Novel Nox homologues in the vasculature: focusing on Nox4 and Nox5

"β-glucan signalling stimulates NOX-2 dependent autophagy and LC-3 associated autophagy (LAP) pathway"

β-Glucan, a complex polysaccharide derived from fungal and yeast cell walls, plays a crucial role in modulating immune responses through their interaction with receptors such as Dectin-1 and Complement receptor 3 (CR-3). This review provides an in-depth analysis of the molecular mechanisms by which β-glucans activate receptor-mediated signalling pathways, focusing particularly on the LC3-associated phagocytosis (LAP) and autophagy pathways. Hence, we explore how β-glucan receptor engagement stimulates NADPH oxidase 2 (NOX-2), leading to the intracellular production of significant level of reactive oxygen species (ROS) essential for both conventional autophagy and LAP. While significant progress has been made in elucidation of downstream signaling by glucans, the regulation of phago-lysosomal maturation and antigen presentation during LAP induction still remains less explored. This review aims to provide a comprehensive overview of these pathways and their regulation by β-glucans. By consolidating the current knowledge, we seek to highlight how these mechanisms can be leveraged for therapeutic applications, particularly in the context of tuberculosis (TB) management, where β-glucans could serve as host-directed adjuvant therapies to combat drug-resistant strains. Despite major advancements in this field, currently key research gaps still persist, including detailed molecular interactions between β-glucan receptors and NOX-2 and the translation of these findings to in-vivo models and clinical investigations. This review underscores the need for further research to explore the therapeutic potential of β-glucans in managing not only tuberculosis but also other diseases such as cancer, cardiovascular conditions, and metabolic disorders.

Role of Oxygen and Its Radicals in Peripheral Nerve Regeneration: From Hypoxia to Physoxia to Hyperoxia

Oxygen is compulsory for mitochondrial function and energy supply, but it has numerous more nuanced roles. The different roles of oxygen in peripheral nerve regeneration range from energy supply, inflammation, phagocytosis, and oxidative cell destruction in the context of reperfusion injury to crucial redox signaling cascades that are necessary for effective axonal outgrowth. A fine balance between reactive oxygen species production and antioxidant activity draws the line between physiological and pathological nerve regeneration. There is compelling evidence that redox signaling mediated by the Nox family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases plays an important role in peripheral nerve regeneration. Further research is needed to better characterize the role of Nox in physiological and pathological circumstances, but the available data suggest that the modulation of Nox activity fosters great therapeutic potential. One of the promising approaches to enhance nerve regeneration by modulating the redox environment is hyperbaric oxygen therapy. In this review, we highlight the influence of various oxygenation states, i.e., hypoxia, physoxia, and hyperoxia, on peripheral nerve repair and regeneration. We summarize the currently available data and knowledge on the effectiveness of using hyperbaric oxygen therapy to treat nerve injuries and discuss future directions.

Therapeutic potential of Ganoderma lucidum polysaccharide peptide in Doxorubicin-induced nephropathy: modulation of renin-angiotensin system and proteinuria

Introduction: In the Doxorubicin (DOX)-induced nephropathy model, proteinuria is a manifestation of progressive kidney injury. The pathophysiology of renal illness is heavily influenced by the renin-angiotensin system (RAS). To reduce renal RAS activation and proteinuria caused by DOX, this study evaluated the effectiveness of Ganoderma lucidum polysaccharide peptide (GL-PP), a new glycopeptide produced from Ganoderma lucidum grown on grass. Methods: Three groups of BALB/c male mice were created: control, DOX, and DOX + GL-PP. GL-PP (100 mg/kg) was administered to mice by intraperitoneal injection for 4 weeks following a single intravenous injection of DOX (10 mg/kg via the tail vein). Results: After 4 weeks, full-length and soluble pro(renin) receptor (fPRR/sPRR) overexpression in DOX mouse kidneys, which is crucial for the RAS pathway, was dramatically inhibited by GL-PP therapy. Additionally, GL-PP successfully reduced elevation of urinary renin activity and angiotensin II levels, supporting the idea that GL-PP inhibits RAS activation. Moreover, GL-PP showed a considerable downregulation of nicotinamide adenine nucleotide phosphate oxidase 4 (NOX4) expression and a decrease in hydrogen peroxide (H2O2) levels. GL-PP treatment effectively reduced glomerular and tubular injury induced by DOX, as evidenced by decreased proteinuria, podocyte damage, inflammation, oxidative stress, apoptosis, and fibrosis. Discussion: GL-PP inhibits intrarenal PRR/sPRR-RAS activation and upregulation of NOX4 and H2O2, suggesting potential therapeutic approaches against DOX-induced nephropathy.

Identification of an inhibitor for atherosclerotic enzyme NOX-1 to inhibit ROS production

Background

NOX-1 overexpression has been observed in various studies, persons with diabetes or cardiovascular conditions. NOX-1 orchestrates the disease pathogenesis of various cardiovascular conditions such as atherosclerotic plaque development and is a very crucial biomarker. Therefore, this study was carried out to deduce the three-dimensional modelled structure of NOX-1 using DeepMind AlphaFold-2 to find meaningful insight into the structural biology. Extensive in silico approaches have been used to determine the active pocket, virtually screen large chemical space to identify potential inhibitors. The role of the key amino acid residues was also deduced using alanine scanning mutagenesis contributing to the catalytic process and to the overall stability of NOX-1.

Results

The modelled structure of NOX-1 protein was validated using ERRAT. The ERRAT statistics with 9 amino acids sliding window have shown a confidence score of 96.937%. According to the Ramachandran statistics, 96.60% of the residues lie within the most favoured region, and 2.80% of residues lie in the additionally allowed region, which gives an overall of 99.4% residues in the three quadrants in the plot. GKT-831 which is a referral drug in this study has shown a GOLD interaction score of 62.12 with respect to the lead molecule zinc000059139266 which has shown a higher GOLD score of 78.07. Alanine scanning mutagenesis studies has shown that Phe201, Leu98 and Leu76 are found to be the key interacting residues in hydrophobic interactions. Similarly, Tyr324, Arg287 and Cys73 are major amino acid residues in the hydrogen bond interactions.

Conclusions

NOX-1 overexpression leads to heightened ROS production resulting in catastrophic outcomes. The modelled structure of NOX-1 has a good stereochemistry with respect to Ramachandran plot. The lead molecule zinc000059139266 has shown to have a very high interaction score of 78.07 compared to the referral drug GKT-831 with a score of 62.12. There is an excellent scope for the lead molecule to progress further into in vitro and in vivo studies.

Oxidative Regulation of Vascular Cav1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders

Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca²⁺ (Ca_v1.2) channel in small arteries and arterioles plays an essential role in regulating Ca²⁺ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Ca_v1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Ca_v1.2 and potential roles of ROS-mediated Ca_v1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.

Skin Microhemodynamics and Mechanisms of Its Regulation in Type 2 Diabetes Mellitus

The review presents modern ideas about peripheral microhemodynamics, approaches to the ana-lysis of skin blood flow oscillations and their diagnostic significance. Disorders of skin microhemodynamics in type 2 diabetes mellitus (DM) and the possibility of their interpretation from the standpoint of external and internal interactions between systems of skin blood flow regulation, based on a comparison of couplings in normal and pathological conditions, including models of pathologies on animals, are considered. The factors and mechanisms of vasomotor regulation, among them receptors and signaling events in endothelial and smooth muscle cells considered as models of microvessels are discussed. Attention was drawn to the disturbance of Ca2+-dependent regulation of coupling between vascular cells and NO-dependent regulation of vasodilation in diabetes mellitus. The main mechanisms of insulin resistance in type 2 DM are considered to be a defect in the number of insulin receptors and impaired signal transduction from the receptor to phosphatidylinositol-3-kinase and downstream targets. Reactive oxygen species plays an important role in vascular dysfunction in hyperglycemia. It is assumed that the considered molecular and cellular mechanisms of microhemodynamics regulation are involved in the formation of skin blood flow oscillations. Parameters of skin blood microcirculation can be used as diagnostic and prognostic markers for assessing the state of the body.

Mechanisms underlying Nrf2 nuclear translocation by non-lethal levels of hydrogen peroxide: p38 MAPK-dependent neutral sphingomyelinase2 membrane trafficking and ceramide/PKCζ/CK2 signaling

Hydrogen peroxide is an aerobic metabolite playing a central role in redox signaling and oxidative stress. H₂O₂ could activate redox sensitive transcription factors, such as Nrf2, AP-1 and NF-κB by different manners. In some cells, treatment with non-lethal levels of H₂O₂ induces rapid activation of Nrf2, which upregulates expression of a set of genes involved in glutathione (GSH) synthesis and defenses against oxidative damage. It depends on two steps, the rapid translational activation of Nrf2 and facilitation of Nrf2 nuclear translocation. We review the molecular mechanisms by which H₂O₂ induces nuclear translocation of Nrf2 in cultured cells by highlighting the role of neutral sphingomyelinase 2 (nSMase2), a GSH sensor. H₂O₂ enters cells through aquaporin channels in the plasma membrane and is rapidly reduced to H₂O by GSH peroxidases to consume cellular GSH, resulting in nSMase2 activation to generate ceramide. H₂O₂ also activates p38 MAP kinase, which enhances transfer of nSMase2 from perinuclear regions to plasma membrane lipid rafts to accelerate ceramide generation. Low levels of ceramide activate PKCζ, which then activates casein kinase 2 (CK2). These protein kinases are able to phosphorylate Nrf2 to stabilize and activate it. Notably, Nrf2 also binds to caveolin-1 (Cav1), which protects Nrf2 from Keap1-mediated degradation and limits Nrf2 nuclear translocation. We propose that Cav1serves as a signaling hub for the control of H₂O₂-mediated phosphorylation of Nrf2 by kinases, which results in release of Nrf2 from Cav1 to facilitate nuclear translocation. In summary, H₂O₂ induces GSH depletion which is recovered by Nrf2 activation dependent on p38/nSMase2/ceramide signaling.

Nox, Nox, Are You There? The Role of NADPH Oxidases in the Peripheral Nervous System

Significance: Reactive oxygen species (ROS) contribute to multiple aspects of peripheral nervous system (PNS) biology ranging from physiological processes (e.g., axonal outgrowth and regeneration) to pathophysiology (e.g., nerve degeneration). Although ROS are derived from multiple sources, NADPH oxidase (Nox) family members are dedicated to ROS generation. Noxs are expressed in the PNS, and their overexpression is associated with detrimental effects on nerve function and contributes, at least in part, to peripheral neuropathies. Recent Advances: Of the seven members, studies mostly focused on Nox1, Nox2, and Nox4, which are expressed in the PNS in a cell-specific manner. We have also recently identified human Nox5 in sural nerve biopsies. When maintained at homeostatic levels, Noxs regulate several aspects of peripheral nerve health, most notably neurite outgrowth and axonal regeneration following nerve lesion. While Nox2 and Nox4 dysregulation is a major source of oxidative stress in PNS disorders, including neuropathic pain and diabetic peripheral neuropathy, recent evidence also implicates Nox1 and Nox5. Critical Issues: Although there is compelling evidence for a direct role of Noxs on nerve function, little is known about their subcellular localization, intercellular regulation, and interaction. These, together with redox signaling, are considered crucial components of nerve redox status. In addition, the lack of isoform-specific inhibitors limits conclusions about the physiological role of Noxs in the PNS and their therapeutic potential in peripheral neuropathies. Future Directions: Future research using isoform-specific genetic and pharmacological approaches are therefore needed to better understand the significance of Nox enzymes in PNS (patho) physiology. Antioxid. Redox Signal. 37, 613-630.

Central role of c-Src in NOX5- mediated redox signalling in vascular smooth muscle cells in human hypertension

AIMS

NOX-derived reactive oxygen species (ROS) are mediators of signalling pathways implicated in vascular smooth muscle cell (VSMC) dysfunction in hypertension. Among the numerous redox-sensitive kinases important in VSMC regulation is c-Src. However, mechanisms linking NOX/ROS to c-Src are unclear, especially in the context of oxidative stress in hypertension. Here, we investigated the role of NOX-induced oxidative stress in VSMCs in human hypertension focusing on NOX5, and explored c-Src, as a putative intermediate connecting NOX5-ROS to downstream effector targets underlying VSMC dysfunction.

METHODS AND RESULTS

VSMC from arteries from normotensive (NT) and hypertensive (HT) subjects were studied. NOX1,2,4,5 expression, ROS generation, oxidation/phosphorylation of signalling molecules, and actin polymerization and migration were assessed in the absence and presence of NOX5 (melittin) and Src (PP2) inhibitors. NOX5 and p22phox-dependent NOXs (NOX1-4) were down-regulated using NOX5 siRNA and p22phox-siRNA approaches. As proof of concept in intact vessels, vascular function was assessed by myography in transgenic mice expressing human NOX5 in a VSMC-specific manner. In HT VSMCs, NOX5 was up-regulated, with associated oxidative stress, hyperoxidation (c-Src, peroxiredoxin, DJ-1), and hyperphosphorylation (c-Src, PKC, ERK1/2, MLC20) of signalling molecules. NOX5 siRNA reduced ROS generation in NT and HT subjects. NOX5 siRNA, but not p22phox-siRNA, blunted c-Src phosphorylation in HT VSMCs. NOX5 siRNA reduced phosphorylation of MLC20 and FAK in NT and HT. In p22phox- silenced HT VSMCs, Ang II-induced phosphorylation of MLC20 was increased, effects blocked by melittin and PP2. NOX5 and c-Src inhibition attenuated actin polymerization and migration in HT VSMCs. In NOX5 transgenic mice, vascular hypercontractilty was decreased by melittin and PP2.

CONCLUSION

We define NOX5/ROS/c-Src as a novel feedforward signalling network in human VSMCs. Amplification of this system in hypertension contributes to VSMC dysfunction. Dampening the NOX5/ROS/c-Src pathway may ameliorate hypertension-associated vascular injury.

Advanced Oxidation Protein Product Promotes Oxidative Accentuation in Renal Epithelial Cells via the Soluble (Pro)renin Receptor-Mediated Intrarenal Renin-Angiotensin System and Nox4-H2O2 Signaling

Full-length (pro)renin receptor (fPRR), a research hotspot of the renin-angiotensin system (RAS), plays a serious role in kidney injury. However, the relationship between fPRR and advanced oxidation protein product (AOPP) remains largely unexplored. This study was aimed at exploring the effect of fPRR, especially its 28 kDa soluble form called soluble PRR (sPRR), in AOPP-induced oxidative stress in HK-2 cells, a renal proximal tubular epithelial cell line. Incubation of HK-2 cells with 100 μg/ml AOPP resulted in significant upregulation of fPRR expression and caused an approximately fourfold increase in medium sPRR secretion. However, unmodified albumin did not demonstrate the same effects under the same concentration. Treatment of HK-2 cells with the site-1 protease (S1P) inhibitor PF429242 (40 μM) or S1P siRNA significantly inhibited AOPP-induced sPRR generation. fPRR decoy inhibitor PRO20 and PF429242 treatment for 24 h remarkably attenuated the AOPP-induced upregulation of RAS components. Furthermore, PF429242 significantly reduced the AOPP-stimulated expression of NADPH oxidase 4 (Nox4) and H₂O₂ expression. The use of a small recombinant protein, named sPRR-His, reversed these alterations. In conclusion, these results provided the first demonstration of AOPP-promoted activation of sPRR. Increased renal proximal tubule Nox4-derived H₂O₂ contributed to the aggravation of oxidative stress. Targeting S1P-derived sPRR is a promising intervention strategy for chronic kidney disease.

Aging under Pressure: The Roles of Reactive Oxygen and Nitrogen Species (RONS) Production and Aging Skeletal Muscle in Endothelial Function and Hypertension-From Biological Processes to Potential Interventions

The proportion of adults living with hypertension increases significantly with advancing age. It is therefore important to consider how health and vitality can be maintained by the aging population until end of life. A primary risk factor for the progression of cardiovascular diseases (CVD) is hypertension, so exploring the factors and processes central to this burden of disease is essential for healthy aging. A loss of skeletal muscle quantity and quality is characteristic in normal aging, with a reduction of vasodilatory capacity caused by endothelial dysfunction, and subsequent increase in peripheral resistance and risk for hypertension. Reactive Oxygen and Nitrogen Species (RONS) encompass the reactive derivatives of NO and superoxide, which are continuously generated in contracting skeletal muscle and are essential mediators for cellular metabolism. They act together as intra and intercellular messengers, gene expression regulators, and induce programmed cell death. In excessive amounts RONS can inflict damage to endothelial and skeletal muscle cells, alter signaling pathways or prematurely promote stress responses and potentially speed up the aging process. The age-related increase in RONS by skeletal muscle and endothelial mitochondria leads to impaired production of NO, resulting in vascular changes and endothelial dysfunction. Changes in vascular morphology is an early occurrence in the etiology of CVDs and, while this is also a normal characteristic of aging, whether it is a cause or a consequence of aging in hypertension remains unclear. This review serves to focus on the roles and mechanisms of biological processes central to hypertension and CVD, with a specific focus on the effects of aging muscle and RONS production, as well as the influence of established and more novel interventions to mediate the increasing risk for hypertension and CVD and improve health outcomes as we age.

Oxidative Stress and Hypertension

A link between oxidative stress and hypertension has been firmly established in multiple animal models of hypertension but remains elusive in humans. While initial studies focused on inactivation of nitric oxide by superoxide, our understanding of relevant reactive oxygen species (superoxide, hydrogen peroxide, and peroxynitrite) and how they modify complex signaling pathways to promote hypertension has expanded significantly. In this review, we summarize recent advances in delineating the primary and secondary sources of reactive oxygen species (nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, endoplasmic reticulum, and mitochondria), the posttranslational oxidative modifications they induce on protein targets important for redox signaling, their interplay with endogenous antioxidant systems, and the role of inflammasome activation and endoplasmic reticular stress in the development of hypertension. We highlight how oxidative stress in different organ systems contributes to hypertension, describe new animal models that have clarified the importance of specific proteins, and discuss clinical studies that shed light on how these processes and pathways are altered in human hypertension. Finally, we focus on the promise of redox proteomics and systems biology to help us fully understand the relationship between ROS and hypertension and their potential for designing and evaluating novel antihypertensive therapies.

Active food ingredients production from cold pressed processing residues of Camellia oleifera and Camellia sinensis seeds for regulation of blood pressure and vascular function

Hypertension is one of the most common illnesses worldwide. Accurate control of blood pressure can help reduce the incidence of complications. Nω-nitro-l-arginine methyl ester (l-NAME) is a nitric oxide synthase inhibitor that increases oxidative stress and inflammatory responses, activating the expression of transforming growth factor-beta (TGF-β), which thickens the vessel wall and ultimately contributes to hypertension. Studies have shown that seeds of Camellia oleifera Abel and Camellia sinensis (L). O. Kuntze (Oolong tea) possesses antibacterial, antioxidant, and anti-inflammatory functions. Therefore, this study aimed was to investigate the functional components in the seed pomace ethanol extracts of C. oleifera Abel (CPE) and Oolong tea (OPE) and to evaluate the ameliorative effects of CPE and OPE on oxidative stress, inflammation, and vascular remodeling in l-NAME induced hypertensive C57BL/6J mice. After 8 weeks of treatment, all CPE and OPE dose groups significantly reduced systolic and diastolic blood pressure, by over 30 mmHg and 15 mmHg, respectively. Additionally, CPE and OPE decreased transforming growth factor-beta (TGF-β) expression in the thoracic aortic and thoracic aortic intima-media thickness. Moreover, CPE and OPE decreased the malondialdehyde concentration in the liver by over 33%, as well as levels of tumor necrosis factor-α, interleukin 6, and interleukin-1β in the kidney and heart. Collectively, CPE and OPE can reduce oxidative stress and vascular remodeling, lowering blood pressure, and reducing the risk of cardiovascular disease.

(Pro)renin receptor decoy peptide PRO20 protects against adriamycin-induced nephropathy by targeting the intrarenal renin-angiotensin system

Adriamycin (ADR) administration in susceptible rodents such as the BALB/c mouse strain produces injury to the glomerulus mimicking human chronic kidney disease due to primary focal segmental glomerulosclerosis. The goal of the present study was to use this model to investigate antiproteinuric actions of the (pro)renin receptor decoy inhibitor PRO20. BALB/c mice were pretreated for 1 day with PRO20 at 500 μg·kg-1·day-1 via an osmotic minipump followed by a single injection of vehicle or ADR (10 mg/kg) via the tail vein. Albuminuria and renal function were analyzed at the fourth week post-ADR administration. ADR-treated mice exhibited severe proteinuria, hypoalbuminemia and hyperlipidemia, glomerulosclerosis, podocyte loss, tubulointerstitial fibrosis, and oxidative stress, accompanied by elevated urinary neutrophil gelatinase-associated lipocalin and kidney injury molecule-1, all of which were significantly attenuated by PRO20. Urinary and renal renin activity and angiotensin II were elevated by ADR and suppressed by PRO20. In parallel, urinary and renal H2O2 levels and renal NADPH oxidase 4 (Nox4) and transient receptor potential channel C6 (TRPC6) expression in response to ADR were all similarly suppressed. Taken together, the results of the present study provide the first evidence that PRO20 can protect against podocyte damage and interstitial fibrosis in ADR nephropathy by preventing activation of the intrarenal renin-angiotensin system and upregulation of Nox4 and TRPC6 expression. PRO20 may have a potential application in the treatment of ADR nephropathy.

Mitochondria and cellular redox state on the route from ageing to Alzheimer's disease

Several theories have been postulated, trying to explain why and how living organisms age. Despite some controversies and still huge open questions, a growing body of evidence suggest alterations of mitochondrial functionality and redox-homeostasis occur during the ageing process. Oxidative damage and mitochondrial dysfunction do not represent the cause of ageing per se but they have to be analyzed within the complexity of those series of processes occurring during lifespan. The establishment of a crosstalk among them is a shared common feature of many chronic age-related diseases, including neurodegenerative disorders, for which ageing is a major risk factor. The challenge is to understand when and how the interplay between these two systems move towards from normal ageing process to a pathological phenotype. Here in this review, we discuss the crosstalk between mitochondria and cytosolic-ROS. Furthermore, through a visual data mining approach, we attempt to describe the dynamic interplay between mitochondria and cellular redox state on the route from ageing to an AD phenotype.

Methylation-dependent antioxidant-redox imbalance regulates hypertensive kidney injury in aging

The prevalence of hypertension increases with age, and oxidative stress is a major contributing factor to the pathogenesis of hypertension-induced kidney damage in aging. The nicotinamide adenine dinucleotide phosphate (NADPH) family is one of the major sources of reactive oxygen species (ROS) generation, and several NADPH oxidase isoforms are highly expressed in the kidney. Although epigenetic protein modification plays a role in organ injury, the methylation of the oxidant-antioxidant defense system and their role in hypertension-induced kidney damage in aging remains underexplored. The present study investigated the role of NADPH oxidase 4, superoxide dismutases (SODs), catalase, and NOS in Ang-II induced kidney damage in aging. Wild type (WT, C57BL/6J) mice aged 12-14 and 75-78 weeks were used and treated with or without Ang-II (1000 ng/kg/min) for 4 weeks with control mice receiving saline. Aged mice with or without Ang-II exhibited higher mean BP, lower renal blood flow, and decreased renal vascular density compared to young mice. While superoxide, 4-HNE, p22^phox, Nox4, iNOS were increased in the aged kidney, the expression of eNOS, MnSOD, CuSOD, catalase, Sirt1, and -3 as well as the ratio of GSH/GSSG, and activities of SODs and catalase were decreased compared to young control mice. The changes further deteriorated with Ang-II treatment. In Ang-II treated aged mice, the expressions of DNMTs were increased and associated with increased methylation of SODs, Sirt1, and Nox4. We conclude that hypermethylation of antioxidant enzymes in the aged kidney during hypertension worsens redox imbalance leading to kidney damage.

Oxidative Stress: A Unifying Paradigm in Hypertension

The etiology of hypertension involves complex interactions among genetic, environmental, and pathophysiologic factors that influence many regulatory systems. Hypertension is characteristically associated with vascular dysfunction, cardiovascular remodelling, renal dysfunction, and stimulation of the sympathetic nervous system. Emerging evidence indicates that the immune system is also important and that activated immune cells migrate and accumulate in tissues promoting inflammation, fibrosis, and target-organ damage. Common to these processes is oxidative stress, defined as an imbalance between oxidants and antioxidants in favour of the oxidants that leads to a disruption of oxidation-reduction (redox) signalling and control and molecular damage. Physiologically, reactive oxygen species (ROS) act as signalling molecules and influence cell function through highly regulated redox-sensitive signal transduction. In hypertension, oxidative stress promotes posttranslational modification (oxidation and phosphorylation) of proteins and aberrant signalling with consequent cell and tissue damage. Many enzymatic systems generate ROS, but NADPH oxidases (Nox) are the major sources in cells of the heart, vessels, kidneys, and immune system. Expression and activity of Nox are increased in hypertension and are the major systems responsible for oxidative stress in cardiovascular disease. Here we provide a unifying concept where oxidative stress is a common mediator underlying pathophysiologic processes in hypertension. We focus on some novel concepts whereby ROS influence vascular function, aldosterone/mineralocorticoid actions, and immunoinflammation, all important processes contributing to the development of hypertension.

Chronic Exposure to Fluoride Affects GSH Level and NOX4 Expression in Rat Model of This Element of Neurotoxicity

Exposure of neural cells to harmful and toxic factors promotes oxidative stress, resulting in disorders of metabolism, cell differentiation, and maturation. The study examined the brains of rats pre- and postnatally exposed to sodium fluoride (NaF 50 mg/L) and activity of NADPH oxidase 4 (NOX4), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), concentration of glutathione (GSH), and total antioxidant capacity (TAC) in the cerebellum, prefrontal cortex, hippocampus, and striatum were measured. Additionally, NOX4 expression was determined by qRT-PCR. Rats exposed to fluorides (F-) showed an increase in NOX4 activity in the cerebellum and hippocampus, a decrease in its activity in the prefrontal cortex and hippocampus, and upregulation of NOX4 expression in hippocampus and its downregulation in other brain structures. Analysis also showed significant changes in the activity of all antioxidant enzymes and a decrease in TAC in brain structures. NOX4 induction and decreased antioxidant activity in central nervous system (CNS) cells may be central mechanisms of fluoride neurotoxicity. NOX4 contributes to blood-brain barrier damage, microglial activation, and neuronal loss, leading to impairment of brain function. Fluoride-induced oxidative stress involves increased reactive oxygen speciaes (ROS) production, which in turn increases the expression of genes encoding pro-inflammatory cytokines.

Calcium Signaling Commands Phagosome Maturation Process

Phagosome-lysosome (P-L) fusion is one of the central immune-effector responses of host. It is known that phagosome maturation process is associated with numerous signaling cascades and among these, important role of calcium (Ca²⁺) signaling has been realized recently. Ca²⁺ plays key roles in actin rearrangement, activation of NADPH oxidase and protein kinase C (PKC). Involvement of Ca²⁺ in these cellular processes directs phagosomal maturation process. Some of the intracellular pathogens have acquired the strategies to modulate Ca²⁺ associated pathways to block P-L fusion process. In this review we have described the mechanism of Ca²⁺ signals that influence P-L fusion by controlling ROS, actin and PKC signaling cascades. We have also discussed the strategies implemented by the intracellular pathogens to manipulate Ca²⁺ signaling to consequently subvert P-L fusion. A detail study of factors associated in manipulating Ca²⁺ signaling may provide new insights for the development of therapeutic tools for more effective treatment options against infectious diseases.

Transcriptional response provides insights into the effect of chronic polystyrene nanoplastic exposure on Daphnia pulex

Nanoplastic pollution is widespread and persistent across global water systems and can cause a negative effect on aquatic organisms, especially the zooplankter which is the keystone of the food chain. The present study uses RNA sequencing to assess the global change in gene expression caused by 21 days of exposure to 75 nm polystyrene (PS) nanoplastics on Daphnia pulex, a model organism for ecotoxicity. With the threshold value at P value < 0.05 and fold change >2, 244 differentially expressed genes were obtained. Combined with real-time PCR validation of several selected genes, our results indicated that a distinct expression profile of key genes, including downregulated trehalose transporter, trehalose 6-phosphate synthase/phosphatase, chitinase and cathepsin-L as well as upregulated doublesex 1 and doublesex and mab-3 related transcription factor-like protein, contributed to the toxic effects of chronic nanoplastic exposure on Daphnia, such as slowed growth, subdued reproductive ability and reproductive pattern shifting. Our study also showed that chronic exposure to nanoplastic changed the sex ratio of D. pulex neonates. By integrating the gene expression pattern in an important model organism, this study gained insight into the molecular mechanisms of the toxic effect of chronic PS nanoplastic exposure on D. pulex, which may also extend to other nanoplastics or aquatic animals.

Vascular smooth muscle contraction in hypertension

Hypertension is a major risk factor for many common chronic diseases, such as heart failure, myocardial infarction, stroke, vascular dementia, and chronic kidney disease. Pathophysiological mechanisms contributing to the development of hypertension include increased vascular resistance, determined in large part by reduced vascular diameter due to increased vascular contraction and arterial remodelling. These processes are regulated by complex-interacting systems such as the renin-angiotensin-aldosterone system, sympathetic nervous system, immune activation, and oxidative stress, which influence vascular smooth muscle function. Vascular smooth muscle cells are highly plastic and in pathological conditions undergo phenotypic changes from a contractile to a proliferative state. Vascular smooth muscle contraction is triggered by an increase in intracellular free calcium concentration ([Ca²⁺]_i), promoting actin–myosin cross-bridge formation. Growing evidence indicates that contraction is also regulated by calcium-independent mechanisms involving RhoA-Rho kinase, protein Kinase C and mitogen-activated protein kinase signalling, reactive oxygen species, and reorganization of the actin cytoskeleton. Activation of immune/inflammatory pathways and non-coding RNAs are also emerging as important regulators of vascular function. Vascular smooth muscle cell [Ca²⁺]_i not only determines the contractile state but also influences activity of many calcium-dependent transcription factors and proteins thereby impacting the cellular phenotype and function. Perturbations in vascular smooth muscle cell signalling and altered function influence vascular reactivity and tone, important determinants of vascular resistance and blood pressure. Here, we discuss mechanisms regulating vascular reactivity and contraction in physiological and pathophysiological conditions and highlight some new advances in the field, focusing specifically on hypertension.

NOX5: Molecular biology and pathophysiology

NEW FINDINGS

What is the topic of this review? This review provides a comprehensive overview of Nox5 from basic biology to human disease and highlights unique features of this Nox isoform What advances does it highlight? Major advances in Nox5 biology relate to crystallization of the molecule and new insights into the pathophysiological role of Nox5. Recent discoveries have unravelled the crystal structure of Nox5, the first Nox isoform to be crystalized. This provides new opportunities to develop drugs or small molecules targeted to Nox5 in an isoform-specific manner, possibly for therapeutic use. Moreover genome wide association studies (GWAS) identified Nox5 as a new blood pressure-associated gene and studies in mice expressing human Nox5 in a cell-specific manner have provided new information about the (patho) physiological role of Nox5 in the cardiovascular system and kidneys. Nox5 seems to be important in the regulation of vascular contraction and kidney function. In cardiovascular disease and diabetic nephropathy, Nox5 activity is increased and this is associated with increased production of reactive oxygen species and oxidative stress implicated in tissue damage.

ABSTRACT

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox), comprise seven family members (Nox1-Nox5 and dual oxidase 1 and 2) and are major producers of reactive oxygen species in mammalian cells. Reactive oxygen species are crucially involved in cell signalling and function. All Noxs share structural homology comprising six transmembrane domains with two haem-binding regions and an NADPH-binding region on the intracellular C-terminus, whereas their regulatory systems, mechanisms of activation and tissue distribution differ. This explains the diverse function of Noxs. Of the Noxs, NOX5 is unique in that rodents lack the gene, it is regulated by Ca2+ , it does not require NADPH oxidase subunits for its activation, and it is not glycosylated. NOX5 localizes in the perinuclear and endoplasmic reticulum regions of cells and traffics to the cell membrane upon activation. It is tightly regulated through numerous post-translational modifications and is activated by vasoactive agents, growth factors and pro-inflammatory cytokines. The exact pathophysiological significance of NOX5 remains unclear, but it seems to be important in the physiological regulation of sperm motility, vascular contraction and lymphocyte differentiation, and NOX5 hyperactivation has been implicated in cardiovascular disease, kidney injury and cancer. The field of NOX5 biology is still in its infancy, but with new insights into its biochemistry and cellular regulation, discovery of the NOX5 crystal structure and genome-wide association studies implicating NOX5 in disease, the time is now ripe to advance NOX5 research. This review provides a comprehensive overview of our current understanding of NOX5, from basic biology to human disease, and highlights the unique characteristics of this enigmatic Nox isoform.

NOX5 as a therapeutic target in cerebral ischemic injury

In this issue of the JCI, Casas et al. define a previously unknown role of the NADPH oxidase catalytic subunit NOX5 in cerebral infarction. Using a mouse expressing human NOX5 in the endothelium, the investigators show that NOX5 is activated and plays a deleterious role in promoting edema, infarction, and ultimately, worsened neurological function following cerebral ischemia. They provide evidence that this is due to the breakdown of the blood-brain barrier (BBB) and that a unique pharmacological inhibitor of NOX5, ML090, if given early, around the time of reoxygenation, can maintain BBB integrity. Future studies of NOX5 inhibition in humans, particularly in the setting of thrombolysis, are warranted.

Vascular Biology of Superoxide-Generating NADPH Oxidase 5-Implications in Hypertension and Cardiovascular Disease

SIGNIFICANCE

NADPH oxidases (Noxs), of which there are seven isoforms (Nox1-5, Duox1/Duox2), are professional oxidases functioning as reactive oxygen species (ROS)-generating enzymes. ROS are signaling molecules important in physiological processes. Increased ROS production and altered redox signaling in the vascular system have been implicated in the pathophysiology of cardiovascular diseases, including hypertension, and have been attributed, in part, to increased Nox activity. Recent Advances: Nox1, Nox2, Nox4, and Nox5 are expressed and functionally active in human vascular cells. While Nox1, Nox2, and Nox4 have been well characterized in models of cardiovascular disease, little is known about Nox5. This may relate to the lack of experimental models because rodents lack NOX5. However, recent studies have advanced the field by (i) elucidating mechanisms of Nox5 regulation, (ii) identifying Nox5 variants, (iii) characterizing Nox5 expression, and (iv) discovering the Nox5 crystal structure. Moreover, studies in human Nox5-expressing mice have highlighted a putative role for Nox5 in cardiovascular disease.

CRITICAL ISSUES

Although growing evidence indicates a role for Nox-derived ROS in cardiovascular (patho)physiology, the exact function of each isoform remains unclear. This is especially true for Nox5.

FUTURE DIRECTIONS

Future directions should focus on clinically relevant studies to discover the functional significance of Noxs, and Nox5 in particular, in human health and disease. Two important recent studies will impact future directions. First, Nox5 is the first Nox to be crystallized. Second, a genome-wide association study identified Nox5 as a novel blood pressure-associated gene. These discoveries, together with advancements in Nox5 biology and biochemistry, will facilitate discovery of drugs that selectively target Noxs to interfere in uncontrolled ROS generation.

Regulation of NADPH Oxidases by G Protein-Coupled Receptors

SIGNIFICANCE

G protein-coupled receptors (GPCR) are the largest group of cell surface receptors, which link cells to their environment. Reactive oxygen species (ROS) can act as important cellular signaling molecules. The family of NADPH oxidases generates ROS in response to activated cell surface receptors. Recent Advances: Various signaling pathways linking GPCRs and activation of NADPH oxidases have been characterized.

CRITICAL ISSUES

Still, a more detailed analysis of G proteins involved in the GPCR-mediated activation of NADPH oxidases is needed. In addition, a more precise discrimination of NADPH oxidase activation due to either upregulation of subunit expression or post-translational subunit modifications is needed. Also, the role of noncanonical modulators of NADPH oxidase activation in the response to GPCRs awaits further analyses.

FUTURE DIRECTIONS

As GPCRs are one of the most popular classes of investigational drug targets, further detailing of G protein-coupled mechanisms in the activation mechanism of NADPH oxidases as well as better understanding of the link between newly identified NADPH oxidase interaction partners and GPCR signaling will provide new opportunities for improved efficiency and decreased off target effects of therapies targeting GPCRs.

A causal link between oxidative stress and inflammation in cardiovascular and renal complications of diabetes

Chronic renal and vascular oxidative stress in association with an enhanced inflammatory burden are determinant processes in the development and progression of diabetic complications including cardiovascular disease (CVD), atherosclerosis and diabetic kidney disease (DKD). Persistent hyperglycaemia in diabetes mellitus increases the production of reactive oxygen species (ROS) and activates mediators of inflammation as well as suppresses antioxidant defence mechanisms ultimately contributing to oxidative stress which leads to vascular and renal injury in diabetes. Furthermore, there is increasing evidence that ROS, inflammation and fibrosis promote each other and are part of a vicious connection leading to development and progression of CVD and kidney disease in diabetes.

NADPH Oxidase 5 Is a Pro-Contractile Nox Isoform and a Point of Cross-Talk for Calcium and Redox Signaling-Implications in Vascular Function

BACKGROUND

NADPH Oxidase 5 (Nox5) is a calcium-sensitive superoxide-generating Nox. It is present in lower forms and higher mammals, but not in rodents. Nox5 is expressed in vascular cells, but the functional significance remains elusive. Given that contraction is controlled by calcium and reactive oxygen species, both associated with Nox5, we questioned the role of Nox5 in pro-contractile signaling and vascular function.

METHODS AND RESULTS

Transgenic mice expressing human Nox5 in a vascular smooth muscle cell-specific manner (Nox5 mice) and Rhodnius prolixus, an arthropod model that expresses Nox5 endogenoulsy, were studied. Reactive oxygen species generation was increased systemically and in the vasculature and heart in Nox5 mice. In Nox5-expressing mice, agonist-induced vasoconstriction was exaggerated and endothelium-dependent vasorelaxation was impaired. Vascular structural and mechanical properties were not influenced by Nox5. Vascular contractile responses in Nox5 mice were normalized by N-acetylcysteine and inhibitors of calcium channels, calmodulin, and endoplasmic reticulum ryanodine receptors, but not by GKT137831 (Nox1/4 inhibitor). At the cellular level, vascular changes in Nox5 mice were associated with increased vascular smooth muscle cell [Ca2+]i, increased reactive oxygen species and nitrotyrosine levels, and hyperphosphorylation of pro-contractile signaling molecules MLC20 (myosin light chain 20) and MYPT1 (myosin phosphatase target subunit 1). Blood pressure was similar in wild-type and Nox5 mice. Nox5 did not amplify angiotensin II effects. In R. prolixus, gastrointestinal smooth muscle contraction was blunted by Nox5 silencing, but not by VAS2870 (Nox1/2/4 inhibitor).

CONCLUSIONS

Nox5 is a pro-contractile Nox isoform important in redox-sensitive contraction. This involves calcium-calmodulin and endoplasmic reticulum-regulated mechanisms. Our findings define a novel function for vascular Nox5, linking calcium and reactive oxygen species to the pro-contractile molecular machinery in vascular smooth muscle cells.

Redox Signaling and Persistent Pulmonary Hypertension of the Newborn

Reactive oxygen species (ROS) are redox-signaling molecules that are critically involved in regulating endothelial cell functions, host defense, aging, and cellular adaptation. Mitochondria are the major sources of ROS and important sources of redox signaling in pulmonary circulation. It is becoming increasingly evident that increased mitochondrial oxidative stress and aberrant signaling through redox-sensitive pathways play a direct causative role in the pathogenesis of many cardiopulmonary disorders including persistent pulmonary hypertension of the newborn (PPHN). This chapter highlights redox signaling in endothelial cells, antioxidant defense mechanism, cell responses to oxidative stress, and their contributions to disease pathogenesis.

Cardiac and renal upregulation of Nox2 and NF-κB and repression of Nox4 and Nrf2 in season- and diabetes-mediated models of vascular oxidative stress in guinea-pig and rat

The superoxide-forming NADPH oxidase homologues, Nox1, Nox2, and Nox5, seem to mediate the pro-atherosclerotic vascular phenotype. The hydrogen peroxide-forming Nox4 afforded vascular protection, likely via NF-E2-related factor-2 (Nrf2) activation and/or Nox2 downregulation in transgenic mice. We hypothesized that oxidative stress in the intact vasculature involves, aside from the upregulation of the superoxide-forming Noxs, the downregulation of the Nox4/Nrf2 pathway. Guinea-pigs and rats were studied either in winter or in summer, and the streptozotocin diabetic rats in winter. Plasma nitrite, and superoxide production by isolated hearts were measured, while frozen tissues served in biochemical analyses. Summer in both species and diabetes in rats downregulated myocardial Nox4 while reciprocally upregulating Nox2 and Nox5 in guinea-pigs, and Nox2 in rats. Simultaneously, myocardial Nrf2 activity and the expression of the Nrf2-directed heme oxygenase-1 and endothelial NO synthase were reduced while activity of the nuclear factor κB (NF-κB) and the expression of NF-κB-directed inducible NO synthase and the vascular cell adhesion molecule-1 were increased. Cardiac superoxide production was increased while plasma nitrite was decreased reciprocally. Analogous disregulation of Noxs, Nrf2, and NF-κB, occurred in diabetic rat kidneys. Given the diversity of the experimental settings and the uniform pattern of the responses, we speculate that: (1) chronic vascular oxidative stress is a nonspecific (model-, species-, organ-independent) response involving the induction of Nox2 (and Nox5 in guinea-pigs) and the NF-κB pathway, and the repression of Nox4 and the Nrf2 pathway; and (2) the systems Nox2-NF-κB and Nox4-Nrf2 regulate each other negatively.

NADPH Oxidase Nox5 Accelerates Renal Injury in Diabetic Nephropathy

NADPH oxidase-derived excessive production of reactive oxygen species (ROS) in the kidney plays a key role in mediating renal injury in diabetes. Pathological changes in diabetes include mesangial expansion and accumulation of extracellular matrix (ECM) leading to glomerulosclerosis. There is a paucity of data about the role of the Nox5 isoform of NADPH oxidase in animal models of diabetic nephropathy since Nox5 is absent in the mouse genome. Thus, we examined the role of Nox5 in human diabetic nephropathy in human mesangial cells and in an inducible human Nox5 transgenic mouse exposed to streptozotocin-induced diabetes. In human kidney biopsies, Nox5 was identified to be expressed in glomeruli, which appeared to be increased in diabetes. Colocalization demonstrated Nox5 expression in mesangial cells. In vitro, silencing of Nox5 in human mesangial cells was associated with attenuation of the hyperglycemia and TGF-β1-induced enhanced ROS production, increased expression of profibrotic and proinflammatory mediators, and increased TRPC6, PKC-α, and PKC-β expression. In vivo, vascular smooth muscle cell/mesangial cell-specific overexpression of Nox5 in a mouse model of diabetic nephropathy showed enhanced glomerular ROS production, accelerated glomerulosclerosis, mesangial expansion, and ECM protein (collagen IV and fibronectin) accumulation as well as increased macrophage infiltration and expression of the proinflammatory chemokine MCP-1. Collectively, this study provides evidence of a role for Nox5 and its derived ROS in promoting progression of diabetic nephropathy.

The emerging role of NADPH oxidase NOX5 in vascular disease

Oxidative stress is a consequence of up-regulation of pro-oxidant enzyme-induced reactive oxygen species (ROS) production and concomitant depletion of antioxidants. Elevated levels of ROS act as an intermediate and are the common denominator for various diseases including diabetes-associated macro-/micro-vascular complications and hypertension. A range of enzymes are capable of generating ROS, but the pro-oxidant enzyme family, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs), are the only enzymes known to be solely dedicated to ROS generation in the vascular tissues, kidney, aortas and eyes. While there is convincing evidence for a role of NOX1 in vascular and eye disease and for NOX4 in renal injury, the role of NOX5 in disease is less clear. Although NOX5 is highly up-regulated in humans in disease, it is absent in rodents. Thus, so far it has not been possible to study NOX5 in traditional mouse or rat models of disease. In the present review, we summarize and critically analyse the emerging evidence for a pathophysiological role of NOX5 in disease including the expression, regulation and molecular and cellular mechanisms which have been demonstrated to be involved in NOX5 activation.

Drug Treatment of Hypertension: Focus on Vascular Health

Hypertension, the most common preventable risk factor for cardiovascular disease and death, is a growing health burden. Serious cardiovascular complications result from target organ damage including cerebrovascular disease, heart failure, ischaemic heart disease and renal failure. While many systems contribute to blood pressure (BP) elevation, the vascular system is particularly important because vascular dysfunction is a cause and consequence of hypertension. Hypertension is characterised by a vascular phenotype of endothelial dysfunction, arterial remodelling, vascular inflammation and increased stiffness. Antihypertensive drugs that influence vascular changes associated with high BP have greater efficacy for reducing cardiovascular risk than drugs that reduce BP, but have little or no effect on the adverse vascular phenotype. Angiotensin converting enzyme ACE inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) improve endothelial function and prevent vascular remodelling. Calcium channel blockers also improve endothelial function, although to a lesser extent than ACEIs and ARBs. Mineralocorticoid receptor blockers improve endothelial function and reduce arterial stiffness, and have recently become more established as antihypertensive drugs. Lifestyle factors are essential in preventing the adverse vascular changes associated with high BP and reducing associated cardiovascular risk. Clinicians and scientists should incorporate these factors into treatment decisions for patients with high BP, as well as in the development of new antihypertensive drugs that promote vascular health.

Enhanced Aerobic Glycolysis by S-Nitrosoglutathione via HIF-1α Associated GLUT1/Aldolase A Axis in Human Endothelial Cells

S-nitrosoglutathione (GSNO)-induced apoptosis is associated with reactive oxygen species and loss of mitochondrial Omi/HtrA2 in human endothelial cells (ECs). But its upstream regulation is still not elucidated. Here, we demonstrate that hypoxia induced factor-1α (HIF-1α)-linked aerobic glycolysis is associated with mitochondrial abnormality by treatment of human EC-derived EA.hy926 cells with GSNO (500 µM) for 6 h. GSNO exposure increased the levels of Aldolase A and glucose transporter-1 (GLUT1) mRNAs and proteins. And selectively enhanced aldolase A activity to form glyceraldehyde 3-phosphate, dihydroxyacetone phosphate, which subsequently increased intracellular levels of methylglyoxal and reactive oxygen species in parallel. Using the biotin switch assay, we found that GSNO increased the S-nitrosylating levels of total protein and HIF-1α. Knockdown of HIF-1α with siRNA attenuated its target aldolase A and GLUT1 expression but not VEGF. In contrast, nitrosylation scanvenger dithiothreitol could decrease all the protein levels. It suggested that aerobic glycolytic flux was more dependent on HIF-1α level, and that HIF-1α S-nitrosylation was crucial for its target expression under the normoxic condition. Moreover, GSNO-induced PI3 K (phosphoinositide 3-kinase)/Akt phosphorylation might contribute to HIF-1α stabilization and nucleus translocation, thereby aiding aldolase A and GLUT1 mRNAs upregulation. Taken together, higher concentration GSNO promotes glycolytic flux enhancement and methylglyoxal formation via HIF-1α S-nitrosylation. These findings reveal the mechanism of enhanced glycolysis-associated mitochondrial dysfunction in ECs by GSNO exposure under normoxic and non-hyperglycemic condition. And offer the early potential targets for vascular pathophysiological evaluation. J. Cell. Biochem. 118: 2443-2453, 2017. © 2017 Wiley Periodicals, Inc.

Endothelium-Derived Hyperpolarization and Coronary Vasodilation: Diverse and Integrated Roles of Epoxyeicosatrienoic Acids, Hydrogen Peroxide, and Gap Junctions

Myocardial perfusion and coronary vascular resistance are regulated by signaling metabolites released from the local myocardium that act either directly on the VSMC or indirectly via stimulation of the endothelium. A prominent mechanism of vasodilation is EDH of the arteriolar smooth muscle, with EETs and H(2)O(2) playing important roles in EDH in the coronary microcirculation. In some cases, EETs and H(2)O(2) are released as transferable hyperpolarizing factors (EDHFs) that act directly on the VSMCs. By contrast, EETs and H(2)O(2) can also promote endothelial KCa activity secondary to the amplification of extracellular Ca(2+) influx and Ca(2+) mobilization from intracellular stores, respectively. The resulting endothelial hyperpolarization may subsequently conduct to the media via myoendothelial gap junctions or potentially lead to the release of a chemically distinct factor(s). Furthermore, in human isolated coronary arterioles dilator signaling involving EETs and H(2)O(2) may be integrated, being either complimentary or inhibitory depending on the stimulus. With an emphasis on the human coronary microcirculation, this review addresses the diverse and integrated mechanisms by which EETs and H(2)O(2) regulate vessel tone and also examines the hypothesis that myoendothelial microdomain signaling facilitates EDH activity in the human heart.

Differential effects of NOX4 and NOX1 on immune cell-mediated inflammation in the aortic sinus of diabetic ApoE−/− mice

Oxidative stress and inflammation are central mediators of atherosclerosis particularly in the context of diabetes. The potential interactions between the major producers of vascular reactive oxygen species (ROS), NADPH oxidase (NOX) enzymes and immune-inflammatory processes remain to be fully elucidated. In the present study we investigated the roles of the NADPH oxidase subunit isoforms, NOX4 and NOX1, in immune cell activation and recruitment to the aortic sinus atherosclerotic plaque in diabetic ApoE−/− mice. Plaque area analysis showed that NOX4- and NOX1-derived ROS contribute to atherosclerosis in the aortic sinus following 10 weeks of diabetes. Immunohistochemical staining of the plaques revealed that NOX4-derived ROS regulate T-cell recruitment. In addition, NOX4-deficient mice showed a reduction in activated CD4+ T-cells in the draining lymph nodes of the aortic sinus coupled with reduced pro-inflammatory gene expression in the aortic sinus. Conversely, NOX1-derived ROS appeared to play a more important role in macrophage accumulation. These findings demonstrate distinct roles for NOX4 and NOX1 in immune-inflammatory responses that drive atherosclerosis in the aortic sinus of diabetic mice.

The CYBA Gene (⁎)49A>G Polymorphism (rs7195830) Is Associated with Hypertension in Patients with Coronary Artery Disease

Purpose. Single nucleotide polymorphisms of the CYBA gene may modify the risk of coronary artery disease (CAD). The aim of the present study was to investigate whether the ^⁎49A>G (rs7195830) polymorphism is associated with CAD. Materials and Methods. CYBA gene ^⁎49A>G polymorphism was determined in 481 subjects: 242 patients with premature CAD and 239 age and sex matched controls using the fluorescently labeled allele-specific oligonucleotides method. Results. The frequency of the ^⁎49G allele carrier state was significantly higher in patients than in controls (84.8% versus 76.6%, resp., P = 0.020), as well as the frequency of the ^⁎49G allele (62.2% versus 54.0%, P = 0.009). Both factors were associated with CAD in the analyzed population (OR = 1.70, 95% CI: 1.04–2.76 for GG+AG versus AA and OR = 1.40, 95% CI: 1.08–1.83 for ^⁎49G versus  ^⁎49A). Carrier state of the ^⁎49G allele was a stronger and independent risk factor for CAD among women (OR = 4.35, 95% CI: 1.50–13.20, P = 0.002), as well as the ^⁎49G allele (OR = 2.25, 95% CI: 1.34–3.77, P = 0.001). The ^⁎49G allele carrier state was also associated with left ventricular hypertrophy in patients with coronary artery disease (P = 0.015). Conclusion. The CYBA gene ^⁎49A>G polymorphism modifies the risk of coronary artery disease.

ROS and ROS-Mediated Cellular Signaling

It has long been recognized that an increase of reactive oxygen species (ROS) can modify the cell-signaling proteins and have functional consequences, which successively mediate pathological processes such as atherosclerosis, diabetes, unchecked growth, neurodegeneration, inflammation, and aging. While numerous articles have demonstrated the impacts of ROS on various signaling pathways and clarify the mechanism of action of cell-signaling proteins, their influence on the level of intracellular ROS, and their complex interactions among multiple ROS associated signaling pathways, the systemic summary is necessary. In this review paper, we particularly focus on the pattern of the generation and homeostasis of intracellular ROS, the mechanisms and targets of ROS impacting on cell-signaling proteins (NF-κB, MAPKs, Keap1-Nrf2-ARE, and PI3K-Akt), ion channels and transporters (Ca(2+) and mPTP), and modifying protein kinase and Ubiquitination/Proteasome System.

Increased expression of NAPDH oxidase 4 in systemic sclerosis dermal fibroblasts: regulation by transforming growth factor β

OBJECTIVE

Systemic sclerosis (SSc) is characterized by severe and often progressive fibrosis of the skin and multiple internal organs. The mechanisms responsible for these alterations remain obscure, although excessive reactive oxygen species (ROS)-mediated oxidative stress has been implicated. NOX-4 is 1 of 7 isoforms of NADPH oxidase responsible for the generation of ROS. The purpose of this study was to examine NOX-4 expression in skin and cultured dermal fibroblasts from SSc patients and to examine its regulation by transforming growth factor β1 (TGFβ1).

METHODS

NOX-4 was assessed in normal and SSc skin by immunohistologic analysis and in normal and SSc cultured dermal fibroblasts by quantitative polymerase chain reaction analysis, fluorescence microscopy, and Western blotting. ROS levels were assessed by fluorescence measurement of H2 O2 production. Specific kinase inhibitors were used to study the TGFβ1 signaling involved in NOX-4 stimulation. NOX-4 inhibition/down-regulation was induced with a selective NOX-4 small-molecule inhibitor and NOX-4 small interfering RNA (siRNA).

RESULTS

In contrast with normal skin fibroblasts, those from SSc skin showed intense NOX-4 staining. Cultured SSc fibroblasts displayed increased NOX-4 expression. TGFβ1 caused potent NOX-4 protein and messenger RNA stimulation in normal and SSc fibroblasts, which was mediated by the protein kinase Cδ (PKCδ) and Smad2/3 pathways. NOX-4 knockdown in SSc fibroblasts reduced the production of ROS and lowered the expression of type I collagen.

CONCLUSION

NOX-4 expression and production were found to be constitutively elevated in SSc skin and cultured SSc dermal fibroblasts. TGFβ1 stimulated NOX-4 expression in normal and SSc fibroblasts through PKCδ and Smad2/3 signaling pathways. A small-molecule NOX-4 inhibitor decreased collagen and fibronectin production by normal and SSc fibroblasts, and NOX-4 siRNA knockdown reduced ROS and collagen production by SSc fibroblasts. These results demonstrate the involvement of NOX-4 in SSc-associated fibrosis and indicate NOX-4 inhibitors as novel therapeutic approaches for SSc.

Key Role of ROS in the Process of 15-Lipoxygenase/15-Hydroxyeicosatetraenoiccid-Induced Pulmonary Vascular Remodeling in Hypoxia Pulmonary Hypertension

We previously reported that 15-lipoxygenase (15-LO) and its metabolite 15-hydroxyeicosatetraenoic acid (15-HETE) were up-regulated in pulmonary arterial cells from both pulmonary artery hypertension patients and hypoxic rats and that these factors mediated the progression of pulmonary hypertension (PH) by affecting the proliferation and apoptosis of pulmonary arterial (PA) cells. However, the underlying mechanisms of the remodeling induced by 15-HETE have remained unclear. As reactive oxygen species (ROS) and 15-LO are both induced by hypoxia, it is possible that ROS are involved in the events of hypoxia-induced 15-LO expression that lead to PH. We employed immunohistochemistry, tube formation assays, bromodeoxyuridine (BrdU) incorporation assays, and cell cycle analyses to explore the role of ROS in the process of 15-HETE-mediated hypoxic pulmonary hypertension (HPH). We found that exogenous 15-HETE facilitated the generation of ROS and that this effect was mainly localized to mitochondria. In particular, the mitochondrial electron transport chain and nicotinamide-adenine dinucleotide phosphate oxidase 4 (Nox4) were responsible for the significant 15-HETE-stimulated increase in ROS production. Moreover, ROS induced by 15-HETE stimulated endothelial cell (EC) migration and promoted pulmonary artery smooth muscle cell (PASMC) proliferation under hypoxia via the p38 MAPK pathway. These results indicated that 15-HETE-regulated ROS mediated hypoxia-induced pulmonary vascular remodeling (PVR) via the p38 MAPK pathway.

The role of oxysterols in vascular ageing

The ageing endothelium progressively loses its remarkable and crucial ability to maintain homeostasis of the vasculature, as it acquires a proinflammatory phenotype. Cellular and structural changes gradually accumulate in the blood vessels, and markedly in artery walls. Most changes in aged arteries are comparable to those occurring during the atherogenic process, the latter being more marked: pro-oxidant and proinflammatory molecules, mainly deriving from or triggered by oxidized low density lipoproteins (oxLDLs), are undoubtedly a major driving force of this process. Oxysterols, quantitatively relevant components of oxLDLs, are likely candidate molecules in the pathogenesis of vascular ageing, because of their marked pro-oxidant, proinflammatory and proapoptotic properties. An increasing bulk of experimental data point to the contribution of a variety of oxysterols of pathophysiological interest, also in the age-related genesis of endothelium dysfunction, intimal thickening due to lipid accumulation, and smooth muscle cell migration and arterial stiffness due to increasing collagen deposition and calcification. This review provides an updated analysis of the molecular mechanisms whereby oxysterols accumulating in the wall of ageing blood vessels may 'activate' endothelial and monocytic cells, through expression of an inflammatory phenotype, and 'convince' smooth muscle cells to proliferate, migrate and, above all, to act as fibroblast-like cells.

CML/RAGE signal induces calcification cascade in diabetes

OBJECTIVE

Vascular calcification is a significant predictor of coronary heart disease events, stroke, and lower-limb amputation. Advanced glycation end-products (AGEs) play a key role in the development of vascular calcification. However, the role of Nε-carboxymethyl-lysine (CML), a major active ingredient of heterogeneous AGEs, in the development of atherosclerotic calcification in diabetic patients and the underlying mechanism remain unclear. Hence, the role and the mechanism of CML in the transmission pathway of diabetic calcification cascade were investigated in the present study.

METHODS

In vivo and in vitro investigations were performed. In study I, 45 diabetic patients hospitalized for above-knee amputation in the Department of Orthopedics, Affiliated Hospital of Jiangsu University were recruited from February 2010 to June 2015. The patients were categorized based on the severity of anterior tibial artery stenosis, which was assessed by color Doppler ultrasound, into mild stenosis (0% < stenosis < 50%, n = 15), moderate stenosis (50 ≤ stenosis < 70%, n = 15), and severe stenosis/occlusion groups (70 ≤ stenosis ≤ 100%, n = 15). In study II, the specific mechanism of CML in the transmission pathway of the diabetic calcification cascade signal was investigated in A7r5 aortic smooth muscle cells under high-lipid, apoptosis-coexisting conditions. ELISA (for serum CML concentration of patients), ultrasound (for plaque size, calcification, blood flow filling, vascular stenosis etc.), H&E staining (for plaque morphology), vonKossa staining (for qualitative analysis of calcification), calcium content assay (for quantitative analysis of calcification), and Western blot analyses of CML, receptor for advanced glycation end products (RAGE), NADPH oxidase 4, phosphorylated p38, core-binding factor α1 (cbfα1), alkaline phosphatase (ALP) and β-actin were then performed.

RESULTS

Morphological analysis revealed extensive calcification lesions in the intima and media of the anterior tibial artery. The extent and area of calcium deposition in the intima significantly increased with disease progression. Interestingly, spotty calcification was predominant in the atherosclerotic plaques of diabetic patients with amputation, and macrocalcification was almost invisible. Pearson correlation analysis revealed that serum CML level exhibited a significant positive correlation with calcium content in the arterial wall (R² = 0.6141, P < 0.0001). Semi-quantitative Western blot analysis suggested that the intensity of CML/RAGE signal increased with progression of atherosclerotic calcification in diabetic patients. In subsequent in vitro study, the related pathway was blocked by anti-RAGE antibody, NADPH oxidase inhibitor DPI, p38MAPK inhibitor SB203580, and anti-cbfa1 antibody in a step-wise manner to observe changes in calcium deposition and molecular signals. Results suggested that CML may play a key role in atherosclerotic calcification mainly through the CML/RAGE- reactive oxygen species (ROS)-p38MAPK-cbfα1-ALP pathway.

CONCLUSION

Spotty calcification was predominant in the atherosclerotic plaques of amputated diabetic patients. CML/RAGE signal may induce the calcification cascade in diabetes via ROS-p38MAPK.

Activation of ENaC in collecting duct cells by prorenin and its receptor PRR: involvement of Nox4-derived hydrogen peroxide

The collecting duct (CD) has been recognized as an important source of prorenin/renin, and it also expresses (pro)renin receptor (PRR). The goal of this study was to examine the hypothesis that prorenin or renin via PRR regulates epithelial Na(+) channel (ENaC) activity in mpkCCD cells. Transepithelial Na(+) transport was measured by using a conventional epithelial volt-ohmmeter and was expressed as the calculated equivalent current (Ieq). Amiloride-inhibitable Ieq was used as a reflection of ENaC activity. Administration of prorenin in the nanomolar range induced a significant increase in Ieq that was detectable as early as 1 min, peaked at 5 min, and gradually returned to baseline within 15 min. These changes in Ieq were completely prevented by a newly developed PRR decoy inhibitor, PRO20. Prorenin-induced Ieq was inhibitable by amiloride. Compared with prorenin, renin was less effective in stimulating Ieq Prorenin-induced Ieq was attenuated by apocynin but enhanced by tempol, the latter effect being prevented by catalase. In response to prorenin treatment, the levels of total reactive oxygen species and H2O2 were both increased, as detected by spin-trap analysis and reactive oxygen species (ROS)-Glo H2O2 assay, respectively. Both siRNA-mediated Nox4 knockdown and the dual Nox1/4 inhibitor GKT137892 attenuated prorenin-induced Ieq Overall, our results demonstrate that activation of PRR by prorenin stimulates ENaC activity in CD cells via Nox4-derived H2O2.

Evidence of the Importance of Nox4 in Production of Hypertension in Dahl Salt-Sensitive Rats

This study reports the consequences of knocking out NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 4 (Nox4) on the development of hypertension and kidney injury in the Dahl salt-sensitive (SS) rat. Zinc finger nuclease injection of single-cell SS embryos was used to create an 8 base-pair frame-shift deletion of Nox4, resulting in a loss of the ≈68 kDa band in Western blot analysis of renal cortical tissue of the knock out of Nox4 in the SS rat (SS(Nox4-/-)) rats. SS(Nox4-/-) rats exhibited a significant reduction of salt-induced hypertension compared with SS rats after 21 days of 4.0% NaCl diet (134±5 versus 151±3 mm Hg in SS) and a significant reduction of albuminuria, tubular casts, and glomerular injury. Optical fluorescence 3-dimensional cryoimaging revealed significantly higher redox ratios (NADH/FAD [reduced nicotinamide adenine dinucleotide/flavin adenine dinucleotide]) in the kidneys of SS(Nox4-/-) rats even when fed the 0.4% NaCl diet, indicating greater levels of mitochondrial electron transport chain metabolic activity and reduced oxidative stress compared with SS rats. Before the development of hypertension, RNA expression levels of Nox subunits Nox2, p67(phox), and p22(phox) were found to be significantly lower (P<0.05) in SS(Nox4-/-) compared with SS rats in the renal cortex. Thus, the mutation of Nox4 seems to modify transcription of several genes in ways that contribute to the protective effects observed in the SS(Nox4-/-) rats. We conclude that the reduced renal injury and attenuated blood pressure response to high salt in the SS(Nox4-/-) rat could be the result of multiple pathways, including gene transcription, mitochondrial energetics, oxidative stress, and protein matrix production impacted by the knock out of Nox4.

The NADPH oxidase Nox4 has anti-atherosclerotic functions

AIMS

Oxidative stress is thought to be a risk for cardiovascular disease and NADPH oxidases of the Nox family are important producers of reactive oxygen species. Within the Nox family, the NADPH oxidase Nox4 has a unique position as it is constitutively active and produces H2O2 rather than [Formula: see text] . Nox4 is therefore incapable of scavenging NO and its low constitutive H2O2 production might even be beneficial. We hypothesized that Nox4 acts as an endogenous anti-atherosclerotic enzyme.

METHODS AND RESULTS

Tamoxifen-induced Nox4-knockout mice were crossed with ApoE⁻/⁻ mice and spontaneous atherosclerosis under regular chow as well as accelerated atherosclerosis in response to partial carotid artery ligation under high-fat diet were determined. Deletion of Nox4 resulted in increased atherosclerosis formation in both models. Mechanistically, pro-atherosclerotic and pro-inflammatory changes in gene expression were observed prior to plaque development. Moreover, inhibition of Nox4 or deletion of the enzyme in the endothelium but not in macrophages resulted in increased adhesion of macrophages to the endothelial surface.

CONCLUSIONS

The H2O2-producing NADPH oxidase Nox4 is an endogenous anti-atherosclerotic enzyme. Nox4 inhibitors, currently under clinical evaluation, should be carefully monitored for cardiovascular side-effects.

Arsenic, reactive oxygen, and endothelial dysfunction

Human exposure to drinking water contaminated with arsenic is a serious global health concern and predisposes to cardiovascular disease states, such as hypertension, atherosclerosis, and microvascular disease. The most sensitive target of arsenic toxicity in the vasculature is the endothelium, and incubation of these cells with low concentrations of arsenite, a naturally occurring and highly toxic inorganic form of arsenic, rapidly induces reactive oxygen species (ROS) formation via activation of a specific NADPH oxidase (Nox2). Arsenite also induces ROS accumulation in vascular smooth muscle cells, but this is relatively delayed because, depending on the vessel from which they originate, these cells often lack Nox2 and/or its essential regulatory cytosolic subunits. The net effect of such activity is attenuation of endothelium-dependent conduit artery dilation via superoxide anion-mediated scavenging of nitric oxide (NO) and inhibition and downregulation of endothelial NO synthase, events that are temporally matched to the accumulation of oxidants across the vessel wall. By contrast, ROS induced by the more toxic organic trivalent arsenic metabolites (monomethylarsonous and dimethylarsinous acids) may originate from sources other than Nox2. As such, the mechanisms through which vascular oxidative stress develops in vivo under continuous exposure to all three of these potent arsenicals are unknown. This review is a comprehensive analysis of the mechanisms that mediate arsenic effects associated with Nox2 activation, ROS activity, and endothelial dysfunction, and also considers future avenues of research into what is a relatively poorly understood topic with major implications for human health.

Mechanism of testosterone deficiency in the transgenic sickle cell mouse

Testosterone deficiency is associated with sickle cell disease (SCD), but its underlying mechanism is not known. We investigated the possible occurrence and mechanism of testosterone deficiency in a mouse model of human SCD. Transgenic sickle male mice (Sickle) exhibited decreased serum and intratesticular testosterone and increased luteinizing hormone (LH) levels compared with wild type (WT) mice, indicating primary hypogonadism in Sickle mice. LH-, dbcAMP-, and pregnenolone- (but not 22-hydroxycholesterol)- stimulated testosterone production by Leydig cells isolated from the Sickle mouse testis was decreased compared to that of WT mice, implying defective Leydig cell steroidogenesis. There also was reduced protein expression of steroidogenic acute regulatory protein (STAR), but not cholesterol side-chain cleavage enzyme (P450scc), in the Sickle mouse testis. These data suggest that the capacity of P450scc to support testosterone production may be limited by the supply of cholesterol to the mitochondria in Sickle mice. The sickle mouse testis exhibited upregulated NADPH oxidase subunit gp91phox and increased oxidative stress, measured as 4-hydroxy-2-nonenal, and unchanged protein expression of an antioxidant glutathione peroxidase-1. Mice heterozygous for the human sickle globin (Hemi) exhibited intermediate hypogonadal changes between those of WT and Sickle mice. These results demonstrate that testosterone deficiency occurs in Sickle mice, mimicking the human condition. The defects in the Leydig cell steroidogenic pathway in Sickle mice, mainly due to reduced availability of cholesterol for testosterone production, may be related to NADPH oxidase-derived oxidative stress. Our findings suggest that targeting testicular oxidative stress or steroidogenesis mechanisms in SCD offers a potential treatment for improving phenotypic changes associated with testosterone deficiency in this disease.

Oxidative stress, redox signalling and endothelial dysfunction in ageing-related neurodegenerative diseases: a role of NADPH oxidase 2

Chronic oxidative stress and oxidative damage of the cerebral microvasculature and brain cells has become one of the most convincing theories in neurodegenerative pathology. Controlled oxidative metabolism and redox signalling in the central nervous system are crucial for maintaining brain function; however, excessive production of reactive oxygen species and enhanced redox signalling damage neurons. While several enzymes and metabolic processes can generate intracellular reactive oxygen species in the brain, recently an O2−-generating enzyme, NADPH oxidase 2 (Nox2), has emerged as a major source of oxidative stress in ageing-related vascular endothelial dysfunction and neurodegenerative diseases. The currently available inhibitors of Nox2 are not specific, and general antioxidant therapy is not effective in the clinic; therefore, insights into the mechanism of Nox2 activation and its signalling pathways are needed for the discovery of novel drug targets to prevent or treat these neurodegenerative diseases. This review summarizes the recent developments in understanding the mechanisms of Nox2 activation and redox-sensitive signalling pathways and biomarkers involved in the pathophysiology of the most common neurodegenerative diseases, such as ageing-related mild cognitive impairment, Alzheimer's disease and Parkinson's disease.