Preclinical Models of Traumatic Brain Injury: Emerging Role of Glutamate in the Pathophysiology of Depression

The Role of Nanotechnology in Understanding the Pathophysiology of Traumatic Brain Injury

Recently, traumatic brain injury (TBI) has been a growing disorder due to frequent brain dysfunction. The Glasgow Coma Scale expresses TBI as classified as having mild, moderate, or severe brain effects, according to the effects on the brain. Brain receptors undergo various modifications in their pathology through chemical synaptic pathways, leading to depression, Alzheimer's, and Parkinson's disease. These brain disorders can be controlled using central receptors such as dopamine, glutamate, and γ-aminobutyric acid, which are clearly explained in this review. Furthermore, there are many complications in TBI's clinical trials and diagnostics, leading to insignificant treatment, causing permanent neuro-damage, physical disability, and even death. Bio-screening and conventional molecular-based therapies are inappropriate due to poor preclinical testing and delayed recovery. Hence, modern nanotechnology utilizing nanopulsed laser therapy and advanced nanoparticle insertion will be suitable for TBI's diagnostics and treatment. In recent days, nanotechnology has an important role in TBI control and provides a higher success rate than conventional therapies. This review highlights the pathophysiology of TBI by comprising the drawbacks of conventional techniques and supports suitable modern alternates for treating TBI.

Traumatic Brain Injury as a Public Health Issue: Epidemiology, Prognostic Factors and Useful Data from Forensic Practice

Traumatic brain injury (TBI) represents a major public health problem, being a leading cause of disability and mortality among young people in developed countries. Head trauma occurs across all age groups, each experiencing consistently high rates of mortality and disability. This review aims to present an overview of TBI epidemiology and its socioeconomic impact, alongside data valuable for prevention, clinical management, and research efforts. Methods: A narrative review of TBI was performed with a particular focus on forensic pathology and public health. In fact, this review highlighted the economic and epidemiological aspects of TBI, as well as autopsy, histology, immunohistochemistry, and miRNA. Results: These data, together with immunohistochemical markers, are crucial for histopathological diagnosis and to determine the timing of injury onset, a fundamental aspect in forensic pathology practice. There is compelling evidence that brain injury biomarkers may enhance predictive models for clinical and prognostic outcomes. By clarifying the cause of death and providing details on survival time after trauma, forensic tools offer valuable information to improve the clinical management of TBI and guide preventive interventions. Conclusions: TBI is one of the most common causes of death today, with high costs for health care spending. Knowing the different mechanisms of TBI, reduces health care costs and helps improve prognosis.

Community-based exercise program, self-reported health-related symptoms, and quality of life in persons with traumatic brain injury 45 + years old

BACKGROUND

Individuals with moderate to severe traumatic brain injury (msTBI) have reported a lack of motivation, lack of time, and fatigue as perceived barriers to exercise.

OBJECTIVE

To evaluate the effects of an exercise program on self-reported health-related symptoms and quality of life in persons 45-years and older with msTBI.

METHODS

Post-hoc analysis of a prospective community-based 12-week exercise program of 20 adults, age 45-80 years, with msTBI. Ten were in aerobic exercise training (AET) program and 10 in a stretching and toning (SAT) program. The AET group was instructed to exercise based on their estimated maximal heart rate (HR) for 150 minutes weekly. The SAT group was to stretch for the same target time without significantly increasing HR or level of exertion. Outcome measures were Traumatic Brain Injury Quality of Life (TBI-QOL) for global, cognitive, emotional, and social health, Patient Health Questionnaire-9 (PHQ-9) for depressive symptoms, and Pittsburgh Sleep Quality Index (PSQI) for sleep quality.

RESULTS

AET was associated with improved self-reported cognitive health and sleep compared to SAT. Moderate to large, positive effect sizes were also observed in the AET group in the QOL categories of global, emotional, and social health, and depressive symptoms.

CONCLUSIONS

This study offers preliminary evidence that AET may improve health-related QOL, especially for cognition and sleep, in middle-aged and older adults with msTBI.

Electrical stimulation methods and protocols for the treatment of traumatic brain injury: a critical review of preclinical research

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of disabilities resulting from cognitive and neurological deficits, as well as psychological disorders. Only recently, preclinical research on electrical stimulation methods as a potential treatment of TBI sequelae has gained more traction. However, the underlying mechanisms of the anticipated improvements induced by these methods are still not fully understood. It remains unclear in which stage after TBI they are best applied to optimize the therapeutic outcome, preferably with persisting effects. Studies with animal models address these questions and investigate beneficial long- and short-term changes mediated by these novel modalities.

METHODS

In this review, we present the state-of-the-art in preclinical research on electrical stimulation methods used to treat TBI sequelae. We analyze publications on the most commonly used electrical stimulation methods, namely transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), deep brain stimulation (DBS) and vagus nerve stimulation (VNS), that aim to treat disabilities caused by TBI. We discuss applied stimulation parameters, such as the amplitude, frequency, and length of stimulation, as well as stimulation time frames, specifically the onset of stimulation, how often stimulation sessions were repeated and the total length of the treatment. These parameters are then analyzed in the context of injury severity, the disability under investigation and the stimulated location, and the resulting therapeutic effects are compared. We provide a comprehensive and critical review and discuss directions for future research. RESULTS AND CONCLUSION: We find that the parameters used in studies on each of these stimulation methods vary widely, making it difficult to draw direct comparisons between stimulation protocols and therapeutic outcome. Persisting beneficial effects and adverse consequences of electrical simulation are rarely investigated, leaving many questions about their suitability for clinical applications. Nevertheless, we conclude that the stimulation methods discussed here show promising results that could be further supported by additional research in this field.

Inhibition of LRRK2 Attenuates Depression-Related Symptoms in Mice with Moderate Traumatic Brain Injury

Moderate traumatic brain injury (mTBI) has been associated with emotional dysregulation such as loss of consciousness, post-traumatic amnesia and major depressive disorder. The gene Leucine-rich repeat kinase 2 (LRRK2) is involved in protein synthesis and degradation, apoptosis, inflammation and oxidative stress, processes that trigger mTBI. The aim of this study was to investigate the role of LRRK2 in reducing depression-related symptoms after mTBI and to determine whether inhibition of LRRK2 mediated by PF-06447475 could have antidepressant effects. Moderate traumatic brain injury was induced by controlled cortical impact (CCI) and mice were treated with PF-06447475 at doses of 1, 2.5 and 5 mg/kg once daily for 14 days. We performed histological, immunohistochemical and molecular analyses of brain tissue 24 days after mTBI. Furthermore, the tissue changes found in the hippocampus and amygdala confirmed the depression-like behavior. PF-treatment with 06447475 significantly reduced the histological damage and behavioral disturbances. Thus, this study has shown that mTBI induction promotes the development of depression-like behavioral changes. LRRK2 inhibition showed an antidepressant effect and restored the changes in the copper/glutamate/N-methyl-D-aspartic acid receptor (Cu/NMDAR) system.

Glutamate Neurotoxicity and Destruction of the Blood–Brain Barrier: Key Pathways for the Development of Neuropsychiatric Consequences of TBI and Their Potential Treatment Strategies

Traumatic brain injury (TBI) is associated with significant cognitive and psychiatric conditions. Neuropsychiatric symptoms can persist for years following brain injury, causing major disruptions in patients’ lives. In this review, we examine the role of glutamate as an aftereffect of TBI that contributes to the development of neuropsychiatric conditions. We hypothesize that TBI causes long-term blood–brain barrier (BBB) dysfunction lasting many years and even decades. We propose that dysfunction in the BBB is the central factor that modulates increased glutamate after TBI and ultimately leads to neurodegenerative processes and subsequent manifestation of neuropsychiatric conditions. Here, we have identified factors that determine the upper and lower levels of glutamate concentration in the brain after TBI. Furthermore, we consider treatments of disruptions to BBB integrity, including repairing the BBB and controlling excess glutamate, as potential therapeutic modalities for the treatment of acute and chronic neuropsychiatric conditions and symptoms. By specifically focusing on the BBB, we hypothesize that restoring BBB integrity will alleviate neurotoxicity and related neurological sequelae.

Emotion Dysregulation Following Trauma: Shared Neurocircuitry of Traumatic Brain Injury and Trauma-Related Psychiatric Disorders

The psychological trauma associated with events resulting in traumatic brain injury (TBI) is an important and frequently overlooked factor that may impede brain recovery and worsen mental health following TBI. Indeed, individuals with comorbid posttraumatic stress disorder (PTSD) and TBI have significantly poorer clinical outcomes than individuals with a sole diagnosis. Emotion dysregulation is a common factor leading to poor cognitive and affective outcomes following TBI. Here, we synthesize how acute postinjury molecular processes stemming from either physical or emotional trauma may adversely impact circuitry subserving emotion regulation and ultimately yield long-term system-level functional and structural changes that are common to TBI and PTSD. In the immediate aftermath of traumatic injury, glucocorticoids stimulate excess glutamatergic activity, particularly in prefrontal cortex-subcortical circuitry implicated in emotion regulation. In human neuroimaging work, assessing this same circuitry well after the acute injury, TBI and PTSD show similar impacts on prefrontal and subcortical connectivity and activation. These neural profiles indicate that emotion regulation may be a useful target for treatment and early intervention to prevent the adverse sequelae of TBI. Ultimately, the success of future TBI and PTSD early interventions depends on the fields' ability to address both the physical and emotional impact of physical injury.

Blood Glutamate Scavenging With Pyruvate as a Novel Preventative and Therapeutic Approach for Depressive-Like Behavior Following Traumatic Brain Injury in a Rat Model

Depression is a common and serious complication following traumatic brain injury (TBI). Both depression and TBI have independently been associated with pathologically elevated extracellular brain glutamate levels. In the setting of TBI, blood glutamate scavenging with pyruvate has been widely shown as an effective method to provide neuroprotection by reducing blood glutamate and subsequent brain glutamate levels. Here we evaluate pyruvate as a novel approach in the treatment and prevention of post-TBI depression-like behavior in a rat model. Rats were divided into five groups: (1) sham-operated control with pyruvate, (2) sham-operated control with placebo, (3) post-TBI with placebo, (4) post-TBI given preventative pyruvate, and (5) post-TBI treated with pyruvate. These groups had an equal number of females and males. Rats were assessed for depressive-like behavior, neurological status, and glutamate levels in the blood and brain. Post-TBI neurological deficits with concurrent elevations in glutamate levels were demonstrated, with peak glutamate levels 24 h after TBI. Following TBI, the administration of either prophylactic or therapeutic pyruvate led to reduced glutamate levels, improved neurologic recovery, and improved depressive-like behavior. Glutamate scavenging with pyruvate may be an effective prophylactic and therapeutic option for post-TBI depression by reducing associated elevations in brain glutamate levels.

Melatonin as a Potential Regulator of Oxidative Stress, and Neuroinflammation: Mechanisms and Implications for the Management of Brain Injury-Induced Neurodegeneration

This review covers the preclinical and clinical literature supporting the role of melatonin in the management of brain injury-induced oxidative stress, neuroinflammation, and neurodegeneration, and reviews the past and current therapeutic strategies. Traumatic brain injury (TBI) is a neurodegenerative condition, unpredictably and potentially progressing into chronic neurodegeneration, with permanent cognitive, neurologic, and motor dysfunction, having no standard therapies. Due to its complex and multi-faceted nature, the TBI has highly heterogeneous pathophysiology, characterized by the highest mortality and disability worldwide. Mounting evidence suggests that the TBI induces oxidative and nitrosative stress, which is involved in the progression of chronic and acute neurodegenerative diseases. Defenses against such conditions are mostly dependent on the usage of antioxidant compounds, the majority of whom are ingested as nutraceuticals or as dietary supplements. A large amount of literature is available regarding the efficacy of antioxidant compounds to counteract the TBI-associated damage in animal and cellular models of the TBI and several clinical studies. Collectively, the studies have suggested that TBI induces oxidative stress, by suppressing the endogenous antioxidant system, such as nuclear factor erythroid 2–related factor-2 (Nrf-2) increasing the lipid peroxidation and elevation of oxidative damage. Moreover, elevated oxidative stress may induce neuroinflammation by activating the microglial cells, releasing and activating the inflammatory cytokines and inflammatory mediators, and energy dyshomeostasis. Thus, melatonin has shown regulatory effects against the TBI-induced autophagic dysfunction, regulation of mitogen-activated protein kinases, such as ERK, activation of the NLRP-3 inflammasome, and release of the inflammatory cytokines. The collective findings strongly suggest that melatonin may regulate TBI-induced neurodegeneration, although further studies should be conducted to better facilitate future therapeutic windows.

Calcium Permeable-AMPA Receptors and Excitotoxicity in Neurological Disorders

Excitotoxicity is one of the primary mechanisms of cell loss in a variety of diseases of the central and peripheral nervous systems. Other than the previously established signaling pathways of excitotoxicity, which depend on the excessive release of glutamate from axon terminals or over-activation of NMDA receptors (NMDARs), Ca²⁺ influx-triggered excitotoxicity through Ca²⁺-permeable (CP)-AMPA receptors (AMPARs) is detected in multiple disease models. In this review, both acute brain insults (e.g., brain trauma or spinal cord injury, ischemia) and chronic neurological disorders, including Epilepsy/Seizures, Huntington’s disease (HD), Parkinson’s disease (PD), Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), chronic pain, and glaucoma, are discussed regarding the CP-AMPAR-mediated excitotoxicity. Considering the low expression or absence of CP-AMPARs in most cells, specific manipulation of the CP-AMPARs might be a more plausible strategy to delay the onset and progression of pathological alterations with fewer side effects than blocking NMDARs.

Lack of Glutamate Receptor Subunit Expression Changes in Hippocampal Dentate Gyrus after Experimental Traumatic Brain Injury in a Rodent Model of Depression

Traumatic brain injury (TBI) affects over 69 million people annually worldwide, and those with pre-existing depression have worse recovery. The molecular mechanisms that may contribute to poor recovery after TBI with co-morbid depression have not been established. TBI and depression have many commonalities including volume changes, myelin disruption, changes in proliferation, and changes in glutamatergic signaling. We used a well-established animal model of depression, the Wistar Kyoto (WKY) rat, to elucidate changes after TBI that may influence the recovery trajectory. We compared the histological and molecular outcomes in the hippocampal dentate gyrus after experimental TBI using the lateral fluid percussion injury (LFPI) in the WKY and the parent Wistar (WIS) strain. We showed that WKY had exaggerated myelin loss after LFPI and baseline deficits in proliferation. In addition, we showed that while after LFPI WIS rats exhibited glutamate receptor subunit changes, namely increased GluN2B, the WKY rats failed to show such injury-related changes. These differential responses to LFPI helped to elucidate the molecular characteristics that influence poor recovery after TBI in those with pre-existing depression and may lead to targets for future therapeutic interventions.

Stress-Associated Molecular and Cellular Hippocampal Mechanisms Common for Epilepsy and Comorbid Depressive Disorders

The review discusses molecular and cellular mechanisms common to the temporal lobe epileptogenesis/epilepsy and depressive disorders. Comorbid temporal lobe epilepsy and depression are associated with dysfunction of the hypothalamic-pituitary-adrenocortical axis. Excessive glucocorticoids disrupt the function and impair the structure of the hippocampus, a brain region key to learning, memory, and emotions. Selective vulnerability of the hippocampus to stress, mediated by the reception of glucocorticoid hormones secreted during stress, is the price of the high functional plasticity and pleiotropy of this limbic structure. Common molecular and cellular mechanisms include the dysfunction of glucocorticoid receptors, neurotransmitters, and neurotrophic factors, development of neuroinflammation, leading to neurodegeneration and loss of hippocampal neurons, as well as disturbances in neurogenesis in the subgranular neurogenic niche and formation of aberrant neural networks. These glucocorticoid-dependent processes underlie altered stress response and the development of chronic stress-induced comorbid pathologies, in particular, temporal lobe epilepsy and depressive disorders.

Non-pharmacological interventions for depressive disorder in patients after traumatic brain injury: A protocol for a systematic review and network meta-analysis

BACKGROUND

Depressive disorder has gradually become one of the most commonly reported disabling psychiatric complication that occurs after traumatic brain injury (TBI). Currently classical antidepressant medications may not have the same effectiveness in patients with TBI as in patients without TBI. Non-pharmacological interventions have been considered to be effective for managing depressive symptoms or treating depressive disorder. But to date the comparative effectiveness of various types of non-pharmacological interventions has been synthesized in few studies, the evidence remains inconclusive. Thus, the purpose of this systematic review and network meta-analyses is to summarize high-quality evidence and identify the most effective non-pharmacological intervention when applied to treat the depressive disorder in patients after TBI.

METHODS

The comprehensive literature search in electronic database including PubMed, Ovid Medline, Cochrane Library, Web of Science database, Embase Database, China National Knowledge Infrastructure (CNKI), and Wanfang Data Chinese database from inception to the search date. Only high-quality randomized controlled trials (RCTs) that have used non-pharmacological interventions to treat depressive disorder after TBI will be considered. Two independent reviewers will identify eligible studies, extract and manage data information, and then determine methodical quality of included studies. Overall efficacy will be assessed as primary outcome. Secondary outcomes involved treatment response, remission rate, overall acceptability, tolerability of treatment, social functioning, occurrence of adverse events, and suicide-related outcome. Cochrane risk of bias assessment tool will be adopted to assess the risk of bias. Study heterogeneity will be measured by the I statistic. Traditional pairwise meta-analyses will be performed using STATA, while WinBUGS with GeMTC package of R software will be used to carry out network meta-analysis.

RESULTS

This systematic review will examine the relative efficacy, effectiveness, safety, tolerability and acceptability of non-pharmacological interventions, and then to identify the most effective non-pharmacological intervention for depressive disorder after TBI.

EXPECTED CONCLUSION

Our work could be used to give clinical recommendations for practice guideline developers, psychiatrist, neurologist, policymakers, researchers as well as individual with depressive disorder after TBI, and will also identify gaps in knowledge that could be the subject of future research.

ETHICS AND DISSEMINATION

Neither ethics approval nor patient informed consent is necessary since this protocol was designed based on the existing literature. The results will be disseminated electronically or in print through publications in peer-reviewed scientific journal.

INPLASY REGISTRATION

INPLASY202080022.

Fasciculation and Elongation Protein Zeta-1 Expression in Reactive Astrocytes in a Rat Model of Frontal Lobe Injury

There are reports that depression induced by frontal lobe injury (FLI) has a devastating effect on human mental health. We previously reported that fasciculation and elongation protein zeta-1 (FEZ1) was essential for astrocytic protection of dopamine neurons. Studies of glutamate-glutamine cycle in mental illness have been reported, whereas not from the perspective of astrocytes. This study was designed to investigate the roles of astrocytic FEZ1 and glutamate-glutamine cycle after FLI. A model of FLI was established by inserting a blade into the right frontal lobe of rats. Behavioral tests were used to observe the behavioral changes of FLI rats. Neuropathologic examinations, including immunohistochemistry, were conducted. Behavioral tests showed that FLI decreased exploratory activity. Western blot analysis revealed that the expression of astroglial proteins overall decreased in the initial injury stage, as well as FEZ1. Immunohistochemistry showed a shift of FEZ1 localization from neurons in sham-lesioned rats to astrocytes in FLI rats, and showed the expression profile of glutamate transporter 1 and glutamine synthetase (GS) was consistent with Western blot observation. Our results indicate that astrocytic FEZ1 and glutamate-glutamine cycle dysfunction may be involved in the pathogenesis of depression after FLI.

Chronic treatment with galantamine rescues reversal learning in an attentional set-shifting test after experimental brain trauma

Approximately 10 million new cases of traumatic brain injury (TBI) are reported each year worldwide with many of these injuries resulting in higher order cognitive impairments. Galantamine (GAL), an acetylcholine esterase inhibitor (AChEI) and positive allosteric modulator of nicotinic acetylcholine receptors (nAChRs), has been reported to ameliorate cognitive deficits after clinical TBI. Previously, we demonstrated that controlled cortical impact (CCI) injury to rats resulted in significant executive function impairments as measured by the attentional set-shifting test (AST), a complex cognitive task analogous to the Wisconsin Card Sorting Test (WCST). We hypothesized that chronic administration of GAL would normalize performance on the AST post-TBI. Isoflurane-anesthetized adult male rats were subjected to moderate CCI (2.8 mm tissue deformation at 4 m/s) or sham injury. Rats were then randomized into one of three treatment groups (i.e., 1 mg/kg GAL, 2 mg/kg GAL, or 1 mL/kg saline vehicle; VEH) or their respective sham controls. GAL or VEH was administered intraperitoneally daily commencing 24 hours post-surgery and until AST testing at 4 weeks post-injury. The AST data revealed significant impairments in the first reversal stage after TBI, seen as increased trials to reach criterion and elevated total errors (p < 0.05). These behavioral flexibility deficits were equally normalized by the administration of both doses of GAL (p < 0.05). Additionally, the higher dose of GAL (2 mg/kg) also significantly reduced cortical lesion volume compared to TBI + VEH controls (p < 0.05). In summary, daily GAL administration provides an efficacious treatment for cognitive deficits and histological recovery after experimental brain trauma. Clinically, these findings are promising considering robust results were attained using a pharmacotherapy already used in the clinic to treat mild dementia.

Aripiprazole and environmental enrichment independently improve functional outcome after cortical impact injury in adult male rats, but their combination does not yield additional benefits

Typical antipsychotic drugs (APDs) with D₂antagonistic properties impede functional outcome after experimental traumatic brain injury (TBI) and reduce the effectiveness of environmental enrichment (EE). Here we test the hypothesis that aripiprazole (ARIP), an atypical APD with partial D₂and 5-HT_1Areceptor agonist activities will improve recovery after TBI and when combined with EE will further enhance the benefits. Anesthetized adult male rats received either a controlled cortical impact of moderate severity or sham injury and then were randomly assigned to EE or standard (STD) housing and once daily intraperitoneal injections of ARIP (0.1 mg/kg) or vehicle (VEH; 1.0 mL/kg) beginning 24 h after injury for 19 days. Motor (beam-walking time and beam-walk score) and cognitive (acquisition of spatial learning and memory) outcomes were assessed on post-operative days 1-5 and 14-19, respectively. Cortical lesion volume was quantified on day 21. There were no statistical differences among the sham groups, regardless of housing or treatment, so the data were pooled. The SHAM group performed better than all TBI groups on motor and spatial learning (p < 0.05) but did not differ from either EE group on memory retention. Regarding TBI, both EE groups improved motor and cognitive outcomes vs. the VEH-treated STD group (p < 0.05) but did not differ from one another (p > 0.05). The ARIP-treated STD group performed better than the VEH-treated STD group on beam-walk score and spatial learning (p < 0.05), but not beam-walking time or memory retention (p > 0.05). Cortical lesion volume was smaller in all treated groups compared to the TBI + STD + VEH group (p < 0.05). The data replicate previous work and extend the findings by demonstrating that 1) ARIP promotes recovery after TBI, but combining treatments does not yield additional benefits, which is contrary to the hypothesis, and 2) unlike APDs that exhibit D₂ receptor antagonism, ARIP does not impede rehabilitation (i.e., EE).