High mobility group protein B1 (HMGB1) in Asthma: comparison of patients with chronic obstructive pulmonary disease and healthy controls

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.

Role of the inflammasome in chronic obstructive pulmonary disease (COPD)

Inflammation is central to the development of chronic obstructive pulmonary disease (COPD), a pulmonary disorder characterized by chronic bronchitis, chronic airway obstruction, emphysema, associated to progressive and irreversible decline of lung function. Emerging genetic and pharmacological evidence suggests that IL-1-like cytokines are highly detected in the sputum and broncho-alveolar lavage (BAL) of COPD patients, implying the involvement of the multiprotein complex inflammasome. So far, scientific evidence has focused on nucleotide-binding oligomerization domain-like receptors protein 3 (NLRP3) inflammasome, a specialized inflammatory signaling platform that governs the maturation and secretion of IL-1-like cytokines through the regulation of caspase-1-dependent proteolytic processing. Some studies revealed that it is involved during airway inflammation typical of COPD. Based on the influence of cigarette smoke in various respiratory diseases, including COPD, in this view we report its effects in inflammatory and immune responses in COPD mouse models and in human subjects affected by COPD. In sharp contrast to what reported on experimental and clinical studies, randomized clinical trials show that indirect inflammasome inhibitors did not have any beneficial effect in moderate to severe COPD patients.

Genetic variance is associated with susceptibility for cigarette smoke-induced DAMP release in mice

Chronic obstructive pulmonary disease (COPD) is characterized by unresolved neutrophilic airway inflammation and is caused by chronic exposure to toxic gases, such as cigarette smoke (CS), in genetically susceptible individuals. Recent data indicate a role for damage-associated molecular patterns (DAMPs) in COPD. Here, we investigated the genetics of CS-induced DAMP release in 28 inbred mouse strains. Subsequently, in lung tissue from a subset of strains, the expression of the identified candidate genes was analyzed. We tested whether small interfering RNA-dependent knockdown of candidate genes altered the susceptibility of the human A549 cell line to CS-induced cell death and DAMP release. Furthermore, we tested whether these genes were differentially regulated by CS exposure in bronchial brushings obtained from individuals with a family history indicative of either the presence or absence of susceptibility for COPD. We observed that, of the four DAMPs tested, double-stranded DNA (dsDNA) showed the highest correlation with neutrophilic airway inflammation. Genetic analyses identified 11 candidate genes governing either CS-induced or basal dsDNA release in mice. Two candidate genes ( Elac2 and Ppt1) showed differential expression in lung tissue on CS exposure between susceptible and nonsusceptible mouse strains. Knockdown of ELAC2 and PPT1 in A549 cells altered susceptibility to CS extract-induced cell death and DAMP release. In bronchial brushings, CS-induced expression of ENOX1 and ARGHGEF11 was significantly different between individuals susceptible or nonsusceptible for COPD. Our study shows that genetic variance in a mouse model is associated with CS-induced DAMP release, and that this might contribute to susceptibility for COPD.

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.

All the "RAGE" in lung disease: The receptor for advanced glycation endproducts (RAGE) is a major mediator of pulmonary inflammatory responses

The receptor for advanced glycation endproducts (RAGE) is a pro-inflammatory pattern recognition receptor (PRR) that has been implicated in the pathogenesis of numerous inflammatory diseases. It was discovered in 1992 on endothelial cells and was named for its ability to bind advanced glycation endproducts and promote vascular inflammation in the vessels of patients with diabetes. Further studies revealed that RAGE is most highly expressed in lung tissue and spurred numerous explorations into RAGE's role in the lung. These studies have found that RAGE is an important mediator in allergic airway inflammation (AAI) and asthma, pulmonary fibrosis, lung cancer, chronic obstructive pulmonary disease (COPD), acute lung injury, pneumonia, cystic fibrosis, and bronchopulmonary dysplasia. RAGE has not yet been targeted in the lungs of paediatric or adult clinical populations, but the development of new ways to inhibit RAGE is setting the stage for the emergence of novel therapeutic agents for patients suffering from these pulmonary conditions.

HMGB1 promotes HLF-1 proliferation and ECM production through activating HIF1-α-regulated aerobic glycolysis

Aerobic glycolysis is a crucial event in fibroblast differentiation, and extracellular matrix (ECM) production in the progression of pulmonary fibrosis (PF). Abnormal high mobility group protein B1 (HMGB1) activation is involved in the pathogenesis of PF. However, whether aerobic glycolysis contributes to HMGB1-induced fibroblast proliferation and ECM production in PF has not yet been determined. In this study, we investigated the effects of HMGB1 on human embryonic lung fibroblast (HLF-1) proliferation, ECM production, and aerobic glycolysis. The lactate dehydrogenase inhibitor oxamic acid (OA), and PFKFB3 inhibitor 3PO were used to block certain crucial steps of aerobic glycolysis. As a result, we observed an increase of HMGB1 in bronchoalveolar lavage fluid (BALF) in bleomycin (BLM)-treated rats as compared to non-treated rats (control group). A concentration-dependent increase of HLF-1 proliferation and expression of α-SMA and α-collagen I were observed in the HMGB1 group, as well as increases of LDHA activation, glucose uptake levels, glycolytic rate, lactate level, and ATP production. OA and 3PO, or suppression of HIF1-α, blocked the effects of HMGB1. In summary, HMGB1 promotes fibroblast proliferation and ECM production though upregulating expression of HIF1-α to induce an increase of aerobic glycolysis.

Functional interactors of three genome-wide association study genes are differentially expressed in severe chronic obstructive pulmonary disease lung tissue

In comparison to genome-wide association studies (GWAS), there has been poor replication of gene expression studies in chronic obstructive pulmonary disease (COPD). We performed microarray gene expression profiling on a large sample of resected lung tissues from subjects with severe COPD. Comparing 111 COPD cases and 40 control smokers, 204 genes were differentially expressed; none were at significant GWAS loci. The top differentially expressed gene was HMGB1, which interacts with AGER, a known COPD GWAS gene. Differentially expressed genes showed enrichment for putative interactors of the first three identified COPD GWAS genes IREB2, HHIP, and FAM13A, based on gene sets derived from protein and RNA binding studies, RNA-interference, a murine smoking model, and expression quantitative trait locus analyses. The gene module most highly associated for COPD in Weighted Gene Co-Expression Network Analysis (WGCNA) was enriched for B cell pathways, and shared seventeen genes with a mouse smoking model and twenty genes with previous emphysema studies. As in other common diseases, genes at COPD GWAS loci were not differentially expressed; however, using a combination of network methods, experimental studies and careful phenotype definition, we found differential expression of putative interactors of these genes, and we replicated previous human and mouse microarray results.

[Effect of heat shock factor 1 on airway hyperresponsiveness and airway inflammation in mice with allergic asthma]

OBJECTIVE

To investigate the effect of heat shock factor 1 (HSF1) on airway hyperresponsiveness and airway inflammation in mice with asthma and possible mechanisms.

METHODS

A total of 36 mice were randomly divided into four groups: control, asthma, HSF1 small interfering RNA negative control (siHSF1-NC), and siHSF1 intervention (n=9 each). Ovalbumin (OVA) sensitization and challenge were performed to induce asthma in the latter three groups. The mice in the siHSF1-NC and siHSF1 groups were treated with siHSF1-NC and siHSF1, respectively. A spirometer was used to measure airway responsiveness at 24 hours after the last challenge. The direct count method was used to calculate the number of eosinophils. ELISA was used to measure the serum level of OVA-specific IgE and levels of interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-13 (IL-13), and interferon-γ (IFN-γ) in lung tissues and bronchoalveolar lavage fluid (BALF). Quantitative real-time PCR was used to measure the mRNA expression of HSF1 in asthmatic mice. Western blot was used to measure the protein expression of HSF1, high-mobility group box 1 (HMGB1), and phosphorylated c-Jun N-terminal kinase (p-JNK).

RESULTS

The asthma group had significant increases in the mRNA and protein expression of HSF1 compared with the control group (P<0.05). The siHSF1 group had significantly reduced mRNA and protein expression of HSF1 compared with the siHSF1-NC group (P<0.05). The knockdown of HSF1 increased airway wall thickness, airway hyperresponsiveness, OVA-specific IgE content, and the number of eosinophils (P<0.05). Compared with the siHSF1-NC group, the siHSF1 group had significantly increased levels of IL-4, IL-5, and IL-13 and significantly reduced expression of IFN-γ in lung tissues and BALF (P<0.05), as well as significantly increased expression of HMGB1 and p-JNK (P<0.05).

CONCLUSIONS

Knockdown of HSF1 aggravates airway hyperresponsiveness and airway inflammation in asthmatic mice, and its possible mechanism may involve the negative regulation of HMGB1 and JNK.

[Effect of heat shock factor 1 on airway hyperresponsiveness and airway inflammation in mice with allergic asthma]

OBJECTIVE

To investigate the effect of heat shock factor 1 (HSF1) on airway hyperresponsiveness and airway inflammation in mice with asthma and possible mechanisms.

METHODS

A total of 36 mice were randomly divided into four groups: control, asthma, HSF1 small interfering RNA negative control (siHSF1-NC), and siHSF1 intervention (n=9 each). Ovalbumin (OVA) sensitization and challenge were performed to induce asthma in the latter three groups. The mice in the siHSF1-NC and siHSF1 groups were treated with siHSF1-NC and siHSF1, respectively. A spirometer was used to measure airway responsiveness at 24 hours after the last challenge. The direct count method was used to calculate the number of eosinophils. ELISA was used to measure the serum level of OVA-specific IgE and levels of interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-13 (IL-13), and interferon-γ (IFN-γ) in lung tissues and bronchoalveolar lavage fluid (BALF). Quantitative real-time PCR was used to measure the mRNA expression of HSF1 in asthmatic mice. Western blot was used to measure the protein expression of HSF1, high-mobility group box 1 (HMGB1), and phosphorylated c-Jun N-terminal kinase (p-JNK).

RESULTS

The asthma group had significant increases in the mRNA and protein expression of HSF1 compared with the control group (P<0.05). The siHSF1 group had significantly reduced mRNA and protein expression of HSF1 compared with the siHSF1-NC group (P<0.05). The knockdown of HSF1 increased airway wall thickness, airway hyperresponsiveness, OVA-specific IgE content, and the number of eosinophils (P<0.05). Compared with the siHSF1-NC group, the siHSF1 group had significantly increased levels of IL-4, IL-5, and IL-13 and significantly reduced expression of IFN-γ in lung tissues and BALF (P<0.05), as well as significantly increased expression of HMGB1 and p-JNK (P<0.05).

CONCLUSIONS

Knockdown of HSF1 aggravates airway hyperresponsiveness and airway inflammation in asthmatic mice, and its possible mechanism may involve the negative regulation of HMGB1 and JNK.

Inflammasomes in the lung

Innate immune responses act as first line defences upon exposure to potentially noxious stimuli. The innate immune system has evolved numerous intracellular and extracellular receptors that undertake surveillance for potentially damaging particulates. Inflammasomes are intracellular innate immune multiprotein complexes that form and are activated following interaction with these stimuli. Inflammasome activation leads to the cleavage of pro-IL-1β and release of the pro-inflammatory cytokine, IL-1β, which initiates acute phase pro-inflammatory responses, and other responses are also involved (IL-18, pyroptosis). However, excessive activation of inflammasomes can result in chronic inflammation, which has been implicated in a range of chronic inflammatory diseases. The airways are constantly exposed to a wide variety of stimuli. Inflammasome activation and downstream responses clears these stimuli. However, excessive activation may drive the pathogenesis of chronic respiratory diseases such as severe asthma and chronic obstructive pulmonary disease. Thus, there is currently intense interest in the role of inflammasomes in chronic inflammatory lung diseases and in their potential for therapeutic targeting. Here we review the known associations between inflammasome-mediated responses and the development and exacerbation of chronic lung diseases.

RAGE deficiency predisposes mice to virus-induced paucigranulocytic asthma

Asthma is a chronic inflammatory disease. Although many patients with asthma develop type-2 dominated eosinophilic inflammation, a number of individuals develop paucigranulocytic asthma, which occurs in the absence of eosinophilia or neutrophilia. The aetiology of paucigranulocytic asthma is unknown. However, both respiratory syncytial virus (RSV) infection and mutations in the receptor for advanced glycation endproducts (RAGE) are risk factors for asthma development. Here, we show that RAGE deficiency impairs anti-viral immunity during an early-life infection with pneumonia virus of mice (PVM; a murine analogue of RSV). The elevated viral load was associated with the release of high mobility group box-1 (HMGB1) which triggered airway smooth muscle remodelling in early-life. Re-infection with PVM in later-life induced many of the cardinal features of asthma in the absence of eosinophilic or neutrophilic inflammation. Anti-HMGB1 mitigated both early-life viral disease and asthma-like features, highlighting HMGB1 as a possible novel therapeutic target.

DOI:http://dx.doi.org/10.7554/eLife.21199.001

T-helper 2 cytokine-induced heat shock protein 70 secretion and its potential association with allergic rhinitis

BACKGROUND

Various inflammatory mediators have been found to be involved in the pathogenesis of allergic disease (AR). The role of heat shock proteins in AR has not been studied. The aim of this study was to investigate the levels of heat shock protein 70 (Hsp70) in the nasal lavage fluids of AR patients and controls to elucidate the role of Hsp70 in the pathogenesis of AR.

METHODS

Using an enzyme-linked immunosorbent assay, the levels of Hsp70, Hsp90, interleukin (IL)-4, IL-13, and IL-8 in nasal lavage fluid from patients were measured and statistically analyzed. Primary human nasal epithelial cells were cultured in vitro and T-helper 2 (Th2) cytokines (IL-4, IL-13) were added to the culture medium. We evaluated the mRNA and protein expression levels of Hsp70 using real-time polymerase chain reaction and western blot assay.

RESULTS

Hsp70 was easily detected in nasal lavage fluid and the levels of Hsp70 were higher in AR patients than in healthy controls. Other clinical characteristics of subjects were not significantly associated with Hsp70 levels. Furthermore, we found that treatment with IL-4 and IL-13 induced the secretion of Hsp70 in human nasal epithelial cells.

CONCLUSION

We found that Hsp70 was abundant and positively detected in nasal lavage fluid samples from all subjects, and that Hsp70 levels were significantly higher in AR patients. We demonstrated, both in vivo and in vitro, that Hsp70 could play an important role in the pathogenesis of AR, and we suggest that Hsp70 can be used as a disease marker for AR.

Respiratory Syncytial Virus Infection Triggers Epithelial HMGB1 Release as a Damage-Associated Molecular Pattern Promoting a Monocytic Inflammatory Response

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infant and elderly populations worldwide. Currently, there is no efficacious vaccine or therapy available for RSV infection. The molecular mechanisms underlying RSV-induced acute airway disease and associated long-term consequences remain largely unknown; however, experimental evidence suggests that the lung inflammatory response plays a fundamental role in the outcome of RSV infection. High-mobility group box 1 (HMGB1) is a nuclear protein that triggers inflammation when released from activated immune or necrotic cells and drives the pathogenesis of various infectious agents. Although HMGB1 has been implicated in many inflammatory diseases, its role in RSV-induced airway inflammation has not been investigated. This study investigates the molecular mechanism of action of extracellularly released HMGB1 in airway epithelial cells (A549 and small airway epithelial cells) to establish its role in RSV infection. Immunofluorescence microscopy and Western blotting results showed that RSV infection of human airway epithelial cells induced a significant release of HMGB1 as a result of translocation of HMGB1 from the cell nuclei to the cytoplasm and subsequent release into the extracellular space. Treating RSV-infected A549 cells with antioxidants significantly inhibited RSV-induced HMGB1 extracellular release. Studies using recombinant HMGB1 triggered immune responses by activating primary human monocytes. Finally, HMGB1 released by airway epithelial cells due to RSV infection appears to function as a paracrine factor priming epithelial cells and monocytes to inflammatory stimuli in the airways.

IMPORTANCE

RSV is a major cause of serious lower respiratory tract infections in young children and causes severe respiratory morbidity and mortality in the elderly. In addition, to date there is no effective treatment or vaccine available for RSV infection. The mechanisms responsible for RSV-induced acute airway disease and associated long-term consequences remain largely unknown. The oxidative stress response in the airways plays a major role in the pathogenesis of RSV. HMGB1 is a ubiquitous redox-sensitive multifunctional protein that serves as both a DNA regulatory protein and an extracellular cytokine signaling molecule that promotes airway inflammation as a damage-associated molecular pattern. This study investigated the mechanism of action of HMGB1 in RSV infection with the aim of identifying new inflammatory pathways at the molecular level that may be amenable to therapeutic interventions.

The epithelial barrier and immunoglobulin A system in allergy

Airway and intestinal epithelial layers represent first-line physical barriers, playing a key role in mucosal immunity. Barrier dysfunction, characterized by alterations such as disruption of cell-cell apical junctions and aberrant epithelial responses, probably constitutes early and key events for chronic immune responses to environmental antigens in the skin and in the gut. For instance, barrier dysfunction drives Th2 responses in atopic disorders or eosinophilic esophagitis. Such epithelial impairment is also a salient feature of allergic asthma and growing evidence indicates that barrier alterations probably play a driving role in this disease. IgA has been identified as the most abundant immunoglobulin in mucosa, where it acts as an active barrier through immune exclusion of inhaled or ingested antigens or pathogens. Historically, it has been thought to represent the serum factor underlying reaginic activity before IgE was discovered. Despite several studies about regulation and major functions of IgA at mucosal surfaces, its role in allergy remains largely unclear. This review aims at summarizing findings about epithelial functions and IgA biology that are relevant to allergy, and to integrate the emerging concepts and the recent developments in mucosal immunology, and how these could translate to clinical observations in allergy.

[Multicenter clinical efficacy observation of integrated Traditional Chinese Medicine-Western Medicine treatment in acute onset period of pulmonary heart disease]

OBJECTIVE

To evaluate the efficacy of integrated Traditional Chinese Medicine-Western Medicine (TCM-WM) in the treatment of acute onset pulmonary heart disease (PHD).

METHODS

A total of 240 patients met the inclusion criteria and were enrolled. These inpatients were divided into group A (treatment group) and B (control group) in order of admission according to the principles of randomization and control. The research was performed simultaneously in three hospitals. Two groups were given basic treatment that included: controlled oxygen therapy, active and effective anti-infection, maintaining airway patency, correcting O2 deficiency and CO2 retention, correcting acid-base imbalance and electrolyte disturbance, reducing pulmonary hypertension and treating right heart failure, nutritional support and treatment of.complications. Group A was given basic treatment and integrated Traditional Chinese Medicine (TCM) differentiating therapy; group B was given basic therapy and a placebo that was similar in appearance and taste to TCM medicinal broth of pharmaceutical preparations, provided by Yibin Pharmaceutical Company (Yibin, China, Wuliangye Group).

RESULTS

The mortality in the treatment group decreased by 4.98% compared with the control group. The treatment group reported improved ventilation, corrected hypoxemia, improved nutritional status and promoted digestive functions. It also significantly improved the patient's self-life skills, improved the patient's quality of life and could shorten the length of hospital stay.

CONCLUSION

Comprehensive integrated TCM-WM treatment showed good clinical efficacy toward the acute onset period of PHD patients.

A Systemic Inflammatory Endotype of Asthma With More Severe Disease Identified by Unbiased Clustering of the Serum Cytokine Profile

Asthma is considered as a clinical and molecularly heterogeneous disorder. Systemic inflammation is suggested to play an important role in a group of asthma patients. We hypothesized that there is a subgroup of patients with asthma characterized by systemic inflammation. In this study, we aimed to discriminate asthma subtypes based on circulating biomarkers and to determine whether a systemic inflammatory endotype of asthma could be identified. In the present cross-sectional study, 50 patients with untreated asthma were prospectively recruited from a single academic outpatient clinic, and characterized with respect to clinical, functional, and inflammatory parameters. The expression profiles of 20 serum cytokines were assessed by anti-human cytokine antibody array. Then, hierarchical clustering analysis was performed based on principal component analysis (PCA)-transformed data to classify the clinical groups. PCA showed that 6 independent components accounted for 80.113% of the variance, and PCA-based hierarchical clustering identified 3 endotypes. One of the endotypes was evidenced by elevated systemic inflammation markers such as leptin, vascular endothelial growth factor (VEGF), and reduced levels of soluble receptor for advanced glycation end products (sRAGE), an anti-inflammatory molecule. More female patients were included, with higher circulating neutrophil counts and more severe symptoms. In conclusion, we identified an endotype of asthma characterized by systemic inflammation and severe symptoms. Increased levels of VEGF, leptin and decreased level of sRAGE may contribute to the systemic inflammation of this asthma endotype.

Delivery of the high-mobility group box 1 box A peptide using heparin in the acute lung injury animal models

In this study, the efficacy of the high-mobility group box-1 box A (HMGB1A)/heparin complex was evaluated for the treatment of acute lung injury (ALI). HMGB1A is an antagonist against wild-type high-mobility group box-1 (wtHMGB1), a pro-inflammatory cytokine that is involved in ALIs. HMGB1A has positive charges and can be captured in the mucus layer after intratracheal administration. To enhance the delivery and therapeutic efficiency of HMGB1A, the HMGB1A/heparin complex was produced using electrostatic interactions, with the expectation that the nano-sized complex with a negative surface charge could efficiently penetrate the mucus layer. Additionally, heparin itself had an anti-inflammatory effect. Complex formation with HMGB1A and heparin was confirmed by atomic force microscopy. The particle size and surface charge of the HMGB1A/heparin complex at a 1:1 weight ratio were 113nm and -25mV, respectively. Intratracheal administration of the complex was performed into an ALI animal model. The results showed that the HMGB1A/heparin complex reduced pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β, more effectively than HMGB1A or heparin alone. Hematoxylin and eosin staining confirmed the decreased inflammatory reaction in the lungs after delivery of the HMGB1A/heparin complex. In conclusion, the HMGB1A/heparin complex might be useful to treat ALI.

High-mobility group box 1 impairs airway epithelial barrier function through the activation of the RAGE/ERK pathway

Recent studies have indicated that high-mobility group box 1 protein (HMGB1) and the receptor for advanced glycation end-products (RAGE) contribute to the pathogenesis of asthma. However, whether the activation of the HMGB1/RAGE axis mediates airway epithelial barrier dysfunction remains unknown. Thus, the aim of this study was to examine the effects of HMGB1 and its synergistic action with interleukin (IL)-1β on airway epithelial barrier properties. We evaluated the effects of recombinant human HMGB1 alone or in combination with IL-1β on ionic and macromolecular barrier permeability, by culturing air-liquid interface 16HBE cells with HMGB1 to mimic the differentiated epithelium. Western blot analysis and immunofluorescence staining were utilized to examine the level and structure of major junction proteins, namely E-cadherin, β-catenin, occludin and claudin-1. Furthermore, we examined the effects of RAGE neutralizing antibodies and mitogen-activated protein kinase (MAPK) inhibitors on epithelial barrier properties in order to elucidate the mechanisms involved. HMGB1 increased FITC-dextran permeability, but suppressed epithelial resistance in a dose-and time-dependent manner. HMGB1-mediated barrier hyperpermeability was accompanied by a disruption of cell-cell contacts, the selective downregulation of occludin and claudin-1, and the redistribution of E-cadherin and β-catenin. HMGB1 in synergy with IL-1β induced a similar, but greater barrier hyperpermeability and induced the disruption of junction proteins. Furthermore, HMGB1 elicited the activation of the RAGE/extracellular signal-related kinase (ERK)1/2 signaling pathway, which correlated with barrier dysfunction in the 16HBE cells. Anti-RAGE antibody and the ERK1/2 inhibitor, U0126, attenuated the HMGB1-mediated changes in barrier permeability, restored the expression levels of occludin and claudin-1 and pevented the redistribution of E-cadherin and β-catenin. Taken together, the findings of our study demonstrate that HMGB1 is capable of inducing potent effects on epithelial barrier function and that RAGE/ERK1/2 is a key signaling pathway involved in the crosstalk between formations of junction proteins and epithelial barrier dysfunction.

Rhinosinusal Inflammation and High Mobility Group Box 1 Protein: A New Target for Therapy

BACKGROUND/AIMS

High mobility group box 1 (HMGB1) is a protein belonging to the class of damage-associated molecular pattern molecules, which activates innate immunity and powerful inflammatory factors. The aim of this review is to show the importance of HMGB1 in the pathogenesis of nasal inflammatory diseases and to suggest that inhibition of HMGB1 may be an innovative therapeutic target.

METHODS

We used immunohistochemistry to study whether HMGB1 increases in chronic rhinosinusitis with nasal polyps and whether its expression is associated with eosinophils and inflammatory cytokines. Using primary cultures of human nasal epithelial cells, we localised lipopolysaccharide-induced active translocation and release of HMGB1 by immunofluorescence assay and Western blot.

RESULTS

Patients with severe symptoms have the highest HMGB1 serum levels. Glycyrrhetic acid inhibits the chemotactic and mitogenic function of HMGB1, binding to the hydrophobic residues that delimit the pockets in box A and B.

CONCLUSIONS

Chronic inflammatory diseases of the nose and paranasal sinuses are increasingly prevalent and are a financial burden for society. HMGB1 has been shown to play a role in several inflammatory diseases of otolaryngological interest. The inhibition of HMGB1 may be an innovative therapeutic target for patients with chronic upper airway inflammatory diseases having nasal obstruction as a major symptom.

The role of airway macrophages in apoptotic cell clearance following acute and chronic lung inflammation

Acute and chronic inflammatory responses in the lung are associated with the accumulation of large quantities of immune and structural cells undergoing apoptosis, which need to be engulfed by phagocytes in a process called ‘efferocytosis’. Apoptotic cell recognition and removal from the lung is mediated predominantly by airway macrophages, though immature dendritic cells and non-professional phagocytes, such as epithelial cells and mesenchymal cells, can also display this function. Efficient clearance of apoptotic cells from the airways is essential for successful resolution of inflammation and the return to lung homeostasis. Disruption of this process leads to secondary necrosis of accumulating apoptotic cells, release of necrotic cell debris and subsequent uncontrolled inflammatory activation of the innate immune system by the released ‘damage associated molecular patterns’ (DAMPS). To control the duration of the immune response and prevent autoimmune reactions, anti-inflammatory signalling cascades are initiated in the phagocyte upon apoptotic cell uptake, mediated by a range of receptors that recognise specific phospholipids or proteins externalised on, or secreted by, the apoptotic cell. However, prolonged activation of apoptotic cell recognition receptors, such as the family of receptor tyrosine kinases Tyro3, Axl and MerTK (TAM), may delay or prevent inflammatory responses to subsequent infections. In this review, we will discuss recent advances in our understanding of the mechanism controlling apoptotic cell recognition and removal from the lung in homeostasis and during inflammation, the contribution of defective efferocytosis to chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease, asthma and cystic fibrosis, and implications of the signals triggered by apoptotic cells in the susceptibility to pulmonary microbial infections.

High mobility group box 1-induced epithelial mesenchymal transition in human airway epithelial cells

Epithelial–mesenchymal transition (EMT) is implicated in bronchial remodeling and loss of lung function in chronic inflammatory airway diseases. Previous studies showed the involvement of the high mobility group box 1 (HMGB1) protein in the pathology of chronic pulmonary inflammatory diseases. However, the role of HMGB1 in EMT of human airway epithelial cells is still unclear. In this study, we used RNA sequencing to show that HMGB1 treatment regulated EMT-related gene expression in human primary-airway epithelial cells. The top five upregulated genes were SNAI2, FGFBP1, VIM, SPARC (osteonectin), and SERPINE1, while the downregulated genes included OCLN, TJP1 (ZO-1), FZD7, CDH1 (E-cadherin), and LAMA5. We found that HMGB1 induced downregulation of E-cadherin and ZO-1, and upregulation of vimentin mRNA transcription and protein translation in a dose-dependent manner. Additionally, we observed that HMGB1 induced AKT phosphorylation, resulting in GSK3β inactivation, cytoplasmic accumulation, and nuclear translocation of β-catenin to induce EMT in human airway epithelial cells. Treatment with PI3K inhibitor (LY294006) and β-catenin shRNA reversed HMGB1-induced EMT. Moreover, HMGB1 induced expression of receptor for advanced glycation products (RAGE), but not that of Toll-like receptor (TLR) 2 or TLR4, and RAGE shRNA inhibited HMGB1-induced EMT in human airway epithelial cells. In conclusion, we found that HMGB1 induced EMT through RAGE and the PI3K/AKT/GSK3β/β-catenin signaling pathway.

Association between HMGB1 and COPD: A Systematic Review

HMGB1 is an alarmin, a protein that warns and activates inflammation. Chronic obstructive pulmonary disease (COPD) is characterised by a progressive airflow obstruction and airway inflammation. Current anti-inflammatory therapies are poorly effective in maintaining lung function and symptoms of COPD. This underlines the need for finding new molecular targets involved in disease pathogenesis in order to block pathology progression. This review aims to analyse latest advances on HMGB1 role, utilisation, and potential application in COPD. To this purpose we reviewed experimental studies that investigated this alarmin as marker as well as a potential treatment in chronic obstructive pulmonary disease. This systematic review was conducted according to PRISMA guidelines. In almost all the studies, it emerged that HMGB1 levels are augmented in smokers and in patients affected by COPD. It emerged that cigarette smoking, the most well-known causative factor of COPD, induces neutrophils death and necrosis. The necrosis of neutrophil cells leads to HMGB1 release, which recruits other neutrophils in a self-maintaining process. According to the results reported in the paper both inhibiting HMGB1 and its receptor (RAGE) and blocking neutrophils necrosis (inducted by cigarette smoking) could be the aim for further studies.

High mobility group box 1: a novel mediator of Th2-type response-induced airway inflammation of acute allergic asthma

BACKGROUND

High mobility group box 1 (HMGB1) is an inflammatory mediator involved into the advanced stage of systemic inflammatory response syndrome (SIRS), and is over-expressed in bacterial sepsis and hemorrhagic shock. Recently, it has been found that the HMGB1 was abnormally expressed in induced sputum and plasma of asthmatic patients. However, the precise role of HMGB1 in the acute allergic asthma is unclear. Therefore, we aim to investigate the role HMGB1 in regulating airway inflammation of acute allergic asthma and its possible mechanism in this study.

METHODS

Forty-eight BALB/c female mice were randomly divided into four groups: control group (Control), asthma group (Asthma), HMGB1 group (HMGB1) and anti-HMGB1 (HMGB1 monoclonal antibody of mice) group (Anti-HMGB1). Acute allergic asthma mice models were established by ovalbumin (OVA)-challenge. Then, we measured the levels of HMGB1 in bronchoalveolar lavage fluid (BALF) and lung tissue of mice. Finally, after exogenous HMGB1 and/or anti-HMGB1 administration, pulmonary function test, histological analysis, Western blot, cytological analysis and ELISA assay were performed to explore the effect of HMGB1 in acute allergic asthma.

RESULTS

The levels of HMGB1 in BALF and lung tissue and the expression of HMGB1 protein in the lung tissue of asthma group were significantly higher than those in control group, respectively (P<0.01). Moreover, the HMGB1 group was showed an increased mucus secretion and infiltration of eosinophils and neutrophils in the airway of asthma mice, and a decrease of pulmonary function, compared to control group (P<0.01, respectively). Meanwhile, exogenous HMGB1 could increase the levels of IL-4, IL-5, IL-6, IL-8 and IL-17, whereas could reduce the IFN-γ in the BALF and lung tissue (P<0.05, respectively). Exogenous HMGB1 could enhance GATA3 expression of Th2 cells and attenuate the T-bet expression of Th1 cells (P<0.05, respectively), which could be abrogated after inhibiting HMGB1.

CONCLUSIONS

HMGB1 could aggravate eosinophilic inflammation in the airway of acute allergic asthma through inducing a dominance of Th2-type response and promoting the neutrophilic inflammation.

Sputum high mobility group box-1 in asthmatic children: a noninvasive sensitive biomarker reflecting disease status

BACKGROUND

The monitoring of asthma is based mainly on clinical history, physical examination, and lung function test evaluation. To improve knowledge of the disease, new biomarkers of airway inflammation, including high mobility group box-1 (HMGB1), are being developed.

OBJECTIVE

To evaluate sputum HMGB1 levels in children with stable, off-therapy, allergic asthma and to evaluate the relation between HMGB1 levels and lung function parameters.

METHODS

Fifty children with asthma (28 boys and 22 girls, median age 11.56 ± 1.41 years) and 44 healthy children (22 boys and 22 girls, median age 11.07 ± 2.12 years) were enrolled. Sputum HMGB1 was assessed in the cohort study. Lung function (predicted percentage of forced expiratory volume in 1 second [FEV1%] and forced expiratory flow between 25% and 75% [FEF25%-75%]), serum total IgE levels, and asthma severity by validated Global Initiative for Asthma criteria were recorded.

RESULTS

Sputum HMGB1 levels were higher in children with asthma than in healthy controls (100.68 ± 10.03 vs 9.60 ± 3.76 ng/mL, P < .0001). Sputum HMGB1 levels also were positively related to total IgE levels in children with asthma (r = 0.6567, P < .0001). An inverse and strict correlation between sputum HMGB1 levels and pulmonary function indices also were observed in children with mild (FEV1%, r = -0.86544, P < .0001; FEF25%-75%, r = -0.53948, P < .05), moderate (FEV1%, r = -0.99548, P < .0001; FEF25%-75%, r = -0.48668, P < .05), and severe (FEV1%, r = -0.90191, P < .0001; FEF25%-75%, r = -0.66777, P < .05) asthma.

CONCLUSION

The present study provides evidence that sputum HMGB1 is a sensitive biomarker of allergic asthma in children because it was increased and correlated directly with asthma severity and inversely with lung function indices.

Circulating soluble receptor for advanced glycation end products (sRAGE) as a biomarker of emphysema and the RAGE axis in the lung

Chronic obstructive pulmonary disease (COPD) is a complex and heterogeneous disease that has been traditionally characterized by incompletely reversible airflow limitation. Yet, the latter is poorly correlated with many other clinically relevant characteristics of the disease. Thus, the identification of biomarkers to more accurately assess this heterogeneity and disease severity may facilitate the discovery and development of new treatments and better management of patients with COPD. One molecule that has attracted attention as a potentially useful biomarker specifically for the emphysema subpopulation is the soluble receptor for advanced glycation end products (sRAGE). As the soluble isoform of a key proinflammatory signaling receptor, sRAGE acts as a "decoy" for RAGE ligands and prevents their interaction with the receptor. Multiple reports have now linked sRAGE to COPD, and more specifically to emphysema, and evidence is accumulating that this link is likely mechanistic in nature. Here we review the current state of knowledge about sRAGE biology, the mechanistic links to COPD, and the evidence for using it as a biomarker for emphysema. We also discuss sRAGE as a potential target for therapeutic intervention in COPD.

Chicken IgY facilitates allergic airway inflammation in a chemical-induced murine asthma model by potentiating IL-4 release

High mobility group box 1 (HMGB1) is a DNA-binding protein that is abundantly expressed in most tissues. Recently, HMGB1 has gained much attention for its regulation of immunity and inflammation. Yet its role in toluene diisocyanate (TDI)-induced asthma still remains poorly characterized. In this study, mice were sensitized and challenged with TDI to establish a TDI-induced asthma model. An IgY anti-HMGB1 antibody or isotype IgY was given intraperitoneally after each challenge. Airway reactivity to methacholine, airway inflammation, bronchial epithelial hyperplasia and shedding were unexpectedly aggravated after administration of the anti-HMGB1 antibody and was accompanied by increased pulmonary expression of HMGB1, especially in those mice treated with IgY. Levels of IL-4, IL-5, IL-13 and TNF-α were also elevated with TDI-induction. Primary lymphocytes from TDI sensitized and challenged mice demonstrated increased secretion of IL-4 after IgY stimulation. To confirm the effect of IgY, a cohort of mice exposed to TDI or vehicle was injected with IgY and the same results were observed after IgY treatment as in TDI asthmatic mice. Taken together, these results show that the IgY anti-HMGB1 antibody can facilitate TDI-induced allergic airway inflammation. Specifically, IgY, rather than anti-HMGB1, plays an important role in the process of exacerbated asthma, shedding light on an underappreciated role of avian IgY.

Cationic polyaspartamide-based nanocomplexes mediate siRNA entry and down-regulation of the pro-inflammatory mediator high mobility group box 1 in airway epithelial cells

High-mobility group box 1 (HMGB1) is a nonhistone protein secreted by airway epithelial cells in hyperinflammatory diseases such as asthma. In order to down-regulate HMGB1 expression in airway epithelial cells, siRNA directed against HMGB1 was delivered through nanocomplexes based on a cationic copolymer of poly(N-2-hydroxyethyl)-d,l-aspartamide (PHEA) by using H441 cells. Two copolymers were used in these experiments bearing respectively spermine side chains (PHEA-Spm) and both spermine and PEG2000 chains (PHEA-PEG-Spm). PHEA-Spm and PHEA-PEG-Spm derivatives complexed dsDNA oligonucleotides with a w/w ratio of 1 and higher as shown by a gel retardation assay. PHEA-Spm and PHEA-PEG-Spm siRNA polyplexes were sized 350-650 nm and 100-400 nm respectively and ranged from negativity/neutrality (at 0.5 ratio) to positivity (at 5 ratio) as ζ potential. Polyplexes formed either at a ratio of 0.5 (partially complexing) or at the ratio of 5 (fully complexing) were tested in subsequent experiments. Epifluorescence revealed that nanocomplexes favored siRNA entry into H441 cells in comparison with naked siRNA. As determined by flow cytometry and a trypan blue assay, PHEA-Spm and PHEA-PEG-Spm allowed siRNA uptake in 42-47% and 30% of cells respectively, however only with PHEA-Spm at w/w ratio of 5 these percentages were significantly higher than those obtained with naked siRNA (20%). Naked siRNA or complexed scrambled siRNA did not exert any effect on HMGB1mRNA levels, whereas PHEA-Spm/siRNA at the w/w ratio of 5 down-regulated HMGB1 mRNA up to 58% of control levels (untransfected cells). PEGylated PHEA-Spm/siRNA nanocomplexes were able to down-regulate HMGB1 mRNA levels up to 61% of control cells. MTT assay revealed excellent biocompatibility of copolymer/siRNA polyplexes with cells. In conclusion, we have found optimal conditions for down-regulation of HMGB1 by siRNA delivery mediated by polyaminoacidic polymers in airway epithelial cells in the absence of cytotoxicity. Functional and in-vivo studies are warranted.

Phosphatidylinositol 3-kinases pathway mediates lung caspase-1 activation and high mobility group box 1 production in a toluene-diisocyanate induced murine asthma model

We have previously demonstrated that downregulating HMGB1 decreases airway neutrophil inflammation in a toluene-diisocyanate (TDI)-induced murine asthma model, yet how HMGB1 is regulated in the lung remains uncertain. In this study, we intended to explore whether PI3K signaling pathway mediates pulmonary HMGB1 production in TDI-induced asthma model and the possible roles of NLRP3 inflammasome and caspase-1 in this process. BALB/c mice were sensitized and challenged with TDI to establish a TDI-induced asthma model. LY294002, a specific inhibitor of PI3K, was given intratracheally 1h before each challenge. Here we showed that airway hypersensitivity, airway infiltration of neutrophils and eosinophils, serum IgE and IL-4 in supernatant of cervical lymphocytes in TDI induced asthmatic mice were all markedly decreased by LY294002, accompanied by suppressed pulmonary expression of HMGB1. At the same time, we observed elevated protein levels of cleaved caspase-1 and IL-1β after TDI challenge, as well as increased immunoreactivity in lung, all of which were significantly recovered by LY294002. While both the protein expression and immunodistribution of NLRP3 in the lung stayed unchanged. These data suggest that PI3K mediates lung caspase-1 activation and HMGB1 production in TDI-induced murine asthma model.

HMGB1 binding to receptor for advanced glycation end products enhances inflammatory responses of human bronchial epithelial cells by activating p38 MAPK and ERK1/2

The proinflammatory factor high mobility group box protein 1 (HMGB1) has been implicated as an important mediator of many chronic inflammatory diseases, including asthma. Human bronchial epithelial cells (HBECs) play a central role in the pathogenesis of asthma. However, the effects of HMGB1 on HBECs and the underlying mechanisms remain unknown. Here, we investigated receptor expression and proinflammatory cytokine production by primary cultures of HBECs stimulated by HMGB1. We then examined the effects of specific receptor blockade and inhibition of p38 MAPK, ERK1/2, or PI3-K on HMGB1-induced expression of proinflammatory cytokines. HMGB1 increased the expression and secretion of TNF-α, TSLP, MMP-9, and VEGF in a dose- and time-dependent manner. HMGB1 also induced elevated expression of RAGE protein. Secretion of TNF-α, VEGF, MMP-9, and TSLP was significantly decreased by RAGE blockade and p38 MAPK pathway inhibition, while a less pronounced effect was mediated by ERK1/2 inhibition. These observations suggest that HMGB1 binds RAGE and promotes activities of p38 MAPK and ERK1/2 pathways in HBECs. This then enhances the expression of TNF-α, VEGF, MMP-9, and TSLP, which are the important inflammatory factors in asthma. These results demonstrate that HMGB1 enhances the inflammatory responses of HBECs, which are involved in the modulation of inflammatory processes in asthma.

Physiologic concentrations of HMGB1 have no impact on cytokine-mediated eosinophil survival or chemotaxis in response to Eotaxin-2 (CCL24)

HMGB1 is an alarmin that can stimulate the innate immune system alone or in a complex with other inflammatory mediators. Given the recent interest in HMGB1 with respect to the pathogenesis of eosinophil-associated disorders, including asthmatic inflammation and chronic rhinosinusitis, we have explored the role of this mediator and in promoting eosinophil activation. HMGB1 receptors RAGE and TLR4 but not TLR2 were detected on freshly isolated human eosinophils from healthy donors. Physiologic and relevant pathophysiologic levels of biologically-active HMGB1 had no effect on survival of human eosinophils alone or in combination with pro-survival cytokines IL-5, IL-3, or GM-CSF, and increasing concentrations of HMGB1 had no impact on surface expression of RAGE, TLR2 or TLR4. Similarly, HMGB1 did not elicit chemotaxis of human eosinophils alone and had no effect in combination with the eosinophil chemotactic agent, eotaxin-2 (CCL24). However, surface expression of TLR2 and TLR4 increased in response to cell stress, notably on eosinophils that remain viable after 48 hours without IL-5. As such, HMGB1 signaling on eosinophils may be substantially more detailed, and may involve complex immunostimulatory pathways other than or in addition to those evaluated here.

High-mobility group box-1 induces vascular remodelling processes via c-Jun activation

Extracellular high-mobility group box-1 (HMGB1) acts as a signalling molecule during inflammation, cell differentiation and angiogenesis. Increased abundance of HMGB1 is associated with several pathological disorders such as cancer, asthma and chronic obstructive pulmonary disease (COPD). In this study, we investigated the relevance of HMGB1 in the pathological remodelling present in patients with idiopathic pulmonary arterial hypertension (IPAH) and pulmonary hypertension (PH) associated with COPD. Remodelled vessels present in COPD with PH and IPAH lung samples were often surrounded by HMGB1-positive cells. Increased HMGB1 serum levels were detected in both patient populations compared to control samples. The effects of physiological HMGB1 concentrations were then examined on cellular responses in vitro. HMGB1 enhanced proliferation of pulmonary arterial smooth muscle cells (PASMC) and primary human arterial endothelial cells (PAEC). HMGB1 stimulated p38, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) phosphorylation. Furthermore, activation of the downstream AP-1 complex proteins c-Fos and c-Jun was observed. Silencing of c-Jun ablated the HMGB1-induced proliferation in PASMC. Thus, an inflammatory component such as HMGB1 can contribute to PASMC and PAEC proliferation and therefore potentially to vascular remodelling and PH pathogenesis.

High mobility group box 1 induced human lung myofibroblasts differentiation and enhanced migration by activation of MMP-9

High mobility group box 1 (HMGB1) is a nuclear protein that involves the binding with DNA and influences chromatin regulation and transcription. HMGB1 is also a cytokine that can activate monocytes and neutrophils involved in inflammation. In this study, we investigated the role of HMGB1 on cellular activation using human fibroblast cell line WI-38. After treatment with 1, 10, and 100 ng/mL of HMGB1 for 24 h, we did not find obviously cytotoxicity and cellular proliferation of WI-38 cells by MTT and BrdU incorporation assay, respectively. However, we found that treatment with 10 and 100 ng/mL of HMGB1 induced the differentiation of lung fibroblasts into myofibroblasts and myofibroblasts showed higher migration ability through activation of matrix metalloproteinase (MMP)-9 activation. To delineate the mechanism underlying HMGB1-induced cellular migration, we examined HMGB1-induced mitogen activated protein kinases (MAPKs), including extracellular signal related kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen activated protein kinase (p38) phosphorylation, as well as nuclear factor (NF)-κB nuclear translocation. Using specific inhibitors and shRNAs of protein kinases, we observed that repression of ERK, JNK, p38, and NF-κB all inhibited HMGB1-induced cellular differentiation, migration and MMP-9 activation in WI-38 cells. In addition, knocking down of RAGE but not TLR2 and TLR4 by shRNAs attenuated HMGB1-induced myofibroblast differentiation and migration. In conclusion, our study demonstrated that HMGB1 induced lung fibroblasts’ differentiation into myofibroblasts and enhanced cell migration through induction of MMP-9 activation and the RAGE-MAPK and NF-κB interaction signaling pathways. Targeting HMGB1 might be a potential therapeutic approach for alleviation of airway remodeling seen in chronic airway inflammatory diseases.

Elevated HMGB1-related interleukin-6 is associated with dynamic responses of monocytes in patients with active pulmonary tuberculosis

There were limited studies assessing the role of HMGB1 in TB infection. In this prospective study, we aimed to assess the levels of HMGB1 in plasma or sputum from active pulmonary tuberculosis (APTB) patients positive for Mtb culture test, and to evaluate its relationship with inflammatory cytokines and innate immune cells. A total of 36 sputum Mtb culture positive APTB patients and 32 healthy volunteers (HV) were included. Differentiated THP-1 cells were treated for 6, 12 and 24 hrs with BCG at a multiplicity of infection of 10. The absolute values and percentages of white blood cells (WBC), neutrophils, lymphocytes, and monocytes were detected by an automatic blood analyzer. Levels of HMGB1, IL-6, IL-10 and TNF-α in plasma, sputum, or cell culture supernatant were measured by ELISA. The blood levels of HMGB1, IL-6, IL-10 and TNF-α, the absolute values of WBC, monocytes and neutrophils, and the percentage of monocytes were significant higher in APTB patients than those in HV groups (P < 0.05). The sputum levels of HMGB1, IL-10, and TNF-α were also significantly higher in APTB patients than those in HV groups (P < 0.05). Meanwhile, plasma level of HMGB1, IL-6, and IL-10 in APTB patients were positively correlated with those in sputum (P < 0.05), respectively. IL-6 was positively correlated with HMGB1 both in plasma and sputum of APTB patients (P < 0.05). HMGB1 and IL-6 is positively correlated with the absolute number of monocytes in APTB patients (P < 0.05). BCG induced HMGB1, IL-6, IL-10 and TNF-α production effectively in PMA-treated THP-1 cells. HMGB1 may be used as an attractive biomarker for APTB diagnosis and prognosis and may reflect the inflammatory status of monocytes in patients with APTB.

Level of secreted HMGB1 correlates with severity of inflammation in chronic rhinosinusitis

OBJECTIVE

High mobility group box 1 (HMGB1) protein is a chromatin protein that functions as a proinflammatory cytokine when secreted in response to inflammatory stimuli. The purpose of this study was to determine the relationship between the HMGB1 level in nasal secretions and the severity of inflammation in chronic rhinosinusitis.

STUDY DESIGN

This was a cross-sectional study.

METHODS

Nasal secretions were obtained by irrigation of the affected sinonasal cavities with normal saline. Total 63 nasal lavage fluid samples were collected from 38 patients with chronic rhinosinusitis who underwent endoscopic sinus surgery. Levels of HMGB1 and tumor necrosis factor alpha, interleukin (IL)-1β, and IL-8 were determined by enzyme-linked immunoassay. Severity of inflammation was assessed by the Lund-Mackay scoring system, which is based on preoperative computed tomography scans. Concurrent medical disorders, presence of nasal polyps, septal deviation, and allergic rhinitis were also investigated.

RESULTS

The level of HMGB1 in nasal lavage fluid was positively correlated with the Lund-Mackay score. The score was the only factor associated with HMGB1 by univariate and multivariate analysis. Other cytokines, with the exception of IL-8, were not correlated with the Lund-Mackay score.

CONCLUSION

Our results showed that HMGB1 is secreted into the extracellular area space in the upper airway, and HMGB1 levels in nasal lavage fluid correlate with severity of inflammation, as assessed by the Lund-Mackay staging system for chronic rhinosinusitis. These results provide evidence for HMGB1 as an inflammatory mediator associated with the severity of chronic rhinosinusitis.

HMGB1 in health and disease

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

HMGB1 contributes to allergen-induced airway remodeling in a murine model of chronic asthma by modulating airway inflammation and activating lung fibroblasts

The pro-inflammation factor high-mobility group box protein 1 (HMGB1) has been implicated in the pathogenesis of asthma. In this study, we used a murine model of chronic asthma to evaluate the effects of HMGB1 on airway remodeling. Female BALB/c mice were randomly divided into four groups: control, ovalbumin (OVA) asthmatic, OVA+isotype antibody and OVA+anti-HMGB1 antibody. Anti-HMGB1 antibody therapy was started on day 21 and was administered three times per week for 6 weeks before intranasal challenge with OVA. In this mouse model, HMGB1 expression is significantly elevated. The anti-HMGB1 antibody group exhibited decreased levels of immunoglobulin E (IgE) and inflammatory mediators and reduced inflammatory cell accumulation, airway hyperresponsiveness (AHR), mucus synthesis, smooth muscle thickness and lung collagen content compared with the OVA groups. Treatment with HMGB1 increased proliferation, migration, collagen secretion and α-smooth muscle actin (SMA) expression in MRC-5 cells. Treatment with the HMGB1/IL-1β complex significantly increased the expression and secretion of transforming growth factor (TGF-β1), matrix metalloproteinase (MMP)-9 and vascular endothelial growth factor (VEGF). Altogether, these results suggest that blocking HMGB1 activity may reverse airway remodeling by suppressing airway inflammation and modulating lung fibroblast phenotype and activation.

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

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

Asthma research in China: a five-year review

Asthma is one of the most common chronic diseases worldwide with increasing morbidity. China has the largest asthmatic population and is one of the countries with the highest asthma mortality. Fortunately, asthma research in China, both clinical and scientific, has developed markedly over the past few years. This has resulted in significant increases in our understanding of Chinese asthma prevalence, risk factors, control status, pathogenesis, and new prevention or treatment strategies. In this review, the major achievements of asthma research in China from 2008 to 2012 are summarized.

Changes of HMGB1 and sRAGE during the recovery of COPD exacerbation

BACKGROUND

Acute exacerbation of chronic obstructive pulmonary disease is associated with increased airway and systemic inflammation. However, the correlation between acute exacerbation/convalescence of chronic obstructive pulmonary disease (COPD) and simultaneous changes of high mobility group protein B1 (HMGB1) and soluble RAGE (sRAGE) levels has not been clearly clarified. The aim of this study was to assess these issues.

METHODS

A total of 44 COPD patients were recruited. Following a structured interview, plasma levels of HMGB1, sRAGE, fibrinogen and serum level of high-sensitivity C-reactive protein (hsCRP) were measured in patients with acute exacerbation of COPD (AECOPD) within 24 h of hospitalization and pre-discharge (convalescence). All patients were examined with spirometry in convalescence of COPD.

RESULTS

There was a significant decline in plasma HMGB1 (P<0.01), sRAGE (P<0.05), fibrinogen (P<0.01) and serum hsCRP (P<0.01) levels from acute exacerbation to convalescence phase of COPD. Changes of sRAGE was significantly correlated with changes of HMGB1 (r=0.4, P=0.007). COPD disease status correlated with the ratio of HMGB1/sRAGE, but not gender, age, course of disease, smoking history and FEV1% pred. Levels of HMGB1 and sRAGE were the highest in the current smoker group, and significantly decreased in ex-smoker group in both acute exacerbation and convalescence phase of COPD, however, their levels in never smoker group were higher than ex-smoker group in either phase of COPD.

CONCLUSIONS

HMGB1 and sRAGE levels were dynamically changed between exacerbation and convalescence phase of COPD, HMGB1 and sRAGE were likely not only a potential marker in COPD exacerbation but also a therapeutic target for COPD treatment.

Ethyl pyruvate decreases airway neutrophil infiltration partly through a high mobility group box 1-dependent mechanism in a chemical-induced murine asthma model

BACKGROUND

Diisocyanates are one of the leading causes of occupational asthma, which is dominated by granulocytic inflammation in the airway. In this study, we intended to explore the role of ethyl pyruvate (EP) on neutrophil infiltration in a toluene-2,4-diisocyanate (TDI)-induced murine asthma model.

METHODS

The experimental mice were first dermally sensitized and then challenged with TDI via oropharyngeal aspiration. The mice were treated intraperitoneally with 100, 50 or 10mg/kg EP 1h before each challenge. One day after the last challenge, airway reactivity to methacholine was measured by a barometric plethysmographic chamber. Total and differential cell counts, along with levels of macrophage inflammatory protein-2 (MIP-2), TNF-α in bronchoalveolar lavage (BAL) fluid and mRNA expression of CXCR2 in the lung were assessed. To depict neutrophils, a naphthol AS-D chloroacetate esterase kit was used. High mobility group box 1 (HMGB1) was determined by western blot and immunohistochemistry.

RESULTS

Treatment with EP dramatically decreased airway hyperresponsiveness in TDI-challenged mice, as well as numbers of neutrophils in BAL fluid and peribronchovascular regions. Both the TDI-induced raised protein level and abnormal distribution of HMGB1 were significantly recovered by EP in a dose-dependent manner. The concentration of MIP-2 in TDI-induced asthma mice was significantly higher than that of the control ones, while EP had few effects on MIP-2. The mRNA expression of CXCR2 didn't change significantly, and TNF-α was not detected in BAL fluids.

CONCLUSION

EP reduces airway neutrophil infiltration partly through downregulating HMGB1 in a chemical-induced murine asthma model.

Smoking exposure induces human lung endothelial cell adaptation to apoptotic stress

Prolonged exposure to cigarette smoking is the main risk factor for emphysema, a component of chronic obstructive pulmonary diseases (COPDs) characterized by destruction of alveolar walls. Moreover, smoking is associated with pulmonary artery remodeling and pulmonary hypertension, even in the absence of COPD, through as yet unexplained mechanisms. In murine models, elevations of intra- and paracellular ceramides in response to smoking have been implicated in the induction of lung endothelial cell apoptosis, but the role of ceramides in human cell counterparts is yet unknown. We modeled paracrine increases (outside-in) of palmitoyl ceramide (Cer16) in primary human lung microvascular cells. In naive cells, isolated from nonsmokers, Cer16 significantly reduced cellular proliferation and induced caspase-independent apoptosis via mitochondrial membrane depolarization, apoptosis-inducing factor translocation, and poly(ADP-ribose) polymerase cleavage. In these cells, caspase-3 was inhibited by ceramide-induced Akt phosphorylation, and by the induction of autophagic microtubule-associated protein-1 light-chain 3 lipidation. In contrast, cells isolated from smokers exhibited increased baseline proliferative features associated with lack of p16(INK4a) expression and Akt hyperphosphorylation. These cells were resistant to Cer16-induced apoptosis, despite presence of both endoplasmic reticulum stress response and mitochondrial membrane depolarization. In cells from smokers, the prominent up-regulation of Akt pathways inhibited ceramide-triggered apoptosis, and was associated with elevated sphingosine and high-mobility group box 1, skewing the cell's response toward autophagy and survival. In conclusion, the cell responses to ceramide are modulated by an intricate cross-talk between Akt signaling and sphingolipid metabolites, and profoundly modified by previous cigarette smoke exposure, which selects for an apoptosis-resistant phenotype.

Soluble receptor for advanced glycation end-products and progression of airway disease

Background

The receptor for advanced glycation end-products (RAGE) is highly expressed in the lung, where it is believed to have a homeostatic role. Reduced plasma levels of soluble RAGE (sRAGE) have been reported in patients with chronic obstructive pulmonary disease (COPD). The aim of the present study was to evaluate the association of plasma sRAGE levels with a longitudinal decline of lung function. We have also measured plasma levels of high mobility group box 1 (HMGB1), a RAGE ligand which has been associated with chronic inflammatory diseases including COPD.

Methods

Baseline plasma concentrations of sRAGE and HMGB1 were measured in non-smokers (n = 32), smokers without COPD (n = 212), and smokers with COPD (n = 51), and the associations of the plasma sRAGE and HMGB1 levels with longitudinal declines of lung function during a 4-year follow-up period were analysed.

Results

The plasma levels of sRAGE were significantly lower in smokers without COPD and in smokers with COPD, as compared to those of non-smokers. Plasma sRAGE levels positively correlated with FVC and FEV₁ and inversely correlated with BMI and pack-years. Lower sRAGE levels were associated with greater declines of FEV₁/FVC over 4 years in all participants. Moreover, multivariate regression analysis indicated that the baseline plasma sRAGE concentration was an independent predictor of FEV₁/FVC decline in all groups. A subgroup analysis showed that decreased sRAGE levels are significantly associated with a more rapid decline of FEV₁/FVC in smokers with COPD. There was no significant correlation between plasma HMGB1 levels and longitudinal decline of lung function.

Conclusions

Lower plasma concentrations of sRAGE were associated with greater progression of airflow limitations over time, especially in smokers with COPD, suggesting that RAGE might have a protective role in the lung.

DAMPs activating innate and adaptive immune responses in COPD

Chronic obstructive pulmonary disease (COPD), a progressive lung disease characterized by sustained neutrophilic airway inflammation, is caused by chronic exposure to noxious stimuli, e.g., cigarette smoke. This chronic exposure can induce immunogenic cell death of structural airway cells, inducing the release of damage-associated molecular patterns (DAMPs). Levels of several DAMPs, including S100 proteins, defensins, and high-mobility group box-1 (HMGB1), are increased in extracellular lung fluids of COPD patients. As DAMPs can attract and activate immune cells upon binding to pattern recognition receptors, we propose that their release may contribute to neutrophilic airway inflammation. In this review, we discuss the novel role of DAMPs in COPD pathogenesis. Relevant DAMPs are categorized based on their subcellular origin, i.e. cytoplasm, endoplasmic reticulum, nucleus, and mitochondria. Furthermore, their potential role in the pathophysiology of COPD will be discussed.

Association of plasma sRAGE, but not esRAGE with lung function impairment in COPD

Rationale

Plasma soluble Receptor for Advanced Glycation End Product (sRAGE) is considered as a biomarker in COPD. The contribution of endogenous sRAGE (esRAGE) to the pool of plasma sRAGE and the implication of both markers in COPD pathogenesis is however not clear yet. The aim of the current study was therefore to measure plasma levels of esRAGE comparative to total sRAGE in patients with COPD and a control group. Further, we established the relations of esRAGE and total sRAGE with disease specific characteristics such as lung function and D_LCO, and with different circulating AGEs.

Methods

Plasma levels of esRAGE and sRAGE were measured in an 88 patients with COPD and in 55 healthy controls. FEV₁ (%predicted) and FEV₁/VC (%) were measured in both groups; D_LCO (%predicted) was measured in patients only. In this study population we previously reported that the AGE N^ϵ-(carboxymethyl) lysine (CML) was decreased, N^ϵ-(carboxyethyl) lysine (CEL) increased and pentosidine was not different in plasma of COPD patients compared to controls.

Results

Plasma esRAGE (COPD: 533.9 ± 412.4, Controls: 848.7 ± 690.3 pg/ml; p = 0.000) was decreased in COPD compared to controls. No significant correlations were observed between plasma esRAGE levels and lung function parameters or plasma AGEs. A positive correlation was present between esRAGE and total sRAGE levels in the circulation. Confirming previous findings, total sRAGE (COPD: 512.6 ± 403.8, Controls: 1834 ± 804.2 pg/ml; p < 0.001) was lower in patients compared to controls and was positively correlated FEV₁ (r = 0.235, p = 0.032), FEV₁/VC (r = 0.218, p = 0.047), and D_LCO (r = 0.308, p = 0.006). sRAGE furthermore did show a significant positive association with CML (r = 0.321, p = 0.003).

Conclusion

Although plasma esRAGE is decreased in COPD patients compared to controls, only total sRAGE showed a significant and independent association with FEV₁, FEV₁/VC and D_LCO, indicating that total sRAGE but not esRAGE may serve as marker of COPD disease state and severity.

Receptor for advanced glycation end products and its ligand high-mobility group box-1 mediate allergic airway sensitization and airway inflammation

BACKGROUND

The receptor for advanced glycation end products (RAGE) shares common ligands and signaling pathways with TLR4, a key mediator of house dust mite (Dermatophagoides pteronyssinus) (HDM) sensitization. We hypothesized that RAGE and its ligand high-mobility group box-1 (HMGB1) cooperate with TLR4 to mediate HDM sensitization.

OBJECTIVES

To determine the requirement for HMGB1 and RAGE, and their relationship with TLR4, in airway sensitization.

METHODS

TLR4(-/-), RAGE(-/-), and RAGE-TLR4(-/-) mice were intranasally exposed to HDM or cockroach (Blatella germanica) extracts, and features of allergic inflammation were measured during the sensitization or challenge phase. Anti-HMGB1 antibody and the IL-1 receptor antagonist Anakinra were used to inhibit HMGB1 and the IL-1 receptor, respectively.

RESULTS

The magnitude of allergic airway inflammation in response to either HDM or cockroach sensitization and/or challenge was significantly reduced in the absence of RAGE but not further diminished in the absence of both RAGE and TLR4. HDM sensitization induced the release of HMGB1 from the airway epithelium in a biphasic manner, which corresponded to the sequential activation of TLR4 then RAGE. Release of HMGB1 in response to cockroach sensitization also was RAGE dependent. Significantly, HMGB1 release occurred downstream of TLR4-induced IL-1α, and upstream of IL-25 and IL-33 production. Adoptive transfer of HDM-pulsed RAGE(+/+)dendritic cells to RAGE(-/-) mice recapitulated the allergic responses after HDM challenge. Immunoneutralization of HMGB1 attenuated HDM-induced allergic airway inflammation.

CONCLUSION

The HMGB1-RAGE axis mediates allergic airway sensitization and airway inflammation. Activation of this axis in response to different allergens acts to amplify the allergic inflammatory response, which exposes it as an attractive target for therapeutic intervention.

Innate immunity but not NLRP3 inflammasome activation correlates with severity of stable COPD

Background

In models of COPD, environmental stressors induce innate immune responses, inflammasome activation and inflammation. However, the interaction between these responses and their role in driving pulmonary inflammation in stable COPD is unknown.

Objectives

To investigate the activation of innate immunity and inflammasome pathways in the bronchial mucosa and bronchoalveolar lavage (BAL) of patients with stable COPD of different severity and control healthy smokers and non-smokers.

Methods

Innate immune mediators (interleukin (IL)-6, IL-7, IL-10, IL-27, IL-37, thymic stromal lymphopoietin (TSLP), interferon γ and their receptors, STAT1 and pSTAT1) and inflammasome components (NLRP3, NALP7, caspase 1, IL-1β and its receptors, IL-18, IL-33, ST2) were measured in the bronchial mucosa using immunohistochemistry. IL-6, soluble IL-6R, sgp130, IL-7, IL-27, HMGB1, IL-33, IL-37 and soluble ST2 were measured in BAL using ELISA.

Results

In bronchial biopsies IL-27+ and pSTAT1+ cells are increased in patients with severe COPD compared with control healthy smokers. IL-7+ cells are increased in patients with COPD and control smokers compared with control non-smokers. In severe stable COPD IL-7R+, IL-27R+ and TSLPR+ cells are increased in comparison with both control groups. The NALP3 inflammasome is not activated in patients with stable COPD compared with control subjects. The inflammasome inhibitory molecules NALP7 and IL-37 are increased in patients with COPD compared with control smokers. IL-6 levels are increased in BAL from patients with stable COPD compared with control smokers with normal lung function whereas IL-1β and IL-18 were similar across all groups.

Conclusions

Increased expression of IL-27, IL-37 and NALP7 in the bronchial mucosa may be involved in progression of stable COPD.

Increased expression of high-mobility group protein B1 in chronic rhinosinusitis

BACKGROUND

Chronic rhinosinusitis (CRS) is an inflammation of the sinonasal mucosa and many inflammatory cells and cytokines are involved in its pathogenesis. High-mobility group protein B1 (HMGB1) is a DNA-binding protein that has a proinflammatory function when secreted into extracellular space. The purpose of this study was to evaluate the expression of HMGB1 in paranasal sinus mucosa and to determine the difference of HMGB1 expression between CRS patients and normal controls.

METHODS

Paranasal sinus mucosa was obtained from 10 patients with CRS and 10 patients without CRS. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR and Western blot analysis were performed to detect mRNA and protein. Sections of the mucosa were immunostained for localization of HMGB1 and image analysis was performed.

RESULTS

RT-PCR and real-time PCR showed that the expression level of HMGB1 mRNA was significantly increased in the tissues of patients with CRS compared with controls. Western blot analysis showed that the expression level of HMGB1 protein was significantly increased in the tissues of CRS. In immunohistochemical staining, the HMGB1 protein was expressed in epithelial cells and inflammatory cells and the expression intensity of HMGB1 protein was stronger in CRS.

CONCLUSION

HMGB1 is increased in the paranasal sinus mucosa of patients with CRS. These results suggest a possible contribution of HMGB1 in the pathophysiology of CRS.