Contribution of high-mobility group box-1 to the development of ventilator-induced lung injury

Therapeutic potential of HMGB1-targeting agents in sepsis

Sepsis refers to a systemic inflammatory response syndrome resulting from a microbial infection. The inflammatory response is partly mediated by innate immune cells (such as macrophages, monocytes and neutrophils), which not only ingest and eliminate invading pathogens but also initiate an inflammatory response upon recognition of pathogen-associated molecular patterns (PAMPs). The prevailing theories of sepsis as a dysregulated inflammatory response, as manifested by excessive release of inflammatory mediators such as tumour necrosis factor and high-mobility group box 1 protein (HMGB1), are supported by extensive studies employing animal models of sepsis. Here we review emerging evidence that support extracellular HMGB1 as a late mediator of experimental sepsis, and discuss the therapeutic potential of several HMGB1-targeting agents (including neutralising antibodies and steroid-like tanshinones) in experimental sepsis.

Potential role of high-mobility group box 1 in cystic fibrosis airway disease

RATIONALE

High-mobility group box 1 (HMGB1) is a potent inflammatory mediator elevated in sepsis and rheumatoid arthritis, although its role in cystic fibrosis (CF) lung disease is unknown.

OBJECTIVES

To determine whether HMGB1 contributes to CF lung inflammation, including neutrophil chemotaxis and lung matrix degradation.

METHODS

We used sputum and serum from subjects with CF and a Scnn1b-transgenic (Scnn1b-Tg) mouse model that overexpresses beta-epithelial Na(+) channel in airways and mimics the CF phenotype, including lung inflammation. Human secretions and murine bronchoalveolar lavage fluid (BALF) was assayed for HMGB1 by Western blot and ELISA. Neutrophil chemotaxis was measured in vitro after incubation with human neutrophils. The collagen fragment proline-glycine-proline (PGP) was measured by tandem mass spectroscopy.

MEASUREMENTS AND MAIN RESULTS

HMGB1 was detected in CF sputum at higher levels than secretions from normal individuals. Scnn1b-Tg mice had elevated levels of HMGB1 by Western blot and ELISA. We demonstrated that dose-dependent chemotaxis of human neutrophils stimulated by purified HMGB1 was partially dependent on CXC chemokine receptors and that this could be duplicated in CF sputum and BALF from Scnn1b-Tg mice. Neutralization by anti-HMGB1 antibody, in both the sputum and BALF-reduced chemotaxis, which suggested that HMGB1 contributed to the chemotactic properties of these samples. Intratracheal administration of purified HMGB1 induced neutrophil influx into the airways of mice and promoted the release of PGP. PGP was also elevated in Scnn1b-Tg mice and CF serum.

CONCLUSIONS

HMGB1 expression contributes to pulmonary inflammation and lung matrix degradation in CF airway disease and deserves further investigation as a biomarker and potential therapeutic target.

Effects of HMGB1 on ischemia-reperfusion injury in the rat heart

BACKGROUND

Coronary ischemia-reperfusion (I/R) injury causes cardiomyocyte necrosis in a multi-step process that includes an inflammatory reaction. A recent study has suggested that high-mobility group box 1 (HMGB1) is a late mediator of lethal sepsis and an early mediator of inflammation and necrosis following I/R injury. In the present study a neutralizing monoclonal antibody (mAb) for HMGB1 was used to clarify the role of HMGB1 in cardiac I/R injury.

METHODS AND RESULTS

Rats underwent 30 min of left coronary artery occlusion followed by 60 min reperfusion. An intravenous injection of anti-HMGB1 mAb or control IgG was administered just before reperfusion. The infarct size was enlarged in the anti-HMGB1 mAb group in comparison with the control group (p<0.05). The treatment of anti-HMGB1 mAb significantly increased the plasma troponin-T and norepinephrine (NE) content in the heart in comparison with the control (p<0.05). Moreover, the production of dihydroxyphenylglycol was reduced in the anti-HMGB1-treated group (p<0.05).

CONCLUSION

This study shows for the first time the effects of treatment with neutralizing anti-HMGB1 mAb on I/R injury in the rat heart. The findings support the novel view that I/R-induced HMGB1 may be an important factor in the modulation of interstitial NE.

High mobility group protein-1 inhibits phagocytosis of apoptotic neutrophils through binding to phosphatidylserine

Phagocytosis of apoptotic cells, also called efferocytosis, is an essential feature of immune responses and critical to resolution of inflammation. Impaired efferocytosis is associated with an unfavorable outcome from inflammatory diseases, including acute lung injury and pulmonary manifestations of cystic fibrosis. High mobility group protein-1 (HMGB1), a nuclear nonhistone DNA-binding protein, has recently been found to be secreted by immune cells upon stimulation with LPS and cytokines. Plasma and tissue levels of HMGB1 are elevated for prolonged periods in chronic and acute inflammatory conditions, including sepsis, rheumatoid arthritis, acute lung injury, burns, and hemorrhage. In this study, we found that HMGB1 inhibits phagocytosis of apoptotic neutrophils by macrophages in vivo and in vitro. Phosphatidylserine (PS) is directly involved in the inhibition of phagocytosis by HMGB1, as blockade of HMGB1 by PS eliminates the effects of HMGB1 on efferocytosis. Confocal and fluorescence resonance energy transfer demonstrate that HMGB1 interacts with PS on the neutrophil surface. However, HMGB1 does not inhibit PS-independent phagocytosis of viable neutrophils. Bronchoalveolar lavage fluid from Scnn(+) mice, a murine model of cystic fibrosis lung disease which contains elevated concentrations of HMGB1, inhibits neutrophil efferocytosis. Anti-HMGB1 Abs reverse the inhibitory effect of Scnn(+) bronchoalveolar lavage on efferocytosis, showing that this effect is due to HMGB1. These findings demonstrate that HMGB1 can modulate phagocytosis of apoptotic neutrophils and suggest an alternative mechanism by which HMGB1 is involved in enhancing inflammatory responses.

Exacerbation of bleomycin-induced injury and fibrosis by pneumonectomy in the residual lung of mice

BACKGROUND

Lung resection after induction chemotherapy and/or radiotherapy for down-staging of locally advanced lung cancer can be complicated with lethal interstitial pneumonia. We studied the effects of pneumonectomy on bleomycin-induced lung injury and fibrosis in mice.

METHODS

The mice underwent left pneumonectomy or a sham thoracotomy after intratracheal administration of saline or bleomycin. Lung permeability index, wet-to-dry weight ratio, histological changes, collagen contents, and concentrations of inflammatory mediators and cell counts in broncho-alveolar lavage (BAL) fluid were assessed in the residual right lung 7 d after surgery.

RESULTS

The index of capillary permeability, lung water content, and inflammatory cell counts in BAL fluid were significantly increased by pneumonectomy. These measurements were highest in the mice with both pneumonectomy and intratracheal administration of bleomycin. Similarly, fibrotic change in lung pathology, as well as an increase in lung collagen content, was most prominent in the mice exposed to both interventions. The BAL fluid concentrations of interleukin-1beta, interleukin-6, RANTES, and high mobility group box 1 were significantly increased by pneumonectomy and enhanced by the additional administration of bleomycin.

CONCLUSIONS

The results of this study indicate that pneumonectomy alone causes noncritical lung injury, which amplifies the inflammatory response to bleomycin and promotes lung fibrosis. Several inflammatory mediators appear to be involved in the exacerbation of bleomycin-induced lung injury and fibrosis.

Role of soluble receptor for advanced glycation end products on endotoxin-induced lung injury

RATIONALE

The interaction of receptor for advanced glycation end products (RAGE) and its ligands often leads to inflammatory processes or tissue injury, although the effect of the blockade of RAGE signaling on lung injury remains to be investigated.

OBJECTIVES

Using a murine model of lung injury induced by intratracheal lipopolysaccharide (LPS), we evaluated RAGE expression in the airspace and the effect of recombinant soluble RAGE (sRAGE) on LPS-induced lung injury.

METHODS

First, the expression of sRAGE in bronchoalveolar lavage (BAL) fluid was determined at 24 hours after intratracheal instillation of LPS or phosphate-buffered saline. Next, to evaluate the effect of sRAGE, BAL fluid was collected for cell counting and measurements of lung permeability and cytokine concentrations 24 hours after intratracheal LPS in the mice with or without intraperitoneal administration of sRAGE 1 hour after the instillation. In another series, lungs were sampled for histopathology and detection of apoptotic cells. The activation of nuclear factor (NF)-kappaB was analyzed 4 hours after LPS instillation.

MEASUREMENTS AND MAIN RESULTS

In response to LPS challenge, a RAGE isoform of 48 kD was detected in the BAL fluid. Treatment with sRAGE significantly attenuated the increases in neutrophil infiltration, lung permeability, production of inflammatory cytokines, NF-kappaB activation, and apoptotic cells in the lung as well as development of pathologic changes after LPS instillation.

CONCLUSIONS

RAGE plays an important role in the pathogenesis of LPS-induced lung injury in mice. It was suggested that sRAGE should be tested as a treatment modality in other models of acute lung injury.

HMGB1 as a predictor of organ dysfunction and outcome in patients with severe sepsis

OBJECTIVE

To study the predictive value of high mobility group box-1 protein (HMGB1) and hospital mortality in adult patients with severe sepsis.

STUDY DESIGN

Prospective observational cohort study in 24 ICUs in Finland.

PATIENTS

Two hundred and forty-seven adult patients with severe sepsis.

MEASUREMENTS AND MAIN RESULTS

Blood samples for HMGB1 analyses were drawn from 247 patients at baseline and from 210 patients 72 h later. The mean APACHE II and SAPS II scores were 24 (SD 9) and 44 (SD 17), respectively. The hospital mortality was 26%. The serum HMGB1 concentrations were measured first by semi-quantitative Western immunoblotting (WB) analysis. The median HMGB1 concentration on day 0 was 108% (IQR 98.5-119) and after 72 h 107% (IQR 98.8-120), which differed from healthy controls (97.5%, IQR 91.3-106.5; p=0.028 and 0.019, respectively). The samples were re-analysed by ELISA (in a subgroup of 170 patients) to confirm the results by WB. The median concentration in healthy controls was 0.65 ng/ml (IQR 0.51-1.0). This was lower than in patients with severe sepsis (3.6 ng/ml, IQR 1.9-6.5, p< 0.001). HMGB1 concentrations (WB and ELISA) did not differ between hospital survivors and non-survivors. In ROC analyses for HMGB1 levels (WB) on day 0 and 72 h with respect to hospital mortality, the areas under the curve were 0.51 and 0.56 (95% CI 0.40-0.61 and 0.47-0.65).

CONCLUSIONS

Serum HMGB1 concentrations were elevated in patients with severe sepsis, but did not differ between survivors and non-survivors and did not predict hospital mortality.

HMGB1 develops enhanced proinflammatory activity by binding to cytokines

High mobility group box 1 protein (HMGB1), originally characterized as a nuclear DNA-binding protein, has also been described to have an extracellular role when it is involved in cellular activation and proinflammatory responses. In this study, FLAG-tagged HMGB1 was inducibly expressed in the presence of culture media with or without added IL-1beta, IFN-gamma, or TNF-alpha. HMGB1 purified from cells grown in culture media alone only minimally increased cytokine production by MH-S macrophages and had no effect on murine neutrophils. In contrast, HMGB1 isolated from cells cultured in the presence of IL-1beta, IFN-gamma, and TNF-alpha had enhanced proinflammatory activity, resulting in increased production of MIP-2 and TNF-alpha by exposed cells. IL-1beta was bound to HMGB1 isolated from cells cultured with this cytokine, and purified HMGB1 incubated with recombinant IL-1beta acquired proinflammatory activity. Addition of anti-IL-1beta Abs or the IL-1 receptor antagonist to cell cultures blocked the proinflammatory activity of HMGB1 purified from IL-1beta-exposed cells, indicating that such activity was dependent on interaction with the IL-1 receptor. These results demonstrate that HMGB1 acquires proinflammatory activity through binding to proinflammatory mediators, such as IL-1beta.

Mechanical ventilation and hemorrhagic shock-resuscitation interact to increase inflammatory cytokine release in rats

OBJECTIVE

To determine whether hemorrhagic shock and resuscitation (HSR) and high lung stress during mechanical ventilation interact to augment lung and systemic inflammatory responses and whether their sequence affects these responses.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Research laboratory.

SUBJECTS

Fifty-six male Wistar rats.

INTERVENTIONS

Controls were immediately killed after anesthesia. High lung stress was produced by mechanical ventilation with high tidal volume of 30 mL/kg and no positive end-expiratory pressure (HV) for 2 hrs. HSR consisted of lessening systemic arterial pressure to 30 mm Hg for 1 hr followed by reinjection of the withdrawn blood. Experimental groups consisted of HSR only and HSR preceded or followed by HV or conventional mechanical ventilation.

MEASUREMENTS AND MAIN RESULTS

Interleukin-1beta, interleukin-6, and macrophage inhibitory protein 2 were determined in lung homogenate, bronchoalveolar lavage fluid, and plasma. HV ventilation alone did not increase plasma or lung cytokine content compared with controls. HSR significantly increased all mediators in lungs and plasma but not macrophage inhibitory protein 2 in plasma. Conventional ventilation, applied either before or after HSR, did not influence lung or systemic mediator release, whereas HV significantly increased mediator release when combined with HSR whatever the sequence of injuries. Lung mediator content was significantly higher in animals ventilated with HV before the HSR stress than in animals submitted to HSR and then ventilated with HV. Plasma macrophage inhibitory protein 2 concentrations followed the same pattern.

CONCLUSIONS

This study shows that HSR and high lung tissue stress interact to increase lung and systemic release of inflammatory mediators in a way that depends on their sequence. Previous injury may sensitize lungs to inadequate mechanical ventilation, but inadequate mechanical ventilation may also sensitize lungs to postoperative complications.

High-mobility group box 1 (HMGB1) protein at the crossroads between innate and adaptive immunity

Tissue damage occurs often in the life of mammals and is usually repaired. Dying cells are swiftly phagocytosed, but before disappearing, they alert surrounding cells to activate homeostatic programs. They release signals that recruit inflammatory cells to the site of injury, promote cell migration and cell division to replace dead cells, and activate the immune system in anticipation of microbial invasion. Many of these events involve high-mobility group box 1 protein (HMGB1), a nuclear protein that is released passively when necrotic cells lose the integrity of their membranes. HMGB1 behaves as a trigger of inflammation, attracting inflammatory cells, and of tissue repair, recruiting stem cells and promoting their proliferation. Moreover, HMGB1 activates dendritic cells (DCs) and promotes their functional maturation and their response to lymph node chemokines. Activated leukocytes actively secrete HMGB1 in the microenvironment. Thus, HMGB1 acts in an autocrine/paracrine fashion and sustains long-term repair and defense programs. DCs secrete HMGB1 several hours after contact with the first maturation stimulus; HMGB1 secretion is critical for their ability to reach the lymph nodes, to sustain the proliferation of antigen-specific T cells, to prevent their activation-dependent apoptosis, and to promote their polarization towards a T-helper 1 phenotype. These immune responses will also be directed against self-antigens that DCs process at the time of injury and can lead to autoimmunity.

Systemic and local high mobility group box 1 concentrations during severe infection

OBJECTIVE

High mobility group box 1 (HMGB1) has been implicated as a late mediator in sepsis. We here sought to determine the extent of HMGB1 release in patients with sepsis stratified to the three most common infectious sources and to determine HMGB1 concentrations at the site of infection during peritonitis or pneumonia.

DESIGN

Observational studies in patients and healthy humans challenged with lipopolysaccharide.

SETTING

Three intensive care units and one clinical research unit.

PATIENTS AND SUBJECTS

Three patient populations were studied: 1) 51 patients with sepsis due to pneumonia (n = 29), peritonitis (n = 12), or urinary tract infection (n = 10); 2) 17 patients with peritonitis; and 3) four patients with community-acquired pneumonia. In addition, eight healthy subjects were studied after intravenous injection of lipopolysaccharide (4 ng/kg).

INTERVENTIONS

One population of healthy volunteers received lipopolysaccharide intravenously.

MEASUREMENTS AND MAIN RESULTS

Patients with severe sepsis due to pneumonia displayed elevated circulating HMGB1 concentrations at both days 0 and 3 after inclusion. Patients with sepsis due to peritonitis had elevated HMGB1 levels at day 0 but not at day 3, whereas urinary tract infection was associated with a delayed HMGB1 response, with elevated levels only at day 3. HMGB1 concentrations did not differ between survivors and nonsurvivors and were not correlated to either disease severity or concurrently measured cytokine levels. In line with these observations, although intravenous lipopolysaccharide injection clearly elevated plasma cytokine levels, HMGB1 remained undetectable. In patients with peritonitis, HMGB1 concentrations in abdominal fluid were more than ten-fold higher than in concurrently obtained plasma. In pneumonia patients, HMGB1 levels were higher in bronchoalveolar lavage fluid obtained from the site of infection than in lavage fluid from healthy controls.

CONCLUSIONS

In severe sepsis, the kinetics of HMGB1 release may differ depending on the primary source of infection. In patients with severe infection, HMGB1 release may predominantly occur at the site of infection.

Systemic inflammation and remote organ injury following trauma require HMGB1

High-mobility group box 1 (HMGB1) is a 30-kDa DNA-binding protein that displays proinflammatory cytokine-like properties. HMGB1-dependent inflammatory processes have been demonstrated in models of sterile injury, including ischemia-reperfusion injury and hemorrhagic shock. Here, we tested the hypothesis that the systemic inflammatory response and associated remote organ injury that occur after peripheral tissue injury are highly dependent on HMGB1. Toll-like receptor 4 (TLR4) wild-type (WT) mice subjected to bilateral femur fracture after treatment with neutralizing antibodies to HMGB1 had lower serum IL-6 and IL-10 levels compared with mice treated with nonimmune control IgG. Similarly, compared with injured mice treated with control IgG, anti-HMGB1 antibody-treated mice had lower serum alanine aminotransferase levels and decreased hepatic and gut mucosal NF-κB DNA binding. TLR4 mutant (C3H/HeJ) mice subjected to bilateral femur fracture had less systemic inflammation and liver injury than WT controls. Residual trauma-induced systemic inflammation and hepatocellular injury were not ameliorated by treatment with a polyclonal anti-HMGB1 antibody, even though HMGB1 levels were transiently elevated just 1 h after injury in both WT and C3H/HeJ mice. Collectively, these data demonstrate a critical role for a TLR4-HMGB1 pathway in the initiation of systemic inflammation and end-organ injury following isolated peripheral tissue injury.

Inhibition of neutrophil elastase attenuates gut mucosal injury evoked by acute alveolar hypoxia in rabbits

The aim of the present study was to examine whether neutrophil and its elastase activity played consequential roles in the progression of gut barrier dysfunction during acute alveolar hypoxia by using a specific neutrophil elastase inhibitor, sivelestat. With our institutional approval, 20 male rabbits (weight, 2.0-2.5 kg) were randomly allocated into two groups: control (n = 11) or sivelestat group (n = 9; bolus, 10 mg/kg, followed by 10 mg/kg per hour). At 4 h of alveolar hypoxia exposure (fraction of inspired oxygen, 0.10) under mechanical ventilation, the white blood cell counts and their function to produce oxygen radicals were measured. Intestinal permeability and myeloperoxidase activity were also assessed concurrently with the examination of histological changes of gut mucosa. The examination of sham animals (n = 4) exposed to normoxia was performed under the same study protocol. The circulating leukocyte counts and the neutrophil chemiluminescence were not different between the groups, whereas the neutrophil elastase activity was significantly increased in the control but not in the sivelestat and sham groups. Permeability, leukocyte accumulation, and myeloperoxidase activity of ileal wall in the control group were significantly elevated, accompanied by apparent destruction of gut mucosa compared with the sivelestat group (P < 0.05). Despite no significant differences in systemic inflammatory responses, the neutrophil elastase activity is a key element in the progression of functional and structural injury of gut mucosa during acute alveolar hypoxia.

HMGB1 and LPS induce distinct patterns of gene expression and activation in neutrophils from patients with sepsis-induced acute lung injury

OBJECTIVES

Circulating levels of the proinflammatory mediator High Mobility Group Box Protein 1 (HMGB1) are increased in septic patients and may contribute to sepsis-induced organ dysfunction. Although HMGB1 has been shown to activate neutrophils from healthy volunteers, the responses of neutrophils from septic patients to HMGB1 have not been reported. In the present study we evaluated gene expression and activation of major intracellular signaling pathways in peripheral blood neutrophils obtained from patients with sepsis-induced acute lung injury after culture with HMGB1 or LPS.

DESIGN

Ex-vivo study performed in neutrophils from patients with sepsis-induced acute lung injury.

SETTING

Immunology and genetics laboratory at an academic medical center.

PATIENTS AND PARTICIPANTS

Twenty-two adult patients with sepsis-induced acute lung injury.

MEASUREMENTS AND RESULTS

Using gene arrays, distinct patterns of gene expression were found in neutrophils from septic patients after stimulation with HMGB1 or LPS. While more than three-quarters of the genes upregulated by HMGB1 in neutrophils from septic patients also demonstrated increased expression after culture with LPS, the majority of genes affected by LPS did not show altered expression in neutrophils stimulated with HMGB1. Culture of neutrophils with HMGB1 induced downregulation of its own expression, a finding not present after exposure to LPS. Although HMGB1 and LPS both increased nuclear translocation of NF-kappaB, the magnitude of this effect was greater in LPS stimulated neutrophils from patients with sepsis-induced acute lung injury.

CONCLUSION

These findings demonstrate that the patterns of gene expression differ between neutrophils from septic patients stimulated with HMGB1 or LPS, and also that neutrophils from septic patients are not anergic but instead demonstrate intact activation of NF-kappaB after exposure to LPS or HMGB1.

HMGB1 and LPS induce distinct patterns of gene expression and activation in neutrophils from patients with sepsis-induced acute lung injury

OBJECTIVES

Circulating levels of the proinflammatory mediator High Mobility Group Box Protein 1 (HMGB1) are increased in septic patients and may contribute to sepsis-induced organ dysfunction. Although HMGB1 has been shown to activate neutrophils from healthy volunteers, the responses of neutrophils from septic patients to HMGB1 have not been reported. In the present study we evaluated gene expression and activation of major intracellular signaling pathways in peripheral blood neutrophils obtained from patients with sepsis-induced acute lung injury after culture with HMGB1 or LPS.

DESIGN

Ex-vivo study performed in neutrophils from patients with sepsis-induced acute lung injury.

SETTING

Immunology and genetics laboratory at an academic medical center.

PATIENTS AND PARTICIPANTS

Twenty-two adult patients with sepsis-induced acute lung injury.

MEASUREMENTS AND RESULTS

Using gene arrays, distinct patterns of gene expression were found in neutrophils from septic patients after stimulation with HMGB1 or LPS. While more than three-quarters of the genes upregulated by HMGB1 in neutrophils from septic patients also demonstrated increased expression after culture with LPS, the majority of genes affected by LPS did not show altered expression in neutrophils stimulated with HMGB1. Culture of neutrophils with HMGB1 induced downregulation of its own expression, a finding not present after exposure to LPS. Although HMGB1 and LPS both increased nuclear translocation of NF-kappaB, the magnitude of this effect was greater in LPS stimulated neutrophils from patients with sepsis-induced acute lung injury.

CONCLUSION

These findings demonstrate that the patterns of gene expression differ between neutrophils from septic patients stimulated with HMGB1 or LPS, and also that neutrophils from septic patients are not anergic but instead demonstrate intact activation of NF-kappaB after exposure to LPS or HMGB1.

Alveolar edema dispersion and alveolar protein permeability during high volume ventilation: effect of positive end-expiratory pressure

OBJECTIVES

To evaluate whether PEEP affects intrapulmonary alveolar edema liquid movement and alveolar permeability to proteins during high volume ventilation.

DESIGN AND SETTING

Experimental study in an animal research laboratory.

SUBJECTS

46 male Wistar rats.

INTERVENTIONS

A (99m)Tc-labeled albumin solution was instilled in a distal airway to produce a zone of alveolar flooding. Conventional ventilation (CV) was applied for 30 min followed by various ventilation strategies for 3 h: CV, spontaneous breathing, and high volume ventilation with different PEEP levels (0, 6, and 8 cmH(2)O) and different tidal volumes. Dispersion of the instilled liquid and systemic leakage of (99m)Tc-albumin from the lungs were studied by scintigraphy.

MEASUREMENTS AND RESULTS

The instillation protocol produced a zone of alveolar flooding that stayed localized during CV or spontaneous breathing. High volume ventilation dispersed alveolar liquid in the lungs. This dispersion was prevented by PEEP even when tidal volume was the same and thus end-inspiratory pressure higher. High volume ventilation resulted in the leakage of instilled (99m)Tc-albumin from the lungs. This increase in alveolar albumin permeability was reduced by PEEP. Albumin permeability was more affected by the amplitude of tidal excursions than by overall lung distension.

CONCLUSIONS

PEEP prevents the dispersion of alveolar edema liquid in the lungs and lessens the increase in alveolar albumin permeability due to high volume ventilation.

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

AIM: To examine the effects of anti-high mobility group box 1 (HMGB1) neutralizing antibody in experimental severe acute pancreatitis (SAP).

METHODS: SAP was induced by creating closed duodenal loop in C3H/HeN mice. SAP was induced immediately after intraperitoneal injection of anti-HMGB1 neutralizing antibody (200 μg). Severity of pancreatitis, organ injury (liver, kidney and lung), and bacterial translocation to pancreas was examined 12 h after induction of SAP.

RESULTS: Anti-HMGB1 neutralizing antibody significantly improved the elevation of the serum amylase level and the histological alterations of pancreas and lung in SAP. Anti-HMGB1 antibody also significantly ameliorated the elevations of serum alanine aminotransferase and creatinine in SAP. However, anti-HMGB1 antibody worsened the bacterial translocation to pancreas.

CONCLUSION: Blockade of HMGB1 attenuated the development of SAP and associated organ dysfunction, suggesting that HMGB1 may act as a key mediator for inflammatory response and organ injury in SAP.