NF-κB Activation Plays a Role in Superoxide-Mediated Cerebral Endothelial Dysfunction After Hypoxia/Reoxygenation

Protective effects of berbamine against arginase-1 deficiency-induced injury in human brain microvascular endothelial cells

Endothelial cell dysfunction plays a crucial role in the early development of cerebral small vessel disease (CSVD). Arginase-1 (ARG1) is expressed in endothelial cells, and its deficiency may exacerbate cerebrovascular damage by increasing reactive oxygen species (ROS) production, thereby inducing endothelial cell apoptosis. Berbamine (BBM) has shown potential in neuroprotection and cardiovascular disease prevention. This study aimed to investigate the impact of ARG1 deficiency on human brain microvascular endothelial cells and the protective effects of BBM against ARG1 deficiency-induced damage. Human brain microvascular endothelial cells (HCMEC/D3) were cultured in vitro, and ARG1 knockdown or overexpression was achieved using plasmid transfection techniques. We examined the effects of ARG1 expression levels on HCMEC/D3 cell viability, migration, apoptosis, adhesion, and angiogenesis through cellular experiments. Additionally, we explored how ARG1 expression levels influenced arginine (Arg), nitric oxide (NO), and ROS levels in HCMEC/D3 cells. The results demonstrated that ARG1 deficiency inhibited HCMEC/D3 cell viability, migration, adhesion, and angiogenesis, while promoting apoptosis and elevating Arg, NO, and ROS levels in HCMEC/D3 cells. Next, the effect of different BBM concentrations on HCMEC/D3 cell viability was assessed using the CCK-8 assay, revealing that BBM at a concentration of 5 µM had no significant impact on cell viability. Subsequently, after successfully knocking down ARG1 in HCMEC/D3 cells, the cells were treated with BBM. The results showed that BBM effectively mitigated the negative effects of ARG1 deficiency on HCMEC/D3 cell viability, migration, apoptosis, adhesion, and angiogenesis, while also reducing Arg, NO, inducible nitric oxide synthase (iNOS), and ROS levels in HCMEC/D3 cells. In conclusion, this study suggests that ARG1 deficiency may damage HCMEC/D3 cells by increasing Arg levels, leading to elevated NO and ROS levels. BBM may provide protection to ARG1-deficient HCMEC/D3 cells by reducing Arg, NO, iNOS, and ROS levels. These findings deepen our understanding of the pathogenesis of CSVD and provide a theoretical basis for the clinical application of BBM.

MnSOD Mimetics in Therapy: Exploring Their Role in Combating Oxidative Stress-Related Diseases

Reactive oxygen species (ROS) are double-edged swords in biological systems-they are essential for normal cellular functions but can cause damage when accumulated due to oxidative stress. Manganese superoxide dismutase (MnSOD), located in the mitochondrial matrix, is a key enzyme that neutralizes superoxide radicals (O2•-), maintaining cellular redox balance and integrity. This review examines the development and therapeutic potential of MnSOD mimetics-synthetic compounds designed to replicate MnSOD's antioxidant activity. We focus on five main types: Mn porphyrins, Mn salens, MitoQ10, nitroxides, and mangafodipir. These mimetics have shown promise in treating a range of oxidative stress-related conditions, including cardiovascular diseases, neurodegenerative disorders, cancer, and metabolic syndromes. By emulating natural antioxidant defenses, MnSOD mimetics offer innovative strategies to combat diseases linked to mitochondrial dysfunction and ROS accumulation. Future research should aim to optimize these compounds for better stability, bioavailability, and safety, paving the way for their translation into effective clinical therapies.

Poor Prestroke Glycemic Control Increases the Rate of Symptomatic Intracranial Hemorrhage after Mechanical Thrombectomy

(1) Background: Diabetes is a well-established risk factor for acute ischemic stroke (AIS). This study evaluated the impact of prestroke glycemic control in diabetic patients on their 3-month clinical outcome after mechanical thrombectomy (MT). (2) Methods: AIS patients with a premorbid modified Rankin scale (mRS) score of 0-2 who were admitted within 6 h after stroke onset and treated with MT between January 2020 and August 2023 were retrospectively analyzed. The study evaluated the effect of prestroke glycemic control on the stroke severity, reperfusion rate, symptomatic intracranial hemorrhage (sICH) and favorable clinical outcome (modified Rankin scale score 0-2) at 3 months after endovascular treatment. (3) Results: A total of 364 patients were analyzed, with 275 cases of non-diabetes (ND), 66 of well-controlled diabetes (WCD) and 23 of poorly controlled diabetes (PCD). There was no significant difference in the baseline neurological deficit expressed according to the National Institutes of Health Stroke Scale among the three groups. The time from stroke onset to groin puncture was similar in the ND, WCD and PCD groups (median 215 min, 194.5 min and 222.5 min, respectively). There was no significant difference in the favorable 3-month clinical outcomes among these three groups (35.2% of ND patients, 42.4% of WCD patients and 39.1% of PCD patients) or full recovery (12.4% of ND patients, 11.0% of WCD patients and 17.4% of PCD patients). The rate of sICH was significantly higher in the PCD group as compared to the ND and WDP groups (21.7% of PCD patients versus 7.6% of ND patients, p = 0.038, and 6.0% of WCD patients, p = 0.046), but the 3-month mortality did not differ between the three groups (21.8% of ND group, 19.7% of WCD group and 26.1% of PCD group). (4) Conclusions: This study shows that poor prestroke glycemic control in AIS diabetic patients does not change the chance of a good clinical functional outcome after endovascular treatment. However, the increased risk of hemorrhagic complications in this group of patients should be considered.

Insight into the transcription factors regulating Ischemic Stroke and Glioma in Response to Shared Stimuli

Cerebral ischemic stroke and glioma are the two leading causes of patient mortality globally. Despite physiological variations, 1 in 10 people who have an ischemic stroke go on to develop brain cancer, most notably gliomas. In addition, glioma treatments have also been shown to increase the risk of ischemic strokes. Stroke occurs more frequently in cancer patients than in the general population, according to traditional literature. Unbelievably, these events share multiple pathways, but the precise mechanism underlying their co-occurrence remains unknown. Transcription factors (TFs), the main components of gene expression programmes, finally determine the fate of cells and homeostasis. Both ischemic stroke and glioma exhibit aberrant expression of a large number of TFs, which are strongly linked to the pathophysiology and progression of both diseases. The precise genomic binding locations of TFs and how TF binding ultimately relates to transcriptional regulation remain elusive despite a strong interest in understanding how TFs regulate gene expression in both stroke and glioma. As a result, the importance of continuing efforts to understand TF-mediated gene regulation is highlighted in this review, along with some of the primary shared events in stroke and glioma.

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.

Nano-titanium dioxide inhalation exposure during gestation drives redox dysregulation and vascular dysfunction across generations

BACKGROUND

Pregnancy is associated with many rapid biological adaptations that support healthy development of the growing fetus. One of which is critical to fetal health and development is the coordination between maternal liver derived substrates and vascular delivery. This crucial adaptation can be potentially derailed by inhalation of toxicants. Engineered nanomaterials (ENM) are commonly used in household and industrial products as well as in medicinal applications. As such, the potential risk of exposure remains a concern, especially during pregnancy. We have previously reported that ENM inhalation leads to upregulation in the production of oxidative species. Therefore, we aimed to determine if F0 dam maternal nano-TiO₂ inhalation exposure (exclusively) resulted in altered H₂O₂ production capacity and changes in downstream redox pathways in the F0 dams and subsequent F1 pups. Additionally, we investigated whether this persisted into adulthood within the F1 generation and how this impacted F1 gestational outcomes and F2 fetal health and development. We hypothesized that maternal nano-TiO₂ inhalation exposure during gestation in the F0 dams would result in upregulated H₂O₂ production in the F0 dams as well as her F1 offspring. Additionally, this toxicological insult would result in gestational vascular dysfunction in the F1 dams yielding smaller F2 generation pups.

RESULTS

Our results indicate upregulation of hepatic H₂O₂ production capacity in F0 dams, F1 offspring at 8 weeks and F1 females at gestational day 20. H₂O₂ production capacity was accompanied by a twofold increase in phosphorylation of the redox sensitive transcription factor NF-κB. In cell culture, naïve hepatocytes exposed to F1-nano-TiO₂ plasma increased H₂O₂ production. Overnight exposure of these hepatocytes to F1 plasma increased H₂O₂ production capacity in a partially NF-κB dependent manner. Pregnant F1- nano-TiO₂ females exhibited estrogen disruption (12.12 ± 3.1 pg/ml vs. 29.81 ± 8.8 pg/ml sham-control) and vascular dysfunction similar to their directly exposed mothers. F1-nano-TiO₂ uterine artery H₂O₂ production capacity was also elevated twofold. Dysfunctional gestational outcomes in the F1-nano-TiO₂ dams resulted in smaller F1 (10.22 ± 0.6 pups vs. sham-controls 12.71 ± 0.96 pups) and F2 pups (4.93 ± 0.47 g vs. 5.78 ± 0.09 g sham-control pups), and fewer F1 male pups (4.38 ± 0.3 pups vs. 6.83 ± 0.84 sham-control pups).

CONCLUSION

In conclusion, this manuscript provides critical evidence of redox dysregulation across generations following maternal ENM inhalation. Furthermore, dysfunctional gestational outcomes are observed in the F1-nano-TiO₂ generation and impact the development of F2 offspring. In total, this data provides strong initial evidence that maternal ENM exposure has robust biological impacts that persists in at least two generations.

The Promoting Effect of Traumatic Brain Injury on the Incidence and Progression of Glioma: A Review of Clinical and Experimental Research

The role of traumatic brain injury in the development of glioma is highly controversial since first presented. This is not unexpected because traumatic brain injuries are overwhelmingly more common than glioma. However, the causes of post-traumatic glioma have been long discussed and still warrant further research. In this review, we have presented an overview of previous cohort studies and case–control studies. We have summarized the roles of microglial cells, macrophages, astrocytes, and stem cells in post-traumatic glioma formation and development, and reviewed various carcinogenic factors involved during traumatic brain injury, especially those reported in experimental studies indicating a relationship with glioma progression. Besides, traumatic brain injury and glioma share several common pathways, including inflammation and oxidative stress; however, the exact mechanism underlying this co-occurrence is yet to be discovered. In this review, we have summarized current epidemiological studies, clinical reports, pathophysiological research, as well as investigations evaluating the probable causes of co-occurrence and treatment possibilities. More efforts should be directed toward elucidating the relationship between traumatic brain injury and glioma, which could likely lead to promising pharmacological interventions towards designing therapeutic strategies.

An Iatrogenic Model of Brain Small-Vessel Disease: Post-Radiation Encephalopathy

We studied 114 primitive cerebral neoplasia, that were surgically treated, and underwent radiotherapy (RT), and compared their results to those obtained by 190 patients diagnosed with subcortical vascular dementia (sVAD). Patients with any form of primitive cerebral neoplasia underwent whole-brain radiotherapy. All the tumor patients had regional field partial brain RT, which encompassed each tumor, with an average margin of 2.6 cm from the initial target tumor volume. We observed in our patients who have been exposed to a higher dose of RT (30-65 Gy) a cognitive and behavior decline similar to that observed in sVAD, with the frontal dysexecutive syndrome, apathy, and gait alterations, but with a more rapid onset and with an overwhelming effect. Multiple mechanisms are likely to be involved in radiation-induced cognitive impairment. The active site of RT brain damage is the white matter areas, particularly the internal capsule, basal ganglia, caudate, hippocampus, and subventricular zone. In all cases, radiation damage inside the brain mainly focuses on the cortical-subcortical frontal loops, which integrate and process the flow of information from the cortical areas, where executive functions are "elaborated" and prepared, towards the thalamus, subthalamus, and cerebellum, where they are continuously refined and executed. The active mechanisms that RT drives are similar to those observed in cerebral small vessel disease (SVD), leading to sVAD. The RT's primary targets, outside the tumor mass, are the blood-brain barrier (BBB), the small vessels, and putative mechanisms that can be taken into account are oxidative stress and neuro-inflammation, strongly associated with the alteration of NMDA receptor subunit composition.

Heavy Metal-Induced Cerebral Small Vessel Disease: Insights into Molecular Mechanisms and Possible Reversal Strategies

Heavy metals are considered a continuous threat to humanity, as they cannot be eradicated. Prolonged exposure to heavy metals/metalloids in humans has been associated with several health risks, including neurodegeneration, vascular dysfunction, metabolic disorders, cancer, etc. Small blood vessels are highly vulnerable to heavy metals as they are directly exposed to the blood circulatory system, which has comparatively higher concentration of heavy metals than other organs. Cerebral small vessel disease (CSVD) is an umbrella term used to describe various pathological processes that affect the cerebral small blood vessels and is accepted as a primary contributor in associated disorders, such as dementia, cognitive disabilities, mood disorder, and ischemic, as well as a hemorrhagic stroke. In this review, we discuss the possible implication of heavy metals/metalloid exposure in CSVD and its associated disorders based on in-vitro, preclinical, and clinical evidences. We briefly discuss the CSVD, prevalence, epidemiology, and risk factors for development such as genetic, traditional, and environmental factors. Toxic effects of specific heavy metal/metalloid intoxication (As, Cd, Pb, Hg, and Cu) in the small vessel associated endothelium and vascular dysfunction too have been reviewed. An attempt has been made to highlight the possible molecular mechanism involved in the pathophysiology, such as oxidative stress, inflammatory pathway, matrix metalloproteinases (MMPs) expression, and amyloid angiopathy in the CSVD and related disorders. Finally, we discussed the role of cellular antioxidant defense enzymes to neutralize the toxic effect, and also highlighted the potential reversal strategies to combat heavy metal-induced vascular changes. In conclusion, heavy metals in small vessels are strongly associated with the development as well as the progression of CSVD. Chelation therapy may be an effective strategy to reduce the toxic metal load and the associated complications.

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 interrelationship between cerebral ischemic stroke and glioma: a comprehensive study of recent reports

Glioma and cerebral ischemic stroke are two major events that lead to patient death worldwide. Although these conditions have different physiological incidences, ~10% of ischemic stroke patients develop cerebral cancer, especially glioma, in the postischemic stages. Additionally, the high proliferation, venous thrombosis and hypercoagulability of the glioma mass increase the significant risk of thromboembolism, including ischemic stroke. Surprisingly, these events share several common pathways, viz. hypoxia, cerebral inflammation, angiogenesis, etc., but the proper mechanism behind this co-occurrence has yet to be discovered. The hypercoagulability and presence of the D-dimer level in stroke are different in cancer patients than in the noncancerous population. Other factors such as atherosclerosis and coagulopathy involved in the pathogenesis of stroke are partially responsible for cancer, and the reverse is also partially true. Based on clinical and neurosurgical experience, the neuronal structures and functions in the brain and spine are observed to change after a progressive attack of ischemia that leads to hypoxia and atrophy. The major population of cancer cells cannot survive in an adverse ischemic environment that excludes cancer stem cells (CSCs). Cancer cells in stroke patients have already metastasized, but early-stage cancer patients also suffer stroke for multiple reasons. Therefore, stroke is an early manifestation of cancer. Stroke and cancer share many factors that result in an increased risk of stroke in cancer patients, and vice-versa. The intricate mechanisms for stroke with and without cancer are different. This review summarizes the current clinical reports, pathophysiology, probable causes of co-occurrence, prognoses, and treatment possibilities.

C-reactive protein promotes inflammation through TLR4/NF-κB/TGF-β pathway in HL-1 cells

Atrial fibrillation (AF) is the most common type of heart arrhythmia. Currently, the pathogenesis of AF is not fully understood yet. A growing body of evidence highlighted the strong association between inflammation and the pathogenesis of AF. C-reactive protein (CRP) is an inflammation marker with increased expression in AF. Therefore, the aim of this study was to determine if CRP promotes inflammation, which may sequentially mediate the onset of AF and the concurrent atrial fibrosis, through TLR4/NF-κB/TGF-β pathway. HL-1 cells were treated with either 25 or 50 μg/ml recombinant human CRP. TGF-β1 and NF-κB inhibitors were given either solely or together to the 50 μg/ml CRP-treated cells. Cell proliferation, apoptosis, the expression of apoptotic factors and TLR4, IL-6, TGF-β1, Smad2, and the phosphorylation of Smad2 were determined. Data showed that CRP induced dose-dependent inhibition on cell proliferation and promoted cell apoptosis, which was induced through both intrinsic and extrinsic pathways. Such effects were reversed by inhibiting TGF-β1 and/or NF-κB. Inhibition of TGF-β1 and/or NF-κB also reduced the expression of TLR4 and IL-6. Inhibition of NF-κB alone weakened the expression of TGF-β1 and phosphorylation of Smad2. Our study demonstrated that CRP is not only a marker, but also an important mediator in the induction of inflammation and likely the pathogenesis of AF. We for the first time reported CRP-induced activation and cross-talk between TLR4 and NF-κB/TGF-β1 signaling pathway in a cardiomyocyte model. Reducing CRP and targeting TLR4/NF-κB/TGF-β1 pathway may provide new insights in the therapeutic interventions to inflammation-induced AF.

FGF21 Protects Against Hypoxia Injury Through Inducing HSP72 in Cerebral Microvascular Endothelial Cells

Background: Fibroblast growth factor 21 (FGF21), a member of a family of atypical FGFs, functions as cytokine to control endocrinology and metabolism. Recently, the roles of FGF21 in cardio-cerebral-vascular diseases have been gradually uncovered. In the present study, we investigated the effect of FGF21 on bEnd.3 cerebral microvascular endothelial cells (CMECs) upon hypoxia stress.

Methods and Results: CMECs were cultured in the condition of 1% O₂ for 8 h to induce hypoxia stimuli. For FGF21 treatment, recombinant FGF21 (50 nM) was added into the culture medium. Various biomedical assays were used to evaluate the hypoxia-induced injury in CMECs. Under normoxia condition, FGF21 had no obvious effect on cell viability and did not cause any cytotoxicity on CMECs. Under hypoxia condition, FGF21 significantly attenuated the hypoxia-induced injury, evidenced by the influences of FGF21 on CMEC viability and LDH release. TUNEL staining assay and immunoblotting of caspase-3 showed that FGF21 reduced hypoxia-induced apoptosis in CMECs. Mechanistically, FGF21 treatment compromised the hypoxia-induced changes of reactive oxygen species, malondialdehyde, total antioxidant activity, and total superoxide dismutase levels. FGF21 administration decreased hypoxia-induced matrix metalloprotein 3 and matrix metalloprotein 2/9 activity in CMECs. Activities of cyclooxygenase-2 and NF-κB-p65, two pro-inflammatory factors, were also upregulated by hypoxia but suppressed by FGF21. At last, we found that FGF21 increased heat shock protein family A member 1A (HSP72) mRNA and protein expression. Blockade of HSP72 by a pharmacological inhibitor VER155008 or specific siRNA-mediated knockdown abrogated the protection of FGF21 against hypoxia in CMECs.

Conclusion: These data demonstrate that FGF21 protects against hypoxia stress-induced injury in CMECs by inducing HSP72 expression, suggesting a therapeutic value of FGF21 in hypoxia-related brain diseases such as ischemic stroke and acute mountain sickness.

Passive heat therapy protects against endothelial cell hypoxia-reoxygenation via effects of elevations in temperature and circulating factors

KEY POINTS

Accumulating evidence indicates that passive heat therapy (chronic use of hot tubs or saunas) has widespread physiological benefits, including enhanced resistance against novel stressors ('stress resistance'). Using a cell culture model to isolate the key stimuli that are likely to underlie physiological adaptation with heat therapy, we showed that both mild elevations in temperature (to 39°C) and exposure to serum from human subjects who have undergone 8 weeks of heat therapy (i.e. altered circulating factors) independently prevented oxidative and inflammatory stress associated with hypoxia-reoxygenation in cultured endothelial cells. Our results elucidate some of the mechanisms (i.e. direct effects of temperature vs. circulating factors) by which heat therapy seems to improve resistance against oxidative and inflammatory stress. Heat therapy may be a promising intervention for reducing cellular damage following ischaemic events, which has broad implications for patients with cardiovascular diseases and conditions characterized by 'chronic' ischaemia (e.g. peripheral artery disease, metabolic diseases, obesity).

ABSTRACT

Repeated exposure to passive heat stress ('heat therapy') has widespread physiological benefits, including cellular protection against novel stressors. Increased heat shock protein (HSP) expression and upregulation of circulating factors may impart this protection. We tested the isolated abilities of mild heat pretreatment and serum from human subjects (n = 10) who had undergone 8 weeks of heat therapy to protect against cellular stress following hypoxia-reoxygenation (H/R), a model of ischaemic cardiovascular events. Cultured human umbilical vein endothelial cells were incubated for 24 h at 37°C (control), 39°C (heat pretreatment) or 37°C with 10% serum collected before and after 8 weeks of passive heat therapy (four to five times per week to increase rectal temperature to ≥ 38.5°C for 60 min). Cells were then collected before and after incubation at 1% O₂ for 16 h (hypoxia; 37°C), followed by 20% O₂ for 4 h (reoxygenation; 37°C) and assessed for markers of cell stress. In control cells, H/R increased nuclear NF-κB p65 protein (i.e. activation) by 106 ± 38%, increased IL-6 release by 37 ± 8% and increased superoxide production by 272 ± 45%. Both heat pretreatment and exposure to heat therapy serum prevented H/R-induced NF-κB activation and attenuated superoxide production; by contrast, only exposure to serum attenuated IL-6 release. H/R also decreased cytoplasmic haemeoxygenase-1 (HO-1) protein (known to suppress NF-κB), in control cells (-25 ± 8%), whereas HO-1 protein increased following H/R in cells pretreated with heat or serum-exposed, providing a possible mechanism of protection against H/R. These data indicate heat therapy is capable of imparting resistance against inflammatory and oxidative stress via direct heat and humoral factors.

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.

Isoflurane preconditioning inhibits the effects of tissue-type plasminogen activator on brain endothelial cell in an in vitro model of ischemic stroke

Tissue-type plasminogen activator (tPA) is the only treatment for ischemic stroke. However, tPA could induce the intracranial hemorrhage (ICH), which is the main cause of death in ischemic stroke patient after tPA treatment. At present, there is no treatment strategy to ameliorate tPA-induced brain injury after ischemia. Therefore, we investigated the effect of pre-treated isoflurane, which is a volatile anesthetic and has beneficial effects on neurological dysfunction, brain edema and infarct volume in ischemic stroke model. In this study, we used oxygen/glucose deprivation and reperfusion (OGD/R) condition to mimic an ischemic stroke in vitro. Matrix metalloproteinases (MMP) activity was measured in endothelial cell media. Also, neuronal cell culture was performed to investigate the effect of pretreated isoflurane on the neuronal cell survival after tPA-induced injury during OGD/R. Isoflurane pretreatment prevented tPA-induced MMP-2 and MMP-9 activity and suppressed tPA-triggered LRP/NF-κB/Cox-2 signaling after OGD/R. Neuronal cells, incubated with endothelial cell conditioned medium (EC-CM) after tPA + OGD/R, showed upregulation of pro-apoptotic molecules. However, neurons incubated with isoflurane-pretreated EC-CM showed increased anti-apoptotic molecules. Our findings suggest that isoflurane pretreatment could attenuate tPA-exaggerated brain ischemic injury, by reducing tPA-induced LRP/NF-κB/Cox-2 in endothelial cells, endothelial MMP-2 and MMP-9 activation, and subsequent pro-apoptotic molecule in neurons after OGD/R.

The impact of tau hyperphosphorylation at Ser262 on memory and learning after global brain ischaemia in a rat model of reversible cardiac arrest

An increase in phosphorylated tau (p-tau) is associated with Alzheimer's disease (AD), and brain hypoxia. Investigation of the association of residue-specific tau hyperphosphorylation and changes in cognition, leads to greater understanding of its potential role in the pathology of memory impairment. The aims of this study are to investigate the involvement of the main metabolic kinases, Liver Kinase B1 (LKB1) and Adenosine Monophosphate Kinase Protein Kinase (AMPK), in tau phosphorylation-derived memory impairment, and to study the potential contribution of the other tau kinases and phosphatases including Glycogen Synthase Kinase (GSK-3β), Protein kinase A (PKA) and Protein Phosphatase 2A (PP2A). Spatial memory and learning were tested in a rat global brain ischemic model of reversible cardiac arrest (CA). The phosphorylation levels of LKB1, AMPK, GSK-3β, PP2A, PKA and tau-specific phosphorylation were assessed in rats, subjected to ischaemia/reperfusion and in clinically diagnosed AD and normal human brains. LKB1 and AMPK phosphorylation increased 4 weeks after CA as did AMPK related p-tau (Ser²⁶²). The animals showed unchanged levels of GSK-3β specific p-tau (Ser²⁰²/Thr²⁰⁵), phospho-PP2A (Tyr³⁰⁷), total GSK-3β, PP2A, phospho-cAMP response element-binding protein (CREB) which is an indicator of PKA activity, and no memory deficits. AD brains had hyperphosphorylated tau in all the residues of Ser²⁶², Ser²⁰² and Thr²⁰⁵, with increased phosphorylation of both AMPK (Thr¹⁷²) and GSK-3β (Ser⁹), and reduced PP2A levels. Our data suggests a crucial role for a combined activation of tau kinases and phosphatases in adversely affecting memory and that hyperphosphorylation of tau in more than one specific site may be required to create memory deficits.

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Short-term brain ischaemia causes AMPK activation and tau phosphorylation at its AMPK-sensitive site (Ser²⁶²).

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Activation of GSK-3β, PP2A and PKA are remained unchanged in short-term brain ischaemia/reperfusion.

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In clinical cases of AD, activation of AMPK, GSK-3β, PP2A and multiple site hyperphosphorylation of tau are observed.

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Hyperphosphorylation of tau (Ser²⁶²) alone without involving the other tau kinases/phosphatase does not affect memory.

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.

Scutellarin Reduces Endothelium Dysfunction through the PKG-I Pathway

Purpose. In this report, we investigated the protective mechanism of scutellarin (SCU) in vitro and in vivo which could be involved in endothelial cGMP-dependent protein kinase (PKG), vasodilator stimulated phosphoprotein (VASP) pathway, and vascular endothelium dysfunction (EtD). Method. Human brain microvascular endothelial cells (HBMECs) with hypoxia reoxygenation (HR) treatment and rats with cerebral ischemia reperfusion (CIR) treatment were applied. Protein and mRNA expression of PKG, VASP, and p-VASP were evaluated by Western blot and RT-PCR methods. Vascular EtD was assessed by using wire myography to determine endothelium-dependent vasorelaxation in isolated rat basilar artery (BA). Result. In cultured HBMECs, SCU (0.1, 1, and 10 μM) increased cell viability, mRNA, protein level, and phosphorylative activity of PKG and VASP against HR injury. In HR model of BA, SCU increased protein level of P-VASP. In rat CIR model, wire myography demonstrated that SCU (45 and 90 mg/kg, i.v.) significantly reduced ischemic size by partially restoring the endothelium dependent vasodilation of BA; PKG inhibitor Rp-8-Br-cGMPS (50 μg/kg, i.v.) reversed this protection of SCU in CIR rats. Conclusion. SCU protects against cerebral vascular EtD through endothelial PKG pathway activation.

Propofol ameliorates endothelial inflammation induced by hypoxia/reoxygenation in human umbilical vein endothelial cells: Role of phosphatase A2

Hypoxia/reoxygenation (H/R) induces endothelial inflammation with augmentation of endothelial adhesion molecules over-expression. Propofol was reported to attenuate endothelial adhesion molecule expression in some situations. Here, we examined the molecular mechanism for how propofol restored H/R-mediated up-regulation of endothelial adhesion molecules in human umbilical vein endothelial cells (HUVECs). Compared with the control group, H/R up-regulated expression of Pin-1 and PP2A, increased p66(Shc)-Ser(36) phosphorylation, induced p66(Shc) mitochondrial translocation, O2(-) accumulation and NF-κB activation, and decreased eNOS-Ser(1177) phosphorylation and nitric oxide (NO) production, thus up-regulating expression of endothelial adhesion molecules and increasing mononuclear-endothelial interaction. More importantly, except that propofol had no effect on H/R-induced p66(Shc)-Ser(36) phosphorylation, most of H/R-mediated changes were alleviated by propofol, resulting in the reduction of endothelial adhesion molecules expression and mononuclear-endothelial adhesion. Moreover, we demonstrated the protective effect of propofol on H/R-induced endothelial inflammation was similar to that of calyculin A, an inhibitor of PP2A. In contrast, FTY720, an activator of PP2A, antagonized the effect of propofol. Our data indicated that propofol down-regulated PP2A expression, leading to reduced dephosphorylation of p66(Shc)-Ser(36) and eNOS-Ser(1177), which is associated with ROS accumulation and NO reduction, resulting in inhibition of endothelial adhesion molecule expression and mononuclear-endothelial interaction.

Uncoupling of eNOS contributes to redox-sensitive leukocyte recruitment and microvascular leakage elicited by methylglyoxal

Elevated levels of the glycolysis metabolite methylglyoxal (MG) have been implicated in impaired leukocyte-endothelial interactions and vascular complications in diabetes, putative mechanisms of which remain elusive. Uncoupling of endothelial nitric oxide synthase (eNOS) was shown to be involved in endothelial dysfunction in diabetes. Whether MG contributes to these effects has not been elucidated. By using intravital microscopy in vivo, we demonstrate that MG-triggered reduction in leukocyte rolling velocity and increases in rolling flux, adhesion, emigration and microvascular permeability were significantly abated by scavenging reactive oxygen species (ROS). In murine cremaster muscle, MG treatment reduced tetrahydrobiopterin (BH4)/total biopterin ratio, increased arginase expression and stimulated ROS and superoxide production. The latter was significantly blunted by ROS scavengers Tempol (300μM) or MnTBAP (300μM), by BH4 supplementation (100μM) or by NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 20μM). In these tissues and cultured murine and human primary endothelial cells, MG increased eNOS monomerization and decreased BH4/total biopterin ratio, effects that were significantly mitigated by supplementation of BH4 or its precursor sepiapterin but not by L-NAME or tetrahydroneopterin, indicative of MG-triggered eNOS uncoupling. MG treatment further decreased the expression of guanosine triphosphate cyclohydrolase I in murine primary endothelial cells. MG-induced leukocyte recruitment was significantly attenuated by supplementation of BH4 or sepiapterin or suppression of superoxide by L-NAME confirming the role of eNOS uncoupling in MG-elicited leukocyte recruitment. Together, our study uncovers eNOS uncoupling as a pivotal mechanism in MG-induced oxidative stress, microvascular hyperpermeability and leukocyte recruitment in vivo.

Obstructive sleep apnea, oxidative stress and cardiovascular disease: lessons from animal studies

Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular (CV) diseases such as arterial hypertension, heart failure, and stroke. Based on human research, sympathetic activation, inflammation, and oxidative stress are thought to play major roles in the pathophysiology of OSA-related CV diseases. Animal models of OSA have shown that endothelial dysfunction, vascular remodelling, and systemic and pulmonary arterial hypertension as well as heart failure can develop in response to chronic intermittent hypoxia (CIH). The available animal data are clearly in favour of oxidative stress playing a key role in the development of all of these CV manifestations of OSA. Presumably, the oxidative stress is due to an activation of NADPH oxidase and other free oxygen radicals producing enzymes within the CV system as evidenced by data from knockout mice and pharmacological interventions. It is hoped that animal models of OSA-related CV disease will continue to contribute to a deeper understanding of their underlying pathophysiology and will foster the way for the development of cardioprotective treatment options other than conventional CPAP therapy.

Heparin inhibits angiotensin II-induced vasoconstriction on isolated mouse mesenteric resistance arteries through Rho-A- and PKA-dependent pathways

Heparin is commonly used to treat intravascular thrombosis in children undergoing extracorporeal membrane oxygenation or cardiopulmonary bypass. These clinical circumstances are associated with elevated plasma levels of angiotensin II (Ang II). However, the mechanisms by which heparin modulates vascular reactivity of Ang II remain unclear. We hypothesized that heparin may offset Ang II-induced vasoconstriction on mesenteric resistance arteries through modulating the Rho-A/Rho kinase pathway. Vascular contractility was studied by using pressurized, resistance-sized mesenteric arteries from mice. Rho-A activation was measured by pull-down assay, and myosin light chain or PKA phosphorylation by immunoblotting. We found that heparin significantly attenuated vasoconstriction induced by Ang II but not that by KCl. The combined effect of Ang II with heparin was almost abolished by a specific Rho kinase inhibitor Y27632. Ang II stimulated Rho-A activation and myosin light chain phosphorylation, both responses were antagonized by heparin. Moreover, the inhibitory effect of heparin on Ang II-induced vasoconstriction was reversed by Rp-cAMPS (cAMP-dependent PKA inhibitor), blunted by ODQ (soluble guanylate cyclase inhibitor), and mimicked by a cell-permeable cGMP analogue, 8-Br-cGMP, but not by a cAMP analogue. PKC and Src kinase were not involved. We conclude that heparin inhibits Ang II-induced vasoconstriction through Rho-A/Rho kinase- and cGMP/PKA-dependent pathways.

Elevated angiopoietin-1 serum levels in patients with Alzheimer's disease

Background. Alzheimer's disease (AD) is the most common cause of dementia in the elderly. AD is characterized by the accumulation of amyloid plaques and neurofibrillary tangles and by massive neuronal loss in the brain. There is epidemiologic and pathologic evidence that AD is associated with vascular risk factors and vascular diseases, contributing to cerebral hypoperfusion with consecutive stimulation of angiogenesis and upregulation of proangiogenic factors such as Angiopoietin-1 (Ang-1). Methods. In the present study, we measured Ang-1 serum levels in 42 patients with AD, 20 patients with mild cognitive impairment (MCI), and in 40 healthy elderly controls by ELISA. Results. We found significantly increased Ang-1 serum levels in patients with AD compared to control subjects (P = 0.003). There was no significant difference between MCI patients and healthy controls (P = 0.553) or between AD and MCI patients (P = 0.054). The degree of cognitive impairment as measured by the mini-mental status examination (MMSE) score was significantly correlated with the Ang-1 serum levels in all patients and healthy controls. Conclusions. We found significantly increased Ang-1 serum levels in AD patients. We could also show an association between Ang-1 serum levels and the cognitive status in all patients and healthy controls. Thus, serum Ang-1 could be a potential candidate for a biomarker panel for AD diagnosis.

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.

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.

Differential effects of NADPH oxidase and xanthine oxidase inhibition on sympathetic reinnervation in postinfarct rat hearts

Superoxide has been shown to play a major role in ventricular remodeling and arrhythmias after myocardial infarction. However, the source of increased myocardial superoxide production and the role of superoxide in sympathetic innervation remain to be further characterized. Male Wistar rats, after coronary artery ligation, were randomized to vehicle, allopurinol, or apocynin for 4weeks. To determine the role of peroxynitrite in sympathetic reinnervation, we also used 3-morpholinosydnonimine (a peroxynitrite generator). The postinfarction period was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine, xanthine oxidase activity, NADPH oxidase activity, and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle-treated infarcted rats compared with sham. Sympathetic hyperinnervation was blunted after administration of allopurinol. Arrhythmic scores in the allopurinol-treated infarcted rats were significantly lower than those in vehicle. For similar levels of ventricular remodeling, apocynin had no beneficial effects on oxidative stress, sympathetic hyperinnervation, or arrhythmia vulnerability. Allopurinol-treated hearts had significantly decreased nerve growth factor expression, which was substantially increased after coadministration of 3-morpholinosydnonimine. These results indicate that xanthine oxidase but not NADPH oxidase largely mediates superoxide production after myocardial infarction. Xanthine oxidase inhibition ameliorates sympathetic innervation and arrhythmias possibly via inhibition of the peroxynitrite-mediated nerve growth factor pathway.

Protecting against vascular disease in brain

Endothelial cells exert an enormous influence on blood vessels throughout the circulation, but their impact is particularly pronounced in the brain. New concepts have emerged recently regarding the role of this cell type and mechanisms that contribute to endothelial dysfunction and vascular disease. Activation of the renin-angiotensin system plays a prominent role in producing these abnormalities. Both oxidative stress and local inflammation are key mechanisms that underlie vascular disease of diverse etiology. Endogenous mechanisms of vascular protection are also present, including antioxidants, anti-inflammatory molecules, and peroxisome proliferator-activated receptor-γ. Despite their clear importance, studies of mechanisms that underlie cerebrovascular disease continue to lag behind studies of vascular biology in general. Identification of endogenous molecules and pathways that protect the vasculature may result in targeted approaches to prevent or slow the progression of vascular disease that causes stroke and contributes to the vascular component of dementia and Alzheimer's disease.

Decreased vasoconstrictor responses in remote cerebral arteries after focal brain ischemia and reperfusion in the rat, in vitro

The effects of brain ischemia and reperfusion on smooth muscle function in remote cerebral and peripheral arteries are hardly known. Maximum vasoconstrictions (E(max)) caused by 120mmol/l KCl and 5-HT in endothelium-denuded ring preparations were measured in ischemic and control cerebral arteries of rats after a 1-h right middle cerebral artery occlusion followed by 0-min (I/NR) or 2-3-min (I/SR) reperfusion, and in peripheral arteries after I/SR. Surprisingly, vasoconstrictions to 5-HT and 120mmol/lK(+) were attenuated in remote brain vessels after I/SR, i.e. in the contralateral middle cerebral artery and the basilar artery, while I/NR depressed E(max) of 5-HT and high KCl only in the ischemic middle cerebral artery. Pretreatment with N-(2-mercaptopropionyl) glycine (MPG, 100mg/kg i.p.), a free radical scavenger, fully prevented the impairment of vasomotor function in the middle cerebral artery on both sides after I/SR. Moreover, vasomotor functions were normal in the coronary, renal and pulmonary arteries after I/SR. In conclusion, focal cerebral ischemia and reperfusion impaired vasoconstrictor responses in remote brain arteries of rats by a mechanism involving free radicals. The lack of similar effects in peripheral vessels indicates poor defence of brain arteries against remote injury caused by reactive oxygen species-dependent mechanisms.

Role of sensory C fibers in hypoxia/reoxygenation-impaired myogenic constriction of cerebral arteries

OBJECTIVE

Hypoxia/reoxygenation (H/R) associated with extracorporeal membrane oxygenation disrupts cerebral autoregulation. However, the underlying mechanisms remain poorly understood. The present study was designed to investigate the role of sensory C-fibers in myogenic responsiveness of cerebral arteries.

METHODS

Arterial diameter and intraluminal pressure were simultaneously measured in vitro on rat posterior cerebral arteries.

RESULTS

Cerebral arteries constricted in response to graded increase in intraluminal pressure (20-100 mmHg, in 20 mmHg increments). In vitro C-fiber desensitization with capsaicin (1 micromol/l, 20 minutes) significantly suppressed myogenic constriction by over 50%, but did not affect 5-hydroxytryptamine (0.01-10 micromol/l) and KCl (120 mmol/l)-induced constriction. Capsazepine (5 micromol/l, 30 minutes), a selective blocker of neuronal vanilloid receptor TRPV1, had similar inhibitory effect on cerebral myogenic constriction to elevated pressure. Cerebral myogenic constriction was significantly attenuated by H/R; the impairment by H/R was further enhanced after C-fiber desensitization (except at a pressure level of 100 mmHg).

DISCUSSION

These findings indicate that C-fiber activity contributes to myogenic constriction of cerebral arteries under normal and H/R conditions. H/R-impaired myogenic responsiveness is exaggerated by C-fiber dysfunction. These results raise the possibility that therapeutic strategies directed toward preserving C-fiber nerve endings or supplying its constituent neuropeptides could be developed.

Vascular dysfunction in cerebrovascular disease: mechanisms and therapeutic intervention

The endothelium plays a crucial role in the control of vascular homoeostasis through maintaining the synthesis of the vasoprotective molecule NO* (nitric oxide). Endothelial dysfunction of cerebral blood vessels, manifested as diminished NO* bioavailability, is a common feature of several vascular-related diseases, including hypertension, hypercholesterolaemia, stroke, subarachnoid haemorrhage and Alzheimer's disease. Over the past several years an enormous amount of research has been devoted to understanding the mechanisms underlying endothelial dysfunction. As such, it has become apparent that, although the diseases associated with impaired NO* function are diverse, the underlying causes are similar. For example, compelling evidence indicates that oxidative stress might be an important mechanism of diminished NO* signalling in diverse models of cardiovascular 'high-risk' states and cerebrovascular disease. Although there are several sources of vascular ROS (reactive oxygen species), the enzyme NADPH oxidase is emerging as a strong candidate for the excessive ROS production that is thought to lead to vascular oxidative stress. The purpose of the present review is to outline some of the mechanisms thought to contribute to endothelial dysfunction in the cerebral vasculature during disease. More specifically, we will highlight current evidence for the involvement of ROS, inflammation, the RhoA/Rho-kinase pathway and amyloid beta-peptides. In addition, we will discuss currently available therapies for improving endothelial function and highlight future therapeutic strategies.

Pathological role of hypoxia in Alzheimer's disease

The majority cases of Alzheimer's disease (AD) are sporadic late-onset form not being linked to APP and PS1 gene mutations. It is believed that the environmental risk factors play an important role in the onset and development of AD. Patients suffering from cerebral ischemia and stroke in which hypoxic conditions occur are much more susceptible to AD. Increasing evidence suggests that hypoxia facilitates the pathogenesis of AD through accelerating the accumulation of Abeta, increasing the hyperphosphorylation of tau, impairing the normal functions of blood-brain barrier, and promoting the degeneration of neurons. Further investigations into the relationship between hypoxia and AD may open the avenue for effective preservation and pharmacological treatments of this neurodegenerative disease.

Resveratrol improves endothelial function: role of TNF{alpha} and vascular oxidative stress

OBJECTIVE

Oxidative stress plays an important role in type 2 diabetes-related endothelial dysfunction. We hypothesized that resveratrol protects against oxidative stress-induced endothelial dysfunction in aortas of diabetic mice by inhibiting tumor necrosis factor alpha (TNFalpha)-induced activation of NAD(P)H oxidase and preserving phosphorylation of endothelial nitric oxide synthase (eNOS).

METHODS AND RESULTS

We examined endothelial-dependent vasorelaxation to acetylcholine (ACh) in diabetic mice (Lepr(db)) and normal controls (m Lepr(db)). Relaxation to ACh was blunted in Lepr(db) compared with m Lepr(db), whereas endothelial-independent vasorelaxation to sodium nitroprusside (SNP) was comparable. Resveratrol improved ACh-induced vasorelaxation in Lepr(db) without affecting dilator response to SNP. Impaired relaxation to ACh in Lepr(db) was partially reversed by incubating the vessels with NAD(P)H oxidase inhibitor apocynin and a membrane-permeable superoxide dismutase mimetic TEMPOL. Dihydroethidium (DHE) staining showed an elevated superoxide (O(2)(.-)) production in Lepr(db), whereas both resveratrol and apocynin significantly reduced O(2)(.-) signal. Resveratrol increased nitrite/nitrate levels and eNOS (Ser1177) phosphorylation, and attenuated H(2)O(2) production and nitrotyrosine (N-Tyr) content in Lepr(db) aortas. Furthermore, resveratrol attenuated the mRNA and protein expression of TNFalpha. Genetic deletion of TNFalpha in diabetic mice (db(TNF-)/db(TNF-)) was associated with a reduced NAD(P)H oxidase activity and vascular O(2)(.-) production and an increased eNOS (Ser1177) phosphorylation, suggesting that TNFalpha plays a pivotal role in aortic dysfunction in diabetes by inducing oxidative stress and reducing NO bioavailability.

CONCLUSIONS

Resveratrol restored endothelial function in type 2 diabetes by inhibiting TNFalpha-induced activation of NAD(P)H oxidase and preserving eNOS phosphorylation, suggesting the potential for new treatment approaches to promote vascular health in metabolic diseases.

The role of oxidative stress and NADPH oxidase in cerebrovascular disease

The study of reactive oxygen species (ROS) and oxidative stress remains a very active area of biological research, particularly in relation to cellular signaling and the role of ROS in disease. In the cerebral circulation, oxidative stress occurs in diverse forms of disease and with aging. Within the vessel wall, ROS produce complex structural and functional changes that have broad implications for regulation of cerebral perfusion and permeability of the blood-brain barrier. These oxidative-stress-induced changes are thought to contribute to the progression of cerebrovascular disease. Here, we highlight recent findings in relation to oxidative stress in the cerebral vasculature, with an emphasis on the emerging role for NADPH oxidases as a source of ROS and the role of ROS in models of disease.

Effects of ginkgo biloba extract EGb761 on expression of RAGE and LRP-1 in cerebral microvascular endothelial cells under chronic hypoxia and hypoglycemia

Alzheimer's disease (AD), characterized by accumulation of amyloid-beta protein (Abeta) in brain parenchyma, is closely associated with brain ischemia. Decreased clearance of Abeta from brain is the main cause of Abeta accumulation in sporadic AD. However, the mechanisms underlying ischemia-mediated AD pathogenesis remain unclear. The receptor for advanced end glycation products (RAGE) and low-density lipoprotein receptor-related protein-1 (LRP-1) expressed at blood brain barrier (BBB) are actively involved in Abeta clearance. RAGE is thought to be a primary transporter of Abeta across BBB into the brain from the systemic circulation, while LRP-1 mediates the transport of Abeta out of the brain. Ginkgo biloba extract EGb761, a traditional Chinese medicine, has been widely used in the treatment of AD. To investigate the effects of EGb761 on the expression of RAGE and LRP-1 in endothelial cells in response to ischemic injury, we cultured bEnd.3 cells, an immortalized mouse cerebral microvessel endothelial cell line, under a chronic hypoxic and hypoglycemic condition (CHH) to mimic ischemic injury of BBB, and then treated with EGb 761. We found that EGb 761 markedly ameliorated the damage (evaluated by MTT assay) from CHH. Moreover, we demonstrated that CHH led to a significant increase in the expression of RAGE both at the mRNA and protein levels at all times (24, 36, and 48 h), conversely; CHH induced a dramatic decrease in LRP-1 mRNA and protein expression at both 36 and 48 h. The results indicated that CHH has differential effects on the expression of RAGE and LRP-1. Furthermore, EGb761 significantly reversed CHH-induced upregulation of RAGE expression and downregulation of LRP-1 expression. Our findings suggest that EGb761 favor clearance of Abeta via regulating the expression of RAGE and LRP-1 during brain ischemia. This may provide a new insight into a possible molecular mechanism underlying brain ischemia-mediated AD pathogenesis, and potential therapeutic application of EGb 761 in treatment of AD.

New targeted therapies for treatment of thrombosis in antiphospholipid syndrome

Antiphospholipid (aPL) antibodies (Abs) are associated with thrombosis and pregnancy loss in antiphospholipid syndrome (APS), a disorder initially characterised in patients with systemic lupus erythematosus (SLE) but now known to occur in the absence of other autoimmune disease. There is strong evidence that aPL Abs are pathogenic in vivo, from studies of animal models of thrombosis, endothelial cell activation and pregnancy loss. In recent years, progress has been made in characterising the molecular basis of this pathogenicity, which includes direct effects on platelets, endothelial cells and monocytes as well as activation of complement. This review summarises the clinical manifestations of APS and current modalities of treatment, and explains recent advances in understanding the molecular events triggered by aPL Abs on target cells in coagulation pathways as well as effects of aPL Abs on complement activation. Based on this information and on additional scientific evidence using in vitro and in vivo models, new potential targeted therapies for treatment and/or prevention of thrombosis in APS are proposed and discussed.

TNF-alpha-induced mitochondrial oxidative stress and cardiac dysfunction: restoration by superoxide dismutase mimetic Tempol

Mitochondria are indispensable for bioenergetics and for the regulation of physiological/signaling events in cellular life. Although TNF-alpha-induced oxidative stress and mitochondrial dysfunction are evident in several pathophysiological states, the molecular mechanisms coupled with impaired cardiac function and its potential reversal by drugs such as Tempol or apocyanin have not yet been explored. Here, we hypothesize that TNF-alpha-induced oxidative stress compromises cardiac function by altering the mitochondrial redox state and the membrane permeability transition pore (MPTP) opening, thereby causing mitochondrial dysfunction. We measured the redox states in the cytosol and mitochondria of the heart to understand the mechanisms related to the MPTP and the antioxidant defense system. Our studies demonstrate that TNF-alpha-induced oxidative stress alters redox homeostasis by impairing the MPTP proteins adenine nucleotide translocator and voltage-dependent anion channel, thereby resulting in the pore opening, causing uncontrolled transport of substances to alter mitochondrial pH, and subsequently leading to dysfunction of mitochondria and attenuated cardiac function. Interestingly, we show that the supplementation of Tempol along with TNF-alpha restores mitochondrial and cardiac function.

In Vivo Effects of an Inhibitor of Nuclear Factor-Kappa B on Thrombogenic Properties of Antiphospholipid Antibodies

It has been shown that endothelial cell (EC) activation and tissue factor (TF) upregulation in EC and monocytes by antiphospholipid antibodies (aPL Abs) leads to a prothrombotic state and involves translocation of nuclear factor-kappa B (NF-kappaB). Here we examined the effects of an NF-kappaB inhibitor on aPL-induced thrombosis, TF activity, and EC in vivo. We treated CD1 mice with IgG from a patient with antiphospholipid syndrome (IgG-APS) or with control IgG (IgG-NHS). The adhesion of leukocytes (number of white blood cells) to EC in cremaster muscle (as an indication of EC activation) as well as the size of an induced thrombus in the femoral vein of the mice were examined. Some mice in each group were infused with 10 microM MG132 (an inhibitor of NF-kappaB). TF activity was determined using a chromogenic assay in homogenates of carotid arteries and in peritoneal cells of mice. In vivo, IgG-APS increased significantly the number of white blood cells adhering to ECs (4.7 +/- 2.2) when compared to control mice (1.5 +/- 0.8), and these effects were significantly reduced when mice were pretreated with MG132 (0.8 +/- 0.2). IgG-APS increased significantly the thrombus size and MG132 inhibited that effect (93%). Treatment of the mice with IgG-APS also induced significantly increased TF function in peritoneal cells and in homogenates of carotid arteries. Pretreatment of the mice with MG132 abrogated those effects significantly. Mice injected with IgG-APS or with IgM-APS with or without the inhibitor had medium-high titers of anticardiolipin antibodies in serum at the time of the surgical procedures. The data show that prothrombotic and proinflammatory properties of IgG-APS and IgM-APS are downregulated in vivo by an NF-kappaB inhibitor. These findings may be important in designing new modalities of targeted therapies to treat thrombosis in patients with APS.

Hyperglycemia in acute ischemic stroke: a vascular perspective

Admission hyperglycemia complicates approximately one-third of acute ischemic strokes and is associated with a worse clinical outcome. Both human and animal studies have showed that hyperglycemia is particularly detrimental in ischemia/reperfusion. Decreased reperfusion blood flow has been observed after middle cerebral artery occlusion in acutely hyperglycemic animals, suggesting the vasculature as an important site of hyperglycemic reperfusion injury. This paper reviews biochemical and molecular pathways in the vasculature that are rapidly affected by hyperglycemia and concludes that these changes result in a pro-vasoconstrictive, pro-thrombotic and pro-inflammatory phenotype that renders the vasculature vulnerable to reperfusion injury. Understanding these pathways should lead to the development of rational therapies that reduce hyperglycemic reperfusion injury and thus improve outcome in this large subset of acute ischemic stroke patients.

Rho-kinase contributes to hypoxia/reoxygenation-induced cerebral endothelial dysfunction

Hypoxia/reoxygenation (H/R) in vitro induced cerebral endothelial dysfunction is mediated by superoxide production. However, the intracellular pathways involved remain unclear. The present study was designed to investigate the involvement of Rho-kinase and its interaction with nitric oxide (NO) in cerebral endothelial dysfunction after H/R. Arterial diameter and intraluminal pressure were simultaneously measured in vitro on rat posterior cerebral arteries. Vascular NO production was determined by measuring stable NO metabolites nitrate/nitrite. H/R selectively inhibited cerebral vasodilation to the endothelium-dependent agonist acetylcholine (ACh, 0.01 to 10 micromol/L) and caused NO deficiency. H/R-impaired vasodilation to ACh was reversed by Y27632 (1 micromol/L), a specific inhibitor of Rho-kinase, but not by chelerythrine (1 micromol/L), a selective inhibitor of protein kinase C. Y27632 had no protective effect in the presence of N-nitro-L-arginine methyl ester (L-NAME; 100 micromol/L), a specific endothelial NO synthase inhibitor. L-NAME (100 micromol/L) alone failed to modulate H/R-impaired vasodilation, so did L-arginine (3 mmol/L), a substrate for NO synthase. However, a stable NO donor diethylenetetra amine-NONOate (5 micromol/L) normalized H/R-impaired dilation to ACh. In conclusion, H/R-induced endothelial dysfunction is associated with activation of Rho-kinase-dependent pathway and NO deficiency. Pretreatment with either Y27632 or the stable NO donor profoundly prevented H/R-mediated cerebral endothelial dysfunction.

NADPH oxidases of the brain: distribution, regulation, and function

The NADPH oxidase is a multi-subunit enzyme that catalyzes the reduction of molecular oxygen to form superoxide (O(2)(-)). While classically linked to the respiratory burst in neutrophils, recent evidence now shows that O(2)(-) (and associated reactive oxygen species, ROS) generated by NADPH oxidase in nonphagocytic cells serves myriad functions in health and disease. An entire new family of NADPH Oxidase (Nox) homologues has emerged, which vary widely in cell and tissue distribution, as well as in function and regulation. A major concept in redox signaling is that while NADPH oxidase-derived ROS are necessary for normal cellular function, excessive oxidative stress can contribute to pathological disease. This certainly is true in the central nervous system (CNS), where normal NADPH oxidase function appears to be required for processes such as neuronal signaling, memory, and central cardiovascular homeostasis, but overproduction of ROS contributes to neurotoxicity, neurodegeneration, and cardiovascular diseases. Despite implications of NADPH oxidase in normal and pathological CNS processes, still relatively little is known about the mechanisms involved. This paper summarizes the evidence for NADPH oxidase distribution, regulation, and function in the CNS, emphasizing the diversity of Nox isoforms and their new and emerging role in neuro-cardiovascular function. In addition, perspectives for future research and novel therapeutic targets are offered.

Vascular effects of a common gene variant of extracellular superoxide dismutase in heart failure

A common gene variant of human extracellular superoxide dismutase (ecSOD), in ∼5% of humans, is associated with increased risk of ischemic heart disease. The purpose of this study was to examine vascular effects of ecSOD with effects of the ecSOD variant (ecSODR213G) in rats with heart failure. Seven weeks after coronary artery ligation, we studied rats with heart failure and sham-operated rats. Adenoviral vectors expressing human ecSOD, ecSODR213G, or a control virus were injected intravenously. In the aorta from rats with heart failure, responses to acetylcholine (69 ± 4% relaxation, means ± SE) and basal levels of nitric oxide (NO) (vasoconstrictor responses to a NO synthase inhibitor) were greatly impaired, and levels of superoxide and peroxynitrite were increased. Gene transfer of ecSOD restored responses to acetylcholine (92 ± 2% relaxation) and basal levels of NO to normal and reduced levels of superoxide [from 2.3 ± 0.2 to 0.9 ± 0.2 relative light units per second per millimeter squared (RLU·s−1·mm−2)] and peroxynitrite (from 2.4 ± 0.2 to 0.9 ± 0.1 RLU·s−1·mm−2) in the aorta from rats with heart failure. Gene transfer of ecSODR213G produced little or no improvement. Responses to nitroprusside were not different among the groups. Expression of endogenous mRNA for SODs (CuZnSOD, MnSOD, and ecSOD) and endothelial NOS in the aorta was not different among the groups. In contrast to ecSOD, gene transfer of ecSODR213G in rats with heart failure has minimal beneficial effect on oxidative stress, endothelial function, or basal bioavailability of NO. We speculate that greatly diminished efficacy of ecSODR213G in protection against oxidative stress and endothelial dysfunction may contribute to increased risk of cardiovascular disease in humans with ecSODR213G.

Reactive oxygen species: influence on cerebral vascular tone

Reactive oxygen species have multiple effects on vascular cells. Defining the sources and the impact of the various reactive oxygen species within the vessel wall has emerged as a major area of study in vascular biology. This review will focus on recent findings related to effects of reactive oxygen species on cerebral vascular tone. Effects of superoxide radical, hydrogen peroxide, and the reactive nitrogen species peroxynitrite are summarized. Although higher concentrations may be important for cerebral vascular biology in disease, relatively low concentrations of reactive oxygen species may function as signaling molecules involved with normal regulation of cerebral vascular tone. The mechanisms by which reactive oxygen species affect vascular tone may be quite complex, and our understanding of these processes is increasing. Additionally, the role of reactive oxygen species as mediators of endothelium-dependent relaxation is addressed. Finally, the consequences of the molecular interactions of superoxide with nitric oxide and arachidonic acid are discussed.