Monocytic cells hyperacetylate chromatin protein HMGB1 to redirect it towards secretion

Selective Blockade of TNFR1 Improves Clinical Disease and Bronchoconstriction in Experimental RSV Infection

Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis in infants and young children. Although some clinical studies have speculated that tumor necrosis factor (TNF)-α is a major contributor of RSV-mediated airway disease, experimental evidence remains unclear or conflicting. TNF-α initiates inflammation and cell death through two distinct receptors: TNF-receptor (TNFR)1 and TNFR2. Here we delineate the function of TNF-α by short-lasting blockade of either receptor in an experimental BALB/c mouse model of RSV infection. We demonstrate that antibody-mediated blockade of TNFR1, but not TNFR2, results in significantly improved clinical disease and bronchoconstriction as well as significant reductions of several inflammatory cytokines and chemokines, including IL-1α, IL-1β, IL-6, Ccl3, Ccl4, and Ccl5. Additionally, TNFR1 blockade was found to significantly reduce neutrophil number and activation status, consistent with the concomitant reduction of pro-neutrophilic chemokines Cxcl1 and Cxcl2. Similar protective activity was also observed when a single-dose of TNFR1 blockade was administered to mice following RSV inoculation, although this treatment resulted in improved alveolar macrophage survival rather than reduced neutrophil activation. Importantly, short-lasting blockade of TNFR1 did not affect RSV peak replication in the lung. This study suggests a potential therapeutic approach for RSV bronchiolitis based on selective blockade of TNFR1.

Duck HMGB2 Mediates Signaling Pathways in the Innate Immunity of Hosts Against Viral Infections

High-mobility group box 2 (HMGB2) belongs to the HMG-box family that participates in a variety of biologic processes. Recent studies have suggested that HMGB2 plays an important role in the innate immunity of fish. Cherry Valley duck is the main duck bred for meat consumption in China, but there is limited research available on the impact of duck HMGB2 (duHMGB2) in antiviral innate immunity. Here, duHMGB2 genes were first cloned and analyzed from the spleen of Cherry Valley ducks. We show that duHMGB2 is widely distributed in most tissues of healthy ducks, and duHMGB2 was differentially expressed in three organs (the spleen, brain, and lung) of ducks during different viral infections. duHMGB2 is mainly expressed in the nucleus of duck embryo fibroblast (DEF) cells. However, duHMGB2 is released into the cytoplasm after viral infection. DuHMGB2 induced expression of several genes that regulate the immune response. Moreover, duHMGB2 activated and upregulatede transcription factor NF-κB promoter activity. We also used single gene manipulations (knockout or overexpression) to confirm that duHMGB2 can inhibit the replication of duck plague virus, duck Tembusu virus, and the novel duck reovirus in DEF cells. These data show that duHMGB2 can activate the antiviral innate immunity of the host. Thus, duHMGB2 may be considered an immune adjuvant against infectious diseases in duck.

Time to Develop Therapeutic Antibodies Against Harmless Proteins Colluding with Sepsis Mediators?

Sepsis refers to a systemic inflammatory response syndrome resulting from microbial infections, and is partly attributable to dysregulated inflammation and associated immunosuppression. A ubiquitous nuclear protein, HMGB1, is secreted by activated leukocytes to orchestrate inflammatory responses during early stages of sepsis. When it is released by injured somatic cells at overwhelmingly higher quantities, HMGB1 may induce macrophage pyroptosis and immunosuppression, thereby impairing the host's ability to eradicate microbial infections. A number of endogenous proteins have been shown to bind HMGB1 to modulate its extracellular functions. Here, we discuss an emerging possibility to develop therapeutic antibodies against harmless proteins that collude with pathogenic mediators for the clinical management of human sepsis and other inflammatory diseases.

Secretory autophagy machinery and vesicular trafficking are involved in HMGB1 secretion

Nuclear protein HMGB1 is secreted in response to various stimuli and functions as a danger-associated molecular pattern. Extracellular HMGB1 induces inflammation, cytokine production, and immune cell recruitment via activation of various receptors. As HMGB1 does not contain an endoplasmic reticulum-targeting signal peptide, HMGB1 is secreted via the endoplasmic reticulum-Golgi independently via an unconventional secretion pathway. However, the mechanism underlying HMGB1 secretion remains largely unknown. Here, we investigated the role of secretory autophagy machinery and vesicular trafficking in HMGB1 secretion. We observed that HSP90AA1 (heat shock protein 90 alpha family class A member 1), a stress-inducible protein, regulates the translocation of HMGB1 from the nucleus to the cytoplasm and its secretion through direct interaction. Additionally, geldanamycin, an HSP90AA1 inhibitor, reduced HMGB1 secretion. GORASP2/GRASP55 (golgi reassembly stacking protein 2), ARF1^Q71L (ADP ribosylation factor 1), and SAR1A^T39N (secretion associated Ras related GTPase 1A), which promoted unconventional protein secretion, increased HMGB1 secretion. HMGB1 secretion was inhibited by an early autophagy inhibitor and diminished in ATG5-deficient cells even when GORASP2 was overexpressed. In contrast, a late autophagy inhibitor increased HMGB1 secretion under the same conditions. The multivesicular body formation inhibitor GW4869 dramatically decreased HMGB1 secretion under HMGB1 secretion-inducing conditions. Thus, we demonstrated that secretory autophagy and multivesicular body formation mediate HMGB1 secretion.

High-mobility group box 1 is a driver of inflammation throughout pregnancy

A proinflammatory response driven by high-mobility group box 1 (HMGB1) is important for the success of both the early stages of pregnancy and parturition initiation. However, the tight regulation of HMGB1 within these two stages is critical, as increased HMGB1 can manifest into pregnancy-related pathologies. Although during the early stages of pregnancy HMGB1 is critical for the development and implantation of the embryo, and uterine decidualization, high levels within the uterine cavity have been linked to pregnancy failure. In addition, chronic inflammation, resultant from increased HMGB1 within the maternal circulation and gestational tissues, also increases the risk for preterm labor, preterm birth, or infant mortality. Due to the link between HMGB1 and several pregnancy pathologies, the possibility of leveraging HMGB1 as a biomarker has been assessed. However, data are limited that demonstrate how known HMGB1 inhibitors could reduce inflammation within pregnancy. Thus, further research is warranted to improve our understanding of the potential of HMGB1 as a therapeutic target to reduce inflammation within pregnancy. This review aims to describe what is understood about the role of HMGB1 that drives inflammation throughout pregnancy and highlight its potential as a biomarker and therapeutic target within this context.

Indirect regulation of HMGB1 release by gasdermin D

The protein high-mobility group box 1 (HMGB1) is released into the extracellular space in response to many inflammatory stimuli, where it is a potent signaling molecule. Although research has focused on downstream HMGB1 signaling, the means by which HMGB1 exits the cell is controversial. Here we demonstrate that HMGB1 is not released from bone marrow-derived macrophages (BMDM) after lipopolysaccharide (LPS) treatment. We also explore whether HMGB1 is released via the pore-forming protein gasdermin D after inflammasome activation, as is the case for IL-1β. HMGB1 is only released under conditions that cause cell lysis (pyroptosis). When pyroptosis is prevented, HMGB1 is not released, despite inflammasome activation and IL-1β secretion. During endotoxemia, gasdermin D knockout mice secrete HMGB1 normally, yet secretion of IL-1β is completely blocked. Together, these data demonstrate that in vitro HMGB1 release after inflammasome activation occurs after cellular rupture, which is probably inflammasome-independent in vivo.

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.

HMGB1 in kidney diseases

High mobility group box 1 (HMGB1) is a highly conserved nucleoprotein involving in numerous biological processes, and well known to trigger immune responses as the damage-associated molecular pattern (DAMP) in the extracellular environment. The role of HMGB1 is distinct due to its multiple functions in different subcellular location. In the nucleus, HMGB1 acts as a chaperone to regulate DNA events including DNA replication, repair and nucleosome stability. While in the cytoplasm, it is engaged in regulating autophagy and apoptosis. A great deal of research has explored its function in the pathogenesis of renal diseases. This review mainly focuses on the role of HMGB1 and summarizes the pathway and treatment targeting HMGB1 in the various renal diseases which may open the windows of opportunities for the development of desirable therapeutic ends in these pathological conditions.

Cystitis-Related Bladder Pain Involves ATP-Dependent HMGB1 Release from Macrophages and Its Downstream H2S/Cav3.2 Signaling in Mice

Cystitis-related bladder pain involves RAGE activation by HMGB1, and increased Ca_v3.2 T-type Ca²⁺ channel activity by H₂S, generated by upregulated cystathionine-γ-lyase (CSE) in mice treated with cyclophosphamide (CPA). We, thus, investigated possible crosstalk between the HMGB1/RAGE and CSE/H₂S/Ca_v3.2 pathways in the bladder pain development. Bladder pain (nociceptive behavior/referred hyperalgesia) and immuno-reactive CSE expression in the bladder were determined in CPA-treated female mice. Cell signaling was analyzed in urothelial T24 and macrophage-like RAW264.7 cells. The CPA-induced bladder pain was abolished by pharmacological inhibition of T-type Ca²⁺ channels or CSE, and genetic deletion of Ca_v3.2. The CPA-induced CSE upregulation, as well as bladder pain was prevented by HMGB1 inactivation, inhibition of HMGB1 release from macrophages, antagonists of RAGE or P2X₄/P2X₇ receptors, and N-acetylcysteine, an antioxidant. Acrolein, a metabolite of CPA, triggered ATP release from T24 cells. Adenosine triphosphate (ATP) stimulated cell migration via P2X₇/P2X₄, and caused HMGB1 release via P2X₇ in RAW264.7 cells, which was dependent on p38MAPK/NF-κB signaling and reactive oxygen species (ROS) accumulation. Together, our data suggest that CPA, once metabolized to acrolein, causes urothelial ATP-mediated, redox-dependent HMGB1 release from macrophages, which in turn causes RAGE-mediated CSE upregulation and subsequent H₂S-targeted Ca_v3.2-dependent nociceptor excitation, resulting in bladder pain.

Abnormal Endothelial Gene Expression Associated With Early Coronary Atherosclerosis

Background We examined feasibility of a unique approach towards gaining insight into heritable risk for early atherosclerosis: surveying gene expression by endothelial cells from living subjects. Methods and Results Subjects aged <50 years (mean age, 37; range, 22-49) without obstructive coronary artery disease underwent coronary reactivity testing that identified them as having normal or abnormal coronary endothelial function. Cultures of Blood Outgrowth Endothelial Cells (BOEC) from 6 normal and 13 abnormal subjects passed rigorous quality control and were used for microarray assessment of gene expression. Of 9 genes differentially expressed at false discovery rate <0.1%, we here focus upon abnormal subjects having elevated expression of HMGB1 (high mobility group box 1) which we unexpectedly found to be linked to low LAMC1 (laminin gamma 1) expression. This linkage was corroborated by 3 of our past studies and confirmed bio-functionally. Compared with normal BOEC, abnormal BOEC released 13±3-fold more HMGB1 in response to lipopolysaccharide; and they deposited one tenth as much LAMC1 into collagen subendothelial matrix during culture. Clinical follow-up data are provided for 4 normal subjects (followed 13.4±0.1 year) and for 12 abnormal subjects (followed 9.1±4.5 years). Conclusions The known pathogenic effects of high-HMGB1 and low-LAMC1 predict that the combination would biologically converge upon the focal adhesion complex, to the detriment of endothelial shear responsiveness. This gene expression pattern may comprise a heritable risk state that promotes early coronary atherosclerosis. If so, the testing could be applied even in childhood, enabling early intervention. This approach offers a way to bridge the information gap between genetics and clinical phenotype.

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.

High Mobility Group Box 1 in Human Cancer

High mobility group box 1 (HMGB1) is an extremely versatile protein that is located predominantly in the nucleus of quiescent eukaryotic cells, where it is critically involved in maintaining genomic structure and function. During cellular stress, however, this multifaceted, cytokine-like protein undergoes posttranslational modifications that promote its translocation to the cytosol, from where it is released extracellularly, either actively or passively, according to cell type and stressor. In the extracellular milieu, HMGB1 triggers innate inflammatory responses that may be beneficial or harmful, depending on the magnitude and duration of release of this pro-inflammatory protein at sites of tissue injury. Heightened awareness of the potentially harmful activities of HMGB1, together with a considerable body of innovative, recent research, have revealed that excessive production of HMGB1, resulting from misdirected, chronic inflammatory responses, appears to contribute to all the stages of tumorigenesis. In the setting of established cancers, the production of HMGB1 by tumor cells per se may also exacerbate inflammation-related immunosuppression. These pro-inflammatory mechanisms of HMGB1-orchestrated tumorigenesis, as well as the prognostic potential of detection of elevated expression of this protein in the tumor microenvironment, represent the major thrusts of this review.

Increased level of high mobility group box 1 in the serum and skin in patients with generalized pustular psoriasis

High-mobility group box 1 (HMGB-1) is a highly abundant pro-inflammatory protein associated with the pathogenesis of inflammatory and autoimmune diseases. HMGB-1 expression level increases in patients with psoriasis vulgaris (PV). However, HMGB-1 expression in patients with generalized pustular psoriasis (GPP) is unknown. In this study, we investigated HMGB-1 expression in GPP. HMGB-1 expression levels were examined in the skin and serum of patients with GPP, PV, atopic dermatitis (AD) and healthy controls (HC) using enzyme-linked immunosorbent assay and immunohistochemistry. The elevation in HMGB-1 expression was significantly higher in GPP patients than in PV, AD and HC patients. In addition, patients with GPP had elevated serum HMGB-1 levels compared with those with AD and HC. Furthermore, serum HMGB-1 levels were significantly decreased after systemic treatment. In the correlation analysis, a significant positive correlation was detected between serum HMGB-1 levels and the Japanese severity score for GPP. HMGB-1 may be involved in the pathogenesis of GPP and can be useful to evaluate disease severity and the effectiveness of GPP treatment.

Influence of Herbal Medicines on HMGB1 Release, SARS-CoV-2 Viral Attachment, Acute Respiratory Failure, and Sepsis. A Literature Review

By attaching to the angiotensin converting enzyme 2 (ACE2) protein on lung and intestinal cells, Sudden Acute Respiratory Syndrome (SARS-CoV-2) can cause respiratory and homeostatic difficulties leading to sepsis. The progression from acute respiratory failure to sepsis has been correlated with the release of high-mobility group box 1 protein (HMGB1). Lack of effective conventional treatment of this septic state has spiked an interest in alternative medicine. This review of herbal extracts has identified multiple candidates which can target the release of HMGB1 and potentially reduce mortality by preventing progression from respiratory distress to sepsis. Some of the identified mixtures have also been shown to interfere with viral attachment. Due to the wide variability in chemical superstructure of the components of assorted herbal extracts, common motifs have been identified. Looking at the most active compounds in each extract it becomes evident that as a group, phenolic compounds have a broad enzyme inhibiting function. They have been shown to act against the priming of SARS-CoV-2 attachment proteins by host and viral enzymes, and the release of HMGB1 by host immune cells. An argument for the value in a nonspecific inhibitory action has been drawn. Hopefully these findings can drive future drug development and clinical procedures.

The α7 nicotinic acetylcholine receptor agonist, GTS-21, attenuates hyperoxia-induced acute inflammatory lung injury by alleviating the accumulation of HMGB1 in the airways and the circulation

BACKGROUND

Oxygen therapy, using supraphysiological concentrations of oxygen (hyperoxia), is routinely administered to patients who require respiratory support including mechanical ventilation (MV). However, prolonged exposure to hyperoxia results in acute lung injury (ALI) and accumulation of high mobility group box 1 (HMGB1) in the airways. We previously showed that airway HMGB1 mediates hyperoxia-induced lung injury in a mouse model of ALI. Cholinergic signaling through the α7 nicotinic acetylcholine receptor (α7nAChR) attenuates several inflammatory conditions. The aim of this study was to determine whether 3-(2,4 dimethoxy-benzylidene)-anabaseine dihydrochloride, GTS-21, an α7nAChR partial agonist, inhibits hyperoxia-induced HMGB1 accumulation in the airways and circulation, and consequently attenuates inflammatory lung injury.

METHODS

Mice were exposed to hyperoxia (≥99% O2) for 3 days and treated concurrently with GTS-21 (0.04, 0.4 and 4 mg/kg, i.p.) or the control vehicle, saline.

RESULTS

The systemic administration of GTS-21 (4 mg/kg) significantly decreased levels of HMGB1 in the airways and the serum. Moreover, GTS-21 (4 mg/kg) significantly reduced hyperoxia-induced acute inflammatory lung injury, as indicated by the decreased total protein content in the airways, reduced infiltration of inflammatory monocytes/macrophages and neutrophils into the lung tissue and airways, and improved lung injury histopathology.

CONCLUSIONS

Our results indicate that GTS-21 can attenuate hyperoxia-induced ALI by inhibiting extracellular HMGB1-mediated inflammatory responses. This suggests that the α7nAChR represents a potential pharmacological target for the treatment regimen of oxidative inflammatory lung injury in patients receiving oxygen therapy.

PCV2 Induces Reactive Oxygen Species To Promote Nucleocytoplasmic Translocation of the Viral DNA Binding Protein HMGB1 To Enhance Its Replication

Porcine circovirus type 2 (PCV2) is an important swine pathogen that causes significant economic losses to the pig industry. PCV2 interacts with host cellular factors to regulate its replication. High-mobility-group box 1 (HMGB1) protein, a major nonhistone protein in the nucleus, was recently discovered to participate in viral infections. Here, we demonstrate that nuclear HMGB1 negatively regulated PCV2 replication as shown by overexpression of HMGB1 or blockage of its nucleocytoplasmic translocation with ethyl pyruvate. The B box domain was essential in restricting PCV2 replication. Nuclear HMGB1 restricted PCV2 replication by sequestering the viral genome via binding to the Ori region. However, PCV2 infection induced translocation of HMGB1 from cell nuclei to the cytoplasmic compartment. Elevation of reactive oxygen species (ROS) induced by PCV2 infection was closely associated with cytosolic translocation of nuclear HMGB1. Treatment of PCV2-infected cells with ethyl pyruvate or N-acetylcysteine downregulated PCV2-induced ROS production, suppressed nucleocytoplasmic HMGB1 translocation, and decreased PCV2 replication. Collectively, these findings offer new insight into the mechanism of the PCV2 evasion strategy: PCV2 manages to escape restriction of its replication by nuclear HMGB1 by inducing ROS to trigger the nuclear-to-cytoplasmic translocation of HMGB1.IMPORTANCE Porcine circovirus type 2 (PCV2) is a small DNA virus that depends heavily on host cells for its infection. This study reports the close relationship between subcellular localization of host high-mobility-group box 1 (HMGB1) protein and viral replication during PCV2 infection. Restriction of PCV2 replication by nuclear HMGB1 is the early step of host defense at the host-pathogen interface. PCV2 then upregulates host reactive oxygen species (ROS) to prevent sequestration of its genome by expelling nuclear HMGB1 into the cytosol. It will be interesting to study if a similar evasion strategy is employed by other circoviruses such as beak and feather disease virus, recently discovered PCV3, and geminiviruses in plants. This study also provides insight into the justification and pharmacological basis of antioxidants as an adjunct therapy in PCV2 infection or possibly other diseases caused by the viruses that deploy the ROS-HMGB1 interaction favoring their replication.

Suppression of Cisplatin-Induced Hepatic Injury in Rats Through Alarmin High-Mobility Group Box-1 Pathway by Ganoderma lucidum: Theoretical and Experimental Study

PURPOSE

Drug-induced liver injury (DILI) is the most common cause of acute liver failure. The aim of this study was to investigate the molecular mechanisms by which Ganoderma lucidum mushroom (GLM) may ameliorate cisplatin (CP)-induced hepatotoxicity theoretically and experimentally.

MATERIALS AND METHODS

Thirty-six male Sprague-Dawley (SD) rats were divided into six groups, two of them are normal and Ganoderma lucidum control groups. Liver injury was induced by a single dose of CP (12 mg/kg i.p) in four groups, one of them is CP control group. Besides cisplatin injection in day 1, rats in groups (4-6) were subjected to GLM (500 mg/kg/day) either every other day or daily oral dose or via i.p injection for 10 consecutive days.

RESULTS

In this study, GLM supplementation caused significant reduction of elevated high-mobility group box-1 (HMGB-1) with a concurrent decline in TNF-α and upregulation of IL-10 compared to the CP group (P<0.05). The histopathological and fibrosis evaluation significantly confirmed the improvement upon simultaneous treatment with GLM. Moreover, immunohistochemical examination also confirmed the recovery following GLM treatment indicated by downregulation of NF-κB, p53 and caspase-3 along with upsurge of B-cell lymphoma 2 (Bcl-2) expression (P<0.05). GLM treatment significantly decreased serum levels of hepatic injury markers; ALT, AST, T. bilirubin as well as oxidative stress markers; MDA and H2O2 with a concomitant increase in hepatic GSH and SOD. Also, the performed docking simulation of ganoderic acid exhibited good fitting and binding with HMGB-1 through hydrogen bond formation with conservative amino acids which gives a strong evidence for its hepatoprotective effect and may interpret the effect of Ganoderma lucidum.

CONCLUSION

GLM attenuated hepatic injury through downregulation of HMGB-1/NF-kB and caspase-3 resulted in modulation of the induced oxidative stress and the subsequent cross-talk between the inflammatory and apoptotic cascade indicating its promising role in DILI.

Immunological Significance of HMGB1 Post-Translational Modification and Redox Biology

Most extracellular proteins are secreted via the classical endoplasmic reticulum (ER)/Golgi-dependent secretion pathway; however, some proteins, including a few danger-associated molecular patterns (DAMPs), are secreted via non-classical ER/Golgi-independent secretion pathways. The evolutionarily conserved high mobility group box1 (HMGB1) is a ubiquitous nuclear protein that can be released by almost all cell types. HMGB1 lacks signal peptide and utilizes diverse non-canonical secretion mechanisms for its extracellular export. Although the post-translational modifications of HMGB1 were demonstrated, the oxidation of HMGB1 and secretion mechanisms are not highlighted yet. We currently investigated that peroxiredoxins I and II (PrxI/II) induce the intramolecular disulfide bond formation of HMGB1 in the nucleus. Disulfide HMGB1 is preferentially transported out of the nucleus by binding to the nuclear exportin chromosome-region maintenance 1 (CRM1). We determined the kinetics of HMGB1 oxidation in bone marrow-derived macrophage as early as a few minutes after lipopolysaccharide treatment, peaking at 4 h while disulfide HMGB1 accumulation was observed within the cells, starting to secrete in the late time point. We have shown that HMGB1 oxidation status, which is known to determine the biological activity in extracellular HMGB1, is crucial for the secretion of HMGB1 from the nucleus. This review summarizes selected aspects of HMGB1 redox biology relevant to the induction and propagation of inflammatory diseases. We implicate the immunological significance and the need for novel HMGB1 inhibitors through mechanism-based studies.

Role of high-mobility group box 1 and its modulation by thrombomodulin/thrombin axis in neuropathic and inflammatory pain

High-mobility group box 1 (HMGB1), a nuclear protein, once released to the extracellular space, facilitates pain signals as well as inflammation. Intraplantar or intraspinal application of HMGB1 elicits hyperalgesia/allodynia in rodents by activating the advanced glycosylation end-product specific receptor (receptor for advanced glycation end-products; RAGE) or Toll-like receptor 4 (TLR4). Endogenous HMGB1 derived from neurons, perineuronal cells or immune cells accumulating in the dorsal root ganglion or sensory nerves participates in somatic and visceral pain consisting of neuropathic and/or inflammatory components. Endothelial thrombomodulin (TM) and recombinant human soluble TM, TMα, markedly increase thrombin-dependent degradation of HMGB1, and systemic administration of TMα prevents and reverses various HMGB1-dependent pathological pain. Low MW compounds that directly inactivate HMGB1 or antagonize HMGB1-targeted receptors would be useful to reduce various forms of intractable pain. Thus, HMGB1 and its receptors are considered to serve as promising targets in developing novel agents to prevent or treat pathological pain. LINKED ARTICLES: This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.4/issuetoc.

HMGB1 mediates lipopolysaccharide-induced inflammation via interacting with GPX4 in colon cancer cells

Background

Inflammation is one of a main reason for colon cancer progression and poor prognosis. The high-mobility group box-1 (HMGB1) and glutathione peroxidase 4 (GPX4) are responsible for inflammation, but the relationship between HMGB1 and GPX4 remains unknown about inflammation in colon cancer.

Methods

RT-qPCR was carried out to investigate the expression of IL1β, IL6 and TNFα in colon cancer cells stimulated with LPS or siHMGB1. To observe the relationship between HMGB1, GPX4 and inflammation or ROS, Western blot assays were adopted. Pull-down, CoIP and immunohistochemistry assays were performed to further investigate the molecular mechanisms of HMGB1 and GPX4 in colon cancer.

Results

We report that HMGB1 mediates lipopolysaccharide (LPS)-induced inflammation in colon cancer cells. Mechanistically, acetylated HMGB1 interacts with GPX4, negatively regulating GPX4 activity. Furthermore, by utilizing siHMGB1 and its inhibitor, our discoveries demonstrate that HMGB1 knockdown can inhibit inflammation and reactive oxygen species (ROS) accumulation via NF-kB.

Conclusion

Collectively, our findings first demonstrate that acetylated HMGB1 can interact with GPX4, leading to inflammation, and providing therapeutic strategies targeting HMGB1 and GPX4 for colon cancer.

High-mobility group box 1 promotes epithelial-to-mesenchymal transition in crystalline silica induced pulmonary inflammation and fibrosis

Silicosis is an inflammatory and fibrotic lung disease caused by prolonged inhalation of silica. The potential role of high-mobility group box-1 (HMGB-1) and its underlying mechanisms in silicosis remain unclear. In this study, intratracheal instillation of a silica suspension was used to establish silicosis in male C57BL/6 mice. To elucidate the effects of HMGB-1 on the pathogenesis of silicosis, we used HMGB-1 neutralizing antibody (anti-HMGB-1) and recombinant HMGB-1 (rmHMGB-1) to abrogate or increase the HMGB-1 levels, respectively. At days 7, 28, and 84, the accumulation of macrophages and neutrophils decreased by anti-HMGB-1 treatment. The expression levels of interleukin-6 and tumor necrosis factor-α in lung increased in response to silica exposure across three time points; anti-HMGB-1 could alleviate those expressions at day 28 and 84. In contrast, rmHMGB-1 aggravated this process. At days 28 and 84, the protein expression of fibronectin and col1a1 decreased in the silica + anti-HMGB-1 groups but increased in silica + rmHMGB-1 groups compared to mice with silica alone. Further study suggested that HMGB-1-mediated epithelial-mesenchymal transition participated in the development of silicosis. In conclusion, the findings demonstrate that HMGB-1 participates in the pathogenesis of silicosis and may represent a potential therapeutic target for the treatment of silicosis.

Acetaminophen Oxidation and Inflammatory Markers - A Review of Hepatic Molecular Mechanisms and Preclinical Studies

Acetaminophen is a widely used analgesic for pain management, especially useful in chronic diseases, such as rheumatoid arthritis. However, easy access to this medicine has increased the occurrence of episodes of poisoning. Patients often develop severe liver damage, which may quickly lead to death. Consequently, numerous studies have been conducted to identify new biomarkers that allow the prediction of the degree of acetaminophen intoxication and thus intervene in a timely manner to save patients' lives. This review highlights the main mechanisms of the induction and progression of liver damage arising from acetaminophen poisoning. In addition, we have discussed the possibility of using new clinical biomarkers for detecting acetaminophen poisoning.

Loss of High-Mobility Group Box 1 (HMGB1) Protein in Rods Accelerates Rod Photoreceptor Degeneration After Retinal Detachment

Purpose

Retinal detachment (RD) disrupts the nutritional support and oxygen delivery to photoreceptors (PRs), ultimately causing cell death. High-mobility group box 1 (HMGB1) can serve as an extracellular alarmin when released from stressed cells. PRs release HMGB1 after RD. The purpose of this study was to investigate the relationship between HMGB1 and PR survival after RD.

Methods

Acute RD was created by injection of hyaluronic acid (1%) into the subretinal space in C57BL/6 mice and mice with a rhodopsin-Cre-mediated conditional knockout (cKO) of HMGB1 in rods (HMGB1ΔRod). Immunofluorescence (IF) in retinal sections was used to localize HMGB1, rhodopsin, and Iba-1 proteins. Optical coherence tomography and electroretinography were used to quantify retinal thickness and function, respectively. The morphology of the retina was assessed by hematoxylin and eosin.

Results

HMGB1 protein was localized to the nuclei of all retinal neurons, including PRs, with cones staining more intensely than rods. HMGB1 protein was also found in the inner and outer segments of cones but not rods. Creation of RD caused a dramatic increase of HMGB1 protein IF in rods. cKO of HMGB1 in rods did not affect retinal structure or function. However, after RD, loss of rods and reduction in the thickness of the outer nuclear layer were significantly increased in the HMGB1ΔRod retinas as compared to the control. Interestingly, depletion of HMGB1 in rods did not affect the activation and mobilization of microglia/macrophages normally seen after RD.

Conclusions

Increased HMGB1 expression in stressed rods may represent an intrinsic mechanism regulating their survival after RD.

Extracellular HMGB1: a therapeutic target in severe pulmonary inflammation including COVID-19?

BACKGROUND

The 2019 novel coronavirus disease (COVID-19) causes for unresolved reasons acute respiratory distress syndrome in vulnerable individuals. There is a need to identify key pathogenic molecules in COVID-19-associated inflammation attainable to target with existing therapeutic compounds. The endogenous damage-associated molecular pattern (DAMP) molecule HMGB1 initiates inflammation via two separate pathways. Disulfide-HMGB1 triggers TLR4 receptors generating pro-inflammatory cytokine release. Extracellular HMGB1, released from dying cells or secreted by activated innate immunity cells, forms complexes with extracellular DNA, RNA and other DAMP or pathogen-associated molecular (DAMP) molecules released after lytic cell death. These complexes are endocytosed via RAGE, constitutively expressed at high levels in the lungs only, and transported to the endolysosomal system, which is disrupted by HMGB1 at high concentrations. Danger molecules thus get access to cytosolic proinflammatory receptors instigating inflammasome activation. It is conceivable that extracellular SARS-CoV-2 RNA may reach the cellular cytosol via HMGB1-assisted transfer combined with lysosome leakage. Extracellular HMGB1 generally exists in vivo bound to other molecules, including PAMPs and DAMPs. It is plausible that these complexes are specifically removed in the lungs revealed by a 40% reduction of HMGB1 plasma levels in arterial versus venous blood. Abundant pulmonary RAGE expression enables endocytosis of danger molecules to be destroyed in the lysosomes at physiological HMGB1 levels, but causing detrimental inflammasome activation at high levels. Stress induces apoptosis in pulmonary endothelial cells from females but necrosis in cells from males.

CONCLUSION

Based on these observations we propose extracellular HMGB1 to be considered as a therapeutic target for COVID-19.

Nuclear HMGB1 promotes the phagocytic ability of macrophages

Phagocytosis is a basic immune response to the invasion of pathogens. High mobility group protein B1 (HMGB1) is a DNA chaperone that is associated with phagocytosis. However, its influence on phagocytosis is debated. In the present study, HMGB1-mutant, HMGB1-overexpressing and HMGB1-silenced RAW264.7 cells were constructed. In addition, HMGB1 conditional knockout mice were constructed to determine the influence of HMGB1 on phagocytosis. Lipopolysaccharide (LPS) was used to stimulate the translocation of HMGB1 from the nucleus to the cytoplasm. Zymosan particles were used to test the phagocytic function of the macrophages. Our results showed that the accumulation of HMGB1 in the nucleus enhances the phagocytic function of the macrophages. By interacting with P53, nuclear HMGB1 may remain in the nucleus and decrease the negative influence of P53 on the phosphorylation of focal adhesion kinase (FAK). The increase in phosphorylated FAK promotes the formation of pseudopods and enhances the phagocytic ability of macrophages.

Corticosterone Induces HMGB1 Release in Primary Cultured Rat Cortical Astrocytes: Involvement of Pannexin-1 and P2X7 Receptor-Dependent Mechanisms

A major risk factor for major depressive disorder (MDD) is stress. Stress leads to the release of high-mobility group box-1 (HMGB1), which in turn leads to neuroinflammation, a potential pathophysiological basis of MDD. The mechanism underlying stress-induced HMGB1 release is not known, but stress-associated glucocorticoids could be involved. To test this, rat primary cultured cortical astrocytes, the most abundant cell type in the central nervous system (CNS), were treated with corticosterone and HMGB1 release was assessed by Western blotting and ELISA. Significant HMGB1 was released with treatment with either corticosterone or dexamethasone, a synthetic glucocorticoid. HMGB1 translocated from the nucleus to the cytoplasm following corticosterone treatment. HMGB1 release was significantly attenuated with glucocorticoid receptor blocking. In addition, inhibition of pannexin-1, and P2X7 receptors led to a significant decrease in corticosterone-induced HMGB1 release. Taken together, corticosterone stimulates astrocytic glucocorticoid receptors and triggers cytoplasmic translocation and extracellular release of nuclear HMGB1 through a mechanism involving pannexin-1 and P2X7 receptors. Thus, under conditions of stress, glucocorticoids induce astrocytic HMGB1 release, leading to a neuroinflammatory state that could mediate neurological disorders such as MDD.

The clearance of dead cells by efferocytosis

Multiple modes of cell death have been identified, each with a unique function and each induced in a setting-dependent manner. As billions of cells die during mammalian embryogenesis and daily in adult organisms, clearing dead cells and associated cellular debris is important in physiology. In this Review, we present an overview of the phagocytosis of dead and dying cells, a process known as efferocytosis. Efferocytosis is performed by macrophages and to a lesser extent by other 'professional' phagocytes (such as monocytes and dendritic cells) and 'non-professional' phagocytes, such as epithelial cells. Recent discoveries have shed light on this process and how it functions to maintain tissue homeostasis, tissue repair and organismal health. Here, we outline the mechanisms of efferocytosis, from the recognition of dying cells through to phagocytic engulfment and homeostatic resolution, and highlight the pathophysiological consequences that can arise when this process is abrogated.

Alarmins in Osteoporosis, RAGE, IL-1, and IL-33 Pathways: A Literature Review

Alarmins are endogenous mediators released by cells following insults or cell death to alert the host’s innate immune system of a situation of danger or harm. Many of these, such as high-mobility group box-1 and 2 (HMGB1, HMGB2) and S100 (calgranulin proteins), act through RAGE (receptor for advanced glycation end products), whereas the IL-1 and IL-33 cytokines bind the IL-1 receptors type I and II, and the cellular receptor ST2, respectively. The alarmin family and their signal pathways share many similarities of cellular and tissue localization, functions, and involvement in various physiological processes and inflammatory diseases including osteoporosis. The aim of the review was to evaluate the role of alarmins in osteoporosis. A bibliographic search of the published scientific literature regarding the role of alarmins in osteoporosis was organized independently by two researchers in the following scientific databases: Pubmed, Scopus, and Web of Science. The keywords used were combined as follows: “alarmins and osteoporosis”, “RAGE and osteoporosis”, “HMGB1 and osteoporosis”, “IL-1 and osteoporosis”, “IL 33 and osteopororsis”, “S100s protein and osteoporosis”. The information was summarized and organized in the present review. We highlight the emerging roles of alarmins in various bone remodeling processes involved in the onset and development of osteoporosis, as well as their potential role as biomarkers of osteoporosis severity and progression. Findings of the research suggest a potential use of alarmins as pharmacological targets in future therapeutic strategies aimed at preventing bone loss and fragility fractures induced by aging and inflammatory diseases.

Alarmin HMGB1 Plays a Detrimental Role in Hippocampal Dysfunction Caused by Hypoxia-Ischemia Insult in Neonatal Mice: Evidence from the Application of the HMGB1 Inhibitor Glycyrrhizin

Hippocampal dysfunction related to cognitive impairment and emotional disorders in young children and adolescents caused by neonatal hypoxic-ischemic brain injury (HIBI) has attracted increasing attention in recent years. Crosstalk between the nervous and immune systems organized by hypoxia-ischemia (HI) insult may contribute to hippocampal dysfunction after HIBI. Extracellular HMGB1 functions as a damage-associated molecular pattern to instigate and amplify inflammatory responses, but whether this molecule is correlated with hippocampal dysfunction after HIBI is largely unknown. Therefore, this study examined hippocampal function after HMGB1 inhibition in an experimental HIBI model to verify the hypothesis that HMGB1 is a key mediator of hippocampal neuropathology in neonatal HIBI. By administering different doses of the HMGB1-specific inhibitor glycyrrhizin (GLY), we first found that GLY reversed the HI insult-induced loss of neurons and myelin in the hippocampal region and neurobehavioral impairments, partially in a dose-dependent manner, and based on this, we determined the optimal drug concentration to be 50 mg/kg. Subsequent analysis found that this neuroprotective effect was achieved through the inhibition of HMGB1 expression and nucleocytoplasmic translocation, a reduction in the abnormal expression of proteins associated with the downstream signaling pathway of HMGB1, a decrease in the inflammatory response, the suppression of increases in microglia/astrocytes, and the inhibition of hippocampal cell apoptosis. Collectively, our discoveries contribute to the rising appreciation of the role of HMGB1 in the neuropathology of hippocampal dysfunction and related behavioral outcomes following HIBI.

Targeting Chromosomal Architectural HMGB Proteins Could Be the Next Frontier in Cancer Therapy

Chromatin-associated architectural proteins are part of a fundamental support system for cellular DNA-dependent processes and can maintain/modulate the efficiency of DNA replication, transcription, and DNA repair. Interestingly, prognostic outcomes of many cancer types have been linked with the expression levels of several of these architectural proteins. The high mobility group box (HMGB) architectural protein family has been well studied in this regard. The differential expression levels of HMGB proteins and/or mRNAs and their implications in cancer etiology and prognosis present the potential of novel targets that can be explored to increase the efficacy of existing cancer therapies. HMGB1, the most studied member of the HMGB protein family, has pleiotropic roles in cells including an association with nucleotide excision repair, base excision repair, mismatch repair, and DNA double-strand break repair. Moreover, the HMGB proteins have been identified in regulating DNA damage responses and cell survival following treatment with DNA-damaging agents and, as such, may play roles in modulating the efficacy of chemotherapeutic drugs by modulating DNA repair pathways. Here, we discuss the functions of HMGB proteins in DNA damage processing and their potential roles in cancer etiology, prognosis, and therapeutics.

HMGB1 Translocation in Neurons after Ischemic Insult: Subcellular Localization in Mitochondria and Peroxisomes

High mobility group box-1 (HMGB1), a nonhistone chromatin DNA-binding protein, is released from neurons into the extracellular space under ischemic, hemorrhagic, and traumatic insults. However, the details of the time-dependent translocation of HMGB1 and the subcellular localization of HMGB1 through the release process in neurons remain unclear. In the present study, we examined the subcellular localization of HMGB1 during translocation of HMGB1 in the cytosolic compartment using a middle cerebral artery occlusion and reperfusion model in rats. Double immunofluorescence microscopy revealed that HMGB1 immunoreactivities were colocalized with MTCO1(mitochondrially encoded cytochrome c oxidase I), a marker of mitochondria, and catalase, a marker of peroxisomes, but not with Rab5/Rab7 (RAS-related GTP-binding protein), LC3A/B (microtubule-associated protein 1 light chain 3), KDEL (KDEL amino acid sequence), and LAMP1 (Lysosomal Associated Membrane Protein 1), which are endosome, phagosome, endoplasmic reticulum, and lysosome markers, respectively. Immunoelectron microscopy confirmed that immune-gold particles for HMGB1 were present inside the mitochondria and peroxisomes. Moreover, HMGB1 was found to be colocalized with Drp1 (Dynamin-related protein 1), which is involved in mitochondrial fission. These results revealed the specific subcellular localization of HMGB1 during its release process under ischemic conditions.

Entamoeba histolytica stimulates the alarmin molecule HMGB1 from macrophages to amplify innate host defenses

Even though Entamoeba histolytica (Eh)-induced host pro-inflammatory responses play a critical role in disease, we know very little about the host factors that regulate this response. Direct contact between host cell and Eh signify the highest level of danger, and to eliminate this threat, the host immune system elicits an augmented immune response. To understand the mechanisms of this response, we investigated the induction and release of the endogenous alarmin molecule high-mobility group box 1 (HMGB1) that act as a pro-inflammatory cytokine and chemoattractant during Eh infection. Eh in contact with macrophage induced a dose- and time-dependent secretion of HMGB1 in the absence of cell death. Secretion of HMGB1 was facilitated by Eh surface Gal-lectin-activated phosphoinositide 3-kinase and nuclear factor-κB signaling and up-regulation of histone acetyltransferase activity to trigger acetylated HMGB1 translocation from the nucleus. Unlike lipopolysaccharide, Eh-induced HMGB1 release was independent of caspase-1-mediated inflammasome and gasdermin D pores. In vivo, Eh inoculation in specific pathogen-free but not germ-free mice was associated with high levels of pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, and keratinocyte-derived chemokine, which was suppressed with HMGB1 neutralization. This study reveals that Eh-induced active secretion of the HMGB1 plays a key role in shaping the pro-inflammatory landscape critical in innate host defense against amebiasis.

The proteome and its dynamics: A missing piece for integrative multi-omics in schizophrenia

The complex and heterogeneous pathophysiology of schizophrenia can be deconstructed by integration of large-scale datasets encompassing genes through behavioral phenotypes. Genome-wide datasets are now available for genetic, epigenetic and transcriptomic variations in schizophrenia, which are then analyzed by newly devised systems biology algorithms. A missing piece, however, is the inclusion of information on the proteome and its dynamics in schizophrenia. Proteomics has lagged behind omics of the genome, transcriptome and epigenome since analytic platforms were relatively less robust for proteins. There has been remarkable progress, however, in the instrumentation of liquid chromatography (LC) and mass spectrometry (MS) (LCMS), experimental paradigms and bioinformatics of the proteome. Here, we present a summary of methodological innovations of recent years in MS based proteomics and the power of new generation proteomics, review proteomics studies that have been conducted in schizophrenia to date, and propose how such data can be analyzed and integrated with other omics results. The function of a protein is determined by multiple molecular properties, i.e., subcellular localization, posttranslational modification (PTMs) and protein-protein interactions (PPIs). Incorporation of these properties poses additional challenges in proteomics and their integration with other omics; yet is a critical next step to close the loop of multi-omics integration. In sum, the recent advent of high-throughput proteome characterization technologies and novel mathematical approaches enable us to incorporate functional properties of the proteome to offer a comprehensive multi-omics based understanding of schizophrenia pathophysiology.

Toddalolactone Protects Lipopolysaccharide-Induced Sepsis and Attenuates Lipopolysaccharide-Induced Inflammatory Response by Modulating HMGB1-NF-κB Translocation

Toddalolactone (TA-8) is a main compound isolated from Toddalia asiatica (L.) Lam., and its anti-inflammatory activity and anti-inflammatory mechanism are less studied. In the present study, we investigated the anti-inflammatory effects of TA-8. Our experimental results showed that TA-8 inhibited the production of pro-inflammatory cytokines by both lipopolysaccharide (LPS)-activated RAW 264.7 cells and septic mice. Moreover, TA-8 suppressed the NF-κB transcriptional activity, reduced the nuclear translocation and phosphorylation of NF-κB, blocked the translocation of HMGB1 from the nucleus to cytosol, and decreased LPS-induced up-regulation of TLR4 and IKBKB expression, and decreased IκBα phosphorylation. In addition, the administration of TA-8 decreased LPS-induced liver damage markers (AST and ALT), attenuated infiltration of inflammatory cells and tissue damage of lung, liver, and kidney, and improved survival in septic mice. Taken together, these results suggested that toddalolactone protects LPS-induced sepsis and attenuates LPS-induced inflammatory response by modulating HMGB1-NF-κB translocation. TA-8 could potentially be a novel anti-inflammatory and immunosuppressive drug candidate in the treatment of sepsis and septic shock.

High-mobility group box 1 protein (HMGB1) from Cherry Valley duck mediates signaling pathways and antiviral activity

High-mobility group box 1 protein (HMGB1) shows endogenous damage-associated molecular patterns (DAMPs) and is also an early warning protein that activates the body's innate immune system. Here, the full-length coding sequence of HMGB1 was cloned from the spleen of Cherry Valley duck and analyzed. We find that duck HMGB1(duHMGB1) is mostly located in the nucleus of duck embryo fibroblast (DEF) cells under normal conditions but released into the cytoplasm after lipopolysaccharide (LPS) stimulation. Knocking-down or overexpressing duHMGB1 had no effect on the baseline apoptosis rate of DEF cells. However, overexpression increased weakly apoptosis after LPS activation. In addition, overexpression strongly activated the IFN-I/IRF7 signaling pathway in DEF cells and significantly increased the transcriptional level of numerous pattern recognition receptors (PRRs), pro-inflammatory cytokines (IL-6, TNF-α), IFNs and antiviral molecules (OAS, PKR, Mx) starting from 48 h post-transfection. Overexpression of duHMGB1 strongly impacted duck virus replication, either by inhibiting it from the first stage of infection for novel duck reovirus (NDRV) and at late stage for duck Tembusu virus (DTMUV) or duck plague virus (DPV), or promoting replication at early stage for DTMUV and DPV infection. Importantly, data from duHMGB1 overexpression and knockdown experiments, time-dependent DEF cells transcriptional immune responses suggest that duHMGB1 and RIG-I receptor might cooperate to promote the expression of antiviral proteins after NDRV infection, as a potential mechanism of duHMGB1-mediated antiviral activity.

Autophagy-based unconventional secretion of HMGB1 by keratinocytes plays a pivotal role in psoriatic skin inflammation

The precise mechanism through which macroautophagy/autophagy affects psoriasis is poorly understood. Here, we found that keratinocyte (KC) autophagy, which was positively correlated with psoriatic severity in patients and mouse models and could be inhibited by mitogen-activated protein kinase (MAPK) family inactivation. The impairment of autophagic flux alleviated psoriasisform inflammation. We also found that an autophagy-based unconventional secretory pathway (autosecretion) dependent on ATG5 (autophagy related 5) and GORASP2 (golgi reassembly stacking protein 2) promoted psoriasiform KC inflammation. Moreover, the alarmin HMGB1 (high mobility group box 1) was more effective than other autosecretory proteins in regulating psoriasiform cutaneous inflammation. HMGB1 neutralization in autophagy-efficient KCs eliminated the differences in psoriasiform inflammation between Krt14^+/+-Atg5^f/f KCs and Krt14^Cre/+-atg5^f/f KCs, and conversely, recombinant HMGB1 almost completely restored psoriasiform inflammation in Krt14^Cre/+-atg5^f/f KCs in vivo. These results suggest that HMGB1-associated autosecretion plays a pivotal role in cutaneous inflammation. Finally, we demonstrated that Krt14^Cre/+-hmgb1^f/f mice displayed attenuated psoriatic inflammation due to the essential crosstalk between KC-specific HMGB1-associated autosecretion and γδT cells. Thus, this study uncovered a novel autophagy mechanism in psoriasis pathogenesis, and the findings imply the clinical significance of investigating and treating psoriasis.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AGER: advanced glycosylation end-product specific receptor; Anti-HMGB1: anti-HMGB1 neutralizing antibody; Anti-IL18: anti-IL18 neutralizing antibody; Anti-IL1B: anti-IL1B neutralizing antibody; ATG5: autophagy related 5; BAF: bafilomycin A₁; BECN1: beclin 1; CASP1: caspase 1; CCL: C-C motif chemokine ligand; CsA: cyclosporine A; ctrl shRNA: lentivirus harboring shRNA against control; CXCL: C-X-C motif chemokine ligand; DCs: dendritic cells; DMEM: dulbecco's modified Eagle's medium; ELISA: enzyme-linked immunosorbent assay; EM: electron microscopy; FBS: fetal bovine serum; GORASP2 shRNA: lentivirus harboring shRNA against GORASP2; GORASP2/GRASP55: golgi reassembly stacking protein 2; GR1: a composite epitope between LY6 (lymphocyte antigen 6 complex) locus C1 and LY6 locus G6D antigens; H&E: hematoxylin and eosin; HMGB1: high mobility group box 1; HMGB1 shRNA: lentivirus harboring shRNA against HMGB1; IFNG/IFN-γ: interferon gamma; IL17A: interleukin 17A; IL18: interleukin 18; IL1A/IL-1α: interleukin 1 alpha; IL1B/IL-1β: interleukin 1 beta; IL22/IL-22: interleukin 22; IL23A: interleukin 23 subunit alpha; IL23R: interleukin 23 receptor; IMQ: imiquimod; ITGAM/CD11B: integrin subunit alpha M; ITGAX/CD11C: integrin subunit alpha X; IVL: involucrin; KC: keratinocyte; KD: knockdown; KO: knockout; Krt14^+/+-Atg5^f/f mice: mice bearing an Atg5 flox allele, in which exon 3 of the Atg5 gene is flanked by two loxP sites; Krt14^+/+-Hmgb1^f/f: mice bearing an Hmgb1 flox allele, in which exon 2 to 4 of the Hmgb1 gene is flanked by two loxP sites; Krt14^Cre/+-atg5^f/f mice: keratinocyte-specific atg5 knockout mice generated by mating Atg5-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt4; Krt14^Cre/+-hmgb1^f/f mice: keratinocyte-specific hmgb1 knockout mice generated by mating Hmgb1-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt14; Krt14-Vegfa mice: mice expressing 164-amino acid Vegfa splice variant recombinase under the control of promoter of Krt14; LAMP1: lysosomal associated membrane protein 1; LDH: lactate dehydrogenase; LORICRIN: loricrin cornified envelope precursor protein; M5: TNF, IL1A, IL17A, IL22 and OSM in combination; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MKI67: marker of proliferation Ki-67; MTT: thiazolyl blue tetrazolium bromide; NFKB/NF-κB: nuclear factor kappa B; NHEKs: primary normal human epidermal keratinocytes; NS: not significant; OSM: oncostatin M; PASI: psoriasis area and severity index; PtdIns3K: class III phosphatidylinositol 3-kinase; qRT-PCR: quantitative RT-PCR; RELA/p65: RELA proto-oncogene, NF-kB subunit; rHMGB1: recombinant HMGB1; rIL18: recombinant interleukin 18; rIL1B: recombinant interleukin 1 beta; S100A: S100 calcium binding protein A; SQSTM1/p62: sequestosome 1; T17: IL17A-producing T; TCR: T-cell receptor; tcrd KO mice: tcrd (T cell receptor delta chain) knockout mice, which show deficient receptor expression in all adult lymphoid and epithelial organs; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor; WOR: wortmannin; WT: wild-type; γδT17 cells: IL17A-producing γδ T cells.

How asbestos and other fibers cause mesothelioma

Mesothelioma has long been associated with the exposure to asbestos, which was largely used in manufacturing activities. Toxicology studies in vitro and in vivo demonstrated that asbestos fibers were carcinogenic, and epidemiology studies revealed that asbestos exposure was paralleled by the increase in the incidence of mesothelioma and related mortality rates. More recently, the role of chronic inflammation and the molecular mechanisms involved in carcinogenesis by mineral fibers were elucidated following the discovery of the roles of HMGB1 and inflammasome. A change of paradigm was the discovery of a prevalence of mesotheliomas attributable to inherited mutations of cancer susceptibility genes. The discovery of BAP1 as a predisposition gene for the development of familial mesothelioma and other cancers implemented genome studies in patients with mesothelioma and routine clinical surveys in individuals at risk to identify germline mutations associated with cancers included in the BAP1 syndrome. A further progress in the approach to asbestos-related malignancy was the adoption of combined genetics and environmental analyses according to the model of gene-environment (GxE) interactions. This review aims at updating on the most recently discovered mechanisms of tumorigenesis and the pivotal role of GxE interactions.

High-Mobility Group Box 1 Protein Signaling in Painful Diabetic Neuropathy

Diabetes is a global epidemic and more than 50% diabetic patients are also diagnosed with neuropathy, which greatly affects the quality of life of the patients. Available treatments are not always successful due to the limited efficacy and complications, such as addiction and dependency. Studies have implicated that high mobility group box1 (HMGB1) protein plays a crucial role in neuroinflammation and the development of neuropathic conditions. HMGB1 is a proinflammatory cytokine that can be released from necrotic cells in passive form or in response to inflammatory signals as an active form. HMGB1 is the ligand for the receptor for advanced glycation end products (RAGE), and toll-like receptors, (TLR)-2 and TLR4, which also indirectly activates C-X-C chemokine receptor type 4 (CXCR4). We investigated whether blocking of HMGB1 can reduce pain and inflammation in diabetic neuropathic animals to further understand the role of HMGB1 in diabetic neuropathy. Type 2 diabetic rats and mice were treated with natural inhibitor of HMGB1, glycyrrhizin (GLC) for five days/week for four weeks at a dose of 50 mg/kg per day by intraperitoneal injection. The animals were divided into three categories: naïve control, diabetic alone, diabetic with GLC treatment. All of the behavioral analyses were conducted before and after the treatment. The expression of inflammatory markers and changes in histone acetylation in the peripheral nervous system were measured by immunohistochemistry and Western blot analysis after the completion of the treatment. Our study revealed that TLR4, HMGB1, CXCR4, and Nod-like receptor protein 3 (NLRP3) levels were increased in the spinal and dorsal root ganglia (DRG) neurons of Type 2 diabetic mice and rats with painful neuropathy. GLC treatment inhibited the increases in TLR4, NLRP3, and CXCR4 expressions and improved the mechanical and thermal pain threshold in these animals. Immunohistochemical studies revealed that hyperglycemia mediated inflammation influenced HMGB1 acetylation and its release from the neurons. It also altered histone 3 acetylation in the microglial cells. The inhibition of HMGB1 by GLC prevented the release of HMGB1 as well as H3K9 acetylation. These findings indicate that the interruption of HMGB1 mediated inflammation could ameliorate diabetic neuropathy and might exhibit a unique target for the treatment.

Fibroblast growth factor 10 alleviates particulate matter-induced lung injury by inhibiting the HMGB1-TLR4 pathway

Exposure to particulate matter (PM) is associated with increased incidence of respiratory diseases. The present study aimed to investigate the roles of fibroblast growth factor 10 (FGF10) in PM-induced lung injury. Mice were intratracheally instilled with FGF10 or phosphate-buffered saline at one hour before instillation of PM for two consecutive days. In addition, the anti-inflammatory impact of FGF10 in vitro and its effect on the high-mobility group box 1 (HMGB1)-toll-like receptor 4 (TLR4) pathway was investigated. It was found that PM exposure is associated with increased inflammatory cell infiltration into the lung and increased vascular protein leakage, while FGF10 pretreatment attenuated both of these effects. FGF10 also decreased the PM-induced expression of interleukin (IL)-6, IL-8, tumor necrosis factor-α and HMGB1 in murine bronchoalveolar lavage fluid and in the supernatants of human bronchial epithelial cells exposed to PM. FGF10 exerted anti-inflammatory and cytoprotective effects by inhibiting the HMGB1-TLR4 pathway. These results indicate that FGF10 may have therapeutic values for PM-induced lung injury.

SIRT6-PARP1 is involved in HMGB1 polyADP-ribosylation and acetylation and promotes chemotherapy-induced autophagy in leukemia

High mobility group box protein 1 (HMGB1) is an evolutionarily conserved non-histone chromatin-binding protein. In a previous study, we showed that treating leukemic cells with chemotherapeutic drugs leads to the translocation of HMGB1, which is involved in autophagy and ultimately promotes chemoresistance in leukemia. However, the underlying translocation mechanism of HMGB1 in chemotherapy-induced autophagy remains unclear. In this study, we showed that knockdown of SIRT6 or PARP1 gene expression significantly inhibited HMGB1 cytoplasmic translocation and autophagy. Meanwhile, we found that SIRT6, an important upstream protein of PARP1, associated with PARP1, leading to the stimulation of polyADP-ribose polymerase activity. We further demonstrated that SIRT6 and PARP1 activation were required for chemotherapy-induced ADP-ribosylation of HMGB1 in leukemic cells and then influenced the acetylation of HMGB1, finally promoting the autophagy of leukemic cells mediated by HMGB1 translocation. These findings provide new insights into the mechanism of chemotherapeutic drug resistance. Targeting the HMGB1 translocation may overcome autophagy-related chemoresistance in leukemia.

Functions and mechanisms of non-histone protein acetylation

Nε-lysine acetylation was discovered more than half a century ago as a post-translational modification of histones and has been extensively studied in the context of transcription regulation. In the past decade, proteomic analyses have revealed that non-histone proteins are frequently acetylated and constitute a major portion of the acetylome in mammalian cells. Indeed, non-histone protein acetylation is involved in key cellular processes relevant to physiology and disease, such as gene transcription, DNA damage repair, cell division, signal transduction, protein folding, autophagy and metabolism. Acetylation affects protein functions through diverse mechanisms, including by regulating protein stability, enzymatic activity, subcellular localization and crosstalk with other post-translational modifications and by controlling protein-protein and protein-DNA interactions. In this Review, we discuss recent progress in our understanding of the scope, functional diversity and mechanisms of non-histone protein acetylation.

Analysis of Circulating HMGB1 in Human Serum

As a ubiquitous nuclear protein, high-mobility group box 1 (HMGB1) is constitutively expressed and can be actively secreted by macrophages/monocytes, as well as passively released from damaged cells following pathological injuries. Studies indicate that HMGB1 functions as a mediator of infection- and injury-elicited inflammatory diseases. Although intracellular HMGB1 functions as a regulator of tumorigenesis, epigenetic anticancer agents or therapeutic γ-ray irradiation could also cause active secretion or passive release of HMGB1, enabling serum HMGB1 to serve as a biomarker for the diagnosis and therapy of various cancers. Here we describe a semiquantitative immune blotting method to measure HMGB1 in human serum, in comparison with a commercially available HMGB1 enzyme-linked immunosorbent assay (ELISA) technique.

Downregulation of HMGB1 by miR-103a-3p Promotes Cell Proliferation, Alleviates Apoptosis and in Flammation in a Cell Model of Osteoarthritis

Background

MiR-103a-3p is a small non-coding RNA and has been reported to be involved in osteogenic proliferation and differentiation, but the role of miR-103a-3p in human osteoarthritis (OA) remains unclear.

Objectives

In this study, we aimed to explore its function and molecular target in chondrocytes during OA pathogenesis.

Materials and Methods

Total 12 experimental OA rat models, together with 12 rats without knee OA lesions were established and cartilage samples were collected. Chondrocytes were treated with LPS in vitro. MiR-103a-3p expression was detected in articular cartilage tissues and chondrocytes using quantitative real-time PCR. Knee OA chondrocytes were transfected with miR-103a-3p mimics, and siHMGB1, respectively. Then cellular proliferation, apoptosis, apoptosis related factors and inflammatory cytokines were analyzed by MTT, flow cytometry, western blot, caspase-3 activity and ELISA, respectively. Potential targets of miR-103a-3p were predicted using series of bioinformatics analysis, then confirmed by luciferase reporter assay.

Results

We first found miR-103a-3p was significantly down-regulated in the articular cartilage tissues from experimental OA rats, as well as in chondrocytes treated with LPS in vitro. The gain-of-function assay further demonstrated that up-regulation of miR-103a-3p significantly promoted cell proliferation, inhibited apoptosis and inflammation, which was accompanied with elevated expression of PCNA, and reduced expression of caspase-3, PARP, IL-1β, IL-6, IL-10 and TNF-α. Furthermore, high mobility group box 1 (HMGB1), an important inflammatory mediator of OA, was a target of miR-103a-3p. Moreover, knockdown of HMGB1 mimicked the effects of miR-103a-3p on chondrocytes treated with LPS.

Conclusions

Taken together, our study suggests that miR-103a-3p inhibits chondrocyte apoptosis and inflammation in OA, which appears to be an attractive approach to OA treatment.

Platinum Derivatives Effects on Anticancer Immune Response

Along with surgery and radiotherapy, chemotherapeutic agents belong to the therapeutic arsenal in cancer treatment. In addition to their direct cytotoxic effects, these agents also impact the host immune system, which might enhance or counteract their antitumor activity. The platinum derivative compounds family, mainly composed of carboplatin, cisplatin and oxaliplatin, belongs to the chemotherapeutical arsenal used in numerous cancer types. Here, we will focus on the effects of these molecules on antitumor immune response. These compounds can induce or not immunogenic cell death (ICD), and some strategies have been found to induce or further enhance it. They also regulate immune cells' fate. Platinum derivatives can lead to their activation. Additionally, they can also dampen immune cells by selective killing or inhibiting their activity, particularly by modulating immune checkpoints' expression.

High Mobility Group Box 1 and TLR4 Signaling Pathway in Gnotobiotic Piglets Colonized/Infected with L. amylovorus, L. mucosae, E. coli Nissle 1917 and S. Typhimurium

High mobility group box 1 (HMGB1) is a DNA-binding nuclear protein that can be actively secreted by immune cells after different immune stimuli or passively released from cells undergoing necrosis. HMGB1 amplifies inflammation, and its hypersecretion contributes to multiple organ dysfunction syndrome and death. We tested possible immunomodulatory effect of commensal Lactobacillus amylovorus (LA), Lactobacillus mucosae (LM) or probiotic Escherichia coli Nissle 1917 (EcN) in infection of gnotobiotic piglets with Salmonella Typhimurium (ST). Transcription of HMGB1 and Toll-like receptors (TLR) 2, 4, and 9 and receptor for advanced glycation end products (RAGE), TLR4-related molecules (MD-2, CD14, and LBP), and adaptor proteins (MyD88 and TRIF) in the ileum and colon were measured by RT-qPCR. Expression of TLR4 and its related molecules were highly upregulated in the ST-infected intestine, which was suppressed by EcN, but not LA nor LM. In contrast, HMGB1 expression was unaffected by ST infection or commensal/probiotic administration. HMGB1 protein levels in the intestine measured by ELISA were increased in ST-infected piglets, but they were decreased by previous colonization with E. coli Nissle 1917 only. We conclude that the stability of HMGB1 mRNA expression in all piglet groups could show its importance for DNA transcription and physiological cell functions. The presence of HMGB1 protein in the intestinal lumen probably indicates cellular damage.

Clinical Implications of Extracellular HMGA1 in Breast Cancer

The unconventional secretion of proteins is generally caused by cellular stress. During the tumorigenesis, tumor cells experience high levels of stress, and the secretion of some theoretically intracellular proteins is activated. Once in the extracellular space, these proteins play different paracrine and autocrine roles and could represent a vulnerability of cancer. One of these proteins is the high mobility group A1 (HMGA1), which is frequently overexpressed in tumors and presents a low expression in normal adult tissues. We have recently described that HMGA1 establishes an autocrine loop in invasive triple-negative breast cancer (TNBC) cells. The secretion of HMGA1 and its binding to the receptor for advanced glycation end products (RAGE) mediates the migration, invasion, and metastasis of TNBC cells and predicts the onset of metastasis in these patients. In this review, we summarized different strategies to exploit the novel tumorigenic phenotype mediated by extracellular HMGA1. We envisioned future clinical applications where the association between its change in subcellular localization and breast cancer progression could be used to predict tumor aggressiveness and guide treatment decisions. Furthermore, we proposed that targeting extracellular HMGA1 as monotherapy using monoclonal antibodies, or in combination with chemotherapy and other targeted therapies, could bring new therapeutic options for TNBC patients.

Methods for the Measurement of Early Events in Toxoplasma gondii Immunity in Mouse Cells

Critical steps in resistance of mice against Toxoplasma gondii occur in the first 2 or 3 h after the pathogen has entered a cell that has been exposed to interferon γ (IFNγ). The newly formed parasitophorous vacuole is attacked by the IFNγ-inducible IRG proteins and disrupted, resulting in death of the parasite and necrotic death of the cell. Here we describe some techniques that we have used to describe and quantify these events in different combinations of the host and the parasite.

Poly (ADP-ribosylation) of HMGB1 facilitates its acetylation and promotes HMGB1 translocation-associated chemotherapy-induced autophagy in leukaemia cells

Acute lymphoblastic leukaemia (ALL) is one of the most common and curable types of cancer in paediatric patients. However, chemotherapeutic resistance is a difficult but common obstacle when treating leukaemia in the clinical setting. Studies have demonstrated that drug resistance is partly attributable to autophagy induced by multiple chemotherapeutic agents. As an evolutionarily conserved non-histone chromatin-binding protein, high mobility group box protein 1 (HMGB1) is considered to be an important factor in autophagy, and regulates autophagy at multiple levels via different subcellular localisations. In the present study, it was revealed that chemotherapeutic drugs induced autophagy in leukaemia cells and that translocation of HMGB1 from the nucleus to the cytoplasm is an important molecular event in this process. It was further demonstrated that poly (ADP-ribosylation) of HMGB1 facilitates its acetylation, thereby inducing HMGB1 translocation and ultimately promoting chemotherapy-induced autophagy in leukaemic cells. Targeted HMGB1 translocation may overcome chemotherapy-induced autophagy in leukaemia.

Anti-Inflammatory Effects of Shenfu Injection against Acute Lung Injury through Inhibiting HMGB1-NF-κB Pathway in a Rat Model of Endotoxin Shock

Shenfu injection (SFI), a Chinese herbal medicine with substances extracted from Ginseng Radix et Rhizoma Rubra and Aconiti Lateralis Radix Praeparata, is widely used as an anti-inflammatory reagent to treat endotoxin shock in China. However, the mechanism of SFI in endotoxin shock remains to be illuminated. High mobility group box 1 (HMGB1), a vital inflammatory factor in the late stage of endotoxin shock, may stimulate multiple signalling cascades, including κB (NF-κB), a nuclear transcription factor, as well as tumour necrosis factor (TNF)-α and interleukin (IL)-1β, among others in the overexpression of downstream proinflammatory cytokines. An investigation into the effects of SFI on the inhibition of the HMGB1-NF-κB pathway revealed the contribution of SFI to acute lung injury (ALI) in a rat model of endotoxin shock. To assess the anti-inflammatory activity of SFI, 5 ml/kg, 10 ml/kg, or 15 ml/kg of SFI was administered to different groups of rats following an injection of LPS, and the mean arterial pressure (MAP) at 5 h and the survival rate at 72 h were measured. 24 h after LPS injection, we observed pathological changes in the lung tissue and measured the mRNA expression, production, translocation, and secretion of HMGB1, as well as the expression of the NF-κB signal pathway-related proteins inhibitor of NF-κB (IκB)-α, P50, and P65. We also evaluated the regulation of SFI on the secretion of inflammatory factors including interleukin-1 beta (IL-1β) and TNF-α. SFI effectively prevented the drop in MAP, relieved lung tissue damage, and increased the survival rate in the endotoxin shock model in dose-dependent manner. SFI inhibited the transcription, expression, translocation, and secretion of HMGB1, increased the expression of toll-like receptor (TLR4), increased the production of IκB-α, and decreased the levels of P65, P50, and TNF-α in the lung tissue of endotoxin shock rats in a dose-dependent manner. Furthermore, SFI decreased the secretion of proinflammatory cytokines TNF-α and IL-1β. In summary, SFI improves the survival rate of endotoxin shock, perhaps through inhibiting the HMGB1-NF-κB pathway and thus preventing cytokine storm.