Possible involvement of oxidative stress as a causative factor in blood-brain barrier dysfunction in stroke-prone spontaneously hypertensive rats

A multifactorial, evidence-based analysis of pathophysiology in Spaceflight Associated Neuro-Ocular Syndrome (SANS)

The National Aeronautics and Space Administration (NASA) in the United States has been studying a fascinating and unique constellation of neuro-ophthalmic findings collectively known as Spaceflight Associated Neuro-Ocular Syndrome (SANS). SANS is unique to the space environment of microgravity and produces novel physiological and pathological findings that have no direct terrestrial equivalent. The neuro-ophthalmic phenomenon is a major physiologic barrier to future planetary spaceflight. The underlying pathophysiology of SANS remains ill-defined, but since its initial report in 2011, several hypotheses have been proposed including increased intracranial pressure, cerebral venous congestion and glymphatic stasis, compartmentalization of CSF within the orbital nerve sheath sub-arachnoid space (SAS), upward brain shift, inflammation, disrupted axoplasmic transport, and radiation exposure. These aetiologies may not be mutually exclusive and may be interconnected, leading to an integrative, multifactorial aetiology of SANS. This paper critically analyses the various hypotheses of this neuro-ophthalmic phenomenon and the connections between the physiologic and anatomical evidence-based changes observed in spaceflight and terrestrial analogues. Continued prospective, longitudinal study and development of practical countermeasures for SANS will be necessary for future human spaceflight missions including the mission to Mars.

Plasma fibroblast growth factor 21 and risk of cognitive impairment among patients with ischemic stroke

BACKGROUND AND AIMS

Previous study reported that plasma fibroblast growth factor 21 (FGF-21) was associated with poor prognosis in patients with ischemic stroke. The purpose of present study was to prospectively investigate the relationship between plasma FGF-21 and post-stroke cognitive impairment (PSCI).

METHODS

A total of 600 patients from 7 hospitals were included in this study and plasma FGF-21 levels were examined for all the participants. Cognitive impairment was evaluated using Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) at 3 months after ischemic stroke onset.

RESULTS

323(53.8 %) or 419(69.8 %) participants had PSCI according to MMSE or MoCA at 3 months, respectively. After adjustment for age, National Institutes of Health stroke score, education, and other covariates, the odds ratio of PSCI defined by MMSE and MoCA for the highest vs lowest quartile of plasma FGF-21 was 1.77(1.05-2.98) and 2.40(1.35-4.29), respectively. Multiple-adjusted spline regression model showed a linear association between FGF-21 levels and PSCI (all P < 0.005 for linearity). Subgroup analyses further confirmed these results.

CONCLUSION

Elevated plasma FGF-21 level was associated with PSCI at 3 months after stroke independently of established conventional risk factors, suggesting that plasma FGF-21 may have potential prognostic value in risk stratification of PSCI.

Effects of Inadequate Folate Intake on the Onset and Progression of Hypertensive Vascular Injury

We investigated the effects of inadequate folate intake on the onset and progression of hypertensive organ injury. In the present study, 5-wk-old male stroke-prone spontaneously hypertensive rats (SHRSP) were fed with a normal-folate (control; 160-170 μg of folate/100 g diet) or low-folate (8-10 μg of folate/100 g diet) diet until they reached 25 wk of age. After the animals reached 10 wk of age, the bodyweight of the rats in the low-folate group was lower than that of the rats in the control group. Regarding blood pressure, both groups had severe hypertension of ≥230 mmHg at 12 wk of age that was not significantly different between the groups. At 16 wk of age, the low-folate group had a low number of blood cell types. The folate levels in the serum, liver, and kidneys of these rats were significantly lower (p<0.01) and the serum homocysteine level in the low-folate group was significantly higher than in the controls. The low-folate group had a significantly lower testicular weight than the control group (p<0.05) and arterial hypertrophy, spermatogenesis arrest, and interstitial connective tissue hyperplasia were observed. However, there was no clear difference in lesions in other organs. These results indicated that under low folate status, SHRSP causes hematopoietic disorders and exacerbates hypertensive vascular injury at various degrees by organ type.

Recent advances in the development of nanomedicines for the treatment of ischemic stroke

Ischemic stroke is still a serious threat to human life and health, but there are few therapeutic options available to treat stroke because of limited blood-brain penetration. The development of nanotechnology may overcome some of the problems related to traditional drug development. In this review, we focus on the potential applications of nanotechnology in stroke. First, we will discuss the main molecular pathological mechanisms of ischemic stroke to develop a targeted strategy. Second, considering the important role of the blood-brain barrier in stroke treatment, we also delve mechanisms by which the blood-brain barrier protects the brain, and the reasons why the therapeutics must pass through the blood-brain barrier to achieve efficacy. Lastly, we provide a comprehensive review related to the application of nanomaterials to treat stroke, including liposomes, polymers, metal nanoparticles, carbon nanotubes, graphene, black phosphorus, hydrogels and dendrimers. To conclude, we will summarize the challenges and future prospects of nanomedicine-based stroke treatments.

Prenatal exposure of bonny light crude oil induces embryotoxicity, impaired cognitive functions and cortico-hippocampal neurodegeneration on fetal outcomes of pregnant sprague-dawley rats

The low Sulfur level, heavy metals and easy production rate of Bonny Light Crude Oil (BLCO) makes it one of Nigeria's most explored oil. This study investigated the memory impairments, embryotoxicity and cortico-hippocampal neurodegeneration induced by prenatal exposure to BLCO of pregnant Sprague-Dawley (S-D) rats. Twenty pregnant rats were divided into 4 groups (A-D) of 5 rats each. Group A received normal saline as placebo. Group B-D received oral doses of BLCO at 0.73 ml/kg, 2 ml/kg and 3.8 ml/kg on pregnancy day 8-12.5 respectively. The pregnant rats were allowed to litter and nurse their pups. At 6 weeks postnatal life, twelve (12) selected young rats (n = 12) were accessed for behavioral study (Y-maze) and then sacrificed for biochemical and histological analysis. The results showed spontaneous abortion, still births and significantly reduced number of live births in the high dose group of BLCO compared to control. Length of gestation was significantly increased in the high dose group when compared to the control. CAT levels reduced significantly with concomitant increase in 8-OHdG among BLCO treated groups compared to control. Spontaneous alteration and number of arm entries decreased in the BLCO groups in comparison to control. Histological observation showed reduced cellular size, chromatolysis and presence of extracellular senile plaques in the prefrontal cortex and mild histological changes in the hippocampus architecture in the BLCO treated groups compared to the control. BLCO is capable of inducing embryotoxicity, impair cognition and cortico-hippocampal neurodegeneration.

A Novel Model of Mixed Vascular Dementia Incorporating Hypertension in a Rat Model of Alzheimer's Disease

Alzheimer's disease (AD) and mixed dementia (MxD) comprise the majority of dementia cases in the growing global aging population. MxD describes the coexistence of AD pathology with vascular pathology, including cerebral small vessel disease (SVD). Cardiovascular disease increases risk for AD and MxD, but mechanistic synergisms between the coexisting pathologies affecting dementia risk, progression and the ultimate clinical manifestations remain elusive. To explore the additive or synergistic interactions between AD and chronic hypertension, we developed a rat model of MxD, produced by breeding APPswe/PS1ΔE9 transgenes into the stroke-prone spontaneously hypertensive rat (SHRSP) background, resulting in the SHRSP/FAD model and three control groups (FAD, SHRSP and non-hypertensive WKY rats, n = 8-11, both sexes, 16-18 months of age). After behavioral testing, rats were euthanized, and tissue assessed for vascular, neuroinflammatory and AD pathology. Hypertension was preserved in the SHRSP/FAD cross. Results showed that SHRSP increased FAD-dependent neuroinflammation (microglia and astrocytes) and tau pathology, but plaque pathology changes were subtle, including fewer plaques with compact cores and slightly reduced plaque burden. Evidence for vascular pathology included a change in the distribution of astrocytic end-foot protein aquaporin-4, normally distributed in microvessels, but in SHRSP/FAD rats largely dissociated from vessels, appearing disorganized or redistributed into neuropil. Other evidence of SVD-like pathology included increased collagen IV staining in cerebral vessels and PECAM1 levels. We identified a plasma biomarker in SHRSP/FAD rats that was the only group to show increased Aqp-4 in plasma exosomes. Evidence of neuron damage in SHRSP/FAD rats included increased caspase-cleaved actin, loss of myelin and reduced calbindin staining in neurons. Further, there were mitochondrial deficits specific to SHRSP/FAD, notably the loss of complex II, accompanying FAD-dependent loss of mitochondrial complex I. Cognitive deficits exhibited by FAD rats were not exacerbated by the introduction of the SHRSP phenotype, nor was the hyperactivity phenotype associated with SHRSP altered by the FAD transgene. This novel rat model of MxD, encompassing an amyloidogenic transgene with a hypertensive phenotype, exhibits several features associated with human vascular or "mixed" dementia and may be a useful tool in delineating the pathophysiology of MxD and development of therapeutics.

Brain perivascular macrophages contribute to the development of hypertension in stroke-prone spontaneously hypertensive rats via sympathetic activation

Hypertension is associated with systemic inflammation. The activation of the sympathetic nervous system is critically involved in the pathogenesis of hypertension. Brain perivascular macrophages (PVMs) can be affected by circulating inflammatory cytokines, and the contribution of brain PVMs to sympathoexcitation has been demonstrated in a heart failure model. We thus investigated whether brain PVMs contribute to the development of hypertension through sympathoexcitation. Stroke-prone spontaneously hypertensive rats (SHRSP) developed hypertension over an 8-week period from 4 to 12 weeks of age. The number of brain PVMs and plasma interleukin-1β levels significantly increased at the ages of 8 and 12 weeks in SHRSP compared with normotensive Wistar-Kyoto rats (WKY). To determine the contribution of brain PVMs to blood pressure elevation, we intracerebroventricularly injected liposome-encapsulated clodronate, which eliminates macrophages by inducing apoptosis, into 8-week-old rats; we then assessed its effects in 10-week-old rats. Clodronate treatment attenuated the increase in mean blood pressure in SHRSP but not in WKY. Clodronate treatment reduced the depressor effect of hexamethonium, an index of sympathetic activity; it also reduced neuronal activity in sympathetic regulatory nuclei such as the hypothalamic paraventricular nucleus and rostral ventrolateral medulla and reduced the expression of cyclooxygenase-2 and prostaglandin E2, a downstream pathway in activated macrophages, in SHRSP but not in WKY. Furthermore, clodronate treatment attenuated the increase in blood pressure and renal sympathetic nerve activity in response to an acute intravenous injection of interleukin-1β in WKY. In conclusion, brain PVMs contribute to the development of hypertension via sympathetic activation. PVMs may be activated by increased levels of circulating interleukin-1β.

The cardiovascular aspects of a Ménière's disease population - A pilot study

INTRODUCTION

MD is considered a rare disease. An adequate model that explains MD's pathophysiology is not well established. Recently, the vascular theory of the disease has been revived.

OBJECTIVES

To characterize a MD population according to its cardiovascular risk and correlate it to the MD clinical course.

METHODS

In this retrospective chart study the data of 31 MD patients observed between January 2017 and April 2018 in a tertiary university hospital were reviewed. Patients included in the study were diagnosed according to the Bárány Society criteria. Lost follow-ups, patients with autoimmune disease, atopy or allergy, major psychiatric disease and migraine were excluded. Age, gender, cardiovascular risk factors, audiometric and vestibular parameters, occurrence of MD attacks in the previous 6 months, vestibular medication in course and time course of MD were recorded and compared between groups (with and without cardiovascular risk factors).

RESULTS

31 patients (61.3% females) mean aged 60.3 years (±9.7) were studied. 74% of the population had at least one risk factor and 51.6% of patients had attacks in the last 6 months. There was a statistically significant difference in the occurrence of MD attacks in the last 6 months (p = 0.014) between MD patients with and without risk factors. Mean PTA thresholds were higher and speech discrimination was lower in individuals with more cardiovascular risk factors.

CONCLUSIONS

Treatment of MD focusing on vascular risk factors may allow a better control of symptoms and result in a decreased need for ablative procedures in this disorder.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

High serum levels of 8-OHdG are an independent predictor of post-stroke depression in Chinese stroke survivors

PURPOSE

Although previous studies have investigated oxidative stress biomarkers in association with depression in non-stroke subjects, the association between oxidative deoxyribonucleic acid damage and post-stroke depression (PSD) remains unelucidated.

PATIENTS AND METHODS

Two hundred forty-one first-ever ischemic stroke patients were consecutively recruited within the first 24 h of stroke onset and were followed up at 1 month. Serum 8-hydroxy-2'-deoxyguanosine (8-OHdG) and catalase (CAT) levels were measured within 24 h of admission using a commercially available enzyme-linked immunosorbent assay. The 17-item Hamilton Depression Scale was used to evaluate depressive symptoms. Diagnosis of PSD was made in line with the Diagnostic and Statistical Manual of Mental Disorders, 4th edition criteria for depression.

RESULTS

Serum levels of 8-OHdG (P<0.001) and CAT (P=0.025) increased in depressed patients at admission. A positive correlation was found between the 8-OHdG and CAT levels in both the total stroke patients (r=0.320, P<0.001) and the depressed patients (r=0.300, P=0.012). The 8-OHdG levels were positively correlated with the 17-item Hamilton Depression Scale scores (r=0.129, P=0.046) in depressed patients. Multivariate analyses found that 8-OHdG levels ≥200.0 ng/L were independently associated with PSD (odds ratio, 7.477; 95% CI, 3.342-16.289, P<0.001) after adjusting for possible relevant confounders.

CONCLUSION

Higher serum 8-OHdG levels at admission were found to be correlated with PSD 1 month after stroke.

High Serum Levels of Malondialdehyde and 8-OHdG are both Associated with Early Cognitive Impairment in Patients with Acute Ischaemic Stroke

Post-stroke cognitive impairment (PSCI) is an increasingly prevalent sequel after stroke that may associate with poor functional outcome and increased risk of recurrent stroke. We aimed to explore the relationship between oxidative stress biomarkers and the presence of PSCI. 193 first-ever acute ischaemic stroke patients were consecutively enrolled in the current study. The oxidative stress biomarkers malondialdehyde (MDA) and 8-hydroxydeoxyquanosine (8-OHdG) were measured within 24 h after admission. Cognition function was evaluated by the Mini-Mental State Examination (MMSE) at 1 month after stroke. Serum levels of 8-OHdG and MDA were both significantly higher in the PSCI (p < 0.001) compared with the non-PSCI group. Both the serum levels of both 8-OHdG and MDA were negatively correlated with the MMSE score. Receiver operating characteristic curve analysis was used to evaluate 8-OHdG and MDA as markers of a high risk of PSCI and produced area under curve values of 0.700 and 0.793. Adjusted logistic regression showed that serum 8-OHdG and MDA levels remained as independent markers of PSCI. High serum levels of malondialdehyde and 8-OHdG are associated with the presence of PSCI at 1 month after stroke.

Hypertension impairs neurovascular coupling and promotes microvascular injury: role in exacerbation of Alzheimer's disease

Hypertension in the elderly substantially increases both the risk of vascular cognitive impairment (VCI) and Alzheimer's disease (AD); however, the underlying mechanisms are not completely understood. This review discusses the effects of hypertension on structural and functional integrity of cerebral microcirculation, including hypertension-induced alterations in neurovascular coupling responses, cellular and molecular mechanisms involved in microvascular damage (capillary rarefaction, blood-brain barrier disruption), and the genesis of cerebral microhemorrhages and their potential role in exacerbation of cognitive decline associated with AD. Understanding and targeting the hypertension-induced cerebromicrovascular alterations that are involved in the onset and progression of AD and contribute to cognitive impairment are expected to have a major role in preserving brain health in high-risk older individuals.

Brain adaptation to hypoxia and hyperoxia in mice

Aims

Hyperoxic breathing might lead to redox imbalance and signaling changes that affect cerebral function. Paradoxically, hypoxic breathing is also believed to cause oxidative stress. Our aim is to dissect the cerebral tissue responses to altered O₂ fractions in breathed air by assessing the redox imbalance and the recruitment of the hypoxia signaling pathways.

Results

Mice were exposed to mild hypoxia (10%O₂), normoxia (21%O₂) or mild hyperoxia (30%O₂) for 28 days, sacrificed and brain tissue excised and analyzed. Although one might expect linear responses to %O₂, only few of the examined variables exhibited this pattern, including neuroprotective phospho- protein kinase B and the erythropoietin receptor. The major reactive oxygen species (ROS) source in brain, NADPH oxidase subunit 4 increased in hypoxia but not in hyperoxia, whereas neither affected nuclear factor (erythroid-derived 2)-like 2, a transcription factor that regulates the expression of antioxidant proteins. As a result of the delicate equilibrium between ROS generation and antioxidant defense, neuron apoptosis and cerebral tissue hydroperoxides increased in both 10%O₂ and 30%O₂, as compared with 21%O₂. Remarkably, the expression level of hypoxia-inducible factor (HIF)−2α (but not HIF-1α) was higher in both 10%O₂ and 30%O₂ with respect to 21%O₂

Innovation

Comparing the in vivo effects driven by mild hypoxia with those driven by mild hyperoxia helps addressing whether clinically relevant situations of O₂ excess and scarcity are toxic for the organism.

Conclusion

Prolonged mild hyperoxia leads to persistent cerebral damage, comparable to that inferred by prolonged mild hypoxia. The underlying mechanism appears related to a model whereby the imbalance between ROS generation and anti-ROS defense is similar, but occurs at higher levels in hypoxia than in hyperoxia.

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Both oxygen scarcity and oxygen excess are harmful for the brain.

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Hypoxia increases ROS more than hyperoxia.

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Hypoxia increases the antioxidant defenses to an extent larger than hyperoxia.

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Both hypoxia and hyperoxia imbalance the ROS generation/ antiROS defense equilibrium.

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These findings have implications for those who need supplemental oxygen therapy.

Notch signaling in cerebrovascular diseases (Review)

The Notch signaling pathway is a crucial regulator of numerous fundamental cellular processes. Increasing evidence suggests that Notch signaling is involved in inflammation and oxidative stress, and thus in the progress of cerebrovascular diseases. In addition, Notch signaling in cerebrovascular diseases is associated with apoptosis, angiogenesis and the function of blood-brain barrier. Despite the contradictory results obtained to date as to whether Notch signaling is harmful or beneficial, the regulation of Notch signaling may provide a novel strategy for the treatment of cerebrovascular diseases.

Evaluation of oxidative stress levels in the conjunctival epithelium of patients with or without dry eye, and dry eye patients treated with preservative-free hyaluronic acid 0.15 % and vitamin B12 eye drops

PURPOSE

Increased levels of oxidative stress have been seen in animal models of dry eye and in the conjunctival epithelial cells of patients with Sjögren's syndrome. The aims of this study were to compare the levels of oxidative stress in patients with dry eye and patients without dry eye and to evaluate the effects of treatment with preservative-free eye drops containing hyaluronic acid 0.15 % and vitamin B12 on oxidative stress and dry eye symptoms.

METHODS

Three cohorts of patients who were to undergo planned cataract surgery were enrolled: patients with dry eye randomized to either no treatment (n = 29) or treatment (n = 32) with hyaluronic acid/vitamin B12 eye drops, and patients without dry eye (n = 42). Patients were assessed by Schirmer's type I test, fluorescein clearance test (FCT), Break Up Time (BUT), and Ocular Surface Disease Index (OSDI). Lipid peroxidation, a marker of oxidative stress, was assessed by LP-CHOLOX test.

RESULTS

Compared with patients without dry eye, patients with dry eye had significantly increased levels of oxidative stress, higher OSDI and FCT scores, and significantly lower Schirmer's test and BUT scores. Treatment with eye drops containing hyaluronic acid 0.15 % and vitamin B12 was associated with significantly reduced levels of oxidative stress and OSDI and FCT scores and significantly increased Schirmer's test and BUT scores.

CONCLUSIONS

These findings indicate that oxidative stress is associated with dry eye and that hyaluronic acid/vitamin B12 eye drops may attenuate oxidative stress and inflammation, improving dry eye symptoms. Further study in controlled clinical trials is warranted.