Treatment of Marmoset Intracerebral Hemorrhage with Humanized Anti-HMGB1 mAb

Intracerebral hemorrhage (ICH) is recognized as a severe clinical problem lacking effective treatment. High mobility group box-1 (HMGB1) exhibits inflammatory cytokine-like activity once released into the extracellular space from the nuclei. We previously demonstrated that intravenous injection of rat anti-HMGB1 monoclonal antibody (mAb) remarkably ameliorated brain injury in a rat ICH model. Therefore, we developed a humanized anti-HMGB1 mAb (OKY001) for clinical use. The present study examined whether and how the humanized anti-HMGB1 mAb ameliorates ICH injury in common marmosets. The results show that administration of humanized anti-HMGB1 mAb inhibited HMGB1 release from the brain into plasma, in association with a decrease of 4-hydroxynonenal (4-HNE) accumulation and a decrease in cerebral iron deposition. In addition, humanized anti-HMGB1 mAb treatment resulted in a reduction in brain injury volume at 12 d after ICH induction. Our in vitro experiment showed that recombinant HMGB1 inhibited hemoglobin uptake by macrophages through CD163 in the presence of haptoglobin, suggesting that the release of excess HMGB1 from the brain may induce a delay in hemoglobin scavenging, thereby allowing the toxic effects of hemoglobin, heme, and Fe2+ to persist. Finally, humanized anti-HMGB1 mAb reduced body weight loss and improved behavioral performance after ICH. Taken together, these results suggest that intravenous injection of humanized anti-HMGB1 mAb has potential as a novel therapeutic strategy for ICH.

Therapeutic effect of anti-HMGB1 antibody in a mouse model of 4-h middle cerebral artery occlusion: comparison with tissue plasminogen activator

OBJECTIVE

Delayed tissue plasminogen activator (tPA) treatment increases the risk of intracerebral hemorrhage in patients with ischemic stroke. We previously demonstrated that tPA treatment caused hemorrhagic complications in a 4-h middle cerebral artery occlusion (MCAO) mouse model when administered after reperfusion. In the present study, we administered an anti-high mobility group box 1 (αHMGB1) antibody to 4-h MCAO mice to evaluate the usability of αHMGB1 antibody treatment in the delayed phase of ischemia, beyond the therapeutic time window of tPA.

METHODS

αHMGB1 antibody, tPA and control IgG were dissolved in normal saline and administered intravenously into the tail vein of the mice after reperfusion. Infarct volume, hemorrhagic volume, brain swelling, functional outcomes and levels of pro-inflammatory cytokines, such as HMGB1, interleukin (IL)-6 and tumor necrosis factor (TNF)-α, were evaluated 24 h after MCAO.

RESULTS

tPA treatment was not only ineffective but also caused a massive intracerebral hemorrhage. Treatment with αHMGB1 antibody reduced the infarct volume and swelling and ameliorated neurologic impairment and motor coordination without hemorrhagic complications by inhibiting HMGB1 activity. Moreover, the αHMGB1 antibody suppressed pathways of secondary inflammatory responses, such as IL-6 and TNF-α, after cerebral ischemia.

CONCLUSION

These results indicate that αHMGB1 antibody may be therapeutically efficient in the delayed phase of ischemia, where tPA treatment is no longer an eligible option. Treatment with an αHMGB1 antibody may be an effective therapeutic option in patients who exceed the tPA therapeutic time window.

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.

A Nonlethal Murine Flame Burn Model Leads to a Transient Reduction in Host Defenses and Enhanced Susceptibility to Lethal Pseudomonas aeruginosa Infection

Of the 486,000 burn injuries that required medical treatment in the United States in 2016, 40,000 people were hospitalized, with >3,000 fatalities. After burn injury, humans are at increased risk of sepsis and mortality from infections caused by Pseudomonas aeruginosa, an opportunistic pathogen. We hypothesize that systemic events were initiated from the burn that increased the host's susceptibility to P. aeruginosa. A nonlethal 10% total body surface area (TBSA), full-thickness flame burn was performed in CD-1 mice without and with subsequent P. aeruginosa (strain M2) infection. The 50% lethal dose for subcutaneous infection with P. aeruginosa M2 at the burn site immediately after the burn decreased by 6 log, with mortality occurring between 18 and 26 h, compared with P. aeruginosa-infected mice without burn injury. Bacteria in distal organs were detected by 18 h, concurrent with the onset of clinical symptoms. Serum proinflammatory cytokines (interleukin-6 [IL-6], IL-1β, gamma interferon, and tumor necrosis factor alpha) and the anti-inflammatory cytokine IL-10 were first detected at 12 h postburn with infection and continued to increase until death. Directly after burn alone, serum levels of HMGB1, a danger-associated molecular pattern and TLR4 agonist, transiently increased to 50 ng/ml before returning to 20 ng/ml. Burn with P. aeruginosa infection increased serum HMGB1 concentrations >10-fold (250 ng/ml) at the time of death. This HMGB1-rich serum stimulated TLR4-mediated NF-κB activation in a TLR4 reporter cell line. Treatment of infected burned mice with P5779, a peptide inhibitor of HMGB1, increased the mean survival from 23 to 42 h (P < 0.0001). We conclude that the high level of serum HMGB1, which preceded the increase in proinflammatory cytokines, is associated with postburn mortality.

Attenuating Effects of Dieckol on High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease by Decreasing the NLRP3 Inflammasome and Pyroptosis

Nonalcoholic fatty liver disease (NAFLD), which promotes serious health problems, is related to the increase in the nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome and pyroptosis by a high-fat diet (HFD). Whether dieckol (DK), a component of Ecklonia cava extracts (ECE), attenuated NAFLD in an HFD-induced NAFLD animal model was evaluated. The expression of high mobility group box 1/Toll-like receptor 4/nuclear factor-κB, which initiated the NLRP3 inflammasome, was increased in the liver of HFD-fed animals and significantly decreased with ECE or DK administration. The expression of NLRP3/ASC/caspase-1, which are components of the NLRP3 inflammasome, and the number of pyroptotic cells were increased by HFD and decreased with ECE or DK administration. The accumulation of triglycerides and free fatty acids in the liver was increased by HFD and decreased with ECE or DK administration. The histological NAFLD score was increased by HFD and decreased with ECE or DK administration. The expression of lipogenic genes (FASN, SREBP-2, PPARγ, and FABP4) increased and that of lipolytic genes (PPARα, CPT1A, ATGL, and HSL) was decreased by HFD and attenuated with ECE or DK administration. In conclusion, ECE or DK attenuated NAFLD by decreasing the NLRP3 inflammasome and pyroptosis.

Autoantibody-mediated impairment of DNASE1L3 activity in sporadic systemic lupus erythematosus

Antibodies to double-stranded DNA (dsDNA) are prevalent in systemic lupus erythematosus (SLE), particularly in patients with lupus nephritis, yet the nature and regulation of antigenic cell-free DNA (cfDNA) are poorly understood. Null mutations in the secreted DNase DNASE1L3 cause human monogenic SLE with anti-dsDNA autoreactivity. We report that >50% of sporadic SLE patients with nephritis manifested reduced DNASE1L3 activity in circulation, which was associated with neutralizing autoantibodies to DNASE1L3. These patients had normal total plasma cfDNA levels but showed accumulation of cfDNA in circulating microparticles. Microparticle-associated cfDNA contained a higher fraction of longer polynucleosomal cfDNA fragments, which bound autoantibodies with higher affinity than mononucleosomal fragments. Autoantibodies to DNASE1L3-sensitive antigens on microparticles were prevalent in SLE nephritis patients and correlated with the accumulation of cfDNA in microparticles and with disease severity. DNASE1L3-sensitive antigens included DNA-associated proteins such as HMGB1. Our results reveal autoantibody-mediated impairment of DNASE1L3 activity as a common nongenetic mechanism facilitating anti-dsDNA autoreactivity in patients with severe sporadic SLE.

Caspase-1 inhibition ameliorates murine acute graft versus host disease by modulating the Th1/Th17/Treg balance

Our previous studies have implicated Caspase-1 signaling in driving the proinflammatory state of acute graft versus host disease (aGVHD). Therefore, we aimed to elucidate the mechanism of Caspase-1 in in murine models of aGVHD through specific inhibition of its activity with the decoy peptide Ac-YVAD-CMK. We transplanted bone marrow from donor C57BL/6 (H-2b) mice into recipient BALB/c (H-2Kd) mice and randomized the recipients into the following treatment cohorts: (1) allogeneic hematopoietic stem cell transplantation and splenic cell infusion control (PBS group); (2) low dose Ac-YVAD-CMK (AC low group); (3) and high dose Ac-YVAD-CMK (AC high group). Indeed, we observed that Caspase-1 inhibition by Ac-YVAD-CMK ameliorated pathological damage and inflammation in the liver, lungs, and colon elicited by aGVHD. This was associated with reduced mortality secondary to aGVHD. Mechanistically, we found that Caspase-1 inhibition modulated donor T cell expansion, restored the balance of Th1/Th17/Treg subsets, and markedly decreased serum levels and aGVHD target organ mRNA expression of IL-1β, IL-18, and HMGB1. Thus, we demonstrate that inhibition of Caspase-1 by Ac-YVAD-CMK mitigates murine aGVHD by regulating Th1/Th17/Treg balance and attenuating its characteristic proinflammatory state.

Long non-coding RNA TUG1 promotes airway remodeling and mucus production in asthmatic mice through the microRNA-181b/HMGB1 axis

MicroRNA-181b (miR-181b) has been well noted with anti-inflammatory properties in several pathological conditions. It has also been suggested to be downregulated in patients with asthma. In this study, we explored the function of miR-181b in airway remodeling in asthmatic mice and the molecular mechanism. A mouse model with asthma was induced by ovalbumin (OVA) challenge, and miR-181b was found to be downregulated in lung tissues in the OVA-challenged mice. Overexpression of miR-181b was introduced in mice, after which the respiratory resistance, inflammatory infiltration, mucus production, and epithelial-mesenchymal transition (EMT) and fibrosis in mouse airway tissues were decreased. The integrated bioinformatics analysis suggested long non-coding RNA (lncRNA) TUG1 as a sponge for miR-181b. miR-181 directly targeted high mobility group box 1 (HMGB1) mRNA. HMGB1 was suggested to enhance activation of the nuclear factor kappa B (NF-κB) signaling. Further upregulation of lncRNA TUG1 blocked the protective functions of miR-181b in asthmatic mice. To conclude, this study evidenced that lncRNA TUG1 reinforces HMGB1 expression through sequestering microRNA-181b, which activates the NF-κB signaling pathway and promotes airway remodeling in asthmatic mice. This study may provide novel ideas in asthma management.

HMGB1-TLR4-IL-23-IL-17A axis accelerates renal ischemia-reperfusion injury via the recruitment and migration of neutrophils

Renal ischemia-reperfusion injury (IRI) is an important cause of setting off acute kidney injury. Neutrophil-mediated immunomodulation has a pivotal role in the evolving of IRI. The HMGB1-TLR4-IL-23-IL-17A axis gives rise to neutrophil activation. Therefore, in the study, the role of the HMGB1-TLR4-IL-23-IL-17A axis in IRI was evaluated. Cell viability, inflammation, apoptosis, oxidative stress, survival, renal function and pathology, and the activation of macrophages and neutrophils were measured. Moreover, we evaluated the acetylation, translocation, and secretion of HMGB1 as well as levels of TLR-4, IL-23, IL-17A, and neutrophil chemokines (KC, LIX, and MIP-2). In vivo, anti-HMGB1 antibody decreased the acetylation, translocation, and secretion of HMGB1, reduced the expression of TLR-4, IL-23, IL-17A, KC, LIX, and MIP-2, alleviated the activation of macrophages and neutrophils, improved the survival rate and renal dysfunction, and decreased inflammation, apoptosis, oxidative stress, and pathological injury of the kidney. However, the intervention with recombinant HMGB1(R-HMGB1) significantly abolish the above effect of anti-HMGB1 in IRI. Neutralization IL-23 or IL-17A can alleviated the neutrophils mediated renal dysfunction by suppressing inflammation, apoptosis, and oxidative stress in IRI. In vitro, we confirmed that hypoxic/deoxygenation (H/R) induces the secretion of HMGB1 though acetylation on HK-2 and HMGB1 promotes the secretion of IL-23 in a HMGB1/TLR-4-dependent manner on macrophages. Together, these results implied that the HMGB1-TLR4-IL-23-IL-17A axis regulates inflammation, oxidative stress, apoptosis, and renal injury in IRI by promoting the recruitment and migration of neutrophils.

Inhibition of hypoxia inducible factor 1 by YC-1 attenuates tissue plasminogen activator induced hemorrhagic transformation by suppressing HMGB1/TLR4/NF-κB mediated neutrophil infiltration in thromboembolic stroke rats

Hemorrhagic transformation (HT) is a frequent complication of ischemic stroke after thrombolytic therapy and seriously affects the prognosis of stroke. Due to the limited therapeutic window and hemorrhagic complications, tissue plasminogen activator (t-PA) is underutilized in acute ischemic stroke. Currently, there are no clinically effective drugs to decrease the incidence of t-PA-induced HT. Hypoxia-inducible factor 1 (HIF-1) is an important transcription factor that maintains oxygen homeostasis and mediates neuroinflammation under hypoxia. However, the effect of HIF-1 on t-PA-induced HT is not clear. The aim of this study was to investigate the role of HIF-1 in t-PA-induced HT by applying YC-1, an inhibitor of HIF-1. In the present study, we found that HIF-1 expression was significantly increased in ischemic brain tissue after delayed t-PA treatment and was mainly localized in neurons and endothelial cells. Inhibition of HIF-1 by YC-1 improved infarct volume and neurological deficits. YC-1 inhibited matrix metalloproteinase protein expression, increased tight junction protein expression, and ameliorated BBB disruption and the occurrence of HT. Furthermore, YC-1 suppressed the release of inflammatory factors, neutrophil infiltration and the activation of the HMGB1/TLR4/NF-κB signaling pathway. These results demonstrated that inhibition of HIF-1 could protect BBB integrity by suppressing HMGB1/TLR4/NF-κB-mediated neutrophil infiltration, thereby reducing the risk of t-PA-induced HT. Thus, HIF-1 may be a potential therapeutic target for t-PA-induced HT.

Recombinant Thrombomodulin Attenuates Preeclamptic Symptoms by Inhibiting High-Mobility Group Box 1 in Mice

Preeclampsia (PE) is a common gestational complication that involves systemic endothelial dysfunction and inflammatory responses primarily due to placental damage. Recombinant thrombomodulin (rTM), a novel anticoagulant clinically used for disseminated intravascular coagulation, is reported to have a unique anti-inflammatory endothelial repair function by inhibiting proinflammatory mediator high-mobility group box 1 (HMGB1). Despite the severe patient outcomes, there are currently no effective therapeutic options to treat PE. Here, we verified the efficacy of rTM as a novel therapeutic agent for PE using a murine model and human trophoblast cells. We revealed the therapeutic potential of rTM in an angiotensin II(Ang II)-induced PE mouse model. Injection of rTM significantly attenuated clinical features of PE, such as hypertension, proteinuria, fetal growth restriction, and impaired placental vasculature. Elevation of maternal soluble fms-like tyrosine kinase-1 (sFlt-1), a well-accepted causal factor of PE that induces systemic endothelial dysfunction, was suppressed in response to rTM treatment. Supporting these findings, our in vitro experiments revealed that rTM reduces Ang II-triggered overproduction of sFlt-1 in human trophoblast cells. Moreover, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), well-known key inflammatory mediators in PE pathogenesis, were diminished by rTM. SiRNA knockdown experiments further determined that these processes were directly mediated by HMGB1. Our studies demonstrate that rTM exerts its clinical effect as HMBG1 inhibitor and ameliorates placental dysfunction, which is central to PE pathogenesis. Our findings suggest that rTM could be a promising therapeutic that significantly improve the outcomes of PE patients.

HMGB1 aggravates lipopolysaccharide-induced acute lung injury through suppressing the activity and function of Tregs

BACKGROUND

CD4⁺CD25⁺FoxP3⁺ T helper cells (Tregs), a subgroup of CD4⁺ T helper cells, are critical effectors that protect against acute lung injury (ALI) by contact-dependent suppression or releasing anti-inflammatory cytokines including interleukin-10 (IL-10), and transforming growth factor (TGF-β). HMGB1 (High mobility group box 1 protein) was identified as a nuclear non-histone DNA-binding chromosomal protein, which participates in the regulation of lung inflammatory response and pathological processes in ALI. Previous studies have suggested that Tregs overexpresses the HMGB1-recognizing receptor. However, the interaction of HMGB1 with Tregs in ALI is still unclear.

OBJECTIVE

To investigate whether HMGB1 aggravates ALI by suppressing immunosuppressive function of Tregs.

METHODS

Anti-HMGB1 antibody and recombinant mouse HMGB1 (rHMGB1) were administered in lipopolysaccharide (LPS)-induced ALI mice and polarized LPS-primed Tregs in vitro. The Tregs pre-stimulated with or without rHMGB1 were adoptively transferred to ALI mice and depleted by Diphtheria toxin (DT). For coculture experiment, isolated Tregs were first pre-stimulated with or without rHMGB1 or anti-HMGB1 antibody, then they were cocultured with bone marrow-derived macrophages (BMMs) under LPS stimulation.

RESULTS

Tregs protected against acute lung pathological injury. HMGB1 modulated the suppressive function of Tregs as follows: reduction in the number of the cells and the activity of Tregs, the secretion of anti-inflammatory cytokines (IL-10, TGF-β) from Tregs, the production of IL-2 from CD4⁺ T cells and CD11c⁺ DCs, and the M2 polarization of macrophages, as well as inducing proinflammatory response of macrophages.

CONCLUSIONS

HMGB1 could aggravate LPS induced-ALI through suppressing the activity and function of Tregs.

Neutrophil Extracellular Traps (NETs) and Damage-Associated Molecular Patterns (DAMPs): Two Potential Targets for COVID-19 Treatment

COVID-19 is a pandemic disease caused by the new coronavirus SARS-CoV-2 that mostly affects the respiratory system. The consequent inflammation is not able to clear viruses. The persistent excessive inflammatory response can build up a clinical picture that is very difficult to manage and potentially fatal. Modulating the immune response plays a key role in fighting the disease. One of the main defence systems is the activation of neutrophils that release neutrophil extracellular traps (NETs) under the stimulus of autophagy. Various molecules can induce NETosis and autophagy; some potent activators are damage-associated molecular patterns (DAMPs) and, in particular, the high-mobility group box 1 (HMGB1). This molecule is released by damaged lung cells and can induce a robust innate immunity response. The increase in HMGB1 and NETosis could lead to sustained inflammation due to SARS-CoV-2 infection. Therefore, blocking these molecules might be useful in COVID-19 treatment and should be further studied in the context of targeted therapy.

HMGB1 amplifies ILC2-induced type-2 inflammation and airway smooth muscle remodelling

Type-2 immunity elicits tissue repair and homeostasis, however dysregulated type-2 responses cause aberrant tissue remodelling, as observed in asthma. Severe respiratory viral infections in infancy predispose to later asthma, however, the processes that mediate tissue damage-induced type-2 inflammation and the origins of airway remodelling remain ill-defined. Here, using a preclinical mouse model of viral bronchiolitis, we find that increased epithelial and mesenchymal high-mobility group box 1 (HMGB1) expression is associated with increased numbers of IL-13-producing type-2 innate lymphoid cell (ILC2s) and the expansion of the airway smooth muscle (ASM) layer. Anti-HMGB1 ablated lung ILC2 numbers and ASM growth in vivo, and inhibited ILC2-mediated ASM cell proliferation in a co-culture model. Furthermore, we identified that HMGB1/RAGE (receptor for advanced glycation endproducts) signalling mediates an ILC2-intrinsic IL-13 auto-amplification loop. In summary, therapeutic targeting of the HMGB1/RAGE signalling axis may act as a novel asthma preventative by dampening ILC2-mediated type-2 inflammation and associated ASM remodelling.

Asthma can start at any time in life, although most often begins in early childhood. Wheezy viral bronchiolitis is a major independent risk factor for subsequent asthma. However, key knowledge gaps exist in relation to the sequelae of severe viral bronchiolitis and the pathogenic processes that promote type-2 inflammation and airway wall remodelling, cardinal features of asthma. Our study addresses this gap by identifying high-mobility group box 1 as a pathogenic cytokine that contributes to group 2 innate lymphoid cell-induced airway smooth muscle growth.

Glycyrrhetinic acid alleviates hepatic inflammation injury in viral hepatitis disease via a HMGB1-TLR4 signaling pathway

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Licorice defect in TCM recipes leads to the hepatotoxicity in administrated mice.

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GA inhibits viral hepatitis by suppressing HMGB1 release and cytokine activity.

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GA treatment effect on infected mice is similar with HMGB1 neutralizing antibody.

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HMGB1-TLR4 axis is involved in murine hepatic injury during MHV infection.

Various human disorders are cured by the use of licorice, a key ingredient of herbal remedies. Glycyrrhizic acid (GL), a triterpenoid glycoside, is the aqueous extract from licorice root. Glycyrrhetinic acid (GA) has been reported to be a major bioactive hydrolysis product of GL and has been regarded as an anti-inflammatory agent for the treatment of a variety of inflammatory diseases, including hepatitis. However, the mechanism by which GA inhibits viral hepatic inflammatory injury is not completely understood. In this study, we found that, by consecutively treating mice with a traditional herbal recipe, licorice plays an important role in the detoxification of mice. We also employed a murine hepatitis virus (MHV) infection model to illustrate that GA treatment inhibited activation of hepatic inflammatory responses by blocking high-mobility group box 1 (HMGB1) cytokine activity. Furthermore, decreased HMGB1 levels and downstream signaling triggered by injection of a neutralizing HMGB1 antibody or TLR4 gene deficiency, also significantly protected against MHV-induced severe hepatic injury. Thus, our findings characterize GA as a hepatoprotective therapy agent in hepatic infectious disease not only by suppressing HMGB1 release and blocking HMGB1 cytokine activity, but also via an underlying viral-induced HMGB1-TLR4 immunological regulation axis that occurs during the cytokine storm. The present study provides a new therapy strategy for the treatment of acute viral hepatitis in the clinical setting.

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

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

SIRT1-regulated HMGB1 release is partially involved in TLR4 signal transduction: A possible anti-neuroinflammatory mechanism of resveratrol in neonatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic brain injury (HIBI) is a knotty disease that lacks appropriate treatment. Inflammation is an important contributor to brain damage, and microglia are responsible for eliciting early and pronounced inflammatory reactions in the immature brain after hypoxic-ischemic (HI) insult. Acetylated HMGB1 can be released from immune cells into the extracellular space, where it acts as a danger-associated molecular pattern molecule to activate TLR4 signalling-mediated inflammatory responses. Resveratrol has neuroprotective and anti-inflammatory effects against HIBI, but whether these effects involve the regulation of the TLR4 signalling pathway and whether HMGB1 participates in this process is still unclear. We investigated the anti-inflammatory effects of resveratrol in HIBI and the molecular mechanisms potentially involved in the effect. The in vivo and in vitro results indicated that the level of cytoplasmic HMGB1 in microglia increased after insult and that treating experimental animals or mouse BV2 microglial cells with resveratrol attenuated HI insult-induced neuroinflammation, which was characterized by improved behavioural defects, reduced microglial activation and TLR4/MyD88/NF-κB signalling, and attenuated primary neuronal damage; this was accompanied by the inhibition of HMGB1 nucleoplasmic transfer and extracellular release. EX527 pretreatment reversed these effects. In addition, co-immunoprecipitation confirmed that SIRT1 was directly involved in the HMGB1 acetylation process in BV2 cells after oxygen glucose deprivation. These data demonstrate that resveratrol plays a neuroprotective role in neonatal HIBI by activating SIRT1 to inhibit HMGB1/TLR4/MyD88/NF-κB signalling and subsequent neuroinflammatory responses.

Papaverine identified as an inhibitor of high mobility group box 1/receptor for advanced glycation end-products interaction suppresses high mobility group box 1-mediated inflammatory responses

The interaction of high mobility group box 1 (HMGB1), which is secreted from immune and dying cells during cellular infection and injury, and receptor for advanced glycation end-products (RAGE) appears to be critical for acute and chronic inflammatory disorders. Here we designed a unique cyclic β-hairpin peptide (Pepb2), which mimics the predicted RAGE-binding domain of HMGB1. Pepb2 competitively inhibited HMGB1/RAGE interaction. We then identified papaverine as a Pepb2 mimetic by in silico 3D-structural similarity screening from the DrugBank library. Papaverine was found to directly inhibit HMGB1/RAGE interaction. It also suppressed the HMGB1-mediated production of pro-inflammatory cytokines, IL-6 and TNF-α, in mouse macrophage-like RAW264.7 cells and bone marrow-derived macrophages. In addition, papaverine attenuated mortality in cecal ligation puncture-induced sepsis model mice. Taken together, these findings indicate that papaverine could become a useful therapeutic against HMGB1/RAGE-mediated sepsis and other inflammatory diseases.

Significance of serum antibodies against HPV E7, Hsp27, Hsp20 and Hp91 in Iranian HPV-exposed women

BACKGROUND

Among different types of human papillomavirus (HPV), types 16 and 18 were known to be high-risk agents causing mainly cervical cancer. Up to now, the potential of HPV E7 protein has been proved as a diagnostic marker of cervical cancer. Moreover, the levels of anti-heat shock protein (Hsp) and anti-high mobility group box-1 (HMGB1) antibodies in cancer patients have been useful in tumor diagnosis. The goal of the present study was to determine the efficiency of the potential serologic markers including HPV E7, Hsp20, Hsp27 proteins and Hp91 peptide in Iranian HPV-exposed women, for the first time.

METHODS

At first, the recombinant HPV E7, Hsp20 and Hsp27 proteins were expressed in E. coli system, and purified by affinity chromatography under native conditions. Then, antibody responses were detected against the recombinant proteins as well as Hp91 peptide as potential markers in 49 Iranian women who were seropositive for HPV-16 and 18 L1 capsids (i.e., HPV-exposed women) and 49 controls using indirect ELISA.

RESULTS

Our data indicated that the seroreactivities of women exposed to HPV16, HPV18 and both of them against the recombinant E7, Hsp20, Hsp27 proteins and Hp91 peptide were significantly higher than those in control group (p < 0.05 for HPV16 or HPV18; p < 0.01 for both of them versus all markers). HPV-exposed women with high antibody responses to HPV-16 and 18 L1 capsids as a commercial biomarker had significant seroreactivity to HPV-16 and 18 E7 and Hsp27 (p < 0.05). The recombinant E7 and Hsp27 proteins showed higher efficiency than Hsp20 and Hp91 for detection of individuals exposed to HPV infections (p < 0.05).

CONCLUSION

Generally, the levels of serum E7 and Hsp27 were increased in HPV-16 and 18 L1- seropositive women suggesting their potential value as a diagnostic marker for HPV infections.

The Endotoxin Delivery Protein HMGB1 Mediates Caspase-11-Dependent Lethality in Sepsis

Caspase-11, a cytosolic endotoxin (lipopolysaccharide: LPS) receptor, mediates pyroptosis, a lytic form of cell death. Caspase-11-dependent pyroptosis mediates lethality in endotoxemia, but it is unclear how LPS is delivered into the cytosol for the activation of caspase-11. Here we discovered that hepatocyte-released high mobility group box 1 (HMGB1) was required for caspase-11-dependent pyroptosis and lethality in endotoxemia and bacterial sepsis. Mechanistically, hepatocyte-released HMGB1 bound LPS and targeted its internalization into the lysosomes of macrophages and endothelial cells via the receptor for advanced glycation end-products (RAGE). Subsequently, HMGB1 permeabilized the phospholipid bilayer in the acidic environment of lysosomes. This resulted in LPS leakage into the cytosol and caspase-11 activation. Depletion of hepatocyte HMGB1, inhibition of hepatocyte HMGB1 release, neutralizing extracellular HMGB1, or RAGE deficiency prevented caspase-11-dependent pyroptosis and death in endotoxemia and bacterial sepsis. These findings indicate that HMGB1 interacts with LPS to mediate caspase-11-dependent pyroptosis in lethal sepsis.

Hypertonic saline resuscitation protects against kidney injury induced by severe burns in rats

BACKGROUND

Proper fluid resuscitation can relieve visceral damage and improve survival in severely burned patients. This study compared the effectiveness of resuscitation with 400mEq/L hypertonic saline (HS) and sodium lactate Ringer's solution (LR) in rats with kidney injury caused by burn trauma.

METHODS

Rats (Sprague-Dawley) underwent burn injury and were randomized into sham, LR, and HS groups. Samples from the kidney were assayed for water content ratio, histopathology, and oxidative stress (superoxide dismutase (SOD) and malondialdehyde (MDA)). Serum sodium, renal function (creatinine and cystatin (Cys)-C), and inflammatory response (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and high mobility group protein box (HMGB)-1) were also examined as serum markers.

RESULTS

Hypertonic saline resuscitation reduced the renal water content ratio and improved renal histopathology caused by severe burns. This effect was accompanied by reductions in serum creatinine and Cys-C as well as TNF-α, IL-1β, and HMGB1. Serum sodium concentration and SOD activity were increased, whereas MDA content was decreased in the kidney tissue of the HS group.

CONCLUSIONS

The data indicate that 400mEq/L HS solution reduces hyponatremia and renal edema, inhibits the release of inflammatory mediators, and alleviates oxidative stress injury, thus protecting against kidney injury induced by severe burns.

High-mobility group box 1 protein contributes to the immunogenicity of rTcdB-treated CT26 cells

Clostridium difficile TcdB is a key virulence factor that causes C. difficile-associated diseases. Our previous studies have shown that recombinant full-length TcdB (rTcdB) induces cell death in CT26 cells, and rTcdB-treated CT26 cells with high immunogenicity could stimulate dendritic cell (DC) activation and T cell activation in vitro. The rTcdB-treated CT26 cells also induce antitumor immunity in mice and protect mice from CT26 cells. High-mobility group box 1 protein (HMGB1) is a non-histone nuclear protein, which has various biological functions within the nucleus and also acts as an extracellular signal molecule involving in inflammatory diseases, cancers or autoimmune diseases. In this study, HMGB1 was found to be released from the rTcdB-treated CT26 cells. HMGB1 knockdown by using specific siRNA weakened the capacity of the BMDCs loaded with the rTcdB-treated CT26 cells to prime T cells in vitro and in vivo. The released HMGB1 from CT26 cells could interact with the receptor TLR4, which is closely related to DC activation and immune responses. The knockdown of HMGB1 also affected the phagocytosis of the rTcdB-treated CT26 cells by DCs in vitro. Furthermore, HMGB1 weakened the antitumor immunity of the rTcdB-treated CT26 cells, which protects mice from rechallenge of the live CT26 cells. Taken together, these results suggest that HMGB1 plays an important role on the immunogenicity of the rTcdB-treated dying CT26 cells.

Expression profiling and microbial ligand binding analysis of high-mobility group box-1 (HMGB1) in turbot (Scophthalmus maximus L.)

High-mobility group box 1 (HMGB1), a highly conserved DNA-binding protein, was involved in nucleosome formation and transcriptional regulation, and could also act as an extracellular cytokine to trigger inflammation and immune responses. In this study, we identified a HMGB1 gene in turbot (Scophthalmus maximus L.). The full-length SaHMGB1 cDNA includes an open reading frame of 615 bp which encoded a 204 amino acid polypeptide with an estimated molecular mass of 23.19 kDa. SaHMGB1 was closely related to several fish HMGB1 and shared 74.4% overall identity with human. In addition, phylogenetic analyses revealed SaHMGB1 showed the closest relationship to Larimichthys crocea. Furthermore, QPCR analysis showed that SaHMGB1 was expressed in all examined tissues with abundant expression levels in brain, gill, intestine, and head kidney, and showed different expression patterns following different bacterial challenge. The significant quick regulation of SaHMGB1 in mucosal surfaces against infection suggest that HMGB1 might play critical roles in mucosal immunity against bacterial challenge. Finally, the in vitro binding assay showed that SaHMGB1 had strong binding ability to LPS, LTA, and PGN. Functional studies should further characterize HMGB1 function to understand the importance of the integrity of the mucosal barriers against infection, and to facilitate selection of the disease resistant family/strain in turbot.

[Increased expression of HMGB1 and TLR4 in intestinal tissues and intestinal immune dysfunction in severely burned rats]

Objective To investigate the expressions of high mobility group box 1 (HMGB1) and Toll-like receptor 4 (TLR4) in the intestinal tract of severely burned rats and their relationship with intestinal immune function. Methods Forty male SD rats were randomly divided into control group (n=10) and severe burn group (n=30). 60% of the rats' body (the back and ventral side) was burned in the severe burn group, and only anesthesia was performed in normal control group. Rats were sacrificed at 6, 12 and 18 hours after injury in the burn group, while sacrificed immediately after anesthesia in control group. The protein levels of HMGB1 and TLR4 in the intestinal tissue were detected by Western blotting. The purity of total T cells (CD3⁺ T), as well as the ratio of Th1 to Th2 cell subsets, was measured by flow cytometry. ELISA was performed to detect the concentrations of IFN-γ, IL-4 and IL-10. Results Compared with the control group, the protein expressions of HMGB1 and TLR4 in the severe burn group were significantly higher than that in the control group at 6, 12 and 18 hours after injury, in a time-dependent manner. A positive correlation between HMGB1 and TLR4 protein expressions in the severe burn group was observed. The ratio of Th1 to total T cells was significantly raised at 6, 12 and 18 hours after burn injury, and the ratio of Th2 to total T cells decreased, and the ratio of Th1/Th2 significantly increased. Th1 cell percentage was positively correlated with HMGB1 and TLR4, while Th2 cell percentage was negatively correlated with HMGB1 and TLR4. Compared with the control group, the levels of IFN-γ and IL-4 in the intestinal tract were significantly elevated at 6, 12 and 18 hours after severe burn injury, while the level of IL-10 was significantly reduced. With the increase of postburn time, the levels of IFN-γ and IL-4 gradually increased, while the level of IL-10 gradually decreased. Conclusion HMGB1 was recruited in the intestinal tissues to activate TLR4 signaling pathway after severe burn, further activates the downstream signal transcripts and releases a series of inflammatory cytokines to induce inflammatory response, which is involved in Th1 and Th2 cell mediated immune function obstacle of rats.

Improving the potency of DNA vaccine encoding HIV-1 Nef antigen using two endogenous adjuvants in mouse model

BACKGROUND

DNA immunization can induce long-term immune responses, which are required to design an effective HIV vaccine. It was shown that antigen-expressing plasmids can increase the protective immunity against infectious diseases such as: influenza and malaria. However, DNA-based immunizations have poor immunogenicity, thus the use of potent immunoadjuvants can enhance their potency.

METHODS

In the current study, preparation of the recombinant HIV-1 Nef, Gp96 and HMGB1 DNA constructs was performed in bacterial system. Then, the immunogenicity of DNA construct harboring HIV-1 Nef gene (pcDNA-Nef) was studied using two endogenous adjuvants (pcDNA-HMGB1 and pcDNA-Gp96) in BALB/c mouse model.

RESULTS

Our data showed that co-injection of pcDNA-Nef with pcDNA-HMGB1 effectively raised both humoral and cell-mediated immune responses in mice as compared to pcDNA-Nef adjuvanted with pcDNA-gp96. Indeed, co-immunization of HIV-1 Nef DNA with HMGB1 DNA significantly induced high levels of IgG2a and IFN-γ directed toward Th1 responses and also cytotoxic T lymphocytes (CTLs) activity in comparison with other immunized groups.

CONCLUSION

These findings suggest that the full length of HMGB1 gene could be a more efficient adjuvant for improvement of therapeutic HIV DNA-based immunization compared to the full length of gp96 gene (Tab. 1, Fig. 3, Ref. 58).

Pioglitazone Confers Neuroprotection Against Ischemia-Induced Pyroptosis due to its Inhibitory Effects on HMGB-1/RAGE and Rac1/ROS Pathway by Activating PPAR-ɤ

BACKGROUND/AIMS

Recent researches highlighted the protective potential of pioglitazone, a PPAR-γ agonist, in the progression of cerebral ischemia-reperfusion injury. However, there has been no study on the application of pioglitazone in treating ischemic stroke through mechanisms involving pyroptosis.

METHODS

The cerebral injury was established by middle cerebral artery occlusion (MCAO). in vitro ischemia in primary cultured astrocytes was induced by the oxygen-glucose deprivation (OGD). ELISA and Western Blot analysis were employed to the levels of PPAR-γ, pyroptosis-related biomarkers and cytoplasmic translocation of HMGB-1 and RAGE expression as well as Rac1 activity, respectively.

RESULTS

We demonstrated that repeated intraperitoneal administration of pioglitazone remarkably reduced the infarct volume, improved neurological deficits and suppressed the Rac1 activity with significant reduction of excessive ROS in rat model of middle cerebral artery occlusion (MCAO). Moreover, pioglitazone alleviated the up-regulation of pyroptosis-related biomarkers and the increased cytoplasmic translocation of HMGB-1 and RAGE expression in cerebral penumbra cortex. Similarly, the protective effects of pioglitazone on cultured astrocytes were characterized by reduced Rac1 activity, pyroptosis related protein expressions and lactate dehydrogenase (LDH) release. However, these protective effects of pioglitazone were neutralized with the use of GW9662, a PPAR-γ inhibitor. Interestingly, Rac1 knockdown in lentivirus with the Rac1 small hair RNA (shRNA) could inhibit the OGD-induced pyroptosis of primary cultured astrocytes. Furthermore, the combination of Rac1-shRNA and pioglitazone can further strengthen the inhibitory effects on pyroptosis induced by OGD.

CONCLUSION

The neuroprotection of pioglitazone was attributable to the alleviated ischemia/hypoxia-induced pyroptosis and was also associated with the PPARγ-mediated suppression of HGMB-1/RAGE signaling pathway. Moreover, the inhibition of Rac1 promoted this function.

Vitamin D reduces inflammatory response in asthmatic mice through HMGB1/TLR4/NF‑κB signaling pathway

The present study aimed to investigate the effects of vitamin D (VD) on inflammatory responses in asthmatic mice and the underlying mechanism, providing a theoretical basis for clinical application of targeted drug therapy, and the development of novel drugs against asthma. Mouse models of asthma were established. Hematoxylin‑eosin staining was performed to observe the pathological changes of the lung tissue. Pulmonary function tests were conducted to determine airway resistance in asthmatic mice. ELISA was performed to measure the serum levels of inflammatory factors. Western blot analysis and reverse transcription‑quantitative polymerase chain reaction were performed to determine the changes in apoptosis‑inducing factors, and high mobility group box 1 protein (HMGB1)/Toll‑like receptor‑4 (TLR4)/nuclear factor (NF)‑κB signaling pathway‑related proteins. VD reduced infiltrated inflammatory factors, attenuated the airway resistance of asthmatic mice, decreased serum levels of interleukin (IL)‑1β, IL‑6, tumor necrosis factor (TNF)‑α, increased serum levels of IL‑10, decreased apoptotic factor Bcl‑2‑associated X and caspase‑3 expression, downregulated HMGB1 and TLR4, NF‑κB and phosphorylated‑NF‑κB p65 expression. When TLR4 expression was inhibited, the anti‑inflammatory effects of VD were attenuated, and HMGB1, TLR4, NF‑κB and p‑NF‑κB p65 expression was increased. VD was able reduce the inflammatory response of asthmatic mice and apoptosis in lung tissue through the HMGB1/TLR4/NF‑κB signaling pathway.

Effects of subconjunctival administration of anti-high mobility group box 1 on dry eye in a mouse model of Sjӧgren's syndrome

Purpose

Extracellular high mobility group box 1 (HMGB1) acts as a damage associated molecular pattern molecule through the Toll-like receptor to promote autoreactive B cell activation, which may be involved in the pathogenesis of Sjӧgren’s syndrome. The aim of this study was to investigate the effect of subconjunctival administration of anti-HMGB1 on dry eye in a mouse model of Sjӧgren’s syndrome.

Methods

Ten weeks-old NOD.B10.H2^b mice were subconjunctivally injected with 0.02 to 2 μg of anti-HMGB1 antibodies or PBS twice a week for two consecutive weeks. Tear volume and corneal staining scores were measured and compared between before- and after-treatment. Goblet cell density was counted in PAS stained forniceal conjunctiva and inflammatory foci score (>50 cells/focus) was measured in extraorbital glands. Flow cytometry was performed to evaluate the changes in BrdU⁺ cells, IL-17-, IL-10-, or IFNγ-secreting cells, functional B cells, and IL-22 secreting innate lymphoid cells (ILC3s) in cervical lymph nodes. The level of IL-22 in intraorbital glands was measured by ELISA.

Results

Injection of 2 μg or 0.02 μg anti-HMGB1 attenuated corneal epithelial erosions and increased tear secretion (p<0.05). Goblet cell density was increased in 0.2 μg and 2 μg anti-HMGB1-treated-mice with marginal significance. The inflammatory foci score, and the number of BrdU⁺ cells, IL-17-, IL-10-, IFNγ-secreting cells, and functional B cells did not significantly change following anti-HMGB1 treatment. Surprisingly, the percentage of ILC3s was significantly increased in the draining lymph nodes (p<0.05), and the expression of IL-22 was significantly increased in the intraorbital glands (p<0.05) after administration of 2 μg anti-HMGB1.

Conclusion

This study shows that subconjunctival administration of anti-HMGB1 attenuates clinical manifestations of dry eye. The improvement of dry eye may involve an increase of ILC3s, rather than modulation of B or plasma cells, as shown using a mouse model of Sjӧgren’s syndrome.

Toll-like receptor signaling and stages of addiction

BACKGROUND

Athina Markou and her colleagues discovered persistent changes in adult behavior following adolescent exposure to ethanol or nicotine consistent with increased risk for developing addiction. Building on Dr. Markou's important work and that of others in the field, researchers at the Bowles Center for Alcohol Studies have found that persistent changes in behavior following adolescent stress or alcohol exposure may be linked to induction of immune signaling in brain.

AIM

This study aims to illuminate the critical interrelationship of the innate immune system (e.g., toll-like receptors [TLRs], high-mobility group box 1 [HMGB1]) in the neurobiology of addiction.

METHOD

This study reviews the relevant research regarding the relationship between the innate immune system and addiction.

CONCLUSION

Emerging evidence indicates that TLRs in brain, particularly those on microglia, respond to endogenous innate immune agonists such as HMGB1 and microRNAs (miRNAs). Multiple TLRs, HMGB1, and miRNAs are induced in the brain by stress, alcohol, and other drugs of abuse and are increased in the postmortem human alcoholic brain. Enhanced TLR-innate immune signaling in brain leads to epigenetic modifications, alterations in synaptic plasticity, and loss of neuronal cell populations, which contribute to cognitive and emotive dysfunctions. Addiction involves progressive stages of drug binges and intoxication, withdrawal-negative affect, and ultimately compulsive drug use and abuse. Toll-like receptor signaling within cortical-limbic circuits is modified by alcohol and stress in a manner consistent with promoting progression through the stages of addiction.

Inhibiting HMGB1 Reduces Cerebral Ischemia Reperfusion Injury in Diabetic Mice

High mobility group box1 (HMGB1) promotes inflammatory injury, and accumulating evidence suggests that it plays a key role in brain ischemia reperfusion (I/R), as well as the development of diabetes mellitus (DM). The purpose of this study was to investigate whether HMGB1 plays a role in brain I/R in a DM mouse model. Diabetes mellitus was induced by a high-calorie diet and streptozotocin treatment, and cerebral ischemia was induced by middle cerebral artery occlusion. We examined HMGB1 levels following cerebral I/R injury in DM and non-DM mice and evaluated the influence of altered HMGB1 levels on the severity of cerebral injury. Serum HMGB1 levels and the inflammatory factors IL-1β, IL-6, and inflammation-related enzyme iNOS were significantly elevated in DM mice with brain I/R compared with non-DM mice with brain I/R. Blocking HMGB1 function by intraperitoneal injection of anti-HMGB1 neutralizing antibodies reversed the inflammatory response and the extent of brain damage, suggesting that HMGB1 plays an important role in cerebral ischemic stroke in diabetic mice.

HMGB1 exacerbates experimental mouse colitis by enhancing innate lymphoid cells 3 inflammatory responses via promoted IL-23 production

In inflammatory bowel diseases (IBD), high mobility group box 1 (HMGB1), as an endogenous inflammatory molecule, can promote inflammatory cytokines secretion by acting on TLR2/4 resulting in tissue damage. The underlying mechanisms remain unclear. Here we report a novel role of HMGB1 in controlling the maintenance and function of intestine-resident group-3 innate lymphoid cells (ILC3s) that are important innate effector cells implicated in mucosal homeostasis and IBD pathogenesis. We showed that mice treated with anti-HMGB1 Ab, or genetically deficient for TLR2-/- or TLR4-/- mice, displayed reduced intestinal inflammation. In these mice, the numbers of colonic ILC3s were significantly reduced, and the levels of IL-17 and IL-22 that can be secreted by ILC3s were also decreased in the colon tissues. Furthermore, HMGB1 promoted DCs via TLR2/4 signaling to produce IL-23, activating ILC3s to produce IL-17 and IL-22. Our data thus indicated that the HMGB1-TLR2/4-DCs-IL-23 cascade pathway enhances the functions of ILC3s to produce IL-17 and IL-22, and this signal way might play a vital role in the development of IBD.

PKM2-dependent glycolysis promotes NLRP3 and AIM2 inflammasome activation

Sepsis, severe sepsis and septic shock are the main cause of mortality in non-cardiac intensive care units. Immunometabolism has been linked to sepsis; however, the precise mechanism by which metabolic reprogramming regulates the inflammatory response is unclear. Here we show that aerobic glycolysis contributes to sepsis by modulating inflammasome activation in macrophages. PKM2-mediated glycolysis promotes inflammasome activation by modulating EIF2AK2 phosphorylation in macrophages. Pharmacological and genetic inhibition of PKM2 or EIF2AK2 attenuates NLRP3 and AIM2 inflammasomes activation, and consequently suppresses the release of IL-1β, IL-18 and HMGB1 by macrophages. Pharmacological inhibition of the PKM2-EIF2AK2 pathway protects mice from lethal endotoxemia and polymicrobial sepsis. Moreover, conditional knockout of PKM2 in myeloid cells protects mice from septic death induced by NLRP3 and AIM2 inflammasome activation. These findings define an important role of PKM2 in immunometabolism and guide future development of therapeutic strategies to treat sepsis.

Relationships between High-mobility Group Protein B1 and Triggering Receptor Expressed on Myeloid Cells Concentrations in Gingival Crevicular Fluid and Chronic Periodontitis

One of the inflammatory mediators which is secreted by inflammatory cells is high-mobility group protein B1 (HMGB1). Interaction of HMGB1 and toll-like receptors (TLRs) leads to increased production of inflammatory cytokines. On the other hand, it was shown that triggering receptor expressed on myeloid cells (TREM-1) also can be activated by TLRs, and its soluble form (sTREM-1) can be formed by cleaving of membrane-bound form of TREM-1 proteinases. Since there is not enough knowledge about the precise role of HMGB1 and sTREM-1 in periodontal diseases, the aim of this study was to evaluate the concentration of HMGB1 and sTREM-1 in gingival crevicular fluid (GCF) samples of patients with chronic periodontitis. Gingival crevicular fluid (GCF) samples were obtained from a total of 24 individuals with clinically healthy gingiva and 24 patients with moderate to severe chronic periodontitis. For collecting GCF samples, periopapers were placed at the entrance of the crevice and left in position for 30 seconds. Then, they were stored at -80°C. Enzyme-linked immunosorbent assay (ELISA) was used for measuring the concentration of HMGB1 and sTREM-1 in GCF samples. The concentration of HMGB1 (p<0.001) and sTREM-1 (p<0.017), was significantly higher in chronic periodontitis group. In addition, there was a significant positive correlation between HMGB1 and sTREM-1 concentration in chronic periodontitis group (p<0.05). We also found significant positive correlation between PD (Pocket depth) and the concentration of HMGB1 (p<0.001) and sTREM-1 (p<0.015). It is concluded that both HMGB1 and sTREM-1 are released during the inflammatory response of periodontal tissues and they can promote inflammatory process, which leads to tissue destruction.

CoVaccine HT™ adjuvant is superior to Freund's adjuvants in eliciting antibodies against the endogenous alarmin HMGB1

Adjuvants are used to enhance the immune response against specific antigens for the production of antibodies, with the choice of adjuvant most critical for poorly immunogenic and self-antigens. This study quantitatively and qualitatively evaluated CoVaccine HT™ and Freund's adjuvants for eliciting therapeutic ovine polyclonal antibodies targeting the endogenous alarmin, high mobility group box-1 (HMGB1). Sheep were immunised with HMGB1 protein in CoVaccine HT™ or Freund's adjuvants, with injection site reactions and antibody titres periodically assessed. The binding affinity of antibodies for HMGB1 and their neutralisation activity was determined in-vitro, with in vivo activity confirmed using a murine model of endotoxemia. Results indicated that CoVaccine HT™ elicited significantly higher antibody tires with stronger affinity and more functional potency than antibodies induced with Freund's adjuvants. These studies provide evidence that CoVaccine HT™ is superior to Freund's adjuvants for the production of antibodies to antigens with low immunogenicity and supports the use of this alternative adjuvant for clinical and experimental use antibodies.

Platelet-derived high-mobility group box 1 promotes recruitment and suppresses apoptosis of monocytes

Platelets are circulating cellular sensors that express and release the damage-associated molecular pattern molecule (DAMP) high-mobility group box 1 (HMGB1) at sites of disrupted vascular and tissue integrity. We have recently identified platelet-derived HMGB1 as a critical mediator of thrombosis. The role of platelet-derived HMGB1 in mediating interactions with monocytes remains unknown. In transgenic mice with platelet-specific ablation of HMGB1 and neutralization studies, we show that HMGB1 derived from platelets promotes recruitment of monocytes and prevents monocytes from undergoing apoptosis. During experimental trauma and hemorrhagic shock, infiltrated monocytes in the lung and liver were significantly attenuated in mice lacking HMGB1 in platelets. Platelet-derived HMGB1 mediated monocyte migration via the receptor for advanced glycation end products (RAGE) and suppressed apoptosis via toll-like receptor 4 (TLR4)-dependent activation of MAPK/ERK (extracellular signal-regulated kinase) in monocytes. In conclusion, we identify platelet-derived HMGB1 as a critical regulator of monocyte recruitment and apoptosis, with potential implications in disease states associated with thrombosis and inflammation.

Escin Increases the Survival Rate of LPS-Induced Septic Mice Through Inhibition of HMGB1 Release from Macrophages

BACKGROUND

Previous studies have described the effects of Escin on improving the survival rate of endotoxemic animals. The purpose of this study was to explore the molecular mechanisms of this potentially beneficial treatment.

METHODS

First, the survival rate of endotoxemic mice was monitored for up to 2 weeks after Escin pretreatment, Escin post-treatment, or Escin post-treatment + rHMGB1. The effects of Escin on the release of pro-inflammatory cytokines such as TNF-α, IL-1β, IL-6 and HMGB1 in the serum of endotoxemic mice and LPS-induced macrophages were evaluated by ELISA. Furthermore, the mRNA and protein levels of HMGB1 in LPS-induced macrophages were measured by qRT-PCR and Western blot, respectively. Additionally, the release of pro-inflammatory cytokines such as TNF-α, IL-1β, IL-6 was evaluated by ELISA in rHMGB1-induced macrophages. Finally, the protein levels and the activity of NF-κB in macrophages were checked by Western blot and ELISA, respectively.

RESULTS

Both pretreatment and post-treatment with Escin could improve the survival rate of endotoxemic mice, while exogenous rHMGB1 reversed this effect. In addition, Escin decreased the level of the pro-inflammatory cytokinesTNF-α,IL-1β, IL-6 and HMGB1 in endotoxemic mice and in LPS-induced macrophages. Escin could also inhibit the mRNA levels and activity of HMGB1. The release of the pro-inflammatory cytokinesTNF-α,IL-1β, IL-6 could be suppressed in rHMGB1-induced macrophages by Escin. Finally, Escin could suppress the activation of NF- κB in LPS-induced macrophages.

CONCLUSION

Escin could improve the survival of mice with LPS-induced endotoxemia. This effect maybe meditated by reducing the release of HMGB1, resulting in the suppression of the release of pro-inflammatory cytokines.

The Receptor for Advanced Glycation End Products Activates the AIM2 Inflammasome in Acute Pancreatitis

Severe acute pancreatitis (AP) is responsible for significant human morbidity and mortality worldwide. Currently, no specific treatments for AP exist, primarily due to the lack of a mechanistic understanding of sterile inflammation and the resultant multisystem organ dysfunction, the pathologic response of AP linked to early death. In this study, we demonstrate that the class III major histocompatibility region III receptor for advanced glycation end products (RAGE) contributes to AP by modulating inflammasome activation in macrophages. RAGE mediated nucleosome-induced absent in melanoma 2 (but not NLRP3) inflammasome activation by modulating dsRNA-dependent protein kinase phosphorylation in macrophages. Pharmacological and genetic inhibition of the RAGE-dsRNA-dependent protein kinase pathway attenuated the release of inflammasome-dependent exosomal leaderless cytokines (e.g., IL-1β and high-mobility group box 1) in vitro. RAGE or absent in melanoma 2 depletion in mice limited tissue injury, reduced systemic inflammation, and protected against AP induced by l-arginine or cerulein in experimental animal models. These findings define a novel role for RAGE in the propagation of the innate immune response with activation of the nucleosome-mediated inflammasome and will help guide future development of therapeutic strategies to treat AP.

Mechanisms of neuroimmune gene induction in alcoholism

RATIONALE

Alcoholism is a primary, chronic relapsing disease of brain reward, motivation, memory, and related circuitry. It is characterized by an individual's continued drinking despite negative consequences related to alcohol use, which is exemplified by alcohol use leading to clinically significant impairment or distress. Chronic alcohol consumption increases the expression of innate immune signaling molecules (ISMs) in the brain that alter cognitive processes and promote alcohol drinking.

OBJECTIVES

Unraveling the mechanisms of alcohol-induced neuroimmune gene induction is complicated by positive loops of multiple cytokines and other signaling molecules that converge on nuclear factor kappa-light-chain-enhancer of activated B cells and activator protein-1 leading to induction of additional neuroimmune signaling molecules that amplify and expand the expression of ISMs.

RESULTS

Studies from our laboratory employing reverse transcription polymerase chain reaction (RT-PCR) to assess mRNA, immunohistochemistry and Western blot analysis to assess protein expression, and others suggest that ethanol increases brain neuroimmune gene and protein expression through two distinct mechanisms involving (1) systemic induction of innate immune molecules that are transported from blood to the brain and (2) the direct release of high-mobility group box 1 (HMGB1) from neurons in the brain. Released HMGB1 signals through multiple receptors, particularly Toll-like receptor (TLR) 4, that potentiate cytokine receptor responses leading to a hyperexcitable state that disrupts neuronal networks and increases excitotoxic neuronal death. Innate immune gene activation in brain is persistent, consistent with the chronic relapsing disease that is alcoholism. Expression of HMGB1, TLRs, and other ISMs is increased several-fold in the human orbital frontal cortex, and expression of these molecules is highly correlated with each other as well as lifetime alcohol consumption and age of drinking onset.

CONCLUSIONS

The persistent and cumulative nature of alcohol on HMGB1 and TLR gene induction support their involvement in alcohol-induced long-term changes in brain function and neurodegeneration.

[Current status and future prospects in HMGB1 and receptor researches]

High mobility group box protein1 (HMGB1), a ubiquitous chromatin component, is released by necrotic cells, apoptotic cells, and cells in profound distress. HMGB1 plays a critical role as a proinflammatory mediator. HMGB1 represents an important new target for drug development in a variety of inflammatory disorders, including stroke, brain injury, arteriosclerosis, and cancer. The antibodies against HMGB1 and its receptors ar hopeful candidates for immunotherapeutic strategy for treating patients with these diseases. HMGB1 forms immunostimulatory complexes by interaction with cytokines and other endogenous or exogenous factors. The HMGB1-partner molecule complexes can enhance the immune response induced by the ligand alone. The current status of HMGB1 works is summarized and future prospects will be provided in this review.

Expression Levels of Proinflammatory Cytokines and NLRP3 Inflammasome in an Experimental Model of Oxazolone-induced Colitis

IL-1β and IL-17A are two cytokines with strong proinflammatory activities and are now known to be involved in a number of chronic inflammatory disorders. High-mobility group box 1 (HMGB1) is a nuclear protein regulating the expression of these proinflammatory cytokines. The NLRP3 inflammasome promotes the maturation of the IL-1β and its activation has been shown as a critical mechanism in the pathogenesis of inflammatory bowel disease (IBD). However, underlying mechanisms to modulate their production in IBD are still unclear. The aim of this study was to investigate the expression levels of mRNA for the NLRP3 inflammasome, HMGB1 and proinflammatory cytokines, IL-1β, IL-17A in the inflamed colon of rats with experimental oxazolone-induced colitis. Experiments were carried out on male wistar rats. IL-1β, IL-17A, HMGB1 and NLRP3 inflammasome mRNA expression were analyzed by real-time reverse transcriptase-polymerase chain reaction. Our results indicated that the expression levels of IL-1β, IL-17A, NLRP3 and HMGB1 were elevated in the inflamed colon of rats with oxazolone-induced colitis.

[EXPRESSION AND FUNCTION OF HIGH MOBILITY GROUP BOX CHROMOSOMAL PROTEIN 1 IN SYNOVIOCYTES OF PATIENTS WITH OSTEOARTHRITIS]

OBJECTIVE

To explore the pathological role of high mobility group box chromosomal protein 1 (HMGB1) in osteoarthritis (OA) by comparing the difference of HMGB1 in the synoviocytes between OA and normal knees.

METHODS

Synoviocyte lines from OA and normal knees were collected and cultured. Immunohistochemistry and Western blot were applied to identify the difference of HMGB1 between the OA and normal synoviocyte lines. The eukaryotic expression vector containing human Pgenesil-1/HMGB1 small interfering RNA (siRNA) were constructed and identified. The synoviocyte lines were transfected with the eukaryotic expression vector of Pgenesil-1/HMGB1 siRNA (Pgenesil-1/HMGB1 siRNA group) and with Pgenesil-1 plasmid (Pgenesil-1 group) and were not transfected as a control (untransfected group). Western blot was applied to identify the difference of HMGB1 among groups, and the levels of interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) protein synthesis in the supernatants were measured by ELISA.

RESULTS

Primary knee synoviocytes cultured in vitro were fibroblast-like cells with long- spindle shape. The immunohistochemistry and immunofluorescence results showed positive staining for HMGB1 in cytoplasm and weak positive staining in the nucleus in the OA synoviocyte line, but positive staining for HMGB1 in the nucleus and weak positive staining in the cytoplasm in the synoviocyte line of normal knee. The level of HMGB1 in the OA synoviocytes (0.687 ± 0.025) was significantly higher than that of normal synoviocytes (0.172 ± 0.030) (t = 32.159, P = 0.000) by Western blot. The recombinant plasmid Pgenesil-1/HMGB1 siRNA was successfully constructed. The expression of HMGB1 protein in Pgenesil-1/HMGB1 siRNA group (0.134 ± 0.048) was significantly lower than that of Pgenesil-1 group (0.581± 0.032) and untransfected group (0.514 ± 0.069) (P < 0.05). ELISA results showed that IL-1β and TNF-α in supernatants of Pgenesil-1/HMGB1 siRNA group were significantly lower than those of Pgenesil-1 group and untransfected group (P < 0.05).

CONCLUSION

The up-regulated expression and expressed location (from nucleus to cytoplasm) of HMGB1 in the synoviocyte are closely related to CA. The siRNA targeting inhibition of HMGB1 gene expression can obviously inhibit II-lp and TNF-a in supernatants of the CA synoviocyte line and delayed the inflammation of CA.

HMGB1 Inhibition During Zymosan-Induced Inflammation: The Potential Therapeutic Action of Riboflavin

Sepsis, also known as systemic inflammatory response syndrome, is a life-threatening condition caused by a pathogenic agent and leading to multiple organ dysfunction syndrome. One of the factors responsible for the excessive intensification of the inflammatory response in the course of inflammation is high-mobility group protein B1 (HMGB1). HMG-1 is a nuclear protein which, after being released to the intercellular space, has a highly pro-inflammatory effect and acts as a late mediator of lethal damage. The purpose of this study was to examine whether the anti-inflammatory action of riboflavin is accompanied by inhibition of HMGB1 release during peritoneal inflammation and zymosan stimulation of macrophages. Peritonitis was induced in male BALB/c and C57BL/6J mice via intraperitoneal injection of zymosan (40 mg/kg). RAW 264.7 macrophages were activated with zymosan (250 µg/ml). Riboflavin (mice, 50 mg/kg; RAW 264.7, 25 µg/ml) was administered 30 min before zymosan, simultaneously with, or 2, 4, 6 h after zymosan. Additionally, mRNA expression of HMGB1 and its intracellular and serum levels were evaluated. The research showed that riboflavin significantly reduces both the expression and the release of HMGB1; however, the effect of riboflavin was time-dependent. The greatest efficacy was found when riboflavin was given 30 min prior to zymosan, and also 2 and 4 h (C57BL/6J; RAW 264.7) or 4 and 6 h (BALB/c) after zymosan. Research showed that riboflavin influences the level of HMGB1 released in the course of inflammation; however, further study is necessary to determine its mechanisms of action.

IL-17 producing innate lymphoid cells 3 (ILC3) but not Th17 cells might be the potential danger factor for preeclampsia and other pregnancy associated diseases

In pregnancy, the immunologic system plays an important role that ensures normal pregnancy development and can as well promote the development of complications. Pregnancy success appears to rely on a discrete balance between the Th cytokines, which are involved in fetal growth and development. Preeclampsia and gestational diabetes are known complications associated with pregnancy. However, the source of the increased IL-17 cytokine in preeclampsia and other pregnancy associated diseases still remains unclear amidst numerous inconsistencies. The recent identification of innate lymphoid cells (ILC) has raised more doubts about the sources of most of the Th associated cytokines. We investigated the source of peripheral IL-17 levels in preeclamptic, gestational diabetics and chronic diabetics compared to healthy pregnancy subjects. To evaluate the source of the increased IL-17 cytokine among preeclampsia, chronic diabetic and gestational diabetic patients we investigated the proportion of Th17 cell populations in peripheral blood mononuclear cells using flow cytometry as well as analyzing levels of IFN-γ, IL-17, IL-1β and HMGB1. This study found that the Th17 cell populations in peripheral blood of preeclamptic, gestational nor chronic diabetes during pregnancy did not correlate with the increased IL-17. We report that the increased IL-17 levels observed in patients with preeclampsia, gestational diabetes and chronic diabetes are associated with innate lymphoid cells 3 (ILC3) and may pose threats to the fetus if disregulated.

The Role of High Mobility Group Box 1 Protein (HMGB1) in the Immunopathology of Experimental Pulmonary Tuberculosis

Background

The high mobility group box 1 (HMGB1) is the prototype of alarmin protein released by stressed or dying cells. The redox state of this protein confers different functions in the regulation of inflammation and immune response.

Aim

Determine the kinetics, cellular sources and function of HMGB1 in experimental tuberculosis.

Methods

BALB/c mice were infected with Mycobacterium tuberculosis strain H37Rv. At different time points, HMGB1 was quantified in bronchial lavage fluid (BALF) and in lungs was determined its cellular sources by immunohistochemistry. HMGB1 was blocked with specific antibodies or recombinant HMGB1 was administered during early or late infection. Bacilli burdens, inflammation and cytokines expression were determined.

Results

The maximal concentration of HMGB1 in BALF was at day one of infection. Bronchial epithelium and macrophages were the most important sources. At day 7 to 21 the oxidized HMGB1 was predominant, while during late infection only the reduced form was seen. Blocking HMGB1 during early infection produced significant decrease of bacilli burdens and high production of pro-inflammatory cytokines, while the opposite was seen when HMGB1 was administered. Blocking HMGB1 activity or administrated it in high amounts during late infection worsening the disease.

Conclusions

HMGB1 is liberated during experimental tuberculosis and promotes or suppress the immune response and inflammation depending on the redox state.

Blocking HMGB1 signal pathway protects early radiation-induced lung injury

It has been reported that HMGB1 participated in various types of lung injury. In this study, we explored whether blocking HMGB1 has a preventive effect on the early radiation-induced lung injury and investigate the mechanism. Mice model of radiation-induced lung injury were accomplished by a single dose irradiation (15 Gy) to the whole thorax. Irradiated mice were treated with HMGB1-neutralizing antibody intraperitoneally dosed 10 μg, 50 μg, 100 μg/mouse respectively and were sacrificed after one week post-irradiation. Lung tissue slices were stained by H&E, and alveolitis was quantified by Szapiel scoring system. The level of cytokines TNF-γ in bronchoalveolar lavage fluid was detected by ELISA method. And p65NF-κB, p50NF-κB protein expression in mice lung tissues was detected by Western blot analysis. The results showed that blocking HMGB1 inhibited the inflammatory response, and thereby decreased the degree of alveolitis of irradiated lung tissue. In addition, HMGB1 antagonist can restrain the expression of type Th2 or Th17 derived inflammatory cytokines TNF-α, IL-6 and IL-17A, promote the expression of Th1 type cytokines INF-γ, and inhibit p65 NF-κB but promote p50 NF-κB activation, which promoted the resolution of the radiation-induced inflammatory response. In conclusion, blocking HMGB1 can reduce the degree of early radiation-induced lung injury, and its mechanism may be related to the promotion of p50NF-κB activation and its downstream molecules expression. Inhibiting HMGB1 may be a new target to deal with early radiation-induced lung injury.

Alcohol exposure after mild focal traumatic brain injury impairs neurological recovery and exacerbates localized neuroinflammation

Traumatic brain injury (TBI) represents a leading cause of morbidity and mortality among young individuals. Alcohol abuse is a risk factor associated with increased TBI incidence. In addition, up to 26% of TBI patients engage in alcohol consumption after TBI. Limited preclinical studies have examined the impact of post-injury alcohol exposure on TBI recovery. The aim of this study was to determine the isolated and combined effects of TBI and alcohol on cognitive, behavioral, and physical recovery, as well as on associated neuroinflammatory changes. Male Sprague-Dawley rats (∼300g) were subjected to a mild focal TBI by lateral fluid percussion (∼30PSI, ∼25ms) under isoflurane anesthesia. On day 4 after TBI, animals were exposed to either sub-chronic intermittent alcohol vapor (95% ethanol 14h on/10h off; BAL∼200mg/dL) or room air for 10days. TBI induced neurological dysfunction reflected by an increased neurological severity score (NSS) showed progressive improvement in injured animals exposed to room air (TBI/air). In contrast, TBI animals exposed to alcohol vapor (TBI/alcohol) showed impaired NSS recovery throughout the 10-day period of alcohol exposure. Open-field exploration test revealed an increased anxiety-like behavior in TBI/alcohol group compared to TBI/air group. Additionally, alcohol-exposed animals showed decreased locomotion and impaired novel object recognition. Immunofluorescence showed enhanced reactive astrocytes, microglial activation, and HMGB1 expression localized to the injured cortex of TBI/alcohol as compared to TBI/air animals. The expression of neuroinflammatory markers showed significant positive correlation with NSS. These findings indicated a close relationship between accentuated neuroinflammation and impaired neurological recovery from post-TBI alcohol exposure. The clinical implications of long-term consequences in TBI patients exposed to alcohol during recovery warrant further investigation.

Extracellular ATP induces P2X7 receptor activation in mouse Kupffer cells, leading to release of IL-1β, HMGB1, and PGE2, decreased MHC class I expression and necrotic cell death

Kupffer cells, which are resident macrophages in liver, can produce various cytokines and chemokines that induce hepatitis and liver fibrosis. It is suggested that extracellular ATP-induced activation of macrophage P2X7 receptor plays an important role in inflammation via release of pro-inflammatory mediators, but the role of P2X7 receptor in Kupffer cells remains unclear. Here, we show that activation of P2X7 receptor in Kupffer cells causes multiple inflammatory responses, using the clonal mouse Kupffer cell line (KUP5) that we previously established. Treatment of LPS-primed Kupffer cells with 3 mM ATP induced Ca(2+) influx, non-selective large pore formation, activation of MAPK, cell lysis, IL-1β release, prostaglandin E2 (PGE2) release, high mobility group box1 (HMGB1) release, and major histocompatibility complex (MHC) class I shedding. These events were significantly suppressed by pretreatment with P2X7 antagonist A438079, indicating involvement of P2X7 receptor activation in these inflammatory responses. Our results suggest that extracellular ATP-induced activation of P2X7 receptor of Kupffer cells plays multiple roles in the inflammatory response in liver. P2X7 receptor might be a new therapeutic target for treatment of liver diseases.

Pathophysiological aspects of sepsis: an overview

Sepsis is defined as severe systemic inflammation in response to invading pathogens, or an uncontrolled hyperinflammatory response, as mediated by the release of various proinflammatory mediators. Although some patients may die rapidly from septic shock accompanied by an overwhelming systemic inflammatory response syndrome (SIRS) triggered by a highly virulent pathogen, most patients survive the initial phase of sepsis, showing multiple organ damage days or weeks later. These patients often demonstrate signs of immune suppression accompanied by enhanced inflammation. Sepsis is a result of a complex process; there is interaction of various pathways, such as inflammation, immunity, coagulation, as well as the neuroendocrine system. This treatise is an attempt to provide a summary of several key regulatory mechanisms and to present the currently recognized molecular pathways that are involved in the pathogenesis of sepsis.