HMG-1 as a late mediator of endotoxin lethality in mice

Apoptotic cells, autoantibodies, and the role of HMGB1 in the subcellular localization of an autoantigen

A current model for the evolution of systemic lupus erythematosus hypothesizes that there is a genetic predisposition coupled with an environmental or infectious trigger. This study investigated whether apoptotic cells given with a proinflammatory signal could induce features of lupus. Balb/c mice were injected with an apoptotic Balb/c-derived myeloid cell line, J774.1, either with or without the DNA-binding protein HMGB1 for five injections over 16 days in an IACUC approved study. Mice were sacrificed at 6 weeks and 12 weeks after treatment. Renal disease was assessed by immunofluorescence and autoantibodies were defined by ELISA. Western blotting was performed to characterize autoantigens. Mice injected with apoptotic cells developed antibodies to histones, SSA, ssDNA, and phospholipids. Antibodies to SSA and ssDNA persisted; however, antibodies to histones, and phospholipid declined at 12 weeks. IgG deposits in the kidney were detected at 6 weeks and persisted through 12 weeks primarily in animals that received both apoptotic cells and HMGB1. Autoantibodies in mice were diverse but the mice that received apoptotic cells developed particularly high titer antibodies to an unknown 78kDa protein. This protein became externalized on the surface of J774.1 cells in the presence of HMGB1. Mice that received apoptotic J774.1 cells with HMGB1 developed more extensive renal IgG deposition. While the mechanism is uncertain, an important effect of HMGB1 was to alter the subcellular distribution of a major autoantigen, making the autoantigen accessible for immune responses. This is the first description of an inflammatory stimulus altering the immunologic availability of a potential autoantigen.

Ethyl pyruvate ameliorates ileus induced by bowel manipulation in mice

BACKGROUND

Ethyl pyruvate (EP) improves survival, decreases proinflammatory cytokine expression, and ameliorates organ dysfunction in mice who have lethal sepsis or were subjected to hemorrhagic shock. Herein, we tested the hypothesis that treatment with EP can prevent the development of ileus after bowel manipulation, a phenomenon that is mediated by an inflammatory response in the bowel wall.

METHODS

C57Bl/6 mice underwent operative manipulation of the small intestine or were subjected to a sham procedure. Some of the mice subjected to gut manipulation were pre- and post-treated with 4 doses of EP (40 or 80 mg/kg per dose), whereas others received similar volumes of the vehicle for EP. Gastrointestinal transit of a nonabsorbable marker was assessed by gavaging the mice with the tracer 24 hours after operation and assessing its concentration 90 minutes later in bowel contents from the stomach, 10 equally long segments of small intestine, the cecum, and 2 equally long segments of colon. The contractile responses of ileal circular smooth muscle to graded concentrations of bethanechol were assessed by using standard organ bath methodology. Expression of interleukin-6 and inducible nitric oxide synthase transcripts in ileal muscularis propria was assessed by using the semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

In sham-operated controls, the mean (+/- SE) geometric center for the transit marker was 10.0 +/- 0.5, whereas for vehicle-treated mice subject to bowel manipulation, the value for this parameter was 3.5 +/- 0.1 (P < .05). When mice subjected to bowel manipulation were treated with several 40 mg/kg doses of EP, the geometric center was 7.3 +/- 1.0 (P < .05 vs sham-operated group). Gut manipulation impaired intestinal smooth muscle contractility in vitro and increased steady-state levels of interleukin-6 and inducible nitric oxide synthase messenger RNA. Treatment with EP ameliorated these effects of gut manipulation.

CONCLUSIONS

EP warrants further evaluation as a therapeutic agent to ameliorate postoperative ileus.

Genes involved in invasion and metastasis of gastric cancer identified by array-based hybridization and serial analysis of gene expression

Gastric cancer (GC) is still a serious health problem and remains the second most common type of fatal cancer worldwide. Comprehensive gene expression analyses may be useful to identify genes associated with invasion/metastasis in GC. Among them, array-based hybridization and serial analysis of gene expression (SAGE) are currently the most common approaches. Over the past 3 years, several large-scale gene expression studies with array-based hybridization and SAGE have been performed and several genes have been identified. This review describes genes associated with invasion/metastasis in GC which have been identified by array-based hybridization and SAGE. We compared the expression levels of the genes identified by array-based hybridization with our SAGE data. In addition, expression of the candidate genes obtained by SAGE was further investigated by quantitative RT-PCR of 40 GC samples. MIA and GW112 were overexpressed in 10 (25%) and 22 (55%) of 40 GC samples, and the overexpression of these two genes was associated with tumor stage, respectively. We also discuss the significance of HMGB1/amphoterin in invasion and metastasis of GC.

More tea for septic patients?--Green tea may reduce endotoxin-induced release of high mobility group box 1 and other pro-inflammatory cytokines

Despite recent advances in antibiotic therapy and intensive care, sepsis remains widespread problems in critically ill patients. The high mortality of sepsis is in part mediated by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (e.g., TNF, IL-1, and IFN-gamma) and late (e.g., HMGB1) pro-inflammatory cytokines. In light of our recent discovery of HMGB1 as a late mediator of lethal systemic inflammation, and the observation that green tea (Camellia sinensis) dose-dependently attenuated bacterial endotoxin-induced HMGB1 release, we propose that regular tea intake might decrease the incidence of and mortality rates from lethal endotoxemia and sepsis.

High mobility group box 1 protein interacts with multiple Toll-like receptors

High mobility group box 1 (HMGB1), originally described as a DNA-binding protein, can also be released extracellularly and functions as a late mediator of inflammatory responses. Although recent reports have indicated that the receptor for advanced glycation end products (RAGE) as well as Toll-like receptor (TLR)2 and TLR4 are involved in cellular activation by HMGB1, there has been little evidence of direct association between HMGB1 and these receptors. To examine this issue, we used fluorescence resonance energy transfer (FRET) and immunoprecipitation to directly investigate cell surface interactions of HMGB1 with TLR2, TLR4, and RAGE. FRET images in RAW264.7 macrophages demonstrated association of HMGB1 with TLR2 and TLR4 but not RAGE. Transient transfections into human embryonic kidney-293 cells showed that HMGB1 induced cellular activation and NF-kappaB-dependent transcription through TLR2 or TLR4 but not RAGE. Coimmunoprecipitation also found interaction between HMGB1 and TLR2 as well as TLR4, but not with RAGE. These studies provide the first direct evidence that HMGB1 can interact with both TLR2 and TLR4 and also supply an explanation for the ability of HMGB1 to induce cellular activation and generate inflammatory responses that are similar to those initiated by LPS.

ISO-1 Binding to the Tautomerase Active Site of MIF Inhibits Its Pro-inflammatory Activity and Increases Survival in Severe Sepsis

MIF is a proinflammatory cytokine that has been implicated in the pathogenesis of sepsis, arthritis, and other inflammatory diseases. Antibodies against MIF are effective in experimental models of inflammation, and there is interest in strategies to inhibit its deleterious cytokine activities. Here we identify a mechanism of inhibiting MIF pro-inflammatory activities by targeting MIF tautomerase activity. We designed small molecules to inhibit this tautomerase activity; a lead molecule, "ISO-1 ((S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester)," significantly inhibits the cytokine activity in vitro. Moreover, ISO-1 inhibits tumor necrosis factor release from macrophages isolated from LPStreated wild type mice but has no effect on cytokine release from MIFdeficient macrophages. The therapeutic importance of the MIF inhibition by ISO-1 is demonstrated by the significant protection from sepsis, induced by cecal ligation and puncture in a clinically relevant time frame. These results identify ISO-1 as the first small molecule inhibitor of MIF proinflammatory activities with therapeutic implications and indicate the potential of the MIF active site as a novel target for therapeutic interventions in human sepsis.

Heat shock response inhibits release of high mobility group box 1 protein induced by endotoxin in murine macrophages

The purpose of this study was to evaluate the kinetic changes and the localization of high-mobility group box 1 protein (HMGB1) and to observe the effect of heat shock response (HSR) on the expression and release of HMGB1 in lipopolysaccharide (LPS)-activated murine macrophage-like RAW 264.7 cells. Reverse transcriptase (RT)-PCR and Western blot were used to examine HMGB1 expression after LPS treatment. The intracellular localization of HMGB1 in normal or LPS-activated cells was investigated by immunocytochemical analysis and HMGB1 released from cultured macrophages by Western blot. HSR was performed by incubating RAW 264.7 cells at 42.5 degrees C for 1 h then recovery at 37 degrees C for 12 h. The effect of HSR on expression and release of HMGB1 was observed. The results showed that a decrease of HMGB1 mRNA expression was observed at 18 h after LPS (500 ng/mL) treatment, although the total intracellular HMGB1 protein levels were not affected. A visible translocation of HMGB1 from the nuclear to the cytoplasm was observed at 20 h after stimulation with LPS (500 ng/mL). Furthermore, HMGB1 was released into the medium by LPS-activated RAW 264.7 cells in a time- and dose-dependent manner. Heat shock pretreatment significantly inhibited LPS-induced release of HMGB1 and the translocation of HMGB1 from the nucleus to the cytoplasm in RAW 264.7 cells. These findings suggest that the release of HMGB1 by LPS-activated macrophages is a late event in the pathogenesis of sepsis and that HSR could inhibit the release and translocation of HMGB1 induced by LPS.

High-mobility group box 1 protein is an inflammatory mediator in necrotizing enterocolitis: protective effect of the macrophage deactivator semapimod

High-mobility group box 1 (HMGB1) is a late mediator of endotoxemia known to stimulate the production of proinflammatory cytokines that are putative mediators of intestinal inflammation associated with necrotizing enterocolitis (NEC). We hypothesized that HMGB1 is also involved in the pathogenesis of NEC. We examined the expression of HMGB1 and the effect of the novel drug semapimod on intestinal inflammation in an experimental model of NEC in neonatal rats. Newborn rats were subjected to hypoxia and fed a conventional formula by gavage (FFH) or were breast fed (BF). Rats were killed on day 4, and the distal ileum was harvested for morphological studies and Western blot analysis. FFH newborn rats but not BF controls developed intestinal inflammation similar to the histological changes observed in human NEC. We found that the expression of HMGB1 and its receptor for advanced glycation end products (RAGE) as well as that of other apoptosis/inflammation-related proteins (Bad, Bax, inducible nitric oxide synthase, and cyclooxygenase 2) was upregulated in the ileal mucosa of FFH newborn rats compared with BF animals. Administration of the drug semapimod inhibited the upregulation of those proteins and partially protected the animals against the FFH-induced intestinal injury. Elevated levels of HMGB1 were also found in ileal samples from infants undergoing intestinal resection for acute NEC. Our results implicate HMGB1 and RAGE as important mediators of enterocyte cell death and hypoxia-induced injury in NEC and support the hypothesis that inhibitors such as semapimod might play a therapeutic role in chronic intestinal inflammation characterized by this animal model.

Recombinant derivatives of the human high-mobility group protein HMGB2 mediate efficient nonviral gene delivery

Certain natural peptides and proteins of mammalian origin are able to bind and condense plasmid DNA, a prerequisite for the formation of transfection-competent complexes that facilitate nonviral gene delivery. Here we have generated recombinant derivatives of the human high-mobility group (HMG) protein HMGB2 and investigated their potential as novel protein-based transfection reagents. A truncated form of HMGB2 encompassing amino acids 1-186 of the molecule was expressed in Escherichia coli at high yield. This HMGB2186 protein purified from bacterial lysates was able to condense plasmid DNA in a concentration-dependent manner, and mediated gene delivery into different established tumor cell lines more efficiently than poly(l-lysine). By attaching, via gene fusion, additional functional domains such as the HIV-1 TAT protein transduction domain (TAT(PTD)-HMGB2186), the nuclear localization sequence of the simian virus 40 (SV40) large T-antigen (SV40(NLS)-HMGB2186), or the importin-beta-binding domain (IBB) of human importin-alpha (IBB-HMGB2186), chimeric fusion proteins were produced which displayed markedly improved transfection efficiency. Addition of chloroquine strongly enhanced gene transfer by all four HMGB2186 derivatives studied, indicating cellular uptake of protein-DNA complexes via endocytosis. The IBB-HMGB2186 molecule in the presence of the endosomolytic reagent was the most effective. Our results show that recombinant derivatives of human HMGB2 facilitate efficient nonviral gene delivery and may become useful reagents for applications in gene therapy.

DAP12 (KARAP) amplifies inflammation and increases mortality from endotoxemia and septic peritonitis

DAP12 (KARAP) is a transmembrane signaling adaptor for a family of innate immunoreceptors that have been shown to activate granulocytes and monocytes/macrophages, amplifying production of inflammatory cytokines. Contrasting with these data, recent studies suggest that DAP12 signaling has an inhibitory role in the macrophage response to microbial products (Hamerman, J.A., N.K. Tchao, C.A. Lowell, and L.L. Lanier. 2005. Nat. Immunol. 6:579–586). To determine the in vivo role for DAP12 signaling in inflammation, we measured the response of wild-type (WT) and DAP12^−/− mice to septic shock. We show that DAP12^−/− mice have improved survival from both endotoxemia and cecal ligation and puncture–induced septic shock. As compared with WT mice, DAP12^−/− mice have decreased plasma cytokine levels and a decreased acute phase response during sepsis, but no defect in the recruitment of cells or bacterial control. In cells isolated after sepsis and stimulated ex vivo, DAP12 signaling augments lipopolysaccharide-mediated cytokine production. These data demonstrate that, during sepsis, DAP12 signaling augments the response to microbial products, amplifying inflammation and contributing to mortality.

Determinants of specific binding of HMGB1 protein to hemicatenated DNA loops

Protein HMGB1 has long been known as one of the most abundant non-histone proteins in the nucleus of mammalian cells, and has regained interest recently for its function as an extracellular cytokine. As a DNA-binding protein, HMGB1 facilitates DNA-protein interactions by increasing the flexibility of the double helix, and binds specifically to distorted DNA structures. We have previously observed that HMGB1 binds with extremely high affinity to a novel DNA structure, hemicatenated DNA loops (hcDNA), in which double-stranded DNA fragments containing a tract of poly(CA).poly(TG) form a loop maintained at its base by a hemicatenane. Here, we show that the single HMGB1 domains A and B, the HMG-box domain of sex determination factor SRY, as well as the prokaryotic HMGB1-like protein HU, specifically interact with hcDNA (Kd approximately 0.5 nM). However, the affinity of full-length HMGB1 for hcDNA is three orders of magnitude higher (Kd<0.5 pM) and requires the simultaneous presence of both HMG-box domains A and B plus the acidic C-terminal tail on the molecule. Interestingly, the high affinity of the full-length protein for hcDNA does not decrease in the presence of magnesium. Experiments including a comparison of HMGB1 binding to hcDNA and to minicircles containing the CA/TG sequence, binding studies with HMGB1 mutated at intercalating amino acid residues (involved in recognition of distorted DNA structures), and exonuclease III footprinting, strongly suggest that the hemicatenane, not the DNA loop, is the main determinant of the affinity of HMGB1 for hcDNA. Experiments with supercoiled CA/TG-minicircles did not reveal any involvement of left-handed Z-DNA in HMGB1 binding. Our results point to a tight structural fit between HMGB1 and DNA hemicatenanes under physiological conditions, and suggest that one of the nuclear functions of HMGB1 could be linked to the possible presence of hemicatenanes in the cell.

HMGB1: guiding immunity from within

Two of the main challenges that eukaryotic multicellular organisms faced during evolution were to eliminate and replace dying cells and to cope with invading microorganisms. The innate immune system evolved to handle both tasks: to scavenge cellular debris and to form the first line of defence against microbes. In this review, we focus on high mobility group box 1 (HMGB1) protein as a common signal that alerts the innate immune system to excessive or deregulated cell death and to microbial invasion. HMGB1, which is well known nuclear protein, has revealed unexpected facets as an extracellular mediator. The role of HMGB1 as an endogenous molecule that facilitates immune responses and has an important role in tissue homeostasis and disease will be highlighted here.

Exogenous high-mobility group box 1 protein induces myocardial regeneration after infarction via enhanced cardiac C-kit+ cell proliferation and differentiation

High-mobility group box 1 protein (HMGB1) is a chromatin protein that is released by inflammatory and necrotic cells. Extracellular HMGB1 signals tissue damage, stimulates the secretion of proinflammatory cytokines and chemokines, and modulates stem cell function. The present study examined exogenous HMGB1 effect on mouse left-ventricular function and myocyte regeneration after infarction. Myocardial infarction was induced in C57BL/6 mice by permanent coronary artery ligation. After 4 hours animals were reoperated and 200 ng of purified HMGB1 was administered in the peri-infarcted left ventricle. This intervention resulted in the formation of new myocytes within the infarcted portion of the wall. The regenerative process involved the proliferation and differentiation of endogenous cardiac c-kit+ progenitor cells. Circulating c-kit+ cells did not significantly contribute to HMGB1-mediated cardiac regeneration. Echocardiographic and hemodynamic parameters at 1, 2, and 4 weeks demonstrated a significant recovery of cardiac performance in HMGB1-treated mice. These effects were not observed in infarcted hearts treated either with the unrelated protein glutathione S-transferase or a truncated form of HMGB1. Thus, HMGB1 appears to be a potent inducer of myocardial regeneration following myocardial infarction.

Essential role of STAT1 in caspase-independent cell death of activated macrophages through the p38 mitogen-activated protein kinase/STAT1/reactive oxygen species pathway

Unlike other immune cells, activation of macrophages by stimulating agents, such as lipopolysaccharide (LPS), confers significant resistance to many apoptotic stimuli, but the underlying mechanism of this phenomenon remains largely unknown. Here, we demonstrate that LPS-induced early caspase activation is essential for macrophage survival because blocking caspase activation with a pancaspase inhibitor (zVAD [benzyloxycarbonyl-Val-Ala-Asp]) rapidly induced death of activated macrophages. This type of death process by zVAD/LPS was principally mediated by intracellular generation of superoxide. STAT1 knockout macrophages demonstrated profoundly decreased superoxide production and were resistant to treatment with zVAD/LPS, indicating the crucial involvement of STAT1 in macrophage death by zVAD/LPS. STAT1 level and activity were reciprocally regulated by caspase activation and were associated with cell death. Activation of STAT1 was critically dependent upon serine phosphorylation induced by p38 mitogen-activated protein kinase (MAPK) because a p38 MAPK inhibitor nullified STAT1 serine phosphorylation, reactive oxygen species (ROS) production, and macrophage death by zVAD/LPS. Conversely, p38 MAPK activation was dependent upon superoxide and was also nullified in STAT1 knockout macrophages, probably due to impaired generation of superoxide. Our findings collectively indicate that STAT1 signaling modulates intracellular oxidative stress in activated macrophages through a positive-feedback mechanism involving the p38 MAPK/STAT1/ROS pathway, which is interrupted by caspase activation. Furthermore, our study may provide significant insights in regards to the unanticipated critical role of STAT1 in the caspase-independent death pathway.

Requirement of HMGB1 and RAGE for the maturation of human plasmacytoid dendritic cells

Dendritic cells (DC) are key components of innate and adaptive immune responses. Plasmacytoid DC (PDC) are a specialized DC subset that produce high amounts of type I interferons in response to microbes. High mobility group box 1 protein (HMGB1) is an abundant nuclear protein, which acts as a potent pro-inflammatory factor when released extracellularly. We show that HMGB1 leaves the nucleus of maturing PDC following TLR9 activation, and that PDC express on the plasma membrane the best-characterized receptor for HMGB1, RAGE. Maturation and type I IFN secretion of PDC is hindered when the HMGB1/RAGE pathway is disrupted. These results reveal HMGB1 and RAGE as the first known autocrine loop modulating the maturation of PDC, and suggest that antagonists of HMGB1/RAGE might have therapeutic potential for the treatment of systemic human diseases.

The multiple organ dysfunction syndrome and late-phase mortality in sepsis

Sepsis is a devastating and common syndrome characterized by systemic inflammation. Sepsis accounts for considerable morbidity and mortality among intensive care unit patients. Although the inflammatory response generated by the immune system represents the body's attempt to clear invading pathogens, it is the failure to modulate this response that leads to dysregulated inflammation and the injury of healthy tissue. A great deal of research has characterized many of the early events and mediators that lead to systemic inflammation and sepsis. However, substantially less is known about the pathogenesis of the late phase of sepsis, which accounts for the vast majority of sepsis-related mortality (ie, the dysfunction and subsequent failure of the major parenchymal organs).

Pathophysiology of Mifepristone-Induced Septic Shock Due toClostridium sordellii

OBJECTIVE:

To explain the role of mifepristone in medical abortions that results in fulminant and lethal septic shock due to Clostridium sordellii.

DATA SOURCES:

MEDLINE, PubMed, and Google Scholar databases were searched (1984–March 2005%). Key search terms were mifepristone, RU38486, RU486, Mifeprex, medical abortion, septic shock, innate immune system, cytokines, and Clostridium sordellii.

STUDY SELECTION AND DATA EXTRACTION:

All articles identified from the data sources were evaluated and all information deemed relevant was included for the information related to the development of the understanding of the pathophysiology of mifepristone-induced septic shock due to C. sordellii.

DATA SYNTHESIS:

The mechanisms of action of mifepristone were incorporated into the pathophysiology of septic shock due to C. sordellii. Mifepristone, by blocking both progesterone and glucocorticoid receptors, interferes with the controlled release and functioning of cortisol and cytokines. Failure of physiologically controlled cortisol and cytokine responses results in an impaired innate immune system that results in disintegration of the body's defense system necessary to prevent the endometrial spread of C. sordellii infection. The abnormal cortisol and cytokine responses due to mifepristone coupled to the release of potent exotoxins and an endotoxin from C. sordellii are the major contributors to the rapid development of lethal septic shock.

CONCLUSIONS:

Theoretically, it appears that the mechanisms of mifepristone action favor the development of infection that leads to septic shock and intensifies the actions of multiple inflammatory cytokines, resulting in fulminant, lethal septic shock.

Release of high mobility group box 1 by dendritic cells controls T cell activation via the receptor for advanced glycation end products

High mobility group box 1 (HMGB1) is an abundant and conserved nuclear protein that is released by necrotic cells and acts in the extracellular environment as a primary proinflammatory signal. In this study we show that human dendritic cells, which are specialized in Ag presentation to T cells, actively release their own HMGB1 into the extracellular milieu upon activation. This secreted HMGB1 is necessary for the up-regulation of CD80, CD83, and CD86 surface markers of human dendritic cells and for IL-12 production. The HMGB1 secreted by dendritic cells is also required for the clonal expansion, survival, and functional polarization of naive T cells. Using neutralizing Abs and receptor for advanced glycation end product-deficient (RAGE(-/-)) cells, we demonstrate that RAGE is required for the effect of HMGB1 on dendritic cells. HMGB1/RAGE interaction results in downstream activation of MAPKs and NF-kappaB. The use of an ancient signal of necrosis, HMGB1, by dendritic cells to sustain their own maturation and for activation of T lymphocytes represents a profitable evolutionary mechanism.

Understanding RAGE, the receptor for advanced glycation end products

Advanced glycation end products (AGEs), S100/calgranulins, HMGB1-proteins, amyloid-beta peptides, and the family of beta-sheet fibrils have been shown to contribute to a number of chronic diseases such as diabetes, amyloidoses, inflammatory conditions, and tumors by promoting cellular dysfunction via binding to cellular surface receptors. The receptor for AGEs (RAGE) is a multiligand receptor of the immunoglobulin superfamily of cell surface molecules acting as counter-receptor for these diverse molecules. Engagement of RAGE converts a brief pulse of cellular activation to sustained cellular dysfunction and tissue destruction. The involvement of RAGE in pathophysiologic processes has been demonstrated in murine models of chronic disease using either a receptor decoy such as soluble RAGE (sRAGE), RAGE neutralizing antibodies, or a dominant-negative form of the receptor. Studies with RAGE-/- mice confirmed that RAGE contributes, at least in part, to the development of late diabetic complications, such as neuropathy and nephropathy, macrovascular disease, and chronic inflammation. Furthermore, deletion of RAGE provided protection from the lethal effects of septic shock caused by cecal ligation and puncture (CLP). In contrast, deletion of RAGE had no effect on the host response in delayed-type hypersensitivity (DTH). Despite the lack of effect seen in adaptive immunity by the deletion of RAGE, administration of the receptor decoy, sRAGE, still afforded a protective effect in RAGE-/- mice. Thus, sRAGE is likely to sequester ligands, thereby preventing their interaction with other receptors in addition to RAGE. These data suggest that, just as RAGE is a multiligand receptor, its ligands are also likely to recognize several receptors in mediating their biologic effects.

Addicted to death: invasive cancer and the immune response to unscheduled cell death

The development of an invasive cancer involves a progressive switch from predominantly apoptotic (scheduled) to necrotic (unscheduled) tumor cell death. This switch is associated with chronic and increasing release of intracellular factors that in turn promote reactive angiogenesis and stromal proliferation and mediates the disordered tumor microenvironment associated with local immune suppression. The authors review the relevant immunobiology of these factors, including the nuclear protein HMGB1; the products of purine metabolism (uric acid, ATP, and adenosine); the S100 family members; and the heat shock proteins, which we believe drive futile cycles of cell death followed by reparative cell growth. The authors also present a novel and provocative hypothesis that suggests that most of the derangements that we associate with progression of cancer and the associated immunologic consequences can indeed be ascribed to the consequences of disordered tumor cell death rather than cell growth. Thus the fundamental defect in invasive human cancers, in the authors' view, is not one of cell growth but rather one of disordered cell death, resulting in turn in a tumor microenvironment that encourages tumor growth, progression, and local immunosuppression, a condition the authors have termed "addicted to death." This new understanding could inform and drive the development of more effective biologic therapies for patients with cancer.

The effects of CpG DNA on HMGB1 release by murine macrophage cell lines

DNA containing cytosine-guanine dinucleotide (CpG) motifs (CpG DNA) has potent immunostimulatory activities that resemble those of lipopolysaccharide (LPS) in its effects on the innate immune system. Among its activities, LPS can induce the release of high mobility group protein (HMGB1) by macrophages, a dual function molecule that can mediate the late effects of LPS. To determine whether CpG DNA can also induce HMGB1 release, the effects of a synthetic CpG oligonucleotide (ODN) on HMGB1 release from RAW 264.7 and J774A.1 cells were assessed by Western blotting of culture supernatants. Under conditions in which the CpG ODN activated the cell lines, as assessed by stimulation of tumor necrosis factor alpha and interleukin-12, it failed to cause HMGB1 release into the media. Although unable to induce HMGB1 release by itself, the CpG ODN nevertheless potentiated the action of LPS. With RAW 264.7 cells, lipoteichoic acid and polyinosinic-polycytidylic acid, like LPS, stimulated HMGB1 release as well as cytokine production. These results indicate that the effects of CpG DNA on macrophages differ from other ligands of Toll-like receptors and may lead to a distinct pattern of immune cell activation in the context of infection or its use as an immunomodulatory agent.

The vagus nerve and the nicotinic anti-inflammatory pathway

Physiological anti-inflammatory mechanisms are selected by evolution to effectively control the immune system and can be exploited for the treatment of inflammatory disorders. Recent studies indicate that the vagus nerve (which is the longest of the cranial nerves and innervates most of the peripheral organs) can modulate the immune response and control inflammation through a 'nicotinic anti-inflammatory pathway' dependent on the alpha7-nicotinic acetylcholine receptor (alpha7nAChR). Nicotine has been used in clinical trials for the treatment of ulcerative colitis, but its clinical applications are limited by its unspecific effects and subsequent toxicity. This article reviews recent advances supporting the therapeutic potential of selective nicotinic agonists in several diseases. Similar to the development of alpha- and beta-agonists for adrenoceptors, selective agonists for alpha7nAChR could represent a promising pharmacological strategy against infectious and inflammatory diseases.

Effect of hemoperfusion using polymyxin B-immobilized fiber on IL-6, HMGB-1, and IFN gamma in a neonatal sepsis model

To evaluate effects of polymyxin B direct hemoperfusion (PMX-DHP) on a neonatal sepsis cecal ligation and perforation (CLP) model, in 24 anesthetized and mechanically ventilated 3-d-old piglets, 16 were assigned to CLP and an arteriovenous extracorporeal circuit from 3 h until 6 h post-CLP, with a PMX-column in PMX-DHP-treated group (8 piglets) and 8 as sham. Plasma lipopolysaccharide (LPS) was measured at before CLP and at 3 and 9 h. Changes in mean systemic blood pressure (mSBP), mean pulmonary blood pressure, serum IL-6, tumor necrosis factor alpha, interferon gamma, and highly mobile group-1 box protein were measured before CLP and at 1, 3, 6, and 9 h. LPS was lower in the sham and PMX-DHP groups than in the control at 9 h. The mSBP was higher in the sham and PMX-DHP groups than in the control at both 6 h. IL-6 was lower in the sham and PMX-DHP groups than in the control at 6 h. HMGB-1 was lower in the PMX-DHP group than in the control at 6 h. IFN-gamma was only detected in the control group at 9 h. Survival times in the PMX-DHP group were longer than in the control. Thus, PMX-DHP improved septic shock in a neonatal septic model.

Therapeutic intervention and targets for sepsis

Sepsis syndrome, a systemic response to infection, can beget devastating outcomes even in previously normal individuals. Recent research in septic patients has led to the discovery that early goal-directed resuscitation guided by continuous monitoring of mixed venous hemoglobin saturation, along with moderate doses of corticosteroids, can reduce mortality. An improved understanding of the complex interaction between the inflammatory and coagulant systems in sepsis pathophysiology has resulted in novel treatments, such as recombinant human activated protein C, which improves survival in patients with severe sepsis and a high risk of death. However, despite an increased understanding of the complex pathophysiology of this syndrome and the discovery of new, effective treatments, severe sepsis still results in significant morbidity and mortality. Consequently, investigations continue into additional therapeutic agents directed against novel targets. Following a review of recent advances in sepsis treatment, we briefly discuss a few of the new, promising therapeutic strategies currently being investigated.

NK/iDC interaction results in IL-18 secretion by DCs at the synaptic cleft followed by NK cell activation and release of the DC maturation factor HMGB1

Interaction of natural killer (NK) cells with autologous immature dendritic cells (DCs) results in reciprocal activation; however, the underlying mechanisms are so far elusive. We show here that NK cells trigger immature DCs to polarize and secrete interleukin 18 (IL-18), a cytokine lacking a secretory leader sequence. This occurs through a Ca2+-dependent and tubulin-mediated recruitment of IL-18-containing secretory lysosomes toward the adhering NK cell. Lysosome exocytosis and IL-18 secretion are restricted at the synaptic cleft, thus allowing activation of the interacting NK cells without spreading of the cytokine. In turn, DC-activated NK cells secrete the proinflammatory cytokine high mobility group B1 (HMGB1), which induces DC maturation and protects DCs from lysis. Also HMGB1 is a leaderless cytokine that undergoes regulated secretion. Differently from IL-18, soluble HMGB1 is consistently detected in NK/DC supernatants. These data point to secretion of leaderless cytokines as a key event for the reciprocal activation of NK cells and DCs. DCs initiate NK cell activation by targeted delivery of IL-18, thus instructing NK cells in the absence of adaptive-type cytokines; in turn, activated NK cells release HMGB1, which promotes inflammation and induces DC maturation, thus favoring the onset of the adaptive immune response.

The "cytokine profile": a code for sepsis

Sepsis--the most common cause of death in hospitalized patients--affects over 18 million people worldwide and has an expected 1% increase of incidence per year. Recent clinical trials indicate that therapeutic approaches effective in diseases with similar pathogenesis have a modest effect against sepsis. Although the reason for this failure remains controversial, recent studies provide new insights and promising experimental strategies. We propose that the current definition of sepsis is too broad and encompasses heterogeneous groups of patients suffering similar, but different, syndromes that are historically grouped under the general diagnosis of sepsis. Future clinical trials might define patient populations and therapeutic strategies according to the profile of expression of cytokines.

Alpha-chemokine receptor blockade reduces high mobility group box 1 protein-induced lung inflammation and injury and improves survival in sepsis

High mobility group box 1 (HMGB1) protein, a late mediator of lethality in sepsis, can induce acute inflammatory lung injury. Here, we identify the critical role of alpha-chemokine receptors in the HMGB1-induced inflammatory injury and show that alpha-chemokine receptor inhibition increases survival in sepsis, in a clinically relevant time frame. Intratracheal instillation of recombinant HMGB1 induces a neutrophilic leukocytosis, preceded by alveolar accumulation of the alpha-chemokine macrophage inflammatory protein-2 and accompanied by injury and increased inflammatory potential within the air spaces. To investigate the role of alpha-chemokine receptors in the injury, we instilled recombinant HMGB1 (0.5 microg) directly into the lungs and administered a subcutaneous alpha-chemokine receptor inhibitor, Antileukinate (200 microg). alpha-Chemokine receptor blockade reduced HMGB1-induced inflammatory injury (neutrophils: 2.9 +/- 3.2 vs. 8.1 +/- 2.4 x 10(4) cells; total protein: 120 +/- 48 vs. 311 +/- 129 microg/ml; reactive nitrogen species: 2.3 +/- 0.3 vs. 3.5 +/- 1.3 microM; and macrophage migration inhibitory factor: 6.4 +/- 4.2 vs. 37.4 +/- 15.9 ng/ml) within the bronchoalveolar lavage fluid, indicating that HMGB1-induced inflammation and injury are alpha-chemokine mediated. Because HMGB1 can mediate late septic lethality, we administered Antileukinate to septic mice and observed increased survival (from 58% in controls to 89%) even when the inhibitor treatment was initiated 24 h after the induction of sepsis. These data demonstrate that alpha-chemokine receptor inhibition can reduce HMGB1-induced lung injury and lethality in established sepsis and may provide a novel treatment in this devastating disease.

Insulin prevents liver damage and preserves liver function in lipopolysaccharide-induced endotoxemic rats

BACKGROUND/AIMS

Liver integrity and function are crucial for survival of patients suffering from trauma, operations or infections. Insulin decreased mortality and prevented the incidence of multi organ failure and infection in critically ill patients. The aim of the present study was to determine whether insulin exerts positive effects on hepatic homeostasis and function during endotoxemia.

METHODS

Endotoxemic rats received either saline or insulin. Hepatic morphology and function was determined by measuring the effect of insulin on liver proteins, enzymes, hepatocyte apoptosis and proliferation including caspases-3 and -9 and Bcl-2. Intrahepatic ATP, glucose and lactate concentration were determined by bioluminescence. To determine possible molecular changes the effect of insulin on hepatic cytokine mRNA and gene profile analysis were assessed.

RESULTS

Insulin significantly improved hepatic protein synthesis by increasing albumin and decreasing c-reactive protein, P<0.05. Insulin attenuated hepatic damage by decreasing AST and ALT, P<0.05. Improved liver morphology was due to decreased hepatocyte apoptosis along with decreased caspase-3 concentration and increased hepatocyte proliferation along with Bcl-2 concentration, P<0.05. Insulin decreased hepatic IL-1beta, IL-6 and MIF mRNA and improved hepatic glucose metabolism and glycolysis, P<0.05. GeneChip analysis revealed an anti-inflammatory effect of insulin.

CONCLUSIONS

Insulin improves hepatic integrity, hepatic glucose metabolism and hepatic function by increasing cell survival and attenuating the hepatic inflammatory response in endotoxemic rats.

Angiogenetic signaling through hypoxia: HMGB1: an angiogenetic switch molecule

The initiation of angiogenesis, called the angiogenetic switch, is a crucial early step in tumor progression and propagation, ensuring an adequate oxygen supply. The rapid growth of tumors is accompanied by a reduced microvessel density, resulting in chronic hypoxia that often leads to necrotic areas within the tumor. These hypoxic and necrotic regions exhibit increased expression of angiogenetic growth factors, eg, vascular endothelial growth factor, and may also attract macrophages, which are known to produce a number of potent angiogenetic cytokines and growth factors. A group of molecules that may act as mediators of angiogenesis are the so-called high-mobility group proteins. Recent studies showed that HMGB1, known as an architectural chromatin-binding protein, can be extracellularly released by passive diffusion from necrotic cells and activated macrophages. To examine the angiogenetic effects of HMGB1 on endothelial cells an in vitro spheroid model was used. The results of the endothelial-sprouting assay clearly show that exogenous HMGB1 induced endothelial cell migration and sprouting in vitro in a dose-dependent manner. Thus, this is the first report showing strong evidence for HMGB1-induced sprouting of endothelial cells.

RAGE limits regeneration after massive liver injury by coordinated suppression of TNF-alpha and NF-kappaB

The exquisite ability of the liver to regenerate is finite. Identification of mechanisms that limit regeneration after massive injury holds the key to expanding the limits of liver transplantation and salvaging livers and hosts overwhelmed by carcinoma and toxic insults. Receptor for advanced glycation endproducts (RAGE) is up-regulated in liver remnants selectively after massive (85%) versus partial (70%) hepatectomy, principally in mononuclear phagocyte-derived dendritic cells (MPDDCs). Blockade of RAGE, using pharmacological antagonists or transgenic mice in which a signaling-deficient RAGE mutant is expressed in cells of mononuclear phagocyte lineage, significantly increases survival after massive liver resection. In the first hours after massive resection, remnants retrieved from RAGE-blocked mice displayed increased activated NF-κB, principally in hepatocytes, and enhanced expression of regeneration-promoting cytokines, TNF-α and IL-6, and the antiinflammatory cytokine, IL-10. Hepatocyte proliferation was increased by RAGE blockade, in parallel with significantly reduced apoptosis. These data highlight central roles for RAGE and MPDDCs in modulation of cell death–promoting mechanisms in massive hepatectomy and suggest that RAGE blockade is a novel strategy to promote regeneration in the massively injured liver.

Macrophage migration inhibitory factor levels correlate with fatal outcome in sepsis

Macrophage migration inhibitory factor (MIF) is a cytokine playing a critical role in the pathophysiology of experimental sepsis. The purpose of this study was to determine the levels of MIF and to compare those to interleukin-6 (IL-6) levels in predicting mortality among critically ill patients with sepsis. The levels of MIF and IL-6 were measured in 25 patients with septic shock, 17 patients with sepsis, and 11 healthy volunteers. The median plasma concentrations of MIF and IL-6 were significantly higher in patients with septic shock and in patients with sepsis than in healthy controls. MIF levels were significantly different between survivors and nonsurvivors, as were IL-6 levels. Discriminatory power in predicting mortality, as assessed by the areas under receiver operating characteristic curves (AUROC), was 0.793 for MIF and 0.680 for IL-6. Finally, high plasma levels of MIF (> 1100 pg/mL) had a sensitivity of 100% and a specificity of 64% to identify the patients who eventually would evolve to a fatal outcome. Thus, our data suggest that an elevated MIF level in recently diagnosed septic patients appears to be an early indicator of poor outcome and a potential entry criterion for future studies with therapeutic intervention aiming at MIF neutralization.

High-mobility group box 1 protein (HMGB1): nuclear weapon in the immune arsenal

High-mobility group box 1 protein (HMGB1), which previously was thought to function only as a nuclear factor that enhances transcription, was recently discovered to be a crucial cytokine that mediates the response to infection, injury and inflammation. These observations have led to the emergence of a new field in immunology that is focused on understanding the mechanisms of HMGB1 release, its biological activities and its pathological effects in sepsis, arthritis, cancer and other diseases. Here, we discuss these features of HMGB1 and summarize recent advances that have led to the preclinical development of therapeutics that modulate HMGB1 release and activity.

Antagonism of RAGE suppresses peripheral nerve regeneration

Axotomy of peripheral nerve triggers events that coordinate a limited inflammatory response to axonal degeneration and initiation of neurite outgrowth. Inflammatory and neurite outgrowth-promoting roles for the receptor for advanced glycation end products (RAGE) have been suggested, so we tested its role in peripheral nerve regeneration. Analysis of immunohistochemical localization of RAGE by confocal microscopy revealed that RAGE was expressed in axons and infiltrating mononuclear phagocytes upon unilateral sciatic nerve crush in mice. Administration of soluble RAGE, the extracellular ligand binding domain of RAGE, or blocking F(ab')2 fragments of antibodies raised to either RAGE or its ligands, S100/calgranulins or amphoterin, reduced functional recovery as assessed by motor and sensory nerve conduction velocities and sciatic functional index and reduced regeneration, as assessed by myelinated fiber density after acute crush of the sciatic nerve. In parallel, in mice subjected to RAGE blockade, decreased numbers of mononuclear phagocytes infiltrated the distal nerve segments after crush. These findings provide the first evidence of an innate function of the ligand/RAGE axis and suggest that RAGE plays an important role in regeneration of the peripheral nervous system.

Skeletal muscle cytokines: regulation by pathogen-associated molecules and catabolic hormones

PURPOSE OF REVIEW

This review will update clinicians and basic scientists who study the molecular mechanisms of muscle wasting associated with infection, trauma, cancer cachexia, and AIDS. A special emphasis is placed on recent studies that examine the interaction of insulin-like growth factor 1 and proinflammatory cytokines as positive and negative regulators of muscle mass.

RECENT FINDINGS

Potential mediators of the wasting syndromes include catabolic hormones, such as glucocorticoids, as well as the inflammatory cytokines tumour necrosis factor, IL-1, and IL-6. Cytokines may function either systemically or locally within muscle per se. Lipopolysaccharide and other pathogen-associated molecules stimulate cytokine expression in muscle. The failure to clear pathogen-associated molecules or the introduction of muscle damage may initiate a protracted activation of enzymes and transcription factors that orchestrate a genetic programme that ultimately produces muscle wasting.

SUMMARY

This review highlights recent advances in our understanding of the expression of the afferent and efferent limbs of the innate immune system in skeletal muscle. A special emphasis is placed on the recognition of pathogen-associated molecules by skeletal muscle cells and how these molecules regulate the expression of inflammatory cytokines and other muscle genes to result in muscle wasting, and when sustained, the erosion of lean body mass.

The N-terminal domain of thrombomodulin sequesters high-mobility group-B1 protein, a novel antiinflammatory mechanism

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

The N-terminal domain of thrombomodulin sequesters high-mobility group-B1 protein, a novel antiinflammatory mechanism

Thrombomodulin (TM) is an endothelial anticoagulant cofactor that promotes thrombin-mediated formation of activated protein C (APC). We have found that the N-terminal lectin-like domain (D1) of TM has unique antiinflammatory properties. TM, via D1, binds high-mobility group-B1 DNA-binding protein (HMGB1), a factor closely associated with necrotic cell damage following its release from the nucleus, thereby preventing in vitro leukocyte activation, in vivo UV irradiation-induced cutaneous inflammation, and in vivo lipopolysaccharide-induced lethality. Our data also demonstrate antiinflammatory properties of a peptide spanning D1 of TM and suggest its therapeutic potential. These findings highlight a novel mechanism, i.e., sequestration of mediators, through which an endothelial cofactor, TM, suppresses inflammation quite distinctly from its anticoagulant cofactor activity, thereby preventing the interaction of these mediators with cell surface receptors on effector cells in the vasculature.

Monocytes promote natural killer cell interferon gamma production in response to the endogenous danger signal HMGB1

Substantial attention has been paid to the role of the toll-like receptor (TLR) ligands of late and their role in regulating the innate immune response. They serve as exogenous danger signals important in informing and driving the distal adaptive immune response to pathogens. Less clear has been the role of the nominal endogenous danger signals released and recognized in stressed cells following genotoxic or metabolic stress as occurs in progressively growing tumors. HMGB1 (high-mobility group B1) is a nuclear protein well characterized for its ability to modify DNA access to transcriptional proteins that is released from necrotic cells as well as secreted through the endosomal route from hematopoietic cells, serving as a late mediator of sepsis. It interacts with high-affinity RAGE (receptor for advanced glycation end products) and TLR2 receptors. Here we show that HMGB1 enhances interferon gamma release from macrophage (but not dendritic cell)-stimulated NK cells. This is effective only when coupled with other pro-inflammatory cytokines particularly with IL-2 in combination with IL-1 or IL-12. We have used this information to suggest that HMGB1, which also promotes epithelial migration and proliferation, drives repair in the absence or inhibition of other factors but enhances inflammation in their presence. The implications for tumorigenesis and tumor progression are quite important as they may be for other states of chronic inflammation.

Persistent elevation of high mobility group box-1 protein (HMGB1) in patients with severe sepsis and septic shock

OBJECTIVE

To study the systemic release and kinetics of high mobility group box-1 protein (HMGB1) in relation to clinical features in a population of patients with severe sepsis or septic shock and to compare these with the kinetics of the cytokines interleukin-6, interleukin-8, interleukin-10, and tumor necrosis factor-alpha.

DESIGN

Prospective study of two cohorts of patients.

SETTING

Intensive care unit and infectious disease clinic at Karolinska University Hospital Huddinge.

PATIENTS

Twenty-six patients with severe sepsis, 33 patients with septic shock, and a reference group of five patients with sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Sixty-four patients were included, ten of whom died within 28 days. Cytokine levels were measured at five time points during the first week after admission and were correlated to Acute Physiology and Chronic Health Evaluation II and Sepsis-related Organ Failure Assessment scores. Two HMGB1 assays were used. Both demonstrated delayed kinetics for HMGB1 with high levels on inclusion that remained high throughout the study period. Serum concentration at 144 hrs, the last sampling point, was 300 times higher, 34,000 +/- 76,000 pg/mL (mean +/- sd), than any of the other cytokines. This study, however, found no predictable correlation between serum levels of HMGB1 and severity of infection. We did quite unexpectedly find significantly lower levels of HMGB1 in nonsurvivors compared with survivors as measured by our main assay, but the other showed no difference between the two groups. Levels of interleukin-6, interleukin-8, interleukin-10, and tumor necrosis factor-alpha correlated significantly with severity of disease, and all were significantly higher in patients with septic shock compared with those with severe sepsis. Neither of these comparisons showed significant correlations for HMGB1.

CONCLUSIONS

This is the first prospective study assessing the release over time of HMGB1 in a population of patients with sepsis, severe sepsis, or septic shock. Levels remained high in the majority of patients up to 1 wk after admittance, indicating that the cytokine indeed is a downstream and late mediator of inflammation. Further studies are required to fully define the relationship of HMGB1 to severity of disease.

Determinants of Plasma Acid-Base Balance

An advanced understanding of acid-base physiology is central to the practice of critical care medicine. Intensivists spend much of their time managing problems that are related to fluids, electrolytes, and blood pH. Recent advances in the understanding of acid-base physiology occurred as the result of the application of basic physical-chemical principles of aqueous solutions to blood plasma. This analysis revealed three independent variables that regulate pH in blood plasma: carbon dioxide, relative electrolyte concentrations, and total weak acid concentrations. All changes in blood pH, in health and in disease, occur through changes in these three variables. This article reviews the physical-chemical approach to acid-base balance and considers clinical implications for these findings.

Extracellular HMGB1 as a proinflammatory cytokine

High mobility group box-1 protein (HMGB1, formerly known as HMG-1), a highly conserved ubiquitous protein, has been for a long time described as a nuclear DNA-binding protein involved in nucleosome stabilization and gene transcription. Recent discoveries indicate that HMGB1 is released from activated innate immune cells or necrotic cells and functions as an important mediator of endotoxemia, sepsis, arthritis, and local inflammation. Therapeutic agents that inhibit HMGB1 release or action confer significant protection against endotoxemia, sepsis, and arthritis in animal models and thus hold potential for the clinical management of various inflammatory diseases.

The nuclear factor HMGB1 mediates hepatic injury after murine liver ischemia-reperfusion

High-mobility group box 1 (HMGB1) is a nuclear factor that is released extracellularly as a late mediator of lethality in sepsis as well as after necrotic, but not apoptotic, death. Here we demonstrate that in contrast to the delayed role of HMGB1 in the systemic inflammation of sepsis, HMGB1 acts as an early mediator of inflammation and organ damage in hepatic ischemia reperfusion (I/R) injury. HMGB1 levels were increased during liver I/R as early as 1 h after reperfusion and then increased in a time-dependent manner up to 24 h. Inhibition of HMGB1 activity with neutralizing antibody significantly decreased liver damage after I/R, whereas administration of recombinant HMGB1 worsened I/R injury. Treatment with neutralizing antibody was associated with less phosphorylation of c-Jun NH₂-terminal kinase and higher nuclear factor–κB DNA binding in the liver after I/R. Toll-like receptor 4 (TLR4)-defective (C3H/Hej) mice exhibited less damage in the hepatic I/R model than did wild-type (C3H/HeOuj) mice. Anti-HMGB1 antibody failed to provide protection in C3H/Hej mice, but successfully reduced damage in C3H/Ouj mice. Together, these results demonstrate that HMGB1 is an early mediator of injury and inflammation in liver I/R and implicates TLR4 as one of the receptors that is involved in the process.

Adrenomedullin and its binding protein attenuate the proinflammatory response after hemorrhage

OBJECTIVE

The neuroendocrine response to hemorrhage is to maintain perfusion to the heart and brain, often at the expense of other organ systems. Systemic inflammation and tissue injury are important components of pathophysiologic consequences of hemorrhage. We have recently shown that administration of adrenomedullin (AM, a potent vasodilator peptide) and adrenomedullin binding protein-1 (AMBP-1) prevented the transition from the hyperdynamic to the hypodynamic stage in the progression of sepsis. However, the effect of AM/AMBP-1 on the inflammatory response after hemorrhage remains unknown. We therefore hypothesized that administration of AM/AMBP-1 during fluid resuscitation in hemorrhaged animals (i.e., posttreatment) attenuates tissue injury and the proinflammatory response.

DESIGN

Prospective, controlled, and randomized animal study.

SETTING

A research institute laboratory.

SUBJECTS

Male adult rats.

INTERVENTIONS

Rats were bled, and then a mean arterial pressure was maintained at 40 mm Hg for 90 mins. They were then resuscitated by infusion of four times the volume of shed blood using Ringer's lactate solution for 60 mins.

MEASUREMENTS AND MAIN RESULTS

Fifteen minutes after the beginning of resuscitation, AM (12 microg/kg of body weight) in combination with AMBP-1 (40 microg/kg of body weight) was administered via a femoral venous catheter for 45 mins. Blood samples were collected 4 hrs postresuscitation and assayed for levels of liver enzymes (i.e., alanine aminotransferase and aspartate aminotransferase), lactate, creatinine, proinflammatory cytokines tumor necrosis factor and high mobility group box 1, and anti-inflammatory cytokine interleukin-10. The results indicate that levels of alanine aminotransferase, aspartate aminotransferase, creatinine, lactate, tumor necrosis factor, and high mobility group box 1 markedly elevated after hemorrhage and resuscitation, and AM/AMBP-1 treatment significantly attenuated these increases. In contrast, the serum concentration of anti-inflammatory cytokine interleukin-10 was increased by the treatment of AM/AMBP-1. Moreover, AM/AMBP-1 treatment significantly improved the survival rate from 35% in vehicle-treated animals to 73% in AM/AMBP-1-treated animals in a low-volume resuscitation model of hemorrhage.

CONCLUSION

The combined administration of AM and AMBP-1 effectively suppresses hemorrhage-elicited organ injury and reduces hemorrhage-induced mortality, partly through down-regulation of proinflammatory cytokines (tumor necrosis factor and high mobility group box 1) and up-regulation of the anti-inflammatory cytokine interleukin-10.

Advanced glycation end products and RAGE: a common thread in aging, diabetes, neurodegeneration, and inflammation

The products of nonenzymatic glycation and oxidation of proteins and lipids, the advanced glycation end products (AGEs), accumulate in a wide variety of environments. AGEs may be generated rapidly or over long times stimulated by a range of distinct triggering mechanisms, thereby accounting for their roles in multiple settings and disease states. A critical property of AGEs is their ability to activate receptor for advanced glycation end products (RAGE), a signal transduction receptor of the immunoglobulin superfamily. It is our hypothesis that due to such interaction, AGEs impart a potent impact in tissues, stimulating processes linked to inflammation and its consequences. We hypothesize that AGEs cause perturbation in a diverse group of diseases, such as diabetes, inflammation, neurodegeneration, and aging. Thus, we propose that targeting this pathway may represent a logical step in the prevention/treatment of the sequelae of these disorders.

Interleukin-32: a cytokine and inducer of TNFalpha

We describe the gene structure, regulation, signal transduction. and functions of a cytokine, interleukin (IL)-32. An IL-18 unresponsive cell was converted to a responsive cell by transfection of the IL-18 receptor beta chain, and IL-18-induced microarray revealed high expression of a cytokine-like gene. Although IL-32 does not share sequence homology with known cytokine families, IL-32 induces various cytokines, human TNFalpha, and IL-8 in THP-1 monocytic cells as well as mouse TNFalpha and MIP-2 in Raw macrophage cells. IL-32 activates typical cytokine signal pathways of nuclear factor-kappa B (NF-kappaB) and p38 mitogen-activated protein kinase. IL-32 mRNA is highly expressed in immune tissue rather than other tissues. Human IL-32 exists as four splice variants, and IL-32 from other species were found as expressed sequence tag clones in the databank. Induced in human peripheral lymphocyte cells after mitogen stimulation, in human epithelial cells by IFNgamma, and in NK cells after exposure to the combination of IL-12 plus IL-18, IL-32 may play a role in inflammatory/autoimmune diseases.