TGFβ1 treatment reduces hippocampal damage, spontaneous recurrent seizures, and learning memory deficits in pilocarpine-treated rats

Interrogating mediators of single-cell transcriptional changes in the acute damaged cerebral cortex: Insights into endothelial-astrocyte interactions

Traumatic brain injury (TBI) induces complex cellular and molecular changes, challenging recovery and therapeutic development. Although molecular pathways have been implicated in TBI pathology, the cellular specificity of these mechanisms remains underexplored. Here, we investigate the role of endothelial cell (EC) EphA4, a receptor tyrosine kinase receptor involved in axonal guidance, in modulating cell-specific transcriptomic changes within the damaged cerebral cortex. Utilizing single-cell RNA sequencing (scRNA-seq) in an experimental TBI model, we mapped transcriptional changes across various cell types, with a focus on astrocytes and ECs. Our analysis reveals that EC-specific knockout (KO) of EphA4 triggers significant alterations in astrocyte gene expression and shifts predominate subclusters. We identified six distinct astrocyte clusters (C0-C5) in the damaged cortex including as C0-Mobp/Plp1+; C1-Slc1a3/Clu+; C2-Hbb-bs/Hba-a1/Ndrg2+; C3-GFAP/Lcn2+; C4-Gli3/Mertk+, and C5-Cox8a+. We validate a new Sox9+ cluster expressing Mertk and Gas, which mediates efferocytosis to facilitate apoptotic cell clearance and anti-inflammatory responses. Transcriptomic and CellChat analyses of EC-KO cells highlights upregulation of neuroprotective pathways, including increased amyloid precursor protein (APP) and Gas6. Key pathways predicted to be modulated in astrocytes from EC-KO mice include oxidative phosphorylation and FOXO signaling, mitochondrial dysfunction and ephrin B signaling. Concurrently, metabolic and signaling pathways in endothelial cells-such as ceramide and sphingosine phosphate metabolism and NGF-stimulated transcription-indicate an adaptive response to a metabolically demanding post-injury hypoxic environment. These findings elucidate potential interplay between astrocytic and endothelial responses as well as transcriptional networks underlying cortical tissue damage.

Analysis of Differential microRNA Expression in the Hippocampus of Scopolamine-Induced Amnesic Mouse Model

Amnesia is characterized by memory deficits linked to various neurodegenerative pathologies and can be induced by the administration of scopolamine, a cholinergic antagonist. Scopolamine-induced amnesia is a well-studied pharmacological animal model that simulates memory impairment caused by aging, brain illnesses, neuropathologies, and trauma. However, the molecular mechanism of amnesia, more importantly in terms of microRNA (miRNA) regulation, is not well understood. Therefore, this study aimed to analyze miRNA profiles in the hippocampus of both control mice and those treated with scopolamine (amnesic mice). Initially, a short cDNA library was prepared for each sample and then sequenced on the Illumina platform. Among the total differentially expressed miRNAs, 113 were significantly upregulated and 96 were downregulated in the scopolamine group in comparison to the control group. Ten upregulated and ten downregulated miRNAs were validated to confirm the reliability of the sequencing results using qRT-PCR (quantitative real-time PCR). Furthermore, we performed a target prediction analysis intersecting the results from TargetScan, miRDB (miRNA database), and Miranda to analyze the targets of the dysregulated miRNAs. We also conducted a pathway analysis to investigate the molecular, cellular, and biological functions of these targets. miRNA‒target interactions were found to play roles in various signaling pathways during amnesia. These results provide an initial insight for the contribution of miRNAs to scopolamine-induced amnesia, as well as their possible application as markers of disease pathology.

Growth Factors and Their Application in the Therapy of Hereditary Neurodegenerative Diseases

Hereditary neurodegenerative diseases (hNDDs) such as Alzheimer's, Parkinson's, Huntington's disease, and others are primarily characterized by their progressive nature, severely compromising both the cognitive and motor abilities of patients. The underlying genetic component in hNDDs contributes to disease risk, creating a complex genetic landscape. Considering the fact that growth factors play crucial roles in regulating cellular processes, such as proliferation, differentiation, and survival, they could have therapeutic potential for hNDDs, provided appropriate dosing and safe delivery approaches are ensured. This article presents a detailed overview of growth factors, and explores their therapeutic potential in treating hNDDs, emphasizing their roles in neuronal survival, growth, and synaptic plasticity. However, challenges such as proper dosing, delivery methods, and patient variability can hinder their clinical application.

Neonatal inflammation increases hippocampal KCC2 expression through methylation-mediated TGF-β1 downregulation leading to impaired hippocampal cognitive function and synaptic plasticity in adult mice

The mechanisms by which neonatal inflammation leads to cognitive deficits in adulthood remain poorly understood. Inhibitory GABAergic synaptic transmission plays a vital role in controlling learning, memory and synaptic plasticity. Since early-life inflammation has been reported to adversely affect the GABAergic synaptic transmission, the aim of this study was to investigate whether and how neonatal inflammation affects GABAergic synaptic transmission resulting in cognitive impairment. Neonatal mice received a daily subcutaneous injection of lipopolysaccharide (LPS, 50 μg/kg) or saline on postnatal days 3-5. It was found that blocking GABAergic synaptic transmission reversed the deficit in hippocampus-dependent memory or the induction failure of long-term potentiation in the dorsal CA1 in adult LPS mice. An increase of mIPSCs amplitude was further detected in adult LPS mice indicative of postsynaptic potentiation of GABAergic transmission. Additionally, neonatal LPS resulted in the increased expression and function of K⁺-Cl^--cotransporter 2 (KCC2) and the decreased expression of transforming growth factor-beta 1 (TGF-β1) in the dorsal CA1 during adulthood. The local TGF-β1 overexpression improved KCC2 expression and function, synaptic plasticity and memory of adult LPS mice. Adult LPS mice show hypermethylation of TGFb1 promoter and negatively correlate with reduced TGF-β1 transcripts. 5-Aza-deoxycytidine restored the changes in TGFb1 promoter methylation and TGF-β1 expression. Altogether, the results suggest that hypermethylation-induced reduction of TGF-β1 leads to enhanced GABAergic synaptic inhibition through increased KCC2 expression, which is a underlying mechanism of neonatal inflammation-induced hippocampus-dependent memory impairment in adult mice.

Activating toll-like receptor 4 after traumatic brain injury inhibits neuroinflammation and the accelerated development of seizures in rats

Toll-like receptor 4 (TLR4) signaling plays a detrimental role in traumatic brain injury (TBI) pathology. Pharmacologic or genetic inactivating TLR4 diminish TBI inflammation and neurological complications. Nonetheless, TLR4 priming alleviates TBI inflammation and seizure susceptibility. We investigated impact of postconditioning with TLR4 agonist monophosphoryl lipid A (MPL) on TBI neuroinflammation and epileptogenesis in rats. TBI was induced in temporo-parietal cortex of rats by Controlled Cortical Impact device. Then rats received a single dose (0.1 μg/rat) of MPL by intracerebroventricular injection. After 24 h, CCI-injured rats received intraperitoneal injection of pentylenetetrazole 35 mg/kg once every other day until acquisition of generalized seizures. The injury size, number of survived neurons, and brain protein level of TNF-α, TGF-β, IL-10, and arginase1 (Arg1) were determined. Astrocytes and macrophage/microglia activation/polarization was assessed by double immunostaining with anti GFAP/Arg1 or anti Iba1/Arg1 antibodies. The CCI-injured rats developed generalized seizures after 5.9 ± 1.3 pentylenetetrazole injections (p < 0.001, compared to 12.3 ± 1.4 injections for sham-operated rats). MPL treatment returned the accelerated rate of epileptogenesis in TBI state to the sham-operated level. MPL did not change damage volume but attenuated number of dead neurons (p < 0.01). MPL decreased TNF-α overexpression (6 h post-TBI p < 0.0001), upregulated expression of TGF-β (48 h post-TBI, p < 0.0001), and IL-10 (48 h post-TBI, p < 0.0001) but did not change Arg1 expression. GFAP/Arg1 and Iba1/Arg1 positive cells were detected in TBI area with no significant change following MPL administration. MPL administration after TBI reduces vulnerability to seizure acquisition through down regulating neural death and inflammation, and up-regulating anti-inflammatory cytokines. This capacity along with the clinical safety, makes MPL a potential candidate for development of drugs against neurological deficits of TBI.

Decreased Resting-State Functional Connectivity of Periaqueductal Gray in Temporal Lobe Epilepsy Comorbid With Migraine

Objective: Patients with temporal lobe epilepsy (TLE) are at high risk for having a comorbid condition of migraine, and these two common diseases are proposed to have some shared pathophysiological mechanisms. Our recent study indicated the dysfunction of periaqueductal gray (PAG), a key pain-modulating structure, contributes to the development of pain hypersensitivity and epileptogenesis in epilepsy. This study is to investigate the functional connectivity of PAG network in epilepsy comorbid with migraine.

Methods: Thirty-two patients with TLE, including 16 epilepsy patients without migraine (EwoM) and 16 epilepsy patients with comorbid migraine (EwM), and 14 matched healthy controls (HCs) were recruited and underwent resting functional magnetic resonance imaging (fMRI) scans to measure the resting-state functional connectivity (RsFC) of PAG network. The frequency and severity of migraine attacks were assessed using the Migraine Disability Assessment Questionnaire (MIDAS) and Visual Analog Scale/Score (VAS). In animal experiments, FluoroGold (FG), a retrograde tracing agent, was injected into PPN and its fluorescence detected in vlPAG to trace the neuronal projection from vlPAG to PPN. FG traced neuron number was used to evaluate the neural transmission activity of vlPAG-PPN pathway. The data were processed and analyzed using DPARSF and SPSS17.0 software. Based on the RsFC finding, the excitatory transmission of PAG and the associated brain structure was studied via retrograde tracing in combination with immunohistochemical labeling of excitatory neurons.

Results: Compared to HCs group, the RsFC between PAG and the left pedunculopontine nucleus (PPN), between PAG and the corpus callosum (CC), was decreased both in EwoM and EwM group, while the RsFC between PAG and the right PPN was increased only in EwoM group but not in EwM group. Compared to EwoM group, the RsFC between PAG and the right PPN was decreased in EwM group. Furthermore, the RsFC between PAG and PPN was negatively correlated with the frequency and severity of migraine attacks. In animal study, a seizure stimulation induced excitatory transmission from PAG to PPN was decreased in rats with chronic epilepsy as compared to that in normal control rats.

Conclusion: The comorbidity of epilepsy and migraine is associated with the decreased RsFC between PAG and PPN.

Inflammation and Cognitive Function in Overweight and Obese Chinese Individuals

BACKGROUND

The role(s) of inflammation in obesity-associated cognitive decline in overweight or obese populations is not completely understood.

OBJECTIVE

To investigate the profile of plasma inflammatory cytokines in overweight and obese Chinese individuals and to assess the relationship between inflammation and cognitive function.

METHODS

We evaluated the cognitive domains of 282 Chinese adults, aged 35 to 64 years, using the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The participants were classified into three groups according to their body mass index. Inflammatory cytokines were determined by immune turbidimetric analysis and enzyme-linked immunosorbent assay. Data were analyzed using covariance and partial correlation analyses after adjusting for gender, age, education level, hypertension, and hyperlipemia.

RESULTS

The total MoCA scores of the overweight and obese groups were significantly lower than that of the control group. The obese group displayed a significantly higher level of tumor necrosis factor-α than the overweight and control groups and a significantly higher level of transforming growth factor-β than the control group. The overweight group displayed a significantly higher interleukin-4 level than the control and obese groups. After adjusting for confounding factors, however, we found no significant correlation between the level of plasma inflammatory cytokines and MMSE or MoCA total score.

CONCLUSIONS

Compared to normal-weight Chinese participants, overweight and obese Chinese participants revealed significant differences in their inflammatory cytokines profile; however, the inflammatory cytokine levels did not correlate with the significantly lower cognitive scores observed in the overweight and obese groups.

Genetic and molecular basis of epilepsy-related cognitive dysfunction

Epilepsy is a common neurological disease characterized by recurrent seizures. About 70 million people were affected by epilepsy or epileptic seizures. Epilepsy is a complicated complex or symptomatic syndromes induced by structural, functional, and genetic causes. Meanwhile, several comorbidities are accompanied by epileptic seizures. Cognitive dysfunction is a long-standing complication associated with epileptic seizures, which severely impairs quality of life. Although the definitive pathogenic mechanisms underlying epilepsy-related cognitive dysfunction remain unclear, accumulating evidence indicates that multiple risk factors are probably involved in the development and progression of cognitive dysfunction in patients with epilepsy. These factors include the underlying etiology, recurrent seizures or status epilepticus, structural damage that induced secondary epilepsy, genetic variants, and molecular alterations. In this review, we summarize several theories that may explain the genetic and molecular basis of epilepsy-related cognitive dysfunction.

Exposure to carbon black nanoparticles increases seizure susceptibility in male mice

Carbon black nanoparticles (CBNPs) can enter the central nervous system through blood circulation and olfactory nerves, affecting brain development or increasing neurological disease susceptibility. However, whether CBNPs exposure affects seizure is unclear. Herein, mice were exposed to two different doses of CBNPs (21 and 103 μg/animal) based on previous studies and the maximum exposure limitation (4 mg/m³) in occupational workplaces set by the Chinese government. In the pentylenetetrazol (PTZ) and kainic acid (KA) seizure models, high-dose CBNPs exposure increased seizure susceptibility in both models and increased spontaneous recurrent seizure (SRS) frequency in the KA model. In vivo local field potential (LFP) recording in KA model mice revealed that both low-dose and high-dose CBNPs exposure increased seizure-like event (SLE) frequency in the SRS interval but shortened SLE duration. Intriguingly, H&E staining and Nissl staining on brain tissue revealed that CBNPs exposure did not cause significant brain tissue morphology or neuronal damage. Detection of inflammatory factors, such as TNF-α, TGF-β1, IL-1β, and IL-6, in brain tissue showed that only high dose of CBNPs exposure increased the expression of cortical TGF-β1. By using the primary cultured neurons, we observed that CBNPs exposure not only significantly decreased the expression of the neuronal marker MAP2 but also enhanced the levels of action potential frequency in the neurons. In general, CBNPs exposure can affect abnormal epileptic discharges during the seizure interval and enhance susceptibility to frequent seizures. Our findings suggest that minimizing CBNPs exposure may be a potential way to prevent or ease seizure.

Hydrogen Alleviates Necroptosis and Cognitive Deficits in Lithium-Pilocarpine Model of Status Epilepticus

Status epilepticus without prompt seizure control always leads to neuronal death and long-term cognitive deficits, but effective intervention is still absent. Here, we found that hydrogen could alleviate the hippocampus-dependent spatial learning and memory deficit in lithium-pilocarpine model of status epilepticus in rats, as evidenced by the results in Morris water maze test. Hydrogen treatment downregulated the expression of necroptosis-related proteins, such as MLKL, phosphorylated-MLKL, and RIPK3 in hippocampus, and further protected neurons and astrocytes from necroptosis which was here first verified to occur in status epilepticus. Hydrogen also protected cells from apoptosis, which was indicated by the decreased cleaved-Caspase 3 expression. Meanwhile, Iba1+ microglial activation by status epilepticus was reduced by hydrogen treatment. These findings confirm the utility of hydrogen treatment in averting cell death including necroptosis and alleviating cognitive deficits caused by status epilepticus. Therefore, hydrogen may provide a potential and powerful clinical treatment for status epilepticus-related cognitive deficits.

Ventrolateral Periaqueductal Gray Matter Neurochemical Lesion Facilitates Epileptogenesis and Enhances Pain Sensitivity in Epileptic Rats

The ventrolateral periaqueductal gray matter (vlPAG) plays a critical role in the pathogenesis of migraine and few studies have shown that vlPAG might be involved in the pathophysiology of epilepsy. But its roles in epileptogenesis and comorbid relationship between migraine and epilepsy have never been reported. In this study, the impairments of vlPAG neuronal network during spontaneous recurrent seizure (SRS) development after status epilepticus (SE) were investigated, and the pain sensitivity as well as the SRS investigated after neurochemical lesion to vlPAG to determine the role of vlPAG in epileptogenesis and in migraine comorbidity with epilepsy. Neuronal loss and alterations of excitatory and inhibitory neural transmission within vlPAG accompanied the development of epileptogenesis induced by SE. On the other hand, neurochemical lesion to vlPAG enhanced frequency and duration of spontaneous seizure event and frequency of epileptiform inter-ictal spike discharges in electroencephalography (EEG), but decreased pain threshold in epileptic rats. This indicates an involvement of the pain regulating structure, vlPAG, in the pathogenesis of epilepsy. This may imply that vlPAG network alterations could be a possible underlying mechanism of the interactive comorbid relationship between epilepsy and migraine.

Correlation of cytokines, BDNF levels, and memory function in patients with opioid use disorder undergoing methadone maintenance treatment

BACKGROUND

Patients with opioid use disorder (OUD) show memory deficiencies and impaired treatment outcomes. Emerging evidence suggests that opioid abuse activates proinflammatory processes by increasing cytokine production and impairing neuroprotection, which damages the memory function in OUD patients. Therefore, we investigated whether plasma-based inflammatory and neurotrophic markers correlate with memory function in OUD patients.

METHOD

OUD patients undergoing methadone maintenance therapy (MMT) were investigated and followed up for 12 weeks. Plasma tumor necrosis factor (TNF)-α, C-reactive protein (CRP), interleukin (IL)-6, transforming growth factor (TGF)-β1, brain-derived neurotrophic factor (BDNF) levels, and Wechsler Memory Scale-Revised (WMS-R) scores were assessed at baseline and after 12 weeks of MMT. Multiple linear regressions and generalized estimating equations (GEEs) were used to examine the correlation between cytokines and memory performance.

RESULTS

We enrolled 89 patients at baseline; 47 patients completed the end-of-study assessments. Although Pearson correlations showed that CRP and TGF-β1 levels were significantly, negatively associated with some memory indices, the results were not significant after correction. The GEE results, controlled for several confounding factors and multiple testing, showed that changes in TNF-α levels were negatively correlated with changes in the visual memory index (P = 0.01), and that changes in IL-6 levels were negatively correlated with changes in the verbal memory index (P = 0.009).

CONCLUSION

Memory performance, TNF-α, and IL-6 levels in OUD patients were negative correlated. Additional studies on regulating TNF-α and IL-6 expression to improve memory function in OUD patients might be warranted.

Rifampicin ameliorates lithium-pilocarpine-induced seizures, consequent hippocampal damage and memory deficit in rats: Impact on oxidative, inflammatory and apoptotic machineries

Epilepsy is one of the serious neurological sequelae of bacterial meningitis. Rifampicin, the well-known broad spectrum antibiotic, is clinically used for chemoprophylaxis of meningitis. Besides its antibiotic effects, rifampicin has been proven to be an effective neuroprotective candidate in various experimental models of neurological diseases. In addition, rifampicin was found to have promising antioxidant, anti-inflammatory and anti-apoptotic effects. Herein, we investigated the anticonvulsant effect of rifampicin at experimental meningitis dose (20 mg/kg, i.p.) using lithium-pilocarpine model of status epilepticus (SE) in rats. Additionally, we studied the effect of rifampicin on seizure induced histopathological, neurochemical and behavioral abnormalities. Our study showed that rifampicin pretreatment attenuated seizure activity and the resulting hippocampal insults marked by hematoxylin and eosin. Markers of oxidative stress, neuroinflammation and apoptosis were evaluated, in the hippocampus, 24 h after SE induction. We found that rifampicin pretreatment suppressed oxidative stress as indicated by normalized malondialdehyde and glutathione levels. Rifampicin pretreatment attenuated SE-induced neuroinflammation and decreased the hippocampal expression of interleukin-1β, tumor necrosis factor-α, nuclear factor kappa-B, and cyclooxygenase-2. Moreover, rifampicin mitigated SE-induced neuronal apoptosis as indicated by fewer positive cytochrome c immunostained cells and lower caspase-3 activity in the hippocampus. Furthermore, Morris water maze testing at 7 days after SE induction showed that rifampicin pretreatment can improve cognitive dysfunction. Therefore, rifampicin, currently used in the management of meningitis, has a potential additional advantage of ameliorating its epileptic sequelae.

ALDH2 modulated changes in cytokine levels and cognitive function in bipolar disorder: A 12-week follow-up study

OBJECTIVES

We investigated the association of the aldehyde dehydrogenase 2 ( ALDH2) polymorphism (rs671), which is involved with the dopaminergic function, and with changes in cytokine levels and cognitive function, in a 12-week follow-up study in patients with bipolar disorder.

METHODS

Patients with a first diagnosis of bipolar disorder were recruited. Symptom severity and levels of plasma cytokines (tumor necrosis factor α, C-reactive protein, interleukin 6 and transforming growth factor β1) were examined during weeks 0, 1, 2, 4, 8 and 12. Neurocognitive function was evaluated at baseline and endpoint. The ALDH2 polymorphism genotype was determined.

RESULTS

A total of 541 patients with bipolar disorder were recruited, and 355 (65.6%) completed the 12-week follow-up. A multiple linear regression analysis showed a significant ( p = 0.000226) association between the ALDH2 polymorphism and changes in C-reactive protein levels. Different aspects of cognitive function improved in patients with different ALDH2 genotypes. Only patients with the ALDH2*1*1 genotype showed significant correlations between improvement of cognitive function and increased transforming growth factor -β1.

CONCLUSION

The ALDH2 gene might influence changes in cytokine levels and cognitive performance in patients with bipolar disorder. Additionally, changes in cytokine levels and cognitive function were correlated only in patients with specific ALDH2 genotypes.

Chronic Trigeminal Nerve Stimulation Protects Against Seizures, Cognitive Impairments, Hippocampal Apoptosis, and Inflammatory Responses in Epileptic Rats

Trigeminal nerve stimulation (TNS) has recently been demonstrated effective in the treatment of epilepsy and mood disorders. Here, we aim to determine the effects of TNS on epileptogenesis, cognitive function, and the associated hippocampal apoptosis and inflammatory responses. Rats were injected with pilocarpine to produce status epilepticus (SE) and the following chronic epilepsy. After SE induction, TNS treatment was conducted for 4 consecutive weeks. A pilocarpine re-injection was then used to induce a seizure in the epileptic rats. The hippocampal neuronal apoptosis induced by seizure was assessed by TUNEL staining and inflammatory responses by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). The spontaneous recurrent seizure (SRS) number was counted through video monitoring, and the cognitive function assessed through Morris Water Maze (MWM) test. TNS treatment attenuated the SRS attacks and improved the cognitive impairment in epileptic rats. A pilocarpine re-injection resulted in less hippocampal neuronal apoptosis and reduced level of interleukin-1 beta (IL-1β), tumor necrosis factor-α (TNF-α), and microglial activation in epileptic rats with TNS treatment in comparison to the epileptic rats without TNS treatment. It is concluded that TNS treatment shortly after SE not only protected against the chronic spontaneous seizures but also improved cognitive impairments. These antiepileptic properties of TNS may be related to its attenuating effects on hippocampal apoptosis and pro-inflammatory responses.

Increased sensitivity to kindling in mice lacking TSP1

The development of a hyperexcitable neuronal network is thought to be a critical event in epilepsy. Thrombospondins (TSPs) regulate synaptogenesis by binding the neuronal α2δ subunit of the voltage-gated calcium channel. TSPs regulate synapse formation during development and in the mature brain following injury. It is unclear if TSPs are involved in hyperexcitability that contributes to the development of epilepsy. Here we explore the development of epilepsy using a pentylenetetrazole (PTZ) kindling model in mice lacking TSP1 and TSP2. Unexpectedly, we found increased sensitivity to PTZ kindling in mice lacking TSP1, while mice lacking TSP2 kindled similar to wild-type. We found that the increased seizure susceptibility in the TSP1 knockout (KO) mice was not due to a compensatory increase in TSP2 mRNA as TSP1/2 KO mice were sensitive to PTZ, similar to the TSP1 KO mice. Furthermore, there were similar levels of TGF-B signal activation during kindling in the TSP1 KO mice compared to wild-type. We observed decreased expression of voltage-dependent calcium channel subunit CACNA2D1 mRNA in TSP1, TSP2, and TSP1/2 KO mice. Decreased CACNA2D2 mRNA was only detected in mice that lacked TSP1 and α2δ-1/2 protein levels in the cortex were lower in the TSP 1/2 KO mice. CACNA2D2 knockout mice have spontaneous seizures and increased PTZ seizure susceptibility. Here we report similar findings, TSP1, and TSP1/2 KO mice have low levels of CACNA2D2 mRNA expression and α2δ-1/2 receptor level in the cortex, and are more susceptible to seizures. CACNA2D2 mutations in mice and humans can cause epilepsy. Our data suggest TSP1 in particular may control CACNA2D2 levels and could be a modifier of seizure susceptibility.

A key role for TGF-β1 in hippocampal synaptic plasticity and memory

Transforming Growth Factor β1 (TGF-β1) is a well-known neuroprotective and neurotrophic factor demonstrated to play a role in synaptic transmission. However, its involvement in physiological mechanisms underlying synaptic plasticity and memory at hippocampal level has not been thoroughly investigated. Here, we examine the role of TGF-β1 in hippocampal long-term potentiation (LTP) and memory in adult wild type mice. Our data provide evidence that administration of exogenous TGF-β1 is able to convert early-phase-LTP into late-phase-LTP. Furthermore, we show that the block of the endogenous TGF-β1 signaling pathway by the specific TGF-β1 inhibitor SB431542, impairs LTP and object recognition memory. The latter impairment was rescued by administration of exogenous TGF-β1, suggesting that endogenously produced TGF-β1 plays a role in physiological mechanisms underlying LTP and memory. Finally, TGF-β1 functional effect correlates with an increased expression of the phosphorylated transcription factor cAMP-Responsive Element Binding protein.

Albumin induces excitatory synaptogenesis through astrocytic TGF-β/ALK5 signaling in a model of acquired epilepsy following blood-brain barrier dysfunction

Post-injury epilepsy (PIE) is a common complication following brain insults, including ischemic, and traumatic brain injuries. At present, there are no means to identify the patients at risk to develop PIE or to prevent its development. Seizures can occur months or years after the insult, do not respond to anti-seizure medications in over third of the patients, and are often associated with significant neuropsychiatric morbidities. We have previously established the critical role of blood-brain barrier dysfunction in PIE, demonstrating that exposure of brain tissue to extravasated serum albumin induces activation of inflammatory transforming growth factor beta (TGF-β) signaling in astrocytes and eventually seizures. However, the link between the acute astrocytic inflammatory responses and reorganization of neural networks that underlie recurrent spontaneous seizures remains unknown. Here we demonstrate in vitro and in vivo that activation of the astrocytic ALK5/TGF-β-pathway induces excitatory, but not inhibitory, synaptogenesis that precedes the appearance of seizures. Moreover, we show that treatment with SJN2511, a specific ALK5/TGF-β inhibitor, prevents synaptogenesis and epilepsy. Our findings point to astrocyte-mediated synaptogenesis as a key epileptogenic process and highlight the manipulation of the TGF-β-pathway as a potential strategy for the prevention of PIE.

Neuronal and astroglial TGFβ-Smad3 signaling pathways differentially regulate dendrite growth and synaptogenesis

To address the role of the transforming growth factor beta (TGFβ)-Smad3 signaling pathway in dendrite growth and associated synaptogenesis, we used small inhibitory RNA to knockdown the Smad3 gene in either cultured neurons and or primary astrocytes. We found that TGFβ1 treatment of primary neurons increased dendrite extensions and the number of synapsin-1-positive synapses. When Smad3 was knockdown in primary neurons, dendrite growth was inhibited and the number of synapsin-1-positive synapses reduced even with TGFβ1 treatment. When astrocyte-conditioned medium (ACM), collected from TGFβ1-treated astrocytes (TGFβ1-stimulated ACM), was added to cultured neurons, dendritic growth was inhibited and the number of synapsin-1-positive puncta reduced. When TGFβ1-stimulated ACM was collected from astrocytes with Smad3 knocked down, this conditioned media promoted the growth of dendrites and the number of synapsin-1-positive puncta in cultured neurons. We further found that TGFβ1 signaling through Smad3 increased the expression of chondroitin sulfate proteoglycans, neurocan, and phosphacan in ACM. Application of chondroitinase ABC to the TGFβ1-stimulated ACM reversed its inhibitory effects on the dendrite growth and the number of synapsin-1-positive puncta. On the other hand, we found that TGFβ1 treatment caused a facilitation of Smad3 phosphorylation and translocation to the nucleus induced by status epilepticus (SE) in wild-type (Smad3(+/+)) mice, and this treatment also caused a promotion of γ-aminobutyric acid-ergic synaptogenesis impaired by SE in Smad3(+/+) as well as in Smad3(-/-) mice, but more dramatic promotion in Smad3(+/+) mice. Thus, we provide evidence for the first time that TGFβ-Smad3 signaling pathways within neuron and astrocyte differentially regulate dendrite growth and synaptogenesis, and this pathway may be involved in the pathogenesis of some central nervous system diseases, such as epilepsy.

Smad3 deficiency increases cortical and hippocampal neuronal loss following traumatic brain injury

Transforming growth factor-β (TGF-β) signaling is involved in pathological processes following brain injury. TGF-β signaling through Smad3 contributes significantly to the immune response and glial scar formation after brain injury. However, TGF-β is also neuroprotective, suggesting that Smad3 signaling may also be involved in neuroprotection after injury. We found expression of the TGF-β type II receptor (TβRII) and Smad3 protein to be strongly and rapidly induced in neurons in the ipsilateral cortex and CA1 region of the hippocampus after stab wound injury. In contrast, astrocytic expression of TβRII and Smad3 was induced more slowly. Comparison of the response of wild-type and Smad3 null mice to cortical stab wound injury showed a more pronounced loss of neuronal viability in Smad3 null mice. Neuronal density was more strongly reduced in Smad3 null mice than in wild-type mice at 1 and 3days post lesion in both the ipsilateral cortex and hippocampal CA1 region. Fluoro-Jade B, TUNEL staining, and cleaved caspase-3 staining also demonstrated increased neuronal degeneration at early time points after injury in the ipsilateral hemisphere in Smad3 null mice. Taken together, our results suggest that TGF-β cytokine family signaling through Smad3 protects neurons in the damaged cortex and hippocampus at early time points after injury.

TGF-β superfamily gene expression and induction of the Runx1 transcription factor in adult neurogenic regions after brain injury

Traumatic brain injury (TBI) increases neurogenesis in the forebrain subventricular zone (SVZ) and the hippocampal dentate gyrus (DG). Transforming growth factor-β (TGF-β) superfamily cytokines are important regulators of adult neurogenesis, but their involvement in the regulation of this process after brain injury is unclear. We subjected adult mice to controlled cortical impact (CCI) injury, and isolated RNA from the SVZ and DG at different post-injury time points. qPCR array analysis showed that cortical injury caused significant alterations in the mRNA expression of components and targets of the TGF-β, BMP, and activin signaling pathways in the SVZ and DG after injury, suggesting that these pathways could regulate post-injury neurogenesis. In both neurogenic regions, the injury also induced expression of Runt-related transcription factor-1 (Runx1), which can interact with intracellular TGF-β Smad signaling pathways. CCI injury strongly induced Runx1 expression in activated and proliferating microglial cells throughout the neurogenic regions. Runx1 protein was also expressed in a subset of Nestin- and GFAP-expressing putative neural stem or progenitor cells in the DG and SVZ after injury. In the DG only, these Runx1+ progenitors proliferated. Our data suggest potential roles for Runx1 in the processes of microglial cell activation and proliferation and in neural stem cell proliferation after TBI.

Molecular mechanisms underlying the analgesic property of intrathecal dexmedetomidine and its neurotoxicity evaluation: an in vivo and in vitro experimental study

Background

Dexmedetomidine (DEX) has been used under perioperative settings as an adjuvant to enhance the analgesic property of local anesthetics by some anesthesiologists. However, the analgesic mechanisms and neurotoxicity of DEX were poorly understood. This study examined the effect of DEX alone on inflammatory pain, and it also examined the underlying molecular mechanisms of DEX in the spinal cord. Furthermore, in vivo and in vitro experiments were performed to investigate the neurotoxicity of DEX on the spinal cord and cortical neurons.

Methods

This study used adult, male Kunming mice. In the acute inflammatory model, the left hind-paws of mice were intradermally injected with pH 5.0 PBS while chronic constrictive injury (CCI) of the sciatic nerve was used to duplicate the neuropathic pain condition. Thermal paw withdrawal latency and mechanical paw withdrawal threshold were tested with a radiant heat test and the Von Frey method, respectively. Locomotor activity and motor coordination were evaluated using the inverted mesh test. Western blotting examined spinal ERK1/2, p-ERK1/2, caspase-3 and β-actin expressions, while spinal c-Fos protein expression was realized with immunohistochemical staining. Hematoxylin eosin (HE) staining was used to examine the pathological impacts of intrathecal DEX on the spinal cord. DAPI (4′,6-diamidino-2-phenylindole) staining was used to observe cell death under an immunofluorescence microscope.

Results

Intra-plantar pH 5.0 PBS-induced acute pain required spinal ERK1/2 activation. Inhibition of spinal ERK1/2 signaling by intrathecal injection of DEX displayed a robust analgesia, via a α2-receptor dependent manner. The analgesic properties of DEX were validated in CCI mice. In vivo studies showed that intrathecal DEX has no significant pathological impacts on the spinal cord, and in vitro experiments indicated that DEX has potential protective effects of lidocaine-induced neural cell death.

Conclusion

Intrathecal injection of DEX alone or as an adjuvant might be potential for pain relief.