Decrease in dystrophin expression prior to disruption of brain-blood barrier within the rat piriform cortex following status epilepticus

Laminin as a Biomarker of Blood-Brain Barrier Disruption under Neuroinflammation: A Systematic Review

Laminin, a non-collagenous glycoprotein present in the brain extracellular matrix, helps to maintain blood–brain barrier (BBB) integrity and regulation. Neuroinflammation can compromise laminin structure and function, increasing BBB permeability. The aim of this paper is to determine if neuroinflammation-induced laminin functional changes may serve as a potential biomarker of alterations in the BBB. The 38 publications included evaluated neuroinflammation, BBB disruption, and laminin, and were assessed for quality and risk of bias (protocol registered in PROSPERO; CRD42020212547). We found that laminin may be a good indicator of BBB overall structural integrity, although changes in expression are dependent on the pathologic or experimental model used. In ischemic stroke, permanent vascular damage correlates with increased laminin expression (β and γ subunits), while transient damage correlates with reduced laminin expression (α subunits). Laminin was reduced in traumatic brain injury and cerebral hemorrhage studies but increased in multiple sclerosis and status epilepticus studies. Despite these observations, there is limited knowledge about the role played by different subunits or isoforms (such as 411 or 511) of laminin in maintaining structural architecture of the BBB under neuroinflammation. Further studies may clarify this aspect and the possibility of using laminin as a biomarker in different pathologies, which have alterations in BBB function in common.

Hippocampal synaptic and membrane function in the DBA/2J-mdx mouse model of Duchenne muscular dystrophy

Dystrophin deficiency is associated with alterations in cell physiology. The functional consequences of dystrophin deficiency are particularly severe for muscle physiology, as observed in Duchenne muscle dystrophy (DMD). DMD is caused by the absence of a 427 kDa isoform of dystrophin. However, in addition to muscular dystrophy symptoms, DMD is frequently associated with memory and attention deficits and epilepsy. While this may be associated with a role for dystrophin in neuronal physiology, it is not clear what neuronal alterations are linked with DMD. Our work shows that CA1 pyramidal neurons from DBA/2J-mdx mice have increased afterhyperpolarization compared to WT controls. All the other electrotonic and electrogenic membrane properties were unaffected by this genotype. Finally, basal synaptic transmission, short-term and long-term synaptic plasticity at Schaffer collateral to CA1 glutamatergic synapses were unchanged between mdx and WT controls. These data show that the excitatory component of hippocampal activity is largely preserved in DBA/2J-mdx mice. Further studies, extending the investigation to the inhibitory GABAergic function, may provide a more complete picture of the functional, network alterations underlying impaired cognition in DMD. In addition, the investigation of changes in neuronal single conductance biophysical properties associated with this genotype, is required to identify the functional alterations associated with dystrophin deficiency and clarify its role in neuronal function.

The Regional Specific Alterations in BBB Permeability are Relevant to the Differential Responses of 67-kDa LR Expression in Endothelial Cells and Astrocytes Following Status Epilepticus

Status epilepticus (a prolonged seizure activity, SE) differently affects vasogenic edema formation and dystrophin-aquaporin 4 (AQP4) expressions between the rat hippocampus and the piriform cortex (PC). In the present study, we explored whether the 67-kDa laminin receptor (LR) expression was relevant to the regional specific susceptibility of vasogenic edema at 3 days after SE. In spite of no difference in expression levels of 67-kDa LR, dystrophin, and AQP4 under physiological conditions, SE-induced serum extravasation was more severe in the PC than the hippocampus. Western blots demonstrated that SE reduced expression levels of 67-kDa LR, dystrophin, and AQP4 in the PC, but not in the hippocampus proper. Immunofluorescent studies revealed that SE increased 67-kDa LR expression in reactive CA1 astrocyte, but reduced it in the PC and the molecular layer of the dentate gyrus due to massive astroglial loss. Furthermore, SE decreased expressions of endothelial 67-kDa LR and SMI-71 (endothelial brain barrier antigen) in these regions. The 67-kDa LR neutralization evoked serum extravasation in these regions of normal animals without astroglial loss. Similar to SE, 67-kDa LR neutralization also reduced dystrophin-AQP4 expressions in the PC more than the total hippocampus. Furthermore, 67-kDa LR IgG infusion increased phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), but not c-Jun N-terminal kinase, independent of phosphoprotein enriched in astrocytes of 15 kDa (PEA15) activity. Co-treatment of U0126 (an ERK1/2 inhibitor) alleviated vasogenic edema formation and the reduced dystrophin-AQP4 expressions induced by 67-kDa LR neutralization. The 67-kDa LR IgG infusion also increased the susceptibility to SE induction. Therefore, our findings suggested that the cellular specific alterations in 67-kDa LR expression might be involved in the severity of SE-induced vasogenic edema formation in regional specific manners, which might affect the susceptibility to SE induction.

Dysfunction of 67-kDa Laminin Receptor Disrupts BBB Integrity via Impaired Dystrophin/AQP4 Complex and p38 MAPK/VEGF Activation Following Status Epilepticus

Status epilepticus (SE, a prolonged seizure activity) impairs brain-blood barrier (BBB) integrity, which results in secondary complications following SE. The non-integrin 67-kDa laminin receptor (67-kDa LR) plays a role in cell adherence to laminin (a major glycoprotein component in basement membrane), and participates laminin-mediated signaling pathways including p38 mitogen-activated protein kinase (p38 MAPK). Thus, we investigated the role of 67-kDa LR in SE-induced vasogenic edema formation in the rat piriform cortex (PC). SE diminished 67-kDa LR expression, but increased laminin expression, in endothelial cells accompanied by the reduced SMI-71 (a rat BBB barrier marker) expression. Astroglial 67-kDa LR expression was also reduced in the PC due to massive astroglial loss. 67-kDa LR neutralization led to serum extravasation in the PC concomitant with the reduced SMI-71 expression. 67-kDa LR neutralization also decreased expressions of dystrophin and aquaporin-4 (AQP4). In addition, it increased p38 MAPK phosphorylation and expressions of vascular endothelial growth factor (VEGF), laminin and endothelial nitric oxide synthase (eNOS), which were abrogated by SB202190, a p38 MAPK inhibitor. Therefore, our findings indicate that 67-kDa LR dysfunction may disrupt dystrophin-AQP4 complex, which would evoke vasogenic edema formation and subsequent laminin over-expression via activating p38 MAPK/VEGF axis.

Sac-1004, a vascular leakage blocker, reduces cerebral ischemia-reperfusion injury by suppressing blood-brain barrier disruption and inflammation

Background

Blood–brain barrier (BBB) breakdown and inflammation are critical events in ischemic stroke, contributing to aggravated brain damage. The BBB mainly consists of microvascular endothelial cells sealed by tight junctions to protect the brain from blood-borne substances. Thus, the maintenance of BBB integrity may be a potential target for neuroprotection. Sac-1004, a pseudo-sugar derivative of cholesterol, enhances the endothelial barrier by the stabilization of the cortical actin ring.

Results

Here, we report on the protective effects of Sac-1004 on cerebral ischemia-reperfusion (I/R) injury. Treatment with Sac-1004 significantly blocked the interleukin-1β-induced monolayer hyperpermeability of human brain microvascular endothelial cells (HBMECs), loss of tight junctions, and formation of actin stress fiber. Sac-1004 suppressed the expression of adhesion molecules, adhesion of U937 cells, and activation of nuclear factor-κB in HBMECs. Using a rat model of transient focal cerebral ischemia, it was shown that Sac-1004 effectively ameliorated neurological deficits and ischemic damage. In addition, Sac-1004 decreased BBB leakage and rescued tight junction-related proteins. Moreover, the staining of CD11b and glial fibrillary acidic protein showed that Sac-1004 inhibited glial activation.

Conclusions

Taken together, these results demonstrate that Sac-1004 has neuroprotective activities through maintaining BBB integrity, suggesting that it is a great therapeutic candidate for stroke.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0897-3) contains supplementary material, which is available to authorized users.

Mannitol induces selective astroglial death in the CA1 region of the rat hippocampus following status epilepticus

In the present study, we addressed the question of whether treatment with mannitol, an osmotic diuretic, affects astrogliovascular responses to status epilepticus (SE). In saline-treated animals, astrocytes exhibited reactive astrogliosis in the CA1-3 regions 2-4 days after SE. In the mannitol-treated animals, a large astroglial empty zone was observed in the CA1 region 2 days after SE. This astroglial loss was unrelated to vasogenic edema formation. There was no difference in SE-induced neuronal loss between saline- and mannitol-treated animals. Furthermore, mannitol treatment did not affect astroglial loss and vasogenic edema formation in the dentate gyrus and the piriform cortex. These findings suggest that mannitol treatment induces selective astroglial loss in the CA1 region independent of vasogenic edema formation following SE. These findings support the hypothesis that the susceptibility of astrocytes to SE is most likely due to the distinctive heterogeneity of astrocytes independent of hemodynamics. [BMB Reports 2015; 48(9): 507-512]

Cellular and regional specific changes in multidrug efflux transporter expression during recovery of vasogenic edema in the rat hippocampus and piriform cortex

In the present study, we investigated the characteristics of drug efflux transporter expressions following status epilepticus (SE). In the hippocampus and piriform cortex (PC), vasogenic edema peaked 3-4 days after SE. The expression of breast cancer resistance protein (BCRP), multidrug resistance protein-4 (MRP4), and p-glycoprotein (p-GP) were decreased 4 days after SE when vasogenic edema was peaked, but subsequently increased 4 weeks after SE. Multidrug resistance protein-1 (MRP1) expression gradually decreased in endothelial cells until 4 weeks after SE. These findings indicate that SE-induced vasogenic edema formation transiently reduced drug efflux pump expressions in endothelial cells. Subsequently, during recovery of vasogenic edema drug efflux pump expressions were differentially upregulated in astrocytes, neuropils, and endothelial cells. Therefore, we suggest that vasogenic edema formation may be a risk factor in pharmacoresistent epilepsy. [BMB Reports 2015; 48(6): 348-353]

Value of Functionalized Superparamagnetic Iron Oxide Nanoparticles in the Diagnosis and Treatment of Acute Temporal Lobe Epilepsy on MRI

Purpose. Although active targeting of drugs using a magnetic-targeted drug delivery system (MTDS) with superparamagnetic iron oxide nanoparticles (SPIONs) is a very effective treatment approach for tumors and other illnesses, successful results of drug-resistant temporal lobe epilepsy (TLE) are unprecedented. A hallmark in the neuropathology of TLE is brain inflammation, in particular the activation of interleukin-1β (IL-1β) induced by activated glial cells, which has been considered a new mechanistic target for treatment. The purpose of this study was to determine the feasibility of the functionalized SPIONs with anti-IL-1β monoclonal antibody (mAb) attached to render MRI diagnoses and simultaneously provide targeted therapy with the neutralization of IL-1β overexpressed in epileptogenic zone of an acute rat model of TLE. Experimental Design. The anti-IL-1β mAb-SPIONs were studied in vivo versus plain SPIONs and saline. Lithium-chloride pilocarpine-induced TLE models (n = 60) were followed by Western blot, Perl's iron staining, Nissl staining, and immunofluorescent double-label staining after MRI examination. Results. The magnetic anti-IL-1β mAb-SPION administered intravenously, which crossed the BBB and was concentrated in the astrocytes and neurons in epileptogenic tissues, rendered these tissues visible on MRI and simultaneously delivered anti-IL-1β mAb to the epileptogenic focus. Conclusions. Our study provides the first evidence that the novel approach enhanced accumulation and the therapeutic effect of anti-IL-1β mAb by MTDS using SPIONs.

ETB receptor-mediated MMP-9 activation induces vasogenic edema via ZO-1 protein degradation following status epilepticus

The blood-brain barrier (BBB) is formed by the endothelial cells with specialized tight junctions (TJs) lining the blood vessels and astroglial endfeet surrounding the blood vessels. Although BBB disruption during brain insults leads to vasogenic edema as one of the primary steps in the epileptogenic process, little is known about the molecular and physiological events concerning vasogenic edema formation. In the present study, status epilepticus (SE) changed the expressions and subcellular localizations of TJ proteins (claudin-5, occludin and zonula occludens-1 (ZO-1)) in endothelial cells of the rat piriform cortex. Among TJ proteins, the alteration in ZO-1 expression was relevant to endothelin B (ETB) receptor-mediated endothelial nitric oxide synthase (eNOS) activation, which increased matrix metalloproteinase-9 (MMP-9) activity. Indeed, BQ788 (an ETB receptor antagonist) effectively attenuated SE-induced vasogenic edema by inhibiting eNOS-mediated MMP-9 activation and ZO-1 protein degradation in endothelial cells, although astroglial endfeet were detached from endothelial cells. Therefore, we suggest that SE-induced ETB receptor/eNOS-mediated MMP-9 activation may lead to impairments of endothelial cell function via TJ protein degradation, which are involved in vasogenic edema formation independent of perivascular astroglial functions.

Endothelial NOS activation induces the blood-brain barrier disruption via ER stress following status epilepticus

The blood-brain barrier (BBB) maintains the unique brain microenvironment, which is separated from the systemic circulating system. Since the endoplasmic reticulum (ER) is an important cell organelle that is responsible for protein synthesis, the correct folding and sorting of proteins contributing to cell survivals, ER stress is a potential cause of cell damage in various diseases. Therefore, it would be worthy to explore the the relationship between the ER stress and BBB disruption during vasogenic edema formation induced by epileptogenic insults. In the present study, we investigated the roles of ER stress in vasogenic edema and its related events in rat epilepsy models provoked by pilocarpine-induced status epilepticus (SE). SE-induced eNOS activation induces BBB breakdown via up-regulation of GRP78 expression and dysfunction of SMI-71 (an endothelial BBB marker) in the piriform cortex (PC). In addition, caveolin-1 peptide (an eNOS inhibitor) effectively attenuated GRP78 expression and down-regulation of SMI-71. Taken together, our findings suggest that eNOS-mediated ER stress may participate in SE-induced vasogenic edema formation. Therefore, the modulation of ER stress may be a considerable strategy for therapy in impairments of endothelial cell function.

Inhibition of the NLRP3 inflammasome provides neuroprotection in rats following amygdala kindling-induced status epilepticus

Background

NLRP3 inflammasome is proposed to regulate inflammation in several neurological diseases, but its role in epilepsy remains largely unknown. This study aimed to investigate the role of the NLRP3 inflammasome in neuroinflammation, spontaneous recurrent seizures (SRS) and hippocampal neuronal loss in rat brain following amygdala kindling-induced status epilepticus (SE).

Methods

We detected the protein levels of IL-1β and NLRP3 inflammasome components by Western blot in the hippocampus of shams and SE rats at different time points following SE. To further examine whether the activation of the NLRP3 inflammasome contributes to SE-associated neuronal damage, we employed a nonviral strategy to knock down NLRP3 and caspase-1 expression in brain before undergoing SE. Proinflammatory cytokine levels and hippocampal neuronal loss were evaluated at 12 hours and at 6 weeks following SE respectively in these NLRP3 and caspase-1 deficient rats. Meanwhile, SRS occurrence was evaluated through a 4-week video recording started 2 weeks after SE in these NLRP3 and caspase-1 deficient rats.

Results

IL-1β levels and NLRP3 inflammasome components levels dramatically increased at 3 hours after SE, and reached a maximum at 12 hours after SE compared with the control group. Knock down of NLRP3 or caspase-1 decreased the levels of IL-1β and IL-18 at 12 hours after SE, which was accompanied by a significant suppression in the development and severity of SRS during the chronic epileptic phase. Meanwhile, knock down of NLRP3 or caspase-1 led to a remarkable reduction of hippocampal neuronal loss in the CA1 and CA3 area of the hippocampus at 6 weeks after SE.

Conclusions

Our study provides the first evidence that the NLRP3 inflammasome was significantly up-regulated following SE. More importantly, we show that inhibition of the NLRP3 inflammasome provides neuroprotection in rats following SE. These findings suggest that NLRP3 may represent a potential target for the treatment of epileptogenesis

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0212-5) contains supplementary material, which is available to authorized users.

Hyperforin attenuates microglia activation and inhibits p65-Ser276 NFκB phosphorylation in the rat piriform cortex following status epilepticus

Hyperforin, a lipophilic constituent of medicinal herb St. John's Wort, has neurobiological effects including antidepressant activity, antibiotic potency, anti-inflammatory activity and anti-tumoral properties. Furthermore, hyperforin activates transient receptor potential conical channel-6 (TRPC6), a nonselective cation channel. To elucidate the roles of hyperforin and TRPC6 in neuroinflammation in vivo, we investigated the effect of hyperforin on neuroinflammatory responses and its related events in the rat piriform cortex (PC) following status epilepticus (SE). Hyperforin attenuated microglial activation, p65-serine 276 NFκB phosphorylation, and suppressed TNF-α expression in the PC following SE. Hyperforin also effectively alleviated SE-induced vasogenic edema formation, neuronal damage, microglial TRPC6 induction and blood-derived monocyte infiltration. Our findings suggest that hyperforin may effectively attenuate microglia-mediated neuroinflammation in the TRPC6-independent manner.

Pathophysiogenesis of mesial temporal lobe epilepsy: is prevention of damage antiepileptogenic?

Temporal lobe epilepsy (TLE) is frequently associated with hippocampal sclerosis, possibly caused by a primary brain injury that occurred a long time before the appearance of neurological symptoms. This type of epilepsy is characterized by refractoriness to drug treatment, so to require surgical resection of mesial temporal regions involved in seizure onset. Even this last therapeutic approach may fail in giving relief to patients. Although prevention of hippocampal damage and epileptogenesis after a primary event could be a key innovative approach to TLE, the lack of clear data on the pathophysiological mechanisms leading to TLE does not allow any rational therapy. Here we address the current knowledge on mechanisms supposed to be involved in epileptogenesis, as well as on the possible innovative treatments that may lead to a preventive approach. Besides loss of principal neurons and of specific interneurons, network rearrangement caused by axonal sprouting and neurogenesis are well known phenomena that are integrated by changes in receptor and channel functioning and modifications in other cellular components. In particular, a growing body of evidence from the study of animal models suggests that disruption of vascular and astrocytic components of the blood-brain barrier takes place in injured brain regions such as the hippocampus and piriform cortex. These events may be counteracted by drugs able to prevent damage to the vascular component, as in the case of the growth hormone secretagogue ghrelin and its analogues. A thoroughly investigation on these new pharmacological tools may lead to design effective preventive therapies.

Damaging effects of a high-fat diet to the brain and cognition: a review of proposed mechanisms

The prevalence of obesity is growing and now includes at least one-third of the adult population in the United States. As obesity and dementia rates reach epidemic proportions, an even greater interest in the effects of nutrition on the brain have become evident. This review discusses various mechanisms by which a high fat diet and/or obesity can alter the brain and cognition. It is well known that a poor diet and obesity can lead to certain disorders such as type II diabetes, metabolic syndrome, and heart disease. However, long-term effects of obesity on the brain need to be further examined. The contribution of insulin resistance and oxidative stress is briefly reviewed from studies in the current literature. The role of inflammation and vascular alterations are described in more detail due to our laboratory's experience in evaluating these specific factors. It is very likely that each of these factors plays a role in diet-induced and/or obesity-induced cognitive decline.

Reduction in heat shock protein 90 correlates to neuronal vulnerability in the rat piriform cortex following status epilepticus

In the present study, we addressed the question of whether the distinct patterns of heat shock protein (HSP) 70 and HSP90 expressions in the brain region represents the regional specific responses to status epilepsticus (SE) in an effort to better understand the role of HSPs in epileptogenic insult. HSP70 immunoreactivity was increased in CA3 pyramidal cells as well as dentate granule cells at 12h-1week after SE. HSP70 immunoreactivity was transiently increased in neurons within the piriform cortex (PC) following SE. Linear regression analysis showed no correlation between the intensity of NeuN and that of HSP70. In contrast to HSP70, HSP90 immunoreactivity was decreased in CA1-3 pyramidal cells at 4days-4weeks after SE. In addition, HSP90 immunoreactivity was decreased in PC neurons at 12h-4weeks after SE. linear regression analysis showed a direct proportional relationship between the intensity of NeuN and that of HSP90. Therefore, these findings suggest that HSP90 degradation may be closely related to neuronal vulnerability to SE insult.

Status epilepticus induces vasogenic edema via tumor necrosis factor-α/ endothelin-1-mediated two different pathways

Status epilepticus (SE) induces vasogenic edema in the piriform cortex with disruptions of the blood-brain barrier (BBB). However, the mechanisms of vasogenic edema formation following SE are still unknown. Here we investigated the endothelin B (ET_B) receptor-mediated pathway of SE-induced vasogenic edema. Following SE, the release of tumor necrosis factor-α (TNF-α) stimulated endothelin-1 (ET-1) release and expression in neurons and endothelial cells. In addition, TNF-α-induced ET-1 increased BBB permeability via ET_B receptor-mediated endothelial nitric oxide synthase (eNOS) activation in endothelial cells. ET_B receptor activation also increased intracellular reactive oxygen species by NADPH oxidase production in astrocytes. These findings suggest that SE results in BBB dysfunctions via endothelial-astroglial interactions through the TNF-α-ET-1-eNOS/NADPH oxidase pathway, and that these ET_B receptor-mediated interactions may be an effective therapeutic strategy for vasogenic edema in various neurological diseases.

Vascular changes in rat hippocampus following a high saturated fat and cholesterol diet

The long-term effects of a diet rich in saturated fat and cholesterol on the hippocampus were evaluated in this study. It has previously been shown that this type of diet is detrimental to health, particularly affecting peripheral organs such as the heart and liver. However, effects on the brain have not been fully evaluated. This study focused on the hippocampus, a brain region instrumental for learning and memory and vulnerable to ischemic damage. Reduced blood-brain barrier (BBB) integrity and increased microgliosis were observed in the hippocampus of rats fed a high-saturated-fat and cholesterol (HFHC) diet for 6 months. Interestingly, an increase in hippocampal protein levels of occludin, a tight junction protein, was found in HFHC-treated rats as well. Further investigation revealed decreased expression of the occludin protein in blood vessels and increased expression in the dentate gyrus hilar neurons and mossy fibers of the hippocampal cornus ammonis 3 in HFHC-treated rats. Our results show alterations in BBB integrity and expression of tight junction proteins after long-term exposure to HFHC diet in rats. These findings may suggest a biologic mechanism for previously observed behavioral deficits occurring in rats fed this diet.

Interleukin-18 attenuates disruption of brain-blood barrier induced by status epilepticus within the rat piriform cortex in interferon-γ independent pathway

Status epilepticus increases brain-blood barrier (BBB) permeability leading to vasogenic edema. This BBB disruption is usually confined within relatively limited cerebral regions including the piriform cortex (PC), and leads to epileptogenesis and contributes to progression of epilepsy. Although cytokines are at least partly responsible for changes in BBB permeability, the role of interleukin-18 (IL-18) in vasogenic edema is not yet explored in detail. In the present study, we investigated the role of IL-18 in SE-induced vasogenic edema formation. Following SE, IL-18/interferon-γ (IFN-γ) system was up-regulated in astrocytes and microglia/macrophages. Recombinant rat (rr) IL-18 infusion decreased vasogenic edema formation, while anti-rat IL-18 infusion increased it. In contrast, rrIFN-γ, and anti-rat IFN-γ infusion showed reverse effects on vasogenic edema formation. rrIL-18 or anti-rat IFN-γ IgG infusion elevated dystrophin expression accompanied by the reduction in vasogenic edema. However, rr-IFN-γ or anti-rat IL-18 IgG infusion significantly decreased dystrophin immunoreactivity within the PC following SE. These findings indicate that IL-18-mediated up-regulation of dystrophin expression may play either a direct or indirect role in maintenance of BBB function following SE. Therefore, our findings suggest that IL-18 may have protective effect on SE-induced BBB disruption in IFN-γ independent mechanism.

Tumor necrosis factor-α-mediated threonine 435 phosphorylation of p65 nuclear factor-κB subunit in endothelial cells induces vasogenic edema and neutrophil infiltration in the rat piriform cortex following status epilepticus

BACKGROUND

Status epilepticus (SE) induces severe vasogenic edema in the piriform cortex (PC) accompanied by neuronal and astroglial damages. To elucidate the mechanism of SE-induced vasogenic edema, we investigated the roles of tumor necrosis factor (TNF)-α in blood-brain barrier (BBB) disruption during vasogenic edema and its related events in rat epilepsy models provoked by pilocarpine-induced SE.

METHODS

SE was induced by pilocarpine in rats that were intracerebroventricularly infused with saline-, and soluble TNF p55 receptor (sTNFp55R) prior to SE induction. Thereafter, we performed Fluoro-Jade B staining and immunohistochemical studies for TNF-α and NF-κB subunits.

RESULTS

Following SE, most activated microglia showed strong TNF-α immunoreactivity. In addition, TNF p75 receptor expression was detected in endothelial cells as well as astrocytes. In addition, only p65-Thr435 phosphorylation was increased in endothelial cells accompanied by SMI-71 expression (an endothelial barrier antigen). Neutralization of TNF-α by soluble TNF p55 receptor (sTNFp55R) infusion attenuated SE-induced vasogenic edema and neuronal damages via inhibition of p65-Thr435 phosphorylation in endothelial cells. Furthermore, sTNFp55R infusion reduced SE-induced neutrophil infiltration in the PC.

CONCLUSION

These findings suggest that impairments of endothelial cell functions via TNF-α-mediated p65-Thr 485 NF-κB phosphorylation may be involved in SE-induced vasogenic edema. Subsequently, vasogenic edema results in extensive neutrophil infiltration and neuronal-astroglial loss.

The roles of P2X7 receptor in regional-specific microglial responses in the rat brain following status epilepticus

Recently, we have reported that astroglial activations in response to status epilepticus (SE) show regional-specific manners in the rat hippocampus. However, it is unknown that microglial responses to SE would show regional-specific patterns. Therefore, the present study was designed to elucidate the regional-specific microglial activation and relationship between P2X7 receptor functions and SE-induced microglial responses in the rat brain. Following SE, microglia appeared amoeboid or phagocytic in the dentate gyrus and the piriform cortex. In contrast, elongated microglia were observed in the CA1 hippocampal regions and the frontoparietal cortex. In the dentate gyrus, the CA1 hippocampal regions, and the frontoparietal cortex, these microglial activation accelerated by BzATP (a P2X7 receptor agonist)-infusion, but inhibited by OxATP (a P2X7 receptor antagonist). However, SE-induced microglial activation in the piriform cortex was not affected by BzATP or OxATP-infusion. Therefore, our findings indicate that SE-induced microglial activation may show regional-specific manners, and suggest that P2X7 receptor function differently modulates SE-induced microglial responses in distinct brain regions.