Epileptogenesis after traumatic brain injury in Plaur-deficient mice

Neuroprotective effects of naltrexone in a mouse model of post-traumatic seizures

Traumatic Brain Injury (TBI) induces neuroinflammatory response that can initiate epileptogenesis, which develops into epilepsy. Recently, we identified anti-convulsive effects of naltrexone, a mu-opioid receptor (MOR) antagonist, used to treat drug addiction. While blocking opioid receptors can reduce inflammation, it is unclear if post-TBI seizures can be prevented by blocking MORs. Here, we tested if naltrexone prevents neuroinflammation and/or seizures post-TBI. TBI was induced by a modified Marmarou Weight-Drop (WD) method on 4-week-old C57BL/6J male mice. Mice were placed in two groups: non-telemetry assessing the acute effects or in telemetry monitoring for interictal events and spontaneous seizures both following TBI and naltrexone. Molecular, histological and neuroimaging techniques were used to evaluate neuroinflammation, neurodegeneration and fiber track integrity at 8 days and 3 months post-TBI. Peripheral immune responses were assessed through serum chemokine/cytokine measurements. Our results show an increase in MOR expression, nitro-oxidative stress, mRNA expression of inflammatory cytokines, microgliosis, neurodegeneration, and white matter damage in the neocortex of TBI mice. Video-EEG revealed increased interictal events in TBI mice, with 71% mice developing post-traumatic seizures (PTS). Naltrexone treatment ameliorated neuroinflammation, neurodegeneration, reduced interictal events and prevented seizures in all TBI mice, which makes naltrexone a promising candidate against PTS, TBI-associated neuroinflammation and epileptogenesis in a WD model of TBI.

Insights into epileptogenesis from post-traumatic epilepsy

Post-traumatic epilepsy (PTE) accounts for 5% of all epilepsies. The incidence of PTE after traumatic brain injury (TBI) depends on the severity of injury, approaching one in three in groups with the most severe injuries. The repeated seizures that characterize PTE impair neurological recovery and increase the risk of poor outcomes after TBI. Given this high risk of recurrent seizures and the relatively short latency period for their development after injury, PTE serves as a model disease to understand human epileptogenesis and trial novel anti-epileptogenic therapies. Epileptogenesis is the process whereby previously normal brain tissue becomes prone to recurrent abnormal electrical activity, ultimately resulting in seizures. In this Review, we describe the clinical course of PTE and highlight promising research into epileptogenesis and treatment using animal models of PTE. Clinical, imaging, EEG and fluid biomarkers are being developed to aid the identification of patients at high risk of PTE who might benefit from anti-epileptogenic therapies. Studies in preclinical models of PTE have identified tractable pathways and novel therapeutic strategies that can potentially prevent epilepsy, which remain to be validated in humans. In addition to improving outcomes after TBI, advances in PTE research are likely to provide therapeutic insights that are relevant to all epilepsies.

Identification of immune infiltration and cuproptosis-related molecular clusters in tuberculosis

Background

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) infection. Cuproptosis is a novel cell death mechanism correlated with various diseases. This study sought to elucidate the role of cuproptosis-related genes (CRGs) in TB.

Methods

Based on the GSE83456 dataset, we analyzed the expression profiles of CRGs and immune cell infiltration in TB. Based on CRGs, the molecular clusters and related immune cell infiltration were explored using 92 TB samples. The Weighted Gene Co-expression Network Analysis (WGCNA) algorithm was utilized to identify the co-expression modules and cluster-specific differentially expressed genes. Subsequently, the optimal machine learning model was determined by comparing the performance of the random forest (RF), support vector machine (SVM), generalized linear model (GLM), and eXtreme Gradient Boosting (XGB). The predictive performance of the machine learning model was assessed by generating calibration curves and decision curve analysis and validated in an external dataset.

Results

11 CRGs were identified as differentially expressed cuproptosis genes. Significant differences in immune cells were observed in TB patients. Two cuproptosis-related molecular clusters expressed genes were identified. Distinct clusters were identified based on the differential expression of CRGs and immune cells. Besides, significant differences in biological functions and pathway activities were observed between the two clusters. A nomogram was generated to facilitate clinical implementation. Next, calibration curves were generated, and decision curve analysis was conducted to validate the accuracy of our model in predicting TB subtypes. XGB machine learning model yielded the best performance in distinguishing TB patients with different clusters. The top five genes from the XGB model were selected as predictor genes. The XGB model exhibited satisfactory performance during validation in an external dataset. Further analysis revealed that these five model-related genes were significantly associated with latent and active TB.

Conclusion

Our study provided hitherto undocumented evidence of the relationship between cuproptosis and TB and established an optimal machine learning model to evaluate the TB subtypes and latent and active TB patients.

Medial prefrontal cortex oxytocin mitigates epilepsy and cognitive impairments induced by traumatic brain injury through reducing neuroinflammation in mice

Traumatic brain injury (TBI) is a major risk factor to develop epilepsy and cognitive impairments. Neuropeptide oxytocin has been previously evidenced to produce antiepileptic effects. However, the involvement of central oxytocin in TBI-induced epileptic status and cognitive dysfunctions is not fully elucidated. In this study, we aim to investigate the role of oxytocin on a TBI model followed by seizure induction to clarify whether the epilepsy and cognitive deficits could be mitigated by oxytocin. TBI was established by weight drop and epileptic behaviors were induced by pentylenetetrazole (PTZ) injection in mice. Moreover, oxytocin was microinjected into the medial prefrontal cortex (mPFC) to observe the effects on the epilepsy and cognition. The blood-brain barrier (BBB) function and the neuroinflammation were measured by Evans Blue staining and enzyme-linked immunosorbent assays, respectively. Mice exposed to TBI demonstrate increased vulnerability to PTZ-mediated seizures and cognitive disturbances with a decrease in peripheral and brain oxytocin levels. Additionally, TBI reduces oxytocin, disrupts the BBB permeability and triggers neuroinflammation in mPFC in PTZ-treated mice. Intra-mPFC oxytocin simultaneously mitigates epilepsy and cognitive impairments. Finally, oxytocin restores BBB integrity and reduces mPFC inflammation in PTZ-treated TBI mice. These findings showed that intra-mPFC oxytocin suppressed the seizure vulnerability and cognitive deficits in TBI mice. The normalization of BBB integrity and inhibition of neuroinflammation may be involved in the antiepileptic and cognition-improved effects of oxytocin, suggesting that targeting inflammatory procedure in mPFC may decrease the risk to develop epilepsy and cognitive impairments in individuals previously experienced TBI.

N6-methyladenosine RNA is modified in the rat hippocampus following traumatic brain injury with hypothermia treatment

Recent studies have suggested a role for N6-methyladenosine (m6A) modification in neurological diseases. Hypothermia, a commonly used treatment for traumatic brain injury, plays a neuroprotective role by altering m6A modifications. In this study, methylated RNA immunoprecipitation sequencing (MeRIP-Seq) was applied to conduct a genome-wide analysis of RNA m6A methylation in the rat hippocampus of Sham and traumatic brain injury (TBI) groups. In addition, we identified the expression of mRNA in the rat hippocampus after TBI with hypothermia treatment. Compared with the Sham group, the sequencing results of the TBI group showed that 951 different m6A peaks and 1226 differentially expressed mRNAs were found. We performed cross-linking analysis of the data of the two groups. The result showed that 92 hyper-methylated genes were upregulated, 13 hyper-methylated genes were downregulated, 25 hypo-methylated genes were upregulated, and 10 hypo-methylated genes were downregulated. Moreover, a total of 758 differential peaks were identified between TBI and hypothermia treatment groups. Among these differential peaks, 173 peaks were altered by TBI and reversed by hypothermia treatment, including Plat, Pdcd5, Rnd3, Sirt1, Plaur, Runx1, Ccr1, Marveld1, Lmnb2, and Chd7. We found that hypothermia treatment transformed some aspects of the TBI-induced m6A methylation landscape of the rat hippocampus.

Post-Traumatic Epilepsy and Comorbidities: Advanced Models, Molecular Mechanisms, Biomarkers, and Novel Therapeutic Interventions

Post-traumatic epilepsy (PTE) is one of the most devastating long-term, network consequences of traumatic brain injury (TBI). There is currently no approved treatment that can prevent onset of spontaneous seizures associated with brain injury, and many cases of PTE are refractory to antiseizure medications. Post-traumatic epileptogenesis is an enduring process by which a normal brain exhibits hypersynchronous excitability after a head injury incident. Understanding the neural networks and molecular pathologies involved in epileptogenesis are key to preventing its development or modifying disease progression. In this article, we describe a critical appraisal of the current state of PTE research with an emphasis on experimental models, molecular mechanisms of post-traumatic epileptogenesis, potential biomarkers, and the burden of PTE-associated comorbidities. The goal of epilepsy research is to identify new therapeutic strategies that can prevent PTE development or interrupt the epileptogenic process and relieve associated neuropsychiatric comorbidities. Therefore, we also describe current preclinical and clinical data on the treatment of PTE sequelae. Differences in injury patterns, latency period, and biomarkers are outlined in the context of animal model validation, pathophysiology, seizure frequency, and behavior. Improving TBI recovery and preventing seizure onset are complex and challenging tasks; however, much progress has been made within this decade demonstrating disease modifying, anti-inflammatory, and neuroprotective strategies, suggesting this goal is pragmatic. Our understanding of PTE is continuously evolving, and improved preclinical models allow for accelerated testing of critically needed novel therapeutic interventions in military and civilian persons at high risk for PTE and its devastating comorbidities.

Blockade of TRPC Channels Limits Cholinergic-Driven Hyperexcitability and Seizure Susceptibility After Traumatic Brain Injury

We investigated the contribution of excitatory transient receptor potential canonical (TRPC) cation channels to posttraumatic hyperexcitability in the brain 7 days following controlled cortical impact model of traumatic brain injury (TBI) to the parietal cortex in male adult mice. We investigated if TRPC1/TRPC4/TRPC5 channel expression is upregulated in excitatory neurons after TBI in contribution to epileptogenic hyperexcitability in key hippocampal and cortical circuits that have substantial cholinergic innervation. This was tested by measuring TRPC1/TRPC4/TRPC5 protein and messenger RNA (mRNA) expression, assays of cholinergic function, neuronal Ca²⁺ imaging in brain slices, and seizure susceptibility after TBI. We found region-specific increases in expression of TRPC1, TRPC4, and TRPC5 subunits in the hippocampus and cortex following TBI. The dentate gyrus, CA3 region, and cortex all exhibited robust upregulation of TRPC4 mRNA and protein. TBI increased cFos activity in dentate gyrus granule cells (DGGCs) and layer 5 pyramidal neurons both at the time of TBI and 7 days post-TBI. DGGCs displayed greater magnitude and duration of acetylcholine-induced rises in intracellular Ca²⁺ in brain slices from mice subjected to TBI. The TBI mice also exhibited greater seizure susceptibility in response to pentylenetetrazol-induced kindling. Blockade of TRPC4/TRPC5 channels with M084 reduced neuronal hyperexcitation and impeded epileptogenic progression of kindling. We observed that the time-dependent upregulation of TRPC4/TRPC5-containing channels alters cholinergic responses and activity of principal neurons acting to increase proexcitatory sensitivity. The underlying mechanism includes acutely decreased acetylcholinesterase function, resulting in greater G_q/11-coupled muscarinic receptor activation of TRPC channels. Overall, our evidence suggests that TBI-induced plasticity of TRPC channels strongly contributes to overt hyperexcitability and primes the hippocampus and cortex for seizures.

Biomarkers for posttraumatic epilepsy

A biomarker is a characteristic that can be objectively measured as an indicator of normal biologic processes, pathogenic processes, or responses to an exposure or intervention, including therapeutic interventions. Biomarker modalities include molecular, histologic, radiographic, or physiologic characteristics. To improve the understanding and use of biomarker terminology in biomedical research, clinical practice, and medical product development, the Food and Drug Administration (FDA)-National Institutes of Health (NIH) Joint Leadership Council developed the BEST Resource (Biomarkers, EndpointS, and other Tools). The seven BEST biomarker categories include the following: (a) susceptibility/risk biomarkers, (b) diagnostic biomarkers, (c) monitoring biomarkers, (d) prognostic biomarkers, (e) predictive biomarkers, (f) pharmacodynamic/response biomarkers, and (g) safety biomarkers. We hypothesize some potential overlap between the reported biomarkers of traumatic brain injury (TBI), epilepsy, and posttraumatic epilepsy (PTE). Here, we tested this hypothesis by reviewing studies focusing on biomarker discovery for posttraumatic epileptogenesis and epilepsy. The biomarker modalities reviewed here include plasma/serum and cerebrospinal fluid molecular biomarkers, imaging biomarkers, and electrophysiologic biomarkers. Most of the reported biomarkers have an area under the receiver operating characteristic curve greater than 0.800, suggesting both high sensitivity and high specificity. Our results revealed little overlap in the biomarker candidates between TBI, epilepsy, and PTE. In addition to using single parameters as biomarkers, machine learning approaches have highlighted the potential for utilizing patterns of markers as biomarkers. Although published data suggest the possibility of identifying biomarkers for PTE, we are still in the early phase of the development curve. Many of the seven biomarker categories lack PTE-related biomarkers. Thus, further exploration using proper, statistically powered, and standardized study designs with validation cohorts, and by developing and applying novel analytical methods, is needed for PTE biomarker discovery.

Novel Approaches to Prevent Epileptogenesis After Traumatic Brain Injury

Traumatic brain injury (TBI) is defined as an alteration in brain function or other evidence of brain pathology caused by an external force. When epilepsy develops following TBI, it is known as post-traumatic epilepsy (PTE). PTE occurs in a subset of patients suffering from different types and severities of TBI, occurs more commonly following severe injury, and greatly impacts the quality of life for patients recovering from TBI. Similar to other types of epilepsy, PTE is often refractory to drug treatment with standard anti-seizure drugs. No therapeutic approaches have proven successful in the clinic to prevent the development of PTE. Therefore, novel treatment strategies are needed to stop the development of PTE and improve the quality of life for patients after TBI. Interestingly, TBI represents an excellent clinical opportunity for intervention to prevent epileptogenesis as typically the time of initiation of epileptogenesis (i.e., TBI) is known, the population of at-risk patients is large, and animal models for preclinical studies of mechanisms and treatment targets are available. If properly identified and treated, there is a true opportunity to prevent epileptogenesis after TBI and stop seizures from ever happening. With that goal in mind, here we review previous attempts to prevent PTE both in animal studies and in humans, we examine how biomarkers could enable better-targeted therapeutics, and we discuss how genetic variation may predispose individuals to PTE. Finally, we highlight exciting new advances in the field that suggest that there may be novel approaches to prevent PTE that should be considered for further clinical development.

Plau/Plaur double-deficiency did not worsen lesion severity or vascular integrity after traumatic brain injury

Binding of urokinase-type plasminogen activator receptor (uPAR) to its ligand uPA or to its plasma membrane partner, platelet-derived growth factor receptor β (PDGFRβ), promotes neuroprotection, cell proliferation, and angiogenesis. Following injury, single deficiency in uPA or uPAR leads in increased tissue loss and compromised vascular remodeling. We hypothesized that double-deficiency of uPAR (Plaur) and uPA (Plau) would result in increased lesion area and poor vascular integrity after traumatic brain injury (TBI). TBI was induced by lateral fluid-percussion injury in Plau/Plaur double-knockout (dKO) and wild-type (Wt) mice. The cortical lesion area was quantified in unfolded cortical maps prepared from thionin-stained sections at 4 d or 30 d post-TBI. The density of PDGFRβ+ pericytes and blood vessels was calculated from immunostained sections. Blood-brain barrier leakage was analyzed using ImageJ® from IgG-immunostained sections. Genotype had no effect on the total area of the cortical lesion at 4 d or 30 d post-TBI (p > 0.05) or its progression as the overall lesion area was comparable at 4 d and 30 d post-TBI in both genotypes (p > 0.05). Subfield analysis, however, indicated that damage to the visual cortex at 4 d post-TBI in dKO-TBI mice was 53 % of that in Wt-TBI mice (p < 0.05). Both genotypes had a higher density of PDGFRβ-positive pericytes at 4 d than at 30 d post-TBI (p < 0.05), but no genotype effect was detected between these time-points (p > 0.05). TBI-induced increase in the density of PDGFRβ+ blood vessels at the region adjacent to the lesion core was comparable in both genotypes (p > 0.05). Genotype had no effect on TBI-induced IgG leakage into the perilesional cortical parenchyma (p > 0.05). Contrary to our expectations, Plau/Plaur double-deficiency did not aggravate TBI-related structural outcome.

Urokinase receptor and tissue plasminogen activator as immediate-early genes in pentylenetetrazole-induced seizures in the mouse brain

Epileptogenesis progressively leads to the rearrangement of normal neuronal networks into more excitable ones and can be viewed as a form of neuroplasticity, the molecular mechanisms of which still remain obscure. Here, we studied pentylenetetrazole seizure-induced regulation of genes for plasminogen activator system in the mouse brain. We found that expression of tissue plasminogen activator (tPA) and urokinase receptor (uPAR) mRNA was strongly increased in the mouse cerebral cortex, hippocampus, striatum and amygdala as early as 3 hr after pentylenetetrazole seizures. Such early activity-induced expression of uPAR in the central nervous system has not been demonstrated before. uPAR mRNA accumulation was followed by elevation of uPAR protein, indicating a complete transcription-translation process. Both tPA gene induction and uPAR gene induction were independent of the protein synthesis, suggesting that they are regulated by neural activity as immediate-early genes. In contrast to tPA and uPAR genes, the expression of which returned to the basal level 6 hr following seizures, urokinase and plasminogen activator inhibitor-1 gene expression showed a delayed activation only at 3 days after seizures. In conclusion, our results suggest an important sensitivity of the brain plasminogen activator system to seizure activity which raises the question of its role in activity-dependent neural tissue remodeling in pathological and normal conditions.

Deficiency of urokinase-type plasminogen activator and its receptor affects social behavior and increases seizure susceptibility

Extracellular proteolysis initiated by the binding of urokinase-type plasminogen activator (uPA) to its receptor (uPAR) regulates the development of inhibitory neuronal circuits in the cerebral cortex and tissue remodeling after epileptogenic brain injury. To study the function of different components of the uPA-uPAR system on behavior and epileptogenesis, and to complement our previous studies on naïve and injured mice deficient in the uPA-encoding gene Plau or the uPAR-encoding gene Plaur, we analyzed the behavioral phenotype, seizure susceptibility, and perineuronal nets surrounding parvalbumin-positive inhibitory interneurons in Plau and Plaur (double knockout dKO) mice. In a climbing test, dKO mice showed reduced interest towards the environment as compared with Wt mice (p < 0.01). In a social approach test, however, dKO mice spent more time than Wt mice exploring the compartment containing a stranger mouse than the empty compartment (p < 0.05). Moreover, in a social interaction test, dKO mice exhibited increased contact time (p < 0.01). Compared with Wt mice, the dKO mice also had a longer single contact duration (p < 0.001) with the stranger mouse. In the elevated plus-maze, grooming, and marble burying tests, the anxiety level of dKO mice did not differ from that of Wt mice. Rearing time in an exploratory activity test, and spatial learning and memory in the Morris swim navigation task were also comparable between dKO and Wt mice. In the pentylenetetrazol (PTZ) seizure-susceptibility test, dKO mice had a shorter latency to the first epileptiform spike (p = 0.0001) and a greater total number of spikes (p < 0.001) than Wt mice. The dKO genotype did not affect the number of cortical perineuronal nets. Our findings indicate that Plau/Plaur-deficiency leads to a more social phenotype toward other mice with diminished interest in the surrounding environment, and increased seizure susceptibility.

Dysregulated Glucose Metabolism as a Therapeutic Target to Reduce Post-traumatic Epilepsy

Traumatic brain injury (TBI) is a significant cause of disability worldwide and can lead to post-traumatic epilepsy. Multiple molecular, cellular, and network pathologies occur following injury which may contribute to epileptogenesis. Efforts to identify mechanisms of disease progression and biomarkers which predict clinical outcomes have focused heavily on metabolic changes. Advances in imaging approaches, combined with well-established biochemical methodologies, have revealed a complex landscape of metabolic changes that occur acutely after TBI and then evolve in the days to weeks after. Based on this rich clinical and preclinical data, combined with the success of metabolic therapies like the ketogenic diet in treating epilepsy, interest has grown in determining whether manipulating metabolic activity following TBI may have therapeutic value to prevent post-traumatic epileptogenesis. Here, we focus on changes in glucose utilization and glycolytic activity in the brain following TBI and during seizures. We review relevant literature and outline potential paths forward to utilize glycolytic inhibitors as a disease-modifying therapy for post-traumatic epilepsy.