In the present study, we examined the mechanisms of oxaliplatin-induced drug resistance in human colorectal cancer cell lines HT29 and HCT116. Our results demonstrate a significant autophagy expression in CRC cells after an oxaliplatin treatment. Administration of oxaliplatin to human CRC cells significantly enhanced the expression of HMGB1, which regulated the autophagy response and negatively regulate the cell apoptosis. Moreover, a decreased oxaliplatin -induced autophagy response and an increased apoptosis level were detected in stable CRC cells harboring HMGB1 shRNA. Then we noted that HMGB1 significantly induced extracellular signal-regulated kinase (ERK)/Extracellular signal-regulated kinase kinase (MEK) phosphorylation. Taken together, these data suggest that HMGB1-mediated autophagy modulates sensitivity of colorectal cancer cells to oxaliplatin via MEK/ERK signaling pathway.

Synovial fibroblasts (SF) play a central role in the inflammatory and destructive process in rheumatoid arthritis (RA). High-mobility group box chromosomal protein 1 (HMGB1) or lipopolysaccharide (LPS) alone failed to induce significant changes in proliferation of cultured SF from RA patients, but premixed HMGB1 with LPS (HMGB1-LPS) significantly facilitated SF proliferation. HMGB1 alone failed to induce IL-6, MMP-3, and MMP-13 production in cultured SF but greatly enhanced LPS-induced expression of IL-6, MMP-3, and MMP-13 at both mRNA and protein levels. HMGB1-LPS synergistically upregulated TLR4 and receptor for advanced glycation endproducts (RAGE) expression on the surface of SF. Both blockers of TLR4 and RAGE significantly inhibited the synergistic effects of HMGB1-LPS on the production of IL-6 and MMPs, but blocking antibodies to TLR2 failed. HMGB1-LPS synergistically increased intracellular levels of phosphorylated p38 and phosphorylated I κ B. Furthermore, both NF- κ B inhibitor Bay11-7085 and p38 inhibitor SB203580 significantly suppressed the enhanced production of IL-6 and MMPs induced by HMGB1-LPS. In conclusion, HMGB1 acts in synergy with LPS to upregulate TLR4 and RAGE expression on the surface of SF in RA and then to augment IL-6, MMP-3, and MMP-13 production, which depends on p38 MAPK and NF-κB activation.

BACKGROUND

Many neurobiological factors may initiate and sustain alcoholism. Recently, dysregulation of the neuroimmune system by chronic ethanol (CE) has implicated Toll-like receptor 4 (TLR4) activation. Even though TLR4s are linked to CE initiation of brain cytokine mRNAs, the means by which CE influences neuroimmune signaling in brain in the absence of infection remains uncertain. Therefore, the hypothesis is tested that release of an endogenous TLR4 agonist, high-mobility group box 1 (HMGB1) and/or corticotropin-releasing factor (CRF) during CE withdrawal are responsible for CE protocols increasing cytokine mRNAs.

METHODS

Acute ethanol (EtOH; 2.75 g/kg) and acute lipopolysaccharide (LPS; 250 μg/kg) dosing on cytokine mRNAs are first compared. Then, the effects of chronic LPS exposure (250 μg/kg for 10 days) on cytokine mRNAs are compared with changes induced by CE protocols (15 days of continuous 7% EtOH diet [CE protocol] or 3 intermittent 5-day cycles of 7% EtOH diet [CIE protocol]). Additionally, TLR4, HMGB1, and downstream effector mRNAs are assessed after CE, CIE, and chronic LPS. To test whether HMGB1 and/or CRF support the CE withdrawal increase in cytokine mRNAs, the HMGB1 antagonists, glycyrrhizin and ethyl pyruvate, and a CRF1 receptor antagonist (CRF1RA) are administered during 24 hours of CE withdrawal.

RESULTS

While cytokine mRNAs were not increased following acute EtOH, acute LPS increased all cytokine mRNAs 4 hours after injection. CE produced no change in cytokine mRNAs prior to CE removal; however, the CE and CIE protocols increased cytokine mRNAs by 24 hours after withdrawal. In contrast, chronic LPS produced no cytokine mRNA changes 24 hours after LPS dosing. TLR4 mRNA was elevated 24 hours following both CE protocols and chronic LPS exposure. While chronic LPS had no effect on HMGB1 mRNA, withdrawal from CE protocols significantly elevated HMGB1 mRNA. Systemic administration of HMGB1 antagonists or a CRF1RA significantly reduced the cytokine mRNA increase following CE withdrawal. The CRF1RA and the HMGB1 antagonist, ethyl pyruvate, also reduced the HMGB1 mRNA increase that followed CE withdrawal.

CONCLUSIONS

By blocking HMGB1 or CRF action during CE withdrawal, evidence is provided that HMGB1 and CRF release are critical for the CE withdrawal induction of selected brain cytokine mRNAs. Consequently, these results clarify a means by which withdrawal from CE exposure activates neuroimmune function in the sterile milieu of brain.

High mobility group box 1 (HMGB1) is a DNA-binding nuclear protein, actively released following cytokine stimulation as well as passively during cell injury and death. Autophagy is a tightly regulated cellular stress pathway involving the lysosomal degradation of cytoplasmic organelles or proteins. Organisms respond to oxidative injury by orchestrating stress responses such as autophagy to prevent further damage. Recently, we reported that HMGB1 is an autophagy sensor in the presence of oxidative stress. Hydrogen peroxide (H 2O 2) and loss of superoxide dismutase 1 (SOD1)-mediated oxidative stress promotes cytosolic HMGB1 expression and extracellular release. Inhibition of HMGB1 release or loss of HMGB1 decreases the number of autolysosomes and autophagic flux in human and mouse cell lines under conditions of oxidative stress. These findings provide insight into how HMGB1, a damage associated molecular pattern (DAMP), triggers autophagy as defense mechanism under conditions of cellular stress.

Receptor for advanced glycation endproducts (RAGE) is a multi-ligand receptor that is able to bind several different ligands, including advanced glycation endproducts, high-mobility group protein (B)1 (HMGB1), S-100 calcium-binding protein, amyloid-β-protein, Mac-1, and phosphatidylserine. Its interaction is engaged in critical cellular processes, such as inflammation, proliferation, apoptosis, autophagy, and migration, and dysregulation of RAGE and its ligands leads to the development of numerous human diseases. In this review, we summarize the signaling pathways regulated by RAGE and its ligands identified up to date and demonstrate the effects of hyper-activation of RAGE signals on human diseases, focused mainly on renal disorders. Finally, we propose that RAGE and its ligands are the potential targets for the diagnosis, monitoring, and treatment of numerous renal diseases.

Allograft blood vessels are important targets of clinical allograft rejection. Perioperative allograft injury to graft vasculature, especially the endothelial cell (EC) lining, increases the risk of subsequent acute and chronic vascular rejection. We hypothesize that allograft EC injured by ischemia-reperfusion (I/R) during transplantation releases mediators, termed "alarmins," that alter and intensify the host antigraft adaptive immune response. We begin with a review of both perioperative I/R injury to graft endothelium and T-cell-mediated vascular rejection. We then describe several alarmins that may be released from injured allografts, including interleukin (IL)-1alpha, ATP, monosodium urate (MSU), and high mobility group protein B1 (HMGB1). These mediators have in common the ability to induce production of IL-1beta from mononuclear phagocytes, and both isoforms of IL-1 act on T cells to enhance destructive adaptive immune responses. Therefore, we propose that IL-1 is the key alarmin that communicates graft injury to the host's adaptive immune system, and we suggest that perioperative targeting of IL-1 represents a promising strategy to attenuate the strength of rejection reactions.

High-mobility group box protein 1 (HMGB1) is a non-histone nuclear protein with alarmin activity. When present in an extracellular location, HMGB1 can activate the innate immune system and promote inflammation in conditions such as sepsis. To exert these activities, HMGB1 must transit from the nucleus, through the cytoplasm, to the outside of the cell. This process can occur during cell activation as well as cell death. In murine macrophages (MPhi), stimulation of TLR3 and TLR4, but not TLR9, can cause HMGB1 translocation. With cell death, necrosis can lead to extracellular HMGB1 by a passive mechanism. With apoptosis, HMGB1 is only released during secondary necrosis, when cell permeability barriers break down. Since agents that stimulate MPhi can also induce apoptosis, HMGB1 release following TLR stimulation may also reflect a contribution from dead cells, suggesting a common mechanism for protein release in activation and death.

OBJECTIVE

Sterile intra-amniotic inflammation is associated with spontaneous preterm labor. Alarmins are proposed to mediate this inflammatory process. The aim of this study was to determine whether intra-amniotic administration of an alarmin, HMGB1, could induce preterm labor/birth.

METHODS

Pregnant B6 mice were intra-amniotically or intraperitoneally injected with HMGB1 or PBS (control). Following injection, the gestational age and the rates of preterm birth and pup mortality were recorded.

RESULTS

Intra-amniotic injection of HMGB1 led to preterm labor/birth [HMGB1 57% (4/7) versus PBS 0% (0/6); P = 0.049) and a high rate of pup mortality at week 1 [HMGB1 60.9 ± 11.7% (25/41) versus PBS 28.9 ± 12.6% (11/38); P = 0.001). Intraperitoneal injection of HMGB1 did not induce preterm labor/birth.

CONCLUSIONS

Intra-amniotic administration of HMGB1 induces preterm labor/birth.

The aim of the study was to determine the effects of fucoidan on rat myocardial ischemia-reperfusion (I/R) model and elucidate the potential mechanisms. Myocardial I/R injury was induced by the occlusion of left anterior descending coronary artery for 30 min followed by reperfusion for 2h. After 2h reperfusion, hemodynamics parameters were detected. Blood samples were collected to determine serum levels of tumor necrosis factor-α (TNF-α) and interleukin 6, 10 (IL-6, 10). Hearts were harvested to assess histopathological changes, infarct size (IS), and the content of myeloperoxidase (MPO). The expression of high-mobility group box 1 (HMGB1), phosphor-IκB-α and phosphor-nuclear factor kappa B (NF-κB) were assayed by western blot. Compared with control group, treatment with fucoidan improved left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP) and the contractility index (P<0.05, P<0.01). Fucoidan reduced the myocardial IS, the levels of TNF-α and IL-6, and the activity of MPO (P<0.05, P<0.01). Fucoidan down-regulated the expression of HMGB1, phosphor-IκB-α and NF-κB, but increased the content of IL-10 when compared with control (P<0.05, P<0.01). Besides, the infiltration of polymorph nuclear leukocytes (PMNs) and histopathological damages in myocardium were decreased in fucoidan treated groups (PMNs, P<0.05, P<0.01). These findings revealed that the administration of fucoidan could regulate the inflammation response via HMGB1 and NF-κB inactivation in I/R-induced myocardial damage.

BACKGROUND

Aseptic trauma engages the innate immune response to trigger a neuroinflammatory reaction that results in postoperative cognitive decline. The authors sought to determine whether high-mobility group box 1 protein (HMGB1), an ubiquitous nucleosomal protein, initiates this process through activation and trafficking of circulating bone marrow-derived macrophages to the brain.

METHODS

The effects of HMGB1 on memory (using trace fear conditioning) were tested in adult C57BL/6J male mice; separate cohorts were tested after bone marrow-derived macrophages were depleted by clodrolip. The effect of anti-HMGB1 neutralizing antibody on the inflammatory and behavioral responses to tibial surgery were investigated.

RESULTS

A single injection of HMGB1 caused memory decline, as evidenced by a decrease in freezing time (52 ± 11% vs. 39 ± 5%; n = 16-17); memory decline was prevented when bone marrow-derived macrophages were depleted (39 ± 5% vs. 50 ± 9%; n = 17). Disabling HMGB1 with a blocking monoclonal antibody, before surgery, reduced postoperative memory decline (52 ± 11% vs. 29 ± 5%; n = 15-16); also, hippocampal expression of monocyte chemotactic protein-1 was prevented by the neutralizing antibody (n = 6). Neither the systemic nor the hippocampal inflammatory responses to surgery occurred in mice pretreated with anti-HMGB1 neutralizing antibody (n = 6).

CONCLUSIONS

Postoperative neuroinflammation and cognitive decline can be prevented by abrogating the effects of HMGB1. Following the earlier characterization of the resolution of surgery-induced memory decline, the mechanisms of its initiation are now described. Together, these data may be used to preoperatively test the risk to surgical patients for the development of exaggerated and prolonged postoperative memory decline that is reflected in delirium and postoperative cognitive dysfunction, respectively.

The action radius of matrix metalloproteinases or MMPs is not restricted to massive extracellular matrix (ECM) degradation, it extends to the proteolysis of numerous secreted and membrane-bound proteins. Although many instances exist in which cells disintegrate, often in conjunction with induction of MMPs, the intracellular MMP substrate repertoire or degradome remains relatively unexplored. We started an unbiased exploration of the proteolytic modification of intracellular proteins by MMPs, using gelatinase B/MMP-9 as a model enzyme. To this end, multidimensional degradomics technology was developed by the integration of broadly available biotechniques. In this way, 100-200 MMP-9 candidate substrates were isolated, of which 69 were identified. Integration of these results with the known biological functions of the substrates revealed many novel MMP-9 substrates from the intracellular matrix (ICM), such as actin, tubulin, gelsolin, moesin, ezrin, Arp2/3 complex subunits, filamin B and stathmin. About 2/3 of the identified candidates were autoantigens described in multiple autoimmune conditions and in cancer (e.g. annexin I, nucleolin, citrate synthase, HMGB1, alpha-enolase, histidyl-tRNA synthetase, HSP27, HSC70, HSP90, snRNP D3). These findings led to the insight that MMPs and other proteases may have novel (immuno)regulatory properties by the clearance of toxic and immunogenic burdens of abundant ICM proteins released after extensive necrosis. In line with the extracellular processing of organ-specific autoantigens, proteolysis might also assist in the generation of immunodominant 'neo-epitopes' from systemic autoantigens. The study of proteolysis of ICM molecules, autoantigens, alarmins and other crucial intracellular molecules may result in the discovery of novel roles for proteolytic modification.

Upon muscle injury, the high mobility group box 1 (HMGB1) protein is upregulated and secreted to initiate reparative responses. Here we show that HMGB1 controls myogenesis both in vitro and in vivo during development and after adult muscle injury. HMGB1 expression in muscle cells is regulated at the translational level: the miRNA miR-1192 inhibits HMGB1 translation and the RNA-binding protein HuR promotes it. HuR binds to a cis-element, HuR binding sites (HuRBS), located in the 3'UTR of the HMGB1 transcript, and at the same time miR-1192 is recruited to an adjacent seed element. The binding of HuR to the HuRBS prevents the recruitment of Argonaute 2 (Ago2), overriding miR-1192-mediated translation inhibition. Depleting HuR reduces myoblast fusion and silencing miR-1192 re-establishes the fusion potential of HuR-depleted cells. We propose that HuR promotes the commitment of myoblasts to myogenesis by enhancing the translation of HMGB1 and suppressing the translation inhibition mediated by miR-1192.

Inflammation is a defensive response of the organism to manage harmful stimuli sensed by innate immune cells. The signal alarm is triggered by the recognition of pathogen-associated molecular patterns, such as microbial components, or host-derived damage-associated molecular patterns (DAMPs), namely high-mobility group box 1 protein (HMGB1) and purine metabolites, through a set of highly conserved receptors in immune cells termed pattern recognition receptors. Among these receptors, membrane-associated toll-like receptors (TLRs) and cytosolic nucleotide binding and oligomerization domain (nod)-like receptors (NLRs) assume particular relevance in the inflammatory process. Once activated, NLRs induce the assembly of multiprotein complexes called inflammasomes, leading to production of proinflammatory cytokines (e.g., interleukin-1) and induction of inflammatory cell death (pyroptosis) through the activation of caspase-1. Although these processes intend to protect the body from insults, prolonged or exacerbated inflammatory responses associated with inflammasome activation are related to a growing number of diseases. Recently, inflammasome activation and autophagy were shown to be linked and to mutually influence each other. Therefore, we aim, in this review, to discuss the recent evidences concerning the cross talk between autophagy and inflammasome activation and its potential roles in disease progression.

Whole body exposure to low linear energy transfer (LET) ionizing radiations (IRs) damages vital intracellular bio-molecules leading to multiple cellular and tissue injuries as well as pathophysiologies such as inflammation, immunosuppression etc. Nearly 70% of damage is caused indirectly by radiolysis of intracellular water leading to formation of reactive oxygen species (ROS) and free radicals and producing a state of oxidative stress. The damage is also caused by direct ionization of biomolecules. The type of radiation injuries is dependent on the absorbed radiation dose. Sub-lethal IR dose produces more of DNA base damages, whereas higher doses produce more DNA single strand break (SSBs), and double strand breaks (DSBs). The Nrf2-ARE pathway is an important oxidative stress regulating pathway. The DNA DSBs repair regulated by MRN complex, immunomodulation and inflammation regulated by HMGB1 and various types of cytokines are some of the key pathways which interact with each other in a complex manner and modify the radiation response. Because the majority of radiation damage is via oxidative stress, it is essential to gain in depth understanding of the mechanisms of Nrf2-ARE pathway and understand its interactions with MRN complex, HMGB1 and cytokines to increase our understanding on the radiation responses. Such information is of tremendous help in development of medical radiation countermeasures, radioprotective drugs and therapeutics. Till date no approved and safe countermeasure is available for human use. This study reviews the Nrf2-ARE pathway and its crosstalk with MRN-complex, HMGB1 and cytokines (TNF-a, IL-6, IFN-? etc.). An attempt is also made to review the modification of some of these pathways in presence of selected antioxidant radioprotective compounds or herbal extracts.

Experimental and epidemiological studies have revealed that chronic inflammation contributes to cancer progression and even predisposes to cellular transformation. Inflammatory infiltrates in papillary thyroid cancer include lymphocytes, macrophages and cytokines. High-mobility group box 1 protein (HMGB1) is a late inflammatory cytokine that signals danger to the immune system through the receptor for advanced glycation end-products (RAGE) and Toll-like receptor. The activation of the above receptors results in the secretion of growth, chemotactic and angiogenic factors that contribute to chronic inflammation. In this study, we suggest that apart from the activation of signal transduction pathways by the activation of RAGE, the indirect inhibition of cell cycle regulators [such as phosphatase and tensin homolog (PTEN)] may also cause an increase in cell growth and motility. MicroRNAs (miRNAs) have increasingly been implicated in regulating the malignant progression of cancer. MiR-221 and miR-222 have been found to be deregulated in human papillary thyroid carcinomas. They are involved in cell proliferation through the inhibition of the cell cycle regulator, p27kip1, in human papillary carcinomas. In this study, we show that HMGB1 increases the expression of miR-221 and miR-222 in primary cultures of excised papillary lesions and in an established papillary cancer cell line (BC PAP). The overexpression of oncogenic miR-221 and miR-222 caused by HMGB1 is associated with an increase in malignancy scores, namely cell growth and motility.

High-mobility group box 1 (HMGB1) is a multifunctional protein with intranuclear and extracellular functions. Although HMGB1 is overexpressed in approximately 85% of gastric cancers, the role of HMGB1 in gastric cancer biology remains unclear. In this study, we investigate the effect of downregulation of HMGB1 on the biological behavior of gastric cancer cells. MGC-803 gastric cancer cells were transduced with HMGB1-specific RNAi lentiviral vectors. Real-time polymerase chain reaction and Western blot analysis of HMGB1 mRNA and protein, respectively, validated the silencing effects. HMGB1-specific silencing significantly decreased cell proliferation. The impact on proliferation was observed at the cell cycle level--the number of cells in the G0/G1 phase increased, whereas that in S and G2/M phases decreased. Cell cycle changes were accompanied by decreases in cyclin D1 expression. Furthermore, HMGB1 silencing sensitized cells to apoptosis that was induced by oxaliplatin and mediated by the caspase-3 pathway. Finally, silencing of HMGB1 expression significantly reduced cellular metastatic ability and MMP-9 expression in MGC-803 cells. In summary, HMGB1 not only plays an essential role in the proliferation and invasion of MGC-803 cells but also represents a potential target for the therapeutic intervention of gastric cancer.

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Ethyl pyruvate (EP) was recently identified as a stable lipophilic derivative of pyruvic acid with significant antineoplastic activities. The high mobility group box-B1 (HMGB1)-receptor for advanced glycation end-products (RAGE) and the protein kinase B (Akt) pathways play a crucial role in tumorigenesis and development of many malignant tumors. We tried to observe the effects of ethyl pyruvate on liver cancer growth and explored its effects in hepatocellular carcinoma model. In this study, three hepatocellular carcinoma cell lines were treated with ethyl pyruvate. An MTT colorimetric assay was used to assess the effects of EP on cell proliferation. Flow cytometry and TUNEL assays were used to analyze apoptosis. Real-time PCR, Western blotting and immunofluorescence demonstrated ethyl pyruvate reduced the HMGB1-RAGE and AKT pathways. The results of hepatoma orthotopic tumor model verified the antitumor effects of ethyl pyruvate in vivo. EP could induce apoptosis and slow the growth of liver cancer. Moreover, EP decreased the expression of HMGB1, RAGE, p-AKT and matrix metallopeptidase-9 (MMP9) and increased the Bax/Bcl-2 ratio. In conclusion, this study demonstrates that ethyl pyruvate induces apoptosis and cell-cycle arrest in G phase in hepatocellular carcinoma cells, plays a critical role in the treatment of cancer.

OBJECTIVE

We have recently shown that ghrelin, a novel orexigenic hormone, is reduced in sepsis. Ghrelin treatment, mediated through ghrelin receptors in the brain, attenuates sepsis-induced inflammation and mortality. Gut barrier dysfunction is common in sepsis. High-mobility group B1 (HMGB1) increases gut permeability both in vitro and in vivo. However, it remains unknown whether ghrelin has any effects on HMGB1 and gut barrier function in sepsis. We hypothesized that ghrelin decreases HMGB1 release and attenuates sepsis-induced gut barrier dysfunction through central ghrelin receptors.

METHODS

Prospective, controlled, and randomized animal study.

METHODS

A research institute laboratory.

METHODS

Male adult Sprague-Dawley rats (275-325 g).

METHODS

Cecal ligation and puncture (CLP) followed by injection/infusion of ghrelin.

RESULTS

Five hours after CLP, a bolus intravenous injection of 2 nmol of ghrelin was followed by a continuous infusion of 12 nmol of ghrelin via an osmotic mini-pump for 15 hrs. Twenty hours after CLP, brain ghrelin levels, serum HMGB1 levels, ileal mucosal permeability to fluorescein isothiocyanate dextran, bacterial counts in the mesenteric lymph nodes complex, and gut water content were determined. In additional groups of animals, bilateral trunk vagotomy was performed at 5 hrs after CLP before ghrelin injection. Furthermore, to confirm the role of central ghrelin receptors in ghrelin's effect, ghrelin (1 nmol) was administered through intracerebroventricular injection at 5 hrs after CLP. Our results showed that brain levels of ghrelin decreased by 34% at 20 hrs after CLP. Intravenous administration of ghrelin completely restored brain levels of ghrelin, significantly reduced the elevated HMGB1 levels, and attenuated gut barrier dysfunction. Vagotomy eliminated ghrelin's inhibition of HMGB1 and attenuation of gut barrier dysfunction. Intracerebroventricular injection of ghrelin decreased serum HMGB1 levels and ameliorated gut barrier dysfunction.

CONCLUSIONS

Ghrelin reduces serum HMGB1 levels and ameliorates gut barrier dysfunction in sepsis by vagus nerve activation via central ghrelin receptors. Ghrelin can be further developed as a novel agent to protect gut barrier function in sepsis.

BACKGROUND

Inflammasome-activated IL-1β plays a major role in lung neutrophilic inflammation induced by inhaled silica. However, the exact mechanisms that contribute to the initial production of precursor IL-1β (pro-IL-1β) are still unclear. Here, we assessed the implication of alarmins (IL-1α, IL-33 and HMGB1) in the lung response to silica particles and found that IL-1α is a master cytokine that regulates IL-1β expression.

METHODS

Pro- and mature IL-1β as well as alarmins were assessed by ELISA, Western Blot or qRT-PCR in macrophage cultures and in mouse lung following nano- and micrometric silica exposure. Implication of these immune mediators in the establishment of lung inflammatory responses to silica was investigated in knock-out mice or after antibody blockade by evaluating pulmonary neutrophil counts, CXCR2 expression and degree of histological injury.

RESULTS

We found that the early release of IL-1α and IL-33, but not HMGB1 in alveolar space preceded the lung expression of pro-IL-1β and neutrophilic inflammation in silica-treated mice. In vitro, the production of pro-IL-1β by alveolar macrophages was significantly induced by recombinant IL-1α but not by IL-33. Neutralization or deletion of IL-1α reduced IL-1β production and neutrophil accumulation after silica in mice. Finally, IL-1α released by J774 macrophages after in vitro exposure to a range of micro- and nanoparticles of silica was correlated with the degree of lung inflammation induced in vivo by these particles.

CONCLUSIONS

We demonstrated that in response to silica exposure, IL-1α is rapidly released from pre-existing stocks in alveolar macrophages and promotes subsequent lung inflammation through the stimulation of IL-1β production. Moreover, we demonstrated that in vitro IL-1α release from macrophages can be used to predict the acute inflammogenic activity of silica micro- and nanoparticles.

In search of the etiology and pathophysiology for autoimmune and chronic inflammatory diseases, many molecules have been identified as endogenous damage-associated molecules with proinflammatory cytokine functions that may be responsible for the sterile inflammation leading to tissue injuries observed in these disorders. HSPs and HMGB1 are intracellular molecular chaperones for peptides and DNAs, respectively. They are released extracellularly upon cellular injury or activation. In vitro studies revealed that HSPs and HMGB1 were capable of inducing the release of proinflammatory cytokines by monocytes and macrophages and the activation and maturation of DCs. These cytokine effects were reported to be mediated by TLR2 and TLR4 signal transduction pathways. Thus, they were called endogenous ligands of TLR2 and TLR4 and might serve as danger signals, alarmins, or damage-associated molecules to the host immune system. It has been suggested that HSPs provide a link between innate and adaptive immune systems, and HMGB1 functions at the cross-road between innate and adaptive immunity. However, recent evidence suggests that highly purified HSPs and HMGB1, although retaining their biological activities, do not have cytokine effects. Thus, HSPs and HMGB1 do not meet the definition of endogenous ligands of TLRs, danger signals, alarmins, or damage-associated molecules. In contrast, HSPs and HMGB1 are found to bind a number of pathogen-associated molecules, such as LPS and bacterial lipopeptides, and enhance the cytokine effects of these molecules. The significance of these cytokine-enhancing effects of HSPs and HMGB1 needs further investigation.

The superficial zone (SZ) of articular cartilage is critical in maintaining tissue function and homeostasis and represents the site of the earliest changes in osteoarthritis. Mechanisms that regulate the unique phenotype of SZ chondrocytes and maintain SZ integrity are unknown. We recently demonstrated that expression of the chromatin protein high mobility group box (HMGB) protein 2 is restricted to the SZ in articular cartilage suggesting a transcriptional regulation involving HMGB2 in SZ. Here, we show that an interaction between HMGB2 and the Wnt/beta-catenin pathway regulates the maintenance of the SZ. We found that the Wnt/beta-catenin pathway is active specifically in the SZ in normal mouse knee joints and colocalizes with HMGB2. Both Wnt signaling and HMGB2 expression decrease with aging in mouse joints. Our molecular studies show that HMGB2 enhances the binding of Lef-1 to its target sequence and potentiates transcriptional activation of the Lef-1-beta-catenin complex. The HMG domain within HMGB2 is crucial for interaction with Lef-1, suggesting that both HMGB2 and HMGB1 may be involved in this function. Furthermore, conditional deletion of beta-catenin in cultured mouse chondrocytes induced apoptosis. These findings define a pathway where protein interactions of HMGB2 and Lef-1 enhance Wnt signaling and promote SZ chondrocyte survival. Loss of the HMGB2-Wnt signaling interaction is a new mechanism in aging-related cartilage pathology.

Up to date many genes are known to be deregulated in tumor development and progression. Genes important in tumorigenesis belong to families such as proteases, kinases and receptors. However, an important family of proteins is rarely discussed: the mediators of transcriptional control, the transcription factors. Usually, changes in transcription factor expression or activity can lead to more than just one downstream modification, as transcription factors are higher, thinking in a hierarchical way of expression control. In this review we summarize the role of the transcription factors AP-1, AP-2alpha, CREB, CtBP, ETS-1, HMGB1, LEF/TCF/beta-catenin, MITF, NFkappaB, PAX3, SKI, Snail and STAT in carcinogenesis focusing on melanoma development and progression.

High mobility group (HMG) proteins are nuclear proteins believed to significantly affect DNA interactions by altering nucleic acid flexibility. Group B (HMGB) proteins contain HMG box domains known to bind to the DNA minor groove without sequence specificity, slightly intercalating base pairs and inducing a strong bend in the DNA helical axis. A dual-beam optical tweezers system is used to extend double-stranded DNA (dsDNA) in the absence as well as presence of a single box derivative of human HMGB2 [HMGB2(box A)] and a double box derivative of rat HMGB1 [HMGB1(box A+box B)]. The single box domain is observed to reduce the persistence length of the double helix, generating sharp DNA bends with an average bending angle of 99+/-9 degrees and, at very high concentrations, stabilizing dsDNA against denaturation. The double box protein contains two consecutive HMG box domains joined by a flexible tether. This protein also reduces the DNA persistence length, induces an average bending angle of 77+/-7 degrees , and stabilizes dsDNA at significantly lower concentrations. These results suggest that single and double box proteins increase DNA flexibility and stability, albeit both effects are achieved at much lower protein concentrations for the double box. In addition, at low concentrations, the single box protein can alter DNA flexibility without stabilizing dsDNA, whereas stabilization at higher concentrations is likely achieved through a cooperative binding mode.