Reactive oxygen species stimulate insulin-like growth factor I synthesis in vascular smooth muscle cells

Dieckol Reduces Muscle Atrophy by Modulating Angiotensin Type II Type 1 Receptor and NADPH Oxidase in Spontaneously Hypertensive Rats

The renin-angiotensin system is involved in the development of hypertension and sarcopenia. Increased levels of angiotensin II (Ang II) lead to upregulation of Ang II type 1 receptor (AT1R), which results in increasing reactive oxygen species (ROS) by NAD(P)H oxidase (Nox). Increased ROS led to increased helper T17 (Th17) and decreased regulatory T (Treg) cells through HIF-1α. Increased Th17 secretes more IL-17, leading to increased NF-κB and muscle atrophy. We evaluated the effect of Ecklonia cava extracts (ECE) and dieckol (DK) on attenuating muscle atrophy by decreasing AT1R and NOX activity in spontaneous hypertensive rats (SHRs). The serum levels of Ang II and expression of AT1R in the muscle were higher in SHRs than in normotensive animals of Wistar-Kyoto rats (2.4 and 1.8 times higher than WKY, respectively). The expression of AT1R decreased by ECE or DK (0.62 and 0.84 times lower than SHR, respectively). In SHRs, the expression of Nox 1, 2, and 4 were increased (1.2-1.15 times higher than WKY) but were decreased by the administration of ECE (0.8-0.9 times lower than SHR) or DK (0.7-0.9 times lower than SHR). The Nox activity was increased in SHRs (2.3 times more than WKY) and it was decreased by ECE (0.9 times lower than SHRs) and DK (0.9 times lower than SHRs). The expression of HIF-1α, a marker of Th17 (RORγt), and cytokine secreted by Th17 (IL-17) was increased in SHRs and was decreased by ECE or DK. The marker of Treg (Foxp3) and cytokine secreted from Treg cells (IL-10) was decreased in SHRs and was increased by ECE or DK. The expression of NF-κB/IL-1β/TNF-α and MuRF-1/MAFbx/atrogin-1 was increased in SHRs and these were decreased by ECE or DK. The cross-sectional area of muscle fiber was decreased in SHRs (0.7 times lower than WKY) and was increased by ECE (1.3 times greater than SHR) or DK (1.5 times greater than SHR). In conclusion, ECE or DK leads to a decreased expression of AT1R and Nox activity which modulates Th17/Treg balance and consequently, decreased muscle atrophy.

Non-thermal plasma promotes hair growth by improving the inter-follicular macroenvironment

Non-thermal plasma (NTP) is widely used in the disinfection and surface modification of biomaterials. NTP treatment can regenerate and improve skin function; however, its effectiveness on hair follicle (HF) growth and its underlying mechanisms need to be elucidated. Herein, we propose an air-based NTP treatment, which generates exogenous nitric oxide (eNO), as a therapeutic strategy for hair growth. The topical application of air-based NTP generates large amounts of eNO, which can be directly detected using a microelectrode NO sensor, in the dermis of mouse dorsal skin. Additionally, NTP-induced eNO has no cytotoxicity in normal human skin cells and promotes hair growth by increasing capillary tube formation, cellular proliferation, and hair/angiogenesis-related protein expression. Furthermore, NTP treatment promotes hair growth with adipogenesis and activation of CD34⁺CD44⁺ stem cells and improves the inter-follicular macroenvironment via increased perifollicular vascularity in the mouse hair regrowth model. Given the importance of the hair follicle (HF) cycle ratio (growth vs. regression vs. resting) in diagnosing alopecia, NTP treatment upregulates the stem cell activity of the HF to promote the anagen : catagen : telogen ratio, leading to improved hair growth. We confirmed the upregulation of increasing Wnt/β-catenin signaling and activation of perifollicular adipose tissue and angiogenesis in HF regeneration. In conclusion, these results show that the eNO from NTP enhances the cellular activities of human skin cells and endothelial cells in vitro and stem cells in vivo, thereby increasing angiogenesis, adipogenesis, and hair growth in the skin dermis. Furthermore, the results of this study suggest that NTP treatment may be a highly efficient alternative in regenerative medicine for achieving enhanced hair growth.

Non-thermal plasma (NTP) is widely used in the disinfection and surface modification of biomaterials.

C2C12 cell model: its role in understanding of insulin resistance at the molecular level and pharmaceutical development at the preclinical stage

OBJECTIVES

The myoblast cell line, C2C12, has been utilised extensively in vitro as an examination model in understanding metabolic disease progression. Although it is indispensable in both preclinical and pharmaceutical research, a comprehensive review of its use in the investigation of insulin resistance progression and pharmaceutical development is not available.

KEY FINDINGS

C2C12 is a well-documented model, which can facilitate our understanding in glucose metabolism, insulin signalling mechanism, insulin resistance, oxidative stress, reactive oxygen species and glucose transporters at cellular and molecular levels. With the aid of the C2C12 model, recent studies revealed that insulin resistance has close relationship with various metabolic diseases in terms of disease progression, pathogenesis and therapeutic management. A holistic, safe and effective disease management is highly of interest. Therefore, significant efforts have been paid to explore novel drug compounds and natural herbs that can elicit therapeutic effects in the targeted sites at both cellular (e.g. mitochondria, glucose transporter) and molecular level (e.g. genes, signalling pathway).

SUMMARY

The use of C2C12 myoblast cell line is meaningful in pharmaceutical and biomedical research due to their expression of GLUT-4 and other features that are representative to human skeletal muscle cells. With the use of the C2C12 cell model, the impact of drug delivery systems (nanoparticles and quantum dots) on skeletal muscle, as well as the relationship between exercise, pancreatic β-cells and endothelial cells, was discovered.

Myocardial Ischemia and Diabetes Mellitus: Role of Oxidative Stress in the Connection between Cardiac Metabolism and Coronary Blood Flow

Ischemic heart disease (IHD) has several risk factors, among which diabetes mellitus represents one of the most important. In diabetic patients, the pathophysiology of myocardial ischemia remains unclear yet: some have atherosclerotic plaque which obstructs coronary blood flow, others show myocardial ischemia due to coronary microvascular dysfunction in the absence of plaques in epicardial vessels. In the cross-talk between myocardial metabolism and coronary blood flow (CBF), ion channels have a main role, and, in diabetic patients, they are involved in the pathophysiology of IHD. The exposition to the different cardiovascular risk factors and the ischemic condition determine an imbalance of the redox state, defined as oxidative stress, which shows itself with oxidant accumulation and antioxidant deficiency. In particular, several products of myocardial metabolism, belonging to oxidative stress, may influence ion channel function, altering their capacity to modulate CBF, in response to myocardial metabolism, and predisposing to myocardial ischemia. For this reason, considering the role of oxidative and ion channels in the pathophysiology of myocardial ischemia, it is allowed to consider new therapeutic perspectives in the treatment of IHD.

Insulin-like growth factor-1 signaling in cardiac aging

Cardiovascular disease (CVD) is the leading cause of death in most developed countries. Aging is associated with enhanced risk of CVD. Insulin-like growth factor-1 (IGF-1) binds to its cognate receptor, IGF-1 receptor (IGF-1R), and exerts pleiotropic effects on cell growth, differentiation, development, and tissue repair. Importantly, IGF-1/IGF-1R signaling is implicated in cardiac aging and longevity. Cardiac aging is an intrinsic process that results in cardiac dysfunction, accompanied by molecular and cellular changes. In this review, we summarize the current state of knowledge regarding the link between the IGF-1/IGF-1R system and cardiac aging. The biological effects of IGF-1R and insulin receptor will be discussed and compared. Furthermore, we describe data regarding how deletion of IGF-1R in cardiomyocytes of aged knockout mice may delay the development of senescence-associated myocardial pathologies. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Controlled Delivery of Extracellular ROS Based on Hematoporphyrin-Incorporated Polyurethane Film for Enhanced Proliferation of Endothelial Cells

The principle of photodynamic treatment (PDT) involves the administration of photosensitizer (PS) at diseased tissues, followed by light irradiation to produce reactive oxygen species (ROS). In cells, a moderate increase in ROS plays an important role as signaling molecule to promote cell proliferation, whereas a severe increase of ROS causes cell damage. Previous studies have shown that low levels of ROS stimulate cell growth through PS drugs-treating PDT and nonthermal plasma treatment. However, these methods have side effects which are associated with low tissue selectivity and remaining of PS residues. To overcome such shortcomings, we designed hematoporphyrin-incorporated polyurethane (PU) film induced generation of extracellular ROS with singlet oxygen and free radicals. The film can easily control ROS production rate by regulating several parameters including light dose, PS dose. Also, its use facilitates targeted delivery of ROS to the specific lesion. Our study demonstrated that extracellular ROS could induce the formation of intracellular ROS. In vascular endothelial cells, a moderated increase in intracellular ROS also stimulated cell proliferation and cell cycle progression by accurate control of optimum levels of ROS with hematoporphyrin-incorporated polymer films. This modulation of cellular growth is expected to be an effective strategy for the design of next-generation PDT.

NADPH oxidases: key modulators in aging and age-related cardiovascular diseases?

Reactive oxygen species (ROS) and oxidative stress have long been linked to aging and diseases prominent in the elderly such as hypertension, atherosclerosis, diabetes and atrial fibrillation (AF). NADPH oxidases (Nox) are a major source of ROS in the vasculature and are key players in mediating redox signalling under physiological and pathophysiological conditions. In this review, we focus on the Nox-mediated ROS signalling pathways involved in the regulation of 'longevity genes' and recapitulate their role in age-associated vascular changes and in the development of age-related cardiovascular diseases (CVDs). This review is predicated on burgeoning knowledge that Nox-derived ROS propagate tightly regulated yet varied signalling pathways, which, at the cellular level, may lead to diminished repair, the aging process and predisposition to CVDs. In addition, we briefly describe emerging Nox therapies and their potential in improving the health of the elderly population.

Apolipoprotein E-/- Mice Lacking Hemopexin Develop Increased Atherosclerosis via Mechanisms That Include Oxidative Stress and Altered Macrophage Function

OBJECTIVE

We previously reported that hemopexin (Hx), a heme scavenger, is significantly increased and associated with proinflammatory high-density lipoprotein under atherogenic conditions. Although it is established that Hx together with macrophages plays a role in mitigating oxidative damage, the role of Hx in the development of atherosclerosis is unknown.

APPROACH AND RESULTS

We used Hx and apoE double-knockout mice (HxE(-/-)) to determine the role of Hx in the development of atherosclerosis. HxE(-/-) mice had significantly more free heme, reactive oxygen species, and proinflammatory high-density lipoprotein in their circulation, when compared with control apoE(-/-) mice. Atherosclerotic plaque area (apoE(-/-)=9.72±2.5×10(4) μm(2) and HxE(-/-)=27.23±3.6×10(4) μm(2)) and macrophage infiltration (apoE(-/-)=38.8±5.8×10(3) μm(2) and HxE(-/-)=103.4±17.8×10(3) μm(2)) in the aortic sinus were significantly higher in the HxE(-/-) mice. Atherosclerotic lesions in the aortas were significantly higher in the HxE(-/-) mice compared with apoE(-/-) mice. Analysis of polarization revealed that macrophages from HxE(-/-) mice were more M1-like. Ex vivo studies demonstrated that HxE(-/-) macrophage cholesterol efflux capacity was significantly reduced when compared with apoE(-/-) mice. Injection of human Hx into HxE(-/-) mice reduced circulating heme levels and human Hx pretreatment of naive bone marrow cells ex vivo resulted in a shift from M1- to M2-like macrophages.

CONCLUSIONS

We conclude that Hx plays a novel protective role in alleviating heme-induced oxidative stress, improving inflammatory properties of high-density lipoprotein, macrophage phenotype and function, and inhibiting the development of atherosclerosis in apoE(-/-) mice.

Aging, atherosclerosis, and IGF-1

Insulin-like growth factor 1 (IGF-1) is an endocrine and autocrine/paracrine growth factor that circulates at high levels in the plasma and is expressed in most cell types. IGF-1 has major effects on development, cell growth and differentiation, and tissue repair. Recent evidence indicates that IGF-1 reduces atherosclerosis burden and improves features of atherosclerotic plaque stability in animal models. Potential mechanisms for this atheroprotective effect include IGF-1-induced reduction in oxidative stress, cell apoptosis, proinflammatory signaling, and endothelial dysfunction. Aging is associated with increased vascular oxidative stress and vascular disease, suggesting that IGF-1 may exert salutary effects on vascular aging processes. In this review, we will provide a comprehensive update on IGF-1's ability to modulate vascular oxidative stress and to limit atherogenesis and the vascular complications of aging.

Oxidative stress and heart failure in altered thyroid States

Increased or reduced action of thyroid hormone on certain molecular pathways in the heart and vasculature causes relevant cardiovascular derangements. It is well established that hyperthyroidism induces a hyperdynamic cardiovascular state, which is associated with a faster heart rate, enhanced left ventricular systolic and diastolic function whereas hypothyroidism is characterized by the opposite changes. Hyperthyroidism and hypothyroidism represent opposite clinical conditions, albeit not mirror images. Recent experimental and clinical studies have suggested the involvement of ROS tissue damage under altered thyroid status. Altered-thyroid state-linked changes in heart modify their susceptibility to oxidants and the extent of the oxidative damage they suffer following oxidative challenge. Chronic increase in the cellular levels of ROS can lead to a catastrophic cycle of DNA damage, mitochondrial dysfunction, further ROS generation and cellular injury. Thus, these cellular events might play an important role in the development and progression of myocardial remodeling and heart failure in altered thyroid states (hypo- and hyper-thyroidism). The present review aims at elucidating the various signaling pathways mediated via ROS and their modulation under altered thyroid state and the possibility of antioxidant therapy.

Reactive oxygen species in skeletal muscle signaling

Generation of reactive oxygen species (ROS) is a ubiquitous phenomenon in eukaryotic cells' life. Up to the 1990s of the past century, ROS have been solely considered as toxic species resulting in oxidative stress, pathogenesis and aging. However, there is now clear evidence that ROS are not merely toxic species but also-within certain concentrations-useful signaling molecules regulating physiological processes. During intense skeletal muscle contractile activity myotubes' mitochondria generate high ROS flows: this renders skeletal muscle a tissue where ROS hold a particular relevance. According to their hormetic nature, in muscles ROS may trigger different signaling pathways leading to diverging responses, from adaptation to cell death. Whether a "positive" or "negative" response will prevail depends on many variables such as, among others, the site of ROS production, the persistence of ROS flow or target cells' antioxidant status. In this light, a specific threshold of physiological ROS concentrations above which ROS exert negative, toxic effects is hard to determine, and the concept of "physiologically compatible" levels of ROS would better fit with such a dynamic scenario. In this review these concepts will be discussed along with the most relevant signaling pathways triggered and/or affected by ROS in skeletal muscle.

Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species

Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), has recently emerged as an efficient tool in medical applications including blood coagulation, sterilization and malignant cell apoptosis. Liquids and porcine aortic endothelial cells were treated with a non-thermal dielectric barrier discharge plasma in vitro. Plasma treatment of phosphate-buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration observed in serum-free medium compared with PBS. Species concentration inside cells peaked 1 h after treatment, followed by a decrease 3 h post treatment. Endothelial cells treated with a plasma dose of 4.2 J cm(-2) had 1.7 times more cells than untreated samples 5 days after plasma treatment. The 4.2 J cm(-2) plasma dose increased two-dimensional migration distance by 40 per cent compared with untreated control, while the number of cells that migrated through a three-dimensional collagen gel increased by 15 per cent. Tube formation was also enhanced by plasma treatment, with tube lengths in plasma-treated samples measuring 2.6 times longer than control samples. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers abrogated these angiogenic effects. These data indicate that plasma enhanced proliferation, migration and tube formation is due to FGF-2 release induced by plasma-produced ROS. Non-thermal plasma may be used as a potential tool for applying ROS in precise doses to enhance vascularization.

Reactive oxygen species play an essential role in IGF-I signaling and IGF-I-induced myocyte hypertrophy in C2C12 myocytes

IGF-I induces skeletal muscle hypertrophy by stimulating protein synthesis and suppressing the protein degradation pathway; the downstream signaling pathways Akt-mammalian target of rapamycin (mTOR)-p70-kDA-S6-kinase (p70S6K), and Forkhead box O1 (FoxO1) play essential roles in this regulation. Reactive oxygen species (ROS) modulate the signaling of various growth factors via redox regulation. However, the role of ROS in IGF-I signaling is not fully understood. In this study, we investigated whether ROS regulate the signaling and biological action of IGF-I in C2C12 myocytes. We found that IGF-I induces ROS in C2C12 myocytes. While treatment with H(2)O(2) significantly enhanced IGF-I-induced phosphorylation of the IGF-I receptor (IGF-IR), IGF-IR phosphorylation was markedly attenuated when cells were treated with antioxidants. The downstream signaling pathway, Akt-mTOR-p70S6K was subsequently down-regulated. Furthermore, the phosphorylation of FoxO1 by IGF-I decreased concomitantly with the restoration of the expression of its target genes, Atrogin-1 and muscle RING finger 1, which are related to muscle atrophy. Nox4 knockdown, which is reportedly to produce ROS in insulin signaling, attenuated IGF-I-induced IGF-IR phosphorylation, indicating that Nox4 is involved in the regulation of IGF-I signaling. Importantly, antioxidant treatments inhibited IGF-I-induced myocyte hypertrophy, demonstrating that ROS are necessary for IGF-I-induced myocyte hypertrophy in vitro. These results indicate that ROS play an essential role in the signaling and biological action of IGF-I in C2C12 myocytes.

Influence of maternal redox status on birth weight

The aim of this study was to determine the influence that maternal redox status, between 30 and 36 weeks of healthy human pregnancy, has on birth weight. Ferric reducing potential (FRP), extracellular superoxide dismutase (ecSOD) activity and erythrocyte reduced glutathione (eGSH) concentration were measured as antioxidant indicators, and serum malondialdehyde (MDA) concentration as a lipoperoxidation indicator. Consumption of dietary micronutrients with antioxidant capacity was recorded. We observed a direct correlation between birth weight and ecSOD activity and eGSH concentration. An interaction between eGSH with FRP and serum ecSOD activity also correlated directly with birth weight. Other correlating factors included maternal thiamine consumption and interactions between vitamins C and E and carotenoids and vitamin E intake. These findings support the notion that antioxidant status has a positive influence on birth weight.

IGF-1, oxidative stress and atheroprotection

Atherosclerosis is a chronic inflammatory disease in which early endothelial dysfunction and subintimal modified lipoprotein deposition progress to complex, advanced lesions that are predisposed to erosion, rupture and thrombosis. Oxidative stress plays a crucial role not only in initial lesion formation but also in lesion progression and destabilization. Although most growth factors are thought to promote vascular smooth muscle cell proliferation and migration, thereby increasing neointima, recent animal studies indicate that insulin-like growth factor (IGF)-1 exerts both pleiotropic anti-oxidant effects and anti-inflammatory effects, which together reduce atherosclerotic burden. This review discusses the effects of IGF-1 in models of vascular injury and atherosclerosis, emphasizing the relationship between oxidative stress and potential atheroprotective actions of IGF-1.

Silibinin induces protective superoxide generation in human breast cancer MCF-7 cells

The pharmacological activity of polyphenolic silibinin from milk thistle (Silybum marianum) is primarily due to its antioxidant property. However, this study found that silibinin promoted sustained superoxide (O(2)(.-)) production that was specifically scavenged by exogenous superoxide dismutase (SOD) in MCF-7 cells, while the activity of endogenous SOD was not changed by silibinin. Previous work proved that silibinin induced MCF-7 cell apoptosis through mitochondrial pathway and this study further proved that O(2)(.-) generation induced by silibinin was also related to mitochondria. It was found that respiratory chain complexes I, II and III were all involved in silibinin-induced O(2)(.-) generation. Moreover, it was found that silibinin-induced O(2)(.-) had protective effect, as exogenous SOD markedly enhanced silibinin-induced apoptosis.

Role of reactive oxygen species in the progression of type 2 diabetes and atherosclerosis

Type 2 diabetes is the most prevalent and serious metabolic disease all over the world, and its hallmarks are pancreatic beta-cell dysfunction and insulin resistance. Under diabetic conditions, chronic hyperglycemia and subsequent augmentation of reactive oxygen species (ROS) deteriorate beta-cell function and increase insulin resistance which leads to the aggravation of type 2 diabetes. In addition, chronic hyperglycemia and ROS are also involved in the development of atherosclerosis which is often observed under diabetic conditions. Taken together, it is likely that ROS play an important role in the development of type 2 diabetes and atherosclerosis.

The insulin-like growth factor family: molecular mechanisms, redox regulation, and clinical implications

Insulin-like growth factor (IGF)-induced signaling networks are vital in modulating multiple fundamental cellular processes, such as cell growth, survival, proliferation, and differentiation. Aberrations in the generation or action of IGF have been suggested to play an important role in several pathological conditions, including metabolic disorders, neurodegenerative diseases, and multiple types of cancer. Yet the exact mechanism involved in the pathogenesis of these diseases by IGFs remains obscure. Redox pathways involving reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the pathogenetic mechanism of various diseases by modifying key signaling pathways involved in cell growth, proliferation, survival, and apoptosis. Furthermore, ROS and RNS have been demonstrated to alter IGF production and/or action, and vice versa, and thereby have the ability to modulate cellular functions, leading to clinical manifestations of diseases. In this review, we provide an overview on the IGF system and discuss the potential role of IGF-1/IGF-1 receptor and redox pathways in the pathophysiology of several diseases.

Involvement of oxidative stress in the pathogenesis of diabetes

Pancreatic beta-cell failure is the common characteristic of type 1 and type 2 diabetes. Type 1 diabetes is induced by pancreatic beta-cell destruction, which is mediated by an autoimmune mechanism and consequent inflammatory process. Various inflammatory cytokines and oxidative stress produced by islet-infiltrating immune cells have been proposed to play an important role in mediating the destruction of beta cells. The JNK pathway is also activated by such cytokines and oxidative stress and is involved in beta-cell destruction. Type 2 diabetes is the most prevalent and serious metabolic disease affecting people all over the world. Pancreatic beta-cell dysfunction and insulin resistance are the hallmark of type 2 diabetes. Once hyperglycemia becomes apparent, beta-cell function gradually deteriorates, and insulin resistance is aggravated. This process is called "glucose toxicity." Under such conditions, oxidative stress is provoked, and the JNK pathway is activated, which is likely involved in pancreatic beta-cell dysfunction and insulin resistance. In addition, oxidative stress and activation of the JNK pathway are involved in the progression of atherosclerosis, which is often observed under diabetic conditions. Taken together, it is likely that oxidative stress and subsequent activation of the JNK pathway are involved in the pathogenesis of type 1 and type 2 diabetes.

Smoking induces glomerulosclerosis in aging estrogen-deficient mice through cross-talk between TGF-beta1 and IGF-I signaling pathways

Smoking is a known risk factor for the progression of chronic kidney diseases. However, its independent contribution to the development of ESRD and the underlying molecular mechanism have not been well elucidated. Although the risk for ESRD is higher in postmenopausal women according to the US Renal Data System, the number of women who smoke is on the rise worldwide. Therefore, the effects of smoking and estrogen status on glomerular function and structure were studied in female B6 mice that were ovariectomized at 3 (young) and 15 mo (aged) of age. The mice received either 17beta-estradiol (E(2)) replacement or placebo (Pla) and were divided further into groups that were exposed to cigarette smoke (S) and not exposed (NS). Six months of exposure to smoke had no effect on young mice, although aging S/Pla mice exhibited a phenotype of increased albumin excretion associated with a moderately increased glomerular collagen type IV deposition compared with NS/Pla mice. S/Pla mice also had a two-fold increase in glomerular TGF-beta, Smad3, and IGF-I receptor mRNA expression compared with the NS group. Mesangial cells that were isolated from S/Pla mice had an increase of IGF-I receptor protein, and IGF-I stimulated a TGF-beta reporter construct promoter three-fold. This was blocked by pretreatment with a neutralizing antibody to IGF-I, LY294002 (phosphatidylinositol-3 kinase inhibitor) or a dominant negative Smad construct. In addition, Smad3 activation was stimulated by IGF-I and blocked by LY294002, suggesting cross-talk between Smad and the phosphatidylinositol-3 kinase/AKT pathways. The smoking phenotype was reversed by E(2) replacement. In conclusion, smoking induces a phenotype in E(2)-deficient mice that is characterized by activation and cross-talk between the TGF-beta1 and IGF-I signaling pathways.

Nitric oxide attenuates IGF-I-induced aortic smooth muscle cell motility by decreasing Rac1 activity: essential role of PTP-PEST and p130cas

Recent data support the hypothesis that reactive oxygen species (ROS) play a central role in the initiation and progression of vascular diseases. An important vasoprotective function related to the regulation of ROS levels appears to be the antioxidant capacity of nitric oxide (NO). We previously reported that treatment with NO decreases phosphotyrosine levels of adapter protein p130(cas) by increasing protein tyrosine phosphatase-proline, glutamate, serine, and threonine sequence protein (PTP-PEST) activity, which leads to the suppression of agonist-induced H(2)O(2) elevation and motility in cultured rat aortic smooth muscle cells (SMCs). The present study was performed to investigate the hypotheses that 1) IGF-I increases the activity of the small GTPase Rac1 as well as H(2)O(2) levels and 2) NO suppresses IGF-I-induced H(2)O(2) elevation by decreasing Rac1 activity via increased PTP-PEST activity and dephosphorylation of p130(cas). We report that IGF-I induces phosphorylation of p130(cas) and activation of Rac1 and that NO attenuates these effects. The effects of NO are mimicked by the overexpression of PTP-PEST or dominant-negative (dn)-p130(cas) and antagonized by the expression of dn-PTP-PEST or p130(cas). We conclude that IGF-I induces rat aortic SMC motility by increasing phosphotyrosine levels of p130(cas) and activating Rac1 and that NO decreases motility by activating PTP-PEST, inducing dephosphorylating p130(cas), and decreasing Rac1 activity. Decreased Rac1 activity lowers intracellular H(2)O(2) levels, thus attenuating cell motility.

Insulin-like growth factor I in inclusion-body myositis and human muscle cultures

Possible pathogenic mechanisms of sporadic inclusion-body myositis (sIBM) include abnormal production and accumulation of amyloid beta (A beta), muscle aging, and increased oxidative stress. Insulin-like growth factor I (IGF-I), an endocrine and autocrine/paracrine trophic factor, provides resistance against A beta toxicity and oxidative stress in vitro and promotes cell survival. In this study we analyzed the IGF-I signaling pathway in sIBM muscle and found that 16.2% +/- 2.5% of nonregenerating fibers showed increased expression of IGF-I, phosphatidylinositide 3'OH-kinase, and Akt. In the majority of sIBM abnormal muscle fibers, increased IGF-I mRNA and protein correlated with the presence of A beta cytoplasmic inclusions. To investigate a possible relationship between A beta toxicity and IGF-I upregulation, normal primary muscle cultures were stimulated for 24 hours with the A beta(25-35) peptide corresponding to the biologically active domain of A beta. This induced an increase of IGF-I mRNA and protein in myotubes at 6 hours, followed by a gradual reduction thereafter. The level of phosphorylated Akt showed similar changes. We suggest that in sIBM. IGF-I overexpression represents a reactive response to A beta toxicity, possibly providing trophic support to vulnerable fibers. Understanding the signaling pathways activated by IGF-I in sIBM may lead to novel therapeutic strategies for the disease.

Nitric oxide attenuates insulin- or IGF-I-stimulated aortic smooth muscle cell motility by decreasing H2O2 levels: essential role of cGMP

Insulin and insulin-like growth factor I (IGF-I) both play important roles in vascular remodeling. Moreover, nitric oxide (NO) is well established as a counterregulatory agent that opposes the actions of several vascular agonists, in part by decreasing smooth muscle motility. We tested the hypothesis that NO blocks insulin or IGF-I-induced rat aortic smooth muscle cell motility via a mechanism involving the attenuation of agonist-induced elevation of hydrogen peroxide levels and cGMP as mediator. Insulin or IGF-I induced an increase of hydrogen peroxide levels and cell motility. Both effects were blocked by catalase or diphenyleneiodonium, indicating that hydrogen peroxide elevation is necessary for induction of cell motility. Two NO donors mimicked the effects of catalase, indicating that NO decreases cell motility by suppressing agonist-induced elevation of hydrogen peroxide. A cGMP analogue mimicked the effect of NO, whereas a guanyl cyclase inhibitor blocked the effect of NO on hydrogen peroxide levels, indicating that elevation of cGMP is both necessary and sufficient to account for the reduction of hydrogen peroxide levels. A NO donor as well as a cGMP analogue attenuated insulin-stimulated NADPH activity, indicating that NO decreases hydrogen peroxide levels by inhibiting the generation of superoxide, via a cGMP-mediated mechanism. Finally, exogenous hydrogen peroxide increased cell motility and reversed the inhibitory effect of cGMP. These results support the view that NO plays an antioxidant role via reduction of hydrogen peroxide in cultured rat aortic smooth muscle cells and that this effect is both necessary and sufficient to account for its capacity to decrease cell motility.

Interleukin-1 and nitric oxide increase NADPH oxidase activity in human coronary artery smooth muscle cells

OBJECTIVE

Cytokines, nitric oxide (NO) and reactive oxygen species (ROS) are well known for their pathogenic effects in development of cardiovascular diseases. Interleukin-1beta (IL-1beta) is known to induce NO generation, however it is not well established if IL-1beta or NO regulate production of ROS, such as superoxide anion. Therefore, the main objective of this study was to evaluate the effect of IL-1beta or NO on enzyme activity of NADPH oxidase (NOX), a superoxide-generating system recently documented to participate in a variety of vascular functions.

METHODS

Human coronary artery smooth muscle cells (SMC) obtained from Clonetics were treated with IL-1beta and NO donor, sodium nitroprusside (SNP), in culture. Nitrites accumulated in supernatants of SMC cultures were measured as an index of NO released following treatment with IL-1beta. NOX enzyme activity was assayed using cytochrome c as the electron acceptor.

RESULTS

Treatment with IL-1beta resulted in a 3-fold increase in the production of NO by SMC. Both IL-1beta and SNP enhanced NOX activity, by 67 and 45%, respectively, following 24 h of treatment.

CONCLUSION

This study suggests that NO or NO- generating cytokines might regulate the production of ROS in the cardiovascular system through modulation of superoxide-generating systems such as NOX.

Expression, regulation, and function of IGF-1, IGF-1R, and IGF-1 binding proteins in blood vessels

The vascular insulin-like growth factor (IGF)-1 system includes the IGFs, the IGF-1 receptor (IGF-1R), and multiple binding proteins. This growth factor system exerts multiple physiologic effects on the vasculature through both endocrine and autocrine/paracrine mechanisms. The effects of IGF-1 are mediated principally through the IGF-1R but are modulated by complex interactions with multiple IGF binding proteins that themselves are regulated by phosphorylation, proteolysis, polymerization, and cell or matrix association. During the last decade, a significant body of evidence has accumulated, indicating that expression of the components of the IGF system are regulated by multiple factors, including growth factors, cytokines, lipoproteins, reactive oxygen species, and hemodynamic forces. In addition, cross-talk between the IGF system and other growth factors and integrin receptors has been demonstrated. There is accumulating evidence of a role for IGF-1 in multiple vascular pathologies, including atherosclerosis, hypertension, restenosis, angiogenesis, and diabetic vascular disease. This review will discuss the regulation of expression of IGF-1, IGF-1R, and IGF binding proteins in the vasculature and summarize evidence implicating involvement of this system in vascular diseases.

The general case for redox control of wound repair

The orthodox view has been that reactive oxygen species are primarily damaging to cells. There is general agreement that while high (3%) doses of H(2)O(2) may serve as a clinical disinfectant, its overall effect on healing is not positive. Current work shows that at very low concentrations, reactive oxygen species may regulate cellular signaling pathways by redox-dependent mechanisms. Recent discoveries show that almost all cells of the wound microenvironment contain specialized enzymes that utilize O(2) to generate reactive oxygen species. Numerous aspects of wound healing are subject to redox control. An understanding of how endogenous reactive oxygen species are generated in wound-related cells may influence the healing process and could result in new redox-based therapeutic strategies. Current results with growth factor therapy of wounds have not met clinical expectations. Many of these growth factors, such as platelet-derived growth factor, rely on reactive oxygen species for functioning. Redox-based strategies may serve as effective adjuncts to jump-start healing of chronic wounds. The understanding of wound-site redox biology is also likely to provide novel insights into the fundamental mechanisms that would help to optimize conditions for oxygen therapy. While a window of therapeutic opportunity seems to exist under conditions of low concentrations of reactive oxygen species, high levels may complicate regeneration and remodeling of nascent tissue.

Up-regulation of functionally impaired insulin-like growth factor-1 receptor in scrapie-infected neuroblastoma cells

A growing body of evidence suggests that an altered level or function of the neurotrophic insulin-like growth factor-1 receptor (IGF-1R), which supports neuronal survival, may underlie neurodegeneration. This study has focused on the expression and function of the IGF-1R in scrapie-infected neuroblastoma cell lines. Our results show that scrapie infection induces a 4-fold increase in the level of IGF-1R in two independently scrapie-infected neuroblastomas, ScN2a and ScN1E-115 cells, and that the increased IGF-1R level was accompanied by increased IGF-1R mRNA levels. In contrast to the elevated IGF-1R expression in ScN2a, receptor binding studies revealed an 80% decrease in specific (125)I-IGF-1-binding sites compared with N2a cells. This decrease in IGF-1R-binding sites was shown to be caused by a 7-fold decrease in IGF-1R affinity. Furthermore, ScN2a showed no significant difference in IGF-1 induced proliferative response, despite the noticeable elevated IGF-1R expression, putatively explained by the reduced IGF-1R binding affinity. Additionally, IGF-1 stimulated IGF-1Rbeta tyrosine phosphorylation showed no major change in the dose-response between the cell types, possibly due to altered tyrosine kinase signaling in scrapie-infected neuroblastoma cells. Altogether these data indicate that scrapie infection affects the expression, binding affinity, and signal transduction mediated by the IGF-1R in neuroblastoma cells. Altered IGF-1R expression and function may weaken the trophic support in scrapie-infected neurons and thereby contribute to neurodegeneration in prion diseases.

Vascular smooth muscle growth: autocrine growth mechanisms

Vascular smooth muscle cells (VSMC) exhibit several growth responses to agonists that regulate their function including proliferation (hyperplasia with an increase in cell number), hypertrophy (an increase in cell size without change in DNA content), endoreduplication (an increase in DNA content and usually size), and apoptosis. Both autocrine growth mechanisms (in which the individual cell synthesizes and/or secretes a substance that stimulates that same cell type to undergo a growth response) and paracrine growth mechanisms (in which the individual cells responding to the growth factor synthesize and/or secrete a substance that stimulates neighboring cells of another cell type) are important in VSMC growth. In this review I discuss the autocrine and paracrine growth factors important for VSMC growth in culture and in vessels. Four mechanisms by which individual agonists signal are described: direct effects of agonists on their receptors, transactivation of tyrosine kinase-coupled receptors, generation of reactive oxygen species, and induction/secretion of other growth and survival factors. Additional growth effects mediated by changes in cell matrix are discussed. The temporal and spatial coordination of these events are shown to modulate the environment in which other growth factors initiate cell cycle events. Finally, the heterogeneous nature of VSMC developmental origin provides another level of complexity in VSMC growth mechanisms.

Nonesterified fatty acids in blood pressure control and cardiovascular complications

The fact that cardiovascular risk factors cluster among individuals with the insulin resistance syndrome strongly suggests a common pathogenetic denominator. For many years, abnormalities of nonesterified fatty acid metabolism have been implicated in the disturbances of carbohydrate and lipid metabolism that characterize the cluster. However, until more recently, evidence implicating fatty acids in the hemodynamic and vascular abnormalities that affect patients with this syndrome was lacking. Observations from epidemiological, clinical, and basic science suggest that fatty acids can raise blood pressure and contribute to the development of hypertension. The effects of fatty acids on blood pressure may be mediated in part by inhibition of endothelial nitric oxide synthase activity and endothelium-dependent vasodilation. Fatty acids can also increase alpha1-adrenoceptor-mediated vascular reactivity and induce vascular smooth muscle migration and proliferation. The adverse effects of fatty acids appear to be mediated in part through induction of oxidative stress. Fatty acids interact with other components of the risk factor cluster, including increased angiotensin II, to synergistically augment oxidative stress in cultured vascular smooth muscle cells. Oxidative stress is implicated in the pathogenesis of insulin resistance, hypertension, vascular remodeling, and vascular complications. A clearer definition of the specific reactive oxygen signaling pathways involved and interventions aimed at altering these pathways could lead to more rationale antioxidant therapy and improved outcomes.

Hydrogen peroxide increases extracellular matrix mRNA through TGF-beta in human mesangial cells

BACKGROUND

Reactive oxygen species (ROS) are excessively produced in pathologic states, including many renal diseases. Transforming growth factor-beta (TGF-beta) may mediate renal fibrotic injury, and ROS may act through the TGF-beta pathway to exert a profibrotic effect.

METHODS

The expression of TGF-beta1 and extracellular matrix (ECM) components were assessed in cultured human mesangial cells (HMCs) incubated with glucose oxidase (GO), an enzyme that continuously generates hydrogen peroxide from glucose. A neutralizing anti-TGF-beta antibody was added to test the hypothesis that hydrogen peroxide acts through activation of the TGF-beta pathway to stimulate ECM expression.

RESULTS

Northern blot analysis revealed significantly increased steady-state levels of TGF-beta1 and ECM proteins (collagen types I, III, and IV, and fibronectin) by approximately twofold. While no significant effect on mRNA stability after treatment with GO was observed, other studies employing promoter-reporter assays, competitive-quantitative reverse transcription-polymerase chain reaction, mink lung epithelial cell proliferation assay, and TGF-beta1 enzyme-linked immunosorbent assay all demonstrated significant stimulation by GO (>1.5-fold) of TGF-beta1 promoter activity, mRNA level, bioactivity, and protein production, respectively. Catalase pretreatment prevented the GO-induced stimulation of TGF-beta1 mRNA. When incubations were performed with a panselective neutralizing anti-TGF-beta antibody, the GO-stimulated expression of ECM molecules was prevented.

CONCLUSIONS

GO-induced hydrogen peroxide production induces TGF-beta1 synthesis and thereby increases ECM gene expression in cultured HMCs. These cellular responses may underlie the development and progression of renal diseases characterized by oxidative stress.

Profiles of antioxidant/electrophile response element (ARE/EpRE) nuclear protein binding and c-Ha-ras transactivation in vascular smooth muscle cells treated with oxidative metabolites of benzo[a]pyrene

Activation of nuclear protein binding to the antioxidant/electrophile response element (ARE/EpRE) by benzo[a]pyrene (BaP) in vascular smooth muscle cells (vSMCs) is associated with transcriptional deregulation of c-Ha-ras. This response may be mediated by oxidative intermediates of BaP generated during the course of cellular metabolism. To test this hypothesis, the profile of ARE/EpRE protein binding and transactivation elicited by BaP was compared with that of 3-hydroxy BaP (3-OH BaP) (0.03 to 3.0 microM), BaP 7,8-dihydrodiol (BaP 7,8-diol) (0.03 to 3.0 microM), BaP 3,6-quinone (BaP 3,6-Q) (0.0003 to 3.0 microM), and H(2)O(2) (25 to 100 microM). Specific protein binding to the consensus c-Ha-ras ARE/EpRE was observed in vSMCs treated with all BaP metabolites at concentrations considerably lower than those required for the parent compound. H(2)O(2), a by-product of BaP 3,6-Q redox cycling, also increased binding to the ARE/EpRE. Treatment of vSMCs with oxidative BaP metabolites or H(2)O(2) transactivated the c-Ha-ras promoter in all instances, but the response was consistently half of the maximal induction elicited by BaP. Similar proteins cross-linked specifically to the consensus c-Ha-ras ARE/EpRE sequence in cells treated with BaP or its oxidative intermediates. The protein binding profile in the c-Ha-ras promoter was similar to that in the NADPH:quinone reductase gene (NQO(1)) and the glutathione S-transferase Ya gene (GSTYa) promoters, but the relative abundance of individual complexes was promoter-specific. We conclude that oxidative intermediates of BaP mediate activation of nuclear protein binding to ARE/EpRE and contribute to transcriptional de-regulation of c-Ha-ras in vSMCs.

Negative feedback regulation of reactive oxygen species on AT1 receptor gene expression

Free radicals as well as the AT1 receptor are involved in the pathogenesis of cardiovascular disease. Both the intracellular mechanisms of AT1 receptor regulation and the effect of free radicals on AT1 receptor expression are currently unknown. This study investigates the role of free radicals in the modulation of AT1 receptor expression and in the angiotensin II-induced AT1 receptor regulation. AT1 receptor mRNA was assessed by Northern blotting and AT1 receptor density by radioligand binding assays, respectively, in vascular smooth muscle cells (VSMC). Free radical release was measured by confocal laser scanning microscopy. AT1 receptor mRNA transcription rate was determined by nuclear run-on assays and AT1 receptor mRNA half-life was measured under transcriptional blockade. Angiotensin II caused a time-dependent decrease of AT1 receptor mRNA expression in rat VSMC in culture (30+/-6% at 4 h with 100 nM angiotensin II). This was followed by a consistent decrease in AT1 receptor density. Angiotensin II caused release of reactive oxygen species in VSMC which was abolished by preincubation with 100 microM diphenylene iodonium (DPI). DPI inhibited partially the down-regulating effect of angiotensin II on the AT1 receptor. Incubation of VSMC with either hydrogen peroxide or xanthine/xanthine oxidase caused a dose-dependent decrease in AT1 receptor mRNA expression which was not mediated by a decreased rate of transcription but rather through destabilization of AT1 receptor mRNA. Experiments which included preincubation of VSMC with various intracellular inhibitors suggested that free radicals caused AT1 receptor downregulation through activation of p38-MAP kinase and intracellular release of calcium. However, angiotensin II-induced AT1 receptor expression was not inhibited by blockade of p38-MAP kinase activation or intracellular calcium release. Free radicals may at least in part mediate angiotensin II-induced AT1 receptor regulation through direct post-transcriptional effects on AT1 receptor mRNA expression which involves intracellular release of calcium and activation of p38-MAP kinase. These findings may help to clarify the intracellular mechanisms involved in AT1 receptor regulation and reveal a novel biological feature for reactive oxygen species.

Role of reactive oxygen species in bradykinin-induced mitogen-activated protein kinase and c-fos induction in vascular cells

Bradykinin stimulates proliferation of aortic vascular smooth muscle cells (VSMCs). We investigated the action of bradykinin on the phosphorylation state of the mitogen-activated protein kinases p42(mapk) and p44(mapk) in VSMCs and tested the hypothesis that reactive oxygen species (ROS) might be involved in the signal transduction pathway linking bradykinin activation of nuclear transcription factors to the phosphorylation of p42(mapk) and p44(mapk). Bradykinin (10(-8) mol/L) rapidly increased (4- to 5-fold) the phosphorylation of p42(mapk) and p44(mapk) in VSMCs. Preincubation of VSMCs with either N-acetyl-L-cysteine and/or alpha-lipoic acid significantly decreased bradykinin-induced cytosolic and nuclear phosphorylation of p42(mapk) and p44(mapk). In addition, the induction c-fos mRNA levels by bradykinin was completely abolished by N-acetyl-L-cysteine and alpha-lipoic acid. Using the cell-permeable fluorescent dye dichlorofluorescein diacetate, we determined that bradykinin (10(-8) mol/L) rapidly increased the generation of ROS in VSMCs. The NADPH oxidase inhibitor diphenylene iodonium (DPI) blocked bradykinin-induced c-fos mRNA expression and p42(mapk) and p44(mapk) activation, implicating NADPH oxidase as the source for the generation of ROS. These findings demonstrate that the phosphorylation of cytosolic and nuclear p42(mapk) and p44(mapk) and the expression of c-fos mRNA in VSMCs in response to bradykinin are mediated via the generation of ROS and implicate ROS as important mediators in the signal transduction pathway through which bradykinin promotes VSMC proliferation in states of vascular injury.

Identification of oxidative stress-regulated genes in rat aortic smooth muscle cells by suppression subtractive hybridization

A suppression subtractive hybridization technique was used to identify reactive oxygen species (ROS)-regulated genes in rat vascular smooth muscle cells. Three genes out of 89 clones, identified as fibronectin, p105 coactivator and ECA39, showed increased expression after treatment with H(2)O(2). The mRNA expressions of these three genes were induced in a time- and dose-dependent manner, independent of protein kinase C activation. Immunohistochemical staining showed that the p105 coactivator expression was markedly induced in the neointima of balloon-injured rat carotid arteries. These results suggest that ROS may play an important role in the development of atherosclerosis by regulating the gene expressions we identified in this study.

Vascular effects of non-esterified fatty acids: implications for the cardiovascular risk factor cluster

Insulin resistance emerges as a central component of the risk factor cluster and is a likely contributor to vascular disease independently of traditional risk factors such as hypertension and diabetes mellitus. However, the intermediary mechanisms by which atherosclerosis is accelerated among patients with the insulin resistance syndrome remain inadequately defined. Most of the attention has centered on hyperinsulinemia and defects of insulin-mediated glucose disposal. However, we observed that obese hypertensive patients have elevated plasma concentrations of non-esterified fatty acids (NEFAs), including oleic acid, which are highly resistant to suppression by insulin. Resistance to insulin's fatty acid lowering action correlate with blood pressure in obese subjects independently of defects in glucose disposal. This observation raises the possibility that NEFAs have biologically significant effects on the cardiovascular system. In fact, oleic acid impairs nitric oxide synthase activity and endothelium-dependent vasorelaxation in vitro. Moreover, raising NEFAs in normal human volunteers to levels observed in obese hypertensive patients impairs lower extremity endothelium-dependent vasodilation and augments local and systemic vascular alpha1-adrenoceptor reactivity in normal volunteers. Thus, raising NEFAs replicates in healthy subjects important functional vascular changes implicated in the hypertension and atherosclerosis observed in patients with the risk factor cluster. At a molecular level, experiments in cultured vascular smooth muscle cells demonstrate that oleic acid activates a mitogenic signaling cascade which includes protein kinase C, reactive oxygen species and extracellular signal-regulated kinases. Each of these signaling events has been implicated in the structural and functional vascular changes which accompany the risk factor cluster. Collectively, these observations raise the possibility that fatty acids contribute to functional and structural vascular changes among insulin-resistant individuals. A better understanding of the signaling mechanisms by which NEFAs exert their vascular effects may facilitate novel and more effective therapeutic approaches to managing the cardiovascular risk factor cluster.

Cyclic stretch regulates autocrine IGF-I in vascular smooth muscle cells: implications in vascular hyperplasia

Vascular smooth muscle cells (VSMC) subjected to acute or chronic stretch display enhanced growth rates in vitro and in vivo. Clinical examples of vascular hyperplasia (e.g., systolic hypertension and postinjury restenosis) suggest that local insulin-like growth factor I (IGF-I) expression is enhanced. Therefore, we investigated the role of in vitro cyclic stretch on rat VSMC IGF-I secretion and cellular growth. In serum-free medium, cyclic stretch (1 Hz at 120% resting length for 48 h) stimulated thymidine incorporation approximately 40% above that seen in nonstretched cells. Graded stretch magnitude (100-125% resting length) yielded graded increases in VSMC growth. Exogenous IGF-I increased growth of serum-starved, nonstretched VSMC in a dose-dependent manner, with maximal growth seen with 10(-7) M. IGF-I secretion from stretched cells was 20- to 30-fold greater than from those cells cultured in a static environment. Stretch-induced increases in growth were completely blocked on addition of anti-IGF-I and partially blocked with platelet-derived growth factor (PDGF) antibodies and with a tyrosine kinase inhibitor (tyrphostin-1). Finally, blockade of stretch-activated cation channels with GdCl3 profoundly inhibited stretch-induced growth. We conclude that stretch increases VSMC IGF-I secretion and that such autocrine IGF-I is required for stretch-induced growth. PDGF and stretch-sensitive cation channels are likely additional components of a complex pathway that regulates stretch-induced VSMC seen in systolic hypertension and postinjury restenosis.

Reactive oxygen species are critical in the oleic acid-mediated mitogenic signaling pathway in vascular smooth muscle cells

Obese hypertensive patients with cardiovascular risk factor clustering have increased plasma nonesterified fatty acid levels and are at high risk for atherosclerotic events. Our previous studies demonstrated that oleic acid induces a mitogenic response in rat aortic smooth muscle cells (RASMCs) through protein kinase C (PKC)- and extracellular signal-regulated kinase (ERK)-dependent pathways. In the present study we investigated the possibility that the generation of reactive oxygen species (ROS) constitutes a critical component of the oleic acid-induced mitogenic signaling pathway in RASMCs. We studied the effect(s) of oleic acid on the generation of ROS using the oxidant-sensitive fluoroprobe 2',7'-dichlorofluorescin diacetate. Relative fluorescence intensity and fluorescent images were obtained with laser confocal scanning microscopy from 1 to 5 minutes, since preliminary studies demonstrated that the peak fluorescence intensity occurred within 5 minutes. Oleic acid (100 micromol/L) induced a time-dependent increase of cell fluorescence that was >8-fold of that seen in control cells at 5 minutes. This was blocked by catalase, which suggests that H2O2 was the principal ROS. The oleic acid-induced increases in H2O2 were blocked when PKC was inhibited with the use of bisindolylmaleimide and when PKC activity was downregulated by exposing RASMCs to phorbol 12-myristate 13-acetate for 24 hours. Stearic and elaidic acids, which are weak PKC activators, did not significantly increase H2O2 production. The increase of H2O2 in response to oleic acid was inhibited by the antioxidant N-acetylcysteine. N-Acetylcysteine also completely blocked ERK activation and the increase of thymidine incorporation in response to oleic acid. The data suggest that generation of H2O2 in RASMCs exposed to oleic acid is PKC dependent. Moreover, H2O2 production emerges as a critical intermediary event in the oleic acid-mediated mitogenic signaling pathway between the activation of PKC and ERK. These observations raise the possibility that the elevated plasma nonesterified fatty acids, including oleic acid, in obese hypertensive patients contribute to vascular growth and remodeling by a PKC-dependent mechanism to generate ROS that subsequently activate ERK.

Angiotensin II induces superoxide anion production by mesangial cells

BACKGROUND

The recognized role of angiotensin II (Ang II) in the pathogenesis of the progression of renal disease cannot be solely attributed to Ang II's hemodynamic effects. Indeed, growth stimulating signals driven by Ang II promote mesangial cell (MC) hypertrophy and extracellular matrix production, prominent features of progressive glomerular injury. Superoxide anion (O2-) avidly interacts with nitric oxide, an endogenous vasodilator that inhibits growth factor stimulated MC growth and matrix production. In addition, O2- acting as an intracellular signal is linked to growth related responses such as activation of mitogen activated protein (MAP) kinases. The studies reported herein were designed to investigate: (a) whether Ang II induces MC O2-production and (b) if increased O2- production elicits growth responses in MC.

METHODS

MC were exposed to Ang II for 24 or 48 hours. In some experiments, in addition to Ang II, MC were exposed to: diphenylenieodonium (DPI), an inhibitor of the flavin containing NADH/NADPH oxidase; losartan (LOS), an Ang II type 1 (AT1) receptor blocker; PD 98059, a MAP kinases inhibitor; the protein kinase C inhibitors Calphostin C or H-7; and the tyrosine kinase inhibitors, herbymycin A or genistein.

RESULTS

Ang II (10(-5) M to 10(-8) M) dose dependently increased MC O2- production up to 125% above control (ED 50 5 x 10(-7) M). LOS as well as DPI, and the PKC inhibitors blocked Ang II stimulated MC O2- production. Ang II dose dependently increased MC 3H-leucine incorporation, and MC protein content, two markers of MC hypertrophy, as well as 3H-thymidine incorporation, a marker of MC hyperplasia. PD98059, a specific inhibitor of MAP kinases prevented Ang II induced MC hypertrophy. Moreover, LOS, DPI, and the PKC inhibitors each independently inhibited MC 3H-leucine incorporation, thereby establishing the specificity of Ang II induced O2- in driving MC hypertrophy.

CONCLUSIONS

The current studies demonstrate a previously unrecognized link between Ang II and MC O2- production that may participate in the pathophysiology of progressive renal disease by concomitantly affecting the hemodynamics of the glomerular microcirculation as well as growth related responses of MC to injury.

Superoxide anion from the adventitia of the rat thoracic aorta inactivates nitric oxide

The purpose of this study was to determine whether superoxide anion is produced endogenously in the rat aortic adventitia and whether sufficient superoxide anion is produced to interfere with the response of the rat aorta to nitric oxide. Relaxation was measured in rings of the rat thoracic aorta, which were oriented so that the adventitial or luminal surface could be preferentially exposed to nitric oxide or sodium nitroprusside. To accomplish this, the rings were mounted (1) with the adventitia facing outward, (2) with the adventitia facing inward after inverting, or (3) with the adventitia facing outward after inverting twice (to control for the inverting procedure). The relaxation to nitric oxide, but not to sodium nitroprusside, was less in rings with the adventitia facing outward compared with those in which it faced inward. In contrast, the response to nitric oxide via either surface was similar when extracellular superoxide anion was scavenged with superoxide dismutase. Incubation of rings with nitro blue tetrazolium (NBT) resulted in blue formazan staining of the adventitia, and lucigenin chemiluminescence was significantly greater when detected from the adventitial compared with the intimal aspect of the artery. The reduction of NBT in intact aortic rings was 30+/-2 pmol x min(-1) x mg(-1) and was significantly decreased by superoxide dismutase to 19+/-2 pmol x min(-1) x mg(-1) and by a synthetic superoxide dismutase mimic, Euk-8, to 11+/-2 pmol x min(-1) x mg(-1). The NADPH oxidase inhibitor, diphenyleneiodonium, decreased NBT reduction to 9+/-1 pmol x min(-1) x mg(-1), whereas inhibitors of xanthine oxidase, mitochondrial oxidases, and nitric oxide synthase were ineffective. Immunohistochemical staining indicated the localization of NADPH oxidase proteins gp91phox, p22phox, p47phox, and p67phox almost exclusively in the adventitia of the rat aorta with no substantial staining in the media. These results indicate that NADPH oxidase located in the adventitia of rat thoracic aorta generates sufficient extracellular superoxide anion to constitute a barrier capable of inactivating nitric oxide. This study suggests that adventitial superoxide anion can play a role in the pathophysiology of the arterial wall.

Oxidized collagen stimulates proliferation of vascular smooth muscle cells

We hypothesize that the vascular smooth muscle proliferation after lung injury results from oxidative damage to the matrix proteins in the walls of pulmonary blood vessels. The smooth muscle cells (SMC) isolated from rat aorta were cultured on the surface coated with oxidized and nonoxidized (control) collagen of type I. Oxidation of collagen was induced by UV irradiation and characterized by fluorescence tridimensional spectral arrays and by gel electrophoresis. From day 1 to 6 of the experiment, SMC proliferated more rapidly on the oxidized collagen than on the control surface. At high SMC population densities (day 9 of experiment) the difference disappeared. After 10 min of trypsinization the cells growing on oxidized collagen rounded and detached completely from the growth surface. The control cells on nonoxidized collagen detached only after 30 min of trypsinization. We conclude that oxidation of collagen of vascular wall matrix may participate in stimulation of SMC proliferation after oxidant tissue injury.