Acute hypertension induces brain injury and blood–brain barrier disruption through reduction of claudins mRNA expression in rat

Blood pressure and the brain: the conundrum of hypertension and dementia

As the population ages, the anticipated rates of dementia worldwide are likely to increase dramatically, especially in low- and middle-income countries; thus, any opportunity to modify dementia risk is especially critical. Hypertension is one risk factor that is highly prevalent, consistently important for late-life brain health, and which could represent a target for prevention of dementia. Furthermore, hypertension is the most significant modifiable risk factor for stroke. This review will summarize existing literature linking hypertension with dementia and brain health more broadly, will discuss potential mechanisms linking hypertension with brain health, and will consider specific factors that may impact not only the relationship between hypertension and the brain but also the importance of treatment, including different associations over the life course.

Analysis of Risk Factors for Hemorrhagic Transformation of Cerebral Infarction and Recurrence of Cerebral Infarction: A Retrospective Study on Cerebral Infarction Patients with or without Hemorrhagic Transformation

Background

Acute ischemic stroke, especially hemorrhage cerebral infarction (HCI), resulted in the leading causes of mortality and long-term disability across populations. However, fewer researches have focused on the risk factors of first admission and recurrence of HCI.

Methods

The study included 1857 patients who underwent cerebral infarction with or without hemorrhagic transformation. Clinical characteristics were collected, and univariate and multivariate analysis were performed to explore the risk factors. The subgroup analysis of cerebral infarction recurrence was performed. ROC analysis was utilized, and AUCs were showed the diagnostic values of the risk factors.

Results

Compared to the patients with non-hemorrhage cerebral infarction, the patients with hemorrhage cerebral infarction were older and had higher Neutrophil infiltration, AST expression, globulin and BUN, while had lower ALT expression, triglyceride, PT, APTT, homocysteine, d-dimer, CRP and glycosylated hemoglobin. Utilizing univariate and multivariate analysis, age, thrombolytic, Hb, AST and glycosylated hemoglobin were the risk factors between the patients with hemorrhagic cerebral infarction and non-hemorrhagic cerebral infarction. ROC analysis was performed to demonstrate that glycosylated hemoglobin was a diagnostic biomarker for the patients with hemorrhagic cerebral infarction and non-hemorrhagic cerebral infarction (AUC = 0.808). Utilizing univariate and multivariate analysis, age, hypertension history, LDL and MRS Score on admission were the risk factors between non-hemorrhagic cerebral infarction patients with first admission or the cerebral infarction recurrence. ROC analysis was performed to demonstrate MRS Score on admission was a diagnostic biomarker for recurrence of cerebral infarction in patients with non-hemorrhagic cerebral infarction (AUC = 0.708). Utilizing univariate and multivariate analysis, only hypertension history was the risk factors between hemorrhagic cerebral infarction patients with first admission or the cerebral infarction recurrence.

Conclusion

In conclusion, age, hypertension history, LDL and MRS Score on admission were the risk factors between cerebral infarction patients with first admission or the cerebral infarction recurrence.

Angiotensin II, blood-brain barrier permeability, and microglia interplay during the transition from pre-to hypertensive phase in spontaneously hypertensive rats

Background

Hypertension is characterized by upregulation of the renin-angiotensin system, increased blood-brain barrier (BBB) permeability, microglia activation within autonomic nuclei, and an intense sympathoexcitation. There is no information on the interplay of these events during the development of neurogenic hypertension. We sought to identify the interaction and time-course changes of Ang II availability, barrier dysfunction, microglia activation, and autonomic imbalance within autonomic areas during the development of neurogenic hypertension.

Methods

Sequential changes of hemodynamic/autonomic parameters, BBB permeability, microglia structure/density (IBA-1), and angiotensin II (Ang II) immunofluorescence were evaluated within the paraventricular hypothalamic nucleus, nucleus of the solitary tract, and rostral ventrolateral medulla of Wistar and spontaneously hypertensive rats (SHRs) aged 4 weeks, 5 weeks, 6 weeks, 8 weeks, and 12 weeks. The somatosensory cortex and hypoglossal nucleus were also analyzed as non-autonomic control areas.

Results

Increased brain Ang II availability (4th-5th week) was the first observed change, followed by the incipient BBB leakage and increased microglia density (6th week). From the 5th-6th weeks on, BBB leakage, Ang II, and IBA-1 densities increased continuously, allowing a parallel increase in both Ang II-microglia colocalization and the transition of microglial cells from highly ramified in the basal surveillant condition (4th-5th week) to shorter process arbors, fewer endpoints, and enlarged soma in the disease-associate condition (6th week to the 12th week). Simultaneously with increased Ang II-microglia colocalization and microglia morphologic phenotypic changes, sympathetic activity and pressure variability increased, autonomic control deteriorated, and blood pressure increased. These responses were not specific for autonomic nuclei but also occurred at a lower magnitude in the somatosensory cortex and hypoglossal nucleus, indicating the predominance of hypertension-induced effects on autonomic areas. No changes were observed in age-matched controls where Ang II density did not change.

Conclusion

Brain Ang II density is the initial stimulus to drive coordinated changes in BBB permeability and microglial reactivity. Increased BBB dysfunction allows access of plasma Ang II and increases its local availability and the colocalization and activation of microglial cells. It is a potent stimulus to augments vasomotor sympathetic activity, autonomic imbalance, and pressure elevation during the establishment of hypertension.

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

The Basic Requirement of Tight Junction Proteins in Blood-Brain Barrier Function and Their Role in Pathologies

This review addresses the role of tight junction proteins at the blood-brain barrier (BBB). Their expression is described, and their role in physiological and pathological processes at the BBB is discussed. Based on this, new approaches are depicted for paracellular drug delivery and diagnostics in the treatment of cerebral diseases. Recent data provide convincing evidence that, in addition to its impairment in the course of diseases, the BBB could be involved in the aetiology of CNS disorders. Further progress will be expected based on new insights in tight junction protein structure and in their involvement in signalling pathways.

Circadian Mechanisms in Brain Fluid Biology

The brain is a complex organ, fundamentally changing across the day to perform basic functions like sleep, thought, and regulating whole-body physiology. This requires a complex symphony of nutrients, hormones, ions, neurotransmitters and more to be properly distributed across the brain to maintain homeostasis throughout 24 hours. These solutes are distributed both by the blood and by cerebrospinal fluid. Cerebrospinal fluid contents are distinct from the general circulation because of regulation at brain barriers including the choroid plexus, glymphatic system, and blood-brain barrier. In this review, we discuss the overlapping circadian (≈24-hour) rhythms in brain fluid biology and at the brain barriers. Our goal is for the reader to gain both a fundamental understanding of brain barriers alongside an understanding of the interactions between these fluids and the circadian timing system. Ultimately, this review will provide new insight into how alterations in these finely tuned clocks may lead to pathology.

Hypertensive Adults Exhibit Lower Myelin Content: A Multicomponent Relaxometry and Diffusion Magnetic Resonance Imaging Study

BACKGROUND

It is unknown whether hypertension plays any role in cerebral myelination. To fill this knowledge gap, we studied 90 cognitively unimpaired adults, age range 40 to 94 years, who are participants in the Baltimore Longitudinal Study of Aging and the Genetic and Epigenetic Signatures of Translational Aging Laboratory Testing to look for potential associations between hypertension and cerebral myelin content across 14 white matter brain regions.

METHODS

Myelin content was probed using our advanced multicomponent magnetic resonance relaxometry method of myelin water fraction, a direct and specific magnetic resonance imaging measure of myelin content, and longitudinal and transverse relaxation rates (R1 and R2), 2 highly sensitive magnetic resonance imaging metrics of myelin content. We also applied diffusion tensor imaging magnetic resonance imaging to measure fractional anisotropy, mean diffusivity, radial diffusivity, and axial diffusivity values, which are metrics of cerebral microstructural tissue integrity, to provide context with previous magnetic resonance imaging findings.

RESULTS

After adjustment of age, sex, systolic blood pressure, smoking status, diabetes status, and cholesterol level, our results indicated that participants with hypertension exhibited lower myelin water fraction, fractional anisotropy, R1 and R2 values and higher mean diffusivity, radial diffusivity, and axial diffusivity values, indicating lower myelin content and higher impairment to the brain microstructure. These associations were significant across several white matter regions, particularly in the corpus callosum, fronto-occipital fasciculus, temporal lobes, internal capsules, and corona radiata.

CONCLUSIONS

These original findings suggest a direct association between myelin content and hypertension and form the basis for further investigations including longitudinal assessments of this relationship.

Hemorrhagic Conversion of Acute Ischemic Stroke

Stroke is a leading cause of morbidity and mortality worldwide; a serious complication of ischemic stroke is hemorrhagic transformation. Current treatment of acute ischemic stroke includes endovascular thrombectomy and thrombolytic therapy. Both of these treatment options are linked with increased risks of hemorrhagic conversion. The diagnosis and timely management of patients with hemorrhagic conversion is critically important to patient outcomes. This review aims to discuss hemorrhagic conversion of acute ischemic stroke including discussion of the pathophysiology, review of risk factors, imaging considerations, and treatment of patients with hemorrhagic conversion.

Trained hypertensive rats exhibit decreased transcellular vesicle trafficking, increased tight junctions' density, restored blood-brain barrier permeability and normalized autonomic control of the circulation

Introduction: Chronic hypertension is accompanied by either blood-brain barrier (BBB) leakage and autonomic dysfunction. There is no consensus on the mechanism determining increased BBB permeability within autonomic areas. While some reports suggested tight junction's breakdown, others indicated the involvement of transcytosis rather than paracellular transport changes. Interestingly, exercise training was able to restore both BBB permeability and autonomic control of the circulation. We sought now to clarify the mechanism(s) governing hypertension- and exercise-induced BBB permeability. Methods: Spontaneously hypertensive rats (SHR) and normotensive controls submitted to 4-week aerobic training (T) or sedentary protocol (S) were chronically cannulated for baseline hemodynamic and autonomic recordings and evaluation of BBB permeability. Brains were harvested for measurement of BBB function (FITC-10 kDa leakage), ultrastructural analysis of BBB constituents (transmission electron microscopy) and caveolin-1 expression (immunofluorescence). Results: In SHR-S the increased pressure, augmented sympathetic vasomotor activity, higher sympathetic and lower parasympathetic modulation of the heart and the reduced baroreflex sensitivity were accompanied by robust FITC-10kDa leakage, large increase in transcytotic vesicles number/capillary, but no change in tight junctions' density within the paraventricular nucleus of the hypothalamus, the nucleus of the solitary tract and the rostral ventrolateral medulla. SHR-T exhibited restored BBB permeability and normalized vesicles counting/capillary simultaneously with a normal autonomic modulation of heart and vessels, resting bradycardia and partial pressure reduction. Caveolin-1 expression ratified the counting of transcellular, not other cytoplasmatic vesicles. Additionally, T caused in both groups significant increases in tight junctions' extension/capillary border. Discussion: Data indicate that transcytosis, not the paracellular transport, is the primary mechanism underlying both hypertension- and exercise-induced BBB permeability changes within autonomic areas. The reduced BBB permeability contributes to normalize the autonomic control of the circulation, which suppresses pressure variability and reduces the occurrence of end-organ damage in the trained SHR. Data also disclose that hypertension does not change but exercise training strengthens the resistance of the paracellular pathway in both strains.

Remodeling of the Neurovascular Unit Following Cerebral Ischemia and Hemorrhage

Formulated as a group effort of the stroke community, the transforming concept of the neurovascular unit (NVU) depicts the structural and functional relationship between brain cells and the vascular structure. Composed of both neural and vascular elements, the NVU forms the blood-brain barrier that regulates cerebral blood flow to meet the oxygen demand of the brain in normal physiology and maintain brain homeostasis. Conversely, the dysregulation and dysfunction of the NVU is an essential pathological feature that underlies neurological disorders spanning from chronic neurodegeneration to acute cerebrovascular events such as ischemic stroke and cerebral hemorrhage, which were the focus of this review. We also discussed how common vascular risk factors of stroke predispose the NVU to pathological changes. We synthesized existing literature and first provided an overview of the basic structure and function of NVU, followed by knowledge of how these components remodel in response to ischemic stroke and brain hemorrhage. A greater understanding of the NVU dysfunction and remodeling will enable the design of targeted therapies and provide a valuable foundation for relevant research in this area.

Changes in the choroid plexuses and brain barriers associated with high blood pressure and ageing

INTRODUCTION

The choroid plexuses, blood vessels, and brain barriers are closely related both in terms of morphology and function. Hypertension causes changes in cerebral blood flow and in small vessels and capillaries of the brain. This review studies the effects of high blood pressure (HBP) on the choroid plexuses and brain barriers.

DEVELOPMENT

The choroid plexuses (ChP) are structures located in the cerebral ventricles, and are highly conserved both phylogenetically and ontogenetically. The ChPs develop during embryogenesis, forming a functional barrier during the first weeks of gestation. They are composed of highly vascularised epithelial tissue covered by microvilli, and their main function is cerebrospinal fluid (CSF) production. The central nervous system (CNS) is protected by the blood-brain barrier (BBB) and the blood-CSF barrier (BCSFB). While the BBB is formed by endothelial cells of the microvasculature of the CNS, the BCSFB is formed by epithelial cells of the choroid plexuses. Chronic hypertension induces vascular remodelling. This prevents hyperperfusion at HBPs, but increases the risk of ischaemia at low blood pressures. In normotensive individuals, in contrast, cerebral circulation is self-regulated, blood flow remains constant, and the integrity of the BBB is preserved.

CONCLUSIONS

HBP induces changes in the choroid plexuses that affect the stroma, blood vessels, and CSF production. HBP also exacerbates age-related ChP dysfunction and causes alterations in the brain barriers, which are more marked in the BCSFB than in the BBB. Brain barrier damage may be determined by quantifying blood S-100β and TTRm levels.

Poloxamer based Urapidil Loaded Chitosan Microparticle in Approach to Improve the Mechanical Strength by Tensile Strength and Entrapment Determination

Background:

The literature review highlighted the issues related to the poor mechanical strength of chitosan-based microparticles. In an attempt to resolve the stated drawback, the microparticles are prepared with a suitable combination of poloxamer-188 (pluronic) and chitosan-based hydrogels.

Objective:

The current study deals with urapidil-loaded chitosan microparticles incorporating chitosan-based hydrogels and small polyanionic electrolytes. The mechanical strength was ascertained by entrapment efficiency and texture analyzer.

Method:

Chitosan-based hydrogels and the combination of poloxamer and further microparticles are prepared by counter-ion aggregation technique in polyanionic electrolyte medium (20 % w/v). During the preparation, poloxamer is incorporated to improve the mechanical strength, which is ascertained in terms of adhesive strength (tensile strength) by texture analyzer and entrapment efficiency. The prepared microparticles are also subjected to micrometric studies, swelling index, surface morphology study, drug-polymer interaction study, and zeta analysis.

Result:

It was observed that there is a remarkable increase in entrapment efficiency (maximum of 78.56 % from SSP4) with the progressive increase in poloxamer-188. In addition to that, adhesive strength was also studied by a texture analyzer for all microparticles. Sodium citrate-based products exhibited superior adhesive strength values compared to sodium sulfate and sodium tripolyphosphate-based and signified the incorporation of poloxamer-188. A significant finding was also recorded for the swelling properties to microenvironmental pH attributed to polyanions. It observed Sodium TPP microparticles continued to swell in phosphate buffer pH 6.8. Zeta value was found to be maximum with -5.2 mV; it could further be improved by adding electrolytes. TPP4 showed a comparatively larger particle size of 8.07 µm. Polydispersity index value ascertained homogenous dispersion of microparticles. SEM study revealed prominent porous surfaces for sodium tripolyphosphate microparticles.

Conclusion:

The study revealed that the addition of poloxamer-188 improved the mechanical strength, identified by entrapment efficiency and texture analysis. SCP4 microparticle was found to be the best formulation among all.

Blood-Brain Barrier Transporters: Opportunities for Therapeutic Development in Ischemic Stroke

Globally, stroke is a leading cause of death and long-term disability. Over the past decades, several efforts have attempted to discover new drugs or repurpose existing therapeutics to promote post-stroke neurological recovery. Preclinical stroke studies have reported successes in identifying novel neuroprotective agents; however, none of these compounds have advanced beyond a phase III clinical trial. One reason for these failures is the lack of consideration of blood-brain barrier (BBB) transport mechanisms that can enable these drugs to achieve efficacious concentrations in ischemic brain tissue. Despite the knowledge that drugs with neuroprotective properties (i.e., statins, memantine, metformin) are substrates for endogenous BBB transporters, preclinical stroke research has not extensively studied the role of transporters in central nervous system (CNS) drug delivery. Here, we review current knowledge on specific BBB uptake transporters (i.e., organic anion transporting polypeptides (OATPs in humans; Oatps in rodents); organic cation transporters (OCTs in humans; Octs in rodents) that can be targeted for improved neuroprotective drug delivery. Additionally, we provide state-of-the-art perspectives on how transporter pharmacology can be integrated into preclinical stroke research. Specifically, we discuss the utility of in vivo stroke models to transporter studies and considerations (i.e., species selection, co-morbid conditions) that will optimize the translational success of stroke pharmacotherapeutic experiments.

A Review of Risk Factors and Predictors for Hemorrhagic Transformation in Patients with Acute Ischemic Stroke

Acute ischemic strokes (AIS) and hemorrhagic strokes lead to disabling neuropsychiatric and cognitive deficits. A serious and fatal complication of AIS is the occurrence of hemorrhagic transformation (HT). HT is cerebral bleeding that occurs after an ischemic event in the infarcted areas. This review summarises how specific risk factors such as demographic factors like age, gender, and race/ethnicity, comorbidities including essential hypertension, atrial fibrillation, diabetes mellitus, congestive heart failure, and ischemic heart disease along with predictors like higher NIHSS score, larger infarction size, cardioembolic strokes, systolic blood pressure/pulse pressure variability, higher plasma glucose levels, and higher body temperature during ischemic event, lower low-density lipoprotein and total cholesterol, early ischemic changes on imaging modalities, and some rare causes make an individual more susceptible to developing HT. We also discuss few other risk factors such as the role of blood-brain barrier, increased arterial stiffness, and globulin levels in patients postreperfusion using thrombolysis and mechanical thrombectomy. In addition, we discuss the implications of dual antiplatelet therapy and the length of treatment in reference to the incidence of developing HT. Current research into inflammatory mediators and biomarkers such as Cyclooxygenase-2, matrix metalloproteinases, and soluble ST2 and their potential role as treatment options for HT is also briefly discussed. Finally, this review calls for more research into use of dual antiplatelet and the timing of antiplatelet and anticoagulant use in reference to hemorrhagic transformation.

Dysfunction of the Blood-brain Barrier in Cerebral Microbleeds: from Bedside to Bench

Cerebral microbleeds (CMBs) are a disorder of cerebral microvessels that are characterized as small (<10 mm), hypointense, round or ovoid lesions seen on T2*-weighted gradient echo MRI. There is a high prevalence of CMBs in community-dwelling healthy older people. An increasing number of studies have demonstrated the significance of CMBs in stroke, dementia, Parkinson's disease, gait disturbances and late-life depression. Blood-brain barrier (BBB) dysfunction is considered to be the event that initializes CMBs development. However, the pathogenesis of CMBs has not yet been clearly elucidated. In this review, we introduce the pathogenesis of CMBs, hypertensive vasculopathy and cerebral amyloid angiopathy, and review recent research that has advanced our understanding of the mechanisms underlying BBB dysfunction and CMBs presence. CMBs-associated risk factors can exacerbate BBB breakdown through the vulnerability of BBB anatomical and functional changes. Finally, we discuss potential pharmacological approaches to target the BBB as therapy for CMBs.

Transcytosis within PVN capillaries: a mechanism determining both hypertension-induced blood-brain barrier dysfunction and exercise-induced correction

Although hypertension disrupts the blood-brain barrier (BBB) integrity within the paraventricular nucleus of hypothalamus (PVN) and increases the leakage into the brain parenchyma, exercise training (T) was shown to correct it. Since there is scarce and contradictory information on the mechanism(s) determining hypertension-induced BBB deficit and nothing is known about T-induced improvement, we sought to evaluate the paracellular and transcellular transport across the BBB within the PVN in both conditions. Spontaneously hypertensive rats (SHR) and WKY submitted to 4-wk aerobic T or sedentary (S) protocol were chronically catheterized for hemodynamic recordings at rest and intra-arterial administration of dyes (Rhodamine-dextran 70 kDa + FITC-dextran 10 kDa). Brains were harvesting for FITC leakage examination, qPCR evaluation of different BBB constituents and protein expression of caveolin-1 and claudin-5, the main markers of transcytosis and paracellular transport, respectively. Hypertension was characterized by increased arterial pressure and heart rate, augmented sympathetic modulation of heart and vessels, and reduced cardiac parasympathetic control, marked FITC extravasation into the PVN which was accompanied by increased caveolin-1 gene and protein expression, without changes in claudin-5 and others tight junctions' components. SHR-T vs. SHR-S showed a partial pressure reduction, resting bradycardia, improvement of autonomic control of the circulation simultaneously with correction of both FITC leakage and caveolin-1 expression; there was a significant increase in claudin-5 expression. Caveolin-1 content was strongly correlated with improved autonomic control after exercise. Data indicated that within the PVN the transcytosis is the main mechanism governing both hypertension-induced BBB leakage, as well as the exercise-induced correction.

Development of Novel Therapeutics Targeting the Blood-Brain Barrier: From Barrier to Carrier

The blood-brain barrier (BBB) is a highly specialized neurovascular unit, initially described as an intact barrier to prevent toxins, pathogens, and potentially harmful substances from entering the brain. An intact BBB is also critical for the maintenance of normal neuronal function. In cerebral vascular diseases and neurological disorders, the BBB can be disrupted, contributing to disease progression. While restoration of BBB integrity serves as a robust biomarker of better clinical outcomes, the restrictive nature of the intact BBB presents a major hurdle for delivery of therapeutics into the brain. Recent studies show that the BBB is actively engaged in crosstalk between neuronal and the circulatory systems, which defines another important role of the BBB: as an interfacing conduit that mediates communication between two sides of the BBB. This role has been subject to extensive investigation for brain-targeted drug delivery and shows promising results. The dual roles of the BBB make it a unique target for drug development. Here, recent developments and novel strategies to target the BBB for therapeutic purposes are reviewed, from both barrier and carrier perspectives.

Contrast-Induced Encephalopathy after Cerebral Angiogram: A Case Series and Review of Literature

Contrast-induced encephalopathy (CIE) is a rare complication that arises from exposure to iodinated contrast medium and can result in a range of symptoms, including cortical blindness, aphasia, focal neurological deficits, and altered mental status. We present 4 individual cases of CIE who presented with stroke-mimic symptoms following surgery with localized iodixanol or ioversol injection. We outline a clinical timeline of all patients, showing that CIE follows a general pattern of delayed onset, worsening symptomology, and ultimately full recovery. All patients received IV hydration, corticosteroids, or both as part of their treatment protocol.

Hemorrhagic Transformation in Ischemic Stroke and the Role of Inflammation

Hemorrhagic transformation (HT) is a common complication in patients with acute ischemic stroke. It occurs when peripheral blood extravasates across a disrupted blood brain barrier (BBB) into the brain following ischemic stroke. Preventing HT is important as it worsens stroke outcome and increases mortality. Factors associated with increased risk of HT include stroke severity, reperfusion therapy (thrombolysis and thrombectomy), hypertension, hyperglycemia, and age. Inflammation and the immune system are important contributors to BBB disruption and HT and are associated with many of the risk factors for HT. In this review, we present the relationship of inflammation and immune activation to HT in the context of reperfusion therapy, hypertension, hyperglycemia, and age. Differences in inflammatory pathways relating to HT are discussed. The role of inflammation to stratify the risk of HT and therapies targeting the immune system to reduce the risk of HT are presented.

Greater intraprocedural systolic blood pressure and blood pressure variability are associated with contrast-induced neurotoxicity after neurointerventional procedures

BACKGROUND

Contrast-induced neurotoxicity (CIN) is a rare complication of neurointerventional procedures and its understanding remains limited. We evaluated the association of CIN with systemic hemodynamics in patients undergoing neuroendovascular interventions.

METHODS

We conducted a 1:2 matched case-control study from a prospectively collected database of 2510 neurointerventional patients. We defined CIN as new neurological deficits presented ≤24 h post-operation after excluding other possible etiologies. We obtained demographic, clinical and imaging data, and baseline and intraprocedural blood pressures (BP) from medical records. The area between baseline and intraprocedural BP was used to measure sustained variability of BP over time. A generalized linear mixed model and generalized estimating equation were used to analyze the BP difference between groups over time.

RESULTS

We evaluated 11 CIN cases and 22 controls. 2746 and 5837 min of continued BP data were analyzed for cases and controls, respectively. CIN cases had higher measurements and greater variability for: Systolic BP (SBP) [median 125 (IQR:121-147) vs. 114 (IQR:107-124) mmHg], median area above baseline [median 350 (IQR:25-1328) vs. 52 (IQR:0-293) mmHg*minutes] and mean arterial pressure (MAP) [median 85 (IQR:79-98) vs. 80 (IQR:74-89) mmHg]. CIN cases demonstrated a significant mean increase in SBP and MAP of 23.41 mmHg (p < 0.01) and 13.79 mmHg (p < 0.01) when compared to controls, respectively, over the perioperative time.

CONCLUSION

Sustained hypertension and high BP variability may contribute to the pathophysiology of CIN. Acute hypertension can increase blood-brain barrier permeability and potentially allow contrast to leak into the brain parenchyma causing direct toxicity and CIN symptoms.

Repairing blood-CNS barriers: Future therapeutic approaches for neuropsychiatric disorders

Central nervous system (CNS) drug development faces significant difficulties that translate into high rates of failure and lack of innovation. The pathophysiology of neurological and psychiatric disorders often results in the breakdown of blood-CNS barriers, disturbing the CNS microenvironment and worsening disease progression. Therefore, restoring the integrity of blood-CNS barriers may have a beneficial influence in several CNS disorders and improve treatment outcomes. In this review, pathways that may be modulated to protect blood-CNS barriers from neuroinflammatory and oxidative insults are featured. First, the participation of the brain endothelium and glial cells in disruption processes is discussed. Then, the relevance of regulatory systems is analysed, specifically the hypothalamic-pituitary axis, the renin-angiotensin system, sleep and circadian rhythms, and glutamate neurotransmission. Lastly, compounds of endogenous and exogenous origin that are known to mediate the repair of blood-CNS barriers are presented. We believe that enhancing the protection of blood-CNS barriers is a promising therapeutic strategy to pursue in the future.

Blood-brain barrier dysfunction: the undervalued frontier of hypertension

The blood-brain barrier (BBB) constitutes the complex anatomic and physiologic interface between the intravascular compartment and the central nervous system, and its integrity is paramount for the maintenance of the very sensitive homeostasis of the central nervous system. Arterial hypertension is a leading cause of morbidity and mortality. The BBB has been shown to be disrupted in essential hypertension. BBB integrity is important for central autonomic control and this may be implicated in the pathophysiology of hypertension. On the other hand, evidence from experimental studies indicates that BBB disruption can be present in both hypertensive disease and dementia syndromes, suggesting a possibly key position of loss of BBB integrity in the pathophysiological pathways linking arterial hypertension with cognitive decline. Although much still remains to be elucidated with respect to the exact underlying mechanisms, the discovery of novel pathological pathways has changed our understanding of adult dementia and central nervous system disease overall, pointing out-in parallel-new potential therapeutic targets. The aim of this review is to summarize current scientific knowledge relevant to the pathophysiologic pathways that are involved in the disruption of the BBB function and potentially mediate hypertension-induced cognitive impairment. In parallel, we underline the differential cognition-preserving effect of several antihypertensive agents of similar blood pressure-lowering capacity, highlighting the presence of previously under-recognized BBB-protective actions of these drugs.

Acute-onset coma after iso-osmolar iodinated contrast injection: a case report of contrast-induced encephalopathy after elective coronary angiography

Background

Contrast-induced encephalopathy (CIE) is a rare complication of coronary angiography (CAG) caused by a direct neurotoxic reaction to iodinated contrast medium. Contrast-induced encephalopathy can result in a variety of neurological symptoms following within minutes to hours after contrast injection. It manifests most frequently as transient cortical blindness, headache, or confusion. In the majority of known cases, symptoms completely resolve solely with supportive care. We present a case where CIE takes a more dramatic course.

Case summary

A 67-year-old woman was scheduled for elective CAG, due to progressive typical chest pain. Within minutes after injection of iso-osmolar iodinated contrast medium, the patient showed a sudden decline in consciousness while all other vital functions remained normal. Shortly, after the patient was admitted to the intensive care unit due to acute-onset coma and respiratory insufficiency. A computed tomography scan of the brain showed bilateral cerebral oedema, which in combination with the development of symptoms after contrast injection led to the diagnosis of CIE. Remarkable decrease of cerebral oedema was observed 1 day later and slowly clinical recovery ensued. After 23 days, the patient was discharged from the cardiology ward. Follow-up at the outpatient clinic showed no lasting neurological deficits.

Discussion

 While most symptoms of CIE are relatively mild and transient in nature, we describe a more devastating course that occurred with the use of only a low quantity of iso-osmolar contrast medium. We emphasize that even the more severe manifestations of CIE can develop at any dosage, and with all types of iodinated contrast medium.

Sleep/Wake Behaviors in Mice During Pregnancy and Pregnancy-Associated Hypertensive Mice

Study Objectives

In humans and other mammals, sleep is altered during pregnancy. However, no studies have been conducted on sleep/wakefulness during pregnancy in mice. In this study, we examined sleep/wakefulness in female C57BL/6 mice during pregnancy. We also examined sleep/wake behaviors in an animal model of preeclampsia, pregnancy-associated hypertensive (PAH) mice, in which increased angiotensin causes hypertension.

Methods

Sleep/wake behaviors of female C57BL/6 and PAH mice were examined based on electroencephalogram (EEG) or electromyogram recordings before, during, and after pregnancy. To examine whether high blood pressure disrupts the integrity of the blood-brain barrier in PAH mice, Evans blue dye was injected intravenously. Angiotensin II receptor blocker (olmesartan)-administered PAH mice and female Tsukuba hypertensive mice were also examined.

Results

C57BL/6 mice showed a decreased total wake time and increased nonrapid eye movement (NREM) sleep time during late pregnancy. Rapid eye movement (REM) sleep time did not change during the course of pregnancy. PAH mice exhibited a general slowing of EEG during late pregnancy and subsequently returned to apparently normal sleep/wakefulness after delivery. All PAH mice exhibited multiple focal leakages of Evans blue dye in the brain. Spike-and-wave discharges were observed in 50% of PAH mice. Olmesartan-administered PAH mice did not show general slowing of EEG. Tsukuba hypertensive mice showed a normal time spent in wakefulness and NREM sleep and a decreased total REM sleep time.

Conclusions

This study showed pregnant-stage-specific changes in sleep/wakefulness in C57BL/6 mice. Furthermore, PAH mice may be useful as an animal model for eclampsia.

Rosiglitazone attenuates cell apoptosis through antioxidative and anti-apoptotic pathways in the hippocampi of spontaneously hypertensive rats

Oxidative stress serves an important role in hypertensive brain damage. Peroxisome proliferator‑activated receptor γ (PPAR‑γ) agonists possess antioxidative and anti‑apoptotic effects. The present study verified the possibility that rosiglitazone serves a neuroprotective role by alleviating oxidative stress and cell apoptosis in the hippocampi of spontaneously hypertensive rats (SHRs). SHRs and age‑matched Wistar‑Kyoto (WKY; both 56 weeks old) rats received gavage administration of vehicle or rosiglitazone (5 mg/kg/day) for eight weeks. Systolic blood pressure (SBP) was measured by the indirect tail‑cuff method. The expression ratio of activated astrocytes was analyzed by glial fibrillary acidic protein immunohistochemistry. PPAR‑γ, inducible nitric oxide synthase (iNOS), gp47phox, B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated X protein (Bax) and caspase‑3 expression were investigated by quantitative polymerase chain reaction and western blot analysis. The number of apoptotic cells in the hippocampus of four groups was detected using the terminal deoxynucleotidyl transferase‑mediated dUTP end‑labeling (TUNEL) method. Compared with the WKY group, the SHR group exhibited decreased Bcl‑2 and PPAR‑γ expression, increased SBP, increased ratio of activated astrocytes and TUNEL‑positive cells, increased expression of iNOS, gp47phox, caspase‑3 and Bax. Rosiglitazone administration increased Bcl‑2 and PPAR‑γ expression, decreased the ratio of activated astrocytes and TUNEL‑positive cells, decreased iNOS, gp47phox, caspase‑3 and Bax expression in the hippocampi of SHRs. However, rosiglitazone did not significantly decreased SBP in the SHR group. Therefore, rosiglitazone exerts neuroprotective effect through antioxidative and anti‑apoptotic pathways, which was independent of blood pressure control.

Fullerenol Nanoparticles Decrease Blood-Brain Barrier Interruption and Brain Edema during Cerebral Ischemia-Reperfusion Injury Probably by Reduction of Interleukin-6 and Matrix Metalloproteinase-9 Transcription

BACKGROUND

The present study aimed to examine the protective role of fullerenol nanoparticles against blood-brain barrier (BBB) interruption and brain edema during cerebral ischemia-reperfusion injury probably by reduction of interleukin-6 (IL-6) and matrix metalloproteinase-9 (MMP-9) transcription.

METHODS

The male Wistar rats (weighting 280-320 g) were randomly assigned into four groups as follows: sham, control ischemic, pretreated ischemic, and posttreated ischemic groups. Cerebral ischemia-reperfusion (IR) injury was performed by occlusion of middle cerebral artery (MCA) for 90 minutes followed by twenty-four hours reperfusion. Rats were administered fullerenol 5mg/kg, intraperitoneally, 30 minutes before induction of IR in pretreated ischemic group and immediately after termination of MCA occlusion in posttreated ischemic group. After twenty-four hours reperfusion, the method of Evans blue dye extravasation (EBE) and RT-PCR were used for determination of BBB permeability and mRNA expression levels of MMP-9 and IL-6, respectively. Neuronal deficit score (NDS) and edema of the ischemic hemispheres were also evaluated.

RESULTS

MCA occlusion increased NDS in control ischemic rats (3.16 ± 0.16) with concomitant increase in EBE (15.30 ± 3.98µg/g) and edema (3.53 ± 0.50%). Fullerenol in both pretreated and posttreated ischemic groups reduced NDS (36% and 68%, respectively), EBE (89% and 91%, respectively) and edema (53% and 81%, respectively). Although MCA occlusion increased the mRNA expression levels of MMP-9 and IL-6 in ischemic hemispheres, fullerenol in both treatment groups noticeably decreased the mRNA expression levels of these genes.

CONCLUSION

In conclusion, fullerenol nanoparticles can protect BBB integrity and attenuate brain edema after cerebral ischemia-reperfusion injury possibly by reduction of IL-6 and MMP-9 transcription.

Maternal high-salt diet alters redox state and mitochondrial function in newborn rat offspring's brain

Excessive salt intake is a common feature of Western dietary patterns, and has been associated with important metabolic changes including cerebral redox state imbalance. Considering that little is known about the effect on progeny of excessive salt intake during pregnancy, the present study investigated the effect of a high-salt diet during pregnancy and lactation on mitochondrial parameters and the redox state of the brains of resulting offspring. Adult female Wistar rats were divided into two dietary groups (n 20 rats/group): control standard chow (0·675 % NaCl) or high-salt chow (7·2 % NaCl), received throughout pregnancy and for 7 d after delivery. On postnatal day 7, the pups were euthanised and their cerebellum, hypothalamus, hippocampus, prefrontal and parietal cortices were dissected. Maternal high-salt diet reduced cerebellar mitochondrial mass and membrane potential, promoted an increase in reactive oxygen species allied to superoxide dismutase activation and decreased offspring cerebellar nitric oxide levels. A significant increase in hypothalamic nitric oxide levels and mitochondrial superoxide in the hippocampus and prefrontal cortex was observed in the maternal high-salt group. Antioxidant enzymes were differentially modulated by oxidant increases in each brain area studied. Taken together, our results suggest that a maternal high-salt diet during pregnancy and lactation programmes the brain metabolism of offspring, favouring impaired mitochondrial function and promoting an oxidative environment; this highlights the adverse effect of high-salt intake in the health state of the offspring.

White matter microstructure and cognitive decline in metabolic syndrome: a review of diffusion tensor imaging

Metabolic syndrome is a cluster of cardiovascular risk factors defined by the presence of abdominal obesity, glucose intolerance, hypertension and/or dyslipidemia. It is a major public health epidemic worldwide, and a known risk factor for the development of cognitive dysfunction and dementia. Several studies have demonstrated a positive association between the presence of metabolic syndrome and worse cognitive outcomes, however, evidence of brain structure pathology is limited. Diffusion tensor imaging has offered new opportunities to detect microstructural white matter changes in metabolic syndrome, and a possibility to detect associations between functional and structural abnormalities. This review analyzes the impact of metabolic syndrome on white matter microstructural integrity, brain structure abnormalities and their relationship to cognitive function. Each of the metabolic syndrome components exerts a specific signature of white matter microstructural abnormalities. Metabolic syndrome and its components exert both additive/synergistic, as well as, independent effects on brain microstructure thus accelerating brain aging and cognitive decline.

Maintenance of Blood-Brain Barrier Integrity in Hypertension: A Novel Benefit of Exercise Training for Autonomic Control

The blood-brain barrier (BBB) is a complex multicellular structure acting as selective barrier controlling the transport of substances between these compartments. Accumulating evidence has shown that chronic hypertension is accompanied by BBB dysfunction, deficient local perfusion and plasma angiotensin II (Ang II) access into the parenchyma of brain areas related to autonomic circulatory control. Knowing that spontaneously hypertensive rats (SHR) exhibit deficient autonomic control and brain Ang II hyperactivity and that exercise training is highly effective in correcting both, we hypothesized that training, by reducing Ang II content, could improve BBB function within autonomic brain areas of the SHR. After confirming the absence of BBB lesion in the pre-hypertensive SHR, but marked fluorescein isothiocyanate dextran (FITC, 10 kD) leakage into the brain parenchyma of the hypothalamic paraventricular nucleus (PVN), nucleus of the solitary tract, and rostral ventrolateral medulla during the established phase of hypertension, adult SHR, and age-matched WKY were submitted to a treadmill training (T) or kept sedentary (S) for 8 weeks. The robust FITC leakage within autonomic areas of the SHR-S was largely reduced and almost normalized since the 2nd week of training (T₂). BBB leakage reduction occurred simultaneously and showed strong correlations with both decreased LF/HF ratio to the heart and reduced vasomotor sympathetic activity (power spectral analysis), these effects preceding the appearance of resting bradycardia (T₄) and partial pressure fall (T₈). In other groups of SHR-T simultaneously infused with icv Ang II or saline (osmotic mini-pumps connected to a lateral ventricle cannula) we proved that decreased local availability of this peptide and reduced microglia activation (IBA1 staining) are crucial mechanisms conditioning the restoration of BBB integrity. Our data also revealed that Ang II-induced BBB lesion was faster within the PVN (T₂), suggesting the prominent role of this nucleus in driven hypertension-induced deficits. These original set of data suggest that reduced local Ang II content (and decreased activation of its downstream pathways) is an essential and early-activated mechanism to maintain BBB integrity in trained SHR and uncovers a novel beneficial effect of exercise training to improve autonomic control even in the presence of hypertension.

Abnormal brain white matter microstructure is associated with both pre-hypertension and hypertension

Objectives

To characterize effects of chronically elevated blood pressure on the brain, we tested for brain white matter microstructural differences associated with normotension, pre-hypertension and hypertension in recently available brain magnetic resonance imaging data from 4659 participants without known neurological or psychiatric disease (62.3±7.4 yrs, 47.0% male) in UK Biobank.

Methods

For assessment of white matter microstructure, we used measures derived from neurite orientation dispersion and density imaging (NODDI) including the intracellular volume fraction (an estimate of neurite density) and isotropic volume fraction (an index of the relative extra-cellular water diffusion). To estimate differences associated specifically with blood pressure, we applied propensity score matching based on age, sex, educational level, body mass index, and history of smoking, diabetes mellitus and cardiovascular disease to perform separate contrasts of non-hypertensive (normotensive or pre-hypertensive, N = 2332) and hypertensive (N = 2337) individuals and of normotensive (N = 741) and pre-hypertensive (N = 1581) individuals (p<0.05 after Bonferroni correction).

Results

The brain white matter intracellular volume fraction was significantly lower, and isotropic volume fraction was higher in hypertensive relative to non-hypertensive individuals (N = 1559, each). The white matter isotropic volume fraction also was higher in pre-hypertensive than in normotensive individuals (N = 694, each) in the right superior longitudinal fasciculus and the right superior thalamic radiation, where the lower intracellular volume fraction was observed in the hypertensives relative to the non-hypertensive group.

Significance

Pathological processes associated with chronically elevated blood pressure are associated with imaging differences suggesting chronic alterations of white matter axonal structure that may affect cognitive functions even with pre-hypertension.

Cerebral Ischemia-Reperfusion Injuries in Vanadyl-Treated Diabetic Rats

BACKGROUND

Ischemic stroke recovery is poor in diabetic mellitus (DM). Vanadium compounds (vanadium) relieve DM signs, but their influences on cerebral ischemia/reperfusion injury (I/RI) are inconclusive. Herein, the intensity of I/RI was inspected in vanadium-treated DM rats.

METHODS

Rats made diabetic with a single intravenous dose of streptozocin (39 mg/kg). Normal and DM rats used water or vanadyl solution for 45 days. Under isoflurane anesthesia, right middle cerebral artery occlusion was performed for 60 minutes and 12 hours reperfusion. Ischemic rats were divided into untreated-control normal (ICN) and diabetic (ICD), vanadium-treated normal (IVTN) and diabetic (IVTD) groups (n=14 each). After neurological deficit score (NDS) test, the rats were sacrificed and their brain removed and stained with triphenyltetrazolium chloride (TTC) to measure cerebral infarct volume (CIV, mm³) or Evans blue extravasation (EBE, μg/g wet-tissue). Data analysis was performed using one-way ANOVA and Tukey's test (SPSS software, version 21.0) and P values <0.05 were considered statistically significant.

RESULTS

Blood glucose (BG, mg/dL) was similar in ICN and IVTN, elevated in IVTD and ICD (245±6 vs. 344±2, P<0.001). The increased CIV in ICN and IVTN was similar (48±2 and 34±5), very high in ICD but lower in IVTD (249±37 vs. 110±16, P<0.001). EBE was absent in non-lesioned hemispheres, similarly increased in lesioned hemispheres of ICN and IVTN (14±1 and 13±1). EBE in IVTD was significantly lower than ICD (21±2 vs. 33±5, P=0.01).

CONCLUSION

I/RI was moderate in normoglycemia and did not change with vanadium. Hyperglycemia robustly intensified I/RI. Vanadium ameliorated hyperglycemia and reduced I/RI. Nonetheless, more investigations are required to link the mechanisms of vanadium on DM and stroke injuries.

Blood-brain barrier dysfunction and recovery after ischemic stroke

The blood-brain barrier (BBB) plays a vital role in regulating the trafficking of fluid, solutes and cells at the blood-brain interface and maintaining the homeostatic microenvironment of the CNS. Under pathological conditions, such as ischemic stroke, the BBB can be disrupted, followed by the extravasation of blood components into the brain and compromise of normal neuronal function. This article reviews recent advances in our knowledge of the mechanisms underlying BBB dysfunction and recovery after ischemic stroke. CNS cells in the neurovascular unit, as well as blood-borne peripheral cells constantly modulate the BBB and influence its breakdown and repair after ischemic stroke. The involvement of stroke risk factors and comorbid conditions further complicate the pathogenesis of neurovascular injury by predisposing the BBB to anatomical and functional changes that can exacerbate BBB dysfunction. Emphasis is also given to the process of long-term structural and functional restoration of the BBB after ischemic injury. With the development of novel research tools, future research on the BBB is likely to reveal promising potential therapeutic targets for protecting the BBB and improving patient outcome after ischemic stroke.

Maternal protein restriction induced-hypertension is associated to oxidative disruption at transcriptional and functional levels in the medulla oblongata

Maternal protein restriction during pregnancy and lactation predisposes the adult offspring to sympathetic overactivity and arterial hypertension. Although the underlying mechanisms are poorly understood, dysregulation of the oxidative balance has been proposed as a putative trigger of neural-induced hypertension. The aim of the study was to evaluate the association between the oxidative status at transcriptional and functional levels in the medulla oblongata and maternal protein restriction induced-hypertension. Wistar rat dams were fed a control (normal protein; 17% protein) or a low protein ((Lp); 8% protein) diet during pregnancy and lactation, and male offspring was studied at 90 days of age. Direct measurements of baseline arterial blood pressure (ABP) and heart rate (HR) were recorded in awakened offspring. In addition, quantitative RT-PCR was used to assess the mRNA expression of superoxide dismutase 1 (SOD1) and 2 (SOD2), catalase (CAT), glutathione peroxidase (GPx), Glutamatergic receptors (Grin1, Gria1 and Grm1) and GABA(A)-receptor-associated protein like 1 (Gabarapl1). Malondialdehyde (MDA) levels, CAT and SOD activities were examined in ventral and dorsal medulla. Lp rats exhibited higher ABP. The mRNA expression levels of SOD2, GPx and Gabarapl1 were down regulated in medullary tissue of Lp rats (P<.05, t test). In addition, we observed that higher MDA levels were associated to decreased SOD (approximately 45%) and CAT (approximately 50%) activities in ventral medulla. Taken together, our data suggest that maternal protein restriction induced-hypertension is associated with medullary oxidative dysfunction at transcriptional level and with impaired antioxidant capacity in the ventral medulla.

Antihypertensive agents do not prevent blood-brain barrier dysfunction and cognitive deficits in dietary-induced obese mice

BACKGROUND

While vascular risk factors including Western-styled diet and obesity are reported to induce cognitive decline and increase dementia risk, recent reports consistently suggest that compromised integrity of cerebrovascular blood-brain barrier (BBB) may have an important role in neurodegeneration and cognitive deficits. A number of studies report that elevated blood pressure increases the permeability of BBB.

METHODS

In this study, we investigated the effects of antihypertensive agents, candesartan or ursodeoxycholic acid (UDCA), on BBB dysfunction and cognitive decline in wild-type mice maintained on high fat and fructose (HFF) diet for 24 weeks.

RESULTS

In HFF-fed mice, significantly increased body weight with elevated blood pressure, plasma insulin and glucose compared with mice fed with low-fat control chow was observed. Concomitantly, significant disruption of BBB and cognitive decline were evident in the HFF-fed obese mice. Hypertension was completely prevented by the coprovision of candesartan or UDCA in mice maintained on HFF diet, while only candesartan significantly reduced the body weight compared with HFF-fed mice. Nevertheless, BBB dysfunction and cognitive decline remained unaffected by candesartan or UDCA.

CONCLUSIONS

These data conclusively indicate that modulation of blood pressure and/or body weight may not be directly associated with BBB dysfunction and cognitive deficits in Western diet-induced obese mice, and hence antihypertensive agents may not be effective in preventing BBB disruption and cognitive decline. The findings may provide important mechanistical insights to obesity-associated cognitive decline and its therapy.

Cerebral Ischemia/Reperfusion Injury in the Hyperthyroid Rat

BACKGROUND

Hyperthyroidism as a risk factor for stroke is not conclusive. There are no definite data on the relationship between ischemic cerebrovascular injury and hyperthyroidism. This study was designed to define whether the outcomes of post-ischemic stroke injury are influenced by chronic hyperthyroidism.

METHODS

Two groups of hyperthyroid (HT) and control euthyroid rats of equal numbers (n=22) were included in the study. Hyperthyroidism was induced for 4 weeks by adding L-thyroxine (300 μg/kg) to drinking water. The middle cerebral artery occlusion technique was used to induce focal cerebral ischemia. Neurological disability (neurological deficit score [NDS]) was evaluated after 24 hours, and the rats were sacrificed to obtain their brain. Triphenyl Tetrazolium Chloride (TTC) staining and Evans Blue (EB) extravasation were used to quantify cerebral infarct volume and cerebrovascular integrity disruption. Data analysis was done using SPSS, version 21.

RESULTS

Thyroid hormones levels, T₃ (314±7 vs. 198±3 ng/dL;P=0.001) and T₄ (9.8±0.3 vs. 3.08±0.07 μg/dL;P=0.001), were significantly higher in the HT group than in the controls. Furthermore, most clinical signs seen in hyperthyroid patients were also present in the HT group. Comparison of the data on cerebral ischemia between the HT and control groups showed significant increases in the NDS (2.76±0.16 vs. 2.23±0.09;P=0.03), cerebral infarct volume (479±12 vs. 266±17 mm³;P=0.001), and EB extravasation (50.08±2.4 vs. 32.6±1.2 μg/g;P=0.001) in the former group.

CONCLUSION

The intensified cerebral infarct size and cerebrovascular integrity disruption suggested that chronic hyperthyroidism aggravated post-stroke injury in the rats. More investigation is required to analyze the pathological mechanisms underlying the association between cerebrovascular disease and hyperthyroidism.

Overproduction of nitric oxide intensifies brain infarction and cerebrovascular damage through reduction of claudin-5 and ZO-1 expression in striatum of ischemic brain

Nitric oxide (NO) overproduction has been demonstrated from different NO-synthase overexpression or hyperactivity after brain ischemia. Here, we examined the effects of inhibition of NO overproduction on brain infarction, cerebrovascular damage and expression of claudin-5 and zonula occludens-1 (ZO-1) in striatum of ischemic brain. The experiment was performed in three groups of rats; sham, control ischemia and ischemic treatment. Brain ischemia was induced by 60min of middle cerebral artery occlusion (MCAO) followed by 24h of reperfusion. Treated rats received L-NAME 30min before induction of ischemia (1mg/kg, i.p.). Infarct volume and histopathological changes of ischemic striatum were assessed by TTC and LFB staining methods, respectively. Ultimately, quantitative RT-PCR was used for assessment of claudins-5 and ZO-1 expression. MCAO in the control group induced infarction (135±25mm³) at large areas of striatum in accompany with neuronal damages, whereas L-NAME significantly reduced infarction (87±16mm³) and neuronal injuries. The mRNA of ZO-1 and claudin-5 decreased in ischemic striatum, whereas inhibition of NO overproduction by L-NAME attenuated this reduction for these genes. Our findings indicated that NO overproduction after brain ischemia plays a crucial role in neuronal damage especially at striatal regions. Hence, inhibition of excessive NO production may save striatal cerebrovascular integrity of ischemic brain.

Posterior Reversible Encephalopathy Syndrome After Transplantation: a Review

Posterior reversible encephalopathy syndrome (PRES) is a rare neurological disease. Recently, an increase in the number of transplantations has led to more cases being associated with PRES than what was previously reported. Calcineurin inhibitors (CNIs) are major risk factors for PRES in posttransplantation patients. The mechanisms of the development of PRES remain to be unclear. The typical clinical symptoms of PRES include seizures, acute encephalopathy syndrome, and visual symptoms. The hyperintense signal on fluid-attenuated inversion recovery image is the characteristic of the imaging appearance in these patients. In addition, other abnormal signals distributed in multiple locations are also reported in some atypical cases. Unfortunately, PRES is often not recognized or diagnosed too late due to complicated differential diagnoses, such as ischemic stroke, progressive multifocal leukoencephalopathy, and neurodegenerative diseases. Thus, this review emphasizes the importance of considering the possibility of PRES when neurological disturbances appear after solid organ transplantation or hematopoietic cell transplantation. Moreover, this review demonstrates the molecular mechanisms of PRES associated with CNIs after transplantation, which aims to help clinicians further understand PRES in the transplantation era.

Chronic Aerobic Exercise Decreases Lectin-Like Low Density Lipoprotein (LOX-1) Receptor Expression in Heart of Diabetic Rat

BACKGROUND

Overexpression of lectin-like low density lipoprotein (LOX-1) receptor plays an important role in hyperglycemia-induced vascular complications such as atherosclerosis. Based on the beneficial effects of exercise on preventing cardiovascular complications of diabetes, we aimed to examine the protective effects of aerobic exercise on expression of LOX-1 receptor and production of free radicals in the heart of diabetic rats.

METHODS

Four groups of rats were used: (n = 5 per group): sedentary normal, trained normal, sedentary diabetes and trained diabetes. Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg/kg). The exercise protocol was consisted of swimming 30 min/day, 5 days/week for eight weeks. Plasma glucose was evaluated at initiation, weeks 4 and 8 of experiment. At the end of experiment, rats were sacrificed and the heart was removed for determination of nitrate, malondialdehyde, and LOX-1 gene expression.

RESULTS

In normal non-diabetic rats, the blood glucose level was <150 mg/dl; however, the induction of diabetes resulted in levels more than >400 mg/dl. Gene expression of LOX-1 was increased in the heart of diabetic rats. Exercise reduced the gene expression of this protein in diabetic states without reducing the blood glucose. Finally, swimming exercise decreased the malondialdehyde and nitrate levels in heart tissue both in control and diabetic rats.

CONCLUSION

Swimming exercise reduces heart expression of the LOX-1 receptor in accompany with reduction of free radicals production. Since these parameters are important in generation of diabetic complications, swimming exercise is a good candidate for reducing these complications.

Hypertension-related alterations in white matter microstructure detectable in middle age

Most studies examining associations between hypertension and brain white matter microstructure have focused on older adults or on cohorts with a large age range. Because hypertension effects on the brain may vary with age, it is important to focus on middle age, when hypertension becomes more prevalent. We used linear mixed-effect models to examine differences in white matter diffusion metrics as a function of hypertension in a well-characterized cohort of middle-aged men (n=316; mean, 61.8 years; range, 56.7-65.6). Diffusion metrics were examined in 9 tracts reported to be sensitive to hypertension in older adults. Relative to normotensive individuals, individuals with long-standing hypertension (>5.6 years) showed reduced fractional anisotropy or increased diffusivity in most tracts. Effects were stronger among carriers than among noncarriers of the apolipoprotein E ε4 allele for 2 tracts connecting frontal regions with other brain areas. Significant differences were observed even after adjustment for potentially related lifestyle and cardiovascular risk factors. Shorter duration of hypertension or better blood pressure control among hypertensive individuals did not lessen the adverse effects. These findings suggest that microstructural white matter alterations appear early in the course of hypertension and may persist despite adequate treatment. Although longitudinal studies are needed to confirm these findings, the results suggest that prevention-rather than management-of hypertension may be vital to preserving brain health in aging.