Three-dimensional measurement of cerebral microvascular plasma perfusion, glial fibrillary acidic protein and microtubule associated protein-2 immunoreactivity after embolic stroke in rats: a double fluorescent labeled laser-scanning confocal microscopic study

Effect of salidroside on neuroprotection and psychiatric sequelae during the COVID-19 pandemic: A review

The coronavirus disease 2019 (COVID-19) pandemic has affected the mental health of individuals worldwide, and the risk of psychiatric sequelae and consequent mental disorders has increased among the general population, health care workers and patients with COVID-19. Achieving effective and widespread prevention of pandemic-related psychiatric sequelae to protect the mental health of the global population is a serious challenge. Salidroside, as a natural agent, has substantial pharmacological activity and health effects, exerts obvious neuroprotective effects, and may be effective in preventing and treating psychiatric sequelae and mental disorders resulting from stress stemming from the COVID-19 pandemic. Herein, we systematically summarise, analyse and discuss the therapeutic effects of salidroside in the prevention and treatment of psychiatric sequelae as well as its roles in preventing the progression of mental disorders, and fully clarify the potential of salidroside as a widely applicable agent for preventing mental disorders caused by stress; the mechanisms underlying the potential protective effects of salidroside are involved in the regulation of the oxidative stress, neuroinflammation, neural regeneration and cell apoptosis in the brain, the network homeostasis of neurotransmission, HPA axis and cholinergic system, and the improvement of synaptic plasticity. Notably, this review innovatively proposes that salidroside is a potential agent for treating stress-induced health issues during the COVID-19 pandemic and provides scientific evidence and a theoretical basis for the use of natural products to combat the current mental health crisis.

Nonalcoholic Fatty Liver Disease and Altered Neuropsychological Functions in Patients with Subcortical Vascular Dementia

NAFLD is the most common cause of abnormality in liver function tests. NAFLD is considered a potential cardiovascular risk factor and is linked to cardiovascular risk factors such as obesity, hypertension, type 2 diabetes, and dyslipidemia. Few previous studies have investigated whether NAFLD could be independently associated with cognitive impairment. The current study aims to find a possible role of NAFLD in the development of subcortical vascular dementia (sVaD). We considered NAFLD as a possible independent vascular risk factor or, considering its metabolic role, associated with other commonly accepted sVaD risk factors, i.e., lack of folate, vitamin B12, and vitamin D-OH25, and increased levels of homocysteine. We studied 319 patients diagnosed with sVaD. All patients underwent an abdominal ultrasound examination to classify steatosis into four levels (1-none up to 4-severe). sVaD patients were divided into two groups according to the presence or absence of NAFLD. Our results demonstrated a strong correlation between NAFLD and sVaD. Patients with the two comorbidities had worse neuropsychological outcomes and a worse metabolic profile. We also found a robust relationship between NAFLD and severe vitamin B12, folate, vitamin D hypovitaminosis, and higher hyperhomocysteinemia levels. This way, it is evident that NAFLD contributes to a more severe metabolic pathway. However, the strong relationship with the three parameters (B12, folate and vitamin D, and homocysteinemia) suggests that NAFLD can contribute to a proinflammatory condition.

Homocysteine in Neurology: A Possible Contributing Factor to Small Vessel Disease

Homocysteine (Hcy) is a sulfur-containing amino acid generated during methionine metabolism, accumulation of which may be caused by genetic defects or the deficit of vitamin B12 and folate. A serum level greater than 15 micro-mols/L is defined as hyperhomocysteinemia (HHcy). Hcy has many roles, the most important being the active participation in the transmethylation reactions, fundamental for the brain. Many studies focused on the role of homocysteine accumulation in vascular or degenerative neurological diseases, but the results are still undefined. More is known in cardiovascular disease. HHcy is a determinant for the development and progression of inflammation, atherosclerotic plaque formation, endothelium, arteriolar damage, smooth muscle cell proliferation, and altered-oxidative stress response. Conversely, few studies focused on the relationship between HHcy and small vessel disease (SVD), despite the evidence that mice with HHcy showed a significant end-feet disruption of astrocytes with a diffuse SVD. A severe reduction of vascular aquaporin-4-water channels, lower levels of high-functioning potassium channels, and higher metalloproteinases are also observed. HHcy modulates the N-homocysteinylation process, promoting a pro-coagulative state and damage of the cellular protein integrity. This altered process could be directly involved in the altered endothelium activation, typical of SVD and protein quality, inhibiting the ubiquitin-proteasome system control. HHcy also promotes a constant enhancement of microglia activation, inducing the sustained pro-inflammatory status observed in SVD. This review article addresses the possible role of HHcy in small-vessel disease and understands its pathogenic impact.

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.

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.

Small vessel disease to subcortical dementia: a dynamic model, which interfaces aging, cholinergic dysregulation and the neurovascular unit

Background

Small vessels have the pivotal role for the brain’s autoregulation. The arteriosclerosis-dependent alteration of the brain perfusion is one of the major determinants in small vessel disease. Endothelium distress can potentiate the flow dysregulation and lead to subcortical vascular dementia (sVAD). sVAD increases morbidity and disability. Epidemiological studies have shown that sVAD shares with cerebrovascular disease most of the common risk factors. The molecular basis of this pathology remains controversial.

Purpose

To detect the possible mechanisms between small vessel disease and sVAD, giving a broad vision on the topic, including pathological aspects, clinical and laboratory findings, metabolic process and cholinergic dysfunction.

Methods

We searched MEDLINE using different search terms (“vascular dementia”, “subcortical vascular dementia”, “small vessel disease”, “cholinergic afferents”, etc). Publications were selected from the past 20 years. Searches were extended to Embase, Cochrane Library, and LILIACS databases. All searches were done from January 1, 1998 up to January 31, 2018.

Results

A total of 560 studies showed up, and appropriate studies were included. Associations between traditional vascular risk factors have been isolated. We remarked that SVD and white matter abnormalities are seen frequently with aging and also that vascular and endothelium changes are related with age; the changes can be accelerated by different vascular risk factors. Vascular function changes can be heavily influenced by genetic and epigenetic factors.

Conclusion

Small vessel disease and the related dementia are two pathologies that deserve attention for their relevance and impact in clinical practice. Hypertension might be a historical problem for SVD and SVAD, but low pressure might be even more dangerous; CBF regional selective decrease seems to be a critical factor for small vessel disease-related dementia. In those patients, endothelium damage is a super-imposed condition. Several issues are still debatable, and more research is needed.

Achyranthes bidentata polypeptide k improves long-term neurological outcomes through reducing downstream microvascular thrombosis in experimental ischemic stroke

Achyranthes bidentata Bl. (A. bidentata) occupies an important position in traditional Chinese medicine owing to the property of promoting the circulation of blood and removing stasis. Achyranthes bidentata polypeptide k (ABPPk) is one of the active components isolated from A. bidentata. We previously demonstrated that ABPPk has potent neuroprotective effects against neuronal apoptosis both in vitro and in vivo, but the roles and mechanisms of ABPPk on long-term functional recovery after ischemic stroke remain unknown. In the current study, we investigated the neuroprotective effects of ABPPk on filament transient middle cerebral artery occlusion (tMCAO) rats and found that ABPPk reduced the infarct volume and maintained the neuronal integrity in the ischemic penumbra. Moreover, we found that ABPPk might reduce the formation of downstream microthrombus through preventing ischemic-induced oxidative damage of brain endothelial cells and activation of tissue factor (TF), plasminogen activator inhibitor-1 (PAI-1), and NF-κB. ABPPk also inhibited polymorphonuclear leukocytes (PMNs) infiltration and matrix metalloproteinase-2/-9 (MMP-2/-9) activation in the ischemic penumbra. Morris water maze, foot fault test, and modified neurological severity score were assessed for a period of 6 weeks following tMCAO. ABPPk improved long-term recognition abilities and neurological outcomes after stroke compared with saline-treated rats. Taken together, these results suggested that ABPPk is beneficial to the improvement of long-term outcomes after transient cerebral ischemia injury and can be used as a potential neuroprotective agent.

Low-dose fractionated irradiation promotes axonal regeneration beyond reactive gliosis and facilitates locomotor function recovery after spinal cord injury in beagle dogs

Injury to the adult central nervous system (CNS) results in the formation of glial scar tissues. Glial scar-induced failure of regenerative axon pathfinding may limit axon regrowth beyond the lesion site and cause incorrect reinnervation and dystrophic appearance of stalled growth after CNS trauma. Glial scars also upregulate chondroitin sulphate proteoglycans (CSPGs) and expression of proinflammatory factor(s) that form a barrier to axonal regeneration. Therefore, interventions for glial scarring are an attractive strategy for augmenting axonal sprouting and regeneration and overcoming the physical and molecular barriers impeding functional repair. The glial reaction occurs shortly after spinal cord injury (SCI) and can persist for days or weeks with upregulation of cell cycle proteins. In this study, we utilised Beagle dogs to establish a preclinical SCI model and examine the efficacy of low-dose fractionated irradiation (LDI) treatment, which was performed once a day for 14 days (2 Gy per dose, 28 Gy in total). Low-dose fractionated irradiation is a stable method for suppressing cell activation and proliferation through interference in the cell cycle. Our results demonstrated that LDI could reduce astrocyte and microglia activation/proliferation and attenuate CSPGs and IL-1β expression. Low-dose fractionated irradiation also promoted and provided a pathway for long-distance axon regeneration beyond the lesion site, induced reinnervation of axonal targets and restored locomotor function after SCI in Beagle dogs. Taken together, our findings suggest that LDI would be a promising therapeutic strategy for targeting glial scarring, promoting axon regeneration and facilitating reconstruction of functional circuits after SCI.

Decline of microtubule-associated protein tau after experimental stroke in differently aged wild-type and 3xTg mice with Alzheimer-like alterations

Stroke therapies are still limited to a minority of patients. Considering time-dependent aspects of stroke, the penumbra concept describes the transition from functional to permanent tissue damage. Thereby, the role of cytoskeletal elements, as for instance microtubules with associated tau remains poorly understood and is therefore not yet considered for therapeutic approaches. This study explored the expression of microtubule-associated protein tau related to neuronal damage in stroke-affected brain regions. Wild-type and triple-transgenic mice of 3, 7 and 12months of age and with an Alzheimer-like background underwent experimental stroke. After 24h, brain sections were used for immunofluorescence labeling of tau and Neuronal Nuclei (NeuN). Potential functional consequences of cellular alterations were explored by statistical relationships to the general health condition, i.e. neurobehavioral deficits and loss of body weight. Immunoreactivity for whole tau decreased significantly in ischemic areas, while the decline at the border zone was more drastic for tau-immunoreactivity compared with the diminished NeuN labeling. Quantitative analyses confirmed pronounced sensitivity for tau-immunoreactivity in the ischemic border zone. Decline of tau- as well as NeuN-immunoreactivity correlated with body weight loss during the 24-h observation period. In conclusion, microtubule-associated protein tau was robustly identified as a highly sensitive cytoskeletal constitute under ischemic conditions, suggesting a pivotal role during the transition process toward long-lasting tissue damage. Consequently, cytoskeletal elements appear as promising targets for novel therapeutic approaches with the objective to impede ischemia-induced irreversible cellular degradation.

Stroke increases neural stem cells and angiogenesis in the neurogenic niche of the adult mouse

The unique cellular and vascular architecture of the adult ventricular-subventricular zone (V/SVZ) neurogenic niche plays an important role in regulating neural stem cell function. However, the in vivo identification of neural stem cells and their relationship to blood vessels within this niche in response to stroke remain largely unknown. Using whole-mount preparation of the lateral ventricle wall, we examined the architecture of neural stem cells and blood vessels in the V/SVZ of adult mouse over the course of 3 months after onset of focal cerebral ischemia. Stroke substantially increased the number of glial fibrillary acidic protein (GFAP) positive neural stem cells that are in contact with the cerebrospinal fluid (CSF) via their apical processes at the center of pinwheel structures formed by ependymal cells residing in the lateral ventricle. Long basal processes of these cells extended to blood vessels beneath the ependymal layer. Moreover, stroke increased V/SVZ endothelial cell proliferation from 2% in non-ischemic mice to 12 and 15% at 7 and 14 days after stroke, respectively. Vascular volume in the V/SVZ was augmented from 3% of the total volume prior to stroke to 6% at 90 days after stroke. Stroke-increased angiogenesis was closely associated with neuroblasts that expanded to nearly encompass the entire lateral ventricular wall in the V/SVZ. These data indicate that stroke induces long-term alterations of the neural stem cell and vascular architecture of the adult V/SVZ neurogenic niche. These post-stroke structural changes may provide insight into neural stem cell mediation of stroke-induced neurogenesis through the interaction of neural stem cells with proteins in the CSF and their sub-ependymal neurovascular interaction.

Critical role of the astrocyte for functional remodeling in contralateral hemisphere of somatosensory cortex after stroke

After ischemic stroke, the corresponding area contralateral to the lesion may partly compensate for the loss of function. We previously reported the remodeling of neuronal circuits in the contralateral somatosensory cortex (SSC) during the first week after infarction for processing bilateral information, resulting in functional compensation. However, the underlying processes in the contralateral hemisphere after stroke have not yet been fully elucidated. Recent studies have shown that astrocytes may play critical roles in synaptic reorganization and functional compensation after a stroke. Thus, we aim to clarify the contribution of astrocytes using a rodent stroke model. In vivo calcium imaging showed a significantly large number of astrocytes in the contralateral SSC responding to ipsilateral limb stimulation at the first week after infarction. Simultaneously, extracellular glutamine level increased, indicating the involvement of astrocytes in the conversion of glutamate to glutamine, which may be an important process for functional recovery. This hypothesis was supported further by the observation that application of (2S,3S)-3-{3-[4-(trifluoromethyl)benzoylamino]benzyloxy} aspartate, a glial glutamate transporter blocker, disturbed the functional recovery. These findings indicate the involvement of astrocytes in functional remodeling/recovery in the area contralateral to the lesion. Our study has provided new insights into the mechanisms underlying synaptic remodeling after cerebral infarction, which contributes to the development of effective therapeutic approaches for patients after a stroke.

Glial reactivity in resistance to methamphetamine-induced neurotoxicity

Neurotoxic regimens of methamphetamine (METH) result in reactive microglia and astrocytes in striatum. Prior data indicate that rats with partial dopamine (DA) loss resulting from prior exposure to METH are resistant to further decreases in striatal DA when re-exposed to METH 30 days later. Such resistant animals also do not show an activated microglia phenotype, suggesting a relation between microglial activation and METH-induced neurotoxicity. To date, the astrocyte response in such resistance has not been examined. Thus, this study examined glial-fibrillary acidic protein (GFAP) and CD11b protein expression in striata of animals administered saline or a neurotoxic regimen of METH on post-natal days 60 and/or 90 (Saline:Saline, Saline:METH, METH:Saline, METH:METH). Consistent with previous work, animals experiencing acute toxicity (Saline:METH) showed both activated microglia and astocytes, whereas those resistant to the acute toxicity (METH:METH) did not show activated microglia. Interestingly, GFAP expression remained elevated in rats exposed to METH at PND60 (METH:Saline), and was not elevated further in resistant rats treated for the second time with METH (METH:METH). These data suggest that astrocytes remain reactive up to 30 days post-METH exposure. In addition, these data indicate that astrocyte reactivity does not reflect acute, METH-induced DA terminal toxicity, whereas microglial reactivity does.

Microtubule-associated protein 2, an early blood marker of ischemic brain injury

The aim of this study was to develop a sensitive and rapid blood marker to detect ischemic brain injury, because imaging techniques have a limited capacity to identify lesions during the first crucial hours without massive tissue destruction. Rats were subjected to middle cerebral artery occlusion for various durations (0.5-3 hr), followed by reperfusion. At different time points after ischemia and/or ischemia-reperfusion, the amounts of glial fibrillary acidic protein (GFAP) and microtubule-associated protein 2 (MAP2) in the cerebrospinal fluid (CSF) and serum were analyzed by Western blotting. Brain infarction was observed in an ischemia-duration-dependent manner. GFAP was drastically increased in the CSF 24 and 48 hr after reperfusion, without change in the serum level. Serum levels of MAP2 remarkably increased as early as 0.5 hr of ischemia, much earlier than the observation of minimal tissue injury 3 hr following occlusion. The serum MAP2 level was further increased by a short period (2 hr) of reperfusion, even in 0.5- and 1-hr ischemic rats, despite not observing any typical tissue injuries 24 hr after reperfusion. These results indicate that the MAP2 protein may be able to detect early neuronal injuries, because the level of this protein in the blood spikes before the appearance of visible macrolesions. Therefore, MAP2 could potentially be used as a novel early marker for the detection of a neurotoxic insult.

CSF transthyretin neuroprotection in a mouse model of brain ischemia

Brain injury caused by ischemia is a major cause of human mortality and physical/cognitive disability worldwide. Experimentally, brain ischemia can be induced surgically by permanent middle cerebral artery occlusion. Using this model, we studied the influence of transthyretin in ischemic stroke. Transthyretin (TTR) is normally responsible for the transport of thyroid hormones and retinol in the blood and CSF. We found that TTR null mice (TTR(-/-) ) did not show significant differences in cortical infarction 24 h after permanent middle cerebral artery occlusion compared with TTR(+/+) control littermates. However, TTR null mice, heterozygous for the heat-shock transcription factor 1 (TTR(-/-) HSF1(+/-) mice), which compromised the stress response, showed a significant increase in cortical infarction, cerebral edema and the microglial-leukocyte response compared with TTR(+/+) HSF1(+/-) mice. Unexpectedly, we observed novel TTR distribution throughout the infarct, localized to disintegrated β-tubulin III(+) neurons and cell debris. Specific elimination of TTR synthesis in the liver by RNAi had no effect on TTR distribution in the infarct, indicating that the observed TTR infiltration derived from CSF and not from the serum. This finding is corroborated by results from 'in situ' hybridization and real time PCR that excluded the presence of transthyretin mRNA in the infarct and peri-infarct areas. Our data suggest that in conditions of a compromised heat-shock response, CSF TTR contributes to control neuronal cell death, edema and inflammation, thereby influencing the survival of endangered neurons in cerebral ischemia.

Rat focal cerebral ischemia induced astrocyte proliferation and delayed neuronal death are attenuated by cyclin-dependent kinase inhibition

Astroglial proliferation and delayed neuronal death are two common pathological processes in the ischemic brain. However, it is not clear if astrogliosis causes delayed neuronal death. In this study, we addressed this potential linkage by examining the relationship between attenuated astrocyte proliferation, induced by cyclin-dependent kinase (CDK) inhibition, and delayed neuronal death in rat ischemic hippocampus. Our results show that following middle cerebral artery occlusion (MCAO), astrocyte hypertrophy and proliferation were closely associated with delayed neuronal death. Importantly, administration of olomoucine, a selective CDK inhibitor, not only suppressed astroglial proliferation and glial scar formation, but also decreased neuronal cell death in the ischemic boundary zone and hippocampal CA1 region at days 1 and 30 after MCAO. These results indicate that reactive astrogliosis and delayed neuronal death, at least in rat hippocampus, are sequential pathological events following MCAO. Therefore, suppressing astroglial cell cycle progression in acute focal cerebral ischemia may be beneficial to neuronal survival. Our study also implies that cell cycle regulation should be considered as a promising future therapeutic intervention in treating those neurological diseases characterized by an excessive astrocyte proliferation.

Inhibiting cell cycle progression reduces reactive astrogliosis initiated by scratch injury in vitro and by cerebral ischemia in vivo

Astrogliosis occurs in a variety of neuropathological disorders and injuries, and excessive astrogliosis can be devastating to the recovery of neuronal function. In this study, we asked whether reactive astrogliosis can be suppressed in the lesion area by cell cycle inhibition and thus have therapeutic benefits. Reactive astrogliosis induced in either cultured astrocytes by hypoxia or scratch injury, or in a middle cerebral artery occlusion (MCAO) ischemia model were combined to address this issue. In the cultured astrocytes, hypoxia induced a cell cycle activation that was associated with upregulation of the proliferating cell nuclear marker (PCNA). Significantly, the cell cycle inhibitor, olomoucine, inhibited hypoxia-induced cell cycle activation by arresting the cells at G1/S and G2/M in a dose-dependent manner and also reversed hypoxia-induced upregulation of PCNA. Also in the cultured astrocytes, scratch injury induced reactive astrogliosis, such as hypertrophy and an increase in BrdU(+) astrocytes, both of which were ameliorated by olomoucine. In the MCAO ischemia mouse model, dense reactive glial fibrillary acidic protein and PCNA immunoreactivity were evident at the boundary zone of focal cerebral ischemia at days 7 and 30 after MCAO. We found that intraperitoneal olomoucine administration significantly inhibited these astrogliosis-associated changes. To demonstrate further that cell cycle regulation impacts on astrogliosis, cyclin D1 gene knockout mice (cyclin D1(-/-)) were subjected to ischemia, and we found that the percentage of Ki67-positive astrocytes in these mice was markedly reduced in the boundary zone. The number of apoptotic neurons and the lesion volume in cyclin D1(-/-) mice also decreased as compared to cyclin D1(+/+) and cyclin D1(+/-) mice at days 3, 7, and 30 after local cerebral ischemia. Together, these in vitro and in vivo results strongly suggest that astrogliosis can be significantly affected by cell cycle inhibition, which therefore emerges as a promising intervention to attenuate reactive glia-related damage to neuronal function in brain pathology.

Expression of cytoskeleton and apoptosis related genes after cerebral infarction

OBJECTIVE

The aim of the study was to investigate the expression and regulation of cytoskeleton and apoptosis related genes in several brain areas after cerebral infarction.

METHODS

Tissues were collected from ten autopsy brains from cerebral infarction patients. Using immunohistochemistry, several cytoskeleton and apoptosis related genes were examined in these tissues. The genes included microtubule-associated protein (MAP), glial fibrillary acidic protein (GFAP), neurofilament protein (NF-200), apoptosis gene bc1-2 and factor VIII related antigen (F-VIII). Based on morphological changes in the damaged areas after infarction, the focus and the surrounding areas of injured brain were divided into four areas.

RESULTS

In area 0, there was almost no cell survival after infraction, and all markers mentioned above were negative in this area. In addition, both MAP-2 and NF200 like immunoreactivities were dramatically down-regulated in area 1. However, in area 2 and area 3, MAP-2 and NF-200 expressed at normal level. GFAP- and F-VIII immunoreactive cells could hardly found in areas 0 and 1. In the short phase of ischemia, both GFAP and F-immmunoreactive cells could be seen in areas 2 and 3, and the number of GFAP and F (positive cells) was strongly increased in the long phase of ischemia. Bcl-2 immunoreactive cells were only seen in area 2.

CONCLUSION

Cerebral infarction causes cell death and physipathological changes of cytoskeleton and apoptosis related genes.

Increased Transcription Factor Expression and Permeability of the Blood Brain Barrier Associated With Cardiopulmonary Bypass in Lambs

BACKGROUND

The pathophysiology of neurocognitive dysfunction and developmental delay after cardiopulmonary bypass (CPB) in infants is not known. It is known that head trauma, stroke, and seizures cause dysfunction of the blood brain barrier (BBB) that is associated with increased inducible transcription factor gene expression in the cells of the barrier. The purpose of this study was to determine the effects of CPB and hypothermic circulatory arrest on expression of the transcription factor FOS and the function of the BBB in an infant animal model.

METHODS

Infant lambs (n = 36; 10-12 days) were exposed to 0, 15, 30, 60, or 120 minutes of normothermic (38 degrees C) CPB or 2 hours of hypothermic circulatory arrest at 16 degrees C. After terminating bypass 15 animals had their brains perfusion-fixed and removed for immunohistochemical analysis of expression of the transcription factor FOS. The other animals were perfused with fluorescent albumin to visualize the brain microvasculature. Brain sections were analyzed with a laser scanning confocal microscope.

RESULTS

Control animals (n = 6, sham operated and cannulated) exhibited normal vasculature with negligible leakage and no FOS protein expression in neurons or endothelial cells anywhere in the brain. Significant FOS expression in barrier-associated structures including the blood vessels, choroid plexus, and ependyma but not neurons occurred at all times on bypass. CPB caused leakage of fluorescent albumin from blood vessels in all animals. Two hours of normothermic CPB (n = 4) caused significant (p < 0.01) leakage in the cerebellum, cortex, hippocampus, and corpus callosum. Animals exposed to circulatory arrest experienced severe leakage throughout the brain (p < 0.001) and FOS expression in all cells.

CONCLUSIONS

These experiments indicate that the BBB is dysfunctional after all time points on normothermic CPB, BBB dysfunction is worsened by hypothermic circulatory arrest, and BBB dysfunction is associated with intense molecular activity within the barrier-forming cells. Dysfunction of the BBB may contribute to neurologic complications after heart surgery.

Signaling at the gliovascular interface

Advances in fluorescent calcium indicating dyes over the past decade have identified calcium signaling as the tool by which astrocytes communicate among themselves and with neighboring neurons. Studies of astrocyte-neuron interactions have shown that calcium signaling is a potent modulator of the strength of both excitatory and inhibitory synapses. The concept that astrocytes possess a mechanism for rapid cell communication has not been incorporated, however, into the supportive functions of astrocytes. Because many of the classical tasks of astrocytes are linked to the blood-brain barrier, we have here examined the expression of proteins required for calcium signaling in their vascular end-foot processes. The gap junction protein, Cx43, was expressed intensively around the vessels interconnecting astrocytic end-foot processes. These gap junctions permitted diffusion of Lucifer yellow, specifically along the path of glial end feet apposed to the vessel wall. The purinergic receptors, P2Y(2) and P2Y(4), were also strongly expressed at the gliovascular interface and colocalized with GFAP around larger vessels in cortex. Multiphoton imaging of freshly prepared brain slices loaded with Fluo-4/AM revealed that ATP mobilized cytosolic calcium in astrocytic end feet, whereas electrical stimulation triggered calcium waves propagating along the vessel wall. Brain endothelial cells and pericytes were physically separated from astrocytes by the basal lamina and responded only weakly to ATP. These observations identify astrocytic end-foot processes plastered at the vessel wall as a center for purinergic signaling. It is speculated that calcium signaling may play a role in astrocytic functions related to the blood-brain barrier, including blood flow regulation, metabolic trafficking, and water homeostasis.

Losses of NG2 and NeuN immunoreactivity but not astrocytic markers during early reperfusion following severe focal cerebral ischemia

The ability of glia to recover essential functions following a period of focal cerebral ischemia is likely to be one important factor influencing the severity of tissue damage that subsequently develops. In this study, we have compared changes in immunoreactivity of markers specific for astrocytes, NG2-positive glia and neurons in tissue subregions during early reperfusion following 3 h of middle cerebral artery occlusion to provide insights into possible differential susceptibility of these cell populations. Under the conditions used, infarction ultimately encompasses most of the perfusion territory of the occluded artery. Nonetheless, alterations in immunoreactivity during the first 3 h of recirculation were restricted to brain regions that had been subjected to severe ischemia. In the striatum, cellular immunoreactivity for NG2 and neuronal markers, NeuN and microtubule-associated protein 2, was greatly reduced by 1 h of reperfusion and declined further at 3 h. NG2 labeling of blood vessels in the striatum appeared post-ischemically, mimicking expression of this protein during development. Less severe changes were seen in the neuronal markers in overlying cerebral cortex. In contrast to the losses of other cellular proteins, immunoreactivity for the astrocytic marker, glial fibrillary acidic protein, was preserved in all tissue that had been subjected to severe ischemia and labeling of another astrocytic protein, glutamine synthetase, was increased by 3 h of reperfusion. These findings provide the first evidence of marked sensitivity of NG2-immunoreactivity to severe ischemia and suggest a greater initial resistance of astrocytes compared with neurons and NG2-positive glia to ischemia-reperfusion damage.

Adjuvant treatment with a glycoprotein IIb/IIIa receptor inhibitor increases the therapeutic window for low-dose tissue plasminogen activator administration in a rat model of embolic stroke

BACKGROUND

Platelet aggregation and fibrin deposition are key events leading to microvascular thrombosis and progressive impairment of downstream microvascular perfusion after stroke. We tested the hypothesis that inhibition of platelet function with a GP IIb/IIIa receptor antagonist would increase the efficacy and safety and increase the time window for thrombolytic therapy for stroke with full- and half-dose tissue plasminogen activator (tPA).

METHODS AND RESULTS

Rats were subjected to embolic middle cerebral artery occlusion. Four hours after ischemia, rats were treated with 7E3 F(ab')2 (6 mg/kg) in combination with tPA at doses of 10 and 5 mg/kg, tPA alone at a dose of 10 or 5 mg/kg, 7E3 F(ab')2 (6 mg/kg) alone, or saline. Combination treatment with 7E3 F(ab')2 and tPA (full- or half-dose) significantly (P<0.05) reduced infarct volume and neurological deficits compared with saline-treated rats. However, treatment with 7E3 F(ab')2 or tPA (full- or half-dose) alone did not reduce infarct volume. Quantitative measurements of cerebral microvessels perfused by FITC-dextran revealed that combination treatment with 7E3 F(ab')2 and full-dose tPA significantly (P<0.05) increased the percentage of FITC-dextran-perfused vessels compared with saline and full-dose tPA-treated rats. In addition, treatment with 7E3 F(ab')2 in combination with full-dose tPA significantly (P<0.05) decreased microvascular platelet accumulation and matrix metalloproteinase 9 immunoreactivity and protected against loss of collagen IV immunoreactivity.

CONCLUSIONS

Combination treatment with 7E3 F(ab')2 with full- and half-dose tPA at 4 hours after ischemia significantly reduces infarct volume and improves neurological outcome. Enhancement of patency and integrity of cerebral microvessels most likely contributes to the benefits observed with this combination therapy.

Microvascular structure after embolic focal cerebral ischemia in the rat

OBJECTIVES

We analyze morphological alterations of cerebral neovascularization after stroke using a new 3D imaging software program.

METHODS

Male Wistar rats underwent unilateral embolic middle cerebral artery occlusion (MCAo) by a single fibrin rich clot. Subjects were sacrificed from 1 to 28 days post infarct. Vessel perimeters were measured on coronal sections stained with endothelial cell-specific antibody to von Willebrand's factor. Vessel segment lengths, diameters and number of vessels were analyzed on cerebral microvessels perfused with FITC-dextran 14 days after ischemia using LSCM and a 3-D vessel quantification program.

RESULTS

The mean number of microvessels with enlarged perimeters significantly increased in the ipsilateral cortex at day 7 when compared to the contralateral cortex (29.7+/-14.7 vs. 3.7+/-2.5, P<0.05). Subsequently, differences in the number of microvessels with enlarged perimeters decreased on days 14 and 28. Fourteen days post-MCA occlusion, microvessel segment length (15.0 vs. 26.0 microm, P<0.05) and diameter (3.14 vs. 3.75 microm, P<0.05) significantly decreased in the ipsilateral hemisphere when compared to the contralateral hemisphere, respectively. Furthermore, the mean total number of these smaller microvessels increased in the ipsilateral hemisphere (57.33+/-14.5 vs. 32.22+/-11.7, P<0.05).

CONCLUSIONS

Focal cerebral ischemia induces morphological changes (early dilated microvessels followed by decreased microvessel segment length and diameter) that are consistent with newly generated microvessels.

Regional variation in brain capillary density and vascular response to ischemia

Differences in brain neuroarchitecture have been extensively studied and recent results demonstrated that regional differences in the physiological properties of glial cells are equally common. Relatively little is known on the topographic differences in vascular supply, distribution and density of brain capillaries in different CNS regions. We developed a simple method consisting of intravascular injection of fluorescent dyes coupled to immunocytochemical techniques that allows for simultaneous observation of glia-neuronal-vascular interactions in immersion-fixed brain specimens from small rodents. This technique permits quantitative evaluation of regional differences in glial/neuronal distribution and the study of their relationship to vascular densities. Variations of this technique also allow the detection of abnormal microvasculature (i.e. 'leaky' vessels), a useful feature for studies of blood-brain barrier function in health and disease. By use of quantitative confocal microscopy, the three-dimensional geometry of cortical and hippocampal structures revealed remarkable differences in vascularization between cortical gray/white matter junction, and hippocampal formation (CA1 and CA3 regions). Significant differences were also observed within the same investigative region: CA1 was characterized by low capillary density compared to neighboring CA3. Following an ischemic insult, CA1 vessels had more extensive blood-brain barrier leakage than CA3 vessels. We conclude that in addition to neuronal and glial heterogeneity, cortical structures are also endowed with region-specific vascular patterns characterized by distinct pathophysiological responses.

Elements of cerebral microvascular ischaemia

Although neuronal cells have long been thought to be the prime target of ischaemic insults, events which occur at the blood-vascular-parenchymal interface are necessary for the initiation of ischaemic tissue injury. This cascade of microvascular events includes fibrin accumulation, endothelium expression of leukocyte adhesion receptors, breakdown of the basal laminae with loss of astrocyte and endothelial cell contacts leading to blood-brain barrier disruption and consequently oedema formation and haemorrhagic transformation. Potential stroke treatments have been studied in the clinic and many have not been particularly successful, probably due to the delicate balance between improved outcome and adverse reactions as well as the window of opportunity for drug treatment after symptom onset. The only acute intervention trial demonstrating any benefit in patients was that of intravenous tissue plasminogen activator (tPA), administered within 3 h of the onset of symptoms of ischaemic stroke. Such treatment improved clinical outcome at 3 months, although there was an increased incidence of symptomatic haemorrhage [New Engl. J. Med. 333 (1995) 1581]. The recent progress made in defining the mechanisms involved in the initiation of ischaemic events, as described in this review, may lead to the identification of new strategies for intervention in the ischaemic cascade.

Up-regulation of neuropilin-1 in neovasculature after focal cerebral ischemia in the adult rat

During development, neuropilin-1 is a receptor for semaphorin 3a-mediated axonal guidance and for vascular endothelial growth factor (VEGF) promotion of angiogenesis. The authors measured neuropilin-1 expression in the adult ischemic brain using Northern blot, in situ hybridization, and immunohistochemistry. Neuropilin-1 mRNA was significantly up-regulated as early as 2 hours and persisted at least 28 days after focal cerebral ischemia. Acute up-regulation of neuropilin-1 mRNA primarily localized to the ischemic neurons. A marked increase in both mRNA and protein of neuropilin-1 was detected in endothelial cells of cerebral blood vessels at the border and in the core of the ischemic lesion 7 days after ischemia, and neuropilin-1 gene expression persisted on these vessels for at least 28 days after ischemia. In these areas, neovascularization was detected using three-dimensional reconstructed images obtained from laser scanning confocal microscopy. Activated astrocytes also exhibited neuropilin-1 immunoreactivity during 7 to 28 days of ischemia. Double immunofluorescent staining showed colocalization of neuropilin-1 and VEGF to cerebral blood vessels and activated astrocytes. These data suggest that in addition to its role in axonal growth, up-regulation of neuropilin-1, in concert with VEGF and its receptors, may contribute to neovascular formation in the adult ischemic brain.

Release of glial tissue-specific proteins after acute stroke: A comparative analysis of serum concentrations of protein S-100B and glial fibrillary acidic protein

BACKGROUND AND PURPOSE

This study was aimed at the comparative analysis of serum concentrations of glial fibrillary acidic protein (GFAP) and protein S-100B in patients with acute stroke.

METHODS

We investigated 32 patients with stroke symptoms consistent with cerebral ischemia in the anterior territory of vascular supply. Serial venous blood samples were taken after admission to the hospital and during the first 4 days after onset of stroke. Evaluation of lesion topography and volume of infarcted brain area was based on cranial CT data. The patients' clinical status was consecutively evaluated by the National Institutes of Health Stroke Scale (NIHSS) and the Barthel Index score at discharge from the hospital.

RESULTS

Protein S-100B and GFAP release was found to be significantly correlated (r=0.96; P:<0.001). The release of both biochemical markers was associated with the volume of brain lesions (S-100B: r=0.957, P:<0.0001; GFAP: r=0.955, P:<0.0001) and the neurological status at discharge from the hospital (S-100B: r=0.821, P:=0.0002; GFAP: r=0.717, P:=0.0003). The highest correlation between both S-100B and GFAP serum concentration and Barthel score was calculated at the last time of blood sampling, 4 days after stroke onset (S-100B: r=0.621, P:<0.001; GFAP: r=0.655, P:<0.001). The release of both astroglia derived proteins differed between different subtypes of stroke. GFAP was found to be a more sensitive marker of brain damage in patients with smaller lacunar lesions or minor strokes.

CONCLUSIONS

Our results indicate that postischemic release patterns of GFAP and S-100B protein may allow insight into the underlying pathophysiology of acute cerebral infarcts and may be used as a valuable tool of clinical stroke treatment.

Measurement of cerebral microvessel diameters after embolic stroke in rat using quantitative laser scanning confocal microscopy

Perfusion of the microcirculation after stroke is central to preserving neuronal function and improving functional outcome. Using laser scanning confocal microscopy (LSCM) and a novel computer software program, MIRAGE, we measured a reduction in cerebral microvessel diameter after 1 and 4 h of embolic middle cerebral artery (MCA) occlusion. The methodology used by MIRAGE for measurement of blood vessel diameter involves a linearly applied spherical inflation technique. Three-dimensional quantitative analysis revealed a significant (P<0.05) mean 10-12% reduction in vessel diameter in the ipsilateral cortex when compared to the homologous region in the contralateral hemisphere. This reduction was seen only in the cortex and not the striatum. A larger reduction in mean vessel diameter in the ipsilateral cortex, 16-30% (P<0.05) was observed when compared to sham control rats. These results are in strong agreement with other studies using different stroke models and imaging techniques. Our work represents a novel application of LSCM technology to the three dimensional investigation of microvessel diameter changes in acute stroke and identifies its potential as an important tool for investigation of cerebral pathology.

Physiological consequences of morphologically detectable synaptic plasticity: potential uses for examining recovery following damage

A growing literature indicates that brain structure is modified in various ways with experience. In this paper we briefly survey evidence that the brain retains the capacity to modify its organization in response to demands, including demands resulting from learning, throughout the lifetime. We attempt to address whether these experience-induced changes are accompanied by physiological changes that indicate a functional reorganization of the brain. The kinds of morphological changes that have been observed following brain injury appear to be very similar to those seen after learning. The similarity suggests that many of the basic mechanisms of synaptic change in the brain may be utilized for both functions. This suggests that we can take advantage of some of the methods used to test the changes in physiology with behavioral manipulations to examine the damaged brain. We advocate utilizing electrophysiological techniques to measure functional recovery from brain injury as these may be useful in evaluating both spontaneous recovery from damage and the therapeutic benefits of training, or other therapies.

Cerebral microvascular obstruction by fibrin is associated with upregulation of PAI-1 acutely after onset of focal embolic ischemia in rats

The mechanisms underlying cerebral microvascular perfusion deficit resulting from occlusion of the middle cerebral artery (MCA) require elucidation. We, therefore, tested the hypothesis that intravascular fibrin deposition in situ directly obstructs cerebral microcirculation and that local changes in type 1 plasminogen activator inhibitor (PAI-1) gene expression contribute to intravascular fibrin deposition after embolic MCA occlusion. Using laser-scanning confocal microscopy (LSCM) in combination with immunofluorescent staining, we simultaneously measured in three dimensions the distribution of microvascular plasma perfusion deficit and fibrin(ogen) immunoreactivity in a rat model of focal cerebral embolic ischemia (n = 12). In addition, using in situ hybridization and immunostaining, we analyzed expression of PAI-1 in ischemic brain (n = 13). A significant (p < 0.05) reduction of cerebral microvascular plasma perfusion accompanied a significant (p < 0.05) increase of intravascular and extravascular fibrin deposition in the ischemic lesion. Microvascular plasma perfusion deficit and fibrin deposition expanded concomitantly from the subcortex to the cortex during 1 and 4 hr of embolic MCA occlusion. Three-dimensional analysis revealed that intravascular fibrin deposition directly blocks microvascular plasma perfusion. Vascular plugs contained erythrocytes, polymorphonuclear leukocytes, and platelets enmeshed in fibrin. In situ hybridization demonstrated induction of PAI-1 mRNA in vascular endothelial cells in the ischemic region at 1 hr of ischemia. PAI-1 mRNA significantly increased at 4 hr of ischemia. Immunohistochemical staining showed the same pattern of increased PAI-1 antigen in the endothelial cells. These data demonstrate, for the first time, that progressive intravascular fibrin deposition directly blocks cerebral microvascular plasma perfusion in the ischemic region during acute focal cerebral embolic ischemia, and upregulation of the PAI-1 gene in the ischemic lesion may foster fibrin deposition through suppression of fibrinolysis.

Maternal exposure to the synthetic cannabinoid HU-210: effects on the endocrine and immune systems of the adult male offspring

Natural and synthetic cannabinoid receptor agonists have been described to exert profound effects on both the neuroendocrine integration and the functional responses of the immune system. In the present study, Wistar rats were exposed to the highly potent cannabinoid agonist HU-210 (1, 5 and 25 microg/kg) during gestation and lactation and the ensuing effects on several endocrine and immune parameters of the adult male offspring were analyzed. Perinatal exposure to HU-210 partially affected the distribution of lymphocyte subpopulations in the spleen and peripheral blood. The major changes observed occur after maternal exposure to the 25 microg/kg dose of HU-210. There was a reduction in the T-helper subpopulation in the spleen and a dose-related decrease in the rate of T(helper)/T(cytotoxic) in peripheral blood lymphocytes. Concanavalin-A and lipopolysaccharide-induced proliferation were normal in all the groups tested. In the same animals, perinatal exposure to HU-210 did not affect basal levels of growth hormone, IGF-1, prolactin, or follicle-stimulating hormone. Basal values of luteinizing hormone were elevated in animals given the 1 microg/kg dose of HU-210. Corticosterone levels were reduced in the animals exposed to the higher dose of HU-210 during gestation and lactation. These animals exhibited a decreased responsiveness of the hypothalamo-pituitary-adrenal (HPA) axis to the stimulation with a single injection of HU-210 (20 microg/kg, i.v.) at adult ages, which may reflect the onset of long-lasting tolerance to the HPA-activating properties of cannabinoids. The opposite pattern of response was found in the animals given the 1 microg/kg dose, in which a sensitization of the corticosterone response to acute HU-210 was observed. The present work reveals that maternal exposure to cannabinoids results in minor changes in the development of the immune system, but may induce long-lasting alterations in the functional status of the HPA axis.