Simvastatin attenuates microglial cells and astrocyte activation and decreases interleukin-1beta level after traumatic brain injury

Astrocytes, reactive astrogliosis, and glial scar formation in traumatic brain injury

Traumatic brain injury is a global health crisis, causing significant death and disability worldwide. Neuroinflammation that follows traumatic brain injury has serious consequences for neuronal survival and cognitive impairments, with astrocytes involved in this response. Following traumatic brain injury, astrocytes rapidly become reactive, and astrogliosis propagates from the injury core to distant brain regions. Homeostatic astroglial proteins are downregulated near the traumatic brain injury core, while pro-inflammatory astroglial genes are overexpressed. This altered gene expression is considered a pathological remodeling of astrocytes that produces serious consequences for neuronal survival and cognitive recovery. In addition, glial scar formed by reactive astrocytes is initially necessary to limit immune cell infiltration, but in the long term impedes axonal reconnection and functional recovery. Current therapeutic strategies for traumatic brain injury are focused on preventing acute complications. Statins, cannabinoids, progesterone, beta-blockers, and cerebrolysin demonstrate neuroprotective benefits but most of them have not been studied in the context of astrocytes. In this review, we discuss the cell signaling pathways activated in reactive astrocytes following traumatic brain injury and we discuss some of the potential new strategies aimed to modulate astroglial responses in traumatic brain injury, especially using cell-targeted strategies with miRNAs or lncRNA, viral vectors, and repurposed drugs.

Delayed simvastatin treatment improves neurological recovery after cryogenic traumatic brain injury through downregulation of ELOVL1 by inhibiting mTOR signaling

Statins are well-tolerated and widely available lipid-lowering medications with neuroprotective effects against traumatic brain injury (TBI). However, whether delayed statin therapy starting in the subacute phase promotes recovery after TBI is unknown. Elongation of the very long-chain fatty acid protein 1 (ELOVL1) is involved in astrocyte-mediated neurotoxicity, but its role in TBI and the relationship between ELOVL1 and statins are unclear. We hypothesized that delayed simvastatin treatment promotes neurological functional recovery after TBI by regulating the ELOVL1-mediated production of very long-chain fatty acids (VLCFAs). ICR male mice received daily intragastric administration of 1, 2 or 5 mg/kg simvastatin on Days 1-14, 3-14, 5-14, or 7-14 after cryogenic TBI (cTBI). The results showed that simvastatin promoted motor functional recovery in a dose-dependent manner, with a wide therapeutic window of at least 7 days postinjury. Meanwhile, simvastatin inhibited astrocyte and microglial overactivation and glial scar formation, and increased total dendritic length, neuronal complexity and spine density on day 14 after cTBI. The up-regulation of ELOVL1 expression and saturated VLCFAs concentrations in the cortex surrounding the lesion caused by cTBI was inhibited by simvastatin, which was related to the inhibition of the mTOR signaling. Overexpression of ELOVL1 in astrocytes surrounding the lesion using HBAAV2/9-GFAP-m-ELOVL1-3xFlag-EGFP partially attenuated the benefits of simvastatin. These results showed that delayed simvastatin treatment promoted functional recovery and brain tissue repair after TBI through the downregulation of ELOVL1 expression by inhibiting mTOR signaling. Astrocytic ELOVL1 may be a potential target for rehabilitation after TBI.

Intravenous Administration of Anti-CD47 Antibody Augments Hematoma Clearance, Mitigates Acute Neuropathology, and Improves Cognitive Function in a Rat Model of Penetrating Traumatic Brain Injury

Traumatic brain injury (TBI)-induced intracerebral hematoma is a major driver of secondary injury pathology such as neuroinflammation, cerebral edema, neurotoxicity, and blood-brain barrier dysfunction, which contribute to neuronal loss, motor deficits, and cognitive impairment. Cluster of differentiation 47 (CD47) is an antiphagocytic cell surface protein inhibiting hematoma clearance. This study was designed to evaluate the safety and efficacy of blockade of CD47 via intravenous (i.v.) administration of anti-CD47 antibodies following penetrating ballistic-like brain injury (PBBI) with significant traumatic intracerebral hemorrhage (tICH). The pharmacokinetic (PK) profile of the anti-CD47 antibody elicited that antibody concentration decayed over 7 days post-administration. Blood tests and necropsy analysis indicated no severe adverse events following treatment. Cerebral hemoglobin levels were significantly increased after injury, however, anti-CD47 antibody administration at 0.1 mg/kg resulted in a significant reduction in cerebral hemoglobin levels at 72 h post-administration, indicating augmentation of hematoma clearance. Immunohistochemistry assessment of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule 1 (IBA1) demonstrated a significant reduction of GFAP levels in the lesion core and peri-lesional area. Based on these analyses, the optimal dose was identified as 0.1 mg/kg. Lesion volume showed a reduction following treatment. Rotarod testing revealed significant motor deficits in all injured groups but no significant therapeutic benefits. Spatial learning performance revealed significant deficits in all injured groups, which were significantly improved by the last testing day. Anti-CD47 antibody treated rats showed significantly improved attention deficits, but not retention scores. These results provide preliminary evidence that blockade of CD47 using i.v. administration of anti-CD47 antibodies may serve as a potential therapeutic for TBI with ICH.

Dysregulated brain-gut axis in the setting of traumatic brain injury: review of mechanisms and anti-inflammatory pharmacotherapies

Traumatic brain injury (TBI) is a chronic and debilitating disease, associated with a high risk of psychiatric and neurodegenerative diseases. Despite significant advancements in improving outcomes, the lack of effective treatments underscore the urgent need for innovative therapeutic strategies. The brain-gut axis has emerged as a crucial bidirectional pathway connecting the brain and the gastrointestinal (GI) system through an intricate network of neuronal, hormonal, and immunological pathways. Four main pathways are primarily implicated in this crosstalk, including the systemic immune system, autonomic and enteric nervous systems, neuroendocrine system, and microbiome. TBI induces profound changes in the gut, initiating an unrestrained vicious cycle that exacerbates brain injury through the brain-gut axis. Alterations in the gut include mucosal damage associated with the malabsorption of nutrients/electrolytes, disintegration of the intestinal barrier, increased infiltration of systemic immune cells, dysmotility, dysbiosis, enteroendocrine cell (EEC) dysfunction and disruption in the enteric nervous system (ENS) and autonomic nervous system (ANS). Collectively, these changes further contribute to brain neuroinflammation and neurodegeneration via the gut-brain axis. In this review article, we elucidate the roles of various anti-inflammatory pharmacotherapies capable of attenuating the dysregulated inflammatory response along the brain-gut axis in TBI. These agents include hormones such as serotonin, ghrelin, and progesterone, ANS regulators such as beta-blockers, lipid-lowering drugs like statins, and intestinal flora modulators such as probiotics and antibiotics. They attenuate neuroinflammation by targeting distinct inflammatory pathways in both the brain and the gut post-TBI. These therapeutic agents exhibit promising potential in mitigating inflammation along the brain-gut axis and enhancing neurocognitive outcomes for TBI patients.

Simvastatin Differentially Modulates Glial Functions in Cultured Cortical and Hypothalamic Astrocytes Derived from Interferon α/β Receptor Knockout mice

Astrocytes have key regulatory roles in central nervous system (CNS), integrating metabolic, inflammatory and synaptic responses. In this regard, type I interferon (IFN) receptor signaling in astrocytes can regulate synaptic plasticity. Simvastatin is a cholesterol-lowering drug that has shown anti-inflammatory properties, but its effects on astrocytes, a main source of cholesterol for neurons, remain to be elucidated. Herein, we investigated the effects of simvastatin in inflammatory and functional parameters of primary cortical and hypothalamic astrocyte cultures obtained from IFNα/β receptor knockout (IFNα/βR-/-) mice. Overall, simvastatin decreased extracellular levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), which were related to a downregulation in gene expression in hypothalamic, but not in cortical astrocytes. Moreover, there was an increase in anti-inflammatory interleukin-10 (IL-10) in both structures. Effects of simvastatin in inflammatory signaling also involved a downregulation of cyclooxygenase 2 (COX-2) gene expression as well as an upregulation of nuclear factor κB subunit p65 (NFκB p65). The expression of cytoprotective genes sirtuin 1 (SIRT1) and nuclear factor erythroid derived 2 like 2 (Nrf2) was also increased by simvastatin. In addition, simvastatin increased glutamine synthetase (GS) activity and glutathione (GSH) levels only in cortical astrocytes. Our findings provide evidence that astrocytes from different regions are important cellular targets of simvastatin in the CNS, even in the absence of IFNα/βR, which was showed by the modulation of cytokine production and release, as well as the expression of cytoprotective genes and functional parameters.

Senolytic therapy is neuroprotective and improves functional outcome long-term after traumatic brain injury in mice

Introduction

Chronic neuroinflammation can exist for months to years following traumatic brain injury (TBI), although the underlying mechanisms remain poorly understood.

Methods

In the current study, we used a controlled cortical impact mouse model of TBI to examine whether proinflammatory senescent cells are present in the brain long-term (months) after TBI and whether ablation of these cells via administration of senolytic drugs can improve long-term functional outcome after TBI. The results revealed that astrocytes and microglia in the cerebral cortex, hippocampus, corpus callosum and lateral posterior thalamus colocalized the senescent cell markers, p16Ink4a or p21Cip1/Waf1 at 5 weeks post injury (5wpi) and 4 months post injury (4mpi) in a controlled cortical impact (CCI) model. Intermittent administration of the senolytic drugs, dasatinib and quercetin (D + Q) beginning 1-month after TBI for 13 weeks significantly ablated p16Ink4a-positive- and p21Cip1/Waf1-positive-cells in the brain of TBI animals, and significantly reduced expression of the major senescence-associated secretory phenotype (SASP) pro-inflammatory factors, interleukin-1β and interleukin-6. Senolytic treatment also significantly attenuated neurodegeneration and enhanced neuron number at 18 weeks after TBI in the ipsilateral cortex, hippocampus, and lateral posterior thalamus. Behavioral testing at 18 weeks after TBI further revealed that senolytic therapy significantly rescued defects in spatial reference memory and recognition memory, as well as depression-like behavior in TBI mice.

Discussion

Taken as a whole, these findings indicate there is robust and widespread induction of senescent cells in the brain long-term after TBI, and that senolytic drug treatment begun 1-month after TBI can efficiently ablate the senescent cells, reduce expression of proinflammatory SASP factors, reduce neurodegeneration, and rescue defects in reference memory, recognition memory, and depressive behavior.

The neuroprotective effect of statin in traumatic brain injury: A systematic review

Despite recent encouraging pharmaceutical and technical breakthroughs in neurosurgical critical care, traumatic brain injury (TBI)-related mortality and morbidity remain substantial clinical issues. Medication of statins was revealed to enhance outcomes following TBI in animal research. In addition to their main role of decreasing serum cholesterol, statins decrease inflammation and enhance cerebral blood flow. However, research on the efficacy of statins in TBI is still limited. This systematic review was conducted to determine the efficacy of statins in enhancing the clinical outcomes of TBI individuals, and specifically investigate the optimal dose and form of statins. The databases of PubMed, DOAJ, EBSCO, and Cochrane were extensively researched. The date of publication within the last fifteen years was the inclusion criterion. Meta-analyses, clinical trials, and randomized controlled trials were prioritized forms of research publications. Ambiguous remarks, irrelevant correlations to the main issue, or a focus on disorders other than TBI were the exclusion criteria. Thirteen research were included in this study. Simvastatin, atorvastatin, and rosuvastatin were the main form of statins discussed in this study. Enhancement of the Glasgow Coma Scale, survival rates, hospital length of stay, and cognitive outcomes were revealed in this study. This study suggests either simvastatin 40 mg, atorvastatin 20 mg, or rosuvastatin 20 mg for 10 days as the optimal therapeutic forms and doses to be applied in the management of TBI. Pre-TBI statin use was linked to lower risk of mortality in TBI individuals compared to nonusers, whereas statin discontinuation was linked to an increase in mortality.

The Potential Therapeutic Application of Simvastatin for Brain Complications and Mechanisms of Action

Statins are common drugs that are clinically used to reduce elevated plasma cholesterol levels. Based on their solubility, statins are considered to be either hydrophilic or lipophilic. Amongst them, simvastatin has the highest lipophilicity to facilitate its ability to cross the blood-brain barrier. Recent studies have suggested that simvastatin could be a promising therapeutic option for different brain complications and diseases ranging from brain tumors (i.e., medulloblastoma and glioblastoma) to neurological disorders (i.e., Alzheimer's disease, Parkinson's disease, and Huntington's disease). Specific mechanisms of disease amelioration, however, are still unclear. Independent studies suggest that simvastatin may reduce the risk of developing certain neurodegenerative disorders. Meanwhile, other studies point towards inducing cell death in brain tumor cell lines. In this review, we outline the potential therapeutic effects of simvastatin on brain complications and review the clinically relevant molecular mechanisms in different cases.

Tackling Neuroinflammation After Traumatic Brain Injury: Complement Inhibition as a Therapy for Secondary Injury

Traumatic brain injury (TBI) is a leading cause of mortality, sensorimotor morbidity, and neurocognitive disability. Neuroinflammation is one of the key drivers causing secondary brain injury after TBI. Therefore, attenuation of the inflammatory response is a potential therapeutic goal. This review summarizes the most important neuroinflammatory pathophysiology resulting from TBI and the clinical trials performed to attenuate neuroinflammation. Studies show that non-selective attenuation of the inflammatory response, in the early phase after TBI, might be detrimental and that there is a gap in the literature regarding pharmacological trials targeting specific pathways. The complement system and its crosstalk with the coagulation system play an important role in the pathophysiology of secondary brain injury after TBI. Therefore, regaining control over the complement cascades by inhibiting overshooting activation might constitute useful therapy. Activation of the complement cascade is an early component of neuroinflammation, making it a potential target to mitigate neuroinflammation in TBI. Therefore, we have described pathophysiological aspects of complement inhibition and summarized animal studies targeting the complement system in TBI. We also present the first clinical trial aimed at inhibition of complement activation in the early days after brain injury to reduce the risk of morbidity and mortality following severe TBI.

Neuro-Inflammation Modulation and Post-Traumatic Brain Injury Lesions: From Bench to Bed-Side

Head trauma is the most common cause of disability in young adults. Known as a silent epidemic, it can cause a mosaic of symptoms, whether neurological (sensory-motor deficits), psychiatric (depressive and anxiety symptoms), or somatic (vertigo, tinnitus, phosphenes). Furthermore, cranial trauma (CT) in children presents several particularities in terms of epidemiology, mechanism, and physiopathology-notably linked to the attack of an immature organ. As in adults, head trauma in children can have lifelong repercussions and can cause social and family isolation, difficulties at school, and, later, socio-professional adversity. Improving management of the pre-hospital and rehabilitation course of these patients reduces secondary morbidity and mortality, but often not without long-term disability. One hypothesized contributor to this process is chronic neuroinflammation, which could accompany primary lesions and facilitate their development into tertiary lesions. Neuroinflammation is a complex process involving different actors such as glial cells (astrocytes, microglia, oligodendrocytes), the permeability of the blood-brain barrier, excitotoxicity, production of oxygen derivatives, cytokine release, tissue damage, and neuronal death. Several studies have investigated the effect of various treatments on the neuroinflammatory response in traumatic brain injury in vitro and in animal and human models. The aim of this review is to examine the various anti-inflammatory therapies that have been implemented.

Reactive Astrocytes in Central Nervous System Injury: Subgroup and Potential Therapy

Traumatic central nervous system (CNS) injury, which includes both traumatic brain injury (TBI) and spinal cord injury (SCI), is associated with irreversible loss of neurological function and high medical care costs. Currently, no effective treatment exists to improve the prognosis of patients. Astrocytes comprise the largest population of glial cells in the CNS and, with the advancements in the field of neurology, are increasingly recognized as having key functions in both the brain and the spinal cord. When stimulated by disease or injury, astrocytes become activated and undergo a series of changes, including alterations in gene expression, hypertrophy, the loss of inherent functions, and the acquisition of new ones. Studies have shown that astrocytes are highly heterogeneous with respect to their gene expression profiles, and this heterogeneity accounts for their observed context-dependent phenotypic diversity. In the inured CNS, activated astrocytes play a dual role both as regulators of neuroinflammation and in scar formation. Identifying the subpopulations of reactive astrocytes that exert beneficial or harmful effects will aid in deciphering the pathological mechanisms underlying CNS injuries and ultimately provide a theoretical basis for the development of effective strategies for the treatment of associated conditions. Following CNS injury, as the disease progresses, astrocyte phenotypes undergo continuous changes. Although current research methods do not allow a comprehensive and accurate classification of astrocyte subpopulations in complex pathological contexts, they can nonetheless aid in understanding the roles of astrocytes in disease. In this review, after a brief introduction to the pathology of CNS injury, we summarize current knowledge regarding astrocyte activation following CNS injury, including: (a) the regulatory factors involved in this process; (b) the functions of different astrocyte subgroups based on the existing classification of astrocytes; and (c) attempts at astrocyte-targeted therapy.

Anti-Inflammatory Properties of Statin-Loaded Biodegradable Lecithin/Chitosan Nanoparticles: A Step Toward Nose-to-Brain Treatment of Neurodegenerative Diseases

Nasal delivery has been indicated as one of the most interesting alternative routes for the brain delivery of neuroprotective drugs. Nanocarriers have emerged as a promising strategy for the delivery of neurotherapeutics across the nasal epithelia. In this work, hybrid lecithin/chitosan nanoparticles (LCNs) were proposed as a drug delivery platform for the nasal administration of simvastatin (SVT) for the treatment of neuroinflammatory diseases. The impact of SVT nanoencapsulation on its transport across the nasal epithelium was investigated, as well as the efficacy of SVT-LCNs in suppressing cytokines release in a cellular model of neuroinflammation. Drug release studies were performed in simulated nasal fluids to investigate SVT release from the nanoparticles under conditions mimicking the physiological environment present in the nasal cavity. It was observed that interaction of nanoparticles with a simulated nasal mucus decreased nanoparticle drug release and/or slowed drug diffusion. On the other hand, it was demonstrated that two antibacterial enzymes commonly present in the nasal secretions, lysozyme and phospholipase A2, promoted drug release from the nanocarrier. Indeed, an enzyme-triggered drug release was observed even in the presence of mucus, with a 5-fold increase in drug release from LCNs. Moreover, chitosan-coated nanoparticles enhanced SVT permeation across a human cell model of the nasal epithelium (×11). The nanoformulation pharmacological activity was assessed using an accepted model of microglia, obtained by activating the human macrophage cell line THP-1 with the Escherichia coli–derived lipopolysaccharide (LPS) as the pro-inflammatory stimulus. SVT-LCNs were demonstrated to suppress the pro-inflammatory signaling more efficiently than the simple drug solution (−75% for IL-6 and −27% for TNF-α vs. −47% and −15% at 10 µM concentration for SVT-LCNs and SVT solution, respectively). Moreover, neither cellular toxicity nor pro-inflammatory responses were evidenced for the treatment with the blank nanoparticles even after 36 h of incubation, indicating a good biocompatibility of the nanomedicine components in vitro. Due to their biocompatibility and ability to promote drug release and absorption at the biointerface, hybrid LCNs appear to be an ideal carrier for achieving nose-to-brain delivery of poorly water-soluble drugs such as SVT.

Statins: Neurobiological underpinnings and mechanisms in mood disorders

Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) treat dyslipidaemia and cardiovascular disease by inhibiting cholesterol biosynthesis. They also have immunomodulatory and anti-inflammatory properties. Beyond cardiovascular disease, cholesterol and inflammation appear to be components of the pathogenesis and pathophysiology of neuropsychiatric disorders. Statins may therefore afford some therapeutic benefit in mood disorders. In this paper, we review the pathophysiology of mood disorders with a focus on pharmacologically relevant pathways, using major depressive disorder and bipolar disorder as exemplars. Statins are discussed in the context of these disorders, with particular focus on the putative mechanisms involved in their anti-inflammatory and immunomodulatory effects. Recent clinical data suggest that statins may have antidepressant properties, however given their interactions with many known biological pathways, it has not been fully elucidated which of these are the major determinants of clinical outcomes in mood disorders. Moreover, it remains unclear what the appropriate dose, or appropriate patient phenotype for adjunctive treatment may be. High quality randomised control trials in concert with complementary biological investigations are needed if the potential clinical effects of statins on mood disorders, as well as their biological correlates, are to be better understood.

Beneficial effects of atorvastatin on sex-specific cognitive impairment induced by a cerebral microhaemorrhage in mice

BACKGROUND AND PURPOSES

Cerebral microhaemorrhages (CMHs) are associated with cognitive decline in humans. In rodents, CMHs induces cognitive impairment in male mice along with sex-specific cortical and hippocampal changes affecting neural, glial and vascular functions. Statins, have been proposed to prevent cognitive decline. We tested here the action of atorvastatin on CMH-induced cognitive impairment in a murine model of CMH.

EXPERIMENTAL APPROACH

Using a multimodal approach combining behavioural tests, in vivo imaging, biochemistry and molecular biology, the effects of oral administration of atorvastatin on the sex-specific changes induced by a cortical CMH were studied in male and female mice (C57BL/6J) at 6-week post-induction using a collagenase-induced model.

KEY RESULTS

Atorvastatin caused specific effects according to the sex-specific CMH-induced changes. In males, atorvastatin improved the visuospatial memory, induced a local modulation of microglial response and enhanced brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (trkB) and vascular endothelial growth factor (VEGF) expression in the cortex. In the hippocampus, atorvastatin increased glucose metabolism and modulated astrocytes morphology. In females, atorvastatin did not modulate visuospatial memory despite the increased expression of cortical BDNF and the decrease in the number of hippocampal astrocytes. Atorvastatin also induced a decrease in the expression of cortical oestrogen receptors but did not modify body weight nor serum cholesterol levels in both sexes.

CONCLUSION AND IMPLICATIONS

Atorvastatin modulated the sex-specific cognitive impairment induced by the CMH with a pathophysiological impact mainly within the cortical area. It could represent a promising candidate for future sex-stratified clinical trials in patients with CMH.

The Effect of Oral Simvastatin on the Clinical Outcome of Patients with Severe Traumatic Brain Injury: A Randomized Clinical Trial

Background

Despite recent promising pharmacological and technological advances in neurosurgical intensive care, the overall TBI-related mortality and morbidity remain high and still pose a major clinical problem. The aim of this study was to evaluate the effect of oral simvastatin on the clinical outcome of patients with severe TBI.

Methods

In a double-blind placebo-controlled randomized clinical trial a total of 98 patients with severe TBI in Imam Khomeini Hospital in Sari, Iran, were evaluated. Patients who meet the inclusion criteria were randomly allocated into two groups (n=49). In addition to supportive therapies, the intervention group received oral simvastatin (40 mg, daily) for 10 days, and the control group received the placebo (10 days). Patients' Glasgow coma scale (GCS) score, in hospital mortality, duration of mechanical ventilation and length of ICU and neurosurgery ward stay were evaluated during three-time intervals (T1: admission, T2: discharge and T3: one month after discharge).

Results

The percentage of conscious patients was 18.9% (7 cases) in the simvastatin group and 3.1% (1 case) in controls (P=0.06) at T2. One month after discharge (T3) the proportion of conscious patients significantly increased in the simvastatin group compared to control group (64.9 % versus 28.1 %; P=0.002). There was no significant difference for the mean of GCS score between the simvastatin group and control group at T1 (6.41 ± 1.30 versus 6.41 ± 1.28, respectively; P = 0.98). However, the mean score of GCS in patients who received simvastatin was significantly greater than controls at T2 and T3 (p<0.05). There was no significant differences between two group in-terms of length of mechanical ventilation, ICU and neurosurgery ward stay.

Conclusion

According to the results of this study it seems that using simvastatin may be an effective and promising therapeutic modality for improving GCS score during TBI recovery.

Neuropharmacology in traumatic brain injury: from preclinical to clinical neuroprotection?

Traumatic brain injury (TBI) constitutes a major health problem worldwide and is a leading cause of death and disability in individuals, contributing to devastating socioeconomic consequences. Despite numerous promising pharmacological strategies reported as neuroprotective in preclinical studies, the translation to clinical trials always failed, albeit the great diversity of therapeutic targets evaluated. In this review, first, we described epidemiologic features, causes, and primary and secondary injuries of TBI. Second, we outlined the current literature on animal models of TBI, and we described their goals, their advantages and disadvantages according to the species used, the type of injury induced, and their clinical relevance. Third, we defined the concept of neuroprotection and discussed its evolution. We also identified the reasons that might explain the failure of clinical translation. Then, we reviewed post‐TBI neuroprotective treatments with a focus on the following pleiotropic drugs, considered “low hanging fruit” with high probability of success: glitazones, glibenclamide, statins, erythropoietin, and progesterone, that were largely tested and demonstrated efficient in preclinical models of TBI. Finally, our review stresses the need to establish a close cooperation between basic researchers and clinicians to ensure the best clinical translation for neuroprotective strategies for TBI.

Biological and Psychological Factors Determining Neuropsychiatric Outcomes in COVID-19

PURPOSE OF REVIEW

We present biological and psychological factors implicated in psychiatric manifestations of SARS-CoV-2, as well as its neuroinvasive capability and immune pathophysiology.

RECENT FINDINGS

Preexisting mental illness leads to worse clinical outcomes in COVID-19. The presence of the virus was reported in the cerebrospinal fluid (CSF) and brain tissue post-mortem. Most common psychiatric manifestations include delirium, mood disorders, anxiety disorders, and posttraumatic stress disorder. "Long-COVID" non-syndromal presentations include "brain-fogginess," autonomic instability, fatigue, and insomnia. SARS-CoV-2 infection can trigger prior vulnerabilities based on the priming of microglia and other cells, induced or perpetuated by aging and mental and physical illnesses. COVID-19 could further induce priming of neuroimmunological substrates leading to exacerbated immune response and autoimmunity targeting structures in the central nervous system (CNS), in response to minor immune activating environmental exposures, including stress, minor infections, allergens, pollutants, and traumatic brain injury.

Melatonin ameliorates spatial memory and motor deficits via preserving the integrity of cortical and hippocampal dendritic spine morphology in mice with neurotrauma

We aimed to elucidate the role of cortical and hippocampal dendritic spines on neurological deficits associated with hippocampal microgliosis, hippocampal neurogenesis, and neuroinflammation in mice with cortical compact impact (CCI) injury. In the present study, we found that CCI reduced spatial memory mean latency (10 s. vs 50 s) and motor dysfunction (130 s. vs 150 s.) in mice, as determined by Morris water maze and rotarod test, respectively. Golgi staining of cortical pyramidal neurons revealed that, compared to the controls, the CCI group treated with vehicle solution had significantly lower values of dendritic order (or dendritic branch number) (4.0 vs 6.2), total spine length (400 μm vs 620 μm) and spine density (40 spines/μm vs 60 spines/μm), but had significantly higher values of dendritic beading (40 beadings/mm vs 20 beadings/mm). Additionally, Sholl analysis showed that, compared to controls, the CCI + NS group mice had significantly lower values of dendritic intersections (1.0 vs 2.0). Immunofluorescence assay also revealed that, compared to controls, the CCI + NS group mice had significantly higher values of the newly formed hippocampal cells (1250/mm² vs 1000/mm²) but significantly lower values of dendritic order (2.0 branch # vs 4.2 branch #), total spine length (180 μm vs 320 μm) and intersection (1.0 vs 3.0). The CCI + NS group mice further showed significantly higher numbers of microglia in the dentate gyrus of the hippocampus and higher concentrations of pro-inflammatory cytokines in the cerebrospinal fluids. All the CCI-induced spatial memory (40 s) and motor (150 s) dysfunction, deranged dendritic and spine morphology of cortical pyramidal neurons or hippocampal newly formed cells, hippocampal microgliosis, and central neuroinflammation were all significantly reduced by melatonin administration during post-CCI. Simultaneously, melatonin therapy caused an enhancement in the compensatory hippocampal neurogenesis and neurotrophic growth factors (e.g., doublecortin-1) and compensatory central anti-inflammatory cytokines. Our results indicate that melatonin attenuates the spatial memory and motor deficits via the modification of cortical and hippocampal dendritic spine morphology, hippocampal microgliosis and neurogenesis, and neuroinflammation in mice with traumatic brain injury.

Statins and Neuropathic Pain: A Narrative Review

The frequently prescribed drug class of statins have pleiotropic effects and have been implicated in neuropathic pain syndromes. This narrative review examines studies of statin-induced neuropathic pain which to date have been conducted only in animal models. However, the pathophysiology of diabetic neuropathy in humans may shed some light on the etiology of neuropathic pain. Statins have exhibited a paradoxical effect in that statins appear to reduce neuropathic pain in animals but have been associated with neuropathic pain in humans. While there are certain postulated mechanisms offering elucidation as to how statins might be associated with neuropathic pain, there is, as the American Heart Association stated, to date no definitive association between statins and neuropathic pain. Statins are important drugs that reduce cardiovascular risk factors and should be prescribed to appropriate patients with these risk factors but some of this population is also at elevated risk for neuropathic pain from other causes.

Mesenchymal Stem Cell-Derived Exosomes Improve Functional Recovery in Rats After Traumatic Brain Injury: A Dose-Response and Therapeutic Window Study

Background. Mesenchymal stem cell (MSC)-derived exosomes play a critical role in regenerative medicine. Objective. To determine the dose- and time-dependent efficacy of exosomes for treatment of traumatic brain injury (TBI). Methods. Male rats were subjected to a unilateral moderate cortical contusion. In the dose-response study, animals received a single intravenous injection of exosomes (50, 100, 200 µg per rat) or vehicle, with treatment initiated at 1 day after injury. In the therapeutic window study, animals received a single intravenous injection of 100 µg exosomes or vehicle starting at 1, 4, or 7 days after injury. Neurological functional tests were performed weekly after TBI for 5 weeks. Spatial learning was measured on days 31 to 35 after TBI using the Morris water maze test. Results. Compared with the vehicle, regardless of the dose and delay in treatment, exosome treatment significantly improved sensorimotor and cognitive function, reduced hippocampal neuronal cell loss, promoted angiogenesis and neurogenesis, and reduced neuroinflammation. Exosome treatment at 100 µg per rat exhibited a significant therapeutic effect compared with the 50- or 200-µg exosome groups. The time-dependent exosome treatment data demonstrated that exosome treatment starting at 1 day post-TBI provided a significantly greater improvement in functional and histological outcomes than exosome treatments at the other 2 delayed treatments. Conclusions. These results indicate that exosomes have a wide range of effective doses for treatment of TBI with a therapeutic window of at least 7 days postinjury. Exosomes may provide a novel therapeutic intervention in TBI.

The effects of statins on microglial cells to protect against neurodegenerative disorders: A mechanistic review

Microglia are the primary innate immune system cells in the central nervous system (CNS). They are crucial for the immunity, neurogenesis, synaptogenesis, neurotrophic support, phagocytosis of cellular debris, and maintaining the CNS integrity and homeostasis. Invasion by pathogens as well as in CNS injuries and damages results in activation of microglia known as microgliosis. The activated microglia have the capacity to release proinflammatory mediators leading to neuroinflammation. However, uncontrolled neuroinflammation can give rise to various neurological disorders (NDs), especially the neurodegenerative diseases including Parkinson's disease (PD) and related disorders, Alzheimer's disease (AD) and other dementias, multiple sclerosis (MS), Huntington's disease (HD), spinocerebellar ataxia (SCA), spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), and stroke. Statins (HMG-CoA reductase inhibitors) are among the most widely prescribed medications for the management of hypercholesterolemia worldwide. It can be used for primary prevention in healthy individuals who are at higher risk of cardiovascular and coronary heart diseases as well as the secondary prevention in patients with cardiovascular and coronary heart diseases disease. A growing body of evidence has indicated that statins have the potential to attenuate the proinflammatory mediators and subsequent NDs by controlling the microglial activation and consequent reduction in neuroinflammatory mediators. In this review, we have discussed the recent studies on the effects of statins on microglia activation and neuroinflammation.

Management of Traumatic Brain Injury: From Present to Future

TBI (traumatic brain injury) is a major cause of death among youth in industrialized societies. Brain damage following traumatic injury is a result of direct and indirect mechanisms; indirect or secondary injury involves the initiation of an acute inflammatory response, including the breakdown of the blood–brain barrier (BBB), brain edema, infiltration of peripheral blood cells, and activation of resident immunocompetent cells, as well as the release of numerous immune mediators such as interleukins and chemotactic factors. TBI can cause changes in molecular signaling and cellular functions and structures, in addition to tissue damage, such as hemorrhage, diffuse axonal damages, and contusions. TBI typically disturbs brain functions such as executive actions, cognitive grade, attention, memory data processing, and language abilities. Animal models have been developed to reproduce the different features of human TBI, better understand its pathophysiology, and discover potential new treatments. For many years, the first approach to manage TBI has been treatment of the injured tissue with interventions designed to reduce the complex secondary-injury cascade. Several studies in the literature have stressed the importance of more closely examining injuries, including endothelial, microglia, astroglia, oligodendroglia, and precursor cells. Significant effort has been invested in developing neuroprotective agents. The aim of this work is to review TBI pathophysiology and existing and potential new therapeutic strategies in the management of inflammatory events and behavioral deficits associated with TBI.

Nose-to-brain co-delivery of repurposed simvastatin and BDNF synergistically attenuates LPS-induced neuroinflammation

A therapeutic strategy that can combat the multifaceted nature of neuroinflammation pathology was investigated. Thus, we fabricated PEG-PdLLA polymersomes and evaluated the efficacy in co-delivery of simvastatin (Sim, as a repurposed anti-inflammatory agent) with brain derived neurotrophic factor (BDNF, as an exogeneous trophic factor supplementation). Using LPS model of neuroinflammation, intranasal administration of combination drug-loaded polymersomes (containing both Sim and BDNF; Sim-BDNF-Ps) markedly down-regulated brain levels of cytokines compared to free drug and single-drug-loaded polymersomes. Further, Sim-BDNF-Ps effectively replenished brain level of BDNF that was depleted following neuroinflammation, resulting in a 2-fold BDNF increase versus untreated LPS control group. We found out that the efficiency of the combination drug-loaded polymersomes to suppress microglia activation in brain regions followed the order: frontal cortex > striatum > hippocampus. Our findings indicated that Sim-BDNF-Ps could effectively inhibit microglial-mediated inflammation as well as potentially resolve the neurotoxic microenvironment that is often associated with neuroinflammation.

Preinjury Statins Are Associated With Improved Survival in Patients With Traumatic Brain Injury

BACKGROUND

Statins have been shown to improve outcomes in traumatic brain injury (TBI) in animal models. The aim of our study was to determine the effect of preinjury statins on outcomes in TBI patients.

METHODS

We performed a 4-y (2014-2017) review of our TBI database and included all patients aged ≥18 y with severe isolated TBI. Patients were stratified into those who were on statins and those who were not and were matched (1:2 ratio) using propensity score matching. The primary outcome was in-hospital mortality. The secondary outcomes were skilled nursing facility disposition, Glasgow Outcome Scale-extended score, and hospital and intensive care unit length of stay (LOS).

RESULTS

We identified 1359 patients, of which 270 were matched (statin: 90, no-statin: 180). Mean age was 55 ± 8y, median Glasgow Coma Scale was 10 (8-12), and median head-abbreviated injury scale was 3 (3-5). Matched groups were similar in age, mechanism of injury, Glasgow Coma Scale, Injury Severity Score, neurosurgical intervention, type and size of intracranial hemorrhage, and preinjury anticoagulant or antiplatelet use. The overall in-hospital mortality rate was 18%. Patients who received statins had lower rates of in-hospital mortality (11% versus 21%, P = 0.01), skilled nursing facility disposition (19% versus 28%; P = 0.04), and a higher median Glasgow Outcome Scale-extended (11 [9-13] versus 9 [8-10]; P = 0.04). No differences were found between the two groups in terms of hospital LOS (6 [4-9] versus 5 [3-8]; P = 0.34) and intensive care unit LOS (3 [3-6] versus 4 [3-5]; P = 0.09).

CONCLUSIONS

Preinjury statin use in isolated traumatic brain injury patients is associated with improved outcomes. This finding warrants further investigations to evaluate the potential beneficial role of statins as a therapeutic drug in a TBI.

LEVEL OF EVIDENCE

Level III Therapeutic.

Simvastatin Attenuates Hippocampal MMP-9 Expression in the Streptozotocin-Induced Cognitive Impairment

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) expression has been implicated in molecular mechanisms of neurodegenerative disorders, and its abnormal level has been reported in Alzheimer’s disease (AD). Some protective mechanisms of statins against neurodegeneration might be mediated by the inhibition of MMP-9 expression. Here, we investigated the effect of simvastatin on the hippocampal MMP-9 expression in the context of AD.

METHODS

We examined the influence of three-week simvastatin (5 mg/kg) administration on hippocampal MMP-9 expression in a rat model of cognitive decline induced by streptozotocin (STZ). Spatial long-term memory and MMP-9 expression were assessed by Morris water maze (MWM) test and quantitative polymerase chain reaction, respectively.

RESULTS

The results showed a decline in the learning and memory in STZ group when compared with the control group. The MMP-9 up-regulated (1.41 ± 0.2 vs. 0.980 ± 0.02, p < 0.05), and cresyl violet staining showed hippocampal cell damage in STZ group compared with the control group. Simvastatin prevented the up-regulation of MMP-9 (1.05 ± 0.05 vs. 1.41 ± 0.2, p < 0.05), improved spatial memory impairment and attenuated hippocampal cell damage. Furthermore, we found a negative correlation (r = 0.77) between MMP-9 expression and cognitive function.

CONCLUSION

Our findings suggest that the neuroprotective influence of simvastatin in battle to cognitive impairment is mediated in part by the modulation of MMP-9 expression. The reduction of MMP-9 expression in simvastatin-treated animals is in correlation with the improvement of cognitive functions. Understanding the protective mechanism of simvastatin will shed light on more efficient therapeutic modalities in AD.

The complexity of neuroinflammation consequent to traumatic brain injury: from research evidence to potential treatments

This review recounts the definitions and research evidence supporting the multifaceted roles of neuroinflammation in the injured brain following trauma. We summarise the literature fluctuating from the protective and detrimental properties that cytokines, leukocytes and glial cells play in the acute and chronic stages of TBI, including the intrinsic factors that influence cytokine responses and microglial functions relative to genetics, sex, and age. We elaborate on the pros and cons that cytokines, chemokines, and microglia play in brain repair, specifically neurogenesis, and how such conflicting roles may be harnessed therapeutically to sustain the survival of new neurons. With a brief review of the clinical and experimental findings demonstrating early and chronic inflammation impacts on outcomes, we focus on the clinical conditions that may be amplified by neuroinflammation, ranging from acute seizures to chronic epilepsy, neuroendocrine dysfunction, dementia, depression, post-traumatic stress disorder and chronic traumatic encephalopathy. Finally, we provide an overview of the therapeutic agents that have been tested to reduce inflammation-driven secondary pathological cascades and speculate the future promise of alternative drugs.

Cytokine Responses in Severe Traumatic Brain Injury: Where There Is Smoke, Is There Fire?

This scoping review will discuss the basic functions and prognostic significance of the commonly researched cytokines implicated in severe traumatic brain injury (sTBI), including tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), transforming growth factor-β (TGF-β), substance P, and soluble CD40 ligand (sCD40L). A scoping review was undertaken with an electronic search for articles from the Ovid MEDLINE, PUBMED and EMBASE databases from 1995 to 2017. Inclusion criteria were original research articles, and reviews including both animal models and human clinical studies of acute (< 3 months) sTBI. Selected articles included both isolated sTBI and sTBI with systemic injury. After applying the inclusion criteria and removing duplicates, 141 full-text articles, 126 original research articles and 15 review articles, were evaluated in compiling this review paper. A single reviewer, CC, completed the review in two phases. During the first phase, titles and abstracts of selected articles were reviewed for inclusion. A second evaluation was then conducted on the full text of all selected articles to ensure relevancy. From our current understanding of the literature, it is unlikely a single biomarker will be sufficient in accurately prognosticating patients with sTBI. Intuitively, a more severe injury will demonstrate higher levels of inflammatory cytokines which may correlate as a marker of severe injury. This does not mean, necessarily, these cytokines have a direct and causal role in the poor outcome of the patient. Further research is required to better delineate the complex systemic inflammatory and CNS interactions that occur during sTBI before they can be applied as a reliable prognostic tool.

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

Current understanding of neuroinflammation after traumatic brain injury and cell-based therapeutic opportunities

Traumatic brain injury (TBI) remains a major cause of death and disability worldwide. Increasing evidence indicates that TBI is an important risk factor for neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and chronic traumatic encephalopathy. Despite improved supportive and rehabilitative care of TBI patients, unfortunately, all late phase clinical trials in TBI have yet to yield a safe and effective neuroprotective treatment. The disappointing clinical trials may be attributed to variability in treatment approaches and heterogeneity of the population of TBI patients as well as a race against time to prevent or reduce inexorable cell death. TBI is not just an acute event but a chronic disease. Among many mechanisms involved in secondary injury after TBI, emerging preclinical studies indicate that posttraumatic prolonged and progressive neuroinflammation is associated with neurodegeneration which may be treatable long after the initiating brain injury. This review provides an overview of recent understanding of neuroinflammation in TBI and preclinical cell-based therapies that target neuroinflammation and promote functional recovery after TBI.

Effects of Simvastatin Beyond Dyslipidemia: Exploring Its Antinociceptive Action in an Animal Model of Complex Regional Pain Syndrome-Type I

Simvastatin is a lipid-lowering agent that blocks the production of cholesterol through inhibition of 3-hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase. In addition, recent evidence has suggested its anti-inflammatory and antinociceptive actions during inflammatory and pain disorders. Herein, we investigated the effects of simvastatin in an animal model of complex regional pain syndrome-type I, and its underlying mechanisms. Chronic post-ischemia pain (CPIP) was induced by ischemia and reperfusion (IR) injury of the left hind paw. Our findings showed that simvastatin inhibited mechanical hyperalgesia induced by CPIP model in single and repeated treatment schedules, respectively; however simvastatin did not alter inflammatory signs during CPIP model. The mechanisms underlying those actions are related to modulation of transient receptor potential (TRP) channels, especially TRMP8. Moreover, simvastatin oral treatment was able to reduce the nociception induced by acidified saline [an acid-sensing ion channels (ASICs) activator] and bradykinin (BK) stimulus, but not by TRPA1, TRPV1 or prostaglandin-E2 (PGE2). Relevantly, the antinociceptive effects of simvastatin did not seem to be associated with modulation of the descending pain circuits, especially noradrenergic, serotoninergic and dopaminergic systems. These results indicate that simvastatin consistently inhibits mechanical hyperalgesia during neuropathic and inflammatory disorders, possibly by modulating the ascending pain signaling (TRPM8/ASIC/BK pathways expressed in the primary sensory neuron). Thus, simvastatin open-up new standpoint in the development of innovative analgesic drugs for treatment of persistent pain, including CRPS-I.

Statins reduce TGF-beta2-modulation of the extracellular matrix in cultured astrocytes of the human optic nerve head

Statins are cholesterol lowering drugs and have shown beneficial effects on glaucoma. With regard to the mechanism of statin action on glaucoma, we investigated the effects of statins on transforming growth factor-beta 2 (TGF-β2)-induced expression of extracellular matrix (ECM) proteins in human astrocytes of the optic nerve head (ONH) lamina cribrosa (LC). By using primary human ONH astrocytes, we found that both simvastatin and lovastatin inhibited TGF-β2-mediated expression of ECM proteins such as connective tissue growth factor, collagen I, fibronectin, and plasminogen activator inhibitor-1. Suppression of ECM related proteins is due to inhibition of Smad2/3 activation as statins inhibit TGF-β2-induced Smad2 phosphorylation and Smad2/3 nuclear accumulation. In ONH astrocytes, TGF-β2 does not induce MAPK activation. In this study we found an anti-fibrotic effect of statins in human astrocytes of the ONH and identified TGF-β2 as a mediator of statin action, which may support a beneficial role for statins in blocking glaucomatous axonal damage induced by ECM remodeling.

Statin discontinuation and mortality in an older adult population with traumatic brain injury: A four-year, multi-centre, observational cohort study

INTRODUCTION

Statin discontinuation has been investigated in a wide range of diseases and injuries, but there is a paucity of data in the older adult population with traumatic brain injury (TBI). The purpose of this study was to re-examine the extent to which early discontinuation of pre-injury statin (PIS) therapy increases the risk of poor patient outcomes in older adult patients suffering a TBI.

METHODS

This was a retrospective observational cohort study of adult trauma patients with a blunt TBI across three trauma centres over four years. Patients were excluded because of no PIS use, age <55years, or a hospital length of stay (LOS) less than three days. Patients found to be intentionally discontinued from statin therapy within 48h of hospital admission for injury-related reasons were excluded. The primary and secondary outcomes were in-hospital mortality and a hospital LOS ≥1 week. Outcomes were analysed using logistic regression.

RESULTS

There were 266 patients in the continuation group, and 131 in the discontinuation group. The statin discontinuation group had a significantly higher proportion of patients with a moderate or severe head injury, intubation in emergency department (ED), and disposition to the intensive care unit or operating room. Overall, 23 (6%) patients died while in the hospital. After adjusting for ED Glasgow coma scale, the odds of dying in the hospital were not significantly larger for patients having been discontinued from PIS, compared to those who were continued (OR=1.75, 95%CI=0.71-4.31, p=0.22). Among patients who received an in-hospital statin, the median (interquartile range) time between hospital admission and first administration of statin medication did not differ between patients who died and those who survived (22.8h [10.96-28.91] vs. 22.9h [11.67-39.80], p=0.94). There were no significant differences between study groups in the proportion of patients with a hospital length of stay >1 week (continuation=29% vs. discontinuation=36%, p=0.19).

CONCLUSION

We did not observe a significantly increased odds of in-hospital mortality following PIS discontinuation, compared to PIS continuation, in an older adult population with TBI. It remains to be seen whether statin discontinuation is a proxy variable for injury severity, or whether it exerts deleterious effects after injury.

A Randomized Controlled Open-Label Pilot Study of Simvastatin Addition to Whole-Brain Radiation Therapy in Patients With Brain Metastases

Statins have been reported to have a potential radiosensitizing effect that has not been evaluated in clinical trials. The aim of this study was to evaluate the efficacy and safety of simvastatin in addition to whole-brain radiation therapy (WBRT) in patients with brain metastases (BM). A prospective randomized, controlled, open-label pilot study was conducted on 50 Egyptian patients with BM who were randomly assigned to receive 30-Gy WBRT (control group: 25 patients) or 30 Gy WBRT + simvastatin 80 mg/day for the WBRT period (simvastatin group: 25 patients). The primary outcome was radiological response at 4 weeks after WBRT. Secondary outcomes were 1-year progression-free survival (PFS), 1-year overall survival (OS), and health-related quality of life (HRQL) that was assessed using the European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire C30 (EORTC QLQ-C30) and its brain module (BN-20), at baseline, after WBRT, and 4 weeks after WBRT. The addition of simvastatin was tolerated. Twenty-one patients were not evaluated for radiological response because of death (n = 16), noncompliance to follow-up (n = 4), and clinical deterioration (n = 1). Response rates were 60% and 78.6% (p = 0.427), 1-year PFS rates were 5.2% and 17.7% (p = 0.392), and 1-year OS rates were 12% and 8% (p = 0.880) for the control group and simvastatin group, respectively. Nonsignificant differences were found between the two arms regarding HRQL scales. The addition of simvastatin 80 mg/day did not improve the clinical outcomes of patients with BM receiving WBRT.

Acute death of astrocytes in blast-exposed rat organotypic hippocampal slice cultures

Blast traumatic brain injury (bTBI) affects civilians, soldiers, and veterans worldwide and presents significant health concerns. The mechanisms of neurodegeneration following bTBI remain elusive and current therapies are largely ineffective. It is important to better characterize blast-evoked cellular changes and underlying mechanisms in order to develop more effective therapies. In the present study, our group utilized rat organotypic hippocampal slice cultures (OHCs) as an in vitro system to model bTBI. OHCs were exposed to either 138 ± 22 kPa (low) or 273 ± 23 kPa (high) overpressures using an open-ended helium-driven shock tube, or were assigned to sham control group. At 2 hours (h) following injury, we have characterized the astrocytic response to a blast overpressure. Immunostaining against the astrocytic marker glial fibrillary acidic protein (GFAP) revealed acute shearing and morphological changes in astrocytes, including clasmatodendrosis. Moreover, overlap of GFAP immunostaining and propidium iodide (PI) indicated astrocytic death. Quantification of the number of dead astrocytes per counting area in the hippocampal cornu Ammonis 1 region (CA1), demonstrated a significant increase in dead astrocytes in the low- and high-blast, compared to sham control OHCs. However only a small number of GFAP-expressing astrocytes were co-labeled with the apoptotic marker Annexin V, suggesting necrosis as the primary type of cell death in the acute phase following blast exposure. Moreover, western blot analyses revealed calpain mediated breakdown of GFAP. The dextran exclusion additionally indicated membrane disruption as a potential mechanism of acute astrocytic death. Furthermore, although blast exposure did not evoke significant changes in glutamate transporter 1 (GLT-1) expression, loss of GLT-1-expressing astrocytes suggests dysregulation of glutamate uptake following injury. Our data illustrate the profound effect of blast overpressure on astrocytes in OHCs at 2 h following injury and suggest increased calpain activity and membrane disruption as potential underlying mechanisms.

The Polarization States of Microglia in TBI: A New Paradigm for Pharmacological Intervention

Traumatic brain injury (TBI) is a serious medical and social problem worldwide. Because of the complex pathophysiological mechanisms of TBI, effective pharmacotherapy is still lacking. The microglial cells are resident tissue macrophages located in the brain and have two major polarization states, M1 phenotype and M2 phenotype, when activated. The M1 phenotype is related to the release of proinflammatory cytokines and secondary brain injury, while the M2 phenotype has been proved to be responsible for the release of anti-inflammation cytokines and for central nervous system (CNS) repair. In animal models, pharmacological strategies inhibiting the M1 phenotype and promoting the M2 phenotype of microglial cells could alleviate cerebral damage and improve neurological function recovery after TBI. In this review, we aimed to summarize the current knowledge about the pathological significance of microglial M1/M2 polarization in the pathophysiology of TBI. In addition, we reviewed several drugs that have provided neuroprotective effects against brain injury following TBI by altering the polarization states of the microglia. We emphasized that future investigation of the regulation mechanisms of microglial M1/M2 polarization in TBI is anticipated, which could contribute to the development of new targets of pharmacological intervention in TBI.

Early electroacupuncture treatment ameliorates neuroinflammation in rats with traumatic brain injury

Background

Neuroinflammation is the leading cause of neurological sequelae after traumatic brain injury (TBI). The aim of the present study was to investigate whether the neuroprotective effects of electroacupuncture (EA) are mediated by anti-neuroinflammatory effects in a rat model of TBI.

Methods

Male Sprague-Dawley rats were randomly divided into three groups: sham-operated, TBI control, and EA-treated. The animals in the sham-operated group underwent a sham operation, those in the TBI control group were subjected to TBI, but not EA, and those in the EA group were treated with EA for 60 min immediately after TBI, daily for 3 consecutive days. EA was applied at the acupuncture points GV20, GV26, LI4, and KI1, using a dense-dispersed wave, at frequencies of 0.2 and 1 Hz, and an amplitude of 1 mA. Cell infarction volume (TTC stain), neuronal apoptosis (markers: TUNEL and Caspase-3), activation of microglia (marker: Iba1) and astrocytes (marker: GFAP), and tumor necrosis factor (TNF)-α expression in the microglia and astrocytes were evaluated by immunofluorescence. Functional outcomes were assessed using the inclined plane test. All tests were performed 72 h after TBI.

Results

We found that TBI-induced loss of grasp strength, infarction volume, neuronal apoptosis, microglial and astrocyte activation, and TNF-α expression in activated microglia and astrocytes were significantly attenuated by EA treatment.

Conclusions

Treatment of TBI in the acute stage with EA for 60 min daily for 3 days could ameliorate neuroinflammation. This may thus represent a mechanism by which functional recovery can occur after TBI.

Systemic administration of cell-free exosomes generated by human bone marrow derived mesenchymal stem cells cultured under 2D and 3D conditions improves functional recovery in rats after traumatic brain injury

Multipotent human bone marrow derived mesenchymal stem cells (hMSCs) improve functional outcome after experimental traumatic brain injury (TBI). The present study was designed to investigate whether systemic administration of cell-free exosomes generated from hMSCs cultured in 2-dimensional (2D) conventional conditions or in 3-dimensional (3D) collagen scaffolds promote functional recovery and neurovascular remodeling in rats after TBI. Wistar rats were subjected to TBI induced by controlled cortical impact; 24 h later tail vein injection of exosomes derived from hMSCs cultured under 2D or 3D conditions or an equal number of liposomes as a treatment control were performed. The modified Morris water maze, neurological severity score and footfault tests were employed to evaluate cognitive and sensorimotor functional recovery. Animals were sacrificed at 35 days after TBI. Histological and immunohistochemical analyses were performed for measurements of lesion volume, neurovascular remodeling (angiogenesis and neurogenesis), and neuroinflammation. Compared with liposome-treated control, exosome-treatments did not reduce lesion size but significantly improved spatial learning at 33-35 days measured by the Morris water maze test, and sensorimotor functional recovery, i.e., reduced neurological deficits and footfault frequency, observed at 14-35 days post injury (p < 0.05). Exosome treatments significantly increased the number of newborn endothelial cells in the lesion boundary zone and dentate gyrus, and significantly increased the number of newborn mature neurons in the dentate gyrus as well as reduced neuroinflammation. Exosomes derived from hMSCs cultured in 3D scaffolds provided better outcome in spatial learning than exosomes from hMSCs cultured in the 2D condition. In conclusion, hMSC-generated exosomes significantly improve functional recovery in rats after TBI, at least in part, by promoting endogenous angiogenesis and neurogenesis and reducing neuroinflammation. Thus, exosomes derived from hMSCs may be a novel cell-free therapy for TBI, and hMSC-scaffold generated exosomes may selectively enhance spatial learning.

Tissue Response to Deep Brain Stimulation and Microlesion: A Comparative Study

OBJECTIVES

Deep brain stimulation (DBS) is used for a variety of movement disorders, including Parkinson's disease. There are several theories regarding the biology and mechanisms of action of DBS. Previously, we observed an up-regulation of neural progenitor cell proliferation in post-mortem tissue suggesting that DBS can influence cellular plasticity in regions beyond the site of stimulation. We wanted to support these observations and investigate the relationship if any, between DBS, neural progenitor cells, and microglia.

METHODS

We used naïve rats in this study for DBS electrode implantation, stimulation, and microlesions. We used immunohistochemistry techniques for labeling microglial and progenitor cells, and fluorescence microscopy for viewing and quantification of labeled cells.

RESULTS

We present data that demonstrates a reciprocal relationship of microglia and neural precursor cells in the presence of acute high frequency stimulation. In our hands, stimulated animals demonstrate significantly lower numbers of activated microglia (p = 0.026) when compared to microlesion and sham animals. The subthalamic region surrounding the DBS stimulating electrode reveals a significant increase in the number of neural precursor cells expressing cell cycle markers, plasticity and precursor cell markers (Ki67; p = 0.0013, MCM2; p = 0.0002).

INTERPRETATION

We conclude that in this animal model, acute DBS results in modest local progenitor cell proliferation and influenced the total number of activated microglia. This could be of clinical significance in patients with PD, as it is thought to progress via neuroinflammatory processes involving microglia, cytokines, and the complement system. Further studies are required to comprehend the behavior of microglia in different activation states and their ability to regulate adult neurogenesis under physiologic and pathologic conditions.

Distinct roles for metalloproteinases during traumatic brain injury

BACKGROUND

Significant protease activations have been reported after traumatic brain injury (TBI). These proteases are responsible for cleavage of transmembrane proteins in neurons, glial, and endothelial cells and this results in the release of their extracellular domains (ectodomains).

METHODS

Two TBI models were employed here, representing both closed head injury (CHI) and open head injury (OHI). In situ zymography, immunohistochemistry, bright field and confocal microscopy, quantification of immunopositive cells and statistical analysis were applied.

RESULTS

We found, using in situ zymography, that gelatinase activity of matrix metalloproteinases (MMP)-2 and MMP-9 was upregulated in cortex of both injury models. Using immunohistochemistry for several MPPs (Matrix metalloproteinases) and ADAMs (disintegrin and metalloproteinases), including MMP-2, -9, ADAM-10, -17, distinct patterns of induction were observed in the two TBI models. In closed head injury, an early increase in protein expression of MMP-2, -9 and ADAM-17 was found as early as 10 min post injury in cortex and peaked at 1 h for all 4 proteases examined. In contrast, after OHI the maximal expression was observed locally neighboring the impact site, at a later time-point, as long as 24 h after the injury for MMP-2 and MMP-9. Confocal microscopy revealed colocalization of the 4 proteases with the neuronal marker NeuN in CHI, but only MMP2 colocalized with NeuN in OHI.

CONCLUSIONS

The findings may lead to a trauma-induced therapeutic strategy triggered soon after a primary insult to improve survival and to reduce brain damage following TBI.

Role of Glia in Memory Deficits Following Traumatic Brain Injury: Biomarkers of Glia Dysfunction

Historically, glial cells have been recognized as a structural component of the brain. However, it has become clear that glial cells are intimately involved in the complexities of neural networks and memory formations. Astrocytes, microglia, and oligodendrocytes have dynamic responsibilities which substantially impact neuronal function and activities. Moreover, the importance of glia following brain injury has come to the forefront in discussions to improve axonal regeneration and functional recovery. The numerous activities of glia following injury can either promote recovery or underlie the pathobiology of memory deficits. This review outlines the pathological states of glial cells which evolve from their positive supporting roles to those which disrupt synaptic function and neuroplasticity following injury. Evidence suggests that glial cells interact extensively with neurons both chemically and physically, reinforcing their role as pivotal for higher brain functions such as learning and memory. Collectively, this mini review surveys investigations of how glial dysfunction following brain injury can alter mechanisms of synaptic plasticity and how this may be related to an increased risk for persistent memory deficits. We also include recent findings, that demonstrate new molecular avenues for clinical biomarker discovery.

Simvastatin Treatment in Traumatic Brain Injury: Operation Brain Trauma Therapy

Simvastatin, the fourth drug selected for testing by Operation Brain Trauma Therapy (OBTT), is a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor used clinically to reduce serum cholesterol. In addition, simvastatin has demonstrated potent antineuroinflammatory and brain edema reducing effects and has shown promise in promoting functional recovery in pre-clinical models of traumatic brain injury (TBI). The purpose of this study was to assess the potential neuroprotective effects of oral administration of simvastatin on neurobehavioral, biomarker, and histopathological outcome measures compared across three pre-clinical TBI animal models. Adult male Sprague-Dawley rats were exposed to either moderate fluid percussion injury (FPI), controlled cortical impact injury (CCI), or penetrating ballistic-like brain injury (PBBI). Simvastatin (1 or 5 mg/kg) was delivered via oral gavage at 3 h post-injury and continued once daily out to 14 days post-injury. Results indicated an intermediate beneficial effect of simvastatin on motor performance on the gridwalk (FPI), balance beam (CCI), and rotarod tasks (PBBI). No significant therapeutic benefit was detected, however, on cognitive outcome across the OBTT TBI models. In fact, Morris water maze (MWM) performance was actually worsened by treatment in the FPI model and scored full negative points for low dose in the MWM latency and swim distance to locate the hidden platform. A detrimental effect on cortical tissue loss was also seen in the FPI model, and there were no benefits on histology across the other models. Simvastatin also produced negative effects on circulating glial fibrillary acidic protein biomarker outcomes that were evident in the FPI and PBBI models. Overall, the current findings do not support the beneficial effects of simvastatin administration over 2 weeks post-TBI using the oral route of administration and, as such, it will not be further pursued by OBTT.