NADPH oxidase activity is higher in cerebral versus systemic arteries of four animal species: role of Nox2

Stroke: Evolution of newer treatment modalities for acute ischemic stroke

Acute ischemic stroke is one of the leading causes of morbidity and mortality worldwide. Restoration of cerebral blood flow to affected ischemic areas has been the cornerstone of therapy for patients for eligible patients as early diagnosis and treatment have shown improved outcomes. However, there has been a paradigm shift in the management approach over the last decade, and with the emphasis currently directed toward including newer modalities such as neuroprotection, stem cell treatment, magnetic stimulation, anti-apoptotic drugs, delayed recanalization, and utilization of artificial intelligence for early diagnosis and suggesting algorithm-based management protocols.

Reactive oxygen species augment contractile responses of saphenous artery in 10-15-day-old but not adult rats: Substantial role of NADPH oxidases

Reactive oxygen species (ROS) produced by NADPH oxidases (NOX, a key source of ROS in vascular cells) are involved in the regulation of vascular tone, but this has been explored mainly for adult organisms. Importantly, the mechanisms of vascular tone regulation differ significantly in early postnatal ontogenesis and adulthood, while the vasomotor role of ROS in immature systemic arteries is poorly understood. We tested the hypothesis that the functional contribution of NADPH oxidase-derived ROS to the regulation of peripheral arterial tone is higher in the early postnatal period than in adulthood. We studied saphenous arteries from 10- to 15-day-old ("young") and 3- to 4-month-old ("adult") male rats using lucigenin-enhanced chemiluminescence, quantitative PCR, Western blotting, and isometric myography. We demonstrated that both basal and NADPH-stimulated superoxide anion radical (O2•-) production was significantly higher in the arteries from young in comparison to adult rats. Importantly, pan-inhibitor of NADPH oxidase VAS2870 (10 μM) reduced NADPH-induced O2•- production in arteries of young rats. Saphenous arteries of both young and adult rats demonstrated high levels of Nox2 and Nox4 mRNAs, while Nox1 and Nox3 mRNAs were not detected. The protein contents of NOX2 and NOX4 were significantly higher in arterial tissue of young compared to adult animals. Moreover, VAS2870 (10 μM) had no effect on methoxamine-induced contractile responses of adult arteries but decreased them significantly in young arteries; such effect of VAS2870 persisted after removal of the endothelium. Finally, NOX2 inhibitor GSK2795039 (10 μM), but not NOX1/4 inhibitor GKT137831 (10 μM) weakened methoxamine-induced contractile responses of arteries from young rats. Thus, ROS produced by NOX2 have a pronounced contractile influence in saphenous artery smooth muscle cells of young, but not adult rats, which is associated with the increased vascular content of NOX2 protein at this age.

Oxidative Stress and Cerebral Vascular Tone: The Role of Reactive Oxygen and Nitrogen Species

The brain's unique characteristics make it exceptionally susceptible to oxidative stress, which arises from an imbalance between reactive oxygen species (ROS) production, reactive nitrogen species (RNS) production, and antioxidant defense mechanisms. This review explores the factors contributing to the brain's vascular tone's vulnerability in the presence of oxidative damage, which can be of clinical interest in critically ill patients or those presenting acute brain injuries. The brain's high metabolic rate and inefficient electron transport chain in mitochondria lead to significant ROS generation. Moreover, non-replicating neuronal cells and low repair capacity increase susceptibility to oxidative insult. ROS can influence cerebral vascular tone and permeability, potentially impacting cerebral autoregulation. Different ROS species, including superoxide and hydrogen peroxide, exhibit vasodilatory or vasoconstrictive effects on cerebral blood vessels. RNS, particularly NO and peroxynitrite, also exert vasoactive effects. This review further investigates the neuroprotective effects of antioxidants, including superoxide dismutase (SOD), vitamin C, vitamin E, and the glutathione redox system. Various studies suggest that these antioxidants could be used as adjunct therapies to protect the cerebral vascular tone under conditions of high oxidative stress. Nevertheless, more extensive research is required to comprehensively grasp the relationship between oxidative stress and cerebrovascular tone, and explore the potential benefits of antioxidants as adjunctive therapies in critical illnesses and acute brain injuries.

Advanced glycated end-products inhibit dilation through constitutive endothelial RAGE and Nox1/4 in rat isolated skeletal muscle arteries

OBJECTIVE

This study investigated the actions of advanced glycated end-products (AGE), their receptors (RAGE), and NAD(P)H oxidase (Nox) subtypes 1, 2, and 4 on mechanisms of endothelium-dependent dilation of the rat cremaster muscle artery (CMA).

METHODS

Immunofluorescence studies were used to examine expression of RAGE in rat arteries. ROS accumulation was measured using luminescence and fluorescence assays. Functional studies were performed using pressure myography.

RESULTS

High levels of RAGE expression were shown in the endothelial cells of the CMA, compared with low endothelial expression in middle cerebral and mesenteric arteries and the aorta. Exogenous AGE (in vitro glycated bovine serum albumin) stimulated H2O2 accumulation in CMA, which was prevented by the RAGE antagonist FPS-ZM1, the NAD(P)H oxidase (Nox) inhibitor apocynin and inhibited by the Nox1/4 inhibitor setanaxib, but not the Nox2 inhibitor GSK2795039. In functional studies, AGE inhibited vasodilation of CMA stimulated by acetylcholine, sodium nitroprusside, and the BKCa activator NS1619, but not adenosine-induced dilation. FPS-ZM1, apocynin, and setanaxib prevented the inhibitory effects of AGE on responses to acetylcholine and NS-1619.

CONCLUSION

These observations suggest RAGE are constitutively expressed in the endothelium of the rat CMA and may be activated by AGE to stimulate Nox1/4 and ROS formation with resulting inhibition of NO and BKCa-mediated endothelium-dependent dilation.

Endothelial NOX4 aggravates eNOS uncoupling by decreasing dihydrofolate reductase after subarachnoid hemorrhage

Endothelial malfunction is a major contributor to early or delayed vasospasm after subarachnoid hemorrhage (SAH). As a representative form of endothelial dysfunction, endothelial nitric oxide synthase (eNOS) uncoupling leads to a reduction in nitric oxide (NO) generated by endothelial cells. In this study, we investigated how the interaction between endothelial NOX4 (nicotinamide adenine dinucleotide phosphate oxidase 4) and DHFR (dihydrofolate reductase) contributes to eNOS uncoupling after SAH. Setanaxib and the adeno-associated virus (AAV) targeting brain vascular endothelia were injected through the tail vein and the expression and localization of proteins were examined by western blot and immunofluorescence staining. The NO content was measured using the NO assay kit, and laser speckle contrast imaging was used to assess cortical perfusion. ROS (reactive oxygen species) level was detected by DHE (dihydroethidium) staining, DCFH-DA (2',7'-dichlorofluorescin diacetate) staining and H₂O₂ (hydrogen peroxide) measurement. The Garcia score was employed to examine neurological function. Setanaxib is widely used for its preferential inhibition for NOX1/4 over other NOX isoforms. After endothelial NOX4 was inhibited by Setanaxib in a mouse model of SAH, the endothelial DHFR level was significantly elevated, which attenuated eNOS uncoupling, increased cortical perfusion, and improved the neurological function. The protective role of inhibiting endothelial NOX4, however, disappeared after knocking down endothelial DHFR. Our results suggest that endothelial DHFR decreased significantly because of the elevated level of endothelial NOX4, which aggravated eNOS uncoupling after SAH, leading to decreased cortical perfusion and worse neurological outcome.

Small Vessel Disease: Ancient Description, Novel Biomarkers

Small vessel disease (SVD) is one of the most frequent pathological conditions which lead to dementia. Biochemical and neuroimaging might help correctly identify the clinical diagnosis of this relevant brain disease. The microvascular alterations which underlie SVD have common origins, similar cognitive outcomes, and common vascular risk factors. Nevertheless, the arteriolosclerosis process, which underlines SVD development, is based on different mechanisms, not all completely understood, which start from a chronic hypoperfusion state and pass through a chronic brain inflammatory condition, inducing a significant endothelium activation and a consequent tissue remodeling action. In a recent review, we focused on the pathophysiology of SVD, which is complex, involving genetic conditions and different co-morbidities (i.e., diabetes, chronic hypoxia condition, and obesity). Currently, many points still remain unclear and discordant. In this paper, we wanted to focus on new biomarkers, which can be the expression of the endothelial dysfunction, or of the oxidative damage, which could be employed as markers of disease progression or for future targets of therapies. Therefore, we described the altered response to the endothelium-derived nitric oxide-vasodilators (ENOV), prostacyclin, C-reactive proteins, and endothelium-derived hyperpolarizing factors (EDHF). At the same time, due to the concomitant endothelial activation and chronic neuroinflammatory status, we described hypoxia-endothelial-related markers, such as HIF 1 alpha, VEGFR2, and neuroglobin, and MMPs. We also described blood-brain barrier disruption biomarkers and imaging techniques, which can also describe perivascular spaces enlargement and dysfunction. More studies should be necessary, in order to implement these results and give them a clinical benefit.

Cross-Talk between Amyloid, Tau Protein and Free Radicals in Post-Ischemic Brain Neurodegeneration in the Form of Alzheimer’s Disease Proteinopathy

Recent years have seen remarkable progress in research into free radicals oxidative stress, particularly in the context of post-ischemic recirculation brain injury. Oxidative stress in post-ischemic tissues violates the integrity of the genome, causing DNA damage, death of neuronal, glial and vascular cells, and impaired neurological outcome after brain ischemia. Indeed, it is now known that DNA damage and repair play a key role in post-stroke white and gray matter remodeling, and restoring the integrity of the blood-brain barrier. This review will present one of the newly characterized mechanisms that emerged with genomic and proteomic development that led to brain ischemia to a new level of post-ischemic neuropathological mechanisms, such as the presence of amyloid plaques and the development of neurofibrillary tangles, which further exacerbate oxidative stress. Finally, we hypothesize that modified amyloid and the tau protein, along with the oxidative stress generated, are new key elements in the vicious circle important in the development of post-ischemic neurodegeneration in a type of Alzheimer’s disease proteinopathy.

Blood-Brain Barrier Disruption by Lipopolysaccharide and Sepsis-Associated Encephalopathy

As a complex multicellular structure of the vascular system at the central nervous system (CNS), the blood-brain barrier (BBB) separates the CNS from the system circulation and regulates the influx and efflux of substances to maintain the steady-state environment of the CNS. Lipopolysaccharide (LPS), the cell wall component of Gram-negative bacteria, can damage the barrier function of BBB and further promote the occurrence and development of sepsis-associated encephalopathy (SAE). Here, we conduct a literature review of the direct and indirect damage mechanisms of LPS to BBB and the relationship between these processes and SAE. We believe that after LPS destroys BBB, a large number of inflammatory factors and neurotoxins will enter and damage the brain tissue, which will activate brain immune cells to mediate inflammatory response and in turn further destroys BBB. This vicious circle will ultimately lead to the progression of SAE. Finally, we present a succinct overview of the treatment of SAE by restoring the BBB barrier function and summarize novel opportunities in controlling the progression of SAE by targeting the BBB.

Small Vessel Disease-Related Dementia: An Invalid Neurovascular Coupling?

The arteriosclerosis-dependent alteration of brain perfusion is one of the major determinants in small vessel disease, since small vessels have a pivotal role in the brain's autoregulation. Nevertheless, as far as we know, endothelium distress can potentiate the flow dysregulation and lead to subcortical vascular dementia that is related to small vessel disease (SVD), also being defined as subcortical vascular dementia (sVAD), as well as microglia activation, chronic hypoxia and hypoperfusion, vessel-tone dysregulation, altered astrocytes, and pericytes functioning blood-brain barrier disruption. The molecular basis of this pathology remains controversial. The apparent consequence (or a first event, too) is the macroscopic alteration of the neurovascular coupling. Here, we examined the possible mechanisms that lead a healthy aging process towards subcortical dementia. We remarked that SVD and white matter abnormalities related to age could be accelerated and potentiated by different vascular risk factors. Vascular function changes can be heavily influenced by genetic and epigenetic factors, which are, to the best of our knowledge, mostly unknown. Metabolic demands, active neurovascular coupling, correct glymphatic process, and adequate oxidative and inflammatory responses could be bulwarks in defense of the correct aging process; their impairments lead to a potentially catastrophic and non-reversible condition.

The need to incorporate aged animals into the preclinical modeling of neurological conditions

Neurological conditions such as traumatic brain injury, stroke, Parkinson's disease, epilepsy, multiple sclerosis, and Alzheimer's disease are serious clinical problems that affect millions of people worldwide. The majority of clinical trials for these common conditions have failed, and there is a critical need to understand why treatments in preclinical animal models do not translate to patients. Many patients with these conditions are middle-aged or older, however, the majority of preclinical studies have used only young-adult animals. Considering that aging involves biological changes that are relevant to the pathobiology of neurological diseases, the lack of aged subjects in preclinical research could contribute to translational failures. This paper details how aging affects biological processes involved in neurological conditions, and reviews aging research in the context of traumatic brain injury, stroke, Parkinson's disease, epilepsy, multiple sclerosis, and Alzheimer's disease. We conclude that aging is an important, but often overlooked, factor that influences biology and outcomes in neurological conditions, and provide suggestions to improve our understanding and treatment of these diseases in aged patients.

Vitamin D in Neurological Diseases: A Rationale for a Pathogenic Impact

It is widely known that vitamin D receptors have been found in neurons and glial cells, and their highest expression is in the hippocampus, hypothalamus, thalamus and subcortical grey nuclei, and substantia nigra. Vitamin D helps the regulation of neurotrophin, neural differentiation, and maturation, through the control operation of growing factors synthesis (i.e., neural growth factor [NGF] and glial cell line-derived growth factor (GDNF), the trafficking of the septohippocampal pathway, and the control of the synthesis process of different neuromodulators (such as acetylcholine [Ach], dopamine [DA], and gamma-aminobutyric [GABA]). Based on these assumptions, we have written this review to summarize the potential role of vitamin D in neurological pathologies. This work could be titanic and the results might have been very fuzzy and even incoherent had we not conjectured to taper our first intentions and devoted our interests towards three mainstreams, demyelinating pathologies, vascular syndromes, and neurodegeneration. As a result of the lack of useful therapeutic options, apart from the disease-modifying strategies, the role of different risk factors should be investigated in neurology, as their correction may lead to the improvement of the cerebral conditions. We have explored the relationships between the gene-environmental influence and long-term vitamin D deficiency, as a risk factor for the development of different types of neurological disorders, along with the role and the rationale of therapeutic trials with vitamin D implementation.

Oxidative Stress: A Major Player in Cerebrovascular Alterations Associated to Neurodegenerative Events

The brain is one of the most exquisite organs in the body with high metabolic demands, and requires a tight regulation of the surrounding environment. This tight control is exerted by the neurovascular unit (NVU) comprising different cell types, where endothelial cells play the commander-in-chief role. Thus, it is assumable that even slight perturbations in NVU might affect, in some cases irreversibly, brain homeostasis and health. In this line, recent findings support the two-hit vascular hypothesis for neurodegenerative conditions, where vascular dysfunction underlies the development of neurodegenerative diseases, such as Alzheimer’s disease (AD). Knowing that endothelial cells are rich in mitochondria and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, two major reactive oxygen species (ROS) sources, this review aims to gather information on how oxidative stress is in the front line of vascular alterations observed in brain aging and neurodegenerative conditions, particularly AD. Also, a brief discussion about the therapeutic strategies aimed to protect against cerebrovascular diseases is included.

Free Radical Damage in Ischemia-Reperfusion Injury: An Obstacle in Acute Ischemic Stroke after Revascularization Therapy

Acute ischemic stroke is a common cause of morbidity and mortality worldwide. Thrombolysis with recombinant tissue plasminogen activator and endovascular thrombectomy are the main revascularization therapies for acute ischemic stroke. However, ischemia-reperfusion injury after revascularization therapy can result in worsening outcomes. Among all possible pathological mechanisms of ischemia-reperfusion injury, free radical damage (mainly oxidative/nitrosative stress injury) has been found to play a key role in the process. Free radicals lead to protein dysfunction, DNA damage, and lipid peroxidation, resulting in cell death. Additionally, free radical damage has a strong connection with inducing hemorrhagic transformation and cerebral edema, which are the major complications of revascularization therapy, and mainly influencing neurological outcomes due to the disruption of the blood-brain barrier. In order to get a better clinical prognosis, more and more studies focus on the pharmaceutical and nonpharmaceutical neuroprotective therapies against free radical damage. This review discusses the pathological mechanisms of free radicals in ischemia-reperfusion injury and adjunctive neuroprotective therapies combined with revascularization therapy against free radical damage.

Oxidative stress in cerebral small vessel disease. Role of reactive species

Cerebral small vessel disease (CSVD) is a wide term describing the condition affecting perforating arterial branches as well as arterioles, venules, and capillaries. Cerebral vascular net is one of the main targets of localised oxidative stress processes causing damage to vasculature, changes in the blood flow and blood-brain barrier and, in consequence, promoting neurodegenerative alterations in the brain tissue. Numerous studies report the fact of oxidation to proteins, sugars, lipids and nucleic acids, occurring in most neurodegenerative diseases mainly in the earliest stages and correlations with the development of cognitive and motor disturbances. The dysfunction of endothelium can be caused by oxidative stress and inflammatory mechanisms as a result of reactions and processes generating extensive reactive oxygen species (ROS) production such as high blood pressure, oxidised low density lipoproteins (oxLDL), very low density lipoproteins (vLDL), diabetes, homocysteinaemia, smoking, and infections. Several animal studies show positive aspects of ROS, especially within cerebral vasculature.

Microvascular NADPH oxidase in health and disease

The systemic and cerebral microcirculation contribute critically to regulation of local and global blood flow and perfusion pressure. Microvascular dysfunction, commonly seen in numerous cardiovascular pathologies, is associated with alterations in the oxidative environment including potentiated production of reactive oxygen species (ROS) and subsequent activation of redox signaling pathways. NADPH oxidases (Noxs) are a primary source of ROS in the vascular system and play a central role in cardiovascular health and disease. In this review, we focus on the roles of Noxs in ROS generation in resistance arterioles and capillaries, and summarize their contributions to microvascular physiology and pathophysiology in both systemic and cerebral microcirculation. In light of the accumulating evidence that Noxs are pivotal players in vascular dysfunction of resistance arterioles, selectively targeting Nox isozymes could emerge as a novel and effective therapeutic strategy for preventing and treating microvascular diseases.

Increased Oxidative Stress and Hypoxia Inducible Factor-1 Expression during Arteriovenous Fistula Maturation

BACKGROUND

The poor clinical results that are frequently reported for arteriovenous fistulae (AVF) for hemodialysis are typically due to failure of AVF maturation. We hypothesized that early AVF maturation is associated with generation of reactive oxygen species and activation of the hypoxia-inducible factor-1 (HIF-1) pathway, potentially promoting neointimal hyperplasia. We tested this hypothesis using a previously reported mouse AVF model that recapitulates human AVF maturation.

METHODS

Aortocaval fistulae were created in C57Bl/6 mice and compared with sham-operated mice. AVFs or inferior vena cavas were analyzed using a microarray, Amplex Red for extracellular H2O2, quantitative polymerase chain reaction, immunohistochemistry, and immunoblotting for HIF-1α and immunofluorescence for NOX-2, nitrotyrosine, heme oxygenase-1 (HO-1), and vascular endothelial growth factor (VEGF)-A.

RESULTS

Oxidative stress was higher in AVF than that in control veins, with more H2O2 (P = 0.007) and enhanced nitrotyrosine immunostaining (P = 0.005). Immunohistochemistry and immunoblot showed increased HIF-1α immunoreactivity in the AVF endothelium; HIF-1 targets NOX-2, HO-1 and VEGF-A were overexpressed in the AVF (P < 0.01). AVF expressed increased numbers of HIF-1α (P < 0.0001) and HO-1 (P < 0.0001) messenger RNA transcripts.

CONCLUSIONS

Oxidative stress increases in mouse AVF during early maturation, with increased expression of HIF-1α and its target genes NOX-2, HO-1, and VEGF-A. These results suggest that clinical strategies to improve AVF maturation could target the HIF-1 pathway.

A microdialysis method to measure in vivo hydrogen peroxide and superoxide in various rodent tissues

Reactive oxygen species (ROS) play a critical role in cell signaling and disease pathogenesis. Despite their biological importance, assessment of ROS often involves measurement of indirect byproducts or measurement of ROS from excised tissue. Herein, we describe a microdialysis technique that utilizes the Amplex Ultrared assay to directly measure hydrogen peroxide (H₂O₂) and superoxide in tissue of living, anesthetized rats and mice. We demonstrate the application of this methodology in the penis, adipose tissue, skeletal muscle, kidney, and liver. We provide data demonstrating the impact of important methodological considerations such as membrane length, perfusion rate, and time-dependence upon probe insertion. In this report, we provide a complete list of equipment, troubleshooting tips, and suggestions for implementing this technique in a new system. The data herein demonstrate the feasibility of measuring both in vivo H₂O₂ and superoxide in the extracellular environment of various rodent tissues, providing a technique with potential application to a vast array of disease states which are subject to oxidative stress.

Cerebral Small Vessel Disease: Targeting Oxidative Stress as a Novel Therapeutic Strategy?

Cerebral small vessel disease (SVD) is a major contributor to stroke, and a leading cause of cognitive impairment and dementia. Despite the devastating effects of cerebral SVD, the pathogenesis of cerebral SVD is still not completely understood. Moreover, there are no specific pharmacological strategies for its prevention or treatment. Cerebral SVD is characterized by marked functional and structural abnormalities of the cerebral microcirculation. The clinical manifestations of these pathological changes include lacunar infarcts, white matter hyperintensities, and cerebral microbleeds. The main purpose of this review is to discuss evidence implicating oxidative stress in the arteriopathy of both non-amyloid and amyloid (cerebral amyloid angiopathy) forms of cerebral SVD and its most important risk factors (hypertension and aging), as well as its contribution to cerebral SVD-related brain injury and cognitive impairment. We also highlight current evidence of the involvement of the NADPH oxidases in the development of oxidative stress, enzymes that are a major source of reactive oxygen species in the cerebral vasculature. Lastly, we discuss potential pharmacological strategies for oxidative stress in cerebral SVD, including some of the historical and emerging NADPH oxidase inhibitors.

Pharmacological modulation of dietary lipid-induced cerebral capillary dysfunction: Considerations for reducing risk for Alzheimer's disease

An increasing body of evidence suggests that cerebrovascular dysfunction and microvessel disease precede the evolution of hallmark pathological features that characterise Alzheimer's disease (AD), consistent with a causal association for onset or progression. Recent studies, principally in genetically unmanipulated animal models, suggest that chronic ingestion of diets enriched in saturated fats and cholesterol may compromise blood-brain barrier (BBB) integrity resulting in inappropriate blood-to-brain extravasation of plasma proteins, including lipid macromolecules that may be enriched in amyloid-β (Aβ). Brain parenchymal retention of blood proteins and lipoprotein bound Aβ is associated with heightened neurovascular inflammation, altered redox homeostasis and nitric oxide (NO) metabolism. Therefore, it is a reasonable proposition that lipid-lowering agents may positively modulate BBB integrity and by extension attenuate risk or progression of AD. In addition to their robust lipid lowering properties, reported beneficial effects of lipid-lowering agents were attributed to their pleiotropic properties via modulation of inflammation, oxidative stress, NO and Aβ metabolism. The review is a contemporary consideration of a complex body of literature intended to synthesise focussed consideration of mechanisms central to regulation of BBB function and integrity. Emphasis is given to dietary fat driven significant epidemiological evidence consistent with heightened risk amongst populations consuming greater amounts of saturated fats and cholesterol. In addition, potential neurovascular benefits associated with the use of hypolipidemic statins, probucol and fenofibrate are also presented in the context of lipid-lowering and pleiotropic properties.

Acupuncture elicits neuroprotective effect by inhibiting NAPDH oxidase-mediated reactive oxygen species production in cerebral ischaemia

In the current study, we aimed to investigate whether NADPH oxidase, a major ROS-producing enzyme, was involved in the antioxidant effect of acupuncture on cognitive impairment after cerebral ischaemia. The cognitive function, infract size, neuron cell loss, level of superoxide anion and expression of NADPH oxidase subunit in hippocampus of two-vessel occlusion (2VO) rats were determined after 2-week acupuncture. Furthermore, the cognitive function and production of O2(-) were determined in the presence and absence of NADPH oxidase agonist (TBCA) and antagonist (Apocynin). The effect of acupuncture on cognitive function after cerebral ischaemia in gp91phox-KO mice was evaluated by Morris water maze. Acupuncture reduced infarct size, attenuated overproduction of O2(-), and reversed consequential cognitive impairment and neuron cell loss in 2VO rats. The elevations of gp91phox and p47phox after 2VO were significantly decreased after acupuncture treatment. However, no differences of gp91phox mRNA were found among any experimental groups. Furthermore, these beneficial effects were reversed by TBCA, whereas apocynin mimicked the effect of acupuncture by improving cognitive function and decreasing O2(-) generation. Acupuncture failed to improve the memory impairment in gp91phox KO mice. Full function of the NADPH oxidase enzyme plays an important role in neuroprotective effects against cognitive impairment via inhibition of NAPDH oxidase-mediated oxidative stress.

Chronic aldosterone administration causes Nox2-mediated increases in reactive oxygen species production and endothelial dysfunction in the cerebral circulation

OBJECTIVES

An elevated plasma aldosterone level is an independent cardiovascular risk factor. Although excess aldosterone promotes cardiovascular disease, no studies have examined the effect of increased plasma aldosterone on the cerebral circulation. A major source of vascular reactive oxygen species (ROS) during cardiovascular disease is the NADPH oxidases. Because Nox2-containing NADPH oxidase (Nox2 oxidase) is highly expressed in the cerebral endothelium, we postulated that it might contribute to ROS generation and vascular dysfunction in response to aldosterone. Here, we examined the effect of aldosterone and Nox2 oxidase on ROS production and endothelial dysfunction in the cerebral circulation, and whether the effects of aldosterone are exacerbated in aged mice.

METHODS AND RESULTS

In adult (average age ∼24-25 weeks) wild-type and Nox2-deficient (Nox2(/y)) mice, neither vehicle nor aldosterone (0.28  mg/kg per day for 14 days) affected blood pressure (measured using tail-cuff). By contrast, aldosterone treatment reduced dilation of the basilar artery (measured using myography) to the endothelium-dependent agonist acetylcholine in wild-type mice (P < 0.05), but had no such effect in Nox2(/y) mice (P > 0.05). Aldosterone increased basal and phorbol dibutyrate-stimulated superoxide production (measured using L-012-enhanced chemiluminesence) in cerebral arteries from wild-type but not from Nox2(/y) mice. In aged wild-type mice (average age ∼70 weeks), aldosterone treatment increased blood pressure, but had a similar effect on cerebral artery superoxide levels as in adult wild-type mice.

CONCLUSION

These data indicate that Nox2 oxidase mediates aldosterone-induced increases in ROS production and endothelial dysfunction in cerebral arteries from adult mice independently of blood pressure changes. Aldosterone-induced hypertension is augmented during aging.

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.

Nox2 knockout delays infarct progression and increases vascular recovery through angiogenesis in mice following ischaemic stroke with reperfusion

Evidence suggests the NADPH oxidases contribute to ischaemic stroke injury and Nox2 is the most widely studied subtype in the context of stroke. There is still conjecture however regarding the benefits of inhibiting Nox2 to improve stroke outcome. The current study aimed to examine the temporal effects of genetic Nox2 deletion on neuronal loss after ischaemic stroke using knockout (KO) mice with 6, 24 and 72 hour recovery. Transient cerebral ischaemia was induced via intraluminal filament occlusion and resulted in reduced infarct volumes in Nox2 KO mice at 24 h post-stroke compared to wild-type controls. No protection was evident at either 6 h or 72 h post-stroke, with both genotypes exhibiting similar volumes of damage. Reactive oxygen species were detected using dihydroethidium and were co-localised with neurons and microglia in both genotypes using immunofluorescent double-labelling. The effect of Nox2 deletion on vascular damage and recovery was also examined 24 h and 72 h post-stroke using an antibody against laminin. Blood vessel density was decreased in the ischaemic core of both genotypes 24 h post-stroke and returned to pre-stroke levels only in Nox2 KO mice by 72 h. Overall, these results are the first to show that genetic Nox2 deletion merely delays the progression of neuronal loss after stroke but does not prevent it. Additionally, we show for the first time that Nox2 deletion increases re-vascularisation of the damaged brain by 72 h, which may be important in promoting endogenous brain repair mechanisms that rely on re-vascularisation.

Blood-brain barrier dysfunction in mice induced by lipopolysaccharide is attenuated by dapsone

Blood-brain barrier (BBB) dysfunction is a key event in the development of many central nervous system (CNS) diseases, such as septic encephalopathy and stroke. 4,4'-Diaminodiphenylsulfone (DDS, Dapsone) has displayed neuroprotective effect, but whether DDS has protective role on BBB integrity is not clear. This study was designed to examine the effect of DDS on lipopolysaccharide (LPS)-induced BBB disruption and oxidative stress in brain vessels. Using in vivo multiphoton imaging, we found that DDS administration significantly restored BBB integrity compromised by LPS. DDS also increased the expression of tight junction proteins occludin, zona occludens-1 (ZO-1) and claudin-5 in brain vessels. Level of reactive oxygen species (ROS) was reduced by DDS treatment, which may due to decreased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and NOX2 expression. Our results showed that LPS-induced BBB dysfunction could be attenuated by DDS, indicated that DDS has a therapeutic potential for treating CNS infection and other BBB related diseases.

Cerebrovascular dysfunction and blood-brain barrier permeability induced by oxidized LDL are prevented by apocynin and magnesium sulfate in female rats

Oxidized low-density lipoprotein (oxLDL) is elevated during several neurologic conditions that involve cerebral edema formation, including severe preeclampsia and eclampsia; however, our understanding of its effect on the cerebral vasculature is limited. We hypothesized that oxLDL induced blood-brain barrier (BBB) disruption and changes in cerebrovascular reactivity occur through NADPH oxidase-derived superoxide. We also investigated the effect of MgSO₄ on oxLDL-induced changes in the cerebral vasculature as this is commonly used in preventing cerebral edema formation. Posterior cerebral arteries from female rats were perfused with 5 µg/mL oxLDL in rat serum with or without 50 µM apocynin or 16 mM MgSO₄ and BBB permeability and vascular reactivity were compared. oxLDL increased BBB permeability and decreased myogenic tone that were prevented by apocynin. oxLDL increased constriction to the nitric oxide synthase inhibitor nitro-L-arginine that was unaffected by apocynin. oxLDL enhanced dilation to the NO donor sodium nitroprusside that was prevented by apocynin. MgSO₄ prevented oxLDL-induced BBB permeability without affecting oxLDL-induced changes in myogenic tone. Thus, oxLDL seems to cause BBB disruption and vascular tone dysregulation through NADPH oxidase-derived superoxide. These results highlight oxLDL and NADPH oxidase as potentially important therapeutic targets in neurologic conditions that involve elevated oxLDL.

Beneficial effects of lifelong caloric restriction on endothelial function are greater in conduit arteries compared to cerebral resistance arteries

Endothelial dysfunction occurs in conduit and cerebral resistance arteries with advancing age. Lifelong caloric restriction (CR) can prevent the onset of age-related dysfunction in many tissues, but its effects on cerebral resistance artery function, as compared with conduit artery function, have not been determined. We measured endothelium-dependent dilation (EDD) in the carotid artery and middle cerebral artery (MCA) from young (5-7 months), old ad libitum fed (AL, 29-32 months), and old lifelong CR (CR, 40 % CR, 29-32 months) B6D2F1 mice. Compared with young, EDD for old AL was 24 % lower in the carotid and 47 % lower in the MCA (p < 0.05). For old CR, EDD was not different from young in the carotid artery (p > 0.05), but was 25 % lower than young in the MCA (p < 0.05). EDD was not different between groups after NO synthase inhibition with N(ω)-nitro-L-arginine methyl ester in the carotid artery or MCA. Superoxide production by the carotid artery and MCA was greater in old AL compared with young and old CR (p < 0.05). In the carotid, incubation with the superoxide scavenger TEMPOL improved EDD for old AL (p > 0.05), with no effect in young or old CR (p > 0.05). In the MCA, incubation with TEMPOL or the NADPH oxidase inhibitor apocynin augmented EDD in old AL (p < 0.05), but reduced EDD in young and old CR (p < 0.05). Thus, age-related endothelial dysfunction is prevented by lifelong CR completely in conduit arteries, but only partially in cerebral resistance arteries. These benefits of lifelong CR on EDD result from lower oxidative stress and greater NO bioavailability.

Hydrogen sulfide protects endothelial nitric oxide function under conditions of acute oxidative stress in vitro

The aim of this study was to examine the ability of H2S, released from NaHS to protect vascular endothelial function under conditions of acute oxidative stress by scavenging superoxide anions (O2(-)) and suppressing vascular superoxide anion production. O2(-) was generated in Krebs' solution by reacting hypoxanthine with xanthine oxidase (Hx-XO) or with the O2(-) generator pyrogallol to model acute oxidative stress in vitro. O2(-) generation was measured by lucigenin-enhanced chemiluminescence. Functional responses in mouse aortic rings were assessed using a small vessel myograph. NaHS scavenged O2(-) in a concentration-dependent manner. Isolated aortic rings exposed to either Hx-XO or pyrogallol displayed significantly attenuated maximum vasorelaxation responses to the endothelium-dependent vasodilator acetylcholine, and significantly reduced NO bioavailability, which was completely reversed if vessels were pre-incubated with NaHS (100 μM). NADPH-stimulated aortic O2(-) production was significantly attenuated by the NADPH oxidase inhibitor diphenyl iodonium. Prior treatment of vessels with NaHS (100 nM-100 μM; 30 min) inhibited NADPH-stimulated aortic O2(-) production in a concentration-dependent manner. This effect persisted when NaHS was washed out prior to measuring NADPH-stimulated O2(-) production. These data show for the first time that NaHS directly scavenges O2(-) and suppresses vascular NADPH oxidase-derived O2(-) production in vitro. Furthermore, these properties protect endothelial function and NO bioavailability in an in vitro model of acute oxidative stress. These results suggest that H2S can elicit vasoprotection by both scavenging O2(-) and by reducing vascular NADPH oxidase-derived O2(-) production.

Nitroxyl (HNO) suppresses vascular Nox2 oxidase activity

Nox2 oxidase activity underlies the oxidative stress and vascular dysfunction associated with several vascular-related diseases. We have reported that nitric oxide (NO) decreases reactive oxygen species production by endothelial Nox2. This study tested the hypothesis that nitroxyl (HNO), the redox sibling of NO, also suppresses vascular Nox2 oxidase activity. Specifically, we examined the influence of two well-characterized HNO donors, Angeli's salt and isopropylamine NONOate (IPA/NO), on Nox2-dependent responses to angiotensin II (reactive oxygen species production and vasoconstriction) in mouse cerebral arteries. Angiotensin II (0.1μmol/L)-stimulated superoxide (measured by lucigenin-enhanced chemiluminescence) and hydrogen peroxide (Amplex red fluorescence) levels in cerebral arteries (pooled basilar and middle cerebral (MCA)) from wild-type (WT) mice were ~60% lower (P<0.05) in the presence of either Angeli's salt (1μmol/L) or IPA/NO (1μmol/L). Similarly, phorbyl 12,13-dibutyrate (10μmol/L; Nox2 activator)-stimulated hydrogen peroxide levels were ~40% lower in the presence of IPA/NO (1μmol/L; P<0.05). The ability of IPA/NO to decrease superoxide levels was reversible and abolished by the HNO scavenger l-cysteine (3mmol/L; P<0.05), but was unaffected by hydroxocobalamin (100μmol/L; NO scavenger), ODQ (10μmol/L; soluble guanylyl cyclase (sGC) inhibitor), or Rp-8-pCPT-cGMPS (10μmol/L; cyclic guanosine monophosphate (cGMP)-dependent protein kinase inhibitor). Angiotensin II-stimulated superoxide was substantially less in arteries from Nox2-deficient (Nox2(-/y)) versus WT mice (P<0.05). In contrast to WT, IPA/NO (1μmol/L) had no effect on superoxide levels in arteries from Nox2(-/y) mice. Finally, angiotensin II (1-1000μmol/L)-induced constriction of WT MCA was virtually abolished by IPA/NO (1μmol/L), whereas constrictor responses to either the thromboxane A2 mimetic U46619 (1-100 nmol/L) or high potassium (122.7mmol/L) were unaffected. In conclusion, HNO suppresses vascular Nox2 oxidase activity via a sGC-cGMP-independent pathway. Thus, HNO donors might be useful therapeutic agents to limit and/or prevent Nox2-dependent vascular dysfunction.

Deficiency of Nox2 prevents angiotensin II-induced inward remodeling in cerebral arterioles

Angiotensin II is an important determinant of inward remodeling in cerebral arterioles. Many of the vascular effects of angiotensin II are mediated by reactive oxygen species (ROS) generated from homologs of NADPH oxidase with Nox2 predominating in small arteries and arterioles. Therefore, we tested the hypothesis that superoxide generated by Nox2 plays a role in angiotensin II-induced cerebral arteriolar remodeling. We examined Nox2-deficient and wild-type (WT) mice in which a pressor or a non-pressor dose of angiotensin II (1000 or 200 ng/kg/day) or saline was infused for 4 weeks via osmotic minipumps. Systolic arterial pressure was measured by a tail-cuff method. Pressure and diameter of cerebral arterioles were measured through an open cranial window in anesthetized mice. Cross-sectional area (by histology) and superoxide level (by hydroethidine staining) of cerebral arterioles were determined ex vivo. The pressor, but not the non-pressor, dose of angiotensin II significantly increased systolic arterial pressure in both WT and Nox2-deficient mice. Both doses of angiotensin II increased superoxide levels and significantly reduced external diameter in maximally dilated cerebral arterioles in WT mice. Increased superoxide and inward remodeling were prevented in Nox2-deficient mice. Moreover, only the pressor dose of AngII increased cross-sectional area of arteriolar wall in WT mice and was prevented in Nox2-deficient mice. In conclusion, superoxide derived from Nox2-containing NADPH oxidase plays an important role in angiotensin II-mediated inward remodeling in cerebral arterioles. This effect appears to be independent of pressure and different from that of hypertrophy.

NADPH Oxidase as a Therapeutic Target for Neuroprotection against Ischaemic Stroke: Future Perspectives

Oxidative stress caused by an excess of reactive oxygen species (ROS) is known to contribute to stroke injury, particularly during reperfusion, and antioxidants targeting this process have resulted in improved outcomes experimentally. Unfortunately these improvements have not been successfully translated to the clinical setting. Targeting the source of oxidative stress may provide a superior therapeutic approach. The NADPH oxidases are a family of enzymes dedicated solely to ROS production and pre-clinical animal studies targeting NADPH oxidases have shown promising results. However there are multiple factors that need to be considered for future drug development: There are several homologues of the catalytic subunit of NADPH oxidase. All have differing physiological roles and may contribute differentially to oxidative damage after stroke. Additionally, the role of ROS in brain repair is largely unexplored, which should be taken into consideration when developing drugs that inhibit specific NADPH oxidases after injury. This article focuses on the current knowledge regarding NADPH oxidase after stroke including in vivo genetic and inhibitor studies. The caution required when interpreting reports of positive outcomes after NADPH oxidase inhibition is also discussed, as effects on long term recovery are yet to be investigated and are likely to affect successful clinical translation.

Which NADPH oxidase isoform is relevant for ischemic stroke? The case for nox 2

Significance and Recent Advances: Ischemic stroke is the leading cause of disability and third in mortality in industrialized nations. Immediate restoration of cerebral blood flow is crucial to salvage brain tissue, but only few patients are eligible for recanalization therapy. Thus, the need for alternative neuroprotective strategies is huge, and antioxidant interventions have long been studied in this context. Reactive oxygen species (ROS) physiologically serve as signaling molecules, but excessive amounts of ROS, as generated during ischemia/reperfusion (I/R), contribute to tissue injury.

CRITICAL ISSUES

Nevertheless and despite a strong rational of ROS being a pharmacological target, all antioxidant interventions failed to improve functional outcome in human clinical trials. Antioxidants may interfere with physiological functions of ROS or do not reach the crucial target structures of ROS-induced injury effectively.

FUTURE DIRECTIONS

Thus, a potentially more promising approach is the inhibition of the source of disease-promoting ROS. Within recent years, NADPH oxidases (Nox) of the Nox family have been identified as mediators of neuronal pathology. As, however, several Nox homologs are expressed in neuronal tissue, and as many of the pharmacological inhibitors employed are rather unspecific, the concept of Nox as mediators of brain damage is far from being settled. In this review, we will discuss the contribution of Nox homologs to I/R injury at large as well as to neuronal damage in particular. We will illustrate that the current data provide evidence for Nox2 as the most important NADPH oxidase mediating cerebral injury.

Increased oxidized low-density lipoprotein causes blood-brain barrier disruption in early-onset preeclampsia through LOX-1

Early-onset preeclampsia (EPE) is a severe form of preeclampsia that involves life-threatening neurological complications. However, the underlying mechanism by which EPE affects the maternal brain is not known. We hypothesized that plasma from women with EPE increases blood-brain barrier (BBB) permeability vs. plasma from women with late-onset preeclampsia (LPE) or normal pregnancy (NP) and investigated its underlying mechanism by perfusing cerebral veins from nonpregnant rats (n=6-7/group) with human plasma from women with EPE, LPE, or NP and measuring permeability. We show that plasma from women with EPE significantly increased BBB permeability vs. plasma from women with LPE or NP (P<0.001). BBB disruption in response to EPE plasma was due to a 260% increase of circulating oxidized LDL (oxLDL) binding to its receptor, LOX-1, and subsequent generation of peroxynitrite (P<0.001). A rat model with pathologically high lipid levels in pregnancy showed symptoms of preeclampsia, including elevated blood pressure, growth-restricted fetuses, and LOX-1-dependent BBB disruption, similar to EPE (P<0.05). Thus, we have identified LOX-1 activation by oxLDL and subsequent peroxynitrite generation as a novel mechanism by which disruption of the BBB occurs in EPE. As increased BBB permeability is a primary means by which seizure and other neurological symptoms ensue, our findings highlight oxLDL, LOX-1, and peroxynitrite as important therapeutic targets in EPE.

Effects of angiotensin II on the cerebral circulation: role of oxidative stress

Oxidative stress has emerged as a key component of many diseases that affect the vasculature. Oxidative stress is characterized as a cellular environment where the generation of oxidant molecules overwhelms endogenous anti-oxidant defense mechanisms. NADPH oxidases are a family of enzymes whose primary purpose is generation of reactive oxygen species (oxidant molecules) and therefore are likely to be key contributors to oxidative stress. Hypertension is associated with oxidative stress in the vasculature and is a major risk factor for stroke and cognitive abnormalities. Angiotensin II (Ang II) is the main effector peptide of the renin-angiotensin system (RAS) and plays a critical role in promoting oxidative stress in the vasculature. In the cerebral circulation, Ang II has been implicated in reactive oxygen species generation, alterations to vasomotor function, impaired neurovascular coupling, inflammation, and vascular remodeling. Furthermore, studies in humans have shown that cerebral blood flow is altered during hypertension and therapeutically targeting the RAS improves cerebral blood flow. Importantly, many of the aforementioned effects have been shown to be dependent on NADPH oxidases. Thus, Ang II, NADPH oxidases and oxidative stress are likely to play key roles in the pathogenesis of hypertension and associated cerebrovascular disease. This review will focus on our current understanding of the contribution of Ang II and NADPH oxidases to oxidative stress in the cerebral circulation.

Pregnancy enhances the effects of hypercholesterolemia on posterior cerebral arteries

In preeclampsia, hyperlipidemia is enhanced compared to normal pregnancy that could adversely affect vascular function. In the cerebral vasculature, this could lead to dysregulation of cerebral blood flow and neurological complications. Here, we examined the effect of excessive hyperlipidemia, as seen in preeclampsia, on cerebral artery function and expression of inflammatory markers in pregnancy. Pregnant and nonpregnant rats received a 14-day high-cholesterol diet or normal chow and posterior cerebral artery function was compared. High cholesterol significantly increased sensitivity of posterior cerebral arteries to the nitric oxide donor sodium nitroprusside that was accompanied by a ~12-fold increased messenger RNA (mRNA) expression of inducible nitric oxide synthase in late-pregnant rats only. Further, high cholesterol significantly increased peroxynitrite-induced dilation and decreased myogenic tone in cerebral arteries from late pregnant compared to nonpregnant animals. These results suggest that pathologically high levels of cholesterol in pregnancy enhance inflammatory responses and peroxynitrite generation in cerebral arteries.

NADPH oxidases as therapeutic targets in ischemic stroke

Reactive oxygen species (ROS) act physiologically as signaling molecules. In pathological conditions, such as ischemic stroke, ROS are released in excessive amounts and upon reperfusion exceed the body's antioxidant detoxifying capacity. This process leads to brain tissue damage during reoxygenation. Consequently, antioxidant strategies have long been suggested as a therapy for experimental stroke, but clinical trials have not yet been able to promote the translation of this concept into patient treatment regimens. As an evolution of this concept, recent studies have targeted the sources of ROS generation-rather than ROS themselves. In this context, NADPH oxidases have been identified as important generators of ROS in the cerebral vasculature under both physiological conditions in general and during ischemia/reoxygenation in particular. Inhibition of NADPH oxidases or genetic deletion of certain NADPH oxidase isoforms has been found to considerably reduce ischemic injury in experimental stroke. This review focuses on recent advances in the understanding of NADPH oxidase-mediated tissue injury in the cerebral vasculature, particularly at the level of the blood-brain barrier, and highlights promising inhibitory strategies that target the NADPH oxidases.

Role of Nox isoforms in angiotensin II-induced oxidative stress and endothelial dysfunction in brain

Angiotensin II (Ang II) promotes vascular disease through several mechanisms including by producing oxidative stress and endothelial dysfunction. Although multiple potential sources of reactive oxygen species exist, the relative importance of each is unclear, particularly in individual vascular beds. In these experiments, we examined the role of NADPH oxidase (Nox1 and Nox2) in Ang II-induced endothelial dysfunction in the cerebral circulation. Treatment with Ang II (1.4 mg·kg(-1)·day(-1) for 7 days), but not vehicle, increased blood pressure in all groups. In wild-type (WT; C57Bl/6) mice, Ang II reduced dilation of the basilar artery to the endothelium-dependent agonist acetylcholine compared with vehicle but had no effect on responses in Nox2-deficient (Nox2(-/y)) mice. Ang II impaired responses to acetylcholine in Nox1 WT (Nox1(+/y)) and caused a small reduction in responses to acetylcholine in Nox1-deficient (Nox1(-/y)) mice. Ang II did not impair responses to the endothelium-independent agonists nitroprusside or papaverine in either group. In WT mice, Ang II increased basal and phorbol-dibutyrate-stimulated superoxide production in the cerebrovasculature, and these increases were abolished in Nox2(-/y) mice. Overall, these data suggest that Nox2 plays a relatively prominent role in mediating Ang II-induced oxidative stress and cerebral endothelial dysfunction, with a minor role for Nox1.

An in vitro ischemic penumbral mimic perfusate increases NADPH oxidase-mediated superoxide production in cultured hippocampal neurons

The currently accepted scheme for reactive oxygen species production during ischemia/reperfusion injury is characterized by a deleterious mitochondria-derived burst of radical generation during reperfusion; however, recent examination of the penumbra suggests a central role for NADPH-oxidase (Nox)-mediated radical generation during the ischemic period. Therefore, we utilized a novel in vitro model of the penumbra to examine the free radical profile of ischemic murine hippocampal neurons using electron paramagnetic resonance spectroscopy, and also the role of Nox in this generation and in cell fate. We report that free radical production increased ~75% at 2 h of ischemia, and this increase was abolished by: (1) scavenging of extracellular free radicals with superoxide dismutase (SOD), (2) a general anion channel antagonist, or (3) the Nox inhibitor apocynin. Similarly, at 24 h of ischemia, [ATP] decreased >95% and vital dye uptake increased 6-fold relative to controls; whereas apocynin, the Cl(-) channel antagonist 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), or the free radical scavenger N-acetyl cysteine (NAC) each provided moderate neuroprotection, ameliorating 13-32% of [ATP]-depletion and 19-56% of vital dye uptake at 24 h. Our results support a cytotoxic role for Nox-mediated free radical production from penumbral neurons during the ischemic period.

Nox2 oxidase activity accounts for the oxidative stress and vasomotor dysfunction in mouse cerebral arteries following ischemic stroke

Background and Purpose

Post-ischemic oxidative stress and vasomotor dysfunction in cerebral arteries may increase the likelihood of cognitive impairment and secondary stroke. However, the underlying mechanisms of post-stroke vascular abnormalities, as distinct from those causing primary brain injury, are poorly understood. We tested whether augmented superoxide-dependent dysfunction occurs in the mouse cerebral circulation following ischemia-reperfusion, and evaluated the role of Nox2 oxidase.

Methods

Cerebral ischemia was induced in male C57Bl6/J wild-type (WT) and Nox2-deficient (Nox2^-/-) mice by middle cerebral artery occlusion (MCAO; 0.5 h), followed by reperfusion (23.5 h). Superoxide production by MCA was measured by L-012-enhanced chemiluminescence. Nitric oxide (NO) function was assessed in cannulated and pressurized MCA via the vasoconstrictor response to N^ω-nitro-L-arginine methyl ester (L-NAME; 100 µmol/L). Expression of Nox2, the nitration marker 3-nitrotyrosine, and leukocyte marker CD45 was assessed in cerebral arteries by Western blotting.

Results

Following ischemia-reperfusion, superoxide production was markedly increased in the MCA of WT, but not Nox2^-/- mice. In WT mice, L-NAME-induced constriction was reduced by ∼50% in ischemic MCA, whereas ischemia-reperfusion had no effect on responses to L-NAME in vessels from Nox2^-/- mice. In ischemic MCA from WT mice, expression of Nox2 and 3-nitrotyrosine were ∼1.4-fold higher than in the contralateral MCA, or in ischemic or contralateral vessels from Nox2^-/- mice. Vascular CD45 levels were unchanged by ischemia-reperfusion.

Conclusions

Excessive superoxide production, impaired NO function and nitrosative stress occur in mouse cerebral arteries after ischemia-reperfusion. These abnormalities appear to be exclusively due to increased activity of vascular Nox2 oxidase.

Calcific aortic valve stenosis: methods, models, and mechanisms

Calcific aortic valve stenosis (CAVS) is a major health problem facing aging societies. The identification of osteoblast-like and osteoclast-like cells in human tissue has led to a major paradigm shift in the field. CAVS was thought to be a passive, degenerative process, whereas now the progression of calcification in CAVS is considered to be actively regulated. Mechanistic studies examining the contributions of true ectopic osteogenesis, nonosseous calcification, and ectopic osteoblast-like cells (that appear to function differently from skeletal osteoblasts) to valvular dysfunction have been facilitated by the development of mouse models of CAVS. Recent studies also suggest that valvular fibrosis, as well as calcification, may play an important role in restricting cusp movement, and CAVS may be more appropriately viewed as a fibrocalcific disease. High-resolution echocardiography and magnetic resonance imaging have emerged as useful tools for testing the efficacy of pharmacological and genetic interventions in vivo. Key studies in humans and animals are reviewed that have shaped current paradigms in the field of CAVS, and suggest promising future areas for research.

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

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

ASIC-like currents in freshly isolated cerebral artery smooth muscle cells are inhibited by endogenous oxidase activity

BACKGROUND/AIMS

The aim of this study was to determine if VSMC ASIC-like currents are regulated by oxidative state.

METHODS

We used whole-cell patch clamp of isolated mouse cerebral VSMCs to determine if 1) reducing agents, such as DTT and GSH, and 2) inhibition of endogenous oxidase activity from NADPH and Xanthine oxidases potentiate active currents and activate electrically silent currents.

RESULTS

Pretreatment with 2 mM DTT or GSH, increased the mean peak amplitude of ASIC-like currents evoked by pH 6.0 from 0.4 ± 0.1 to 14.9 ± 3.6 pA/pF, and from 0.9 ± 0.3 to 11.3 ± 2.4 pA/pF, respectively. Pretreatment with apocynin, a NADPH oxidase inhibitor, mimics the effect of the reducing agents, with the mean peak current amplitude increased from 0.9 ± 0.5 to 7.0 ± 2.6 pA/pF and from 0.5 ± 0.2 to 26.4 ± 6.8 pA/pF by 50 and 200 μM apocynin, respectively. Pretreatment with allopurinol, a xanthine oxidase inhibitor, also potentiates the VSMC ASIC-like activity.

CONCLUSION

These findings suggest that VSMC ASIC-like channels are regulated by oxidative state and may be inhibited by basal endogenous oxidative sources such as NADPH and xanthine oxidase.

Hypoxic relaxation of penile arteries: involvement of endothelial nitric oxide and modulation by reactive oxygen species

Although obesity-related cardiovascular disease and hypoxia are associated with erectile dysfunction, little is known about the direct effects of hypoxia on penile arteries. In the present study, the effects of acute hypoxia (Po(2) = approximately 10 Torr, 20 min) were investigated in isolated penile arteries to determine the influence of endothelium removal, nitric oxide (NO) synthase (NOS), cyclooxygenase (COX), NADPH oxidase, changes in reactive oxygen species (ROS), and a high-fat diet. Hypoxia-relaxed penile arteries contracted with phenylephrine by approximately 50%. Relaxation to hypoxia and acetylcholine was reduced by endothelium removal and by inhibition of NOS (N(omega)-nitro-l-arginine) and COX (indomethacin) but was enhanced by Tempol and by NADPH oxidase inhibition with apocynin and gp91ds-tat. Basal superoxide levels detected by lucigenin chemiluminescence were reduced by Tempol and gp91ds-tat and were enhanced by NOS blockade. Hypoxic relaxant responses were enhanced by catalase and ebselen. Exogenous peroxide evoked relaxations of penile arteries, which were partially inhibited by endothelium removal and by the inhibition of COX and extracellular signal-regulated mitogen-activated protein kinase (MAPK) but enhanced by p38 MAPK blockade. The NO-dependent component of relaxation to hypoxia was impaired in penile arteries from high-fat diet-fed, obese rats associated with increased superoxide production. Thus hypoxic relaxation of penile arteries is partially mediated by endothelial NO in a manner that is normally attenuated by endogenous ROS production. Obesity further increases superoxide production and impairs the influence of NO. Therefore, cardiovascular disease involving decreased NO bioavailability and/or enhanced ROS generation may contribute to erectile dysfunction through impairing the relaxation of penile arteries to hypoxia.