Neutrophil sequestration in liver and lung is differentially regulated by C-X-C chemokines during experimental peritonitis

Neutrophil Elastase Inhibitors Suppress Oxidative Stress in Lung during Liver Transplantation

Background

Neutrophil infiltration plays a critical role in the pathogenesis of acute lung injury following liver transplantation (LT). Neutrophil elastase is released from neutrophils during pulmonary polymorphonuclear neutrophil activation and sequestration. The aim of the study was to investigate whether the inhibition of neutrophil elastase could lead to the restoration of pulmonary function following LT.

Methods

In in vivo experiments, lung tissue and bronchoalveolar lavage fluid (BALF) were collected at 2, 4, 8, and 24 h after rats were subjected to orthotopic autologous LT (OALT), and neutrophil infiltration was detected. Next, neutrophil elastase inhibitors, sivelestat sodium hydrate (exogenous) and serpin family B member 1 (SERPINB1) (endogenous), were administered to rats before OALT, and neutrophil infiltration, pulmonary oxidative stress, and barrier function were measured at 8 h after OALT.

Results

Obvious neutrophil infiltration occurred from 2 h and peaked at 8 h in the lungs of rats after they were subjected to OALT, as evidenced by an increase in naphthol-positive cells, BALF neutrophil elastase activity, and lung myeloperoxidase activity. Treatment with neutrophil elastase inhibitors, either sivelestat sodium hydrate or SERPINB1, effectively reduced lung naphthol-positive cells and BALF inflammatory cell content, increased expression of lung HO-1 and tight junction proteins ZO-1 and occludin, and increased the activity of superoxide dismutase.

Conclusion

Neutrophil elastase inhibitors, sivelestat sodium hydrate and SERPINB1, both reduced lung neutrophil infiltration and pulmonary oxidative stress and finally restored pulmonary barrier function.

A Pathophysiological Insight into Sepsis and Its Correlation with Postmortem Diagnosis

BACKGROUND

Sepsis is among the leading causes of death worldwide and is the focus of a great deal of attention from policymakers and caregivers. However, sepsis poses significant challenges from a clinical point of view regarding its early detection and the best organization of sepsis care. Furthermore, we do not yet have reliable tools for measuring the incidence of sepsis. Methods based on analyses of insurance claims are unreliable, and postmortem diagnosis is still challenging since autopsy findings are often nonspecific.

AIM

The objective of this review is to assess the state of our knowledge of the molecular and biohumoral mechanisms of sepsis and to correlate them with our postmortem diagnosis ability.

CONCLUSION

The diagnosis of sepsis-related deaths is an illustrative example of the reciprocal value of autopsy both for clinicians and for pathologists. A complete methodological approach, integrating clinical data by means of autopsy and histological and laboratory findings aiming to identify and demonstrate the host response to infectious insults, is mandatory to illuminate the exact cause of death. This would help clinicians to compare pre- and postmortem findings and to reliably measure the incidence of sepsis.

IL-15 Superagonist Expands mCD8+ T, NK and NKT Cells after Burn Injury but Fails to Improve Outcome during Burn Wound Infection

Background

Severely burned patients are highly susceptible to opportunistic infections and sepsis, owing to the loss of the protective skin barrier and immunological dysfunction. Interleukin-15 (IL-15) belongs to the IL-2 family of common gamma chain cytokines and stimulates the proliferation and activation of T (specifically memory CD8), NK and NKT cells. It has been shown to preserve T cell function and improve survival during cecal ligation and puncture (CLP)-induced sepsis in mice. However, the therapeutic efficacy of IL-15 or IL-15 superagonist (SA) during infection after burn injury has not been evaluated. Moreover, very few, if any, studies have examined, in detail, the effect of burn injury and infection on the adaptive immune system. Thus, we examined the effect of burn and sepsis on adaptive immune cell populations and the effect of IL-15 SA treatment on the host response to infection.

Methods

Mice were subjected to a 35% total body surface area burn, followed by wound infection with Pseudomonas aeruginosa. In some experiments, IL-15 SA was administered after burn injury, but before infection. Leukocytes in spleen, liver and peritoneal cavity were characterized using flow cytometry. Bacterial clearance, organ injury and survival were also assessed.

Results

Burn wound infection led to a significant decline in total white blood cell and lymphocyte counts and induced organ injury and sepsis. Burn injury caused decline in CD4⁺ and CD8⁺ T cells in the spleen, which was worsened by infection. IL-15 treatment inhibited this decline and significantly increased cell numbers and activation, as determined by CD69 expression, of CD4⁺, CD8⁺, B, NK and NKT cells in the spleen and liver after burn injury. However, IL-15 SA treatment failed to prevent burn wound sepsis-induced loss of CD4⁺, CD8⁺, B, NK and NKT cells and failed to improve bacterial clearance and survival.

Conclusion

Cutaneous burn injury and infection cause significant adaptive immune dysfunction. IL-15 SA does not augment host resistance to burn wound sepsis in mice despite inducing proliferation and activation of lymphocyte subsets.

Anti-inflammatory effects of miR-21 in the macrophage response to peritonitis

We investigated the role of microRNA-21 in the macrophage response to peritonitis; microRNA-21 expression increases in peritoneal macrophages after lipopolysaccharide stimulation but is delayed until 48 hours after cecal ligation and puncture. MicroRNA-21-null mice and bone marrow-derived cell lines were exposed to cecal ligation and puncture or lipopolysaccharide, and survival, microRNA-21 levels, target messenger RNAs and proteins, and cytokines were assayed. Macrophages were also transfected with microRNA-21 mimics and antagomirs, and similar endpoints were measured. Survival in microRNA-21-null mice was significantly decreased after lipopolysaccharide-induced peritonitis but unchanged after cecal ligation and puncture compared with similarly treated wild-type mice. MicroRNA-21 expression, tumor necrosis factor-α, interleukin 6, and programmed cell death protein 4 levels were increased after lipopolysaccharide addition in peritoneal cells. Pelino1 and sprouty (SPRY) messenger RNAs were similarly increased early, whereas programmed cell death protein 4 messenger RNA was decreased after lipopolysaccharide, and all microR-21 target messenger RNAs were subsequently decreased by 24 hours after lipopolysaccharide. Transfection with mimics and antagomirs led to appropriate responses in microRNA-21 and tumor necrosis factor-α. Knockdown of microRNA-21 in bone marrow-derived cells showed increased tumor necrosis factor-α and decreased interleukin 10 in response to lipopolysaccharide. Target proteins were unaffected by knockdown as was extracellular signal-regulated kinase; however, the nuclear factor κB p65 subunit was increased after lipopolysaccharide in the microRNA-21 knockout cells. In contrast, there was little change in these parameters after cecal ligation and puncture induction between null and wild-type mice. MicroRNA-21 is beneficial to survival in mice following lipopolysaccharide peritonitis. Overexpression of microRNA-21 decreased tumor necrosis factor-α secretion, whereas suppression of microRNA-21 expression increased tumor necrosis factor-α and interleukin 6, and decreased interleukin 10 levels after lipopolysaccharide. Protein targets of microRNA-21 were not different following suppression of microRNA-21. Nuclear factor κB was increased by suppression of microRNA-21. These findings demonstrate microRNA-21 is beneficial in modulating the macrophage response to lipopolysaccharide peritonitis and an improved understanding of the anti-inflammatory effects of microRNA-21 may result in novel, targeted therapy against peritonitis and sepsis.

Transcriptomic analysis of peritoneal cells in a mouse model of sepsis: confirmatory and novel results in early and late sepsis

BACKGROUND

The events leading to sepsis start with an invasive infection of a primary organ of the body followed by an overwhelming systemic response. Intra-abdominal infections are the second most common cause of sepsis. Peritoneal fluid is the primary site of infection in these cases. A microarray-based approach was used to study the temporal changes in cells from the peritoneal cavity of septic mice and to identify potential biomarkers and therapeutic targets for this subset of sepsis patients.

RESULTS

We conducted microarray analysis of the peritoneal cells of mice infected with a non-pathogenic strain of Escherichia coli. Differentially expressed genes were identified at two early (1 h, 2 h) and one late time point (18 h). A multiplexed bead array analysis was used to confirm protein expression for several cytokines which showed differential expression at different time points based on the microarray data. Gene Ontology based hypothesis testing identified a positive bias of differentially expressed genes associated with cellular development and cell death at 2 h and 18 h respectively. Most differentially expressed genes common to all 3 time points had an immune response related function, consistent with the observation that a few bacteria are still present at 18 h.

CONCLUSIONS

Transcriptional regulators like PLAGL2, EBF1, TCF7, KLF10 and SBNO2, previously not described in sepsis, are differentially expressed at early and late time points. Expression pattern for key biomarkers in this study is similar to that reported in human sepsis, indicating the suitability of this model for future studies of sepsis, and the observed differences in gene expression suggest species differences or differences in the response of blood leukocytes and peritoneal leukocytes.

Protection against sepsis-induced lung injury by selective inhibition of protein kinase C-δ (δ-PKC)

Inflammation and proinflammatory mediators are activators of δ-PKC. In vitro, δ-PKC regulates proinflammatory signaling in neutrophils and endothelial and epithelial cells, cells that can contribute to lung tissue damage associated with inflammation. In this study, a specific δ-PKC TAT peptide inhibitor was used to test the hypothesis that inhibition of δ-PKC would attenuate lung injury in an animal model of ARDS. Experimental ARDS was induced in rats via 2CLP, a model of polymicrobial sepsis. Following 2CLP surgery, the δ-PKC TAT inhibitory peptide (2CLP+δ-PKC TAT in PBS) or PBS (2CLP+PBS) was administered intratracheally. Controls consisted of SO, where animals underwent a laparotomy without 2CLP. Twenty-four hours after SO or 2CLP, blood, BALF, and lung tissue were collected. 2CLP induced δ-PKC phosphorylation in the lung within 24 h. Treatment with the δ-PKC TAT inhibitory peptide significantly decreased pulmonary δ-PKC phosphorylation, indicating effective inhibition of δ-PKC activation. Plasma and BALF levels of the chemokines CINC-1 and MIP-2 were elevated in 2CLP + PBS rats as compared with SO rats. Treatment with δ-PKC TAT reduced 2CLP-induced elevations in chemokine levels in BALF and plasma, suggesting that δ-PKC modulated chemokine expression. Most importantly, intratracheal administration of δ-PKC TAT peptide significantly attenuated inflammatory cell infiltration, disruption of lung architecture, and pulmonary edema associated with 2CLP. Thus, δ-PKC is an important regulator of proinflammatory events in the lung. Targeted inhibition of δ-PKC exerted a lung-protective effect 24 h after 2CLP.

The effects of interleukin-1beta in tumor necrosis factor-alpha-induced acute pulmonary inflammation in mice

We determined the role of interleukin-1β (IL-1β) signaling on tumor necrosis factor alpha-induced (TNF-α) lung neutrophil influx as well as neutrophil chemoattractant macrophage inflammatory protein (MIP-2) and KC and soluble TNF-α receptor (TNFR) levels utilizing wildtype (WT), TNF receptor double knockout (TNFR1/TNFR2 KO), and IL-1β KO mice after oropharyngeal instillation with TNF-α. A significant increase in neutrophil accumulation in bronchoalveolar lavage fluid (BALF) and lung interstitium was detected in the WT mice six hours after TNF-α exposure. This correlated with an increase in BALF MIP-2. In contrast, BALF neutrophil numbers were not increased by TNF-α treatment of IL-1β KOs, correlating with a failure to induce BALF MIP-2 and a trend toward increased BALF soluble TNFR1. TNF-α-instillation increased lavage and serum KC and soluble TNFR2 irrespective of IL-1β expression. These results suggest IL-1β contributes, in part, to TNF-α-mediated, chemokine release, and neutrophil recruitment to the lung, potentially associated with altered soluble TNFR1 release into the BALF.

Intratracheal synthetic CpG oligodeoxynucleotide causes acute lung injury with systemic inflammatory response

Bacterial genome is characterized by frequent unmethylated cytosine-phosphate-guanine (CpG) motifs. Deleterious effects can occur when synthetic oligodeoxynucleotides (ODN) with unmethylated CpG dinucleotides (CpG-ODN) are administered in a systemic fashion. We aimed to evaluate the effect of intratracheal CpG-ODN on lung inflammation and systemic inflammatory response. C57BL/6J mice received intratracheal administration of CpG-ODN (0.01, 0.1, 1.0, 10, or 100 μM) or control ODN without CpG motif. Bronchoalveolar lavage (BAL) fluid was obtained 3 or 6 h or 1, 2, 7, or 14 days after the instillation and subjected to a differential cell count and cytokine measurement. Lung permeability was evaluated as the BAL fluid-to-plasma ratio of the concentration of human serum albumin that was injected 1 h before euthanasia. Nuclear factor (NF)-κB DNA binding activity was also evaluated in lung homogenates. Intratracheal administration of 10 μM or higher concentration of CpG-ODN induced significant inflammatory cell accumulation into the airspace. The peak accumulation of neutrophils and lymphocytes occurred 1 and 2 days after the CpG-ODN administration, respectively. Lung permeability was increased 1 day after the 10 μM CpG-ODN challenge. CpG-ODN also induced nuclear translocation of NF-κB and upregulation of various inflammatory cytokines in BAL fluid and plasma. Histopathology of the lungs and liver revealed acute lung injury and liver damage with necrosis, respectively. Control ODN without CpG motif did not induce any inflammatory change. Since intratracheal CpG-ODN induced acute lung injury as well as systemic inflammatory response, therapeutic strategies to neutralize bacterial DNA that is released after administration of bactericidal agents should be considered.

Thoracic epidural anesthesia time-dependently modulates pulmonary endothelial dysfunction in septic rats

Introduction

Increasing evidence indicates that epidural anesthesia improves postoperative pulmonary function. The underlying mechanisms, however, remain to be determined. Because pulmonary nitric oxide has been identified to play a critical role in pulmonary dysfunction in sepsis, we hypothesized that thoracic epidural anesthesia (TEA) modulates endothelial dysfunction via a nitric oxide-dependent pathway.

Methods

Thirty-six Sprague-Dawley rats underwent sham laparotomy or induction of peritoneal sepsis caused by cecal ligation and puncture (CLP). Septic animals were then treated with either bupivacaine 0.5% or normal saline epidurally (15 μl/h^-1) for 6 hours or 24 hours after injury. Previous experiments demonstrated that these time points correspond with a hyperdynamic (at 6 hours) and hypodynamic circulation (at 24 hours), respectively. In addition, two sham control groups received either bupivacaine 0.5% or normal saline epidurally (15 μl/h^-1). Six and 24 hours after injury, hemodynamic measurements and arterial blood gas analyses were performed in awake, spontaneously breathing rats. Exhaled nitric oxide, bradykinin-induced pulmonary vasoconstriction (a surrogate marker of endothelial dysfunction), pulmonary wet/dry-weight ratio (an estimate of pulmonary edema), and myeloperoxidase activity (MPO, a surrogate marker of neutrophil infiltration into lung tisssue) were investigated at 6 and 24 hours by using an established model of isolated and perfused lungs.

Results

In hyperdynamic sepsis, treatment with TEA resulted in reduced bradykinin-induced pulmonary vasoconstriction (P < 0.05) and lower levels of exhaled NO as compared with those in untreated septic rats (P < 0.05). However, the development of pulmonary edema or MPO activity in the lungs was not alleviated by sympathetic blockade in this phase of sepsis. Conversely, TEA led to an increased bradykinin-induced pulmonary vasoconstriction and pulmonary edema despite reduced exNO levels and pulmonary MPO activity in hypodynamic sepsis (each P < 0.05 versus CLP 24 h). Pulmonary gas exchange was only marginally affected under the influence of TEA in hypodynamic sepsis. Mean arterial pressure and heart rate were not affected beyond the changes caused by sepsis itself.

Conclusions

The results of the present study suggest that TEA modulates the NO pathway and exerts positive effects on pulmonary endothelial integrity only in hyperdynamic sepsis. Whether the negative effects on endothelial function in hypodynamic sepsis have an impact on overall morbidity and mortality remains to be determined in future studies.

An age-associated increase in pulmonary inflammation after burn injury is abrogated by CXCR2 inhibition

Burn patients over the age of 60 are at a greater risk for developing pulmonary complications than younger patients. The mechanisms for this, however, have yet to be elucidated. The objective of this study was to determine whether increased chemoattraction plays a role in the age-related differences in pulmonary inflammation after burn injury. At 6 or 24 h after receiving sham or 15% total body surface area scald injury, lungs from young and aged mice were analyzed for leukocyte content by histological examination and immunostaining. Lungs were then homogenized, and levels of neutrophil chemokines, MIP-2 and KC, were measured. At 6 h after burn, the number of neutrophils was four times higher in the lungs of both burn groups compared with aged-matched controls (P<0.05), but no age difference was evident. At 24 h, in contrast, neutrophils returned to sham levels in the lungs of young, burn-injured mice (P<0.05) but did not change in the lungs of aged, burn-injured mice. Pulmonary levels of the neutrophil chemokine KC but not MIP-2 were consistently three times higher in aged, burn-injured mice compared with young, burn-injured mice at both time-points analyzed. Administration with anti-CXCR2 antibody completely abrogated the excessive pulmonary neutrophil content by 24 h (P<0.05), while not affecting the inflammatory response of the wounds. These studies show that CXCR2-mediated chemoattraction is involved in the pulmonary inflammatory response after burn and suggest that aged individuals sustaining a burn injury may benefit from treatment strategies that target neutrophil chemokines.

A major ingredient of green tea rescues mice from lethal sepsis partly by inhibiting HMGB1

Background

The pathogenesis of sepsis is mediated in part by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (e.g., TNF, IL-1, and IFN-γ) and late (e.g., HMGB1) pro-inflammatory cytokines. Our recent discovery of HMGB1 as a late mediator of lethal sepsis has prompted investigation for development of new experimental therapeutics. We previously reported that green tea brewed from the leaves of the plant Camellia sinensis is effective in inhibiting endotoxin-induced HMGB1 release.

Methods and Findings

Here we demonstrate that its major component, (-)-epigallocatechin-3-gallate (EGCG), but not catechin or ethyl gallate, dose-dependently abrogated HMGB1 release in macrophage/monocyte cultures, even when given 2–6 hours post LPS stimulation. Intraperitoneal administration of EGCG protected mice against lethal endotoxemia, and rescued mice from lethal sepsis even when the first dose was given 24 hours after cecal ligation and puncture. The therapeutic effects were partly attributable to: 1) attenuation of systemic accumulation of proinflammatory mediator (e.g., HMGB1) and surrogate marker (e.g., IL-6 and KC) of lethal sepsis; and 2) suppression of HMGB1-mediated inflammatory responses by preventing clustering of exogenous HMGB1 on macrophage cell surface.

Conclusions

Taken together, these data suggest a novel mechanism by which the major green tea component, EGCG, protects against lethal endotoxemia and sepsis.

Heterogeneity of endothelial cells from different organ sites in T-cell subset recruitment

Chemokines and adhesion molecules play a critical role in the recruitment of leukocytes into specific organ sites. Little is known, however, regarding the repertoire of chemokines and adhesion molecules expressed within different vascular beds. In this study, we compare adhesion molecule expression, chemokine induction, and T-cell subset-endothelial interactions under defined flow conditions on resting and tumor necrosis factor (TNF)-alpha-activated murine lung endothelial cells (MLECs) and heart endothelial cells (MHECs). Our study revealed that only MHECs exhibited high constitutive VCAM-1 expression. Exposure to TNF-alpha up-regulated adhesion molecule expression and chemokine production in both MLECs and MHECs. However, high levels of Regulated on Activation Normal T cell Expressed And Secreted (RANTES) expression were detected only in TNF-alpha-activated MHECs. TNF-alpha-stimulated MLECs and MHECs both supported T-helper cell interactions under defined flow conditions. Most T cells instantaneously arrested on MHECs but exhibited a rolling phenotype on MLECs. Blocking studies revealed that T-cell arrest on MHECs was mediated by constitutive VCAM-1 and TNF-alpha-induced RANTES. These findings are consistent with the hypothesis that functional heterogeneity of endothelial cells from different sites exists and some of it is retained in vitro. Furthermore, these results provide an insight into the molecular mechanisms that may mediate T-helper cell recruitment to these organs.

CXC chemokine redundancy ensures local neutrophil recruitment during acute inflammation

Previous publications demonstrated that elevated systemic levels of interleukin (IL)-8 decrease local neutrophil recruitment. We tested whether sustained, high plasma levels of IL-8 would prevent local inflammation after inflammatory insults. Mice carrying the transgene for human IL-8 were separated on the basis of their plasma levels of IL-8 into IL-8-positive (plasma levels >90 ng/ml) and IL-8-negative (IL-8 below detection). Presence of the IL-8 transgene did not improve survival or morbidity nor did it alter peritoneal neutrophil recruitment induced by the cecal ligation and puncture model of sepsis. In an acute lung injury model created by intratracheal injection of acid, IL-8-positive mice showed no reduction in alveolar neutrophil recruitment. There was no difference in the local recruitment of neutrophils when either thioglycollate or glycogen was injected intraperitoneally. We examined the chemotactic response to murine chemokines to test how neutrophil recruitment occurs in the setting of elevated plasma IL-8 and found that neutrophils from both IL-8-positive and -negative mice respond equally well to recombinant KC or macrophage inflammatory protein (MIP)-2. We measured KC and MIP-2 in the peritoneum after thioglycollate injection and demonstrated that IL-8-positive mice have significantly higher levels of the chemokines compared to the IL-8-negative mice. Antibody inhibition of KC and MIP-2 in the IL-8-positive mice significantly decreased peritoneal neutrophil recruitment in response to thioglycollate, clarifying their important role in the local neutrophil recruitment. Our data demonstrate that despite the presence of high plasma levels of IL-8, neutrophils may still be recruited to sites of local inflammation because of chemokine redundancy.