Neurogenesis after traumatic brain injury - The complex role of HMGB1 and neuroinflammation

Prolonged loss of nuclear HMGB1 in neurons following modeled TBI and implications for long-term genetic health

Under normal physiological conditions high mobility group box protein 1 (HMGB1) stabilizes chromatin, controls transcription, and contributes to DNA repair. Cellular stress or injury results in HMGB1 release from the nucleus acting as a proinflammatory cytokine. The objective of this study was to characterize the temporal progression of nuclear HMGB1 loss up to one week following modeled TBI in 250 g male rats and correlate these changes with the response of DNA damage proteins. HMGB1 was present in the cytoplasm and absent from the nucleus of neurons within 6 h of injury. Quantitative immunohistochemistry and Western blot analysis showed a significant decrease in nuclear HMGB1 expression at 6 and 24 h post-injury compared to controls. Approximately 20 % of neurons were lacking nuclear HMGB1 expression at 7 days post-injury. Cells which were negative for nuclear HMGB1 expression labelled positive for HIF1α, PARP, and γH2AX, indicators of oxidative stress and DNA damage. Nuclear HIF1α expression was detected at 6 h after injury. Nuclear expression of HIF1α, PARP, and γH2AX was observed at 7 days post-injury, suggesting activation of oxidative stress response mechanisms and DNA damage repair pathways. The temporal changes in HMGB1 translocation in conjunction with expression of DNA damage markers suggest a relationship between injury-induced HMGB1 loss in neurons and subsequent DNA damage. These results highlight a potential injury response mechanism with long-term implications in relation to genetic health of surviving neurons.

Immunity in neuromodulation: probing neural and immune pathways in brain disorders

Immunity finely regulates brain function. It is directly involved in the pathological processes of neurodegenerative diseases such as Parkinson's and Alzheimer's disease, post-stroke conditions, multiple sclerosis, traumatic brain injury, and psychiatric disorders (mood disorders, major depressive disorder (MDD), anxiety disorders, psychosis disorders and schizophrenia, and neurodevelopmental disorders (NDD)). Neuromodulation is currently a leading therapeutic strategy for the treatment of these disorders, but little is yet known about its immune impact on neuronal function and its precise beneficial or harmful consequences. We review relevant clinical and preclinical studies and identify several specific immune modifications. These data not only provide insights into how neuromodulation acts to optimize immune-brain interactions, but also pave the way for a better understanding of these interactions in pathological processes.

Cellular Stem Cell Therapy for Treating Traumatic Brain Injury: Strategies for Enhancement of Therapeutic Efficacy

Traumatic brain injury (TBI) influences a considerable population globally. TBI notably impacts both fatalities and disabilities worldwide. The mortality related to TBI is a significant concern in public health, affecting persons across various age groups and demographic profiles. More research and preventative interventions are required to alleviate TBIs' effects and optimize patient outcomes. Stem cell (SC) treatment exhibits promise as a viable strategy for addressing TBI due to its capacity to possibly restore or regenerate the compromised cells within the central nervous system. Additionally, it can influence the inflammatory response and increase neurogenesis and neuroplasticity. Increasing evidence has shown that SC transplantation has the potential to enhance functional recovery and decrease the extent of lesions in animal models of TBI. Nevertheless, several hurdles and ambiguities persist in determining the most effective source, dosage, administration method, timing, and mechanism of action for SC treatment for TBI. Further investigation is required to prove the safety and effectiveness of SC treatment for TBI in human subjects. This review brings insight into the strategies for utilizing SCs as cellular therapy for TBI, mainly based on preclinical investigations and TBI-induced animal models. In addition, this study also addresses many elements related to cell transfusion in the context of TBI, including considerations of cell amount, method, and timing. Integrating biomaterials and genetically altering SCs as potential strategies to enhance therapeutic efficacy are also presented. We also describe the potential of SCs in treating TBI and evaluate the effectiveness of cellular therapy and its corresponding outcomes.

The environment as an important component of neurorehabilitation: introducing the BEEhive - brain and enriched environment (BEE) lab (hive)

PURPOSE

Contemporary healthcare design often overlooks the environment as a resource for supporting patient well-being and rehabilitation, particularly in neurotrauma care. The prioritisation of safety and efficiency has created stressful spaces that negatively impact patient needs. This paper explores whether environmental enrichment can enhance rehabilitation outcomes for individuals recovering from neurotrauma. It also introduces the BEEhive laboratory, a multidisciplinary initiative integrating environmental enrichment principles into healthcare.

METHODOLOGY

This paper reviews literature on the role of environmental enrichment in neurotrauma rehabilitation, synthesising empirical evidence on its benefits, and highlighting its potential to improve various aspects of neurorehabilitation. The findings are applied to the BEEhive laboratory's objectives.

RESULTS

Environmental enrichment is shown to stimulate neurogenesis, increase rehabilitation engagement, reduce disruptive behaviours and depressive symptoms, facilitate social relationships, improve cognitive functioning, reduce stress, and alleviate boredom. Despite these benefits, its application in neurotrauma rehabilitation remains underexplored. The BEEhive laboratory aims to address this gap through multidisciplinary collaboration, implementing strategies to enhance patient outcomes.

CONCLUSION

To optimise rehabilitation outcomes, healthcare environments must holistically support well-being. Environmentally focused, sustainable interventions in neurotrauma care, exemplified by the BEEhive initiative, are crucial for bridging the gap between research and practice, fostering innovative approaches to neurotrauma rehabilitation.

Targeting HMGB1 and Its Interaction with Receptors: Challenges and Future Directions

High mobility group box 1 (HMGB1) is a nonhistone chromatin protein predominantly located in the nucleus. However, under pathological conditions, HMGB1 can translocate from the nucleus to the cytoplasm and subsequently be released into the extracellular space through both active secretion and passive release mechanisms. The distinct cellular locations of HMGB1 facilitate its interaction with various endogenous and exogenous factors, allowing it to perform diverse functions across a range of diseases. This Perspective provides a comprehensive overview of the structure, release mechanisms, and multifaceted roles of HMGB1 in disease contexts. Furthermore, it introduces the development of both small molecule and macromolecule inhibitors targeting HMGB1 and its interaction with receptors. A detailed analysis of the predicted pockets is also presented, aiming to establish a foundation for the future design and development of HMGB1 inhibitors.

High Mobility Group Box 1 (HMGB1): Molecular Signaling and Potential Therapeutic Strategies

High Mobility Group Box 1 (HMGB1) is a highly conserved non-histone chromatin-associated protein across species, primarily recognized for its regulatory impact on vital cellular processes, like autophagy, cell survival, and apoptosis. HMGB1 exhibits dual functionality based on its localization: both as a non-histone protein in the nucleus and as an inducer of inflammatory cytokines upon extracellular release. Pathophysiological insights reveal that HMGB1 plays a significant role in the onset and progression of a vast array of diseases, viz., atherosclerosis, kidney damage, cancer, and neurodegeneration. However, a clear mechanistic understanding of HMGB1 release, translocation, and associated signaling cascades in mediating such physiological dysfunctions remains obscure. This review presents a detailed outline of HMGB1 structure-function relationship and its regulatory role in disease onset and progression from a signaling perspective. This review also presents an insight into the status of HMGB1 druggability, potential limitations in understanding HMGB1 pathophysiology, and future perspective of studies that can be undertaken to address the existing scientific gap. Based on existing paradigm of various studies, HMGB1 is a critical regulator of inflammatory cascades and drives the onset and progression of a broad spectrum of dysfunctions. Studies focusing on HMGB1 druggability have enabled the development of biologics with potential clinical benefits. However, deeper understanding of post-translational modifications, redox states, translocation mechanisms, and mitochondrial interactions can potentially enable the development of better courses of therapy against HMGB1-mediated physiological dysfunctions.

Candidate Molecular Biomarkers of Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI) is one of the leading causes of mortality and disability among young and middle-aged individuals. Adequate and timely diagnosis of primary brain injuries, as well as the prompt prevention and treatment of secondary injury mechanisms, significantly determine the potential for reducing mortality and severe disabling consequences. Therefore, it is crucial to have objective markers that indicate the severity of the injury. A number of molecular factors-proteins and metabolites-detected in the blood immediately after trauma and associated with the development and severity of TBI can serve in this role. TBI is a heterogeneous condition with respect to its etiology, clinical form, and genesis, being accompanied by brain cell damage and disruption of blood-brain barrier permeability. Two oppositely directed flows of substances and signals are observed: one is the flow of metabolites, proteins, and nucleic acids from damaged brain cells into the bloodstream through the damaged blood-brain barrier; the other is the infiltration of immune cells (neutrophils and macrophages) and serological proteins. Both flows aggravate brain tissue damage after TBI. Therefore, it is extremely important to study the key signaling events that regulate these flows and repair the damaged tissues, as well as to enhance the effectiveness of treatments for patients after TBI.

RAGE mediates hippocampal pericyte responses and neurovascular unit lesions after TBI

Traumatic brain injury impairs brain function through various mechanisms. Recent studies have shown that alterations in pericytes in various diseases affect neurovascular function, but the effects of TBI on hippocampal pericytes remain unclear. Here, we investigated the effects of RAGE activation on pericytes after TBI using male C57BL/6 J mice. Hippocampal samples were collected at different time points within 7 days after TBI, the expression of PDGFR-β, NG2 and the HMGB1-S100B/RAGE signaling pathway was assessed by Western blotting, and the integrity of the hippocampal BBB at different time points was measured by immunofluorescence. RAGE-associated BBB damage in hippocampal pericytes occurred early after cortical impact. By culturing primary mouse brain microvascular pericytes, we determined the different effects of HMGB1-S100B on pericyte RAGE. To investigate whether RAGE blockade could protect neurological function after TBI, we reproduced the process of CCI by administering FPS-ZM1 to RAGE-/- mice. TEM images and BBB damage-related assays showed that inhibition of RAGE resulted in a significant improvement in the number of hippocampal vascular basement membranes and tight junctions and a reduction in perivascular oedema compared with those in the untreated group. In contrast, mouse behavioural testing and doublecortin staining indicated that targeting the HMGB1-S100B/RAGE axis after CCI could protect neurological function by reducing pericyte-associated BBB damage. In conclusion, the present study provides experimental evidence for the strong correlation between the pericyte HMGB1-S100B/RAGE axis and NVU damage in the hippocampus at the early stage of TBI and further demonstrates that pericyte RAGE serves as an important target for the protection of neurological function after TBI.

Microglia-induced neuroinflammation in hippocampal neurogenesis following traumatic brain injury

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

'Comprehensive review of emerging drug targets in traumatic brain injury (TBI): challenges and future scope

Traumatic brain injury (TBI) is a complex brain problem that causes significant morbidity and mortality among people of all age groups. The complex pathophysiology, varied symptoms, and inadequate treatment further precipitate the problem. Further, TBI produces several psychiatric problems and other related complications in post-TBI survival patients, which are often treated symptomatically or inadequately. Several approaches, including neuroprotective agents targeting several pathways of oxidative stress, neuroinflammation, cytokines, immune system GABA, glutamatergic, microglia, and astrocytes, are being tried by researchers to develop effective treatments or magic bullets to manage the condition effectively. The problem of TBI is therefore treated as a challenge among pharmaceutical scientists or researchers to develop drugs for the effective management of this problem. The goal of the present comprehensive review is to provide an overview of the several pharmacological targets, processes, and cellular pathways that researchers are focusing on, along with an update on their current state.

Endogenous Ligands of TLR4 in Microglia: Potential Targets for Related Neurological Diseases

Chronic inflammation mediated by microglia is a cause of some neuroinflammatory diseases. TLR4, a natural immune receptor on microglia, plays an important role in the occurrence of inflammation and the process of diseases. TLR4 can be activated by a variety of ligands to trigger inflammatory responses, including endogenous ligands HMGB1, S100A8/9, Heme, and Fetuin-A. As ligands derived from the body itself, they have the ability to bind directly to TLR4 and can be used as inducers of aseptic inflammation. In the past 20 years, targeting ligands rather than receptors has become an emerging therapeutic strategy for the treatment of diseases, so understanding the relationship between microglia, TLR4, TLR4 ligands, and corresponding diseases may have new implications for the treatment of diseases. In the article, we will discuss the TLR4 and the endogenous substances that can activate the TLR4 signaling pathway and present literature support for their role in neuroinflammatory diseases.

The longitudinal biochemical profiling of TBI in a drop weight model of TBI

Traumatic brain injury (TBI) is a major cause of mortality and disability worldwide, particularly among individuals under the age of 45. It is a complex, and heterogeneous disease with a multifaceted pathophysiology that remains to be elucidated. Metabolomics has the potential to identify metabolic pathways and unique biochemical profiles associated with TBI. Herein, we employed a longitudinal metabolomics approach to study TBI in a weight drop mouse model to reveal metabolic changes associated with TBI pathogenesis, severity, and secondary injury. Using proton nuclear magnetic resonance (1H NMR) spectroscopy, we biochemically profiled post-mortem brain from mice that suffered mild TBI (N = 25; 13 male and 12 female), severe TBI (N = 24; 11 male and 13 female) and sham controls (N = 16; 11 male and 5 female) at baseline, day 1 and day 7 following the injury. 1H NMR-based metabolomics, in combination with bioinformatic analyses, highlights a few significant metabolites associated with TBI severity and perturbed metabolism related to the injury. We report that the concentrations of taurine, creatinine, adenine, dimethylamine, histidine, N-Acetyl aspartate, and glucose 1-phosphate are all associated with TBI severity. Longitudinal metabolic observation of brain tissue revealed that mild TBI and severe TBI lead distinct metabolic profile changes. A multi-class model was able to classify the severity of injury as well as time after TBI with estimated 86% accuracy. Further, we identified a high degree of correlation between respective hemisphere metabolic profiles (r > 0.84, p < 0.05, Pearson correlation). This study highlights the metabolic changes associated with underlying TBI severity and secondary injury. While comprehensive, future studies should investigate whether: (a) the biochemical pathways highlighted here are recapitulated in the brain of TBI sufferers and (b) if the panel of biomarkers are also as effective in less invasively harvested biomatrices, for objective and rapid identification of TBI severity and prognosis.

Apelin-Overexpressing Neural Stem Cells in Conjunction with a Silk Fibroin Nanofiber Scaffold for the Treatment of Traumatic Brain Injury

Traumatic brain injury (TBI), especially moderate or severe TBI, is one of the most devastating injuries to the nervous system, as the existing therapies for neurological defect repair have difficulty achieving satisfactory results. Neural stem cells (NSCs) therapy is a potentially effective treatment option, especially after specific genetic modifications and when used in combination with biomimetic biological scaffolds. In this study, tussah silk fibroin (TSF) scaffolds with interconnected nanofibrous structures were fabricated using a top-down method. We constructed the apelin-overexpressing NSCs that were cocultured with a TSF nanofiber scaffold (TSFNS) that simulated the extracellular matrix in vitro. To verify the therapeutic efficacy of engineered NSCs in vivo, we constructed TBI models and randomized the C57BL/6 mice into three groups: a control group, an NSC-ctrl group (transplantation of NSCs integrated on TSFNS), and an NSC-apelin group (transplantation of apelin-overexpressing NSCs integrated on TSFNS). The neurological functions of the model mice were evaluated in stages. Specimens were obtained 24 days after transplantation for immunohistochemistry, immunofluorescence, and western blot experiments, and statistical analysis was performed. The results showed that the combination of the TSFNS and apelin overexpression guided extension and elevated the proliferation and differentiation of NSCs both in vivo and in vitro. Moreover, the transplantation of TSFNS-NSCs-Apelin reduced lesion volume, enhanced angiogenesis, inhibited neuronal apoptosis, reduced blood-brain barrier damage, and mitigated neuroinflammation. In summary, TSFNS-NSC-Apelin therapy could build a microenvironment that is more conducive to neural repair to promote the recovery of injured neurological function.

Research progress on pleiotropic neuroprotective drugs for traumatic brain injury

Traumatic brain injury (TBI) has become one of the most important causes of death and disability worldwide. A series of neuroinflammatory responses induced after TBI are key factors for persistent neuronal damage, but at the same time, such inflammatory responses can also promote debris removal and tissue repair after TBI. The concept of pleiotropic neuroprotection delves beyond the single-target treatment approach, considering the multifaceted impacts following TBI. This notion embarks deeper into the research-oriented treatment paradigm, focusing on multi-target interventions that inhibit post-TBI neuroinflammation with enhanced therapeutic efficacy. With an enriched comprehension of TBI's physiological mechanisms, this review dissects the advancements in developing pleiotropic neuroprotective pharmaceuticals to mitigate TBI. The aim is to provide insights that may contribute to the early clinical management of the condition.

The correlation between the severity of cerebral microbleeds and serum HMGB1 levels and cognitive impairment in patients with cerebral small vessel disease

Objective

The study investigated the correlation and predictive value between the severity of cerebral microbleeds (CMBs) and the level of serum High Mobility Group Protein B1 (HMGB1) and the occurrence of cognitive impairment in patients with cerebral small vessel disease (CSVD).

Methods

A total of 139 patients with CSVD admitted to the Department of Neurology of the First Affiliated Hospital of Xinxiang Medical University from December 2020 to December 2022 were selected as study subjects. The Montreal Cognitive Assessment (MoCA) scale was used to assess the cognitive function and was divided into the cognitive impairment group and the cognitive normal group. Magnetic Resonance Imaging (MRI) and Susceptibility Weighted Imaging (SWI) were used to screen and assess the severity of CMBs. Serum HMGB1 levels of CSVD patients were measured by enzyme linked immunosorbent assay (ELISA). Multivariable logistic regression analysis was used to explore risk factors for cognitive impairment and CMBs. Pearson correlation analysis was used to investigate the correlation between HMGB1 and cognitive function. Receiver Operating Characteristics (ROC) curves were used to assess the predictive value of HMGB1 for the occurrence of cognitive impairment in patients with CMBs.

Results

High Mobility Group Protein B1, uric acid (UA), glycosylated hemoglobin (HbA1c), CMBs, lacunar cerebral infarction (LI), years of education, and history of hypertension were risk factors for cognitive impairment (P < 0.05); HMGB1 was significantly and negatively associated with total MoCA score, visuospatial/executive ability, and delayed recall ability (P < 0.05). HMGB1 was significantly and positively correlated with the number of CMBs (P < 0.05). The area under the ROC curve for HMGB1 predicting cognitive impairment in patients with CMBs was 0.807 (P < 0.001).

Conclusion

Serum HMGB1 levels are associated with the development of cognitive impairment in CSVD patients, and serum HMGB1 levels have a high predictive value for the development of cognitive impairment in CSVD patients with combined CMBs, which can be used for early clinical identification and intervention of vascular cognitive impairment.

The Effects of Extrinsic and Intrinsic Factors on Neurogenesis

In the mammalian brain, neurogenesis is maintained throughout adulthood primarily in two typical niches, the subgranular zone (SGZ) of the dentate gyrus and the subventricular zone (SVZ) of the lateral ventricles and in other nonclassic neurogenic areas (e.g., the amygdala and striatum). During prenatal and early postnatal development, neural stem cells (NSCs) differentiate into neurons and migrate to appropriate areas such as the olfactory bulb where they integrate into existing neural networks; these phenomena constitute the multistep process of neurogenesis. Alterations in any of these processes impair neurogenesis and may even lead to brain dysfunction, including cognitive impairment and neurodegeneration. Here, we first summarize the main properties of mammalian neurogenic niches to describe the cellular and molecular mechanisms of neurogenesis. Accumulating evidence indicates that neurogenesis plays an integral role in neuronal plasticity in the brain and cognition in the postnatal period. Given that neurogenesis can be highly modulated by a number of extrinsic and intrinsic factors, we discuss the impact of extrinsic (e.g., alcohol) and intrinsic (e.g., hormones) modulators on neurogenesis. Additionally, we provide an overview of the contribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection to persistent neurological sequelae such as neurodegeneration, neurogenic defects and accelerated neuronal cell death. Together, our review provides a link between extrinsic/intrinsic factors and neurogenesis and explains the possible mechanisms of abnormal neurogenesis underlying neurological disorders.

PARP1 Activation Induces HMGB1 Secretion Promoting Intestinal Inflammation in Mice and Human Intestinal Organoids

Extracellular High-mobility group box 1 (HMGB1) contributes to the pathogenesis of inflammatory disorders, including inflammatory bowel diseases (IBD). Poly (ADP-ribose) polymerase 1 (PARP1) has been recently reported to promote HMGB1 acetylation and its secretion outside cells. In this study, the relationship between HMGB1 and PARP1 in controlling intestinal inflammation was explored. C57BL6/J wild type (WT) and PARP1^-/- mice were treated with DSS to induce acute colitis, or with the DSS and PARP1 inhibitor, PJ34. Human intestinal organoids, which are originated from ulcerative colitis (UC) patients, were exposed to pro-inflammatory cytokines (INFγ + TNFα) to induce intestinal inflammation, or coexposed to cytokines and PJ34. Results show that PARP1^-/- mice develop less severe colitis than WT mice, evidenced by a significant decrease in fecal and serum HMGB1, and, similarly, treating WT mice with PJ34 reduces the secreted HMGB1. The exposure of intestinal organoids to pro-inflammatory cytokines results in PARP1 activation and HMGB1 secretion; nevertheless, the co-exposure to PJ34, significantly reduces the release of HMGB1, improving inflammation and oxidative stress. Finally, HMGB1 release during inflammation is associated with its PARP1-induced PARylation in RAW264.7 cells. These findings offer novel evidence that PARP1 favors HMGB1 secretion in intestinal inflammation and suggest that impairing PARP1 might be a novel approach to manage IBD.

RAGE Inhibitors in Neurodegenerative Diseases

Nonenzymatic reactions of reducing sugars with primary amino groups of amino acids, proteins, and nucleic acids, followed by oxidative degradations would lead to the formation of advanced glycation endproducts (AGEs). The AGEs exert multifactorial effects on cell damage leading to the onset of neurological disorders. The interaction of AGEs with the receptors for advanced glycation endproducts (RAGE) contribute to the activation of intracellular signaling and the expression of the pro-inflammatory transcription factors and various inflammatory cytokines. This inflammatory signaling cascade is associated with various neurological diseases, including Alzheimer's disease (AD), secondary effects of traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and diabetic neuropathy, and other AGE-related diseases, including diabetes and atherosclerosis. Furthermore, the imbalance of gut microbiota and intestinal inflammation are also associated with endothelial dysfunction, disrupted blood-brain barrier (BBB) and thereby the onset and progression of AD and other neurological diseases. AGEs and RAGE play an important role in altering the gut microbiota composition and thereby increase the gut permeability and affect the modulation of the immune-related cytokines. The inhibition of the AGE-RAGE interactions, through small molecule-based therapeutics, prevents the inflammatory cascade of events associated with AGE-RAGE interactions, and thereby attenuates the disease progression. Some of the RAGE antagonists, such as Azeliragon, are currently in clinical development for treating neurological diseases, including AD, although currently there have been no FDA-approved therapeutics based on the RAGE antagonists. This review outlines the AGE-RAGE interactions as a leading cause of the onset of neurological diseases and the current efforts on developing therapeutics for neurological diseases based on the RAGE antagonists.

Migratory Response of Cells in Neurogenic Niches to Neuronal Death: The Onset of Harmonic Repair?

Harmonic mechanisms orchestrate neurogenesis in the healthy brain within specific neurogenic niches, which generate neurons from neural stem cells as a homeostatic mechanism. These newly generated neurons integrate into existing neuronal circuits to participate in different brain tasks. Despite the mechanisms that protect the mammalian brain, this organ is susceptible to many different types of damage that result in the loss of neuronal tissue and therefore in alterations in the functionality of the affected regions. Nevertheless, the mammalian brain has developed mechanisms to respond to these injuries, potentiating its capacity to generate new neurons from neural stem cells and altering the homeostatic processes that occur in neurogenic niches. These alterations may lead to the generation of new neurons within the damaged brain regions. Notwithstanding, the activation of these repair mechanisms, regeneration of neuronal tissue within brain injuries does not naturally occur. In this review, we discuss how the different neurogenic niches respond to different types of brain injuries, focusing on the capacity of the progenitors generated in these niches to migrate to the injured regions and activate repair mechanisms. We conclude that the search for pharmacological drugs that stimulate the migration of newly generated neurons to brain injuries may result in the development of therapies to repair the damaged brain tissue.

[A pilot study on the effects of early use of valproate sodium on neuroinflammation after traumatic brain injury]

OBJECTIVES

To study the effect of early use of sodium valproate on neuroinflammation after traumatic brain injury (TBI).

METHODS

A total of 45 children who visited in Xuzhou Children's Hospital Affiliated to Xuzhou Medical University from August 2021 to August 2022 were enrolled in this prospective study, among whom 15 healthy children served as the healthy control group, and 30 children with TBI were divided into a sodium valproate treatment group and a conventional treatment group using a random number table (n=15 each). The children in the sodium valproate treatment group were given sodium valproate in addition to conventional treatment, and those in the conventional group were given an equal volume of 5% glucose solution in addition to conventional treatment. The serum concentrations of nucleotide-binding oligomerization domain-like receptor protein 3(NLRP3), high-mobility group box 1 (HMGB1), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were measured in the healthy control group on the day of physical examination and in the children with TBI on days 1, 3, and 5 after admission. Glasgow Outcome Scale-Extended (GOS-E) score was evaluated for the children with TBI 2 months after discharge.

RESULTS

Compared with the healthy control group, the children with TBI had significantly higher serum concentrations of NLRP3, HMGB1, TNF-α, and IL-1β on day 1 after admission (P<0.017). The concentration of NLRP3 on day 5 after admission was significantly higher than that on days 1 and 3 after admission in the children with TBI (P<0.017). On days 3 and 5 after admission, the sodium valproate treatment group had a significantly lower concentration of NLRP3 than the conventional treatment group (P<0.05). For the conventional treatment group, there was no significant difference in the concentration of HMGB1 on days 1, 3, and 5 after admission (P>0.017), while for the sodium valproate treatment group, the concentration of HMGB1 on day 5 after admission was significantly lower than that on days 1 and 3 after admission (P<0.017). On day 5 after admission, the sodium valproate treatment group had a significantly lower concentration of HMGB1 than the conventional treatment group (P<0.05). For the children with TBI, the concentration of TNF-α on day 1 after admission was significantly lower than that on days 3 and 5 after admission (P<0.017). On days 3 and 5 after admission, the sodium valproate treatment group had a significantly lower concentration of TNF-α than the conventional treatment group (P<0.05). The concentration of IL-1β on day 3 after admission was significantly lower than that on days 1 and 5 after admission (P<0.017) in the children with TBI. On days 3 and 5 after admission, the sodium valproate treatment group had a significantly lower concentration of IL-1β than the conventional treatment group (P<0.05). The GOS-E score was significantly higher in the sodium valproate treatment group than that in the conventional treatment group 2 months after discharge (P<0.05).

CONCLUSIONS

Early use of sodium valproate can reduce the release of neuroinflammatory factors and improve the prognosis of children with TBI.

Hyperbaric Oxygenation Prevents Loss of Immature Neurons in the Adult Hippocampal Dentate Gyrus Following Brain Injury

A growing body of evidence suggests that hyperbaric oxygenation (HBO) may affect the activity of adult neural stem cells (NSCs). Since the role of NSCs in recovery from brain injury is still unclear, the purpose of this study was to investigate the effects of sensorimotor cortex ablation (SCA) and HBO treatment (HBOT) on the processes of neurogenesis in the adult dentate gyrus (DG), a region of the hippocampus that is the site of adult neurogenesis. Ten-week-old Wistar rats were divided into groups: Control (C, intact animals), Sham control (S, animals that underwent the surgical procedure without opening the skull), SCA (animals in whom the right sensorimotor cortex was removed via suction ablation), and SCA + HBO (operated animals that passed HBOT). HBOT protocol: pressure applied at 2.5 absolute atmospheres for 60 min, once daily for 10 days. Using immunohistochemistry and double immunofluorescence labeling, we show that SCA causes significant loss of neurons in the DG. Newborn neurons in the subgranular zone (SGZ), inner-third, and partially mid-third of the granule cell layer are predominantly affected by SCA. HBOT decreases the SCA-caused loss of immature neurons, prevents reduction of dendritic arborization, and increases proliferation of progenitor cells. Our results suggest a protective effect of HBO by reducing the vulnerability of immature neurons in the adult DG to SCA injury.

The Dialogue Between Neuroinflammation and Adult Neurogenesis: Mechanisms Involved and Alterations in Neurological Diseases

Adult neurogenesis occurs mainly in the subgranular zone of the hippocampal dentate gyrus and the subventricular zone of the lateral ventricles. Evidence supports the critical role of adult neurogenesis in various conditions, including cognitive dysfunction, Alzheimer's disease (AD), and Parkinson's disease (PD). Several factors can alter adult neurogenesis, including genetic, epigenetic, age, physical activity, diet, sleep status, sex hormones, and central nervous system (CNS) disorders, exerting either pro-neurogenic or anti-neurogenic effects. Compelling evidence suggests that any insult or injury to the CNS, such as traumatic brain injury (TBI), infectious diseases, or neurodegenerative disorders, can provoke an inflammatory response in the CNS. This inflammation could either promote or inhibit neurogenesis, depending on various factors, such as chronicity and severity of the inflammation and underlying neurological disorders. Notably, neuroinflammation, driven by different immune components such as activated glia, cytokines, chemokines, and reactive oxygen species, can regulate every step of adult neurogenesis, including cell proliferation, differentiation, migration, survival of newborn neurons, maturation, synaptogenesis, and neuritogenesis. Therefore, this review aims to present recent findings regarding the effects of various components of the immune system on adult neurogenesis and to provide a better understanding of the role of neuroinflammation and neurogenesis in the context of neurological disorders, including AD, PD, ischemic stroke (IS), seizure/epilepsy, TBI, sleep deprivation, cognitive impairment, and anxiety- and depressive-like behaviors. For each disorder, some of the most recent therapeutic candidates, such as curcumin, ginseng, astragaloside, boswellic acids, andrographolide, caffeine, royal jelly, estrogen, metformin, and minocycline, have been discussed based on the available preclinical and clinical evidence.

The SIRT1-HMGB1 axis: Therapeutic potential to ameliorate inflammatory responses and tumor occurrence

Inflammation is a common complication of many chronic diseases. It includes inflammation of the parenchyma and vascular systems. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylase, which can directly participate in the suppression of inflammation. It can also regulate the activity of other proteins. Among them, high mobility group box 1 (HMGB1) signaling can be inhibited by deacetylating four lysine residues (55, 88, 90, and 177) in quiescent endothelial cells. HMGB1 is a ubiquitous nuclear protein, once translocated outside the cell, which can interact with various target cell receptors including the receptor for advanced glycation end-products (RAGE), toll-like receptor (TLR) 2, and TLR4 and stimulates the release of pro-inflammatory cyto-/chemokines. And SIRT1 has been reported to inhibit the activity of HMGB1. Both are related to the occurrence and development of inflammation and associated diseases but show an antagonistic relationship in controlling inflammation. Therefore, in this review, we introduce how this signaling axis regulates the emergence of inflammation-related responses and tumor occurrence, providing a new experimental perspective for future inflammation research. In addition, it explores diverse upstream regulators and some natural/synthetic activators of SIRT1 as a possible treatment for inflammatory responses and tumor occurrence which may encourage the development of new anti-inflammatory drugs. Meanwhile, this review also introduces the potential molecular mechanism of the SIRT1-HMGB1 pathway to improve inflammation, suggesting that SIRT1 and HMGB1 proteins may be potential targets for treating inflammation.

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

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.

Inhibition of Heat Shock Protein 90 Attenuates the Damage of Blood-Brain Barrier Integrity in Traumatic Brain Injury Mouse Model

Heat shock protein 90 (HSP90) is widely found in brain tissue. HSP90 inhibition has been proven to have neuroprotective effects on ischemic strokes. In order to study the role of HSP90 in traumatic brain injury (TBI), we carried out the present study. A novel inhibitor of the HSP90 protein, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DA), has been investigated for its function on the blood-brain barrier (BBB) damage after traumatic brain injury (TBI) in mouse models. These C57BL/6 mice were used as a TBI model and received 17-DA (0.1 mg/kg/d, intraperitoneally) until the experiment ended. To find out whether 17-DA may protect against TBI in vitro, bEnd.3 cells belonging to mouse brain microvascular endothelium were used. The HSP90 protein expressions were raised after TBI at the pericontusional area, especially at 3 d. Our study suggested that 17-DA-treated mice improved the recovery ability of neurological deficits and decreased brain edema, Evans blue extravasation, and the loss of tight junction proteins (TJPs) post-TBI. 17-DA significantly promoted cell proliferation and alleviated apoptosis by inhibiting the generation of intracellular reactive oxygen species (ROS) to downregulate cleaved caspase-3, matrix metallopeptidase- (MMP-) 2, MMP-9, and P-P65 in bEnd.3 cells after the injury. As a result, we assumed that the HSP90 protein was activated post-TBI, and inhibition of HSP90 protein reduced the disruption of BBB and improved the neurobehavioral scores in a mouse model of TBI through the action of 17-DA, which inhibited ROS generation and regulated MMP-2, MMP-9, NF-κB, and caspase-associated pathways. Thus, blocking HSP90 protein may be a potential therapeutic strategy for TBI.

Nonoxid-HMGB1 Attenuates Cognitive Impairment After Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is a major global burden of health. As an accepted inflammatory mediator, high mobility group box 1 (HMGB1) is found to be effective in facilitating neurogenesis and axonal regeneration. SH3RF2 (also known as POSHER), an E3 ligase SH3 domain-containing ring finger 2, belongs to the SH3RF family of proteins. Here, we aimed to investigate the role of redox states of HMGB1 on neurite outgrowth and regeneration both in vitro and in vivo. In this study, distinct recombinant HMGB1 redox isoforms were used. Sequencing for RNA-seq and data analysis were performed to find the potential downstream target of nonoxid-HMGB1 (3S-HMGB1). Protein changes and distribution of SH3RF2 were evaluated by western blot assays and immunofluorescence. Lentivirus and adeno-associated virus were used to regulate the expression of genes. Nonoxid-HMGB1-enriched exosomes were constructed and used to treat TBI rats. Neurological function was evaluated by OF test and NOR test. Results demonstrated that nonoxid-HMGB1 and fr-HMGB1, but not ds-HMGB1, promoted neurite outgrowth and axon elongation. RNA-seq and western blot assay indicated a significant increase of SH3RF2 in neurons after treated with nonoxid-HMGB1 or fr-HMGB1. Notably, the beneficial effects of nonoxid-HMGB1 were attenuated by downregulation of SH3RF2. Furthermore, nonoxid-HMGB1 ameliorated cognitive impairment in rats post-TBI via SH3RF2. Altogether, our experimental results suggest that one of the promoting neurite outgrowth and regeneration mechanisms of nonoxid-HMGB1 is mediated through the upregulated expression of SH3RF2. Nonoxid-HMGB1 is an attractive therapeutic candidate for the treatment of TBI.

Toll-like receptors 2 and 4 differentially regulate the self-renewal and differentiation of spinal cord neural precursor cells

BACKGROUND

Toll-like receptors (TLRs) represent critical effectors in the host defense response against various pathogens; however, their known function during development has also highlighted a potential role in cell fate determination and neural differentiation. While glial cells and neural precursor cells (NPCs) of the spinal cord express both TLR2 and TLR4, their influence on self-renewal and cell differentiation remains incompletely described.

METHODS

TLR2, TLR4 knock-out and the wild type mice were employed for spinal cord tissue analysis and NPCs isolation at early post-natal stage. Sox2, FoxJ1 and Ki67 expression among others served to identify the undifferentiated and proliferative NPCs; GFAP, Olig2 and β-III-tubulin markers served to identify astrocytes, oligodendrocytes and neurons respectively after NPC spontaneous differentiation. Multiple comparisons were analyzed using one-way ANOVA, with appropriate corrections such as Tukey's post hoc tests used for comparisons.

RESULTS

We discovered that the deletion of TLR2 or TLR4 significantly reduced the number of Sox2-expressing NPCs in the neonatal mouse spinal cord. While TLR2-knockout NPCs displayed enhanced self-renewal, increased proliferation and apoptosis, and delayed neural differentiation, the absence of TLR4 promoted the neural differentiation of NPCs without affecting proliferation, producing long projecting neurons. TLR4 knock-out NPCs showed significantly higher expression of Neurogenin1, that would be involved in the activation of this neurogenic program by a ligand and microenvironment-independent mechanism. Interestingly, the absence of both TLR2 and TLR4, which induces also a significant reduction in the expression of TLR1, in NPCs impeded oligodendrocyte precursor cell maturation to a similar degree.

CONCLUSIONS

Our data suggest that Toll-like receptors are needed to maintain Sox2 positive neural progenitors in the spinal cord, however possess distinct regulatory roles in mouse neonatal spinal cord NPCs-while TLR2 and TLR4 play a similar role in oligodendrocytic differentiation, they differentially influence neural differentiation.

Aquaporin 4 in Traumatic Brain Injury: From Molecular Pathways to Therapeutic Target

Traumatic brain injury (TBI) is known as an acute degenerative pathology of the central nervous system, and has been shown to increase brain aquaporin 4 (AQP4) expression. Various molecular mechanisms affect AQP4 expression, including neuronal high mobility group box 1, forkhead box O3a, vascular endothelial growth factor, hypoxia-inducible factor-1 α (HIF-1 α) sirtuin 2, NF-κB, Malat1, nerve growth factor and Angiotensin II receptor type 1. In addition, inhibition of AQP4 with FK-506, MK-801 (indirectly by targeting N-methyl-D-aspartate receptor), inactivation of adenosine A2A receptor, levetiracetam, adjudin, progesterone, estrogen, V1aR inhibitor, hypertonic saline, erythropoietin, poloxamer 188, brilliant blue G, HIF-1alpha inhibitor, normobaric oxygen therapy, astaxanthin, epigallocatechin-3-gallate, sesamin, thaliporphine, magnesium, prebiotic fiber, resveratrol and omega-3, as well as AQP4 gene silencing lead to reduced edema upon TBI. This review summarizes current knowledge and evidence on the relationship between AQP4 and TBI, and the potential mechanisms involved.

Revisiting Excitotoxicity in Traumatic Brain Injury: From Bench to Bedside

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality. Consequences vary from mild cognitive impairment to death and, no matter the severity of subsequent sequelae, it represents a high burden for affected patients and for the health care system. Brain trauma can cause neuronal death through mechanical forces that disrupt cell architecture, and other secondary consequences through mechanisms such as inflammation, oxidative stress, programmed cell death, and, most importantly, excitotoxicity. This review aims to provide a comprehensive understanding of the many classical and novel pathways implicated in tissue damage following TBI. We summarize the preclinical evidence of potential therapeutic interventions and describe the available clinical evaluation of novel drug targets such as vitamin B12 and ifenprodil, among others.

Neurological Symptoms and Their Associations With Inflammatory Biomarkers in the Chronic Phase Following Traumatic Brain Injuries

BACKGROUND

The underlying biological mechanisms for neurological symptoms following a traumatic brain injury (TBI) remain poorly understood. This study investigated the associations between serum inflammatory biomarkers and neurological symptoms in the chronic phase following moderate to severe TBI.

METHODS

The serum interleukin [IL]-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, and the tumor necrosis factor [TNF]-α in 72 TBI patients 6 months to 2 years post injury were measured. Neurological symptoms including depression, chronic headache, sleep disturbance, irritability, anxiety, and global neurological disability was assessed. The associations between the biomarkers and the neurological symptoms were assessed using correlation and regression analysis.

RESULTS

It was found that the most common post-injury symptom was sleep disturbance (84.7%), followed by chronic headaches (59.7%), irritability (55.6%), and depression (54.2%). TNF-α was a protective factor for chronic headache (OR = 0.473, 95% CI = 0.235-0.952). IL-6 was positively associated with sleep disturbance (r = 0.274, p = 0.021), while IL-5 and IL-12p70 were negatively associated with the degree of global neurological disability (r = -0.325, p = 0.006; r = -0.319, p = 0.007).

CONCLUSION

This study provides preliminary evidence for the association between chronic inflammation with neurological symptoms following a TBI, which suggests that anti-inflammatory could be a potential target for post-TBI neurological rehabilitation. Further research with larger sample sizes and more related biomarkers are still needed, however, to elucidate the inflammatory mechanisms for this association.

The Role of HMGB1 in Traumatic Brain Injury-Bridging the Gap Between the Laboratory and Clinical Studies

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is amongst the leading causes of mortality and morbidity worldwide. However, several pharmacological strategies in the clinical setting remain unsuccessful. Mounting evidence implicates High Mobility Group Box protein 1 (HMGB1) as a unique alternative target following brain injury. Herein, we discuss current understanding of HMGB1 in TBI and obstacles to clinical translation.

RECENT FINDINGS

HMGB1 plays a pivotal role as a 'master-switch' of neuro-inflammation following injury and in the regulation of neurogenesis during normal development. Animal models point towards the involvement of HMGB1 signalling in prolonged activation of glial cells and widespread neuronal death. Early experimental studies demonstrate positive effects of HMGB1 antagonism on both immunohistochemical and neuro-behavioural parameters following injury. Raised serum/CSF HMGB1 in humans is associated with poor outcomes post-TBI. HMGB1 is a promising therapeutic target post-TBI. However, further studies elucidating receptor, cell, isoform, and temporal effects are required prior to clinical translation.

Co-Ultra PEALut Enhances Endogenous Repair Response Following Moderate Traumatic Brain Injury

This study aimed to assess the neuro-regenerative properties of co-ultramicronized PEALut (Glialia^®), composed of palmitoylethanolamide (PEA) and the flavonoid luteolin (Lut), in an in vivo model of traumatic brain injury (TBI) and patients affected by moderate TBI. An increase in neurogenesis was seen in the mice at 72 h and 7 d after TBI. The co-ultra PEALut treatment helped the neuronal reconstitution process to restore the basal level of both novel and mature neurons; moreover, it induced a significant upregulation of the neurotrophic factors, which ultimately led to progress in terms of memory recall during behavioral testing. Moreover, our preliminary findings in a clinical trial suggested that Glialia^® treatment facilitated neural recovery on working memory. Thus, co-ultra PEALut (Glialia^®) could represent a valuable therapeutic agent for intensifying the endogenous repair response in order to better treat TBI.

Circulating HMGB1 is elevated in veterans with Gulf War Illness and triggers the persistent pro-inflammatory microglia phenotype in male C57Bl/6J mice

Gulf War Illness (GWI) is a chronic, multi-symptom peripheral and CNS condition with persistent microglial dysregulation, but the mechanisms driving the continuous neuroimmune pathology are poorly understood. The alarmin HMGB1 is an autocrine and paracrine pro-inflammatory signal, but the role of circulating HMGB1 in persistent neuroinflammation and GWI remains largely unknown. Using the LPS model of the persistent microglial pro-inflammatory response, male C57Bl/6J mice injected with LPS (5 mg/kg IP) exhibited persistent changes in microglia morphology and elevated pro-inflammatory markers in the hippocampus, cortex, and midbrain 7 days after LPS injection, while the peripheral immune response had resolved. Ex vivo serum analysis revealed an augmented pro-inflammatory response to LPS when microglia cells were cultured with the 7-day LPS serum, indicating the presence of bioactive circulating factors that prime the microglial pro-inflammatory response. Elevated circulating HMGB1 levels were identified in the mouse serum 7 days after LPS administration and in the serum of veterans with GWI. Tail vein injection of rHMGB1 in male C57Bl/6 J mice elevated TNFα mRNA levels in the liver, hippocampus, and cortex, demonstrating HMGB1-induced peripheral and CNS effects. Microglia isolated at 7 days after LPS injection revealed a unique transcriptional profile of 17 genes when compared to the acute 3 H LPS response, 6 of which were also upregulated in the midbrain by rHMGB1, highlighting a distinct signature of the persistent pro-inflammatory microglia phenotype. These findings indicate that circulating HMGB1 is elevated in GWI, regulates the microglial neuroimmune response, and drives chronic neuroinflammation that persists long after the initial instigating peripheral stimulus.

LPS Primes Brain Responsiveness to High Mobility Group Box-1 Protein

High mobility group box (HMGB)1 action contributes to late phases of sepsis, but the effects of increased endogenous plasma HMGB1 levels on brain cells during inflammation are unclear. Here, we aimed to further investigate the role of HMGB1 in the brain during septic-like lipopolysaccharide-induced inflammation in rats (LPS, 10 mg/kg, i.p.). HMGB-1 mRNA expression and release were measured in the periphery/brain by RT-PCR, immunohistochemistry and ELISA. In vitro experiments with disulfide-HMGB1 in primary neuro-glial cell cultures of the area postrema (AP), a circumventricular organ with a leaky blood–brain barrier and direct access to circulating mediators like HMGB1 and LPS, were performed to determine the direct influence of HMGB1 on this pivotal brain structure for immune-to-brain communication. Indeed, HMGB1 plasma levels stayed elevated after LPS injection. Immunohistochemistry of brains and AP cultures confirmed LPS-stimulated cytoplasmatic translocation of HMGB1 indicative of local HMGB1 release. Moreover, disulfide-HMGB1 stimulation induced nuclear factor (NF)-κB activation and a significant release of interleukin-6, but not tumor necrosis factor α, into AP culture supernatants. However, only a few AP cells directly responded to HMGB1 with increased intracellular calcium concentration. Interestingly, priming with LPS induced a seven-fold higher percentage of responsive cells to HMGB1. We conclude that, as a humoral and local mediator, HMGB1 enhances brain inflammatory responses, after LPS priming, linked to sustained sepsis symptoms.

DAMPs and RAGE Pathophysiology at the Acute Phase of Brain Injury: An Overview

Early or primary injury due to brain aggression, such as mechanical trauma, hemorrhage or is-chemia, triggers the release of damage-associated molecular patterns (DAMPs) in the extracellular space. Some DAMPs, such as S100B, participate in the regulation of cell growth and survival but may also trigger cellular damage as their concentration increases in the extracellular space. When DAMPs bind to pattern-recognition receptors, such as the receptor of advanced glycation end-products (RAGE), they lead to non-infectious inflammation that will contribute to necrotic cell clearance but may also worsen brain injury. In this narrative review, we describe the role and ki-netics of DAMPs and RAGE at the acute phase of brain injury. We searched the MEDLINE database for “DAMPs” or “RAGE” or “S100B” and “traumatic brain injury” or “subarachnoid hemorrhage” or “stroke”. We selected original articles reporting data on acute brain injury pathophysiology, from which we describe DAMPs release and clearance upon acute brain injury, and the implication of RAGE in the development of brain injury. We will also discuss the clinical strategies that emerge from this overview in terms of biomarkers and therapeutic perspectives