Anti-high mobility group box 1 monoclonal antibody ameliorates experimental autoimmune encephalomyelitis

Asymptomatic herpes simplex virus brain infection elicits cellular senescence phenotypes in the central nervous system of mice suffering multiple sclerosis-like disease

Experimental autoimmune encephalomyelitis (EAE) is a demyelinating disease affecting the central nervous system (CNS) in animals that parallels several clinical and molecular traits of multiple sclerosis in humans. Herpes simplex virus type 1 (HSV-1) infection mainly causes cold sores and eye diseases, yet eventually, it can also reach the CNS, leading to acute encephalitis. Notably, a significant proportion of healthy individuals are likely to have asymptomatic HSV-1 brain infection with chronic brain inflammation due to persistent latent infection in neurons. Because cellular senescence is suggested as a potential factor contributing to the development of various neurodegenerative disorders, including multiple sclerosis, and viral infections may induce a premature senescence state in the CNS, potentially increasing susceptibility to such disorders, here we examine the presence of senescence-related markers in the brains and spinal cords of mice with asymptomatic HSV-1 brain infection, EAE, and both conditions. Across all scenarios, we find a significant increases of senescence biomarkers in the CNS with some differences depending on the analyzed group. Notably, some senescence biomarkers are exclusively observed in mice with the combined conditions. These results indicate that asymptomatic HSV-1 brain infection and EAE associate with a significant expression of senescence biomarkers in the CNS.

IL-33 and HMGB1 modulate the progression of EAE via oppositely regulating each other

Interleukin-33 (IL-33) and high mobility group box 1 (HMGB1) have been reported to play crucial and distinct roles in experimental autoimmune encephalomyelitis (EAE). However, little is known about their interaction in the progression of EAE. In this study, the dynamic expression and release of IL-33 and HMGB1 in different stages of EAE in vivo, and their interaction in vitro were explored. We found that HMGB1 was dominant in pre-onset stage of EAE, while IL-33 was dominant in peak stage. Moreover, both blockade of extracellular HMGB1 in the central nervous system (CNS) and conditional knockout of HMGB1 in astrocytes decreased IL-33 release. HMGB1 promoted the release of IL-33, while IL-33 reduced the release of HMGB1 from primary astrocytes in vitro. Taken together, IL-33 and HMGB1 in the CNS jointly participate in the EAE progression and the inhibitory effect of IL-33 on HMGB1 may be involved in the self-limiting of EAE.

The role of high mobility group box 1 in neuroinflammatory related diseases

High mobility group box 1 (HMGB1) is a ubiquitous and highly conserved non-histone DNA-binding protein with different biological functions according to its subcellular localization. It is widely believed that HMGB1, which is released into the extracellular space, plays a key role in the inflammatory response. In recent years, numerous studies have shown that the development of various neurological diseases such as epilepsy, Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), cerebrovascular disease and traumatic brain injury (TBI) are inextricably linked to inflammation. We will review the mechanisms of HMGB1 and its receptors in nervous system inflammation to provide a basis for further development of new HMGB1-based therapies.

HMGB1 in nervous system diseases: A common biomarker and potential therapeutic target

High-mobility group box-1 (HMGB1) is a nuclear protein associated with early inflammatory changes upon extracellular secretion expressed in various cells, including neurons and microglia. With the progress of research, neuroinflammation is believed to be involved in the pathogenesis of neurological diseases such as Parkinson's, epilepsy, and autism. As a key promoter of neuroinflammation, HMGB1 is thought to be involved in the pathogenesis of Parkinson's disease, stroke, traumatic brain injury, epilepsy, autism, depression, multiple sclerosis, and amyotrophic lateral sclerosis. However, in the clinic, HMGB1 has not been described as a biomarker for the above-mentioned diseases. However, the current preclinical research results show that HMGB1 antagonists have positive significance in the treatment of Parkinson's disease, stroke, traumatic brain injury, epilepsy, and other diseases. This review discusses the possible mechanisms by which HMGB1 mediates Parkinson's disease, stroke, traumatic brain injury, epilepsy, autism, depression, multiple sclerosis, amyotrophic lateral sclerosis, and the potential of HMGB1 as a biomarker for these diseases. Future research needs to further explore the underlying molecular mechanisms and clinical translation.

The Role of High Mobility Group Box 1 (HMGB1) in Neurodegeneration: A Systematic Review

BACKGROUND

High mobility group box 1 (HMGB1) protein is a damage-associated molecular pattern (DAMP) that plays an important role in the repair and regeneration of tissue injury. It also acts as a pro-inflammatory cytokine through the activation of toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE), to elicit the neuroinflammatory response. HMGB1 may aggravate several cellular responses, which may lead to pathological inflammation and cellular death. Thus, there have been a considerable amount of research into the pathological role of HMGB1 in diseases. However, whether the mechanism of action of HMGB1 is similar in all neurodegenerative disease pathology remains to be determined.

OBJECTIVE

Therefore, this systematic review aimed to critically evaluate and elucidate the role of HMGB1 in the pathology of neurodegeneration based on the available literature.

METHODS

A comprehensive literature search was performed on four databases; EMBASE, PubMed, Scopus, and CINAHL Plus.

RESULTS

A total of 85 articles were selected for critical appraisal, after subjecting to the inclusion and exclusion criteria in this study. The selected articles revealed that HMGB1 levels were found elevated in most neurodegeneration except in Huntington's disease and Spinocerebellar ataxia, where the levels were found decreased. This review also showcased that HMGB1 may act on distinctive pathways to elicit its pathological response leading to the various neurodegeneration processes/ diseases.

CONCLUSION

While there have been promising findings in HMGB1 intervention research, further studies may still be required before any HMGB1 intervention may be recommended as a therapeutic target for neurodegenerative diseases.

Involvement of TLR2-TLR4, NLRP3, and IL-17 in pain induced by a novel Sprague-Dawley rat model of experimental autoimmune encephalomyelitis

Up to 92% of patients suffering from multiple sclerosis (MS) experience pain, most without adequate treatment, and many report pain long before motor symptoms associated with MS diagnosis. In the most commonly studied rodent model of MS, experimental autoimmune encephalomyelitis (EAE), motor impairments/disabilities caused by EAE can interfere with pain testing. In this study, we characterize a novel low-dose myelin-oligodendrocyte-glycoprotein (MOG)-induced Sprague-Dawley (SD) model of EAE-related pain in male rats, optimized to minimize motor impairments/disabilities. Adult male SD rats were treated with increasing doses of intradermal myelin-oligodendrocyte-glycoprotein (MOG1-125) (0, 4, 8, and 16 μg) in incomplete Freund's adjuvant (IFA) vehicle to induce mild EAE. Von Frey testing and motor assessments were conducted prior to EAE induction and then weekly thereafter to assess EAE-induced pain and motor impairment. Results from these studies demonstrated that doses of 8 and 16 μg MOG1-125 were sufficient to produce stable mechanical allodynia for up to 1 month in the absence of hindpaw motor impairments/disabilities. In the follow-up studies, these doses of MOG1-125, were administered to create allodynia in the absence of confounded motor impairments. Then, 2 weeks later, rats began daily subcutaneous injections of the Toll-like receptor 2 and 4 (TLR2-TLR4) antagonist (+)-naltrexone [(+)-NTX] or saline for an additional 13 days. We found that (+)-NTX also reverses EAE-induced mechanical allodynia in the MOG-induced SD rat model of EAE, supporting parallels between models, but now allowing a protracted timecourse to be examined completely free of motor confounds. Exploring further mechanisms, we demonstrated that both spinal NOD-like receptor protein 3 (NLRP3) and interleukin-17 (IL-17) are necessary for EAE-induced pain, as intrathecal injections of NLRP3 antagonist MCC950 and IL-17 neutralizing antibody both acutely reversed EAE-induced pain. Finally, we show that spinal glial immunoreactivity induced by EAE is reversed by (+)-NTX, and that spinal demyelination correlates with the severity of motor impairments/disabilities. These findings characterize an optimized MOG-induced SD rat model of EAE for the study of pain with minimal motor impairments/disabilities. Finally, these studies support the role of TLR2-TLR4 antagonists as a potential treatment for MS-related pain and other pain and inflammatory-related disorders.

Anti-high mobility group box protein 1 monoclonal antibody downregulating P-glycoprotein as novel epilepsy therapeutics

Epilepsy, a neurological illness, is characterized by recurrent uncontrolled seizures. There are many treatments of options that can be used as the therapy of epilepsy. However, anti-seizure medications as the primary treatment choice for epilepsy show many possible adverse effects and even pharmacoresistance to the therapy. High Mobility Group Box 1 (HMGB1) as an initiator and amplifier of the neuroinflammation is responsible for the onset and progression of epilepsy by overexpressing P-glycoprotein on the blood brain barrier. HMGB1 proteins then activate TLR4 in neurons and astrocytes, in which proinflammatory cytokines are produced. Anti-HMGB1 mAb works by blocking the HMGB1, reducing inflammatory activity in the brain that may affect epileptogenesis. Through the process, anti-HMGB1 mAb reduces the TLR4 activity and other receptors that may involve in promote signal of epilepsy such as RAGE. Several studies have shown that anti-HMGB1 has the potential to inhibit the increase in serum HMGB1 in plasma and brain tissue. Further research is needed to identify the mechanism of the inhibiting of overexpression of P-glycoprotein through anti-HMGB1 mAb.

Neurons Are a Primary Driver of Inflammation via Release of HMGB1

Recent data show that activation of nociceptive (sensory) nerves turns on localized inflammation within the innervated area in a retrograde manner (antidromically), even in the absence of tissue injury or molecular markers of foreign invaders. This neuroinflammatory process is activated and sustained by the release of neuronal products, such as neuropeptides, with the subsequent amplification via recruitment of immunocompetent cells, including macrophages and lymphocytes. High mobility group box 1 protein (HMGB1) is a highly conserved, well characterized damage-associated molecular pattern molecule expressed by many cells, including nociceptors and is a marker of inflammatory diseases. In this review, we summarize recent evidence showing that neuronal HMGB1 is required for the development of neuroinflammation, as knock out limited to neurons or its neutralization via antibodies ameliorate injury in models of nerve injury and of arthritis. Further, the results of study show that HMGB1 is actively released during neuronal depolarization and thus plays a previously unrecognized key etiologic role in the initiation and amplification of neuroinflammation. Direct targeting of HMGB1 is a promising approach for novel anti-inflammatory therapy.

NLRP3 Inflammasome-Dependent Increases in High Mobility Group Box 1 Involved in the Cognitive Dysfunction Caused by Tau-Overexpression

Tau hyperphosphorylation is a characteristic alteration present in a range of neurological conditions, such as traumatic brain injury (TBI) and neurodegenerative diseases. Treatments targeting high-mobility group box protein 1 (HMGB1) induce neuroprotective effects in these neuropathologic conditions. However, little is known about the interactions between hyperphosphorylated tau and HMGB1 in neuroinflammation. We established a model of TBI with controlled cortical impacts (CCIs) and a tau hyperphosphorylation model by injecting the virus encoding human P301S tau in mice, and immunofluorescence, western blotting analysis, and behavioral tests were performed to clarify the interaction between phosphorylated tau (p-tau) and HMGB1 levels. We demonstrated that p-tau and HMGB1 were elevated in the spatial memory-related brain regions in mice with TBI and tau-overexpression. Animals with tau-overexpression also had significantly increased nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation, which manifested as increases in apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), activating caspase-1 and interleukin 1 beta (IL-1β) levels. In addition, NLRP3^–/– mice and the HMGB1 inhibitor, glycyrrhizin, were used to explore therapeutic strategies for diseases with p-tau overexpression. Compared with wild-type (WT) mice with tau-overexpression, downregulation of p-tau and HMGB1 was observed in NLRP3^–/– mice, indicating that HMGB1 alterations were NLRP3-dependent. Moreover, treatment with glycyrrhizin at a late stage markedly reduced p-tau levels and improved performance in the Y- and T-mazes and the ability of tau-overexpressing mice to build nests, which revealed improvements in spatial memory and advanced hippocampal function. The findings identified that p-tau has a triggering role in the modulation of neuroinflammation and spatial memory in an NLRP3-dependent manner, and suggest that treatment with HMGB1 inhibitors may be a better therapeutic strategy for tauopathies.

Toll-like receptor 2 and 4 antagonism for the treatment of experimental autoimmune encephalomyelitis (EAE)-related pain

Neuropathic pain is a major symptom of multiple sclerosis (MS) with up to 92% of patients reporting bodily pain, and 85% reporting pain severe enough to cause functional disability. None of the available therapeutics target MS pain. Toll-like receptors 2 and 4 (TLR2/TLR4) have emerged as targets for treating a wide array of autoimmune disorders, including MS, as well as having demonstrated success at suppressing pain in diverse animal models. The current series of studies tested systemic TLR2/TLR4 antagonists in males and females in a low-dose Myelin oligodendrocyte glycoprotein (MOG) experimental autoimmune encephalomyelitis (EAE) model, with reduced motor dysfunction to allow unconfounded testing of allodynia through 50+ days post-MOG. The data demonstrated that blocking TLR2/TLR4 suppressed EAE-related pain, equally in males and females; upregulation of dorsal spinal cord proinflammatory gene expression for TLR2, TLR4, NLRP3, interleukin-1β, IkBα, TNF-α and interleukin-17; and upregulation of dorsal spinal cord expression of glial immunoreactivity markers. In support of these results, intrathecal interleukin-1 receptor antagonist reversed EAE-induced allodynia, both early and late after EAE induction. In contrast, blocking TLR2/TLR4 did not suppress EAE-induced motor disturbances induced by a higher MOG dose. These data suggest that blocking TLR2/TLR4 prevents the production of proinflammatory factors involved in low dose EAE pathology. Moreover, in this EAE model, TLR2/TLR4 antagonists were highly effective in reducing pain, whereas motor impairment, as seen in high dose MOG EAE, is not affected.

High Mobility Group Box-1 and Blood-Brain Barrier Disruption

Increasing evidence suggests that inflammatory responses are involved in the progression of brain injuries induced by a diverse range of insults, including ischemia, hemorrhage, trauma, epilepsy, and degenerative diseases. During the processes of inflammation, disruption of the blood–brain barrier (BBB) may play a critical role in the enhancement of inflammatory responses and may initiate brain damage because the BBB constitutes an interface between the brain parenchyma and the bloodstream containing blood cells and plasma. The BBB has a distinct structure compared with those in peripheral tissues: it is composed of vascular endothelial cells with tight junctions, numerous pericytes surrounding endothelial cells, astrocytic endfeet, and a basement membrane structure. Under physiological conditions, the BBB should function as an important element in the neurovascular unit (NVU). High mobility group box-1 (HMGB1), a nonhistone nuclear protein, is ubiquitously expressed in almost all kinds of cells. HMGB1 plays important roles in the maintenance of chromatin structure, the regulation of transcription activity, and DNA repair in nuclei. On the other hand, HMGB1 is considered to be a representative damage-associated molecular pattern (DAMP) because it is translocated and released extracellularly from different types of brain cells, including neurons and glia, contributing to the pathophysiology of many diseases in the central nervous system (CNS). The regulation of HMGB1 release or the neutralization of extracellular HMGB1 produces beneficial effects on brain injuries induced by ischemia, hemorrhage, trauma, epilepsy, and Alzheimer’s amyloidpathy in animal models and is associated with improvement of the neurological symptoms. In the present review, we focus on the dynamics of HMGB1 translocation in different disease conditions in the CNS and discuss the functional roles of extracellular HMGB1 in BBB disruption and brain inflammation. There might be common as well as distinct inflammatory processes for each CNS disease. This review will provide novel insights toward an improved understanding of a common pathophysiological process of CNS diseases, namely, BBB disruption mediated by HMGB1. It is proposed that HMGB1 might be an excellent target for the treatment of CNS diseases with BBB disruption.

HMGB1 as a therapeutic target in disease

High-mobility group box 1 (HMGB1) was initially recognized as a ubiquitous nuclear protein involved in maintaining the nucleosome integrity and facilitating gene transcription. HMGB1 has since been reevaluated to be a prototypical damage-associated molecular pattern (DAMP) protein, and together with its exogenous counterpart, pathogen-associated molecular pattern (PAMP), completes the body's alarmin system against disturbances in homeostasis. HMGB1 can be released into the extracellular matrix (ECM) by either granulocytes or necrotic cells to serve as a chemotaxis/cytokine during infection, endotoxemia, hypoxia, ischemia-reperfusion events, and cancer. Different isoforms of HMGB1 present with distinctive physiological functions in ECM-fully-reduced HMGB1 (all thiol) acts as the initial damage signal to recruit circulating myeloid cells, disulfide HMGB1 behaves as a cytokine to activate macrophages and neutrophils, and both signals are turned off when HMGB1 is terminally oxidized into the final sulfonate form. Targeting HMGB1 constitutes a favorable therapeutic strategy for inflammation and inflammatory diseases. Antagonists such as ethyl pyruvate inhibit HMGB1 by interfering with its cytoplasmic exportation, while others such as glycyrrhizin directly bind to HMGB1 and render it unavailable for its receptors. The fact that a mixture of different HMGB1 isoforms is present in the ECM poses a challenge in pinpointing the exact role of an individual antagonist. A more discriminative probe for HMGB1 may be necessary to advance our knowledge of HMGB1, HMGB1 antagonists, and inflammatory-related diseases.

Role of Innate Immune Receptor TLR4 and its endogenous ligands in epileptogenesis

Understanding the interplay between the innate immune system, neuroinflammation, and epilepsy might offer a novel perspective in the quest of exploring new treatment strategies. Due to the complex pathology underlying epileptogenesis, no disease-modifying treatment is currently available that might prevent epilepsy after a plausible epileptogenic insult despite the advances in pre-clinical and clinical research. Neuroinflammation underlies the etiopathogenesis of epilepsy and convulsive disorders with Toll-like receptor (TLR) signal transduction being highly involved. Among TLR family members, TLR4 is an innate immune system receptor and lipopolysaccharide (LPS) sensor that has been reported to contribute to epileptogenesis by regulating neuronal excitability. Herein, we discuss available evidence on the role of TLR4 and its endogenous ligands, the high mobility group box 1 (HMGB1) protein, the heat shock proteins (HSPs) and the myeloid related protein 8 (MRP8), in epileptogenesis and post-traumatic epilepsy (PTE). Moreover, we provide an account of the promising findings of TLR4 modulation/inhibition in experimental animal models with therapeutic impact on seizures.

Differential Characteristics of HMGB2 Versus HMGB1 and their Perspectives in Ovary and Prostate Cancer

We have summarized common and differential functions of HMGB1 and HMGB2 proteins with reference to pathological processes, with a special focus on cancer. Currently, several "omic" approaches help us compare the relative expression of these 2 proteins in healthy and cancerous human specimens, as well as in a wide range of cancer-derived cell lines, or in fetal versus adult cells. Molecules that interfere with HMGB1 functions, though through different mechanisms, have been extensively tested as therapeutic agents in animal models in recent years, and their effects are summarized. The review concludes with a discussion on the perspectives of HMGB molecules as targets in prostate and ovarian cancers.

Peroxiredoxins are involved in the pathogenesis of multiple sclerosis and neuromyelitis optica spectrum disorder

Peroxiredoxins (PRXs) are intracellular anti-oxidative enzymes but work as inflammatory amplifiers under the extracellular condition. To date, the function of PRXs in the pathogenesis of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) is not fully understood. The aim of this study was to investigate whether PRXs play a role in the pathogenesis of MS and NMOSD. We analyzed levels of PRXs (PRX1, PRX5 and PRX6) in the cerebrospinal fluid (CSF) and serum of 16 patients with MS, 16 patients with NMOSD and 15 patients with other neurological disorders (ONDs). We identified potential correlations between significantly elevated PRXs levels and the clinical variables in patients with MS and NMOSD. Additionally, pathological analyses of PRXs (PRX1-6) in the central nervous system (CNS) were performed using the experimental autoimmune encephalomyelitis (EAE), animal model of MS. We found that serum levels of PRX5 and PRX6 in patients with MS and NMOSD were higher compared with those in patients with ONDs (P < 0·05). Furthermore, high levels of PRX5 and PRX6 were partly associated with blood-brain barrier dysfunction and disease duration in NMOSD patients. No significant elevation was found in CSF PRXs levels of MS and NMOSD. Spinal cords from EAE mice showed remarkable PRX5 staining, especially in CD45⁺ infiltrating cells. In conclusion, PRX5 and PRX6 may play a role in the pathogeneses of MS and NMOSD.

HMGB1-Mediated Neuroinflammatory Responses in Brain Injuries: Potential Mechanisms and Therapeutic Opportunities

Brain injuries are devastating conditions, representing a global cause of mortality and morbidity, with no effective treatment to date. Increased evidence supports the role of neuroinflammation in driving several forms of brain injuries. High mobility group box 1 (HMGB1) protein is a pro-inflammatory-like cytokine with an initiator role in neuroinflammation that has been implicated in Traumatic brain injury (TBI) as well as in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Herein, we discuss the implication of HMGB1-induced neuroinflammatory responses in these brain injuries, mediated through binding to the receptor for advanced glycation end products (RAGE), toll-like receptor4 (TLR4) and other inflammatory mediators. Moreover, we provide evidence on the biomarker potential of HMGB1 and the significance of its nucleocytoplasmic translocation during brain injuries along with the promising neuroprotective effects observed upon HMGB1 inhibition/neutralization in TBI and EBI induced by SAH. Overall, this review addresses the current advances on neuroinflammation driven by HMGB1 in brain injuries indicating a future treatment opportunity that may overcome current therapeutic gaps.

In vitro studies on non-canonical DNA binding specificities of KAP6 and HMO1 and mechanistic insights into DNA bound and unbinding dynamics of KAP6

High mobility group box (HMGB) members are DNA binding proteins with varied functions present across kingdoms. The mechanism by which HMGBs with varying number of HMG boxes are able to carry out similar functions, are poorly understood. Moreover, how non-canonical DNAs are recognized by HMGB proteins is not clear. To address these, we carried out detailed biochemical and computational studies to characterize two HMGB members- Kinetoplast associated protein (KAP6) of Trypanosoma and High mobility group protein 1 (HMO1) from yeast. Here, we report that KAP6 binds non-canonical DNAs tighter than B-form DNA. Among non-canonical DNAs, KAP6 has the highest affinity for splayed and flap structures, but least for Holliday Junction (HJ). In contrast, HMO1 binds tighter to HJ. Computational analysis show that the secondary structural elements involved in DNA interaction are conserved in HMGB members KAP6 and mitochondrial transcription factor A. Simulation analyses revealed that the ~90° bend in DNA induced by KAP6 HMG box is a result of two ~45° bends, by Helix 1 and Helix 2 of the protein. Our data also suggests that the orthologs of HMO1 and KAP6 are oligomers in solution, which could be necessary for their functioning such as DNA bending and looping.

Anti-HMGB1 monoclonal antibody therapy for a wide range of CNS and PNS diseases

High mobility group box-1 (HMGB1), a representative damage associated-molecular pattern (DAMP), has been reported to be involved in many inflammatory diseases. Several drugs are thought to have potential to control the translocation and secretion of HMGB1, or to neutralize extracellular HMGB1 by binding to it. One of these drugs, anti-HMGB1 monoclonal antibody (mAb), is highly specific for HMGB1 and has been shown to be effective for the treatment of a wide range of CNS diseases when modeled in animals, including stroke, traumatic brain injury, Parkinson's disease, epilepsy and Alzheimer's disease. Thus, anti-HMGB1 mAb not only is useful for target validation but also has extensive potential for the treatment of the above-mentioned diseases. In this review, we summarize existing knowledge on the effects of anti-HMGB1 mAb on CNS and PNS diseases, the common features of translocation and secretion of HMGB1 and the functional roles of HMGB1 in these diseases. The existing literature suggests that anti-HMGB1 mAb therapy would be effective for a wide range of CNS and PNS diseases.

Relationship of High-mobility group box 1 levels and multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disorder of the central nervous system (CNS) affecting more than 2.5 million people worldwide. However, the exact etiology of MS remains unknown, recent research indicated that High-mobility group box 1(HMGB1) might contribute to MS pathogenesis. By evaluating HMGB1 levels of peripheral blood mononuclear cells (PBMC), serum and cerebrospinal fluid (CSF) in multiple sclerosis (MS) patients and the controls, to reveal the relationship of HMGB1 levels and MS patients.

METHODS

The PubMed, EMBASE, the Cochrane library, China National Knowledge Infrastructure (CNKI) and WanFangData were searched for relevant studies. Pooled standardized mean difference (SMD) and 95% confidence interval (CI) were calculated as effect size, random-effects model was used when I² > 50%. Subgroup analysis was conducted by subtype of MS, categories of controls, country and mean age.

RESULTS

A total of 7 studies with 364 patients of MS and 222 controls were included. The results of this study showed that HMGB1 protein levels of PBMC and CSF in patients with MS were significantly higher than those of controls (SMD = 4.36, 95% CI = 3.69-5.02, and SMD = 0.85, 95% CI = 0.42-1.28, respectively), but we found no significant difference in HMGB1 mRNA level of PBMC and serum HMGB1 protein level between MS patients and controls. In the subgroup analysis, RRMS patients had a higher HMGB1 level in serum (p < 0.05) and CSF (p < 0.01) compared to healthy controls and non-inflammatory neurological disorder controls. In Asians, MS patients had a considerably higher HMGB1 level in serum (p < 0.05), PBMC (protein) (p < 0.01) and CSF (p < 0.01) compared to healthy controls and non-inflammatory neurological disorder controls.

CONCLUSION

MS patients had higher HMGB1 protein levels in PBMC and CSF compared to controls. HMGB1 might be a new treatment target for MS.

Glycyrrhizin, an HMGB1 inhibitor, exhibits neuroprotective effects in rats after lithium-pilocarpine-induced status epilepticus

Objectives

It has been proven that extracellular HMGB1 is involved in progression of neurologic disorders, such as stroke, traumatic brain injury, meningitis and epilepsy. Glycyrrhizin (GL) is a direct inhibitor of HMGB1, and blocks HMGB1 release into the extracellular. We aim in this study to investigate the neuroprotective effects of GL in a rat model after lithium-pilocarpine-induced status epilepticus (SE).

Methods

Adult male SD rats were divided into three groups: Sham group, SE-group and (SE + GL)-treated group. The HMGB1 expression in serum and hippocampus, the damage extent of blood brain barrier (BBB) and hippocampal neuronal damage were evaluated by enzyme-linked immunosorbent assay, immunohistochemistry, western blot and nissl's staining.

Key findings

Glycyrrhizin markedly reduced HMGB1 expression in serum and hippocampus, prevented HMGB1 translocation from nucleus to cytoplasm in hippocampal CA1, CA3 and hilus areas of SE rats. Meanwhile, GL significantly ameliorated neuronal damage in the CA1, CA3 and hilus areas of hippocampus, and protected BBB disruption after SE. The administration of GL significantly decreased the mortality from 25 to 8.9% in rats.

Conclusions

Glycyrrhizin may exert neuroprotective effects via inhibiting HMGB1 and protect BBB permeability in lithium-pilocarpine-induced rats with SE.

Glycyrrhizin, a Potential Drug for Autoimmune Encephalomyelitis by Inhibiting High-Mobility Group Box 1

Autoimmune encephalomyelitis is a chronic autoimmune disease caused by immune-mediated sterile inflammatory response and demyelination in the central nervous system (CNS). High-mobility group box protein 1 (HMGB1) is a ubiquitous nuclear protein, which can be released from damaged cells and induce proinflammatory responses in autoimmune encephalomyelitis. Glycyrrhizin (GL), a major constituent of licorice root, can inhibit the proinflammatory bioactivities of HMGB1. In this article, we bring some insight into the effects of GL on CNS inflammatory diseases and discuss the therapeutic potential of GL in autoimmune encephalomyelitis in the future.

HMGB1: A Common Biomarker and Potential Target for TBI, Neuroinflammation, Epilepsy, and Cognitive Dysfunction

High mobility group box protein 1 (HMGB1) is a ubiquitous nuclear protein released by glia and neurons upon inflammasome activation and activates receptor for advanced glycation end products (RAGE) and toll-like receptor (TLR) 4 on the target cells. HMGB1/TLR4 axis is a key initiator of neuroinflammation. In recent days, more attention has been paid to HMGB1 due to its contribution in traumatic brain injury (TBI), neuroinflammatory conditions, epileptogenesis, and cognitive impairments and has emerged as a novel target for those conditions. Nevertheless, HMGB1 has not been portrayed as a common prognostic biomarker for these HMGB1 mediated pathologies. The current review discusses the contribution of HMGB1/TLR4/RAGE signaling in several brain injury, neuroinflammation mediated disorders, epileptogenesis and cognitive dysfunctions and in the light of available evidence, argued the possibilities of HMGB1 as a common viable biomarker of the above mentioned neurological dysfunctions. Furthermore, the review also addresses the result of preclinical studies focused on HMGB1 targeted therapy by the HMGB1 antagonist in several ranges of HMGB1 mediated conditions and noted an encouraging result. These findings suggest HMGB1 as a potential candidate to be a common biomarker of TBI, neuroinflammation, epileptogenesis, and cognitive dysfunctions which can be used for early prediction and progression of those neurological diseases. Future study should explore toward the translational implication of HMGB1 which can open the windows of opportunities for the development of innovative therapeutics that could prevent several associated HMGB1 mediated pathologies discussed herein.

Glycyrrhizin Protects Mice Against Experimental Autoimmune Encephalomyelitis by Inhibiting High-Mobility Group Box 1 (HMGB1) Expression and Neuronal HMGB1 Release

The inflammatory mediator high-mobility group box 1 (HMGB1) plays a critical role in the pathogenesis of human multiple sclerosis (MS) and mouse experimental autoimmune encephalomyelitis (EAE). Glycyrrhizin (GL), a glycoconjugated triterpene extracted from licorice root, has the ability to inhibit the functions of HMGB1; however, GL’s function against EAE has not been thoroughly characterized to date. To determine the benefit of GL as a modulator of neuroinflammation, we used an in vivo study to examine GL’s effect on EAE along with primary cultured cortical neurons to study the GL effect on HMGB1 release. Treatment of EAE mice with GL from onset to the peak stage of disease resulted in marked attenuation of EAE severity, reduced inflammatory cell infiltration and demyelination, decreased tumor necrosis factor-alpha (TNF-α), IFN-γ, IL-17A, IL-6, and transforming growth factor-beta 1, and increased IL-4 both in serum and spinal cord homogenate. Moreover, HMGB1 levels in different body fluids were reduced, accompanied by a decrease in neuronal damage, activated astrocytes and microglia, as well as HMGB1-positive astrocytes and microglia. GL significantly reversed HMGB1 release into the medium induced by TNF-α stimulation in primary cultured cortical neurons. Taken together, the results indicate that GL has a strong neuroprotective effect on EAE mice by reducing HMGB1 expression and release and thus can be used to treat central nervous system inflammatory diseases, such as MS.

Recombinant thrombomodulin ameliorates experimental autoimmune encephalomyelitis by suppressing high mobility group box 1 and inflammatory cytokines

Recombinant thrombomodulin (rTM) has pleiotrophic properties, including anti-coagulation and anti-inflammation; however, its effectiveness as a treatment for multiple sclerosis (MS) has not been evaluated fully. High mobility group box 1 (HMGB1) and proinflammatory cytokines, working as inflammatory mediators, are reportedly involved in the inflammatory pathogenesis of MS. The aim of this study was to determine whether rTM can be a potential therapeutic agent for experimental autoimmune encephalomyelitis (EAE). EAE mice received rTM treatment (1 mg or 0·1 mg/kg/day) from days 11 to 15 after immunization. The clinical variables, plasma levels of inflammatory cytokines and HMGB1 and pathological findings in EAE were evaluated. rTM administration ameliorated the clinical and pathological severity of EAE. An immunohistochemical study of the spinal cord showed weaker cytoplasmic HMGB1 staining in the rTM-treated EAE mice than in the untreated EAE mice. Plasma levels of inflammatory cytokines and HMGB1 were suppressed by rTM treatment. In conclusion, rTM down-regulated inflammatory mediators in the peripheral circulation and prevented HMGB1 release from nuclei in the central nervous system, suppressing EAE-related inflammation. rTM could have a novel therapeutic potential for patients with MS.

High-mobility group box 1 in multiple sclerosis

This study is one in series determining the potential of RAGE axis (receptor for advanced glycation end products, isoforms, ligands) as a biomarker in multiple sclerosis (MS). We evaluated serum levels of RAGE ligand, the high-mobility group box (HMGB)1 in MS patients, and assessed the correlation between HMGB1 serum levels and the use of disease-modifying drugs (DMDs), and between HMGB1 serum levels and indicators of MS disease severity. HMGB1 serum levels were compared between 96 (23 males) MS patients and 34 age- and gender-matched healthy controls (HCs) using enzyme-linked immunosorbent assays. DMD-naïve MS patients had significantly higher HMGB1 serum levels compared with DMD-treated (P = 0.04) and compared with HCs (P = 0.01). HMGB1 serum levels were not significantly different between total MS patients (DMD-naïve plus DMD-treated) and HCs (P = 0.09). DMD-naïve MS patients in clinical relapse tended to have lower HMGB1 serum levels than clinically stable RRMS patients (P = 0.07). HMGB1 serum levels showed 0.65 area under the curve (95 % CI 0.55-0.95) sensitivity/specificity for MS clinical relapse. The role of HMGB1 in MS disease pathology and DMD modulation of this protein warrant further investigations.

Does enoxaparin interfere with HMGB1 signaling after TBI? A potential mechanism for reduced cerebral edema and neurologic recovery

BACKGROUND

Enoxaparin (ENX) has been shown to reduce cerebral edema and improve neurologic recovery after traumatic brain injury (TBI), through blunting of cerebral leukocyte (LEU) recruitment. High mobility group box 1 (HMGB1) protein may induce inflammation through LEU activation. We hypothesized that ENX after TBI reduces LEU-mediated edema through blockade of HMGB1 signaling.

METHODS

Twenty-three CD1 mice underwent severe TBI by controlled cortical impact and were randomized to one of four groups receiving either monoclonal antibody against HMGB1 (MAb) or isotype (Iso) and either ENX (1 mg/kg) or normal saline (NS): NS + Iso (n = 5), NS + MAb (n = 6), ENX + Iso (n = 6), ENX + MAb (n = 6). ENX or NS was administered 2, 8, 14, 23 and 32 hours after TBI. MAb or Iso (25 μg) was administered 2 hours after TBI. At 48 hours, cerebral intravital microscopy served to visualize live LEU interacting with endothelium and microvascular fluorescein isothiocyanate-albumin leakage. The Neurological Severity Score (NSS) graded neurologic recovery; wet-to-dry ratios determined cerebral/lung edema. Analysis of variance with Bonferroni correction was used for statistical analyses.

RESULTS

ENX and MAb similarly reduced in vivo pial LEU rolling without demonstrating additive effect. In vivo albumin leakage was greatest in vehicle-treated animals but decreased by 25% with either MAb or ENX but by 50% when both were combined. Controlled cortical impact-induced cerebral wet-to-dry ratios were reduced by MAb or ENX without additive effect. Postinjury lung water was reduced by ENX but not by MAb. Neurologic recovery at 24 hours and 48 hours was similarly improved with ENX, MAb, or both treatments combined.

CONCLUSION

Mirroring ENX, HMGB1 signaling blockade reduces LEU recruitment, cerebrovascular permeability, and cerebral edema following TBI. ENX further reduced lung edema indicating a multifaceted effect beyond HMGB1 blockade. Further study is needed to determine how ENX may play a role in blunting HMGB1 signaling in brain injury patients.

Ti–O based nanomaterials ameliorate experimental autoimmune encephalomyelitis and collagen-induced arthritis

Administration of Ti–O based nanomaterials ameliorated the clinical severity of experimental autoimmune encephalomyelitis and collagen induced arthritis, thus provide novel therapeutic approach for multiple sclerosis and rheumatoid arthritis.

Serum high mobility group box 1 is upregulated in myasthenia gravis

OBJECTIVE

High mobility group box 1 (HMGB1) functions as an inflammatory mediator and is implicated in the pathogenesis of various autoimmune diseases. Our primary aim is to determine whether HMGB1 is involved in the pathogenesis of myasthenia gravis (MG).

METHODS

Serum HMGB1 levels of 60 patients with anti-acetylcholine receptor (AChR) antibody-positive MG without immunosuppressive treatment and of 10 patients with anti-muscle-specific receptor tyrosine kinase (MuSK) antibody-positive MG were compared with those in 40 controls. We also investigated the potential correlation between serum HMGB1 levels and the clinical variables in patients with MG.

RESULTS

Serum HMGB1 levels in patients with anti-AChR antibody-positive MG were higher than those in controls (7.80 ± 7.47 vs 4.13 ± 2.55 ng/mL, p=0.004) and were decreased after treatment (p=0.051). Although not significant, patients with anti-MuSK antibody-positive MG showed higher serum HMGB1 levels than the controls (p=0.178). There were correlations between serum HMGB1 levels and phenotypes of anti-AChR antibody-positive MG: patients with generalised MG showed higher HMGB1 levels than those of patients with ocular MG (p=0.059) and controls (p=0.002); patients with thymoma showed higher HMGB1 levels than those without thymoma (p=0.094) and controls (p=0.001).

CONCLUSIONS

Serum HMGB1 is elevated in patients with MG and may play a key role in the inflammation of the neuromuscular junction.

Role of high mobility group box protein 1 (HMGB1) in peripheral blood from patients with multiple sclerosis

Background

High mobility group box protein 1 (HMGB1) is a transcriptional regulator that is receiving increasing attention in autoimmune disorders including multiple sclerosis (MS). Here, we investigated the role of HMGB1 in the peripheral blood compartment from MS patients.

Methods

HMGB1 mRNA expression levels were determined by PCR in peripheral blood mononuclear cells (PBMC) of 29 healthy controls and 57 untreated MS patients (26 with relapsing-remitting MS - RRMS, 13 with secondary progressive MS - SPMS, and 18 with primary progressive MS - PPMS). HMGB1 protein levels were measured by ELISA in serum samples from 18 HC and 37 untreated MS patients (13 with RRMS, 14 with SPMS, and 10 with PPMS).

Results

HMGB1 expression levels were increased in PBMC from the whole MS group compared with controls (P = 0.03). Further stratification of the MS group revealed higher expression levels in PBMC from patients with relapse-onset MS, and differences were statistically significant for RRMS patients compared with PPMS patients and controls (P = 4 × 10⁻⁵ and P = 0.005, respectively) and also for SPMS patients compared with PPMS patients (P = 0.001). HMGB1 serum levels were increased in the whole MS group compared with controls (P = 2 × 10⁻⁴). In MS clinical forms, the highest HMGB1 serum levels were observed in RRMS patients, and differences were statistically significant compared to PPMS patients (P = 5 × 10⁻⁵), SPMS patients (P = 0.001), and controls (P = 0.001).

Conclusions

These results point to a role of HMGB1 mRNA and protein levels as disease activity biomarkers to discriminate the more inflammatory relapse-onset MS forms, particularly RRMS, from the less inflammatory PPMS form of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0269-9) contains supplementary material, which is available to authorized users.

HMGB1 expression patterns during the progression of experimental autoimmune encephalomyelitis

High mobility group box 1 (HMGB1), a nonhistone chromatin associated protein, plays different roles according to the expression pattern such as the amount, cell location and sub-cellular location. It has been recently demonstrated that the systemic HMGB1 is associated with autoimmune encephalomyelitis. However, the dynamic change of HMGB1 expression pattern in spinal cords that may be involved in the progression of disease is not fully understood. In this study, the amount, cell location and subcellular location of HMGB1 in adult mice spinal cords during various stages of experimental autoimmune encephalomyelitis (EAE) are investigated. HMGB1 is expressed in the nuclei of spinal cord resident cells such as some astrocytes, microglia and a few neurons in normal situation. During EAE progression, the total and extracellular HMGB1 in the spinal cord are increased, more HMGB1 positive astrocytes and microglia are observed, and the intra-neurons HMGB1 in the ventral horn and around the central canal localize majorly in the cytoplasm accompanied by the increasing extracellular HMGB1. Blockade of HMGB1 in central nervous system (CNS) locally attenuates the severity of EAE significantly. Our findings indicate that the HMGB1 expression pattern in the spinal cord is associated with the progression of EAE. HMGB1 may be a potential target for autoimmune encephalomyelitis (multiple sclerosis in human) therapy.

[Novel therapeutic target in neuromyelitis optica and multiple sclerosis: high mobility group box 1 (HMGB1)]

High mobility group box 1 (HMGB1) is a nuclear protein, and released from necrotic cells. Recently, It has been known that HMGB1 is released from monocyte/macrophage, neurons, and endothelial cells, and that HMGB1 is involved in sepsis, brain infarction, etc. We have reported that HMGB1 concentrations were elevated in cerebrospinal fluid (CSF) from patients with neuromyelitis optica (NMO) and multiple sclerosis (MS) and that the elevation was significant in CSF from NMO patients. Moreover, we have also reported that experimental autoimmune encephalitis (EAE) induced in C57BL/6 mice by immunization with myelin oligodendrocyte glycoprotein peptide (35-55) showed decrease of clinical and pathological severity by treatment with monoclonal anti-HMGB1 antibody. Thus, we think that HMGB1 is associated with pathophysiology in central nervous system in NMO and MS (especially in NMO), and that HMGB1 can be a target molecule for NMO and MS.

Continuous hemodiafiltration therapy reduces damage of multi-organs by ameliorating of HMGB1/TLR4/NFκB in a dog sepsis model

In the present study, we investigated whether CVVH can reduce HMGB1, TLR4, NF-κB and other serum cytokine levels, preventing organ injury in a dog sepsis model. A total of 10 dogs were injected with LPS and treated with either CVVH group (n = 5) or nothing (Control, n = 5) for 24 h. EILSA was used for examining the concentration of TNF-α, IL-6, HMGB 1 and TLR4. The histological change of lung, liver and kidney tissues was determined. The mRNA expression of HMGB1, TLR4 and NF-κB was examined by RT-PCR. The protein of HMGB1 and phosphated NF-κB was examined by Western-blot. The levels of serum HMGB1 came to the peak at 8 h, 16 h and then declined. The LPS-induced increase in HMGB1 level was suppressed by CVVH compared with Control. Likewise, serum TNF-α and IL-6 levels decreased with CVVH along with a significant improvement in the function of main organs. Histologic examination revealed significant reduction in inflammation in lung; liver and kidney tissues harvested 24 h after CVVH compared with Control. The mRNA of HMGB1, TLR4 and NF-κB in the kidney was expressed at high level after LPS administration, which was significantly decreased by CVVH. The increased protein expression of HMGB1 and phosphated NF-κB was reduced after CVVH compared with control. CVVH by reducing the level of HMGB1, TLR4, NF-κB and other cytokines could weaken the cascade of cytokines and restore the immune system, and reduce the damage of important organs in sepsis.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Modulation of the kallikrein/kinin system by the angiotensin-converting enzyme inhibitor alleviates experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Bradykinin is the end-product of the kallikrein/kinin system, which has been recognized as an endogenous target for combating CNS inflammation. Angiotensin-converting enzyme (ACE) inhibitors influence the kallikrein/kinin system and reportedly have immunomodulatory characteristics. The objectives of this study were to determine whether bradykinin is involved in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and whether bradykinin control by the ACE inhibitor could be a therapeutic target in MS. The ACE inhibitor enalapril (1·0 or 0·2 mg/kg/day) was administered orally to EAE mice and the serum levels of bradykinin and cytokines in EAE mice were analysed. As a result, the administration of enalapril increased serum bradykinin levels, decreased the clinical and pathological severity of EAE and attenuated interleukin-17-positive cell invasion into the CNS. Additionally, bradykinin receptor antagonist administration reduced the favourable effects of enalapril. Our results suggest that bradykinin is involved in the pathomechanism underlying CNS inflammation in EAE, possibly through inhibiting cell migration into CNS. Control of the kallikrein/kinin system using ACE inhibitors could be a potential therapeutic strategy in MS.

HMGB1 is involved in chronic rejection of cardiac allograft via promoting inflammatory-like mDCs

Chronic rejection that leads to diffuse narrowing and occlusion of graft vessels is the most important cause of morbidity and mortality following cardiac transplantation. The role and underlying mechanism of high-mobility group box 1 (HMGB1), as an established inflammatory mediator in acute rejection, remains poorly understood in chronic rejection. Here, we assessed the effects and mechanisms of HMGB1 on the chronic rejection using single MHC Class II-mismatched mouse cardiac transplantation model. It was found that HMGB1 was increased accompanying with the development of chronic rejection, while blockade of HMGB1 with specific neutralizing mAb substantially ameliorated chronic rejection-mediated vasculopathy and fibrosis of allograft, as well as markedly decreased T cell infiltration and production of IL-17A and interferon-gamma in allograft and recipient's spleen. Further, anti-HMGB1 antibody treatment significantly declined the number and frequency of mature dendritic cells (DCs) in allograft and recipient's spleen, especially CD11b(+) Ly6C(high) matured DCs that share the phenotypes with inflammatory-DCs. These findings indicate that HMGB1 contributes to chronic rejection, and HMGB1 blockade may be a novel mean to disrupt the proinflammatory loop after heart transplantation.

How is inflammation initiated? Individual influences of IL-1, IL-18 and HMGB1

Pro-inflammatory cytokines are crucial for fighting infection and establishing immunity. Recently, other proteins, such as danger-associated molecular patterns (DAMPs), have also been appreciated for their role in inflammation and immunity. Following the formation and activation of multiprotein complexes, termed inflammasomes, two cytokines, IL-1β and IL-18, along with the DAMP High Mobility Group Box 1 (HMGB1), are released from cells. Although these proteins all lack classical secretion signals and are released by inflammasome activation, they each lead to different downstream consequences. This review examines how various inflammasomes promote the release of IL-1β, IL-18 and HMGB1 to combat pathogenic situations. Each of these effector molecules plays distinct roles during sterile inflammation, responding to viral, bacterial and parasite infection, and tailoring the innate immune response to specific threats.

Role of HMGB1/TLR signaling pathway in Helicobacter pylori infection

High mobility group box 1 protein (HMGB1), as a mediator of late inflammation, provides a wide therapeutic window. Extracellular HMGB1 as an endogenous injury-related molecule promotes the development of inflammation and damage by binding to its receptors. Studies have discovered that lipopolysaccharide and vacuolating cytotoxin A (VacA) of Helicobacter pylori (H. pylori) are strong stimulating factors of HMGB1 expression, and its extracellular receptors Toll-like receptors (TLRs) are closely associated with H. pylori infection and pathogenicity. Therefore, the HMGB1/TLR signaling pathway may play an important role in inflammatory response and immune abnormalities caused by H. pylori infection. This article will discuss the role of the HMGB1/TLR signaling pathway in H. pylori infection.