Abstract

Reactive oxygen species (ROS) have been shown to function as important signaling molecules in the cardiovascular system. Vascular smooth muscle cells (VSMCs) contain several sources of ROS, among which the NADPH oxidases are predominant. In VSMCs, ROS mediate many pathophysiological processes, such as growth, migration, apoptosis and secretion of inflammatory cytokines, as well as physiological processes, such as differentiation, by direct and indirect effects at multiple signaling levels. Therefore, it becomes critical to understand the different roles ROS play in the physiology and pathophysiology of VSMCs.

1. Introduction

Reactive oxygen species (ROS) are a class of oxygen-derived molecules, which have long been thought to have deleterious effects on cells. It is now well established that they can also act as second messengers, influencing discrete signal transduction pathways in various systems, including the cardiovascular system [1].

Vascular smooth muscle cells (VSMCs) form the medial layer of blood vessels and represent a dynamic component of the vasculature. In the normal media they have a differentiated, contractile phenotype. With pathological stimuli, they can undergo hypertrophy or adopt a “de-differentiated” phenotype, and synthesize excess extracellular matrix and inflammatory cytokines, divide and migrate towards the intima. ROS have been implicated in all of these responses.

Sources of ROS

VSMCs contain numerous sources of ROS, including the NADPH oxidases, xanthine oxidase, the mitochondrial respiratory chain, lipoxygenases and nitric oxide synthases [2]. In VSMCs, most investigators have focused on the mitochondria and NADPH oxidases as major sources of ROS [3-5].

Mitochondria

Mitochondria generate ROS as byproducts during ATP production via electron transfer through cytochrome c oxidases. Mitochondrial-derived ROS have been implicated in regulation of vasomotor tone (pulmonary artery vasoconstriction [6] and cerebral artery vasodilation [7]), and in the response to hypoxia, where mitochondria have been proposed to act as oxygen sensors [6,8]. The role of mitochondria in vascular biology has been thoroughly reviewed, and will not be discussed further here [5].

NADPH oxidases

NADPH oxidases (Nox) are multiprotein complexes of various compositions depending on the cell type. The enzymes, originally described in phagocytes, consist of two membrane-bound subunits (the small subunit p22phox bound to the catalytic subunit Nox2) and potentially three cytosolic subunits, Rac1 (in non-phagocytes) or Rac2 (in phagocytes), p47phox and p67phox, which are recruited upon activation to the membrane-bound Nox/p22phox complex. All VSMCs express p22phox, while the catalytic subunit is Nox1, Nox2, Nox4 and/or Nox5. The distribution of catalytic subunits in VSMCs is tissue- and species-specific. Aortic SMCs express Nox1 and Nox4 in rodents, and also Nox5 in humans (Jay D. and Griendling K.K., 2004, unpublished). In contrast, VSMCs from human resistance arteries contain Nox2 and Nox4, but no Nox1 [9]. The expression of p47phox and rac1 is well documented, whereas that of p67phox is controversial [10]. A functional role for p47phox has been shown using VSMCs from p47phox knockout mice, in which agonist stimulation of ROS is decreased [11,12]. New homologues of the p47phox and p67phox subunits, NoxO1 and NoxA1, were recently described in other cell types, but their presence and potential functional role in VSMCs remains to be confirmed [13,14]. Nox-derived ROS have been implicated in functional responses of VSMCs such as hypertrophy, proliferation, migration and inflammation [15].

Nox regulation

The NADPH oxidases are activated by agonists acutely (minutes), and are also chronically (hours) upregulated to further enhance ROS production. These two phases are differentially regulated.

Nox activation

The classic mechanism of activation of the phagocytic NADPH oxidase involves stimulus-induced activation and translocation of p47phox, p67phox and Rac to the membrane. These proteins then interact with the other two subunits, p22phox and Nox2, resulting in production of superoxide by the sequential transfer of two electrons from NADPH to molecular oxygen. In non-phagocytic cells, this paradigm has also been demonstrated, although the intimate mechanisms, the upstream players and the intracellular compartments where activation occurs are cell- and agonist-specific.

In contrast to the phagocytic oxidase, which is inactive in resting neutrophils, the vascular oxidases have basal activity as well as agonist-stimulated activity [16]. Nox4 is constitutively active in VSMCs [17], and stimulation with PMA, arachidonic acid or calcium ionophore does not further increase its activity [18]. It is, however, activated by TGF-β in fibroblasts [19]. In contrast, Nox1 and Nox2 are activated in response to PMA via protein kinase C (PKC)-dependent recruitment of p47phox to the plasma membrane (see below) [9,20]. Additionally, one report suggested that NoxA1 is important for Nox1-dependent release of ROS in VSMCs [21]. All Nox enzymes appear to require p22phox for activity, except for Nox5 [22,23], which is activated directly by calcium.

Rac1

Rac1 is critical for Nox1 and Nox2 activation. In rat aortic SMCs, Ang II-induced ROS production occurs in two phases: a low magnitude burst that peaks in seconds, and a greater, sustained release that lasts for hours [24]. The initial burst of superoxide appears to be critical for the subsequent, long-term release of ROS in response to Ang II. Recently, our understanding of NADPH oxidase activation was facilitated by elucidation of proximal Ang II signaling in VSMCs [25,26] (Fig. 1).

Fig. 1

Pathways of NADPH oxidase activation in response to Ang II in VSMCs. See text for details. Final proof for proteins with dotted line has yet to be obtained.

Fig. 1

Pathways of NADPH oxidase activation in response to Ang II in VSMCs. See text for details. Final proof for proteins with dotted line has yet to be obtained.

Ang II receptor (AT1-R) signaling is strictly compartmentalized to microdomains in the plasma membrane called lipid rafts. After ligand binding, AT1-R is tethered to caveolin-1, which moves the receptor into lipid rafts/caveolae and also recruits and transactivates the epidermal growth factor receptor (EGFR) [27]. EGFR transactivation mediates many ROS-sensitive downstream pathways, including activation of the phosphatidylinositol 3-kinase (PI3K)–Akt pathway, which is required for Ang II-induced protein synthesis in VSMCs. Eventually, EGFRs migrate with tyrosine-phosphorylated caveolin to focal adhesions. All of these steps have been demonstrated to require NADPH oxidase-mediated release of ROS [28].

The mechanism of rapid ROS release is still unclear, but it is known that it requires PKC-dependent activation of p47phox (see below) [29]. ROS then activate the non-receptor tyrosine kinase c-Src, which subsequently orchestrates the signaling in lipid rafts. Inhibition of c-Src mitigates most downstream ROS-sensitive signaling and long-term activation of the NADPH oxidase. To maintain NADPH oxidase activity, the small G protein Rac1 must be activated by a Rac-guanine nucleotide exchange factor (GEF) and translocated to caveolae in a manner that requires active remodeling of the cytoskeleton [30]. How Src recruits and activates Rac1 is unclear. However, Ushio-Fukai et al. [31] recently demonstrated that within 1min of Ang II stimulation, c-Src binds to and activates c-Abl. c-Abl then tyrosine-phosphorylates SOS-1 (a RacGEF) and translocates Rac1 to lipid rafts, where it is activated by SOS-1 [27] and stimulates NADPH activity.

Although not directly addressed in these studies, Nox1 is the most likely candidate for the NADPH oxidase that mediates these events in rat aortic SMCs, because of its location in caveolae [32] and its requirement for Rac1 activation, and because depletion of Nox1 prevents Ang II-induced activation of the ROS-sensitive Akt and p38MAPK [20]. Other work has shown a requirement for PI3K in Nox1 activation, because PI3K inhibitors prevent Ang II-induced ROS release in VSMCs [24]. Furthermore, in Caco2 cells, Nox1 is recruited to EGFR and activated in response to EGF by binding to another Rac-GEF, β-PIX, which is activated via PI3K [33].

p47phox

Ang II also activates three classes of phospholipases (PL), PLC, PLD and PLA2[34] that are capable of inducing NA(P)DH oxidase activation in VSMCs. PLA2 releases arachidonic acid and lysophospholipids in response to Ang II [35]. Arachidonic acid metabolites mediate Ang II-induced ROS production in rat aortic SMCs [36]. Also, exogenous lysophosphatidylcholine triggers rapid translocation of p47phox to the membrane, resulting in increased NADPH oxidase activity, ERK1/2 activation and growth [37]. PLCs produce IP3, which increases calcium influx from sarcoplasmic reticulum, and diacylglycerol (DAG), a potent PKC activator. PLD generates phosphatidic acid (PA), which can either directly bind to p47phox, increasing its membrane affinity [38], or can act indirectly through production of DAG. Of importance, addition of exogenous PA increases oxidase activity [3,39], and inhibition of endogenous PLD activity decreases ROS production by Ang II [39]. In VSMCs, PLD is the most potent activator of PKC [40], which is involved in the phosphorylation of p47phox. This triggers a conformational change in the autoinhibitory loop, exposing the Phox homology and SH3 domains and allowing them to interact with membrane phospholipids and p22phox [38]. Inhibition of PKC profoundly inhibits the early activation phase of NADPH oxidase in response to Ang II in VSMCs, while the later phase is only partially inhibited [24]. In SMC from resistance vessels, p47phox is phosphorylated and translocates to the membrane in response to short term treatment with Ang II [9]. Recent evidence suggests that the PKC-β isoform mediates oxidase activation, since antisense oligonucleotides and a PKC-β-specific inhibitor block Ang II-induced production of ROS in VSMCs [41].

Another mediator of p47phox phosphorylation and translocation to membranes in VSMCs is c-Src [29]. Since Src is also required for cytoskeletal reorganization, it may exert its effects on p47phox by modulating the actin cytoskeleton. Indeed, Touyz et al. [42,43] have shown that Ang II induces p47phox association with the actin cytoskeleton through interaction with cortactin (a predominant substrate of Src). This association is blocked by pre-treatment with cytochalasin B, which disrupts the actin cytoskeleton. Therefore, Src seems to be responsible for activation of both p47phox and Rac1 in VSMCs.

Many other stimuli were found to activate a p47phox-regulated NADPH oxidase in VSMCs, including PDGF [11] and phenylephrine [44], but the precise mechanisms are not yet elucidated.

Regulation of Nox expression

Agonists such as Ang II or PDGF induce Nox-dependent ROS release not only acutely for signaling events, but also over the long term. This effect is mediated by modulation of expression of Nox subunits. For example, prolonged treatment with Ang II, PDGF or serum upregulates Nox1 and downregulates Nox4 in rat aortic SMCs [20]. Both PDGF and PGF-2α upregulate Nox1 by the convergence of PKC-δ and EGFR/ERK/PI3K signaling pathways on ATF-1 transcription factor activation [45]. Conversely, Nox4 expression appears to be controlled by TGF-β1 in pulmonary artery SMCs [46] and cardiac fibroblasts [19]. Nox2 transcription is upregulated by Ang II in VSMC from small vessels [9]. Because all but Nox5 catalytic subunits require p22phox for activity, increased expression of one catalytic subunit would require excess or increased availability of p22phox. In neutrophils, p22phox interacts with Nox2 in the endoplasmic reticulum, a process that requires the incorporation of heme [47]. This interaction stabilizes the two proteins and prevents degradation via the cytosolic proteasome. Indeed, in VSMCs, expression of p22phox and Nox1 leads to increased levels of the complementary protein [22,23]. It is thus possible that induction of a Nox protein leads to a concomitant increase in p22phox simply via increased p22phox stability or processing.

A recent elegant study by Janiszewski et al. [48] suggested a novel role for protein disulfide isomerase (PDI) in the regulation of Nox activity. These authors showed that PDI associates with Nox1, Nox2 and Nox4, and that PDI inhibitors diminish basal and Ang II-stimulated oxidase activity. The mechanism by which PDI regulates NADPH oxidase activity is unclear, but could involve stabilization of the intermolecular complex, mediation of the redox regulation of NADPH oxidase activity (as shown for H2O2[49]), or regulation of protein processing or trafficking between endoplasmic reticulum and the cell membrane.

Role of ROS in VSMC physiology and pathophysiology

ROS are involved in many of the physiological and pathophysiological processes of VSMCs: growth, migration, secretion of inflammatory cytokines, extracellular matrix and matrix metalloproteinases, contraction, differentiation, and death (apoptosis). In this review, we will concentrate on growth, differentiation and migration of VSMCs, as the other processes have been reviewed recently elsewhere [50].

ROS signaling related to growth and survival

Growth of VSMCs involves both hypertrophy and hyperplasia. Many growth-related signaling pathways are shared by multiple agonists; therefore, we will focus on Ang II as a prototypical hypertrophic agent and PDGF as a model for proliferative agonists (Fig. 2).

Fig. 2

ROS signaling related to growth of VSMCs. See text for details.

Fig. 2

ROS signaling related to growth of VSMCs. See text for details.

Angiotensin II

Non-receptor and receptor tyrosine kinases

Many of the growth pathways triggered in response to Ang II are mediated by ROS. As noted above, after binding to AT1 receptors, Ang II stimulates acute production of ROS by NADPH oxidase and activation of c-Src. It is not known exactly how ROS affect Src activity in VSMCs. Src activity is modulated by kinases (Csk, Chk, PDGFR, ErbB2/HER2, PKC, PKA, CDK1) and phosphatases (PTP1B, SHP1, SHP2, CD45, PTP-BL), as well as through redox modification of cysteine residues [51]. Src signals to a variety of downstream effectors including EGFR, p85 (the regulatory subunit of PI3K), RasGAP, Shc, several integrin signaling proteins (tensin, vinculin, cortactin, talin, and paxillin), focal adhesion kinase, PLCγ, Janus kinase (JAK)-2 [51,52], phosphoinositide-dependent kinase-1 (PDK1), and c-Abl.

Transactivation of tyrosine kinase receptors by G protein-coupled receptors is a common pathway for further transmission of ROS-sensitive signals. Ang II transactivates the EGFR [28], IGF-1R [53], and PDGFR [54], of which EGFR and PDGFR transactivation are redox-sensitive. Ang II-mediated transactivation of PDGFR is through Shc [54], whereas EGFR transactivation appears to involve Src-mediated matrix-metalloproteinase (MMP)-activated release of the heparin-binding EGF-like growth factor (HB-EGF) [55]. The transactivated EGFR perpetuates the ROS production from Nox in response to Ang II in a feed-forward mechanism [24].

S-glutathiolation and activation of Ras

The precise mechanism by which ROS directly modify specific signaling proteins is an active area of investigation. Proteins containing cysteine residues in their active sites are potential candidates for H2O2, whereas those containing Fe–S centers are potential targets for superoxide [56]. The small GTPase Ras is one of these proteins, whose activation is dependent upon S-glutathiolation at Cys118 and is redox-sensitive in response to Ang II in VSMCs [57]. This is a mechanism by which Ras confers ROS-sensitivity to downstream signaling molecules such as p38MAPK and Akt, leading to hypertrophy. S-glutathiolation, together with S-nitrosylation and disulfide modifications, are general mechanisms for redox-regulation of proteins. For a better understanding of these modifications, please refer to an excellent recent review [58].

PI3K, MAPKs and JAKs

Another important mediator of Ang II responses in VSMCs is PI3K, which can be activated by Src via EGFR transactivation and Ras. The products of PI3K, PtdIns, activate Rac1 and subsequent ROS release from NADPH oxidases [24]. PtdIns also target PDK1, a signal integrator that activates the AGC family of serine/threonine kinases, including Akt, p70S6 kinase, PKC, PRK, and p21-activated protein kinase-1 (PAK1). However, recent evidence from Taniyama et al. [59] shows that in VSMCs, Ang II triggers a Pyk-2- and Src-dependent, but PI3K-independent, phosphorylation of PDK1 at multiple tyrosine residues. The phosphorylation at Tyr9 is ROS-sensitive and is required for the subsequent phosphorylation at Tyr373/376[59,60]. Tyrosine phosphorylated PDK1 modulates the formation of focal adhesions in response to Ang II, possibly by regulating paxillin phosphorylation [59]. Another target of PI3K is Akt, which is an important integrator of Ang II responses leading to hypertrophy and survival [61]. ROS sensitivity of Akt is conferred by the phosphorylation of MAPKAPK-2 by p38MAPK (another redox-sensitive kinase [62]), leading to recruitment of MAPKAPK-2 to the constitutively associated Akt–p38MAPK complex and phosphorylation of Akt specifically on Ser473[63]. Downstream, Akt inhibits glycogen synthase kinase-3, and activates p70S6 kinase and the transcription factors AP-1 and E2F [64].

Besides p38MAPK and MAPKAPK-2, other mitogen-activated protein kinases (MAPKs), are involved in Ang II-stimulated growth pathways and are sensitive to ROS. c-Jun NH2 terminal kinase (JNK) activation in response to Ang II is blocked by several antioxidants, demonstrating its redox sensitivity [65]. The ROS sensitivity of extracellular regulated kinase1/2 (ERK1/2) has been subject to controversy, since some groups have found it sensitive [66,67] and others have found it insensitive to ROS in VSMCs [53,62,65]. Of note, Ang II induces nitration and activation of MEK1 and ERK1/2, the latter being dependent upon NADPH oxidase and iNOS release of ROS [67], implicating a potential crosstalk between the two ROS generators. Another ROS-sensitive MAPK, ERK5, appears to be activated primarily by Nox in response to Ang II, and by mitochondrial-derived ROS in response to endothelin-1 [68].

Janus tyrosine kinases (JAKs) activate ERK1/2 and STATs in VSMCs that are required for both Ang II and PDGF-induced growth. Schieffer et al. [69] demonstrated that JAK2 activation in response to Ang II is attenuated by NADPH oxidase inhibitors. The mechanism of activation of JAK2 by oxidants in VSMCs is unclear, although in fibroblasts, it is dependent on Fyn kinase and the Shc-Grb2-Sos complex [70]. Another possible mechanism involves modulation of phosphatases such as SHP1 and SHP2 [41]. Downstream consequences of ROS-mediated JAK activation include STAT1 and STAT3 phosphorylation and nuclear translocation, increased expression of heat shock protein-70, and activation of ERK1/2 [71].

Transcription factors

Many of the effects of Ang II involve transcription of growth-related genes. One of the most well studied ROS-sensitive transcription factors is AP-1, a heterodimer of Fos and Jun. Its activation is dependent upon p22phox, inasmuch as the antisense p22phox oligonucleotides inhibit AP-1 binding to DNA in response to Ang II and PDGF-AA [72]. AP-1 regulates diverse biological functions, including cell proliferation, protein synthesis, apoptosis and secretion of inflammatory and profibrotic factors. Some of these downstream events such as MMP-1 and endothelin-1 expression are ROS-sensitive in response to Ang II [73]. Another transcription factor that is central to smooth muscle cell proliferation, survival and induction of inflammatory cytokines is NFκB. Its ROS sensitivity in VSMC has been suggested by a few studies [73,74] and is well established in other cell types [75]. Of importance, NFκB regulates a set of genes which inhibit further ROS production, with subsequent inhibition of apoptotic cascades [76]. Other ROS-sensitive transcription factors include cyclic AMP response element-binding protein (CREB) [77], hypoxia-inducible factor-1α (HIF-1α) [78] and the growth arrest homeobox gene, Gax [79].

Of special interest, Id3 and GKLF are two novel redox-sensitive transcription factors that mediate proliferation and growth arrest, respectively, in response to agonists such as Ang II and serum [80]. Mueller et al. [81] showed that Ang II-induced superoxide increases Id3 expression, allowing it to bind to and inactivate the basic helix-loop-helix transcription factor E2A. This results in inhibition of cell cycle proteins p21WAF1/Cip1, p27Kip1, p53 and Rb, and progression through the cell cycle. GKLF has different regulation and opposing functions to Id3: it is upregulated by hydroxyl radicals/H2O2 via p38MAPK and calcium, and promotes growth arrest by stimulating the aforementioned cell cycle proteins [80]. The idea that different ROS target different signaling pathways is appealing, and together with different localization of their sources [32] may explain the diverse outcomes of ROS production in cells.

Translation initiation

As noted in the above sections, ROS mediate Ang II signaling at almost all levels, from receptors, to second messengers and kinase cascades, to transcription factors and gene expression. While gene expression starts in the nucleus, it ends in the cytosol with mRNA translation into protein. This represents an important site of convergence of both ROS-sensitive and insensitive signaling pathways leading to growth [82]. The rate-limiting step in translation initiation is represented by the dissociation of phosphorylated PHAS-1 from eIF4E, which then becomes phosphorylated and starts translation. Two PHAS-1 phosphorylation sites, Thr70 and Ser65, have a differential sensitivity to ROS [82]. The phosphorylation of ROS-insensitive Thr70 is regulated by ERK1/2 and PI3K pathways, whereas phosphorylation of ROS-sensitive Ser65 is regulated by p38MAPK, Akt and the PP2A [82].

PDGF

PDGFR

PDGF is well known for its proliferative and migratory effects on VSMCs. The binding of PDGF to its receptor induces receptor dimerization and intrinsic tyrosine kinase activation, leading to receptor autophosphorylation, along with recruitment and phosphorylation of several target proteins, including those containing Src homology (SH2) domains [83]. PDGF-induced NADPH oxidase activation in VSMCs involves the heterotrimeric Gi1,2 protein [84] and Rac1 [85]. H2O2 may provide negative feedback by inducing an inhibitory phosphorylation of the PDGFR via Src- and PKC-δ-dependent phosphorylation of the PDGFβ-R at Tyr1021[86].

Phosphatases

Most previous work on the ROS sensitivity of PDGF signaling has focused on phosphatases. These molecules are directly inhibited by ROS through reversible modifications of cysteine residues in their catalytic sites. Among them, the protein tyrosine phosphatases (PTPs) are important targets of ROS, since phosphorylation of proteins at tyrosine residues plays a critical role in many cellular functions. Currently, at least seven cytoplasmic PTPs are known to be expressed in VSMCs: low M(r) protein tyrosine phosphatase (LMW-PTP), SHP-2, PTP36, PTP2, PTP1B, FAP1 [87], and PTP-PEST [88]. A few studies have suggested a relationship between ROS and SHP-1 and -2 in VSMCs [41]; however, direct proof for regulation of these phosphatases remains to be established. Studies performed in adipocytes indicate that Nox4-derived ROS inhibit PTP1B activity in response to insulin [89]. Recently, Bhanoori et al. [90,91] suggested that inhibition of PTP1B by ROS production results in prolonged activation of the PDGFR and the JAK/STAT pathway, leading to inhibition of AP-1, and an increase in apoptosis. Oxidative inhibition of the LMW-PTP, whose role in VSMC includes inhibition of proliferation and migration [87], involves formation of a disulfide bond between Cys-12 and Cys-17, which protects the catalytic Cys-12 from further and irreversible oxidation [92]. Another phosphatase inactivated by PDGF is PTEN (phosphatase and tensin homologue), a lipid and protein phosphatase. PTEN is oxidized and inactivated by H2O2, most likely produced by Nox enzymes, in various cells in response to EGF, PDGF and insulin [93]. However, its regulation in VSMCs is not elucidated yet.

Antioxidant molecules: thioredoxin

For ROS to serve as signaling molecules, both their production and removal must be regulated by agonists. In this context, Schulze et al. [94] demonstrated that activation of the reductase thioredoxin (Trx) is critical for the ROS-dependent proliferation of VSMC in response to PDGF. PDGF decreases expression of the endogenous inhibitor of Trx, thioredoxin interacting protein (Txnip), allowing Trx to be released from Txnip and to translocate to the nucleus, where it promotes transcription of growth genes. Interestingly, Txnip binds to the ROS-sensitive cysteine-sulfide center of Trx, and Txnip downregulation by PDGF is inhibited by antioxidants. This affords new insight into how oxidants and antioxidants converge to produce a physiologic response. Initially, PDGF induces an increase in oxidants at the membrane, where the NADPH oxidase is located; then, as a result of complex signaling pathways, the action of Trx in the nucleus is facilitated, to reduce and activate transcription factors such as NF-κB and redox factor-1 (Ref-1).

Transcription factors

Among the ROS-sensitive transcription factors responsive to PDGF, Ref-1 is of particular interest. It is known to have two enzymatic functions, ascribed to its C- and N-terminal domains. The C-terminus has DNA repair activity, whereas the N-terminal region contains the redox regulatory domain, which reduces transcription factors such as AP-1, NF-κB, ATF/CREB and HIF1-α, increasing their binding to DNA [56]. For example, Ref-1 antisense oligodeoxynucleotides inhibit AP-1 binding to DNA and the transition of VSMCs from G0/G1 to S-phase in response to PDGF [95]. The inhibition of AP-1 binding to DNA is reversed by chemical reduction, suggesting that Ref-1 functions through reduction of AP-1.

ROS signaling related to migration

One of the most potent migratory stimuli for VSMCs is PDGF. As noted above, many of the pathways stimulated by PDGF are mediated by ROS, which is also true for migratory signals. In VSMCs, antioxidants block migration in response to PDGF [83]. Conversely, increased migration in a wound-scratch assay was observed in VSMCs extracted from p22phox-overexpressing mouse aortas [96]. Similar to Ang II, PDGF activates c-Src and Rac1 leading to NADPH oxidase release of ROS [83,85]. Upon release, ROS mediate PDGF-induced migration by activating PAK1 via tyrosine phosphorylation of PDK1 [83]. The mechanism of Rac1-Nox activation is unclear, but may involve c-Abl, because PDGF-induced activation of Rac1 is abolished in c-Abl knockout fibroblasts [97].

Several other factors have been shown to induce ROS-dependent migration of vascular SMCs, including insulin-like growth factor-1 (IGF1) [88], thrombin [98], VEGF [99] and MCP-1 [100]. Interestingly, migration in response to IGF1 is mediated by Rac1-inducible ROS and p130Cas, which can be inhibited by NO-mediated activation of PTP-PEST [88]. Another migratory agent, lysophosphatidic acid, also utilizes ROS to activate PAK1, without the involvement of transactivated EGFR or PDGFR [101]. Clearly, more work is necessary to fully understand the ROS sensitivity of the complex signaling pathways involved in migration.

ROS signaling related to differentiation

Besides mediating pathophysiological processes such as growth and migration, ROS have been implicated in physiological processes as well, such as differentiation [102]. VSMCs of the normal media of blood vessels are in a contractile, differentiated state, but are plastic, so that they can switch to a proliferative, synthetic phenotype in response to proatherogenic stimuli. Therefore, it becomes crucial to understand the different roles of ROS in physiological and pathophysiological signaling.

Su et al. [102] provided the first evidence that the expression of differentiation markers in quiescent VSMCs is dependent upon release of ROS, but their source remained obscure. Recently, Clempus et al. [103] suggested Nox4 as a possible source because siRNA against Nox4 downregulates smooth muscle-specific differentiation markers. Of interest, Nox4 changes localization from smooth muscle α-actin stress fibers in differentiated cells to focal adhesions in de-differentiated cells. The change in localization happens early in the de-differentiation process, suggesting that Nox4 might contribute to the maintenance of the differentiated phenotype by regulating the structure and/or function of the contractile apparatus. Maintenance of the polymerized actin cytoskeleton is required for the nuclear translocation of transcription factors with smooth muscle-specific activity [104]. However, regulation of differentiation by Nox4 may involve several mechanisms. Phosphatases are potential targets of Nox4-derived ROS, and indeed an association has been shown between Nox4 and PTP1B [89]. Future research is necessary to reveal the mechanisms by which ROS regulate differentiation in VSMCs.

Conclusion

Our understanding of the regulation of VSMC function by ROS has expanded enormously in the last 10 years. Much work remains to be done, however, especially in elucidating the precise mechanisms by which ROS modify the function of specific proteins. Additional studies on the ROS-sensitive signaling pathways involved in migration and differentiation are also necessary.

Mechanistic studies such as these will open up new avenues for therapeutic intervention targeted to specific disease processes.

Acknowledgements

We would like to acknowledge Dr. Bernard Lassègue for suggestions and critical reading of the manuscript. Authors' work is supported by NIH grants HL 58000, HL 38206, HL 58863, and HL 75209.

References

[1]
Finkel
T.
Signal transduction by reactive oxygen species in non-phagocytic cells
J Leukoc Biol
 
1999
65
337
340
[2]
Tsutsui
M.
Neuronal nitric oxide synthase as a novel anti-atherogenic factor
J Atheroscler Thromb
 
2004
11
41
48
[3]
Griendling
K.K.
Minieri
C.A.
Ollerenshaw
J.D.
Alexander
R.W.
Angiotensin II stimulates NADH and NADPH oxidase activity in cultured vascular smooth muscle cells
Circ Res
 
1994
74
1141
1148
[4]
Marumo
T.
Schini-Kerth
V.B.
Fisslthaler
B.
Busse
R.
Platelet-derived growth factor stimulated superoxide anion production modulates activation of transcription factor NF-kappaB and expression of monocyte chemoattractant protein-1 in human aortic smooth muscle cells
Circ
 
1997
96
2361
2367
[5]
Ramachandran
A.
Levonen
A.L.
Brookes
P.S.
Ceaser
E.
Shiva
S.
Barone
M.C.
et al
Mitochondria, nitric oxide, and cardiovascular dysfunction
Free Radic Biol Med
 
2002
33
1465
1474
[6]
Schumacker
P.T.
Current paradigms in cellular oxygen sensing
Adv Exp Med Biol
 
2003
543
57
71
[7]
Beardsley
A.
Fang
K.
Mertz
H.
Castranova
V.
Friend
S.
Liu
J.
Loss of caveolin-1 polarity impedes endothelial cell polarization and directional movement
J Biol Chem
 
2005
280
3541
3547
[8]
Sato
H.
Sato
M.
Kanai
H.
Uchiyama
T.
Iso
T.
Ohyama
Y.
et al
Mitochondrial reactive oxygen species and c-Src play a critical role in hypoxic response in vascular smooth muscle cells
Cardiovasc Res
 
2005
67
714
722
[9]
Touyz
R.M.
Chen
X.
Tabet
F.
Yao
G.
He
G.
Quinn
M.T.
et al
Expression of a functionally active gp91phox-containing neutrophil-type NAD(P)H oxidase in smooth muscle cells from human resistance arteries: regulation by angiotensin II
Circ Res
 
2002
90
1205
1213
[10]
Lassègue
B.
Clempus
R.E.
Vascular NAD(P)H oxidases: specific features, expression, and regulation
Am J Physiol Regul Integr Comp Physiol
 
2003
285
R277
R297
[11]
Lavigne
M.C.
Malech
H.L.
Holland
S.M.
Leto
T.L.
Genetic demonstration of p47phox-dependent superoxide anion production in murine vascular smooth muscle cells
Circulation
 
2001
104
79
84
[12]
Brandes
R.P.
Miller
F.J.
Beer
S.
Haendeler
J.
Hoffmann
J.
Ha
T.
et al
The vascular NADPH oxidase subunit p47phox is involved in redox-mediated gene expression
Free Radic Biol Med
 
2002
32
1116
1122
[13]
Geiszt
M.
Lekstrom
K.
Witta
J.
Leto
T.L.
Proteins homologous to p47phox and p67phox support superoxide production by NAD(P)H oxidase 1 in colon epithelial cells
J Biol Chem
 
2003
278
20006
20012
[14]
Takeya
R.
Ueno
N.
Kami
K.
Taura
M.
Kohjima
M.
Izaki
T.
et al
Novel human homologues of p47phox and p67phox participate in activation of superoxide-producing NADPH oxidases
J Biol Chem
 
2003
278
25234
25246
[15]
Griendling
K.K.
Sorescu
D.
Ushio-Fukai
M.
NAD(P)H oxidase: role in cardiovascular biology and disease
Circ Res
 
2000
86
494
501
[16]
Sorescu
D.
Somers
M.J.
Lassegue
B.
Grant
S.
Harrison
D.G.
Griendling
K.K.
Electron spin resonance characterization of the NAD(P)H oxidase in vascular smooth muscle cells
Free Radic Biol Med
 
2001
30
603
612
[17]
Ellmark
S.H.
Dusting
G.J.
Fui
M.N.
Guzzo-Pernell
N.
Drummond
G.R.
The contribution of Nox4 to NADPH oxidase activity in mouse vascular smooth muscle
Cardiovasc Res
 
2005
65
495
504
[18]
Martyn
K.D.
Frederick
L.M.
von Loehneysen
K.
Dinauer
M.C.
Knaus
U.G.
Functional analysis of Nox4 reveals unique characteristics compared to other NADPH oxidases
Cell Signal
 
2006
18
69
82
[19]
Cucoranu
I.
Clempus
R.
Dikalova
A.
Phelan
P.J.
Ariyan
S.
Dikalov
S.
et al
NAD(P)H oxidase 4 mediates transforming growth factor-beta1-induced differentiation of cardiac fibroblasts into myofibroblasts
Circ Res
 
2005
97
900
907
[20]
Lassègue
B.
Sorescu
D.
Szöcs
K.
Yin
Q.
Akers
M.
Zhang
Y.
et al
Novel gp91phox homologues in vascular smooth muscle cells: nox1 mediates angiotensin II-induced superoxide formation and redox-sensitive signaling pathways
Circ Res
 
2001
88
888
894
[21]
Ambasta
R.K.
Schreiber
J.G.
Busse
R.
Brandes
R.P.
Noxa1 is a critical component of the vascular NADPH oxidase
Circulation
 
2004
110
SIII-157
[Abstract]
[22]
Hanna
I.R.
Dikalova
A.
Hilenski
L.
Quinn
M.T.
Griendling
K.K.
Nox 1 binds p22phox to form a functional oxidase in vascular smooth muscle cells (VSMCs)
Circulation
 
2002
106
II-164
[23]
Ambasta
R.K.
Kumar
P.
Griendling
K.K.
Schmidt
H.H.
Busse
R.
Brandes
R.P.
Direct interaction of the novel Nox proteins with p22phox is required for the formation of a functionally active NADPH oxidase
J Biol Chem
 
2004
279
45935
45941
[24]
Seshiah
P.N.
Weber
D.S.
Rocic
P.
Valppu
L.
Taniyama
Y.
Griendling
K.K.
Angiotensin II stimulation of NAD(P)H oxidase activity: upstream mediators
Circ Res
 
2002
91
406
413
[25]
Griendling
K.K.
Sorescu
D.
Lassègue
B.
Ushio-Fukai
M.
Modulation of protein kinase activity and gene expression by reactive oxygen species and their role in vascular physiology and pathophysiology
Arterioscler Thromb Vasc Biol
 
2000
20
2175
2183
[26]
Touyz
R.M.
Schiffrin
E.L.
Reactive oxygen species in vascular biology: implications in hypertension
Histochem Cell Biol
 
2004
122
4
339
352
[27]
Zuo
L.
Ushio-Fukai
M.
Ikeda
S.
Hilenski
L.
Patrushev
N.
Alexander
R.W.
Caveolin-1 is essential for activation of Rac1 and NAD(P)H oxidase after angiotensin II type 1 receptor stimulation in vascular smooth muscle cells: role in redox signaling and vascular hypertrophy
Arterioscler Thromb Vasc Biol
 
2005
25
1824
1830
[28]
Ushio-Fukai
M.
Griendling
K.K.
Becker
P.L.
Hilenski
L.
Halleran
S.
Alexander
R.W.
Epidermal growth factor receptor transactivation by angiotensin II requires reactive oxygen species in vascular smooth muscle cells
Arterioscler Thromb Vasc Biol
 
2001
21
489
495
[29]
Touyz
R.M.
Yao
G.
Schiffrin
E.L.
c-Src induces phosphorylation and translocation of p47phox: role in superoxide generation by angiotensin II in human vascular smooth muscle cells
Arterioscler Thromb Vasc Biol
 
2003
23
981
987
[30]
Zuo
L.
Ushio-Fukai
M.
Hilenski
L.L.
Alexander
R.W.
Microtubules regulate angiotensin II type 1 receptor and Rac1 localization in caveolae/lipid rafts: role in redox signaling
Arterioscler Thromb Vasc Biol
 
2004
24
1223
1228
[31]
Ushio-Fukai
M.
Zuo
L.
Ikeda
S.
Tojo
T.
Patrushev
N.A.
Alexander
R.W.
cAbl tyrosine kinase mediates reactive oxygen species- and caveolin-dependent at1 receptor signaling in vascular smooth muscle: role in vascular hypertrophy
Circ Res
 
2005
97
829
836
[32]
Hilenski
L.L.
Clempus
R.E.
Quinn
M.T.
Lambeth
J.D.
Griendling
K.K.
Distinct subcellular localizations of Nox1 and Nox4 in vascular smooth muscle cells
Arterioscler Thromb Vasc Biol
 
2004
24
677
683
[33]
Park
H.S.
Lee
S.H.
Park
D.
Lee
J.S.
Ryu
S.H.
Lee
W.J.
et al
Sequential activation of phosphatidylinositol 3-kinase, beta Pix, Rac1, and Nox1 in growth factor-induced production of H2O2
Mol Cell Biol
 
2004
24
4384
4394
[34]
Touyz
R.M.
Berry
C.
Recent advances in angiotensin II signaling
Braz J Med Biol Res
 
2002
35
1001
1015
[35]
Bonventre
J.V.
Phospholipase A2 and signal transduction
J Am Soc Nephrol
 
1992
3
128
150
[36]
Zafari
A.M.
Ushio-Fukai
M.
Minieri
C.A.
Akers
M.
Lassègue
B.
Griendling
K.K.
Arachidonic acid metabolites mediate angiotensin II-induced NADH/NADPH oxidase activity and hypertrophy in vascular smooth muscle cells
Antioxid Redox Signal
 
1
1999
167
179
[37]
Yamakawa
T.
Tanaka
S.
Yamakawa
Y.
Kamei
J.
Numaguchi
K.
Motley
E.D.
et al
Lysophosphatidylcholine activates extracellular signal-regulated kinases 1/2 through reactive oxygen species in rat vascular smooth muscle cells
Arterioscler Thromb Vasc Biol
 
2002
22
752
758
[38]
Karathanassis
D.
Stahelin
R.V.
Bravo
J.
Perisic
O.
Pacold
C.M.
Cho
W.
et al
Binding of the PX domain of p47(phox) to phosphatidylinositol 3,4-bisphosphate and phosphatidic acid is masked by an intramolecular interaction
Embo J
 
2002
21
5057
5068
[39]
Touyz
R.M.
Schiffrin
E.L.
Ang II-stimulated superoxide production is mediated via phospholipase D in human vascular smooth muscle cells
Hypertension
 
1999
34
976
982
[40]
Lassègue
B.
Alexander
R.W.
Clark
M.
Akers
M.A.
Griendling
K.K.
Phosphatidylcholine is a major source of phosphatidic acid and diacylglycerol in angiotensin II-stimulated vascular smooth muscle cells
Biochem J
 
1993
292
509
517
[41]
Shaw
S.
Wang
X.
Redd
H.
Alexander
G.D.
Isales
C.M.
Marrero
M.B.
High glucose augments the angiotensin II-induced activation of JAK2 in vascular smooth muscle cells via the polyol pathway
J Biol Chem
 
2003
278
30634
30641
[42]
Touyz
R.M.
Yao
G.
Schiffrin
E.L.
Role of the actin cytoskeleton in angiotensin II signaling in human vascular smooth muscle cells
Can J Physiol Pharm
 
2005
83
91
97
[43]
Touyz
R.M.
Yao
G.
Quinn
M.T.
Pagano
P.J.
Schiffrin
E.L.
p47phox associates with the cytoskeleton through cortactin in human vascular smooth muscle cells: role in NAD(P)H oxidase regulation by angiotensin II
Arterioscler Thromb Vasc Biol
 
2005
25
512
518
[44]
Bleeke
T.
Zhang
H.
Madamanchi
N.
Patterson
C.
Faber
J.E.
Catecholamine-induced vascular wall growth is dependent on generation of reactive oxygen species
Circ Res
 
2004
94
37
45
[45]
Fan
C.Y.
Katsuyama
M.
Yabe-Nishimura
C.
PKCdelta mediates up-regulation of NOX1, a catalytic subunit of NADPH oxidase, via transactivation of the EGF receptor: possible involvement of PKCdelta in vascular hypertrophy
Biochem J
 
2005
390
761
767
[46]
Sturrock
A.
Cahill
B.
Norman
K.
Huecksteadt
T.P.
Hill
K.
Sanders
K.
et al
Transforming growth factor {beta}1 induces Nox 4 NAD(P)H oxidase and reactive oxygen species-dependent proliferation in human pulmonary artery smooth muscle cells
Am J Physiol Lung Cell Mol Physiol
 
2005
[47]
DeLeo
F.R.
Burritt
J.B.
Yu
L.
Jesaitis
A.J.
Dinauer
M.C.
Nauseef
W.M.
Processing and maturation of flavocytochrome b558 include incorporation of heme as a prerequisite for heterodimer assembly
J Biol Chem
 
2000
275
13986
13993
[48]
Janiszewski
M.
Lopes
L.R.
Carmo
A.O.
Pedro
M.A.
Brandes
R.P.
Santos
C.X.
et al
Regulation of NAD(P)H oxidase by associated protein disulfide isomerase in vascular smooth muscle cells
J Biol Chem
 
2005
280
40813
40819
[49]
Li
W.G.
Miller
F.J.
Jr.
Zhang
H.J.
Spitz
D.R.
Oberley
L.W.
Weintraub
N.L.
H(2)O(2)-induced O(2) production by a non-phagocytic NAD(P)H oxidase causes oxidant injury
J Biol Chem
 
2001
276
29251
29256
[50]
Taniyama
Y.
Griendling
K.K.
Reactive oxygen species in the vasculature: molecular and cellular mechanisms
Hypertension
 
2003
42
1075
1081
[51]
Roskoski
R.
Jr.
Src kinase regulation by phosphorylation and dephosphorylation
Biochem Biophys Res Commun
 
2005
331
1
14
[52]
Griendling
K.K.
Ushio-Fukai
M.
Reactive oxygen species as mediators of angiotensin II signaling
Regul Pept
 
2000
91
21
27
[53]
Touyz
R.M.
Cruzado
M.
Tabet
F.
Yao
G.
Salomon
S.
Schiffrin
E.L.
Redox-dependent MAP kinase signaling by Ang II in vascular smooth muscle cells: role of receptor tyrosine kinase transactivation
Can J Physiol Pharm
 
2003
81
159
167
[54]
Heeneman
S.
Haendeler
J.
Saito
Y.
Ishida
M.
Berk
B.C.
Angiotensin II induces transactivation of two different populations of the PDGfβ-receptor: key role for the adaptor protein
Shc J Biol Chem
 
2000
275
15926
15932
[55]
Eguchi
S.
Dempsey
P.J.
Frank
G.D.
Motley
E.D.
Inagami
T.
Activation of MAPKs by angiotensin II in vascular smooth muscle cells. Metalloprotease-dependent EGF receptor activation is required for activation of ERK and p38 MAPK but not for JNK
J Biol Chem
 
2001
276
7957
7962
[56]
Liu
H.
Colavitti
R.
Rovira
I.I.
Finkel
T.
Redox-dependent transcriptional regulation
Circ Res
 
2005
97
967
974
[57]
Adachi
T.
Pimentel
D.R.
Heibeck
T.
Hou
X.
Lee
Y.J.
Jiang
B.
et al
S-glutathiolation of ras mediates redox-sensitive signaling by angiotensin II in vascular smooth muscle cells
J Biol Chem
 
2004
279
29857
29862
[58]
Forman
H.J.
Fukuto
J.M.
Torres
M.
Redox signaling: thiol chemistry defines which reactive oxygen and nitrogen species can act as second messengers
Am J Physiol Cell Physiol
 
2004
287
C246
C256
[59]
Taniyama
Y.
Weber
D.S.
Rocic
P.
Hilenski
L.
Akers
M.L.
Park
J.
et al
Pyk2- and Src-dependent tyrosine phosphorylation of PDK1 regulates focal adhesions
Mol Cell Biol
 
2003
23
8019
8029
[60]
Taniyama
Y.
Hitomi
H.
Shah
A.
Alexander
R.W.
Griendling
K.K.
Mechanisms of reactive oxygen species-dependent downregulation of insulin receptor substrate-1 by angiotensin II
Arterioscler Thromb Vasc Biol
 
2005
25
1142
1147
[61]
Ushio-Fukai
M.
Alexander
R.W.
Akers
M.
Yin
Q.
Fujio
Y.
Walsh
K.
et al
Reactive oxygen species mediate the activation of Akt/Protein kinase b by angiotensin II in vascular smooth muscle cells
J Biol Chem
 
1999
274
22699
22704
[62]
Ushio-Fukai
M.
Alexander
R.W.
Akers
M.
Griendling
K.K.
p38MAP kinase is a critical component of the redox-sensitive signaling pathways by angiotensin II: role in vascular smooth muscle cell hypertrophy
J Biol Chem
 
1998
273
15022
15029
[63]
Taniyama
Y.
Ushio-Fukai
M.
Hitomi
H.
Rocic
P.
Kingsley
M.J.
Pfahnl
C.
et al
Role of p38 MAPK and MAPKAPK-2 in angiotensin II-induced akt activation in vascular smooth muscle cells
Am J Physiol Cell Physiol
 
2004
287
C494
C499
[64]
Coffer
P.J.
Jin
J.
Woodgett
J.R.
Protein kinase B (c-Akt): a multifunctional mediator of phosphatidylinositol 3-kinase activation
Biochem J
 
1998
335
1
13
[65]
Viedt
C.
Soto
U.
Krieger-Brauer
H.I.
Fei
J.
Elsing
C.
Kubler
W.
et al
Differential activation of mitogen-activated protein kinases in smooth muscle cells by angiotensin II: involvement of p22phox and reactive oxygen species
Arterioscler Thromb Vasc Biol
 
2000
20
940
948
[66]
Frank
G.D.
Eguchi
S.
Yamakawa
T.
Tanaka
S.
Inagami
T.
Motley
E.D.
Involvement of reactive oxygen species in the activation of tyrosine kinase and extracellular signal-regulated kinase by angiotensin II
Endocrinology
 
2000
141
3120
3126
[67]
Pinzar
E.
Wang
T.
Garrido
M.R.
Xu
W.
Levy
P.
Bottari
S.P.
Angiotensin II induces tyrosine nitration and activation of ERK1/2 in vascular smooth muscle cells
FEBS Lett
 
2005
579
5100
5104
[68]
Touyz
R.M.
Yao
G.
Viel
E.
Amiri
F.
Schiffrin
E.L.
Angiotensin II and endothelin-1 regulate MAP kinases through different redox-dependent mechanisms in human vascular smooth muscle cells
J Hypertens
 
2004
22
1141
1149
[69]
Schieffer
B.
Luchtefeld
M.
Braun
S.
Hilfiker
A.
Hilfiker-Kleiner
D.
Drexler
H.
Role of NAD(P)H oxidase in angiotensin II-induced JAK/STAT signaling and cytokine induction
Circ Res
 
2000
87
1195
1201
[70]
Abe
J.I.
Berk
B.C.
Fyn and JAK2 mediate ras activation by reactive oxygen species
J Biol Chem
 
1999
274
21003
21010
[71]
Madamanchi
N.R.
Li
S.
Patterson
C.
Runge
M.S.
Reactive oxygen species regulate heat-shock protein 70 via the JAK/STAT pathway
Arterioscler Thromb Vasc Biol
 
2001
21
321
326
[72]
Viedt
C.
Fei
J.
Krieger-Brauer
H.I.
Brandes
R.P.
Teupser
D.
Kamimura
M.
et al
Role of p22phox in angiotensin II and platelet-derived growth factor AA induced activator protein 1 activation in vascular smooth muscle cells
J Mol Med
 
2004
82
31
38
[73]
Browatzki
M.
Larsen
D.
Pfeiffer
C.A.
Gehrke
S.G.
Schmidt
J.
Kranzhofer
A.
et al
Angiotensin II stimulates matrix metalloproteinase secretion in human vascular smooth muscle cells via nuclear factor-kappaB and activator protein 1 in a redox-sensitive manner
J Vasc Res
 
2005
42
415
423
[74]
Ortego
M.
Bustos
C.
Hernandez-Presa
M.A.
Tunon
J.
Diaz
C.
Hernandez
G.
et al
Atorvastatin reduces NF-kappaB activation and chemokine expression in vascular smooth muscle cells and mononuclear cells
Atherosclerosis
 
1999
147
253
261
[75]
Sulciner
D.J.
Irani
K.
Yu
Z.X.
Ferrans
V.J.
Goldschmidt-Clermont
P.
Finkel
T.
Rac1 regulates a cytokine-stimulated, redox-dependent pathway necessary for NF-kappaB activation
Mol Cell Biol
 
1996
16
7115
7121
[76]
Sakon
S.
Xue
X.
Takekawa
M.
Sasazuki
T.
Okazaki
T.
Kojima
Y.
et al
NF-kappaB inhibits TNF-induced accumulation of ROS that mediate prolonged MAPK activation and necrotic cell death
Embo J
 
2003
22
3898
3909
[77]
Ichiki
T.
Tokunou
T.
Fukuyama
K.
Iino
N.
Masuda
S.
Takeshita
A.
Cyclic AMP response element-binding protein mediates reactive oxygen species-induced c-fos expression
Hypertension
 
2003
42
177
183
[78]
Görlach
A.
Diebold
I.
Schini-Kerth
V.B.
Berchner-Pfannschmidt
U.
Roth
U.
Brandes
R.P.
et al
Thrombin activates the hypoxia-inducible factor-1 signaling pathway in vascular smooth muscle cells: role of the p22(phox)-containing NADPH oxidase
Circ Res
 
2001
89
47
54
[79]
Saito
T.
Itoh
H.
Yamashita
J.
Doi
K.
Chun
T.H.
Tanaka
T.
et al
Angiotensin II suppresses growth arrest specific homeobox (Gax) expression via redox-sensitive mitogen-activated protein kinase (MAPK)
Regul Pept
 
2005
127
159
167
[80]
Nickenig
G.
Baudler
S.
Muller
C.
Werner
C.
Werner
N.
Welzel
H.
et al
Redox-sensitive vascular smooth muscle cell proliferation is mediated by GKLF and Id3 in vitro and in vivo
FASEB J
 
2002
16
1077
1086
[81]
Mueller
C.
Baudler
S.
Welzel
H.
Bohm
M.
Nickenig
G.
Identification of a novel redox-sensitive gene, Id3, which mediates angiotensin II-induced cell growth
Circulation
 
2002
105
2423
2428
[82]
Rocic
P.
Seshiah
P.
Griendling
K.K.
Reactive oxygen species-sensitivity of angiotensin II-dependent translation initiation in vascular smooth muscle cells
J Biol Chem
 
2003
278
36973
36979
[83]
Weber
D.S.
Taniyama
Y.
Rocic
P.
Seshiah
P.N.
Dechert
M.A.
Gerthoffer
W.T.
et al
Phosphoinositide-dependent kinase 1 and p21-activated protein kinase mediate reactive oxygen species-dependent regulation of platelet-derived growth factor-induced smooth muscle cell migration
Circ Res
 
2004
94
1219
1226
[84]
Kreuzer
J.
Viedt
C.
Brandes
R.P.
Seeger
F.
Rosenkranz
A.S.
Sauer
H.
et al
Platelet-derived growth factor activates production of reactive oxygen species by NAD(P)H oxidase in smooth muscle cells through Gi1,2
FASEB J
 
2003
17
38
40
[85]
Kong
G.
Lee
S.
Kim
K.S.
Inhibition of rac1 reduces PDGF-induced reactive oxygen species and proliferation in vascular smooth muscle cells
J Korean Med Sci
 
2001
16
712
718
[86]
Saito
S.
Frank
G.D.
Mifune
M.
Ohba
M.
Utsunomiya
H.
Motley
E.D.
et al
Ligand-independent trans-activation of the platelet-derived growth factor receptor by reactive oxygen species requires protein kinase C-delta and c-Src
J Biol Chem
 
2002
277
44695
44700
[87]
Shimizu
H.
Shiota
M.
Yamada
N.
Miyazaki
K.
Ishida
N.
Kim
S.
et al
Low M(r) protein tyrosine phosphatase inhibits growth and migration of vascular smooth muscle cells induced by platelet-derived growth factor
Biochem Biophys Res Commun
 
2001
289
602
607
[88]
Ceacareanu
A.C.
Ceacareanu
B.
Zhuang
D.
Chang
Y.
Ray
R.M.
Desai
L.
et al
Nitric oxide attenuates IGF-1-induced aortic smooth muscle cell motility by decreasing Rac1 activity: essential role of PTP-PEST and p130cas
Am J Physiol Cell Physiol
 
2005
[89]
Mahadev
K.
Motoshima
H.
Wu
X.
Ruddy
J.M.
Arnold
R.S.
Cheng
G.
et al
The NAD(P)H oxidase homolog Nox4 modulates insulin-stimulated generation of H2O2 and plays an integral role in insulin signal transduction
Mol Cell Biol
 
2004
24
1844
1854
[90]
Bhanoori
M.
Yellaturu
C.R.
Ghosh
S.K.
Hassid
A.
Jennings
L.K.
Rao
G.N.
Thiol alkylation inhibits the mitogenic effects of platelet-derived growth factor and renders it proapoptotic via activation of STATs and p53 and induction of expression of caspase1 and p21(waf1/cip1)
Oncogene
 
2003
22
117
130
[91]
Yellaturu
C.R.
Bhanoori
M.
Neeli
I.
Rao
G.N.
N-Ethylmaleimide inhibits platelet-derived growth factor BB-stimulated Akt phosphorylation via activation of protein phosphatase 2A
J Biol Chem
 
2002
277
40148
40155
[92]
Chiarugi
P.
Fiaschi
T.
Taddei
M.L.
Talini
D.
Giannoni
E.
Raugei
G.
et al
Two vicinal cysteines confer a peculiar redox regulation to low molecular weight protein tyrosine phosphatase in response to platelet-derived growth factor receptor stimulation
J Biol Chem
 
2001
276
33478
33487
[93]
Kwon
J.
Lee
S.R.
Yang
K.S.
Ahn
Y.
Kim
Y.J.
Stadtman
E.R.
et al
Reversible oxidation and inactivation of the tumor suppressor PTEN in cells stimulated with peptide growth factors
Proc Natl Acad Sci U S A
 
2004
101
16419
16424
[94]
Schulze
P.C.
De Keulenaer
G.W.
Yoshioka
J.
Kassik
K.A.
Lee
R.T.
Vitamin D3-upregulated protein-1 (VDUP-1) regulates redox-dependent vascular smooth muscle cell proliferation through interaction with thioredoxin
Circ Res
 
2002
91
689
695
[95]
He
T.
Weintraub
N.L.
Goswami
P.C.
Chatterjee
P.
Flaherty
D.M.
Domann
F.E.
et al
Redox factor-1 contributes to the regulation of progression from G0/G1 to S by PDGF in vascular smooth muscle cells
Am J Physiol Heart Circ Physiol
 
2003
285
H804
H812
[96]
Sung
H.J.
Eskin
S.G.
Sakurai
Y.
Yee
A.
Kataoka
N.
McIntire
L.V.
Oxidative stress produced with cell migration increases synthetic phenotype of vascular smooth muscle cells
Ann Biomed Eng
 
2005
33
1546
1554
[97]
Boureux
A.
Furstoss
O.
Simon
V.
Roche
S.
Abl tyrosine kinase regulates a Rac/JNK and a Rac/Nox pathway for DNA synthesis and Myc expression induced by growth factors
J Cell Sci
 
2005
118
3717
3726
[98]
Wang
Z.
Castresana
M.R.
Newman
W.H.
Reactive oxygen species-sensitive p38 MAPK controls thrombin-induced migration of vascular smooth muscle cells
J Mol Cell Cardiol
 
2004
36
49
56
[99]
Wang
Z.
Castresana
M.R.
Newman
W.H.
Reactive oxygen and NF-kappaB in VEGF-induced migration of human vascular smooth muscle cells
Biochem Biophys Res Commun
 
2001
285
669
674
[100]
Lo
I.C.
Shih
J.M.
Jiang
M.J.
Reactive oxygen species and ERK 1/2 mediate monocyte chemotactic protein-1-stimulated smooth muscle cell migration
J Biomed Sci
 
2005
12
377
388
[101]
Schmitz
U.
Thommes
K.
Beier
I.
Vetter
H.
Lysophosphatidic acid stimulates p21-activated kinase in vascular smooth muscle cells
Biochem Biophys Res Commun
 
2002
291
687
691
[102]
Su
B.
Mitra
S.
Gregg
H.
Flavahan
S.
Chotani
M.A.
Clark
K.R.
et al
Redox regulation of vascular smooth muscle cell differentiation
Circ Res
 
2001
89
39
46
[103]
Clempus
R.E.
Sorescu
D.
Lassegue
B.
Dikalova
A.
Griendling
K.K.
Nox4-derived ROS are required for the differentiation of vascular smooth muscle cells
Circulation
 
2004
110
SIII-157
[Abstract]
[104]
Du
K.L.
Chen
M.
Li
J.
Lepore
J.J.
Mericko
P.
Parmacek
M.S.
Megakaryoblastic leukemia factor-1 transduces cytoskeletal signals and induces smooth muscle cell differentiation from undifferentiated embryonic stem cells
J Biol Chem
 
2004
279
17578
17586

Author notes

Time for primary review 20 days