Inhibition Of NADPH Oxidase Activity Research Articles

Superoxide Mediates Depressive Effects Induced by Hydrogen Sulfide in Rostral Ventrolateral Medulla of Spontaneously Hypertensive Rats.

Hydrogen sulfide (H2S) plays a crucial role in the regulation of blood pressure and oxidative stress. In the present study, we tested the hypothesis that H2S exerts its cardiovascular effects by reducing oxidative stress via inhibition of NADPH oxidase activity in the rostral ventrolateral medulla (RVLM). We examined cell distributions of cystathionine-β-synthase (CBS) and effects of H2S on reactive oxygen species (ROS) and mean arterial blood pressure (MAP) in spontaneously hypertensive rats (SHRs). We found that CBS was expressed in neurons of the RVLM, and the expression was lower in SHRs than in Wistar-Kyoto rats. Microinjection of NaHS (H2S donor), S-adenosyl-l-methionine (SAM, a CBS agonist), or Apocynin (NADPH oxidase inhibitor) into the RVLM reduced the ROS level, NADPH oxidase activity, and MAP, whereas microinjection of hydroxylamine hydrochloride (HA, a CBS inhibitor) increased MAP. Furthermore, intracerebroventricular infusion of NaHS inhibited phosphorylation of p47phox, a key step of NADPH oxidase activation. Since decreasing ROS level in the RVLM reduces MAP and heart rate and increasing H2S reduces ROS production, we conclude that H2S exerts an antihypertensive effect via suppressing ROS production. H2S, as an antioxidant, may be a potential target for cardiovascular diseases.

Hypothesis: Spirulina may Slow the Growth and Spread of Ovarian Cancer by Interfering with Growth Factor Activity of Lysophophatidic Acid

Lysophosphatidic acid (LPA) has emerged as a key autocrine growth factor for most ovarian cancers, promoting their proliferation, survival, invasiveness, dissemination within the peritoneal cavity, and angiogenic capacity. Effective LPA signaling requires activation of endosomal NADPH oxidase activity. Free bilirubin is now known to function intracellularly as a potent inhibitor of NADPH oxidase complexes. The cyanobacterial chromophore phycocyanobilin (PhyCB), via intracellular conversion to the bilirubin homolog phycocyanorubin, can likewise inhibit NADPH oxidase activity, and is orally active in this regard. The cell wall polysaccharides of cyanobacteria may also aid cancer control by activating innate immunity and inhibiting angiogenesis. Hence, consumption of edible cyanobacteria such as spirulina may have potential for slowing the growth and spread of ovarian cancer – as it has recently been shown to do with a human pancreatic adenocarcinoma.

Polydatin prevents angiotensin II-induced cardiac hypertrophy and myocardial superoxide generation.

Our studies and others recently demonstrate that polydatin, a resveratrol glucoside, has antioxidative and cardioprotective effects. This study aims to investigate the direct effects of polydatin on Ang II-induced cardiac hypertrophy to explore the potential role of polydatin in cardioprotection. Our results showed that in primary cultured cardiomyocytes, polydatin blocked Ang II-induced cardiac hypertrophy in a dose-dependent manner, which were associated with reduction in the cell surface area and [(3)H]leucine incorporation, as well as attenuation of the mRNA expressions of atrial natriuretic factor and β-myosin heavy chain. Furthermore, polydatin prevented rat cardiac hypertrophy induced by Ang II infusion, as assessed by heart weight-to-body weight ratio, cross-sectional area of cardiomyocyte, and gene expression of hypertrophic markers. Further investigation demonstrated that polydatin attenuated the Ang II-induced increase in the reactive oxygen species levels and NADPH oxidase activity invivo and invitro. Polydatin also blocked the Ang II-stimulated increases of Nox4 and Nox2 expression in cultured cardiomyocytes and the hearts of Ang II-infused rats. Our results indicate that polydatin has the potential to protect against Ang II-mediated cardiac hypertrophy through suppression of NADPH oxidase activity and superoxide production. These observations may shed new light on the understanding of the cardioprotective effect of polydatin.

Oregonin from the Bark of Alnus japonica restrained ischemia-reperfusion-induced mesentery oxidative stress by inhibiting NADPH oxidase activation.

NADPH oxidase activation results in ROS overproduction that is the pathological basis of I/R injury. This study aimed to investigate potential effects of ORG on I/R-induced ROS production in rat mesenteric microvasculature and underlying mechanisms. Mesenteric I/R in Male Wistar rats (200~250g) was induced by ligation of the mesenteric artery and vein for 10minutes followed by reperfusion for 60minutes by releasing of the occlusion. The rats were infused intravenously with or without ORG (5mg/kg per hour) 10minutes before ischemia (pretreatment) or 20minutes after reperfusion (posttreatment). The DHR fluorescence intensity on, the leukocytes adherent to, and mast cell degranulation out of mesenteric venules were determined using an intravital microscope. NADPH oxidase subunit p47(phox) membrane translocation in intestine tissues was detected by Western blotting. Pre- or posttreatment with ORG inhibited I/R-induced DHR fluorescence intensity on the venular walls and leukocytes adhesion, ORG pretreatment inhibited mast cell degranulation as well. Furthermore, the translocation of p47(phox) from cytosol to membrane was suppressed markedly by ORG after I/R. The results suggested that ORG restrained I/R-induced ROS production, which might be correlated with its inhibitive effect on NADPH activation.

Abstract 806: Selective killing of cancer cells with mitochondrial respiratory dysfunction induced by activation of oncogenic Ras

Abstract Mitochondrial dysfunction is an important mechanism by which cancer cells become resistant to chemotherapeutic agents. Oncogenic Ras activation is often observed in human cancer and was reported to cause mitochondrial dysfunction by compromising mitochondrial electron transport chain. Therefore, identification of new agents capable of effectively killing mitochondrial defective cancer cells would have important therapeutic implications. Our previous work has discovered that mitochondrial respiratory dysfunction could cause increased NADPH oxidase (NOX) activity to support cell survival in the metabolic switch from mitochondrial oxidative phosphorylation to glycolysis. Mitochondrial respiratory dysfunction can also cause profound redox alteration to adapt ROS stress. Here, we report that targeted inhibition of NOX and glutathione synthesis has synergy effect in killing mitochondrial respiratory dysfunction cells, including cancer cells harboring oncogenic Ras activation. Activation of NOX and increased glutathione antioxidants are always observed in Ras activated cells. Treatment of these cancer cells with DPI and BSO to inhibit NOX activity and antioxidant adaptation function resulted in an elevated ROS stress, increased gamma-H2AX expression, leading to massive death of the cancer cells, such as Panc-1 and HCT116 cells. Antioxidant NAC and catalase attenuated the BSO and DPI induced cell death in mitochondrial respiratory dysfunction cells. The synergistic effect of BSO and DPI to kill oncogenic Ras bearing HCT116 cells was further confirmed using colony formation assay. Our results suggest that DPI, in synergy with BSO, is a promising compound capable of killing cancer cells bearing oncogenic Ras mutations through a ROS-mediated mechanism and warrants further investigations. Citation Format: Weiqin Lu, Yaying Yang, Craig Logsdon, Peng Huang. Selective killing of cancer cells with mitochondrial respiratory dysfunction induced by activation of oncogenic Ras. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 806. doi:10.1158/1538-7445.AM2014-806

Abscisic acid and lateral root organ defective/NUMEROUS INFECTIONS AND POLYPHENOLICS modulate root elongation via reactive oxygen species in Medicago truncatula.

Abscisic acid (ABA) modulates root growth in plants grown under normal and stress conditions and can rescue the root growth defects of the Medicago truncatula lateral root-organ defective (latd) mutant. Here, we demonstrate that reactive oxygen species (ROS) function downstream of ABA in the regulation of root growth by controlling cell elongation. We also show that the MtLATD/NUMEROUS INFECTIONS AND POLYPHENOLICS (NIP) nitrate transporter is required for ROS homeostasis and cell elongation in roots and that this balance is perturbed in latd mutants, leading to an excess of superoxide and hydrogen peroxide and a corresponding decrease in cell elongation. We found that expression of the superoxide-generating NADPH oxidase genes, MtRbohA and MtRbohC (for respiratory burst oxidase homologs), is increased in latd roots and that inhibition of NADPH oxidase activity pharmacologically can both reduce latd root ROS levels and increase cell length, implicating NADPH oxidase function in latd root growth defects. Finally, we demonstrate that ABA treatment alleviates ectopic ROS accumulation in latd roots, restores MtRbohC expression to wild-type levels, and promotes an increase in cell length. Reducing the expression of MtRbohC using RNA interference leads to increased root elongation in both wild-type and latd roots. These results reveal a mechanism by which the MtLATD/NIP nitrate transporter and ABA modulate root elongation via superoxide generation by the MtRbohC NADPH oxidase.

Andrographolide inhibits TNFα-induced ICAM-1 expression via suppression of NADPH oxidase activation and induction of HO-1 and GCLM expression through the PI3K/Akt/Nrf2 and PI3K/Akt/AP-1 pathways in human endothelial cells

Andrographolide, the major bioactive component of Andrographis paniculata, has been demonstrated to have various biological properties including anti-inflammation, antioxidation, and anti-hepatotoxicity. Oxidative stress is considered a major risk factor in aging, inflammation, cancer, atherosclerosis, and diabetes mellitus. NADPH oxidase is a major source of endogenous reactive oxygen species (ROS). In this study, we used EA.hy926 endothelial-like cells to explore the anti-inflammatory activity of andrographolide. Andrographolide attenuated TNFα-induced ROS generation, Src phosphorylation, membrane translocation of the NADPH oxidase subunits p47phox and p67phox, and ICAM-1 gene expression. In the small hairpin RNA interference assay, shp47phox abolished TNFα-induced p65 nuclear translocation, ICAM-1 gene expression, and adhesion of HL-60 cells. Andrographolide induced the gene expression of heme oxygenase 1 (HO-1) and glutamate cysteine ligase modifier subunit (GCLM) in a time-dependent manner. Cellular glutathione (GSH) content was increased by andrographolide. shGCLM attenuated the andrographolide-induced increase in GSH content and reversed the andrographolide inhibition of HL-60 adhesion. shHO-1 showed a similar effect on andrographolide inhibition of HL-60 adhesion to shGCLM. The mechanism underlying the up-regulation of HO-1 and GCLM by andrographolide was dependent on the PI3K/Akt pathway, and both the Nrf2 and AP-1 transcriptional factors were involved. Our results suggest that andrographolide attenuates TNFα-induced ICAM-1 expression at least partially through suppression of NADPH oxidase activation and induction of HO-1 and GCLM expression, which is PI3K/Akt pathway-dependent.

Suppression of NADPH oxidase- and mitochondrion-derived superoxide by Notoginsenoside R1 protects against cerebral ischemia–reperfusion injury through estrogen receptor-dependent activation of Akt/Nrf2 pathways

Notoginsenoside R1 (NGR1) is a novel phytoestrogen that is isolated from Panax notoginseng. We have recently found that NGR1 showed neuroprotection in vitro against oxidative stress through estrogen receptor (ER)-dependent activation of Akt/Nrf2 pathways. However, whether NGR1 has neuroprotective effect against cerebral ischemia–reperfusion (I/R) injury in vivo is unknown. In this study, we used in vivo and in vitro models of cerebral I/R injury that demonstrate middle cerebral artery occlusion and reperfusion in rats, as well as oxygen–glucose deprivation followed by reoxygenation (OGD/R) in primary cortical neurons. These models were used to evaluate NGR1 neuroprotection. Three-day pretreatment with NGR1 (20 mg/kg; i.p.) significantly improved neurologic outcomes and reduced cerebral infarct volume. Pretreatment of primary cortical neurons with NGR1 (25 μM) for 24 h prevented apoptosis and oxidative stress induced by OGD/R. NGR1 inhibited apoptosis by inhibiting mitochondrial membrane potential disruption, caspase-3 activation, and DNA fragmentation. NGR1 prevented oxidative stress by suppressing NADPH oxidase- and mitochondrion-derived superoxide and inhibiting production of malondialdehyde, protein carbonyl, and 8-hydroxydeoxyguanosine in vivo and in vitro. NGR1 induced ER-dependent activation of Akt/Nrf2 pathways by increasing ERα, ERβ, phospho-Akt, phospho-GSK3β, nuclear Nrf2, and HO-1 expression in vivo and in vitro. Pretreatment with ICI-182780, LY294002, or Snpp abolished NGR1-mediated neuroprotection against oxidative stress and apoptosis in vitro. In conclusion, NGR1 showed neuroprotection against cerebral I/R injury in vivo and in vitro. The mechanism of NGR1 neuroprotection involves inhibition of NADPH oxidase activity and mitochondrial dysfunction via ER-dependent activation of Akt/Nrf2 pathways.

Amyloid-β and proinflammatory cytokines utilize a prion protein-dependent pathway to activate NADPH oxidase and induce cofilin-actin rods in hippocampal neurons.

Neurites of neurons under acute or chronic stress form bundles of filaments (rods) containing 1∶1 cofilin∶actin, which impair transport and synaptic function. Rods contain disulfide cross-linked cofilin and are induced by treatments resulting in oxidative stress. Rods form rapidly (5–30 min) in >80% of cultured hippocampal or cortical neurons treated with excitotoxic levels of glutamate or energy depleted (hypoxia/ischemia or mitochondrial inhibitors). In contrast, slow rod formation (50% of maximum response in ∼6 h) occurs in a subpopulation (∼20%) of hippocampal neurons upon exposure to soluble human amyloid-β dimer/trimer (Aβd/t) at subnanomolar concentrations. Here we show that proinflammatory cytokines (TNFα, IL-1β, IL-6) also induce rods at the same rate and within the same neuronal population as Aβd/t. Neurons from prion (PrPC)-null mice form rods in response to glutamate or antimycin A, but not in response to proinflammatory cytokines or Aβd/t. Two pathways inducing rod formation were confirmed by demonstrating that NADPH-oxidase (NOX) activity is required for prion-dependent rod formation, but not for rods induced by glutamate or energy depletion. Surprisingly, overexpression of PrPC is by itself sufficient to induce rods in over 40% of hippocampal neurons through the NOX-dependent pathway. Persistence of PrPC-dependent rods requires the continuous activity of NOX. Removing inducers or inhibiting NOX activity in cells containing PrPC-dependent rods causes rod disappearance with a half-life of about 36 min. Cofilin-actin rods provide a mechanism for synapse loss bridging the amyloid and cytokine hypotheses for Alzheimer disease, and may explain how functionally diverse Aβ-binding membrane proteins induce synaptic dysfunction.

ROCK1 deficiency enhances protective effects of antioxidants against apoptosis and cell detachment.

We have recently reported that the homologous Rho kinases, ROCK1 and ROCK2, play different roles in regulating stress-induced stress fiber disassembly and cell detachment, and the ROCK1 deficiency in mouse embryonic fibroblasts (MEF) has remarkable anti-apoptotic, anti-detachment and pro-survival effects against doxorubicin, a chemotherapeutic drug. This study investigated the roles of ROCK isoforms in doxorubicin-induced reactive oxygen species (ROS) generation which is believed to be the major mechanism underlying its cytotoxicity to normal cells, and especially to cardiomyocytes. Different antioxidants have been shown to provide a protective role reported in numerous experimental studies, but clinical trials of antioxidant therapy showed insufficient benefit against the cardiac side effect. We found that both ROCK1−/− and ROCK2−/− MEFs exhibited reduced ROS production in response to doxorubicin treatment. Interestingly, only ROCK1 deficiency, but not ROCK2 deficiency, significantly enhanced the protective effects of antioxidants against doxorubicin-induced cytotoxicity. First, ROCK1 deficiency and N-acetylcysteine (an anti-oxidant) treatment synergistically reduced ROS levels, caspase activation and cell detachment. In addition, the reduction of ROS generation in ROCK1−/− MEFs in response to doxorubicin treatment was in part through inhibiting NADPH oxidase activity. Furthermore, ROCK1 deficiency enhanced the inhibitory effects of diphenyleneiodonium (an inhibitor of NADPH oxidase) on ROS generation and caspase 3 activation induced by doxorubicin. Finally, ROCK1 deficiency had greater protective effects than antioxidant treatment, especially on reducing actin cytoskeleton remodeling. ROCK1 deficiency not only reduced actomyosin contraction but also preserved central stress fiber stability, whereas antioxidant treatment only reduced actomyosin contraction without preserving central stress fibers. These results reveal a novel strategy to enhance the protective effect of antioxidant therapy by targeting the ROCK1 pathway to stabilize the actin cytoskeleton and boost the inhibitory effects on ROS production, apoptosis and cell detachment.

Oxygen radicals elicit paralysis and collapse of spinal cord neuron growth cones upon exposure to proinflammatory cytokines.

A persistent inflammatory and oxidative stress is a hallmark of most chronic CNS pathologies (Alzheimer's (ALS)) as well as the aging CNS orchestrated by the proinflammatory cytokines tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β). Loss of the integrity and plasticity of neuronal morphology and connectivity comprises an early step in neuronal degeneration and ultimate decline of cognitive function. We examined in vitro whether TNFα or IL-1β impaired morphology and motility of growth cones in spinal cord neuron cultures. TNFα and IL-1β paralyzed growth cone motility and induced growth cone collapse in a dose-dependent manner reflected by complete attenuation of neurite outgrowth. Scavenging reactive oxygen species (ROS) or inhibiting NADPH oxidase activity rescued loss of neuronal motility and morphology. TNFα and IL-1β provoked rapid, NOX-mediated generation of ROS in advancing growth cones, which preceded paralysis of motility and collapse of morphology. Increases in ROS intermediates were accompanied by an aberrant, nonproductive reorganization of actin filaments. These findings suggest that NADPH oxidase serves as a pivotal source of oxidative stress in neurons and together with disruption of actin filament reorganization contributes to the progressive degeneration of neuronal morphology in the diseased or aging CNS.

Selective inhibition of NADPH oxidase reverses the over contraction of diabetic rat aorta

Abnormal vascular responsiveness in diabetes has been attributed to a number of changes in contractile pathways, affected in part by the overproduction of reactive oxygen species (ROS). It has been reported that NADPH oxidase (NOX) is increased in diabetic (streptozotocin treated; STZ) rat arteries; however the pharmacological agents used to inhibit NOX activity are known to be unsuitable for in vitro studies and have a high level of non-selectivity. Here we have used the highly selective NOX inhibitor VAS2870 in diabetic rat aorta and compared its effects with apocynin, SOD, and allopurinol on phenylephrine and U46619 induced contraction.Male Wistar rats were injected intraperitoneally with 65mg/kg STZ and development of diabetes was confirmed by testing blood glucose levels. Rats were killed by CO2 asphyxiation, and the thoracic aorta removed and mounted in an organ bath under a tension of 1g. Diabetic rat aortas exhibit a greatly increased response to phenylephrine, which was reduced to a level consistent with control rat aorta by 10−5M VAS2870 and 150U/ml SOD. Incubation with VAS2870 led to an increase in normal rat aorta contraction, but led to a significant reduction in phenylephrine and U46619 induced tone in diabetic rat aorta, which indicates that ROS in diabetic rats directly contributes to these contractile responses. Apocynin and allopurinol had no effect on contraction in diabetic or normal rat aorta. This data is the first to show that selective inhibition of NOX reduces diabetic arterial contraction in direct comparison with inhibition of other known contributors of ROS.

Combined incubation of colon carcinoma cells with phorbol ester and mitochondrial uncoupling agents results in synergic elevated reactive oxygen species levels and increased γ-glutamyltransferase expression

The NADPH oxidase (NOX) is a significant determinant for the expression and activity of γ-glutamyltransferase (GGT), which is frequently upregulated after increased levels of reactive oxygen species (ROS) and oxidative stress. Earlier studies on human colon carcinoma HT-29 cells have shown that treatment with phorbol 12-myristate 13-acetate (PMA) activates NOX thus increasing the intracellular level of ROS and upregulating GGT. Another important source of cellular ROS is the mitochondria, and treatment with the mitochondria uncoupler carbonylcyanide-4-(trifluoromethoxy)-phenylhydrazone (FCCP) results in increased ROS levels. The present study shows that when HT-29 cells were simultaneously treated with both agents, a significant and synergic increase in intracellular ROS was detected. NOX activity contributed at least 50% of this increase as inhibiting NOX activity with apocynin or downregulating the NOX activity using siRNA against p22 phox reduced the synergic ROS production. The combined FCCP and PMA treatment also provoked highly increased GGT mRNA levels after 24h whereas only minor and delayed increases in GGT protein and enzyme activity levels were detected. The results strongly indicate that ROS production by both mitochondria and NOX is involved in the regulation of GGT expression in colon carcinoma cells.

Taxifolin prevents diabetic cardiomyopathy in vivo and in vitro by inhibition of oxidative stress and cell apoptosis

Diabetic cardiomyopathy has been increasingly recognized as an important cause of heart failure in diabetic patients. Excessive oxidative stress has been suggested to play a critical role in the development of diabetic cardiomyopathy. The objective of this study was to investigate the potential protective effects and mechanisms of taxifolin on cardiac function of streptozotocin-induced diabetic mice and on hyperglycemia-induced apoptosis of H9c2 cardiac myoblasts. In vivo study revealed that taxifolin improved diastolic dysfunction, ameliorated myocardium structure abnormality, inhibited myocyte apoptosis and enhanced endogenous antioxidant enzymes activities. Interestingly, taxifolin reduced angiotensin II level in myocardium, inhibited NADPH oxidase activity, and increased JAK/STAT3 activation. In vitro investigation demonstrated that taxifolin inhibited 33mM glucoseinduced H9c2 cells apoptosis by decreasing intracellular ROS level. It also inhibited caspase-3 and caspase-9 activation, restored mitochondrial membrane potential, and regulated the expression of proteins related to the intrinsic pathway of apoptosis, thus inhibiting the release of cytochrome c from mitochondria into the cytoplasm. In conclusion, taxifolin exerted cardioprotective effects against diabetic cardiomyopathy by inhibiting oxidative stress and cardiac myocyte apoptosis and might be a potential agent in the treatment of diabetic cardiomyopathy.

Protectin DX, a Double Lipoxygenase Product of DHA, Inhibits Both ROS Production in Human Neutrophils and Cyclooxygenase Activities

Neutrophils play a major role in inflammation by releasing large amounts of reactive oxygen species (ROS) produced by NADPH oxidase (NOX) and myeloperoxidase (MPO). This ROS overproduction is mediated by phosphorylation of the NOX subunits in an uncontrolled manner. Therefore, targeting neutrophil subunits would represent a promising strategy to moderate NOX activity, lower ROS, and other inflammatory agents, such as cytokines and leukotrienes, produced by neutrophils. For this purpose, we investigated the effects of protectin DX (PDX)-a docosahexaenoic acid di-hydroxylated product which inhibits blood platelet aggregation-on neutrophil activation in vitro. We found that PDX decreases ROS production, inhibits NOX activation and MPO release from neutrophils. We also confirm, that PDX is an anti-aggregatory and anti-inflammatory agent by inhibiting both cyclooxygenase-1 and -2 (COX-1 and COX-2, E.C. 1.14.99.1) as well as COX-2 in lipopolysaccharides-treated human neutrophils. However, PDX has no effect on the 5-lipoxygenase pathway that produces the chemotactic agent leukotriene B4 (LTB4). Taken together, our results suggest that PDX could be a protective agent against neutrophil invasion in chronic inflammatory diseases.

Inhibition of NADPH Oxidase Activation in Oligodendrocytes Reduces Cytotoxicity Following Trauma

Spinal cord injury is a debilitating neurological disorder that initiates a cascade of cellular events that result in a period of secondary damage that can last for months after the initial trauma. The ensuing outcome of these prolonged cellular perturbations is the induction of neuronal and glial cell death through excitotoxic mechanisms and subsequent free radical production. We have previously shown that astrocytes can directly induce oligodendrocyte death following trauma, but the mechanisms regulating this process within the oligodendrocyte remain unclear. Here we provide evidence demonstrating that astrocytes directly regulate oligodendrocyte death after trauma by inducing activation of NADPH oxidase within oligodendrocytes. Spinal cord injury resulted in a significant increase in oxidative damage which correlated with elevated expression of the gp91 phox subunit of the NADPH oxidase enzyme. Immunohistochemical analysis confirmed the presence of gp91 phox in oligodendrocytes in vitro and at 1 week following spinal cord injury. Exposure of oligodendrocytes to media from injured astrocytes resulted in an increase in oligodendrocyte NADPH oxidase activity. Inhibition of NADPH oxidase activation was sufficient to attenuate oligodendrocyte death in vitro and at 1 week following spinal cord injury, suggesting that excitotoxicity of oligodendrocytes after trauma is dependent on the intrinsic activation of the NADPH oxidase enzyme. Acute administration of the NADPH oxidase inhibitor apocynin and the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate channel blocker 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione significantly improved locomotor behavior and preserved descending axon fibers following spinal cord injury. These studies lead to a better understanding of oligodendrocyte death after trauma and identify potential therapeutic targets in disorders involving demyelination and oligodendrocyte death.

Curcumin and resveratrol act by different ways on NADPH oxidase activity and reactive oxygen species produced by equine neutrophils

In neutrophils (PMNs), superoxide anion (O2−), the first reactive oxygen species (ROS) produced to kill pathogenic agents, is generated by NADPH oxidase, an enzymatic complex formed by the translocation of cytosolic subunits to the membrane flavocytochrome b558. In horses, excessive activation of PMNs is often associated with deadly pathologies and the modulation of their ROS production by acting on NADPH oxidase is a prime target to manage inflammation. We developed a cell-free assay to measure the activity of equine NADPH oxidase assembled in vitro, in order to test the effects of natural or synthetic compounds on the enzyme activity or assembly. The cell-free assay was validated with diphenyleneiodonium chloride and Gp91ds-tat, two inhibitors largely described for human NADPH oxidase. The anti-oxidant effects of curcumin and resveratrol at final concentration ranging from 10−4 to 10−6 M were studied on whole cells by chemiluminescence (CL) and by cell-free assay, in which the molecule was added before or after the enzyme assembly. The CL assay demonstrated that curcumin efficiently inhibited the O2− production and easily entered into PMNs or interacted with their membrane. Cell-free assay showed that curcumin acted on the reconstitution of NADPH oxidase even at 10−5M, while resveratrol appeared to be an O2− scavenger rather than an inhibitor of NADPH oxidase activity, since it acted from outside the cell in CL and after the complex assembly in cell-free assay. By acting directly on NADPH oxidase, curcumin should be a good candidate for the treatment of acute or inflammatory diseases involving an excessive ROS production.

Activation of Rap1 inhibits NADPH oxidase‐dependent ROS generation in retinal pigment epithelium and reduces choroidal neovascularization

Activation of Rap1 GTPase can improve the integrity of the barrier of the retina pigment epithelium (RPE) and reduce choroidal neovascularization (CNV). Inhibition of NADPH oxidase activation also reduces CNV. We hypothesize that Rap1 inhibits NADPH oxidase-generated ROS and thereby reduces CNV formation. Using a murine model of laser-induced CNV, we determined that reduced Rap1 activity in RPE/choroid occurred with CNV formation and that activation of Rap1 by 2'-O-Me-cAMP (8CPT)-reduced laser-induced CNV via inhibiting NADPH oxidase-generated ROS. In RPE, inhibition of Rap1 by Rap1 GTPase-activating protein (Rap1GAP) increased ROS generation, whereas activation of Rap1 by 8CPT reduced ROS by interfering with the assembly of NADPH oxidase membrane subunit p22phox with NOX4 or cytoplasmic subunit p47phox. Activation of NADPH oxidase with Rap1GAP reduced RPE barrier integrity via cadherin phosphorylation and facilitated choroidal EC migration across the RPE monolayer. Rap1GAP-induced ROS generation was inhibited by active Rap1a, but not Rap1b, and activation of Rap1a by 8CPT in Rap1b(-/-) mice reduced laser-induced CNV, in correlation with decreased ROS generation in RPE/choroid. These findings provide evidence that active Rap1 reduces CNV by interfering with the assembly of NADPH oxidase subunits and increasing the integrity of the RPE barrier.

Putrescine Mediates Aluminum Tolerance in Red Kidney Bean by Modulating Aluminum‐Induced Oxidative Stress

ABSTRACTPolyamines are important molecules modulating numerous environment stresses in plants. In the present study, the role of putrescine (Put) in the Al tolerance of red kidney bean (Phaseolus vulgaris) was investigated. In roots of red kidney bean, Al stress led to a marked increase of both free Put content and Put‐biosynthetic enzymes activities, and arginine decarboxylase pathway played a predominant role in Al‐induced increase in Put accumulation. Treatment of seedlings with Put reduced Al‐induced lipid peroxidation and reactive oxygen species (ROS) generation, thus alleviating Al‐induced inhibition of root elongation and Al accumulation in root apices. On the other hand, treatment with Put biosynthesis inhibitors reduced Al‐induced Put accumulation and enhanced Al toxicity of red kidney bean. Furthermore, Put treatment inhibited Al‐induced NADPH oxidase activity in roots, while Put biosynthesis inhibitors enhanced NADPH oxidase activity under Al stress. In addition, application of NADPH oxidase inhibitor reduced Al‐induced ROS generation, suggesting that ROS generation under Al stress is mediated, at least in part, by NADPH oxidase. Taken together, these results indicate that Put plays an important role in Al tolerance of red kidney bean by inhibiting NADPH oxidase activity, thus reducing Al‐induced oxidative stress.

Renal Dopamine Receptors, Oxidative Stress, and Hypertension

Dopamine, which is synthesized in the kidney, independent of renal nerves, plays an important role in the regulation of fluid and electrolyte balance and systemic blood pressure. Lack of any of the five dopamine receptor subtypes (D1R, D2R, D3R, D4R, and D5R) results in hypertension. D1R, D2R, and D5R have been reported to be important in the maintenance of a normal redox balance. In the kidney, the antioxidant effects of these receptors are caused by direct and indirect inhibition of pro-oxidant enzymes, specifically, nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase, and stimulation of anti-oxidant enzymes, which can also indirectly inhibit NADPH oxidase activity. Thus, stimulation of the D2R increases the expression of endogenous anti-oxidants, such as Parkinson protein 7 (PARK7 or DJ-1), paraoxonase 2 (PON2), and heme oxygenase 2 (HO-2), all of which can inhibit NADPH oxidase activity. The D5R decreases NADPH oxidase activity, via the inhibition of phospholipase D2, and increases the expression of HO-1, another antioxidant. D1R inhibits NADPH oxidase activity via protein kinase A and protein kinase C cross-talk. In this review, we provide an overview of the protective roles of a specific dopamine receptor subtype on renal oxidative stress, the different mechanisms involved in this effect, and the role of oxidative stress and impairment of dopamine receptor function in the hypertension that arises from the genetic ablation of a specific dopamine receptor gene in mice.