Detection of Hydrogen Peroxide with Fluorescent Dyes

SIGNIFICANCE

Hydrogen peroxide (H₂O₂) is a powerful effector of redox signaling. It is able to oxidize cysteine residues, metal ion centers, and lipids. Understanding H₂O₂-mediated signaling requires, to some extent, measurement of H₂O₂ level. Recent Advances: Chemically and genetically encoded fluorescent probes for the detection of H₂O₂ are currently the most sensitive and popular. Novel probes are constantly being developed, with the latest progress particular with boronates and genetically encoded probes.

CRITICAL ISSUES

All currently available probes display limitations in terms of sensitivity, local and temporal resolution, and specificity in the detection of low H₂O₂ concentrations. In this review, we discuss the power of fluorescent probes and the systems in which they have been successfully employed. Moreover, we recommend approaches for overcoming probe limitations and for the avoidance of artifacts.

FUTURE DIRECTIONS

Constant improvements will lead to the generation of probes that are not only more sensitive but also specifically tailored to individual cellular compartments. Antioxid. Redox Signal. 29, 585-602.

Autophagy Protects From Uremic Vascular Media Calcification

Chronic kidney disease and diabetes mellitus are associated with extensive media calcification, which leads to increased cardiovascular morbidity and mortality. Here, we investigated the role of autophagy in the pathogenesis of uremic vascular media calcification. DBA/2 mice were fed with high-phosphate diet (HPD) in order to cause vascular calcification. DBA/2 mice on standard chow diet were used as control. In parallel, autophagy and its response to rapamycin, 3-methyladenine (3-MA), and bafilomycin were studied in an in vitro model using mouse vascular smooth muscle cells (MOVAS). DBA/2 mice on HPD developed severe vascular media calcification, which is mirrored in vitro by culturing MOVAS under calcifying conditions. Both, in vitro and in vivo, autophagy significantly increased in MOVAS under calcifying conditions and in aortas of HPD mice, respectively. Histologically, autophagy was located to the aortic Tunica media, but also vascular endothelial cells, and was found to continuously increase during HPD treatment. 3-MA as well as bafilomycin blocked autophagy in MOVAS and increased calcification. Vice versa, rapamycin treatment further increased autophagy and resulted in a significant decrease of vascular calcification in vitro and in vivo. Rapamycin reduced Runx2 transcription levels in aortas and MOVAS to control levels, whereas it increased α-smooth muscle actin and Sm22α transcription in MOVAS to control levels. Furthermore, rapamycin-treated HPD mice survived significantly longer compared to HPD controls. These findings indicate that autophagy is an endogenous response of vascular smooth muscle cells (VSMC) to protect from calcification in uremia. Induction of autophagy by rapamycin protects cells and mice from uremic media calcification possibly by inhibiting osteogenic transdifferentiation of VSMC.

NoxO1 Controls Proliferation of Colon Epithelial Cells

Aim

Reactive oxygen species (ROS) produced by enzymes of the NADPH oxidase family serve as second messengers for cellular signaling. Processes such as differentiation and proliferation are regulated by NADPH oxidases. In the intestine, due to the exceedingly fast and constant renewal of the epithelium both processes have to be highly controlled and balanced. Nox1 is the major NADPH oxidase expressed in the gut, and its function is regulated by cytosolic subunits such as NoxO1. We hypothesize that the NoxO1-controlled activity of Nox1 contributes to a proper epithelial homeostasis and renewal in the gut.

Results

NoxO1 is highly expressed in the colon. Knockout of NoxO1 reduces the production of superoxide in colon crypts and is not subsidized by an elevated expression of its homolog p47phox. Knockout of NoxO1 increases the proliferative capacity and prevents apoptosis of colon epithelial cells. In mouse models of dextran sulfate sodium (DSS)-induced colitis and azoxymethane/DSS induced colon cancer, NoxO1 has a protective role and may influence the population of natural killer cells.

Conclusion

NoxO1 affects colon epithelium homeostasis and prevents inflammation.

The NADPH organizers NoxO1 and p47phox are both mediators of diabetes-induced vascular dysfunction in mice

AIM

NADPH oxidases are important sources of reactive oxygen species (ROS). Several Nox homologues are present together in the vascular system but whether they exhibit crosstalk at the activity level is unknown. To address this, vessel function of knockout mice for the cytosolic Nox organizer proteins p47phox, NoxO1 and a p47phox-NoxO1-double knockout were studied under normal condition and during streptozotocin-induced diabetes.

RESULTS

In the mouse aorta, mRNA expression for NoxO1 was predominant in smooth muscle and endothelial cells, whereas p47phox was markedly expressed in adventitial cells comprising leukocytes and tissue resident macrophages. Knockout of either NoxO1 or p47phox resulted in lower basal blood pressure. Deletion of any of the two subunits also prevented diabetes-induced vascular dysfunction. mRNA expression analysis by MACE (Massive Analysis of cDNA ends) identified substantial gene expression differences between the mouse lines and in response to diabetes. Deletion of p47phox induced inflammatory activation with increased markers of myeloid cells and cytokine and chemokine induction. In contrast, deletion of NoxO1 resulted in an attenuated interferon gamma signature and reduced expression of genes related to antigen presentation. This aspect was also reflected by a reduced number of circulating lymphocytes in NoxO1-/- mice.

INNOVATION AND CONCLUSION

ROS production stimulated by NoxO1 and p47phox limit endothelium-dependent relaxation and maintain blood pressure in mice. However, NoxO1 and p47phox cannot substitute each other despite their similar effect on vascular function. Deletion of NoxO1 induced an anti-inflammatory phenotype, whereas p47phox deletion rather elicited a hyper-inflammatory response.

Lung Ischaemia-Reperfusion Injury: The Role of Reactive Oxygen Species

Lung ischaemia-reperfusion injury (LIRI) occurs in many lung diseases and during surgical procedures such as lung transplantation. The re-establishment of blood flow and oxygen delivery into the previously ischaemic lung exacerbates the ischaemic injury and leads to increased microvascular permeability and pulmonary vascular resistance as well as to vigorous activation of the immune response. These events initiate the irreversible damage of the lung with subsequent oedema formation that can result in systemic hypoxaemia and multi-organ failure. Alterations in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been suggested as crucial mediators of such responses during ischaemia-reperfusion in the lung. Among numerous potential sources of ROS/RNS within cells, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, nitric oxide synthases and mitochondria have been investigated during LIRI. Against this background, we aim to review here the extensive literature about the ROS-mediated cellular signalling during LIRI, as well as the effectiveness of antioxidants as treatment option for LIRI.

Redox stress in Marfan syndrome: Dissecting the role of the NADPH oxidase NOX4 in aortic aneurysm

Marfan syndrome (MFS) is characterized by the formation of ascending aortic aneurysms resulting from altered assembly of extracellular matrix fibrillin-containing microfibrils and dysfunction of TGF-β signaling. Here we identify the molecular targets of redox stress in aortic aneurysms from MFS patients, and investigate the role of NOX4, whose expression is strongly induced by TGF-β, in aneurysm formation and progression in a murine model of MFS. Working models included aortae and cultured vascular smooth muscle cells (VSMC) from MFS patients, and a NOX4-deficient Marfan mouse model (Fbn1^C1039G/+-Nox4^-/-). Increased tyrosine nitration and reactive oxygen species levels were found in the tunica media of human aortic aneurysms and in cultured VSMC. Proteomic analysis identified nitrated and carbonylated proteins, which included smooth muscle α-actin (αSMA) and annexin A2. NOX4 immunostaining increased in the tunica media of human Marfan aorta and was transcriptionally overexpressed in VSMC. Fbn1^C1039G/+-Nox4^-/- mice aortas showed a reduction of fragmented elastic fibers, which was accompanied by an amelioration in the Marfan-associated enlargement of the aortic root. Increase in the contractile phenotype marker calponin in the tunica media of MFS mice aortas was abrogated in Fbn1^C1039G/+-Nox4^-/- mice. Endothelial dysfunction evaluated by myography in the Marfan ascending aorta was prevented by the absence of Nox4 or catalase-induced H₂O₂ decomposition. We conclude that redox stress occurs in MFS, whose targets are actin-based cytoskeleton members and regulators of extracellular matrix homeostasis. Likewise, NOX4 have an impact in the progression of the aortic dilation in MFS and in the structural organization of the aortic tunica media, the VSMC phenotypic modulation, and endothelial function.

Targeting of NADPH oxidase in vitro and in vivo suppresses fibroblast activation and experimental skin fibrosis

Although there is increasing evidence that oxidative stress is involved in collagen synthesis and myofibroblast activation, the NADPH oxidase (Nox) system is incompletely investigated in the context of human dermal fibroblasts (HDFs) and skin fibrosis. Using the pan-Nox inhibitor diphenyleneiodonium (DPI) as an initial tool, we show that gene expression of collagen type I, α-smooth muscle actin (α-SMA) and fibronectin 1 is suppressed in HDFs. Detailed expression analysis of all Nox isoforms and adaptors revealed expression of RNA and protein expression of Nox4, p22^phox and Poldip2 but neither Nox1 nor Nox2. Nox4 could be immunolocalized to the endoplasmic reticulum. Importantly, TGF-β₁ had a dose- and time-dependent upregulating effect on NADH activity and Nox4 gene expression in HDFs. Genetic silencing of Nox4 as demonstrated by siRNA in HDFs as well as in murine fibroblasts established from Nox4 knockout mice confirmed that TGF-β₁ -mediated collagen type I gene, α-SMA and fibronectin 1 gene expressions were Nox4-dependent. This TGF-β₁ effect was mediated by Smad3 as shown by in silico promoter analysis, pharmacological inhibition and gene silencing of Smad3. The relevance of these findings is highlighted in the bleomycin-induced scleroderma mouse model. DPI treatment attenuated skin fibrosis and myofibroblast activation. Moreover, Nox4 knockdown by siRNA reduced skin collagen synthesis, α-SMA and fibronectin 1 expression in vivo. Finally, analyses of HDFs from patients with systemic sclerosis confirmed the expression of Nox4 and its adaptors, whereas Nox1 and Nox2 were not detectable. Our findings indicate that Nox4 targeting is a promising future treatment for fibrotic skin diseases.

Nox4 reprograms cardiac substrate metabolism via protein O-GlcNAcylation to enhance stress adaptation

Cardiac hypertrophic remodeling during chronic hemodynamic stress is associated with a switch in preferred energy substrate from fatty acids to glucose, usually considered to be energetically favorable. The mechanistic interrelationship between altered energy metabolism, remodeling, and function remains unclear. The ROS-generating NADPH oxidase-4 (Nox4) is upregulated in the overloaded heart, where it ameliorates adverse remodeling. Here, we show that Nox4 redirects glucose metabolism away from oxidation but increases fatty acid oxidation, thereby maintaining cardiac energetics during acute or chronic stresses. The changes in glucose and fatty acid metabolism are interlinked via a Nox4-ATF4–dependent increase in the hexosamine biosynthetic pathway, which mediates the attachment of O-linked N-acetylglucosamine (O-GlcNAcylation) to the fatty acid transporter CD36 and enhances fatty acid utilization. These data uncover a potentially novel redox pathway that regulates protein O-GlcNAcylation and reprograms cardiac substrate metabolism to favorably modify adaptation to chronic stress. Our results also suggest that increased fatty acid oxidation in the chronically stressed heart may be beneficial.

Nox4 reprograms intermediary metabolism in the heart through an ATF4-mediated enhancement of protein O-GlcNAcylation, and the resulting switch to increased fatty acid oxidation protects the overloaded heart.

Aggression and violence in psychiatric hospitals with and without open door policies: A 15-year naturalistic observational study

Aggressive behavior and violence in psychiatric patients have often been quoted to justify more restrictive settings in psychiatric facilities. However, the effects of open vs. locked door policies on aggressive incidents remain unclear. This study had a naturalistic observational design and analyzed the occurrence of aggressive behavior as well as the use of seclusion or restraint in 21 German hospitals. The analysis included data from 1998 to 2012 and contained a total of n = 314,330 cases, either treated in one of 17 hospitals with (n = 68,135) or in one of 4 hospitals without an open door policy (n = 246,195). We also analyzed the data according to participants' stay on open, partially open, or locked wards. To compare hospital and ward types, we used generalized linear mixed-effects models on a propensity score matched subset (n = 126,268) and on the total dataset. The effect of open vs. locked door policy was non-significant in all analyses of aggressive behavior during treatment. Restraint or seclusion during treatment was less likely in hospitals with an open door policy. On open wards, any aggressive behavior and restraint or seclusion were less likely, whereas bodily harm was more likely than on closed wards. Hospitals with open door policies did not differ from hospitals with locked wards regarding different forms of aggression. Other restrictive interventions used to control aggression were significantly reduced in open settings. Open wards seem to have a positive effect on reducing aggression. Future research should focus on mental health care policies targeted at empowering treatment approaches, respecting the patient's autonomy and promoting reductions of institutional coercion.

European contribution to the study of ROS: A summary of the findings and prospects for the future from the COST action BM1203 (EU-ROS)

The European Cooperation in Science and Technology (COST) provides an ideal framework to establish multi-disciplinary research networks. COST Action BM1203 (EU-ROS) represents a consortium of researchers from different disciplines who are dedicated to providing new insights and tools for better understanding redox biology and medicine and, in the long run, to finding new therapeutic strategies to target dysregulated redox processes in various diseases. This report highlights the major achievements of EU-ROS as well as research updates and new perspectives arising from its members. The EU-ROS consortium comprised more than 140 active members who worked together for four years on the topics briefly described below. The formation of reactive oxygen and nitrogen species (RONS) is an established hallmark of our aerobic environment and metabolism but RONS also act as messengers via redox regulation of essential cellular processes. The fact that many diseases have been found to be associated with oxidative stress established the theory of oxidative stress as a trigger of diseases that can be corrected by antioxidant therapy. However, while experimental studies support this thesis, clinical studies still generate controversial results, due to complex pathophysiology of oxidative stress in humans. For future improvement of antioxidant therapy and better understanding of redox-associated disease progression detailed knowledge on the sources and targets of RONS formation and discrimination of their detrimental or beneficial roles is required. In order to advance this important area of biology and medicine, highly synergistic approaches combining a variety of diverse and contrasting disciplines are needed.

Organizers and activators: Cytosolic Nox proteins impacting on vascular function

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

[Descemetectomy : An alternative to transplantation?]

Due to rising demand worldwide it is becoming increasingly more difficult to satisfy the needs for human corneal transplants. At this point transplantation is the only possible cure for endothelial diseases, such as Fuchs endothelial dystrophy. In this article we present descemetectomy, a circumscribed removal of Descemet's membrane (DMx) without subsequent transplantation, as new possible treatment option on the basis of a clinical case.

Vascular CXCR4 Limits Atherosclerosis by Maintaining Arterial Integrity: Evidence From Mouse and Human Studies

BACKGROUND

The CXCL12/CXCR4 chemokine ligand/receptor axis controls (progenitor) cell homeostasis and trafficking. So far, an atheroprotective role of CXCL12/CXCR4 has only been implied through pharmacological intervention, in particular, because the somatic deletion of the CXCR4 gene in mice is embryonically lethal. Moreover, cell-specific effects of CXCR4 in the arterial wall and underlying mechanisms remain elusive, prompting us to investigate the relevance of CXCR4 in vascular cell types for atheroprotection.

METHODS

We examined the role of vascular CXCR4 in atherosclerosis and plaque composition by inducing an endothelial cell (BmxCreER^T2-driven)-specific or smooth muscle cell (SMC, SmmhcCreER^T2- or TaglnCre-driven)-specific deficiency of CXCR4 in an apolipoprotein E-deficient mouse model. To identify underlying mechanisms for effects of CXCR4, we studied endothelial permeability, intravital leukocyte adhesion, involvement of the Akt/WNT/β-catenin signaling pathway and relevant phosphatases in VE-cadherin expression and function, vascular tone in aortic rings, cholesterol efflux from macrophages, and expression of SMC phenotypic markers. Finally, we analyzed associations of common genetic variants at the CXCR4 locus with the risk for coronary heart disease, along with CXCR4 transcript expression in human atherosclerotic plaques.

RESULTS

The cell-specific deletion of CXCR4 in arterial endothelial cells (n=12-15) or SMCs (n=13-24) markedly increased atherosclerotic lesion formation in hyperlipidemic mice. Endothelial barrier function was promoted by CXCL12/CXCR4, which triggered Akt/WNT/β-catenin signaling to drive VE-cadherin expression and stabilized junctional VE-cadherin complexes through associated phosphatases. Conversely, endothelial CXCR4 deficiency caused arterial leakage and inflammatory leukocyte recruitment during atherogenesis. In arterial SMCs, CXCR4 sustained normal vascular reactivity and contractile responses, whereas CXCR4 deficiency favored a synthetic phenotype, the occurrence of macrophage-like SMCs in the lesions, and impaired cholesterol efflux. Regression analyses in humans (n=259 796) identified the C-allele at rs2322864 within the CXCR4 locus to be associated with increased risk for coronary heart disease. In line, C/C risk genotype carriers showed reduced CXCR4 expression in carotid artery plaques (n=188), which was furthermore associated with symptomatic disease.

CONCLUSIONS

Our data clearly establish that vascular CXCR4 limits atherosclerosis by maintaining arterial integrity, preserving endothelial barrier function, and a normal contractile SMC phenotype. Enhancing these beneficial functions of arterial CXCR4 by selective modulators might open novel therapeutic options in atherosclerosis.

Knock out of the NADPH oxidase Nox4 has no impact on life span in mice

The free radical theory of aging suggests reactive oxygen species as a main reason for accumulation of damage events eventually leading to aging. Nox4, a member of the family of NADPH oxidases constitutively produces ROS and therefore has the potential to be a main driver of aging. Herein we analyzed the life span of Nox4 deficient mice and found no difference when compared to their wildtype littermates. Accordingly neither Tert expression nor telomere length was different in cells isolated from those animals. In fact, Nox4 mRNA expression in lungs of wildtype mice dropped with age. We conclude that Nox4 has no influence on lifespan of healthy mice.

[Seasonal and Perennial Allergic Rhinoconjunctivitis]

Seasonsal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC) as well as intermittent and persistent allergic rhinitis are widespread diseases. Because a combined occurrence of ocular and nasal symptoms is very common the summarising term allergic rhinoconjunctivitis is frequently used. SAC and PAC representing the two acute forms of allergic conjunctivitis account for more than 90% of all cases of allergic conjunctivitis. Compared to the chronic forms of allergic conjunctivitis their course of disease is milder. Nevertheless because of their high prevalence and the proven influence on patients' quality of life they possess clinical and socioeconomic relevance. Allergic rhinoconjunctivitis is caused by a type 1 IgE-mediated hypersensitivitity reaction that is provoked by aeroallergens in the majority of cases. The pathognomonic sign is itching. Besides, typical ocular findings are chemosis, conjunctival injection,watery secretion and lid swelling. Otorhinolaryngologists' findings include rhinorrhea, postnasal drip and sneezing. Problems in breathing through the nose resulting from nasal obstruction can cause impaired nighttime sleep and daytime somnolence. In addition to a reduction of allergen exposure by modification of environment and life style factors, in mild forms of SAC and PAC artificial tears are recommended. Topical antihistamines can generate rapid relief from acute symptoms and itching. Topical mast cell stabilisers however provide long-term effects. Dual action drugs that combine antihistamines and mast cell stabilisers show increased patient compliance due to reduced application frequency. Use of topical steroids should be cautious and only temporary. For prolonged treatment periods unpreserved anti-allergic eye-drops should be preferred. Combined topical antihistamines and new-generation topical nasal steroids often used by otorhinolaryngologists demonstrate a good safety profile without systemic side effects. In summary, allergic rhinoconjunctivitis represents a common disease pattern that can be treated effectively. Once it is diagnosed correctly targeted treatment results in improved patients' quality of life quickly.

Tissue engineered vascularized periosteal flap enriched with MSC/EPCs for the treatment of large bone defects in rats

Vascularized periosteal flaps are used for complex cases if the reconstruction of large bone defects is necessary in modern trauma and orthopedic surgery. In this study, we combined this surgical procedure with β-TCP scaffold and mesenchymal stem cells (MSCs) + endothelial progenitor cells (EPCs) as a tissue engineering approach to obtain optimum conditions for bone healing in rats. A critical size femoral defect was created in 80 rats allocated into 4 groups. Defects were treated according to the following protocol: i) vascularized periosteal flap alone; ii) vascularized periosteal flap + β-TCP scaffold; iii) vascularized periosteal flap + β-TCP scaffold + ligated vascular pedicle; and ii) vascularized periosteal flap + β-TCP scaffold + MSCs/EPCs. After 8 weeks, femur bones were extracted and analyzed for new bone formation, vascularization, proliferation and inflammatory processes and strength. Bone mineral density (BMD) and biomechanical stability at week 8 were highest in group 4 (flap + β-TCP scaffold + MSCs/EPCs) compared to all the other groups. Stability was significantly higher in group 4 (flap + β-TCP scaffold + MSCs/EPCs) in comparison to group 3 (ligated flap + β-TCP scaffold). BMD was found to be significantly lower in group 3 (ligated flap + β-TCP scaffold) compared to group 1 (flap) and group 4 (flap + β-TCP scaffold + MSCs/EPCs). The highest density of blood vessels was observed in group 4 (flap + β-TCP + MSCs/EPCs) and the values were significantly increased in comparison to group 3 (ligated flap), but not to group 1 (flap) and group 2 (flap + β-TCP). The highest amounts of proliferating cells were observed in group 4 (flap + β-TCP scaffold + MSC/EPCs). The percentage of proliferating cells was significantly higher in group 4 (flap + β-TCP scaffold + MSCs/EPCs) in comparison to all the other groups after 8 weeks. Our data thus indicate that critical size defect healing could be improved if MSCs/EPCs are added to β-TCP scaffold in combination with a periosteal flap. Even after 8 weeks, the amount of proliferating cells was increased. The flap blood supply is essential for bone healing and the reduction of inflammatory processes.

Cytochrome P450 enzymes but not NADPH oxidases are the source of the NADPH-dependent lucigenin chemiluminescence in membrane assays

Measuring NADPH oxidase (Nox)-derived reactive oxygen species (ROS) in living tissues and cells is a constant challenge. All probes available display limitations regarding sensitivity, specificity or demand highly specialized detection techniques. In search for a presumably easy, versatile, sensitive and specific technique, numerous studies have used NADPH-stimulated assays in membrane fractions which have been suggested to reflect Nox activity. However, we previously found an unaltered activity with these assays in triple Nox knockout mouse (Nox1-Nox2-Nox4^-/-) tissue and cells compared to wild type. Moreover, the high ROS production of intact cells overexpressing Nox enzymes could not be recapitulated in NADPH-stimulated membrane assays. Thus, the signal obtained in these assays has to derive from a source other than NADPH oxidases. Using a combination of native protein electrophoresis, NADPH-stimulated assays and mass spectrometry, mitochondrial proteins and cytochrome P450 were identified as possible source of the assay signal. Cells lacking functional mitochondrial complexes, however, displayed a normal activity in NADPH-stimulated membrane assays suggesting that mitochondrial oxidoreductases are unlikely sources of the signal. Microsomes overexpressing P450 reductase, cytochromes b5 and P450 generated a NADPH-dependent signal in assays utilizing lucigenin, L-012 and dihydroethidium (DHE). Knockout of the cytochrome P450 reductase by CRISPR/Cas9 technology (POR^-/-) in HEK293 cells overexpressing Nox4 or Nox5 did not interfere with ROS production in intact cells. However, POR^-/- abolished the signal in NADPH-stimulated assays using membrane fractions from the very same cells. Moreover, membranes of rat smooth muscle cells treated with angiotensin II showed an increased NADPH-dependent signal with lucigenin which was abolished by the knockout of POR but not by knockout of p22phox.

IN CONCLUSION

the cytochrome P450 system accounts for the majority of the signal of Nox activity chemiluminescence based assays.

Redox-guided axonal regrowth requires cyclic GMP dependent protein kinase 1: Implication for neuropathic pain

Cyclic GMP-dependent protein kinase 1 (PKG1) mediates presynaptic nociceptive long-term potentiation (LTP) in the spinal cord and contributes to inflammatory pain in rodents but the present study revealed opposite effects in the context of neuropathic pain. We used a set of loss-of-function models for in vivo and in vitro studies to address this controversy: peripheral neuron specific deletion (SNS-PKG1^-/-), inducible deletion in subsets of neurons (SLICK-PKG1^-/-) and redox-dead PKG1 mutants. In contrast to inflammatory pain, SNS-PKG1^-/- mice developed stronger neuropathic hyperalgesia associated with an impairment of nerve regeneration, suggesting specific repair functions of PKG1. Although PKG1 accumulated at the site of injury, its activity was lost in the proximal nerve due to a reduction of oxidation-dependent dimerization, which was a consequence of mitochondrial damage in injured axons. In vitro, PKG1 deficiency or its redox-insensitivity resulted in enhanced outgrowth and reduction of growth cone collapse in response to redox signals, which presented as oxidative hotspots in growing cones. At the molecular level, PKG1 deficiency caused a depletion of phosphorylated cofilin, which is essential for growth cone collapse and guidance. Hence, redox-mediated guidance required PKG1 and consequently, its deficiency in vivo resulted in defective repair and enhanced neuropathic pain after nerve injury. PKG1-dependent repair functions will outweigh its signaling functions in spinal nociceptive LTP, so that inhibition of PKG1 is no option for neuropathic pain.

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Axonal injury leads mitochondrial damage.

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The loss of signaling ROS is associated with a reduction of redox-dependent autoactivation of PKG1.

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Loss of PKG1 impairs peripheral nerve regeneration and aggravates neuropathic pain in mice.

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Oxidative hot spots are generated in spiky growth cones and trigger growth cone collapse via PKG1.

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Malfunctioning of this redox-PKG1 guided growth cone collapse leads to aberrant outgrowth.

The NADPH Oxidase Nox2 Mediates Vitamin D-Induced Vascular Regeneration in Male Mice

1α,25-dihydroxy-vitamin D3 (1,25D) exerts protective effects in the vascular system and promotes myeloid cell differentiation, which are important sources of reactive oxygen species. Given that myeloid cell reactive oxygen species derives from Nox-family NADPH oxidases, we hypothesized that this enzyme family contributes to the beneficial effects of 1,25D on vascular regeneration. The function of Nox enzymes in this context was studied in the murine carotid artery electric injury regeneration model. Male mice were treated with daily injections of 1,25D (100 ng/kg · d) for 5 days and carotid injury was induced after 3 days. After injury, 1,25D increased the expression of Nox2 in the carotid artery. As determined by Evans blue staining on day 6, 1,25D improved vascular regeneration in a Nox2-dependent manner. Healing was lost in mice knockout for Nox2, but not in Nox1 or Nox4, knockout mice. Tissue specific knockouts demonstrated that the myeloid, but not the endothelial Nox2, was required for this effect. Mechanistically, the combination of injury and 1,25D induced the mobilization of angiogenic myeloid cells (AMCs) and increased the vascular expression of the cytokine stem cell derived factor (SDF)1, which attracts AMCs to the site of injury. Vitamin D in a Nox2-dependent manner activated MAPKs, and these are known to contribute to SDF1 induction. Accordingly, SDF1 induction was lost after deletion of Nox2. By inducing SDF1 and enhancing the number of AMCs, VitD3 is a novel approach to promote vascular repair.