HMGB1 in health and disease

Molecules of Damage-Associated Patterns in Bronchoalveolar Lavage Fluid and Serum in Chronic Obstructive Pulmonary Disease

Chronic exposure to detrimental environmental factors may induce immunogenic cell death of structural airway cells in chronic obstructive pulmonary disease (COPD). Damage-associated molecular patterns (DAMPs) is a family of heterogeneous molecules released from injured or dead cells, which activate innate and adaptive immune responses on binding to the pattern recognition receptors on cells. This study seeks to define the content of DAMPs in the bronchoalveolar lavage fluid (BALF) and serum of COPD patients, and the possible association of these molecules with clinical disease features. Thirty COPD in advanced disease stages were enrolled into the study. Pulmonary function tests, arterial blood gas content, 6-minute walk test, and BODE index were assessed. The content of DAMPs was estimated using the commercial sandwich-ELISA kits. We found differential alterations in the content of various DAMP molecules. In the main, BALF DAMPs positively associated with age, forced expiratory volume in one second (FEV1), and residual volume (RV); and inversely with PaO₂, residual volume/total lung capacity (RV/TLC) ratio, and the disease severity staging. In serum, DAMPS positively associated with the intensity of smoking and inversely with age, PaO₂, and TLC. In conclusion, DAMPs are present in both BALF and serum of COPD patients, which points to enhanced both local in the lung environment as well as systemic pro-inflammatory vein in this disease. These molecules appear involved with the lung damage and clinical variables featuring COPD. However, since the involvement of various DAMPs in COPD is variable, the exact role they play is by far unsettled and is open to further exploration.

Persistent Increase in Microglial RAGE Contributes to Chronic Stress-Induced Priming of Depressive-like Behavior

BACKGROUND

Chronic stress-induced inflammatory responses occur in part via danger-associated molecular pattern (DAMP) molecules, such as high mobility group box 1 protein (HMGB1), but the receptor(s) underlying DAMP signaling have not been identified.

METHODS

Microglia morphology and DAMP signaling in enriched rat hippocampal microglia were examined during the development and expression of chronic unpredictable stress (CUS)-induced behavioral deficits, including long-term, persistent changes after CUS.

RESULTS

The results show that CUS promotes significant morphological changes and causes robust upregulation of HMGB1 messenger RNA in enriched hippocampal microglia, an effect that persists for up to 6 weeks after CUS exposure. This coincides with robust and persistent upregulation of receptor for advanced glycation end products (RAGE) messenger RNA, but not toll-like receptor 4 in hippocampal microglia. CUS also increased surface expression of RAGE protein on hippocampal microglia as determined by flow cytometry and returned to basal levels 5 weeks after CUS. Importantly, exposure to short-term stress was sufficient to increase RAGE surface expression as well as anhedonic behavior, reflecting a primed state that results from a persistent increase in RAGE messenger RNA expression. Further evidence for DAMP signaling in behavioral responses is provided by evidence that HMGB1 infusion into the hippocampus was sufficient to cause anhedonic behavior and by evidence that RAGE knockout mice were resilient to stress-induced anhedonia.

CONCLUSIONS

Together, the results provide evidence of persistent microglial HMGB1-RAGE expression that increases vulnerability to depressive-like behaviors long after chronic stress exposure.

Endogenous DAMPs, Category I: Constitutively Expressed, Native Molecules (Cat. I DAMPs)

This chapter provides the reader with a collection of endogenous DAMPs in terms of constitutively expressed native molecules. The first class of this category refers to DAMPs, which are passively released from necrotic cells, and includes the most prominent subclasses of high mobility group box I and heat shock proteins. Further subclasses of DAMPs that are passively released from necrotic cells include S100 proteins, nucleic acids, histones, pro-forms of interleukin-1-family members, mitochondria-derived N-formylated peptides, F-actin, and heme. A particular subclass of these passively released DAMPs are molecules, which indirectly activate the inflammasome, including adenosine-5′-triphosphate, monosodium urate crystals, cholesterol crystals, some lipolytic species, and beta-amyloid. All these passively released DAMPs are characterized by their capability to promote necroinflammatory responses. The second class of this Category I refers to molecules, which are exposed on the surface of stressed cells. They include the subclass of phagocytosis-facilitating molecules such as calreticulin, as well as the subclass of MHC-I-related molecules such as MHC-I-related molecule A and B. These DAMPs are capable of inducing the activation of innate lymphoid cells and unconventional T cells. One of these DAMPs, the major histocompatibility complex I-related molecule A, is shown to act as a bona fide transplantation antigen. In sum, the endogenous constitutively expressed native molecules represent an impressive category of DAMPs with extraordinary properties, which play a critical role in the pathogenesis of many human diseases.

Post-translational modifications of high mobility group box 1 and cancer

Post-translational modifications (PTMs) of High mobility group box 1 (HMGB1) have not been investigated as extensively as those of other HMG proteins but accumulating evidence has shown the remarkable biological significances induced by the post-translational: acetylation, methylation and phosphorylation, oxidation, glycosylation and ADP-ribosylation of the HMGB1 to modulate its interactions with DNA and other proteins. Although HMGB1 is localized in the nucleus in almost all cells at baseline, it can be rapidly mobilized to other sites within the cell, including the cytoplasm and mitochondria, as well as into the extracellular; hence there is an increasing interest by researches into the complex relationship between the PTMs of HMGB1 protein and its diverse biological activities. The PTMs of HMGB1 could also have effects on gene expression following changes in its DNA-binding properties and in extracellular environment displays immunological activity and could serve as a potential target for new therapy. Our reviewed identifies covalent modifications of HMGB1, and highlighted how these PTMs affect the functions of HMGB1 protein in a variety of cellular and extra cellular processes as well as diseases and therapy.

High mobility group box 1 promotes sorafenib resistance in HepG2 cells and in vivo

BACKGROUND

Primary liver cancer is a lethal malignancy with a high mortality worldwide. Currently, sorafenib is the most effective molecular-targeted drug against hepatocellular carcinoma (HCC). However, the sorafenib resistance rate is high. The molecular mechanism of this resistance has not been fully elucidated. High mobility group box 1 (HMGB1) is a multifaceted protein that plays a key role in the proliferation, apoptosis, metastasis and angiogenesis of HCC cells. In addition, HMGB1 has been suggested to contribute to chemotherapy resistance in tumours, including lung cancer, osteosarcoma, neuroblastoma, leukaemia, and colorectal cancer. This study investigated the association between HMGB1 and sorafenib resistance in HCC.

METHODS

HepG2 cells with HMGB1 knockdown or overexpression were generated. The efficacy of sorafenib in these cells was tested using flow cytometry and a cell counting assay. The subcellular localization of HMGB1 in HepG2 cells following sorafenib treatment was measured by western blotting and confocal microscopy. A murine subcutaneous HCC model was generated to examine the association between HMGB1 and the sensitivity of sorafenib treatment.

RESULTS

The HMGB1 knockdown cells exhibited a significantly higher apoptotic level and lower cell viability than the normal HMGB1 expressing cells following the sorafenib treatment. In addition, the cell viability observed in the HMGB1 overexpressing cells was higher than that observed in the control cells following the sorafenib intervention. Sorafenib had a better tumour inhibition effect in the HMGB1 knockdown group in vivo. The amount of mitochondrial HMGB1 decreased, while the amount of cytosolic HMGB1 increased following the exposure to sorafenib. Altogether, HMGB1 translocated from the mitochondria to the cytoplasm outside the mitochondria following the exposure of HepG2 cells to sorafenib.

CONCLUSIONS

A novel potential role of HMGB1 in the regulation of sorafenib therapy resistance in HCC was observed. The knockdown of HMGB1 restores sensitivity to sorafenib and enhances HepG2 cell death, while HMGB1 overexpression blunts these effects. The translocation of HMGB1 from the mitochondria to the cytosol following sorafenib treatment provides new insight into sorafenib resistance in HCC.

HMGB3 modulates ROS production via activating TLR cascade in Apostichopus japonicus

High mobility group box protein 3 (HMGB3) regulates proliferation and inflammatory response in vertebrates. However, its functional roles in invertebrates are largely unknown. In this study, a HMGB3 homologue molecule was identified from Apostichopus japonicus (designated as AjHMGB3) by RACE approach. The full-length cDNA of AjHMGB3 was of 2298 bp with an open reading frame of 1320 bp encoding a 439-amino-acid (aa) residue protein. Structural analysis then conducted and the results revealed that AjHMGB3 processed two conserved HMGBs (133-204 and 210-279 aa) and an acidic tail. The results of subsequent multiple sequence alignment and phylogenetic analysis both indicated that AjHMGB3 belongs to a new member of HMGB3 protein subfamily. Furthermore, AjHMGB3 was expressed in all examined tissues except in tentacles and particularly highly expressed in the intestine, as indicated by spatial expression analysis results. The Vibrio splendidus challenge in vivo and lipolysaccharide (LPS) stimulation in vitro can significantly upregulate the mRNA expression of AjHMGB3 in coelomocytes. This finding is consistent with the expression profiles of TLR cascade members. We further investigated the expression profiles of AjMyD88 and Ajp105 after the gain- or loss-of-function of AjHMGB3 in coelomocytes. The results showed that AjMyD88 and Ajp105 were upregulated 2.19- and 2.83-fold in AjHMGB3 overexpressed treatment and downregulated 0.38- and 0.43-fold in the AjHMGB3 silencing group. The p50 subunit displayed expression profiles that are identical to those of AjMyD88 and Ajp105 according to the Western blot results. In the same condition, the respiratory burst was increased by 37.5% in the AjHMGB3 overexpressed group and depressed by 28.2% in the AjHMGB3 knock-down group. Our present findings collectively suggested that AjHMGB3 acted as an NF-κB activator and produced ROS production in sea cucumbers.

Dengue fatal cases present virus-specific HMGB1 response in peripheral organs

Dengue is an important infectious disease that presents high incidence and yields a relevant number of fatal cases (about 20,000) every year worldwide. Despite its epidemiological relevance, there are many knowledge gaps concerning dengue pathogenesis, especially with regards to the circumstances that drive a mild clinical course to a severe disease. In this work, we investigated the participation of high mobility group box 1 (HMGB1), an important modulator of inflammation, in dengue fatal cases. Histopathological and ultrastructural analyses revealed that liver, lung and heart post-mortem samples were marked by tissue abnormalities, such as necrosis and apoptotic cell death. These observations go in line with an HMGB1-mediated response and raised concerns regarding the participation of this cytokine in promoting/perpetuating inflammation in severe dengue. Further experiments of immunohistochemistry (IHC) showed increased expression of cytoplasmic HMGB1 in dengue-extracted tissues when compared to non-dengue controls. Co-staining of DENV RNA and HMGB1 in the host cell cytoplasm, as found by in situ hybridization and IHC, confirmed the virus specific induction of the HMGB1-mediated response in these peripheral tissues. This report brings the first in-situ evidence of the participation of HMGB1 in severe dengue and highlights novel considerations in the development of dengue immunopathogenesis.

Proteomic Analysis of Extracellular HMGB1 Identifies Binding Partners and Exposes Its Potential Role in Airway Epithelial Cell Homeostasis

The release of damage-associated molecular patterns (DAMPs) by airway epithelial cells is believed to play a crucial role in the initiation and development of chronic airway conditions such as asthma and chronic obstructive pulmonary disease (COPD). Intriguingly, the classic DAMP high-mobility group box-1 (HMGB1) is detected in the culture supernatant of airway epithelial cells under basal conditions, indicating a role for HMGB1 in the regulation of epithelial cellular and immune homeostasis. To gain contextual insight into the potential role of HMGB1 in airway epithelial cell homeostasis, we used the orthogonal and complementary methods of high-resolution clear native electrophoresis, immunoprecipitation, and pull-downs coupled to liquid chromatography-tandem mass spectrometry (LC-MS/MS) to profile HMGB1 and its binding partners in the culture supernatant of unstimulated airway epithelial cells. We found that HMGB1 presents exclusively as a protein complex under basal conditions. Moreover, protein network analysis performed on 185 binding proteins revealed 14 that directly associate with HMGB1: amyloid precursor protein, F-actin-capping protein subunit alpha-1 (CAPZA1), glyceraldehyde-3 phosphate dehydrogenase (GAPDH), ubiquitin, several members of the heat shock protein family (HSPA8, HSP90B1, HSP90AA1), XRCC5 and XRCC6, high mobility group A1 (HMGA1), histone 3 (H3F3B), the FACT (facilitates chromatin transcription) complex constituents SUPT1H and SSRP1, and heterogeneous ribonucleoprotein K (HNRNPK). These studies provide a new understanding of the extracellular functions of HMGB1 in cellular and immune homeostasis at the airway mucosal surface and could have implications for therapeutic targeting.

HMGB1-induced angiogenesis in perforated disc cells of human temporomandibular joint

High mobility group 1 protein (HMGB1), a highly conserved nuclear DNA‐binding protein and inflammatory mediator, has been recently found to be involved in angiogenesis. Our previous study has demonstrated the elevation of HMGB1 in the tissue of perforated disc of temporomandibular joint (TMJ). Here, we investigated a novel mediator of HMGB1 in regulating hypoxia‐inducible factor‐1α (HIF‐1α) and vascular endothelial growth factor (VEGF) to mediate angiogenesis in perforated disc cells of TMJ. HMGB1 increased the expression of HIF‐1α and VEGF in a dose‐ and time‐dependent manner in these cells. Moreover, immunofluorescence assay exhibits that the HIF‐1α were activated by HMGB1. In addition, HMGB1 activated extracellular signal‐related kinase 1/2 (Erk1/2), Jun N‐terminal kinase (JNK), but not P38 in these cells. Furthermore, both U0126 (ErK inhibitor) and SP600125 (JNK inhibitor) significantly suppressed the enhanced production of HIF‐1α and VEGF induced by HMGB1. Tube formation of human umbilical vein endothelial cells (HUVECs) was significantly increased by exposure to conditioned medium derived from HMGB1‐stimulated perforated disc cells, while attenuated with pre‐treatment of inhibitors for VEGF, HIF‐1α, Erk and JNK, individually. Therefore, abundance of HMGB1 mediates activation of HIF‐1α in disc cells via Erk and JNK pathway and then, initiates VEGF secretion, thereby leading to disc angiogenesis and accelerating degenerative change of the perforated disc.

New serological markers for liver damage

The liver is the most important detoxification organ in the human body, and the damage to the liver will seriously affect the health of the body. Alanine transaminase (ALT) and aspartate transaminase (AST) are the most widely used clinical biochemical markers for liver injury. However, elevated serum ALT and AST levels can also occur in other diseases, which reduces their diagnostic value in liver injury. In order to diagnose liver damage more accurately, we need to find serum markers for liver injury.

HMGB1, TGF-β and NF-κB are associated with chronic allograft nephropathy

The present study aimed to investigate the association between high mobility group protein B1 (HMGB1), transforming growth factor-β1 (TGF-β1), nuclear factor-κB (NF-κB) and chronic allograft nephropathy (CAN) and to identify the clinical significance of HMGB1, TGF-β1, NF-κB on patients with CAN. Between September 2012 and November 2014, 27 patients with CAN diagnosed by biopsy were enrolled in the present study and a further 30 patients that underwent nephrectomy following trauma were selected as the control group. Immunohistochemical staining with HMGB1, TGF-β1 and NF-κB expression in the renal tissues, and western blot analysis were used to measure the relative expression of HMGB1, TGF-β1 and NF-κB. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to estimate the relative expression of HMGB1, TGF-β1 and NF-κB mRNA. Statistical analysis was used to calculate the association between HMGB1, TGF-β1 and NF-κB expression and CAN grade. Immunohistochemical staining demonstrated that HMGB1, TGF-β1 and NF-κB had markedly positive expression rates in renal tubular epithelial cell cytoplasm and membranes in CAN renal tissues, and the positive rates of HMGB1, TGF-β1 and NF-κB increased with the aggravation of CAN pathological grade (I, II and III). The results of western blot analysis indicated that the expression levels of HMGB1, TGF-β1 and NF-κB were significantly higher in the CAN group, compared with the normal group (P<0.05), and the expression levels increased with the progression of CAN grade. A positive association among HMGB1, TGF-β1 and NF-κB expression was identified. RT-qPCR analysis demonstrated that the expression of HMGB1, TGF-β1 and NF-κB mRNA in the CAN group was significantly higher than in the normal group (P<0.05), and the relative expression level of HMGB1, TGF-β1 and NF-κB mRNA not only increased with the aggravation of CAN grade, but was also positively associated with the expression of HMGB1, TGF-β1 and NF-κB, respectively. The abnormal expression of HMGB1, TGF-β1 and NF-κB is therefore, an important manifestation of CAN and the expression of HMGB1, TGF-β1 and NF-κB mRNA in the renal tissues are significantly associated with CAN pathological progression. HMGB1, TGF-β1 and NF-κB may form a signaling pathway that leads to the occurrence of CAN, which induces renal interstitial fibrosis.

Adenovirus Core Protein VII Downregulates the DNA Damage Response on the Host Genome

Viral manipulation of cellular proteins allows viruses to suppress host defenses and generate infectious progeny. Due to the linear double-stranded DNA nature of the adenovirus genome, the cellular DNA damage response (DDR) is considered a barrier to successful infection. The adenovirus genome is packaged with protein VII, a virally encoded histone-like core protein that is suggested to protect incoming viral genomes from detection by the cellular DNA damage machinery. We showed that protein VII localizes to host chromatin during infection, leading us to hypothesize that protein VII may affect DNA damage responses on the cellular genome. Here we show that protein VII at cellular chromatin results in a significant decrease in accumulation of phosphorylated H2AX (γH2AX) following irradiation, indicating that protein VII inhibits DDR signaling. The oncoprotein SET was recently suggested to modulate the DDR by affecting access of repair proteins to chromatin. Since protein VII binds SET, we investigated a role for SET in DDR inhibition by protein VII. We show that knockdown of SET partially rescues the protein VII-induced decrease in γH2AX accumulation on the host genome, suggesting that SET is required for inhibition. Finally, we show that knockdown of SET also allows ATM to localize to incoming viral genomes bound by protein VII during infection with a mutant lacking early region E4. Together, our data suggest that the protein VII-SET interaction contributes to DDR evasion by adenovirus. Our results provide an additional example of a strategy used by adenovirus to abrogate the host DDR and show how viruses can modify cellular processes through manipulation of host chromatin.IMPORTANCE The DNA damage response (DDR) is a cellular network that is crucial for maintaining genome integrity. DNA viruses replicating in the nucleus challenge the resident genome and must overcome cellular responses, including the DDR. Adenoviruses are prevalent human pathogens that can cause a multitude of diseases, such as respiratory infections and conjunctivitis. Here we describe how a small adenovirus core protein that localizes to host chromatin during infection can globally downregulate the DDR. Our study focuses on key players in the damage signaling pathway and highlights how viral manipulation of chromatin may influence access of DDR proteins to the host genome.

Long noncoding RNA PCAT-1 promotes invasion and metastasis via the miR-129-5p-HMGB1 signaling pathway in hepatocellular carcinoma

OBJECTIVE

The long non-coding RNA (lncRNA) prostate cancer-associated transcript 1(PCAT-1) has been shown to be dysregulated and exert vital roles in tumorigenesis and progression of various malignancies. However, the precise molecular mechanism in the metastasis and invasion of HCC remain unclear.

METHODS

The expression levels of PCAT1 derived from human HCC tissues and cell lines were analyzed through quantitative real-time PCR. QRT-PCR was also applied to detect the expression of HMGB1 and miR-129-5p. Wound healing assay and transwell assays were performed to analyze cell migration and invasion ability. The mRNA levels and protein expression of HMGB1 were detected by western-blotting analysis and immunohistochemistry, respectively. Luciferase assays were used to investigate binding seeds beteen miRNA-129-5p and other transcripts, such as PCAT-1, HMGB1.

RESULT

In this study, our founding demonstrated that PCAT-1 was not only aberrantly upregulated in HCC tissues and cell lines, but also associated with TNM stage, metastasis and Histological grade. In vitro, downregulation of PCAT-1 could reduce the invasion and migration of HCC cells. Moreover, our results showed that PCAT-1 could act as an endogenous RNA by directly binding to miR-129-5p. In addition, Luciferase reporter assay and western blotting analyses showed that PCAT-1 repressed inhibitory effect of miR-129-5p and reverse high mobility group box 1 (HMGB1) expression, a target gene of miR-129-5p.

CONCLUSION

PCAT-1 functions as competing endogenous RNA (ceRNA) to provide a better understanding for HCC metastasis, and serves as a potential diagnostic and therapeutic target via PCAT-1/miR-129-5p/HMGB1 regulatory crosstalk for the deadly disease.

M2-like macrophages in the fibrotic liver protect mice against lethal insults through conferring apoptosis resistance to hepatocytes

Acute injury in the setting of liver fibrosis is an interesting and still unsettled issue. Most recently, several prominent studies have indicated the favourable effects of liver fibrosis against acute insults. Nevertheless, the underlying mechanisms governing this hepatoprotection remain obscure. In the present study, we hypothesized that macrophages and their M1/M2 activation critically involve in the hepatoprotection conferred by liver fibrosis. Our findings demonstrated that liver fibrosis manifested a beneficial role for host survival and apoptosis resistance. Hepatoprotection in the fibrotic liver was tightly related to innate immune tolerance. Macrophages undertook crucial but divergent roles in homeostasis and fibrosis: depleting macrophages in control mice protected from acute insult; conversely, depleting macrophages in fibrotic liver weakened the hepatoprotection and gave rise to exacerbated liver injury upon insult. The contradictory effects of macrophages can be ascribed, to a great extent, to the heterogeneity in macrophage activation. Macrophages in fibrotic mice exhibited M2-preponderant activation, which was not the case in acutely injured liver. Adoptive transfer of M2-like macrophages conferred control mice conspicuous protection against insult. In vitro, M2-polarized macrophages protected hepatocytes against apoptosis. Together, M2-like macrophages in fibrotic liver exert the protective effects against lethal insults through conferring apoptosis resistance to hepatocytes.

Characterization of NLRP3-like gene from Apostichopus japonicus provides new evidence on inflammation response in invertebrates

Inflammatory/defensive response after pathogen invasion is considered a local defense reaction in vertebrates. Inflammation response in Apostichopus japonicus was hardly determined due to scarce information available for nucleotide binding domain-like receptor family, pyrin domain-containing (NLRP) family. In the present study, invertebrate NLRP homologue was identified from A. japonicus (designated as AjNLRP3-like) by rapid amplification of cDNA ends. Full-length cDNA of AjNLRP3-like measured 2970 bp with 2265 bp open reading frame encoding a 754-amino acid (aa) residue protein. Structural analysis revealed that AjNLRP3-like processed characteristic domains of pyrin (32-102aa) and NACHT (183-339aa). Multiple sequence alignment and phylogenetic analysis supported that AjNLRP3-like belongs to a new member of NLRP3 protein subfamily. Spatial expression analysis revealed that AjNLRP3-like was ubiquitously expressed in all examined tissues with larger magnitude in coelomocytes. Both Vibrio splendidus challenge in vivo and lipopolysaccharide stimulation in vitro significantly upregulated mRNA expression of AjNLRP3-like when compared with the control group. NLRP3-mediated inflammation response depended on release of lysosomal cathepsin B (CTSB) and subsequent activation of high-mobility group box (HMGB) in vertebrates. We investigated expression profiles of AjNLRP3-like and AjHMGB after AjCTSB knock-down and discovered that AjNLRP3-like was depressed by 0.66-fold and 0.47-fold, whereas AjHMGB was depressed by 0.70-fold and 0.50-fold at 24 and 48 h in AjCTSB-silenced group, respectively. Similarly, down-regulation of AjHMGB was also observed after AjNLRP3-like knock-down. This study therefore suggests that A. japonicus feature similar inflammatory events as those in vertebrates, and activation of AjNLRP3-like depends on AjCTSB expression and release of AjHMGB.

New prognostic biomarkers and therapeutic effect of bevacizumab for patients with non-small-cell lung cancer

BACKGROUND

Several biomarkers have emerged as potential prognostic and predictive markers for non-small-cell lung cancer (NSCLC). Successful inhibition of angiogenesis with the antivascular endothelial growth factor antibody, bevacizumab, has improved the efficacy seen with standard cytotoxic therapy of NSCLC. However, despite such enhanced treatment strategies, the prognosis for patients with advanced NSCLC remains poor.

PATIENTS AND METHODS

We assessed potential biomarkers in 161 NSCLC patients and 42 control patients. Enzyme-linked immunosorbent assay methods were used to evaluate three biomarkers: platelet-derived microparticle (PDMP), high-mobility group box-1 (HMGB1), and plasminogen activator inhibitor-1 (PAI-1). We studied the effects of bevacizumab on the expression of these markers. We also analyzed the relationship of the newly designed risk factor (NDRF) to overall survival and disease-free survival. The NDRF classification of patients was determined from the levels of PDMP, HMGB1, and PAI-1. To determine the individual prognostic power of PDMP, HMGB1, and PAI-1, we evaluated associations between their levels and patient outcomes by Kaplan-Meier survival analysis in a derivation cohort.

RESULTS

PDMP, HMGB1, and PAI-1 levels were higher in NSCLC patients compared with control patients. Notably, the difference in PDMP levels exhibited the strongest statistical significance (p<0.001). Multivariate analysis showed that HMGB1 and PAI-1 levels were significantly correlated with PDMP levels. Patients who received standard chemotherapy with bevacizumab exhibited significantly reduced levels of all three markers compared with patients who received standard chemotherapy. NDRF3 status (high levels of all three markers) was significantly correlated with a poor prognosis (p<0.05 for overall survival and disease-free survival).

CONCLUSION

Our results demonstrate that abnormal levels of PDMP, HMGB1, and PAI-1 are related to each other in NSCLC. Moreover, our findings suggest that the vascular complications associated with these markers may contribute to a poor prognosis for NSCLC patients.

Protective effect of high mobility group box-1 silence on diabetic retinopathy: an in vivo study

PURPOSE

To explore the effects of HMGB1 silence on cell apoptosis, inflammatory response and endothelial permeability barrier.

METHODS

Retinal tissues were isolated from 8 week-old SD rats and cells were cultured and identified. Effects of HMGB1 silence were detected by qRT-PCR and Western blot. Proliferation capability of cells was detected by MTT assay and LDH activity assays. Cell apoptosis was analyzed by flow cytometry, Hoechst staining and Caspase-3 activity assay. Furthermore, concentrations of VEGF, ICAM-1, VCAM-1, TNF-α and MCP-1 in the cell media were measured.

RESULTS

Results of our study showed that high concentration of glucose caused increased cell apoptosis and inflammatory response, and also influenced the endothelial permeability barrier. Whereas, these damaging effects of high concentration of glucose could be relieved by HMGB1 silence.

CONCLUSION

The present study indicates that HMGB silence is a promising therapeutic option for diabetic retinopathy, and also provides theoretical basis for further exploration of diabetic retinopathy treatment.

Blockade of high-mobility group box 1 attenuates intestinal mucosal barrier dysfunction in experimental acute pancreatitis

The release of inflammatory cytokines, that plays a dominant role in local pancreatic inflammation and systemic complications in severe acute pancreatitis (SAP). High-mobility group box 1 (HMGB1) is implicated in the mechanism of organ dysfunction and bacterial translocation in SAP. This current study aims to investigate possible role of HMGB1 in the intestinal mucosal barrier dysfunction of SAP, and the effect of anti-HMGB1 antibody treatment in intestinal mucosal injury in SAP. Our data revealed that the HMGB1 expression was significantly increased in AP mice induced by caerulein and LPS, and the inhibition of HMGB1 played a protective role in intestinal mucosal barrier dysfunction, reduced the serum level of other proinflammatory cytokines include IL-1β, IL-6, TNF-α. Next we investigated the downstream receptors involving in HMGB1 signaling. We found that the expressions of toll-like receptor (TLR) 4 and TLR9 were elevated in ileum of AP mice, the administration of HMGB1 neutralizing antibody significantly reduced the TLR4 and TLR9 expression. It was concluded that HMGB1 contributed the mechanism to the intestinal mucosal barrier dysfunction during AP. Blockade of HMGB1 by administration of HMGB1 neutralizing antibody may be a beneficial therapeutic strategy in improving intestinal mucosal barrier dysfunction in SAP.

Immunogenic Apoptotic Cell Death and Anticancer Immunity

For many years it has been thought that apoptotic cells rapidly cleared by phagocytic cells do not trigger an immune response but rather have anti-inflammatory properties. However, accumulating experimental data indicate that certain anticancer therapies can induce an immunogenic form of apoptosis associated with the emission of damage-associated molecular patterns (DAMPs), which function as adjuvants to activate host antitumor immune responses. In this review, we will first discuss recent advances and the significance of danger signaling pathways involved in the emission of DAMPs, including calreticulin, ATP, and HMGB1. We will also emphasize that switching on a particular signaling pathway depends on the immunogenic cell death stimulus. Further, we address the role of ER stress in danger signaling and the classification of immunogenic cell death inducers in relation to how ER stress is triggered. In the final part, we discuss the role of radiotherapy-induced immunogenic apoptosis and the relationship of its immunogenicity to the fraction dose and concomitant chemotherapy.

MicroRNA-200c inhibits epithelial-mesenchymal transition, invasion, and migration of lung cancer by targeting HMGB1

MicroRNAs (miRs) play critical roles in cancer development, proliferation, epithelial-mesenchymal transition (EMT), invasion, and migration through regulating the expression of oncogenes and tumour suppressor genes. Previous studies have indicated that miR-200c acts as a tumour suppressor in various cancers by downregulating high-mobility group box 1 (HMGB1) and thereby suppressing EMT and metastasis. In addition, miR-200c was reported to be downregulated and correlated with poor outcomes in non-small cell lung cancer (NSCLC). However, its functional role in HMGB1 regulation in NSCLC is still unclear. This study aimed to clarify whether miR-200c acts as a tumour suppressor in NSCLC by downregulating HMGB1, which is associated with EMT, invasion, cytoskeleton rearrangement, and migration in vitro and in vivo. In order to demonstrate HMGB1 downregulation by miR-200c, the NSCLC cell line A549 was transfected with miR-200c mimic or inhibitor. The mimic significantly reduced HMGB1 expression and suppressed EMT, invasion, and migration, while the inhibitor generated the opposite effects. Additionally, using xenograft mouse models, we confirmed that HMGB1 overexpression increased tumour EMT. In summary, our results demonstrated that miR-200c could suppress EMT, invasion, and migration of NSCLC cells by downregulating HMGB1.

HMGB3 promotes growth and migration in colorectal cancer by regulating WNT/β-catenin pathway

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths and a major health problem. High mobility group box 3 (HMGB3), a member of the high-mobility group box (HMGB) family, was reported to be over-expressed in gastric carcinoma and bladder cancer. However, the function of HMGB3 in CRC remains unclear. Here, we found that HMGB3 was up-regulated in CRC at both mRNA and protein levels. qRT-PCR results showed that high expression of HMGB3 had positive correlation with serosal invasion, lymph metastasis, and tumor–node–metastasis (TNM) stage in CRC patient. Functional experiments showed that HMGB3 can promote CRC cells proliferation and migration in vitro. Moreover, we found HMGB3 can active WNT/β-catenin pathway to increase the expression level of c-Myc and MMP7. These results may be the reason for HMGB3 oncogene role in CRC. In summary, our data indicated that HMGB3 may serve as an oncoprotein and could be used as a potential prognostic marker in CRC.

Expression of High-Mobility Group Box 1 Protein (HMGB1) and Toll-Like Receptor 9 (TLR9) in Retinas of Diabetic Rats

Background

Diabetic retinopathy (DR) and diabetic optic neuropathy are important complications of diabetes mellitus (DM) which can lead to blindness in diabetic patients. Recent studies showed that chronic low-grade inflammation is thought to be one of the important pathophysiological mechanisms in the occurrence and development of DR and diabetes optic neuropathy. This study explored the expressions of inflammatory factors HMGB-1 and TLR9.

Material/Methods

SD rats were randomly divided into a diabetic mellitus group and a control group. A DM rat model was produced by intraperitoneal injection of 1% STZ with 60 mg/Kg weight. At 4, 8, and 16 weeks after injection, the rats were sacrificed and eyeballs were enucleated for HE staining, immunohistochemistry, Western blot, and RT-PCR.

Results

We found that, compared with the control group, levels of HMGB1 and TLR9 in retinas were significantly increased in DM groups of different time courses. Furthermore, a significant correlation was found between HMGB1 and TLR9 (all P<0.05).

Conclusions

Our results demonstrated that the HMGB1-TLR9 signaling pathway may be involved in the pathogenesis of diabetic retinopathy. Blockage of HMGB1 and/or TLR9 may represent a novel approach to treating diabetic retinopathy and diabetic optic neuropathy.

Association between HMGB1 and asthma: a literature review

Background

Recently, some studies demonstrated that HMGB1, as proinflammatory mediator belonging to the alarmin family, has a key role in different acute and chronic immune disorders. Asthma is a complex disease characterised by recurrent and reversible airflow obstruction associated to airway hyper-responsiveness and airway inflammation.

Objective

This literature review aims to analyse advances on HMGB1 role, employment and potential diagnostic application in asthma.

Methods

We reviewed experimental studies that investigated the pathogenetic role of HMGB in bronchial airway hyper-responsiveness, inflammation and the correlation between HMGB1 level and asthma.

Results

A total of 19 studies assessing the association between HMGB1 and asthma were identified.

Conclusions

What emerged from this literature review was the confirmation of HMGB-1 involvement in diseases characterised by chronic inflammation, especially in pulmonary pathologies. Findings reported suggest a potential role of the alarmin in being a stadiation method and a marker of therapeutic efficacy; finally, inhibiting HMGB1 in humans in order to contrast inflammation should be the aim for future further studies.

High-mobility group box-1 and receptor for advanced glycation end products in preterm infants with brain injury

BACKGROUND

High-mobility group box-1 (HMGB1) protein acts as an important pro-infl ammatory mediator, which is capable of activating inflammation and tissue repair. HMGB1 can bind to its receptor such as advanced glycation end products (RAGE). RAGE, in turn, can promote the production of pro-inflammatory cytokines. Soluble RAGE (sRAGE) is a truncated form of the receptor comprising the extracellular domain of RAGE and can inhibit RAGE-activation. The objective of this study was to investigate whether HMGB1 and RAGE are involved in the development of brain injury in preterm infants.

METHODS

In total, 108 infants ≤34 weeks gestation at birth were divided into 3 groups according to cranial altrasound scan: mild brain damage (n=33), severe brain damage (n=8) and no brain damage (n=67). All the placentas were submitted for pathologic evaluation. Histological chorioamnionitis (HCA) was defined as neutrophil infi ltration of amniotic membranes, umbilical cord or chorionic plate. Expressions of HMGB1 and RAGE proteins were assessed by immunohistochemical analysis. The concentration of HMGB1 and sRAGE in umbilical cord blood were measured by enzyme-linked immunosorbent assay.

RESULTS

The frequency of HCA was 30.12%. HCA was associated with elevated concentrations of HMGB1 and decreased sRAGE in umbilical cord blood. The severe brain injury group demonstrated higher cord blood HMGB1 concentrations (P<0.001) and lower sRAGE concentrations (P<0.001) than both other groups. Brain injury in the premature infants was linked to intense staining for HMGB1/RAGE, particularly in infl ammatory cells.

CONCLUSIONS

Changes of cord blood HMGB1 and sRAGE of premature infants had direct relationship with the degree of infl ammation and severity of brain damage. Monitoring sRAGE and HMGB1 levels may be helpful to predict intrauterine infection and brain injury in premature infants.

Glycyrrhizin Reduces HMGB1 and Bacterial Load in Pseudomonas aeruginosa Keratitis

Purpose

High mobility group box 1 (HMGB1) contributes to poor disease outcome in Pseudomonas aeruginosa keratitis. This study tests the prophylactic effect of treatment with HMGB1 inhibitors, glycyrrhizin (GLY) and its derivative, carbenoxolone (CBX), for Pseudomonas keratitis.

Methods

We treated C57BL/6 (B6) mice subconjunctivally with GLY or CBX, infected with a noncytotoxic clinical isolate (KEI 1025) or a cytotoxic strain (ATCC 19660) of P. aeruginosa, and injected intraperitoneally with either agent. Clinical score, photography with a slit lamp, real-time RT-PCR, ELISA, myeloperoxidase (MPO) assay, bacterial plate count, histopathology, and absorbance assays were used to assess treatment efficacy and bacteriostatic activity.

Results

After KEI 1025 infection, GLY treatment reduced HMGB1 (mRNA and protein levels) and improved disease outcome with significant reduction in mRNA levels of IL-1β, TLR4, CXCL2, and IL-12; protein expression (IL-1β, CXCL2); neutrophil infiltrate; and bacterial load. Treatment with GLY enhanced antimicrobial proteins, including CRAMP and mBD2, but not mBD3. Glycyrrhizin also reduced clinical scores and improved disease outcome in corneas infected with strain 19660. However, neither HMGB1 mRNA or protein levels were reduced, but rather, CXCL2 expression (mRNA and protein), neutrophil infiltrate, and bacterial load were reduced statistically. Treatment with GLY initiated 6 hours after infection reduced plate count; GLY also was bacteriostatic for KEI 1025 and ATCC 19660.

Conclusions

Glycyrrhizin reduces HMGB1 and is protective against P. aeruginosa-induced keratitis with a clinical isolate that is noncytotoxic. It was similar, but less effective when used after infection with a cytotoxic strain, which did not reduce HMGB1.

Hyperoxia provokes a time- and dose-dependent inflammatory response in mechanically ventilated mice, irrespective of tidal volumes

Background

Mechanical ventilation and hyperoxia have the potential to independently promote lung injury and inflammation. Our purpose was to study both time- and dose-dependent effects of supplemental oxygen in an experimental model of mechanically ventilated mice.

Methods

Healthy male C57Bl/6J mice, aged 9–10 weeks, were intraperitoneally anesthetized and randomly assigned to the mechanically ventilated group or the control group. In total, 100 mice were tracheotomized and mechanically ventilated for either 8 or 12 h after allocation to different settings for the applied fractions of inspired oxygen (FiO₂, 30, 50, or 90%) and tidal volumes (7.5 or 15 ml/kg). After euthanisation arterial blood, bronchoalveolar lavage fluid (BALf) and tissues were collected for analyses.

Results

Mechanical ventilation significantly increased the lung injury score (P < 0.05), mean protein content (P < 0.001), and the mean number of cells (P < 0.01), including neutrophils in BALf (P < 0.001). In mice ventilated for 12 h, a significant increase in TNF-α, IFN-γ, IL-1β, IL-10, and MCP-1 (P < 0.01) was observed with 90% FiO₂, whereas IL-6 showed a decreasing trend (P for trend = 0.03) across FiO₂ groups. KC, MIP-2, and sRAGE were similar between FiO₂ groups. HMGB-1 was significantly higher in BALf of mechanically ventilated mice compared to controls and showed a gradual increase in expression with increasing FiO₂. Cytokine and chemokine levels in BALf did not markedly differ between FiO₂ groups after 8 h of ventilation. Differences between the tidal volume groups were small and did not appear to significantly interact with the oxygen levels.

Conclusions

We demonstrated a severe vascular leakage and a pro-inflammatory pulmonary response in mechanically ventilated mice, which was enhanced by severe hyperoxia and longer duration of mechanical ventilation. Prolonged ventilation with high oxygen concentrations induced a time-dependent immune response characterized by elevated levels of neutrophils, cytokines, and chemokines in the pulmonary compartment.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-017-0142-5) contains supplementary material, which is available to authorized users.

New intracellular activities of matrix metalloproteinases shine in the moonlight

Adaption of a single protein to perform multiple independent functions facilitates functional plasticity of the proteome allowing a limited number of protein-coding genes to perform a multitude of cellular processes. Multifunctionality is achievable by post-translational modifications and by modulating subcellular localization. Matrix metalloproteinases (MMPs), classically viewed as degraders of the extracellular matrix (ECM) responsible for matrix protein turnover, are more recently recognized as regulators of a range of extracellular bioactive molecules including chemokines, cytokines, and their binders. However, growing evidence has convincingly identified select MMPs in intracellular compartments with unexpected physiological and pathological roles. Intracellular MMPs have both proteolytic and non-proteolytic functions, including signal transduction and transcription factor activity thereby challenging their traditional designation as extracellular proteases. This review highlights current knowledge of subcellular location and activity of these "moonlighting" MMPs. Intracellular roles herald a new era of MMP research, rejuvenating interest in targeting these proteases in therapeutic strategies. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

Alarmins and central nervous system inflammation in HIV-associated neurological disorders

In the era of highly active antiretroviral therapy (HAART), HIV-1-associated neurocognitive disorders (HAND) persist in infected individuals with adequate immunological and virological status. Risk factors for cognitive impairment include hepatitis C virus co-infection, host genetic factors predisposing to HAND, the early establishment of the virus in the CNS and its persistence under HAART; thus, the CNS is an important reservoir for HIV. Microglial cells are permissive to HIV-1, and NLRP3 inflammasome-associated genes were found expressed in brains of HIV-1-infected persons, contributing to brain disease. Inflammasomes can be triggered by alarmins or danger-associated molecular patterns (DAMPs), which directly stimulate the production of proinflammatory mediators by glial cells, contribute to blood-brain barrier injury through induction of release of various proteases and allow the passage of infected macrophages, and trigger IL-1β release from primed cells. Amongst alarmins involved in HIV-1-induced neuropathogenesis, IL-33 and high-mobility group box 1 (HMGB1) are of particular interest. Neurocognitive alterations were recently associated with dysregulation of the IL-33/ST2 axis in the CNS, leading to the induction of neuronal apoptosis, decrease in synaptic function and neuroinflammation. Specific biomarkers, including HMGB1 and anti-HMGB1 antibodies, have been identified in cerebrospinal fluid from patients with HAND, correlated with immune activation and identifying a very early stage of neurocognitive impairment that precedes changes in metabolites detected by magnetic resonance spectroscopy. Moreover, HMGB1 plays a crucial role in HIV-1 persistence in dendritic cells and in the constitution of viral reservoirs. In this review, the mechanisms whereby alarmins contribute to HIV-1-induced CNS inflammation and neuropathogenesis will be discussed.

Plasma Levels of High-Mobility Group Box 1 during Peptide Vaccination in Patients with Recurrent Ovarian Cancer

High-mobility group box 1 (HMGB1) is a nuclear protein that is known to be secreted into extracellular fluids from injured cells, activated macrophages, and tumor cells. The clinical correlation of circulating HMGB1 levels with various diseases including cancer has been reported. However, there is no information on HMGB1 levels in cancer patients treated with peptide vaccination. In the present study, we investigated the plasma levels of HMGB1 during personalized peptide vaccination in patients with recurrent ovarian cancer. Frozen plasma samples of 39 patients from previously conducted clinical trials were used in this study. HMGB1 levels were decreased after the 1st cycle of vaccination from their prevaccination levels. However, no correlation was observed between HMGB1 and overall survival (OS). The correlation between plasma HMGB1 levels and other biomarker levels was further analyzed by scatter plot, revealing that HMGB1 levels after the 1st cycle of vaccination were significantly correlated with myeloid-derived suppressor cell (MDSC) frequency after the 1st cycle of vaccination (r = 0.357, p = 0.032). Chi-square test showed that epitope spreading was significantly related with changes of HMGB1 (p = 0.030). These results suggest that plasma HMGB1 is a possible biomarker for cancer vaccine therapy, although direct correlation with OS has not been obtained. This trial is registered with Clinical Trial Registry under trial numbers UMIN000003083 and UMIN000001482.

High ASMA+ Fibroblasts and Low Cytoplasmic HMGB1+ Breast Cancer Cells Predict Poor Prognosis

INTRODUCTION

The influence of cancer-associated fibroblasts (CAFs) and high mobility group box 1 (HMGB1) has been recognized in several cancers, although their roles in breast cancer are unclear. The present study aimed to determine the levels and prognostic significance of α-smooth muscle actin-positive (ASMA⁺) CAFs, plus HMGB1 and receptor for advanced glycation end products (RAGE) in cancer cells.

MATERIALS AND METHODS

A total of 127 breast samples, including 96 malignant and 31 benign, were examined for ASMA, HMGB1, and RAGE by immunohistochemistry. The χ² test and Fisher's exact test were used to test the association of each protein with clinicopathologic parameters. The Kaplan-Meier method or log-rank test and Cox regression were used for survival analysis.

RESULTS

ASMA⁺ fibroblast infiltration was significantly increased in the tumor stroma compared with that in benign breast tissue. The levels of cytoplasmic HMGB1 and RAGE were significantly greater in the breast cancer tissue than in the benign breast tissues. High ASMA expression correlated significantly with large tumor size, clinical stage III-IV, and angiolymphatic and perinodal invasion. In contrast, increased cytoplasmic HMGB1 correlated significantly with small tumor size, pT stage, early clinical stage, luminal subtype (but not triple-negative subtype), and estrogen receptor and progesterone receptor expression. The levels of ASMA (hazard ratio, 14.162; P = .010) and tumor cytoplasmic HMGB1 (hazard ratio, 0.221; P = .005) could serve as independent prognostic markers for metastatic relapse in breast cancer patients. The ASMA-high/HMGB1-low profile provided the most reliable prediction of metastatic relapse.

CONCLUSION

We present for the first time, to the best of our knowledge, the potential clinical implications of the combined assessment of ASMA⁺ fibroblasts and cytoplasmic HMGB1 in breast cancer.

Ischemic preconditioning modulates ROS to confer protection in liver ischemia and reperfusion

Ischemia reperfusion (IR) injury is a significant cause of morbidity and mortality in liver transplantation. When oxygen is reintroduced to the liver graft it initiates a cascade of molecular reactions leading to the release of reactive oxygen species (ROS) and pro-inflammatory cytokines. These soluble mediators propagate a sterile immune response to cause significant tissue damage. Ischemic preconditioning (IPC) is one method that reduces hepatocellular injury by altering the immune response and inhibiting the production of ROS. Studies quantifying the effects of IPC in humans have demonstrated an improved liver enzyme panel in patients receiving grafts pretreated with IPC as compared to patients receiving the standard of care. In our review, we explore current literature in the field in order to describe the mechanism through which IPC regulates the production of ROS and improves IR injury.

Intracellular HMGB1 as a novel tumor suppressor of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) driven by oncogenic K-Ras remains among the most lethal human cancers despite recent advances in modern medicine. The pathogenesis of PDAC is partly attributable to intrinsic chromosome instability and extrinsic inflammation activation. However, the molecular link between these two events in pancreatic tumorigenesis has not yet been fully established. Here, we show that intracellular high mobility group box 1 (HMGB1) remarkably suppresses oncogenic K-Ras-driven pancreatic tumorigenesis by inhibiting chromosome instability-mediated pro-inflammatory nucleosome release. Conditional genetic ablation of either single or both alleles of HMGB1 in the pancreas renders mice extremely sensitive to oncogenic K-Ras-driven initiation of precursor lesions at birth, including pancreatic intraepithelial neoplasms, intraductal papillary mucinous neoplasms, and mucinous cystic neoplasms. Loss of HMGB1 in the pancreas is associated with oxidative DNA damage and chromosomal instability characterized by chromosome rearrangements and telomere abnormalities. These lead to inflammatory nucleosome release and propagate K-Ras-driven pancreatic tumorigenesis. Extracellular nucleosomes promote interleukin 6 (IL-6) secretion by infiltrating macrophages/neutrophils and enhance oncogenic K-Ras signaling activation in pancreatic lesions. Neutralizing antibodies to IL-6 or histone H3 or knockout of the receptor for advanced glycation end products all limit K-Ras signaling activation, prevent cancer development and metastasis/invasion, and prolong animal survival in Pdx1-Cre;K-Ras^G12D/+;Hmgb1^−/− mice. Pharmacological inhibition of HMGB1 loss by glycyrrhizin limits oncogenic K-Ras-driven tumorigenesis in mice under inflammatory conditions. Diminished nuclear and total cellular expression of HMGB1 in PDAC patients correlates with poor overall survival, supporting intracellular HMGB1 as a novel tumor suppressor with prognostic and therapeutic relevance in PDAC.

Metformin directly binds the alarmin HMGB1 and inhibits its proinflammatory activity

Metformin is the first-line drug in the treatment of type 2 diabetes. In addition to its hypoglycemic effect, metformin has an anti-inflammatory function, but the precise mechanism promoting this activity remains unclear. High mobility group box 1 (HMGB1) is an alarmin that is released from necrotic cells and induces inflammatory responses by its cytokine-like activity and is, therefore, a target of anti-inflammatory therapies. Here we identified HMGB1 as a novel metformin-binding protein by affinity purification using a biotinylated metformin analogue. Metformin directly bound to the C-terminal acidic tail of HMGB1. Both in vitro and in vivo, metformin inhibited inflammatory responses induced by full-length HMGB1 but not by HMGB1 lacking the acidic tail. In an acetaminophen-induced acute liver injury model in which HMGB1 released from injured cells exacerbates the initial injury, metformin effectively reduced liver injury and had no additional inhibitory effects when the extracellular HMGB1 was blocked by anti-HMGB1-neutralizing antibody. In summary, we report for the first time that metformin suppresses inflammation by inhibiting the extracellular activity of HMGB1. Because HMGB1 plays a major role in inflammation, our results suggest possible new ways to manage HMGB1-induced inflammation.

Association of Serum HMGB2 Levels With In-Stent Restenosis

Objective—

In a previous study, we established diabetic and nondiabetic minipig models with coronary artery in-stent restenosis (ISR). Mass spectrometry showed that high-mobility group box (HMGB) 2 level was higher in ISR than in non-ISR tissue from diabetic minipigs. We here investigated whether serum HMGB2 levels were related to ISR in coronary artery disease patients. The effect of HMGB2 was evaluated in mice with femoral artery wire injury and in human aortic smooth muscle cells.

Approach and Results—

From 2513 patients undergoing coronary artery intervention and follow-up angiography at ≈1 year, 262 patients were diagnosed with ISR, and 298 patients with no ISR were randomly included as controls. Serum HMGB2 levels were significantly higher in patients with ISR than in those without ISR and were associated with ISR severity. Multivariable logistic regression analysis showed that HMGB2 level was independently associated with ISR. In experiments, HMGB2 expression was increased in vascular tissue after injury. Perivascular HMGB2 administration promoted injury-induced neointimal hyperplasia in C57Bl/6 mice compared with in the control, whereas such pathophysiological features were attenuated in Hmgb2 –/– mice. Mechanistically, HMGB2 enhanced neointimal hyperplasia in mice and proliferation and migration in human aortic smooth muscle cells by inducing reactive oxygen species through increased p47phox phosphorylation. Knocking down p47phox, however, inhibited HMGB2-induced effects in human aortic smooth muscle cells. Finally, HMGB2-induced effects were significantly declined in receptor of advanced glycation end products knockdown or deficient cells, but not in Toll-like receptor 4 knockdown or deficient cells.

Conclusions—

Serum HMGB2 levels were associated with ISR in patients. HMGB2 promoted neointimal hyperplasia in mice with arterial wire injury through reactive oxygen species activation.

High-mobility group box 1 is an important mediator of microglial activation induced by cortical spreading depression

Single episodes of cortical spreading depression (CSD) are believed to cause typical migraine aura, whereas clusters of spreading depolarizations have been observed in cerebral ischemia and subarachnoid hemorrhage. We recently demonstrated that the release of high-mobility group box 1 (HMGB1) from cortical neurons after CSD in a rodent model is dependent on the number of CSD episodes, such that only multiple CSD episodes can induce significant HMGB1 release. Here, we report that only multiple CSD inductions caused microglial hypertrophy (activation) accompanied by a greater impact on the transcription activity of the HMGB1 receptor genes, TLR2 and TLR4, while the total number of cortical microglia was not affected. Both an HMGB1-neurtalizing antibody and the HMGB1 inhibitor glycyrrhizin abrogated multiple CSD-induced microglial hypertrophy. Moreover, multiple CSD inductions failed to induce microglial hypertrophy in TLR2/4 double knockout mice. These results strongly implicate the HMGB1-TLR2/4 axis in the activation of microglia following multiple CSD inductions. Increased expression of the lysosomal acid hydrolase cathepsin D was detected in activated microglia by immunostaining, suggesting that lysosomal phagocytic activity may be enhanced in multiple CSD-activated microglia.

Alarmins and Their Receptors as Modulators and Indicators of Alloimmune Responses

Cell damage and death releases alarmins, self-derived immunomodulatory molecules that recruit and activate the immune system. Unfortunately, numerous processes critical to the transplantation of allogeneic materials result in the destruction of donor and recipient cells and may trigger alarmin release. Alarmins, often described as damage-associated molecular patterns, together with exogenous pathogen-associated molecular patterns, are potent orchestrators of immune responses; however, the precise role that alarmins play in alloimmune responses remains relatively undefined. We examined evolving concepts regarding how alarmins affect solid organ and allogeneic hematopoietic cell transplantation outcomes and the mechanisms by which self molecules are released. We describe how, once released, alarmins may act alone or in conjunction with nonself materials to contribute to cytokine networks controlling alloimmune responses and their intensity. It is becoming recognized that this class of molecules has pleotropic functions, and certain alarmins can promote both inflammatory and regulatory responses in transplant models. Emerging evidence indicates that alarmins and their receptors may be promising transplantation biomarkers. Developing the therapeutic ability to support alarmin regulatory mechanisms and the predictive value of alarmin pathway biomarkers for early intervention may provide opportunities to benefit graft recipients.

HMGB1 Mediates Autophagy Dysfunction via Perturbing Beclin1-Vps34 Complex in Dopaminergic Cell Model

Parkinson’s disease (PD), a progressive neurodegenerative disorder, is characterized by irreversible dopaminergic neuron loss and intra-neuronal α-synuclein aggregation. High mobility group box 1 (HMGB1) has been proven to be involved in autophagy dysfunction induced by α-synuclein accumulation, and the Beclin1-vacuolar protein sorting 34 (Vps34) complex is of great importance to the initiation of autophagy. Nevertheless, the concrete interaction mechanism between HMGB1, α-synuclein and autophagy remains elusive, especially in the context of PD. Here in this study, we investigated the interaction between HMGB1 and α-synuclein in rotenone-induced PD cell models and their roles in autophagy flux. Results revealed elevated expression and cytosolic translocation of endogenous HMGB1 upon rotenone exposure. Besides, HMGB1 was found to be able to co-localize and interact with α-synuclein. Moreover, it had also been proven that HMGB1 could aggravate α-synuclein aggregation induced autophagy dysfunction via perturbing Beclin1-Vps34 complex formation. Based on these findings, we propose that HMGB1 is involved in rotenone-induced dopaminergic cell death via interacting with α-synuclein, perturbing the autophagy process, aggravating protein aggregation and finally propelling dopaminergic neurons to move from morbidity to mortality.

The self-association of HMGB1 and its possible role in the binding to DNA and cell membrane receptors

High mobility group box 1 (HMGB1), a chromatin protein, interacts with DNA and controls gene expression. However, when HMGB1 is released from apoptotic or damaged cells, it triggers proinflammatory reactions by interacting with various receptors, mainly receptor for advanced glycation end-products (RAGE) and toll-like receptors (TLRs). The self-association of HMGB1 has been found to be crucial for its DNA-related biological functions. It is influenced by several factors, such as ionic strength, pH, specific divalent metal cations, redox environment and acetylation. This self-association may also play a role in the interaction with RAGE and TLRs and the concomitant inflammatory responses. Future studies should address the potential role of HMGB1 self-association on its interactions with DNA, RAGE and TLRs, as well as the influence of physicochemical factors in different cellular environments on these interactions.

Repeated Social Defeat, Neuroinflammation, and Behavior: Monocytes Carry the Signal

Mounting evidence indicates that proinflammatory signaling in the brain affects mood, cognition, and behavior and is linked with the etiology of psychiatric disorders, including anxiety and depression. The purpose of this review is to focus on stress-induced bidirectional communication pathways between the central nervous system (CNS) and peripheral immune system that converge to promote a heightened neuroinflammatory environment. These communication pathways involve sympathetic outflow from the brain to the peripheral immune system that biases hematopoietic stem cells to differentiate into a glucocorticoid-resistant and primed myeloid lineage immune cell. In conjunction, microglia-dependent neuroinflammatory events promote myeloid cell trafficking to the brain that reinforces stress-related behavior, and is argued to play a role in stress-related psychiatric disorders. We will discuss evidence implicating a key role for endothelial cells that comprise the blood-brain barrier in propagating peripheral-to-central immune communication. We will also discuss novel neuron-to-glia communication pathways involving endogenous danger signals that have recently been argued to facilitate neuroinflammation under various conditions, including stress. These findings help elucidate the complex communication that occurs in response to stress and highlight novel therapeutic targets against the development of stress-related psychiatric disorders.

Upregulation of heat shock protein 70 and the differential protein expression induced by tumor necrosis factor-alpha enhances migration and inhibits apoptosis of hepatocellular carcinoma cell HepG2

Tumor necrosis factor alpha (TNFα) plays diverse roles in liver damage and hepatocarcinogenesis with its multipotent bioactivity. However, the influence of TNFα on protein expression of hepatocellular carcinoma (HCC) is incompletely understood. Therefore, we aimed to investigate the differential protein expression of HCC in response to TNFα stimulus. We observed that HepG2 cell revealed a higher resistance to TNFα-induced apoptosis as compared to the non-tumorigenic hepatocyte THLE-2. By using a label-free quantitative proteomic analysis, we found that 520 proteins were differentially expressed in the HepG2 cells exposed to TNFα, including 211 up-regulated and 309 down-regulated proteins. We further confirmed several proteins with significant expression change (TNFα/control ratio>2.0 or <0.5) by immunoblotting using specific antibodies. We also analyzed the differential expressed proteins using Gene ontology and KEGG annotations, and the results implicated that TNFα might regulate ribosome, spliceosome, antigen processing and presentation, and energy metabolism in HepG2 cells. Moreover, we demonstrated that upregulation of heat shock protein 70 (HSP70) was involved in both the promoted migration and the inhibited apoptosis of HepG2 cells in response to TNFα. Collectively, these findings indicate that TNFα alters protein expression such as HSP70, which triggering specific molecular processes and signaling cascades that promote migration and inhibit apoptosis of HepG2 cells.

Ds-HMGB1 and fr-HMGB induce depressive behavior through neuroinflammation in contrast to nonoxid-HMGB1

High mobility group box 1 (HMGB1) has been implicated as a key factor in several neuroinflammatory conditions. Our previous study suggested that the release of central HMGB1 acts as a late-phase mediator in lipopolysaccharide (LPS)-induced depression. Recent findings indicate that the redox state of HMGB1 is a critical determinant of its immunomodulatory properties. Here, we aimed to investigate the potential mechanisms that link the redox states of HMGB1 to depression in mice. Distinct redox forms of recombinant HMGB1 (rHMGB1) were used that included fully reduced HMGB (fr-HMGB1), which acted as a chemokine, and disulfide-HMGB1 (ds-HMGB1), which possessed cytokine activity. Fr-HMGB1 in vivo was partially oxidized into ds-HMGB1; thus, the mutant protein non-oxidizable chemokine-HMGB (nonoxid-HMGB1) was applied. Concurrent with depressive behavior induced by four-week stress exposure, the HMGB1 concentrations in the serum and cerebral cortex substantially increased. Therefore, a single dose of rHMGB1 (200ng/5μl/mice) or vehicle was administered to mice via intracerebroventricular (i.c.v.) injection. The receptor inhibitors of TLR4/RAGE/CXCR4 (TAK-242/FPS-ZM1/AMD3100) (3mg/kg) were intraperitoneally injected 30min prior to rHMGB1 treatment. Depressive-like behavior was measured 20h post i.c.v. injection. Administration of fr-HMGB1 prolonged the immobility duration in the tail suspension test (TST) and decreased sucrose preference. In addition to depressive behavior, the hippocampal TNF-α protein slightly increased. These depressive behaviors and upregulation of hippocampal TNF-α were alleviated or abrogated by pretreatment with the inhibitors AMD3100, FPS-ZM1, and TAK-242. Alternatively, nonoxid-HMGB1 failed to induce TNF-α protein or prolong the immobility duration. As expected, ds-HMGB1 administration substantially upregulated hippocampal TNF-α protein, increased the immobility time in the TST and decreased sucrose preference. Moreover, both glycyrrhizin and TAK-242 improved ds-HMGB1-induced depressive behavior. Furthermore, TAK-242 significantly blocked the upregulation of hippocampal TNF-α protein and protected hippocampal myelin basic protein from ds-HMGB1-induced reduction. These drugs had no effect on the total or central distance in the open field test. Collectively, this initial experiment demonstrates the role and receptor mechanisms of HMGB1 under different redox states on the induction of depressive-like behavior. Both ds-HMGB1 and fr-HMGB1 may induce depressive-like behavior in vivo mainly via neuroinflammatory response activation.

Emerging role of HMGB1 in lung diseases: friend or foe

Lung diseases remain a serious problem for public health. The immune status of the body is considered to be the main influencing factor for the progression of lung diseases. HMGB1 (high‐mobility group box 1) emerges as an important molecule of the body immune network. Accumulating data have demonstrated that HMGB1 is crucially implicated in lung diseases and acts as independent biomarker and therapeutic target for related lung diseases. This review provides an overview of updated understanding of HMGB1 structure, release styles, receptors and function. Furthermore, we discuss the potential role of HMGB1 in a variety of lung diseases. Further exploration of molecular mechanisms underlying the function of HMGB1 in lung diseases will provide novel preventive and therapeutic strategies for lung diseases.

Proinflammatory effect of high-mobility group protein B1 on keratinocytes: an autocrine mechanism underlying psoriasis development

Psoriasis is an autoimmune skin disease, in which keratinocytes play a crucial pathogenic role. High-mobility group protein B1 (HMGB1) is an inflammatory factor that can be released from keratinocyte nuclei in psoriatic lesions. We aimed to investigate the proinflammatory effect of HMGB1 on keratinocytes and the contribution of HMGB1 to psoriasis development. Normal human keratinocytes were treated with recombinant human HMGB1, and the production of inflammatory factors and the intermediary signalling pathways were examined. Furthermore, the imiquimod-induced psoriasis-like mouse model was used to investigate the role of HMGB1 in psoriasis development in vivo. A total of 11 inflammatory factors were shown to be upregulated by HMGB1 in keratinocytes, among which interleukin (IL)-18 showed the greatest change. We then found that activation of the nuclear factor-κB signalling pathway and inflammasomes accounted for HMGB1-induced IL-18 expression and secretion. Moreover, HMGB1 and downstream IL-18 contributed to the development of psoriasiform dermatitis in the imiquimod-treated mice. In addition, T-helper 17 immune response in the psoriasis-like mouse model could be inhibited by both HMGB1 and IL-18 blockade. Our findings indicate that HMGB1 secreted from keratinocytes can facilitate the production and secretion of inflammatory factors such as IL-18 in keratinocytes in an autocrine way, thus promoting the development of psoriasis. Blocking the proinflammatory function of the HMGB1-IL-18 axis may be useful for psoriasis treatment in the future. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The Role of HMGB1 in the Pathogenesis of Type 2 Diabetes

Significance. With an alarming increase in recent years, diabetes mellitus has become a global challenge. Despite advances in treatment of diabetes mellitus, currently, medications available are unable to control the progression of diabetes and its complications. Growing evidence suggests that inflammation is an important pathogenic mediator in the development of diabetes mellitus. The perspectives including suggestions for new therapies involving the shift from metabolic stress to inflammation should be taken into account. Critical Issues. High-mobility group box 1 (HMGB1), a nonhistone nuclear protein regulating gene expression, was rediscovered as an endogenous danger signal molecule to trigger inflammatory responses when released into extracellular milieu in the late 1990s. Given the similarities of inflammatory response in the development of T2D, we will discuss the potential implication of HMGB1 in the pathogenesis of T2D. Importantly, we will summarize and renovate the role of HMGB1 and HMGB1-mediated inflammatory pathways in adipose tissue inflammation, insulin resistance, and islet dysfunction. Future Directions. HMGB1 and its downstream receptors RAGE and TLRs may serve as potential antidiabetic targets. Current and forthcoming projects in this territory will pave the way for prospective approaches targeting the center of HMGB1-mediated inflammation to improve T2D and its complications.

Expression of aldehyde dehydrogenase family 1 member A1 and high mobility group box 1 in oropharyngeal squamous cell carcinoma in association with survival time

Despite the development of novel multimodal treatment combinations in advanced oropharyngeal squamous cell carcinoma (OSCC), outcomes remain poor. The identification of specifically validated biomarkers is required to understand the underlying molecular mechanisms, to evaluate treatment efficiency and to develop novel therapeutic targets. The present study, therefore, examined the presence of aldehyde dehydrogenase family 1 member A1 (ALDH1A1) and high mobility group box 1 (HMGB1) expression in primary OSCC and analyzed the impact on survival time. In 59 patients with OSCC, the expression of ALDH1A1, p16 and HMGB1, and their clinicopathological data were analyzed. HMGB1 positivity was significantly increased in patients with T1-2 stage disease compared with T3-4 stage disease (P<0.001), whereas ALDH1A1 positivity was not. ALDH1A1⁺ tumors showed significantly lower differentiation than ALDH1A1^- tumors (P=0.018). Multivariate analysis showed that ALDH1A1 positivity (P=0.041) and nodal status (N2-3) (P=0.036) predicted a poor prognosis. In this patient cohort, ALDH1A1 and nodal status were identified as independent predictors of a shorter overall survival time. The study results, therefore, provide evidence of the prognostic value of ALDH1A1 as a marker for cancer stem cells and nodal status in OSCC patients.