Treatment of traumatic brain injury with anti-inflammatory drugs

The H4R antagonist, JNJ-7777120 treatments ameliorate mild traumatic brain injury by reducing oxidative damage, inflammatory and apoptotic responses through blockage of the ERK1/2/NF-κB pathway in a rat model

Growing evidence reveals that microglia activation and neuroinflammatory responses trigger cell loss in the brain. Histamine is a critical neurotransmitter and promotes inflammatory responses; thus, the histaminergic system is a potential target for treating neurodegenerative processes. JNJ-7777120, a histamine H4 receptor (H4R) antagonist, has been shown to alleviate inflammation, brain damage, and behavioral deficits effectively, but there is no report on its role in brain trauma. Herein, we investigated the neuroprotective effects of JNJ-7777120 (shortly JNJ) in a mild traumatic brain injury (mTBI). mTBI setup was performed using a weight-drop model in adult male Sprague-Dawley rats. JNJ (1 mg/kg, twice/day for 7 days) was intraperitoneally administered following mTBI. Modified neurological severity score and beam-walking test used to assess motor, sensory, reflex, and balance functions (post-TBI days-1/3/7) showed that JNJ had significantly improved these functions. HE-staining revealed reduced neurodegenerative cells after JNJ-treatments compared to vehicle (2.85 % DMSO) treated group. JNJ also decreased the injury-induced apoptosis (Bax/Bcl-2, cleaved-Cas-3, cleaved-PARP1), oxidative (4HNE, MDA), and inflammatory (IBA1, TNF-α, IL-1β, IL-6, and IL-10) responses. Furthermore, blocking the activation of the ERK1/2/NF-κB pathway was determined to be involved in its therapeutic mechanism. The network pharmacology analyses for JNJ-7777120 and TBI confirmed the importance of targeting neurotransmitter receptor activity, signaling receptor activity, and kinase activation. Our results provide the first proof of the efficacy of an H4R antagonist in a mild TBI rat model and suggest that H4R targeting by JNJ-treatment might be a promising therapeutic approach to clinically halt the progression of brain injury.

Partially hydrolyzed guar gum alleviates neurological deficits and gastrointestinal dysfunction in mice with traumatic brain injury

Traumatic brain injury (TBI)-associated neuroinflammation and neurotoxicity can induce gastrointestinal dysfunction through the brain-gut axis. Partially hydrolyzed guar gum (PHGG) was demonstrated to exert beneficial health effects by altering gut microbiota and short-chain fatty acids (SCFAs) production. Our study aimed to explore the effects of PHGG on gastrointestinal dysfunction in TBI mouse models. Controlled cortical impact (CCI)-induced TBI mouse models were administrated with PHGG (600 mg/kg/d) for 21 consecutive days. Behavioral tests (modified neurological severity score and beam walk test) and Y‑maze assay were performed to evaluate neurological functions and cognitive impairment. Enzyme-linked immunosorbent assay, reverse transcription-quantitative polymerase chain reaction, and western blotting examined the levels of inflammatory cytokines, intestinal mucosal damage markers, intestinal tight junction proteins, and NLRP3 inflammasome-related molecules in the serum, cerebral cortex, and colon tissues. The histological changes in the cerebral cortex and colon tissues were observed through hematoxylin and eosin and Nissl staining. Liquid chromatography/mass spectrometry analyzed SCFA amounts in the cecum contents and bile acid levels in the serum. PHGG administration alleviated neurological deficits and cognitive perturbations, reduced neuroinflammation, and attenuated cortical tissue damage and neuron loss in TBI mice. PHGG ameliorated intestinal barrier impairment, upregulated intestinal production of SCFAs, and elevated serum bile acid levels in TBI mice. Besides, PHGG treatment repressed NLRP3 inflammasome activation in TBI mice. Overexpressing NLRP3 reversed the beneficial effects of PHGG against TBI in mice. PHGG ameliorates neuroinflammation and gastrointestinal dysfunction in TBI murine models by inhibiting NLRP3 inflammasome activation.

Neuroprotective and neuroregenerative drugs after severe traumatic brain injury : A narrative review from a clinical perspective

Traumatic brain injuries cause enormous individual and socioeconomic burdens. Survivors frequently struggle with motor handicaps as well as impaired cognition and emotion. In addition to the primary mechanical brain damage, complex secondary mechanisms are the main drivers of functional impairment. Many of these pathophysiological mechanisms are now well known: excitotoxic amino acids, breakdown of the blood-brain barrier, neuroinflammation with subsequent damage to cell organelles and membranes, cerebral edema, and apoptotic processes triggering neuronal death; however, paracrine resilience factors may counteract these processes. Specific neuroprotective and neuroregenerative intensive care therapies are few. This review highlights medical approaches aimed at mitigating secondary damage and promoting neurotrophic processes in severe traumatic brain injury. Some pharmacologic attempts that appeared very promising in experimental settings have had disappointing clinical results (progesterone, cyclosporine A, ronopterin, erythropoietin, dexanabinol). Thus, the search for drugs that can effectively limit ongoing posttraumatic neurological damage is ongoing. Some medications appear to be beneficial: N‑methyl-D-aspartate receptor (NMDA) antagonists (esketamine, amantadine, Mg++) reduce excitotoxicity and statins and cerebrolysin are known to counteract neuroinflammation. By supporting the impaired mitochondrial energy supply, oxidative processes are inhibited and neuroregenerative processes, such as neurogenesis, angiogenesis and synaptogenesis are promoted by citicoline and cerebrolysin. First clinical evidence shows an improvement in cognitive and thymopsychic outcomes, underlined by own clinical experience combining different therapeutic approaches. Accordingly, adjuvant treatment with neuroprotective substances appears to be a promising option, although more randomized prospective studies are still needed.

Microglial depletion rescues spatial memory impairment caused by LPS administration in adult mice

Recent studies have highlighted the importance of microglia, the resident macrophages in the brain, in regulating cognitive functions such as learning and memory in both healthy and diseased states. However, there are conflicting results and the underlying mechanisms are not fully understood. In this study, we examined the effect of depleting adult microglia on spatial learning and memory under both physiological conditions and lipopolysaccharide (LPS)-induced neuroinflammation. Our results revealed that microglial depletion by PLX5622 caused mild spatial memory impairment in mice under physiological conditions; however, it prevented memory deficits induced by systemic LPS insult. Inactivating microglia through minocycline administration replicated the protective effect of microglial depletion on LPS-induced memory impairment. Furthermore, our study showed that PLX5622 treatment suppressed LPS-induced neuroinflammation, microglial activation, and synaptic dysfunction. These results strengthen the evidence for the involvement of microglial immunoactivation in LPS-induced synaptic and cognitive malfunctions. They also suggest that targeting microglia may be a potential approach to treating neuroinflammation-associated cognitive dysfunction seen in neurodegenerative diseases.

Probiotic-based therapy as a new useful strategy for the treatment of patients with traumatic brain injury

BACKGROUND

In the new era, microbial-based medicine is one of the best strategies that try to modify the normal flora with the aim of treating some disorders. This systematic review and meta-analysis was performed to evaluate the use of probiotics in the treatment of the clinical outcomes in cases with traumatic brain injury..

METHODS

In this regard, the search strategy was done using databases such as PubMed, Embase, Scopus, CENTRAL, and Google Scholar, from 2006 until April 2024. All studies about the efficacy of probiotic supplementation on the clinical outcomes in traumatic brain injury patients were retrieved. During the assessment process of the eligible studies, we evaluated clinical characteristics such as the Glasgow Coma Scale score, the Sequential Organ Failure Assessment score, the Acute Physiology and Chronic Health Evaluation II score, referral rate and hospitalization period in the intensive care unit, mortality rate, as well as opportunistic infections in both groups of case and control..

RESULTS

In this study, the authors analyzed data from 6 articles including 391 cases with traumatic brain injury. Our results showed that the probiotic therapy increases the Glasgow Coma Scale score in patients with the average age of more than 50 years. However, there was no a significant difference in the Sequential Organ Failure Assessment and the Acute Physiology and Chronic Health Evaluation scores between the group that had received probiotics and the control group. Although probiotic-based treatment did not significantly affect the intensive care unit admission (or length of stay), but, the risk of infection, and also mortality was significantly lower in the probiotic group (OR: 0.53; 95% CI: 0.3 to 0.8, as well as OR: 0.41; 95% CI: 0.2 to 0.7, respectively)..

CONCLUSIONS

Overall, due to the modification of microbial flora, probiotic supplements can balance microflora disturbances, which in turn leads to improvement the clinical outcomes in patients with brain injury. Therefore, probiotic-based therapy can be considered as a promising strategy for the treatment of the central nervous system disorders. However, given the limited evidence, more clinical trial studies need to strengthen our results..

Effects of 6-week olanzapine treatment on serum IL-2, IL-4, IL-8, IL-10, and TNF-α levels in drug-naive individuals with first-episode schizophrenia

BACKGROUND

Schizophrenia is a complex neuropsychiatric disorder. Growing evidence indicates that the activation of the inflammatory response system with interleukin (IL)-2, IL-4, IL-8, IL-10, and tumor necrosis factor-alpha (TNF-α) plays an important role in the pathogenesis of schizophrenia,. However, clinical data on cytokine levels in patients with schizophrenia treated with antipsychotics are inconsistent or inconclusive. In this study, we have examined inflammatory factors' alterations and their relationship to changes in clinical symptoms before and after olanzapine treatment of drug-naive patients with first-episode schizophrenia.

METHODS

We recruited 142 hospitalized patients with first-episode schizophrenia as a study group; blood samples were collected, and the patients were assessed for clinical symptoms at baseline and after 6 weeks of olanzapine treatment. One hundred individuals with no history of mental illness were also recruited as healthy controls. Blood samples were collected, and the serum levels of IL-2, IL-4, IL-8, IL-10, and TNF-α were determined using an enzyme cycling assay. The severity of clinical symptoms was assessed according to the Positive and Negative Syndrome Scale (PANSS).

RESULTS

Individuals with schizophrenia had lower IL-8 levels and higher IL-10 levels than healthy controls (P < 0.001). Positive correlations were detected between serum IL-2 and IL-10 concentrations and each subscale of the PANSS (all P < 0.05). Moreover, a negative correlation existed between the serum IL-8 concentration and the PANSS negative score (r = - 0.172, P = 0.040). After 6 weeks of treatment, serum IL-8 levels in the patient group were lower than at baseline (P < 0.001), whereas serum IL-10 and TNF-α levels were higher than at baseline (all P < 0.05). Therefore, serum IL-10 can be determined as an independent risk factor for outcome in patients with first-episode schizophrenia (P = 0.02, OR = 2.327). Furthermore, serum IL-2, IL-10, and TNF-α levels were significantly lower, whereas the serum IL-8 level was significantly higher (P < 0.001) in the healthy control group than in the "response" and "no-response" treatment groups respectively.

CONCLUSIONS

Our results indicate that serum IL-2, IL-8, IL-10, and TNF-α levels may be involved in the pathophysiological mechanisms of schizophrenia and correlate with the effects of olanzapine.

Perispinal etanercept stroke trial design: PESTO and beyond

INTRODUCTION

Perispinal etanercept (PSE) is an innovative treatment designed to improve stroke recovery by addressing chronic post-stroke neuroinflammation. Basic science evidence, randomized clinical trial (RCT) evidence and 14 years of favorable clinical experience support the use of PSE to treat chronic stroke. This article provides guidance for the design of future PSE RCTs in accordance with current FDA recommendations.

AREAS COVERED

Scientific background and essential elements of PSE RCT design.

EXPERT OPINION

Intimate familiarity with PSE, its novel method of drug delivery, and the characteristics of ideal enriched study populations are necessary for those designing future PSE stroke trials. The design elements needed to enable a PSE RCT to generate valid results include a suitable research question; a homogeneous study population selected using a prospective enrichment strategy; a primary outcome measure responsive to the neurological improvements that result from PSE; trialists with expertise in perispinal delivery; optimal etanercept dosing; and steps taken to minimize the number of placebo responders. RCTs failing to incorporate these elements, such as the PESTO trial, are incapable of reaching reliable conclusions regarding PSE efficacy. SF-36 has not been validated in PSE trials and is unsuitable for use as a primary outcome measure in PSE RCTs.

Investigating the Effect of High-Dose Vitamin D3 Administration on Inflammatory Biomarkers in Patients with Moderate to Severe Traumatic Brain Injury: A Randomized Clinical Trial

Background

Traumatic brain injury (TBI) is one of the most common neurological disorders worldwide. We aimed to investigate the efficacy of high-dose vitamin D3 on inflammatory biomarkers in patients with moderate to severe TBI.

Methods

Thirty-five moderate to severe TBI patients were randomly assigned to intervention and control groups. Patients in the intervention group received a single intramuscular (IM) dose of 300,000 IU vitamin D. The primary endpoints were interleukin levels (IL-1β and IL-6), and the secondary endpoints were changes in neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), Glasgow Coma scale (GCS), and Glasgow Outcome Scale-Extended (GOS-E) scores compared between intervention and control arms of the study. The linear Generalized Estimating Equations were used for trend analysis and evaluating the association of independent factors to each outcome.

Results

The results revealed a significant decrease in IL-1β levels (-2.71±3.02, in the intervention group: P=0.001 vs. -0.14±3.70, in the control group: P=0.876) and IL-6 (-88.05±148.45, in the intervention group: P=0.0001 vs. -35.54±175.79, in the control groupL P=0.325) 3 days after the intervention. The improvement in the GCS score (P=0.001), reduction in NLR (P=0.001) and PLR (P=0.002), and improvement in the GOS-E score (P=0.039) was found to be greater in the vitamin D3 arm of the study than the control group.

Conclusion

Administration of high-dose vitamin D3 in the acute phase of TBI could be effective in lowering the inflammatory markers and improving the level of consciousness and long-term performance outcomes.Trial Registration Number: IRCT20180522039777N2.

Daidzin improves neurobehavioral outcome in rat model of traumatic brain injury

Traumatic brain injury (TBI) is associated with the etiology of multiple neurological disorders, including neurodegeneration, leading to various cognitive deficits. Daidzin (obtained from kudzu root and soybean leaves) is known for its neuroprotective effects through multiple mechanisms. This study aimed to investigate the pharmacological effects of Daidzin on sensory, and biochemical parameters, cognitive functions, anxiety, and depressive-like behaviors in the TBI rat model. Rats were divided into four groups (Control, TBI, TBI + Ibuprofen (30 mg/kg), and TBI + Daidzin (5 mg/kg)). Rats were subjected to TBI by dropping a 200 g rod from a height of 26 cm, resulting in an impact force of 0.51 J on the exposed crania. Ibuprofen (30 mg/kg) was used as a positive control reference/standard drug and Daidzin (5 mg/kg) as the test drug. Neurological severity score (NSS) assessment was done to determine the intactness of sensory and motor responses. Brain tissue edema and acetylcholine levels were determined in the cortex and hippocampus. Cognitive functions such as hippocampus-dependent memory, novel object recognition, exploration, depressive and anxiety-like behaviors were measured. Treatment with Daidzin improved NSS, reduced hippocampal and cortical edema, and improved levels of acetylcholine in TBI-induced rats. Furthermore, Daidzin treatment improved hippocampus-dependent memory, exploration behavior, and novel object recognition while reducing depressive and anxiety-like behavior. Our study revealed that Daidzin has a therapeutic potential comparable to Ibuprofen and can offer neuroprotection and enhanced cognitive and behavioral outcomes in rats after TBI.

Selective COX-2 Inhibitors as Neuroprotective Agents in Traumatic Brain Injury

Traumatic brain injury (TBI) is a significant contributor to mortality and morbidity in people, both young and old. There are currently no approved therapeutic interventions for TBI. Following TBI, cyclooxygenase (COX) enzymes generate prostaglandins and reactive oxygen species that perpetuate inflammation, with COX-1 and COX-2 isoforms providing differing responses. Selective COX-2 inhibitors have shown potential as neuroprotective agents. Results from animal models of TBI suggest potential treatment through the alleviation of secondary injury mechanisms involving neuroinflammation and neuronal cell death. Additionally, early clinical trials have shown that the use of celecoxib improves patient mortality and outcomes. This review aims to summarize the therapeutic effects of COX-2 inhibitors observed in TBI animal models, highlighting pertinent studies elucidating molecular pathways and expounding upon their mechanistic actions. We then investigated the current state of evidence for the utilization of COX-2 inhibitors for TBI patients.

Individual-level analysis of MRI T2 relaxometry in mild traumatic brain injury: Possible indications of brain inflammation

Mild traumatic brain injury (mTBI), often called concussion, is a prevalent condition that can have significant implications for people's health, functioning and well-being. Current clinical practice relies on self-reported symptoms to guide decision-making regarding return to sport, employment, and education. Unfortunately, reliance on subjective evaluations may fail to accurately reflect the resolution of neuropathology, exposing individuals with mTBI to an increased risk of further head trauma. No objective technique currently exists to assess the microstructural alterations to brain tissue which characterise mTBI. MRI-based T2 relaxation is a quantitative imaging technique that is susceptible to detecting fluid properties in the brain and is hypothesised to indicate neuroinflammation. This study aimed to investigate the potential of individual-level T2 relaxometry to evaluate cellular damage from mTBI. 20 male participants with acute sports-related mTBI (within 14 days post-injury) and 44 healthy controls were recruited for this study. Each mTBI participant's voxel-wise T2 relaxometry map was analysed against healthy control averages using a voxel-wise z-test with false discovery rate correction. Five participants were re-scanned after clinical recovery and results were compared to their acute T2 relaxometry maps to assess reduction in potential neuroinflammation. T2 relaxation times were significantly increased in 19/20 (95 %) mTBI participants compared to healthy controls, in regions including the hippocampus, frontal cortex, parietal cortex, insula, cingulate cortex and cerebellum. Results suggest the presence of increased cerebral fluid in individuals with mTBI. Longitudinal results indicated a reduction in T2 relaxation for all five participants, indicating a possible resolution over time. This research highlights the potential of individual-level T2 relaxometry MRI as a non-invasive method for assessing subtle brain pathology in mTBI. Identifying and monitoring changes in the fluid content in the brain could aid in predicting recovery and developing individualised treatment plans for individuals with mTBI. Future research should validate this measure with other markers of inflammation (e.g. from blood biomarkers) to test whether T2-relaxometry is related to subtle brain inflammation in mTBI. In addition, future research should utilise larger control groups to establish normative ranges and compute robust z-score analyses.

Early Celecoxib use in Patients with Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) can cause rapid brain inflammation. There is debate over the safety and efficacy of anti-inflammatory agents in its treatment. With a particular focus on cyclooxygenase 2 (COX2) selective inhibition, we sought to determine the impact of celecoxib versus no celecoxib treatment on outcomes in patients with TBI and compare these with outcomes associated with nonselective COX inhibition (ibuprofen) and corticosteroid (dexamethasone) treatment.

METHODS

This retrospective cohort study used TriNetX, a large publicly available global health research network, to gather clinical data extracted from the electronic medical records. Using International Classification of Diseases, Tenth Revision and pharmacy codes, we identified patients with TBI who were and were not treated with celecoxib, ibuprofen, and dexamethasone. Analysis was performed on propensity-matched and unmatched cohorts, which were matched on demographics, comorbidities, and neurological injuries. Our primary end point was 1-year survival. Secondary end points were ventilator and tracheostomy dependence, gastrostomy tube placement, seizures, and craniotomy.

RESULTS

After propensity score matching, a total of 1443 patients were identified in both the celecoxib and no celecoxib cohorts. Ninety-two (6.4%) patients in the celecoxib cohort died within 1 year following TBI versus 145 (10.0%) in the no celecoxib cohort (odds ratio 0.61; 95% confidence interval 0.46-0.80; p = 0.0003). The 1-year survival rate was 96.1% in the celecoxib cohort versus 93.1% in the no celecoxib cohort (p < 0.0001). At the end of the 1-year period, celecoxib was associated with significantly lower gastrostomy tube dependence (p = 0.017), seizure activity (p = 0.027), and myocardial infarction (p = 0.021) compared with the control cohort. Ibuprofen was also associated with higher 1-year survival probability and lower rates of post-TBI complications. Dexamethasone was broadly associated with higher morbidity but was associated with higher 1-year survival probability compared with the no dexamethasone cohort.

CONCLUSIONS

Early celecoxib and ibuprofen use within 5 days post TBI was associated with higher 1-year survival probabilities and fewer complications. With emerging yet controversial preclinical evidence to suggest that COX inhibition improves TBI outcomes, this population-level study offers suggestive support for these drugs' clinical benefit, which should be pursued in prospective clinical studies.

Medication utilization in traumatic brain injury patients-insights from a population-based matched cohort study

Introduction

Traumatic brain injury (TBI) is associated with health problems across multiple domains and TBI patients are reported to have high rates of medication use. However, prior evidence is thin due to methodological limitations. Our aim was thus to examine the use of a wide spectrum of medications prescribed to address pain and somatic conditions in a population-based cohort of TBI patients, and to compare this to a sex- and age-matched cohort. We also examined how patient factors such as sex, age, and TBI severity were associated with medication use.

Methods

We assessed Swedish nationwide registers to include all individuals treated for TBI in hospitals or specialist outpatient care between 2006 and 2012. We examined dispensed prescriptions for eight different non-psychotropic medication classes for the 12 months before, and 12 months after, the TBI. We applied a fixed-effects model to compare TBI patients with the matched population cohort. We also stratified TBI patients by sex, age, TBI severity and carried out comparisons using a generalized linear model.

Results

We identified 239,425 individuals with an incident TBI and 239,425 matched individuals. TBI patients were more likely to use any medication [Odds ratio (OR) = 2.03, 95% Confidence Interval (CI) = 2.00-2.05], to present with polypharmacy (OR = 1.96, 95% CI = 1.90-2.02), and to use each of the eight medication classes before their TBI, as compared to the matched population cohort. Following the TBI, TBI patients were more likely to use any medication (OR = 1.83, 95% CI = 1.80-1.86), to present with polypharmacy (OR = 1.74, 95% CI = 1.67-1.80), and to use all medication classes, although differences were attenuated. However, differences increased for antibiotics/antivirals (OR = 2.02, 95% CI = 1.99-2.05) and NSAIDs/antirheumatics (OR = 1.62, 95% CI = 1.59-1.65) post-TBI. We also found that females and older patients were more likely to use medications after their TBI than males and younger patients, respectively. Patients with more severe TBIs demonstrated increased use of antibiotics/ antivirals and NSAIDs/antirheumatics than those with less severe TBIs.

Discussion

Taken together, our results point to poor overall health in TBI patients, suggesting that medical follow-up should be routine, particularly in females with TBI, and include a review of medication use to address potential polypharmacy.

Trends and hotspots in research of traumatic brain injury from 2000 to 2022: A bibliometric study

Traumatic brain injury (TBI) is a major health concern globally, which is characterized by high morbidity and mortality rates. Since the 21st century, TBI has received increasing attention and the number of publications is growing rapidly. This study aimed to characterize the volume and quality of scholarly output on TBI and identify the most impactful literature, research trends, and hotspots from the year 2000-2022. We searched publications on TBI through the Web of Science Core Collection-Science Citation Index Expanded database which were published from 2000 to 2022. Basic information of each paper, including publication year, countries, authors, affiliations, journal, fundings, subject areas, and keywords were collected for further analysis by using Microsoft Excel, VOSviewer, and CiteSpace software. A total of 47231 TBI-related publications were identified through database retrieval. The annual number of publications on TBI has increased steadily over the past twenty years and the number in the year 2022 is sevenfold higher than that in 2000. The United States of America (USA) was the leading country in both numbers of publications and citations, which is consistent with the finding that it had the most funding agencies. Menon DK was the author with the highest influence and the University of California System was the most productive affiliation. Moreover, keywords analysis suggested that the research topics can be mainly divided into six categories: management, rehabilitation, mechanisms, concussion, neuroimaging, and neuroendocrine. This study visualized the trends and focuses of scientific research related to TBI, both quantitatively and qualitatively. The USA had a relatively high academic impact owing to its productive experts and institutions in this field. Neuroinflammation, machine learning, tranexamic acid, and extracellular vesicles are currently hot topics in the field of TBI.

Navigating the Complexities of Traumatic Encephalopathy Syndrome (TES): Current State and Future Challenges

Chronic traumatic encephalopathy (CTE) is a unique neurodegenerative disease that is associated with repetitive head impacts (RHI) in both civilian and military settings. In 2014, the research criteria for the clinical manifestation of CTE, traumatic encephalopathy syndrome (TES), were proposed to improve the clinical identification and understanding of the complex neuropathological phenomena underlying CTE. This review provides a comprehensive overview of the current understanding of the neuropathological and clinical features of CTE, proposed biomarkers of traumatic brain injury (TBI) in both research and clinical settings, and a range of treatments based on previous preclinical and clinical research studies. Due to the heterogeneity of TBI, there is no universally agreed-upon serum, CSF, or neuroimaging marker for its diagnosis. However, as our understanding of this complex disease continues to evolve, it is likely that there will be more robust, early diagnostic methods and effective clinical treatments. This is especially important given the increasing evidence of a correlation between TBI and neurodegenerative conditions, such as Alzheimer's disease and CTE. As public awareness of these conditions grows, it is imperative to prioritize both basic and clinical research, as well as the implementation of necessary safe and preventative measures.

Astrogliosis marker 11C-SL25.1188 PET in traumatic brain injury with persistent symptoms

Traumatic brain injury (TBI) is common but little is known why up to a third of patients have persisting symptoms. Astrogliosis, a pathophysiological response to brain injury, may be a potential therapeutic target, but demonstration of astrogliosis in the brain of humans with TBI and persistent symptoms is lacking. Astroglial marker monoamine oxidase B (MAO-B) total distribution volume (11C-SL25.1188 VT), an index of MAO-B density, was measured in 29 TBI and 29 similarly aged healthy control cases with 11C-SL25.1188 PET, prioritizing prefrontal cortex (PFC) and cortex proximal to cortical convexity. Correlations of PFC 11C-SL25.1188 VT with psychomotor and processing speed; and serum blood measures implicated in astrogliosis were determined. 11C-SL25.1188 VT was greater in TBI in PFC (P = 0.00064) and cortex (P = 0.00038). PFC 11C-SL25.1188 VT inversely correlated with Comprehensive Trail Making Test psychomotor and processing speed (r = -0.48, P = 0.01). In participants scanned within 2 years of last TBI, PFC 11C-SL25.1188 VT correlated with serum glial fibrillary acid protein (r = 0.51, P = 0.037) and total tau (r = 0.74, P = 0.001). Elevated 11C-SL25.1188 VT argues strongly for astrogliosis and therapeutics modifying astrogliosis towards curative phenotypes should be tested in TBI with persistent symptoms. Given substantive effect size, astrogliosis PET markers should be applied to stratify cases and/or assess target engagement for putative therapeutics targeting astrogliosis.

The multifaceted roles of activating transcription factor 3 (ATF3) in inflammatory responses - Potential target to regulate neuroinflammation in acute brain injury

Activating transcription factor 3 (ATF3) is one of the most important transcription factors that respond to and exert dual effects on inflammatory responses. Recently, the involvement of ATF3 in the neuroinflammatory response to acute brain injury (ABI) has been highlighted. It functions by regulating neuroimmune activation and the production of neuroinflammatory mediators. Notably, recent clinical evidence suggests that ATF3 may serve as a potential ideal biomarker of the long-term prognosis of ABI patients. This mini-review describes the essential inflammation modulatory roles of ATF3 in different disease contexts and summarizes the regulatory mechanisms of ATF3 in the ABI-induced neuroinflammation.

Treating Traumatic Brain Injury with Minocycline

Traumatic brain injury (TBI) results in both rapid and delayed brain damage. The speed, complexity, and persistence of TBI present large obstacles to drug development. Preclinical studies from multiple laboratories have tested the FDA-approved anti-microbial drug minocycline (MINO) to treat traumatic brain injury. At concentrations greater than needed for anti-microbial action, MINO readily inhibits microglial activation. MINO has additional pleotropic effects including anti-inflammatory, anti-oxidant, and anti-apoptotic activities. MINO inhibits multiple proteins that promote brain injury including metalloproteases, caspases, calpain, and polyADP-ribose-polymerase-1. At these elevated doses, MINO is well tolerated and enters the brain even when the blood-brain barrier is intact. Most preclinical studies with a first dose of MINO at less than 1 h after injury have shown improved multiple outcomes after TBI. Fewer studies with more delayed dosing have yielded similar results. A small number of clinical trials for TBI have established the safety of MINO and suggested some drug efficacy. Studies are also ongoing that either improve MINO pharmacology or combine MINO with other drugs to increase its therapeutic efficacy against TBI. This review builds upon a previous, recent review by some of the authors (Lawless and Bergold, Neural Regen Res 17:2589-92, 2022). The present review includes the additional preclinical studies examining the efficacy of minocycline in preclinical TBI models. This review also includes recommendations for a clinical trial to test MINO to treat TBI.

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.

Colony-Stimulating Factor-1 Receptor Inhibition Transiently Attenuated the Peripheral Immune Response to Experimental Traumatic Brain Injury

To investigate microglial mechanisms in central and peripheral inflammation after experimental traumatic brain injury (TBI), we inhibited the colony-stimulating factor-1 receptor (CSF-1R) with PLX5622 (PLX). We hypothesized that microglia depletion would attenuate central inflammation acutely with no effect on peripheral inflammation. After randomization, male mice (n = 105) were fed PLX or control diets (21 days) and then received midline fluid percussion injury or sham injury. Brain and blood were collected at 1, 3, or 7 days post-injury (DPI). Immune cell populations were quantified in the brain and blood by flow cytometry. Cytokines (interleukin [IL]-6, IL-1β, tumor necrosis factor-α, interferon-γ, IL-17A, and IL-10) were quantified in the blood using a multi-plex enzyme-linked immunosorbent assay. Data were analyzed using Bayesian multi-variate, multi-level models. PLX depleted microglia at all time points and reduced neutrophils in the brain at 7 DPI. PLX also depleted CD115+ monocytes, reduced myeloid cells, neutrophils, and Ly6Clow monocytes in blood, and elevated IL-6. TBI induced a central and peripheral immune response. TBI elevated leukocytes, microglia, and macrophages in the brain and elevated peripheral myeloid cells, neutrophils, Ly6Cint monocytes, and IL-1β in the blood. TBI lowered peripheral CD115+ and Ly6Clow monocytes in the blood. TBI PLX mice had fewer leukocytes and microglia in the brain at 1 DPI, with elevated neutrophils at 7 DPI compared to TBI mice on a control diet. TBI PLX mice also had fewer peripheral myeloid cells, CD115+, and Ly6Clow monocytes in the blood at 3 DPI, but elevated Ly6Chigh, Ly6Cint, and CD115+ monocyte populations at 7 DPI, compared to TBI mice on a control diet. TBI PLX mice had elevated proinflammatory cytokines and lower anti-inflammatory cytokines in the blood at 7 DPI compared to TBI mice on a control diet. CSF-1R inhibition reduced the immune response to TBI at 1 and 3 DPI, but elevated peripheral inflammation at 7 DPI.

Antidiabetic Drugs Can Reduce the Harmful Impact of Chronic Smoking on Post-Traumatic Brain Injuries

Traumatic Brain Injury (TBI) is a primary cause of cerebrovascular and neurological disorders worldwide. The current scientific researchers believe that premorbid conditions such as tobacco smoking (TS) can exacerbate post-TBI brain injury and negatively affect recovery. This is related to vascular endothelial dysfunction resulting from the exposure to TS-released reactive oxygen species (ROS), nicotine, and oxidative stress (OS) stimuli impacting the blood-brain barrier (BBB) endothelium. Interestingly, these pathogenic modulators of BBB impairment are similar to those associated with hyperglycemia. Antidiabetic drugs such as metformin (MF) and rosiglitazone (RSG) were shown to prevent/reduce BBB damage promoted by chronic TS exposure. Thus, using in vivo approaches, we evaluated the effectiveness of post-TBI treatment with MF or RSG to reduce the TS-enhancement of BBB damage and brain injury after TBI. For this purpose, we employed an in vivo weight-drop TBI model using male C57BL/6J mice chronically exposed to TS with and without post-traumatic treatment with MF or RSG. Our results revealed that these antidiabetic drugs counteracted TS-promoted downregulation of nuclear factor erythroid 2-related factor 2 (NRF2) expression and concomitantly dampened TS-enhanced OS, inflammation, and loss of BBB integrity following TBI. In conclusion, our findings suggest that MF and RSG could reduce the harmful impact of chronic smoking on post-traumatic brain injuries.

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.

Cdk5 mediates rotational force-induced brain injury

Millions of traumatic brain injuries (TBIs) occur annually. TBIs commonly result from falls, traffic accidents, and sports-related injuries, all of which involve rotational acceleration/deceleration of the brain. During these injuries, the brain endures a multitude of primary insults including compression of brain tissue, damaged vasculature, and diffuse axonal injury. All of these deleterious effects can contribute to secondary brain ischemia, cellular death, and neuroinflammation that progress for weeks, months, and lifetime after injury. While the linear effects of head trauma have been extensively modeled, less is known about how rotational injuries mediate neuronal damage following injury. Here, we developed a new model of repetitive rotational head trauma in rodents and demonstrated acute and prolonged pathological, behavioral, and electrophysiological effects of rotational TBI (rTBI). We identify aberrant Cyclin-dependent kinase 5 (Cdk5) activity as a principal mediator of rTBI. We utilized Cdk5-enriched phosphoproteomics to uncover potential downstream mediators of rTBI and show pharmacological inhibition of Cdk5 reduces the cognitive and pathological consequences of injury. These studies contribute meaningfully to our understanding of the mechanisms of rTBI and how they may be effectively treated.

Comparison of Antioxidant Capacity and Network Pharmacology of Phloretin and Phlorizin against Neuroinflammation in Traumatic Brain Injury

Neuroinflammation is a hallmark of traumatic brain injury (TBI)'s acute and chronic phases. Despite the medical and scientific advances in recent years, there is still no effective treatment that mitigates the oxidative and inflammatory damage that affects neurons and glial cells. Therefore, searching for compounds with a broader spectrum of action that can regulate various inflammatory signaling pathways is of clinical interest. In this study, we determined not only the in vitro antioxidant capacity of apple pomace phenolics, namely, phlorizin and its metabolite, phloretin, but we also hypothesize that the use of these bioactive molecules may have potential use in TBI. We explored the antioxidant effects of both compounds in vitro (DPPH, iron-reducing capacity (IRC), and Folin-Ciocalteu reducing capacity (FCRC)), and using network pharmacology, we investigated the proteins involved in their protective effects in TBI. Our results showed that the antioxidant properties of phloretin were superior to those of phlorizin in the DPPH (12.95 vs. 3.52 mg ascorbic acid equivalent (AAE)/L), FCRC (86.73 vs. 73.69 mg gallic acid equivalent (GAE)/L), and iron-reducing capacity (1.15 vs. 0.88 mg GAE/L) assays. Next, we examined the molecular signature of both compounds and found 11 proteins in common to be regulated by them and involved in TBI. Meta-analysis and GO functional enrichment demonstrated their implication in matrix metalloproteinases, p53 signaling, and cell secretion/transport. Using MCODE and Pearson's correlation analysis, a subcluster was generated. We identified ESR1 (estrogen receptor alpha) as a critical cellular hub being regulated by both compounds and with potential therapeutic use in TBI. In conclusion, our study suggests that because of their vast antioxidant effects, probably acting on estrogen receptors, phloretin and phlorizin may be repurposed for TBI treatment due to their ease of obtaining and low cost.

Recombinant High-Density Lipoprotein Boosts the Therapeutic Efficacy of Mild Hypothermia in Traumatic Brain Injury

Traumatic brain injury (TBI) leads to neuropsychiatric symptoms and increased risk of neurodegenerative disorders. Mild hypothermia is commonly used in patients suffering from severe TBI. However, its effect for long-term protection is limited, mostly because of its insufficient anti-inflammatory and neuroprotective efficacy and restricted treatment duration. Recombinant high-density lipoprotein (rHDL), which possesses anti-inflammatory and antioxidant activity and blood-brain barrier (BBB) permeability, was expected to potentially strengthen the therapeutic effect of mild hypothermia in TBI treatment. To test this hypothesis and optimize the regimen for combination therapy, the efficacy of mild hypothermia plus concurrent or sequential rHDL on oxidative stress, inflammatory reaction, and cell survival in the damaged brain cells was evaluated. It was found that the effect of combining mild hypothermia with concurrent rHDL was modest, as mild hypothermia inhibited the cellular uptake and lesion-site-targeting delivery of rHDL. In contrast, the combination of mild hypothermia with sequential rHDL more powerfully improved the anti-inflammatory and antioxidant activities, promoted nerve cell survival and BBB restoration, and ameliorated neurologic changes, which thus remarkably restored the spatial learning and memory ability of TBI mice. Collectively, these findings suggest that rHDL may serve as a novel nanomedicine for adjunctive therapy of TBI and highlight the importance of timing of combination therapy for optimal treatment outcome.

Neurobiological Mechanisms Of Depression Following Traumatic Brain Injury

OBJECTIVE

Depression is among the most pervasive and debilitating neuropsychiatric sequelae experienced by patients following a traumatic brain injury (TBI). While the individual mechanisms underlying depression and TBI have been widely studied, the neurobiological bases of depression after TBI remain largely unknown. This article highlights the potential mechanisms of action implicated in depression after TBI.

RESULTS

We review putative mechanisms of action including neuroinflammation, neuroendocrine dysregulation, metabolic abnormalities, and neurotransmitter and circuitry dysfunction. We also identify the current limitations in the field and propose directions for future research.

CONCLUSION

An improved understanding of the underlying mechanisms will aid the development of precision-guided and personalized treatments for patients suffering from depression after TBI.

Effects of Probiotics Supplementation on CRP, IL-6, and Length of ICU Stay in Traumatic Brain Injuries and Multiple Trauma Patients: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

METHOD

This meta-analysis aims to evaluate the effectiveness of probiotics in reducing inflammatory biomarkers and the length of intensive care unit (ICU) stays. PubMed-Medline, SCOPUS, Embase, and Google Scholar databases up to July 2021 were searched. The meta-analysis was carried out using random-effect analysis. To determine the sources of heterogeneity, subgroup analyses were performed. In case of the presence of publication bias, trim and fill analysis was carried out. The Cochrane Collaboration tool was used for checking the quality assessment. We hypothesized that probiotics would improve inflammatory markers (CRP and IL-6) and the length of ICU stay in traumatic brain injury and multiple trauma patients.

RESULTS

The present meta-analysis, which includes a total of seven studies, showed that there were no significant effects of probiotics supplementation on interleukin (IL)-6 (Hedges's g = -2.46 pg/ml; 95% CI: -12.16, 7.25; P=0.39), C-reactive protein (CRP) (Hedges's g = -1.10 mg/L; 95% CI: -2.27, 0.06; P=0.06), and the length of staying in ICU. The overall number of RCTs included in the analysis and the total sample size were insufficient to make firm conclusions.

CONCLUSION

As a result, more carefully designed RCTs are needed to investigate the effect of probiotics on inflammatory biomarkers and the length of ICU stay in traumatic brain injuries and multiple trauma patients in greater detail.

TREM2 activation alleviates neural damage via Akt/CREB/BDNF signalling after traumatic brain injury in mice

BACKGROUND

Neuroinflammation is one of the most important processes in secondary injury after traumatic brain injury (TBI). Triggering receptor expressed on myeloid cells 2 (TREM2) has been proven to exert neuroprotective effects in neurodegenerative diseases and stroke by modulating neuroinflammation, and promoting phagocytosis and cell survival. However, the role of TREM2 in TBI has not yet been elucidated. In this study, we are the first to use COG1410, an agonist of TREM2, to assess the effects of TREM2 activation in a murine TBI model.

METHODS

Adult male wild-type (WT) C57BL/6 mice and adult male TREM2 KO mice were subjected to different treatments. TBI was established by the controlled cortical impact (CCI) method. COG1410 was delivered 1 h after CCI via tail vein injection. Western blot analysis, immunofluorescence, laser speckle contrast imaging (LSCI), neurological behaviour tests, brain electrophysiological monitoring, Evans blue assays, magnetic resonance imaging (MRI), and brain water content measurement were performed in this study.

RESULTS

The expression of endogenous TREM2 peaked at 3 d after CCI, and it was mainly expressed on microglia and neurons. We found that COG1410 improved neurological functions within 3 d, as well as neurological functions and brain electrophysiological activity at 2 weeks after CCI. COG1410 exerted neuroprotective effects by inhibiting neutrophil infiltration and microglial activation, and suppressing neuroinflammation after CCI. In addition, COG1410 treatment alleviated blood brain barrier (BBB) disruption and brain oedema; furthermore, COG1410 promoted cerebral blood flow (CBF) recovery at traumatic injury sites after CCI. In addition, COG1410 suppressed neural apoptosis at 3 d after CCI. TREM2 activation upregulated p-Akt, p-CREB, BDNF, and Bcl-2 and suppressed TNF-α, IL-1β, Bax, and cleaved caspase-3 at 3 d after CCI. Moreover, TREM2 knockout abolished the effects of COG1410 on vascular phenotypes and microglial states. Finally, the neuroprotective effects of COG1410 were suppressed by TREM2 depletion.

CONCLUSIONS

Altogether, we are the first to demonstrate that TREM2 activation by COG1410 alleviated neural damage through activation of Akt/CREB/BDNF signalling axis in microglia after CCI. Finally, COG1410 treatment improved neurological behaviour and brain electrophysiological activity after CCI.

Persistent neuroinflammation and behavioural deficits after single mild traumatic brain injury

Despite an apparently silent imaging, some patients with mild traumatic brain injury (TBI) experience cognitive dysfunctions, which may persist chronically. Brain changes responsible for these dysfunctions are unclear and commonly overlooked. It is thus crucial to increase our understanding of the mechanisms linking the initial event to the functional deficits, and to provide objective evidence of brain tissue alterations underpinning these deficits. We first set up a murine model of closed-head controlled cortical impact, which provoked persistent cognitive and sensorimotor deficits, despite no evidence of brain contusion or bleeding on MRI, thus recapitulating features of mild TBI. Molecular MRI for P-selectin, a key adhesion molecule, detected no sign of cerebrovascular inflammation after mild TBI, as confirmed by immunostainings. By contrast, in vivo PET imaging with the TSPO ligand [18F]DPA-714 demonstrated persisting signs of neuroinflammation in the ipsilateral cortex and hippocampus after mild TBI. Interestingly, immunohistochemical analyses confirmed these spatio-temporal profiles, showing a robust parenchymal astrogliosis and microgliosis, at least up to 3 weeks post-injury in both the cortex and hippocampus. In conclusion, we show that even one single mild TBI induces long-term behavioural deficits, associated with a persistent neuro-inflammatory status that can be detected by PET imaging.

Enhanced drug delivery by a prodrug approach effectively relieves neuroinflammation in mice

AIMS

Neuroinflammation is a prominent hallmark in several neurodegenerative diseases (NDs). Halting neuroinflammation can slow down the progression of NDs. Improving the efficacy of clinically available non-steroidal anti-inflammatory drugs (NSAIDs) is a promising approach that may lead to fast-track and effective disease-modifying therapies for NDs. Here, we aimed to utilize the L-type amino acid transporter 1 (LAT1) to improve the efficacy of salicylic acid as an example of an NSAID prodrug, for which brain uptake and intracellular localization have been reported earlier.

MAIN METHODS

Firstly, we confirmed the improved LAT1 utilization of the salicylic acid prodrug (SA-AA) in freshly isolated primary mouse microglial cells. Secondly, we performed behavioural rotarod, open field, and four-limb hanging tests in mice, and a whole-brain proteome analysis.

KEY FINDINGS

The SA-AA prodrug alleviated the lipopolysaccharide (LPS)-induced inflammation in the rotarod and hanging tests. The proteome analysis indicated decreased neuroinflammation at the molecular level. We identified 399 proteins linked to neuroinflammation out of 7416 proteins detected in the mouse brain. Among them, Gps2, Vamp8, Slc6a3, Slc18a2, Slc5a7, Rgs9, Lrrc1, Ppp1r1b, Gnal, and Adcy5/6 were associated with the drug's effects. The SA-AA prodrug attenuated the LPS-induced neuroinflammation through the regulation of critical pathways of neuroinflammation such as the cellular response to stress and transmission across chemical synapses.

SIGNIFICANCE

The efficacy of NSAIDs can be improved via the utilization of LAT1 and repurposed for the treatment of neuroinflammation. This improved brain delivery and microglia localisation can be applied to other inflammatory modulators to achieve effective and targeted CNS therapies.

What microglia depletion approaches tell us about the role of microglia on synaptic function and behavior

Microglia are dynamic cells, constantly surveying their surroundings and interacting with neurons and synapses. Indeed, a wealth of knowledge has revealed a critical role of microglia in modulating synaptic transmission and plasticity in the developing brain. In the past decade, novel pharmacological and genetic strategies have allowed the acute removal of microglia, opening the possibility to explore and understand the role of microglia also in the adult brain. In this review, we summarized and discussed the contribution of microglia depletion strategies to the current understanding of the role of microglia on synaptic function, learning and memory, and behavior both in physiological and pathological conditions. We first described the available microglia depletion methods highlighting their main strengths and weaknesses. We then reviewed the impact of microglia depletion on structural and functional synaptic plasticity. Next, we focused our analysis on the effects of microglia depletion on behavior, including general locomotor activity, sensory perception, motor function, sociability, learning and memory both in healthy animals and animal models of disease. Finally, we integrated the findings from the reviewed studies and discussed the emerging roles of microglia on the maintenance of synaptic function, learning, memory strength and forgetfulness, and the implications of microglia depletion in models of brain disease.

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

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

Photobiomodulation for the treatment of neuroinflammation: A systematic review of controlled laboratory animal studies

Background

Neuroinflammation is a response that involves different cell lineages of the central nervous system, such as neurons and glial cells. Among the non-pharmacological interventions for neuroinflammation, photobiomodulation (PBM) is gaining prominence because of its beneficial effects found in experimental brain research. We systematically reviewed the effects of PBM on laboratory animal models, specially to investigate potential benefits of PBM as an efficient anti-inflammatory therapy.

Methods

We conducted a systematic search on the bibliographic databases (PubMed and ScienceDirect) with the keywords based on MeSH terms: photobiomodulation, low-level laser therapy, brain, neuroinflammation, inflammation, cytokine, and microglia. Data search was limited from 2009 to June 2022. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. The initial systematic search identified 140 articles. Among them, 54 articles were removed for duplication and 59 articles by screening. Therefore, 27 studies met the inclusion criteria.

Results

The studies showed that PBM has anti-inflammatory properties in several conditions, such as traumatic brain injury, edema formation and hyperalgesia, ischemia, neurodegenerative conditions, aging, epilepsy, depression, and spinal cord injury.

Conclusion

Taken together, these results indicate that transcranial PBM therapy is a promising strategy to treat brain pathological conditions induced by neuroinflammation.

Understanding Acquired Brain Injury: A Review

Any type of brain injury that transpires post-birth is referred to as Acquired Brain Injury (ABI). In general, ABI does not result from congenital disorders, degenerative diseases, or by brain trauma at birth. Although the human brain is protected from the external world by layers of tissues and bone, floating in nutrient-rich cerebrospinal fluid (CSF); it remains susceptible to harm and impairment. Brain damage resulting from ABI leads to changes in the normal neuronal tissue activity and/or structure in one or multiple areas of the brain, which can often affect normal brain functions. Impairment sustained from an ABI can last anywhere from days to a lifetime depending on the severity of the injury; however, many patients face trouble integrating themselves back into the community due to possible psychological and physiological outcomes. In this review, we discuss ABI pathologies, their types, and cellular mechanisms and summarize the therapeutic approaches for a better understanding of the subject and to create awareness among the public.

Plants and their Bioactive Compounds as a Possible Treatment for Traumatic Brain Injury-Induced Multi-Organ Dysfunction Syndrome

BACKGROUND & OBJECTIVE

Traumatic brain injury is an outcome of the physical or mechanical impact of external forces on the brain. Thus, the silent epidemic has complex pathophysiology affecting the brain along with extracranial or systemic complications in more than one organ system, including the heart, lungs, liver, kidney, gastrointestinal and endocrine system. which is referred to as Multi-Organ Dysfunction Syndrome. It is driven by three interconnected mechanisms such as systemic hyperinflammation, paroxysmal sympathetic hyperactivity, and immunosuppression-induced sepsis. These multifaceted pathologies accelerate the risk of mortality in clinical settings by interfering with the functions of distant organs through hypertension, cardiac arrhythmias, acute lung injury, neurogenic pulmonary edema, reduced gastrointestinal motility, Cushing ulcers, acute liver failure, acute kidney injury, coagulopathy, endocrine dysfunction, and many other impairments. The pharmaceutical treatment approach for this is highly specific in its mode of action and linked to a variety of side effects, including hallucinations, seizures, anaphylaxis, teeth, bone staining, etc. Therefore, alternative natural medicine treatments are widely accepted due to their broad complementary or synergistic effects on the physiological system with minor side effects.

CONCLUSION

This review is a compilation of the possible mechanisms behind the occurrence of multiorgan dysfunction and reported medicinal plants with organoprotective activity that have not been yet explored against traumatic brain injury and thereby, highlighting the marked possibilities of their effectiveness in the management of multiorgan dysfunction. As a result, we attempted to respond to the hypothesis against the usage of medicinal plants to treat neurodegenerative diseases.

Microglial polarization in TBI: Signaling pathways and influencing pharmaceuticals

Traumatic brain injury (TBI) is a serious disease that threatens life and health of people. It poses a great economic burden on the healthcare system. Thus, seeking effective therapy to cure a patient with TBI is a matter of great urgency. Microglia are macrophages in the central nervous system (CNS) and play an important role in neuroinflammation. When TBI occurs, the human body environment changes dramatically and microglia polarize to one of two different phenotypes: M1 and M2. M1 microglia play a role in promoting the development of inflammation, while M2 microglia play a role in inhibiting inflammation. How to regulate the polarization direction of microglia is of great significance for the treatment of patients with TBI. The polarization of microglia involves many cellular signal transduction pathways, such as the TLR-4/NF-κB, JAK/STAT, HMGB1, MAPK, and PPAR-γ pathways. These provide a theoretical basis for us to seek therapeutic drugs for the patient with TBI. There are several drugs that target these pathways, including fingolimod, minocycline, Tak-242 and erythropoietin (EPO), and CSF-1. In this study, we will review signaling pathways involved in microglial polarization and medications that influence this process.

Interleukin-6 as a prognostic biomarker of clinical outcomes after traumatic brain injury: a systematic review

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. There are currently no early biomarkers for prognosis in routine clinical use. Interleukin-6 (IL-6) is a potential biomarker in the context of the established role of neuroinflammation in TBI recovery. Therefore, a systematic review of the literature was performed to assess and summarise the evidence for IL-6 secretion representing a useful biomarker for clinical outcomes. A multi-database literature search between January 1946 and July 2021 was performed. Studies were included if they reported adult TBI patients with IL-6 concentration in serum, cerebrospinal fluid (CSF) and/or brain parenchyma analysed with respect to functional outcome and/or mortality. A synthesis without meta-analysis is reported. Fifteen studies were included, reporting 699 patients. Most patients were male (71.7%), and the pooled mean age was 40.8 years; 78.1% sustained severe TBI. Eleven studies reported IL-6 levels in serum, six in CSF and one in the parenchyma. Five studies on serum demonstrated higher IL-6 concentrations were associated with poorer outcomes, and five showed no signification association. In CSF studies, one found higher IL-6 levels were associated with poorer outcomes, one found them to predict better outcomes and three found no association. Greater parenchymal IL-6 was associated with better outcomes. Despite some inconsistency in findings, it appears that exaggerated IL-6 secretion predicts poor outcomes after TBI. Future efforts require standardisation of IL-6 measurement practices as well as assessment of the importance of IL-6 concentration dynamics with respect to clinical outcomes, ideally within large prospective studies. Prospero registration number: CRD42021271200

Astrocyte-targeted gene delivery of interleukin 2 specifically increases brain-resident regulatory T cell numbers and protects against pathological neuroinflammation

The ability of immune-modulating biologics to prevent and reverse pathology has transformed recent clinical practice. Full utility in the neuroinflammation space, however, requires identification of both effective targets for local immune modulation and a delivery system capable of crossing the blood-brain barrier. The recent identification and characterization of a small population of regulatory T (Treg) cells resident in the brain presents one such potential therapeutic target. Here, we identified brain interleukin 2 (IL-2) levels as a limiting factor for brain-resident Treg cells. We developed a gene-delivery approach for astrocytes, with a small-molecule on-switch to allow temporal control, and enhanced production in reactive astrocytes to spatially direct delivery to inflammatory sites. Mice with brain-specific IL-2 delivery were protected in traumatic brain injury, stroke and multiple sclerosis models, without impacting the peripheral immune system. These results validate brain-specific IL-2 gene delivery as effective protection against neuroinflammation, and provide a versatile platform for delivery of diverse biologics to neuroinflammatory patients.

Microtubule Dynamics Following Central and Peripheral Nervous System Axotomy

Disturbance in the neuronal network leads to instability in the microtubule (MT) railroad of axons, causing hindrance in the intra-axonal transport and making it difficult to re-establish the broken network. Peripheral nervous system (PNS) neurons can stabilize their MTs, leading to the formation of regeneration-promoting structures called "growth cones". However, central nervous system (CNS) neurons lack this intrinsic reparative capability and, instead, form growth-incompetent structures called "retraction bulbs", which have a disarrayed MT network. It is evident from various studies that although axonal regeneration depends on both cell-extrinsic and cell-intrinsic factors, any therapy that aims at axonal regeneration ultimately converges onto MTs. Understanding the neuronal MT dynamics will help develop effective therapeutic strategies in diseases where the MT network gets disrupted, such as spinal cord injury, traumatic brain injury, multiple sclerosis, and amyotrophic lateral sclerosis. It is also essential to know the factors that aid or inhibit MT stabilization. In this review, we have discussed the MT dynamics postaxotomy in the CNS and PNS, and factors that can directly influence MT stability in various diseases.

Neuroinflammation Following Traumatic Brain Injury: Take It Seriously or Not

Traumatic brain injury (TBI) is associated with high mortality and disability, with a substantial socioeconomic burden. With the standardization of the treatment process, there is increasing interest in the role that the secondary insult of TBI plays in outcome heterogeneity. The secondary insult is neither detrimental nor beneficial in an absolute sense, among which the inflammatory response was a complex cascade of events and can thus be regarded as a double-edged sword. Therefore, clinicians should take the generation and balance of neuroinflammation following TBI seriously. In this review, we summarize the current human and animal model studies of neuroinflammation and provide a better understanding of the inflammatory response in the different stages of TBI. In particular, advances in neuroinflammation using proteomic and transcriptomic techniques have enabled us to identify a functional specific delineation of the immune cell in TBI patients. Based on recent advances in our understanding of immune cell activation, we present the difference between diffuse axonal injury and focal brain injury. In addition, we give a figurative profiling of the general paradigm in the pre- and post-injury inflammatory settings employing a bow-tie framework.

Hydroxychloroquine attenuates neuroinflammation following traumatic brain injury by regulating the TLR4/NF-κB signaling pathway

Background

After traumatic brain injury (TBI), an acute, robust inflammatory cascade occurs that is characterized by the activation of resident cells such as microglia, the migration and recruitment of peripheral immune cells and the release of inflammatory mediators that induce secondary cell death and impede neurological recovery. In addition, neuroinflammation can alter blood–brain barrier (BBB) permeability. Controlling inflammatory responses is considered a promising therapeutic approach for TBI. Hydroxychloroquine (HCQ) has already been used clinically for decades, and it is still widely used to treat various autoimmune diseases. However, the effects of HCQ on inflammation and the potential mechanism after TBI remain to be defined. The aim of the current study was to elucidate whether HCQ could improve the neurological recovery of mice post-TBI by inhibiting the inflammatory response via the TLR4/NF-κB signaling pathway.

Methods

C57BL/6 mice were subjected to controlled cortical impact (CCI) and randomly divided into groups that received intraperitoneal HCQ or vehicle daily after TBI. TAK-242 (3.0 mg/kg), an exogenous TLR4 antagonist, was injected intraperitoneally 1 h before TBI. Behavioral assessments were performed on days 1 and 3 post-TBI, and the gene expression levels of inflammatory cytokines were analyzed by qRT-PCR. The presence of infiltrated immune cells was examined by flow cytometry and immunostaining. In addition, BBB permeability, tight junction expression and brain edema were investigated.

Results

HCQ administration significantly ameliorated TBI-induced neurological deficits. HCQ alleviated neuroinflammation, the activation and accumulation of microglia and immune cell infiltration in the brain, attenuated BBB disruption and brain edema, and upregulated tight junction expression. Combined administration of HCQ and TAK-242 did not enhance the neuroprotective effects of HCQ.

Conclusions

HCQ reduced proinflammatory cytokine expression, and the underlying mechanism may involve suppressing the TLR4/NF-κB signaling pathway, suggesting that HCQ is a potential therapeutic agent for TBI treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02430-0.

Pro-resolving lipid mediators in traumatic brain injury: emerging concepts and translational approach

Despite the high mortality and disability associated with traumatic brain injury (TBI), effective pharmacologic treatments are lacking. Of emerging interest, bioactive lipids, including specialized pro-resolving lipid mediators of inflammation (SPMs), act to attenuate inflammation after injury resolution. The SPM lipidome may serve as a biomarker of disease and predictor of clinical outcomes, and the use of exogenous SPM administration represents a novel therapeutic strategy for TBI. This review article provides a comprehensive discussion of the current pre-clinical and clinical literature supporting the importance of bioactive lipids, including SPMs, in TBI recovery. We additionally propose a translational approach to answer important clinical and scientific questions to advance the study of bioactive lipids and SPMs towards clinical research. Given the morbidity and mortality associated with TBI with limited treatment options, novel approaches are needed.

Controlled Decompression Alleviates Brain Injury via Attenuating Oxidative Damage and Neuroinflammation in Acute Intracranial Hypertension

BACKGROUND

The benefits of controlled decompression (CDC) for patients with acute intracranial hypertension especially in terms of alleviating the complications caused by rapid decompression (RDC) have been confirmed by clinical studies. This study is aimed at evaluating the therapeutic potency of CDC with ubiquitin C-terminal hydrolase-L1 (UCH-L1) and glial fibrillary acidic protein (GFAP) by investigating the potential molecular mechanism in the acute intracranial hypertension (AICH) rabbit model.

METHODS

Male New Zealand white rabbits were randomly subdivided into the sham-operated (SH) group, CDC group, and RDC group. Blood plasma samples and brain tissue were collected 2 days before operation (baseline) and at 3, 6, 24, and 72 hours after operation to measure the levels of UCH-L1, GFAP, oxidative stress indicators, and inflammatory cytokines by performing ELISA or Western blot. The neurological score of the rabbits and brain water content was graded 24 h after surgery. qPCR, immunofluorescence, and FJ-C staining were conducted.

RESULTS

CDC improved neurological function, lowered brain water content, ameliorated neuronal degeneration, attenuated oxidative damage, and inflammatory responses to a greater extent than RDC. Plasma UCH-L1 level was significantly lower in the CDC group at 3 h postoperatively than in the RDC group. CDC reduced plasma GFAP levels to various degrees at 3 h, 6 h, and 24 h postoperatively compared with RDC. Immunofluorescence confirmed that the expression of UCH-L1 and GFAP in the cortex of the CDC group was lower than that of the RDC group.

CONCLUSIONS

Our data collectively demonstrate that CDC could attenuate oxidative damage and inflammatory responses, downregulate UCH-L1 and GFAP levels, and contribute to an improved neuroprotective effect compared with RDC.

Animal model of repeated low-level blast traumatic brain injury displays acute and chronic neurobehavioral and neuropathological changes

Blast-induced neurotrauma (BINT) is not only a signature injury to soldiers in combat field and training facilities but may also a growing concern in civilian population due to recent increases in the use of improvised explosives by insurgent groups. Unlike moderate or severe BINT, repeated low-level blast (rLLB) is different in its etiology as well as pathology. Due to the constant use of heavy weaponry as part of combat readiness, rLLB usually occurs in service members undergoing training as part of combat readiness. rLLB does not display overt pathological symptoms; however, earlier studies report chronic neurocognitive changes such as altered mood, irritability, and aggressive behavior, all of which may be caused by subtle neuropathological manifestations. Current animal models of rLLB for investigation of neurobehavioral and neuropathological alterations have not been adequate and do not sufficiently represent rLLB conditions. Here, we developed a rat model of rLLB by applying controlled low-level blast pressures (<10 psi) repeated successively five times to mimic the pressures experienced by service members. Using this model, we assessed anxiety-like symptoms, motor coordination, and short-term memory as a function of time. We also examined levels of superoxide-producing enzyme NADPH oxidase, microglial activation, and reactive astrocytosis as factors likely contributing to these neurobehavioral changes. Animals exposed to rLLB displayed acute and chronic anxiety-like symptoms, motor and short-term memory impairments. These changes were paralleled by increased microglial activation and reactive astrocytosis. Conversely, animals exposed to a single low-level blast did not display significant changes. Collectively, this study demonstrates that, unlike a single low-level blast, rLLB exerts a cumulative impact on different brain regions and produces chronic neuropathological changes in so doing, may be responsible for neurobehavioral alterations.

Inflammatory cytokines TNFα, IL-1β, and IL-6 are induced in endotoxin- stimulated microglia through different signaling cascades

By using an animal model in which inflammatory cytokines are induced in lipopolysaccharide (LPS)-injected rat brain, we investigated the induction of tumor necrosis factor alpha (TNFα), interleukin-1beta (IL-1β), and IL-6. Immunoblotting and immunohistochemistry revealed that all three cytokines were transiently induced in the cerebral cortex at about 12 h after LPS injection. To clarify which glial cell type induced the cytokines, we examined the respective abilities of astrocytes and microglia in vitro. Primary microglia largely induced TNFα, IL-1β and IL-6 in response to LPS, but primary astrocytes induced only limited levels of TNFα. Thus, we used specific inhibitors to focus on microglia in surveying signaling molecules involved in the induction of TNFα, IL-1β, and IL-6. The experiments using mitogen-activated protein kinases (MAPK) inhibitors revealed that c-Jun N-terminal kinase (JNK)/p38, external signal regulated kinase (ERK)/JNK, and ERK/JNK/p38 are necessary for the induction of TNFα, IL-1β, and IL-6, respectively. The experiments using protein kinase C (PKC) inhibitor clarified that PKCα is required for the induction of all these cytokines in LPS-stimulated microglia. Furthermore, LPS-dependent IL-1β/IL-6 induction was suppressed by pretreatment with a nitric oxide (NO) scavenger, suggesting that NO is involved in the signaling cascade of IL-1β/IL-6 induction. Thus, an inducible NO synthase induced in the LPS-injected cerebral cortex might be related to the induction of IL-1β/IL-6 through the production of NO in vivo. Taken together, these results demonstrated that microglia induce different kinds of inflammatory cytokine through specific combinations of MAPKs and by the presence or absence of NO.

Background to new treatments for COVID-19, including its chronicity, through altering elements of the cytokine storm

Anti-tumour necrosis factor (TNF) biologicals, Dexamethasone and rIL-7 are of considerable interest in treating COVID-19 patients who are in danger of, or have become, seriously ill. Yet reducing sepsis mortality by lowering circulating levels of TNF lost favour when positive endpoints in earlier simplistic models could not be reproduced in well-conducted human trials. Newer information with anti-TNF biologicals has encouraged reintroducing this concept for treating COVID-19. Viral models have had encouraging outcomes, as have the effects of anti-TNF biologicals on community-acquired COVID-19 during their long-term use to treat chronic inflammatory states. The positive outcome of a large scale trial of dexamethasone, and its higher potency late in the disease, harmonises well with its capacity to enhance levels of IL-7Rα, the receptor for IL-7, a cytokine that enhances lymphocyte development and is increased during the cytokine storm. Lymphoid germinal centres required for antibody-based immunity can be harmed by TNF, and restored by reducing TNF. Thus the IL-7- enhancing activity of dexamethasone may explain its higher potency when lymphocytes are depleted later in the infection, while employing anti-TNF, for several reasons, is much more logical earlier in the infection. This implies dexamethasone could prove to be synergistic with rIL-7, currently being trialed as a COVID-19 therapeutic. The principles behind these COVID-19 therapies are consistent with the observed chronic hypoxia through reduced mitochondrial function, and also the increased severity of this disease in ApoE4-positive individuals. Many of the debilitating persistent aspects of this disease are predictably susceptible to treatment with perispinal etanercept, since they have cerebral origins.

(-)-Syringaresinol suppressed LPS-induced microglia activation via downregulation of NF-κB p65 signaling and interaction with ERβ

Albiziae Cortex (AC) is a well-known traditional Chinese medicine with sedative-hypnotic effects and neuroprotective ability. However, the bioactive components of AC responsible for the neuro-protective actitivity remain unknown. Here, we investigated the anti-neuroinflammatory effects of (-)-syringaresinol (SYR) extracted from AC in microglia cells and wild-type mice. As a result, (-)-SYR significantly reduced lipopolysaccharide (LPS)-induced production of interleukin - 6 (IL-6), tumor necrosis factor α (TNF-α), interleukin -1 beta (IL-1β), cycloxygenase-2 (COX-2), and nitric oxide (NO) in BV2 microglia cells. (-)-SYR also significantly reduced M1 marker CD40 expression and increased M2 marker CD206 expression. Moreover, we found that (-)-SYR inhibited LPS-induced NF-κB activation by suppressing the translocation of NF-κB p65 into the nucleus in a concentration-dependent manner. Meanwhile, estrogen receptor β (ERβ) was found to be implied in the anti-inflammatory activity of (-)-SYR in BV2 microglia. In vivo experiments revealed that administration of (-)-SYR in mice significantly reduced microglia/astrocytes activation and mRNA levels of proinflammatory mediators. Taken together, our data indicated that (-)-SYR exerted the anti-neuroinflammatory effects by inhibiting NF-κB activation and modulation of microglia polarization, and via interaction with ERβ. The anti-neuroinflammatory activity of (-)-SYR may provide a new therapeutic avenue for the treatment of brain diseases associated with inflammation.

Impact of Curcumin on Traumatic Brain Injury and Involved Molecular Signaling Pathways

Traumatic Brain Injury (TBI) is one of the main causes of mortality and morbidity worldwide with no suitable treatment. The present study was designed to review the present literature about the protective effects of curcumin and the underlying mechanism against TBI. All published English language papers from beginning to 2019 were selected in this study. The findings indicate that curcumin may be effective against TBI outcomes by modulating the molecular signaling pathways involved in oxidative stress, inflammation, apoptosis, and autophagy. However, more experimental studies should be done to identify all mechanisms involved in the pathogenesis of TBI. Patents for Curcumin and chronic inflammation and traumatic brain injury management (WO2017097805A1 and US9101580B2) were published. In conclusion, the present study confirmed the potential therapeutic impact of curcumin for treating TBI.