Mitochondrial damage and dysfunction in traumatic brain injury

Microglia-induced neuroinflammation in hippocampal neurogenesis following traumatic brain injury

Traumatic brain injury (TBI) is one of the most causes of death and disability among people, leading to a wide range of neurological deficits. The important process of neurogenesis in the hippocampus, which includes the production, maturation and integration of new neurons, is affected by TBI due to microglia activation and the inflammatory response. During brain development, microglia are involved in forming or removing synapses, regulating the number of neurons, and repairing damage. However, in response to injury, activated microglia release a variety of pro-inflammatory cytokines, chemokines and other neurotoxic mediators that exacerbate post-TBI injury. These microglia-related changes can negatively affect hippocampal neurogenesis and disrupt learning and memory processes. To date, the intracellular signaling pathways that trigger microglia activation following TBI, as well as the effects of microglia on hippocampal neurogenesis, are poorly understood. In this review article, we discuss the effects of microglia-induced neuroinflammation on hippocampal neurogenesis following TBI, as well as the intracellular signaling pathways of microglia activation.

Logic "AND Gate Circuit" Based Mussel Inspired Polydopamine Nanocomposite as Bioactive Antioxidant for Management of Oxidative Stress and Neurogenesis in Traumatic Brain Injury

In the intricate landscape of Traumatic Brain Injury (TBI), the management of TBI remains a challenging task due to the extremely complex pathophysiological conditions and excessive release of reactive oxygen species (ROS) at the injury site and the limited regenerative capacities of the central nervous system (CNS). Existing pharmaceutical interventions are limited in their ability to efficiently cross the blood-brain barrier (BBB) and expeditiously target areas of brain inflammation. In response to these challenges herein, we designed novel mussel inspired polydopamine (PDA)-coated mesoporous silica nanoparticles (PDA-AMSNs) with excellent antioxidative ability to deliver a new potential therapeutic GSK-3β inhibitor lead small molecule abbreviated as Neuro Chemical Modulator (NCM) at the TBI site using a neuroprotective peptide hydrogel (PANAP). PDA-AMSNs loaded with NCM (i.e., PDA-AMSN-D) into the matrix of PANAP were injected into the damaged area in an in vivo cryogenic brain injury model (CBI). This approach is specifically built while keeping the logic AND gate circuit as the primary focus. Where NCM and PDA-AMSNs act as two input signals and neurological functional recovery as a single output. Therapeutically, PDA-AMSN-D significantly decreased infarct volume, enhanced neurogenesis, rejuvenated BBB senescence, and accelerated neurological function recovery in a CBI.

Amantadine for Traumatic Brain Injury-Supporting Evidence and Mode of Action

Traumatic brain injury (TBI) is an important global clinical issue, requiring not only prevention but also effective treatment. Following TBI, diverse parallel and intertwined pathological mechanisms affecting biochemical, neurochemical, and inflammatory pathways can have a severe impact on the patient's quality of life. The current review summarizes the evidence for the utility of amantadine in TBI in connection to its mechanism of action. Amantadine, the drug combining multiple mechanisms of action, may offer both neuroprotective and neuroactivating effects in TBI patients. Indeed, the use of amantadine in TBI has been encouraged by several clinical practice guidelines/recommendations. Amantadine is also available as an infusion, which may be of particular benefit in unconscious patients with TBI due to immediate delivery to the central nervous system and the possibility of precise dosing. In other situations, orally administered amantadine may be used. There are several questions that remain to be addressed: can amantadine be effective in disorders of consciousness requiring long-term treatment and in combination with drugs approved for the treatment of TBI? Do the observed beneficial effects of amantadine extend to disorders of consciousness due to factors other than TBI? Well-controlled clinical studies are warranted to ultimately confirm its utility in the TBI and provide answers to these questions.

L-Carnitine in the Treatment of Psychiatric and Neurological Manifestations: A Systematic Review

OBJECTIVE

L-carnitine (LC), a vital nutritional supplement, plays a crucial role in myocardial health and exhibits significant cardioprotective effects. LC, being the principal constituent of clinical-grade supplements, finds extensive application in the recovery and treatment of diverse cardiovascular and cerebrovascular disorders. However, controversies persist regarding the utilization of LC in nervous system diseases, with varying effects observed across numerous mental and neurological disorders. This article primarily aims to gather and analyze database information to comprehensively summarize the therapeutic potential of LC in patients suffering from nervous system diseases while providing valuable references for further research.

METHODS

A comprehensive search was conducted in PubMed, Web Of Science, Embase, Ovid Medline, Cochrane Library and Clinicaltrials.gov databases. The literature pertaining to the impact of LC supplementation on neurological or psychiatric disorders in patients was reviewed up until November 2023. No language or temporal restrictions were imposed on the search.

RESULTS

A total of 1479 articles were retrieved, and after the removal of duplicates through both automated and manual exclusion processes, 962 articles remained. Subsequently, a meticulous re-screening led to the identification of 60 relevant articles. Among these, there were 12 publications focusing on hepatic encephalopathy (HE), while neurodegenerative diseases (NDs) and peripheral nervous system diseases (PNSDs) were represented by 9 and 6 articles, respectively. Additionally, stroke was addressed in five publications, whereas Raynaud's syndrome (RS) and cognitive disorder (CD) each had three dedicated studies. Furthermore, migraine, depression, and amyotrophic lateral sclerosis (ALS) each accounted for two publications. Lastly, one article was found for other symptoms under investigation.

CONCLUSION

In summary, LC has demonstrated favorable therapeutic effects in the management of HE, Alzheimer's disease (AD), carpal tunnel syndrome (CTS), CD, migraine, neurofibromatosis (NF), PNSDs, RS, and stroke. However, its efficacy appears to be relatively limited in conditions such as ALS, ataxia, attention deficit hyperactivity disorder (ADHD), depression, chronic fatigue syndrome (CFS), Down syndrome (DS), and sciatica.

Insertional effect following electrode implantation: an underreported but important phenomenon

Deep brain stimulation has revolutionized the treatment of movement disorders and is gaining momentum in the treatment of several other neuropsychiatric disorders. In almost all applications of this therapy, the insertion of electrodes into the target has been shown to induce some degree of clinical improvement prior to stimulation onset. Disregarding this phenomenon, commonly referred to as 'insertional effect', can lead to biased results in clinical trials, as patients receiving sham stimulation may still experience some degree of symptom amelioration. Similar to the clinical scenario, an improvement in behavioural performance following electrode implantation has also been reported in preclinical models. From a neurohistopathologic perspective, the insertion of electrodes into the brain causes an initial trauma and inflammatory response, the activation of astrocytes, a focal release of gliotransmitters, the hyperexcitability of neurons in the vicinity of the implants, as well as neuroplastic and circuitry changes at a distance from the target. Taken together, it would appear that electrode insertion is not an inert process, but rather triggers a cascade of biological processes, and, as such, should be considered alongside the active delivery of stimulation as an active part of the deep brain stimulation therapy.

Tau Phosphorylation Patterns in the Rat Cerebral Cortex After Traumatic Brain Injury and Sodium Selenate Effects: An Epibios4rx Project 2 Study

Sodium selenate (SS) activates protein phosphatase 2 (PP2A) and reduces phosphorylated tau (pTAU) and late post-traumatic seizures after lateral fluid percussion injury (LFPI). In EpiBioS4Rx Project 2, a multi-center international study for post-traumatic targets, biomarkers, and treatments, we tested the target relevance and modification by SS of pTAU forms and PP2A and in the LFPI model, at two sites: Einstein and Melbourne. In Experiment 1, adult male rats were assigned to LFPI and sham (both sites) and naïve controls (Einstein). Motor function was monitored by neuroscores. Brains were studied with immunohistochemistry (IHC), Western blots (WBs), or PP2A activity assay, from 2 days to 8 weeks post-operatively. In Experiment 2, LFPI rats received SS for 7 days (SS0.33: 0.33 mg/kg/day; SS1: 1 mg/kg/day, subcutaneously) or vehicle (Veh) post-LFPI and pTAU, PR55 expression, or PP2A activity were studied at 2 days and 1 week (on treatment), or 2 weeks (1 week off treatment). Plasma selenium and SS levels were measured. In Experiment 1 IHC, LFPI rats had higher cortical pTAU-Ser202/Thr205-immunoreactivity (AT8-ir) and pTAU-Ser199/202-ir at 2 days, and pTAU-Thr231-ir (AT180-ir) at 2 days, 2 weeks, and 8 weeks, ipsilaterally to LFPI, than controls. LFPI-2d rats also had higher AT8/total-TAU5-ir in cortical extracts ipsilateral to the lesion (WB). PP2A (PR55-ir) showed time- and region-dependent changes in IHC, but not in WB. PP2A activity was lower in LFPI-1wk than in sham rats. In Experiment 2, SS did not affect neuroscores or cellular AT8-ir, AT180-ir, or PR55-ir in IHC. In WB, total cortical AT8/total-TAU-ir was lower in SS0.33 and SS1 LFPI rats than in Veh rats (2 days, 1 week); total cortical PR55-ir (WB) and PP2A activity were higher in SS1 than Veh rats (2 days). SS dose dependently increased plasma selenium and SS levels. Concordant across-sites data confirm time and pTAU form-specific cortical increases ipsilateral to LFPI. The discordant SS effects may either suggest SS-induced reduction in the numbers of cells with increased pTAU-ir, need for longer treatment, or the involvement of other mechanisms of action.

Building a pathway to recovery: Targeting ECM remodeling in CNS injuries

Extracellular matrix (ECM) is a complex and dynamic network of proteoglycans, proteins, and other macromolecules that surrounds cells in tissues. The ECM provides structural support to cells and plays a critical role in regulating various cellular functions. ECM remodeling is a dynamic process involving the breakdown and reconstruction of the ECM. This process occurs naturally during tissue growth, wound healing, and tissue repair. However, in the context of central nervous system (CNS) injuries, dysregulated ECM remodeling can lead to the formation of fibrotic and glial scars. CNS injuries encompass various traumatic events, including concussions and fractures. Following CNS trauma, the formation of glial and fibrotic scars becomes prominent. Glial scars primarily consist of reactive astrocytes, while fibrotic scars are characterized by an abundance of ECM proteins. ECM remodeling plays a pivotal and tightly regulated role in the development of these scars after spinal cord and brain injuries. Various factors like ECM components, ECM remodeling enzymes, cell surface receptors of ECM molecules, and downstream pathways of ECM molecules are responsible for the remodeling of the ECM. The aim of this review article is to explore the changes in ECM during normal physiological conditions and following CNS injuries. Additionally, we discuss various approaches that target various factors responsible for ECM remodeling, with a focus on promoting axon regeneration and functional recovery after CNS injuries. By targeting ECM remodeling, it may be possible to enhance axonal regeneration and facilitate functional recovery after CNS injuries.

Cellular and Molecular Pathophysiology of Traumatic Brain Injury: What Have We Learned So Far?

Traumatic brain injury (TBI) is one of the leading causes of long-lasting morbidity and mortality worldwide, being a devastating condition related to the impairment of the nervous system after an external traumatic event resulting in transitory or permanent functional disability, with a significant burden to the healthcare system. Harmful events underlying TBI can be classified into two sequential stages, primary and secondary, which are both associated with breakdown of the tissue homeostasis due to impairment of the blood-brain barrier, osmotic imbalance, inflammatory processes, oxidative stress, excitotoxicity, and apoptotic cell death, ultimately resulting in a loss of tissue functionality. The present study provides an updated review concerning the roles of brain edema, inflammation, excitotoxicity, and oxidative stress on brain changes resulting from a TBI. The proper characterization of the phenomena resulting from TBI can contribute to the improvement of care, rehabilitation and quality of life of the affected people.

Dexamethasone-Enhanced Continuous Online Microdialysis for Neuromonitoring of O2 after Brain Injury

Traumatic brain injury (TBI) is a major public health crisis in many regions of the world. Severe TBI may cause a primary brain lesion with a surrounding penumbra of tissue that is vulnerable to secondary injury. Secondary injury presents as progressive expansion of the lesion, possibly leading to severe disability, a persistent vegetive state, or death. Real time neuromonitoring to detect and monitor secondary injury is urgently needed. Dexamethasone-enhanced continuous online microdialysis (Dex-enhanced coMD) is an emerging paradigm for chronic neuromonitoring after brain injury. The present study employed Dex-enhanced coMD to monitor brain K⁺ and O₂ during manually induced spreading depolarization in the cortex of anesthetized rats and after controlled cortical impact, a widely used rodent model of TBI, in behaving rats. Consistent with prior reports on glucose, O₂ exhibited a variety of responses to spreading depolarization and a prolonged, essentially permanent decline in the days after controlled cortical impact. These findings confirm that Dex-enhanced coMD delivers valuable information regarding the impact of spreading depolarization and controlled cortical impact on O₂ levels in the rat cortex.

The Beneficial Role of Photobiomodulation in Neurodegenerative Diseases

Photobiomodulation (PBM), also known as Low-level Laser Therapy (LLLT), involves the use of light from a laser or light-emitting diode (LED) in the treatment of various disorders and it has recently gained increasing interest. Progressive neuronal loss with attendant consequences such as cognitive and/or motor decline characterize neurodegenerative diseases. The available therapeutic drugs have only been able to provide symptomatic relief and may also present with some side effects, thus precluding their use in treatment. Recently, there has been an exponential increase in interest and attention in the use of PBM as a therapy in various neurodegenerative diseases in animal studies. Because of the financial and social burden of neurodegenerative diseases on the sufferers and the need for the discovery of potential therapeutic inventions in their management, it is pertinent to examine the beneficial effects of PBM and the various cellular mechanisms by which it modulates neural activity. Here, we highlight the various ways by which PBM may possess beneficial effects on neural activity and has been reported in various neurodegenerative conditions (Alzheimer's disease, Parkinson's disease, epilepsy, TBI, stroke) with the hope that it may serve as an alternative therapy in the management of neurodegenerative diseases because of the biological side effects associated with drugs currently used in the treatment of neurodegenerative diseases.

Timely expression of PGAM5 and its cleavage control mitochondrial homeostasis during neurite re-growth after traumatic brain injury

BACKGROUND

Patients suffered from severe traumatic brain injury (TBI) have twice the risk of developing into neurodegenerative diseases later in their life. Thus, early intervention is needed not only to treat TBI but also to reduce neurodegenerative diseases in the future. Physiological functions of neurons highly depend on mitochondria. Thus, when mitochondrial integrity is compromised by injury, neurons would initiate a cascade of events to maintain homeostasis of mitochondria. However, what protein senses mitochondrial dysfunction and how mitochondrial homeostasis is maintained during regeneration remains unclear.

RESULTS

We found that TBI-increased transcription of a mitochondrial protein, phosphoglycerate mutase 5 (PGAM5), during acute phase was via topological remodeling of a novel enhancer-promoter interaction. This up-regulated PGAM5 correlated with mitophagy, whereas presenilins-associated rhomboid-like protein (PARL)-dependent PGAM5 cleavage at a later stage of TBI enhanced mitochondrial transcription factor A (TFAM) expression and mitochondrial mass. To test whether PGAM5 cleavage and TFAM expression were sufficient for functional recovery, mitochondrial oxidative phosphorylation uncoupler carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) was used to uncouple electron transport chain and reduce mitochondrial function. As a result, FCCP triggered PGAM5 cleavage, TFAM expression and recovery of motor function deficits of CCI mice.

CONCLUSIONS

Findings from this study implicate that PGAM5 may act as a mitochondrial sensor for brain injury to activate its own transcription at acute phase, serving to remove damaged mitochondria through mitophagy. Subsequently, PGAM5 is cleaved by PARL, and TFAM expression is increased for mitochondrial biogenesis at a later stage after TBI. Taken together, this study concludes that timely regulation of PGAM5 expression and its own cleavage are required for neurite re-growth and functional recovery.

Human umbilical cord-derived mesenchymal stem cells-harvested mitochondrial transplantation improved motor function in TBI models through rescuing neuronal cells from apoptosis and alleviating astrogliosis and microglia activation

Each year, traumatic brain injury (TBI) causes a high rate of mortality throughout the world and those who survive have lasting disabilities. Given that the brain is a particularly dynamic organ with a high energy consumption rate, the inefficiency of current TBI treatment options highlights the necessity of repairing damaged brain tissue at the cellular and molecular levels, which according to research is aggravated due to ATP deficiency and reactive oxygen species surplus. Taking into account that mitochondria contribute to generating energy and controlling cellular stress, mitochondrial transplantation as a new treatment approach has lately reduced complications in a number of diseases by supplying healthy and functional mitochondria to the damaged tissue. For this reason, in this study, we used this technique to transplant human umbilical cord-derived mesenchymal stem cells (hUC-MSCs)-derived mitochondria as a suitable source for mitochondrial isolation into rat models of TBI to examine its therapeutic benefit and the results showed that the successful mitochondrial internalisation in the neuronal cells significantly reduced the number of brain cells undergoing apoptosis, alleviated astrogliosis and microglia activation, retained normal brain morphology and cytoarchitecture, and improved sensorimotor functions in a rat model of TBI. These data indicate that human umbilical cord-derived mesenchymal stem cells-isolated mitochondrial transplantation improves motor function in a rat model of TBI via rescuing neuronal cells from apoptosis and alleviating astrogliosis and microglia activation, maybe as a result of restoring the lost mitochondrial content.

Mitophagy and Traumatic Brain Injury: Regulatory Mechanisms and Therapeutic Potentials

Traumatic brain injury (TBI), a kind of external trauma-induced brain function alteration, has posed a financial burden on the public health system. TBI pathogenesis involves a complicated set of events, including primary and secondary injuries that can cause mitochondrial damage. Mitophagy, a process in which defective mitochondria are specifically degraded, segregates and degrades defective mitochondria allowing a healthier mitochondrial network. Mitophagy ensures that mitochondria remain healthy during TBI, determining whether neurons live or die. Mitophagy acts as a critical regulator in maintaining neuronal survival and healthy. This review will discuss the TBI pathophysiology and the consequences of the damage it causes to mitochondria. This review article will explore the mitophagy process, its key factors, and pathways and reveal the role of mitophagy in TBI. Mitophagy will be further recognized as a therapeutic approach in TBI. This review will offer new insights into mitophagy's role in TBI progression.

FAM3A Ameliorates Brain Impairment Induced by Hypoxia-Ischemia in Neonatal Rat

Hypoxia-ischemia (HI) during crucial periods of brain formation can lead to changes in brain morphology, propagation of neuronal stimuli, and permanent neurodevelopmental impairment, which can have profound effects on cognitive function later in life. FAM3A, a subgroup of family with sequence similarity 3 (FAM3) gene family, is ubiquitously expressed in almost all cells. Overexpression of FAM3A has been evidenced to reduce hyperglycemia via the PI3K/Akt signaling pathway and protect mitochondrial function in neuronal HT22 cells. This study aims to evaluate the protective role of FAM3A in HI-induced brain impairment. Experimentally, maternal rats underwent uterine artery bilateral ligation to induce neonatal HI on day 14 of gestation. At 6 weeks of age, cognitive development assessments including NSS, wire grip, and water maze were carried out. The animals were then sacrificed to assess cerebral mitochondrial function as well as levels of FAM3A, TNF-α and IFN-γ. Results suggest that HI significantly reduced FAM3A expression in rat brain tissues, and that overexpression of FAM3A through lentiviral transduction effectively improved cognitive and motor functions in HI rats as reflected by improved NSS evaluation, cerebral water content, limb strength, as well as spatial learning and memory. At the molecular level, overexpression of FAM3A was able to promote ATP production, balance mitochondrial membrane potential, and reduce levels of pro-inflammatory cytokines TNF-α and IFN-γ. We conclude that FAM3A overexpression may have a protective effect on neuron morphology, cerebral mitochondrial as well as cognitive function. Created with Biorender.com.

Oxidative stress and mitochondrial dysfunction following traumatic brain injury: From mechanistic view to targeted therapeutic opportunities

Traumatic brain injury (TBI) is one of the most prevalent causes of permanent physical and cognitive disabilities. TBI pathology results from primary insults and a multi-mechanistic biochemical process, termed as secondary brain injury. Currently, there are no pharmacological agents for definitive treatment of patients with TBI. This article is presented with the purpose of reviewing molecular mechanisms of TBI pathology, as well as potential strategies and agents against pathological pathways. In this review article, materials were obtained by searching PubMed, Scopus, Elsevier, Web of Science, and Google Scholar. This search was considered without time limitation. Evidence indicates that oxidative stress and mitochondrial dysfunction are two key mediators of the secondary injury cascade in TBI pathology. TBI-induced oxidative damage results in the structural and functional impairments of cellular and subcellular components, such as mitochondria. Impairments of mitochondrial electron transfer chain and mitochondrial membrane potential result in a vicious cycle of free radical formation and cell apoptosis. The results of some preclinical and clinical studies, evaluating mitochondria-targeted therapies, such as mitochondria-targeted antioxidants and compounds with pleiotropic effects after TBI, are promising. As a proposed strategy in recent years, mitochondria-targeted multipotential therapy is a new hope, waiting to be confirmed. Moreover, based on the available findings, biologics, such as stem cell-based therapy and transplantation of mitochondria are novel potential strategies for the treatment of TBI; however, more studies are needed to clearly confirm the safety and efficacy of these strategies.

Progress Toward a Multiomic Understanding of Traumatic Brain Injury: A Review

Traumatic brain injury (TBI) is not a single disease state but describes an array of conditions associated with insult or injury to the brain. While some individuals with TBI recover within a few days or months, others present with persistent symptoms that can cause disability, neuropsychological trauma, and even death. Understanding, diagnosing, and treating TBI is extremely complex for many reasons, including the variable biomechanics of head impact, differences in severity and location of injury, and individual patient characteristics. Because of these confounding factors, the development of reliable diagnostics and targeted treatments for brain injury remains elusive. We argue that the development of effective diagnostic and therapeutic strategies for TBI requires a deep understanding of human neurophysiology at the molecular level and that the framework of multiomics may provide some effective solutions for the diagnosis and treatment of this challenging condition. To this end, we present here a comprehensive review of TBI biomarker candidates from across the multiomic disciplines and compare them with known signatures associated with other neuropsychological conditions, including Alzheimer’s disease and Parkinson’s disease. We believe that this integrated view will facilitate a deeper understanding of the pathophysiology of TBI and its potential links to other neurological diseases.

Impact of ketogenic diet and ketone diester supplementation on body weight, blood glucose, and ketones in Sprague Dawley rats fed over two weeks

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Ketogenic diet influenced ketones, weight, and glucose in rats.

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Ketone diester supplement (20% by weight) was similar to ketogenic diet, but its effects on ketones and weight was smaller and it did not affect glucose.

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Changeover from standard diet to ketogenic diet resulted in sex-specific glucose changes.

Ketogenic diets consist of low carbohydrate/high fat, shifting energy reliance from glucose to ketone bodies. Ketone diester supplement to a standard diet (ketone ester) increases ketone bodies by adding a substance without altering other consumed foods. We evaluated weight, glucose, and ketone concentrations in rats fed ketogenic diet and ketone ester feeds. We hypothesized that these feeds would increase ketones and decrease glucose and weight. We tested 16 male and 16 female Sprague Dawley rats randomly assigned to standard diet, ketogenic diet, or ketone ester for two weeks. Weight and blood glucose and ketones were measured daily. Group means were compared by analysis of variance. Ketogenic diet and ketone ester both increased ketones and decreased weight compared to standard diet (p < 0.001). Glucose decreased only in ketogenic diet (p = 0.010), driven by a decrease from higher starting concentrations observed in standard diet males. Sex interacted with weight, with male gains impacted more by both ketogenic diet and ketone ester than female gains. Ketogenic diet had a larger effect size than ketone ester with regard to increased ketones and decreased weight. Ketogenic diet glucose significantly decreased over time because standard diet concentrations in males were high prior to initializing ketogenic diet. This suggests sex differences in energy substrate utilization. Ketogenic diet ketones peaked at 72 h then decreased to near basal levels at about 10 days, suggesting “fat adaption.” While this work is part of a larger project examining blast exposure, these results are relevant to any military forces considering ketone-increasing foods.

Rescuing mitochondria in traumatic brain injury and intracerebral hemorrhages - A potential therapeutic approach

Mitochondria are dynamic organelles responsible for cellular energy production. Besides, regulating energy homeostasis, mitochondria are responsible for calcium homeostasis, signal transmission, and the fate of cellular survival in case of injury and pathologies. Accumulating reports have suggested multiple roles of mitochondria in neuropathologies, neurodegeneration, and immune activation under physiological and pathological conditions. Mitochondrial dysfunction, which occurs at the initial phase of brain injury, involves oxidative stress, inflammation, deficits in mitochondrial bioenergetics, biogenesis, transport, and autophagy. Thus, development of targeted therapeutics to protect mitochondria may improve functional outcomes following traumatic brain injury (TBI) and intracerebral hemorrhages (ICH). In this review, we summarize mitochondrial dysfunction related to TBI and ICH, including the mechanisms involved, and discuss therapeutic approaches with special emphasis on past and current clinical trials.

Repeated mild traumatic brain injuries perturb the mitochondrial biogenesis via DNA methylation in the hippocampus of rat

Mitochondrial biogenesis in the brain is impaired in various neurological disorders including traumatic brain injury (TBI). The long-lasting effects of TBI may be, in part, attributed to epigenetic mechanisms such as DNA methylation. However, the role of DNA methylation on regulatory elements of nuclear and mitochondrial genome in mitochondrial biogenesis is not known. We examined the epigenetic regulation of mitochondrial transcription factor A (TFAM), and further probed its implications in mitochondrial dysfunction in the hippocampus of rats subjected to repeated mild TBI (rMTBI) using weight drop injury paradigm. rMTBI-induced hypermethylation at TFAM promoter resulted in deficits in its protein levels in mitochondria after immediate (48 h) and protracted (30 d) time points. Further, rMTBI also caused hypomethylation of mitochondrial DNA (mtDNA) promoters (HSP1 and HSP2), which further culminated into low binding of TFAM. rMTBI-induced changes weakened mitochondrial biogenesis in terms of reduced mtDNA-encoded rRNA, mRNA, and protein levels leading to shortages of ATP. To verify the potential role of mtDNA methylation in rMTBI-induced persistent mitochondrial dysfunction, rMTBI-induced rats were treated with methionine, a methyl donor. Methionine treatment restored the methylation levels on HSP1 and HSP2 resulting in efficient binding of TFAM and normalized the rRNA, mRNA, and protein levels. These findings suggest the crucial role of DNA methylation at nuclear and mitochondrial promoter regions in mitochondrial gene expression and ATP activity in the hippocampus after rMTBI.

Effects of Pyruvate Administration on Mitochondrial Enzymes, Neurological Behaviors, and Neurodegeneration after Traumatic Brain Injury

Traumatic brain injury (TBI) is known to increase the susceptibility to various age-related neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). Although the role of damaged mitochondrial electron transport chain (ETC) in the progression of AD and PD has been identified, its relationship with altered expression of neurodegenerative proteins has not been examined before. This study aimed to investigate 1) how TBI could affect mitochondrial ETC and neurodegeneration in rat brain regions related to behavioral alteration, and 2) if administration of the key mitochondrial substrate pyruvate can improve the outcome of mild TBI (mTBI). In a rat lateral fluid percussion injury model of mTBI, sodium pyruvate in sterile distilled water (1 g/kg body weight) was administered orally daily for 7 days. The protein expression of mitochondrial ETC enzymes, and neurodegeneration proteins in the hippocampus and cerebral cortex and was assessed on Day 7. The hippocampal and cortical expressions of ETC complex I, III, IV, V were significantly and variably impaired following mTBI. Pyruvate treatment altered ETC complex expression, reduced the nitrosyl stress and the MBP expression in the injured brain area, but increased the expression of the glial fibrillary acidic protein (GFAP) and Tau proteins. Pyruvate after mTBI augmented the Rotarod performance but decreased the horizontal and vertical open field locomotion activities and worsened neurobehavioural severity score, indicating a debilitating therapeutic effect on the acute phase of mTBI. These results suggest bidirectional neuroprotective and neurodegenerative modulating effects of pyruvate on TBI-induced alteration in mitochondrial activity and motor behavior. Pyruvate could potentially stimulate the proliferation of astrogliosis, and lactate acidosis, and caution should be exercised when used as a therapy in the acute phase of mTBI. More effective interventions targeted at multiple mechanisms are needed for the prevention and treatment of TBI-induced long-term neurodegeneration.

Inhibiting Mitochondrial Cytochrome c Oxidase Downregulates Gene Transcription After Traumatic Brain Injury in Drosophila

Traumatic brain injuries (TBIs) caused by a sudden impact to the head alter behavior and impair physical and cognitive function. Besides the severity, type and area of the brain affected, the outcome of TBI is also influenced by the patient’s biological sex. Previous studies reporting mitochondrial dysfunction mainly focused on exponential reactive oxygen species (ROS) generation, increased mitochondrial membrane potential, and altered mitochondrial dynamics as a key player in the outcome to brain injury. In this study, we evaluated the effect of a near-infrared (NIR) light exposure on gene expression in a Drosophila TBI model. NIR interacts with cytochrome c oxidase (COX) of the electron transport chain to reduce mitochondrial membrane potential hyperpolarization, attenuate ROS generation, and apoptosis. We subjected w¹¹¹⁸ male and female flies to TBI using a high-impact trauma (HIT) device and subsequently exposed the isolated fly brains to a COX-inhibitory wavelength of 750 nm for 2 hours (hr). Genome-wide 3′-mRNA-sequencing of fly brains revealed that injured w¹¹¹⁸ females exhibit greater changes in transcription compared to males at 1, 2, and 4 hours (hr) after TBI. Inhibiting COX by exposure to NIR downregulates gene expression in injured females but has minimal effect in injured males. Our results suggest that mitochondrial COX modulation with NIR alters gene expression in Drosophila following TBI and the response to injury and NIR exposure varies by biological sex.

An Overview and Therapeutic Promise of Nutraceuticals against Sports-Related Brain Injury

Sports-related traumatic brain injury (TBI) is one of the common neurological maladies experienced by athletes. Earlier the term 'punch drunk syndrome' was used in the case TBI of boxers and now this term is replaced by chronic traumatic encephalopathy (CTE). Sports-related brain injury can either be short term or long term. A common instance of brain injury encompasses subdural hematoma, concussion, cognitive dysfunction, amnesia, headache, vision issue, axonopathy, or even death if remain undiagnosed or untreated. Further, chronic TBI may lead to pathogenesis of neuroinflammation and neurodegeneration via tauopathy, formation of neurofibrillary tangles, and damage to the blood-brain barrier, microglial, and astrocyte activation. Thus, altered pathological, neurochemical, and neurometabolic attributes lead to the modulation of multiple signaling pathways and cause neurological dysfunction. Available pharmaceutical interventions are based on one drug one target hypothesis and thereby unable to cover altered multiple signaling pathways. However, in recent time's pharmacological intervention of nutrients and nutraceuticals have been explored as they exert a multifactorial mode of action and maintain over homeostasis of the body. There are various reports available showing the positive therapeutic effect of nutraceuticals in sport-related brain injury. Therefore, in the current article we have discussed the pathology, neurological consequence, sequelae, and perpetuation of sports-related brain injury. Further, we have discussed various nutraceutical supplements as well as available animal models to explore the neuroprotective effect/ upshots of these nutraceuticals in sports-related brain injury.

"Omics" in traumatic brain injury: novel approaches to a complex disease

BACKGROUND

To date, there is neither any pharmacological treatment with efficacy in traumatic brain injury (TBI) nor any method to halt the disease progress. This is due to an incomplete understanding of the vast complexity of the biological cascades and failure to appreciate the diversity of secondary injury mechanisms in TBI. In recent years, techniques for high-throughput characterization and quantification of biological molecules that include genomics, proteomics, and metabolomics have evolved and referred to as omics.

METHODS

In this narrative review, we highlight how omics technology can be applied to potentiate diagnostics and prognostication as well as to advance our understanding of injury mechanisms in TBI.

RESULTS

The omics platforms provide possibilities to study function, dynamics, and alterations of molecular pathways of normal and TBI disease states. Through advanced bioinformatics, large datasets of molecular information from small biological samples can be analyzed in detail and provide valuable knowledge of pathophysiological mechanisms, to include in prognostic modeling when connected to clinically relevant data. In such a complex disease as TBI, omics enables broad categories of studies from gene compositions associated with susceptibility to secondary injury or poor outcome, to potential alterations in metabolites following TBI.

CONCLUSION

The field of omics in TBI research is rapidly evolving. The recent data and novel methods reviewed herein may form the basis for improved precision medicine approaches, development of pharmacological approaches, and individualization of therapeutic efforts by implementing mathematical "big data" predictive modeling in the near future.

Disruption of mitochondrial functions and oxidative stress contribute to neurologic dysfunction in organic acidurias

Organic acidurias (OADs) are inherited disorders of amino acid metabolism biochemically characterized by accumulation of short-chain carboxylic acids in tissues and biological fluids of the affected patients and clinically by predominant neurological manifestations. Some of these disorders are amenable to treatment, which significantly decreases mortality and morbidity, but it is still ineffective to prevent long-term neurologic and systemic complications. Although pathogenesis of OADs is still poorly established, recent human and animal data, such as lactic acidosis, mitochondrial morphological alterations, decreased activities of respiratory chain complexes and altered parameters of oxidative stress, found in tissues from patients and from genetic mice models with these diseases indicate that disruption of critical mitochondrial functions and oxidative stress play an important role in their pathophysiology. Furthermore, organic acids that accumulate in the most prevalent OADs were shown to compromise bioenergetics, by decreasing ATP synthesis, mitochondrial membrane potential, reducing equivalent content and calcium retention capacity, besides inducing mitochondrial swelling, reactive oxygen and nitrogen species generation and apoptosis. It is therefore presumed that secondary mitochondrial dysfunction and oxidative stress caused by major metabolites accumulating in OADs contribute to tissue damage in these pathologies.

Pesticide use and incident Parkinson's disease in a cohort of farmers and their spouses

BACKGROUND

Extensive literature suggests an association between general pesticide use and Parkinson's disease (PD). However, with few exceptions, little is known about associations between specific pesticides and PD.

OBJECTIVE

We evaluated use of pesticides and incident PD in 38,274 pesticide applicators and 27,836 of their spouses in the Agricultural Health Study cohort followed over 20 years.

METHODS

We used self-reported information on ever-use of 50 specific pesticides as of enrollment for both applicators and spouses, and considered intensity-weighted lifetime days (IWLD) reported at enrollment and through the first 5-year follow-up among applicators. We estimated covariate-adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox regression. We also examined heterogeneity in associations by history of head injury and chemical resistant glove use.

RESULTS

A total of 373 applicators and 118 spouses self-reported incident doctor-diagnosed PD. Ever-use of the insecticide terbufos (HR:1.31, 95%CI:1.02-1.68) and the herbicides trifluralin (HR:1.29, 95%CI: 0.99-1.70) and 2,4,5-T (HR:1.57, 95%CI:1.21-2.04) was associated with elevated PD risk. On the other hand, diazinon (HR:0.73, 95%CI: 0.58-0.94) and 2,4,5-TP (HR:0.39, 95%CI:0.25-0.62) were associated with reduced risk. We observed heterogeneity in ever-use associations by head injury and chemical-resistant glove use for some pesticides, with higher risk among those who reported a history of head injury, or who did not use gloves. PD risk was also elevated for applicators in the highest category of IWLD for dichlorvos, permethrin (animal use), and benomyl.

CONCLUSIONS

We found evidence of increased PD risk for some pesticides. Our results also suggest higher susceptibility for pesticide-associated PD among individuals with head injury as well as protection with use of chemical resistant gloves, although further research is needed to understand the impact of head injury. Research on current and newer pesticides, including mechanisms relevant to PD, is important given widespread pesticide use.

Formoterol, a β2-adrenoreceptor agonist, induces mitochondrial biogenesis and promotes cognitive recovery after traumatic brain injury

Traumatic brain injury (TBI) leads to acute necrosis at the site of injury followed by a sequence of secondary events lasting from hours to weeks and often years. Targeting mitochondrial impairment following TBI has shown improvements in brain mitochondrial bioenergetics and neuronal function. Recently formoterol, a highly selective β₂-adrenoreceptor agonist, was found to induce mitochondrial biogenesis (MB) via Gβγ-Akt-eNOS-sGC pathway. Activation of MB is a novel approach that has been shown to restore mitochondrial function in several disease and injury models. We hypothesized that activation of MB as a target of formoterol after TBI would mitigate mitochondrial dysfunction, enhance neuronal function and improve behavioral outcomes. TBI-injured C57BL/6 male mice were injected (i.p.) with vehicle (normal saline) or formoterol (0.3 mg/kg) at 15 min, 8 h, 16 h, 24 h and then daily after controlled cortical impact (CCI) until euthanasia. After CCI, mitochondrial copy number and bioenergetic function were decreased in the ipsilateral cortex of the CCI-vehicle group. Compared to CCI-vehicle, cortical and hippocampal mitochondrial respiration rates as well as cortical mitochondrial DNA copy number were increased in the CCI-formoterol group. Mitochondrial Ca²⁺ buffering capacity in the hippocampus was higher in the CCI-formoterol group compared to CCI-vehicle group. Both assessments of cognitive performance, novel object recognition (NOR) and Morris water maze (MWM), decreased following CCI and were restored in the CCI-formoterol group. Although no changes were seen in the amount of cortical tissue spared between CCI-formoterol and CCI-vehicle groups, elevated levels of hippocampal neurons and improved white matter sparing in the corpus callosum were observed in CCI-formoterol group. Collectively, these results indicate that formoterol-mediated MB activation may be a potential therapeutic target to restore mitochondrial bioenergetics and promote functional recovery after TBI.

Mitochondrial biogenesis as a therapeutic target for traumatic and neurodegenerative CNS diseases

Central nervous system (CNS) diseases, both traumatic and neurodegenerative, are characterized by impaired mitochondrial bioenergetics and often disturbed mitochondrial dynamics. The dysregulation observed in these pathologies leads to defective respiratory chain function and reduced ATP production, thereby promoting neuronal death. As such, attenuation of mitochondrial dysfunction through induction of mitochondrial biogenesis (MB) is a promising, though still underexplored, therapeutic strategy. MB is a multifaceted process involving the integration of highly regulated transcriptional events, lipid membrane and protein synthesis/assembly and replication of mtDNA. Several nuclear transcription factors promote the expression of genes involved in oxidative phosphorylation, mitochondrial import and export systems, antioxidant defense and mitochondrial gene transcription. Of these, the nuclear-encoded peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is the most commonly studied and is widely accepted as the 'master regulator' of MB. Several recent preclinical studies document that reestablishment of mitochondrial homeostasis through increased MB results in inhibited injury progression and increased functional recovery. This perspective will briefly review the role of mitochondrial dysfunction in the propagation of CNS diseases, while also describing current research strategies that mediate mitochondrial dysfunction and compounds that induce MB for the treatment of acute and chronic neuropathologies.

Matching early arterial oxygenation to long-term outcome in severe traumatic brain injury: target values

OBJECTIVE

The aim of this study was to examine the relationship between early arterial oxygenation thresholds and long-term outcome after severe traumatic brain injury (TBI).

METHODS

In a post hoc analysis of a randomized trial, adults with severe TBI were classified based on exposure to different levels of arterial oxygenation as measured using the average of arterial partial pressure of oxygen (PaO2) values obtained within 24 hours of admission. Potentially important PaO2 thresholds were defined a priori. The primary outcome was Glasgow Outcome Scale-Extended (GOSE) score at 6 months. Secondary outcomes were cognitive outcomes measured using a battery of 9 neuropsychological tests administered at 6 months, and 6-month mortality.

RESULTS

In adjusted analyses, oxygenation thresholds of 150 and 200 mm Hg were associated with better functional outcome at 6 months (adjusted OR for better functional outcome on GOSE 1.82 [95% CI 1.12-2.94] and 1.59 [95% CI 1.06-2.37], respectively) and improved cognitive outcome at 6 months (adjusted beta coefficients for better cognitive percentile across 9 neuropsychological tests: 6.9 [95% CI 1.3-12.5] and 6.8 [95% CI 2.4-11.3], respectively). There was no significant association between oxygenation level and 6-month mortality except at a PaO2 threshold of 200 mm Hg (OR for death 0.36, 95% CI 0.18-0.71). Higher or lower oxygenation thresholds were not associated with functional or cognitive outcome.

CONCLUSIONS

In this observational study, the relationship between early arterial oxygenation and long-term functional and cognitive TBI outcomes appears to be U-shaped. Mild levels of hyperoxemia within the first 24 hours after injury were associated with better long-term functional and cognitive outcomes. These findings highlight the importance of examining balanced oxygen supplementation as a potential strategy to improve TBI outcomes in future research.

Traumatic Brain Injuries: Pathophysiology and Potential Therapeutic Targets

Traumatic brain injury (TBI) remains one of the leading causes of morbidity and mortality amongst civilians and military personnel globally. Despite advances in our knowledge of the complex pathophysiology of TBI, the underlying mechanisms are yet to be fully elucidated. While initial brain insult involves acute and irreversible primary damage to the parenchyma, the ensuing secondary brain injuries often progress slowly over months to years, hence providing a window for therapeutic interventions. To date, hallmark events during delayed secondary CNS damage include Wallerian degeneration of axons, mitochondrial dysfunction, excitotoxicity, oxidative stress and apoptotic cell death of neurons and glia. Extensive research has been directed to the identification of druggable targets associated with these processes. Furthermore, tremendous effort has been put forth to improve the bioavailability of therapeutics to CNS by devising strategies for efficient, specific and controlled delivery of bioactive agents to cellular targets. Here, we give an overview of the pathophysiology of TBI and the underlying molecular mechanisms, followed by an update on novel therapeutic targets and agents. Recent development of various approaches of drug delivery to the CNS is also discussed.

A Critical Review of Microelectrode Arrays and Strategies for Improving Neural Interfaces

Though neural interface systems (NISs) can provide a potential solution for mitigating the effects of limb loss and central nervous system damage, the microelectrode array (MEA) component of NISs remains a significant limiting factor to their widespread clinical applications. Several strategies can be applied to MEA designs to increase their biocompatibility. Herein, an overview of NISs and their applications is provided, along with a detailed discussion of strategies for alleviating the foreign body response (FBR) and abnormalities seen at the interface of MEAs and the brain tissue following MEA implantation. Various surface modifications, including natural/synthetic surface coatings, hydrogels, and topography alterations, have shown to be highly successful in improving neural cell adhesion, reducing gliosis, and increasing MEA longevity. Different MEA surface geometries, such as those seen in the Utah and Michigan arrays, can help alleviate the resultant FBR by reducing insertion damage, while providing new avenues for improving MEA recording performance and resolution. Increasing overall flexibility of MEAs as well as reducing their stiffness is also shown to reduce MEA induced micromotion along with FBR severity. By combining multiple different properties into a single MEA, the severity and duration of an FBR postimplantation can be reduced substantially.

Current progress of mitochondrial transplantation that promotes neuronal regeneration

Background

Mitochondria are the major source of intracellular adenosine triphosphate (ATP) and play an essential role in a plethora of physiological functions, including the regulation of metabolism and the maintenance of cellular homeostasis. Mutations of mitochondrial DNA, proteins and impaired mitochondrial function have been implicated in the neurodegenerative diseases, stroke and injury of the central nervous system (CNS). The dynamic feature of mitochondrial fusion, fission, trafficking and turnover have also been documented in these diseases.

Perspectives

A major bottleneck of traditional approach to correct mitochondria-related disorders is the difficulty of drugs or gene targeting agents to arrive at specific sub-compartments of mitochondria. Moreover, the diverse nature of mitochondrial mutations among patients makes it impossible to develop one drug for one disease. To this end, mitochondrial transplantation presents a new paradigm of therapeutic intervention that benefits neuronal survival and regeneration for neurodegenerative diseases, stroke, and CNS injury. Supplement of healthy mitochondria to damaged neurons has been reported to promote neuronal viability, activity and neurite re-growth. In this review, we provide an overview of the recent advance and development on mitochondrial therapy.

Conclusion

Key parameters for the success of mitochondrial transplantation depend on the source and quality of isolated mitochondria, delivery protocol, and cellular uptake of supplemented mitochondria. To expedite clinical application of the mitochondrial transplantation, current isolation protocol needs optimization to obtain high percentage of functional mitochondria, isolated mitochondria may be packaged by biomaterials for successful delivery to brain allowing for efficient neuronal uptake.

Effects of Phenelzine Administration on Mitochondrial Function, Calcium Handling, and Cytoskeletal Degradation after Experimental Traumatic Brain Injury

Traumatic brain injury (TBI) results in the production of peroxynitrite (PN), leading to oxidative damage of lipids and protein. PN-mediated lipid peroxidation (LP) results in production of reactive aldehydes 4-hydroxynonenal (4-HNE) and acrolein. The goal of these studies was to explore the hypothesis that interrupting secondary oxidative damage following a TBI via phenelzine (PZ), analdehyde scavenger, would protect against LP-mediated mitochondrial and neuronal damage. Male Sprague-Dawley rats received a severe (2.2 mm) controlled cortical impact (CCI)-TBI. PZ was administered subcutaneously (s.c.) at 15 min (10 mg/kg) and 12 h (5 mg/kg) post-injury and for the therapeutic window/delay study, PZ was administered at 1 h (10 mg/kg) and 24 h (5 mg/kg). Mitochondrial and cellular protein samples were obtained at 24 and 72 h post-injury (hpi). Administration of PZ significantly improved mitochondrial respiration at 24 and 72 h compared with vehicle-treated animals. These results demonstrate that PZ administration preserves mitochondrial bioenergetics at 24 h and that this protection is maintained out to 72 hpi. Additionally, delaying the administration still elicited significant protective effects. PZ administration also improved mitochondrial Ca2+ buffering (CB) capacity and mitochondrial membrane potential parameters compared with vehicle-treated animals at 24 h. Although PZ treatment attenuated aldehyde accumulation post-injury, the effects were insignificant. The amount of α-spectrin breakdown in cortical tissue was reduced by PZ administration at 24 h, but not at 72 hpi compared with vehicle-treated animals. In conclusion, these results indicate that acute PZ treatment successfully attenuates LP-mediated oxidative damage eliciting multiple neuroprotective effects following TBI.

In search of antiepileptogenic treatments for post-traumatic epilepsy

Post-traumatic epilepsy (PTE) is diagnosed in 20% of individuals with acquired epilepsy, and can impact significantly the quality of life due to the seizures and other functional or cognitive and behavioral outcomes of the traumatic brain injury (TBI) and PTE. There is no available antiepileptogenic or disease modifying treatment for PTE. Animal models of TBI and PTE have been developed, offering useful insights on the value of inflammatory, neurodegenerative pathways, hemorrhages and iron accumulation, calcium channels and other target pathways that could be used for treatment development. Most of the existing preclinical studies test efficacy towards pathologies of functional recovery after TBI, while a few studies are emerging testing the effects towards induced or spontaneous seizures. Here we review the existing preclinical trials testing new candidate treatments for TBI sequelae and PTE, and discuss future directions for efforts aiming at developing antiepileptogenic and disease-modifying treatments.

Pioglitazone Therapy and Fractures: Systematic Review and Meta- Analysis

INTRODUCTION

Thiazolidinediones are a group of synthetic medications used in type 2 diabetes treatment. Among available thiazolidinediones, pioglitazone is gaining increased attention due to its lower cardiovascular risk in type 2 diabetes mellitus sufferers and seems a promising future therapy. Accumulating evidence suggests that diabetic patients may exert bone fractures due to such treatments. Simultaneously, the female population is thought to be at greater risk. Still, the safety outcomes of pioglitazone treatment especially in terms of fractures are questionable and need to be clarified.

METHODS

We searched MEDLINE, Scopus, PsyInfo, eLIBRARY.ru electronic databases and clinical trial registries for studies reporting an association between pioglitazone and bone fractures in type 2 diabetes mellitus patients published before Feb 15, 2016. Among 1536 sources that were initially identified, six studies including 3172 patients proved relevant for further analysis.

RESULT

Pooled analysis of the included studies demonstrated that after treatment with pioglitazone patients with type 2 diabetes mellitus had no significant increase in fracture risk [odds ratio (OR): 1.18, 95% confidence interval (CI): 0.82 to 1.71, p=0.38] compared to other antidiabetic drugs or placebo. Additionally, no association was found between the risk of fractures and pioglitazone therapy duration. The gender of the patients involved was not relevant to the risk of fractures, too.

CONCLUSION

Pioglitazone treatment in diabetic patients does not increase the incidence of bone fractures. Moreover, there is no significant association between patients' fractures, their gender and the period of exposure to pioglitazone. Additional longitudinal studies need to be undertaken to obtain more detailed information on bone fragility and pioglitazone therapy.

Neuroinflammation, oxidative stress, and blood-brain barrier (BBB) disruption in acute Utah electrode array implants and the effect of deferoxamine as an iron chelator on acute foreign body response

The use of intracortical microelectrode arrays has gained significant attention in being able to help restore function in paralysis patients and study the brain in various neurological disorders. Electrode implantation in the cortex causes vasculature or blood-brain barrier (BBB) disruption and thus elicits a foreign body response (FBR) that results in chronic inflammation and may lead to poor electrode performance. In this study, a comprehensive insight into the acute molecular mechanisms occurring at the Utah electrode array-tissue interface is provided to understand the oxidative stress, neuroinflammation, and neurovascular unit (astrocytes, pericytes, and endothelial cells) disruption that occurs following microelectrode implantation. Quantitative real time polymerase chain reaction (qRT-PCR) was used to quantify the gene expression at acute time-points of 48-hr, 72-hr, and 7-days for factors mediating oxidative stress, inflammation, and BBB disruption in rats implanted with a non-functional 4 × 4 Utah array in the somatosensory cortex. During vascular disruption, free iron released into the brain parenchyma can exacerbate the FBR, leading to oxidative stress and thus further contributing to BBB degradation. To reduce the free iron released into the brain tissue, the effects of an iron chelator, deferoxamine mesylate (DFX), was also evaluated.

Acute Mitochondrial Impairment Underlies Prolonged Cellular Dysfunction after Repeated Mild Traumatic Brain Injuries

Mild traumatic brain injuries (mTBI), accounting for more than 80% of TBIs, can cause cognitive and behavioral impairments, the severity and duration of which increase after additional mTBIs. While mTBI does not cause widespread neuronal death, the mechanisms underlying increased cellular susceptibility to subsequent head impacts remain unknown. To investigate the hypothesis that altered mitochondrial bioenergetics underlie cellular vulnerability to repeated insults, we employed a mouse model of mild closed head injury (CHI) to examine mitochondrial function and oxidative stress, because these mechanisms are often intertwined. Mitochondrial respiration was assayed (Seahorse XFe24 Flux Analyzer) from cortex and hippocampus collected at 6 h, 24 h, 48 h, and 96 h post-injury. State III (adenosine diphosphate [ADP]-mediated) respiration was significantly decreased in the hippocampal mitochondria of the CHI group compared with sham at 48 h post-injury. Further, cortex-derived mitochondria exhibited a decrease in State III respiration at 24 h and 48 h post-injury. No significant differences were observed at 6 h or 96 h post-injury in either region of interest. A second CHI repeated either 48 h or 96 h after the first did not worsen State III respiration at 48 h after the final injury compared with a single CHI, but CHI repeated at a 48 h interval prolonged cortical mitochondrial dysfunction to 96 h after the final injury. Markers of oxidative stress were significantly elevated after two CHIs delivered 48 h apart, but not after single CHI or two CHI delivered 96 h apart. This study establishes that mTBI results in early mitochondrial dysfunction, which may be a determinant for cellular vulnerability to repeated head impacts. Thus, therapies targeting mitochondrial impairment could improve outcomes after repeated mTBI.

Mitochondrial Metabolism in Major Neurological Diseases

Mitochondria are bilayer sub-cellular organelles that are an integral part of normal cellular physiology. They are responsible for producing the majority of a cell's ATP, thus supplying energy for a variety of key cellular processes, especially in the brain. Although energy production is a key aspect of mitochondrial metabolism, its role extends far beyond energy production to cell signaling and epigenetic regulation⁻functions that contribute to cellular proliferation, differentiation, apoptosis, migration, and autophagy. Recent research on neurological disorders suggest a major metabolic component in disease pathophysiology, and mitochondria have been shown to be in the center of metabolic dysregulation and possibly disease manifestation. This review will discuss the basic functions of mitochondria and how alterations in mitochondrial activity lead to neurological disease progression.

Protection Before Impact: the Potential Neuroprotective Role of Nutritional Supplementation in Sports-Related Head Trauma

Even in the presence of underreporting, sports-related concussions/mild traumatic brain injuries (mTBI) are on the rise. In the absence of proper diagnosis, an athlete may return to play prior to full recovery, increasing the risk of second-impact syndrome or protracted symptoms. Recent evidence has demonstrated that sub-concussive impacts, those sustained routinely in practice and competition, result in a quantifiable pathophysiological response and the accumulation of both concussive and sub-concussive impacts sustained over a lifetime of sports participation may lead to long-term neurological impairments and an increased risk of developing neurodegenerative diseases. The pathophysiological, neurometabolic, and neurochemical cascade that initiates subsequent to the injury is complex and involves multiple mechanisms. While pharmaceutical treatments may target one mechanism, specific nutrients and nutraceuticals have been discovered to impact several pathways, presenting a broader approach. Several studies have demonstrated the neuroprotective effect of nutritional supplementation in the treatment of mTBI. However, given that many concussions go unreported and sub-concussive impacts result in a pathophysiological response that, too, may contribute to long-term brain health, protection prior to impact is warranted. This review discusses the current literature regarding the role of nutritional supplements that, when provided before mTBI and traumatic brain injury, may provide neurological protection.

Disentangling oxidation/hydrolysis reactions of brain mitochondrial cardiolipins in pathogenesis of traumatic injury

Mechanical injury to the brain triggers multiple biochemical events whose specific contributions to the pathogenesis define clinical manifestations and the overall outcome. Among many factors, mitochondrial injury has recently attracted much attention due to the importance of the organelle for bioenergetics as well as intra- and extracellular signaling and cell death. Assuming the essentiality of a mitochondria-unique phospholipid, cardiolipin (CL), for the structural and functional organization of mitochondria, here we applied global (phospho) lipidomics and redox lipidomics to reveal and identify CL modifications during controlled cortical impact (CCI). We revealed 2 major pathways activated in the CCI-injured brain as time-specific responses: early accumulation of oxidized CL (CLox) products was followed by hydrolytic reactions yielding monolyso-CLs (mCLs) and free fatty acids. To quantitatively assess possible specific roles of peroxidation and hydrolysis of mitochondrial CL, we performed comparative studies of CL modifications using an animal model of Barth syndrome where deficiency of CL reacylation (Tafazzin [Taz] deficiency) was associated exclusively with the accumulation of mCLs (but not CLox). By comparing the in vitro and in vivo results with genetic manipulation of major CL-, CLox-, and mCL-metabolizing enzymes, calcium-independent phospholipase A2γ and Taz, we concluded that the 2 processes - CL oxidation and CL hydrolysis - act as mutually synergistically enhancing components of the pathogenic mechanism of mitochondrial injury in traumatic brain injury. This emphasizes the need for combined therapeutic approaches preventing the formation of both CLox and mCL.

L-Carnitine and extendin-4 improve outcomes following moderate brain contusion injury

There is a need for pharmaceutical agents that can reduce neuronal loss and improve functional deficits following traumatic brain injury (TBI). Previous research suggests that oxidative stress and mitochondrial dysfunction play a major role in neuronal damage after TBI. Therefore, this study aimed to investigate two drugs known to have antioxidant effects, L-carnitine and exendin-4, in rats with moderate contusive TBI. L-carnitine (1.5 mM in drinking water) or exendin-4 (15 µg/kg/day, ip) were given immediately after the injury for 2 weeks. Neurological function and brain histology were examined (24 h and 6 weeks post injury). The rats with TBI showed slight sensory, motor and memory functional deficits at 24 h, but recovered by 6 weeks. Both treatments improved sensory and motor functions at 24 h, while only exendin-4 improved memory. Both treatments reduced cortical contusion at 24 h and 6 weeks, however neither affected gliosis and inflammatory cell activation. Oxidative stress was alleviated and mitochondrial reactive oxygen species was reduced by both treatments, however only mitochondrial functional marker protein transporter translocase of outer membrane 20 was increased at 24 h post injury. In conclusion, L-carnitine and exendin-4 treatments immediately after TBI can improve neurological functional outcome and tissue integrity by reducing oxidative stress.

Synaptic Mitochondria are More Susceptible to Traumatic Brain Injury-induced Oxidative Damage and Respiratory Dysfunction than Non-synaptic Mitochondria

Traumatic brain injury (TBI) results in mitochondrial dysfunction and induction of lipid peroxidation (LP). Lipid peroxidation-derived neurotoxic aldehydes such as 4-HNE and acrolein bind to mitochondrial proteins, inducing additional oxidative damage and further exacerbating mitochondrial dysfunction and LP. Mitochondria are heterogeneous, consisting of both synaptic and non-synaptic populations. Synaptic mitochondria are reported to be more vulnerable to injury; however, this is the first study to characterize the temporal profile of synaptic and non-synaptic mitochondria following TBI, including investigation of respiratory dysfunction and oxidative damage to mitochondrial proteins between 3 and 120 h following injury. These results indicate that synaptic mitochondria are indeed the more vulnerable population, showing both more rapid and severe impairments than non-synaptic mitochondria. By 24 h, synaptic respiration is significantly impaired compared to synaptic sham, whereas non-synaptic respiration does not decline significantly until 48 h. Decreases in respiration are associated with increases in oxidative damage to synaptic and non-synaptic mitochondrial proteins at 48 h and 72 h, respectively. These results indicate that the therapeutic window for mitochondria-targeted pharmacological neuroprotectants to prevent respiratory dysfunction is shorter for the more vulnerable synaptic mitochondria than for the non-synaptic population.

Mitochondrial therapy promotes regeneration of injured hippocampal neurons

Due to the inhibitory microenvironment and reduced intrinsic growth capacity of neurons, neuronal regeneration of central nervous system remains challenging. Neurons are highly energy demanding and require sufficient mitochondria to support cellular activities. In response to stimuli, mitochondria undergo fusion/fission cycles to adapt to environment. It is thus logical to hypothesize that the plasticity of mitochondrial dynamics is required for neuronal regeneration. In this study, we examined the role of mitochondrial dynamics during regeneration of rat hippocampal neurons. Quantitative analysis showed that injury induced mitochondrial fission. As mitochondrial dysfunction has been implicated in neurodegenerative diseases, we tested the possibility that the mitochondrial therapy may promote neuronal regeneration. Supplying freshly isolated mitochondria to the injured hippocampal neurons not only significantly increased neurite re-growth but also restored membrane potential of injured hippocampal neurons. Together, our findings support the importance of mitochondrial dynamics during regeneration of injured hippocampal neurons and highlight the therapeutic prospect of mitochondria to the injured central nervous system.

Proteomic differences between focal and diffuse traumatic brain injury in human brain tissue

The early molecular response to severe traumatic brain injury (TBI) was evaluated using biopsies of structurally normal-appearing cortex, obtained at location for intracranial pressure (ICP) monitoring, from 16 severe TBI patients. Mass spectrometry (MS; label free and stable isotope dimethyl labeling) quantitation proteomics showed a strikingly different molecular pattern in TBI in comparison to cortical biopsies from 11 idiopathic normal pressure hydrocephalus patients. Diffuse TBI showed increased expression of peptides related to neurodegeneration (Tau and Fascin, p < 0.05), reduced expression related to antioxidant defense (Glutathione S-transferase Mu 3, Peroxiredoxin-6, Thioredoxin-dependent peroxide reductase; p < 0.05) and increased expression of potential biomarkers (e.g. Neurogranin, Fatty acid-binding protein, heart p < 0.05) compared to focal TBI. Proteomics of human brain biopsies displayed considerable molecular heterogeneity among the different TBI subtypes with consequences for the pathophysiology and development of targeted treatments for TBI.

Hypertonic sodium lactate reverses brain oxygenation and metabolism dysfunction after traumatic brain injury

BACKGROUND

The mechanisms by which hypertonic sodium lactate (HSL) solution act in injured brain are unclear. We investigated the effects of HSL on brain metabolism, oxygenation, and perfusion in a rodent model of diffuse traumatic brain injury (TBI).

METHODS

Thirty minutes after trauma, anaesthetised adult rats were randomly assigned to receive a 3 h infusion of either a saline solution (TBI-saline group) or HSL (TBI-HSL group). The sham-saline and sham-HSL groups received no insult. Three series of experiments were conducted up to 4 h after TBI (or equivalent) to investigate: 1) brain oedema using diffusion-weighted magnetic resonance imaging and brain metabolism using localized ¹H-magnetic resonance spectroscopy (n = 10 rats per group). The respiratory control ratio was then determined using oxygraphic analysis of extracted mitochondria, 2) brain oxygenation and perfusion using quantitative blood-oxygenation-level-dependent magnetic resonance approach (n = 10 rats per group), and 3) mitochondrial ultrastructural changes (n = 1 rat per group).

RESULTS

Compared with the TBI-saline group, the TBI-HSL and the sham-operated groups had reduced brain oedema. Concomitantly, the TBI-HSL group had lower intracellular lactate/creatine ratio [0.049 (0.047-0.098) vs 0.097 (0.079-0.157); P < 0.05], higher mitochondrial respiratory control ratio, higher tissue oxygen saturation [77% (71-79) vs 66% (55-73); P < 0.05], and reduced mitochondrial cristae thickness in astrocytes [27.5 (22.5-38.4) nm vs 38.4 (31.0-47.5) nm; P < 0.01] compared with the TBI-saline group. Serum sodium and lactate concentrations and serum osmolality were higher in the TBI-HSL than in the TBI-saline group.

CONCLUSIONS

These findings indicate that the hypertonic sodium lactate solution can reverse brain oxygenation and metabolism dysfunction after traumatic brain injury through vasodilatory, mitochondrial, and anti-oedema effects.

NaHS restores mitochondrial function and inhibits autophagy by activating the PI3K/Akt/mTOR signalling pathway to improve functional recovery after traumatic brain injury

Traumatic brain injury (TBI) is one of the most serious public health problems in the world. TBI causes neurological deficits by triggering secondary injuries. Hydrogen sulfide (H₂S), a gaseous mediator, has been reported to exert neuroprotective effects in central nervous system diseases, such as TBI. However, the molecular mechanisms involved in this effect are still unclear. The present study was designed to explore the ability of NaHS, a H₂S donor, to provide neuroprotection in a mouse model of TBI and to discover the associated molecular mechanisms of these protective effects. Here, we found that administration of NaHS not only maintained the integrity of the blood brain barrier (BBB), protected neurons from apoptosis, and promoted remyelination and axonal reparation but also protected mitochondrial function. In addition, we found that autophagy was inhibited after treatment with NaHS following TBI, an effect that was induced by activation of the PI3K/AKT/mTOR signalling pathway. Our study indicated that H₂S treatment is beneficial for TBI, pointing to H₂S as a potential therapeutic target for treating TBI.

Traumatic Brain Injury Impairs Myogenic Constriction of Cerebral Arteries: Role of Mitochondria-Derived H2O2 and TRPV4-Dependent Activation of BKca Channels

Traumatic brain injury (TBI) impairs autoregulation of cerebral blood flow, which contributes to the development of secondary brain injury, increasing mortality of patients. Impairment of pressure-induced myogenic constriction of cerebral arteries plays a critical role in autoregulatory dysfunction; however, the underlying cellular and molecular mechanisms are not well understood. To determine the role of mitochondria-derived H₂O₂ and large-conductance calcium-activated potassium channels (BK_Ca) in myogenic autoregulatory dysfunction, middle cerebral arteries (MCAs) were isolated from rats with severe weight drop-impact acceleration brain injury. We found that 24 h post-TBI MCAs exhibited impaired myogenic constriction, which was restored by treatment with a mitochondria-targeted antioxidant (mitoTEMPO), by scavenging of H₂O₂ (polyethylene glycol [PEG]-catalase) and by blocking both BK_Ca channels (paxilline) and transient receptor potential cation channel subfamily V member 4 (TRPV4) channels (HC 067047). Further, exogenous administration of H₂O₂ elicited significant dilation of MCAs, which was inhibited by blocking either BK_Ca or TRPV4 channels. Vasodilation induced by the TRPV4 agonist GSK1016790A was inhibited by paxilline. In cultured vascular smooth muscle cells H₂O₂ activated BK_Ca currents, which were inhibited by blockade of TRPV4 channels. Collectively, our results suggest that after TBI, excessive mitochondria-derived H₂O₂ activates BK_Ca channels via a TRPV4-dependent pathway in the vascular smooth muscle cells, which impairs pressure-induced constriction of cerebral arteries. Future studies should elucidate the therapeutic potential of pharmacological targeting of this pathway in TBI, to restore autoregulatory function in order to prevent secondary brain damage and decrease mortality.