Management of traumatic brain injury: some current evidence and applications

Effect of CTLA-4 Inhibition on Inflammation and Apoptosis After Spinal Cord Injury

Spinal cord injury (SCI) encompasses various pathological processes, notably neuroinflammation and apoptosis, both of which play significant roles. CTLA-4, a well-known immune molecule that suppresses T cell-mediated immune responses, is a key area of research and a focal point for targeted therapy development in treating tumors and autoimmune disorders. Despite its prominence, the impact of CTLA-4 inhibition on inflammation and apoptosis subsequent to SCI remains unexplored. This study aimed to investigate the influence of CTLA-4 on SCI. A weight-drop technique was used to establish a rat model of SCI. To examine the safeguarding effect of CTLA-4 on the restoration of motor function in rats with SCI, the Basso-Beattie-Bresnahan (BBB) scale and inclined plane test were employed to assess locomotion. Neuronal degeneration and apoptosis were assessed using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) and Fluoro-Jade B labeling, respectively, and the activity of microglial cells was examined by immunofluorescence. To evaluate the impact of CTLA4 on SCI, the levels of inflammatory markers were measured. After treatment with the CTLA-4 inhibitor ipilimumab, the rats showed worse neurological impairment and more severe neuroinflammation after SCI. Furthermore, the combination therapy with ipilimumab and durvalumab after SCI had more pronounced effects than treatment with either inhibitor alone. These findings indicate that CTLA-4 contributes to neuroinflammation and apoptosis after SCI, presenting a promising new therapeutic target for this traumatic condition.

Open craniocerebral trauma in a patient at work: A case report

BACKGROUND: Craniocerebral injuries belong to the category of bodily injuries which are characterised by high mortality and a high percentage of permanent effects in the form of disability. The likelihood of this injury exists in the workplace too. Performing works at a height or using high-pressure or mechanical machinery exposes employees to a higher risk of a craniocerebral injury. CASE REPORT: This case study deals with the topic of open craniocerebral trauma suffered by a 20-year-old man who was wearing no head protection at his place of work. It details the management of this trauma at the site of the accident, during transfer to the hospital and during hospitalisation. CONCLUSION: Fast transport, effective diagnostics and implementation of surgical treatment contributed to a good final result.

The changing landscape of the use of medical marijuana after traumatic brain injury: a narrative review

OBJECTIVE

To summarize the potential therapeutic benefits of medical marijuana for patients with traumatic brain injury (TBI).

METHODS

A systematic search was conducted using PubMed and Cochran's library for information regard the safety and efficacy of medical marijuana as a therapeutic agent. We investigated, in depth, articles specifically evaluating medical marijuana's use in TBI, as well as articles that summarized the effects of marijuana in general. Articles from the year 2000-2020 were included.

RESULTS

A total of 37 articles met our inclusion criteria. An additional 3 articles were obtained from reference lists.

CONCLUSION

Studies have shown that medical marijuana can potentially aid the recovery from TBI by modulating the endocannabinoid system, reducing inflammation and secondary injury. Adverse cognitive and physiological effects have been observed in the acute setting as well as chronically, though more research is necessitated. There is also the concern of significant drug-drug interactions that have not been thoroughly studied. Thus, while there is evidence that medical marijuana can be beneficial in the treatment of TBI, more research is necessitated to fully explore the long-term efficacy and adverse effects.

A novel CX3CR1 inhibitor AZD8797 facilitates early recovery of rat acute spinal cord injury by inhibiting inflammation and apoptosis

The present study aimed to evaluate the effect of the CX3CR1 inhibitor AZD8797 in early recovery after acute SCI and elucidate its potential mechanism in blocking inflammation and apoptosis. Adult rats were sacrificed after 3, 7, 10, or 14 days of SCI. The injured spinal tissues were collected for assessing C-X3-C motif chemokine ligand 1(CX3CL1)/C-X3-C motif chemokine receptor 1 (CX3CR1) expression at each time point via western blotting (WB) and quantitative PCR. The cellular localization of the proteins was detected by immunofluorescence. Another batch of rats (subdivided into sham, injury model, AZD8797 and methylprednisolone groups) were used to evaluate locomotive recovery with a Basso Beattie Bresnahan score. Based on the expression level of CX3CR1, these rats were sacrificed at the most prominent stage of CX3CR1 expression (10 days after SCI), for assessing the serum levels of tumor necrosis factor-α/interleukin (IL)-6/IL-1β and the expression of CX3CL1/CX3CR1/caspase 3/Bcl-2/Bax in the spinal cord tissues through WB and ELISA. Additionally, apoptosis and necrosis in the injured spinal cord were evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining/fluoro-jade B staining. Expression levels of both CX3CR1 and CX3CL1 reached their peak 10 days after the injury, followed by a dramatic downward trend at 14 days. The enhanced expression of CX3CR1 was detected in astrocytes and microglia of the injured spinal cord. AZD8797 improved locomotive recovery after 10 days of SCI and was as effective as methylprednisolone. The effect of AZD8797 was mediated by suppressing apoptosis, necrosis and inflammatory responses, as assessed by WB/ELISA and morphological examinations. The current study has demonstrated that AZD8797 can effectively block overwhelming inflammation, apoptosis and necrosis after SCI and facilitate early recovery of locomotive function.

Inflammation resolution and specialized pro-resolving lipid mediators in CNS diseases

Introduction: Inflammation resolution induced by specialized pro-resolving lipid mediators (SPMs) is a new concept. The application of SPMs is a promising therapeutic strategy that can potentially supersede anti-inflammatory drugs. Most CNS diseases are associated with hyperreactive inflammatory damage. CNS inflammation causes irreversible neuronal loss and permanent functional impairments. Given the high mortality and morbidity rates, the investigation of therapeutic strategies to ameliorate inflammatory damage is necessary.Areas covered: In this review, we explore inflammation resolution in CNS disorders. We discuss the underlying mechanisms and dynamic changes of SPMs and their precursors in neurological diseases and examine how this can potentially be incorporated into the clinic. References were selected from PubMed; most were published between 2010 and 2019.Expert opinion: Inflammation resolution is a natural process that emerges after acute or chronic inflammation. The evidence that SPMs can effectively ameliorate hyperreactive inflammation, shorten resolution time and accelerate tissue regeneration in CNS disorders. Adjuvants and nanotechnology offer opportunities for SPM drug design; however, more preclinical studies are necessary to investigate basic, critical issues such as safety.

Management and outcome of traumatic brain injury patients at Muhimbili Orthopaedic Institute Dar es Salaam, Tanzania

INTRODUCTION

Traumatic brain Injuries represents a significant cause of morbidity and mortality worldwide and road traffic crashes accounts for a significant proportion of these injuries. However, access to neurosurgical care is poor in low income countries like Tanzania. The aim of this study was to assess the management and outcome of Traumatic brain injury patients at a tertiary level health facility in Tanzania.

METHODS

A retrospective observational study of Traumatic brain injury patients attended at Muhimbili Orthopedic Institute between January 2014 and June 2014.

RESULTS

A total of 627 Traumatic brain injury (TBI) patients were seen, 86% were males. Majority (73%) were between 15 - 45 years age group. Road traffic crashes were the leading cause of injury (59.3%). Majority 401/627 (64%) sustained mild TBI, 114/627 (18.2%) moderate TBI and 112/627 (17.8%) severe TBI. All mild TBI patients had good recovery. Among patients with moderate and severe TBI; 19.1% had good recovery, 50.2% recovered with disabilities and 30.7% died. Independent factors associated with mortality were: Severe TBI (Odds Ratio (OR) 3.16. 95%CI 3.42-10.52) and Systolic blood pressure at referring hospital of more than 90mmHg (Odds Ratio (OR) 0.13, 95%CI 0.04-0.49).

CONCLUSION

Traumatic brain injury is a public health problem in Tanzania, mostly due to road traffic crashes. It is therefore important to reinforce preventive measures for road traffic crashes. There is also a need to develop and implement protocols for pre-hospital as well as in-hospital management of brain trauma in Tanzania.

Clinical Evaluation of the Concussed Athlete: A View From the Sideline

CONTEXT

The sideline assessment of concussion is challenging, given its variable presentations, the limited sensitivity and specificity of sideline assessment tools, and how the presentation of the injury evolves over time. In addition, the diagnostic process, as well as the tools used to assess and manage concussion, continue to progress as research and what we know about concussion advance. This paper focuses on the initial assessment on the sideline by reviewing the concussion-evaluation literature, drawing from clinical experience to emphasize a standardized approach, and underscoring the importance of both familiarity with the athlete and clinical judgment.

OBJECTIVE

To review the evidence regarding the clinical assessment of sport-related concussion on the sideline. Additional considerations included making same-day return-to-play decisions, the sensitivity and specificity of sideline testing, and the importance of ongoing assessment and follow-up of injured athletes.

DATA SOURCES

I conducted a systematic literature review of the assessment of concussion on the sideline. The PubMed and MEDLINE databases were searched using the key term athletic injuries with concussion and mild traumatic brain injury. The search was refined by adding the key terms sideline assessment and on-field assessment. In addition, select additional position statements and guidelines on concussion were included in the review.

RESULTS

The PubMed search using athletic injuries and concussion as key terms produced 1492 results. Refining the search by sideline assessment and on-field assessment produced 29 and 35 results, respectively. When athletic injuries and traumatic brain injury were combined, 1912 results were identified. Refining the search by sideline assessment and on-field assessment led to 28 and 35 results, respectively. Only papers that were English-language titles, original work, and limited to human participants and included sideline assessments of sport-related concussion in athletes older than 13 years were considered for this discussion. A total of 96 papers were reviewed, including systematic reviews, consensus guidelines, and position statements.

CONCLUSIONS

The sideline assessment of sport-related concussion is challenging given the elusiveness and variability of presentation, reliance on athlete-reported symptoms, and the varying specificity and sensitivity values of sideline assessment tools. In addition, the recognition of injury and assessment often occur in a time-pressured environment, requiring rapid disposition and decision making. Clinicians should begin the evaluation by assessing for cervical spine injury, intracranial bleeding, and other injuries that can present in a similar fashion or in addition to concussion. The sideline concussion evaluation should consist of a symptom assessment and a neurologic examination that addresses cognition (briefly), cranial nerve function, and balance. Emerging tools that assess visual tracking may provide additional information. The sensitivity and specificity of commonly implemented sideline assessment tools are generally good to very good, especially for symptom scores and cognitive evaluations performed within 48 hours of injury, and they are improved when a baseline evaluation is available for comparison. Serial assessments are often necessary as objective signs and symptoms may be delayed. A standardized assessment is paramount in evaluating the athlete with a suspected concussion, but there is no replacement for being familiar with the athlete and using clinical judgment when the athlete seems "not right" despite a "normal" sideline assessment. Ultimately, the clinician should err on the side of caution when making a return-to-play decision.

Traumatic Brain Injury in the Pediatric Population

Traumatic brain injury (TBI) is a common injury among children. Most TBIs are mild and do not require hospitalization. However, whether or not the patients require acute hospitalization, TBIs may have long-lasting consequences. There is little research on the nutrient needs of these patients, and recommendations are frequently based on data from adults with TBI. It is clear that calorie and protein needs are elevated with acute TBI. However, calorie needs are also decreased by therapies such as sedation, chemical paralysis, and barbiturate coma. Long-term calorie needs may be lower for "comatose" patients. Enteral feeding is preferred and possible for patients with TBI, though gastric feeding may be problematic in some patients. In the acute phase, patients with TBI can also have dysregulation of fluid and electrolyte balance, which may require alterations in nutrition care. Dysphagia is common after moderately severe TBI and requires a multidisciplinary approach for treatment. Future opportunities for research on pediatric TBI are numerous and may include ongoing clarification of macronutrient needs, as well as investigation into the roles of specific nutrients such as zinc, antioxidants, and anti-inflammatory compounds.

Noninvasive assessment of hemodynamic and brain metabolism parameters following closed head injury in a mouse model by comparative diffuse optical reflectance approaches

Optical techniques have gained substantial interest over the past four decades for biomedical imaging due to their unique advantages, which may suggest their use as alternatives to conventional methodologies. Several optical techniques have been successfully adapted to clinical practice and biomedical research to monitor tissue structure and function in both humans and animal models. This paper reviews the analysis of the optical properties of brain tissue in the wavelength range between 500 and 1000 nm by three different diffuse optical reflectance methods: spatially modulated illumination, orthogonal diffuse light spectroscopy, and dual-wavelength laser speckle imaging, to monitor changes in brain tissue morphology, chromophore content, and metabolism following head injury. After induction of closed head injury upon anesthetized mice by weight-drop method, significant changes in hemoglobin oxygen saturation, blood flow, and metabolism were readily detectible by all three optical setups, up to 1 h post-trauma. Furthermore, the experimental results clearly demonstrate the feasibility and reliability of the three methodologies, and the differences between the system performances and capabilities are also discussed. The long-term goal of this line of study is to combine these optical systems to study brain pathophysiology in high spatiotemporal resolution using additional models of brain trauma. Such combined use of complementary algorithms should fill the gaps in each system's capabilities, toward the development of a noninvasive, quantitative tool to expand our knowledge of the principles underlying brain function following trauma, and to monitor the efficacy of therapeutic interventions in the clinic.

Early management of traumatic brain injury in a Tertiary hospital in Central Kenya: A clinical audit

Background:

Traumatic brain injury (TBI) is a major cause of death and disability worldwide and is mostly attributed to road traffic accidents in resource-poor areas. However, access to neurosurgical care is poor in these settings and patients in need of neurosurgical procedures are often managed by general practitioners or surgeons.

Materials and Methods:

A retrospective clinical audit of the initial management of patients with TBI in Thika Level 5 Hospital (TL5H), a Tertiary Hospital in Central Kenya. Seventeen audit criteria divided into five clinical domains were identified and patient case notes reviewed for compliance with each criterion. Data were analyzed separately for those below 13 years owing to differences in response to brain trauma in those below this age.

Results:

Overall, there was poor compliance with audit criteria in both groups. Among those below 13 years of age, only 3 out of 17 criteria achieved compliance and 4 out of 17 criteria achieved compliance for those above 13 years of age. Assessment for the need for a cervical radiograph (7.1% and 8.8% compliance) and administration of oxygen (21.4% and 20.6% compliance) had the worst performance in both groups.

Conclusion:

Poor compliance to audit criteria indicates the low quality of care for patients with TBI in TL5H. Quality improvement strategies with follow-up audits are needed to improve care. There is a need to develop and enforce evidence-based protocols and guidelines for use in the management of patients with TBI in sub-Saharan Africa.

Analysis of the Role of CX3CL1 (Fractalkine) and Its Receptor CX3CR1 in Traumatic Brain and Spinal Cord Injury: Insight into Recent Advances in Actions of Neurochemokine Agents

CX3CL1 (fractalkine) is the only member of the CX3C (delta) subfamily of chemokines which is unique and combines the properties of both chemoattractant and adhesion molecules. The two-form ligand can exist either in a soluble form, like all other chemokines, and as a membrane-anchored molecule. CX3CL1 discloses its biological properties through interaction with one dedicated CX3CR1 receptor which belongs to a family of G protein-coupled receptors (GPCR). The CX3CL1/CX3CR1 axis acts in many physiological phenomena including those occurring in the central nervous system (CNS), by regulating the interactions between neurons, microglia, and immune cells. Apart from the role under physiological conditions, the CX3CL1/CX3CR1 axis was implied to have a role in different neuropathologies such as traumatic brain injury (TBI) and spinal cord injury (SCI). CNS injuries represent a serious public health problem, despite improvements in therapeutic management. To date, no effective treatment has been determined, so they constitute a leading cause of death and severe disability. The course of TBI and SCI has two consecutive poorly demarcated phases: the initial, primary injury and secondary injury. Recent evidence has implicated the role of the CX3CL1/CX3CR1 axis in neuroinflammatory processes occurring after CNS injuries. The importance of the CX3CL1/CX3CR1 axis in the pathophysiology of TBI and SCI in the context of systemic and direct local immune response is still under investigation. This paper, based on a review of the literature, updates and summarizes the current knowledge about CX3CL1/CX3CR1 axis involvement in TBI and SCI pathogenesis, indicating possible molecular and cellular mechanisms with a potential target for therapeutic intervention.

A critical review of anaesthetised animal models and alternatives for military research, testing and training, with a focus on blast damage, haemorrhage and resuscitation

Military research, testing, and surgical and resuscitation training, are aimed at mitigating the consequences of warfare and terrorism to armed forces and civilians. Traumatisation and tissue damage due to explosions, and acute loss of blood due to haemorrhage, remain crucial, potentially preventable, causes of battlefield casualties and mortalities. There is also the additional threat from inhalation of chemical and aerosolised biological weapons. The use of anaesthetised animal models, and their respective replacement alternatives, for military purposes -- particularly for blast injury, haemorrhaging and resuscitation training -- is critically reviewed. Scientific problems with the animal models include the use of crude, uncontrolled and non-standardised methods for traumatisation, an inability to model all key trauma mechanisms, and complex modulating effects of general anaesthesia on target organ physiology. Such effects depend on the anaesthetic and influence the cardiovascular system, respiration, breathing, cerebral haemodynamics, neuroprotection, and the integrity of the blood-brain barrier. Some anaesthetics also bind to the NMDA brain receptor with possible differential consequences in control and anaesthetised animals. There is also some evidence for gender-specific effects. Despite the fact that these issues are widely known, there is little published information on their potential, at best, to complicate data interpretation and, at worst, to invalidate animal models. There is also a paucity of detail on the anaesthesiology used in studies, and this can hinder correct data evaluation. Welfare issues relate mainly to the possibility of acute pain as a side-effect of traumatisation in recovered animals. Moreover, there is the increased potential for animals to suffer when anaesthesia is temporary, and the procedures invasive. These dilemmas can be addressed, however, as a diverse range of replacement approaches exist, including computer and mathematical dynamic modelling of the human body, cadavers, interactive human patient simulators for training, in vitro techniques involving organotypic cultures of target organs, and epidemiological and clinical studies. While the first four of these have long proven useful for developing protective measures and predicting the consequences of trauma, and although many phenomena and their sequelae arising from different forms of trauma in vivo can be induced and reproduced in vitro, non-animal approaches require further development, and their validation and use need to be coordinated and harmonised. Recommendations to these ends are proposed, and the scientific and welfare problems associated with animal models are addressed, with the future focus being on the use of batteries of complementary replacement methods deployed in integrated strategies, and on greater transparency and scientific cooperation.

Association between peripheral oxidative stress and white matter damage in acute traumatic brain injury

The oxidative stress is believed to be one of the mechanisms involved in the neuronal damage after acute traumatic brain injury (TBI). However, the disease severity correlation between oxidative stress biomarker level and deep brain microstructural changes in acute TBI remains unknown. In present study, twenty-four patients with acute TBI and 24 healthy volunteers underwent DTI. The peripheral blood oxidative biomarkers, like serum thiol and thiobarbituric acid-reactive substances (TBARS) concentrations, were also obtained. The DTI metrics of the deep brain regions, as well as the fractional anisotropy (FA) and apparent diffusion coefficient, were measured and correlated with disease severity, serum thiol, and TBARS levels. We found that patients with TBI displayed lower FAs in deep brain regions with abundant WMs and further correlated with increased serum TBARS level. Our study has shown a level of anatomic detail to the relationship between white matter (WM) damage and increased systemic oxidative stress in TBI which suggests common inflammatory processes that covary in both the peripheral and central reactions after TBI.

Epilepsy after head injury in dogs: a natural model of posttraumatic epilepsy

PURPOSE

In humans, traumatic brain injury (TBI) is one of the most common causes of acquired (symptomatic) epilepsy, but as yet there is no treatment to prevent the development of epilepsy after TBI. Animal models of posttraumatic epilepsy (PTE) are important to characterize epileptogenic mechanisms of TBI and to identify clinically effective antiepileptogenic treatments. The prevalence and phenomenology of naturally occurring canine epilepsy are similar to those in human epilepsy. However, the risk of epilepsy after TBI has not been systemically studied in dogs. We therefore performed a large retrospective study in 1,000 dogs referred to our clinical department over a period of 11.5 years with the aim to determine the incidence of early and late seizures after head trauma in this species.

METHODS

Two strategies were used: in group I (n = 392), we evaluated whether dogs referred for the treatment of a head trauma (group Ia) or other trauma (group Ib) developed seizures after the trauma, whereas in group II (n = 608) we evaluated whether dogs referred for the treatment of recurrent epileptic seizures had a history of head trauma. Data for this study were obtained from our clinical database, questionnaires sent to the dogs' owners, and owner interviews.

KEY FINDINGS

In group Ia, 6.6% of the dogs developed PTE, which was significantly different from group Ib (1.9%), indicating that head trauma increased the risk of developing epilepsy by a factor of 3.4. The risk of PTE increased with severity of TBI; 14.3% of the dogs with skull fracture developed PTE. In group II, 15.5% of the dogs with epilepsy had a history of head injury, which was significantly higher than the incidence of PTE determined for group Ia.

SIGNIFICANCE

Our study indicates that head trauma in dogs is associated with a significant risk of developing epilepsy. Therefore, dogs with severe TBI are an interesting natural model of PTE that provides a novel translational platform for studies on human PTE.

National athletic trainers' association position statement: preventing sudden death in sports

OBJECTIVE

To present recommendations for the prevention and screening, recognition, and treatment of the most common conditions resulting in sudden death in organized sports.

BACKGROUND

Cardiac conditions, head injuries, neck injuries, exertional heat stroke, exertional sickling, asthma, and other factors (eg, lightning, diabetes) are the most common causes of death in athletes.

RECOMMENDATIONS

These guidelines are intended to provide relevant information on preventing sudden death in sports and to give specific recommendations for certified athletic trainers and others participating in athletic health care.

Outcomes of patients with severe traumatic brain injury who have Glasgow Coma Scale scores of 3 or 4 and are over 65 years old

The goal of this study was to investigate the outcomes of patients with traumatic brain injury (TBI) who had Glasgow Coma Scale (GCS) scores of 3 or 4, and were aged 66 years or older. Between January 2001 and December 2005, 13 European centers enrolled patients with severe brain trauma. Data sets of all patients who had a GCS score of 3 or 4 and were 66 years of age or older were analyzed. Outcomes were classified according to the Glasgow Outcome Scale (GOS) 12 months post-trauma as "favorable" (GOS score of 4 or 5), or "unfavorable" (GOS score of 1-3); relevant data for patients of the two groups were compared. Variables were analyzed by univariate analyses (chi-square, Wilcoxon-Mann-Whitney, and Fisher's exact tests), and a p value of <0.05 was considered significant. We analyzed 100 patients identified from the database as having GCS scores of 3 or 4 and age over 65 years. Factors having significant effects on outcomes were worse results of the Injury Severity Score (ISS), Trauma and Injury Severity Score (TRISS), and Abbreviated Injury Scale (AIS) for the head. Closed or partially closed basal cisterns and/or midline shift >15 mm were also associated with unfavorable outcomes, as was subarachnoid hemorrhage (SAH). Patients with GCS scores of 3 or 4 who are older than 65 years have a poor, but not hopeless, prognosis. Confirmed factors predicting poor prognosis for this group of patients were closed basal cisterns and midline shift >15 mm on the first CT scan. Factors possibly related to favorable outcomes were female gender, lower trauma severity, open or partially open basal cisterns, and no midline shift on the first CT scan.

Impact of early pharmacological treatment on cognitive and behavioral outcome after traumatic brain injury in adults: a meta-analysis

Early pharmacological treatment has the potential to reduce some of the disabling cognitive and behavioral problems that result from traumatic brain injury (TBI). Although a large number of treatments have been developed, clinical research has yielded inconsistent findings with respect to the effectiveness of these pharmacological treatments on cognitive and behavioral outcomes. Furthermore, their relative efficacy has not been evaluated, thereby hindering advances in the treatment of TBI. A meta-analysis of research that examined the impact of pharmacological treatments on cognitive and behavioral outcomes in the early stages after TBI between January 1980 and May 2008 was therefore undertaken. The PubMed and PsycINFO databases were searched using 35 terms. All articles were screened using detailed inclusion criteria. Weighted Cohen's d effect sizes, percent overlap statistics, and fail-safe N statistics were calculated for each pharmacological agent. Studies that used different experimental designs were examined separately. Eleven pharmacological treatments were investigated by 22 clinical studies, comprising 6472 TBI patients in the treatment groups and 6460 TBI controls. One dopamine agonist (amantadine) and 1 bradykinin antagonist (CP-0127 [Bradycor]) produced marked treatment benefits (d > or = 0.8) for a single measure of arousal (Glasgow Coma Scale). Notably, drug dosage and the measure chosen to assess outcome influenced the probability of finding a treatment benefit.

Translocator protein (18 kDa) TSPO: an emerging therapeutic target in neurotrauma

Traumatic brain injury (TBI) induces physical, cognitive, and psychosocial deficits that affect millions of patients. TBI activates numerous cellular mechanisms and molecular cascades that produce detrimental outcomes, including neuronal death and loss of function. The mitochondrion is one of the major targets of TBI, as seen by increased mitochondrial activity in activated and proliferating microglia (due to high energy requirements and/or calcium overload) as well as increased reactive oxygen species, changes in mitochondrial permeability transition, release of cytochrome c, caspase activation, reduced ATP levels, and cell death in neurons. Translocator protein (TSPO) is an 18-kDa outer mitochondrial membrane protein that interacts with the mitochondria permeability transition pore and binds with high affinity to cholesterol and various classes of drug ligands, including some benzodiazepines such as 4'-chlorodiazepam (Ro5-4864). Although TSPO levels in the brain are low, they are increased after brain injury and inflammation. This finding has led to the proposed use of TSPO expression as a marker of brain injury and repair. TSPO drug ligands have been shown to participate in the control of mitochondrial respiration and function, mitochondrial steroid and neurosteroid formation, as well as apoptosis. This review and commentary will outline our current knowledge of the benefits of targeting TSPO for TBI treatment and the mechanisms underlying the neuroprotective effects of TSPO drug ligands in neurotrauma.