The multifunctional alarmin HMGB1 with roles in the pathophysiology of sepsis and cancer

HMGB1 as an extracellular pro-inflammatory cytokine: Implications for drug-induced organic damage

Drug-induced organic damage encompasses various intricate mechanisms, wherein HMGB1, a non-histone chromosome-binding protein, assumes a significant role as a pivotal hub gene. The regulatory functions of HMGB1 within the nucleus and extracellular milieu are interlinked. HMGB1 exerts a crucial regulatory influence on key biological processes including cell survival, inflammatory regulation, and immune response. HMGB1 can be released extracellularly from the cell during these processes, where it functions as a pro-inflammation cytokine. HMGB1 interacts with multiple cell membrane receptors, primarily Toll-like receptors (TLRs) and receptor for advanced glycation end products (RAGE), to stimulate immune cells and trigger inflammatory response. The excessive or uncontrolled HMGB1 release leads to heightened inflammatory responses and cellular demise, instigating inflammatory damage or exacerbating inflammation and cellular demise in different diseases. Therefore, a thorough review on the significance of HMGB1 in drug-induced organic damage is highly important for the advancement of pharmaceuticals, ensuring their effectiveness and safety in treating inflammation as well as immune-related diseases. In this review, we initially outline the characteristics and functions of HMGB1, emphasizing their relevance in disease pathology. Then, we comprehensively summarize the prospect of HMGB1 as a promising therapeutic target for treating drug-induced toxicity. Lastly, we discuss major challenges and propose potential avenues for advancing the development of HMGB1-based therapeutics.

HMGB1 prefers to interact with structural RNAs and regulates rRNA methylation modification and translation in HeLa cells

BACKGROUND

High-mobility group B1 (HMGB1) is both a DNA binding nuclear factor modulating transcription and a crucial cytokine that mediates the response to both infectious and noninfectious inflammation such as autoimmunity, cancer, trauma, and ischemia reperfusion injury. HMGB1 has been proposed to control ribosome biogenesis, similar as the other members of a class of HMGB proteins.

RESULTS

Here, we report that HMGB1 selectively promotes transcription of genes involved in the regulation of transcription, osteoclast differentiation and apoptotic process. Improved RNA immunoprecipitation by UV cross-linking and deep sequencing (iRIP-seq) experiment revealed that HMGB1 selectively bound to mRNAs functioning not only in signal transduction and gene expression, but also in axon guidance, focal adhesion, and extracellular matrix organization. Importantly, HMGB1-bound reads were strongly enriched in specific structured RNAs, including the domain II of 28S rRNA, H/ACA box snoRNAs including snoRNA63 and scaRNAs. RTL-P experiment showed that overexpression of HMGB1 led to a decreased methylation modification of 28S rRNA at position Am2388, Cm2409, and Gm2411. We further showed that HMGB1 overexpression increased ribosome RNA expression levels and enhanced protein synthesis.

CONCLUSION

Taken together, our results support a model in which HMGB1 binds to multiple RNA species in human cancer cells, which could at least partially contribute to HMGB1-modulated rRNA modification, protein synthesis function of ribosomes, and differential gene expression including rRNA genes. These findings provide additional mechanistic clues to HMGB1 functions in cancers and cell differentiation.

Expression of high-mobility group box-1 in eutopic/ectopic endometrium and correlations with inflammation-related factors in adenomyosis

OBJECTIVE

To investigate the expression of HMGB1 and toll-like receptor 4 (TLR4) in adenomyosis eutopic/ectopic endometrium.

METHODS

Twenty patients with adenomyosis and 20 controls, all undergoing laparoscopy, were recruited from September 2015 to July 2016. Samples were collected from the endometrium without adenomyosis (CE), the eutopic endometrium with adenomyosis (EuE), and the ectopic endometrium with adenomyosis (EE). The mRNA and protein expression of HMGB1 and TLR4, and interleukin-6 (IL-6) and interleukin-8 (IL-8) RNA expression levels were measured.

RESULTS

The average age of the adenomyosis women was 43.4 ± 5.3 years; their BMI was 23.3 ± 2.3 kg/m2. The control group included women aged 38.8 ± 9.8 years, with BMI 22.2 ± 3.4 kg/m2. The mRNA expression levels of HMGB1, TLR4, IL-6, and IL-8 in the EE and EuE groups were higher than those in the CE group (p < .01), and those in the EE group were higher than those in the EuE group (p < .01). The protein expression levels of HMGB1 and TLR4 in the EE and EuE groups were higher than those in the CE group (p < .01); they were higher in the EE group than the ones in the EuE group (p < .01). HMGB1 mRNA was significantly positively correlated with TLR4 in EuE and EC patients (r = 0.538 and r = 0.916, p < .01), as well as with IL-6 (r = 0.470 and r = 0.976, p < .01) and IL-8 (r = 0.574 and r = 0.650, p < .01).

CONCLUSIONS

The overexpression of HMGB1 and TLR4 in EuE and EE is positively correlated with IL-6 and IL-8 expression. The HMGB1 signaling-mediated immune-inflammatory system might be involved in the development of adenomyosis.

Fibrosis as a Risk Factor for Cutaneous Squamous Cell Carcinoma in Recessive Dystrophic Epidermolysis Bullosa: A Systematic Review

Recessive dystrophic epidermolysis bullosa (RDEB) is a severe subtype of epidermolysis bullosa caused by changes in collagen VII with a high risk of early development of cutaneous squamous cell carcinoma (cSCC). This review aimed to discuss the relationship between the recurrent healing process, the appearance of fibrosis, and malignant epithelial transformation in RDEB. We searched PubMed, the Regional Portal of the Virtual Health Library, and Embase for articles on the relationship between blistering, recurrent scarring, and fibrosis in the context of cSCC and RDEB. That alterations of collagen VII result in blister formation, scar deficiency associated with inflammation, and increased expression of transforming growth factor β. These events promote the differentiation of myofibroblasts and the expression of profibrotic proteins, leading to structural changes and the establishment of a microenvironment favorable to carcinogenesis. Patients with RDEB and areas of recurrent scarring and fibrosis may be more prone to the development of cSCC.

High Mobility Group Box 1 (HMGB1): Potential Target in Sepsis-Associated Encephalopathy

Sepsis-associated encephalopathy (SAE) remains a challenge for intensivists that is exacerbated by lack of an effective diagnostic tool and an unambiguous definition to properly identify SAE patients. Risk factors for SAE development include age, genetic factors as well as pre-existing neuropsychiatric conditions. Sepsis due to certain infection sites/origins might be more prone to encephalopathy development than other cases. Currently, ICU management of SAE is mainly based on non-pharmacological support. Pre-clinical studies have described the role of the alarmin high mobility group box 1 (HMGB1) in the complex pathogenesis of SAE. Although there are limited data available about the role of HMGB1 in neuroinflammation following sepsis, it has been implicated in other neurologic disorders, where its translocation from the nucleus to the extracellular space has been found to trigger neuroinflammatory reactions and disrupt the blood–brain barrier. Negating the inflammatory cascade, by targeting HMGB1, may be a strategy to complement non-pharmacologic interventions directed against encephalopathy. This review describes inflammatory cascades implicating HMGB1 and strategies for its use to mitigate sepsis-induced encephalopathy.

Review: The role of HMGB1 in spinal cord injury

High mobility group box 1 (HMGB1) has dual functions as a nonhistone nucleoprotein and an extracellular inflammatory cytokine. In the resting state, HMGB1 is mainly located in the nucleus and regulates key nuclear activities. After spinal cord injury, HMGB1 is rapidly expressed by neurons, microglia and ependymal cells, and it is either actively or passively released into the extracellular matrix and blood circulation; furthermore, it also participates in the pathophysiological process of spinal cord injury. HMGB1 can regulate the activation of M1 microglia, exacerbate the inflammatory response, and regulate the expression of inflammatory factors through Rage and TLR2/4, resulting in neuronal death. However, some studies have shown that HMGB1 is beneficial for the survival, regeneration and differentiation of neurons and that it promotes the recovery of motor function. This article reviews the specific timing of secretion and translocation, the release mechanism and the role of HMGB1 in spinal cord injury. Furthermore, the role and mechanism of HMGB1 in spinal cord injury and, the challenges that still need to be addressed are identified, and this work will provide a basis for future studies.

Oxidative Stress and High-Mobility Group Box 1 Assay in Dogs with Gastrointestinal Parasites

This study aimed to evaluate the concentration of reactive oxidative metabolites, the antioxidant barrier, thiol groups of plasma compounds, and high-mobility group box 1 in shelter dogs naturally infected with helminths. In addition, the correlation between clinical signs and oxidative stress was investigated. Sixty-six (41 male and 25 female) adult mixed-breed dogs housed in a shelter with the diagnosis of gastrointestinal nematodes (i.e., Ancylostoma spp., Uncinaria stenocephala, Toxocara canis, Toxascaris leonina, or Trichuris vulpis) were enrolled in Group 1 (G1) and twenty healthy adult dogs were included in Group 2 (G2), which served as the control. A clinical assessment was performed using a physician-based scoring system. Oxidative stress variables and high-mobility group box 1 were assessed and compared by the means of unpaired t-tests (p < 0.05). Spearman’s rank correlation was performed to calculate the correlation between oxidative stress variables, high-mobility group box 1, hematological parameters, and clinical signs. The results showed statistically significant values for reactive oxidative metabolites, thiol groups of plasma compounds, and high-mobility group box 1 in G1. Negative correlations between thiol groups and the number of red cells and hemoglobin were recorded. These preliminary results support the potential role of oxidative stress and HGMB-1 in the pathogenesis of gastrointestinal helminthiasis in dogs.

Chromatin-Associated Molecular Patterns (CAMPs) in sepsis

Several molecular patterns have been identified that recognize pattern recognition receptors. Pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) are commonly used terminologies to classify molecules originating from pathogen and endogenous molecules, respectively, to heighten the immune response in sepsis. Herein, we focus on a subgroup of endogenous molecules that may be detected as foreign and similarly trigger immune signaling pathways. These chromatin-associated molecules, i.e., chromatin containing nuclear DNA and histones, extracellular RNA, mitochondrial DNA, telomeric repeat-containing RNA, DNA- or RNA-binding proteins, and extracellular traps, may be newly classified as chromatin-associated molecular patterns (CAMPs). Herein, we review the release of CAMPs from cells, their mechanism of action and downstream immune signaling pathways, and targeted therapeutic approaches to mitigate inflammation and tissue injury in inflammation and sepsis.

The C-Terminal Acidic Tail Modulates the Anticancer Properties of HMGB1

Energy metabolism reprogramming was recently listed as a hallmark of cancer. In this process, the switch from pyruvate kinase isoenzyme type M1 to pyruvate kinase isoenzyme type M2 (PKM2) is believed to play a crucial role. Interestingly, the activity of the active form of PKM2 can efficiently be inhibited by the high-mobility group box 1 (HMGB1) protein, leading to a rapid blockage of glucose-dependent aerobic respiration and cancer cell death. HMGB1 is a member of the HMG protein family. It contains two DNA-binding HMG-box domains and an acidic C-terminal tail capable of positively or negatively modulating its biological properties. In this work, we report that the deletion of the C-terminal tail of HMGB1 increases its activity towards a large panel of cancer cells without affecting the viability of normal immortalized fibroblasts. Moreover, in silico analysis suggests that the truncated form of HMGB1 retains the capacity of the full-length protein to interact with PKM2. However, based on the capacity of the cells to circumvent oxidative phosphorylation inhibition, we were able to identify either a cytotoxic or cytostatic effect of the proteins. Together, our study provides new insights in the characterization of the anticancer activity of HMGB1.

The Effects of a Meldonium Pre-Treatment on the Course of the LPS-Induced Sepsis in Rats

A dysregulated and overwhelming response to an infection accompanied by the exaggerated pro-inflammatory state and metabolism disturbance leads to the fatal outcome in sepsis. Previously we showed that meldonium, an anti-ischemic drug clinically used to treat myocardial and cerebral ischemia, strongly increases mortality in faecal-induced peritonitis (FIP) in rats. We postulated that the same mechanism that is responsible for the otherwise strong anti-inflammatory effects of meldonium could be the culprit of the increased mortality. In the present study, we applied the LPS-induced model of sepsis to explore the presence of any differences from and/or similarities to the FIP model. When it comes to energy production, despite some shared similarities, it is evident that LPS and FIP models of sepsis differ greatly. A different profile of sympathoadrenal activation may account for this observation, as it was lacking in the FIP model, whereas in the LPS model it was strong enough to overcome the effects of meldonium. Therefore, choosing the appropriate model of sepsis induction is of great importance, especially if energy homeostasis is the main focus of the study. Even when differences in the experimental design of the two models are acknowledged, the role of different patterns of energy production cannot be excluded. On that account, our results draw attention to the importance of uninterrupted energy production in sepsis but also call for much-needed revisions of the current recommendations for its treatment.

miR-340-5p inhibits pancreatic acinar cell inflammation and apoptosis via targeted inhibition of HMGB1

Acute pancreatitis (AP) is a common gastrointestinal disease that affects 1 million individuals worldwide. Inflammation and apoptosis are considered to be important pathogenic mechanisms of AP, and high mobility group box 1 (HMGB1) has been shown to play a particularly important role in the etiology of this disease. MicroRNAs (miRs) are emerging as critical regulators of gene expression and, as such, they represent a promising area of therapeutic target identification and development for a variety of diseases, including AP. Using the online database query (microRNA.org), the current study identified a site in the 3' untranslated region of HMGB1 mRNA that was a viable target for miR-340-5p. The present study aimed to investigate the association between miR-340-5p and HMGB1 expression in pancreatic acinar cells following lipopolysaccharide (LPS) treatment by performing luciferase, western blotting and reverse transcription-quantitative PCR assays. The results suggest that miR-340-5p attenuates the induction of HMGB1 by LPS, thereby inhibiting inflammation and apoptosis via blunted activation of Toll-like receptor 4 and enhanced AKT signaling. Thus, the therapeutic application of miR-340-5p may be a useful strategy in AP via upregulation of HMGB1 and subsequent promotion of inflammation and apoptosis.

Damage-Associated Molecular Patterns As Double-Edged Swords in Sepsis

Significance: Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host response to infection. This leads to an uncontrolled inflammatory response at the onset of infection, followed by immunosuppression. The development of a specific treatment modality for sepsis is still challenging, reflecting our inadequate understanding of its pathophysiology. Understanding the mechanism and transition of the early hyperinflammation to late stage of immunosuppression in sepsis is critical for developing sepsis therapeutics. Recent Advances: Damage-associated molecular patterns (DAMPs) are intracellular molecules and released upon tissue injury and cell death in sepsis. DAMPs are recognized by pattern recognition receptors to initiate inflammatory cascades. DAMPs not only elicit an inflammatory response but also they subsequently induce immunosuppression, both are equally important for exacerbating sepsis. Recent advances on a new DAMP, extracellular cold-inducible RNA-binding protein for fueling inflammation and immunosuppression in sepsis, have added a new avenue into the dual functions of DAMPs in sepsis. Critical Issues: The molecular modification of DAMPs and their binding to pattern recognition receptors transit dynamically by the cellular environment in pathophysiologic conditions. Correlation between the dynamic changes of the impacts of DAMPs and the clinical outcomes in sepsis still lacks adequate understanding. Here, we focus on the impacts of DAMPs that cause inflammation as well as induce immunosuppression in sepsis. We further discuss the therapeutic potential by targeting DAMPs to attenuate inflammation and immunosuppression for mitigating sepsis. Future Directions: Uncovering pathways of the transition from inflammation to immunosuppression of DAMPs is a potential therapeutic avenue for mitigating sepsis.

Granisetron attenuates liver injury and inflammation in a rat model of cecal ligation and puncture-induced sepsis

BACKGROUND AND AIMS

Sepsis induced liver injury is recognized as a serious complication in intensive care units, it is deeply associated with oxidative stress, inflammation and subsequent pyroptosis. Hepatic pyroptosis known to aggravate sepsis-induced liver injury. Previous studies proved that granisetron has anti-inflammatory and antioxidant properties. Accordingly, this study aimed to evaluate the efficacy of granisetron on sepsis-induced liver damage using a cecal ligation and puncture (CLP) model in rats.

MAIN METHODS

Male albino rats were randomly divided into four groups: a sham control group, a granisetron control group, a CLP-induced sepsis group and a granisetron-treated CLP group. Markers of oxidative stress, inflammation, pyroptosis-related proteins and liver function were measured in addition to the histopathological study.

KEY FINDINGS

Granisetron pretreatment significantly decreased mortality and improved liver function, as indicated by decreased ALT, AST, and total bilirubin and increased albumin content. Moreover, granisetron increased GPx activity and downregulated hepatic MDA. Furthermore, granisetron administration significantly reduced TNF-α, IL-6, HMGB1 and NF-κB. It also decreased the expression of receptor for advanced glycation end and TLR4 in the liver tissue. Interestingly, granisetron inhibited pyroptosis as it reduced NLRP3, IL-1β and caspase-1. Granisetron was shown to increase Nrf2 and HO-1. In addition, granisetron treatment repaired, to some extent, the abnormal architecture of hepatic tissue.

SIGNIFICANCE

Our results suggested that granisetron is a potential therapeutic agent for sepsis-associated liver injury, possibly acting by inhibiting oxidative stress, inflammation and subsequent pyroptosis.

Naturally Occurring HMGB1 Inhibitor, Glycyrrhizin, Modulates Chronic Seizures-Induced Memory Dysfunction in Zebrafish Model

Glycyrrhizin (GL) is a well-known pharmacological inhibitor of high mobility group box 1 (HMGB1) and is abundantly present in the licorice root (Glycyrrhiza radix). HMGB1 protein, a key mediator of neuroinflammation, has been implicated in several neurological disorders, including epilepsy. Epilepsy is a devastating neurological disorder with no effective disease-modifying treatment strategies yet, suggesting a pressing need for exploring novel therapeutic options. In the current investigation, using a second hit pentylenetetrazol (PTZ) induced chronic seizure model in adult zebrafish, regulated mRNA expression of HMGB1 was inhibited by pretreatment with GL (25, 50, and 100 mg/kg, ip). A molecular docking study suggests that GL establishes different binding interactions with the various amino acid chains of HMGB1 and Toll-like receptor-4 (TLR4). Our finding suggests that GL pretreatment reduces/suppresses second hit PTZ induced seizure, as shown by the reduction in the seizure score. GL also regulates the second hit PTZ induced behavioral impairment and rescued second hit PTZ related memory impairment as demonstrated by an increase in the inflection ratio (IR) at the 3 h and 24 h T-maze trial. GL inhibited seizure-induced neuronal activity as demonstrated by reduced C-fos mRNA expression. GL also modulated mRNA expression of BDNF, CREB-1, and NPY. The possible mechanism underlying the anticonvulsive effect of GL could be attributed to its anti-inflammatory activity, as demonstrated by the downregulated mRNA expression level of HMGB1, TLR4, NF-kB, and TNF-α. Overall, our finding suggests that GL exerts an anticonvulsive effect and ameliorates seizure-related memory disruption plausibly through regulating of the HMGB1-TLR4-NF-kB axis.

The Effects of a Meldonium Pre-Treatment on the Course of the Faecal-Induced Sepsis in Rats

Sepsis is a life-threatening condition caused by the dysregulated and overwhelming response to infection, accompanied by an exaggerated pro-inflammatory state and lipid metabolism disturbance leading to sequential organ failure. Meldonium is an anti-ischemic and anti-inflammatory agent which negatively interferes with lipid metabolism by shifting energy production from fatty acid oxidation to glycolysis, as a less oxygen-demanding pathway. Thus, we investigated the effects of a four-week meldonium pre-treatment on faecal-induced sepsis in Sprague-Dawley male rats. Surprisingly, under septic conditions, meldonium increased animal mortality rate compared with the meldonium non-treated group. However, analysis of the tissue oxidative status did not provide support for the detrimental effects of meldonium, nor did the analysis of the tissue inflammatory status showing anti-inflammatory, anti-apoptotic, and anti-necrotic effects of meldonium. After performing tissue lipidomic analysis, we concluded that the potential cause of the meldonium harmful effect is to be found in the overall decreased lipid metabolism. The present study underlines the importance of uninterrupted energy production in sepsis, closely drawing attention to the possible harmful effects of lipid-mobilization impairment caused by certain therapeutics. This could lead to the much-needed revision of the existing guidelines in the clinical treatment of sepsis while paving the way for discovering new therapeutic approaches.

The extracellular innate-immune effector HMGB1 limits pathogenic bacterial biofilm proliferation

Herein, we describe an extracellular function of the vertebrate high-mobility group box 1 protein (HMGB1) in the proliferation of bacterial biofilms. Within host cells, HMGB1 functions as a DNA architectural protein, similar to the ubiquitous DNABII family of bacterial proteins; despite that, these proteins share no amino acid sequence identity. Extracellularly, HMGB1 induces a proinflammatory immune response, whereas the DNABII proteins stabilize the extracellular DNA-dependent matrix that maintains bacterial biofilms. We showed that when both proteins converged on extracellular DNA within bacterial biofilms, HMGB1, unlike the DNABII proteins, disrupted biofilms both in vitro (including the high-priority ESKAPEE pathogens) and in vivo in 2 distinct animal models, albeit with induction of a strong inflammatory response that we attenuated by a single engineered amino acid change. We propose a model where extracellular HMGB1 balances the degree of induced inflammation and biofilm containment without excessive release of biofilm-resident bacteria.

Increased plasma levels of damage-associated molecular patterns during systemic anticancer therapy in patients with advanced lung cancer

Background

Immunogenic cell death (ICD) characterized by the release of damage-associated molecular patterns (DAMPs) from dying cancer cells may contribute to the synergistic antitumor effect of cytotoxic chemotherapy combined with an immune checkpoint inhibitor. The kinetics of circulating DAMP levels in cancer patients have remained largely uncharacterized, however.

Methods

We evaluated the possible effects of various systemic anticancer therapy modalities on the kinetics of plasma DAMP concentrations in a prospective observational study of patients with advanced lung cancer. The plasma concentrations of high-mobility group box 1 (HMGB1), calreticulin (CRT), heat shock protein 70 (HSP70), annexin A1, and histone H3 were thus determined in 121 such patients at four time points during the first cycle of treatment.

Results

The mean of the maximum fold change in HMGB1, HSP70, or annexin A1 concentration observed during treatment was significantly greater than the corresponding baseline value (P<0.005). The maximum fold changes in HMGB1 and CRT concentrations tended to be associated with clinical response as evaluated by RECIST criteria, although the changes in the levels of these two DAMPs were not correlated, suggestive of differential induction mechanisms. Among the various treatment modalities administered, platinum-based combination or single-agent chemotherapy tended to elicit robust increases in the concentrations of HMGB1 and CRT.

Conclusions

Serial monitoring of plasma revealed that systemic anticancer therapy increased the circulating levels of HMGB1 and CRT and that these changes tended to be associated with clinical response, suggesting that agents capable of releasing these DAMPs into plasma might induce ICD in advanced lung cancer patients.

Chronic stress promotes acute myeloid leukemia progression through HMGB1/NLRP3/IL-1β signaling pathway

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy with poor prognosis and overall survival. Clinical investigations show that chronic stress is commonly present in the course of AML and associated with adverse outcome. However, the underlying molecular mechanisms are elusive. In the present study, a chronic restraint stress mouse model was established to evaluate the effect of stress on AML. We found that mice under chronic stress exhibited significantly increased liver and spleen infiltration of leukemic cells and poorer overall survival. This was accompanied by elevated cellular NLR family pyrin domain containing 3 (NLRP3) and interleukin-1β (IL-1β) in the liver or bone marrow, and secreted IL-1β in the plasma, indicating the activation of inflammasomes under chronic restraint stress. High mobility group box 1 (HMGB1) expression was markedly increased in newly diagnosed AML patients, but reduced in complete remission AML patients. The expression level of HMGB1 was positively correlated with NLRP3 mRNA in AML patients. Knockdown of HMGB1 significantly decreased NLRP3 and IL-1β expression in AML cell lines, and secreted IL-1β in supernatant of AML cell culture, while HMGB1 stimulation caused contrary effects. These results implied that HMGB1 could be involved in the regulation of inflammasome activation in AML development. Mice model showed that chronic restraint stress-facilitated proliferation and infiltration of AML cells were largely abrogated by knocking down HMGB1. Knockdown of HMGB1 also ameliorated overall survival and remarkably neutralized NLRP3 and IL-1β expression under chronic restraint stress. These findings provide evidences that chronic stress promotes AML progression via HMGB1/NLRP3/IL-1β dependent mechanism, suggesting that HMGB1 is a potential therapeutic target for AML. KEY MESSAGES: • Chronic restraint stress promoted acute myeloid leukemia (AML) progression and mediated NLRP3 inflammasome activation in xenograft mice. • HMGB1 mediated NLRP3 inflammasome activation in AML cells. • Knockdown of HMGB1 inhibited AML progression under chronic stress in vivo.

Free light chains injure proximal tubule cells through the STAT1/HMGB1/TLR axis

Free light chains (FLCs) induce inflammatory pathways in proximal tubule cells (PTCs). The role of TLRs in these responses is unknown. Here we present findings on the role of TLRs in FLC-induced PTC injury. We exposed human kidney PTC cultures to κ and λ FLCs and used cell supernatants and pellets for ELISA and gene expression studies. We also analyzed tissues from Stat1-/- and littermate control mice treated with daily i.p. injections of a κ FLC for 10 days. FLCs increased the expression of TLR2, TLR4, and TLR6 via HMGB1, a damage-associated molecular pattern. Countering TLR2, TLR4, and TLR6 through GIT-27 or specific TLR siRNAs reduced downstream cytokine responses. Blocking HMGB1 through siRNA or pharmacologic inhibition, or via STAT1 inhibition, reduced FLC-induced TLR2, TLR4, and TLR6 expression. Blocking endocytosis of FLCs through silencing of megalin/cubilin, with bafilomycin A1 or hypertonic sucrose, attenuated FLC-induced cytokine responses in PTCs. IHC showed decreased TLR4 and TLR6 expression in kidney sections from Stat1-/- mice compared with their littermate controls. PTCs exposed to FLCs released HMGB1, which induced expression of TLR2, TLR4, and TLR6 and downstream inflammation. Blocking FLCs' endocytosis, Stat1 knockdown, HMGB1 inhibition, and TLR knockdown each rescued PTCs from FLC-induced injury.

High Mobility Group Box 1 Expression in Oral Inflammation and Regeneration

High mobility group box 1 (HMGB1) is a non-histone DNA-binding protein of about 30 kDa. It is released from a variety of cells into the extracellular milieu in response to inflammatory stimuli and acts on specific cell-surface receptors, such as receptors for advanced glycation end-products (RAGE), Toll-like receptor (TLR)2, TLR4, with or without forming a complex with other molecules. HMGB1 mediates various mechanisms such as inflammation, cell migration, proliferation, and differentiation. On the other hand, HMGB1 enhances chemotaxis acting through the C-X-C motif chemokine ligand (CXCL)12/C-X-C chemokine receptor (CXCR)4 axis and is involved in regeneration. In the oral cavity, high levels of HMGB1 have been detected in the gingival tissue from periodontitis and peri-implantitis patients, and it has been shown that secreted HMGB1 induces pro-inflammatory cytokine expression, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, which prolong inflammation. In contrast, wound healing after tooth extraction or titanium dental implant osseointegration requires an initial acute inflammation, which is regulated by secreted HMGB1. This indicates that secreted HMGB1 regulates angiogenesis and bone remodeling by osteoclast and osteoblast activation and promotes bone healing in oral tissue repair. Therefore, HMGB1 can prolong inflammation in the periodontal tissue and, conversely, can regenerate or repair damaged tissues in the oral cavity. In this review, we highlight the role of HMGB1 in the oral cavity by comparing its function and regulation with its function in other diseases. We also discuss the necessity for further studies in this field to provide more specific scientific evidence for dentistry.

High mobility group box 1 (HMGB1): a pivotal regulator of hematopoietic malignancies

High mobility group box 1 (HMGB1) is a nonhistone chromatin-associated protein that has been widely reported to play a pivotal role in the pathogenesis of hematopoietic malignancies. As a representative damage-associated molecular pattern (DAMP), HMGB1 normally exists inside cells but can be secreted into the extracellular environment through passive or active release. Extracellular HMGB1 binds with several different receptors and interactors to mediate the proliferation, differentiation, mobilization, and senescence of hematopoietic stem cells (HSCs). HMGB1 is also involved in the formation of the inflammatory bone marrow (BM) microenvironment by activating proinflammatory signaling pathways. Moreover, HMGB1-dependent autophagy induces chemotherapy resistance in leukemia and multiple myeloma. In this review, we systematically summarize the emerging roles of HMGB1 in carcinogenesis, progression, prognosis, and potential clinical applications in different hematopoietic malignancies. In summary, targeting the regulation of HMGB1 activity in HSCs and the BM microenvironment is highly beneficial in the diagnosis and treatment of various hematopoietic malignancies.

Glycyrrhizin Ameliorates Radiation Enteritis in Mice Accompanied by the Regulation of the HMGB1/TLR4 Pathway

Radiation enteritis is a common side effect of radiotherapy for abdominal and pelvic malignancies, which can lead to a decrease in patients' tolerance to radiotherapy and the quality of life. It has been demonstrated that glycyrrhizin (GL) possesses significant anti-inflammatory activity. However, little is known about its anti-inflammatory effect in radiation enteritis. In the present study, we aimed to investigate the potential anti-inflammatory effects of GL on radiation enteritis and elucidate the possible underlying molecular mechanisms involved. The C57BL/6 mice were subjected to 6.5 Gy abdominal X-ray irradiation to establish a model of radiation enteritis. Hematoxylin and eosin staining was performed to analyze the pathological changes in the jejunum. The expression of TNF-α in the jejunum was analyzed by immunochemistry. The levels of inflammatory cytokines, such as TNF-α, IL-6, IL-1β, and HMGB1 in the serum were determined by enzyme-linked immunosorbent assay. The intestinal absorption capacity was tested using the D-xylose absorption assay. The levels of HMGB1 and TLR4 were analyzed by western blotting and immunofluorescence staining. We found that GL significantly alleviated the intestinal damage and reduced the levels of inflammatory cytokines, such as TNF-α, IL-6, IL-1β, and HMGB1 levels. Furthermore, the HMGB1/TLR4 signaling pathway was significantly downregulated by GL treatment. In conclusion, these findings indicate that GL has a protective effect against radiation enteritis through the inhibition of the intestinal damage and the inflammatory responses, as well as the HMGB1/TLR4 signaling pathway. Thereby, GL might be a potential therapeutic agent for the treatment of radiation enteritis.

Aberrant Expression of High Mobility Group Box Protein 1 in the Idiopathic Inflammatory Myopathies

Introduction

High Mobility Group Box Protein 1 (HMGB1) is a DNA-binding protein that exerts inflammatory or pro-repair effects upon translocation from the nucleus. We postulate aberrant HMGB1 expression in immune-mediated necrotising myopathy (IMNM).

Methods

Herein, we compare HMGB1 expression (serological and sarcoplasmic) in patients with IMNM with that of other myositis subtypes using immunohistochemistry and ELISA.

Results

IMNM (n = 62) and inclusion body myositis (IBM, n = 14) patients had increased sarcoplasmic HMGB1 compared with other myositis patients (n = 46). Sarcoplasmic HMGB1 expression correlated with muscle weakness and histological myonecrosis, inflammation, regeneration and autophagy. Serum HMGB1 levels were elevated in patients with IMNM, dermatomyositis and polymositis, and those myositis patients with extramuscular inflammatory features.

Discussion

Aberrant HMGB1 expression occurs in myositis patients and correlates with weakness. A unique expression profile of elevated sarcoplasmic and serum HMGB1 was detected in IMNM.

Sepsis-associated pathways segregate cancer groups

BACKGROUND

Sepsis and cancer are both leading causes of death, and occurrence of any one, increases the likelihood of the other. While cancer patients are susceptible to sepsis, survivors of sepsis are also susceptible to develop certain cancers. This mutual dependence for susceptibility suggests shared biology between the two disease categories. Earlier analysis had revealed a cancer-related pathway to be up-regulated in Septic Shock (SS), an advanced stage of sepsis. This has motivated a more comprehensive comparison of the transcriptomes of SS and cancer.

METHODS

Gene Set Enrichment Analysis was performed to detect the pathways enriched in SS and cancer. Thereafter, hierarchical clustering was applied to identify relative segregation of 17 cancer types into two groups vis-a-vis SS. Biological significance of the selected pathways was explored by network analysis. Clinical significance of the pathways was tested by survival analysis. A robust classifier of cancer groups was developed based on machine learning.

RESULTS

A total of 66 pathways were observed to be enriched in both SS and cancer. However, clustering segregated cancer types into two categories based on the direction of transcriptomic change. In general, there was up-regulation in SS and one group of cancer (termed Sepsis-Like Cancer, or SLC), but not in other cancers (termed Cancer Alone, or CA). The SLC group mainly consisted of malignancies of the gastrointestinal tract (head and neck, oesophagus, stomach, liver and biliary system) often associated with infection. Machine learning classifier successfully segregated the two cancer groups with high accuracy (> 98%). Additionally, pathway up-regulation was observed to be associated with survival in the SLC group of cancers.

CONCLUSION

Transcriptome-based systems biology approach segregates cancer into two groups (SLC and CA) based on similarity with SS. Host response to infection plays a key role in pathogenesis of SS and SLC. However, we hypothesize that some component of the host response is protective in both SS and SLC.

MicroRNA-548 regulates high mobility group box 1 expression in patients with preterm birth and chorioamnionitis

High mobility group box 1 (HMGB1) is a prototypic alarmin and plays an important role in the pathogenesis of inflammatory process in spontaneous preterm birth. This study was conducted to compare the levels of HMGB1 in amniotic fluid and amnion membranes in women with chorioamnionitis/intra-amniotic inflammation to the levels in healthy controls. We also aimed to elucidate the involvement of microRNA-548 (miR-548) in regulating HMGB1 expression and its function in human amniotic epithelial cells (hAECs). A bioinformatics analysis predicted the binding of HMGB1 by the miR-548 cluster. A repressed and forced expression assay in hAECs was performed to investigate the causal relationship between the miR-548 cluster and HMGB1. The levels of HMGB1 in amniotic fluid and amnion membranes were significantly higher in patients with intra-amniotic inflammation/chorioamnionitis than in those without inflammation. The miR-548 was significantly under-expressed in amnion membranes from patients with chorioamnionitis than in normal term controls. Repressed expression of miR-548 up-regulated HMGB1 expression in hAECs and increased its release from hAECs. Moreover, forced expression of miR-548 suppressed HMGB1 and inflammatory cytokines in hAECs, which increased when treated with lipopolysaccharide. These results suggest miR-548 can alter the inflammatory responses in hAECs, and might be involved in the pathogenesis of preterm birth by regulating HMGB1.

Pathophysiologic Characterization of a Novel Rabbit Model of Biliary Tract Infection-Derived Sepsis

Biliary tract infection (BTI)-derived sepsis remains a serious problem with significant morbidity and mortality in the modern era of critical care management. Current animal models of BTI have relied mostly on injecting purified bacteria or their toxins into the biliary tract. These models do not fully reflect pathophysiology or disease processes of clinical cholangitis or cholecystitis. In the current study, we developed a novel model of BTI by performing cholecystocolonic anastomosis (CCA) in rabbits and characterized pathophysiologic changes in this model. This model is intended to mimic the clinical process of cholecystocolonic fistula with reflux cholangitis, a severe form of BTI. Adult male rabbits were subjected to BTI-derived sepsis through an anastomosis of the gall bladder to the colon (i.e., CCA). The animals were monitored for 7 days to record survival. In additional groups of animals, various bacterial, hemodynamic, histological and biochemical parameters were measured at 12, 24, 48 and 72 h after CCA. The anastomosis between the gallbladder and the colon required about 5–8 min to finish. The median survival time for rabbits after CCA was 96 h. The positive rates of bacterial culture at 72 h after CCA were 83.3% and 100% in the blood and liver, respectively. The most common microorganism was Escherichia coli followed by Enterococcus. Plasma Tumor Necrosis Factor-α (TNF-α), Lnterleukin-10 (IL-10), Lnterleukin-6 (IL-6), and High-mobility group box 1 protein (HMGB-1) levels were greatly elevated after CCA. The cardiac index and heart rate increased slightly at 12 h after CCA and then continued to decrease. Systemic hypotension developed 48 h after CCA. Histological studies showed reflux cholangitis with acute lung and kidney injury. Cholecystocolonic anastomosis produces polymicrobial sepsis in rabbits, which mimics many aspects of human BTI-derived sepsis. It is reproducible and easy to perform and may serve as an excellent model for future sepsis research.

Involvement of Alveolar Epithelial Cell Necroptosis in Idiopathic Pulmonary Fibrosis Pathogenesis

Alveolar epithelial cell (AEC) injury leading to cell death is involved in the process of fibrosis development during idiopathic pulmonary fibrosis (IPF). Among regulated/programmed cell death, the excessive apoptosis of AECs has been widely implicated in IPF pathogenesis. Necroptosis is a type of regulated/programmed necrosis. A multiprotein complex composed of receptor-interacting protein kinase (RIPK)-1 and -3 plays a key regulatory role in initiating necroptosis. Although necroptosis participates in disease pathogeneses through the release of damage-associated molecular patterns, its association with IPF progression remains elusive. In this study, we attempted to illuminate the involvement of RIPK3-regulated necroptosis in IPF pathogenesis. IPF lung tissues were used to detect necroptosis, and the role of RIPK3 was determined using cell culturing models of AECs. Lung fibrosis models of bleomycin (BLM) treatment were also used. RIPK3 expression levels were increased in IPF lungs, and both apoptosis and necroptosis were detected mainly in AECs. Necrostatin-1 and RIPK3 knockout experiments in AECs revealed the participation of necroptosis in BLM and hydrogen peroxide-induced cell death. BLM treatment induced RIPK3 expression in AECs and increased high-mobility group box 1 and IL-1β levels in mouse lungs. The efficient attenuation of BLM-induced lung inflammation and fibrosis was determined in RIPK3 knockout mice and by necrostatin-1 with a concomitant reduction in high-mobility group box 1 and IL-1β. RIPK3-regulated necroptosis in AECs is involved in the mechanism of lung fibrosis development through the release of damage-associated molecular patterns as part of the pathogenic sequence of IPF.

Role of oral flora in chemotherapy-induced oral mucositis in vivo

OBJECTIVE

To determine if commensal oral microflora impacts the severity of chemotherapy-induced oral mucositis (OM).

DESIGN

Specific-pathogen-free (SPF) and germ-free Swiss Webster mice in the experimental groups were dosed with 5-fluorouracil (5-FU) to induce OM. Mice in the control group received phosphate buffered saline. Comparative analyses of the epithelial thickness and cell proliferation/turnover rates, as well as the expression levels of metalloproteinases and pro-inflammatory mediators in the oral mucosa between the control and experimental groups were determined by histopathological and immunohistochemical analyses.

RESULTS

5-FU-treated SPF and germ-free mice showed characteristic features of OM with reduced oral epithelial thickness, presence of inflammatory cells in the connective tissues, and increased levels of expression of metalloproteinases and pro-inflammatory cytokines compared to the respective control groups. When 5-FU-treated SPF and germ-free mice were compared, 5-FU-treated germ-free mice exhibited less severe epithelial destruction with higher expression of the cell proliferation marker Ki67, coupled with lower expression levels of metalloproteinases and pro-inflammatory cytokine in the oral mucosa.

CONCLUSION

This study provides the first histopathological evidence that oral flora has a detrimental effect on chemotherapy-induced OM in vivo.

Icariin and icaritin ameliorated hippocampus neuroinflammation via inhibiting HMGB1-related pro-inflammatory signals in lipopolysaccharide-induced inflammation model in C57BL/6 J mice

Inflammation is a defensive response of the body and is at the center of many diseases' process like depression. High mobility group protein box 1 (HMGB1), has been proved to function as a pro-inflammatory cytokine. We aim to explore the role of HMGB1 played in the neuroinflammation here. In this study, we used LPS to induce an acute inflammatory response, and to measure the anti-neuroinflammation effect of icariin (ICA) and icaritin (ICT). We found that LPS could increase the expression of HMGB1 in serum and hippocampus, along with a high expression of HMGB1 in the cytoplasm and a high expression of RAGE, which could be rescued by ICA and ICT, and ethyl pyruvate (EP) pretreatment showed similar effects here. We speculated that the translocation of HMGB1 from the nucleus to the cytoplasm played an important role in neuroinflammatory process, and HMGB1-RAGE signal was involved in this process. Furthermore, we found that ICA and ICT treatment activated TLR4-XBP1s related NF-κB signal, which we thought was relevant with the neuroprotective effect of ICA and ICT. However, EP pretreatment suppressed TLR4-XBP1s- endoplasmic reticulum stress related NF-κB signal to anti-inflammatory response, which was almost absolutely opposite with ICA and ICT treatment. We speculated that it might be caused by the duration of inflammation. We supposed that ICA and ICT could ameliorate neuroinflammation in hippocampus via suppressing HMGB1-RAGE signaling and might show a neuroprotective effect via activating TLR4-XBP1s related NF-κB signal at the same time, making it possible to act as an anti-neuroinflammatory drugs.

Emerging Role of HMGB1 in the Pathogenesis of Schistosomiasis Liver Fibrosis

In chronic schistosomiasis, liver fibrosis is linked to portal hypertension, which is a condition associated with high mortality and morbidity. High mobility group box 1 (HMGB1) was originally described as a nuclear protein that functions as a structural co-factor in transcriptional regulation. However, HMGB1 can also be secreted into the extracellular milieu under appropriate signal stimulation. Extracellular HMGB1 acts as a multifunctional cytokine that contributes to infection, injury, inflammation, and immune responses by binding to specific cell-surface receptors. HMGB1 is involved in fibrotic diseases. From a clinical perspective, HMGB1 inhibition may represent a promising therapeutic approach for treating tissue fibrosis. In this study, we demonstrate elevated levels of HMGB1 in the sera in experimental mice or in patients with schistosomiasis. Using immunohistochemistry, we demonstrated that HMGB1 trafficking in the hepatocytes of mice suffering from acute schistosomiasis was inhibited by Glycyrrhizin, a well-known HMGB1 direct inhibitor, as well as by DIC, a novel and potential anti-HMGB1 compound. HMGB1 inhibition led to significant downregulation of IL-6, IL4, IL-5, IL-13, IL-17A, which are involved in the exacerbation of the immune response and liver fibrogenesis. Importantly, infected mice that were treated with DIC or GZR to inhibit HMGB1 pro-inflammatory activity showed a significant increase in survival and a reduction of over 50% in the area of liver fibrosis. Taken together, our findings indicate that HMGB1 is a key mediator of schistosomotic granuloma formation and liver fibrosis and may represent an outstanding target for the treatment of schistosomiasis.

Dexmedetomidine Protects Against Traumatic Brain Injury-Induced Acute Lung Injury in Mice

Background

Traumatic brain injury (TBI) leads to acute lung injury (ALI), in which the inflammatory response plays an important role in its pathophysiology. Recent studies suggest that dexmedetomidine (Dex) plays a protective role in acute inflammatory diseases. However, whether Dex has a protective effect on TBI-induced ALI is not clear. The aim of this study was to investigate the effect of Dex on TBI-induced ALI in mice.

Material/Methods

Mice were randomly divided into 5 groups: 1) sham group; 2) TBI group; 3) TBI+Dex group; 4) TBI+atipamezole (Atip) group; and 5) TBI+Dex+Atip group. Dex (50 μg/kg) was intraperitoneal injected immediately after TBI. The α₂ adrenergic antagonist Atip (250 μg/kg) was intraperitoneal injected 15 minutes prior to Dex treatment. Then 24 hours later, the protein concentration in the bronchoalveolar lavage fluid (BALF), lung wet to dry weight ratio, hematoxylin and eosin (H&E) staining of lungs, the level of high-mobility group box protein 1(HMGB1) in serum, and the receptor for advanced glycation end products (RAGE) expression in lung were detected.

Results

Dex ameliorated the score of lung histological examination, as well as the severity of pulmonary edema and permeability. Moreover, Dex was observed to significantly suppress the expression of HMGBI and RAGE. However, the protective effects of Dex were partially reversed by the administration of Atip.

Conclusions

Dex may protect against TBI-induced ALI via the HMGB1-RAGE signal pathway, and this protective effect is partly dependent on its α₂ adrenoceptor agonist action.

Mechanism underlying the effect of long-term exposure to low dose of pesticides on DNA integrity

Pesticides, including herbicides, insecticides and fungicides, are widely used in intensive agriculture. Recently, the long-term effects of pesticide exposure were found to be associated with many diseases. In this study, we evaluated the long-term effect of low-level exposure to a mixture of pesticides on DNA damage response (DDR) in relation to individual detoxifying variability. A residential population chronically exposed to pesticides was enrolled, biological/environmental pesticide levels; paroxonase 1 (PON-1) activity and 192 Q/R polymorphism and DDR were evaluated at three different periods of pesticide exposure. OGG1-dependent DNA repair activity was decreased in relation to pesticide exposure. The increase of DNA lesions and pesticide levels in the intensive pesticide-spraying period was independent on PON-1 activity. Next, human bronchial epithelial and neuronal cells were used as a model for in vitro evaluation of the mechanistic effect of pesticides. Pesticides induced mitochondrial dysfunction leading to ROS formation. ROS from mitochondria induced DNA damage, which in turn induced OGG1-dependent DNA repair activity through 8-oxoguanine DNA glycosylase 1 (OGG1) expression and activation. Even though OGG1 was overexpressed, an inhibition of its activity, associated with DNA lesion accumulation, was found at prolonged pesticide-exposure. A post-translational regulation of OGG1 by pesticide may be postulated. Taken together, long-term exposure to low-levels of pesticides affects DDR resulting in accumulation of DNA lesions that eventually may lead to cancer or neurological disorders.

ATP/P2X7-NLRP3 axis of dendritic cells participates in the regulation of airway inflammation and hyper-responsiveness in asthma by mediating HMGB1 expression and secretion

The ATP/P2X7 axis of dendritic cells (DCs) mediates the activation of NLRP3 inflammasome and promotes secretion of interleukin (IL)-1β and IL-18 to induce T helper (Th) 2, Th17 differentiation in the pathogenesis of asthma. NLRP3 inflammasome also regulates high mobility protein 1 (HMGB1) release in DCs. Recent studies demonstrated the correlation between HMGB1 expression and airway inflammation and hyper-responsiveness (AHR) in asthma. However, the relationship between the ATP/P2X7-NLRP3 axis and HMGB1 in DCs in asthma is still unclear. ATP, apyrase, Brilliant Blue G, BzATP, glibenclamide, and Z-YVAD-FMK were administered to ovalbumin (OVA)-induced murine asthmatic model. For in vitro studies, bone marrow-derived mononuclear cells (BMDCs) were primed with LPS and stimulated with the same reagents. Activation of the ATP/P2X7 axis aggravated airway inflammation and AHR in the lung and induced Th2, Th17 polarization in asthmatic mice. Inhibition of NLRP3 inflammasome weakened cardinal features of asthma and blocked Th2, Th17 polarization. In vitro and vivo, ATP/P2X7 axis activated NLRP3 inflammasome and induced HMGB1 expression and release from DCs. Inhibition of NLRP3 inflammasome reduced HMGB1 expression and release. The ATP/P2X7-NLRP3 axis of DCs participates in mediating airway inflammation, AHR, and promoting Th2, Th17 inflammatory responses in asthmatic mice by inducing HMGB1 expression and secretion.

Ethyl pyruvate reverses development of Pseudomonas aeruginosa pneumonia during sepsis-induced immunosuppression

Sepsis is characterized by an innate immune response and the following immune dysfunction which can increase the emergence of secondary infections. Ethyl pyruvate (EP) has multiple immunoregulation functions in several serious illnesses, such as burn injury, severe sepsis and acute respiratory syndrome. However, little data was shown the effect of EP administration on immunosuppression post-CLP and the following secondary infection. The cecal ligation and puncture (CLP) followed by the induction of Pseudomonas aeruginosa (PA) was used as a clinically relevant two-hit model of sepsis. We assessed the survival rate, lung damage and lung bacterial clearance in vehicle or EP treatment group to demonstrate the lung response to Pseudomonas aeruginosa of septic mice. Then cytokines including lung IL-6, IL-1β, IL-10 and plasma HMGB1, apoptosis of splenic immune cells and Foxp3 level on regulatory T cells (Tregs) were studied to demonstrate the mechanisms of EP administration on two-hit mice. We found that the susceptibility of septic mice to Secondary Pseudomonas aeruginosa pneumonia could be down-regulated by ethyl pyruvate treatment and the protective effects of EP may via decreasing lung IL-10 and plasma HMGB1 expression, inhibiting the function of Tregs and relieving the apoptosis of splenic immune cells. The "immune paralysis" post-sepsis still remains a rigorous challenge for curing sepsis, our study may aid in the development of new therapeutic strategies to this problem.

High Mobility Group Box 1 Protein Level as a Novel Biomarker for the Development of Peri-Implant Disease

Peri-implant disease is a chronic inflammation of the soft and hard tissues around a dental implant, resulting from bacterial infection. Recent evidence indicates that some pro-inflammatory cytokines and chemokines released by immunocytes are substantially responsible for the progress and consequence of inflammation. High mobility group box 1 (HMGB1) is released into the extracellular matrix and acts as a key pro-inflammatory factor during injury, necrosis and inflammation. A higher concentration of HMGB1 has been found in gingival crevicular fluid from inflammatory gingival tissue than from healthy sites. HMGB1 mRNA and protein are overexpressed in murine periodontal ligament fibroblasts stimulated with lipopolysaccharide (LPS) and IL-1β. Thus, this study sought to assess HMGB1 expression in peri-implant crevicular fluid (PICF) at each stage of peri-implant disease and to investigate the correlation between HMGB1 and peri-implant disease progress. The results demonstrated that the HMGB1 expression level in PICF is indicative of the progress of peri-implant disease and hence may be a useful diagnostic and prognostic biomarker for peri-implant tissue.

Therapeutic targeting of HMGB1 during experimental sepsis modulates the inflammatory cytokine profile to one associated with improved clinical outcomes

Sepsis remains a significant health burden and a major clinical need exists for therapeutics to dampen the excessive and uncontrolled immune activation. Nuclear protein high mobility group box protein 1 (HMGB1) is released following cell death and is a late mediator in sepsis pathogenesis. While approaches targeting HMGB1 have demonstrated reduced mortality in pre-clinical models of sepsis, the impact of HMGB1 blockade on the complex septic inflammatory milieu and the development of subsequent immunosuppression remain enigmatic. Analysis of plasma samples obtained from septic shock patients established an association between increased HMGB1 and non-survival, higher APACHE II scores, and increased pro-inflammatory cytokine responses. Pre-clinically, administration of neutralising ovine anti-HMGB1 polyclonal antibodies improved survival in murine endotoxaemia and caecal ligation and puncture-induced sepsis models, and altered early cytokine profiles to one which corresponded to patterns observed in the surviving patient cohort. Additionally, anti-HMGB1 treated murine sepsis survivors were significantly more resistant to secondary bacterial infection and exhibited altered innate immune cell phenotypes and cytokine responses. These findings demonstrate that anti-HMGB1 antibodies alter inflammation in murine sepsis models and reduce sepsis mortality without potentiating immunosuppression.

Toll-like receptor 4 is critical for the development of resection-associated hepatic steatosis

BACKGROUND

A significant number of children with short bowel syndrome experience intestinal failure-associated liver disease. We recently demonstrated accelerated hepatic steatosis after 50% small bowel resection (SBR) in mice. Since SBR is associated with alterations in the gut microbiome, the purpose of this study was to determine whether TLR4 signaling is critical to the development of resection-associated hepatic steatosis.

METHODS

Male C57BL6 (control) and TLR4-knockout (KO) mice underwent 50% proximal SBR. Liver sections were analyzed to obtain the percent lipid content, and Ileal sections were assessed for morphological adaptation. Intestinal TLR4 mRNA expression was measured at 7days and 10weeks.

RESULTS

Compared to controls, TLR4 KO mice demonstrated similar weight gain and morphological adaptation after SBR. Hepatic steatosis was decreased 32-fold in the absence of TLR4. Intestinal TLR4 mRNA expression was significantly elevated 7days after SBR. We also found that TLR4 expression in the intestine was 20-fold higher in whole bowel sections compared with isolated enterocytes.

CONCLUSIONS

TLR4 signaling is critical for the development of resection-associated steatosis, but not involved in intestinal adaptation after massive SBR. Further studies are needed to delineate the mechanism for TLR4 signaling in the genesis of resection-associated liver injury.

LEVEL OF EVIDENCE

Animal study, not clinical.

The dual role and therapeutic potential of high-mobility group box 1 in cancer

High-mobility group box 1 (HMGB1) is an abundant protein in most eukaryocytes. It can bind to several receptors such as advanced glycation end products (RAGE) and Toll-like receptors (TLRs), in direct or indirect way. The biological effects of HMGB1 depend on its expression and subcellular location. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription, telomere maintenance, and genome stability. While outside the nucleus, it possesses more complicated functions, including regulating cell proliferation, autophagy, inflammation and immunity. During tumor development, HMGB1 has been characterized as both a pro- and anti-tumoral protein by either promoting or suppressing tumor growth, proliferation, angiogenesis, invasion and metastasis. However, the current knowledge concerning the positive and negative effects of HMGB1 on tumor development is not explicit. Here, we evaluate the role of HMGB1 in tumor development and attempt to reconcile the dual effects of HMGB1 in carcinogenesis. Furthermore, we would like to present current strategies targeting against HMGB1, its receptor or release, which have shown potentially therapeutic value in cancer intervention.

HMGB1 attenuates TGF-β-induced epithelial-mesenchymal transition of FaDu hypopharyngeal carcinoma cells through regulation of RAGE expression

Abnormal expression of high-mobility group box-1 (HMGB1) protein occurs in many tumors and is closely associated with tumor invasion and metastasis. However, a role for HMGB1 in epithelial-mesenchymal transition (EMT) in hypopharyngeal carcinoma has not been previously reported. We cultured cells of the hypopharyngeal carcinoma cell line FaDu in vitro and then treated them with 5 ng/ml TGF-β1 for 48 h to induce EMT. Vimentin, Snail, and HMGB1 expression patterns were then detected using immunofluorescence staining; HMGB1 mRNA and protein expression were verified by RT-PCR and western blot analyses. HMGB1 was then silenced in FaDu cells using RNAi, followed by detection of Vimentin, Snail, and HMGB1 expressions by immunofluorescence staining. The mRNA expression levels of Vimentin, Snail, HMGB1, and E-cadherin were verified by RT-PCR, while protein expression of HMGB1 and receptor for advanced glycation end products (RAGE) were detected by western blot analysis. The biological behavior of FaDu cells was observed before and after HMGB1 silencing using wound healing and cell invasion assays. Following culture with 5 ng/ml TGF-β1 for 48 h, the morphology of FaDu cells changed from a regular cobblestone-like appearance into a spindle-like shape. Expression levels of Vimentin, Snail, and HMGB1 were upregulated at both mRNA and protein levels as determined by RT-PCR, immunofluorescence, and western blotting. After HMGB1 silencing, mRNA expression levels of the epithelial cell marker E-cadherin were upregulated. Meanwhile, expression levels of the mesenchymal markers Vimentin and Snail were decreased. Western blotting revealed that HMGB1 and RAGE were downregulated. RNAi-mediated inhibition of HMGB1 expression decreased the capacities of FaDu cells for invasion and metastasis as determined by wound healing and cell invasion assays. HMGB1 is essential for maintaining the interstitial cell phenotype in TGF-β1-induced EMT of FaDu cells, and silencing HMGB1 greatly inhibits the invasive and metastatic ability of these cells.

Bio-HMGB1 from breast cancer contributes to M-MDSC differentiation from bone marrow progenitor cells and facilitates conversion of monocytes into MDSC-like cells

Myeloid-derived suppressor cells (MDSC) constitute the major cell population that regulates immune responses. They are known to accumulate in tumors, chronic inflammatory and autoimmune diseases. Previous data indicate that high mobility group box 1(HMGB1) facilitates MDSC differentiation from bone marrow, suppresses NK cells, CD4+ and CD8+ T cells and is involved in cancer development. However, it remains unclear what potential mechanisms of HMGB1 facilitate MDSC differentiation. In the present work, we clearly demonstrate that HMGB1 secreted by cancer cells is N-glycosylated at Asn37, which facilitates monocytic (M)-MDSC differentiation from bone marrow via the p38/NFκB/Erk1/2 pathway and also contributes to conversion of monocytes into MDSC-like cells; HMGB1 blockade by a monoclonal antibody against the HMGB1 B box obviously reduced the accumulation of M-MDSC in tumor-bearing mice, delaying tumor growth and development; additionally, MDSC expansion and HMGB1 up-regulation were also found in breast cancer patients. All these data indicate that HMGB1 might be a potential tumor immunotherapy target.

Association of high mobility group BOX-1 and receptor for advanced glycation endproducts with clinicopathological features of haematological malignancies: a systematic review

High-mobility group box 1 (HMGB1) is a versatile protein with nuclear and extracellular functions. In the extracellular milieu, HMGB1 binds to several receptors, notably the receptor for advanced glycation end-products (RAGE). The expressions of HMGB1 and RAGE have been described in a variety of cancers. However, the clinical values of HMGB1 and RAGE in haematological malignancies have yet to be evaluated. A systematic search through PubMed and the Web of Science for articles discussing the role of HMGB1 and RAGE in haematological malignancies produced 15 articles. Overexpression of HMGB1 was reported to be associated with malignancy and, in certain studies, poor prognosis and tumour aggressiveness. Only one included study investigated the clinical value of RAGE, in which no significant difference was found between expression of RAGE in CLL neoplastic cells and nonmalignant controls. The discussed associations of HMGB1 and RAGE with clinicopathological characteristics of patients with haematological malignancies warrants further investigation into the prognostic and diagnostic value of both of these molecules.

CoVaccine HT™ adjuvant is superior to Freund's adjuvants in eliciting antibodies against the endogenous alarmin HMGB1

Adjuvants are used to enhance the immune response against specific antigens for the production of antibodies, with the choice of adjuvant most critical for poorly immunogenic and self-antigens. This study quantitatively and qualitatively evaluated CoVaccine HT™ and Freund's adjuvants for eliciting therapeutic ovine polyclonal antibodies targeting the endogenous alarmin, high mobility group box-1 (HMGB1). Sheep were immunised with HMGB1 protein in CoVaccine HT™ or Freund's adjuvants, with injection site reactions and antibody titres periodically assessed. The binding affinity of antibodies for HMGB1 and their neutralisation activity was determined in-vitro, with in vivo activity confirmed using a murine model of endotoxemia. Results indicated that CoVaccine HT™ elicited significantly higher antibody tires with stronger affinity and more functional potency than antibodies induced with Freund's adjuvants. These studies provide evidence that CoVaccine HT™ is superior to Freund's adjuvants for the production of antibodies to antigens with low immunogenicity and supports the use of this alternative adjuvant for clinical and experimental use antibodies.

Dysregulated innate immune function in the aetiopathogenesis of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic muscle conditions that are believed to be autoimmune in nature. They have distinct pathological features, but the aetiopathogenesis of each subtype remains largely unknown. Recently, there has been increased interest in the complex role the innate immune system plays in initiating and perpetuating these conditions, and how this may differ between subtypes. This article summarises the traditional paradigms of IIM pathogenesis and reviews the accumulating evidence for disturbances in innate immune processes in these rare, but debilitating chronic conditions.

Short Communication: Effect of Antiretroviral Therapy on Circulating Damage-Associated Molecular Pattern Molecules and CD4 Immune Reconstitution in HIV-Infected Individuals

We examined levels of the damage-associated molecular pattern molecules, HMGB1 and S100A9, in individuals for whom stored samples were available before and after antiretroviral therapy (ART) initiation, to determine their association with CD4 reconstitution. Mean HMGB1 levels (1.95 ng/ml vs. 3.02 ng/ml) and the proportion of individuals with detectable S100A9 (19.6% vs. 43.1%) significantly increased after ART. Detectable post-ART S100A9 was independently associated with impaired immune reconstitution.

Rituximab-induced HMGB1 release is associated with inhibition of STAT3 activity in human diffuse large B-cell lymphoma

Treatment with rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) has greatly improved clinical outcomes in patients with diffuse large B-cell lymphoma (DLBCL) compared with CHOP. The mechanism of rituximab-induced cell death is poorly understood. We found that rituximab does not enhance the directly killing efficacy of CHOP, as tested on a panel of DLBCL cell lines. Rituximab induced a rapid release of HMGB1 (High mobility group protein B 1). This release is independent of cell death but significantly correlated with an inhibition on STAT3 activity. In the resting state, HMGB1 co-localizes and interacts with STAT3 in the nucleus of DLBCL cells. Treatment with rituximab breaks this binding and triggers HMGB1 release. Treatment with R-CHOP but not CHOP significantly increased plasma HMGB1 and decreased IL-10 concentrations in DLBCL patients compared with controls. The conditioned medium from rituximab-treated DLBCL cells is able to trigger dendritic cell maturation, phagocytosis, and IFN-g secretion by cytotoxic T cells. In conclusion, our results demonstrate that rituximab induces an inhibition on STAT3 activity, leading to increased HMGB1 release and decreased IL-10 secretion, which elicits immune responses, suggesting that indirect effects on the immune system rather than direct killing contribute to elimination of DLBCL.

The neutrophil elastase inhibitor, sivelestat, attenuates sepsis-related kidney injury in rats

Sepsis-induced acute kidney injury (AKI) represents a major cause of mortality in intensive care units. Sivelestat, a selective inhibitor of neutrophil elastase (NE), can attenuate sepsis-related acute lung injury. However, whether sivelestat can preserve kidney function during sepsis remains unclear. In this study, we thus examined the effects of sivelestat on sepsis-related AKI. Cecal ligation and puncture (CLP) was performed to induce multiple bacterial infection in male Sprague-Dawley rats, and subsequently, 50 or 100 mg/kg sivelestat were administered by intraperitoneal injection immediately after the surgical procedure. In the untreated rats with sepsis, the mean arterial pressure (MAP) and glomerular filtration rate (GFR) were decreased, whereas serum blood urea nitrogen (BUN) and neutrophil gelatinase-associated lipocalin (NGAL) levels were increased. We found that sivelestat promoted the survival of the rats with sepsis, restored the impairment of MAP and GFR, and inhibited the increased BUN and NGAL levels; specifically, the higher dose was more effective. In addition, sivelestat suppressed the CLP-induced macrophage infiltration, the overproduction of pro-inflammatory mediators (tumor necrosis factor-α, interleukin-1β, high-mobility group box 1 and inducible nitric oxide synthase) and serine/threonine kinase (Akt) pathway activation in the rats. Collectively, our data suggest that the inhibition of NE activity with the inhibitor, sivelestat, is beneficial in ameliorating sepsis-related kidney injury.

Characterization of the Inflammatory Properties of Actively Released HMGB1 in Juvenile Idiopathic Arthritis

AIMS

Pathogenic effects of the endogenous inflammatory mediator high mobility group box protein 1 (HMGB1) have been described in several inflammatory diseases. Recent reports have underlined the importance of post-translational modifications (PTMs) in determination of HMGB1 function and release mechanisms. We investigated the occurrence of PTMs of HMGB1 obtained from synovial fluid (SF) of juvenile idiopathic arthritis (JIA) patients.

RESULTS

Analyses of 17 JIA patients confirmed high HMGB1 levels in SF. Liquid chromatography tandem mass-spectrometry (LC-MS/MS) analyses of PTMs revealed that total HMGB1 levels were not associated with increased lactate dehydrogenase activity but strongly correlated with nuclear location sequence 2 (NLS2) hyperacetylation, indicating active release of HMGB1. The correlation between total HMGB1 levels and NLS2 hypoacetylation suggests additional, acetylation-independent release mechanisms. Monomethylation of lysine 43 (K43), a proposed neutrophil-specific PTM, was strongly associated with high HMGB1 levels, implying that neutrophils are a source of released HMGB1. Analysis of cysteine redox isoforms, fully reduced HMGB1, disulfide HMGB1, and oxidized HMGB1, revealed that HMGB1 acts as both a chemotactic and a cytokine-inducing mediator. These properties were associated with actively released HMGB1.

INNOVATION

This is the first report that characterizes HMGB1-specific PTMs during a chronic inflammatory condition.

CONCLUSION

HMGB1 in SF from JIA patients is actively released through both acetylation-dependent and -nondependent manners. The presence of various functional HMGB1 redox isoforms confirms the complexity of their pathogenic role during chronic inflammation. Defining HMGB1 release pathways and redox isoforms is critical for the understanding of the contribution of HMGB1 during inflammatory processes.