Vascular effects following homozygous disruption of p47(phox) : An essential component of NADPH oxidase

Nox2 Deficiency Reduces Cartilage Damage and Ectopic Bone Formation in an Experimental Model for Osteoarthritis

Osteoarthritis (OA) is a destructive disease of the joint with age and obesity being its most important risk factors. Around 50% of OA patients suffer from inflammation of the synovial joint capsule, which is characterized by increased abundance and activation of synovial macrophages that produce reactive oxygen species (ROS) via NADPH-oxidase 2 (NOX2). Both ROS and high blood levels of low-density lipoprotein (LDL) are implicated in OA pathophysiology, which may interact to form oxidized LDL (oxLDL) and thereby promote disease. Therefore, targeting NOX2 could be a viable treatment strategy for OA. Collagenase-induced OA (CiOA) was used to compare pathology between wild-type (WT) and Nox2 knockout (Nox2^−/−) C57Bl/6 mice. Mice were either fed a standard diet or Western diet (WD) to study a possible interaction between NOX2-derived ROS and LDL. Synovial inflammation, cartilage damage and ectopic bone size were assessed on histology. Extracellular ROS production by macrophages was measured in vitro using the Amplex Red assay. Nox2^−/− macrophages produced basal levels of ROS but were unable to increase ROS production in response to the alarmin S100A8 or the phorbol ester PMA. Interestingly, Nox2 deficiency reduced cartilage damage, synovial lining thickness and ectopic bone size, whereas these disease parameters were not affected by WD-feeding. These results suggest that NOX2-derived ROS are involved in CiOA development.

Regulation of NADPH Oxidase-Mediated Superoxide Production by Acetylation and Deacetylation

Oral treatment of apolipoprotein E-knockout (ApoE-KO) mice with the putative sirtuin 1 (SIRT1) activator resveratrol led to a reduction of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in the heart. In contrast, the SIRT1 inhibitor EX527 enhanced the superoxide production in isolated human polymorphonuclear granulocytes. In human monocytic THP-1 cells, phorbol ester-stimulated superoxide production was enhanced by inhibitors of histone deacetylases (HDACs; including quisinostat, trichostatin A (TSA), PCI34051, and tubastatin A) and decreased by inhibitors of histone acetyltransferases [such as garcinol, curcumin, and histone acetyltransferase (HAT) Inhibitor II]. These results indicate that protein acetylation and deacetylation may represent crucial mechanisms regulating NADPH oxidase-mediated superoxide production. In cell-free systems, incubation of recombinant Rac1 with SIRT1 resulted in decreased Rac1 acetylation. Mass spectrometry analyses identified lysine 166 (K166) in Rac1 as a residue targeted by SIRT1. Deacetylation of Rac1 by SIRT1 markedly reduced the interaction of Rac1 with p67phox in in vitro assays. Computational modeling analyses revealed that K166 deacetylation of Rac1 led to a 5-fold reduction in its binding affinity to guanosine-5'-triphosphate, and a 21-fold decrease in its binding potential to p67phox. The latter is crucial for Rac1-mediated recruitment of p67phox to the membrane and for p67phox activation. In conclusion, both SIRT1 and non-sirtuin deacetylases play a role in regulating NADPH oxidase activity. Rac1 can be directly deacetylated by SIRT1 in a cell-free system, leading to an inhibition of Rac1-p67phox interaction. The downstream targets of non-sirtuin deacetylases are still unknown. The in vivo significance of these findings needs to be investigated in future studies.

Role of reactive oxygen species in atherosclerosis: Lessons from murine genetic models

Atherosclerosis is a multifactorial chronic and inflammatory disease of medium and large arteries, and the major cause of cardiovascular morbidity and mortality worldwide. The pathogenesis of atherosclerosis involves a number of risk factors and complex events including hypercholesterolemia, endothelial dysfunction, increased permeability to low density lipoproteins (LDL) and their sequestration on extracellular matrix in the intima of lesion-prone areas. These events promote LDL modifications, particularly by oxidation, which generates acute and chronic inflammatory responses implicated in atherogenesis and lesion progression. Reactive oxygen species (ROS) (which include both free radical and non-free radical oxygen intermediates), play a key-role at each step of atherogenesis, in endothelial dysfunction, LDL oxidation, and inflammatory events involved in the initiation and development of atherosclerosis lesions. Most advanced knowledge supporting the "oxidative theory of atherosclerosis" i.e. the nature and the cellular sources of ROS and antioxidant defences, as well as the mechanisms involved in the redox balance, is based on the use of genetically engineered animals, i.e. transgenic, genetically modified, or altered for systems producing or neutralizing ROS in the vessels. This review summarizes the results obtained from animals genetically manipulated for various sources of ROS or antioxidant defences in the vascular wall, and their relevance (advance or limitation), for understanding the place and role of ROS in atherosclerosis.

Microarray and proteome array in an atherosclerosis mouse model for identification of biomarkers in whole blood

Cardiovascular disease (CVD) is highly fatal, and 80 percent of the mortality is attributed to heart attack and stroke. Atherosclerosis is a disease that increases a patient's risk to CVD and is characterized by atheroma formed by immune cells, lipids, and smooth muscle cells. When an atherosclerotic lesion grows and blocks blood vessels or when an atheroma ruptures and blocks blood vessels by embolism, sudden angina, or stroke can occur. It is therefore important to diagnose atherosclerosis early and prevent its progression to more severe disease. Although myeloperoxidase, plasma fibrinogen, cardiac troponin-I, and C-reactive protein have been considered as diagnostic markers for multiple cardiac risks, specific biomarkers for atherosclerosis have not been clearly determined yet. Particularly, reliable biomarkers for the diagnosis of atherosclerosis using whole blood are not yet available. In this study, we screened potential biomarker genes and proteins from whole blood of apolipoprotein E knockout (ApoE-/- ) mice maintained on a Western diet, by comparing them to ApoE+/+ mice. We used whole blood for microarray and proteome array. Candidate genes and proteins identified from each method were confirmed with quantitative real-time PCR and ELISA. Based on our data, we speculate that Lilrb4a, n-R5s136, and IL-5 are potential targets that can be developed into novel biomarkers of atherosclerosis. Our study contributes to the diagnosis of atherosclerosis using whole blood in clinical settings.

Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation

Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.

Reactive Oxygen Species in Metabolic and Inflammatory Signaling

Reactive oxygen species (ROS) are well known for their role in mediating both physiological and pathophysiological signal transduction. Enzymes and subcellular compartments that typically produce ROS are associated with metabolic regulation, and diseases associated with metabolic dysfunction may be influenced by changes in redox balance. In this review, we summarize the current literature surrounding ROS and their role in metabolic and inflammatory regulation, focusing on ROS signal transduction and its relationship to disease progression. In particular, we examine ROS production in compartments such as the cytoplasm, mitochondria, peroxisome, and endoplasmic reticulum and discuss how ROS influence metabolic processes such as proteasome function, autophagy, and general inflammatory signaling. We also summarize and highlight the role of ROS in the regulation metabolic/inflammatory diseases including atherosclerosis, diabetes mellitus, and stroke. In order to develop therapies that target oxidative signaling, it is vital to understand the balance ROS signaling plays in both physiology and pathophysiology, and how manipulation of this balance and the identity of the ROS may influence cellular and tissue homeostasis. An increased understanding of specific sources of ROS production and an appreciation for how ROS influence cellular metabolism may help guide us in the effort to treat cardiovascular diseases.

Cellular and Oxidative Mechanisms Associated with Interleukin-6 Signaling in the Vasculature

Reactive oxygen species, particularly superoxide, promote endothelial dysfunction and alterations in vascular structure. It is increasingly recognized that inflammatory cytokines, such as interleukin-6 (IL-6), contribute to endothelial dysfunction and vascular hypertrophy and fibrosis. IL-6 is increased in a number of cardiovascular diseases, including hypertension. IL-6 is also associated with a higher incidence of future cardiovascular events and all-cause mortality. Both immune and vascular cells produce IL-6 in response to a number of stimuli, such as angiotensin II. The vasculature is responsive to IL-6 produced from vascular and non-vascular sources via classical IL-6 signaling involving a membrane-bound IL-6 receptor (IL-6R) and membrane-bound gp130 via Jak/STAT as well as SHP2-dependent signaling pathways. IL-6 signaling is unique because it can also occur via a soluble IL-6 receptor (sIL-6R) which allows for IL-6 signaling in tissues that do not normally express IL-6R through a process referred to as IL-6 trans-signaling. IL-6 signaling mediates a vast array of effects in the vascular wall, including endothelial activation, vascular permeability, immune cell recruitment, endothelial dysfunction, as well as vascular hypertrophy and fibrosis. Many of the effects of IL-6 on vascular function and structure are representative of loss or reductions in nitric oxide (NO) bioavailability. IL-6 has direct effects on endothelial nitric oxide synthase activity and expression as well as increasing vascular superoxide, which rapidly inactivates NO thereby limiting NO bioavailability. The goal of this review is to highlight both the cellular and oxidative mechanisms associated with IL-6-signaling in the vascular wall in general, in hypertension, and in response to angiotensin II.

Organizers and activators: Cytosolic Nox proteins impacting on vascular function

NADPH oxidases of the Nox family are important enzymatic sources of reactive oxygen species (ROS) in the cardiovascular system. Of the 7 members of the Nox family, at least three depend for their activation on specific cytosolic proteins. These are p47phox and its homologue NoxO1 and p67phox and its homologue NoxA1. Also the Rho-GTPase Rac is important but as this protein has many additional functions, it will not be covered here. The Nox1 enzyme is preferentially activated by the combination of NoxO1 with NoxA1, whereas Nox2 gains highest activity with p47phox together with p67phox. As p47phox, different to NoxO1 contains an auto inhibitory region it has to be phosphorylated prior to complex formation. In the cardio-vascular system, all cytosolic Nox proteins are expressed but the evidence for their contribution to ROS production is not well established. Most data have been collected for p47phox, whereas NoxA1 has basically not yet been studied. In this article the specific aspects of cytosolic Nox proteins in the cardiovascular system with respect to Nox activation, their expression and their importance will be reviewed. Finally, it will be discussed whether cytosolic Nox proteins are suitable pharmacological targets to tamper with vascular ROS production.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

The Importance of NADPH Oxidases and Redox Signaling in Angiogenesis

Eukaryotic cells have to cope with the constant generation of reactive oxygen species (ROS). Although the excessive production of ROS might be deleterious for cell biology, there is a plethora of evidence showing that moderate levels of ROS are important for the control of cell signaling and gene expression. The family of the nicotinamide adenine dinucleotide phosphate oxidases (NADPH oxidases or Nox) has evolved to produce ROS in response to different signals; therefore, they fulfil a central role in the control of redox signaling. The role of NADPH oxidases in vascular physiology has been a field of intense study over the last two decades. In this review we will briefly analyze how ROS can regulate signaling and gene expression. We will address the implication of NADPH oxidases and redox signaling in angiogenesis, and finally, the therapeutic possibilities derived from this knowledge will be discussed.

The Pathophysiological Role of NOX2 in Hypertension and Organ Damage

NADPH oxidases (NOXs) represent one of the major sources of reactive oxygen species in the vascular district. Reactive oxygen species are responsible for vascular damage that leads to several cardiovascular pathological conditions. Among NOX isoforms, NOX2 is widely expressed in many cells types, such as cardiomyocytes, endothelial cells, and vascular smooth muscle cells, confirming its pivotal role in vascular pathophysiology. Studies in mice models with systemic deletion of NOX2, as well as in transgenic mice overexpressing NOX2, have demonstrated the undeniable involvement of NOX2 in the development of hypertension, atherosclerosis, diabetes mellitus, cardiac hypertrophy, platelet aggregation, and aging. Of note, the inhibition of NOX2 has been found to be protective for cardiovascular homeostasis. Here, we review the evidence demonstrating that the modulation of NOX2 activity is able to improve vascular physiology, suggesting that NOX2 may be a potential target for therapeutic applications.

Reactive oxygen species in endothelial function - from disease to adaptation -

Endothelial function is largely dictated by its ability to rapidly sense environmental cues and adapt to these stimuli through changes in vascular tone, inflammation/immune recruitment, and angiogenesis. When any one of these abilities is compromised, the endothelium becomes dysfunctional, which ultimately leads to disease. Reactive oxygen species (ROS) have been established at the forefront of endothelial dysfunction; however, more careful examination has demonstrated that ROS are fundamental to each of the sensing/signaling roles of the endothelium. The purpose of this review is to document endothelial ROS production in both disease and physiological adaptation. Through understanding new endothelial signaling paradigms, we will gain insight into more targeted therapeutic strategies for vascular diseases.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Assessment of atherosclerosis in chronic granulomatous disease

BACKGROUND

Patients with chronic granulomatous disease (CGD) experience immunodeficiency because of defects in the phagocyte NADPH oxidase and the concomitant reduction in reactive oxygen intermediates. This may result in a reduction in atherosclerotic injury.

METHODS AND RESULTS

We prospectively assessed the prevalence of cardiovascular risk factors, biomarkers of inflammation and neutrophil activation, and the presence of magnetic resonance imaging and computed tomography quantified subclinical atherosclerosis in the carotid and coronary arteries of 41 patients with CGD and 25 healthy controls in the same age range. Univariable and multivariable associations among risk factors, inflammatory markers, and atherosclerosis burden were assessed. Patients with CGD had significant elevations in traditional risk factors and inflammatory markers compared with control subjects, including hypertension, high-sensitivity C-reactive protein, oxidized low-density lipoprotein, and low high-density lipoprotein. Despite this, patients with CGD had a 22% lower internal carotid artery wall volume compared with control subjects (361.3±76.4 mm(3) versus 463.5±104.7 mm(3); P<0.001). This difference was comparable in p47(phox)- and gp91(phox)-deficient subtypes of CGD and independent of risk factors in multivariate regression analysis. In contrast, the prevalence of coronary arterial calcification was similar between patients with CGD and control subjects (14.6%, CGD; 6.3%, controls; P=0.39).

CONCLUSIONS

The observation by magnetic resonance imaging and computerized tomography of reduced carotid but not coronary artery atherosclerosis in patients with CGD despite the high prevalence of traditional risk factors raises questions about the role of NADPH oxidase in the pathogenesis of clinically significant atherosclerosis. Additional high-resolution studies in multiple vascular beds are required to address the therapeutic potential of NADPH oxidase inhibition in cardiovascular diseases.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01063309.

Rosuvastatin prevents angiotensin II-induced vascular changes by inhibition of NAD(P)H oxidase and COX-1

BACKGROUND AND PURPOSE

NAD(P)H oxidase and COX-1 participate in vascular damage induced by angiotensin II. We investigated the effect of rosuvastatin on endothelial dysfunction, vascular remodelling, changes in extracellular matrix components and mechanical properties of small mesenteric arteries from angiotensin II-infused rats.

EXPERIMENTAL APPROACH

Male rats received angiotensin II (120 ng·kg⁻¹ ·min⁻¹ , subcutaneously) for 14 days with or without rosuvastatin (10 mg·kg⁻¹ ·day⁻¹ , oral gavage) or vehicle. Vascular functions and morphological parameters were assessed by pressurized myography.

KEY RESULTS

In angiotensin II-infused rats, ACh-induced relaxation was attenuated compared with controls, less sensitive to L-NAME, enhanced by SC-560 (COX-1 inhibitor) or SQ-29548 (prostanoid TP receptor antagonist), and normalized by the antioxidant ascorbic acid or NAD(P)H oxidase inhibitors. After rosuvastatin, relaxations to ACh were normalized, fully sensitive to L-NAME, and no longer affected by SC-560, SQ-29548 or NAD(P)H oxidase inhibitors. Angiotensin II enhanced intravascular superoxide generation, eutrophic remodelling, collagen and fibronectin depositions, and decreased elastin content, resulting in increased vessel stiffness. All these changes were prevented by rosuvastatin. Angiotensin II increased phosphorylation of NAD(P)H oxidase subunit p47phox and its binding to subunit p67phox, effects inhibited by rosuvastatin. Rosuvastatin down-regulated vascular Nox4/NAD(P)H isoform and COX-1 expression, attenuated the vascular release of 6-keto-PGF1α , and enhanced copper/zinc-superoxide dismutase expression.

CONCLUSION AND IMPLICATIONS

Rosuvastatin prevents angiotensin II-induced alterations in resistance arteries in terms of function, structure, mechanics and composition. These effects depend on restoration of NO availability, prevention of NAD(P)H oxidase-derived oxidant excess, reversal of COX-1 induction and its prostanoid production, and stimulation of endogenous vascular antioxidant defences.

Vascular oxidative stress, nitric oxide and atherosclerosis

In the vascular wall, reactive oxygen species (ROS) are produced by several enzyme systems including NADPH oxidase, xanthine oxidase, uncoupled endothelial nitric oxide synthase (eNOS) and the mitochondrial electron transport chain. On the other hand, the vasculature is protected by antioxidant enzyme systems, including superoxide dismutases, catalase, glutathione peroxidases and paraoxonases, which detoxify ROS. Cardiovascular risk factors such as hypercholesterolemia, hypertension, and diabetes mellitus enhance ROS generation, resulting in oxidative stress. This leads to oxidative modification of lipoproteins and phospholipids, mechanisms that contribute to atherogenesis. In addition, oxidation of tetrahydrobiopterin may cause eNOS uncoupling and thus potentiation of oxidative stress and reduction of eNOS-derived NO, which is a protective principle in the vasculature. This review summarizes the latest advances in the role of ROS-producing enzymes, antioxidative enzymes as well as NO synthases in the initiation and development of atherosclerosis.

Endothelial NADPH oxidases: which NOX to target in vascular disease?

NADPH oxidases (NOXs) are reactive oxygen species (ROS)-generating enzymes implicated in the pathophysiology of vascular diseases such as hypertension and stroke. Endothelial cells express four NOX isoforms including the superoxide-generating enzymes NOX1, NOX2, and NOX5 and the hydrogen peroxide-generating enzyme NOX4. Studies on arteries from patients with coronary artery disease, and in animals with experimentally induced hypertension, diabetes, or atherosclerosis, suggest that NOX1, NOX2, and NOX5 promote endothelial dysfunction, inflammation, and apoptosis in the vessel wall, whereas NOX4 is by contrast vasoprotective in increasing nitric oxide bioavailability and suppressing cell death pathways. Based on these findings and promising preclinical studies with the NOX1/NOX2 antagonist, apocynin, we suggest that the field is poised for clinical evaluation of NOX inhibitors as therapeutics for cardiovascular disease.

NADPH oxidases in vascular pathology

SIGNIFICANCE

Reactive oxygen species (ROS) play a critical role in vascular disease. While there are many possible sources of ROS, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases play a central role. They are a source of "kindling radicals," which affect other enzymes, such as nitric oxide synthase endothelial nitric oxide synthase or xanthine oxidase. This is important, as risk factors for atherosclerosis (hypertension, diabetes, hypercholesterolemia, and smoking) regulate the expression and activity of NADPH oxidases in the vessel wall.

RECENT ADVANCES

There are seven isoforms in mammals: Nox1, Nox2, Nox3, Nox4, Nox5, Duox1 and Duox2. Nox1, Nox2, Nox4, and Nox5 are expressed in endothelium, vascular smooth muscle cells, fibroblasts, or perivascular adipocytes. Other homologues have not been found or are expressed at very low levels; their roles have not been established. Nox1/Nox2 promote the development of endothelial dysfunction, hypertension, and inflammation. Nox4 may have a role in protecting the vasculature during stress; however, when its activity is increased, it may be detrimental. Calcium-dependent Nox5 has been implicated in oxidative damage in human atherosclerosis.

CRITICAL ISSUES

NADPH oxidase-derived ROS play a role in vascular pathology as well as in the maintenance of normal physiological vascular function. We also discuss recently elucidated mechanisms such as the role of NADPH oxidases in vascular protection, vascular inflammation, pulmonary hypertension, tumor angiogenesis, and central nervous system regulation of vascular function and hypertension.

FUTURE DIRECTIONS

Understanding the role of individual oxidases and interactions between homologues in vascular disease is critical for efficient pharmacological regulation of vascular NADPH oxidases in both the laboratory and clinical practice.

Hemodynamic regulation of reactive oxygen species: implications for vascular diseases

SIGNIFICANCE

Arterial blood vessels functionally and structurally adapt to altering hemodynamic forces in order to accommodate changing needs and to provide stress homeostasis. This ability is achieved at the cellular level by converting mechanical stimulation into biochemical signals (i.e., mechanotransduction). Physiological mechanical stress helps maintain vascular structure and function, whereas pathologic or aberrant stress may impair cellular mechano-signaling, and initiate or augment cellular processes that drive disease.

RECENT ADVANCES

Reactive oxygen species (ROS) may represent an intriguing class of mechanically regulated second messengers. Chronically enhanced ROS generation may be induced by adverse mechanical stresses, and is associated with a multitude of vascular diseases. Although a causal relationship has clearly been demonstrated in large numbers of animal studies, an effective ROS-modulating therapy still remains to be established by clinical studies.

CRITICAL ISSUES AND FUTURE DIRECTIONS

This review article focuses on the role of various mechanical forces (in the form of laminar shear stress, oscillatory shear stress, or cyclic stretch) as modulators of ROS-driven signaling, and their subsequent effects on vascular biology and homeostasis, as well as on specific diseases such as arteriosclerosis, hypertension, and abdominal aortic aneurysms. Specifically, it highlights the significance of the various NADPH oxidase (NOX) isoforms as critical ROS generators in the vasculature. Directed targeting of defined components in the complex network of ROS (mechano-)signaling may represent a key for successful translation of experimental findings into clinical practice.

Altered vascular activation due to deficiency of the NADPH oxidase component p22phox

BACKGROUND

Reactive oxygen species generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase play important roles in vascular activation. The p22(phox) subunit is necessary for the activity of NADPH oxidase complexes utilizing Nox1, Nox2, Nox3, and Nox4 catalytic subunits.

METHODS

We assessed p22(phox)-deficient mice and human tissue for altered vascular activation.

RESULTS

Mice deficient in p22(phox) were smaller than their wild-type littermates but showed no alteration in basal blood pressure. The wild-type littermates were relatively resistant to forming intimal hyperplasia following carotid ligation, and the intimal hyperplasia that developed was not altered by p22(phox) deficiency. However, at the site of carotid artery ligation, the p22(phox)-deficient mice showed significantly less vascular elastic fiber loss compared with their wild-type littermates. This preservation of elastic fibers was associated with a reduced matrix metallopeptidase (MMP) 12/tissue inhibitor of metalloproteinase (TIMP) 1 expression ratio. A similar decrease in the relative MMP12/TIMP1 expression ratio occurred in human coronary artery smooth muscle cells upon knockdown of the hydrogen peroxide responsive kinase CK1αLS. In the ligated carotid arteries, the p22(phox)-deficient mice showed reduced expression of heterogeneous nuclear ribonucleoprotein C (hnRNP-C), suggesting reduced activity of CK1αLS. In a lung biopsy from a human patient with p22(phox) deficiency, there was also reduced vascular hnRNP-C expression.

CONCLUSIONS

These findings indicate that NADPH oxidase complexes modulate aspects of vascular activation including vascular elastic fiber loss, the MMP12/TIMP1 expression ratio, and the expression of hnRNP-C. Furthermore, these findings suggest that the effects of NADPH oxidase on vascular activation are mediated in part by protein kinase CK1αLS.

Inhibition of NADPH oxidase by apocynin attenuates progression of atherosclerosis

Of the multiple sources of reactive oxygen species (ROS) in the blood vessel, NADPH oxidases are the primary source. Whereas several studies have implicated NADPH oxidases in the initiation of atherosclerosis, their roles in disease progression are incompletely understood. Our objective was to determine the potential clinical relevance of inhibiting NADPH oxidase in established atherosclerosis. Using a hypercholesteremic murine model of atherosclerosis (ApoE^−/−/LDLR^−/− (AS) mice on normal chow diet), we first established a time-dependent relationship between superoxide levels and lesion size in AS mice. Next, we identified NADPH oxidase as the primary source of ROS in atherosclerotic lesions. Treatment of aortic segments from AS mice with apocynin, which interferes with NADPH oxidase activation in part by preventing translocation of the subunit p47^phox, significantly reduced superoxide levels. Moreover, addition of apocynin to the drinking water of AS mice produced a decrease in lesion size as compared to untreated AS mice, with the effect most pronounced in the thoracoabdominal aorta but absent from the aortic arch. Granulocyte function in AS+apocynin mice was suppressed, confirming efficacy of apocynin treatment. We conclude that apocynin attenuates the progression of atherosclerosis in hypercholesterolemic mice, potentially by its ability to inhibit generation of superoxide by NADPH oxidase.

Actions of "antioxidants" in the protection against atherosclerosis

This review addresses the role of oxidative processes in atherosclerosis and its resulting cardiovascular disease by focusing on the outcome of antioxidant interventions. Although there is unambiguous evidence for the presence of heightened oxidative stress and resulting damage in atherosclerosis, it remains to be established whether this represents a cause or a consequence of the disease. This critical question is complicated further by the increasing realization that oxidative processes, including those related to signaling, are part of normal cell function. Overall, the results from animal interventions suggest that antioxidants provide benefit neither generally nor consistently. Where benefit is observed, it appears to be achieved at least in part via modulation of biological processes such as increase in nitric oxide bioavailability and induction of protective enzymes such as heme oxygenase-1, rather than via inhibition of oxidative processes and lipid oxidation in the arterial wall. Exceptions to this may be situations of multiple/excessive stress, the relevance of which for humans is not clear. This interpretation is consistent with the overall disappointing outcome of antioxidant interventions in humans and can be rationalized by the spatial compartmentalization of cellular oxidative signaling and/or damage, complex roles of oxidant-producing enzymes, and the multifactorial nature of atherosclerosis.

Biochemistry, physiology, and pathophysiology of NADPH oxidases in the cardiovascular system

The NADPH oxidase (Nox) enzymes are critical mediators of cardiovascular physiology and pathophysiology. These proteins are expressed in virtually all cardiovascular cells, and regulate such diverse functions as differentiation, proliferation, apoptosis, senescence, inflammatory responses and oxygen sensing. They target a number of important signaling molecules, including kinases, phosphatases, transcription factors, ion channels, and proteins that regulate the cytoskeleton. Nox enzymes have been implicated in many different cardiovascular pathologies: atherosclerosis, hypertension, cardiac hypertrophy and remodeling, angiogenesis and collateral formation, stroke, and heart failure. In this review, we discuss in detail the biochemistry of Nox enzymes expressed in the cardiovascular system (Nox1, 2, 4, and 5), their roles in cardiovascular cell biology, and their contributions to disease development.

The Nox family of NADPH oxidases: friend or foe of the vascular system?

NADPH (nicotinamide adenine dinucleotide phosphate) oxidases are important sources of reactive oxygen species (ROS). In the vascular system, ROS can have both beneficial and detrimental effects. Under physiologic conditions, ROS are involved in signaling pathways that regulate vascular tone as well as cellular processes like proliferation, migration and differentiation. However, high doses of ROS, which are produced after induction or activation of NADPH oxidases in response to cardiovascular risk factors and inflammation, contribute to the development of endothelial dysfunction and vascular disease. In vascular cells, the NADPH oxidase isoforms Nox1, Nox2, Nox4, and Nox5 are expressed, which differ in their activity, response to stimuli, and the type of ROS released. This review focuses on the specific role of different NADPH oxidase isoforms in vascular physiology and their potential contributions to vascular diseases.

New perspectives on endothelin-1 in atherosclerosis and diabetes mellitus

Endothelin-1 (ET-1) is a vasoconstrictor, proinflammatory and proliferative endothelial cell-derived peptide that is of significant importance in the regulation of vascular function. It is involved in the development of endothelial dysfunction including important interactions with nitric oxide. The expression and functional effects of ET-1 and its receptors are markedly altered during development of cardiovascular disease. Increased production of ET-1 and its receptors mediate many pathophysiological events contributing to the development of atherosclerosis and vascular complications in diabetes mellitus. The present review focuses on the pathophysiological role of ET-1 and the potential importance of ET receptors as a therapeutic target for treatment of these conditions.

Endothelial-specific Nox2 overexpression increases vascular superoxide and macrophage recruitment in ApoE⁻/⁻ mice

Aims

Vascular disease states are associated with endothelial dysfunction and increased production of reactive oxygen species derived from NADPH oxidases. However, it remains unclear whether a primary increase in superoxide production specifically in the endothelium alters the initiation or progression of atherosclerosis.

Methods and results

Mice overexpressing Nox2 specifically in the endothelium (Nox2-Tg) were crossed with ApoE^−/− mice to produce Nox2-Tg ApoE^−/− mice and ApoE^−/− littermates. Endothelial overexpression of Nox2 in ApoE^−/− mice did not alter blood pressure, but significantly increased vascular superoxide production compared with ApoE^−/− littermates, measured using both lucigenin chemiluminescence and 2-hydroxyethidium production (ApoE^−/−, 19.9 ± 6.3 vs. Nox2-Tg ApoE^−/−, 47.0 ± 7.0 nmol 2-hydroxyethidium/aorta, P< 0.05). Increased endothelial superoxide production increased endothelial levels of vascular cell adhesion protein 1 and enhanced macrophage recruitment in early lesions in the aortic roots of 9-week-old mice, indicating increased atherosclerotic plaque initiation. However, endothelial-specific Nox2 overexpression did not alter native or angiotensin II-driven atherosclerosis in either the aortic root or the descending aorta.

Conclusion

Endothelial-targeted Nox2 overexpression in ApoE^−/− mice is sufficient to increase vascular superoxide production and increase macrophage recruitment possible via activation of endothelial cells. However, this initial increase in macrophage recruitment did not alter the progression of atherosclerosis. These results indicate that Nox-mediated reactive oxygen species signalling has important cell-specific and distinct temporal roles in the initiation and progression of atherosclerosis.

Resveratrol reduces vascular cell senescence through attenuation of oxidative stress by SIRT1/NADPH oxidase-dependent mechanisms

OBJECTIVE

Senescence of vascular cells contributes to the development of cardiovascular diseases and the overall aging. This study was undertaken to investigate the effects of resveratrol (Res) on amelioration of vascular cell aging and the role of SIRT1/nicotinamide adenine dinucleotide phosphate (NADPH) oxidase pathway.

METHODS AND RESULTS

Adult male Wistar rats were treated with a high-fat/sucrose diet (HFS) in the presence or absence of Res for 3 months. HFS and in vitro treatment with high glucose increased the senescence cells and reactive oxygen species production in rat aorta and cultured bovine aortic endothelial cells (BAECs), respectively, which was attenuated by Res treatment. Res protected against HFS- or high-glucose-induced increase in NADPH oxidase p47phox expression and decrease in SIRT1 level. Apocynin, a NADPH oxidase inhibitor, down-regulated p47phox protein expression, but had no influence on SIRT1 protein; sirtinol, a SIRT1 inhibitor, aggravated the decrease in SIRT1 protein level and the increase in p47phox protein expression induced by high glucose.

CONCLUSION

Our studies suggested that Res was able to reverse the senescence process in aorta induced by HFS in rats or induced by the exposure to high glucose in cultured BAECs. The underlying mechanism is at least SIRT1/NADPH oxidase pathway dependent.

Differential roles of NADPH oxidases in vascular physiology and pathophysiology

Reactive oxygen species (ROS) are produced by all vascular cells and regulate the major physiological functions of the vasculature. Production and removal of ROS are tightly controlled and occur in discrete subcellular locations, allowing for specific, compartmentalized signaling. Among the many sources of ROS in the vessel wall, NADPH oxidases are implicated in physiological functions such as control of vasomotor tone, regulation of extracellular matrix and phenotypic modulation of vascular smooth muscle cells. They are involved in the response to injury, whether as an oxygen sensor during hypoxia, as a regulator of protein processing, as an angiogenic stimulus, or as a mechanism of wound healing. These enzymes have also been linked to processes leading to disease development, including migration, proliferation, hypertrophy, apoptosis and autophagy. As a result, NADPH oxidases participate in atherogenesis, systemic and pulmonary hypertension and diabetic vascular disease. The role of ROS in each of these processes and diseases is complex, and a more full understanding of the sources, targets, cell-specific responses and counterbalancing mechanisms is critical for the rational development of future therapeutics.

Combating oxidative stress in vascular disease: NADPH oxidases as therapeutic targets

NADPH oxidases are a family of enzymes that generate reactive oxygen species (ROS). The NOX1 (NADPH oxidase 1) and NOX2 oxidases are the major sources of ROS in the artery wall in conditions such as hypertension, hypercholesterolaemia, diabetes and ageing, and so they are important contributors to the oxidative stress, endothelial dysfunction and vascular inflammation that underlies arterial remodelling and atherogenesis. In this Review, we advance the concept that compared to the use of conventional antioxidants, inhibiting NOX1 and NOX2 oxidases is a superior approach for combating oxidative stress. We briefly describe some common and emerging putative NADPH oxidase inhibitors. In addition, we highlight the crucial role of the NADPH oxidase regulatory subunit, p47phox, in the activity of vascular NOX1 and NOX2 oxidases, and suggest how a better understanding of its specific molecular interactions may enable the development of novel isoform-selective drugs to prevent or treat cardiovascular diseases.

NADPH oxidases in cardiovascular disease: insights from in vivo models and clinical studies

NADPH oxidase family enzymes (or NOXs) are the major sources of reactive oxygen species (ROS) that are implicated in the pathophysiology of many cardiovascular diseases. These enzymes appear to be especially important in the modulation of redox-sensitive signalling pathways that underlie key cellular functions such as growth, differentiation, migration and proliferation. Seven distinct members of the family have been identified of which four (namely NOX1, 2, 4 and 5) may have cardiovascular functions. In this article, we review our current understanding of the roles of NOX enzymes in several common cardiovascular disease states, with a focus on data from genetic studies and clinical data where available.

Role for Nox1 NADPH oxidase in atherosclerosis

OBJECTIVE

Examine the contribution of Nox1 NADPH oxidase to atherogenesis.

METHODS AND RESULTS

Male apolipoprotein E deficient mice (ApoE(-/-)) and male mice deficient in both apolipoprotein E and Nox1 (ApoE(-/-) Nox1(-/y)) received an atherogenic diet for 18 weeks. Mean blood pressures, body weights, and serum cholesterol levels were similar between the two groups of mice. Deficiency of Nox1 decreased superoxide levels and reduced lesion area in the aortic arch from 43% (ApoE(-/-)) to 28% (ApoE(-/-) Nox1(-/y)). The reduction in lesion size at the level of the aortic valve in ApoE(-/-)/Nox1(-/y) was accompanied by a decrease in macrophage infiltration as compared to ApoE(-/-) mice. Carotid artery ligation in ApoE(-/-) mice induced accelerated intimal hyperplasia with decreased cellular proliferation and increased collagen content in the neointima of vessels deficient in Nox1.

CONCLUSIONS

Nox1-derived ROS modify lesion composition and contribute to lesion size in a murine model of atherosclerosis.

NADPH oxidase links endoplasmic reticulum stress, oxidative stress, and PKR activation to induce apoptosis

The endoplasmic reticulum (ER) is a cellular membrane organelle that plays important roles in virus replication and maturation. Accumulating evidence indicates that virus infection often disturbs ER homeostasis and leads to ER stress, which is associated with a variety of prevalent diseases. To cope with the deleterious effects of virus-induced ER stress, cells activate critical signaling pathways including the unfolded protein response (UPR) and intrinsic mitochondrial apoptosis, which have complex effects on virus replication and pathogenesis. In this review, we present a comprehensive summary of recent research in this field, which revealed that about 36 viruses trigger ER stress and differentially activate ER stress-related signaling pathways. We also highlight the strategies evolved by viruses to modulate ER stress-related signaling networks including immune responses in order to ensure their survival and pathogenesis. Together, the knowledge gained from this field will shed light on unveiling the mechanisms of virus replication and pathogenesis and provide insight for future research as well as antiviral development.

NADPH oxidase links endoplasmic reticulum stress, oxidative stress, and PKR activation to induce apoptosis

ER stress signaling involving calcium and CaMKII induces NADPH oxidase and oxidative stress, which amplify CHOP-mediated apoptosis via PKR activation.

Endoplasmic reticulum (ER)–induced apoptosis and oxidative stress contribute to several chronic disease processes, yet molecular and cellular mechanisms linking ER stress and oxidative stress in the setting of apoptosis are poorly understood and infrequently explored in vivo. In this paper, we focus on a previously elucidated ER stress–apoptosis pathway whose molecular components have been identified and documented to cause apoptosis in vivo. We now show that nicotinamide adenine dinucleotide phosphate reduced oxidase (NOX) and NOX-mediated oxidative stress are induced by this pathway and that apoptosis is blocked by both genetic deletion of the NOX subunit NOX2 and by the antioxidant N-acetylcysteine. Unexpectedly, NOX and oxidative stress further amplify CCAAT/enhancer binding protein homologous protein (CHOP) induction through activation of the double-stranded RNA–dependent protein kinase (PKR). In vivo, NOX2 deficiency protects ER-stressed mice from renal cell CHOP induction and apoptosis and prevents renal dysfunction. These data provide new insight into how ER stress, oxidative stress, and PKR activation can be integrated to induce apoptosis in a pathophysiologically relevant manner.

Effect of early particulate air pollution exposure on obesity in mice: role of p47phox

OBJECTIVE

To evaluate the role of early-life exposure to airborne fine particulate matter (diameter, <2.5 μm [PM(2.5)]) pollution on metabolic parameters, inflammation, and adiposity; and to investigate the involvement of oxidative stress pathways in the development of metabolic abnormalities.

METHODS AND RESULTS

PM(2.5) inhalation exposure (6 h/d, 5 d/wk) was performed in C57BL/6 mice (wild type) and mice deficient in the cytosolic subunit of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase p47(phox) (p47(phox-/-)) beginning at the age of 3 weeks for a duration of 10 weeks. Both groups were simultaneously fed a normal diet or a high-fat diet for 10 weeks. PM(2.5)-exposed C57BL/6 mice fed a normal diet exhibited metabolic abnormalities after exposure to PM(2.5) or FA for 10 weeks. Consistent with insulin resistance, these abnormalities included enlarged subcutaneous and visceral fat contents, increased macrophage infiltration in visceral adipose tissue, and vascular dysfunction. Ex vivo-labeled and infused monocytes demonstrated increased adherence in the microcirculation of normal diet- or high-fat diet-fed PM(2.5)-exposed mice. p47(phox-/-) mice exhibited an improvement in parameters of insulin resistance, vascular function, and visceral inflammation in response to PM(2.5).

CONCLUSIONS

Early-life exposure to high levels of PM(2.5) is a risk factor for subsequent development of insulin resistance, adiposity, and inflammation. Reactive oxygen species generation by NADPH oxidase appears to mediate this risk.

Nox isoforms in vascular pathophysiology: insights from transgenic and knockout mouse models

Elevated reactive oxygen species (ROS) formation in the vascular wall is a key feature of cardiovascular diseases and a likely contributor to oxidative stress, endothelial dysfunction and vascular inflammation. The NADPH oxidases are a family of ROS generating enzymes, of which four members (Nox1, Nox2, Nox4 and Nox5) are expressed in blood vessels. Numerous studies have demonstrated that expression and activity of at least two isoforms of NADPH oxidase - Nox1 and Nox2 - are up-regulated in animal models of hypertension, diabetes and atherosclerosis. However, these observations are merely suggestive of a role for NADPH oxidases in vessel pathology and by no means establish cause and effect. Furthermore, questions surrounding the specificity of current pharmacological inhibitors of NADPH oxidase mean that findings obtained with these compounds must be viewed with caution. Here, we review the literature on studies utilising genetically-modified mouse strains to investigate the roles of NADPH oxidases in experimental models of vascular disease. While several studies on transgenic over-expressing or knockout mice support roles for Nox1- and/or Nox2-containing oxidases as sources of excessive vascular ROS production and causes of endothelial dysfunction in hypertension, atherosclerosis and diabetes, there are still no published reports on the effects of genetic modification of Nox4 or Nox5 in vascular or indeed any other contexts. Further understanding of the roles of specific isoforms of NADPH oxidase in vascular (patho)physiology should provide direction for future programs aimed at developing selective inhibitors of these enzymes as novel therapeutics in cardiovascular disease.

Effect of long-term treatment with antioxidants (vitamin C, vitamin E, coenzyme Q10 and selenium) on arterial compliance, humoral factors and inflammatory markers in patients with multiple cardiovascular risk factors

Background

Antioxidant supplementations have the potential to alleviate the atherosclerotic damage caused by excessive production of reactive oxygen species (ROS). The present study evaluated the effects of prolonged antioxidant treatment on arterial elasticity, inflammatory and metabolic measures in patients with multiple cardiovascular risk factors.

Methods

Study participants were randomly assigned to two groups. Group 1 received oral supplementation with 2 capsules per day of Mid Life Guard, SupHerb, Israel. In each capsule vitamin C (500 mg) vitamin E (200 iu), co-enzyme Q10 (60 mg) and selenium (100 mcg), Group 2 received matching placebo(SupHerb) for 6 months. Patients were evaluated for lipid profile, HbA1C, insulin, C-peptide, hs-CRP, endothelin, aldosterone, plasma renin activity and Homeostasis model assessment-insulin resistance (HOMA-IR). Arterial elasticity was evaluated using pulse wave contour analysis (HDI CR 2000, Eagan, Minnesota).

Results

Antioxidant-treated patients exhibited significant increases in large arterial elasticity index (LAEI) as well as small arterial elasticity index (SAEI). A significant decline HbA1C and a significant increase in HDL-cholesterol were also observed. In the placebo group, significant changes in LAEI, SAEI or metabolic measures were not observed.

Conclusions

Antioxidant supplementation significantly increased large and small artery elasticity in patients with multiple cardiovascular risk factors. This beneficial vascular effect was associated with an improvement in glucose and lipid metabolism as well as decrease in blood pressure.

Role of NADPH oxidase in host defense against aspergillosis

NADPH oxidase plays a critical role in antimicrobial host defense, as evident in chronic granulomatous disease (CGD), an inherited disorder of the NADPH oxidase characterized by severe bacterial and fungal diseases. Invasive aspergillosis and other moulds are the major cause of mortality in CGD. We also learn from CGD patients that NADPH oxidase plays an important role in regulating inflammation; CGD patients are prone to developing inflammatory diseases such as inflammatory bowel disease, obstructive granulomata of the genitourinary tract, and hypersensitivity pneumonitis. Indeed, the NADPH oxidase plays an essential role in calibrating innate and T-cell responses to control the growth of inhaled fungi while protecting against excessive and injurious inflammation. Knowledge gained on the mechanisms by which NADPH oxidase kills fungi and regulates inflammation may lead to new therapeutics for CGD and will have broad relevance to understanding host-pathogen interactions between mammals and ubiquitous moulds to which we are continually exposed.

Chronic granulomatous disease

Chronic granulomatous disease (CGD) was first described in the 1950s and has become a paradigm for genetic neutrophil diseases. It is characterized by recurrent infections with a narrow spectrum of bacteria and fungi as well as a common set of inflammatory complications most notably including inflammatory bowel disease. Over the last half century major advances in management have profoundly altered the major clinical issues and the life expectancy of CGD. With X-linked and autosomal recessive forms, it has been an important disease for the development of bone marrow transplantation and gene therapy. Some of the recent developments in infectious syndromes, inflammatory complications, and curative approaches are discussed in this review.

A copy number variation in human NCF1 and its pseudogenes

BACKGROUND

Neutrophil cytosolic factor-1 (NCF1) is a component of NADPH oxidase. The NCF1 gene colocalizes with two pseudogenes (NCF1B and NCF1C). These two pseudogenes have a GT deletion in exon 2, resulting in a frameshift and an early stop codon. Here, we report a copy number variation (CNV) of the NCF1 pseudogenes and their alternative spliced expressions.

RESULTS

We examined three normal populations (86 individuals). We observed the 2:2:2 pattern (NCF1B:NCF1:NCF1C) in only 26 individuals. On average, each African- American has 1.4 +/- 0.8 (Mean +/- SD) copies of NCF1B and 2.3 +/- 0.6 copies of NCF1C; each Caucasian has 1.8 +/- 0.7 copies of NCF1B and 1.9 +/- 0.4 copies of NCF1C; and each Mexican has 1.6 +/- 0.6 copies of NCF1B and 1.0 +/- 0.4 copies of NCF1C. Mexicans have significantly less NCF1C copies than African-Americans (p = 6e-15) and Caucasians (p = 3e-11). Mendelian transmission of this CNV was observed in two CEPH pedigrees. Moreover, we cloned two alternative spliced transcripts generated from these two pseudogenes that adopt alternative exon-2 instead of their defective exon 2. The NCF1 pseudogene expression responded robustly to PMA induction during macrophage differentiation. NCF1B decreased from 32.9% to 8.3% in the cDNA pool transcribed from 3 gene copies. NCF1Psis also displayed distinct expression patterns in different human tissues.

CONCLUSIONS

Our results suggest that these two pseudogenes may adopt an alternative exon-2 in different tissues and in response to external stimuli. The GT deletion is insufficient to define them as functionless pseudogenes; this CNV may have biological relevance.

Lipoprotein modification and macrophage uptake: role of pathologic cholesterol transport in atherogenesis

Low-density lipoprotein (LDL) is a major extracellular carrier of cholesterol and, as such, plays important physiologic roles in cellular function and regulation of metabolic pathways. However, under pathologic conditions of hyperlipidemia, oxidative stress and/or genetic disorders, specific components of LDL become oxidized or otherwise modified, and the transport of cholesterol by modified LDL is diverted from its physiologic targets toward excessive cholesterol accumulation in macrophages and the formation of macrophage "foam" cells in the vascular wall. This pathologic deposition of modified lipoproteins and the attendant pro-inflammatory reactions in the artery wall lead to the development of atherosclerotic lesions. Continued accumulation of immunogenic modified lipoproteins and a pro-inflammatory milieu result in the progression of atherosclerotic lesions, which may obstruct the arterial lumen and/or eventually rupture and thrombose, causing myocardial infarction or stroke. In this review, we survey mechanisms of LDL modification and macrophage lipoprotein uptake, including results of recent in vivo experiments, and discuss unresolved problems and controversial issues in this growing field. Future directions in studying foam cell formation may include introducing novel animal models, such as hypercholesterolemic zebrafish, enabling dynamic in vivo observation of macrophage lipid uptake.

Angiotensin II induces a region-specific hyperplasia of the ascending aorta through regulation of inhibitor of differentiation 3

RATIONALE

Angiotensin II (Ang II) has diverse effects on smooth muscle cells (SMCs). The diversity of effects may relate to the regional location of this cell type.

OBJECTIVE

The aim of this study was to define whether Ang II exerted divergent effects on smooth muscle cells in the aorta and determine the role of blood pressure and specific oxidant mechanisms.

METHODS AND RESULTS

Ang II (1000 ng/kg per minute) infusion for 28 days into mice increased systolic blood pressure and promoted medial expansion of equivalent magnitude throughout the entire aorta. Both effects were ablated by angiotensin II type 1a (AT(1a)) receptor deficiency. Similar increases in systolic blood pressure by administration of norepinephrine promoted no changes in aortic medial thickness. Increased medial thickness was attributable to SMC expansion owing to hypertrophy in most aortic regions, with the exception of hyperplasia of the ascending aorta. Deficiency of the p47(phox) component of NADPH oxidase ablated Ang II-induced medial expansion in all aortic regions. Analysis of mRNA and protein throughout the aorta revealed a much higher abundance of the inhibitor of differentiation 3 (Id3) in the ascending aorta compared to all other regions. A functional role was demonstrated by Id3 deficiency inhibiting Ang II-induced SMC hyperplasia of the ascending aorta.

CONCLUSIONS

In conclusion, Ang II promotes both aortic medial hypertrophy and hyperplasia in a region-specific manner via an oxidant mechanism. The ascending aortic hyperplasia is dependent on Id3.

Transcriptional responses to oxidative stress: pathological and toxicological implications

The utilization of molecular oxygen as the terminal electron acceptor for energy production has in many ways shaped the evolution of complex life, physiology, and certain disease processes. The generation of reactive oxygen species (ROS), either as by-products of O(2) metabolism or by specialized enzymes, has the potential to damage cellular components and functions. Exposure to a variety of exogenous toxicants also promotes ROS production directly or through indirect means to cause toxicity. Oxidative stress activates the expression of a wide range of genes that mediate the pathogenic effect of ROS or are required for the detection and detoxification of the oxidants. In many cases, these are mediated by specific transcription factors whose expression, structure, stability, nuclear targeting, or DNA-binding affinity is regulated by the level of oxidative stress. This review examines major transcription factors that mediate transcriptional responses to oxidative stress, focusing on recent progress in the signaling pathways and mechanisms of activation of transcription factors by oxidative stress and the implications of this regulation in the development of disease and chemical toxicity.

Mitochondrial ATP-sensitive K(+) channels as redox signals to liver mitochondria in response to hypertriglyceridemia

We have recently demonstrated that hypertriglyceridemic (HTG) mice present both elevated body metabolic rates and mild mitochondrial uncoupling in the liver owing to stimulated activity of the ATP-sensitive potassium channel (mitoK(ATP)). Because lipid excess normally leads to cell redox imbalance, we examined the hepatic oxidative status in this model. Cell redox imbalance was evidenced by increased total levels of carbonylated proteins, malondialdehydes, and GSSG/GSH ratios in HTG livers compared to wild type. In addition, the activities of the extramitochondrial enzymes NADPH oxidase and xanthine oxidase were elevated in HTG livers. In contrast, Mn-superoxide dismutase activity and content, a mitochondrial matrix marker, were significantly decreased in HTG livers. Isolated HTG liver mitochondria presented lower rates of H(2)O(2) production, which were reversed by mitoK(ATP) antagonists. In vivo antioxidant treatment with N-acetylcysteine decreased both mitoK(ATP) activity and metabolic rates in HTG mice. These data indicate that high levels of triglycerides increase reactive oxygen generation by extramitochondrial enzymes that promote mitoK(ATP) activation. The mild uncoupling mediated by mitoK(ATP) increases metabolic rates and protects mitochondria against oxidative damage. Therefore, a biological role for mitoK(ATP) as a redox sensor is shown here for the first time in an in vivo model of systemic and cellular lipid excess.

Direct evidence of a role for Nox2 in superoxide production, reduced nitric oxide bioavailability, and early atherosclerotic plaque formation in ApoE-/- mice

The Nox family NADPH oxidases are reactive oxygen species (ROS)-generating enzymes that are strongly implicated in atherogenesis. However, no studies have examined which Nox isoform(s) are involved. Here we investigated the role of the Nox2-containing NADPH oxidase in atherogenesis in apolipoprotein E-null (ApoE(-/-)) mice. Wild-type (C57Bl6/J), ApoE(-/-), and Nox2(-/y)/ApoE(-/-) mice were maintained on a high-fat (21%) diet from 5 wk of age until they were 12 or 19 wk old. Mice were euthanized and their aortas removed for measurement of Nox2 expression (Western blot analysis and immunohistochemistry), ROS production (L012-enhanced chemiluminescence), nitric oxide (NO) bioavailability (contractions to N(omega)-nitro-L-arginine), and atherosclerotic plaque development along the aorta and in the aortic sinus. Nox2 expression was upregulated in the aortic endothelium of ApoE(-/-) mice before the appearance of lesions, and this was associated with elevated ROS levels. Within developing plaques, macrophages were also a prominent source of Nox2. The absence of Nox2 in Nox2(-/y)/ApoE(-/-) double-knockout mice had minimal effects on plasma lipids or lesion development in the aortic sinus in animals up to 19 wk of age. However, an en face examination of the aorta from the arch to the iliac bifurcation revealed a 50% reduction in lesion area in Nox2(-/y)/ApoE(-/-) versus ApoE(-/-) mice, and this was associated with a marked decrease in aortic ROS production and an increased NO bioavailability. In conclusion, this is the first demonstration of a role for Nox2-NADPH oxidase in vascular ROS production, reduced NO bioavailability, and early lesion development in ApoE(-/-) mice, highlighting this Nox isoform as a potential target for future therapies for atherosclerosis.

Acute effects of different types of oil consumption on endothelial function, oxidative stress status and vascular inflammation in healthy volunteers

Consumption of different types of oil may have different effects on cardiovascular risk. The exact role of maize oil, cod liver oil, soya oil and extra virgin olive oil on endothelial function, oxidative stress and inflammation is unknown. We evaluated the effect of acute consumption of these types of oil on endothelial function, oxidative stress and inflammation in healthy adults. Thirty-seven healthy volunteers were randomised to receive an oral amount of each type of oil or water. Endothelial function was evaluated by gauge-strain plethysmography at baseline and 1, 2 and 3 h after consumption. Oxidative stress status was determined by total lipid peroxides (PEROX), while inflammatory process was estimated by measuring the soluble form of vascular adhesion molecule 1. Serum levels of the two previous markers were measured at baseline and 3 h after oil consumption. Reactive hyperaemia (RH) was significantly decreased after maize oil consumption compared with controls (P < 0.05). However, the consumption of cod liver oil and soya oil induced a significant improvement of RH after 1 h, compared with controls (P < 0.05). There was no significant effect of any type of oil consumption on endothelium-independent dilatation, total lipid PEROX and vascular adhesion molecule 1 serum levels. Consumption of maize oil leads to impaired endothelial function, while soya oil and cod liver oil slightly improve endothelial function. However, all types of oils did not affect inflammatory process and systemic oxidative stress, suggesting that their effect on endothelial function may not be mediated by free radicals bioavailability.

Reactive Oxygen Species–Mediated Signal Transduction in the Endothelium

The endothelium is an important component of vascular homeostasis that is a target for injury in the setting of vascular disease. One means of promoting a maladaptive endothelial cell phenotype such as that seen in atherosclerosis is excess oxidative stress. Although this term once was almost exclusively used to describe low-density lipoprotein (LDL) and lipid oxidation in the vasculature, we now understand that the intracellular oxidant milieu is an important modulator of vascular cell function. Indeed, considerable data indicate that reactive oxygen species (ROS) are an important means of cellular signaling, although the precise mechanisms whereby ROS accomplish this are still under investigation. In this review, the data linking ROS to kinase activation and cell signaling in the endothelium is discussed, with a particular emphasis on the roles of protein thiol modification.

Nitric oxide, NAD(P)H oxidase, and atherosclerosis

The endothelial cell layer plays a major role in the development and progression of atherosclerosis. Endothelial NO synthase (eNOS) produces nitric oxide (NO) from L-arginine. NO can rapidly react with reactive oxygen species to form peroxynitrite. This reduces NO availability, impairs vasodilatation, and mediates proinflammatory and prothrombotic processes such as leukocyte adhesion and platelet aggregation. In the vessel wall, specific NAD(P)H oxidase complexes are major sources of reactive oxygen species. These NAD(P)H oxidases can transfer electrons across membranes to oxygen and generate superoxide anions. The short-lived superoxide anion rapidly dismutates to hydrogen peroxide, which can further increase the production of reactive oxygen species. This can lead to uncoupling of eNOS switching enzymatic activity from NO to superoxide production. This review describes the structure and regulation of different NAD(P)H oxidase complexes. We will also focus on NO/superoxide anion balance as modulated by hemodynamic forces, vasoconstrictors, and oxidized low-density lipoprotein. We will then summarize the recent advances defining the role of nitric oxide and NAD(P)H oxidase-derived reactive oxygen species in the development and progression of atherosclerosis. In conclusion, novel mechanisms affecting the vascular NO/superoxide anion balance will allow the development of therapeutic strategies in the treatment of cardiovascular diseases.

The role of the scavenger receptor CD36 in regulating mononuclear phagocyte trafficking to atherosclerotic lesions and vascular inflammation

AIMS

CD36 has been shown to associate with non-receptor Src kinases to activate mitogen-activated protein kinases and trigger cytoskeletal remodelling, important events in foam cell formation and macrophage migration. Yet, its role in regulating circulating mononuclear phagocyte trafficking to atherosclerotic lesions has not been investigated. The aim of the present study was to investigate the role of CD36 in modulating the recruitment of mononuclear phagocytes to the arterial wall and the associated vascular inflammation, using both pharmacological and genetic approaches.

METHODS AND RESULTS

Apolipoprotein E-deficient (apoE(-/-)) mice fed a high-fat, high-cholesterol diet were treated daily with a CD36 ligand, EP 80317 (300 microg/kg), or 0.9% NaCl for 6 or 12 weeks. Forty-eight hours before sacrifice, mice were injected iv with (111)Indium-labelled macrophages. A 65% (P < 0.001) reduction of labelled macrophage accumulation at aortic lesions was observed in EP 80317-treated mice, mainly at the level of the aortic arch and iliac arteries, correlating with a 43% reduction of atherosclerotic lesion areas. This was associated with reduced phosphorylation of the focal adhesion kinase Pyk2 following stimulation with oxidized phospholipid in a Src kinase- and CD36-dependent manner. At the vascular level, EP 80317 treatment reduced the expression of pro-inflammatory proteins, including NADPH oxidase, inducible nitric oxide synthase, vascular endothelial cell adhesion molecule-1, and CCL2 chemokine. Plasma IL-6 levels were also reduced by 40% (P < 0.05). In contrast, none of these proteins was modulated in EP 80317-treated apoE/CD36 double knockout (apoE(-/-)/CD36(-/-)) mice.

CONCLUSION

Our results support a role for CD36 signalling in the regulation of mononuclear phagocyte trafficking to atherosclerotic-prone sites and in the associated vascular wall inflammation.

Macrophages generate reactive oxygen species in response to minimally oxidized low-density lipoprotein: toll-like receptor 4- and spleen tyrosine kinase-dependent activation of NADPH oxidase 2

Oxidative modification of low-density lipoprotein (LDL) plays a causative role in the development of atherosclerosis. In this study, we demonstrate that minimally oxidized LDL (mmLDL) stimulates intracellular reactive oxygen species (ROS) generation in macrophages through NADPH oxidase 2 (gp91phox/Nox2), which, in turn, induces production of RANTES and migration of smooth muscle cells. Peritoneal macrophages from gp91phox/Nox2(-/-) mice or J774 macrophages in which Nox2 was knocked down by small interfering RNA failed to generate ROS in response to mmLDL. Because mmLDL-induced cytoskeletal changes were dependent on Toll-like receptor (TLR)4, we analyzed ROS generation in peritoneal macrophages from wild-type, TLR4(-/-), or MyD88(-/-) mice and found that mmLDL-mediated ROS was generated in a TLR4-dependent, but MyD88-independent, manner. Furthermore, we found that ROS generation required the recruitment and activation of spleen tyrosine kinase (Syk) and that mmLDL also induced phospholipase PLCgamma1 phosphorylation and protein kinase C membrane translocation. Importantly, the phospholipase Cgamma1 phosphorylation was reduced in J774 cells expressing Syk-specific short hairpin RNA. Nox2 modulated mmLDL activation of macrophages by regulating the expression of proinflammatory cytokines interleukin-1beta, interleukin-6, and RANTES. We showed that purified RANTES was able to stimulate migration of mouse aortic smooth muscle cells and addition of neutralizing antibody against RANTES abolished the migration of mouse aortic smooth muscle cells stimulated by mmLDL-stimulated macrophages. These results suggest that mmLDL induces generation of ROS through sequential activation of TLR4, Syk, phospholipase Cgamma1, protein kinase C, and gp91phox/Nox2 and thereby stimulates expression of proinflammatory cytokines. These data help explain mechanisms by which endogenous ligands, such as mmLDL, can induce TLR4-dependent, proatherogenic activation of macrophages.