Angiotensin II, NADPH oxidase, and redox signaling in the vasculature.
TL;DR: There is still a paucity of information on how Ang II exerts cell-specific effects through ROS and how Nox isoforms are differentially regulated by Ang II, and exact mechanisms whereby ROS induce oxidative modifications of signaling molecules mediating Ang II actions remain elusive.
Abstract: Significance: Angiotensin II (Ang II) influences the function of many cell types and regulates many organ systems, in large part through redox-sensitive processes. In the vascular system, Ang II is a potent vasoconstrictor and also promotes inflammation, hypertrophy, and fibrosis, which are important in vascular damage and remodeling in cardiovascular diseases. The diverse actions of Ang II are mediated via Ang II type 1 and Ang II type 2 receptors, which couple to various signaling molecules, including NADPH oxidase (Nox), which generates reactive oxygen species (ROS). ROS are now recognized as signaling molecules, critically placed in pathways activated by Ang II. Mechanisms linking Nox and Ang II are complex and not fully understood. Recent Advances: Ang II regulates vascular cell production of ROS through various recently characterized Noxs, including Nox1, Nox2, Nox4, and Nox5. Activation of these Noxs leads to ROS generation, which in turn influences many downstream signaling targets of Ang II, including MAP kinases, RhoA/Rho kinase, transcription factors, protein tyrosine phosphatases, and tyrosine kinases. Activation of these redox-sensitive pathways regulates vascular cell growth, inflammation, contraction, and senescence. Critical Issues: Although there is much evidence indicating a role for Nox/ROS in Ang II function, there is still a paucity of information on how Ang II exerts cell-specific effects through ROS and how Nox isoforms are differentially regulated by Ang II. Moreover, exact mechanisms whereby ROS induce oxidative modifications of signaling molecules mediating Ang II actions remain elusive. Future Directions: Future research should elucidate these issues to better understand the significance of Ang II and ROS in vascular (patho) biology. Antioxid. Redox Signal. 19, 1110–1120.
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TL;DR: The possibility that multiple ROS sources contribute to reperfusion injury in most tissues is supported by evidence demonstrating that redox-signaling enables ROS produced by one enzymatic source to activate and enhance ROS production by a second source.
Abstract: Reperfusion injury, the paradoxical tissue response that is manifested by blood flow-deprived and oxygen-starved organs following the restoration of blood flow and tissue oxygenation, has been a focus of basic and clinical research for over 4-decades. While a variety of molecular mechanisms have been proposed to explain this phenomenon, excess production of reactive oxygen species (ROS) continues to receive much attention as a critical factor in the genesis of reperfusion injury. As a consequence, considerable effort has been devoted to identifying the dominant cellular and enzymatic sources of excess ROS production following ischemia-reperfusion (I/R). Of the potential ROS sources described to date, xanthine oxidase, NADPH oxidase (Nox), mitochondria, and uncoupled nitric oxide synthase have gained a status as the most likely contributors to reperfusion-induced oxidative stress and represent priority targets for therapeutic intervention against reperfusion-induced organ dysfunction and tissue damage. Although all four enzymatic sources are present in most tissues and are likely to play some role in reperfusion injury, priority and emphasis has been given to specific ROS sources that are enriched in certain tissues, such as xanthine oxidase in the gastrointestinal tract and mitochondria in the metabolically active heart and brain. The possibility that multiple ROS sources contribute to reperfusion injury in most tissues is supported by evidence demonstrating that redox-signaling enables ROS produced by one enzymatic source (e.g., Nox) to activate and enhance ROS production by a second source (e.g., mitochondria). This review provides a synopsis of the evidence implicating ROS in reperfusion injury, the clinical implications of this phenomenon, and summarizes current understanding of the four most frequently invoked enzymatic sources of ROS production in post-ischemic tissue.
910 citations
Cites background from "Angiotensin II, NADPH oxidase, and ..."
...Finally, angiotensin II, perhaps the most studied and best characterized stimulant for NADPH oxidase activation [269], has been implicated in reperfusion-induced NADPH oxidase activation, inflammation, and injury in several tissues [270–274]....
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TL;DR: It is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.
Abstract: The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG I...
618 citations
TL;DR: This Review discusses the identification of new pathways for enhancing NO synthase activity; ways to amplify the nitrate–nitrite–NO pathway; novel classes of NO-donating drugs; drugs that limit NO metabolism through effects on reactive oxygen species; and ways to modulate downstream phosphodiesterases and soluble guanylyl cyclases.
Abstract: Nitric oxide (NO) is a key signalling molecule in the cardiovascular, immune and central nervous systems, and crucial steps in the regulation of NO bioavailability in health and disease are well characterized. Although early approaches to therapeutically modulate NO bioavailability failed in clinical trials, an enhanced understanding of fundamental subcellular signalling has enabled a range of novel therapeutic approaches to be identified. These include the identification of: new pathways for enhancing NO synthase activity; ways to amplify the nitrate-nitrite-NO pathway; novel classes of NO-donating drugs; drugs that limit NO metabolism through effects on reactive oxygen species; and ways to modulate downstream phosphodiesterases and soluble guanylyl cyclases. In this Review, we discuss these latest developments, with a focus on cardiovascular disease.
414 citations
TL;DR: Oxidative stress and inflammation, key mechanisms of endothelial dysfunction and arterial damage, link these risk factors to vascular disease, arterial stiffness, and aging.
Abstract: Age-related decline in function is a physiological phenomenon occurring in all organ systems. However, acceleration and early occurrence of this process are observed in cardiovascular pathologies, including hypertension.1,2 In the vascular system, this is characterized by progressive pathological remodeling with stiffening,3 typically associated with extracellular matrix (ECM) alterations in collagen and elastin.4 This is, in part, dependent on cellular senescence and growth arrest.5 Although hypertension and atherosclerosis are associated with accumulation of cellular senescence markers in the vascular wall, these conditions are often associated with vascular dysfunction rather than simple loss of proliferative capacity.6 For example, risk factors for cardiovascular disease, such as hypertension, smoking, hyperlipidaemia, or diabetes mellitus are associated with accelerated decline of vascular function.2 This is why vascular age determination has been introduced in key clinical guidelines for cardiovascular prevention, to indicate to the patient how their lifestyle contributes to the acceleration of vascular function deterioration.7
Oxidative stress and inflammation, key mechanisms of endothelial dysfunction and arterial damage, link these risk factors to vascular disease, arterial stiffness, and aging. These underlie macro- and microangiopathy, renal dysfunction, cardiac ischemia, and cognitive decline (Figure). Several novel pathways regulating these mechanisms of accelerated vascular aging have been elucidated in recent issues of Hypertension and are further discussed in the present Best Papers in Hypertension review.
Figure.
Central role of oxidative stress in accelerated vascular aging in hypertension. AT1R indicates angiotensin II receptor type 1; BH2, dihydrobiopterin; BH4, tetrahydrobiopterin; BMP, bone morphogenic protein; CypD, cyclophilin D; eNOS, endothelial NO synthase; ET1R, endothelin 1 receptor; H2O2, hydrogen peroxide; MMP, matrix metalloproteinase; Nox, NADPH oxidase; O2−., superoxide anion; RANTES, regulated on activation, normal T cell expressed and secreted chemokine; and SmgGDS, GTP-binding protein dissociation …
408 citations
Cites background from "Angiotensin II, NADPH oxidase, and ..."
...amide adenine dinucleotide phosphate (NADPH) oxidases, in vascular disease is widely accepted.(27,28) Various homologues...
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TL;DR: This review aims at giving an introduction into oxidative stress in CVD, with special focus on endothelial dysfunction, and then examining in detail the role of oxidative Stress in the most prevalent of these diseases.
Abstract: Cardiovascular diseases (CVD) are complex entities with heterogenous pathophysiologic mechanisms and increased oxidative stress has been viewed as one of the potential common etiologies. A fine balance between the presence of reactive oxygen species (ROS) and antioxidants is essential for the proper normal functioning of the cell. A basal concentration of ROS is indispensable for the manifestation of cellular functions, whereas excessive levels of ROS cause damage to cellular macromolecules such as DNA, lipids and proteins, eventually leading to necrosis and apoptotic cell death. CVD is the main cause of death worldwide with several conditions being affected by oxidative stress. Increased ROS lead to decreased nitric oxide availability and vasoconstriction, promoting arterial hypertension. ROS also negatively influence myocardial calcium handling, causing arrhythmia, and augment cardiac remodeling by inducing hypertrophic signaling and apoptosis. Finally, ROS have also been shown to promote atherosclerotic plaque formation. This review aims at giving an introduction into oxidative stress in CVD, with special focus on endothelial dysfunction, and then examining in detail the role of oxidative stress in the most prevalent of these diseases. Finally, potential nutraceuticals and diets that might be beneficial in diminishing the burden of oxidative stress in CVD are presented.
379 citations
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TL;DR: The ability of Ang II to stimulate superoxide anion formation is examined and the identity of the oxidases responsible for its production is investigated to suggest that Ang II specifically activates enzyme systems that promote superoxide generation and raise the possibility that these pathways function as second messengers for long-term responses, such as hypertrophy or hyperplasia.
Abstract: The signaling pathways involved in the long-term metabolic effects of angiotensin II (Ang II) in vascular smooth muscle cells are incompletely understood but include the generation of molecules likely to affect oxidase activity. We examined the ability of Ang II to stimulate superoxide anion formation and investigated the identity of the oxidases responsible for its production. Treatment of vascular smooth muscle cells with Ang II for 4 to 6 hours caused a 2.7 +/- 0.4-fold increase in intracellular superoxide anion formation as detected by lucigenin assay. This superoxide appeared to result from activation of both the NADPH and NADH oxidases. NADPH oxidase activity increased from 3.23 +/- 0.61 to 11.80 +/- 1.72 nmol O2-/min per milligram protein after 4 hours of Ang II, whereas NADH oxidase activity increased from 16.76 +/- 2.13 to 45.00 +/- 4.57 nmol O2-/min per milligram protein. The NADPH oxidase activity was stimulated by exogenous phosphatidic and arachidonic acids and was partially inhibited by the specific inhibitor diphenylene iodinium. NADH oxidase activity was increased by arachidonic and linoleic acids, was insensitive to exogenous phosphatidic acid, and was inhibited by high concentrations of quinacrine. Both of these oxidases appear to reside in the plasma membrane, on the basis of migration of the activity after cellular fractionation and their apparent insensitivity to the mitochondrial poison KCN. These observations suggest that Ang II specifically activates enzyme systems that promote superoxide generation and raise the possibility that these pathways function as second messengers for long-term responses, such as hypertrophy or hyperplasia.
2,716 citations
TL;DR: Forms of hypertension associated with elevated circulating levels of angiotensin II may have unique vascular effects not shared by other forms of hypertension because they increase vascular smooth muscle .O2- production via NADH/NADPH oxidase activation.
Abstract: We tested the hypothesis that angiotensin II-induced hypertension is associated with an increase in vascular .O2- production, and characterized the oxidase involved in this process. Infusion of angiotensin II (0.7 mg/kg per d) increased systolic blood pressure and doubled vascular .O2- production (assessed by lucigenin chemiluminescence), predominantly from the vascular media. NE infusion (2.75 mg/kg per d) produced a similar degree of hypertension, but did not increase vascular .O2- production. Studies using various enzyme inhibitors and vascular homogenates suggested that the predominant source of .O2- activated by angiotensin II infusion is an NADH/NADPH-dependent, membrane-bound oxidase. Angiotensin II-, but not NE-, induced hypertension was associated with impaired relaxations to acetylcholine, the calcium ionophore A23187, and nitroglycerin. These relaxations were variably corrected by treatment of vessels with liposome-encapsulated superoxide dismutase. When Losartan was administered concomitantly with angiotensin II, vascular .O2- production and relaxations were normalized, demonstrating a role for the angiotensin type-1 receptor in these processes. We conclude that forms of hypertension associated with elevated circulating levels of angiotensin II may have unique vascular effects not shared by other forms of hypertension because they increase vascular smooth muscle .O2- production via NADH/NADPH oxidase activation.
2,435 citations
TL;DR: This review focuses on the structure and function of AT(1) receptors and the major signaling mechanisms by which angiotensin influences cardiovascular physiology and pathology.
Abstract: The renin-angiotensin system is a central component of the physiological and pathological responses of cardiovascular system. Its primary effector hormone, angiotensin II (ANG II), not only mediates immediate physiological effects of vasoconstriction and blood pressure regulation, but is also implicated in inflammation, endothelial dysfunction, atherosclerosis, hypertension, and congestive heart failure. The myriad effects of ANG II depend on time (acute vs. chronic) and on the cells/tissues upon which it acts. In addition to inducing G protein- and non-G protein-related signaling pathways, ANG II, via AT(1) receptors, carries out its functions via MAP kinases (ERK 1/2, JNK, p38MAPK), receptor tyrosine kinases [PDGF, EGFR, insulin receptor], and nonreceptor tyrosine kinases [Src, JAK/STAT, focal adhesion kinase (FAK)]. AT(1)R-mediated NAD(P)H oxidase activation leads to generation of reactive oxygen species, widely implicated in vascular inflammation and fibrosis. ANG II also promotes the association of scaffolding proteins, such as paxillin, talin, and p130Cas, leading to focal adhesion and extracellular matrix formation. These signaling cascades lead to contraction, smooth muscle cell growth, hypertrophy, and cell migration, events that contribute to normal vascular function, and to disease progression. This review focuses on the structure and function of AT(1) receptors and the major signaling mechanisms by which angiotensin influences cardiovascular physiology and pathology.
1,746 citations
TL;DR: This review will describe only aspects of the biology of oxygen radicals that currently engage the interest of the writer and Hopefully they will also be of interest to the reader.
1,234 citations
TL;DR: Members of this enzyme family appear to be important in vascular biology and disease and constitute promising targets for future therapeutic interventions.
Abstract: The importance of reactive oxygen species (ROS) in vascular physiology and pathology is becoming increasingly evident. All cell types in the vascular wall produce ROS derived from superoxide-generating protein complexes similar to the leukocyte NADPH oxidase. Specific features of the vascular enzymes include constitutive and inducible activities, substrate specificity, and intracellular superoxide production. Most phagocyte enzyme subunits are found in vascular cells, including the catalytic gp91phox (aka, nox2), which was the earliest member of the newly discovered nox family. However, smooth muscle frequently expresses nox1 rather than gp91phox, and nox4 is additionally present in all cell types. In cell culture, agonists increase ROS production by activating multiple signals, including protein kinase C and Rac, and by upregulating oxidase subunits. The oxidases are also upregulated in vascular disease and are involved in the development of atherosclerosis and a significant part of angiotensin II-induced hypertension, possibly via nox1 and nox4. Likewise, enhanced vascular oxidase activity is associated with diabetes. Therefore, members of this enzyme family appear to be important in vascular biology and disease and constitute promising targets for future therapeutic interventions.
1,015 citations