The cytokine temporal profile in rat cortex after controlled cortical impact

3D Neurovascular Unit Tissue Model to Assess Responses to Traumatic Brain Injury

The neurovascular unit (NVU) is a critical interface in the central nervous system that links vascular interactions with glial and neural tissue. Disruption of the NVU has been linked to the onset and progression of neurodegenerative diseases. Despite its significance the NVU remains challenging to study in a physiologically relevant manner. Here, a 3D cell triculture model of the NVU is developed that incorporates human primary brain microvascular endothelial cells, astrocytes, and pericytes into a tissue system that can be sustained in vitro for several weeks. This tissue model helps recapitulate the complexity of the NVU and can be used to interrogate the mechanisms of disease and cell-cell interactions. The NVU tissue model displays elevated cell death and inflammatory responses following mechanical damage, to emulate traumatic brain injury (TBI) under controlled laboratory conditions, including lactate dehydrogenase (LDH) release, elevated inflammatory markers TNF-α and monocyte chemoattractant cytokines MCP-2 and MCP-3 and reduced expression of the tight junction marker ZO-1. This 3D tissue model serves as a tool for deciphering mechanisms of TBIs and immune responses associated with the NVU.

Roles of HMGB1 on life-threatening traumatic brain injury and sequential peripheral organ damage

Traumatic brain injury (TBI) has been found to be associated with certain peripheral organ injuries; however, a few studies have explored the chronological influences of TBI on multiple organs and the systemic effects of therapeutic interventions. Particularly, high-mobility group box 1 (HMGB1) is a potential therapeutic target for TBI; however, its effects on peripheral organs remain unclear. Therefore, this study aimed to determine whether severe TBI can lead to multiple organ injury and how HMGB1 inhibition affects peripheral organs. This study used a weight drop-induced TBI mouse model and found that severe TBI can trigger short-lived systemic inflammation, in the lungs and liver, but not in the kidneys, regardless of the severity of the injury. TBI led to an increase in circulating HMGB1 and enhanced gene expressions of its receptors in every organ. Anti-HMGB1 antibody treatment reduced neuroinflammation but increased inflammation in peripheral organs. This study also found that HMGB1 inhibition appears to have a beneficial role in early neuroinflammation but could lead to detrimental effects on peripheral organs through decreased peripheral immune suppression. This study provides novel insights into the chronological changes in multiple organs due to TBI and the unique roles of HMGB1 between the brain and other organs.

Cortical spheroids show strain-dependent cell viability loss and neurite disruption following sustained compression injury

Sustained compressive injury (SCI) in the brain is observed in numerous injury and pathological scenarios, including tumors, ischemic stroke, and traumatic brain injury-related tissue swelling. Sustained compressive injury is characterized by tissue loading over time, and currently, there are few in vitro models suitable to study neural cell responses to strain-dependent sustained compressive injury. Here, we present an in vitro model of sustained compressive neural injury via centrifugation. Spheroids were made from neonatal rat cortical cells seeded at 4000 cells/spheroid and cultured for 14 days in vitro. A subset of spheroids was centrifuged at 104, 209, 313 or 419 rads/s for 2 minutes. Modeling the physical deformation of the spheroids via finite element analyses, we found that spheroids centrifuged at the aforementioned angular velocities experienced pressures of 10, 38, 84 and 149 kPa, respectively, and compressive (resp. tensile) strains of 10% (5%), 18% (9%), 27% (14%) and 35% (18%), respectively. Quantification of LIVE-DEAD assay and Hoechst 33342 nuclear staining showed that centrifuged spheroids subjected to pressures above 10 kPa exhibited significantly higher DNA damage than control spheroids at 2, 8, and 24 hours post-injury. Immunohistochemistry of β3-tubulin networks at 2, 8, and 24 hours post-centrifugation injury showed increasing degradation of microtubules over time with increasing strain. Our findings show that cellular injuries occur as a result of specific levels and timings of sustained tissue strains. This experimental SCI model provides a high throughput in vitro platform to examine cellular injury, to gain insights into brain injury that could be targeted with therapeutic strategies.

Role of mitochondrial dysfunction in acute traumatic brain injury: Evidence from bioinformatics analysis

Background

The intricate regulatory relationship between mitochondrial dysfunction, apoptosis, and immune cells remains largely elusive following traumatic brain injury (TBI).

Methods

The GSE45997 dataset from the Gene Expression Omnibus database and utilized GEO2R to screen for differentially expressed genes (DEGs). Functional enrichment analyses were performed. Mitochondrial gene data from the MitoCarta3.0 database were combined with the DEGs to identify mitochondria-related DEGs (MitoDEGs). The hub MitoDEGs related to apoptosis were further screened. Animal models of TBI were established to investigate the mechanisms underlying mitochondrial dysfunction regulation of apoptosis. Furthermore, we explored the relationship between MitoDEGs/hub MitoDEGs and immune cells using the Spearman correlation method.

Results

Fifty-seven MitoDEGs were significantly enriched in pathways related to fatty acid degradation and metabolism. We identified three upregulated hub MitoDEGs, namely Dnm1l, Mcl1 and Casp3, were associated with apoptosis. In the animal experiments, we observed significant expression levels of microtubule-associated protein 1 light chain 3 beta (LC3B) surrounding the injury site. Most LC3B-expressing cells exhibited positive staining for Beclin 1 and colocalization analysis revealed the simultaneous presence of Beclin 1 and caspase-3. The Western blot analysis further unveiled a significant upregulation of cleaved caspase-3 levels and LC3B II/LC3B I ratio after TBI. Moreover, the quantity of myeloid cell leukaemia-1 immunoreactive cells was notably higher than that in the control group. Spearman correlation analysis demonstrated strong associations between plasma cells, marginal zone B cells, native CD4 T cells, monocytes, and MitoDEGs/hub MitoDEGs.

Conclusions

This study sheds light on enhanced fatty acid metabolism following mitochondrial dysfunction and its potential association with apoptosis and immune cell activation, thereby providing new mechanistic insights into the acute phase of 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.

Sleep, inflammation, and hemodynamics in rodent models of traumatic brain injury

Traumatic brain injury (TBI) can induce dysregulation of sleep. Sleep disturbances include hypersomnia and hyposomnia, sleep fragmentation, difficulty falling asleep, and altered electroencephalograms. TBI results in inflammation and altered hemodynamics, such as changes in blood brain barrier permeability and cerebral blood flow. Both inflammation and altered hemodynamics, which are known sleep regulators, contribute to sleep impairments post-TBI. TBIs are heterogenous in cause and biomechanics, which leads to different molecular and symptomatic outcomes. Animal models of TBI have been developed to model the heterogeneity of TBIs observed in the clinic. This review discusses the intricate relationship between sleep, inflammation, and hemodynamics in pre-clinical rodent models of TBI.

Inflammation, brain connectivity, and neuromodulation in post-traumatic headache

Post-traumatic headache (PTH) is a debilitating condition that affects individuals with different levels of traumatic brain injury (TBI) severity. The difficulties in developing an effective treatment are related to a lack of understanding the complicated mechanisms and neurobiological changes in brain function after a brain injury. Preclinical studies have indicated that peripheral and central sensitization of the trigeminal nociceptive pathways contributes to PTH. While recent brain imaging studies have uncovered widespread changes in brain functional connectivity following trauma, understanding exactly how these networks contribute to PTH after injury remains unknown. Stimulation of peripheral (trigeminal or vagus) nerves show promising efficacies in PTH experimental animals, likely mediated by influencing TBI-induced pathological plasticity by decreasing neuroinflammation and neuronal apoptosis. Non-invasive brain stimulations, such as transcranial magnetic or direct current stimulations, show analgesia for multiple chronic pain conditions, including PTH. Better mechanistic understanding of analgesia achieved by neuromodulations can define peripheral and central mechanisms involved in the development, the resolution, and the management of PTH.

Effects of a Subanesthetic Ketamine Infusion on Inflammatory and Behavioral Outcomes after Closed Head Injury in Rats

Traumatic brain injury (TBI) affects millions of people annually, and most cases are classified as mild TBI (mTBI). Ketamine is a potent trauma analgesic and anesthetic with anti-inflammatory properties. However, ketamine's effects on post-mTBI outcomes are not well characterized. For the current study, we used the Closed-Head Impact Model of Engineered Rotational Acceleration (CHIMERA), which replicates the biomechanics of a closed-head impact with resulting free head movement. Adult male Sprague-Dawley rats sustained a single-session, repeated-impacts CHIMERA injury. An hour after the injury, rats received an intravenous ketamine infusion (0, 10, or 20 mg/kg, 2 h period), during which locomotor activity was monitored. Catheter blood samples were collected at 1, 3, 5, and 24 h after the CHIMERA injury for plasma cytokine assays. Behavioral assays were conducted on post-injury days (PID) 1 to 4 and included rotarod, locomotor activity, acoustic startle reflex (ASR), and pre-pulse inhibition (PPI). Brain tissue samples were collected at PID 4 and processed for GFAP (astrocytes), Iba-1 (microglia), and silver staining (axonal injury). Ketamine dose-dependently altered locomotor activity during the infusion and reduced KC/GRO, TNF-α, and IL-1β levels after the infusion. CHIMERA produced a delayed deficit in rotarod performance (PID 3) and significant axonal damage in the optic tract (PID 4), without significant changes in other behavioral or histological measures. Notably, subanesthetic doses of intravenous ketamine infusion after mTBI did not produce adverse effects on behavioral outcomes in PID 1-4 or neuroinflammation on PID 4. A further study is warranted to thoroughly investigate beneficial effects of IV ketamine on mTBI given multi-modal properties of ketamine in traumatic injury and stress.

Inhibition of P2X4 and P2X7 receptors improves histological and behavioral outcomes after experimental traumatic brain injury in rats

Release of large amounts of adenosine triphosphate (ATP), a gliotransmitter, into the extracellular space by traumatic brain injury (TBI) is considered to activate the microglia followed by release of inflammatory cytokines resulting in excessive inflammatory response that induces secondary brain injury. The present study investigated whether antagonists of ATP receptors (P2X4 and/or P2X7) on microglia are beneficial for reducing the post-injury inflammatory response that leads to secondary injury, a prognostic aggravation factor of TBI. Adult male Sprague-Dawley rats were subjected to cortical contusion injury (CCI) and randomly assigned to injury and drug treatment conditions, as follows: i) No surgical intervention (naïve group); ii) dimethyl sulfoxide treatment after CCI (CCI-control group); iii) 5-BDBD (antagonist of P2X4 receptor) treatment after CCI (CCI-5-BDBD group); iv) CCI-AZ11645373 (antagonist of P2X7 receptor) treatment after CCI (CCI-AZ11645373 group); v) or 5-BDBD and AZ11645373 treatment after CCI (CCI-5-BDBD + AZ11645373 group). In the CCI-5-BDBD, CCI-AZ11645373, and CCI-5-BDBD + AZ11645373 groups, expression of activated microglia was suppressed in the ipsilateral cortex and hippocampus 3 days after the CCI. Western blotting with ionized calcium-binding adaptor molecule 1 antibody revealed that administration of CCI-5-BDBD and/or CCI-AZ11645373 suppressed expression of microglia and reduced expression of inflammatory cytokine mRNA 3 days after the CCI. Furthermore, the plus maze test, which reflects the spatial memory function and involves the hippocampal function, showed improvement 28 days after secondary injury to the hippocampus. These findings confirmed that blocking the P2X4 and P2X7 receptors, which are ATP receptors central in gliotransmission, suppresses microglial activation and subsequent cytokine expression after brain injury, and demonstrates the potential as an effective treatment for reducing secondary brain injury.

Novel, thalidomide-like, non-cereblon binding drug tetrafluorobornylphthalimide mitigates inflammation and brain injury

BACKGROUND

Quelling microglial-induced excessive neuroinflammation is a potential treatment strategy across neurological disorders, including traumatic brain injury (TBI), and can be achieved by thalidomide-like drugs albeit this approved drug class is compromised by potential teratogenicity. Tetrafluorobornylphthalimide (TFBP) and tetrafluoronorbornylphthalimide (TFNBP) were generated to retain the core phthalimide structure of thalidomide immunomodulatory imide drug (IMiD) class. However, the classical glutarimide ring was replaced by a bridged ring structure. TFBP/TFNBP were hence designed to retain beneficial anti-inflammatory properties of IMiDs but, importantly, hinder cereblon binding that underlies the adverse action of thalidomide-like drugs.

METHODS

TFBP/TFNBP were synthesized and evaluated for cereblon binding and anti-inflammatory actions in human and rodent cell cultures. Teratogenic potential was assessed in chicken embryos, and in vivo anti-inflammatory actions in rodents challenged with either lipopolysaccharide (LPS) or controlled cortical impact (CCI) moderate traumatic brain injury (TBI). Molecular modeling was performed to provide insight into drug/cereblon binding interactions.

RESULTS

TFBP/TFNBP reduced markers of inflammation in mouse macrophage-like RAW264.7 cell cultures and in rodents challenged with LPS, lowering proinflammatory cytokines. Binding studies demonstrated minimal interaction with cereblon, with no resulting degradation of teratogenicity-associated transcription factor SALL4 or of teratogenicity in chicken embryo assays. To evaluate the biological relevance of its anti-inflammatory actions, two doses of TFBP were administered to mice at 1 and 24 h post-injury following CCI TBI. Compared to vehicle treatment, TFBP reduced TBI lesion size together with TBI-induction of an activated microglial phenotype, as evaluated by immunohistochemistry 2-weeks post-injury. Behavioral evaluations at 1- and 2-weeks post-injury demonstrated TFBP provided more rapid recovery of TBI-induced motor coordination and balance impairments, versus vehicle treated mice.

CONCLUSION

TFBP and TFNBP represent a new class of thalidomide-like IMiDs that lower proinflammatory cytokine generation but lack binding to cereblon, the main teratogenicity-associated mechanism. This aspect makes TFBP and TFNBP potentially safer than classic IMiDs for clinical use. TFBP provides a strategy to mitigate excessive neuroinflammation associated with moderate severity TBI to, thereby, improve behavioral outcome measures and warrants further investigation in neurological disorders involving a neuroinflammatory component.

Multiplex Assessment of Serum Chemokines CCL2, CCL5, CXCL1, CXCL10, and CXCL13 Following Traumatic Brain Injury

Chemokines may promote neuroinflammation following traumatic brain injury (TBI), thereby exacerbating secondary injury. This study was designed to investigate the contributions of chemokines (CCL2, CCL5, CXCL1, CXCL10, and CXCL13) to TBI severity and clinical outcome. Peripheral blood was drawn from 92 TBI patients on admission, and 40 controls were recruited. Serum concentrations of CCL2, CCL5, CXCL1, CXCL10, and CXCL13 on admission were measured by ELISA. Preoperative clinical severity was evaluated using the Glasgow Coma Scale (GCS), and clinical outcome at 90 days post-TBI was evaluated using the Glasgow Outcome Scale (GOS). The associations were evaluated by calculating Spearman's correlation coefficients. A binary logistic regression model was used to identify clinicodemographic factors influencing outcome, and ROC curves were constructed. Serum concentrations of CCL2, CCL5, CXCL1, CXCL10, and CXCL13 were elevated significantly after TBI and negatively correlated with GCS and GOS scores except CCL5. CCL2 may be considered as an independent predictor to predict severity and outcome. Moreover, combination of GCS score, CCL2, and CXCL10 can be a better assessment prognosis of moderate and severe TBI.

Chlorinated Polycyclic Aromatic Hydrocarbons Induce Immunosuppression in THP-1 Macrophages Characterized by Disrupted Amino Acid Metabolism

Frequent chlorinated polycyclic aromatic hydrocarbon (Cl-PAH) occurrence in environmental samples and emerging detection in human serum have warned of their underestimated risks. Studies showed that some Cl-PAHs exhibit dioxin-like properties, implying immunotoxic potential but lacking direct evidence and specific mechanisms. Here, we integrated a high-content screening (HCS) system and high-resolution mass spectrometry to investigate the immune dysfunction and metabolic disruption induced by Cl-PAHs and their parent PAHs (PPAHs) in THP-1 macrophages. Both 9-chloroanthracene and 2,7-dichlorofluorene exerted clear immunosuppression on THP-1 mφs, while their PPAHs exhibited different immune disturbances. Interestingly, Cl-PAH/PPAHs induced complex alterations in the multicytokine/chemokine network, including biphasic alterations with initial inhibition and later enhancement. Furthermore, the protein-protein interaction results revealed that inflammatory cytokines are the core of this complicated network regulation. Connecting immune phenotypes and metabolomics, amino acid metabolism reprogramming was identified as a potential cause of Cl-PAH/PAH-induced immunotoxicity. Phytosphingosine and l-kynurenine were proposed as candidate immunosuppression biomarkers upon Cl-PAH exposure. This article provides direct immunotoxicity evidence of Cl-PAHs without activating AhR for the first time and discusses the contribution of metabolites to Cl-PAH/PPAH-induced immune responses in macrophages, highlighting the potential of developing new methods based on immunometabolism mechanisms for toxic risk evaluation of environmental chemicals.

Altered amyloid precursor protein, tau-regulatory proteins, neuronal numbers and behaviour, but no tau pathology, synaptic and inflammatory changes or memory deficits, at 1 month following repetitive mild traumatic brain injury

Repetitive mild traumatic brain injury, commonly experienced following sports injuries, results in various secondary injury processes and is increasingly recognised as a risk factor for the development of neurodegenerative conditions such as chronic traumatic encephalopathy, which is characterised by tau pathology. We aimed to characterise the underlying pathological mechanisms that might contribute to the onset of neurodegeneration and behavioural changes in the less-explored subacute (1-month) period following single or repetitive controlled cortical impact injury (five impacts, 48 h apart) in 12-week-old male and female C57Bl6 mice. We conducted motor and cognitive testing, extensively characterised the status of tau and its regulatory proteins via western blot and quantified neuronal populations using stereology. We report that r-mTBI resulted in neurobehavioural deficits, gait impairments and anxiety-like behaviour at 1 month post-injury, effects not seen following a single injury. R-mTBI caused a significant increase in amyloid precursor protein, an increased trend towards tau phosphorylation and significant changes in kinase/phosphatase proteins that may promote a downstream increase in tau phosphorylation, but no changes in synaptic or neuroinflammatory markers. Lastly, we report neuronal loss in various brain regions following both single and repeat injuries. We demonstrate herein that repeated impacts are required to promote the initiation of a cascade of biochemical events that are consistent with the onset of neurodegeneration subacutely post-injury. Identifying the timeframe in which these changes occur and the pathological mechanisms involved will be crucial for the development of future therapeutics to prevent the onset or mitigate the progression of neurodegeneration following r-mTBI.

Activity of a Novel Anti-Inflammatory Agent F-3,6'-dithiopomalidomide as a Treatment for Traumatic Brain Injury

Traumatic brain injury (TBI) is a major risk factor for several neurodegenerative disorders, including Parkinson's disease (PD) and Alzheimer's disease (AD). Neuroinflammation is a cause of later secondary cell death following TBI, has the potential to aggravate the initial impact, and provides a therapeutic target, albeit that has failed to translate into clinical trial success. Thalidomide-like compounds have neuroinflammation reduction properties across cellular and animal models of TBI and neurodegenerative disorders. They lower the generation of proinflammatory cytokines, particularly TNF-α which is pivotal in microglial cell activation. Unfortunately, thalidomide-like drugs possess adverse effects in humans before achieving anti-inflammatory drug levels. We developed F-3,6'-dithiopomalidomide (F-3,6'-DP) as a novel thalidomide-like compound to ameliorate inflammation. F-3,6'-DP binds to cereblon but does not efficiently trigger the degradation of the transcription factors (SALL4, Ikaros, and Aiolos) associated with the teratogenic and anti-proliferative responses of thalidomide-like drugs. We utilized a phenotypic drug discovery approach that employed cellular and animal models in the selection and development of F-3,6'-DP. F-3,6'-DP significantly mitigated LPS-induced inflammatory markers in RAW 264.7 cells, and lowered proinflammatory cytokine/chemokine levels in the plasma and brain of rats challenged with systemic LPS. We subsequently examined immunohistochemical, biochemical, and behavioral measures following controlled cortical impact (CCI) in mice, a model of moderate TBI known to induce inflammation. F-3,6'-DP decreased CCI-induced neuroinflammation, neuronal loss, and behavioral deficits when administered after TBI. F-3,6'-DP represents a novel class of thalidomide-like drugs that do not lower classical cereblon-associated transcription factors but retain anti-inflammatory actions and possess efficacy in the treatment of TBI and potentially longer-term neurodegenerative disorders.

Possible anti-inflammatory, antioxidant and neuroprotective effects of apigenin in the setting of mild traumatic brain injury: an investigation

OBJECTIVE

Apigenin is a plant flavone proven with biological properties such as anti-inflammatory, antioxidant, and antimicrobial effects. This study, it was aimed to examine the possible anti-inflammatory, antioxidant and neuroprotective effects of apigenin in the setting of mild traumatic brain injury (TBI) model.

METHODS

Wistar albino male rats were randomly assigned to groups: control (n = 9), TBI (n = 9), TBI + vehicle (n = 8), and TBI + Apigenin (20 and 40 mg/kg, immediately after trauma; n = 6 and n = 7). TBI was performed by dropping a 300 g weight from a height of 1 meter onto the skull under anesthesia. Neurological examination and tail suspension test applied before and 24 hours after trauma, as well as Y-maze and object recognition tests, after that rats were decapitated. In brain tissue, luminol- and lucigenin-enhanced chemiluminescence levels and cytokine ELISA levels were measured. Histological damage was scored. Data was analyzed with one-way ANOVA.

RESULTS

After TBI, luminol (p < 0.001) and lucigenin (p < 0.001) levels increased, and luminol and lucigenin levels decreased with apigenin treatments (p < 0.01-0.001). The tail suspension test score increased with trauma (p < 0.01). According to the pre-traumatic values, the number of entrances to the arms (p < 0.01) in the Y-maze decreased after trauma (p < 0.01). In the object recognition test, discrimination (p < 0.05) and recognition indexes (p < 0.05) decreased with trauma. There was no significant difference among trauma apigenin groups in behavioral tests. Interleukin (IL)-10 levels, one of the anti-inflammatory cytokines, decreased with trauma (p < 0.05), and increased with 20 and 40 mg apigenin treatment (p < 0.001 and p < 0.01, respectively). The histological damage score in cortex were decreased in apigenin 20 mg treatment group significantly (p < 0.05), the decrease observed in apigenin 40 mg group was not significant.

CONCLUSION

The results of this study revelead that apigenin 20 and 40 mg treatment may have neuroprotective effects in mild TBI via decreasing the the level of luminol and lucigenin and increasing the IL-10 levels. Additionally, apigenin 20 mg treatment ameliorated the trauma-induced cortical tissue damage.

Interleukin-4 reduces lesion volume and improves neurological function in the acute phase after experimental traumatic brain injury in mice

Little is known about the impact of Interleukin-4 (IL-4) on secondary brain damage in the acute phase after experimental traumatic brain injury (TBI). Therefore, we evaluated the effect of IL-4-Knockout on structural damage as well as functional impairment in the acute phase after experimental TBI in mice. 28 C57Bl/6 wildtype and 20 C57BL/6-Il4tm1Nnt/J Interleukin-4-Knockout (IL-4-KO) mice were subjected to Controlled Cortical Impact (CCI). Contusion volumes, body weight and functional outcome (Video Open Field Test (VOF), Hole Board Test (HB), CatWalkXT®) were determined on postoperative days one (D1), three (D3) and seven (D7). Contusion volume (13.45 +/- 0.88 mm³ vs. 9.50 +/- 0.97 mm³, p=0.015) and weight loss (-2.92 +/- 0.52% vs. -0.85 +/- 0.67%, p=0.027) were significantly higher and exploration behavior significantly more impaired (e.g., 150.44 +/- 18.71 fields explored vs. 211.56 +/- 18.90 fields explored, p=0.028 in the VOF; 23.31 +/- 2.03 holes explored vs. 35.65 +/- 1.93 holes explored, p<0.001 in the HB) in IL-4-KO mice on D1. Gait impairment was significantly more pronounced in IL-4-KO mice throughout the first week after CCI (e.g., 0.07 +/- 0.01s vs. 0.00 +/- 0.01s, p=0.047 for right hindpaw Swing on D1; -1.76 +/- 1.34 U vs. 2.53 +/- 0.90 U, p=0.01 for right forepaw Mean Intensity on D3; -0.01 +/- 0.01cm² vs. 0.05 +/- 0.01cm², p=0.015 for left forepaw Mean Area on D7). In conclusion, IL-4 reduces structural damage and improves functional outcome in the acute phase after CCI. Neurobehavioral outcome assessment in IL-4-related studies should focus on motor function on the first three days after trauma induction.

Transcriptional Profiling in a Novel Swine Model of Traumatic Brain Injury

Transcriptomic investigations of traumatic brain injury (TBI) can give us deep insights into the pathological and compensatory processes post-injury. Thus far, transcriptomic studies in TBI have mostly used microarrays and have focused on rodent models. However, a large animal model of TBI bears a much stronger resemblance to human TBI with regard to the anatomical details, mechanics of injury, genetics, and, possibly, molecular response. Because of the advantages of a large animal TBI model, we investigated the gene expression changes between injured and uninjured sides of pig cerebral cortex after TBI. Given acute inflammation that follows after TBI and the important role that immune response plays in neuroplasticity and recovery, we hypothesized that transcriptional changes involving immune function will be upregulated. Eight female 4-week-old piglets were injured on the right hemisphere with controlled cortical impact (CCI). At 5 days after TBI, pericontusional cortex tissues from the injured side and contralateral cortical tissues were collected. After RNA extraction, library preparation and sequencing as well as gene expression changes between the ipsi- and contralateral sides were compared. There were 6642 genes that were differentially expressed between the ipsi- and contralateral sides, and 1993 genes among them had at least 3-fold differences. Differentially expressed genes were enriched for biological processes related to immune system activation, regulation of immune response, and leukocyte activation. Many of the differentially expressed genes, such as CD4, CD86, IL1A, IL23R, and IL1R1, were major regulators of immune function. This study demonstrated some of the major transcriptional changes between the pericontusional and contralateral tissue at an acute time point after TBI in pigs.

Lu Tong Ke Li protects neurons from injury by regulating inflammation in rats with brain trauma

Currently, there is no effective therapy for traumatic brain injury (TBI). Therefore, this study was conducted to determine the protective effect of Lu Tong Ke Li (LTKL), a Chinese medicine, for TBI in experimental animals. The TBI rat model was induced using the modified Feeney's protocol. The rats were divided into four groups: Sham group, Control group, LTKL  lower-dose group (LTL, 2 g/kg/day, p.o.), and LTKL higher-dose group (LTH, 4 g/kg/day, p.o.). The Neurological Severity Score (NSS) was used to examine neurological function. Magnetic resonance imaging was performed to check the brain tissue lesions in rats. Cell apoptosis in the damaged area was evaluated using the Terminal deoxynucleotidyl transferase deoxy-UTP-nick end labeling assay. Reverse-transcription polymerase chain reaction was used to investigate the expression of inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin 1β (IL-1β), and interleukin 10 (IL-10). The TBI rat model was successfully constructed. Neurological function was enhanced at 14, 21, and 28 days post TBI in the LTH groups, indicated by gradually decreased NSS scores. Administration of LTH led to fewer brain defects in the damaged area, and the number of apoptosis cells in the brain injury area markedly decreased. LTKL treatment led to upregulation of IL-10 expression and downregulation of TNF-α and IL-1β expressions at the molecular level. LTKL can improve the neurobehavior of TBI. The neuroprotective effect was probably related to regulation of inflammation cytokines. Our results provide crucial evidence of the potentially useful application of LTKL in the therapy of TBI in clinic practice in the future.

The Therapeutic Prospects of Targeting IL-1R1 for the Modulation of Neuroinflammation in Central Nervous System Disorders

The interleukin-1 receptor type 1 (IL-1R1) holds pivotal roles in the immune system, as it is positioned at the “epicenter” of the inflammatory signaling networks. Increased levels of the cytokine IL-1 are a recognized feature of the immune response in the central nervous system (CNS) during injury and disease, i.e., neuroinflammation. Despite IL-1/IL-1R1 signaling within the CNS having been the subject of several studies, the roles of IL-1R1 in the CNS cellular milieu still cause controversy. Without much doubt, however, the persistent activation of the IL-1/IL-1R1 signaling pathway is intimately linked with the pathogenesis of a plethora of CNS disease states, ranging from Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS), all the way to schizophrenia and prion diseases. Importantly, a growing body of evidence is showing that blocking IL-1R1 signaling via pharmacological or genetic means in different experimental models of said CNS diseases leads to reduced neuroinflammation and delayed disease progression. The aim of this paper is to review the recent progress in the study of the biological roles of IL-1R1, as well as to highlight key aspects that render IL-1R1 a promising target for the development of novel disease-modifying treatments for multiple CNS indications.

Mitoquinone Helps Combat the Neurological, Cognitive, and Molecular Consequences of Open Head Traumatic Brain Injury at Chronic Time Point

Traumatic brain injury (TBI) is a heterogeneous disease in its origin, neuropathology, and prognosis, with no FDA-approved treatments. The pathology of TBI is complicated and not sufficiently understood, which is the reason why more than 30 clinical trials in the past three decades turned out unsuccessful in phase III. The multifaceted pathophysiology of TBI involves a cascade of metabolic and molecular events including inflammation, oxidative stress, excitotoxicity, and mitochondrial dysfunction. In this study, an open head TBI mouse model, induced by controlled cortical impact (CCI), was used to investigate the chronic protective effects of mitoquinone (MitoQ) administration 30 days post-injury. Neurological functions were assessed with the Garcia neuroscore, pole climbing, grip strength, and adhesive removal tests, whereas cognitive and behavioral functions were assessed using the object recognition, Morris water maze, and forced swim tests. As for molecular effects, immunofluorescence staining was conducted to investigate microgliosis, astrocytosis, neuronal cell count, and axonal integrity. The results show that MitoQ enhanced neurological and cognitive functions 30 days post-injury. MitoQ also decreased the activation of astrocytes and microglia, which was accompanied by improved axonal integrity and neuronal cell count in the cortex. Therefore, we conclude that MitoQ has neuroprotective effects in a moderate open head CCI mouse model by decreasing oxidative stress, neuroinflammation, and axonal injury.

Neuroinflammatory Cytokine Response, Neuronal Death, and Microglial Proliferation in the Hippocampus of Rats During the Early Period After Lateral Fluid Percussion-Induced Traumatic Injury of the Neocortex

Time course of changes in neuroinflammatory processes in the dorsal and ventral hippocampus was studied during the early period after lateral fluid percussion-induced neocortical traumatic brain injury (TBI) in the ipsilateral and contralateral hemispheres. In the ipsilateral hippocampus, neuroinflammation (increase in expression of pro-inflammatory cytokines) was evident from day 1 after TBI and ceased by day 14, while in the contralateral hippocampus, it was mainly limited to the dorsal part on day 1. TBI induced an increase in hippocampal corticosterone level on day 3 bilaterally and an accumulation of Il1b on day 1 in the ipsilateral hippocampus. Activation of microglia was observed from day 7 in different hippocampal areas of both hemispheres. Neuronal cell loss was detected in the ipsilateral dentate gyrus on day 3 and extended to the contralateral hippocampus by day 7 after TBI. The data suggest that TBI results in distant hippocampal damage (delayed neurodegeneration in the dentate gyrus and microglia proliferation in both the ipsilateral and contralateral hippocampus), the time course of this damage being different from that of the neuroinflammatory response.

The neuroprotection of hyperbaric oxygen therapy against traumatic brain injury via NF-κB/MAPKs-CXCL1 signaling pathways

It is well known that hyperbaric oxygen (HBO) therapy achieves neuroprotective effects by modulating neuroinflammatory responses. However, its underlying therapeutic mechanisms are not yet fully elucidated. Based on our previous studies, we further investigated whether HBO therapy exerts neuroprotective effects in vivo by regulating the nuclear factor-kappa B (NF-κB)/ mitogen-activated protein kinases (MAPKs) chemokine (C-X-C motif) ligand (CXCL)1 inflammatory pathway. In our study, a rat model of traumatic brain injury (TBI) was established by controlled cortical impact (CCI) to verify that the expression of CXCL1 and chemokine (C-X-C motif) receptor (CXCR)2 increased after TBI, and CXCL1 was mainly expressed in astrocytes, while CXCR2 was mainly expressed in neurons. Increased apoptosis of cortical nerve cells in the injured cortex was also found after TBI. Reduced nerve cell apoptosis with improved neurological function was observed after application of a CXCR2 antagonist. The expression of phospho-extracellular signal-regulated kinase (p-ERK), phospho-c-Jun N-terminal kinase (p-JNK) and p-NF-κB increased after TBI, and application of ERK, JNK and NF-κB inhibitors decreased expression of CXCL1 and CXCR2 in rats. We further found that HBO therapy down-regulated the expression of p-ERK, p-JNK, p-NF-κB, CXCL1, and CXCR2, and reduced nerve cell apoptosis, improved the neurological function of TBI rats, and ultimately alleviated the secondary injury. In conclusion, HBO therapy may exert neuroprotective effect by regulating the NF-κB/MAPKs (JNK and ERK)-CXCL1 inflammatory pathways following TBI, which probably provide the theoretical and experimental basis for the clinical application of HBO therapy in the treatment of TBI.

Hyperbaric oxygen therapy improves neurological function via the p38-MAPK/CCL2 signaling pathway following traumatic brain injury

OBJECTIVE

The anti-inflammatory mechanisms of hyperbaric oxygenation (HBO) treatment on traumatic brain injury (TBI)-induced neuroinflammation remain unclear. The aim of this study was expected the effect of HBO on CCL2-related signaling pathway following severe TBI in rats.

METHODS

The severe TBI model in rats was induced by controlled cortical impact. TBI rats were treated with CCR2 antagonist, p38 inhibitor, or HBO. Modified neurological severity scores and Morris water maze were used to evaluate neurological and cognitive function. The expression levels of CCL2 and CCR2 were measured by ELISA and real-time fluorescence quantitative PCR. Phospho-p38 expression was analyzed by western blotting.

RESULTS

TBI-induced upregulation of CCL2, CCR2, and p38 in the injured cortex. Application of CCR2 antagonist improved neurological and cognitive function of TBI rats. Application of p38 inhibitor decreased expression of CCL2 and CCR2 in the injured of TBI rats, meanwhile improved neurological and cognitive function. HBO improved neurological and cognitive function by decreasing the expressions of CCL2, CCR2, and phospho-p38.

CONCLUSIONS

This study indicates that the p38-MAPK-CCL2 signaling pathway could mediate neuroinflammation and HBO therapy can modulate neuroinflammation by modulating the p38-MAPK-CCL2 signaling pathways following TBI. This study may provide theoretical evidence for HBO treatment in the treatment of TBI.

Traumatic Brain Injury: An Age-Dependent View of Post-Traumatic Neuroinflammation and Its Treatment

Traumatic brain injury (TBI) is a leading cause of death and disability all over the world. TBI leads to (1) an inflammatory response, (2) white matter injuries and (3) neurodegenerative pathologies in the long term. In humans, TBI occurs most often in children and adolescents or in the elderly, and it is well known that immune responses and the neuroregenerative capacities of the brain, among other factors, vary over a lifetime. Thus, age-at-injury can influence the consequences of TBI. Furthermore, age-at-injury also influences the pharmacological effects of drugs. However, the post-TBI inflammatory, neuronal and functional consequences have been mostly studied in experimental young adult animal models. The specificity and the mechanisms underlying the consequences of TBI and pharmacological responses are poorly understood in extreme ages. In this review, we detail the variations of these age-dependent inflammatory responses and consequences after TBI, from an experimental point of view. We investigate the evolution of microglial, astrocyte and other immune cells responses, and the consequences in terms of neuronal death and functional deficits in neonates, juvenile, adolescent and aged male animals, following a single TBI. We also describe the pharmacological responses to anti-inflammatory or neuroprotective agents, highlighting the need for an age-specific approach to the development of therapies of TBI.

Co-Expression Network Analysis of MicroRNAs and Proteins in Severe Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI) represents one of the leading causes of mortality and morbidity worldwide, placing an enormous socioeconomic burden on healthcare services and communities around the world. Survivors of TBI can experience complications ranging from temporary neurological and psychosocial problems to long-term, severe disability and neurodegenerative disease. The current lack of therapeutic agents able to mitigate the effects of secondary brain injury highlights the urgent need for novel target discovery. This study comprises two independent systematic reviews, investigating both microRNA (miRNA) and proteomic expression in rat models of severe TBI (sTBI). The results were combined to perform integrated miRNA-protein co-expression analyses with the aim of uncovering the potential roles of miRNAs in sTBI and to ultimately identify new targets for therapy. Thirty-four studies were included in total. Bioinformatic analysis was performed to identify any miRNA–protein associations. Endocytosis and TNF signalling pathways were highlighted as common pathways involving both miRNAs and proteins found to be differentially expressed in rat brain tissue following sTBI, suggesting efforts to find novel therapeutic targets that should be focused here. Further high-quality investigations are required to ascertain the involvement of these pathways and their miRNAs in the pathogenesis of TBI and other CNS diseases and to therefore uncover those targets with the greatest therapeutic potential.

Neuroprotective Effect of Cinnamaldehyde on Secondary Brain Injury After Traumatic Brain Injury in a Rat Model

OBJECTIVE

The aim of this study was to investigate the possible neuroprotective effects of cinnamaldehyde (CA) on secondary brain injury after traumatic brain injury (TBI) in a rat model.

METHODS

Rats were randomly divided into 4 groups: control (n = 9), TBI (n = 9), vehicle (0.1% Tween 80; n = 8), and CA (100 mg/kg) (n = 9). TBI was induced by the weight-drop model. In brain tissues, myeloperoxidase activity and the levels of luminol-enhanced and lucigenin-enhanced chemiluminescence were measured. Interleukin 1β, interleukin 6, tumor necrosis factor α, tumor growth factor β, caspase-3, and cleaved caspase-3 were evaluated with an enzyme-linked immunosorbent assay method. Brain injury was histopathologically graded after hematoxylin-eosin staining. Y-maze and novel object recognition tests were performed before TBI and within 24 hours of TBI.

RESULTS

Higher myeloperoxidase activity levels in the TBI group (P < 0.001) were suppressed in the CA group (P < 0.05). Luminol-enhanced and lucigenin-enhanced chemiluminescence, which were increased in the TBI group (P < 0.001, for both), were decreased in the group that received CA treatment (P < 0.001 for both). Compared with the increased histologic damage scores in the cerebral cortex and dentate gyrus of the TBI group (P < 0.001), scores of the CA group were lower (P < 0.001). Decreased number of entries and spontaneous alternation percentage in the Y-maze test of the TBI group (P < 0.05 and P < 0.01, respectively) were not evident in the CA group.

CONCLUSIONS

CA has shown neuroprotective effects by limiting neutrophil recruitment, suppressing reactive oxygen species and reducing histologic damage and acute hippocampal dysfunction.

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.

Inflammation in Traumatic Brain Injury

There is an increasing evidence that inflammation contributes to clinical and functional outcomes in traumatic brain injury (TBI). Many successful target-engaging, lesion-reducing, symptom-alleviating, and function-improving interventions in animal models of TBI have failed to show efficacy in clinical trials. Timing and immunological context are paramount for the direction, quality, and intensity of immune responses to TBI and the resulting neuroanatomical, clinical, and functional course. We present components of the immune system implicated in TBI, potential immune targets, and target-engaging interventions. The main objective of our article is to point toward modifiable molecular and cellular mechanisms that may modify the outcomes in TBI, and contribute to increasing the translational value of interventions that have been identified in animal models of TBI.

The effect of head cooling and remote ischemic conditioning on patients with traumatic brain injury

Cerebral impairment caused by an external force to the head is known as traumatic brain injury (TBI). The aim of this study was to determine the role of local hypothermia and remote ischemic conditioning (RIC) on oxidative stress, inflammatory response after TBI, and other involved variables. The present study is a clinical trial on 84 patients with TBI who were divided into 4 groups. The head cooling for 1.5 to 6 hr was performed in the first three days after TBI. RIC intervention was performed within the golden time after TBI in the form of four 5-min cycles with full cuff and 5 min of emptying of cuff. The group receiving the head cooling technique recovered better than the group receiving the RIC technique. Generally, combination of the two interventions of head cooling and RIC techniques is more effective on the improvement of clinical status of patients than each separate technique.

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The effect of the head cooling method in controlling secondary injury in patients with TBI.

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The effect of the RIC method in controlling secondary injury in patients with TBI.

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Comparison of two interventions of head cooling and RIC.

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Evaluation of clinical and paraclinical parameters.

Pathogenic Functions of Tumor Necrosis Factor Receptor- Factor 6 Signaling Traumatic Brain Injury

Neuroinflammation contributes to delayed (secondary) neurodegeneration following traumatic brain injury (TBI). Tumor necrosis factor receptor-associated factor 6 (TRAF6) signaling may promote post-TBI neuroinflammation, thereby exacerbating secondary injury. This study investigated the pathogenic functions of TRAF6 signaling following TBI in vivo and in vitro. A rat TBI model was established by air pressure contusion while lipopolysaccharide (LPS) exposure was used to induce inflammatory-like responses in cultured astrocytes. Model rats were examined for cell-specific expression of TRAF6, NF-κB, phosphorylated (p)-NF-κB, MAPKs (ERK, JNK, and p38), p-MAPKs, chemokines (CCL2 and CXCL1), and chemokine receptors (CCR2 and CXCR2) by immunofluorescence, RT-qPCR, western blotting, and ELISA, for apoptosis by TUNEL staining, and spatial cognition by Morris water maze testing. These measurements were compared between TBI model rats receiving intracerebral injections of TRAF6-targeted RNAi vector (AAV9-TRAF6-RNAi), empty vector, MAPK/NF-κB inhibitors, or vehicle. Primary astrocytes were stimulated with LPS following TRAF6 siRNA or control transfection, and NF-κB, MAPKs, chemokine, and chemokine receptor expression levels evaluated by western blotting and ELISA. TRAF6 was expressed mainly in astrocytes and neurons of injured cortex, peaking 3 days post-TBI. Knockdown by AAV9-TRAF6-RNAi improved spatial learning and memory, decreased TUNEL-positive cell number in injured cortex, and downregulated expression levels of p-NF-κB, p-ERK, p-JNK, p-p38, CCL2, CCR2, CXCL1, and CXCR2 post-TBI. Inhibitors of NF-κB, ERK, JNK, and p38 significantly suppressed CCL2, CCR2, CXCL1, and CXCR2 expression following TBI. Furthermore, TRAF6-siRNA inhibited LPS-induced NF-κB, ERK, JNK, p38, CCL2, and CXCL1 upregulation in cultured astrocytes. Targeting TRAF6-MAPKs/NF-κB-chemokine signaling pathways may provide a novel therapeutic approach for reducing post-TBI neuroinflammation and concomitant secondary injury.

Assessment of the Effects of Stretch-Injury on Primary Rat Microglia

Mechanical stretch-injury is a prominent force involved in the etiology of traumatic brain injury (TBI). It is known to directly cause damage and dysfunction in neurons, astrocytes, and endothelial cells. However, the deleterious effects of stretch-injury on microglia, the brain's primary immunocompetent cell, are currently unknown. The Cell Injury Controller II (CICII), a validated cellular neurotrauma model, was used to induce a mechanical stretch-injury in primary rat microglia. Statistical analysis utilized Student's t test and one- and two-way ANOVAs with Tukey's and Sidak's multiple comparisons, respectively. Cells exposed to stretch-injury showed no signs of membrane permeability, necrosis, or apoptosis, as measured by media-derived lactate dehydrogenase (LDH) and cleaved-caspase 3 immunocytochemistry, respectively. Interestingly, injured cells displayed a functional deficit in nitric oxide production (NO), identified by media assay and immunocytochemistry, at 6, 12, 18, and 48 h post-injury. Furthermore, gene expression analysis revealed the expression of inflammatory cytokines IL-6 and IL-10, and enzyme arginase-1 was significantly downregulated at 12 h post-injury. Time course evaluation of migration, using a cell exclusion zone assay, showed stretch-injured cells display decreased migration into the exclusion zone at 48- and 72-h post-stretch. Lastly, coinciding with the functional immune deficits was a significant change in morphology, with process length decreasing and cell diameter increasing following an injury at 12 h. Taken together, the data demonstrate that stretch-injury produces significant alterations in microglial function, which may have a marked impact on their response to injury or their interaction with other cells.

Genetic Factors That Could Affect Concussion Risk in Elite Rugby

Elite rugby league and union have some of the highest reported rates of concussion (mild traumatic brain injury) in professional sport due in part to their full-contact high-velocity collision-based nature. Currently, concussions are the most commonly reported match injury during the tackle for both the ball carrier and the tackler (8-28 concussions per 1000 player match hours) and reports exist of reduced cognitive function and long-term health consequences that can end a playing career and produce continued ill health. Concussion is a complex phenotype, influenced by environmental factors and an individual's genetic predisposition. This article reviews concussion incidence within elite rugby and addresses the biomechanics and pathophysiology of concussion and how genetic predisposition may influence incidence, severity and outcome. Associations have been reported between a variety of genetic variants and traumatic brain injury. However, little effort has been devoted to the study of genetic associations with concussion within elite rugby players. Due to a growing understanding of the molecular characteristics underpinning the pathophysiology of concussion, investigating genetic variation within elite rugby is a viable and worthy proposition. Therefore, we propose from this review that several genetic variants within or near candidate genes of interest, namely APOE, MAPT, IL6R, COMT, SLC6A4, 5-HTTLPR, DRD2, DRD4, ANKK1, BDNF and GRIN2A, warrant further study within elite rugby and other sports involving high-velocity collisions.

Sodium Butyrate and Indole-3-propionic Acid Prevent the Increase of Cytokines and Kynurenine Levels in LPS-induced Human Primary Astrocytes

The crosstalk between central nervous system (CNS) and gut microbiota plays key roles in neuroinflammation and chronic immune activation that are common features of all neurodegenerative diseases. Imbalance in the microbiota can lead to an increase in the intestinal permeability allowing toxins to diffuse and reach the CNS, as well as impairing the production of neuroprotective metabolites such as sodium butyrate (SB) and indole-3-propionic acid (IPA). The aim of the present study was to evaluate the effect of SB and IPA on LPS-induced production of cytokines and tryptophan metabolites in human astrocytes. Primary cultures of human astrocytes were pre-incubated with SB or IPA for 1 hour before treatment with LPS. Cell viability was not affected at 24, 48 or 72 hours after pre-treatment with SB, IPA or LPS treatment. SB was able to significantly prevent the increase of GM-CSF, MCP-1, IL-6 IL-12, and IL-13 triggered by LPS. SB and IPA also prevented inflammation indicated by the increase in kynurenine and kynurenine/tryptophan ratio induced by LPS treatment. IPA pre-treatment prevented the LPS-induced increase in MCP-1, IL-12, IL-13, and TNF-α levels 24 hours after pre-treatment, but had no effect on tryptophan metabolites. The present study showed for the first time that bacterial metabolites SB and IPA have potential anti-inflammatory effect on primary human astrocytes with potential therapeutic benefit in neurodegenerative disease characterized by the presence of chronic low-grade inflammation.

Modeling of post-traumatic epilepsy and experimental research aimed at its prevention

Research on the prevention of post-traumatic epilepsy (PTE) has seen remarkable advances regarding its physiopathology in recent years. From the search for biomarkers that might be used to indicate individual susceptibility to the development of new animal models and the investigation of new drugs, a great deal of knowledge has been amassed. Various groups have concentrated efforts in generating new animal models of traumatic brain injury (TBI) in an attempt to provide the means to further produce knowledge on the subject. Here we forward the hypothesis that restricting the search of biomarkers and of new drugs to prevent PTE by using only a limited set of TBI models might hamper the understanding of this relevant and yet not preventable medical condition.

Sensorimotor dysfunction in a mild mouse model of cortical contusion injury without significant neuronal loss is associated with increases in inflammatory proteins with innate but not adaptive immune functions

Traumatic brain injury is a leading cause of mortality and morbidity in the United States. Acute trauma to the brain triggers chronic secondary injury mechanisms that contribute to long-term neurological impairment. We have developed a single, unilateral contusion injury model of sensorimotor dysfunction in adult mice. By targeting a topographically defined neurological circuit with a mild impact, we are able to track sustained behavioral deficits in sensorimotor function in the absence of tissue cavitation or neuronal loss in the contused cortex of these mice. Stereological histopathology and multiplex enzyme-linked immunosorbent assay proteomic screening confirm contusion resulted in chronic gliosis and the robust expression of innate immune cytokines and monocyte attractant chemokines IL-1β, IL-5, IL-6, TNFα, CXCL1, CXCL2, CXCL10, CCL2, and CCL3 in the contused cortex. In contrast, the expression of neuroinflammatory proteins with adaptive immune functions was not significantly modulated by injury. Our data support widespread activation of innate but not adaptive immune responses, confirming an association between sensorimotor dysfunction with innate immune activation in the absence of tissue or neuronal loss in our mice.

Neuroinflammation evoked by brain injury in a rat model of lacunar infarct

Stroke is the leading cause of long-term, severe disability worldwide. Immediately after the stroke, endogenous inflammatory processes are upregulated, leading to the local neuroinflammation and the potentiation of brain tissue destruction. The innate immune response is triggered as early as 24 h post-brain ischemia, followed by adaptive immunity activation. Together these immune cells produce many inflammatory mediators, i.e., cytokines, growth factors, and chemokines. Our study examines the immune response components in the early stage of deep brain lacunar infarct in the rat brain, highly relevant to the clinical scenario. The lesion was induced by stereotactic injection of ouabain into the adult rat striatum. Ouabain is a Na/K ATPase pump inhibitor that causes excitotoxicity and brings metabolic and structural changes in the cells leading to focal brain injury. We have shown a surge of neurodegenerative changes in the peri-infarct area in the first days after brain injury. Immunohistochemical analysis revealed early microglial activation and the gradual infiltration of immune cells with a significant increase of CD4⁺ and CD8⁺ T lymphocytes in the ipsilateral hemisphere. In our studies, we identified the higher level of pro-inflammatory cytokines, i.e., interleukin-1α, interleukin-1β, tumor necrosis factor-α, and interferon-γ, but a lower level of anti-inflammatory cytokines, i.e., interleukin-10 and transforming growth factor-β2 in the injured brain than in normal rats. Concomitantly focal brain injury showed a significant increase in the level of chemokines, i.e., monocyte chemoattractant protein-1 and CC motif chemokine ligand 5 compared to control. Our findings provide new insights into an early inflammatory reaction in our model of the deep-brain lacunar infarct. The results of this study may highlight future stroke immunotherapies for targeting the acute immune response accompanied by the insult.

APOE4 genetic polymorphism results in impaired recovery in a repeated mild traumatic brain injury model and treatment with Bryostatin-1 improves outcomes

After traumatic brain injury (TBI), some people have worse recovery than others. Single nucleotide polymorphisms (SNPs) in Apolipoprotein E (APOE) are known to increase risk for developing Alzheimer’s disease, however there is controversy from human and rodent studies as to whether ApoE4 is a risk factor for worse outcomes after brain trauma. To resolve these conflicting studies we have explored the effect of the human APOE4 gene in a reproducible mouse model that mimics common human injuries. We have investigated cellular and behavioral outcomes in genetically engineered human APOE targeted replacement (TR) mice following repeated mild TBI (rmTBI) using a lateral fluid percussion injury model. Relative to injured APOE3 TR mice, injured APOE4 TR mice had more inflammation, neurodegeneration, apoptosis, p-tau, and activated microglia and less total brain-derived neurotrophic factor (BDNF) in the cortex and/or hippocampus at 1 and/or 21 days post-injury. We utilized a novel personalized approach to treating APOE4 susceptible mice by administering Bryostatin-1, which improved cellular as well as motor and cognitive behavior outcomes at 1 DPI in the APOE4 injured mice. This study demonstrates that APOE4 is a risk factor for poor outcomes after rmTBI and highlights how personalized therapeutics can be a powerful treatment option.

Cellular infiltration in traumatic brain injury

Traumatic brain injury leads to cellular damage which in turn results in the rapid release of damage-associated molecular patterns (DAMPs) that prompt resident cells to release cytokines and chemokines. These in turn rapidly recruit neutrophils, which assist in limiting the spread of injury and removing cellular debris. Microglia continuously survey the CNS (central nervous system) compartment and identify structural abnormalities in neurons contributing to the response. After some days, when neutrophil numbers start to decline, activated microglia and astrocytes assemble at the injury site—segregating injured tissue from healthy tissue and facilitating restorative processes. Monocytes infiltrate the injury site to produce chemokines that recruit astrocytes which successively extend their processes towards monocytes during the recovery phase. In this fashion, monocytes infiltration serves to help repair the injured brain. Neurons and astrocytes also moderate brain inflammation via downregulation of cytotoxic inflammation. Depending on the severity of the brain injury, T and B cells can also be recruited to the brain pathology sites at later time points.

Capsaicin-sensitive fibers mediate periorbital allodynia and activation of inflammatory cells after traumatic brain injury in rats: Involvement of TRPV1 channels in post-traumatic headache

Post-traumatic headache (PTH) is a condition that frequently affects individuals after traumatic brain injury (TBI). Inflammation is one of the major causes of this disability. However, little is known about the trigger for, and endurance of, this painful process. Thus, the involvement of fibers containing the transient receptor potential vanilloid 1 (TRPV1) channels on the PTH and inflammation after TBI through neonatal treatment with capsaicin are investigated. Fluid percussion injury (FPI) in adult male Wistar rats caused periorbital allodynia in one, three and seven days after injury, and the neonatal treatment reversed the painful sensation in seven days. The lack of TRPV1 channels reduced the activation of macrophages and glial cells induced by TBI in the trigeminal system, which were characterized by glial fibrillary acidic protein (GFAP) and ionized calcium binding adapter molecule-1 (IBA-1) immune content in the ipsilateral trigeminal ganglion, brainstem, and perilesional cortex. Immunofluorescence analyses of the ipsilateral Sp5C nucleus demonstrated a hypertrophic astrocytes profile after TBI which was reduced with treatment. Moreover, effects of succinate sumatriptan (SUMA - 1 mg/kg), TRPV1 selective antagonist capsazepine (CPZ - 2 mg/kg), and TRP non-selective antagonist ruthenium red (RR - 3 mg/kg) were evaluated. Although all mentioned drugs reduced the painful sensation, SUMA and CPZ demonstrated a stronger effect compared to the RR treatment, reinforcing the involvement of TRPV1 channels in periorbital allodynia after TBI. Hence, this report suggests that TRPV1-containing fibers and TRPV1 channels are able to induce inflammation of the trigeminal system and maintain the painful sensation after TBI.

Revisiting Traumatic Brain Injury: From Molecular Mechanisms to Therapeutic Interventions

Studying the complex molecular mechanisms involved in traumatic brain injury (TBI) is crucial for developing new therapies for TBI. Current treatments for TBI are primarily focused on patient stabilization and symptom mitigation. However, the field lacks defined therapies to prevent cell death, oxidative stress, and inflammatory cascades which lead to chronic pathology. Little can be done to treat the mechanical damage that occurs during the primary insult of a TBI; however, secondary injury mechanisms, such as inflammation, blood-brain barrier (BBB) breakdown, edema formation, excitotoxicity, oxidative stress, and cell death, can be targeted by therapeutic interventions. Elucidating the many mechanisms underlying secondary injury and studying targets of neuroprotective therapeutic agents is critical for developing new treatments. Therefore, we present a review on the molecular events following TBI from inflammation to programmed cell death and discuss current research and the latest therapeutic strategies to help understand TBI-mediated secondary injury.

Neuroinflammation after SCI: Current Insights and Therapeutic Potential of Intravenous Immunoglobulin

Traumatic spinal cord injury (SCI) elicits a complex cascade of cellular and molecular inflammatory events. Although certain aspects of the inflammatory response are essential to wound healing and repair, post-SCI inflammation is, on balance, thought to be detrimental to recovery by causing "bystander damage" and the spread of pathology into spared but vulnerable regions of the spinal cord. Much of the research to date has therefore focused on understanding the inflammatory drivers of secondary tissue loss after SCI, to define therapeutic targets and positively modulate this response. Numerous experimental studies have demonstrated that modulation of the inflammatory response to SCI can indeed lead to significant neuroprotection and improved recovery. However, it is now also recognized that broadscale immunosuppression is not necessarily beneficial and may even carry the risk of contributing to the development of serious adverse events. Immune modulation rather than suppression is therefore now considered a more promising approach to target harmful post-traumatic inflammation following a major neurotraumatic event such as SCI. One promising immunomodulatory agent is intravenous immunoglobulin (IVIG), a plasma product that contains mostly immunoglobulin G (IgG) from thousands of healthy donors. IVIG is currently already widely used to treat a range of autoimmune diseases, but recent studies have found that it also holds great promise for treating acute neurological conditions, including SCI. This review provides an overview of the inflammatory response to SCI, immunomodulatory approaches that are currently in clinical trials, proposed mechanisms of action for IVIG therapy, and the putative relevance of these in the context of neurotraumatic events.

The Mitochondria-Associated ER Membranes Are Novel Subcellular Locations Enriched for Inflammatory-Responsive MicroRNAs

The mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are specific ER domains that contact the mitochondria and function to facilitate communication between ER and mitochondria. Disruption of contact between the mitochondria and ER is associated with a variety of pathophysiological conditions including neurodegenerative diseases. Considering the many cellular functions of MAMs, we hypothesized that MAMs play an important role in regulating microRNA (miRNA) activity linked to its unique location between mitochondria and ER. Here we present new findings from human and rat brains indicating that the MAMs are subcellular sites enriched for specific miRNAs. We employed subcellular fractionation and TaqMan® RT-qPCR miRNA analysis to quantify miRNA levels in subcellular fractions isolated from male rat brains and six human brain samples. We found that MAMs contain a substantial number of miRNAs and the profile differs significantly from that of cytosolic, mitochondria, or ER. Interestingly, MAMs are particularly enriched in inflammatory-responsive miRNAs, including miR-146a, miR-142-3p, and miR-142-5p in both human and rat brains; miR-223 MAM enrichment was observed only in human brain samples. Further, mitochondrial uncoupling or traumatic brain injury in male rats resulted in the alteration of inflammatory miRNA enrichment in the isolated subcellular fractions. These observations demonstrate that miRNAs are distributed differentially in organelles and may re-distribute between organelles and the cytosol in response to cellular stress and metabolic demands.

Cosyntropin Attenuates Neuroinflammation in a Mouse Model of Traumatic Brain Injury

Aim: Traumatic brain injury (TBI) is a leading cause of mortality/morbidity and is associated with chronic neuroinflammation. Melanocortin receptor agonists including adrenocorticotropic hormone (ACTH) ameliorate inflammation and provide a novel therapeutic approach. We examined the effect of long-acting cosyntropin (CoSyn), a synthetic ACTH analog, on the early inflammatory response and functional outcome following experimental TBI.

Methods: The controlled cortical impact model was used to induce TBI in mice. Mice were assigned to injury and treatment protocols resulting in four experimental groups including sham + saline, sham + CoSyn, TBI + saline, and TBI + CoSyn. Treatment was administered subcutaneously 3 h post-injury and daily injections were given for up to 7 days post-injury. The early inflammatory response was evaluated at 3 days post-injury through the evaluation of cytokine expression (IL1β and TNFα) and immune cell response. Quantification of immune cell response included cell counts of microglia/macrophages (Iba1+ cells) and neutrophils (MPO+ cells) in the cortex and hippocampus. Behavioral testing (n = 10–14 animals/group) included open field (OF) and novel object recognition (NOR) during the first week following injury and Morris water maze (MWM) at 10–15 days post-injury.

Results: Immune cell quantification showed decreased accumulation of Iba1+ cells in the perilesional cortex and CA1 region of the hippocampus for CoSyn-treated TBI animals compared to saline-treated. Reduced numbers of MPO+ cells were also found in the perilesional cortex and hippocampus in CoSyn treated TBI mice compared to their saline-treated counterparts. Furthermore, CoSyn treatment reduced IL1β expression in the cortex of TBI mice. Behavioral testing showed a treatment effect of CoSyn for NOR with CoSyn increasing the discrimination ratio in both TBI and Sham groups, indicating increased memory performance. CoSyn also decreased latency to find platform during the early training period of the MWM when comparing CoSyn to saline-treated TBI mice suggesting moderate improvements in spatial memory following CoSyn treatment.

Conclusion: Reduced microglia/macrophage accumulation and neutrophil infiltration in conjunction with moderate improvements in spatial learning in our CoSyn treated TBI mice suggests a beneficial anti-inflammatory effect of CoSyn following TBI.

Evaluation of M2-like macrophage enrichment after diffuse traumatic brain injury through transient interleukin-4 expression from engineered mesenchymal stromal cells

BACKGROUND

Appropriately modulating inflammation after traumatic brain injury (TBI) may prevent disabilities for the millions of those inflicted annually. In TBI, cellular mediators of inflammation, including macrophages and microglia, possess a range of phenotypes relevant for an immunomodulatory therapeutic approach. It is thought that early phenotypic modulation of these cells will have a cascading healing effect. In fact, an anti-inflammatory, "M2-like" macrophage phenotype after TBI has been associated with neurogenesis, axonal regeneration, and improved white matter integrity (WMI). There already exist clinical trials seeking an M2-like bias through mesenchymal stem/stromal cells (MSCs). However, MSCs do not endogenously synthesize key signals that induce robust M2-like phenotypes such as interleukin-4 (IL-4).

METHODS

To enrich M2-like macrophages in a clinically relevant manner, we augmented MSCs with synthetic IL-4 mRNA to transiently express IL-4. These IL-4 expressing MSCs (IL-4 MSCs) were characterized for expression and functionality and then delivered in a modified mouse TBI model of closed head injury. Groups were assessed for functional deficits and MR imaging. Brain tissue was analyzed through flow cytometry, multi-plex ELISA, qPCR, histology, and RNA sequencing.

RESULTS

We observed that IL-4 MSCs indeed induce a robust M2-like macrophage phenotype and promote anti-inflammatory gene expression after TBI. However, here we demonstrate that acute enrichment of M2-like macrophages did not translate to improved functional or histological outcomes, or improvements in WMI on MR imaging. To further understand whether dysfunctional pathways underlie the lack of therapeutic effect, we report transcriptomic analysis of injured and treated brains. Through this, we discovered that inflammation persists despite acute enrichment of M2-like macrophages in the brain.

CONCLUSION

The results demonstrate that MSCs can be engineered to induce a stronger M2-like macrophage response in vivo. However, they also suggest that acute enrichment of only M2-like macrophages after diffuse TBI cannot orchestrate neurogenesis, axonal regeneration, or improve WMI. Here, we also discuss our modified TBI model and methods to assess severity, behavioral studies, and propose that IL-4 expressing MSCs may also have relevance in other cavitary diseases or in improving biomaterial integration into tissues.

IL-13 Ameliorates Neuroinflammation and Promotes Functional Recovery after Traumatic Brain Injury

Microglia play essential roles in neuroinflammatory responses after traumatic brain injury (TBI). Our previous studies showed that phenotypes of microglia, as well as infiltrating macrophages, altered at different stages after CNS injury, which was correlated to functional outcomes. IL-13 is an anti-inflammatory cytokine that has been reported to protect against demyelination and spinal cord injury through immunomodulation. The effects of IL-13 in microglia/macrophage-mediated immune responses after TBI remain unknown. In this study, we showed that intranasal administration of IL-13 in male C57BL/6J mice accelerated functional recovery in the controlled cortical impact model of TBI. IL-13 treatment increased the time to fall off in the Rotarod test, reduced the number of foot faults in the foot fault test, and improved the score in the wire hang test up to 28 d after TBI. Consistent with functional improvement, IL-13 reduced neuronal tissue loss and preserved white matter integrity 6 d after TBI. Furthermore, IL-13 ameliorated the elevation of proinflammatory factors and reduced the number of proinflammatory microglia/macrophages 6 d after TBI. Additionally, IL-13 enhanced microglia/macrophage phagocytosis of damaged neurons in the peri-lesion areas. In vitro studies confirmed that IL-13 treatment inhibited the production of proinflammatory cytokines in rat primary microglia in response to LPS or dead neuron stimulation and increased the ability of microglia to engulf fluorophore-labeled latex beads or dead neurons. Collectively, we demonstrated that IL-13 treatment improved neurologic outcomes after TBI through adjusting microglia/macrophage phenotypes and inhibiting inflammatory responses. IL-13 may represent a potential immunotherapy to promote long-term recovery from TBI.

PKC Mediates LPS-Induced IL-1β Expression and Participates in the Pro-inflammatory Effect of A2AR Under High Glutamate Concentrations in Mouse Microglia

Pathogens such as bacterial lipopolysaccharide (LPS) play an important role in promoting the production of the inflammatory cytokines interleukin-1 beta (IL-1β) and tumour necrosis factor-α (TNF-α) in response to infection or damage in microglia. However, whether different signalling pathways regulate these two inflammatory factors remains unclear. The protein kinase C (PKC) family is involved in the regulation of inflammation, and our previous research showed that the activation of the PKC pathway played a key role in the LPS-induced transformation of the adenosine A_2A receptor (A_2AR) from anti-inflammatory activity to pro-inflammatory activity under high glutamate concentrations. Therefore, in the current study, we investigated the role of PKC in the LPS-induced production of these inflammatory cytokines in mouse primary microglia. GF109203X, a specific PKC inhibitor, inhibited the LPS-induced expression of IL-1β messenger ribonucleic acid and intracellular protein in a dose-dependent manner. Moreover, 5 µM GF109203X prevented LPS-induced IL-1β expression but did not significantly affect LPS-induced TNF-α expression. PKC promoted IL-1β expression by regulating the activity of NF-κB but did not significantly impact the activity of ERK1/2. A_2AR activation by CGS21680, an A_2AR agonist, facilitated LPS-induced IL-1β expression through the PKC pathway at high glutamate concentrations but did not significantly affect LPS-induced TNF-α expression. Taken together, these results suggest a new direction for specific intervention with LPS-induced inflammatory factors in response to specific signalling pathways and provide a mechanism for A_2AR targeting, especially after brain injury, to influence inflammation by interfering with A_2AR.

CCL20-CCR6 axis modulated traumatic brain injury-induced visual pathologies

BACKGROUND

Traumatic brain injury (TBI) is a major cause of death and disability in the USA and the world; it constitutes 30% of injury-related deaths (Taylor et al., MMWR Surveill Summ 66:1-16, 2017). Contact sports athletes often experience repetitive TBI (rTBI), which exerts a cumulative effect later in life. Visual impairment is a common after-effect of TBI. Previously, we have shown that C-C chemokine 20 (CCL20) plays a critical role in neurodegeneration and inflammation following TBI (Das et al., J Neuroinflammation 8:148, 2011). C-C chemokine receptor 6 (CCR6) is the only receptor that CCL20 interacts with. The objective of the present study was to investigate the role of CCL20-CCR6 axis in mediating rTBI-induced visual dysfunction (TVD).

METHODS

Wild type (WT) or CCR6 knock out (CCR6-/-) mice were subjected to closed head rTBI. Pioglitazone (PG) is a peroxisome proliferator-activated receptor γ (PPARγ) agonist which downregulates CCL20 production. Subsets of WT mice were treated with PG following final rTBI. A subset of mice was also treated with anti-CCL20 antibody to neutralize the CCL20 produced after rTBI. Histopathological assessments were performed to show cerebral pathologies, retinal pathologies, and inflammatory changes induced by rTBI.

RESULTS

rTBI induced cerebral neurodegeneration, retinal degeneration, microgliosis, astrogliosis, and CCL20 expression. CCR6-/- mice showed reduced retinal degeneration, microgliosis, and inflammation. Treatment with CCL20 neutralization antibody or PG showed reduced CCL20 expression along with reduced retinal degeneration and inflammation. rTBI-induced GFAP-positive glial activation in the optic nerve was not affected by knocking out CCR6.

CONCLUSION

The present data indicate that rTBI-induced retinal pathology is mediated at least in part by CCL20 in a CCR6-dependent manner.