Blockade of high mobility group box-1 protein attenuates experimental severe acute pancreatitis

Targeting circulating high mobility group box-1 and histones by extracorporeal blood purification as an immunomodulation strategy against critical illnesses

Both high mobility group box-1 (HMGB1) and histones are major damage-associated molecular patterns (DAPMs) that mediate lethal systemic inflammation, activation of the complement and coagulation system, endothelial injury and multiple organ dysfunction syndrome in critical illnesses. Although accumulating evidence collectively shows that targeting HMGB1 or histones by their specific antibodies or inhibitors could significantly mitigate aberrant immune responses in multiple critically ill animal models, routine clinical use of such agents is still not recommended by any guideline. In contrast, extracorporeal blood purification, which has been widely used to replace dysfunctional organs and remove exogenous or endogenous toxins in intensive care units, may also exert an immunomodulatory effect by eliminating inflammatory mediators such as cytokines, endotoxin, HMGB1 and histones in patients with critical illnesses. In this review, we summarize the multiple immunopathological roles of HMGB1 and histones in mediating inflammation, immune thrombosis and organ dysfunction and discuss the rationale for the removal of these DAMPs using various hemofilters. The latest preclinical and clinical evidence for the use of extracorporeal blood purification to improve the clinical outcome of critically ill patients by targeting circulating HMGB1 and histones is also gathered.

Damage associated molecular patterns and neutrophil extracellular traps in acute pancreatitis

Previous researches have emphasized a trypsin-centered theory of acute pancreatitis (AP) for more than a century. With additional studies into the pathogenesis of AP, new mechanisms have been explored. Among them, the role of immune response bears great importance. Pro-inflammatory substances, especially damage-associated molecular patterns (DAMPs), play an essential role in activating, signaling, and steering inflammation. Meanwhile, activated neutrophils attach great importance to the immune defense by forming neutrophil extracellular traps (NETs), which cause ductal obstruction, premature trypsinogen activation, and modulate inflammation. In this review, we discuss the latest advances in understanding the pathological role of DAMPs and NETs in AP and shed light on the flexible crosstalk between these vital inflammatory mediators. We, then highlight the potentially promising treatment for AP targeting DAMPs and NETs, with a focus on novel insights into the mechanism, diagnosis, and management of AP.

Ethyl pyruvate, a versatile protector in inflammation and autoimmunity

Ethyl pyruvate (EP) has potent influence on redox processes, cellular metabolism, and inflammation. It has been intensively studied in numerous animal models of systemic and organ-specific disorders whose pathogenesis involves a strong immune component. Here, basic chemical and biological properties of EP are discussed, with an emphasis on its redox and metabolic activity. Further, its influence on myeloid and T cells is considered, as well as on intracellular signaling beyond its effect on immune cells. Also, the effects of EP on animal models of chronic inflammatory and autoimmune disorders are presented. Finally, a possibility to apply EP as a treatment for such diseases in humans is discussed. Scientific papers cited in this review were identified using the PubMed search engine that relies on the MEDLINE database. The reference list covers the most important findings in the field in the past twenty years.

Calycosin attenuates severe acute pancreatitis-associated acute lung injury by curtailing high mobility group box 1 - induced inflammation

BACKGROUND

Acute lung injury (ALI) is a common and life-threatening complication of severe acute pancreatitis (SAP). There are currently limited effective treatment options for SAP and associated ALI. Calycosin (Cal), a bioactive constituent extracted from the medicinal herb Radix Astragali exhibits potent anti-inflammatory properties, but its effect on SAP and associated ALI has yet to be determined.

AIM

To identify the roles of Cal in SAP-ALI and the underlying mechanism.

METHODS

SAP was induced via two intraperitoneal injections of L-arg (4 g/kg) and Cal (25 or 50 mg/kg) were injected 1 h prior to the first L-arg challenge. Mice were sacrificed 72 h after the induction of SAP and associated ALI was examined histologically and biochemically. An in vitro model of lipopolysaccharide (LPS)-induced ALI was established using A549 cells. Immunofluorescence analysis and western blot were evaluated in cells. Molecular docking analyses were conducted to examine the interaction of Cal with HMGB1.

RESULTS

Cal treatment substantially reduced the serum amylase levels and alleviated histopathological injury associated with SAP and ALI. Neutrophil infiltration and lung tissue levels of neutrophil mediator myeloperoxidase were reduced in line with protective effects of Cal against ALI in SAP. Cal treatment also attenuated the serum levels and mRNA expression of pro-inflammatory cytokines tumor necrosis factor-α, interleukin-6, IL-1β, HMGB1 and chemokine (CXC motif) ligand 1 in lung tissue. Immunofluorescence and western blot analyses showed that Cal treatment markedly suppressed the expression of HMGB1 and phosphorylated nuclear factor-kappa B (NF-κB) p65 in lung tissues and an in vitro model of LPS-induced ALI in A549 cells suggesting a role for HGMB1 in the pathogenesis of ALI. Furthermore, molecular docking analysis provided evidence for the direct interaction of Cal with HGMB1.

CONCLUSION

Cal protects mice against L-arg-induced SAP and associated ALI by attenuating local and systemic neutrophil infiltration and inflammatory response via inhibition of HGMB1 and the NF-κB signaling pathway.

Exosomes derived from miR-129-5p modified bone marrow mesenchymal stem cells represses ventricular remolding of mice with myocardial infarction

Myocardial infraction (MI) is a severe disease with great mortality. Mesenchymal stem cells-derived exosomes display protection against MI. MicroRNA-129-5p was reported to exert anti-inflammation activity by targeting high mobility group box 1 (HMGB1). In the present study, the effects of MSCs derived exosomes overexpressing miR-129-5p on MI were evaluated. Bone marrow mesenchymal stem cells (BMSCs) were transfected with miR-129-5p for exosomes isolation. Myocardial infraction mice model was established and administrated exosomes overexpressing miR-129-5p. The cardiac function, expression of HMGB1, inflammatory cytokines, apoptosis and fibrosis in heart tissues were measured. miR-129-5p inhibited HMGB1 expression in BMSCs. Myocardial infraction mice treated with exosomes overexpressing miR-129-5p had enhanced cardiac function and decreased expression of HMGB1 and production of inflammatory cytokines. Exosomes overexpressing miR-129-5p further prevented apoptosis and fibrosis. Exosome-mediated transfer of miR-129-5p suppressed inflammation in MI mice by targeting HMGB1.

NUTM2A-AS1 silencing alleviates LPS-induced apoptosis and inflammation in dental pulp cells through targeting let-7c-5p/HMGB1 axis

BACKGROUND

Long non-coding RNA (lncRNA) NUTM2A antisense RNA 1 (NUTM2A-AS1) has been reported to be abnormally up-regulated in pulpitis tissues. However, the function of NUTM2A-AS1 in pulpitis remains unclear. The aim of this study was to investigate the role and working mechanism of NUTM2A-AS1 in pulpitis using lipopolysaccharide (LPS)-treated human dental pulp cells (HDPCs).

METHODS

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry and lactate dehydrogenase (LDH) release detection assay were conducted to analyze the viability of HDPCs. Cell inflammatory response was analyzed through measuring the protein levels of interleukin-6 (IL-6) and IL-8. Western blot assay and quantitative real-time polymerase chain reaction (qRT-PCR) were applied to measure protein expression and RNA expression, respectively. Bioinformatic database StarBase was used to predict the possible targets of NUTM2A-AS1 and let-7c-5p, and dual-luciferase reporter assay was conducted to verify these intermolecular interactions.

RESULTS

LPS stimulation restrained cell viability and induced cell apoptosis and inflammation of HDPCs. LPS exposure up-regulated the expression of NUTM2A-AS1 and High-Mobility Group Box 1 (HMGB1) and down-regulated the level of let-7c-5p. LPS-induced injury in HDPCs was partly attenuated by the silencing of NUTM2A-AS1 or HMGB1. Let-7c-5p was confirmed as a direct target of NUTM2A-AS1, and let-7c-5p bound to the 3' untranslated region (3'UTR) of HMGB1 messenger RNA (mRNA) in HDPCs. HMGB1 overexpression largely overturned NUTM2A-AS1 silencing-mediated effects in LPS-induced HDPCs.

CONCLUSION

NUTM2A-AS1 knockdown attenuated LPS-induced damage in HDPCs partly through targeting let-7c-5p/HMGB1 axis.

Gut Barrier Dysfunction Induced by Aggressive Fluid Resuscitation in Severe Acute Pancreatitis is Alleviated by Necroptosis Inhibition in Rats

Fluid resuscitation is the first-line antishock treatment in severe acute pancreatitis (SAP). Currently, although mentions of complications related to aggressive fluid resuscitation are very frequent, a lack of proper handling of complications remains. One of the most important complications is intestinal barrier injury, including intestinal ischemia-reperfusion injury following aggressive fluid resuscitation. Once injured, the intestinal barrier may serve as the source of additional diseases, including systemic inflammatory response syndrome and multiple organ dysfunction syndrome, which aggravate SAP. This study focused on the underlying mechanisms of gut barrier dysfunction in rats induced by aggressive fluid resuscitation in SAP. This study further indicated the important role of necroptosis in intestinal barrier injury which could be relieved by using necroptosis-specific inhibitor Nec-1 before aggressive fluid resuscitation, thus reducing intestinal barrier damage. We also found pancreas damage after intestinal ischemia/reperfusion challenge and indicated the effects of high mobility group protein B1 in the vicious cycle between SAP and intestinal barrier damage.

NLRP3 Inflammasome-Mediated Inflammation in Acute Pancreatitis

The discovery of inflammasomes has enriched our knowledge in the pathogenesis of multiple inflammatory diseases. The NLR pyrin domain-containing protein 3 (NLRP3) has emerged as the most versatile and well-characterized inflammasome, consisting of an intracellular multi-protein complex that acts as a central driver of inflammation. Its activation depends on a tightly regulated two-step process, which includes a wide variety of unrelated stimuli. It is therefore not surprising that the specific regulatory mechanisms of NLRP3 inflammasome activation remain unclear. Inflammasome-mediated inflammation has become increasingly important in acute pancreatitis, an inflammatory disorder of the pancreas that is one of the fatal diseases of the gastrointestinal tract. This review presents an update on the progress of research into the contribution of the NLRP3 inflammasome to acute pancreatic injury, examining the mechanisms of NLRP3 activation by multiple signaling events, the downstream interleukin 1 family of cytokines involved and the current state of the literature on NLRP3 inflammasome-specific inhibitors.

Targeting the receptor for advanced glycation end products (RAGE) in type 1 diabetes

Type 1 diabetes (T1D) is one of the most common chronic diseases manifesting in early life, with the prevalence increasing worldwide at a rate of approximately 3% per annum. The prolonged hyperglycaemia characteristic of T1D upregulates the receptor for advanced glycation end products (RAGE) and accelerates the formation of RAGE ligands, including advanced glycation end products, high-mobility group protein B1, S100 calcium-binding proteins, and amyloid-beta. Interestingly, changes in the expression of RAGE and these ligands are evident in patients before the onset of T1D. RAGE signals via various proinflammatory cascades, resulting in the production of reactive oxygen species and cytokines. A large number of proinflammatory ligands that can signal via RAGE have been implicated in several chronic diseases, including T1D. Therefore, it is unsurprising that RAGE has become a potential therapeutic target for the treatment and prevention of disease. In this review, we will explore how RAGE might be targeted to prevent the development of T1D.

Evaluation of serum C-reactive protein and high mobility group box 1 concentrations in 22 dogs with acute pancreatitis: a pilot study

Background: High mobility group box 1 (HMGB1) is an important mediator of systemic inflammatory response syndrome (SIRS) in humans with severe acute pancreatitis (AP), but there is little information regarding its role in dogs. Aim: To compare the serum concentrations of C-reactive protein (CRP) and HMGB1 in healthy dogs and those with AP with or without SIRS. Methods: The study included 22 dogs with AP and 20 healthy dogs. CRP and HMGB1 were assessed by ELISA. Statistical analyses were conducted by non-parametric tests. Results: Median (interquartile range) serum CRP and HMGB1 concentrations were significantly (P < 0.05) higher in dogs with AP [60.56 (14.50-140.10) µg/mL and 0.35 (0.03-1.12) ng/mL, respectively] than in healthy dogs [2.23 (1.75-5.14) µg/mL and 0.02 (0.01-0.05) ng/mL, respectively]. After the recommended treatments for AP, serum CRP concentration in AP dogs significantly decreased, but that of HMGB1 in AP dogs significantly increased. There was also a significant difference in median serum HMGB1 concentration between AP dogs with and without SIRS. The use of serum HMGB1 concentration of 0.35 ng/mL to distinguish AP dogs with and without SIRS was associated with a sensitivity of 87.5% and a specificity of 71.5%. A positive correlation was identified between HMGB1 and clinical severity of AP. All AP dogs had a positive outcome during hospitalization [6.0 (1.5-6.0) days]. Conclusion: Results indicate that HMGB1 might be a useful biomarker for the progression of AP and may play a role in progression of AP into SIRS in dogs.

HMGB1 mediates the development of tendinopathy due to mechanical overloading

Mechanical overloading is a major cause of tendinopathy, but the underlying pathogenesis of tendinopathy is unclear. Here we report that high mobility group box1 (HMGB1) is released to the tendon extracellular matrix and initiates an inflammatory cascade in response to mechanical overloading in a mouse model. Moreover, administration of glycyrrhizin (GL), a naturally occurring triterpene and a specific inhibitor of HMGB1, inhibits the tendon’s inflammatory reactions. Also, while prolonged mechanical overloading in the form of long-term intensive treadmill running induces Achilles tendinopathy in mice, administration of GL completely blocks the tendinopathy development. Additionally, mechanical overloading of tendon cells in vitro induces HMGB1 release to the extracellular milieu, thereby eliciting inflammatory and catabolic responses as marked by increased production of prostaglandin E₂ (PGE₂) and matrix metalloproteinase-3 (MMP-3) in tendon cells. Application of GL abolishes the cellular inflammatory/catabolic responses. Collectively, these findings point to HMGB1 as a key molecule that is responsible for the induction of tendinopathy due to mechanical overloading placed on the tendon.

High Serum Levels of High-Mobility Group Box 1 (HMGB1) and Low Levels of Heat Shock Protein 70 (Hsp70) are Associated with Poor Prognosis in Patients with Acute Pancreatitis

INTRODUCTION

Cell damage in Acute Pancreatitis (AP) lead to release of cytokines and HMGB1 and Hsp70. While Hsp70 plays a role in cytoprotection, when released to extracellular milieu constitutes, as HMGB1, a danger signal and trigger pro-inflammatory responses. These molecules seem to be related to the clinical progression; but because no evidence exists about them as molecular network in AP development, we quantify HSP70, HMGB1, and cytokines in patients with AP and search for correlations with severity and prognosis.

METHODS

Fifteen patients with AP were included. The average age was 52 years. Six patients had mild pancreatitis, 4 were moderately severe and 5 with a severe form. Blood samples were taken within the first 24 h, at 3d and 7d from the start. Serum HMGB1 and Hsp70 were determined using ELISA; TNF-α, IL-1β, IL-6, IL-8, IL-10 and IL-12p70 were determined by bead based immuassay.

RESULTS

Of all 15 patients recruited, 4 were women. Eight patients had APACHEII score higher than 8. Two patients died from AP related complications. Increase in serum HMGB1 and decrease of Hsp70 were associated with the severity and mortality. TNF-α, IL-6 and IL-8 were higher in patients that did not survive, in those with an APACHE II >8, and in those with severe AP.

CONCLUSIONS

High HMGB1 and low Hsp70 were associated with poor prognosis. Hsp70 might play a protective role in AP. TNF-α, IL-6, IL-8, HMGB1 and Hsp70 during hospital admissions might serve to evaluate risk of death due to AP.

Acute Pancreatitis: A Multifaceted Set of Organelle and Cellular Interactions

Acute pancreatitis is an inflammatory disorder of the exocrine pancreas associated with tissue injury and necrosis. The disease can be mild, involving only the pancreas, and resolve spontaneously within days or severe, with systemic inflammatory response syndrome-associated extrapancreatic organ failure and even death. Importantly, there are no therapeutic agents currently in use that can alter the course of the disease. This article emphasizes emerging findings that stressors (environmental and genetic) that cause acute pancreatitis initially cause injury to organelles of the acinar cell (endoplasmic reticulum, mitochondria, and endolysosomal-autophagy system), and that disorders in the functions of the organelles lead to inappropriate intracellular activation of trypsinogen and inflammatory pathways. We also review emerging work on the role of damage-associated molecular patterns in mediating the local and systemic inflammatory response in addition to known cytokines and chemokine pathways. In the review, we provide considerations for correction of organelle functions in acute pancreatitis to create a discussion for clinical trial treatment and design options.

Diclofenac Sodium Treatment Ameliorates Extrapancreatic Organ Injuries in a Murine Model of Acute Pancreatitis Induced by Caerulein

Aim

We determined the effects of diclofenac sodium, octreotide, and their combination on extrapancreatic organ injuries in caerulein-induced acute pancreatitis in mice.

Methods

A total of 58 BALB-C male mice (25 g) were divided into seven groups and used to create a caerulein-induced acute pancreatitis model. Diclofenac sodium, octreotide, and their combination were given for treatment of caerulin-induced acute pancreatitis in mice. At the end of the experiment, the lung, liver, kidney, and stomach were removed for histopathologic assessment.

Results

Histopathologic investigation revealed a statistically significant difference between the groups in mean congestion, edema, tubular injury, perirenal fat tissue inflammation, and tubular stasis scores in kidney tissue (P < 0.001, P < 0.001, P < 0.001, P < 0.001, and P = 0.048, respectively); mean congestion, edema, neutrophil inflammation, mononuclear inflammation, and emphysematous change scores in the lung (P < 0.001, P < 0.001, P < 0.001, P = 0.030, and P < 0.001, respectively); mean congestion, edema, and neutrophil inflammation scores in the stomach (P = 0.008, P = 0.014, and P < 0.001, respectively); and mean congestion and hydropic degeneration scores in the liver (P = 0.029 and P = 0.002, respectively).

Conclusion

Diclofenac sodium alone ameliorates lung edema due to caerulin-induced acute pancreatitis.

The Dual Role of HMGB1 in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of exocrine pancreatic cancer with a 9% five-year survival rate. High mobility group box 1 (HMGB1) is a nuclear protein that can act as a DNA chaperone in the sustainment of chromosome structure and function. When released into the extracellular space, HMGB1 becomes the most well-characterized damage-associated molecular pattern (DAMP) to trigger immune responses. Recent evidence indicates that intracellular HMGB1 is a novel tumor suppressor in PDAC, which is connected to its role in the prevention of oxidative stress, genomic instability, and histone release. However, since extracellular HMGB1 is a DAMP and pro-inflammatory cytokine, cancer cells can also exploit it to survive through the receptor for advanced glycation endproducts (RAGE) in the pancreatic tumor microenvironment. Interestingly, targeting the HMGB1-RAGE pathway has become a new anticancer therapy strategy for PDAC.

High-fat diet modifies cytokine gene expression and exacerbates the effects of acute pancreatitis in the liver of rats

BACKGROUND

Obese patients have a higher risk of developing different metabolic syndromes (MeS), including acute pancreatitis (AP). Although obese individuals are more prone to MeS and more susceptible to local and systemic inflammation in response to AP, thus causing long-lasting hospitalization, higher morbidity and mortality, their underlying mechanisms remain unclear. This study aimed to investigate the relationship between obesity and the outcomes of AP in the rat model of AP.

METHODS

To assess the link between obesity and AP, 40 male albino rats were divided into two groups: control and those given a high-fat diet for 12 weeks. This was followed by the injection of a single dose of L-arginine (250 mg/100 gm) in half of each group to induce AP.

RESULTS

Data evaluation was done using 2-way ANOVA. Values were considered significant when p≤0.05. Markers of AP were evaluated in the serum and ascitic fluid. Moreover, the systemic inflammatory markers, such as IL-6, TNF-α, HMGB1 and TLR4, were quantified in the liver of all groups. Results showed that the OAP group had the highest levels of liver enzymes and amylase aside from several signs of liver damage, such as fat necrosis and steatosis.

CONCLUSIONS

The inflammatory cytokine levels are synchronized, creating an early responsive stage and late inflammatory stage to realize the best defense mechanism. Results also indicate that obesity is a main determinant of the severity of AP at the late stage.

DAMPs and sterile inflammation in drug hepatotoxicity

Drug hepatotoxicity is the leading cause of acute liver failure (ALF) in the developed countries. The early diagnosis and treatment are still problematic, and one important reason is the lack of reliable mechanistic biomarkers and therapeutic targets; therefore, searching for new biomarkers and therapeutic targets is urgent. Drug hepatotoxicity induces severe liver cells damage and death. Dead and damaged cells release endogenous damage-associated molecular patterns (DAMPs). Increased circulating levels of DAMPs (HMGB1, histones and DNA) can reflect the severity of drug hepatotoxicity. Elevated plasma HMGB1 concentrations can serve as early and sensitive mechanistic biomarker for clinical acetaminophen hepatotoxicity. DAMPS significantly contribute to liver injury and inhibiting the release of DAMPs ameliorates experimental hepatotoxicity. In addition, HMGB1 mediates 80% of gut bacterial translocation (BT) during acetaminophen toxicity. Gut BT triggers systemic inflammation, leading to multiple organ injury and mortality. Moreover, DAMPs can trigger and extend sterile inflammation, which contributes to early phase liver injury but improves liver regeneration at the late phase of acetaminophen overdose, because anti-inflammatory treatment reduces liver injury at early phase but impairs liver regeneration at late phase of acetaminophen toxicity, whereas pro-inflammatory therapy improves late phase liver regeneration. DAMPs are promising mechanistic biomarkers and could also be the potential therapeutic targets for drug hepatotoxicity. DAMPs-triggered sterile inflammation contributes to liver injury at early phase but improves liver regeneration at later phase of acetaminophen hepatotoxicity; therefore, anti-inflammatory therapy would be beneficial at early phase but should be avoided at the late phase of acetaminophen overdose.

High-Mobility Group Box 1 Protein Regulates Autophagy in LO2 Cells Following Anoxia-Reoxygenation Injury

The mechanisms of autophagy during liver ischemia-reperfusion injury are not completely understood. This study aimed to assess the role of high-mobility group box 1 protein (HMGB1) in autophagy in LO2 cells following anoxia-reoxygenation injury. LO2 cells were pretreated with the HMGB1 inhibitor ammonium glycyrrhizinate (1000 μmol/L) or the HMGB1 agonist recombinant HMGB1 (rHMGB1, 10 ng/mL) at proper concentrations before induction of anoxia-reoxygenation injury. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels and cell viability were evaluated. Then, the expression levels of LC3 and Beclin-1, which are classical autophagy markers, were assessed by Western blot. Autophagosomes were detected by electron microscopy. Our results showed that rHMGB1-treated cells had increased AST and ALT levels in the culture medium, aggravated cell injury, enhanced expression of beclin-1 and LC3 proteins, and increased number of autophagosomes. However, glycyrrhizinate treatment alleviated ALT and AST levels in culture medium, relieved cell injury, reduced beclin-1 and LC3 protein expression levels, and decreased autophagosome number. These findings indicated that HMGB1 likely regulates autophagy in LO2 cells exposed to anoxia-reoxygenation injury.

Bile and circulating HMGB1 contributes to systemic inflammation in obstructive jaundice

BACKGROUND

Obstructive jaundice (OJ) patients with cholangitis are prone to sepsis; however, the underlying mechanisms are still not clear and need to be clarified.

METHODS

Analyzing all available published data related to the title of this article.

RESULTS

OJ leads to absence of gut luminal bile and accumulation of hepatic and circulating bile acids. Absence of gut luminal bile deprives the gut from its antiinflammatory, endotoxin-binding, bacteriostatic, mucosal-trophic, epithelial tight-junction maintaining, and gut motility-regulating effects, leading to gut bacterial overgrowth, mucosal atrophy, mucosal tight-junction loss, and gut motility dysfunction. These alterations promote intestinal endotoxin and bacterial translocation (BT) into portal and systemic circulation. Gut BT triggers systemic inflammation, which can lead to multiple organ dysfunctions in OJ. The accumulation of hepatic and circulating bile acids kills/damages hepatocyte and Kupffer cells, and it also significantly decreases the number of liver natural killer T-cells in OJ. This results in impaired hepatic and systemic immune function, which facilitates BT. In addition, neutralizing bile HMGB1 can reverse endotoxemic bile-induced gut BT and mucosal injury in mice, suggesting that bile HMGB1 in OJ patients can be responsible for internal drainage-related clinical complications. Moreover, the elevated circulating HMGB1 level may contribute to multiple organ injuries, and it might also mediate gut BT in OJ.

CONCLUSIONS

HMGB1 may significantly contribute to systemic inflammation and multiple organ dysfunctions in OJ.

Augmenter of liver regeneration (ALR) regulates acute pancreatitis via inhibiting HMGB1/TLR4/NF-κB signaling pathway

This research aimed to explore the effect of augmenter of liver regeneration (ALR) in acute pancreatitis (AP) of mice and the underlying mechanism. Caerulein were given to mice to get AP models. AP mice were given saline, ALR plasmids or negative control plasmids. Then, pancreas tissues were fixed and stained for histological examination. The levels of serum amylase, serum lipase, MPO, HMGB1, TNF-α, IL-1β as well as MCP-1 were detected by ELISA assay. The mRNA levels of TLR4, p65, IκBα, iNOS, COX-2 and GAPDH were examined by RT-qPCR. The protein levels of HMGB1, TLR4, MD2, MyD88, IκBα and GAPDH were detected by western blotting. ALR decreased serum amylase as well as lipase levels and alleviated the histopathological alterations of the pancreas in AP mice. ALR decreased the MPO activity of pancreas in AP Mice. ALR decreased the HMGB1/TLR4 signaling pathway in AP Mice. ALR decreased pancreas IL-1β and MCP-1 in AP mice, and also decreased plasma TNF-α and IL-1β in AP mice. ALR attenuated the cerulein-caused increase in p65 mRNA and protein levels, but had no effects on mRNA and protein levels of IκBα. The AP mice significantly promoted the mRNA levels of iNOS and COX-2 that was inhibited by ALR. HNE formation was also increased in AP mice, but it was decreased by ALR. ALR alleviates acute pancreatitis by inhibiting HMGB1/TLR4/NF-κB signaling pathway. It is promising to alleviate the syndromes of patients with acute via targeting ALR.

Adiponectin suppression of late inflammatory mediator, HMGB1-induced cytokine expression in RAW264 macrophage cells

High-mobility group protein B1 (HMGB1) is a late inflammatory mediator released from inflammatory cells when stimulated, resulting in exaggerating septic symptoms. We recently demonstrated that full-length adiponectin, a potent anti-inflammatory adipokine, inhibits lipopolysaccharide-induced HMGB1 release. However, the effects of adiponectin on HMGB1-induced exaggerating signals currently remain unknown. This study aimed to investigate the effects of adiponectin on the pro-inflammatory function of HMGB1 in RAW264 macrophage cells. The treatment of RAW264 cells with HMGB1 significantly up-regulated the mRNA expression of tumour necrosis factor-α, interleukin-1β and C-X-C motif chemokine 10. HMGB1-induced cytokine expression was markedly suppressed by a toll-like receptor 4 (TLR4) antagonist and slightly suppressed by an antagonist of the receptor for advanced glycation end products. A prior treatment with full-length or globular adiponectin dose-dependently suppressed all types of HMGB1-induced cytokine expression, and this suppression was abolished by compound C, an AMPK inhibitor, but not by the haem oxygenase (HO)-1 inhibitor, zinc protoporphyrin IX. Both forms of adiponectin also reduced the mRNA expression of TLR4. These results suggest that full-length and globular adiponectin suppress HMGB1-induced cytokine expression through an AMPK-mediated HO-1-independent pathway.

Role of Inflammasomes in the Development of Gastrointestinal Diseases

Many diseases of the gastrointestinal tract have been attributed to chronic inflammation, and a few have identified the role of inflammasomes in their pathogenesis. Inflammasomes are a group of protein complexes comprising of several intracellular proteins that link the sensing of microbial products and metabolic stress to the proteolytic activation of the proinflammatory cytokines. Recent studies have implicated activation of several families of NOD-like receptors (NLRs) which are major components of inflammasomes in the development and exacerbation of many diseases of human systems. In this chapter, we discuss the role of inflammasomes in some of the most prevalent diseases of the gastrointestinal tract and highlight potential targets for treatment.

The HMGB1/RAGE Pro-Inflammatory Axis in the Human Placenta: Modulating Effect of Low Molecular Weight Heparin

We evaluated whether physiological and pre-eclamptic (PE) placentae, characterized by exacerbated inflammation, presented alterations in pro-inflammatory High Mobility Group Box 1 (HMGB1) and its Receptor of Advanced Glycation End products (RAGE) expression. Moreover, we investigated, in physiological placental tissue, the ability of Low Molecular Weight Heparin (LMWH) to modify HMGB1 structural conformation thus inhibiting RAGE binding and HMGB1/RAGE axis inflammatory activity. HMGB1, RAGE, IL-6 and TNFα (HMGB1/RAGE targets) mRNA expression were assessed by Real Time PCR. HMGB1, RAGE protein levels were assessed by western blot assay. Physiological term placental explants were treated by 0.5 U LMWH for 24 or 48 h. HMGB1 and RAGE expression and association were evaluated in LMWH explants by RAGE immunoprecipitation followed by HMGB1 immunoblot. HMGB1 spatial localization was evaluated by immuofluorescent staining (IF). HMGB1 expression was increased in PE relative to physiological placentae while RAGE was unvaried. 24 h LMWH treatment significantly up-regulated HMGB1 expression but inhibited HMGB1/RAGE complex formation in physiological explants. RAGE expression decreased in treated relative to untreated explants at 48 h. IF showed HMGB1 localization in both cytoplasm and nucleus of mesenchymal and endothelial cells but not in the trophoblast. IL-6 and TNFα gene expression were significantly increased at 24 h relative to controls, while they were significantly down-regulated in 48 h vs. 24 h LMWH explants. Our data depicted a new molecular mechanism through which LMWH exerts its anti-inflammatory effect on PE placentae, underlying the importance of HMGB1/RAGE axis in PE inflammatory response.

Blockade of high-mobility group box 1 attenuates intestinal mucosal barrier dysfunction in experimental acute pancreatitis. Sci Rep. 2017;7:6799. [PMID: 28754974 PMCID: PMC5533736 DOI: 10.1038/s41598-017-07094-y]

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

HMGB1 and Extracellular Histones Significantly Contribute to Systemic Inflammation and Multiple Organ Failure in Acute Liver Failure

Acute liver failure (ALF) is the culmination of severe liver cell injury from a variety of causes. ALF occurs when the extent of hepatocyte death exceeds the hepatic regenerative capacity. ALF has a high mortality that is associated with multiple organ failure (MOF) and sepsis; however, the underlying mechanisms are still not clear. Emerging evidence shows that ALF patients/animals have high concentrations of circulating HMGB1, which can contribute to multiple organ injuries and mediate gut bacterial translocation (BT). BT triggers/induces systemic inflammatory responses syndrome (SIRS), which can lead to MOF in ALF. Blockade of HMGB1 significantly decreases BT and improves hepatocyte regeneration in experimental acute fatal liver injury. Therefore, HMGB1 seems to be an important factor that links BT and systemic inflammation in ALF. ALF patients/animals also have high levels of circulating histones, which might be the major mediators of systemic inflammation in patients with ALF. Extracellular histones kill endothelial cells and elicit immunostimulatory effect to induce multiple organ injuries. Neutralization of histones can attenuate acute liver, lung, and brain injuries. In conclusion, HMGB1 and histones play a significant role in inducing systemic inflammation and MOF in ALF.

Increased admission serum cold-inducible RNA-binding protein concentration is associated with prognosis of severe acute pancreatitis

BACKGROUND

Cold-inducible RNA-binding protein (CIRP) is a pro-inflammatory cytokine. This study assessed its relation to disease severity and major adverse events (namely local complications, organ failure and in-hospital mortality) of severe acute pancreatitis (SAP) and its discriminatory ability for SAP.

METHODS

This prospective and observational study recruited a total of 102 SAP patients, 48 patients with mild acute pancreatitis and 102 healthy individuals. Serum CIRP concentrations were determined using enzyme-linked immunosorbent assay.

RESULTS

Serum CIRP concentrations were significantly higher in patients compared to controls. Serum CIRP concentrations were highly correlated with the circulating concentrations of common inflammatory mediators (i.e., procalcitonin, C-reactive protein and white blood cell) and the traditional predictors of disease severity (namely Acute Physiology and Chronic Health Care Evaluation II score, Ranson score, multiple organ dysfunction score and sequential organ failure assessment score). CIRP in serum was an independent predictor for major adverse events. Serum CIRP concentrations showed high predictive value for major adverse events, and possessed high discriminatory performance for SAP. Moreover, its effects significantly exceeded those of the preceding inflammatory mediators.

CONCLUSIONS

Increased serum CIRP concentrations clearly reflect SAP severity and prognosis and significantly distinguish SAP, substantializing CIRP as a potential SAP biomarker.

Association between high mobility group box‑1 protein expression and cell death in acute pancreatitis

The present study used caerulein stimulation of AR42J rat pancreatic cells as an in vitro acute pancreatitis (AP) model to investigate proteins differentially expressed in apoptosis and necrosis. AR42J cells were stimulated with 10‑8mol/l caerulein and incubated for 24 h. Apoptosis and necrosis were detected using flow cytometry. The sorted Annexin V‑positive cells (apoptotic) and the Annexin V/propidium iodide double‑positive cells (necrotic) were analysed using proteomics. Results showed that numerous proteins were differentially expressed in these 2 groups. Functional enrichment analysis was performed on the differentially expressed genes using the Database for Annotation, Visualization and Integrated Discovery. High mobility group box‑1 protein (HMGB1) was specifically expressed in the necrosis group. Models of varying degrees of AP were established using caerulein at concentrations of 10‑9, 10‑8, 10‑7, 10‑6 and 10‑5 mol/l. The percentage of apoptotic and necrotic cells in each group was determined using flow cytometry. Protein expression levels of HMGB1 were detected by western blot analysis. The present study showed that as the concentration of caerulein increased, the percentage of necrotic cells and the protein expression levels of HMGB1 increased. HMGB1 is involved in many biological processes, including the chromosomal protein glycyl lysine isopeptide cross‑link. HMGB1 may be involved in the early stage of pancreatitis, potentially by inducing the development of cell death by necrosis. These results provide an experimental basis for clinical intervention in AP.

Immunopathogenesis of pancreatitis

The conventional view of the pathogenesis of acute and chronic pancreatitis is that it is due to a genetic- or environment-based abnormality of intracellular acinar trypsinogen activation and thus to the induction of acinar cell injury that, in turn, sets in motion an intra-pancreatic inflammatory process. More recent studies, reviewed here, present strong evidence that while such trypsinogen activation is likely a necessary first step in the inflammatory cascade underlying pancreatitis, sustained pancreatic inflammation is dependent on damage-associated molecular patterns-mediated cytokine activation causing the translocation of commensal (gut) organisms into the circulation and their induction of innate immune responses in acinar cells. Quite unexpectedly, these recent studies reveal that the innate responses involve activation of responses by an innate factor, nucleotide-binding oligomerization domain 1 (NOD1), and that such NOD1 responses have a critical role in the activation/production of nuclear factor-kappa B and type I interferon. In addition, they reveal that chronic inflammation and its accompanying fibrosis are dependent on the generation of IL-33 by injured acinar cells and its downstream induction of T cells producing IL-13. These recent studies thus establish that pancreatitis is quite a unique form of inflammation and one susceptible to newer, more innovative therapy.

HMGB1 and Histones Play a Significant Role in Inducing Systemic Inflammation and Multiple Organ Dysfunctions in Severe Acute Pancreatitis. Int J Inflam. 2017;2017:1817564. [PMID: 28316860 PMCID: PMC5339498 DOI: 10.1155/2017/1817564]

Severe acute pancreatitis (SAP) starts as a local inflammation of pancreatic tissue that induces the development of multiple extrapancreatic organs dysfunction; however, the underlying mechanisms are still not clear. Ischemia-reperfusion, circulating inflammatory cytokines, and possible bile cytokines significantly contribute to gut mucosal injury and intestinal bacterial translocation (BT) during SAP. Circulating HMGB1 level is significantly increased in SAP patients and HMGB1 is an important factor that mediates (at least partly) gut BT during SAP. Gut BT plays a critical role in triggering/inducing systemic inflammation/sepsis in critical illness, and profound systemic inflammatory response syndrome (SIRS) can lead to multiple organ dysfunction syndrome (MODS) during SAP, and systemic inflammation with multiorgan dysfunction is the cause of death in experimental SAP. Therefore, HMGB1 is an important factor that links gut BT and systemic inflammation. Furthermore, HMGB1 significantly contributes to multiple organ injuries. The SAP patients also have significantly increased circulating histones and cell-free DNAs levels, which can reflect the disease severity and contribute to multiple organ injuries in SAP. Hepatic Kupffer cells (KCs) are the predominant source of circulating inflammatory cytokines in SAP, and new evidence indicates that hepatocyte is another important source of circulating HMGB1 in SAP; therefore, treating the liver injury is important in SAP.

A New Chemical Compound, NecroX-7, Acts as a Necrosis Modulator by Inhibiting High-Mobility Group Box 1 Protein Release During Massive Ischemia-Reperfusion Injury

BACKGROUND

Necrotic cell death is common in a wide variety of pathologic conditions, including ischemia-reperfusion (IR) injury. The aim of this study was to develop an IR injury-induced hepatic necrosis model in dogs by means of selective left hepatic inflow occlusion and to test the efficacy of a new chemical compound, NecroX-7, against the IR injury-induced hepatic damage.

METHODS

A group of male Beagle dogs received intravenous infusions of either vehicle or different doses of NecroX-7 (1.5, 4.5, or 13 mg/kg) for a 20-minute period before a 90-minute left hepatic inflow occlusion followed by reperfusion.

RESULTS

The gross morphology in the NecroX-7-treated groups after occlusion appeared to be less congested and less swollen than that in vehicle-treated control group. Circulating alanine transaminase and aspartate transaminase levels in the control group were elevated during the course of IR, and were effectively blocked in the 4.5 and 13 mg/kg NecroX-7-treated groups. The serum levels of high-mobility group box 1 protein showed a peak at 8 hours after occlusion in control group, and this elevation was significantly blunted by 4.5 mg/kg NecroX-7 treatment. Histologic analysis showed a marked ischemia or IR injury-induced hepatocytic degenerations, sinusoidal and portal vein congestions, and inflammatory cell infiltrations in the control group, whereas the treatment groups showed significantly diminished histopathology in a dose-dependent manner.

CONCLUSIONS

These results demonstrated that NecroX-7 attenuated the hepatocyte lethality caused by hepatic IR injury in a large animal setting. We conclude that NecroX-7 may provide a wide variety of therapeutic options for IR injury in human patients.

Ethyl pyruvate is a novel anti-inflammatory agent to treat multiple inflammatory organ injuries

Ethyl pyruvate (EP) is a simple derivative of pyruvic acid, which is an important endogenous metabolite that can scavenge reactive oxygen species (ROS). Treatment with EP is able to ameliorate systemic inflammation and multiple organ dysfunctions in multiple animal models, such as acute pancreatitis, alcoholic liver injury, acute respiratory distress syndrome (ARDS), acute viral myocarditis, acute kidney injury and sepsis. Recent studies have demonstrated that prolonged treatment with EP can ameliorate experimental ulcerative colitis and slow multiple tumor growth. It has become evident that EP has pharmacological anti-inflammatory effect to inhibit multiple early inflammatory cytokines and the late inflammatory cytokine HMGB1 release, and the anti-tumor activity is likely associated with its anti-inflammatory effect. EP has been tested in human volunteers and in a clinical trial of patients undergoing cardiac surgery in USA and shown to be safe at clinical relevant doses, even though EP fails to improve outcome of the heart surgery, EP is still a promising agent to treat patients with multiple inflammatory organ injuries and the other clinical trials are on the way. This review focuses on how EP is able to ameliorate multiple organ injuries and summarize recently published EP investigations.

Graphical Abstract

HMGB1 translocation and release mediate cigarette smoke-induced pulmonary inflammation in mice through a TLR4/MyD88-dependent signaling pathway

Cigarette smoke (CS) increases up-regulation of TLR4-mediated signaling and induces TLR4-dependent inflammation in lungs. CS exposure–induced HMGB1 translocation and release of HMGB1 controls CS-induced inflammatory response. MGB1 induces TLR4-mediated proinflammatory cytokine production and activates NF-κB and JNK/p38 pathways.

We performed studies to determine the role of high-mobility group box 1 (HMGB1) in cigarette smoke (CS)–induced pulmonary inflammation. After mice were exposed to five cigarettes four times a day for 3 d, toll-like receptor 4 (TLR4) expression and TLR4-mediated signaling were significantly up-regulated, and HMGB1 had translocated from the nucleus to the cytoplasm in lung epithelial cells and then been released into the extracellular lung space. On CS exposure, inflammatory cell recruitment and proinflammatory cytokine production were significantly increased in lung tissue and bronchoalveolar lavage, and these effects depended on the TLR4 signaling pathway. HMGB1 inhibition decreased the CS-induced inflammatory response, whereas treatment with exogenous HMGB1 aggravated the damage and increased the phosphorylation of JNK, p38, and IκBα in the lungs of wild-type mice but not in TLR4-knockout mice. Blockade of TLR4 action or TLR4 knockout significantly inhibited HMGB1-induced proinflammatory cytokine production in mouse tracheal epithelial (MTE) cells and lung tissues. In addition, a MyD88 deficiency inhibited JNK, p38, and IκBα phosphorylation, and this effect was associated with the suppressed production of TNF-α and IL-1β in MTE cells and lung tissues in response to CS stimulation. Thus HMGB1 activates the NF-κB and JNK/p38 pathways through TLR4/MyD88-dependent signaling and induces an inflammatory response in lungs exposed to CS.

HMGB1 as biomarker and drug target

High Mobility Group Box 1 protein was discovered as a nuclear protein, but it has a "second life" outside the cell where it acts as a damage-associated molecular pattern. HMGB1 is passively released or actively secreted in a number of diseases, including trauma, chronic inflammatory disorders, autoimmune diseases and cancer. Extracellular HMGB1 triggers and sustains the inflammatory response by inducing cytokine release and by recruiting leucocytes. These characteristics make extracellular HMGB1 a key molecular target in multiple diseases. A number of strategies have been used to prevent HMGB1 release or to inhibit its activities. Current pharmacological strategies include antibodies, peptides, decoy receptors and small molecules. Noteworthy, salicylic acid, a metabolite of aspirin, has been recently found to inhibit HMGB1. HMGB1 undergoes extensive post-translational modifications, in particular acetylation and oxidation, which modulate its functions. Notably, high levels of serum HMGB1, in particular of the hyper-acetylated and disulfide isoforms, are sensitive disease biomarkers and are associated with different disease stages. In the future, the development of isoform-specific HMGB1 inhibitors may potentiate and fine-tune the pharmacological control of inflammation. We review here the current therapeutic strategies targeting HMGB1, in particular the emerging and relatively unexplored small molecules-based approach.

Key Role of DAMP in Inflammation, Cancer, and Tissue Repair

PURPOSE

This review aimed to take stock of the current status of research on damage-associated molecular pattern (DAMP) protein. We discuss the Janus-faced role of DAMP molecules in inflammation, cancer, and tissue repair. The high-mobility group box (HMGB)-1 and adenosine triphosphate proteins are well-known DAMP molecules and have been primarily associated with inflammation. However, as we shall see, recent data have linked these molecules to tissue repair. HMGB1 is associated with cancer-related inflammation. It activates nuclear factor kB, which is involved in cancer regulation via its receptor for advanced glycation end-products (RAGE), Toll-like receptors 2 and 4. Proinflammatory activity and tissue repair may lead to pharmacologic intervention, by blocking DAMP RAGE and Toll like receptor 2 and 4 role in inflammation and by increasing their concentration in tissue repair, respectively.

METHODS

We conducted a MEDLINE search for articles pertaining to the various issues related to DAMP, and we discuss the most relevant articles especially (ie, not only those published in journals with a higher impact factor).

FINDINGS

A cluster of remarkable articles on DAMP have appeared in the literature in recent years. Regarding inflammation, several strategies have been proposed to target HMGB1, from antibodies to recombinant box A, which interacts with RAGE, competing with the full molecule. In tissue repair, it was reported that the overexpression of HMGB1 or the administration of exogenous HMGB1 significantly increased the number of vessels and promoted recovery in skin-wound, ischemic injury.

IMPLICATIONS

Due to the bivalent nature of DAMP, it is often difficult to explain the relative role of DAMP in inflammation versus its role in tissue repair. However, this point is crucial as DAMP-related treatments move into clinical practice.

Regulation of autophagy by systemic admission of microRNA-141 to target HMGB1 in l-arginine-induced acute pancreatitis in vivo

BACKGROUND & AIMS

MicroRNAs are endogenous, non-coding RNAs of approximately 20-22 nucleotides that regulate gene expression by binding to the 3' untranslated region (UTR) of target mRNAs and can be applied in gene therapy. Acute pancreatitis is an inflammatory pancreatic disease that carries considerable morbidity and mortality. The purpose of this study was to explore the therapeutic potential of microRNA-141 (miR-141) for acute pancreatitis in vivo.

METHODS

AP was induced by two hourly intra-peritoneal (i.p.) injections of l-arginine (200mg × 2/100 g.BW). Control mice received normal saline injections. In a separate group, normal saline, empty adenoviral vector and miR-141 adenoviral vector were given to the mice via tail vein hydrodynamically at 72 h before the first l-arginine injection. All the mice were euthanized at 24 h after the last l-arginine injection, and the pancreatic tissues were assessed by qRT-PCR, Western blotting and electron microscopy.

RESULTS

miR-141 directly inhibited HMGB1 expression in mouse hepal-6 cell. Furthermore, systemic administration of the miR-141 knock-down the expression of HMGB1 protein and further antagonized the downstream protein Beclin-1, leading to the reduction of autophagosomes and autolysosomes, blockade of the LC3-II level and the increased levels of p62 protein after injection of l-arginine. In addition, the level of Lamp-2 was not significantly different.

CONCLUSIONS

For the first time miR-141 was applied in acute pancreatitis treatment in vivo. Inhibition of HMGB1 by miR-141 may block the process of autophagosome formation through the HMGB1/Beclin-1 pathway. The miR-141 appears to be a promising candidate for the gene therapy of acute pancreatitis.

Circulating nucleosomes as predictive markers of severe acute pancreatitis

Background

The components of nucleosomes, which contain DNA and histones, are released into the circulation from damaged cells and can promote inflammation. We studied whether the on-admission levels of circulating nucleosomes predict the development of severe acute pancreatitis (AP), in particular among the patients who present without clinical signs of organ dysfunction.

Methods

This is a prospective study of 74 AP patients admitted to Helsinki University Hospital from 2003 to 2007. Twenty-three patients had mild, 27 moderately severe, and 24 severe AP as defined by the revised Atlanta criteria. 14/24 severe AP patients had no sign of organ dysfunction on admission (modified marshall score <2). Blood samples were obtained on admission and the plasma levels of nucleosomes were measured using enzyme-linked immunosorbent assay.

Results

The on-admission levels of nucleosomes were significantly higher in severe AP than in mild or moderately severe AP (p < 0.001 for all), higher in non-survivors (n = 8) than in survivors (p = 0.019), and correlated with the on-admission levels of C-reactive protein (p < 0.001) and creatinine (p < 0.001). Among the AP patients who presented without organ dysfunction, the on-admission nucleosome level was an independent predictor of severe AP (p = 0.038, gender-adjusted forward-stepping logistic regression).

Conclusions

Circulating nucleosome levels may be helpful in identifying, on admission to hospital, the AP patients who present without clinical signs of organ dysfunction, and, yet, are bound to develop organ dysfunction during hospitalization.

The protective effect of neutralizing high-mobility group box1 against chronic cyclosporine nephrotoxicity in mice

BACKGROUND

High-mobility group box1 (HMGB1) is known to be involved in innate immune response through interaction with receptor for advanced glycation end products (RAGE) and toll-like receptors (TLRs), besides its proper role within the nucleus. Immunological pathways, including TLR signaling, are also involved in chronic cyclosporine (CsA) nephrotoxicity. This study was designed to determine whether neutralizing HMGB1 prevents chronic CsA nephrotoxicity.

METHODS

Chronic CsA nephrotoxicity was induced by CsA subcutaneous injection daily for 4weeks under salt-depletion in mice. Anti-HMGB1 neutralizing antibody for HMGB1 blockade (600mcg/mouse) was administered weekly to mice in the anti-HMGB1 treatment group. The effects of HMGB1 neutralization were evaluated in terms of renal function as well as histological and immunopathological examination.

RESULTS

Anti-HMGB1 administration prevented the increases in serum creatinine and 24h albuminuria and the decrease in creatinine clearance associated with CsA treatment. Increased tubulointerstitial fibrosis and transforming growth factor (TGF)-β immunohistochemical staining associated with CsA treatment were also prevented by anti-HMGB1 administration. Anti-HMGB1 administration prevented the activation of the TLR4 signaling pathway, which resulted in the reduction of nuclear factor kappa B (NF-κB) expression. In cultured tubular cells, anti-HMGB1 pretreatment also prevented the increases in fibronectin and collagen IV levels associated with CsA treatment.

CONCLUSIONS

Neutralizing HMGB1 with an anti-HMGB1 antibody ameliorated chronic CsA nephrotoxicity via inhibition of the TLR4 signaling pathway. Our study suggests that HMGB1 blockade can be beneficial for increasing allograft survival in renal transplant recipients by protecting against calcineurin inhibitor-induced nephrotoxicity.

TLR4-mediated NF-κB signaling pathway mediates HMGB1-induced pancreatic injury in mice with severe acute pancreatitis

Severe acute pancreatitis (SAP) is an extremely dangerous acute abdominal disorder which causes multiple complications and has a high mortality rate. Previous research has suggested that high-mobility group box 1 (HMGB1) plays an important role in the pathogenesis of SAP; however, the mechanisms underlying this strong correlation remain unclear. In this study, to further investigate whether HMGB1 acts as a stimulating factor, and whether Toll-like receptor 4 (TLR4) acts as its major mediator in the development of pancreatic injury during SAP, recombinant human HMGB1 (rhHMGB1) and TLR4-deficient mice were used. We found that HMGB1 and TLR4 were highly expressed, and nuclear factor-κB (NF-κB) was activated in our mouse model of SAP. We noted that the rhHMGB1 pancreas-targeted injection activated the TLR4-mediated NF-κB signaling pathway and induced pancreatic injury in wild-type mice. In TLR4-deficient mice, the rhHMGB1-induced activation of NF-κB and pathological changes in the pancreas were less evident than in wild-type mice. Therefore, this study provides evidence that HMGB1 promotes the pathogenesis of pancreatitis, and its downstream TLR4-mediated NF-κB signaling pathway is a potential important mediator in the development of this form of pancreatic injury.

Anti-high mobility group box 1 antibody exerts neuroprotection in a rat model of Parkinson's disease

The high mobility group box-1 (HMGB1) exists as an architectural nuclear protein in the normal state, but displays an inflammatory cytokine-like activity in the extracellular space under pathological condition. Inflammation in the pathogenesis of Parkinson's disease (PD) has been documented. In this study, we investigated the involvement of HMGB1 in the pathology and the neuroprotective effects of neutralizing anti-HMGB1 monoclonal antibody (mAb) on an animal model of PD. Adult female Sprague-Dawley rats were initially injected with 6-hydroxydopmaine (6-OHDA, 20 μg/4 μl) into the right striatum, then anti-HMGB1 mAb (1 mg/kg), or control mAb was intravenously administered immediately, at 6 and 24 h after 6-OHDA injection. The treatment with anti-HMGB1 mAb significantly preserved dopaminergic neurons in substantia nigra pars compacta and dopaminergic terminals inherent in the striatum, and attenuated PD behavioral symptoms compared to the control mAb-treated group. HMGB1 was retained in the nucleus of neurons and astrocytes by inhibiting the proinflammation-induced oxidative stress in the anti-HMGB1 mAb-treated group, whereas HMGB1 translocation was observed in neurons at 1 day and astrocytes at 7 days after 6-OHDA injection in the control mAb-treated group. Anti-HMGB1 mAb inhibited the activation of microglia, disruption of blood-brain-barrier (BBB), and the expression of inflammation cytokines such as IL-1β and IL-6. These results suggested that HMGB1 released from neurons and astrocytes was at least partly involved in the mechanism and pathway of degeneration of dopaminergic neurons induced by 6-OHDA exposure. Intravenous administration of anti-HMGB1 mAb stands as a novel therapy for PD possibly acting through the suppression of neuroinflammation and the attenuation of disruption of BBB associated with the disease.

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

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

TLR4-HMGB1-, MyD88- and TRIF-dependent signaling in mouse intestinal ischemia/reperfusion injury

AIM: To characterize high-mobility group protein 1-toll-like receptor 4 (HMGB1-TLR4) and downstream signaling pathways in intestinal ischemia/reperfusion (I/R) injury.

METHODS: Forty specific-pathogen-free male C57BL/6 mice were randomly divided into five groups (n = 8 per group): sham, control, anti-HMGB1, anti-myeloid differentiation gene 88 (MyD88), and anti-translocating-chain-associating membrane protein (TRIF) antibody groups. Vehicle with the control IgG antibody, anti-HMGB1, anti-MyD88, or anti-TRIF antibodies (all 1 mg/kg, 0.025%) were injected via the caudal vein 30 min prior to ischemia. After anesthetization, the abdominal wall was opened and the superior mesenteric artery was exposed, followed by 60 min mesenteric ischemia and then 60 min reperfusion. For the sham group, the abdominal wall was opened for 120 min without I/R. Levels of serum nuclear factor (NF)-κB p65, interleukin (IL)-6, and tumor necrosis factor (TNF)-α were measured, along with myeloperoxidase activity in the lung and liver. In addition,morphologic changes that occurred in the lung and intestinal tissues were evaluated. Levels of mRNA transcripts encoding HMGB1 and NF-κB were measured by real-time quantitative PCR, and levels of HMGB1 and NF-κB protein were measured by Western blot. Results were analyzed using one-way analysis of variance.

RESULTS: Blocking HMGB1, MyD88, and TRIF expression by injecting anti-HMGB1, anti-MyD88, or anti-TRIF antibodies prior to ischemia reduced the levels of inflammatory cytokines in serum; NF-κB p65: 104.64 ± 11.89, 228.53 ± 24.85, 145.00 ± 33.63, 191.12 ± 13.22, and 183.73 ± 10.81 (P < 0.05); IL-6: 50.02 ± 6.33, 104.91 ± 31.18, 62.28 ± 6.73, 85.90 ± 17.37, and 78.14 ± 7.38 (P < 0.05); TNF-α, 43.79 ± 4.18, 70.81 ± 6.97, 52.76 ± 5.71, 63.19 ± 5.47, and 59.70 ± 4.63 (P < 0.05) for the sham, control, anti-HMGB1, anti-MyD88, and anti-TRIF groups, respectively (all in pg/mL).Antibodies also alleviated tissue injury in the lung and small intestine compared with the control group in the mouse intestinal I/R model. The administration of anti-HMGB1, anti-MyD88, and anti-TRIF antibodies markedly reduced damage caused by I/R, for which anti-HMGB1 antibody had the most obvious effect.

CONCLUSION: HMGB1 and its downstream signaling pathway play important roles in the mouse intestinal I/R injury, and the effect of the TRIF-dependent pathway is slightly greater.

The effect of lornoxicam on TLR2 and TLR4 messenger RNA expression and tumor necrosis factor-α, interleukin-6, and interleukin-8 secretion in patients with systemic complications of acute pancreatitis

OBJECTIVES

To assess the effects of the cyclooxygenase-1/cyclooxygenase-2 inhibitor lornoxicam on systemic complications in patients with acute pancreatitis, Toll-like receptor (TLR)2 and TLR4 messenger RNA expression, and cytokine secretion (IL-6, IL-8, tumor necrosis factor-α).

METHODS

Adult patients with acute pancreatitis were randomized to standard therapy or standard therapy plus lornoxicam. Standard therapy included analgesics, spasmolytics, octreotide, pantoprazole, and intravenous fluids. The TLR2 and TLR4 expression levels and TLR2- and TLR4-mediated cytokine production in peripheral blood mononuclear cells were assessed in patients with severe complications and in healthy volunteers (n = 15).

RESULTS

A total of 334 patients received standard therapy (n = 246) or standard therapy plus lornoxicam (n = 88), 172 (51.5%) of whom developed systemic complications. Occurrence of complications was higher with standard therapy compared with lornoxicam (57.3% versus 35.2%; P = 0.00034), as was mortality (19.1% versus 6.8%; P = 0.006). The TLR2 and TLR4 expression and TLR2 and TLR4-mediated cytokine production were significantly higher in patients with systemic complications of acute pancreatitis compared with healthy volunteers. Relative TLR2 expression and cytokine production were significantly reduced in patients receiving lornoxicam versus standard therapy.

CONCLUSIONS

The use of lornoxicam at the onset of acute pancreatitis decreased TLR2 and TLR4 expression and the production of proinflammatory cytokines, thereby reducing the risk of systemic complications and mortality.

Sodium Butyrate Reduces Organ Injuries in Mice with Severe Acute Pancreatitis Through Inhibiting HMGB1 Expression

OBJECTIVE

The present study was designed to evaluate the effect of sodium butyrate on pancreas damage and to investigate the role of high-mobility group box-1 (HMGB1) and nuclear factor-κB (NF-κB) in the development of severe acute pancreatitis (SAP) in a mouse model.

METHODS

The SAP model was established by intraperitoneal injection of two doses of 20 % L-2 arginine (200 mg/g). Female Sprague-Dawley mice were randomly allocated into three groups (n = 48/group): the control, untreated SAP, and sodium butyrate-treated SAP groups. The animals were euthanized at 0, 12, 24, and 48 h after the establishment of the SAP. Histopathology of the pancreas was performed, and the NF-κB levels were determined by immunohistochemistry. The serum levels of tumor necrosis factor (TNFα), interleukin-6 (IL-6), and HMGB1 were measured by ELISA. The HMGB1 mRNA levels were determined by qRT-PCR.

RESULTS

The sodium butyrate-treated SAP animals showed significantly improved pancreas histopathology and lower serum amylase levels than the untreated SAP animals. In the SAP group, the mRNA levels of HMGB1 were remarkably increased at the 12 h, peaked at 24 h, and remained at a high level up to 48 h after L-2 arginine injection. The levels of TNFα and IL-6 were decreased at 48 h. Treatment with sodium butyrate reduced the pathological lesions, the serum levels of HMGB1, TNFα, and IL-6, the HMGB1 mRNA levels, and NF-κB activity.

CONCLUSION

Sodium butyrate inhibits the NF-κB activation and reduces pancreas injury in SAP through the modulation of HMGB1 and other inflammatory cytokine responses.

Spatial and temporal differences of HMGB1 expression in the pancreas of rats with acute pancreatitis

We aimed to investigate the spatial and temporal differences in expression between HMGB1 and early-stage inflammatory cytokines (IL-1, IL-6 and TNF-α) in pancreas tissue in rats with acute pancreatitis. SD rats (BW 350 ± 30 g, n = 48) were randomly divided into the experimental group (n = 36) which were injected with 5% sodium taurocholate into the bilipancreatic duct retrogradely to produce acute necrotic pancreatitis (ANP) rat models, and the sham-operated (SO) group (n = 12) injected with equal dose of saline. The rats were sacrificed at different time points at 0 h, 3 h, 6 h, 12 h, and 24 h post modeling, respectively. The peripheral blood amylase and different inflammatory factors in ANP rats at different time points were detected by ELISA, and the expression of HMGB1 in the pancreatic tissue was detected by immunohistochemistry, Western blot and Q-PCR methods. Results showed that the serum amylase in the ANP model rats was significantly higher than the sham-operated group (P < 0.05). The early inflammatory factors (IL-1, TNF-α and IL-6) increased quickly at 3 h after the model induction, reached the peak level at 6 h (higher than SO group, P < 0.05), then decreased at 12 h, and at 24 h the levels were lower than those at 12 h (P < 0.05). The HMGB1 level in the pancreatitis tissue did not change significantly at 3 h and 6 h (P > 0.05), however, it increased remarkably at 12 h, and maintained up to 24 h (P > 0.05). As a late inflammatory factor, the expression of HMGB1 in acute pancreatitis was obviously later than the early inflammatory factors IL-1, TNF-α and IL-6. HMGB1 may play a key role in maintaining the development of the acute pancreatitis.

Inflammasomes in pancreatic physiology and disease

In this review we summarize the role of inflammasomes in pancreatic physiology and disease with a focus on acute pancreatitis where much recent progress has been made. New findings have identified inducers of and cell specificity of inflammasome component expression in the pancreas, the contribution of inflammasome-regulated effectors to pancreatitis, and metabolic regulation of inflammasome activation, which are strong determinants of injury in pancreatitis. New areas of pancreatic biology will be highlighted in the context of our evolving understanding of gut microbiome- and injury-induced inflammasome priming, pyroptosis, and innate immune-mediated regulation of cell metabolism.