Post-Injury Administration of Galantamine Reduces Traumatic Brain Injury Pathology and Improves Outcome

Enhancing cognitive recovery in chronic traumatic brain injury through simultaneous allosteric modulation of α7 nicotinic acetylcholine and α5 GABAA receptors

Traumatic brain injury (TBI) leads to changes in the neural circuitry of the hippocampus that result in chronic learning and memory deficits. However, effective therapeutic strategies to ameliorate these chronic learning and memory impairments after TBI are limited. Two pharmacological targets for enhancing cognition are nicotinic acetylcholine receptors (nAChRs) and GABAA receptors (GABAARs), both of which regulate hippocampal network activity to form declarative memories. A promising compound, 522-054, both allosterically enhances α7 nAChRs and inhibits α5 subunit-containing GABAARs. Administration of 522-054 enhances long-term potentiation (LTP) and cognitive functioning in non-injured animals. In this study, we assessed the effects of 522-054 on hippocampal synaptic plasticity and learning and memory deficits in the chronic post-TBI recovery period. Adult male Sprague Dawley rats received moderate parasagittal fluid-percussion brain injury or sham surgery. At 12 wk after injury, we assessed basal synaptic transmission and LTP at the Schaffer collateral-CA1 synapse of the hippocampus. Bath application of 522-054 to hippocampal slices reduced deficits in basal synaptic transmission and recovered TBI-induced impairments in LTP. Moreover, treatment of animals with 522-054 at 12 wk post-TBI improved cue and contextual fear memory and water maze acquisition and retention without a measurable effect on cortical or hippocampal atrophy. These results suggest that dual allosteric modulation of α7 nAChR and α5 GABAAR signaling may be a potential therapy for treating cognitive deficits during chronic recovery from TBI.

CC Chemokine Family Members' Modulation as a Novel Approach for Treating Central Nervous System and Peripheral Nervous System Injury-A Review of Clinical and Experimental Findings

Despite significant progress in modern medicine and pharmacology, damage to the nervous system with various etiologies still poses a challenge to doctors and scientists. Injuries lead to neuroimmunological changes in the central nervous system (CNS), which may result in both secondary damage and the development of tactile and thermal hypersensitivity. In our review, based on the analysis of many experimental and clinical studies, we indicate that the mechanisms occurring both at the level of the brain after direct damage and at the level of the spinal cord after peripheral nerve damage have a common immunological basis. This suggests that there are opportunities for similar pharmacological therapeutic interventions in the damage of various etiologies. Experimental data indicate that after CNS/PNS damage, the levels of 16 among the 28 CC-family chemokines, i.e., CCL1, CCL2, CCL3, CCL4, CCL5, CCL6, CCL7, CCL8, CCL9, CCL11, CCL12, CCL17, CCL19, CCL20, CCL21, and CCL22, increase in the brain and/or spinal cord and have strong proinflammatory and/or pronociceptive effects. According to the available literature data, further investigation is still needed for understanding the role of the remaining chemokines, especially six of them which were found in humans but not in mice/rats, i.e., CCL13, CCL14, CCL15, CCL16, CCL18, and CCL23. Over the past several years, the results of studies in which available pharmacological tools were used indicated that blocking individual receptors, e.g., CCR1 (J113863 and BX513), CCR2 (RS504393, CCX872, INCB3344, and AZ889), CCR3 (SB328437), CCR4 (C021 and AZD-2098), and CCR5 (maraviroc, AZD-5672, and TAK-220), has beneficial effects after damage to both the CNS and PNS. Recently, experimental data have proved that blockades exerted by double antagonists CCR1/3 (UCB 35625) and CCR2/5 (cenicriviroc) have very good anti-inflammatory and antinociceptive effects. In addition, both single (J113863, RS504393, SB328437, C021, and maraviroc) and dual (cenicriviroc) chemokine receptor antagonists enhanced the analgesic effect of opioid drugs. This review will display the evidence that a multidirectional strategy based on the modulation of neuronal-glial-immune interactions can significantly improve the health of patients after CNS and PNS damage by changing the activity of chemokines belonging to the CC family. Moreover, in the case of pain, the combined administration of such antagonists with opioid drugs could reduce therapeutic doses and minimize the risk of complications.

Combined Use of Guanfacine and N-Acetylcysteine for the Treatment of Cognitive Deficits After Traumatic Brain Injury

Traumatic Brain Injury (TBI) is a significant contributor to disability across the world. TBIs vary in severity, and most cases are designated mild TBI (mTBI), involving only brief loss of consciousness and no intracranial findings on imaging. Despite this categorization, many persons continue to report persistent cognitive changes in the months to years after injury, with particular impairment in the cognitive and executive functions of the pre-frontal cortex. For these persons, there are no currently approved medications, and treatment is limited to symptom management and cognitive or behavioral therapy. The current case studies explored the use of the alpha-2A adrenoreceptor agonist, guanfacine, combined with the antioxidant, N-acetylcysteine (NAC), in the treatment of post-TBI cognitive symptoms, based on guanfacine's ability to strengthen pre-frontal cortical function, and the open-label use of NAC in treating TBI. Two persons from our TBI clinic were treated with this combined regimen, with neuropsychological testing performed pre- and post-treatment. Guanfacine + NAC improved attention, processing speed, memory, and executive functioning with minimal side effects in both persons. These results encourage future placebo-controlled trials to more firmly establish the efficacy of guanfacine and NAC for the treatment of cognitive deficits caused by TBI.

Enhancing cognitive function in chronic TBI: The Role of α7 nicotinic acetylcholine receptor modulation

Traumatic brain injury (TBI) results in several pathological changes within the hippocampus that result in adverse effects on learning and memory. Therapeutic strategies to enhance learning and memory after TBI are still in the early stages of clinical development. One strategy is to target the α7 nicotinic acetylcholine receptor (nAChR), which is highly expressed in the hippocampus and contributes to the formation of long-term memory. In our previous study, we found that AVL-3288, a positive allosteric modulator of the α7 nAChR, improved cognitive recovery in rats after moderate fluid-percussion injury (FPI). However, whether AVL-3288 improved cognitive recovery specifically through the α7 nAChR was not definitively determined. In this study we utilized Chrna7 knockout mice and compared their recovery to wild-type mice treated with AVL-3288 after TBI. We hypothesized that AVL-3288 treatment would improve learning and memory in wild-type mice, but not Chrna7-/- mice after TBI. Adult male C57BL/6 wild-type and Chrna7-/- mice received sham surgery or moderate controlled cortical impact (CCI) and recovered for 3 months. Mice were then treated with vehicle or AVL-3288 at 30 min prior to contextual fear conditioning. At 3 months after CCI, expression of α7 nAChR, choline acetyltransferase (ChAT), high-affinity choline transporter (ChT), and vesicular acetylcholine transporter (VAChT) were found to be significantly decreased in the hippocampus. Treatment of wild-type mice at 3 months after CCI with AVL-3288 significantly improved cue and contextual fear conditioning, whereas no beneficial effects were observed in Chrna7-/- mice. Parietal cortex and hippocampal atrophy were not improved with AVL-3288 treatment in either wild-type or Chrna7-/- mice. Our results indicate that AVL-3288 improves cognition during the chronic recovery phase of TBI through modulation of the α7 nAChR.

Managing the "big black brain" in low resource setting: A case report of early outcome after hinge craniotomy

Background

The big black brain (BBB) phenomenon is described as an infant's response to an acute subdural hematoma (SDH). It is characterized by hypodensity and swelling of the supratentorial compartment as a whole. Numerous factors may contribute to the formation of the BBB. Due to its high morbidity and mortality, the management of BBB is still debatable. In this report, we describe a 2-month-old boy who had bilateral hemispheric hypodensity and underwent hinge craniotomy.

Case Description

The patient was referred to our hospital with decreased consciousness. The patient had a history of seizures and cardiopulmonary arrest. There is no history of trauma. The computed tomography revealed a subacute SDH on the left parietal and occipital lobe along with hypodensity in both hemispheres with preservation of posterior fossa, consistent with hemispheric hypodensity. We performed a hinge craniotomy for the emergency procedure and evacuated only the hemisphere with the bleeding side. The patient cried spontaneously 24 hours after the procedure and was discharged six days later.

Conclusion

Early outcomes of hinge craniotomy as an alternative procedure for treating the BBB were positive. However, long-term outcomes, particularly the infant's development, should be monitored.

Galantamine ameliorates hyperoxia-induced brain injury in neonatal mice

Introduction

Prolonged oxygen therapy in preterm infants often leads to cognitive impairment. Hyperoxia leads to excess free radical production with subsequent neuroinflammation, astrogliosis, microgliosis and apoptosis. We hypothesized that Galantamine, an acetyl choline esterase inhibitor and an FDA approved treatment of Alzheimer's disease, will reduce hyperoxic brain injury in neonatal mice and will improve learning and memory.

Methods

Mouse pups at postnatal day 1 (P1) were placed in a hyperoxia chamber (FiO₂ 95%) for 7 days. Pups were injected IP daily with Galantamine (5 mg/kg/dose) or saline for 7 days.

Results

Hyperoxia caused significant neurodegeneration in cholinergic nuclei of the basal forebrain cholinergic system (BFCS), laterodorsal tegmental (LDT) nucleus and nucleus ambiguus (NA). Galantamine ameliorated this neuronal loss. Treated hyperoxic group showed a significant increase of choline acetyl transferase (ChAT) expression and a decrease of acetyl choline esterase activity, thus increasing acetyl choline levels in hyperoxia environment. Hyperoxia increased pro-inflammatory cytokines namely IL -1β, IL-6 and TNF α, HMGB1, NF-κB activation. Galantamine showed its potent anti- inflammatory effect, by blunting cytokines surges among treated group. Treatment with Galantamine increased myelination while reducing apoptosis, microgliosis, astrogliosis and ROS production. Long term neurobehavioral outcomes at P60 showed improved locomotor activity, coordination, learning and memory, along with increased hippocampal volumes on MRI with Galantamine treated versus non treated hyperoxia group.

Conclusion

Together our findings suggest a potential therapeutic role for Galantamine in attenuating hyperoxia-induced brain injury.

Galantamine beyond Alzheimer's disease-a fact or artefact?

Galantamine is US-Food and Drug Administration FDA-approved for mild-to-moderate Alzheimer's disease. However, its unique pharmacological portfolio speaks to the idea of a pluripotent agent with a broad therapeutic potential. Here, authors briefly discuss these off-label clinical indications synthesizing the extant evidence.

Dynamics of Choline-Containing Phospholipids in Traumatic Brain Injury and Associated Comorbidities

The incidences of traumatic brain injuries (TBIs) are increasing globally because of expanding population and increased dependencies on motorized vehicles and machines. This has resulted in increased socio-economic burden on the healthcare system, as TBIs are often associated with mental and physical morbidities with lifelong dependencies, and have severely limited therapeutic options. There is an emerging need to identify the molecular mechanisms orchestrating these injuries to life-long neurodegenerative disease and a therapeutic strategy to counter them. This review highlights the dynamics and role of choline-containing phospholipids during TBIs and how they can be used to evaluate the severity of injuries and later targeted to mitigate neuro-degradation, based on clinical and preclinical studies. Choline-based phospholipids are involved in maintaining the structural integrity of the neuronal/glial cell membranes and are simultaneously the essential component of various biochemical pathways, such as cholinergic neuronal transmission in the brain. Choline or its metabolite levels increase during acute and chronic phases of TBI because of excitotoxicity, ischemia and oxidative stress; this can serve as useful biomarker to predict the severity and prognosis of TBIs. Moreover, the effect of choline-replenishing agents as a post-TBI management strategy has been reviewed in clinical and preclinical studies. Overall, this review determines the theranostic potential of choline phospholipids and provides new insights in the management of TBI.

Regulators of cholinergic signaling in disorders of the central nervous system

Cholinergic signaling is crucial in cognitive processes, and degenerating cholinergic projections are a pathological hallmark in dementia. Use of cholinesterase inhibitors is currently the main treatment option to alleviate symptoms of Alzheimer's disease and has been postulated as a therapeutic strategy in acute brain damage (stroke and traumatic brain injury). However, the benefits of this treatment are still not clear. Importantly, cholinergic receptors are expressed both by neurons and by astrocytes and microglia, and binding of acetylcholine to the α7 nicotinic receptor in glial cells results in anti-inflammatory response. Similarly, the brain fine-tunes the peripheral immune response over the cholinergic anti-inflammatory axis. All of these processes are of importance for the outcome of acute and chronic neurological disease. Here, we summarize the main findings about the role of cholinergic signaling in brain disorders and provide insights into the complexity of molecular regulators of cholinergic responses, such as microRNAs and transfer RNA fragments, both of which may fine-tune the orchestra of cholinergic mRNAs. The available data suggest that these small noncoding RNA regulators may include promising biomarkers for predicting disease course and assessing treatment responses and might also serve as drug targets to attenuate signaling cascades during overwhelming inflammation and to ameliorate regenerative capacities of neuroinflammation.

Long term neuroprotective effects of acute single dose MK-801treatment against traumatic brain injury in immature rats

Because brain development continues during adolescence, childhood trauma is a major health problem in pediatric ages. It is known traumatic brain injury (TBI) results in damage in hippocampal and cortical areas of the brain and impairs cognitive functions. The study aims to investigate the long-term effects of MK-801 (dizocilpine), an N-methyl d-aspartate (NMDA) receptor antagonist, on hippocampal damage, locomotor activity, and cognitive functions following TBI in immature rats. MK-801 (1 mg/kg) was injected intraperitoneally immediately after TBI. Thirty-seven litters were randomly allocated into three groups at 7 days (P7) of postnatal age: a control group, a trauma group, and an MK-801 treatment group. The control group received no treatment; the trauma group received saline as vehicle control for the MK-801 group and the MK-801 group received a single dose of 1 mg/kg MK-801 immediately after TBI. Hippocampal damage was examined by Hematoxylin-Eosin staining. Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), NMDA-R, and glial fibrillar acidic protein (GFAP) immunohistochemistry and, BDNF, NGF, and NMDA-R ELISA protein levels were evaluated 125 days after trauma. Histopathological and immunohistochemical evaluations showed that treatment with MK-801 significantly ameliorated the trauma-induced hippocampal neuron loss and increased BDNF, NGF, NMDA-R, GFAP expressions in CA1, CA3, and DG hippocampal regions. Additionally, treatment with MK-801 decreased anxiety and increased hippocampus-dependent memory of animals subjected to brain injury after TBI. These results show that acute treatment of MK-801 has a neuroprotective role against trauma-induced hippocampal neuron loss and associated cognitive impairment in rats.

α7-Acetylcholine Receptor Signaling Reduces Neuroinflammation After Subarachnoid Hemorrhage in Mice

Aneurysmal subarachnoid hemorrhage (aSAH) causes a robust inflammatory response which leads worse brain injury and poor outcomes. We investigated if stimulation of nicotinic acetylcholine α7 receptors (α7-AChR) (receptors shown to have anti-inflammatory effects) would reduce inflammation and improve outcomes. To investigate the level of peripheral inflammation after aSAH, inflammatory markers were measured in plasma samples collected in a cohort of aSAH patients. To study the effect of α7-AChR stimulation, SAH was induced in adult mice which were then treated with a α7-AChR agonist, galantamine, or vehicle. A battery of motor and cognitive tests were performed 24 h after subarachnoid hemorrhage. Mice were euthanized and tissue collected for analysis of markers of inflammation or activation of α7-AChR-mediated transduction cascades. A separate cohort of mice was allowed to survive for 28 days to assess long-term neurological deficits and histological outcome. Microglia cell culture subjected to hemoglobin toxicity was used to assess the effects of α7-AChR agonism. Analysis of eighty-two patient plasma samples confirmed enhanced systemic inflammation after aSAH. α7-AChR agonism reduced neuroinflammation at 24 h after SAH in male and female mice, which was associated with improved outcomes. This coincided with JAK2/STAT3 and IRAK-M activity modulations and a robust improvement in neurological/cognitive status that was effectively reversed by interfering with various components of these signaling pathways. Pharmacologic inhibition partially reversed the α7-AChR agonist's benefits, supporting α7-AChR as a target of the agonist's therapeutic effect. The cell culture experiment showed that α7-AChR agonism is directly beneficial to microglia. Our results demonstrate that activation of α7-AChR represents an attractive target for treatment of SAH. Our findings suggest that α7-AChR agonists, and specifically galantamine, might provide therapeutic benefit to aSAH patients.

Agonism of the α7-acetylcholine receptor/PI3K/Akt pathway promotes neuronal survival after subarachnoid hemorrhage in mice

Subarachnoid hemorrhage (SAH) results in severe neuronal dysfunction and degeneration. Since the nicotinic acetylcholine α₇ receptors (α₇-AChR) are involved in neuronal function and survival, we investigated if stimulation of α₇-AChR would promote neuronal survival and improve behavioral outcome following SAH in mice. Male mice subjected to SAH were treated with either galantamine (α₇-AChR agonist) or vehicle. Neurobehavioral testing was performed 24 h after SAH, and mice were euthanized for analysis of neuronal cell death or a cell survival (PI3K/Akt) signaling pathway. Neuron cell cultures were subjected to hemoglobin toxicity to assess the direct effects of α₇-AChR agonism independent of other cells. Treatment with the α₇-AChR agonist promoted neuronal survival and improved functional outcomes 24 h post-SAH. The improved outcomes corresponded with increased PI3K/Akt activity. Antagonism of α₇-AChR or PI3K effectively reversed galantamine's beneficial effects. Tissue from α₇-AChR knockout mice confirmed α₇-AChR's role in neuronal survival after SAH. Data from the neuronal cell culture experiment supported a direct effect of α₇-AChR agonism in promoting cell survival. Our findings indicate that α₇-AChR is a therapeutic target following SAH which can promote neuronal survival, thereby improving neurobehavioral outcome. Thus, the clinically relevant α₇-AChR agonist, galantamine, might be a potential candidate for human use to improve outcome after SAH.

JM-20 Treatment After Mild Traumatic Brain Injury Reduces Glial Cell Pro-inflammatory Signaling and Behavioral and Cognitive Deficits by Increasing Neurotrophin Expression

Traumatic brain injury (TBI) is considered a public health problem and is often related to motor and cognitive disabilities, besides behavioral and emotional changes that may remain for the rest of the subject's life. Resident astrocytes and microglia are the first cell types to start the inflammatory cascades following TBI. It is widely known that continuous or excessive neuroinflammation may trigger many neuropathologies. Despite the large numbers of TBI cases, there is no effective pharmacological treatment available. This study aimed to investigate the effects of the new hybrid molecule 3-ethoxycarbonyl-2-methyl-4-(2-nitrophenyl)-4,11-dihydro1H-pyrido[2,3-b][1,5]benzodiazepine (JM-20) on TBI outcomes. Male Wistar rats were submitted to a weight drop model of mild TBI and treated with a single dose of JM-20 (8 mg/kg). Twenty-four hours after TBI, JM-20-treated animals showed improvements on locomotor and exploratory activities, and short-term memory deficits induced by TBI improved as well. Brain edema was present in TBI animals and the JM-20 treatment was able to prevent this change. JM-20 was also able to attenuate neuroinflammation cascades by preventing glial cells-microglia and astrocytes-from exacerbated activation, consequently reducing pro-inflammatory cytokine levels (TNF-α and IL-1β). BDNF mRNA level was decreased 24 h after TBI because of neuroinflammation cascades; however, JM-20 restored the levels. JM-20 also increased GDNF and NGF levels. These results support the JM-20 neuroprotective role to treat mild TBI by reducing the initial damage and limiting long-term secondary degeneration after TBI.

Sleep Deprivation Induces Cognitive Impairment by Increasing Blood-Brain Barrier Permeability via CD44

Sleep deprivation occurs frequently in older adults, which can result in delirium and cognitive impairment. CD44 is a key molecular in blood-brain barrier (BBB) regulation. However, whether CD44 participates in the role of sleep deprivation in cognitive impairment remains unclear. In this study, the effect of sleep deprivation on cognitive ability, tissue inflammation, BBB permeability, and astrocyte activity were evaluated in vivo. The differentially expressed genes (DEGs) were identified by RNA sequencing. A CD44 overexpression in the BBB model was performed in vitro to assess the effect and mechanisms of CD44. Sleep deprivation impaired the learning and memory ability and increased the levels of inflammatory cytokines, along with increased BBB permeability and activated astrocytes in hippocampus tissue. RNA sequencing of the hippocampus tissue revealed that 329 genes were upregulated in sleep deprivation-induced mice compared to control mice, and 147 genes were downregulated. GO and pathways showed that DEGs were mainly involved in BBB permeability and astrocyte activation, including nervous system development, neuron development, and brain development, and neuroactive ligand-receptor interaction. Moreover, the PCR analysis revealed that CD44 was dramatically increased in mice with sleep deprivation induction. The overexpression of CD44 in astrocytes promoted BBB permeability in vitro and induced the expression of the downstream gene NANOG. Our results indicate that sleep deprivation upregulated CD44 expression in hippocampus tissue, and increased BBB permeability, resulting in cognitive impairment.

Disruption of basal forebrain cholinergic neurons after traumatic brain injury does not compromise environmental enrichment-mediated cognitive benefits

Environmental enrichment (EE) attenuates traumatic brain injury (TBI)-induced loss of medial septal (MS) choline acetyltransferase (ChAT)-cells and enhances spatial learning and memory vs. standard (STD) housing. Whether basal forebrain cholinergic neurons (BFCNs) are important mediators of EE-induced benefits after TBI requires further investigation. Anesthetized female rats were randomly assigned to intraseptal infusions of the immunotoxin 192-IgG-saporin (SAP; 0.22 μg in 1.0 μL) or vehicle (VEH; 1.0 μL IgG) followed immediately by a cortical impact (2.8 mm deformation depth at 4 m/s) or sham injury and divided into EE and STD housing. Spatial learning and memory retention were assessed on post-operative days 14-19. MS ChAT⁺ cells were quantified at 3 weeks. SAP significantly reduced ChAT⁺ cells in both the EE and STD groups. Cognitive performance was improved in the EE groups, regardless of VEH or SAP infusion, vs. the STD-housed groups (p's < 0.05). No cognitive differences were revealed between the TBI + EE + SAP and TBI + EE + VEH groups (p > 0.05) or between the TBI + STD + SAP and TBI + STD + VEH groups (p > 0.05). These data show that despite significant MS ChAT⁺ cell loss, the EE-mediated benefit in cognitive recovery is not compromised.

A Review on Tramiprosate (Homotaurine) in Alzheimer's Disease and Other Neurocognitive Disorders

Alzheimer's disease (AD) is the most prevalent neurodegenerative condition, especially among elderly people. The presence of cortical β-amyloid deposition, together with tau phosphorylation and intracellular accumulation of neurofibrillary tangles (NFT) is the main neuropathologic criteria for AD diagnosis. Additionally, a role of inflammatory, mitochondrial, and metabolic factors has been suggested. Tramiprosate binds to soluble amyloid, thus inhibiting its aggregation in the brain. It reduced oligomeric and fibrillar (plaque) amyloid, diminished hippocampal atrophy, improved cholinergic transmission, and stabilized cognition in preclinical and clinical studies. In this narrative review, current information on the efficacy and safety of tramiprosate, both in AD and in other neurocognitive disorders, is presented. Possible directions for future studies with tramiprosate are also discussed.

Traumatic brain injury and hippocampal neurogenesis: Functional implications

In the adult brain, self-renewing radial-glia like (RGL) progenitor cells have been shown to reside in the subventricular zone and the subgranular zone of the hippocampus. A large body of evidence shows that experiences such as learning, enriched environment and stress can alter proliferation and differentiation of RGL progenitor cells. The progenitor cells present in the subgranular zone of the hippocampus divide to give rise to newborn neurons that migrate to the dentate gyrus where they differentiate into adult granule neurons. These newborn neurons have been found to have a unique role in certain types of hippocampus-dependent learning and memory, including goal-directed behaviors that require pattern separation. Experimental traumatic brain injury (TBI) in rodents has been shown to alter hippocampal neurogenesis, including triggering the acute loss of newborn neurons, as well as progenitor cell hyper-proliferation. In this review, we discuss the role of hippocampal neurogenesis in learning and memory. Furthermore, we review evidence for the molecular mechanisms that contribute to newborn neuron loss, as well as increased progenitor cell proliferation after TBI. Finally, we discuss strategies aimed at enhancing neurogenesis after TBI and their possible therapeutic benefits.

Curcumin alleviates neuroinflammation, enhances hippocampal neurogenesis, and improves spatial memory after traumatic brain injury

Cognitive decline is one of the most obvious symptoms of traumatic brain injury (TBI). Previous studies have demonstrated that cognitive decline is related to substantially increased neuroinflammation and decreased neurogenesis in the hippocampus in a rat model of TBI. Using this model, we explored the role of curcumin (Cur) in ameliorating TBI-impaired spatial memory because Cur has been shown to exhibit anti-chronic-neuroinflammatory, neurogenesis-promoting, and memory-improving properties. Animals received daily Cur or vehicle treatment for 28 days after TBI and also received 50-bromodeoxyuridine(BrdU) for the first 7 days of the treatment for assaying neurogenesis. An optimal Cur dose of 30 mg/kg, selected from a range of 10-50 mg/kg, was used for the present study. Neuroinflammation was evaluated by astrocyte hypertrophy, activated microglia, and inflammatory factors in the hippocampus. Behavioral water-maze studies were conducted for 5 days, starting at 35-day post-TBI. The tropomyosin receptor kinase B (Trkb) inhibitor, ANA-12, was used to test the role of the brain-derived neurotrophic factor (BDNF)/ TrkB/Phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in regulating inflammation and neurogenesis in the hippocampus. Treatment with Cur ameliorated the spatial memory of TBI rats, reduced TBI-induced chronic inflammation, typified by diminished astrocyte hypertrophy, reduction in activated microglia, declined inflammatory factors, and increased neurogenesis in the hippocampus. We also found that BDNF/Trkb/PI3K/Akt signaling was involved in the effects of Cur in TBI rats. Thus, Cur treatment can ameliorate the spatial memory in a murine model of TBI, which may be attributable to decreased chronic neuroinflammation, increased hippocampal neurogenesis, and/or BDNF/Trkb/PI3K/Akt signaling.

Positive allosteric modulation of the α7 nicotinic acetylcholine receptor as a treatment for cognitive deficits after traumatic brain injury

Cognitive impairments are a common consequence of traumatic brain injury (TBI). The hippocampus is a subcortical structure that plays a key role in the formation of declarative memories and is highly vulnerable to TBI. The α7 nicotinic acetylcholine receptor (nAChR) is highly expressed in the hippocampus and reduced expression and function of this receptor are linked with cognitive impairments in Alzheimer's disease and schizophrenia. Positive allosteric modulation of α7 nAChRs with AVL-3288 enhances receptor currents and improves cognitive functioning in naïve animals and healthy human subjects. Therefore, we hypothesized that targeting the α7 nAChR with the positive allosteric modulator AVL-3288 would enhance cognitive functioning in the chronic recovery period of TBI. To test this hypothesis, adult male Sprague Dawley rats received moderate parasagittal fluid-percussion brain injury or sham surgery. At 3 months after recovery, animals were treated with vehicle or AVL-3288 at 30 min prior to cue and contextual fear conditioning and the water maze task. Treatment of TBI animals with AVL-3288 rescued learning and memory deficits in water maze retention and working memory. AVL-3288 treatment also improved cue and contextual fear memory when tested at 24 hr and 1 month after training, when TBI animals were treated acutely just during fear conditioning at 3 months post-TBI. Hippocampal atrophy but not cortical atrophy was reduced with AVL-3288 treatment in the chronic recovery phase of TBI. AVL-3288 application to acute hippocampal slices from animals at 3 months after TBI rescued basal synaptic transmission deficits and long-term potentiation (LTP) in area CA1. Our results demonstrate that AVL-3288 improves hippocampal synaptic plasticity, and learning and memory performance after TBI in the chronic recovery period. Enhancing cholinergic transmission through positive allosteric modulation of the α7 nAChR may be a novel therapeutic to improve cognition after TBI.

Traumatic Brain Injury Induces Tau Aggregation and Spreading

The misfolding and aggregation of tau protein into neurofibrillary tangles is the main underlying hallmark of tauopathies. Most tauopathies have a sporadic origin and can be associated with multiple risk factors. Traumatic brain injury (TBI) has been suggested as a risk factor for tauopathies by triggering disease onset and facilitating its progression. Several studies indicate that TBI seems to be a risk factor to development of Alzheimer disease and chronic traumatic encephalopathy, because there is a relationship of TBI severity and propensity to development of these illnesses. In this study, we evaluated whether moderate to severe TBI can trigger the initial formation of pathological tau that would induce the development of the pathology throughout the brain. To this end, we subjected tau transgenic mice to TBI and assessed tau phosphorylation and aggregation pattern to create a spatial heat map of tau deposition and spreading in the brain. Our results suggest that brain injured tau transgenic mice have an accelerated tau pathology in different brain regions that increases over time compared with sham mice. The appearance of pathological tau occurs in regions distant to the injury area that are connected synaptically, suggesting dissemination of tau aggregates. Overall, this work posits TBI as a risk factor for tauopathies through the induction of tau hyperphosphorylation and aggregation.

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

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

Multi-Center Pre-clinical Consortia to Enhance Translation of Therapies and Biomarkers for Traumatic Brain Injury: Operation Brain Trauma Therapy and Beyond

Current approaches have failed to yield success in the translation of neuroprotective therapies from the pre-clinical to the clinical arena for traumatic brain injury (TBI). Numerous explanations have been put forth in both the pre-clinical and clinical arenas. Operation Brain Trauma Therapy (OBTT), a pre-clinical therapy and biomarker screening consortium has, to date, evaluated 10 therapies and assessed three serum biomarkers in nearly 1,500 animals across three rat models and a micro pig model of TBI. OBTT provides a unique platform to exploit heterogeneity of TBI and execute the research needed to identify effective injury specific therapies toward precision medicine. It also represents one of the first multi-center pre-clinical consortia for TBI, and through its work has yielded insight into the challenges and opportunities of this approach. In this review, important concepts related to consortium infrastructure, modeling, therapy selection, dosing and target engagement, outcomes, analytical approaches, reproducibility, and standardization will be discussed, with a focus on strategies to embellish and improve the chances for future success. We also address issues spanning the continuum of care. Linking the findings of optimized pre-clinical consortia to novel clinical trial designs has great potential to help address the barriers in translation and produce successes in both therapy and biomarker development across the field of TBI and beyond.