Beneficial Versus Detrimental Effects of Neutrophils Are Determined by the Nature of the Insult

Multilevel omics for the discovery of biomarkers in pediatric sepsis

Severe sepsis causes organ dysfunction and continues to be the leading reason for pediatric death worldwide. Early recognition of sepsis could substantially promote precision treatment and reduce the risk of pediatric death. The host cellular response to infection during sepsis between adults and pediatrics could be significantly different. A growing body of studies focused on finding markers in pediatric sepsis in recent years using multi-omics approaches. This narrative review summarized the progress in studying pediatric sepsis biomarkers from genome, transcript, protein, and metabolite levels according to the omics technique that has been applied for biomarker screening. It is most likely not a single biomarker could work for precision diagnosis of sepsis, but a panel of markers and probably a combination of markers detected at multi-levels. Importantly, we emphasize the importance of group distinction of infectious agents in sepsis patients for biomarker identification, because the host response to infection of bacteria, virus, or fungus could be substantially different and thus the results of biomarker screening. Further studies on the investigation of sepsis biomarkers that were caused by a specific group of infectious agents should be encouraged in the future, which will better improve the clinical execution of personalized medicine for pediatric sepsis.

Sex differences in the inflammatory response to stroke

Ischemic stroke is a leading cause of morbidity and mortality and disproportionally affects women, in part due to their higher longevity. Older women have poorer outcomes after stroke with high rates of cognitive deficits, depression, and reduced quality of life. Post-stroke inflammatory responses are also sexually dimorphic and drive differences in infarct size and recovery. Factors that influence sex-specific immune responses can be both intrinsic and extrinsic. Differences in gonadal hormone exposure, sex chromosome compliment, and environmental/social factors can drive changes in transcriptional and metabolic profiles. In addition, how these variables interact, changes across the lifespan. After the onset of ischemic injury, necrosis and apoptosis occur, which activate microglia and other glial cells within the central nervous system, promoting the release of cytokines and chemokines and neuroinflammation. Cells involved in innate and adaptive immune responses also have dual functions after stroke as they can enhance inflammation acutely, but also contribute to suppression of the inflammatory cascade and later repair. In this review, we provide an overview of the current literature on sex-specific inflammatory responses to ischemic stroke. Understanding these differences is critical to identifying therapeutic options for both men and women.

Sex-Specific Immune Responses in Stroke

In both acute and chronic diseases, functional differences in host immune responses arise from a multitude of intrinsic and extrinsic factors. Two of the most important factors affecting the immune response are biological sex and aging. Ischemic stroke is a debilitating disease that predominately affects older individuals. Epidemiological studies have shown that older women have poorer functional outcomes compared with men, in part due to the older age at which they experience their first stroke and the increased comorbidities seen with aging. The immune response also differs in men and women, which could lead to altered inflammatory events that contribute to sex differences in poststroke recovery. Intrinsic factors including host genetics and chromosomal sex play a crucial role both in shaping the host immune system and in the neuroimmune response to brain injury. Ischemic stroke leads to altered intracellular communication between astrocytes, neurons, and resident immune cells in the central nervous system. Increased production of cytokines and chemokines orchestrate the infiltration of peripheral immune cells and promote neuroinflammation. To maintain immunosurveillance, the host immune and central nervous system are highly regulated by a diverse population of immune cells which are strategically distributed within the neurovascular unit and become activated with injury. In this review, we provide a comprehensive overview of sex-specific host immune responses in ischemic stroke.

A place for neutrophils in the beneficial pathogen-agnostic effects of the BCG vaccine

The BCG vaccine has long been recognized for reducing the risk to suffer from infectious diseases unrelated to its target disease, tuberculosis. Evidence from human trials demonstrate substantial reductions in all-cause mortality, especially in the first week of life. Observational studies have identified an association between BCG vaccination and reduced risk of respiratory infectious disease and clinical malaria later in childhood. The mechanistic basis for these pathogen-agnostic benefits, also known as beneficial non-specific effects (NSE) of BCG have been attributed to trained immunity, or epigenetic reprogramming of hematopoietic cells that give rise to innate immune cells responding more efficiently to a broad range of pathogens. Furthermore, within trained immunity, the focus so far has been on enhanced monocyte function. However, polymorphonuclear cells, namely neutrophils, are not only major constituents of the hematopoietic compartment but functionally as well as numerically represent a prominent component of the immune system. The beneficial NSEs of the BCG vaccine on newborn sepsis was recently demonstrated to be driven by a BCG-mediated numeric increase of neutrophils (emergency granulopoiesis (EG)). And experimental evidence in animal models suggest that BCG can modulate neutrophil function as well. Together, these findings suggest that neutrophils are crucial to at least the immediate beneficial NSE of the BCG vaccine. Efforts to uncover the full gamut of mechanisms underpinning the broad beneficial effects of BCG should therefore include neutrophils at the forefront.

Identification of a Four-Gene Signature for Diagnosing Paediatric Sepsis

Aim

Early diagnosis of paediatric sepsis is crucial for the proper treatment of children and reduction of hospitalization and mortality. Biomarkers are a convenient and effective method for diagnosing any disease. However, huge differences among the studies reporting biomarkers for diagnosing sepsis have limited their clinical application. Therefore, in this study, we aimed to evaluate the diagnostic value of key genes involved in paediatric sepsis based on the data of the Gene Expression Omnibus database.

Methods

We used the GSE119217 dataset to identify differentially expressed genes (DEGs) between patients with and without paediatric sepsis. The most relevant gene modules of paediatric sepsis were screened through the weighted gene coexpression network analysis (WGCNA). Common genes (CGs) were found between DEGs and WGCNA. Genes with a potential diagnostic value in paediatric sepsis were selected from the CGs using least absolute shrinkage and selection operator regression and support vector machine recursive feature elimination. The principal component analysis, receiver operating characteristic curves, and C-index were used to verify the diagnostic value of the identified genes in six other independent sepsis datasets. Subsequently, a meta-analysis of the selected genes was performed to evaluate the value of these genes as biomarkers in paediatric sepsis.

Results

A total of 41 CGs were selected from the GSE119217 dataset. A four-gene signature composed of ANXA3, CD177, GRAMD1C, and TIGD3 effectively distinguished patients with paediatric sepsis from those in the control group. The signature was verified using six other independent datasets. In addition, the meta-analysis results showed that the pooled sensitivity, specificity, and area under the curve values were 1.00, 0.98, and 1.00, respectively.

Conclusion

The four-gene signature can be used as new biomarkers to distinguish patients with paediatric sepsis from healthy individuals.

Different Tidal Volumes May Jeopardize Pulmonary Redox and Inflammatory Status in Healthy Rats Undergoing Mechanical Ventilation

Mechanical ventilation (MV) is essential for the treatment of critical patients since it may provide a desired gas exchange. However, MV itself can trigger ventilator-associated lung injury in patients. We hypothesized that the mechanisms of lung injury through redox imbalance might also be associated with pulmonary inflammatory status, which has not been so far described. We tested it by delivering different tidal volumes to normal lungs undergoing MV. Healthy Wistar rats were divided into spontaneously breathing animals (control group, CG), and rats were submitted to MV (controlled ventilation mode) with tidal volumes of 4 mL/kg (MVG4), 8 mL/kg (MVG8), or 12 mL/kg (MVG12), zero end-expiratory pressure (ZEEP), and normoxia (FiO₂ = 21%) for 1 hour. After ventilation and euthanasia, arterial blood, bronchoalveolar lavage fluid (BALF), and lungs were collected for subsequent analysis. MVG12 presented lower PaCO₂ and bicarbonate content in the arterial blood than CG, MVG4, and MVG8. Neutrophil influx in BALF and MPO activity in lung tissue homogenate were significantly higher in MVG12 than in CG. The levels of CCL5, TNF-α, IL-1, and IL-6 in lung tissue homogenate were higher in MVG12 than in CG and MVG4. In the lung parenchyma, the lipid peroxidation was more important in MVG12 than in CG, MVG4, and MVG8, while there was more protein oxidation in MVG12 than in CG and MVG4. The stereological analysis confirmed the histological pulmonary changes in MVG12. The association of controlled mode ventilation and high tidal volume, without PEEP and normoxia, impaired pulmonary histoarchitecture and triggered redox imbalance and lung inflammation in healthy adult rats.

Innate Neutrophil Memory Dynamics in Disease Pathogenesis

Neutrophils, the most abundant leukocytes in circulation and the first responders to infection and inflammation, closely modulate both acute and chronic inflammatory processes. Resting neutrophils constantly patrol vasculature and migrate to tissues when challenges occur. When infection and/or inflammation recede, tissue neutrophils will be subsequently cleaned up by macrophages which collectively contribute to the resolution of inflammation. While most studies focus on the anti-microbial function of neutrophils including phagocytosis, degranulation, and neutrophil extracellular traps (NETs) formation, recent research highlighted additional contributions of neutrophils beyond simply controlling infectious agents. Neutrophils with resolving characteristics may alter the activities of neighboring cells and facilitate inflammation resolution, modulate long-term macrophage and adaptive immune responses, therefore having important impacts on host pathophysiology. The focus of this chapter is to provide an updated assessment of recent progress in the emerging field of neutrophil programming and memory in the context of both acute and chronic diseases.

Survival and Pulmonary Injury After Neonatal Sepsis: PD1/PDL1's Contributions to Mouse and Human Immunopathology

Morbidity and mortality associated with neonatal sepsis remains a healthcare crisis. PD1-/- neonatal mice endured experimental sepsis, in the form of cecal slurry (CS), and showed improved rates of survival compared to wildtype (WT) counterparts. End-organ injury, particularly of the lung, contributes to the devastation set forth by neonatal sepsis. PDL1-/- neonatal mice, in contrast to PD1-/- neonatal mice did not have a significant improvement in survival after CS. Because of this, we focused subsequent studies on the impact of PD1 gene deficiency on lung injury. Here, we observed that at 24 h post-CS (but not at 4 or 12 h) there was a marked increase in pulmonary edema (PE), neutrophil influx, myeloperoxidase (MPO) levels, and cytokine expression sham (Sh) WT mice. Regarding pulmonary endothelial cell (EC) adhesion molecule expression, we observed that Zona occludens-1 (ZO-1) within the cell shifted from a membranous location to a peri-nuclear location after CS in WT murine cultured ECs at 24hrs, but remained membranous among PD1-/- lungs. To expand the scope of this inquiry, we investigated human neonatal lung tissue. We observed that the lungs of human newborns exposed to intrauterine infection had significantly higher numbers of PD1+ cells compared to specimens who died from non-infectious causes. Together, these data suggest that PD1/PDL1, a pathway typically thought to govern adaptive immune processes in adult animals, can modulate the largely innate neonatal pulmonary immune response to experimental septic insult. The potential future significance of this area of study includes that PD1/PDL1 checkpoint proteins may be viable therapeutic targets in the septic neonate.

Annexin A3 in sepsis: novel perspectives from an exploration of public transcriptome data

According to publicly available transcriptome datasets, the abundance of Annexin A3 (ANXA3) is robustly increased during the course of sepsis; however, no studies have examined the biological significance or clinical relevance of ANXA3 in this pathology. Here we explored this interpretation gap and identified possible directions for future research. Based on reference transcriptome datasets, we found that ANXA3 expression is restricted to neutrophils, is upregulated in vitro after exposure to plasma obtained from septic patients, and is associated with adverse clinical outcomes. Secondly, an increase in ANXA3 transcript abundance was also observed in vivo, in the blood of septic patients in multiple independent studies. ANXA3 is known to mediate calcium-dependent granules-phagosome fusion in support of microbicidal activity in neutrophils. More recent work has also shown that ANXA3 enhances proliferation and survival of tumour cells via a Caspase-3-dependent mechanism. And this same molecule is also known to play a critical role in regulation of apoptotic events in neutrophils. Thus, we posit that during sepsis ANXA3 might either play a beneficial role, by facilitating microbial clearance and resolution of the infection; or a detrimental role, by prolonging neutrophil survival, which is known to contribute to sepsis-mediated organ damage.

Effects of volume-controlled ventilation vs. pressure-controlled ventilation on respiratory function and inflammatory factors in patients undergoing video-assisted thoracoscopic radical resection of pulmonary carcinoma

Background

The best ventilation approach for patients undergoing video-assisted thoracic surgery (ATS) for pulmonary carcinoma remains undefined. This study aimed to assess hemodynamics, airway pressure, arterial blood gas, and inflammatory factors in patients undergoing VATS for pulmonary carcinoma under volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV).

Methods

This was a prospective study of 60 patients with pulmonary carcinoma treated at a tertiary center in 2015-2016. The subjects were randomized to the VCV or PCV group after anesthesia and total lung ventilation (TLV). Hemodynamics and blood gas parameters were compared between the two groups pre-OLV (one-lung ventilation) (T1) and after 30 (T2), 60 (T3), and 120 (T4) minutes of OLV. Radial artery blood was collected to measure interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α levels.

Results

Hemodynamic and blood gas parameters were similar between the two groups (all P>0.05). During OLV, airway resistance (RAW) was significantly lower in the PCV group compared with the VCV group at T2 (26.0±3.8 vs. 29.9±7.3 cmH₂O/L/s), T3 (26.0±3.7 vs. 30.2±7.7 cmH₂O/L/s), and T4 (25.8±4.1 vs. 29.6±6.7 cmH₂O/L/s). Similar trends were found for peak pressure (Ppeak) and plateau pressure (Pplat). Mean pressure (Pmean) was similar between the two groups. Compared with the PCV group, TNF-α and IL-6 levels in the VCV group were significantly increased (all P<0.05). The levels of the anti-inflammatory mediator IL-10 were higher in the PCV group compared with the VCV group.

Conclusions

PCV for OLV during radical resection of pulmonary carcinoma by VATS could reduce Ppeak and downregulate pro-inflammatory factors, likely decreasing airway injury.

A novel role for coinhibitory receptors/checkpoint proteins in the immunopathology of sepsis

Coinhibitory molecules, such as PD-1, CTLA-4, 2B4, and BTLA, are an important new family of mediators in the pathophysiology of severe bacterial and/or fungal infection, as well as the combined insults of shock and sepsis. Further, the expression of these molecules may serve as indicators of the immune status of the septic individual. Using PD-1:PD-L as an example, we discuss in this review how such checkpoint molecules may affect the host response to infection by mediating the balance between effective immune defense and immune-mediated tissue injury. Additionally, we explore how the up-regulation of PD-1 and/or PD-L1 expression on not only adaptive immune cells (e.g., T cells), but also on innate immune cells (e.g., macrophages, monocytes, and neutrophils), as well as nonimmune cells during sepsis and/or shock contributes to functional alterations often with detrimental sequelae.

The Influence of Programmed Cell Death in Myeloid Cells on Host Resilience to Infection with Legionella pneumophila or Streptococcus pyogenes

Pathogen clearance and host resilience/tolerance to infection are both important factors in surviving an infection. Cells of the myeloid lineage play important roles in both of these processes. Neutrophils, monocytes, macrophages, and dendritic cells all have important roles in initiation of the immune response and clearance of bacterial pathogens. If these cells are not properly regulated they can result in excessive inflammation and immunopathology leading to decreased host resilience. Programmed cell death (PCD) is one possible mechanism that myeloid cells may use to prevent excessive inflammation. Myeloid cell subsets play roles in tissue repair, immune response resolution, and maintenance of homeostasis, so excessive PCD may also influence host resilience in this way. In addition, myeloid cell death is one mechanism used to control pathogen replication and dissemination. Many of these functions for PCD have been well defined in vitro, but the role in vivo is less well understood. We created a mouse that constitutively expresses the pro-survival B-cell lymphoma (bcl)-2 protein in myeloid cells (CD68(bcl2tg), thus decreasing PCD specifically in myeloid cells. Using this mouse model we explored the impact that decreased cell death of these cells has on infection with two different bacterial pathogens, Legionella pneumophila and Streptococcus pyogenes. Both of these pathogens target multiple cell death pathways in myeloid cells, and the expression of bcl2 resulted in decreased PCD after infection. We examined both pathogen clearance and host resilience and found that myeloid cell death was crucial for host resilience. Surprisingly, the decreased myeloid PCD had minimal impact on pathogen clearance. These data indicate that the most important role of PCD during infection with these bacteria is to minimize inflammation and increase host resilience, not to aid in the clearance or prevent the spread of the pathogen.

Neutrophil-mediated inflammation in the pathogenesis of Clostridium difficile infections

Clostridium difficile is the most important cause of nosocomial infectious diarrhea in the western world. C. difficile infections are a major healthcare burden with approximately 500,000 new cases every year and an estimated annual cost of nearly $1 billion in the U.S. Furthermore, the infections are no longer restricted to health care facilities, and recent studies indicate spread of C. difficile infection to the community as well. The clinical spectrum of C. difficile infection ranges from asymptomatic colonization to severe diarrhea, fulminant colitis and death. This spectrum results from a complex interplay between bacterial virulence factors, the colonic microbiome and the host inflammatory response. The overall vigor of host inflammatory response is believed to be an important determinant of C. difficile disease severity, and a more robust immune response is associated with worse outcomes. Neutrophils are the primary cells that respond to C. difficile invasion and neutrophilic inflammation is the hallmark of C. difficile-associated disease. In this review, we will focus on the role of neutrophils (infiltration to infected tissue, pathogen clearance and resolution of inflammation) in the immuno-pathogenesis of C. difficile-associated disease (CDAD).

The immune response after fracture trauma is different in old compared to young patients

BACKGROUND

Despite significant medical progress and improved treatment, surgical procedures of proximal femur fractures in older patients are still associated with a high postoperative complication and mortality rate. Recently, several authors investigated the phenomenon of immunoageing, indicating differences in the ageing immune system. The aim of the present multi-center prospective clinical trial was to analyze differences in the posttraumatic immune response of old patients compared to young patients.

METHODS

Blood was collected from young patients (<50 y, n = 20) with long bone fractures (YF), old patients (>70 y, n = 21) with proximal femur fractures (OF) upon clinical admission and within 6 hours after surgery, and two healthy age matched control groups (YH & OH). Serum TRAIL- and cytokine concentrations were analyzed via cytometric bead array, Fas-Ligand and TNF-Receptor-I via ELISA. CD15(+) magnetic bead-isolated neutrophils (PMN) were TUNEL stained.

RESULTS

IL-6 was significantly increased only in OF after trauma and surgery whereas YF patient exhibited a marked decrease of TNF after trauma. Interestingly, a significant increase of GM-CSF serum levels was observed in YF only, whereas OF exhibited a decrease of systemic IFN-γ concentrations after trauma and after surgery. The healthy controls, old and young, had more or less similar inflammation levels. Moreover, TRAIL serum levels were diminished in OF after trauma and even further after surgery whereas in YF this was only observed after the surgical procedure. Fas-L concentrations were reduced only in YF after surgery or trauma. PMN apoptosis was significantly reduced only in YF, indicating activation of the innate immune system.

DISCUSSION

In summary, our data suggest that the posttraumatic immune response is differently regulated in old and young trauma patients. The operative procedure further impacts these differences after trauma. Whether the decreased activation of PMNs and phagocytes along with the observed dysregulation of the posttraumatic inflammatory response contributes to the high perioperative mortality rate of the elderly suffering from a proximal femoral fracture requires further investigation.

Effect of siRNA against NF-κB on sepsis‑induced acute lung injury in a mouse model

The aim of the present study was to explore the protective effect of small interfering RNA (siRNA) against nuclear factor κB (NF-κB) p65 on sepsis-induced acute lung injury (ALI) in mice. In total, 70 male Kunming mice were randomly divided into a healthy control group, a sepsis group, a specific interfering group and a scrambled control group (Sc), and the latter three groups were divided into post-operational 6 and 12 h subgroups, each of which consisted of 10 mice. The mice were administered with NF-κB siRNA, scrambled siRNA and normal saline via tail vein injection. Following 1 h, a mouse model of septic ALI was produced by cecal ligation and puncture (CLP) in the two siRNA groups and the sepsis control group. At 6 and 12 h post-operation, the experimental mice were sacrificed and the lung tissue samples were collected. Histopathological changes, wet/dry ratio of lung weight, NF-κB protein and NF-κB p65 mRNA levels, matrix metalloproteinase-9 (MMP-9) mRNA and protein activity were detected. Compared with the sepsis group and the Sc at the corresponding time, the expression levels of NF-κB p65 mRNA, the lung injury of experimental mice, the wet/dry ratio and the levels of MMP-9 mRNA and protein activity decreased, and significant differences were observed at 6 h post-operation (P<0.05). RNA interference against NF-κB p65 was able to decrease the expression of NF-κB and further inhibit the early phasic excessive inflammatory reaction in sepsis, which may alleviate ALI.

Apoptotic and inflammatory signaling via Fas and tumor necrosis factor receptor I contribute to the development of chest trauma-induced septic acute lung injury

BACKGROUND

Direct acute lung injury (ALI) is still associated with a high mortality, whereas the underlying pathomechanisms are not yet fully understood. In this regard, epithelial cell death in the lungs has been attributed an important role in the pathogenesis of this clinical entity. Based on this background here, we hypothesized that signaling through Fas and tumor necrosis factor receptor 1 (TNFR-1) is involved in mediating apoptosis and inflammation in chest trauma induced septic ALI.

METHODS

Male C57BL/6 mice (wild-type [WT]), male mutant mice expressing nonfunctional Fas receptor (B6.MRL-Faslpr/J [lpr]) (lpr) and male TNFR-1-deficient mice (TNFR-1(-/-)) were subjected to a model of direct ALI consisting of blunt chest trauma followed by cecal ligation and puncture.Cytokine/chemokine concentrations of plasma, bronchoalveolar lavage (BAL) fluids, and lung tissue were investigated as well as BAL protein and lung myeloperoxidase. Lung histology was assessed; lung caspase 3, TUNEL-positive cells, and apoptotic polymorphonuclear neutrophil were measured, followed by a survival study.

RESULTS

Cytokine/chemokine levels in plasma, BAL, and lung tissue were markedly increased in WT animals following ALI, whereas lpr and TNFR-1((-/-) showed significantly decreased levels. BAL protein levels were substantially elevated following ALI, but lpr animals presented markedly diminished protein levels compared with WT and TNFR-1(-/-) animals. Lung myeloperoxidase level was only increased 12 hours after ALI in WT animals, whereas lung myeloperoxidase levels in lpr and TNFR-1(-/-) animals were not increased compared with sham. Lung histology revealed beneficial effects in lpr and TNFR-1(-/-). Lung active caspase 3 after ALI was substantially decreased in lpr and TNFR-1(-/-) mice compared with WT. Interestingly, an early but not persisting survival benefit was observed in lpr and TNFR-1 animals(-/-).

CONCLUSION

Pathomechanistically, Fas and TNFR-1 signaling contributed to the apoptotic and inflammatory response in a clinically relevant double-hit model of trauma-induced septic ALI. Moreover, this was associated with a temporary survival benefit.

Acute lung injury in thoracic surgery

PURPOSE OF REVIEW

This review will analyze the risk factors of acute lung injury (ALI) in patients undergoing thoracic surgery. Evidence for the occurrence of lung injury following mechanical ventilation and one-lung ventilation (OLV) and the strategies to avoid it will also be discussed.

RECENT FINDINGS

Post-thoracotomy ALI has become one of the leading causes of operative death. The pathogenesis of ALI implicates a multiple-hit sequence of various triggering factors (e.g. preoperative conditions, surgery-induced inflammation, ventilator-induced injury, fluid overload, and transfusion). Conventional ventilation during OLV is performed with high tidal volumes equal to those being used in two-lung ventilation, high FiO(2), and without positive end-expiratory pressure. This practice was originally recommended to improve oxygenation and decrease shunt fraction during OLV. However, a number of recent studies using experimental models or human patients have shown low tidal volumes to be associated with a decrease in inflammatory mediators and a reduction in pulmonary postoperative complications. However, the application of such protective strategies could be harmful if not still properly used.

SUMMARY

The goal of ventilation is to minimize lung trauma by avoiding overdistension and repetitive alveolar collapse, while providing adequate oxygenation. Protective ventilation is not simply synonymous of low tidal volume ventilation, but it also involves positive end-expiratory pressure, lower FiO(2), recruitment maneuvers, and lower ventilatory pressures.

Pathogenesis of indirect (secondary) acute lung injury

At present, therapeutic interventions to treat acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) remain largely limited to lung-protective strategies, as no real molecular-pathophysiologic-driven therapeutic intervention has yet become available. This is in part the result of the heterogeneous nature of the etiological processes that contribute to the state of ALI/ARDS. This article sets out to understand the development of ALI resulting from indirect pulmonary insults, such as extrapulmonary sepsis and trauma, shock, burn injury or mass transfusion, as opposed to direct pulmonary challenges, such as pneumonia, aspiration or lung contusion. Here, we consider not only the experimental and clinical data concerning the roles of various immune (neutrophil, macrophage, lymphocyte and dendritic) as well as nonimmune (epithelial and endothelial) cells in orchestrating the development of ALI resulting from indirect pulmonary stimuli, but also how these cell populations might be targeted therapeutically.

Neutrophil IL-10 suppresses peritoneal inflammatory monocytes during polymicrobial sepsis

Septic peritonitis remains a major cause of death. Neutrophils and inflammatory monocytes are principal components of the innate immune system and are essential for defense against a range of microbial pathogens. Their role and interaction in polymicrobial sepsis have not been defined clearly. Using a murine model of CLP to induce moderate sepsis, we found that neutrophil depletion did not alter survival, whereas depletion of neutrophils and inflammatory monocytes markedly reduced survival. After neutrophil depletion, inflammatory monocytes had greater phagocytic capacity and oxidative burst, and increased expression of costimulatory molecules, TNF, and iNOS. Notably, peritoneal neutrophils produced IL-10 following CLP. Adoptive i.p. transfer of WT but not IL-10(-/-) neutrophils into septic mice reduced monocyte expression of TNF. In vitro experiments confirmed that monocyte suppression was mediated by neutrophil-derived IL-10. Thus, during septic peritonitis, neutrophils suppress peritoneal inflammatory monocytes through IL-10 and are dispensable for survival.

Polymorphonuclear cell priming associated with NF-kB activation in patients with severe injury is partially dependent on macrophage migration inhibitory factor

BACKGROUND

Severe trauma may induce alternations of cytokine response and polymorphonuclear cell (PMN) activity in patients. This study investigated the correlation of plasma migration inhibitory factor (MIF) level and PMN activation after severe injury, and their relationship with clinical outcomes.

STUDY DESIGN

A prospective observational study was performed at the emergency department and intensive care unit of a university hospital. Thirty-two severe blunt trauma patients (Injury Severity Score greater than 16) with systemic inflammatory response syndrome (SIRS) were enrolled. Age- and gender-matched healthy persons were the controls. Patient blood samples were obtained within 24 hours of and at 72 hours after injury. PMNs were isolated and measured for NF-kBp65 translocation and respiratory burst. Plasma MIF, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8, and IL-10 concentrations were measured. Control PMNs were incubated with patient plasma preincubated with anti-MIF antibody or anti-IL-6 antibody; cytokine blockade effects were evaluated.

RESULTS

Twelve patients developed organ failure. Compared with patients without organ failure, patients with organ failure had lower blood pressure and a higher base deficit on admission, higher NF-kBp65 translocation and respiratory burst of PMNs, and higher plasma MIF (968 ± 246 pg/mL vs 564 ± 299 pg/mL) and IL-6 (202 ± 91 pg/mL vs 119 ± 84 pg/mL) levels within 24 hours after injury. Plasma MIF had significant positive correlation with NF-kB translocation of PMNs within 24 hours of incurring trauma (R = 0.668). The presence of anti-MIF antibody in patients' plasma obtained within 24 hours, but not at 72 hours, after injury could significantly partially block the NF-kBp65 translocation and respiratory activity of PMNs in the controls.

CONCLUSIONS

An early increase of plasma MIF associates with NF-kB translocation and respiratory burst in PMNs of severe trauma patients and correlates with higher morbidity. MIF is one of the important factors responsible for early PMN activation and may provide a target of immunomodulation after injury.

Rosette nanotubes inhibit bovine neutrophil chemotaxis

Migration of activated neutrophils that have prolonged lifespan into inflamed organs is an important component of host defense but also contributes to tissue damage and mortality. In this report, we used biologically-inspired RGD-tagged rosette nanotubes (RNT) to inhibit neutrophil chemotaxis. We hypothesize that RGD-RNT will block neutrophil migration through inhibition of MAPK. In this report, RNT conjugated to lysine (K–RNT) and arginine-glycine-aspartic acid-serine-lysine (RGDSK-RNT) were co-assembled in a molar ratio of 95/5. The effect of the resulting composite RNT (RGDSK/K–RNT) on neutrophil chemotaxis, cell signaling and apoptosis was then investigated. Exposure to RGDSK/K–RNT reduced bovine neutrophil migration when compared to the non-treated group (p < 0.001). Similar effect was seen following treatment with ERK1/2 or p38 MAPK inhibitors. Phosphorylation of the ERK1/2 and p38 MAPK was inhibited at 5 min by RGDSK/K–RNT (p < 0.05). The RGDSD/K-RNT did not affect the migration of neutrophils pre-treated with αvβ3 integrin antibody suggesting that both bind to the same receptor. RGDSK/K–RNT did not induce apoptosis in bovine neutrophils, which was suppressed by pre-exposing them to LPS (p < 0.001). We conclude that RGDSK/K–RNT inhibit phosphorylation of ERK1/2 and p38 MAPK and inhibit chemotaxis of bovine neutrophils.

[Protective ventilation therapy. Also relevant for the operating room?]

General anesthesia and mechanical ventilation affect gas exchange, ventilation and pulmonary perfusion and there is an increasing body of evidence that mechanical ventilation itself promotes lung injury. Lung protective mechanical ventilation in patients suffering from acute lung injury or acute respiratory distress syndrome by means of reduced tidal volumes and limited plateau pressures has been shown to result in reduction of systemic inflammatory mediators, increased ventilator-free days and reduction in mortality. Experimental studies suggest that mechanical ventilation of uninjured lungs may also induce lung damage; however, the clinical relevance remains unknown. Human prospective studies comparing mechanical ventilation strategies during general anesthesia have shown inconsistent results with respect to inflammatory mediators. There is a lack of clinical evidence that lung protective ventilation strategies as used in patients with lung injury may improve clinical outcome of patients with uninjured lungs. The question of which ventilatory strategy will best protect normal human lungs remains unanswered.

Acute lung injury and outcomes after thoracic surgery

PURPOSE OF REVIEW

The present review evaluates the evidence available in the literature tracking perioperative mortality and morbidity as well as the pathogenesis and management of acute lung injury (ALI) in patients undergoing thoracotomy.

RECENT FINDINGS

Over the last decade, despite increasing age and comorbid conditions, the operative mortality has remained unchanged for patients undergoing lung resection, whereas procedure-related complications have declined. Better clinical outcomes are achieved in high-volume hospitals and when procedures are performed by a thoracic surgeon. Postthoracotomy ALI has become the leading cause of operative death, its incidence has remained stable (2-5%) and earlier diagnosis can be made by assessing the extravascular lung water volume with the single-indicator dilution technique. The pathogenesis of ALI implicates a multiple-hit sequence of various triggering factors (e.g. oxidative stress and surgical-induced inflammation) in addition to injurious ventilatory settings and genetic predisposition.

SUMMARY

Knowledge of the perioperative risk factors of major complications and understanding of the mechanisms of postthoracotomy ALI enable anesthesiologists to implement 'protective' lung strategies including the use of low tidal volume (VT) with recruitment maneuvers, a goal-directed fluid approach and prophylactic treatment with inhaled beta2-adrenergic agonists.

Epithelial cell apoptosis and neutrophil recruitment in acute lung injury-a unifying hypothesis? What we have learned from small interfering RNAs

In spite of protective ventilatory strategies, Acute Lung Injury (ALI) remains associated with high morbidity and mortality. One reason for the lack of therapeutic options might be that ALI is a co-morbid event associated with a diverse family of diseases and, thus, may be the result of distinct pathological processes. Among them, activated neutrophil- (PMN-) induced tissue injury and epithelial cell apoptosis mediated lung damage represent two potentially important candidate pathomechanisms that have been put forward. Several approaches have been undertaken to test these hypotheses, with substantial success in the treatment of experimental forms of ALI. With this in mind, we will summarize these two current hypotheses of ALI briefly, emphasizing the role of apoptosis in regulating PMN and/or lung epithelial cell responses. In addition, the contribution that Fas-mediated inflammation may play as a potential biological link between lung cell apoptosis and PMN recruitment will be considered, as well as the in vivo application of small interfering RNA (siRNA) as a novel approach to the inhibition of ALI and its therapeutic implications.

Role of Programmed Cell Death in the Immunopathogenesis of Sepsis

Apoptosis is an important mechanism during the immunopathogenesis of sepsis. Early programmed cell death of lymphocytes substantially impairs innate and adaptive immunity reducing the capacity to ward off the invading pathogen. Apoptosis of parenchymal cells (e.g. in the lung, liver and gut) may also promote organ failure and death. Several experimental therapeutic strategies have now been developed to beneficially influence these mechanisms; however, their potential clinical benefit is yet to be evaluated.