Duration and magnitude of hypotension and monocyte deactivation in patients with community-acquired pneumonia.

The objective was to examine the relationship of duration and magnitude of arterial hypotension to subsequent cellular immune suppression and cytokinemia in patients hospitalized with community-acquired pneumonia (CAP). We studied an observational cohort of 525 subjects hospitalized after presenting to the emergency department with radiographic and clinical signs of CAP. We compared the duration and magnitude of hypotension, using the cardiovascular Sequential Organ Failure Assessment (CV SOFA) subscore, to day 3 monocyte expression of human leukocyte antigen-DR (mHLA-DR), a previously validated marker of cellular immune suppression. A significant association of CV SOFA with decreased mHLA-DR expression was present in univariate analysis (P < 0.001) and persisted after adjustment for illness severity and other covariates (P = 0.01). With CV SOFA separated into components of magnitude and duration, after covariate adjustment, only duration was associated with day 3 mHLA-DR expression (P = 0.03). Levels of key proinflammatory and anti-inflammatory cytokines (interleukin 6 [IL-6], IL-10, tumor necrosis factor) increased with hypotension exposure and were also associated with mHLA-DR expression. In patients admitted with CAP, arterial hypotension over the first 3 days is associated with markers of monocyte deactivation. The duration of exposure to hypotension may be more important than the magnitude, and monocyte deactivation correlates with IL-6 and IL-10 release. These results suggest that persistent hypotension might contribute to immunosuppression following septic shock.

Characterizing accelerated capture of deoligomerized TNF within hemoadsorption beads used to treat sepsis.

Sepsis is a systemic inflammatory response to infection, characterized by overexpression of cytokines in the circulating blood. Removal of cytokines and other inflammatory mediators from the blood may help attenuate systemic inflammation during sepsis and improve patient outcomes. In this work, we examined the dynamics of TNF capture within porous, polymeric sorbent beads used in a cytokine adsorption device. We sought to quantify how perturbation of TNF oligomeric structure accelerates TNF removal within the device. TNF was incubated with 10% DMSO for 24 h, which promoted complete monomerization of trimeric TNF, and accelerated TNF capture within the sorbent device compared with native TNF; removal halftime = 13.3 ± 1.5 min versus 112.8 ± 13.3 min, respectively. Intramolecular crosslinking stabilized the trimeric TNF structure and prevented DMSO monomerization. Results demonstrate that TNF is an unstable oligomeric molecule that can be dissociated into its smaller monomeric constituents to facilitate faster capture by hemoadsorption beads. Strategies to promote localized TNF deoligomerization at the sorbent surface may significantly accelerate TNF capture rates from the circulating blood using hemoadsorption as a treatment for sepsis. This concept could be extended to improve removal of other oligomeric molecules using size exclusion filtration materials for a variety of disease states.

Understanding the potential role of statins in pneumonia and sepsis.

OBJECTIVE: To examine the association of statin use with clinical outcomes and circulating biomarkers in community-acquired pneumonia and sepsis. DESIGN: Multicenter inception cohort study. SETTING: Emergency departments of 28 U.S. hospitals. PATIENTS: A total of 1895 subjects hospitalized with community-acquired pneumonia. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Our approach consisted of two different comparison cohorts, each reflecting methods used in prior publications in this area. We first compared subjects with prior statin use (prior use cohort), defined as a history of statin use in the week before admission, with those with no prior use. We then compared prior statin users whose statins were continued inhospital (continued use cohort) with those with either no prior use or no inhospital use. We adjusted for patient characteristics, including demographics, comorbid conditions, and illness severity, and accounted for healthy user effect and indication bias using propensity analysis. We determined risk of severe sepsis and 90-day mortality. We measured markers inflammation (tumor necrosis factor, interleukin-6, interleukin-10), coagulation (antithrombin, factor IX, plasminogen activator inhibitor, d-dimer, thrombin antithrombin complex), and lymphocyte cell surface protein expression during the first week of hospitalization. There were no differences in severe sepsis risk between statin users and nonusers for prior (30.8% vs. 30.7%, p = .98) or continued statin use (30.2% vs. 30.8%, p = .85) in univariate analyses and after adjusting for patient characteristics and propensity for statin use. Ninety-day mortality was similar in prior statin users (9.2% vs. 12.0%, p = .11) and lower in continued statin users (7.9% vs. 12.1%, p = .02). After adjusting for patient characteristics and propensity for statin use, there was no mortality benefit for prior (odds ratio, 0.90 [0.63-1.29]; p = .57) or continued statin use (odds ratio, 0.73 [0.47-1.13]; p = .15). Only antithrombin activity over time was higher in statin subjects, yet the magnitude of the difference was modest. There were no differences in other coagulation, inflammatory, or lymphocyte cell surface markers. CONCLUSIONS: We found no evidence of a protective effect for statin use on clinical outcomes and only modest differences in circulating biomarkers in community-acquired pneumonia, perhaps as a result of healthy user effects and indication bias.

Small interfering RNA mediated Poly (ADP-ribose) Polymerase-1 inhibition upregulates the heat shock response in a murine fibroblast cell line.

Poly (ADP-ribose) polymerase-1 (PARP-1) is a highly conserved multifunctional enzyme, and its catalytic activity is stimulated by DNA breaks. The activation of PARP-1 and subsequent depletion of nicotinamide adenine dinucleotide (NAD+) and adenosine triphosphate (ATP) contributes to significant cytotoxicity in inflammation of various etiologies. On the contrary, induction of heat shock response and production of heat shock protein 70 (HSP-70) is a cytoprotective defense mechanism in inflammation. Recent data suggests that PARP-1 modulates the expression of a number of cellular proteins at the transcriptional level. In this study, small interfering RNA (siRNA) mediated PARP-1 knockdown in murine wild-type fibroblasts augmented heat shock response as compared to untreated cells (as evaluated by quantitative analysis of HSP-70 mRNA and HSP-70 protein expression). These events were associated with increased DNA binding of the heat shock factor-1 (HSF-1), the major transcription factor of the heat shock response. Co-immunoprecipitation experiments in nuclear extracts of the wild type cells demonstrated that PARP-1directly interacted with HSF-1. These data demonstrate that, in wild type fibroblasts, PARP-1 plays a pivotal role in modulating the heat shock response both through direct interaction with HSF-1 and poly (ADP-ribosylation).

Extracellular activation of arginase-1 decreases enterocyte inducible nitric oxide synthase activity during systemic inflammation.

Liver dysfunction secondary to severe inflammation is associated with the release of enzymes normally sequestered within hepatocytes. The purpose of these studies was to test the hypothesis that these enzymes are released, at least in part, to modulate potentially deleterious inflammatory processes in distant tissues like the gut. Human Caco-2(BBe) enterocyte-like cells were exposed to cytomix (IFN-gamma, TNF-alpha, and IL-1beta) in the absence or presence of human liver cytosol (LC). Nitric oxide (NO(*)) and inducible nitric oxide synthase (iNOS) protein production were measured by the Griess assay and Western analysis, respectively. Cytomix induced the expression of iNOS and release of NO(*). LC protein (400 microg/ml) added to the basal compartment but not apical compartment completely blocked the release of NO(*) but only slightly decreased the magnitude of iNOS protein induction. Ultrafiltration and ultracentrifugation studies demonstrated that microsome-associated arginase-1 activity was the iNOS-suppressing activity in LC. Liver arginase required activation by a <10-kDa factor that was present in supernatants of cytomix-stimulated cells. The selective iNOS inhibitor l-N(6)-(1-iminoethyl)-lysine.2HCl prevented production of this factor. The biotin switch assay detected increased S-nitrosylation of arginase-1 after incubation with supernatants from immunostimulated Caco-2 cells. Serum from endotoxemic mice contained significantly greater arginase activity compared with serum from control mice. Furthermore, the ratio of mucosal monomeric to dimeric iNOS increased in endotoxemic mice compared with controls. Thus reciprocal activation of arginase-1 and modulation of mucosal iNOS activity may be protective because it would be expected to decrease NO(*)-dependent intestinal barrier dysfunction on that basis.

Comparison of distinct protein isoforms of the receptor for advanced glycation end-products expressed in murine tissues and cell lines.

The receptor for advanced glycation end-products (RAGE) is thought to be expressed ubiquitously as various protein isoforms. Our objective was to use Northern blotting, immunoblotting, and sensitivity to N-glycanase digestion to survey RAGE isoforms expressed in cell lines and mouse tissues in order to obtain a more comprehensive view of the RAGE expressome. Pulmonary RAGE mRNA (1.4 kb) was smaller than cell-line and tissue RAGE mRNA (6 kb-10 kb). Three anti-RAGE antibodies that recognized three distinct RAGE epitopes were used for protein studies (N-16, H-300, and alphaES). Lung expressed three predominant protein isoforms with apparent molecular masses of 45.1, 52.6, and 57.4 kDa (N-16/H-300) and four isoforms at 25.0, 46.9, 52.5, and 54.2 kDa (alphaES). These isoforms were expressed exclusively in lung. Heart, ileum, and kidney expressed a 44.0-kDa isoform (N-16), whereas aorta and pancreas expressed a 53.3-kDa isoform (alphaES). Each of these isoforms were absent in tissue extracts prepared from RAGE(-/-) mice. Cell lines expressed a 70.0-kDa isoform, and a subset expressed a 30.0-kDa isoform (alphaES). Lung RAGE appeared to contain two N-linked glycans. Tissue and cell-line RAGE isoforms were completely insensitive to PNGase F digestion. Thus, numerous RAGE protein isoforms are detectable in tissues and cell lines. Canonical transmembrane and soluble RAGE appear to be expressed solely in lung (N-16/H-300). Non-pulmonary tissues and cell lines, regardless of the source tissue, both express distinct RAGE protein isoforms containing the N-terminal N-16 epitope or the alphaES RAGE epitope encoded by alternate exon 9, but lacking the H-300 epitope.

Midregional proadrenomedullin as a prognostic tool in community-acquired pneumonia.

BACKGROUND: Midregional proadrenomedullin (MR-proADM) is a potential prognostic biomarker in patients with community-acquired pneumonia (CAP). Previous work has been hampered by sample size and illness spectrum limits. We sought to describe the pattern of MR-proADM in a broad CAP cohort, confirm its prognostic role, and compare its performance to procalcitonin, a novel biomarker of infection. METHODS: We conducted a multicenter prospective cohort study in 28 community and teaching EDs. Patients with a clinical and radiographic diagnosis of CAP were enrolled. We stratified MR-proADM levels a priori into quartiles and quantified severity of illness using the pneumonia severity index (PSI); and confusion (abbreviated mental test score of or= 7 mmol/L, respiratory rate >or= 30 breaths/min, BP < 90 mm Hg systolic or < 60 mm Hg diastolic, age >or= 65 years (CURB-65). The primary outcome was 30-day mortality. RESULTS: A total of 1,653 patients formed the study cohort. MR-proADM levels consistently rose with PSI class and 30-day mortality (p < 0.001). MR-proADM had a higher area under the curve for 30-day mortality than procalcitonin (0.76 vs 0.65, respectively; p < 0.001), but adding MR-proADM to the PSI in all subjects minimally improved performance. Among low-risk subjects (PSI classes I to III), mortality was low and did not differ by MR-proADM quartile. However, among high-risk subjects (PSI class IV/V; n = 546), subjects in the highest MR-proADM quartile (n = 232; 42%) had higher 30-day mortality than those in MR-proADM quartiles 1 to 3 (23% vs 9%, respectively; p < 0.0001). Similar results were seen with CURB-65. MR-proADM and procalcitonin levels were generally concordant; only 6% of PSI class IV/V subjects in the highest MR-proADM quartile had very low procalcitonin levels (< 0.1 ng/mL). CONCLUSIONS: In our multicenter CAP cohort, MR-proADM levels correlate with increasing severity of illness and death. High MR-proADM levels offer additional risk stratification in high-risk CAP patients, but otherwise MR-proADM levels do not alter PSI-based risk assessment in most CAP patients.

Drag-reducing hyaluronic acid increases survival in profoundly hemorrhaged rats.

We tested the hypothesis that the infusion of a small volume of a drag-reducing polymer (DRP) solution can prolong survival in rats subjected to lethal hemorrhagic shock (HS; shed 51% of estimated blood volume) in the absence of complete resuscitation with fluids or blood. In this set of experiments, we used a newly designed mixture of hyaluronic acid (molecular weight, approximately 2.0 x 10 d; 0.4 mg/mL) and polyethylene oxide (molecular weight, approximately 4 x 10 d; 0.05 mg/mL) dissolved in sterile phosphate-buffered saline. Anesthetized rats were subjected to a volume-controlled HS. During the first 20 min, blood (21.7 mL/kg) was withdrawn. During the next 40 min, additional blood (14 mL/kg) was withdrawn, and during the final 20 min, saline vehicle or saline + DRP (2.8 mL/kg) was simultaneously infused. The survival rate of the rats treated with the hyaluronic acid/polyethylene oxide was significantly higher (P < 0.01). The mean survival times for control and DRP-treated animals were 100.4 +/- 9.5 vs. 154.8 +/- 7.0 min (P < 0.001). MAP was higher (P < 0.005) and skin perfusion was significantly improved in the DRP-treated group after the end of the DRP infusion. These results support the use of nanomolar concentrations of DRP to prolong survival in rats after lethal HS in the absence of fluid resuscitation. The DRP formulation studied here warrants further evaluation for the amelioration of critical illness associated with profound shock when access to resuscitation fluids may not be possible or delayed.

Preconditioning with high mobility group box 1 (HMGB1) induces lipopolysaccharide (LPS) tolerance.

High mobility group box protein 1 (HMGB1) modulates the innate immune response when present in the extracellular compartment. Receptors for HMGB1 include TLR4, TLR2, and the receptor for advanced glycation end products (RAGE). We tested the hypothesis that extracellular HMGB1 can induce LPS tolerance. HMGB1 dose-response experiments were performed on IFN-gamma-differentiated human monocyte-like THP-1 cells. Treatment with 1 microg/ml HMGB1 18 h before exposure to LPS (1 microg/ml) decreased TNF release, NF-kappaB nuclear DNA-binding activity, phosphorylation, and degradation of IkappaBalpha. Preconditioning with HMGB1 alone and HMGB1 in the presence of polymyxin B decreased LPS-mediated, NF-kappaB-dependent luciferase reporter gene expression. The specificity of HMGB1 in tolerance induction was supported further by showing that boiled HMGB1 failed to induce tolerance, and antibodies against HMGB1 blocked the induction of LPS tolerance. Bone marrow-derived macrophages obtained from C57Bl/6 wild-type mice became LPS-tolerant following HMGB1 exposure ex vivo, but macrophages derived from RAGE-deficient mice failed to develop tolerance and responded normally to LPS. Mice preconditioned with HMGB1 (20 microg) 1 h before LPS injection (10 mg/kg) had lower circulating TNF compared with control mice preconditioned with saline vehicle. Similarly, decreased nuclear DNA binding of hepatic NF-kappaB was observed in mice preconditioned with HMGB1. Taken together, these results suggest that extracellular HMGB1 induces LPS tolerance, and the RAGE receptor is required for this induction.

Hemigramicidin-TEMPO conjugates: novel mitochondria-targeted antioxidants.

Reactive oxygen species (ROS) are reactive, partially reduced derivatives of molecular oxygen. ROS are important in the pathogenesis of a wide range of acute pathologic processes, including ischemia/reperfusion injury, sepsis, and shock. Accordingly, effective ROS scavengers might be useful therapeutic agents for these conditions. Since mitochondria are the primary sites for ROS production within cells, it seems reasonable that targeting ROS scavengers to these organelles could be a particularly effective strategy. Indeed, a number of compounds or classes of compounds have been described that are based on this concept. One approach consists of coupling a payload--the portion of the molecule with ROS-scavenging activities--to a targeting moiety--the portion of the molecule that promotes selective accumulation within mitochondria. For example, the payload portion of XJB-5-131 consists of a stable nitroxide radical, which has been extensively investigated as a cytoprotective agent in a number of experimental models of oxidative stress. The targeting portion of XJB-5-131 consists of a portion of the membrane-active cyclopeptide antibiotic, gramicidin S. The gramicidin segment was used to target the nitroxide payload to mitochondria because antibiotics of this type have a high affinity for bacterial membranes and because of the close relationship between bacteria and mitochondria. In a rat model of hemorrhagic shock, delayed treatment with XJB-5-131 has been shown to prolong survival time in the absence of resuscitation with blood or a large volume of crystalloid fluid. Compounds like XJB-5-131 warrant further evaluation for the treatment of hemorrhagic shock as well as other acute conditions associated with increased mitochondrial production of ROS.

Understanding the inflammatory cytokine response in pneumonia and sepsis: results of the Genetic and Inflammatory Markers of Sepsis (GenIMS) Study.

BACKGROUND: Severe sepsis is common and frequently fatal, and community-acquired pneumonia (CAP) is the leading cause. Although severe sepsis is often attributed to uncontrolled and unbalanced inflammation, evidence from humans with infection syndromes across the breadth of disease is lacking. In this study we describe the systemic cytokine response to pneumonia and determine if specific patterns, including the balance of proinflammatory and anti-inflammatory markers, are associated with severe sepsis and death. METHODS: This is a cohort study of 1886 subjects hospitalized with CAP through the emergency departments in 28 US academic and community hospitals. We defined severe sepsis as CAP complicated by new-onset organ dysfunction, following international consensus conference criteria. We measured plasma tumor necrosis factor, IL-6 (interleukin 6), and IL-10 levels daily for the first week and weekly thereafter. Our main outcome measures were severe sepsis and 90-day mortality. RESULTS: A total of 583 patients developed severe sepsis (31%), of whom 149 died (26%). Systemic cytokine level elevation occurred in 82% of all subjects with CAP. Mean cytokine concentrations were highest at presentation, declined rapidly over the first few days, but remained elevated throughout the first week, beyond resolution of clinical signs of infection. Cytokine levels were highest in fatal severe sepsis and lowest in CAP with no severe sepsis. Unbalanced (high/low) cytokine patterns were unusual (4.6%) and not associated with decreased survival. Highest risk of death was with combined high levels of the proinflammatory IL-6 and anti-inflammatory IL-10 cytokine activity (hazard ratio, 20.5; 95% confidence interval, 10.8-39.0) (P<.001). CONCLUSIONS: The circulating cytokine response to pneumonia is heterogeneous and continues for more than a week after presentation, with considerable overlap between those who do and do not develop severe sepsis. Unbalanced activation is uncommon, and mortality is highest when both proinflammatory and anti-inflammatory cytokine levels are high.

Hemigramicidin-TEMPO conjugates: novel mitochondria-targeted anti-oxidants.

Oxidative damage to various cellular constituents (such as, proteins and lipids) mediated by reactive oxygen species (ROS) is thought to be an important mechanism underlying the pathogenesis of a variety of acute and chronic diseases. Mitochondria are the main source of ROS within most cells. Accordingly, there is increasing interest in the development of pharmacological ROS scavengers, which are specifically targeted to and concentrated within mitochondria. Numerous compounds with these general characteristics have been synthesized and evaluated in a variety of in vitro and in vivo models of redox stress. Among the more promising of these mitochondria-targeted anti-oxidants are those that employ various peptides (or peptide-like moieties) derived from the antibiotic, gramicidin S, as the targeting construct and employ the stable free radical, 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (4-NH(2)-TEMPO), as the ROS scavenging "payload." One of these hemigramicidin-TEMPO conjugates, XJB-5-131, has been shown to ameliorate intestinal mucosal injury and prolong survival in rats subjected to lethal hemorrhage.

Circulating high-mobility group box 1 (HMGB1) concentrations are elevated in both uncomplicated pneumonia and pneumonia with severe sepsis.

OBJECTIVE: High-mobility group box 1 (HMGB1) has been proposed as a late mediator of sepsis, but human data are sparse and conflicting. We describe plasma HMGB1 concentrations in humans with community-acquired pneumonia (CAP), the most common cause of severe sepsis, and test the hypotheses that HMGB1 levels are higher in CAP than healthy controls, higher in CAP with severe sepsis than CAP without severe sepsis, and higher in severe sepsis nonsurvivors than survivors. DESIGN: Random, outcome-stratified sample from a prospective study of 1,895 subjects hospitalized with CAP. SETTING: Twenty-eight U.S. teaching and community hospitals. PATIENTS: There were 122 CAP subjects (43 never developed severe sepsis, 49 developed severe sepsis and survived hospitalization, and 30 developed severe sepsis and died) and 38 healthy controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Median day of onset of severe sepsis was day of admission. HMGB1 was measured daily for the first week and analyzed using repeated-measures models with and without multivariable adjustment for baseline characteristics. HMGB1 concentrations were higher in CAP subjects compared with controls (median concentration on day of admission vs. controls, 190 vs. 0 ng/mL, p = .0001; 93.7% of all CAP measurements were elevated). HMGB1 remained elevated throughout the hospital course with no significant trend (p = .64) and did not differ between those with and without severe sepsis (p = .30). HMGB1 concentrations were higher in severe sepsis nonsurvivors than survivors (p = .001). HMGB1 concentrations remained elevated at discharge (median final HMGB1 measure, 176 ng/mL). Findings persisted in multivariable models and were robust to sensitivity analyses using alternative definitions of severe sepsis. CONCLUSIONS: HMGB1 is elevated in almost all CAP subjects, and higher circulating HMGB1 is associated with mortality. But immunodetectable HMGB1 levels were also persistently elevated in those patients who fared well. Thus, additional work is needed to understand the biological activities of serum HMGB1 in sepsis.

Treatment with a novel hemigramicidin-TEMPO conjugate prolongs survival in a rat model of lethal hemorrhagic shock.

OBJECTIVE: We sought to develop a therapeutic agent that would permit prolongation of survival in rats subjected to lethal hemorrhagic shock (HS), even in the absence of resuscitation with asanguinous fluids or blood. METHODS AND RESULTS: We synthesized a series of compounds that consist of the electron scavenger and superoxide dismutase mimic, 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (4-NH2-TEMPO), conjugated to fragments and analogs of the membrane-active cyclopeptide antibiotic, gramicidin S. Using an in vivo assay, wherein isolated intestinal segments were loaded inside the lumen with various test compounds, we studied these compounds for their ability to prevent ileal mucosal barrier dysfunction induced by subjecting rats to profound HS for 2 hours. The most active compound in this assay, XJB-5-131, ameliorated peroxidation of the mitochondrial phospholipid, cardiolipin, in ileal mucosal samples from rats subjected to HS. XJB-5-131 also ameliorated HS-induced activation of the pro-apoptotic enzymes, caspases 3 and 7, in ileal mucosa. Intravenous treatment with XJB-5-131 (2 micromol/kg) significantly prolonged the survival of rats subjected to profound blood loss (33.5 mL/kg) despite administration of only a minimal volume of crystalloid solution (2.8 mL/kg) and the absence of blood transfusion. CONCLUSION: These data support the view that mitochondrially targeted electron acceptors and SOD mimics are potentially valuable therapeutics for the treatment of serious acute conditions, such as HS, which are associated with marked tissue ischemia.

LPS increases hepatic HIF-1alpha protein and expression of the HIF-1-dependent gene aldolase A in rats.

BACKGROUND: Cellular adaptation to hypoxia is mediated in part by the transcription factor hypoxia-inducible factor 1 (HIF-1). Accumulating data suggest that pro-inflammatory mediators can up-regulate HIF-1alpha protein expression and HIF-1 DNA-binding activity in the absence of hypoxia. Accordingly, we investigated HIF-1 mediated signaling in endotoxemic rats. MATERIALS AND METHODS: We studied three groups of male Sprague Dawley rats. Controls (N = 5) were injected i.p. with saline. Endotoxemic rats (N = 9) received a sublethal dose of lipopolysaccaride (Escherichia coli; 5 mg/kg, i.p.). A third group of rats (N = 5) received the HIF-1 stabilizing agent CoCl(2) (14 mg/kg, i.p.) at T = 0 h and T = 16 h. At T = 18 h, liver microvascular perfusion was measured using laser Doppler flowmetry and hepatic tissue samples were obtained. RNA was isolated and mRNA levels of the HIF-1 dependent genes aldolase A and vascular endothelial growth factor (VEGF) were determined using quantitative real-time RT-PCR. HIF-1alpha content was estimated by immunoprecipitation followed by Western blotting. RESULTS: HIF-1alpha increased in hepatic tissue after treatment with LPS or CoCl(2). LPS markedly increased hepatic expression of aldolase A, but failed to alter expression of VEGF. CoCl(2) increased aldolase A and VEGF mRNA expression. Although hepatic microvascular perfusion was comparable in saline- and LPS-treated rats, hepatic microvascular blood flow and aldolase A expression were significantly inversely correlated among endotoxemic rats (r = 0.773; P = 0.003). CONCLUSIONS: Increased expression of aldolase A in endotoxemic rats is mediated by both hypoxia-dependent and hypoxia-independent mechanisms.

The phase 2 enzyme inducers ethacrynic acid, DL-sulforaphane, and oltipraz inhibit lipopolysaccharide-induced high-mobility group box 1 secretion by RAW 264.7 cells.

The diuretic ethacrynic acid (EA) has been shown to inhibit signaling by the proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB). Accordingly, we sought to determine whether this compound is capable of inhibiting the release of cytokines [interleukin (IL)-6 and IL-10] and NO from RAW 264.7 murine macrophage-like cells stimulated with lipopolysaccharide (LPS). Additionally, we sought to determine whether EA can inhibit secretion of high-mobility group box 1 (HMGB1), a nuclear protein that is secreted by immunostimulated macrophages and functions in the extracellular milieu as a proinflammatory mediator. In a concentration-dependent manner, EA inhibited secretion of IL-6, IL-10, nitric oxide, and HMGB1. As expected, EA inhibited NF-kappaB DNA binding in LPS-stimulated RAW 264.7 cells. Treating these cells with pyrrolidine dithiocarbamate, SN50 (amino acid sequence AAVALLPAVLLALLAPVQRKRQKLMP) or 5-(thien-3-yl)-3-aminothiophene-2-carboxamide (SC-514) also inhibited LPS-induced NF-kappaB DNA binding, but these compounds failed to inhibit LPS-induced HMGB1 secretion. These findings suggested that inhibition of HMGB1 secretion by EA might occur via a mechanism unrelated to the NF-kappaB signaling pathway. Because EA is an electrophilic compound that is known to be capable of inducing expression of so-called phase 2 proteins, we sought to determine whether two other phase 2 enzyme inducers, oltipraz and DL-sulforaphane, also are capable of inhibiting HMGB1 release from immunostimulated macrophages. Incubating RAW 264.7 cells with either oltipraz or DL-sulforaphane inhibited LPS-induced HMGB1 secretion. Moreover, both EA and DL-sulforaphane inhibited relocalization of nuclear HMGB1 into the cytoplasm of LPS-stimulated RAW 264.7 cells. These data suggest that phase 2 inducers may exert anti-inflammatory effects by inhibiting secretion of the cytokine-like nuclear protein HMGB1.

HMGB1 is secreted by immunostimulated enterocytes and contributes to cytomix-induced hyperpermeability of Caco-2 monolayers.

High-mobility group box 1 (HMGB1), a cytokine-like proinflammatory protein, is secreted by activated macrophages and released by necrotic cells. We hypothesized that immunostimulated enterocytes might be another source for this mediator. Accordingly, Caco-2 cells or primary mouse intestinal epithelial cells (IECs) were incubated with "cytomix" (a mixture of TNF, IL-1beta, and IFN-gamma) for various periods. HMGB1 in cell culture supernatants was detected by Western blot analysis and visualized in Caco-2 cells with the use of fluorescence confocal and immunotransmission electron microscopy. Caco-2 cells growing on filters in diffusion chambers were stimulated with cytomix for 48 h in the absence or presence of anti-HMGB1 antibody, and permeability to fluorescein isothiocyanate-dextran (average molecular mass, 4 kDa; FD4) was assessed. Cytomix-stimulated Caco-2 cells secreted HMGB1 into the apical but not the basolateral compartments of diffusion chambers. Although undetectable at 6 and 12 h after the start of incubation with cytomix, HMGB1 was present in supernatants after 24 h of incubation. HMGB1 secretion by Caco-2 monolayers also was induced when the cells were exposed to FSL-1, a Toll-like receptor (Tlr)-2 agonist, or flagellin, a Tlr5 agonist, but not lipopolysaccharide, a Tlr4 agonist. Cytomix also induced HMGB1 secretion by primary IECs. Cytoplasmic HMGB1 is localized within vesicles in Caco-2 cells and is secreted, at least in part, associated with exosomes. Incubating Caco-2 cells with cytomix increased FD4 permeation, but this effect was significantly decreased in the presence of anti-HMGB1 antibody. Collectively, these data support the view that HMGB1 is secreted by immunostimulated enterocytes. This process may exacerbate inflammation-induced epithelial hyperpermeability via an autocrine feedback loop.