The genetic variation of the human HMGB1 gene

High Mobility Group Proteins in Sepsis

Sepsis, a systemic inflammatory response disease, is the most severe complication of infection and a deadly disease. High mobility group proteins (HMGs) are non-histone nuclear proteins binding nucleosomes and regulate chromosome architecture and gene transcription, which act as a potent pro-inflammatory cytokine involved in the delayed endotoxin lethality and systemic inflammatory response. HMGs increase in serum and tissues during infection, especially in sepsis. A growing number of studies have demonstrated HMGs are not only cytokines which can mediate inflammation, but also potential therapeutic targets in sepsis. To reduce sepsis-related mortality, a better understanding of HMGs is essential. In this review, we described the structure and function of HMGs, summarized the definition, epidemiology and pathophysiology of sepsis, and discussed the HMGs-related mechanisms in sepsis from the perspectives of non-coding RNAs (microRNA, long non-coding RNA, circular RNA), programmed cell death (apoptosis, necroptosis and pyroptosis), drugs and other pathophysiological aspects to provide new targets and ideas for the diagnosis and treatment of sepsis.

Serum Level of High-Mobility Group Box Protein 1 as a Potential Treatment Target in Egyptian Sickle Cell Disease Patients

Background: During tissue injury, high mobility group box 1 (HMGB1) is passively released from necrotic cells and actively secreted by inflammatory cells. Extracellular HMGB1 acts as an amplifier of Toll-Like Receptor (TLR)-dependent inflammation rather than a primary trigger of inflammation. We studied HMGB1 quantitative trait locus reference sequence 2249825 (rs2249825) and its serum level in both sickle cell disease (SCD) patients and healthy subjects to explore its possible role in the pathogenesis of vaso-occlusive crises (VOCs). Methods: HMGB1 rs2249825 was assayed in peripheral blood samples using real-time polymerase chain reaction (RT-PCR). While the serum level was assayed using a two-site enzyme-linked immunosorbent technique (ELISA). Results: Both the SCD patients and the control group had comparable HMGB1 rs2249825 genotype frequencies (P-value >0.05). SCD patients at their steady-state showed statistically significantly higher serum HMGB1 levels than the healthy controls, a median of 0.6 ng/ml with a range of 0.1- 85 ng/ml versus a median of 0.3 ng/ml and a range of 0.1-3 ng/ml (P-value <0.001), respectively. Statistically significant skewed high serum HMGB1 in the VOC samples in contrast to the steady-state samples was observed in the SCD patients with a median of 3.2 ng/ml and a range of 0.3-76.4 ng/ml versus a median of 0.2 ng/ml and a range 0.2-7.4 ng/ml (P-value <0.0001), respectively.     Conclusion: HMGB1 could have a role in the VOC pathogenesis, hence it is suggested as a potential additive therapeutic target in SCD in general and in vaso-occlusions in specific. Keywords: Sickle cell disease, HMGB1, Hemoglobin S

High-Mobility Group Box-1 and Its Potential Role in Perioperative Neurocognitive Disorders

Aseptic surgical trauma provokes the release of HMGB1, which engages the innate immune response after binding to pattern-recognition receptors on circulating bone marrow-derived monocytes (BM-DM). The initial systemic inflammation, together with HMGB1, disrupts the blood-brain barrier allowing penetration of CCR2-expressing BM-DMs into the hippocampus, attracted by the chemokine MCP-1 that is upregulated by HMGB1. Within the brain parenchyma quiescent microglia are activated and, together with the translocated BM-DMs, release proinflammatory cytokines that disrupt synaptic plasticity and hence memory formation and retention, resulting in postoperative cognitive decline (PCD). Neutralizing antibodies to HMGB1 prevents the inflammatory response to trauma and PCD.

Decreased Expression of the High Mobility Group Box 1 (HMGB1) Gene in Peripheral Blood in Patients with Mild or Moderate Clostridioides difficile Infection

Cytokines are mediators of inflammation induced in the course of Clostridioides difficile infection (CDI). High Mobility Group Box 1 (HMGB1) is a cytokine playing an important role in the pathogenesis of numerous inflammatory and autoimmune diseases. The aim of the study was to assess the HMGB1 gene expression in the course of CDI. We have performed a prospective case-control study- including 55 adult patients, among them 27 with CDI, who were hospitalized from October 2018 to February 2020 and 28 healthy volunteers. We assessed: a complete blood count with differential leukocyte count, blood creatinine, albumin, and C-reactive protein (CRP) levels. Then, the expression of the HMGB1 gene was evaluated using quantitative Real-Time PCR. Patients with CDI were found to have a significant increase in white blood cells (WBC), neutrophil count, and CRP levels, they also exhibited decreased levels of albumin compared with controls. The HMGB1 gene expression was significantly lower among patients with CDI compared with the control group and significantly, inversely correlated with CRP level in blood. In conclusion, we have observed a decreased expression of the HMGB1 gene in peripheral blood of patients with mild or moderate CDI, which hypothetically could reflect their diminished capability to fight the pathogen.

Abnormal Endothelial Gene Expression Associated With Early Coronary Atherosclerosis

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

Association of High Mobility Group Box Protein B1 Gene Polymorphisms with Pneumonia Susceptibility and Severity

OBJECTIVE

To investigate the relationship between the high mobility group box protein B1 (HMGB1) single nucleotide polymorphisms (SNPs) rs1412125, rs2249825, and rs1045411 with pneumonia in terms of susceptibility, severity, and inflammatory response.

METHODS

The genotypes of HMGB1 rs1412125 (-1615T > C), rs2249825 (3814C > G), and rs1045411 (2262C > T) loci in 328 patients with community-acquired pneumonia (CAP) and 317 healthy subjects were analyzed by Sanger sequencing. The expression and secretion of the inflammatory cytokines HMGB1, interleukin (IL)-10, tumor necrosis factor-alpha (TNF-α), and IL-6 were determined after lipopolysaccharide (LPS) stimulation of peripheral whole blood cells.

RESULTS

The risk of CAP was higher in carriers of the mutant HMGB1 rs1412125 and rs2249825 alleles than those that had the wild type alleles (adjusted odds ratio [OR] = 1.241; 95% confidence interval [CI] = 1.061-1.448; p = 0.007; adjusted OR = 1.225; 95% CI = 1.038-1.427; p = 0.016, respectively). Moreover, the mutation-carrying patients with CAP were more likely to develop severe community-acquired pneumonia (SCAP). There was no correlation between the HMGB1 rs1045411 SNP alleles and CAP or SCAP (p > 0.05). The expression and secretion of the inflammatory cytokines HMGB1, IL-10, TNF-α, and IL-6 was significantly higher in LPS-stimulated peripheral blood among patients with mutations at the rs1412125 and rs2249825 loci compared with those with wild type alleles (p < 0.05). The 30-day mortality rates for CAP patients with mutations at the rs1412125 and rs2249825 loci of HMGB1 were significantly higher than those that had wild type alleles. The mortality rate difference between rs1045411 wild-type CAP patients and mutant was not significant (p = 0.789).

CONCLUSION

SNPs at the rs1412125 and rs2249825 loci of HMGB1 are associated with pneumonia in terms of susceptibility, severity, and inflammatory response.

Genetic predisposition to ischaemic stroke by RAGE and HMGB1 gene variants in Chinese Han population

Emerging evidence suggests that the multiligand receptor for advanced glycation end products (RAGE) and its ligand high mobility group box 1 protein (HMGB1) contribute to the pathophysiology of ischaemic stroke (IS). The present study aimed to investigate the association of RAGE and HMGB1 variants with the risk of IS. A total of 1,034 patients and 1,015 age- and sex-matched healthy controls were genotyped to detect five genetic variants of the RAGE gene and four genetic variants of the HMGB1 gene using the Multiplex SNaPshot assay. We found that the rs2070600 variant of RAGE was associated with an increased risk of IS (OR = 1.19, 95% CI: 1.02-1.38, P = 0.043), whereas the rs2249825 variant of HMGB1 was associated with a decreased risk of IS (OR = 0.83, 95% CI: 0.71-0.98, P = 0.041). Further stratification by IS subtypes revealed that the presence of the TT genotype of the RAGE rs2070600 variant confers a higher risk of the large artery atherosclerosis subtype of IS (P = 0.036). Moreover, patients with the variant T allele of the RAGE rs2070600 variant presented with reduced serum soluble RAGE production. Patients carrying the variant G allele of the HMGB1 rs2249825 variant exhibited significantly lower infarct volumes than those with the major CC genotype. These clues may help in the development of optimal personalized therapeutic approaches for IS patients.

Impact of High-Mobility Group Box 1 Polymorphism on Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND AND OBJECTIVE

The high-mobility group box 1 (HMGB1) protein is a eukaryotic, ubiquitously expressed protein that serves as a biomarker for various diseases and is involved in the promotion of a proinflammatory response to cell injury. In aneurysmal subarachnoid hemorrhage (aSAH), increased HMGB1 levels have been linked to poor outcome and an increased risk for cerebral vasospasm. The role of HMGB1 polymorphisms in aSAH has not been previously investigated.

METHODS

Patients with aSAH and controls enrolled in the prospective, 2-center CARAS (Cerebral Aneurysm Renin Angiotensin System) study were evaluated. The 3814 C/G HMGB1 single nucleotide polymorphism (SNP) rs2249825 was detected using 5'exonuclease (Taqman) genotyping assays from blood samples from patients with aSAH and controls. Associations between aSAH and its clinical sequelae with the HMGB1 SNP were assessed.

RESULTS

Samples from 149 patients with aSAH and 50 controls were available for analysis. No increased risk for aSAH associated with the SNP was found compared with the control group. Delayed cerebral ischemia (DCI) was defined as a cerebral infarction at the time of discharge from the intensive care unit and identified in 21.2% of patients with aSAH. In multivariable logistic regression analysis, the G allele of rs2249825 was independently associated with DCI (odds ratio, 5.695; 95% confidence interval, 1.804-17.975; P = 0.003).

CONCLUSIONS

The minor allele G of rs2249825 was associated with an increased risk for DCI, or cerebral infarction, after aSAH. This finding may be attributable to an increased HMGB1 protein expression in these patients.

Serum levels of HMGB1 have a diagnostic role in metastatic renal cell cancer

RCC constitutes approximately 90% of all renal malignancies and 2-3% of all malignant tumours in adults. In spite of the improvement in radiologic methods, nearly 30% of the early metastatic RCC patients are incidentally diagnosed. HMGB1 is an extracellular signalling molecule that plays a role both in inflammation and carcinogenesis. Patients who were followed in Medical Oncology Departments of Denizli Government Hospital and Antalya Education and Research Hospital with a histopathological diagnosis of RCC between years 2010-2012 were enrolled in this study. HMGB1 levels were also assessed in a manually performed quantitative sandwich-enzyme-linked immunosorbent assay (ELISA) assay kit. In our study, we showed that the serum level of HMGB1, whether 149.9 pg/ml or not is important in differential diagnosis between patient and control group.

Association of single-nucleotide polymorphisms of high-mobility group box 1 with susceptibility and clinicopathological characteristics of uterine cervical neoplasia in Taiwanese women

To date, no study associated the genetic polymorphisms of high-mobility group box 1 protein (HMGB1) with the development of uterine cervical cancer. We therefore conducted this study to investigate the associations of HMGB1 single-nucleotide polymorphisms (SNPs) with cervical carcinogenesis and clinicopathological characteristics of cancer patients. Five hundred two women, including 112 with invasive cancer, 85 with precancerous lesions of the uterine cervix, and 305 normal controls, were consecutively enrolled into this study. Analysis of HMGB1 SNPs was done by real-time polymerase chain reaction and genotyping. Our results found that the risk of susceptibility to cervical invasive cancer was 1.85 (95 % CI 1.12-3.04; p = 0.016) in women with TC and 1.99 (95 % CI 1.24-3.23; p = 0.005) in women with TC/CC after adjusting for age, using TT as a comparison reference in HMGB1 SNP rs1412125. In rs2249825, the increased risk was also seen for the development of cervical invasive cancer in women with CG [adjusted odds ratio (AOR) 2.04, 95 % CI 1.22-3.40; p = 0.006] or CG/GG (AOR 2.02, 95 % CI 1.22-3.32; p = 0.006) using CC as a comparison reference. An additional integrated in silico analysis confirmed that rs2249825 creates a binding site for v-Myb, which may affect HMGB1 expression. In conclusion, Taiwanese women with TC or TC/CC in HMGB1 SNP rs1412125 as well as CG or CG/GG in rs2249825 were susceptible to the development of cervical invasive cancer.

Prognostic Significance of Tag SNP rs1045411 in HMGB1 of the Aggressive Gastric Cancer in a Chinese Population

Compelling evidences have suggested that high mobility group box-1 (HMGB1) gene plays a crucial role in cancer development and progression. This study aimed to evaluate the effects of single nucleotide polymorphisms (SNPs) in HMGB1 gene on the survival of gastric cancer (GC) patients. Three tag SNPs from HMGB1 gene were selected and genotyped using Sequenom iPEX genotyping system in a cohort of 1030 GC patients (704 in training set, 326 in validation set). Multivariate Cox proportional hazard model and Kaplan-Meier Curve were used for prognosis analysis. AG/AA genotypes of SNP rs1045411 in HMGB1 gene were significantly associated with better overall survival (OS) in a set of 704 GC patients when compared with GG genotypes (HR = 0.77, 95% CI: 0.60-0.97, P = 0.032). This prognostic effect was verified in an independent validation set and pooled analysis (HR = 0.80, 95% CI: 0.62-0.99, P = 0.046; HR = 0.78, 95% CI: 0.55-0.98, P = 0.043, respectively). In stratified analysis, the protective effect of rs1045411 AG/AA genotypes was more prominent in patients with adverse strata, compared with patients with favorable strata. Furthermore, strong joint predictive effects on OS of GC patients were noted between rs1045411 genotypes and Lauren classification, differentiation, stage or adjuvant chemotherapy. Additionally, functional assay indicated a significant effect of rs1045411 on HMGB1 expression. Our results suggest that rs1045411 in HMGB1 is significantly associated with clinical outcomes of Chinese GC patients after surgery, especially in those with aggressive status, which warrants further validation in other ethnic populations.

Associations between Single Nucleotide Polymorphisms of High Mobility Group Box 1 Protein and Clinical Outcomes in Korean Sepsis Patients

PURPOSE

High mobility group box 1 (HMGB1) plays a central role in the pathogenesis of sepsis and multiple organ dysfunction syndromes. We investigated the associations of a single nucleotide polymorphism (SNP; rs1045411) in HMGB1 with various clinical parameters, severity, and prognosis in patients with sepsis, severe sepsis, or septic shock.

MATERIALS AND METHODS

We enrolled 212 adult patients followed for 28 days. All patients were genotyped for rs1045411, and the serum levels of HMGB1 and several cytokines were measured.

RESULTS

The proportions of patients according to genotype were GG (71.2%), GA (26.4%), and AA (2.4%). Among patients with chronic lung disease comorbidity, patients with a variant A allele had higher positive blood culture rates and higher levels of various cytokines [interleukin (IL)-1β, IL-6, IL-10, IL-17, and tumor necrosis factor-α] than those with the GG genotype. In the analysis of those with diabetes as a comorbidity, patients with a variant A allele had higher blood culture and Gram-negative culture rates than those with GG genotypes; these patients also had a higher levels of IL-17. In the analysis of those with sepsis caused by a respiratory tract infection, patients with a variant A allele had higher levels of IL-10 and IL-17 (all p<0.05). This polymorphism had no significant impact on patient survival.

CONCLUSION

The variant A allele of rs1045411 appears to be associated with a more severe inflammatory response than the GG genotype under specific conditions.

High mobility group box 1 gene polymorphism is associated with the risk of postoperative atrial fibrillation after coronary artery bypass surgery

Background

The inflammatory response triggered by cardiac surgery with cardiopulmonary bypass (CPB) is a primary cause of postoperative atrial fibrillation (POAF). The objective of this study was to determine the relationships between rs2249825 (C/G) polymorphism in high-mobility group box protein 1 (HMGB1) and POAF in patients who underwent coronary artery bypass grafting (CABG) under CPB.

Methods

A prospective cohort study was carried out between February 2011 and January 2014. Patients who had no history of atrial fibrillation undergoing CABG with CPB were recruited in this study, and were matched based on preoperative characteristics. Blood samples were obtained before, and at 4, and 24 h after CPB. HMGB1 level was measured by enzyme immunoassay. Patients were genotyped for single nucleotide polymorphisms of HMGB1 (rs2249825). Patients were genotyped for single nucleotide polymorphisms of HMGB1 (rs2249825) using pyrosequencing method. The primary clinical end point was the incidence of POAF after surgery.

Results

After matching, a total of 128 patients undergoing elective CABG with CPB were eligible for analysis. Plasma HMGB1 concentrations were increased 4 h after CPB (p <0.0001) and were still increased at 24 h (p <0.0001). The frequencies of CC, CG, GG genotypes were 21 (56.8 %), 29 (37.8 %), and 2 (5.4 %) in patients with POAF and 81.3, 16.5, and 2.2 % in patients without POAF (p = 0.016). CG + GG genotype was associated with high HMGB1 levels compared with the genotype CC at 4 h (p = 0.023), and 24 h (p = 0.015) after CPB. Multivariate analysis showed that age older than 60 years (OR = 1.40; 95 % CI: 1.03 to 1.89; p = 0.021) and allele G of polymorphisms (OR = 1.61; 95 % CI: 1.08 to 2.04; p = 0.034) were independent risk factors for POAF.

Conclusions

The HMGB1 rs2249825 was associated with the susceptibility to POAF after CABG with CPB in a Chinese Han population.

Circulating HMGB1 and RAGE as Clinical Biomarkers in Malignant and Autoimmune Diseases

High molecular group box 1 (HMGB1) is a highly conserved member of the HMG-box-family; abundantly expressed in almost all human cells and released in apoptosis; necrosis or by activated immune cells. Once in the extracellular space, HMGB1 can act as a danger associated molecular pattern (DAMP), thus stimulating or inhibiting certain functions of the immune system; depending on the “combinatorial cocktail” of the surrounding milieu. HMGB1 exerts its various functions through binding to a multitude of membrane-bound receptors such as TLR-2; -4 and -9; IL-1 and RAGE (receptor for advanced glycation end products); partly complex-bound with intracellular fragments like nucleosomes. Soluble RAGE in the extracellular space, however, acts as a decoy receptor by binding to HMGB1 and inhibiting its effects. This review aims to outline today’s knowledge of structure, intra- and extracellular functions including mechanisms of release and finally the clinical relevance of HMGB1 and RAGE as clinical biomarkers in therapy monitoring, prediction and prognosis of malignant and autoimmune disease.

HMGB1 genetic polymorphisms in oral squamous cell carcinoma and oral lichen planus patients

OBJECTIVES

This study examined the single nucleotide polymorphisms (SNPs) in high-mobility group box 1 (HMGB1) gene in patients with oral squamous cell carcinoma (OSCC) and oral lichen planus (OLP).

MATERIALS AND METHODS

The study was conducted on 93 patients with OSCC, 53 patients with OLP, and 100 controls, all Caucasians of the same ethnicity, matched by age. HMGB1 genotypes for 4 SNPs, 2262G/A (rs1045411), 1177G/C (rs3742305), 3814C/G (rs2249825), and rs4540927, were assessed using TaqMan SNP Genotyping Assays, Applied Biosystems.

RESULTS

The HMGB1 1177GG genotype was associated with lymph-node metastasis and tumor stage in OSCCs (P = 0.016 and P = 0.030, respectively). Genotype 1177GG resulted in poorer recurrence-free survival (RFS), P = 0.000. The 1177G/C polymorphism was an independent predictor of RFS compared to GG genotype, P = 0.001. The three polymorphisms were in linkage disequilibrium (LD). The AGC and GGC haplotypes were associated with an increased oral cancer risk, determined over the haplotype odds ratios (HOR = 13.316, P = 0.015, and HOR = 5.769, P = 0.029, respectively). The AGC haplotype was related to erosive OLP progression to OSCC (HOR = 12.179, P = 0.001).

CONCLUSIONS

HMGB1 polymorphism 1177G/C could be associated with tumor progression and recurrence-free survival in patients with OSCC. The haplotypes of HMGB1 gene might be associated with susceptibility to OSCC and OLP progression to OSCC.

Cytosolic HMGB1 controls the cellular autophagy/apoptosis checkpoint during inflammation

The intracellular protein HMGB1 is released from cells and acts as a damage-associated molecular pattern molecule during many diseases, including inflammatory bowel disease (IBD); however, the intracellular function of HMGB1 during inflammation is poorly understood. Here, we demonstrated that cytosolic HMGB1 regulates apoptosis by protecting the autophagy proteins beclin 1 and ATG5 from calpain-mediated cleavage during inflammation. Colitis in mice with an intestinal epithelial cell-specific Hmgb1 deletion and patients with IBD were both characterized by increased calpain activation, beclin 1 and ATG5 cleavage, and intestinal epithelial cell (IEC) death compared with controls. In vitro cleavage assays and studies of enteroids verified that HMGB1 protects beclin 1 and ATG5 from calpain-mediated cleavage events that generate proapoptotic protein fragments. Together, our results indicate that HMGB1 is essential for mitigating the extent and severity of inflammation-associated cellular injury by controlling the switch between the proautophagic and proapoptotic functions of beclin 1 and ATG5 during inflammation. Moreover, these studies demonstrate that HMGB1 is pivotal for reducing tissue injury in IBD and other complex inflammatory disorders.

Association of HMGB1 and HMGB2 genetic polymorphisms with lung cancer chemotherapy response

The aim of the present study was to investigate the association of genetic polymorphisms in high mobility group box 1 and 2 (HMGB1 and HMGB2, respectively) with platinum-based chemotherapy responses in Chinese lung cancer patients. In total, 338 Chinese lung cancer patients (154 responders and 184 non-responders) were recruited to the study. All patients received at least two cycles of first-line platinum-based chemotherapy. Three tagging single nucleotide polymorphisms (SNPs) of HMGB1 and two tagging SNPs of HMGB2 were detected in patients. We found that rs1412125 and rs2249825 of HMGB1 were significantly associated with the platinum-based chemotherapy response in both recessive and genotypic models. In addition, rs1412125 showed significant association with platinum-based chemotherapy response for the subgroup of patients aged >55 years in additive, recessive and genotypic models. No significant associations were detected between other SNPs and the platinum-based chemotherapy response. The HMGB1 SNPs (rs1412125 and rs2249825) were associated with platinum-based chemotherapy responses in Chinese lung cancer patients. In conclusion, HMGB1 SNPs may serve as potential biomarkers for predicting the efficacy of platinum-based chemotherapy.

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 gene polymorphisms in patients with chronic hepatitis B virus infection

AIM: To characterize high mobility group box chromosomal protein 1 (HMGB1) polymorphisms in patients infected with hepatitis B virus (HBV) and determine the different patterns in patient subgroups.

METHODS: A total of 1495 unrelated Han Chinese HBV carriers were recruited in this hospital-based case-control study. The HMGB1 1176 G/C polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism assay.

RESULTS: A significant association was observed between HMGB1 1176 G/C polymorphism and outcome of HBV infection. The subjects bearing 1176G/G genotype had an increased risk of susceptibility to chronic hepatitis B, liver cirrhosis and severe hepatitis B when compared with those bearing at least one 1176C allele.

CONCLUSION: Patients with 1176G/G genotype of HMGB1 gene are more likely to have a progressive status in HBV infection.

High mobility group box 1 and kidney diseases (Review)

High mobility group box 1 (HMGB1), a non-histone DNA-binding protein, regulates nucleosome function and transcription in the nuclei of all metazoans and plants. However, extracellular HMGB1, which is actively or passively released under different conditions, can act as a key inflammatory mediator through MyD88/mitogen-activated protein kinase signaling by binding to its receptors including the receptor for advanced glycation end products or Toll-like receptors. A growing body of evidence indicates that HMGB1 plays an important role in kidney diseases, such as glomerulonephritis, lupus nephritis, antineutrophilic cytoplasmatic antibody-associated vaculitis, diabetic nephropathy, renal allograft rejection and acute kidney injury. In this review, we focus on the biology of HMGB1 and the association of HMGB1 with kidney diseases.

Influence of Polymorphism −308 G/A of the Tnf-α Gene on High Mobility Group Box-1 Protein in Rheumatoid and Spondylo-Arthritis Patients

Single nucleotide polymorphism (SNP) in the human Tumor Necrosis Factor-α(TNF-α) gene promoter, the −308 G/A variant, has been associated with increased TNF-α levels that may amplify the severity of rheumatoid arthritis (RA) and a poor responsiveness to TNF-α blockade therapy. High mobility group box protein (HMGB-1) is a pro-inflammatory cytokine that plays a pivotal role in the pathogenesis of RA and may be an original target of therapy. The aim of this study is to investigate whether the −308 G/A variant of the TNF-α gene is associated with altered expression of HMBG-1. A total of 110 consecutive patients with rheumatoid arthritis and spondylo-arthritis (ankylosing spondylitis, psoriatic arthritis and spondylitis associated with inflammatory bowel disease) referring to the Rheumatology Unit of Messina University Hospital were enrolled. Patients were genotyped for the −308 TNF-α gene promoter polymorphism. Clinical status was also assessed. HMGB-1 and TNF-α mRNA(Real Time PCR) from total blood and plasmatic HMGB-1 (Western Blot analysis) and TNF-α (ELISA) protein were also evaluated. Irrespective of the underlying disease, patients carrying the G/A genotype showed enhanced HMGB-1 and TNF-α mRNA levels and increased circulating concentration of the inflammatory cytokines when compared to patients with G/G genotype. The data suggest that subjects carrying the TNF-α −308G/A genotype have enhanced expression of HMGB-1 protein that may explain, at least in part, the increased severity of the disease.

Clinical relevance of single nucleotide polymorphisms of the high mobility group box 1 protein gene in patients with major trauma in southwest China

BACKGROUND

High-mobility group box protein 1 (HMGB1) is a pivotal late mediator involved in the development of sepsis and multiple organ dysfunction syndrome (MODS) in critically ill patients. While several single nucleotide polymorphisms (SNPs) have been demonstrated to be critical determinants for outcome of critically ill patients, little is known about the clinical relevance of SNPs of the HMGB1 gene up to date.

METHODS

A total of 3 tag SNPs of the HMGB1 gene were selected using HapMap database and linkage disequilibrium analysis. The tag SNPs were genotyped using a pyrosequencing methodology in 556 unrelated patients with major trauma. Peripheral whole blood samples obtained immediately after admission were determined for HMGB1 production in response to ex vivo lipopolysaccharide (LPS) stimulation.

RESULTS

The rs2249825 SNP and the haplotype TCG were significantly associated with LPS-induced HMGB1 production by peripheral blood leukocytes. There were also significant differences in sepsis morbidity rate and MOD scores among patients with different genotypes of the rs2249825. In addition, the patients with the wild-type haplotype TCG had a lesser sepsis morbidity rate and MOD scores than those without the TCG haplotype.

CONCLUSION

A total of 3 SNPs might act as tag SNPs for the entire HMGB1 gene. The rs2249825 and the haplotype TCG might be used as relevant risk estimate for the development of sepsis and MODS in patients with major trauma.

Association of HMGB1 polymorphisms with outcome after allogeneic hematopoietic cell transplantation

Several studies have demonstrated that genetic variation in cytokine genes can modulate the immune reactions after allogeneic hematopoietic cell transplantation (HCT). High mobility group box 1 protein (HMBG1) is a pleiotropic cytokine that functions as a pro-inflammatory signal, important for the activation of antigen presenting cells (APCs) and propagation of inflammation. HMGB1 is implicated in the pathophysiology of a variety of inflammatory diseases, and we have recently found the variation in the HMGB1 gene to be associated with mortality in patients with systemic inflammatory response syndrome. To assess the impact of the genetic variation in HMGB1 on outcome after allogeneic HCT, we genotyped 276 and 146 patient/donor pairs treated with allogeneic HCT for hematologic malignancies following myeloablative (MA) or nonmyeloablative (NMA) conditioning. Associations between genotypes and outcome were only observed in the cohort treated with MA conditioning. Patient homozygosity or heterozygosity for the-1377delA minor allele was associated with increased risk of relapse (hazard ratio [HR] 2.11, P = .02) and increased relapse related mortality (RRM) (P = .03). Furthermore, patient homozygosity for the 3814C > G minor allele was associated with increased overall survival (OS; HR 0.13, P = .04), progression free survival (PFS; HR 0.30, P = .05) and decreased probability of RRM (P = .03). Patient carriage of the 2351insT minor allele reduced the risk of grade II to IV acute graft-versus-host disease (aGVHD) (HR 0.60, P = .01), whereas donor homozygosity was associated with chronic GVHD (cGVHD) (HR 1.54, P = .01). Our findings suggest that the inherited variation in HMGB1 is associated with outcome after allogeneic HCT following MA conditioning. None of the polymorphisms were associated with treatment-related mortality (TRM).

HMGB1 and HMGB2 proteins up-regulate cellular expression of human topoisomerase IIalpha

Topoisomerase IIα (topo IIα) is a nuclear enzyme involved in several critical processes, including chromosome replication, segregation and recombination. Previously we have shown that chromosomal protein HMGB1 interacts with topo IIα, and stimulates its catalytic activity. Here we show the effect of HMGB1 on the activity of the human topo IIα gene promoter in different cell lines. We demonstrate that HMGB1, but not a mutant of HMGB1 incapable of DNA bending, up-regulates the activity of the topo IIα promoter in human cells that lack functional retinoblastoma protein pRb. Transient over-expression of pRb in pRb-negative Saos-2 cells inhibits the ability of HMGB1 to activate the topo IIα promoter. The involvement of HMGB1 and its close relative, HMGB2, in modulation of activity of the topo IIα gene is further supported by knock-down of HMGB1/2, as evidenced by significantly decreased levels of topo IIα mRNA and protein. Our experiments suggest a mechanism of up-regulation of cellular expression of topo IIα by HMGB1/2 in pRb-negative cells by modulation of binding of transcription factor NF-Y to the topo IIα promoter, and the results are discussed in the framework of previously observed pRb-inactivation, and increased levels of HMGB1/2 and topo IIα in tumors.

Association of HMGB1 polymorphisms with outcome in patients with systemic inflammatory response syndrome

Introduction

High mobility group box 1 protein (HMGB1) is a pleiotropic cytokine, recently implicated in the pathophysiology of the systemic inflammatory response syndrome (SIRS) and sepsis. Data from experimental sepsis models show that administration of anti-HMGB1 antibodies significantly decreased mortality, even when administration was delayed for 24 hours, providing a window of opportunity for therapeutic intervention if transferred into a clinical setting. Whether genetic variation in the human HMGB1 gene is associated with disease susceptibility is unknown.

Methods

We sequenced the HMGB1 gene in 239 prospectively monitored patients with SIRS admitted to an intensive care unit and we measured the corresponding HMGB1 serum concentrations. Blood donors served as control individuals. Outcome parameters according to different HMGB1 genotypes were compared.

Results

Homozygosity and heterozygosity for a promoter variant (-1377delA) was associated with a decreased overall 4-year survival (15% versus 44%, hazard ratio = 1.80; P = 0.01) and with a decreased number of SIRS criteria. Carriage of an exon 4 variant (982C>T) was significantly associated with an increased number of SIRS criteria, a higher Simplified Acute Physiology Score II score, a lower PaO₂/FiO₂ ratio and lower serum HMGB1 levels (P = 0.01), and with a significantly higher probability of early death due to infection (P = 0.04). HMGB1 was undetectable in the control individuals.

Conclusion

The present article is the first report of clinical implications of variation in the human HMGB1 gene. Two polymorphisms were determined as significant risk factors associated with early and late mortality, which may provide insight into the molecular background of SIRS and sepsis, suggesting a possible role for HMGB1 genetics in future prognostic evaluation.

High mobility group protein B1 is an activator of apoptotic response to antimetabolite drugs

We explored the role of a chromatin-associated nuclear protein high mobility group protein B1 (HMGB1) in apoptotic response to widely used anticancer drugs. A murine fibroblast model system generated from Hmgb1(+)(/)(+) and Hmgb1(-/-) mice was used to assess the role of HMGB1 protein in cellular response to anticancer nucleoside analogs and precursors, which act without destroying the integrity of DNA. Chemosensitivity experiments with 5-fluorouracil, cytosine arabinoside (araC), and mercaptopurine (MP) demonstrated that Hmgb1(-/-) mouse embryonic fibroblasts (MEFs) were 3 to 10 times more resistant to these drugs compared with Hmgb1(+)(/)(+) MEFs. Hmgb1-deficient cells showed compromised cell cycle arrest and reduced caspase activation after treatment with MP and araC. Phosphorylation of p53 at Ser12 (corresponding to Ser9 in human p53) and Ser18 (corresponding to Ser15 in human p53), as well as phosphorylation of H2AX after drug treatment, was reduced in Hmgb1-deficient cells. trans-Activation experiments demonstrated diminished activation of proapoptotic promoters Bax, Puma, and Noxa in Hmgb1-deficient cells after treatment with MP or araC, consistent with reduced transcriptional activity of p53. We have demonstrated for the first time that Hmgb1 is an essential activator of cellular response to genotoxic stress caused by chemotherapeutic agents (thiopurines, cytarabine, and 5-fluorouracil), which acts at early steps of antimetabolite-induced stress by stimulating phosphorylation of two DNA damage markers, p53 and H2AX. This finding makes HMGB1 a potential target for modulating activity of chemotherapeutic antimetabolites. Identification of proteins sensitive to DNA lesions that occur without the loss of DNA integrity provides new insights into the determinants of drug sensitivity in cancer cells.