The Concentration of Selected Inflammatory Cytokines (IL-6, IL-8, CXCL5, IL-33) and Damage-Associated Molecular Patterns (HMGB-1, HSP-70) Released in an Early Response to Distal Forearm Fracture and the Performed Closed Reduction With Kirschner Wire Fixation in Children

The evaluation of trauma after surgery through objective analysis of biochemical markers can help in selecting the most appropriate therapy. Thus the aim of the study was the evaluation of the concentration of selected inflammatory cytokines (IL-6, IL-8, CXCL5, IL-33), C-reactive protein (CRP), and damaged-associated molecular patterns (DAMPs): HMGB-1, HSP-70 in the plasma of children in response to bone fracture and 12-14 hours after subsequent surgery performed by closed reduction with percutaneous Kirschner wire fixation (CRKF). The study will answer the question if the CRFK procedure leads to excessive production of inflammatory and damage markers. Blood samples from 29 children with distal forearm fractures were collected 30 min. before CRKF procedure and 12-14 hours after performance of the procedure. The control group was composed of 17 healthy children. IL-6 and CRP concentrations were analyzed using routinely performed in vitro diagnostics tests; the remaining proteins were analyzed with the use of the ELISA method. Increased values of IL-6, CRP, and HSP-70 represented an early inflammatory response to distal forearm fractures classified as SH-II type according to the Salter-Harris classification system. However, the median CRP concentration was within the reference values not indicative of inflammation. The CRKF procedure may be a good solution for the treatment of bone fractures, as damaged associated molecular patterns - HMGB-1 and HSP-70 - did not significantly differ 12-14 hours after the approach was applied as compared to the control group. Moreover, the increase in IL-6 concentration after the CRKF procedure was 1.5-fold to the level before CRKF, while the increase of this marker in response to the distal forearm fracture was 4.3-fold compared to the control group. Based on this data, it appears reasonable to suggest that the CRKF approach caused less damage and inflammatory response in comparison to the response to the fracture itself.

IFN-τ Attenuates LPS-Induced Endometritis by Restraining HMGB1/NF-κB Activation in bEECs

Endometritis is a common inflammatory disease in uterine tissues that leads to animal infertility. Among the causes, Escherichia coli infection is one of the main reasons. Interferon-tau (IFN-τ) is the initial pregnancy signal for ruminant embryos and can induce immune tolerance in humans and other species. However, there are scarce reports on whether IFN-τ has a regulatory effect on endometrial inflammatory damage through HMGB1-NF-κB signalling. The purpose of this study was to investigate the regulatory mechanism of IFN-τ in HMGB1-NF-κB signalling in LPS-induced endometritis. ELISA and qPCR were used to detect the expression of LPS-induced pro-inflammatory cytokines in bovine endometrial epithelial cells (bEECs or BEND) under IFN-τ intervention, and the levels of HMGB1, p-IKK and p-p65 were detected by Western blotting. The nuclear translocation of NF-κB p65 was determined through immunofluorescence. In addition, bEECs were transfected with si-HMGB1 to elucidate the key role of HMGB1 and IFN-τ in the endometrial inflammatory cascade. The results indicated that IFN-τ inhibits the expression of related pro-inflammatory cytokines in an inflammatory injury model of bovine endometrial epithelial cells induced by LPS. Furthermore, experiments have proven that IFN-τ has protective effects on E. coli endotoxin-induced endometritis in mice in vivo. IFN-τ inhibited the HMGB1-NF-κB axis and significantly reduced the secretion of pro-inflammatory cytokines, the expression of HMGB1 protein and the levels of IKK and NF-κB p65 phosphorylation. In summary, our results showed that IFN-τ resists E. coli endotoxin-induced endometritis by attenuating HMGB1/NF-κB signalling.

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

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

The expression changes and correlation analysis of high mobility group box-1 and tissue factor in the serum of rats with sepsis

OBJECTIVE

To investigate the expression changes of high mobility group box-1 (HMGB-1) and tissue factor (TF) and their correlation in the serum of sepsis rat models.

MATERIALS AND METHODS

30 rats were divided into the sham-operated group, 15 rats were in the control group. The cecal ligation and puncture method was used to make the animal model with abdominal infection induced by sepsis. There were 15 rats in the sepsis group among which they were divided into 3 subgroups at different time points after modeling (after 6 hours, 12 hours, 24 hours). Cardiac function indicators of the rats in each subgroup were monitored, including heart rate (HR), left ventricular end-diastolic pressure (LVEDP) and left ventricular developed pressure (LVDP), and enzyme-linked immunosorbent assay (ELISA) was used to test the changes of the expression levels of HMGB-1 and TF in the serum of the rats after 6 hours, 12 hours, 24 hours. Pearson correlation analysis was used to analyze the correlation between HMGB-1 and TF.

RESULTS

HR and LVEDP of the rats in the sepsis group were significantly higher than those of the rats in the control group. The differences were statistically significant (p<0.050). LVDP of the rats in the sepsis group was markedly lower than that of the rats in the control group. The differences were statistically significant (p<0.050). The expressions of HMGB-1 and TF of the rats in the subgroups of the sepsis group were higher than those of the rats in the control group after 6 hours, 12 hours, 24 hours; the expression levels of HMGB-1 and TF of the rats with sepsis increased with time. The differences were statistically significant (p<0.050). When the expressions of HMGB-1 and TF of the rats in the sepsis group were compared with each other within the group the differences were significantly different (p<0.050). The expressions of HMGB-1 and TF in the subgroups at the 24th hour were significantly higher than those at the 6th hour. The differences were statistically significant (p<0.050). The differences of the expression of TF of the rats in the control group were not statistically significant (p>0.050). There was a significant positive correlation between HMGB-1 and TF of the rats in the sepsis group (r=0.772, p=0.002).

CONCLUSIONS

The expression levels of HMGB-1 and TF of the rats with sepsis gradually increased with time, and the level of HMGB-1 was positively correlated with the level of TF.

[Prokaryotic expression and purification of recombinant rat HMGB1-A]

Objective To obtain the recombinant A-domain of high mobility group box 1 (HMGB1-A) protein. Methods Using genetic engineering techniques, we cloned and recombined rat HMGB1-A gene. Using prokaryotic expression technique, we expressed and purified the recombinant rat HMGB1-A protein, which was verified by Western blotting. Results Agarose gel electrophoresis analysis showed that HMGB1-A cassette gene size was about 250 bp; double digestion for identifying the recombinant clone pUC-A showed that the product size was about 3000 bp, 250 bp; PCR for identifying the recombinant clone pGEX-A showed that the product size was about 250 bp. SDS-PAGE revealed that the product size was about 36 000, which was consistent with the expectation. Conclusion The recombinant rat HMGB1-A was successfully expressed and purified.

miR-193a-3p interaction with HMGB1 downregulates human endothelial cell proliferation and migration

Circulating endothelial colony forming cells (ECFCs) contribute to vascular repair where they are a target for therapy. Since ECFC proliferative potential is increased in cord versus peripheral blood and to define regulatory factors controlling this proliferation, we compared the miRNA profiles of cord blood and peripheral blood ECFC-derived cells. Of the top 25 differentially regulated miRNAs selected, 22 were more highly expressed in peripheral blood ECFC-derived cells. After validating candidate miRNAs by q-RT-PCR, we selected miR-193a-3p for further investigation. The miR-193a-3p mimic reduced cord blood ECFC-derived cell proliferation, migration and vascular tubule formation, while the miR-193a-3p inhibitor significantly enhanced these parameters in peripheral blood ECFC-derived cells. Using in silico miRNA target database analyses combined with proteome arrays and luciferase reporter assays of miR-193a-3p mimic treated cord blood ECFC-derived cells, we identified 2 novel miR-193a-3p targets, the high mobility group box-1 (HMGB1) and the hypoxia upregulated-1 (HYOU1) gene products. HMGB1 silencing in cord blood ECFC-derived cells confirmed its role in regulating vascular function. Thus, we show, for the first time, that miR-193a-3p negatively regulates human ECFC vasculo/angiogenesis and propose that antagonising miR-193a-3p in less proliferative and less angiogenic ECFC-derived cells will enhance their vasculo/angiogenic function.

Quercetin Protects Mice from ConA-Induced Hepatitis by Inhibiting HMGB1-TLR Expression and Down-Regulating the Nuclear Factor Kappa B Pathway

The dietary flavonoid quercetin has hepatoprotective effects. We analyzed the effects of quercetin on concanavalin A (ConA)-induced hepatitis in mice and its underlying molecular mechanisms of action. Mice were administered quercetin (50 mg/kg body weight, i.p.) or vehicle 30 min before intravenous administration of ConA. Quercetin pretreatment significantly reduced the ConA-induced elevations in plasma aminotransferase concentrations and liver necrosis, as well as reducing serum concentrations of the pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interferon-γ, and interleukin-4. Quercetin pretreatment also reduced expression of high-mobility group box 1 protein (HMGB1) and toll-like receptor (TLR)-2 and TLR-4 messenger RNA (mRNA) and protein in liver tissues. Quercetin pretreatment significantly inhibited degradation of inhibitory kappa B alpha and modulated ConA-induced nuclear translocation in the liver of nuclear factor kappa B (NF-κB) p65. These results demonstrate that quercetin protects against ConA-mediated hepatitis in mice by attenuating the HMGB1-TLRs-NF-κB signaling pathway.

HMGB1/RAGE Signaling and Pro-Inflammatory Cytokine Responses in Non-HIV Adults with Active Pulmonary Tuberculosis

BACKGROUND

We aimed to study the pathogenic roles of High-Mobility Group Box 1 (HMGB1) / Receptor-for-Advanced-Glycation-End-products (RAGE) signaling and pro-inflammatory cytokines in patients with active pulmonary tuberculosis (PTB).

METHODS

A prospective study was conducted among non-HIV adults newly-diagnosed with active PTB at two acute-care hospitals (n = 80); age-and-sex matched asymptomatic individuals (tested for latent TB) were used for comparison (n = 45). Plasma concentrations of 8 cytokines/chemokines, HMGB1, soluble-RAGE, and transmembrane-RAGE expressed on monocytes/dendritic cells, were measured. Gene expression (mRNA) of HMGB1, RAGE, and inflammasome-NALP3 was quantified. Patients' PBMCs were stimulated with recombinant-HMGB1 and MTB-antigen (lipoarabinomannan) for cytokine induction ex vivo.

RESULTS

In active PTB, plasma IL-8/CXCL8 [median(IQR), 6.0(3.6-15.1) vs 3.6(3.6-3.6) pg/ml, P<0.001] and IL-6 were elevated, which significantly correlated with mycobacterial load, extent of lung consolidation (rs +0.509, P<0.001), severity-score (rs +0.317, P = 0.004), and fever and hospitalization durations (rs +0.407, P<0.001). IL-18 and sTNFR1 also increased. Plasma IL-8/CXCL8 (adjusted OR 1.12, 95%CI 1.02-1.23 per unit increase, P = 0.021) and HMGB1 (adjusted OR 1.42 per unit increase, 95%CI 1.08-1.87, P = 0.012) concentrations were independent predictors for respiratory failure, as well as for ICU admission/death. Gene expression of HMGB1, RAGE, and inflammasome-NALP3 were upregulated (1.2-2.8 fold). Transmembrane-RAGE was increased, whereas the decoy soluble-RAGE was significantly depleted. RAGE and HMGB1 gene expressions positively correlated with cytokine levels (IL-8/CXCL8, IL-6, sTNFR1) and clinico-/radiographical severity (e.g. extent of consolidation rs +0.240, P = 0.034). Ex vivo, recombinant-HMGB1 potentiated cytokine release (e.g. TNF-α) when combined with lipoarabinomannan.

CONCLUSION

In patients with active PTB, HMGB1/RAGE signaling and pro-inflammatory cytokines may play important roles in pathogenesis and disease manifestations. Our clinico-immunological data can provide basis for the development of new strategies for disease monitoring, management and control.

MicroRNA‑451 protects against cardiomyocyte anoxia/reoxygenation injury by inhibiting high mobility group box 1 expression

High mobility group box 1 (HMGB1) protein serves an important role in myocardial ischemia/reperfusion (I/R) injury. MicroRNAs (miRNAs) are a group of small non‑coding RNAs that regulate numerous signaling pathways involved in myocardial I/R injury. The present study aimed to investigate whether miR‑451 protects against cardiomyocyte anoxia/reoxygenation (A/R) injury by attenuating HMGB1 expression. Neonatal rat ventricular cardiomyocytes were prepared and then subjected to A/R injury. The effect of upregulation or downregulation of miR‑451 on cell viability, apoptosis, superoxide dismutase (SOD) activity, and the expression of cleaved‑caspase‑3 and HMGB1 were measured accordingly. A luciferase assay was performed to further confirm whether miR‑451 can directly recognize the 3'‑untranslated region of HMGB1 in HEK293 cells. The expression of miR‑451 was significantly decreased in the cardiomyocytes during A/R, and upregulation of miR‑451 led to increased miR‑451 expression (P<0.05). Upregulation of miR‑451 significantly attenuated the loss of cardiomyocyte viability (P<0.05) and increased the intracellular levels of SOD during A/R (P<0.05). Furthermore, upregulation of miR‑451 significantly decreased the apoptosis of cardiomyocytes during A/R (P<0.05). The HMGB1 mRNA and protein expression levels were significantly downregulated in the Ad‑miR‑451 group compared with those in the A/R group (P<0.05). In addition, upregulation of miR‑451 reduced its translocation from the nucleus to the cytoplasm. The luciferase assay confirmed that HMGB1 mRNA is a direct target of miR‑451 in cardiomyocytes. In conclusion, the present study suggested that upregulation of miR‑451 could protect against A/R‑induced cardiomyocyte injury by inhibiting HMGB1 expression.

HMGB1 promotes HCC progression partly by downregulating p21 via ERK/c-Myc pathway and upregulating MMP-2

High-mobility group box 1 (HMGB1) was found to be over-expressed in many kinds of human cancer, which binds with several receptors and activates RAGE-Ras-MAPK, Toll-like receptors, NF-κB, and Src family kinase signaling pathways and plays a crucial role in tumorigenesis and cancer progression. However, the function and mechanism of HMGB1 in hepatocellular carcinoma (HCC) remain unclear. The aim of this study was to investigate the effect of HMGB1 on HCC progression and explore new molecular mechanism. HMGB1 transient knockdown, stable knockdown, and re-expression were performed by transfection with specific siRNA, shRNA, or expression vector in HCCLM3 cells. Results showed that transient knockdown HMGB1 prevented cell proliferation, promoted apoptosis, induced S phase arrest, and inhibited migration and invasion in vitro, and stable knockdown HMGB1 inhibited xenograft growth in Balb/c athymic mice in vivo. Molecular mechanism investigation revealed that knockdown HMGB1 significantly reduced the activation of MAPKs, including ERK1/2, p38, SAPK/JNK, as well as MAPKKs (MEK1/2, SEK1) and its substrates (c-Jun, c-Myc); downregulated NF-κB/p65 expression and phosphorylation level; decreased MMP-2 expression and activity; and upregulated p21 expression. Interestingly, c-Myc was firstly found to be involved in the promoting function of HMGB1 on HCC progression, which provided a novel clue for the inhibitory effect of HMGB1 on p21 expression by a p53-independent pathway. Collectively, these findings indicated that HMGB1 promoted HCC progression partly by enhancing the ERK1/2 and NF-κB pathways, upregulating MMP-2, and downregulating p21 via an ERK/c-Myc pathway.

Melatonin relieves neuropathic allodynia through spinal MT2-enhanced PP2Ac and downstream HDAC4 shuttling-dependent epigenetic modification of hmgb1 transcription

Melatonin (MLT; N-acetyl-5-methoxytryptamine) exhibits analgesic properties in chronic pain conditions. While researches linking MLT to epigenetic mechanisms have grown exponentially over recent years, very few studies have investigated the contribution of MLT-associated epigenetic modification to pain states. Here, we report that together with behavioral allodynia, spinal nerve ligation (SNL) induced a decrease in the expression of catalytic subunit of phosphatase 2A (PP2Ac) and enhanced histone deacetylase 4 (HDAC4) phosphorylation and cytoplasmic accumulation, which epigenetically alleviated HDAC4-suppressed hmgb1 gene transcription, resulting in increased high-mobility group protein B1 (HMGB1) expression selectively in the ipsilateral dorsal horn of rats. Focal knock-down of spinal PP2Ac expression also resulted in behavioral allodynia in association with similar protein expression as observed with SNL. Notably, intrathecal administration with MLT increased PP2Ac expression, HDAC4 dephosphorylation and nuclear accumulation, restored HDAC4-mediated hmgb1 suppression and relieved SNL-sensitized behavioral pain; these effects were all inhibited by spinal injection of 4P-PDOT (a MT2 receptor antagonist, 30 minutes before MLT) and okadaic acid (OA, a PP2A inhibitor, 3 hr after MLT). Our findings demonstrate a novel mechanism by which MLT ameliorates neuropathic allodynia via epigenetic modification. This MLT-exhibited anti-allodynia is mediated by MT2-enhanced PP2Ac expression that couples PP2Ac with HDAC4 to induce HDAC4 dephosphorylation and nuclear import, herein increases HDAC4 binding to the promoter of hmgb1 gene and upregulates HMGB1 expression in dorsal horn neurons.

Ketamine effect on HMGB1 and TLR4 expression in rats with acute lung injury

Acute lung injury (ALI) is a common emergency and severe case in clinic. High mobility group protein box 1 (HMGB1) can be treated as a new anti-inflammatory treatment target. Toll-like receptor 4 (TLR4) is an important receptor of HMGB1. Ketamine is a widely used intravenous anesthetic with good anti-inflammatory and immune regulating function. Whether it can protect ALI through inhibiting HMGB1 and TLR4 expression in lung tissue still needs further investigation. Male SD rats were randomly divided into control, lipopolysaccharide (LPS) group and ketamine intervention group with 15 rats in each group. The rats were euthanatized at 24 h after modeling and the bronchoalveolar lavage fluid (BALF) was collected for HMGB1 and TLR4 level detection. Western Blot was applied to analyze HMGB1 and TLR4 protein expression in the lung tissue. HMGB1 and TLR4 concentration in BALF were 5.369 ± 1.564 ng/ml and 43.980 ± 7.524 pg/ml in the control, respectively. They were 12.358 ± 4.681 ng/ml and 102.538 ± 8.412 pg/ml in LPS group, and 7.399 ± 2.346 ng/ml and 87.208 ± 7.558 pg/ml in ketamine intervention group, respectively. Their levels increased significantly in LPS group and down-regulated after ketamine intervention. HMGB1 and TLR4 protein expression in lung tissue elevated obviously in LPS group, and decreased after ketamine treatment. HMGB1 and TLR4 protein level showed positive correlation in lung tissue (r = 0.921, P < 0.001). Ketamine can inhibit HMGB1 and TLR4 expression in ALI, and alleviate LPS induced rat lung injury.

Expression level and distribution of HMGB1 in Sombati's cell model and kainic acid-induced epilepsy model

OBJECTIVE

Observe the expression and distribution of HMGB1 in Sombati's cell model and kainic acid-induced epileptic rats' model.

MATERIALS AND METHODS

Dissociated hippocampal neurons from neonatal SD rats and cultured those for 9 days, then changed medium to Mg2+-free medium for 3 hours to induce Sombati's cell model. The expression level of HMGB1 in the neurons was detected at 24h and 72h by Western Blotting. Appropriate kainic acid was injected into the lateral ventricles to induced epileptic rats' model in vivo trial, the expression level and distribution of HMGB1 at 24h and 72h were established by immunohistochemistry.

RESULTS

The expression level of HMGB1 showed significantly different between model group and control group both in vitro and in vivo trials. At 24h, the expression level of HMGB1 in the model group was lower than the control group (p < 0.05), and became higher than the control group at 72h (p < 0.05). From the in vivotrial, a nucleus-to-cytoplasm translocation was also discovered.

CONCLUSIONS

This investigation indicates that HMGB1 plays a crucial role in the pathophysiology of epilepsy, by altering its quantity and distribution.

Endothelin-1 Upregulates the Expression of High Mobility Group Box 1 in Human Bronchial Epithelial Cells

Both endothelin-1 (ET-1) and high mobility group box 1 (HMGB1) reportedly are closely involved in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). In this study, we explored the regulatory effects of ET-1 on the expression of HMGB1 in human bronchial epithelial cells (HBEpCs). Primary HBEpCs were treated with ET-1 with or without transcription inhibitor actinomycin D, ETA receptor blocker BQ123, ETB receptor blocker BQ788, focal adhesion kinase (FAK) inhibitor or shRNA, or different kinase inhibitors. ET-1 increased the HMGB1 mRNA level in a statistically significant dose- and time-dependent manner within 8 hours of treatment, which was reflected in the dose-dependent induction of the HMGB1 protein level and the FAK activity. BQ123 and FAK inhibitor or shRNA, but not BQ788, completely abolished the promoting effect of ET-1 on the expression of HMGB1. Luciferase reporter assays revealed that neither ET-1 nor ETA nor FAK inhibition had any significant effect on the HMGB1 gene promoter activity. In the presence of the transcription inhibitor actinomycin D, the HMGB1 mRNA level markedly decreased over time, and ET-1 dose-dependently rescued the HMGB1 mRNA level. This effect of ET-1 was completely abolished by BQ123 and FAK inhibitor or shRNA, but not by BQ788. In conclusion, this study provides the first evidence that ET-1 upregulates the expression of HMGB1 in HBEpCs by increasing the stability of HMGB1 mRNA via the ETA receptor by a FAK-dependent mechanism. It adds new insights into the molecular mechanisms underlying ALI/ARDS.

Expression of HMGB1/RAGE protein in renal carcinoma and its clinical significance

OBJECTIVE

To investigate the expression of high mobility group protein B1 (HMGB1) and its receptor, receptor for advanced glycation end-product (RAGE), in renal cancer tissue and surrounding normal tissue and to analyze the relationship between the expression level of the protein and receptor as well as the clinical pathological characteristics and prognosis in renal cancer patients.

METHODS

A total of 80 renal carcinoma patients who were surgically treated in our hospital from February 2004 to December 2012 were included in this study. Normal paratumoral tissues were collected as a control. All diagnoses were confirmed with a postoperative pathological examination. All patients had complete pathological data. The expression of HMGB1/RAGE proteins in renal cancer tissue and paratumoral tissue was examined using immunohistochemical methods.

RESULTS

The positive expression rate of HMGB1 was 71% in renal cancer tissue, which was significantly higher than that in the paratumoral normal tissue (25%). The positive expression rate of RAGE was 72% in renal cancer tissue, which was significantly higher than that in the paratumoral normal tissue (27%). Further analysis did not indicate a correlation between the positive expression of HMGB1 and RAGE proteins and gender, age and tumor size (P > 0.05), whereas the expression patterns were shown to correlate with tumor differentiation, clinical stage and lymph node metastasis (P < 0.05). The expression of HMGB1 exhibited a significant positive correlation with RAGE level (P < 0.05), the expression of HMGB1/RAGE proteins exhibited a negative correlation with the prognosis of patients, and the five-year survival rate of patients with positive expression was significantly lower than that of patients with negative expression (P < 0.05).

CONCLUSION

HMGB1/RAGE exhibited significantly elevated expression in renal cancer tissues that was closely related to the clinical prognosis of patients; thus, the expression levels may become a new target in the treatment of renal carcinoma.

Protective effects of tanshinone IIA on myocardial ischemia reperfusion injury by reducing oxidative stress, HMGB1 expression, and inflammatory reaction

CONTEXT

Although there were reports on the protective functions of tanshinone IIA (TSA) on rat myocardial ischemia, the exerting mechanism has not been completely clarified.

OBJECTIVE

An attempt was made to further verify the protective effect of TSA on myocardial ischemia reperfusion injury and elucidate its underlying mechanism.

MATERIALS AND METHODS

The rats were given TSA (10, 20, and 40 mg/kg bw per day) in intraperitoneal injection for 15 d. Rami anterior descending branch of coronary artery was ligated for 30 min and then re-perfused for 120 min to establish a reperfusion model. Effects of TSA on the infarct area, creatine kinase (CK), aspartate aminotransferase (AST), high mobility group box B1 protein (HMGB1), and inflammation and oxidation were investigated.

RESULTS

Compared with those in the IR group, infarct size percentages of rats' myocardium in L-TSA, M-TSA, and H-TSA groups were reduced by 1.21, 4.26, and 12.50%, respectively, CK activities by 7.4, 11.2, and 12.5%, respectively, and AST activities also declined (p < 0.05). Furthermore, compared with those in the IR group, SOD and GSH-Px activities increased, and MDA, TNF-α, IL-6, and iNOS levels decreased in L-TSA, M-TSA, and H-TSA groups (p < 0.05). Meanwhile, compared with those in the IR group, HMGB1 expressions in L-TSA, M-TSA, and H-TSA groups were lowered by 21.9, 32.4, and 35.6%, respectively.

DISCUSSION AND CONCLUSION

The protective function of TSA on myocardial ischemia reperfusion injury may be possibly exerted by inhibiting the increase of ROS caused by the reperfusion to attenuate the expression of HMGB1 and inhibit inflammation.

The association of HMGB1 expression with clinicopathological significance and prognosis in hepatocellular carcinoma: a meta-analysis and literature review

Background

Hepatocellular carcinoma (HCC) is the fifth most common cancer, and it is the second most common cancer-related mortality globally. The prognostic value of high mobility group box 1 (HMGB1) remains controversial. The purpose of this study is to conduct a meta-analysis and literature review to evaluate the association of HMGB1 expression with the prognosis of patients with HCC.

Methods

A detailed literature search was made in Medline, Google Scholar and others for related research publications. The data were extracted and assessed by two reviewers independently. Analysis of pooled data were performed, Hazard Ratio (HR) and mean difference with corresponding confidence intervals (CIs) were calculated and summarized respectively.

Results

10 relevant articles were included for this meta-analysis study. HMGB1 mRNA levels in HCC were significantly higher than those in normal (p<0.00001) and para-tumor tissues (p = 0.002) respectively. The protein levels of HMGB1 in HCC were significantly higher than those in para-tumor tissues (p = 0.005). Two studies reported the serum HMGB1 levels in patients with HCC of TNM stages, and indicating significantly different between stage I and II, stage II and III, as well as stage III and IV (two studies showed p<0.01 and p<0.001 respectively). The overall survival (OS) was significantly shorter in HCC patients with high HMGB1 expression compared those with low HMGB1 expression and the pooled HR was 1.31 with 95% CI 1.20–1.44, Z = 5.82, p<0.0001. Two additional studies showed that there were higher serum HMGB1 levels in patients with chronic hepatitis than those in healthy people (p<0.05).

Conclusions

The results of this meta-analysis suggest that HMGB1 mRNA and protein tissue levels in the patients with HCC are significantly higher than those in para-tumor and normal liver tissues respectively. Tissue HMGB1 overexpression is a potential biomarker for HCC diagnosis, and it is significantly associated with the prognosis of patients with HCC.

Overexpression of HMGB1 in melanoma predicts patient survival and suppression of HMGB1 induces cell cycle arrest and senescence in association with p21 (Waf1/Cip1) up-regulation via a p53-independent, Sp1-dependent pathway

Although laboratory studies have implicated the high mobility group box 1 (HMGB1) in melanoma, its clinical relevance remains unclear. We analyzed nearly 100 cases of human melanoma and found that HMGB1 was highly overexpressed in melanoma samples relative to normal skin and nevi tissues. Significantly, higher levels of HMGB1 correlated with more advanced disease stages and with poorer survival in melanoma patients. Unlike the well-documented pro-inflammatory role of the extracellular HMGB1, we found that its intracellular activity is necessary for melanoma cell proliferation. An absolute dependency of melanoma cell proliferation on HMGB1 was underscored by the marked response of cell cycle arrest and senescence to HMGB1 knockdown. We demonstrated that HMGB1 deficiency-induced inhibition of cell proliferation was mediated by p21, which was induced via a Sp1-dependent mechanism. Taken together, our data demonstrate a novel oncogenic role of HMGB1 in promoting human melanoma cell proliferation and have important implications in melanoma patient care.

HMGB1 contributes to regeneration after spinal cord injury in adult zebrafish

High mobility group box 1 (HMGB1, also called amphoterin) facilitates neurite outgrowth in early development, yet can exacerbate pathology and inhibit regeneration by inducing adverse neuroinflammation when released from dying cells, suggesting that HMGB1 plays a critical, yet undefined role in neuroregeneration. We explored whether HMGB1 contributes to recovery after complete spinal cord transection in adult zebrafish. Quantitative PCR and in situ hybridization revealed that HMGB1 mRNA levels decreased between 12 h to 11 days after spinal cord injury (SCI), then returned to basal levels by 21 days. Western blot and immunohistological analyses indicated that the time course of HMGB1 protein expression after SCI parallels that of mRNA. Immunofluorescence staining revealed that HMGB1 translocates from nuclei into the cytoplasm of spinal motoneurons at 4 and 12 h (acute stage) following SCI, then accumulates in the nuclei of motoneurons during the ensuing chronic stage (after 6 days following SCI). Immunohistology of transgenic zebrafish, expressing green fluorescent protein in blood vessels, showed enhanced HMGB1 expression in blood vessels in the vicinity of motoneurons. Application of anti-sense HMGB1 morpholinos inhibited locomotor recovery by 34 % and decreased axonal regeneration by 34 % compared to fish treated with a control morpholino. The present study shows that HMGB1 expression increases in both endothelial cells and motoneurons, suggesting that HMGB1 promotes recovery from SCI not only through enhancing neuroregeneration, but also by increasing angiogenesis. The inflammatory effects of HMGB1 are minimized through the decrease in HMGB1 expression during the acute stage.

The effects of glycyrrhizin on acute pancreatitis in mice

OBJECTIVE

This study aimed to investigate the effects of glycyrrhizin on acute pancreatitis in mice.

MATERIALS AND METHODS

Sixty Balb/c mice were randomly divided into four groups as control group, model group, low dose group and high dose group (n=15). Acute pancreatitis was induced by intraperitoneal injection of Caerulein (100 µg/kg) hourly for 6 times. Mice in low dose group and high dose group received intraperitoneal administration of 15 mg/kg and 45 mg/kg glycyrrhizin respectively 4 hours before Caerulein injection. Mice in four groups were sacrificed in three equal lots at 8, 16 and 24 hours after model construction. High Mobility Group Box-1 (HMGB1) expression and serum levels of amylase, TNF-α and IL-6 were determined. The pancreatic tissues were taken for histopathologic analysis.

RESULTS

Amylase, TNF-α, IL-6 and HMGB1 levels were significantly higher and pancreas lesion was severer in model group than in control group. However, Amylase, TNF-α, IL-6 and HMGB1 levels in low dose group and high dose group decreased significantly compared with model group. The pancreas lesion was also improved after administration of glycyrrhizin.

CONCLUSIONS

Glycyrrhizin could decrease the levels of pro-inflammatory cytokines and downregulate the expression of HMGB1 which finally improved the pancreas lesion in mice with acute pancreatitis.

LPS may enhance expression and release of HMGB1 in human nasal epithelial cells in vitro

Chronic rhinosinusitis with nasal polyps is a common disease with still unclear pathophysiologic mechanisms. The airway epithelial barrier has been shown to be involved in different chronic disorders, including rhinitis, nasal polyposis and asthma. High mobility group box 1 (HMGB1), a primarily nuclear protein, is involved in the induction of airway inflammation in patients with chronic rhinosinusitis, allergy, asthma and COPD. Pathogen-derived lipopolysaccharide is widely used as a trigger for inflammation. However, the molecular dialogue between LPS and HMGB1 in the delayed inflammatory processes remains to be explored, and the regulation of HMGB1 release through LPS from epithelial cells has not been extensively studied in patients with chronic rhinosinusitis and nasal polyps. The objective of the present study was to investigate the relocation of HMGB1 in LPS-induced human nasal epithelial cells in vitro. We obtained epithelial cells of nasal polyps from 10 patients requiring surgery for sinusitis at the ENT Department of the Chinese PLA General Hospital. The primary cultured human nasal epithelial (HNE) cells were stimulated with LPS. The expression and translocation of HMGB1 in intracellular and culture supernatants were determined using Western blot and immunofluorescence assay. HMGB1 protein was released in a time-dependent fashion in culture supernatants: in fact, expression of HMGB1 protein in HNE cells showed no significant changes at 0-24 h after exposure to 100 μg/ml LPS, but increased significantly at 48 and 72 hr. Immunofluorescence analysis revealed the transfer of HMGB1 from nuclei to cytoplasm in response to LPS exposure after 24 hr. These data reveal a hitherto unrecognized association between HMGB1 and LPS in human nasal epithelial cells. LPS can affect HMGB1 translocation and release, suggesting the involvement of HMGB1, through inflammatory mediators, in chronic rhinosinusitis with nasal polyps.

Cytosolic HMGB1 expression in human renal clear cell cancer indicates higher pathological T classifications and tumor grades

PURPOSE

High mobility group box (HMGB) proteins are nuclear nonhistone chromosomal proteins that bend DNA, bind preferentially to distorted DNA structures, and promote the assembly of site-specific DNA binding proteins. Recent reports indicate that HMGB1 functions as a proinflammatory cytokine. Here, we studied expressions of HMGB1 and HMGB2 in human renal cancer.

MATERIAL AND METHODS

Immunohistological expressions of HMGB1 and HMGB2 were assessed in 39 surgically resected human renal cancer specimens.

RESULTS

HMGB1 was expressed in the nucleus in 37 out of 39 (94.9%) renal clear cell cancers,while its expression in the cytosol was noted in 19 cases (48.7%). Cytosolic HMGB1 is expressed more frequently in cancers beyond the pT1b classification than in those at the pT1a classification. Higher tumor grades (≥ G2) were also significantly linked with the cytosolic expression of HMGB1. HMGB2 was expressed in the nucleus in 35 of 39 (89.7%) renal clear cell cancers, while its expression in the cytosol was observed in only 7 case (17.9%). Linkage between cytosolic expression of HMGB2 and T classifications was weakly observed, while that between nuclear expression and T classifications was not.

CONCLUSION

HMGB1 expressed in the cytoplasm may be an effective marker indicating higher T classifications and tumor grades.

Receptor for advanced glycation end products (RAGE) on iNKT cells mediates lung ischemia-reperfusion injury

Activation of invariant natural killer T (iNKT) cells and signaling through receptor for advanced glycation end products (RAGE) are known to independently mediate lung ischemia-reperfusion (IR) injury. This study tests the hypothesis that activation of RAGE specifically on iNKT cells via alveolar macrophage-produced high mobility group box 1 (HMGB1) is critical for the initiation of lung IR injury. A murine in vivo hilar clamp model was utilized, which demonstrated that RAGE(-/-) mice were significantly protected from IR injury. Treatment of WT mice with soluble RAGE (a decoy receptor), or anti-HMGB1 antibody, attenuated lung IR injury and inflammation, whereas treatment with recombinant HMGB1 enhanced IR injury in WT mice but not RAGE(-/-) mice. Importantly, lung dysfunction, cytokine production and neutrophil infiltration were significantly attenuated after IR in Jα18(-/-) mice reconstituted with RAGE(-/-) iNKT cells (versus WT iNKT cells). In vitro studies demonstrated that, after hypoxia-reoxygenation, alveolar macrophage-derived HMGB1 augmented IL-17 production from iNKT cells in a RAGE-dependent manner. These results suggest that HMGB1-mediated RAGE activation on iNKT cells is critical for initiation of lung IR injury and that a crosstalk between macrophages and iNKT cells via the HMGB1/RAGE axis mediates IL-17 production by iNKT cells causing neutrophil infiltration and lung IR injury.

Receptor for advanced glycation end products regulates adipocyte hypertrophy and insulin sensitivity in mice: involvement of Toll-like receptor 2

Receptor for advanced glycation end products (RAGE) has been shown to be involved in adiposity as well as atherosclerosis even in nondiabetic conditions. In this study, we examined mechanisms underlying how RAGE regulates adiposity and insulin sensitivity. RAGE overexpression in 3T3-L1 preadipocytes using adenoviral gene transfer accelerated adipocyte hypertrophy, whereas inhibitions of RAGE by small interfering RNA significantly decrease adipocyte hypertrophy. Furthermore, double knockdown of high mobility group box-1 and S100b, both of which are RAGE ligands endogenously expressed in 3T3-L1 cells, also canceled RAGE-medicated adipocyte hypertrophy, implicating a fundamental role of ligands-RAGE ligation. Adipocyte hypertrophy induced by RAGE overexpression is associated with suppression of glucose transporter type 4 and adiponectin mRNA expression, attenuated insulin-stimulated glucose uptake, and insulin-stimulated signaling. Toll-like receptor (Tlr)2 mRNA, but not Tlr4 mRNA, is rapidly upregulated by RAGE overexpression, and inhibition of Tlr2 almost completely abrogates RAGE-mediated adipocyte hypertrophy. Finally, RAGE(-/-) mice exhibited significantly less body weight, epididymal fat weight, epididymal adipocyte size, higher serum adiponectin levels, and higher insulin sensitivity than wild-type mice. RAGE deficiency is associated with early suppression of Tlr2 mRNA expression in adipose tissues. Thus, RAGE appears to be involved in mouse adipocyte hypertrophy and insulin sensitivity, whereas Tlr2 regulation may partly play a role.

MicroRNA 181a influences the expression of HMGB1 and CD4 in acute Leukemias

Dysregulation of microRNAs (miRs) has been linked to several types of cancer. In the present study, we investigated the expression of miR-181a in different leukemia cell lines and healthy hematopoietic cells, as well as its influence on cell proliferation, metabolic activity and potential targets. Expression of miR-181a differed between various leukemia cell lines and mature blood cells. Inhibition of miR 181a expression in T- and B-Acute Lymphoblastic Leukemia (ALL) cells revealed an influence on the potential targets High-Mobility-Group-Protein B1 (HMGB1) and Cluster of Differentiation 4 (CD4). Overexpression of miR-181a in AML cells led to a significant decrease in cell proliferation and metabolic activity. The present data indicate a possible role of this specific miRNA in immunogenicity.

Melatonin attenuates inflammation and promotes regeneration in rabbits with fulminant hepatitis of viral origin

The objective of the present study was to investigate the effect of melatonin on the liver inflammatory and regenerative response in an animal model of fulminant hepatic failure (FHF) of viral origin. Rabbits were experimentally infected with 2×10(4) hemagglutination units of a rabbit hemorrhagic disease virus (RHDV) isolate and received melatonin at two concentrations of 10 or 20mg/kg at 0, 12 and 24hr postinfection. RHDV infection induced an inflammatory response, with increased expression of toll-like receptor 4, high-mobility group box (HMGB)1, interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and C-reactive protein, and decreased expression of decay accelerating factor (DAF/CD55). These effects were significantly reduced by melatonin. Matrix metalloproteinase-9 expression was also lowered in melatonin-treated rabbits. RHDV infection inhibited the hepatic regenerative/proliferative response, with a reduced expression of hepatocyte growth factor (HGF), epidermal growth factor, platelet-derived growth factor (PDGF)-B and vascular endothelial growth factor and their receptors; these responses were prevented by melatonin administration. Melatonin treatment also resulted in reduced expression of phosphorylated Janus kinase and enhanced expression of extracellular mitogen-activated protein kinase (ERK) and signal transducer and activator of transcription (STAT) 3. Our findings show that anti-inflammatory effects and stimulation of regenerative mechanisms contribute to the beneficial effects of melatonin in rabbits with experimental infection by RHDV and support a potential hepatoprotective role of melatonin in FHF.

Potential role of high mobility group box protein 1 and intermittent PTH (1-34) in periodontal tissue repair following orthodontic tooth movement in rats

OBJECTIVES

Recent studies indicate that high mobility group box protein 1 (HMGB1) can be released by necrotic and damaged cells and functions as an alarmin that is recognized by the innate immune system. Little is known about the role of HMGB1 within the periodontal ligament (PDL). Therefore, we examined HMGB1 expression by PDL cells in vitro and compared the findings to an in vivo model of orthodontically induced tooth root resorption. In addition, we addressed the question of whether a potentially anabolic intermittent administration of parathyroid hormone (iPTH) would modulate the expression of HMGB1.

MATERIALS AND METHODS

In confluent PDL cell cultures, HMGB1 messenger RNA (mRNA) expression was quantified by real-time polymerase chain reaction. In a rat model comprising 25 animals, mechanical loading for 5 days was followed by administration of either iPTH (1-34) systemically or sham injections for up to 56 days. HMGB1 expression was determined by means of immunohistochemistry and histomorphometry.

RESULTS

The in vitro experiments revealed an inhibitory effect of iPTH on basal HMGB1 mRNA expression in confluent PDL cells. In vivo, the mechanical force-induced enhanced HMGB1 protein expression declined time dependently. Intermittent PTH further inhibited HMGB1 expression. The significantly higher basal HMGB1 protein expression in the former compression side was followed by a more pronounced time- and iPTH-dependent decline in the same area.

CONCLUSIONS

These data indicate a major role for HMGB1 in the regulation of PDL wound healing following mechanical load-induced tissue injury.

CLINICAL RELEVANCE

The findings point to the potential benefit of iPTH in the attempt to support these immune-associated reparative processes.

Immunogenic tumor cell death induced by chemoradiotherapy in patients with esophageal squamous cell carcinoma

Although it has been shown that chemoradiotherapy may induce immunogenic cell death, which could trigger T-cell immunity mediated by high-mobility group box 1 protein (HMGB1) and calreticulin, there is still limited information to support this theory directly in a clinical setting. In the present study, we evaluated antigen-specific T-cell responses against six cancer-testis antigens in peripheral blood lymphocytes from patients with esophageal squamous cell carcinoma (ESCC) receiving chemoradiation. Expression of HMGB1 and calreticulin within tumor microenvironment was also analyzed in resected samples with and without chemoradiotherapy in relation to patients survival. Tumor antigen-specific T-cell responses were confirmed in six (38%) of 16 patients with ESCC after chemoradiotherapy coexisting with elevated serum HMGB1. In addition, HMGB1 within tumor microenvironment was significantly upregulated in patients with ESCC with preoperative chemoradiotherapy, but not in those without chemoradiotherapy, and the degree of HMGB1 positively correlated with patient survival (n=88). Both irradiation and chemotherapeutic drugs induced upregulation of HMGB1 and calreticulin in nine ESCC cell lines. Furthermore, HMGB1 was able to induce maturation of dendritic cells. Together, our findings indicate that chemoradiation induces tumor antigen-specific T-cell responses, and HMGB1 production is related to clinical outcome after chemoradiation.

Emerging role of NF-κB signaling in the induction of senescence-associated secretory phenotype (SASP)

The major hallmark of cellular senescence is an irreversible cell cycle arrest and thus it is a potent tumor suppressor mechanism. Genotoxic insults, e.g. oxidative stress, are important inducers of the senescent phenotype which is characterized by an accumulation of senescence-associated heterochromatic foci (SAHF) and DNA segments with chromatin alterations reinforcing senescence (DNA-SCARS). Interestingly, senescent cells secrete pro-inflammatory factors and thus the condition has been called the senescence-associated secretory phenotype (SASP). Emerging data has revealed that NF-κB signaling is the major signaling pathway which stimulates the appearance of SASP. It is known that DNA damage provokes NF-κB signaling via a variety of signaling complexes containing NEMO protein, an NF-κB essential modifier, as well as via the activation of signaling pathways of p38MAPK and RIG-1, retinoic acid inducible gene-1. Genomic instability evoked by cellular stress triggers epigenetic changes, e.g. release of HMGB1 proteins which are also potent enhancers of inflammatory responses. Moreover, environmental stress and chronic inflammation can stimulate p38MAPK and ceramide signaling and induce cellular senescence with pro-inflammatory responses. On the other hand, two cyclin-dependent kinase inhibitors, p16INK4a and p14ARF, are effective inhibitors of NF-κB signaling. We will review in detail the signaling pathways which activate NF-κB signaling and trigger SASP in senescent cells.

[Ethyl pyruvate inhibited HMGB1 expression induced by LPS in macrophages]

AIM

To elucidate the mechanism of ethyl pyruvate (EP) inhabit high mobility group protein B1 (HMGB1)expression and releasing in macrophage induced by lipopolysaccharide(LPS).

METHODS

The murine macrophage-like cell line RAW264.7 cultured in vitro divided into LPS group and LPS+EP group. The expression of HMGB1 mRNA in cultured cell was determined by RT-PCR. The cytoplasmic and nuclear HMGB1 levels were detected by Western blot. The contents of HMGB1 and TNF-α and IL-6 protein in cultured cells supernatant were detected by ELISA. Immunocytochemistry and confocal laser-scanning microscopy were used to confirm the relocation and distribution of intracellular HMGB1 protein in RAW264.7 cells.

RESULTS

HMGB1 mRNA expression in the LPS+EP group was significantly lower than in LPS alone, at 24, 36 and 48 hours. In the LPS+EP stimulation group, the cytoplasm stained weakly while the nuclear stain was stronger than that of the LPS group at the same time points. Both TNF-α and IL-6 levels in LPS+EP group were significantly lower than those in the LPS group at the same time points. EP also effectively prevented the release of HMGB1 protein.

CONCLUSION

EP inhibits HMGB1 expression and release from LPS-stimulated macrophages.

Different inhibitory effects of kynurenic acid and a novel kynurenic acid analogue on tumour necrosis factor-α (TNF-α) production by mononuclear cells, HMGB1 production by monocytes and HNP1-3 secretion by neutrophils

Kynurenic acid (KynA), a broad spectrum antagonist of excitatory amino acid receptors, may serve as a protective agent in neurological disorders. The potential anti-inflammatory effect of KynA in human leukocytes has not been characterized. The aim of this study was to compare the effects of KynA with those of a new analogue, 2-(2-N,N-dimethylaminoethylamine-1-carbonyl)-1H-quinolin-4-one hydrochloride on tumour necrosis factor-α (TNF-α) production and high mobility group box protein 1 (HMGB1) secretion. The effects of KynA on granulocyte activation were investigated via the secretion of human neutrophil peptide 1-3 (HNP1-3). Peripheral blood mononuclear cells and granulocytes or CD14 positive monocytes were applied as effector cells, or whole blood cultures were used. TNF-α, HMGB1 and HNP1-3 concentrations were determined by ELISA, TNF-α and HNP1-3 mRNA expressions were quantified by reverse transcription PCR. KynA attenuated the TNF-α production of human mononuclear cells activated by heat-inactivated Staphylococcus aureus, inhibiting TNF-α production at the transcription level. Furthermore, KynA diminished HMGB1 secretion by U 937 monocytic cells and by peripheral blood monocytes. KynA inhibited the HNP1-3 secretion in whole blood and in granulocyte cultures. The suppressive effect of the KynA analogue was more potent than that of an equimolar concentration KynA in TNF-α, HMGB1 and HNP1-3 inhibition. These results suggest that the new KynA analogue has a more potent immunoregulatory effect than KynA on human mononuclear cells, monocytes and granulocytes and indicate the potential benefits of further exploration of its uses in human inflammatory disease.

[The expression, identification of human HMGB1 B box and preparation of monoclonal antibodies against HMGB1 B box]

AIM

To express human HMGB1 B box protein and obtain monoclonal antibodies (mAbs) against HMGB1 B box for further study of the function of human HMGB1 protein.

METHODS

pET28-HMGB1 B box plasmid transfected the DH5α, then expressed. And the extracted protein was purified by protein purification system. BALB/c mice were immunized with recombinant human HMGB1 B box protein. Hybridoma cell lines secreting mAb against human HMGB1 B box protein were screened by ELISA and subcloning approach. The characteristics of these mAbs were identified by ELISA and Western blot.

RESULTS

Two hybridoma cell lines (1D2F4E3 and 2D4E3A2) stable secreting specific mAbs were successfully obtained.Western blot exhitited the two mAbs binded specifically to human HMGB1 B box protein. The immunoglobulin (Ig) class of two mAbs belonged to IgG, their titers were 1×10(6);, and the A(450); of mAb1D2F4E3, 2D4E3A2 were 0.324±0.093, 0.296±0.085, respectively.

CONCLUSION

Two of high specificity mAbs against human HMGB1 B box protein have been successfully prepared, which laid the foundation for further study of biological function of human HMGB1 protein.

High-mobility group B1 (HMGB1) and receptor for advanced glycation end-products (RAGE) expression in canine lymphoma

BACKGROUND

Canine lymphoma is a commonly occurring, spontaneously developing neoplasia similar to human non-Hodgkin's lymphoma and, thus, is used as a valuable model for human malignancy. HMGB1 and RAGE are strongly associated with tumour progression and vascularisation. Consequently, deregulated RAGE and HMGB1 may play an important role in the mechanisms involved in lymphoma progression.

MATERIALS AND METHODS

Expression patterns of HMGB1 and RAGE were analysed in 22 canine lymphoma and three canine non-neoplastic control samples via real time PCR and canine beta-glucuronidase gene (GUSB) as endogenous control.

RESULTS

HMGB1 was up-regulated in the neoplastic samples, while RAGE expression remained inconspicuous.

CONCLUSION

This study demonstrated similar mechanisms in lymphoma progression in humans and dogs due to overexpression of HMGB1, which was described in human lymphomas. RAGE remained stable in terms of expression indicating that the extracellular HMGB1-induced effects are regulated by HMGB1 itself.

[Respiratory syncytial virus increases the expression and release of high mobility group Box-1 protein in the lung tissue of mice]

OBJECTIVE

To investigate the expression and release of high mobility group Box-1 protein (HMGB1) in the lung tissue of mice with respiratory syncytial virus (RSV) infection.

METHODS

Eighteen mice were randomized into PBS control group, RSV group and RSV/ribavirin group. Seven days after RSV infection in the mice in the latter two groups, the bronchoalveolar lavage fluid (BALF) was collected for cell counting and classification, and the levels of IL-4, IFN-gamma and HMGB1 in the supernatants of the BALF were detected. The left lungs of the mice were harvested for pathological examination with HE staining, and the right lungs were taken for detecting the expression of HMGB1 by Western blotting.

RESULTS

RSV induced a TH1 inflammation in the lung tissue as shown by significantly increased IFN-gamma and decreased IL-4 levels in the BALF. The total BALF cells, neutrophils and macrophages in the RSV group were significantly higher than those in the control group (P<0.05), and the cell counts were significantly decreased by ribavirin treatment (P<0.05). HE staining showed neutrophil and lymphocyte infiltration in the lumen and submucous layer of the airway in RSV group. The level of HMGB1 in the BALF significantly increased in the RSV group as compared with that in the control group (P<0.05), but was lowered by ribavirin treatment (P<0.05). The expression of the HMGB1 in the lung tissue significantly increased in the RSV group in comparison with that in the control group (P<0.05), and was not significantly decreased by ribavirin treatment (P>0.05).

CONCLUSIONS

The increased expression and release of HMGB1 in the lung tissue of mice with RSV infection is probably involved in the development of RSV infection-related lung diseases.

[Expression of human HMGB1 A box in E. coli and its inhibitory effects on monocytes]

AIM

To clone human high mobility guoup box1 A box (HMGB1 A box) and express it in escherichia coli effectly, investigate the inhibit effection of the purpose protern to the activation of monocytes stimulated by immunocomplex.

METHODS

According to human HMGB1 gene order which was optimized by our laboratory the PCR primer was designed which containing restriction enzyme cutting site. The HMGB1 A box gene was cloned following the whole gene synthesis template of human HMGB1, then the PCR product was inserted into clone vector pMD19-T. The positive colone was identified by colony PCR, zymography analysis and DNA sequencing. Recombinant colne vector was digested by restriction enzymes Nde I and Xho I and separated by agarose gel electrophoresis, then the fragment was inserted into the corresponding sites of expression vector pQE-T7-2. The positive recombinant expression vector was identified by colony PCR and the recombinant strains was induced by IPTG, then the purpose protein was identified by SDS-PAGE and Western blot. The recombinant protein of human HMGB1 A box was purificated by Ni(2+)-NTA chromatography and the inhibit effection of the purpose protern to the activation of monocyte stimulated by immunocomplex was identified by RT-PCR.

RESULTS

We acquired expression strains of recombinant human HMGB1 A box, the target protein account for up to 40% of the whole protein of E.coli. Western blot showed recombinant protein can specificly reacted with anti-human HMGB1 polyclonal antibody and anti-His-Tag polyclonal antibody.The purpose protein was found more than 90% after purified, and can effectively inhibit the production of BAFF, IFN-gamma and TNF-alpha in monocyte which were induced by IC.

CONCLUSION

A recombinant bacterial strain for expressing human HMGB1A box with biological activities was constructed successfully.

Tanshinone II A down-regulates HMGB1, RAGE, TLR4, NF-kappaB expression, ameliorates BBB permeability and endothelial cell function, and protects rat brains against focal ischemia

Inflammatory damage plays an important role in cerebral ischemic pathogenesis. HMGB1-induced NF-kappaB activation pathway has been gaining recognition as a key contributor to the proinflammatory response. Tanshinone II A (Tan II A) has been proved to elicit a series of biologic effects through its antiinflammatory property. But the mechanism underlying is poorly understood. This study evaluated the Tan II A's protective role in cerebral ischemia and its potential mechanism. Male Sprague-Dawley rats were subjected to pMCAO. Experiment 1 was used to evaluate the longitudinal expression of HMGB1, RAGE and TLR4 and NF-kappaB in the cerebral ischemia. Experiment 2 was used to detect Tan II A's neuroprotection. At 24 h after pMCAO, neurologic deficit, brain water content and infarct size were measured. Immunohistochemistry, RT-PCR, Western blot and confocal microscope were used to analyze the expression of HMGB1, RAGE, TLR4 and NF-kappaB. Experiment 3 was used to detect Tan II A's influence on BBB. The expressions of HMGB1, TLR4, RAGE and NF-kappaB were up-regulated in ischemic brain. Compared with pMCAO group, the expressions of these factors significantly decreased in Tan II A-H group, the neurologic deficit, infarct volume and brain water content were alleviated (P<0.05) and claudin-5 was predominantly expressed in brain capillaries. Tan II A protected the brain from damage caused by pMCAO; this effect may be through down-regulation of HMGB1, RAGE and TLR4, NF-kappaB and up-regulation claudin-5 expression.

The role of damage associated molecular pattern molecules in acetaminophen-induced liver injury in mice

The idiosyncratic nature, severity and poor diagnosis of drug-induced liver injury (DILI) make these reactions a major safety issue during drug development, as well as the most common cause for the withdrawal of drugs from the pharmaceutical market. Elucidation of the underlying mechanism(s) is necessary for identifying predisposing factors and developing strategies in the treatment and prevention of DILI. Acetaminophen (APAP) is a widely used over the counter therapeutic that is known to be effective and safe at therapeutic doses. However, in overdose situations fatal and non-fatal hepatic necrosis can result. Evidence suggests that the chemically reactive metabolite of the drug initiates hepatocyte damage and that inflammatory innate immune responses also occur within the liver, leading to the exacerbation and progression of tissue injury. Here we investigate whether following APAP-induced liver injury (AILI) damaged hepatocytes release "danger" signals or damage associated molecular pattern (DAMP) molecules, which induce pro-inflammatory activation of hepatic macrophages, further contributing to the progression of liver injury. Our study demonstrated a clear activation of Kupffer cells following early exposure to APAP (1h). Activation of a murine macrophage cell line, RAW cells, was also observed following treatment with liver perfusate from APAP-treated mice, or with culture supernatant of APAP-challenged hepatocytes. Moreover, in these media, the DAMP molecules, heat-shock protein-70 (HSP-70) and high mobility group box-1 (HMGB1) were detected. Overall, these findings reveal that DAMP molecules released from damaged and necrotic hepatocytes may serve as a crucial link between the initial hepatocyte damage and the activation of innate immune cells following APAP-exposure, and that DAMPs may represent a potential therapeutic target for AILI.

Potential role of high-mobility group box 1 in cystic fibrosis airway disease

RATIONALE

High-mobility group box 1 (HMGB1) is a potent inflammatory mediator elevated in sepsis and rheumatoid arthritis, although its role in cystic fibrosis (CF) lung disease is unknown.

OBJECTIVES

To determine whether HMGB1 contributes to CF lung inflammation, including neutrophil chemotaxis and lung matrix degradation.

METHODS

We used sputum and serum from subjects with CF and a Scnn1b-transgenic (Scnn1b-Tg) mouse model that overexpresses beta-epithelial Na(+) channel in airways and mimics the CF phenotype, including lung inflammation. Human secretions and murine bronchoalveolar lavage fluid (BALF) was assayed for HMGB1 by Western blot and ELISA. Neutrophil chemotaxis was measured in vitro after incubation with human neutrophils. The collagen fragment proline-glycine-proline (PGP) was measured by tandem mass spectroscopy.

MEASUREMENTS AND MAIN RESULTS

HMGB1 was detected in CF sputum at higher levels than secretions from normal individuals. Scnn1b-Tg mice had elevated levels of HMGB1 by Western blot and ELISA. We demonstrated that dose-dependent chemotaxis of human neutrophils stimulated by purified HMGB1 was partially dependent on CXC chemokine receptors and that this could be duplicated in CF sputum and BALF from Scnn1b-Tg mice. Neutralization by anti-HMGB1 antibody, in both the sputum and BALF-reduced chemotaxis, which suggested that HMGB1 contributed to the chemotactic properties of these samples. Intratracheal administration of purified HMGB1 induced neutrophil influx into the airways of mice and promoted the release of PGP. PGP was also elevated in Scnn1b-Tg mice and CF serum.

CONCLUSIONS

HMGB1 expression contributes to pulmonary inflammation and lung matrix degradation in CF airway disease and deserves further investigation as a biomarker and potential therapeutic target.

Clinical significance of serum HMGB-1 and sRAGE levels in systemic sclerosis: association with disease severity

INTRODUCTION

The high mobility group box 1 protein (HMGB-1)/advanced glycation end products (RAGE) system is recently shown to play an important part in immune/inflammatory disorders. However, the association of this system in systemic sclerosis (SSc) remains unknown.

MATERIALS AND METHODS

To determine clinical association of serum levels of HMGB-1 and soluble RAGE (sRAGE) in patients with SSc, sera from 70 patients with SSc and 25 healthy controls were examined by enzyme-linked immunosorbent assay. Sera from tight-skin mice and bleomycin-induced scleroderma mice, animal models for SSc, were also examined. Skin HMGB-1 and RAGE expression was assessed by immunohistochemistry.

RESULTS AND DISCUSSION

Serum HMGB-1 and sRAGE levels in SSc were higher than those in controls. Similarly, HMGB-1 and sRAGE levels in animal SSc models were higher than those in control mice. SSc patients with elevated HMGB-1 and sRAGE levels had more frequent involvement of several organs and immunological abnormalities compared to those with normal levels. Furthermore, HMGB-1 and sRAGE levels correlated positively with modified Rodnan total skin thickness score and negatively with pulmonary function test.

CONCLUSIONS

HMGB-1 and sRAGE expression in the sclerotic skin was more intense than normal skin. These results suggest that elevated serum HMGB-1 and sRAGE levels are associated with the disease severity and immunological abnormalities in SSc.

Sodium salicylate switches glucose depletion-induced necrosis to autophagy and inhibits high mobility group box protein 1 release in A549 lung adenocarcinoma cells

Sodium salicylate, the active metabolite of aspirin, has been shown to exert anti-inflammatory activities by inhibiting the expression of various pro-inflammatory factors, and has potent anti-cancer effects against a number of human cancers including colon, lung, breast and leukemia. Necrotic cell death is emerging as one of the crucial factors that trigger an inflammatory response since during necrotic death the cell membrane is ruptured and the intracellular constituents including high mobility group box 1 (HMGB1) are released into the extracellular space, thereby activating an inflammatory response. In contrast, autophagic death is regarded as a form of tumour suppressive cell death, as indicated in tumour suppressors such as beclin 1 in autophagic pathways. To better understand the anti-inflammatory properties of sodium salicylate and its effect on necrotic cell death in A549 cells induced by glucose depletion (GD), a common characteristic of the tumour micro-environment, was examined. While GD induced mostly necrotic death in A549 cells, salicylate suppresssed GD-induced necrosis and HMGB1 release. In addition, salicylate shifted the cell death pattern to autophagy by inhibiting GD-induced Cu/Zn superoxide dismutase release and ROS production. These results indicate that the activity of salicylate to prevent necrotic death may contribute to its anti-inflammatory action and suppress tumour development possibly through switching the cell death mode from tumour-promoting necrotic cell death to tumour-suppressive autophagic cell death.

[Effect of N-acetylcysteine on HMGB1 and RAGE expression in the lungs of asthmatic mice]

OBJECTIVE

To investigate the expression of HMGB1 and RAGE mRNA in the lungs of asthmatic mice and the effect of N-acetylcysteine (NAC) on their expression.

METHODS

Twenty-one female BALB/c mice were randomly divided into control group, asthma group and NAC group (n=7). The expressions of HMGB1 and RAGE mRNA and their distributions in the lungs were detected by RT-PCR and immunohistochemical method.

RESULTS

The expression levels of HMGB1 and RAGE mRNA were not significantly different between the control group (0.88-/+0.02 and 1.20-/+0.20, respectively) and the asthma model group (0.86-/+0.05 and 1.21-/+0.08, P>0.05). After NAC treatment, both of HMGB1 and RAGE mRNA levels (0.98-/+0.05 and 1.58-/+0.21) were significantly higher than those in the other two groups (P<0.05). HMGB1 was found in the nuclei and membrane of the bronchial and alveolar epithelial cells, and RAGE was located on the membrane of the alveolar epithelial cells.

CONCLUSION

HMGB1 and RAGE may play a role in the oxidative stress during asthma, but the exact mechanism needs further investigation.

Role of Janus kinase/signal transducer and activator of transcription pathway in regulation of expression and inflammation-promoting activity of high mobility group box protein 1 in rat peritoneal macrophages

Signal transduction mechanism in the regulation of high mobility group box protein 1 (HMGB1) has not yet been well elucidated. Our data showed for the first time that Janus kinase-signal transduction and activator of transcription (JAK/STAT) pathway played a major role in the regulation of expression and inflammatory effect of HMGB1. The study was carried out in the following sequence. Firstly, the role of JAK/STAT pathway in the regulation of expression of HMGB1 was examined. After stimulation with 75 ng/mL LPS in vitro, significant increases in HMGB1 expression and prompt activation of JAK/STAT pathway were demonstrated in cultured macrophages. On the other hand, administration of AG490 (specific inhibitor for JAK2), fludarabine (specific inhibitor for STAT1) or rapamycin (specific inhibitor for STAT3) markedly suppressed HMGB1 expression. Secondly, the role of JAK/STAT pathway in the regulation of TNF-alpha expression induced by HMGB1 was examined. When macrophages were stimulated with 10 microg/mL HMGB1 in vitro, significant increases in TNF-alpha expression and prompt activation of JAK/STAT pathway were demonstrated, whereas inhibitors of JAK/STAT pathway significantly suppressed TNF-alpha expression. Taken together, our data strongly indicated that expression and inflammatory effect of HMGB1 could be mediated by JAK/STAT pathway and suggested a possible clinical strategy to control an inflammatory effect of HMGB1 in sepsis.

[A research on blockage of receptor-interacting protein 2 expression by small interfering RNA in murine macrophages]

OBJECTIVE

To provide evidence that blocking the receptor-interacting protein 2 (Rip2) expression can decrease inflammatory cytokine production by macrophage and protect mice from endotoxin lethality.

METHODS

Murine Rip2 small interfering RNA (siRNA) plamids were constructed and transfected into macrophages and Rip2 expression was assessed with RT-PCR and Western blot. Cell proliferation was assayed with MTT; TNFalpha concentration was assayed with ELISA and high-mobility group box 1 protein (HMGB1) level with semi quantitative Western blot after lipopolysaccharide (LPS) stimulation. LPS challenge was given after the plasmids were injected into mice and the survival rate was calculated. Rip2 and HMGB1 expression in liver was assessed with Western blot and serum TNFalpha level with ELISA.

RESULTS

Rip2 siRNA plasmids could block the mRNA and protein expression of Rip2 and promote cell proliferation. Blocking of Rip2 could attenuate LPS-induced TNFalpha and HMGB1 production. HMGB1 expression in liver were decreased to (40.21 +/- 11.03) pg/g and serum TNFalpha level was decreased to (300.43 +/- 59.26) ng/L (P < 0.05). The survival rate of endotoxemic mice was also improved (P < 0.05).

CONCLUSION

The results demonstrate that Rip2 siRNA plasmids can block the expression of Rip2, and decrease the production of TNFalpha and HMGB1, thus protect mice from lethal endotoxemia.

[Advances in high mobility group box-1 protein mediated multiple organ dysfunction and its potential interventional strategies]

High mobility group box-1 protein (HMGB1) has recently been shown as a crucial late mediator of inflammation and sepsis, and is involved in mediating multi-organ functional lesions, including acute lung, liver, and intestine injuries. As a delayed inflammatory cytokine, HMGB1 provides a wider therapeutic time window for clinical intervention. HMGB1 has been proven to be a promising therapeutic target to prevent the development of multiple organ dysfunction syndrome in experimental models of severe sepsis. The pharmacological strategies include neutralization of antibodies or specific HMGB1 antagonists, suppression of HMGB1 secretion (ethyl pyruvate, agonists for alpha7-nicotinic acetylcholine receptors), and down-regulation of HMGB1 expression (sodium butyrate, signaling inhibitors for Janus kinase/signal transducer and activator of transcription).

Fibroblasts mediate induction of high mobility group box protein 1 in lung epithelial cancer cells by diffusible factors

Cancer development is associated with the high mobility group box protein 1 (HMGB1), which modulates the transcriptional activity in the nucleus, but it is also present in the cytoplasm and outside the cell in certain conditions. As the progression of lung cancer is supported by mitogenic stimuli of stromal fibroblasts, we studied the impact of lung fibroblasts (WI-38) on the expression and localization of HMGB1 in lung epithelial cancer cells (H358). HMGB1 was mainly localized in the nucleus of non-mitotic H358 cells but highly distributed in the cytoplasm of mitotic cells. Conditioned medium (CM) from WI-38 fibroblasts enhanced the expression of HMGB1 at the mRNA and protein level compared to the control CM from H358 cells. In particular, the amount of cytoplasmic HMGB1 was elevated in response to fibroblast CM, which was reduced by inhibiting the basic fibroblast growth factor with blocking antibodies. Although cytoplasmic HMGB1 can be released from the cell, we did not determine a significant amount of extracellular HMGB1 in these conditions. This might partially be based on the sensitivity of HMGB1 to extracellular proteases as CM caused fast proteolysis of the cytoplasmic HMGB1 preparations. Our data suggest that diffusible factors of fibroblasts support the biological function of cancer cells via HMGB1 activation.

[Effect of Xuebijing injection on renal high mobility group box-1 protein expression and acute kidney injury in rats after scald injury]

OBJECTIVE

To investigate the change in renal high mobility group box-1 protein (HMGB1) levels, and the effect of Chinese traditional medicine-Xuebijing injection on HMGB1 expression as well as acute kidney injury in rats after scald injury.

METHODS

Wistar rats were subjected to 30% full-thickness scald injury followed with delayed resuscitation. Totally 78 animals were divided into sham scald group (n=18), scald injury group (n=30), and Xuebijing injection treatment group (n=30). All animals were sacrificed at 8, 24, and 72 hours postburn. Renal tissue and blood samples were harvested to determine HMGB1 mRNA as well as protein expression and organ functional parameters. HMGB1 mRNA level was semi-quantitatively measured by the reverse transcription polymerase chain reaction taking GAPDH as an internal standard, and protein expressions of HMGB1 were detected by both Western blot and immunohistochemistry. Serum creatinine (Cr) contents were measured by automatic biochemistry analyzer. In addition, pathological lesions in kidney were observed under light microscope using HE staining.

RESULTS

Compared with sham scald group, both mRNA and protein expressions of HMGB1 were significantly enhanced in the kidney at 8, 24, and 72 hours after scald injury (P<0.05, P<0.01), meanwhile serum Cr contents were markedly increased following acute insults (P<0.05, P<0.01). Treatment with Xuebijing injection could markedly down-regulated renal HMGB1 mRNA expression and protein release at 24 hours and 72 hours (P<0.05, P<0.01), and significantly reduced serum Cr content following scald injury (P<0.05). Many inflammatory cells in renal tissues were observed using light microscope following scald. The histological morphology of kidney lesions was a-HMGB1, a late mediator, appears to be inmeliorated after treatment with Xuebijing injection.

CONCLUSIONS

volved in the pathogenesis of excessive inflammatory response and acute kidney damage. Treatment with Xuebijing injection can inhibit HMGB1 synthesis and release in renal tissues, and may prevent the development of acute kidney injury induced by serious scald injury.

Tolerization with BLP down-regulates HMGB1-a critical mediator of sepsis-related lethality

Tolerization with bacterial lipoprotein (BLP) affords a significant survival benefit in sepsis. Given that high mobility group box protein-1 (HMGB1) is a recognized mediator of sepsis-related lethality, we determined if tolerization with BLP leads to alterations in HMGB1. In vitro, BLP tolerization led to a reduction in HMGB1 gene transcription. This was mirrored at the protein level, as HMGB1 protein expression and release were reduced significantly in BLP-tolerized human THP-1 monocytic cells. BLP tolerance in vivo led to a highly significant, long-term survival benefit following challenge with lethal dose BLP in C57BL/6 mice. This was associated with an attenuation of HMGB1 release into the circulation, as evidenced by negligible serum HMGB1 levels in BLP-tolerized mice. Moreover, HMGB1 levels in peritoneal macrophages from BLP-tolerized mice were reduced significantly. Hence, tolerization with BLP leads to a down-regulation of HMGB1 protein synthesis and release. The improved survival associated with BLP tolerance could thus be explained by a reduction in HMGB1, were the latter associated with lethality in BLP-related sepsis. In testing this hypothesis, it was noted that neutralization of HMGB1, using anti-HMGB1 antibodies, abrogated BLP-associated lethality almost completely. To conclude, tolerization with BLP leads to a down-regulation of HMGB1, thus offering a novel means of targeting the latter. HMGB1 is also a mediator of lethality in BLP-related sepsis.

RETRACTED ARTICLE: Nafamostat mesilate inhibits the expression of HMGB1 in lipopolysaccharide-induced acute lung injury

PURPOSE

High mobility group box 1 (HMGB1) protein has recently been shown to be an important late mediator of acute lung injury and a promising therapeutic target. Nafamostat mesilate (NM) is a broad-range synthetic protease inhibitor with some anti-inflammatory action. The purpose of this study was to evaluate the effect of NM on HMGB1 in lipopolysaccharide (LPS)-induced lung injury in rats.

METHODS

Male Wistar rats were given either saline (LPS group) or NM (NM+LPS group) 30 min before the intravenous injection of a bolus of LPS (5 mg.kg(-1)). After the administration of LPS, injury to the lung and the expression of HMGB1, tumor necrosis factor-alpha (TNF-alpha), and plasminogen activator inhibitor-1 (PAI-1) were examined.

RESULTS

Histological examination revealed that interstitial edema, leukocytic infiltration, and HMGB1 protein expression were markedly reduced in the NM+LPS group compared to the LPS group. Furthermore, the LPS-induced increases in PAI-1 activity and in plasma TNF-alpha concentrations were also lower in the rats given both NM and LPS than in the rats given LPS alone.

CONCLUSIONS

The anticoagulatory activity of NM may have inhibited PAI-1, while its anti-inflammatory activity blockaded TNF-alpha, thereby indirectly inhibiting HMGB1 and reducing tissue damage in the lung. These findings indicate that NM can inhibit the lung injury induced by LPS in rats. NM is an excellent candidate for use in new therapeutic strategies to prevent or minimize lung injury.

Toll-like receptor 9-dependent activation by DNA-containing immune complexes is mediated by HMGB1 and RAGE

Increased concentrations of DNA-containing immune complexes in the serum are associated with systemic autoimmune diseases such as lupus. Stimulation of Toll-like receptor 9 (TLR9) by DNA is important in the activation of plasmacytoid dendritic cells and B cells. Here we show that HMGB1, a nuclear DNA-binding protein released from necrotic cells, was an essential component of DNA-containing immune complexes that stimulated cytokine production through a TLR9-MyD88 pathway involving the multivalent receptor RAGE. Moreover, binding of HMGB1 to class A CpG oligodeoxynucleotides considerably augmented cytokine production by means of TLR9 and RAGE. Our data demonstrate a mechanism by which HMGB1 and RAGE activate plasmacytoid dendritic cells and B cells in response to DNA and contribute to autoimmune pathogenesis.