response similar between Tg^p22smc mice and wild-type mice. Following injury, carotid arteries from Tg^p22smc mice demonstrated elevated activation of Akt at day 3, while p38 MAPK and Src activation was elevated at day 7 compared to wild-type mice. Both increased activation and temporal regulation of these signaling pathways may contribute to enhanced vascular growth in response to injury in this transgenic model of elevated vascular ROS.

NADPH oxidase p47phox siRNA attenuates adventitial fibroblasts proliferation and migration in apoE(-/-) mouse

BACKGROUND

Reactive oxide species (ROS) derived from NADPH oxidases is involved in atherosclerosis. However, as a key component of NADPH oxidase, how p47phox regulates NADPH oxidases activity, ROS production and adventitial fibroblasts (AFs) function remains unclear.

METHODS

p47phox in aortic arteries of apoE(-/-) mice fed with hyperlipid diet was detected by immunohistochemistry. NADPH oxidase activity, superoxide anion (O2(-)) generation and p47phox expression were analyzed in primary AFs treated by diphenyleneiodonium (DPI). The proliferation and migration of AFs were also analyzed.

RESULTS

p47phox expression was low in the aortic adventitia but high in the site of intimal injury with continuous hyperlipidic diet. Compared to AFs from wild-type mice, AFs derived from apoE(-/-) mice exhibited elevated NADPH oxidase activity, O2(-) production and higher mRNA and protein levels of p47phox, correlated with increased capability of proliferation and migration. DPI inhibited NADPH oxidase activity and AFs proliferation and migration in a dose-dependent manner. In addition, siRNA mediated knockdown of p47phox attenuated the proliferation and migration of AFs derived from apoE(-/-) mice.

CONCLUSION

p47phox plays a critical role in the regulation of adventitial fibroblast proliferation and migration and may be a new therapeutic target for neointimal hyperplasia.

Sex-based differential regulation of oxidative stress in the vasculature by nitric oxide

Background

Nitric oxide (^•NO) is more effective at inhibiting neointimal hyperplasia following arterial injury in male versus female rodents, though the etiology is unclear. Given that superoxide (O₂^•−) regulates cellular proliferation, and ^•NO regulates superoxide dismutase-1 (SOD-1) in the vasculature, we hypothesized that ^•NO differentially regulates SOD-1 based on sex.

Materials and methods

Male and female vascular smooth muscle cells (VSMC) were harvested from the aortae of Sprague-Dawley rats. O₂^•− levels were quantified by electron paramagnetic resonance (EPR) and HPLC. sod-1 gene expression was assayed by qPCR. SOD-1, SOD-2, and catalase protein levels were detected by Western blot. SOD-1 activity was measured via colorimetric assay. The rat carotid artery injury model was performed on Sprague-Dawley rats ±^•NO treatment and SOD-1 protein levels were examined by Western blot.

Results

In vitro, male VSMC have higher O₂^•− levels and lower SOD − 1 activity at baseline compared to female VSMC (P < 0.05). ^•NO decreased O₂^•− levels and increased SOD − 1 activity in male (P<0.05) but not female VSMC. ^•NO also increased sod− 1 gene expression and SOD − 1 protein levels in male (P<0.05) but not female VSMC. In vivo, SOD-1 levels were 3.7-fold higher in female versus male carotid arteries at baseline. After injury, SOD-1 levels decreased in both sexes, but ^•NO increased SOD-1 levels 3-fold above controls in males, but returned to baseline in females.

Conclusions

Our results provide evidence that regulation of the redox environment at baseline and following exposure to ^•NO is sex-dependent in the vasculature. These data suggest that sex-based differential redox regulation may be one mechanism by which ^•NO is more effective at inhibiting neointimal hyperplasia in male versus female rodents.

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The baseline redox environment in the vascular is sex-dependent.

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Nitric oxide differentially affects the vascular redox environment between the sexes.

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Nitric oxide decreases superoxide (O₂^.) levels, by increasing SOD-1 activity, sod1 gene expression and SOD-1 protein levels in male vascular smooth muscle cells, but not in females.

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Sex-based differential redox regulation may be one mechanism by which is more effective at inhibiting neointimal hyperplasia in male versus female rodents.

Nitric oxide inhibits neointimal hyperplasia following vascular injury via differential, cell-specific modulation of SOD-1 in the arterial wall

Superoxide (O2(•-)) promotes neointimal hyperplasia following arterial injury. Conversely, nitric oxide ((•)NO) inhibits neointimal hyperplasia through various cell-specific mechanisms, including redox regulation. What remains unclear is whether (•)NO exerts cell-specific regulation of the vascular redox environment following arterial injury to inhibit neointimal hyperplasia. Therefore, the aim of the present study was to assess whether (•)NO exerts cell-specific, differential modulation of O2(•-) levels throughout the arterial wall, establish the mechanism of such modulation, and determine if it regulates (•)NO-dependent inhibition of neointimal hyperplasia. In vivo, (•)NO increased superoxide dismutase-1 (SOD-1) levels following carotid artery balloon injury in a rat model. In vitro, (•)NO increased SOD-1 levels in vascular smooth muscle cells (VSMC), but had no effect on SOD-1 in endothelial cells or adventitial fibroblasts. This SOD-1 increase was associated with an increase in sod1 gene expression, increase in SOD-1 activity, and decrease in O2(•-) levels. Lastly, to determine the role of SOD-1 in (•)NO-mediated inhibition of neointimal hyperplasia, we performed the femoral artery wire injury model in wild type and SOD-1 knockout (KO) mice, with and without (•)NO. Interestingly, (•)NO inhibited neointimal hyperplasia only in wild type mice, with no effect in SOD-1 KO mice. In conclusion, these data show the cell-specific modulation of O2(•-) by (•)NO through regulation of SOD-1 in the vasculature, highlighting its importance on the inhibition of neointimal hyperplasia. These results also shed light into the mechanism of (•)NO-dependent redox balance, and suggest a novel VSMC redox target to prevent neointimal hyperplasia.

Oxidative stress-induced cyclin D1 depletion and its role in cell cycle processing

BACKGROUND

Cyclin D1 is immediately down-regulated in response to reactive oxygen species (ROS) and implicated in the induction of cell cycle arrest in G2 phase by an unknown mechanism. Either treatment with a protease inhibitor alone or expression of protease-resistant cyclin D1 T286A resulted in only a partial relief from the ROS-induced cell cycle arrest, indicating the presence of an additional control mechanism.

METHODS

Cells were exposed to hydrogen peroxide (H2O2), and analyzed to assess the changes in cyclin D1 level and its effects on cell cycle processing by kinase assay, de novo synthesis, gene silencing, and polysomal analysis, etc.

RESULTS

Exposure of cells to excessive H2O2 induced ubiquitin-dependent proteasomal degradation of cyclin D1, which was subsequently followed by translational repression. This dual control mechanism was found to contribute to the induction of cell cycle arrest in G2 phase under oxidative stress. Silencing of an eIF2α kinase PERK significantly retarded cyclin D1 depletion, and contributed largely to rescuing cells from G2 arrest. Also the cyclin D1 level was found to be correlated with Chk1 activity.

CONCLUSIONS

In addition to an immediate removal of the pre-existing cyclin D1 under oxidative stress, the following translational repression appear to be required for ensuring full depletion of cyclin D1 and cell cycle arrest. Oxidative stress-induced cyclin D1 depletion is linked to the regulation of G2/M transit via the Chk1-Cdc2 DNA damage checkpoint pathway.

GENERAL SIGNIFICANCE

The control of cyclin D1 is a gate keeping program to protect cells from severe oxidative damages.

Redox-sensitive transcription factor Nrf2 regulates vascular smooth muscle cell migration and neointimal hyperplasia

OBJECTIVE

Reactive oxygen species are important mediators for platelet-derived growth factor (PDGF) signaling in vascular smooth muscle cells, whereas excess reactive oxygen species-induced oxidative stress contributes to the development and progression of vascular diseases, such as atherosclerosis. Activation of the redox-sensitive transcription factor, nuclear factor erythroid 2-related factor 2 (Nrf2), is pivotal in cellular defense against oxidative stress by transcriptional upregulation of antioxidant proteins. This study aimed to elucidate the role of Nrf2 in PDGF-mediated vascular smooth muscle cell migration and neointimal hyperplasia.

APPROACH AND RESULTS

PDGF promoted nuclear translocation of Nrf2, followed by the induction of target genes, including NAD(P)H:quinone oxidoreductase-1, heme oxygenase-1, and thioredoxin-1. Nrf2 depletion by small interfering RNA enhanced PDGF-promoted Rac1 activation and reactive oxygen species production and persistently phosphorylated downstream extracellular signal-regulated kinase-1/2. Nrf2 depletion enhanced vascular smooth muscle cell migration in response to PDGF and wound scratch. In vivo, Nrf2-deficient mice showed enhanced neointimal hyperplasia in a wire injury model.

CONCLUSIONS

These findings suggest that the Nrf2 system is important for PDGF-stimulated vascular smooth muscle cell migration by regulating reactive oxygen species elimination, which may contribute to neointimal hyperplasia after vascular injury. Our findings provide insight into the Nrf2 system as a novel therapeutic target for vascular remodeling and atherosclerosis.

Protein disulfide isomerase is required for platelet-derived growth factor-induced vascular smooth muscle cell migration, Nox1 NADPH oxidase expression, and RhoGTPase activation

Vascular Smooth Muscle Cell (VSMC) migration into vessel neointima is a therapeutic target for atherosclerosis and postinjury restenosis. Nox1 NADPH oxidase-derived oxidants synergize with growth factors to support VSMC migration. We previously described the interaction between NADPH oxidases and the endoplasmic reticulum redox chaperone protein disulfide isomerase (PDI) in many cell types. However, physiological implications, as well as mechanisms of such association, are yet unclear. We show here that platelet-derived growth factor (PDGF) promoted subcellular redistribution of PDI concomitant to Nox1-dependent reactive oxygen species production and that siRNA-mediated PDI silencing inhibited such reactive oxygen species production, while nearly totally suppressing the increase in Nox1 expression, with no change in Nox4. Furthermore, PDI silencing inhibited PDGF-induced VSMC migration assessed by distinct methods, whereas PDI overexpression increased spontaneous basal VSMC migration. To address possible mechanisms of PDI effects, we searched for PDI interactome by systems biology analysis of physical protein-protein interaction networks, which indicated convergence with small GTPases and their regulator RhoGDI. PDI silencing decreased PDGF-induced Rac1 and RhoA activities, without changing their expression. PDI co-immunoprecipitated with RhoGDI at base line, whereas such association was decreased after PDGF. Also, PDI co-immunoprecipitated with Rac1 and RhoA in a PDGF-independent way and displayed detectable spots of perinuclear co-localization with Rac1 and RhoGDI. Moreover, PDI silencing promoted strong cytoskeletal changes: disorganization of stress fibers, decreased number of focal adhesions, and reduced number of RhoGDI-containing vesicular recycling adhesion structures. Overall, these data suggest that PDI is required to support Nox1/redox and GTPase-dependent VSMC migration.

Physiological and pathological role of the ubiquitin-proteasome system in the vascular smooth muscle cell

Vascular smooth muscle cell (VSMC) plasticity implies a capacity for rapid change and adaptability through processes requiring protein turnover. The ubiquitin-proteasome system (UPS) is at the core of protein turnover as the main pathway for the degradation of proteins related to cell-cycle regulation, signalling, apoptosis, and differentiation. This review briefly addresses some structural UPS aspects under the perspective of VSMC (patho)biology. The UPS loss-of-function promotes direct cell effects and many indirect effects related to the adaptation to apoptosis/survival signalling, oxidative stress, and endoplasmic reticulum stress. The UPS regulates redox homeostasis and is redox-regulated. Also, the UPS closely interacts with endoplasmic reticulum (ER) homeostasis as the effector of un/misfolded protein degradation, and ER stress is strongly involved in atherosclerosis. Inhibition of cell cycle-controlling ubiquitin ligases or the proteasome reduces VSMC proliferation and prevents modulation of their synthetic phenotype. Proteasome inhibition also strongly promotes VSMC apoptosis and reduces neointima. In atherosclerosis models, proteasome inhibitors display vasculoprotective effects and reduce inflammation. However, worsening of atherosclerosis or vascular dysfunction has also been reported. Proteasome inhibitors sensitize VSMC to increased ER stress-mediated cell death and suppress unfolded protein response signalling. Taken together, these observations show that the UPS has powerful effects in the control of VSMC phenotype and survival signalling. However, more profound knowledge of mechanisms is needed in order to render the UPS an operational therapeutic target.

Increased expression of Nox1 in neointimal smooth muscle cells promotes activation of matrix metalloproteinase-9

OBJECTIVE

Vascular injury causes neointimal hypertrophy, which is characterized by redox-mediated matrix degradation and smooth muscle cell (SMC) migration and proliferation. We hypothesized that, as compared to the adjacent medial SMCs, neointimal SMCs produce increased superoxide via NADPH oxidase, which induces redox-sensitive intracellular signaling to activate matrix metalloproteinase-9 (MMP-9).

METHODS AND RESULTS

Two weeks after balloon injury, rat aorta developed a prominent neointima, containing increased expression of NADPH oxidase and reactive oxygen species (ROS) as compared to the medial layer. Next, SMCs were isolated from either the neointima or the media and studied in culture. Neointimal-derived SMCs exhibited increased Nox1 expression and ROS levels as compared to medial SMCs. Neointimal SMCs had higher cell growth rates than medial SMCs. ROS-dependent ERK1/2 phosphorylation was greater in neointimal SMCs. MMP-9 activity, as detected by gel zymography, was greater in neointimal SMCs under resting and stimulated conditions and was prevented by expression of an antisense to Nox1 or treatment with an ERK1/2 inhibitor.

CONCLUSIONS

Following vascular injury, the increased expression of Nox1 in SMCs within the neointima initiates redox-dependent phosphorylation of ERK1/2 and subsequent MMP-9 activation.

Hydrogen-rich saline prevents neointima formation after carotid balloon injury by suppressing ROS and the TNF-α/NF-κB pathway

BACKGROUND

Reactive oxygen species (ROS) play a pivotal role in neointima hyperplasia after balloon injury. Molecular hydrogen has emerged as a novel antioxidant and has been proven effective in treating many diseases.

OBJECTIVES

We aimed to determine the mechanism by which hydrogen affects neointima formation.

METHODS

We assessed the influence of a hydrogen-rich saline solution (HRSS) by daily injection in rats. Rats were euthanized to evaluate the neointima. ROS, malondialdehyde (MDA) and superoxide dismutase (SOD) and reduced glutathione (GSH), were detected in the injured artery. Macrophage infiltration and the production of inflammatory factors (i.e., IL-6, TNF-α and NF-κB) were also observed. The in vitro effects of hydrogen on vascular smooth muscle cell (VSMC) proliferation were also measured.

RESULTS

HRSS decreased the neointima area significantly. The neointima/media ratio was also reduced by HRSS. There was a decline in the number of PCNA-positive cells in the intima treated with HRSS. Meanwhile, HRSS ameliorated the ROS and MDA levels and increased SOD, reduced GSH levels in the injured carotid. In addition, the levels of inflammatory factors, such as IL-6, TNF-α and NF-κB p65, were attenuated by HRSS. In vitro studies also confirmed the anti-proliferative capability of the hydrogen solution and ROS generation in VSMCs induced by PDGF-BB.

CONCLUSION

HRSS may have a protective role in the prevention of neointima hyperplasia and restenosis after angioplasty. HRSS may partially exert its role by neutralizing the local ROS and suppressing the TNF-α/NF-κB pathway.

The vascular adventitia: its role in the arterial injury response

The belief that the adventitia serves only a structural purpose has changed over the last decade. Studies have begun to elucidate the role the adventitia plays in the arterial response to injury. The adventitial fibroblast plays an integral part in the development of neointimal hyperplasia. Adiponectin, an adipokine produced from periadventitial adipose tissue, exhibits numerous vasoprotective properties. Stem cells arise, in part, from the adventitia, and stem cell recruitment into the adventitia from the vasa vasorum has been shown to be important in the development of neointimal hyperplasia. The exact role the vasa vasorum plays in neointimal growth is poorly understood and different studies endorse conflicting viewpoints. Thus, understanding the nuances of adventitial pathophysiology will allow us to better appreciate the mechanisms behind the pathology of neointimal hyperplasia. This review will summarize recent findings on the active role the adventitia plays toward the development of neointimal hyperplasia.

Lipoteichoic acid-induced TNF-α and IL-6 gene expressions and oxidative stress production in macrophages are suppressed by ketamine through downregulating Toll-like receptor 2-mediated activation oF ERK1/2 and NFκB

Lipoteichoic acid (LTA), a gram-positive bacterial outer membrane component, can cause septic shock. Our previous studies showed that ketamine has anti-inflammatory and antioxidant effects on gram-negative LPS-induced macrophage activation. In this study, we further evaluated the effects of ketamine on the regulation of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production in macrophages and its possible mechanisms. Exposure of macrophages to a therapeutic concentration of ketamine (100 microM) inhibited LTA-induced TNF-alpha and IL-6 expressions at protein or mRNA levels. In parallel, ketamine at 100 microM reduced LTA-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). Sequentially, ketamine reduced the LTA-triggered translocation of nuclear factor-kappaB (NFkappaB) from the cytoplasm to nuclei and its transactivation activity. Pretreatment with PD98059, an inhibitor of ERK, decreased LTA-enhanced NFkappaB activation and TNF-alpha and IL-6 mRNA syntheses. Cotreatment with ketamine and PD98059 synergistically suppressed the LTA-induced translocation and transactivation of NFkappaB and biosyntheses of TNF-alpha and IL-6 mRNA. Application of Toll-like receptor 2 (TLR2) small interfering RNA (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LTA-augmented NFkappaB transactivation and consequent production of TNF-alpha and IL-6 mRNA. Cotreatment with ketamine and TLR2 siRNA synergistically lowered TNF-alpha and IL-6 mRNA syntheses in LTA-activated macrophages. Ketamine and TLR2 siRNA could reduce the LTA-induced increases in production of nitrite and intracellular reactive oxygen species in macrophages, and their combination had better effects than a single exposure. Thus, this study shows that one possible mechanism involved in ketamine-induced inhibition of LTA-induced TNF-alpha and IL-6 gene expressions and oxidative stress production is through downregulating TLR2-mediated phosphorylation of ERK1/2 and the subsequent translocation and transactivation of NFkappaB.

Mitochondria control functional CaV1.2 expression in smooth muscle cells of cerebral arteries

RATIONALE

Physiological functions of mitochondria in contractile arterial myocytes are poorly understood. Mitochondria can uptake calcium (Ca(2+)), but intracellular Ca(2+) signals that regulate mitochondrial Ca(2+) concentration ([Ca(2+)](mito)) and physiological functions of changes in [Ca(2+)](mito) in arterial myocytes are unclear.

OBJECTIVE

To identify Ca(2+) signals that regulate [Ca(2+)](mito), examine the significance of changes in [Ca(2+)](mito), and test the hypothesis that [Ca(2+)](mito) controls functional ion channel transcription in myocytes of resistance-size cerebral arteries.

METHODS AND RESULTS

Endothelin (ET)-1 activated Ca(2+) waves and elevated global Ca(2+) concentration ([Ca(2+)](i)) via inositol 1,4,5-trisphosphate receptor (IP(3)R) activation. IP(3)R-mediated sarcoplasmic reticulum (SR) Ca(2+) release increased [Ca(2+)](mito) and induced mitochondrial depolarization, which stimulated mitochondrial reactive oxygen species (mitoROS) generation that elevated cytosolic ROS. In contrast, a global [Ca(2+)](i) elevation did not alter [Ca(2+)](mito), mitochondrial potential, or mitoROS generation. ET-1 stimulated nuclear translocation of nuclear factor (NF)-kappaB p50 subunit and ET-1-induced IP(3)R-mediated mitoROS elevated NF-kappaB-dependent transcriptional activity. ET-1 elevated voltage-dependent Ca(2+) (Ca(V)1.2) channel expression, leading to an increase in both pressure (myogenic tone)- and depolarization-induced vasoconstriction. Baseline Ca(V)1.2 expression and the ET-1-induced elevation in Ca(V)1.2 expression were both reduced by IP(3)R inhibition, mitochondrial electron transport chain block, antioxidant treatment, and NF-kappaB subunit knockdown, leading to vasodilation.

CONCLUSIONS

IP(3)R-mediated SR Ca(2+) release elevates [Ca(2+)](mito), which induces mitoROS generation. MitoROS activate NF-kappaB, which stimulates Ca(V)1.2 channel transcription. Thus, mitochondria sense IP(3)R-mediated SR Ca(2+) release to control NF-kappaB-dependent Ca(V)1.2 channel expression in arterial myocytes, thereby modulating arterial contractility.

Redox control of vascular smooth muscle migration

Vascular smooth muscle cell migration is important during vascular development and contributes to lesion formation in the adult vasculature. The mechanisms regulating migration of this cell type are therefore of great interest. Recent work has shown that reactive oxygen species (ROS) derived from NADPH oxidases are important mediators of promigratory signaling pathways. ROS regulate the intracellular signals responsible for lamellipodia formation, actin cytoskeleton remodeling, focal adhesion turnover, and contraction of the cell body. In addition, they contribute to matrix remodeling, a critical step to initiate and support vascular smooth muscle cell motility. Despite these recent advances in our understanding of the redox mechanisms that contribute to migration, additional work is needed to evaluate fully the potential of ROS-sensitive molecular signals as therapeutic targets to prevent inappropriate smooth muscle cell migration.

Role of nuclear factor kappaB in cardiovascular health and disease

Cardiovascular pathologies are still the primary cause of death worldwide. The molecular mechanisms behind these pathologies have not been fully elucidated. Unravelling them will bring us closer to therapeutic strategies to prevent or treat cardiovascular disease. One of the major transcription factors that has been linked to both cardiovascular health and disease is NF-kappaB (nuclear factor kappaB). The NF-kappaB family controls multiple processes, including immunity, inflammation, cell survival, differentiation and proliferation, and regulates cellular responses to stress, hypoxia, stretch and ischaemia. It is therefore not surprising that NF-kappaB has been shown to influence numerous cardiovascular diseases including atherosclerosis, myocardial ischaemia/reperfusion injury, ischaemic preconditioning, vein graft disease, cardiac hypertrophy and heart failure. The function of NF-kappaB is largely dictated by the genes that it targets for transcription and varies according to stimulus and cell type. Thus NF-kappaB has divergent functions and can protect cardiovascular tissues from injury or contribute to pathogenesis depending on the cellular and physiological context. The present review will focus on recent studies on the function of NF-kappaB in the cardiovascular system.

NOX and inflammation in the vascular adventitia

Vascular inflammation has traditionally been thought to be initiated at the luminal surface and progress through the media toward the adventitial layer. In recent years, however, evidence has emerged suggesting that the vascular adventitia is activated early in a variety of cardiovascular diseases and that it plays an important role in the initiation and progression of vascular inflammation. Adventitial fibroblasts have been shown to produce substantial amounts of NAD(P)H oxidase-derived reactive oxygen species (ROS) in response to vascular injury. Additionally, inflammatory cytokines, lipids, and various hormones, implicated in fibroblast proliferation and migration, lead to recruitment of inflammatory cells to the adventitial layer and impairment of endothelium-dependent relaxation. Early in the development of vascular disease, there is clear evidence for progression toward a denser vasa vasorum which delivers oxygen and nutrients to an increasingly hypoxic and nutrient-deficient media. This expanded vascularization appears to provide enhanced delivery of inflammatory cells to the adventitia and outer media. Combined adventitial fibroblast and inflammatory cell-derived ROS therefore are expected to synergize their local effect on adventitial parenchymal cells, leading to further cytokine release and a feed-forward propagation of adventitial ROS production. In fact, data from our laboratory and others suggest a broader paracrine positive feedback role for adventitia-derived ROS in medial smooth muscle cell hypertrophy and neointimal hyperplasia. A likely candidate responsible for the adventitia-derived paracrine signaling across the vessel wall is the superoxide anion metabolite hydrogen peroxide, which is highly stable, cell permeant, and capable of activating downstream signaling mechanisms in smooth muscle cells, leading to phenotypic modulation of smooth muscle cells. This review addresses the role of adventitial NAD(P)H oxidase-derived ROS from a nontraditional, perivascular vantage of promoting vascular inflammation and will discuss how ROS derived from adventitial NAD(P)H oxidases may be a catalyst for vascular remodeling and dysfunction.

Flavonoids from Inula britannica L. inhibit injury-induced neointimal formation by suppressing oxidative-stress generation

AIM OF THE STUDY

We aimed to investigate whether and how the total flavonoid extracts (TFE) from Inula britannica L. block neointimal hyperplasia induced by balloon injury in rats.

MATERIALS AND METHODS

Rats were administered orally TFE doses of 12.5, 25 and 50 mg/kg/d by gastric gavage from 3 days before balloon injury to 14 days after the injury. The ratio of intima (I) to media (M) thickness (I/M) in carotid arteries was examined by morphological analyses. The MDA content and SOD activity in plasma were measured. The O(2)(-) production in vascular tissues was detected in situ. The expression of p47(phox) in carotid arteries was analyzed by Western blot analysis and immunohistochemistry.

RESULTS

The rats treated with TFE 50 mg/kg/d showed a reduction in neointimal hyperplasia, and the ratio of I/M of balloon injured-carotid arteries was significantly reduced by over 70% after TFE treatment, compared with the injured group. The inhibitory effect of TFE on neointimal hyperplasia was almost consistent with that of atorvastatin, a positive control. The plasma SOD activity was obviously increased by TFE treatment (P<0.01), while plasma MDA production was markedly decreased by TFE treatment (P<0.05). On day 14 after balloon injury, the carotid arteries showed an increase in O(2)(-) production that was most evident in the neointimal and medial layer of the vessel. Thus, TFE significantly inhibited injury-induced O(2)(-) production and p47(phox) expression in carotid arteries.

CONCLUSION

Our results suggest that TFE inhibit the neointimal hyperplasia after balloon injury, at least partly, by suppressing oxidative-stress generation.

Lipopolysaccharide triggers macrophage activation of inflammatory cytokine expression, chemotaxis, phagocytosis, and oxidative ability via a toll-like receptor 4-dependent pathway: validated by RNA interference

RNA interference has been extensively used to knock-down the translation of certain genes. Toll-like receptor 4 (TLR4) produced by macrophages can be activated in response to endotoxin stimulation. This study used the RNA interference technique to evaluate the roles of TLR4 in lipopolysaccharide (LPS)-stimulated activation of macrophages from the aspects of cytokine production, chemotaxis, phagocytosis, and oxidative ability. Exposure of macrophages to 1, 25, 50, 100 ng/mL LPS for 1, 6, and 24 h did not affect cell viability. Meanwhile, treatment with 100 ng/mL LPS induced interleukin (IL)-1beta protein and mRNA syntheses in a time-dependent manner. Application of TLR4 small interference (si)RNA into macrophages decreased the levels of this receptor, and simultaneously ameliorated LPS-induced IL-1beta and IL-6 mRNA production. Transwell analysis showed that LPS increased chemotactic activity of macrophages, but application of TLR4 siRNA reduced such an effect. Phagocytic activities of macrophages were significantly augmented following LPS treatment. However, knocking-down the translation of TLR4 mRNA using RNA interference lowered the LPS-enhanced phagocytic activity. Analysis of flow cytometry revealed that LPS increased oxidative ability of macrophages, but TLR4 siRNA inhibited such development. This study used RNA interference techniques to show that TLR4 can mediate LPS-induced macrophage activations of IL-1beta and IL-6 gene expression, chemotaxis, phagocytosis, and oxidative ability.

Nitric Oxide Generation by NO Donors Is Enhanced Following Balloon Injury in the Porcine Coronary Artery

Vasospasm is a complication of cardiological procedures such as balloon angioplasty and may be related to vascular oxidant stress. Although nitric oxide donor drugs are often administered to prevent vasospasm, the response to these drugs in balloon-injured arteries has not been studied. Pig coronary arteries were balloon-injured in vitro and relaxations to nitric oxide (NO)-donating and NO-independent vasodilators studied. Generation of superoxide in response to injury was assayed using dihydroethidium. NO formation on addition of the NO donor drugs was studied using an amperometric sensor. Expression of nitrotyrosine, a peroxynitrite marker, was probed using immunocytochemistry. In vitro injury enhanced sensitivity to the NO donors SNAP and SpermineNONOate but blunted the response to isoprenaline or chromakalim. With both donors, NO formation was significantly enhanced in the presence of an injured vessel. Vascular superoxide generation was also increased throughout the vessel wall and a small increase in nitrotyrosine was detected in the injured vessel media following addition of SNAP. In conclusion, injured vessels were more sensitive to NO donors and this appears to be due to enhanced NO generation by the donor molecule. Increased formation of peroxynitrite within the injured vessel may contribute to the enhanced relaxation in injured vessels.

Angiotensin II modulates CD40 expression in vascular smooth muscle cells

The signalling pathway CD40/CD40L (CD40 ligand) plays an important role in atherosclerotic plaque formation and rupture. AngII (angiotensin II), which induces oxidative stress and inflammation, is also implicated in the progression of atherosclerosis. In the present study, we tested the hypothesis that AngII increases CD40/CD40L activity in vascular cells and that ROS (reactive oxygen species) are part of the signalling cascade that controls CD40/CD40L expression. Human CASMCs (coronary artery smooth muscle cells) in culture exposed to IL (interleukin)-1β or TNF-α (tumour necrosis factor-α) had increased superoxide generation and enhanced CD40 expression, detected by EPR (electron paramagnetic resonance) and immunoblotting respectively. Both phenomena were abolished by previous incubation with membrane-permeant antioxidants or cell transfection with p22phoxantisense. AngII (50–200 nmol/l) induced an early and sustained increase in CD40 mRNA and protein expression in CASMCs, which was blocked by treatment with antioxidants. Increased CD40 expression led to enhanced activity of the pathway, as AngII-treated cells stimulated with recombinant CD40L released higher amounts of IL-8 and had increased COX-2 (cyclo-oxygenase-2) expression. We conclude that AngII stimulation of vascular cells leads to a ROS-dependent increase in CD40/CD40L signalling pathway activity. This phenomenon may be an important mechanism modulating the arterial injury observed in atherosclerosis-related vasculopathy.

Inhibition of apoptotic signaling and neointimal hyperplasia by tempol and nitric oxide synthase following vascular injury

OBJECTIVES

We hypothesized that redox-mediated apoptosis of medial smooth muscle cells (SMC) during the acute phase of vascular injury contributes to the pathophysiology of vascular disease.

METHODS

Apoptosis of medial SMC (1-14 days following balloon injury) was identified in rat carotid arteries by in situ DNA labeling. NADPH-derived superoxide and expression of Bcl-xL, Bax, caspase-3 and caspase-9 were assessed. The antioxidant tempol was administered in drinking water throughout the experimental period, and local adenoviral-mediated gene transfer of eNOS was performed prior to vascular injury.

RESULTS

Balloon injury increased NADPH-dependent superoxide production, medial SMC apoptosis, Bax-positive medial SMC index, Bax/Bcl-xL ratio, and caspase-3 and caspase-9 expression in the injured arteries. Treatment with tempol or eNOS gene transfer decreased superoxide levels and medial SMC apoptosis, with a concomitant increase in medial SMC density. Inhibition of superoxide was associated with a decreased Bax/Bcl-xL ratio, and caspase-3 and -9 expression. Tempol treatment and eNOS gene therapy significantly reduced neointima formation.

CONCLUSION

Vascular generation of reactive oxygen species participates in Bax activation and medial SMC apoptosis. These effects likely contribute to the shedding of cell-cell adhesion molecules and promote medial SMC migration and proliferation responsible for neointimal hyperplasia.

Nox4 oxidase overexpression specifically decreases endogenous Nox4 mRNA and inhibits angiotensin II-induced adventitial myofibroblast migration

The vascular adventitia is emerging as an important modulator of vessel remodeling. Adventitial myofibroblasts migrate to the neointima after balloon angioplasty, contributing to restenosis. We postulated that angiotensin II (Ang II) enhances adventitial myofibroblast migration in vitro via reduced nicotinamide-adenine dinucleotide phosphate oxidase-derived H(2)O(2) and that Nox4-based oxidase promotes migration. Ang II increased myofibroblast migration in a concentration-dependent manner, with a peak increase of 1023+/-83%. Rat adventitial myofibroblasts were cotransfected with human Nox4 and human p22-phox plasmids or an empty vector. PCR showed an 8-fold increase in human Nox4 and human p22-phox plasmid expression. Using RT-PCR with primers specifically designed for rat reduced nicotinamide-adenine dinucleotide phosphate oxidases, endogenous Nox levels were determined. Ang II decreased endogenous Nox4 and Nox1 mRNA to 41% and 27% of control, respectively, but had no effect on Nox2. Cotransfection with human Nox4 and human p22-phox plasmids combined with Ang II reduced endogenous Nox4 mRNA levels (37+/-5% of control; P<0.05), whereas it had no significant effect on Nox1 or Nox2. In empty vector-transfected cells, Ang II increased myofibroblast migration by 192+/-32% versus vehicle (P<0.01) while increasing H(2)O(2) (473+/-22% versus control; P<0.001). Cotransfection with human Nox4 and human p22-phox plasmids decreased Ang II-induced migration (46+/-6%; P<0.001) in parallel with attenuation of H(2)O(2) production (23+/-8% versus empty vector; P<0.05). Our data suggest that Nox4 promotes Ang II-induced myofibroblast migration via an H(2)O(2)-dependent pathway. The data also suggest that Nox4 causes feedback inhibition of its own expression in adventitial myofibroblasts.

Therapeutic effect of magnesium lithospermate B on neointimal formation after balloon-induced vascular injury

Vascular smooth muscle cell (VSMC) proliferation and migration in response to platelet-derived growth factor (PDGF) play an important role in the development of atherosclerosis and restenosis. Recent evidence indicates that PDGF increases intracellular levels of reactive oxygen species in VSMCs and that both PDGF-induced VSMC proliferation and migration are reactive oxygen species-dependent. Danshen is a representative oriental medicine used for the treatment of vascular disease. Previously, we reported that magnesium lithospermate B, an active component of Danshen, is a potent antioxidant. Thus we investigated the therapeutic potential of magnesium lithospermate B in neointimal formation after carotid artery injury in rats along with its effects on the PDGF signaling pathway for stimulating VSMC proliferation and migration in vitro. PDGF is dimeric glycoprotein composed of two A or two B chains. In this study, we used PDGF-BB, which is one of the isoforms of PDGF (i.e., PDGF-AA, PDGF-BB, and PDGF-AB). Our results demonstrated that magnesium lithospermate B directly scavenged reactive oxygen species in a xanthine/xanthine oxidase system and reduced PDGF-BB-induced intracellular reactive oxygen species generation in VSMCs. In a rat carotid artery balloon injury model, magnesium lithospermate B treatment (10 mg/kg/day, i.p) showed a significant effect on the prevention of neointimal formation compared with vehicle treatment. In cultured VSMCs, magnesium lithospermate B significantly attenuated PDGF-BB-induced cell proliferation and migration as measured by 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2-tetrazolium bromide (MTT) assay and transwell migration assays, respectively. Further, magnesium lithospermate B inhibited PDGF-BB-induced phosphorylation of phospatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathways by scavenging reactive oxygen species. Together, these data indicated that magnesium lithospermate B, a potent reactive oxygen species scavenger, prevented both injury-induced neointimal formation in vivo and PDGF-BB-induced VSMC proliferation and migration in vitro, suggesting that magnesium lithospermate B may be a promising agent to prevent atherosclerosis and restenosis following angioplasty.

Sphingosine-1-phosphate-induced oxygen free radical generation in smooth muscle cell migration requires Galpha12/13 protein-mediated phospholipase C activation

BACKGROUND

Sphingosine-1-phosphate (S-1-P) is a bioactive sphingolipid that stimulates the migration of vascular smooth muscle cell (VSMC) through G-protein coupled receptors; it has been shown to activate reduced nicotinamide dinucleotide phosphate hydrogen (NAD[P]H) oxidase. The role of phospholipase C (PLC) in oxygen free radical generation, and the regulation of VSMC migration in response to S-1-P, are poorly understood.

METHODS

Rat arterial VSMC were cultured in vitro. Oxygen free radical generation was measured by fluorescent redox indicator assays in response to S-1-P (0.1microM) in the presence and absence of the active PLC inhibitor (U73122; U7, 10nM) or its inactive analog U73343 (InactiveU7, 10nM). Activation of PLC was assessed by immunoprecipitation and Western blotting for the phosphorylated isozymes (beta and gamma). Small interfering (si) RNA to the G-proteins Galphai, Galphaq, and Galpha12/13 was used to downregulate specific proteins. Statistics were by one-way analysis of variance (n = 6).

RESULTS

S-1-P induced time-dependent activation of PLC-beta and PLC-gamma; PLC-beta but not PLC-gamma activation was blocked by U7 but not by InactiveU7. PLC-beta activation was Galphai-independent (not blocked by pertussis toxin, a Galphai inhibitor, or Galphai2 and Galphai3 siRNA) and Galphaq-independent (not blocked by glycoprotein [GP] 2A, a Galphaq inhibitor, or Galphaq siRNA). PLC-beta activation and cell migration was blocked by siRNA to Galpha12/13. Oxygen free radical generation induced by S-1-P, as measured by dihydroethidium staining, was significantly inhibited by U7 but not by InactiveU7. Inhibition of oxygen free radicals with the inhibitor diphenyleneiodonium resulted in decreased cell migration to S-1-P. VSMC mitogen-activated protein kinase activation and VSMC migration in response to S-1-P was inhibited by PLC- inhibition.

CONCLUSION

S-1-P induces oxygen free radical generation through a Galpha12/13, PLC-beta-mediated mechanism that facilitates VSMC migration. To our knowledge, this is the first description of PLC-mediated oxygen free radical generation as a mediator of S-1-P VSMC migration and illustrates the need for the definition of cell signaling to allow targeted strategies in molecular therapeutics for restenosis.

Pro-healing drug-eluting stents: a role for antioxidants?

Current strategies to lower the incidence of ISR (in-stent restenosis) following PCI (percutaneous coronary intervention) are aimed at modifying arterial healing after stent injury. This can impair endothelial recovery and render the vessel prone to acute thrombosis. As early restoration of endothelial integrity inhibits neointimal growth and thrombosis, alternative approaches which encourage this process may provide a more effective long-term result after PCI. Oxidative stress is enhanced after PCI and participates in the regulation of endothelial regeneration and neointimal growth. Moreover, evidence suggests antioxidants improve re-endothelialization and inhibit ISR. By promoting, rather than blocking, the healing process, antioxidant and other therapies may offer an alternative or additional approach over the antiproliferative approaches common to many current devices.

Endothelium-targeted transgenic GTP-cyclohydrolase I overexpression inhibits neointima formation in mouse carotid artery

1. Tetrahydrobiopterin (BH(4)) is an essential cofactor that maintains the normal function of endothelial nitric oxide (NO) synthase. Restenosis is a key complication after transluminal angioplasty. Guanosine 5'-triphosphate-cyclohydrolase I (GTPCH) is the first rate-limiting enzyme for de novo BH(4) synthesis. However, the role of GTPCH in restenosis is not fully understood. The present study tested the hypothesis that endothelial-targeted GTPCH overexpression retards neointimal formation, a hallmark of restenosis, in mouse carotid artery. 2. Transluminal wire injury was induced in the left carotid arteries of adult male wild-type C57BL/6 (WT) and endothelial GTPCH transgenic (Tg-GCH) mice. Re-endothelialization was confirmed with in vivo Evans blue staining. Endothelium-dependent and -independent relaxations were measured using isometric tension recording. Morphological analysis was performed 2 and 4 weeks after carotid injury to assess neointimal formation. Fluorescence-based high-performance liquid chromatography (HPLC) was used to determine GTPCH activity and BH(4) levels. Basal NO release following carotid injury was assessed by N(G)-nitro-L-arginine methyl ester-induced vascular contraction. 3. The endothelium was completely removed upon transluminal wire injury and full re-endothelialization was achieved at Day 10. Endothelium-dependent relaxation was impaired 10 days and 4 weeks after carotid injury, whereas endothelium-independent relaxation remained unaffected. Morphological analysis revealed that the endothelial-specific overexpression of GTPCH reduced neointimal formation and medial hypertrophy 2 and 4 weeks after carotid injury. Both arterial GTPCH enzyme activity and BH(4) levels were significantly elevated in Tg-GCH mice compared with WT mice and basal NO release of the injured carotid artery tended to increase in Tg-GCH mice. 4. These findings suggest that the endothelial overexpression of GTPCH increased endothelial BH(4) synthesis and played a preventive role in neointimal formation induced by endothelium denudation.

Disruption of skeletal myocytes initiates superoxide release: contribution of NADPH oxidase

Generation of reactive oxygen species (ROS) as an early local reaction to muscle crush injury has frequently been predicted. However, although it is known that severe inflammatory reactions occurring after major muscle trauma originate mainly from early local incidents within the injured tissue, no detailed studies exist on the local generation of ROS in response to myocyte destruction thus far. Therefore, in this study, ROS formation after lethal mechanical damage was examined using a model of scraping injury to cultured C2C12 skeletal myocytes and superoxide detection by lucigenin chemiluminescence, nitrotetrazolium blue chloride reduction, or electron spin resonance spectroscopy. Mechanical rupture of myocytes resulted in an immediate release of superoxide from the damaged cells that could be substantially blocked by the superoxide scavengers superoxide dismutase (51%), tiron (95%), and MAMA/NO (93%) and by hypoxia (83% inhibition). Superoxide generation was primarily confined to the myocytes' membrane fraction and 7- to 8-fold enhanced by the addition of NADH or NADPH. The NADPH-enhanced superoxide generation could largely be diminished by the NAD(P)H oxidase inhibitors diphenyleneiodonium and apocynin in cell lysates (97% and 35% inhibition, respectively) and in isolated membrane fractions (61% and 63% inhibition). We thus conclude that immediately after myocyte damage, large amounts of superoxide are formed that predominantly originate from membrane-bound electron-transferring enzymes, especially NAD(P)H oxidase. This suggests a decisive role of ROS in the pathogenesis of tissue trauma, with superoxide being an initiator of the signaling mechanism from injured myocytes to the surrounding tissue and, potentially, to the whole body.

Pigment epithelium-derived factor inhibits neointimal hyperplasia after vascular injury by blocking NADPH oxidase-mediated reactive oxygen species generation

Pigment epithelium-derived factor (PEDF) inhibits cytokine-induced endothelial cell activation through its antioxidative properties. However, the effect of PEDF on restenosis remains to be elucidated. Because the pathophysiological feature of restenosis is characterized by increased superoxide formation and accumulation of smooth muscle cells (SMCs), PEDF may inhibit this process via suppression of reactive oxygen species generation. We investigated here whether PEDF could prevent neointimal formation after balloon injury. PEDF levels were decreased in balloon-injured arteries. Adenoviral vector encoding human PEDF (Ad-PEDF) prevented neointimal formation. Expression and superoxide generation of the membrane components of NADPH oxidase, p22(phox) and gp91(phox), in the neointima were also suppressed by Ad-PEDF. Ad-PEDF reduced G(1) cyclin (cyclin D1 and E) expression and increased p27, a cyclin-dependent kinase inhibitor. In vitro, PEDF inhibited platelet-derived growth factor-BB-induced SMC proliferation and migration by blocking reactive oxygen species generation through suppression of NADPH oxidase activity via down-regulation of p22(PHOX) and gp91(PHOX). PEDF down-regulated G(1) cyclins and up-regulated p27 levels in platelet-derived growth factor-BB-exposed SMCs as well. These results demonstrate that PEDF could inhibit neointimal formation via suppression of NADPH oxidase-mediated reactive oxygen species generation. Our present study suggests that substitution of PEDF may be a novel therapeutic strategy for restenosis after balloon angioplasty.

Apocynin normalizes hyperreactivity to phenylephrine in mesenteric arteries from cholesterol-fed mice by improving endothelium-derived hyperpolarizing factor response

We studied the relationship among endothelial function, oxidative stress, and phenylephrine (PE; alpha(1)-adrenoceptor agonist)-induced contraction in mesenteric arteries from high-cholesterol (HC)-diet-fed mice. In HC mice (vs age-matched normal-diet-fed mice): (1) PE-induced contraction in endothelium-intact rings was enhanced (endothelial denudation increased contraction in "normal-diet" rings, but did not enhance it further in "HC" rings); (2) the enhanced PE-induced contraction was further enhanced in the presence of N(G)-nitro-L-arginine (L-NNA; nitric oxide synthase inhibitor) or L-NNA plus indomethacin (cyclooxygenase inhibitor) [to preserve endothelium-derived hyperpolarizing factor (EDHF)], but unchanged in the presence of charybdotoxin plus apamin (to block EDHF); (3) ACh-induced EDHF-type relaxation was reduced; and (4) oxidative stress [indicated by the plasma 8-isoprostane level (reliable systemic marker) and aortic superoxide production] was greater. In HC mice, PE-induced contraction was normalized by apocynin [NAD(P)H oxidase inhibitor] or tempol (superoxide dismutase mimetic), but enhanced by NADH [NAD(P)H oxidase substrate]. Oral dietary supplementation with apocynin (30 mg/kg/day for 4 weeks) corrected the above abnormalities. Hence: (1) PE-induced contraction is modulated by the endothelium, and the enhanced contractility in HC mice results from defective EDHF signaling and elevated oxidative stress, and (2) apocynin normalizes PE-induced contraction in HC mice by improving EDHF signaling.

De novo ICAM-1 synthesis in the mouse lung: model of assessment of protein expression in lungs

Because most studies addressing the regulatory mechanisms of intercellular adhesion molecule (ICAM)-1 expression have used cultured endothelial cells, we set out to develop an isolated mouse lung preparation to study gene and protein expression in its proper cellular context in the organ. Lungs from CD1 mice were isolated and perfused (2 ml/min, 37°C) with a recirculating volume of RPMI 1640 solution supplemented with 3 g/100 ml albumin. Lungs maintained their isogravimetric state for 4 h. Tumor necrosis factor (TNF-α; 2,000 U/ml) was added to the perfusate for 0.5, 1, 2, or 3.5 h to induce ICAM-1 expression or lungs received no treatment (control). After quick-freezing the lungs using liquid nitrogen at different time points, the prepared tissue homogenates were analyzed for ICAM-1 protein expression by Western blotting and NF-κB activation by electrophoretic mobility shift assay. TNF-α caused a progressive increase in NF-κB activity after 0.5 h and ICAM-1 protein expression two- to threefold of basal after 2 h. Untreated lungs expressed a low and constant level of ICAM-1 between 0 and 3.5 h. TNF-α failed to induce NF-κB activation and ICAM-1 expression in lungs of NADPH oxidase-deficient mice lacking p47phox. We disaggregated mouse lungs using collagenase and stained the cells for ICAM-1 and VE-cadherin (used as an endothelial marker) to assess the in situ endothelial-specific expression of ICAM-1. We observed that TNF-α challenge resulted in increased ICAM-1 expression in endothelial cells freshly isolated from lungs. These data show the role of NADPH oxidase-derived oxidant signaling in the mechanism of NF-κB activation and ICAM-1 expression in mouse lung endothelial cells. Moreover, the general method presented herein has potential value in assessing mechanisms of gene and protein expression in the isolated-perfused mouse lung model.

Adventitial delivery of dominant-negative p67phox attenuates neointimal hyperplasia of the rat carotid artery

Several essential components of NADPH oxidase, including p22phox, gp91phox (nox2) and its homologs nox1 and nox4, p47phox, p67phox, and rac1, are present in the vasculature. We previously reported that p67phox is essential for adventitial fibroblast NADPH oxidase O2- production. Thus we postulated that inhibition of adventitial p67phox activity would attenuate angioplasty-induced hyperplasia. To test this hypothesis, we treated the adventitia of carotid arteries with a control adenovirus (Ad-control), a virus expressing dominant-negative p67phox (Ad-p67dn), or a virus expressing a competitive peptide (gp91ds) targeting the p47phox-gp91phox interaction (Ad-gp91ds). Common carotid arteries (CCAs) from male Sprague-Dawley rats were transfected with Ad-control, Ad-p67dn, or Ad-gp91ds in pluronic gel. After 2 days, a 2-F (Fogarty) catheter was used to injure CCAs in vivo. After 14 days, CCAs were perfusion-fixed and analyzed. In 13 experiments, digital morphometry suggested a reduction of neointimal hyperplasia with Ad-p67dn compared with Ad-control; however, the reduction did not reach statistical significance (P = 0.058). In contrast, a significant reduction was achieved with Ad-gp91ds (P = 0.006). No changes in medial area or remodeling were observed with either treatment. Moreover, adventitial fibroblast proliferation in vitro was inhibited by Ad-gp91ds but not by Ad-p67dn, despite confirmation that Ad-p67dn inhibits NADPH oxidase in fibroblasts. These data appear to suggest that a multicomponent vascular NADPH oxidase plays a role in neointimal hyperplasia. However, inhibition of p47phox may be more effective than inhibition of p67phox at attenuating neointimal growth.