Nuclear factor-kappaB activation in neonatal mouse lung protects against lipopolysaccharide-induced inflammation

Endothelial-specific loss of IKKβ disrupts pulmonary endothelial angiogenesis and impairs postnatal lung growth

Pulmonary angiogenesis drives alveolarization, but the transcriptional regulators directing pulmonary angiogenesis remain poorly defined. Global, pharmacological inhibition of nuclear factor-kappa B (NF-κB) impairs pulmonary angiogenesis and alveolarization. However, establishing a definitive role for NF-κB in pulmonary vascular development has been hindered by embryonic lethality induced by constitutive deletion of NF-κB family members. We created a mouse model allowing inducible deletion of the NF-κB activator, IKKβ, in endothelial cells (ECs) and assessed the effect on lung structure, endothelial angiogenic function, and the lung transcriptome. Embryonic deletion of IKKβ permitted lung vascular development but resulted in a disorganized vascular plexus, while postnatal deletion significantly decreased radial alveolar counts, vascular density, and proliferation of both endothelial and nonendothelial lung cells. Loss of IKKβ impaired survival, proliferation, migration, and angiogenesis in primary lung ECs in vitro, in association with decreased expression of VEGFR2 and activation of downstream effectors. Loss of endothelial IKKβ in vivo induced broad changes in the lung transcriptome with downregulation of genes related to mitotic cell cycle, extracellular matrix (ECM)-receptor interaction, and vascular development, and the upregulation of genes related to inflammation. Computational deconvolution suggested that loss of endothelial IKKβ decreased general capillary, aerocyte capillary, and alveolar type I cell abundance. Taken together, these data definitively establish an essential role for endogenous endothelial IKKβ signaling during alveolarization. A deeper understanding of the mechanisms directing this developmental, physiological activation of IKKβ in the lung vasculature may provide novel targets for the development of strategies to enhance beneficial proangiogenic signaling in lung development and disease.NEW & NOTEWORTHY This study highlights the cell-specific complexity of nuclear factor kappa B signaling in the developing lung by demonstrating that inducible loss of IKKβ in endothelial cells impairs alveolarization, disrupts EC angiogenic function, and broadly represses genes important for vascular development.

Stem/Progenitor Cells and Related Therapy in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly seen in preterm infants, and is triggered by infection, mechanical ventilation, and oxygen toxicity. Among other problems, lifelong limitations in lung function and impaired psychomotor development may result. Despite major advances in understanding the disease pathologies, successful interventions are still limited to only a few drug therapies with a restricted therapeutic benefit, and which sometimes have significant side effects. As a more promising therapeutic option, mesenchymal stem cells (MSCs) have been in focus for several years due to their anti-inflammatory effects and their secretion of growth and development promoting factors. Preclinical studies provide evidence in that MSCs have the potential to contribute to the repair of lung injuries. This review provides an overview of MSCs, and other stem/progenitor cells present in the lung, their identifying characteristics, and their differentiation potential, including cytokine/growth factor involvement. Furthermore, animal studies and clinical trials using stem cells or their secretome are reviewed. To bring MSC-based therapeutic options further to clinical use, standardized protocols are needed, and upcoming side effects must be critically evaluated. To fill these gaps of knowledge, the MSCs' behavior and the effects of their secretome have to be examined in more (pre-) clinical studies, from which only few have been designed to date.

Mechanical Power Is Associated With Mortality in Pediatric Acute Respiratory Distress Syndrome

OBJECTIVES

Mechanical power (MP) transferred from the ventilator to the lungs has been proposed as a summary variable that may impact mortality in children with acute respiratory distress syndrome (ARDS). To date, no study has shown an association between higher MP and mortality in children with ARDS.

DESIGN

Secondary analysis of a prospective observational study.

SETTING

Single-center, tertiary, academic PICU.

PATIENTS

Five hundred forty-six intubated children with ARDS enrolled between January 2013 and December 2019 receiving pressure-controlled ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Higher MP was associated with increased mortality (adjusted hazard ratio [HR] 1.34 per 1 sd increase, 95% CI 1.08-1.65; p = 0.007). When assessing the contribution of individual components of MP, only positive end-expiratory pressure (PEEP) was associated with mortality (HR 1.32; p = 0.007), whereas tidal volume, respiratory rate, and driving pressure (ΔP = [peak inspiratory pressure (PIP)-PEEP]) were not. Finally, we tested whether there remained an association when specific terms were removed from the MP equation by calculating MP from static strain (remove ΔP), MP from dynamic strain (remove PEEP), and mechanical energy (remove respiratory rate). MP from static strain (HR 1.44; p < 0.001), MP from dynamic strain (HR 1.25; p = 0.042), and mechanical energy (HR 1.29; p = 0.009) were all associated with mortality. MP was associated with ventilator-free days only when using MP normalized to predicted body weight, but not when using measured weight.

CONCLUSIONS

Higher MP was associated with mortality in pediatric ARDS, and PEEP appears to be the component most consistently driving this association. As higher PEEP is used in sicker patients, the association between MP and mortality may reflect a marker of illness severity rather than MP itself being causal for mortality. However, our results support future trials testing different levels of PEEP in children with ARDS as a potential means to improve outcome.

Dam-Infant Rhesus Macaque Pairs to Dissect Age-Dependent Responses to SARS-CoV-2 Infection

The global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its associated coronavirus disease (COVID-19) has led to a pandemic of unprecedented scale. An intriguing feature of the infection is the minimal disease in most children, a demographic at higher risk for other respiratory viral diseases. To investigate age-dependent effects of SARS-CoV-2 pathogenesis, we inoculated two rhesus macaque monkey dam-infant pairs with SARS-CoV-2 and conducted virological and transcriptomic analyses of the respiratory tract and evaluated systemic cytokine and Ab responses. Viral RNA levels in all sampled mucosal secretions were comparable across dam-infant pairs in the respiratory tract. Despite comparable viral loads, adult macaques showed higher IL-6 in serum at day 1 postinfection whereas CXCL10 was induced in all animals. Both groups mounted neutralizing Ab responses, with infants showing a more rapid induction at day 7. Transcriptome analysis of tracheal airway cells isolated at day 14 postinfection revealed significant upregulation of multiple IFN-stimulated genes in infants compared with adults. In contrast, a profibrotic transcriptomic signature with genes associated with cilia structure and function, extracellular matrix composition and metabolism, coagulation, angiogenesis, and hypoxia was induced in adults compared with infants. Our study in rhesus macaque monkey dam-infant pairs suggests age-dependent differential airway responses to SARS-CoV-2 infection and describes a model that can be used to investigate SARS-CoV-2 pathogenesis between infants and adults.

Absence of IκBβ/NFκB signaling does not attenuate acetaminophen-induced hepatic injury

Acetaminophen (N-acetyl-p-aminophenol [APAP]) toxicity is a common cause of acute liver failure. Innate immune signaling and specifically NFκB activation play a complex role in mediating the hepatic response to toxic APAP exposures. While inflammatory innate immune responses contribute to APAP-induced injury, these same pathways play a role in regeneration and repair. Previous studies have shown that attenuating IκBβ/NFκB signaling downstream of TLR4 activation can limit injury, but whether this pathway contributes to APAP-induced hepatic injury is unknown. We hypothesized that the absence of IκBβ/NFκB signaling in the setting of toxic APAP exposure would attenuate APAP-induced hepatic injury. To test this, we exposed adult male WT and IκBβ-/- mice to APAP (280 mg/kg, IP) and evaluated liver histology at early (2-24 hr) and late (48-72 hr) time points. Furthermore, we interrogated the hepatic expression of NFκB inflammatory (Cxcl1, Tnf, Il1b, Il6, Ptgs2, and Ccl2), anti-inflammatory (Il10, Tnfaip3, and Nfkbia), and Nrf2/antioxidant (Gclc, Hmox, and Nqo1) target genes previously demonstrated to play a role in APAP-induced injury. Conflicting with our hypothesis, we found that hepatic injury was similar in WT and IκBβ-/- mice. Acutely, the induced expression of some target genes was similar in WT and IκBβ-/- mice (Tnfaip3, Nfkbia, and Gclc), while others were either not induced (Cxcl1, Tnf, Ptgs2, and Il10) or significantly attenuated (Ccl2) in IκBβ-/- mice. At later time points, APAP-induced hepatic expression of Il1b, Il6, and Gclc was significantly attenuated in IκBβ-/- mice. Based on these findings, the therapeutic potential of targeting IκBβ/NFκB signaling to treat toxic APAP-induced hepatic injury is likely limited.

Bronchopulmonary dysplasia: Incidence and severity in premature infants born at high altitude

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the most common cause of chronic lung disease in children born prematurely. There is little information about the epidemiology and severity of BPD places with high altitude. This study aimed to evaluate the frequency of BPD severity levels and the associated risk factors with severity in a cohort of preterm newborns ≤36weeks of gestational age born in Rionegro, Colombia MATERIALS AND METHODS: We carried out a retrospective analytical cohort of preterm newborns without major malformations from Rionegro, Colombia between 2011 and 2018 admitted to neonatal intensive unit at high altitude (2200 m above sea level). The main outcomes were the incidence and severity of BPD.

RESULTS

The BPD incidence was 23.5% 95% (confidence interval [CI], 19.6-27.7). BPD was grade 1 in 69.9%, grade 2 in 15.5% and grade 3 in 14.5% of patients. After modeling regression analysis, the final variables associated with BPD severity levels were: sepsis (odds ratio [OR], 4.15; 95% CI, 1.33-12.96) and pulmonary hypertension (OR: 3.86; 95% CI, 1.30-11.4).

CONCLUSION

The incidence of BPD was higher and similar to cities with higher altitudes. In our population, the variables associated with BPD severity levels were: sepsis and pulmonary hypertension. It is necessary to increase the awareness of risk factors, the effect of clinical practices, and early recognition of BPD to reduce morbidity in patients with this pathology.

Lung development and immune status under chronic LPS exposure in rat pups with and without CD26/DPP4 deficiency

Dipeptidyl-peptidase IV (CD26), a multifactorial integral type II protein, is expressed in the lungs during development and is involved in inflammation processes. We tested whether daily LPS administration influences the CD26-dependent retardation in morphological lung development and induces alterations in the immune status. Newborn Fischer rats with and without CD26 deficiency were nebulized with 1 µg LPS/2 ml NaCl for 10 min from days postpartum (dpp) 3 to 9. We used stereological methods and fluorescence activated cell sorting (FACS) to determine morphological lung maturation and alterations in the pulmonary leukocyte content on dpp 7, 10, and 14. Daily LPS application did not change the lung volume but resulted in a significant retardation of alveolarization in both substrains proved by significantly lower values of septal surface and volume as well as higher mean free distances in airspaces. Looking at the immune status after LPS exposure compared to controls, a significantly higher percentage of B lymphocytes and decrease of CD4⁺CD25⁺ T cells were found in both subtypes, on dpp7 a significantly higher percentage of CD4 T⁺ cells in CD26⁺ pups, and a significantly higher percentage of monocytes in CD26⁻ pups. The percentage of T cells was significantly higher in the CD26-deficient group on each dpp. Thus, daily postnatal exposition to low doses of LPS for 1 week resulted in a delay in formation of secondary septa, which remained up to dpp 14 in CD26⁻ pups. The retardation was accompanied by moderate parenchymal inflammation and CD26-dependent changes in the pulmonary immune cell composition.

Early Changes and Indicators Characterizing Lung Aging in Neonatal Chronic Lung Disease

Infants suffering from neonatal chronic lung disease, i.e., bronchopulmonary dysplasia, are facing long-term consequences determined by individual genetic background, presence of infections, and postnatal treatment strategies such as mechanical ventilation and oxygen toxicity. The adverse effects provoked by these measures include inflammatory processes, oxidative stress, altered growth factor signaling, and remodeling of the extracellular matrix. Both, acute and long-term consequences are determined by the capacity of the immature lung to respond to the challenges outlined above. The subsequent impairment of lung growth translates into an altered trajectory of lung function later in life. Here, knowledge about second and third hit events provoked through environmental insults are of specific importance when advocating lifestyle recommendations to this patient population. A profound exchange between the different health care professionals involved is urgently needed and needs to consider disease origin while future monitoring and treatment strategies are developed.

P2X7 Receptor Induces Pyroptotic Inflammation and Cartilage Degradation in Osteoarthritis via NF-κB/NLRP3 Crosstalk

Osteoarthritis (OA) is an urgent public health problem; however, the underlying causal mechanisms remain unclear, especially in terms of inflammatory mediators in cartilage degradation and chondrocyte imbalance. P2X7 receptor (P2X7R) is a critical inflammation switch, but few studies have examined its function and mechanisms in OA-like pyroptotic inflammation of chondrocytes. In this study, Sprague–Dawley rats were injected in the knee with monosodium iodoacetate (MIA) to induce OA, followed by multiple intra-articular injections with P2X7R antagonist A740003, P2X7R agonist BzATP, NF-κB inhibitor Bay 11-7082, and NLRP3 inhibitor CY-09. Primary rat chondrocytes were harvested and treated similarly. We assessed cell viability, damage, and death via cell viability assay, lactate dehydrogenase (LDH) release, and flow cytometry. Concentrations of adenosine triphosphate (ATP) and interleukin- (IL-) 1β in cell culture supernatant and joint cavity lavage fluid were analyzed by enzyme-linked immunosorbent assay. Changes in expression levels of P2X7 and inflammation-related indicators were analyzed by immunofluorescence, quantitative reverse-transcription polymerase chain reaction, and western blotting. Cell morphology changes and pyroptosis were observed using transmission electron microscopy. Histology, immunohistochemistry, and microcomputed tomography were used to analyze damage to bone and cartilage tissues and assess the severity of OA. Similar to MIA, BzATP reduced cell viability and collagen II expression in a dose-dependent manner. Conversely, A740003 ameliorated MIA-induced cartilage degradation and OA-like pyroptotic inflammation by rescuing P2X7, MMP13, NF-κB p65, NLRP3, caspase-1 (TUNEL-positive and active), and IL-1β upregulation. Additionally, A740003 reduced the caspase-1/propidium iodide double-positive rate, LDH concentration, and reactive oxygen species production. These effects also occurred via coincubation with Bay 11-7082 and CY-09. In conclusion, activated P2X7 promoted extracellular matrix degradation and pyroptotic inflammation in OA chondrocytes through NF-κB/NLRP3 crosstalk, thus, aggravating the symptoms of OA. The study findings suggest P2X7 as a potential target for inflammation treatment, providing new avenues for OA research and therapy.

A Review of Placenta and Umbilical Cord-Derived Stem Cells and the Immunomodulatory Basis of Their Therapeutic Potential in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating lung disorder of preterm infants as a result of an aberrant reparative response following exposures to various antenatal and postnatal insults. Despite sophisticated medical treatment in this modern era, the incidence of BPD remains unabated. The current strategies to prevent and treat BPD have met with limited success. The emergence of stem cell therapy may be a potential breakthrough in mitigating this complex chronic lung disorder. Over the last two decades, the human placenta and umbilical cord have gained increasing attention as a highly potential source of stem cells. Placenta-derived stem cells (PDSCs) and umbilical cord-derived stem cells (UCDSCs) display several advantages such as immune tolerance and are generally devoid of ethical constraints, in addition to their stemness qualities. They possess the characteristics of both embryonic and mesenchymal stromal/stem cells. Recently, there are many preclinical studies investigating the use of these cells as therapeutic agents in neonatal disease models for clinical applications. In this review, we describe the preclinical and clinical studies using PDSCs and UCDSCs as treatment in animal models of BPD. The source of these stem cells, routes of administration, and effects on immunomodulation, inflammation and regeneration in the injured lung are also discussed. Lastly, a brief description summarized the completed and ongoing clinical trials using PDSCs and UCDSCs as therapeutic agents in preventing or treating BPD. Due to the complexity of BPD, the development of a safe and efficient therapeutic agent remains a major challenge to both clinicians and researchers.

Hyperoxia Injury in the Developing Lung Is Mediated by Mesenchymal Expression of Wnt5A

Rationale: Bronchopulmonary dysplasia (BPD) is a leading complication of preterm birth that affects infants born in the saccular stage of lung development at <32 weeks of gestation. Although the mechanisms driving BPD remain uncertain, exposure to hyperoxia is thought to contribute to disease pathogenesis.Objectives: To determine the effects of hyperoxia on epithelial-mesenchymal interactions and to define the mediators of activated Wnt/β-catenin signaling after hyperoxia injury.Methods: Three hyperoxia models were used: A three-dimensional organotypic coculture using primary human lung cells, precision-cut lung slices (PCLS), and a murine in vivo hyperoxia model. Comparisons of normoxia- and hyperoxia-exposed samples were made by real-time quantitative PCR, RNA in situ hybridization, quantitative confocal microscopy, and lung morphometry.Measurements and Main Results: Examination of an array of Wnt ligands in the three-dimensional organotypic coculture revealed increased mesenchymal expression of WNT5A. Inhibition of Wnt5A abrogated the BPD transcriptomic phenotype induced by hyperoxia. In the PCLS model, Wnt5A inhibition improved alveolarization following hyperoxia exposure, and treatment with recombinant Wnt5a reproduced features of the BPD phenotype in PCLS cultured in normoxic conditions. Chemical inhibition of NF-κB with BAY11-7082 reduced Wnt5a expression in the PCLS hyperoxia model and in vivo mouse hyperoxia model, with improved alveolarization in the PCLS model.Conclusions: Increased mesenchymal Wnt5A during saccular-stage hyperoxia injury contributes to the impaired alveolarization and septal thickening observed in BPD. Precise targeting of Wnt5A may represent a potential therapeutic strategy for the treatment of BPD.

Understanding the age divide in COVID-19: why are children overwhelmingly spared?

The rapid emergence and subsequent global dissemination of SARS-CoV-2 disease (COVID-19) has resulted in over 4 million cases worldwide. The disease has a marked predilection for adults, and children are relatively spared. Understanding the age-based differences in pathophysiological pathways and processes relevant to the onset and progression of disease both in the clinical course and in experimental disease models may hold the key to the identification of therapeutic targets. The differences in the clinical course are highlighted by the lack of progression of the SARS-CoV-2 infection beyond mild symptoms in a majority of children, whereas in adults the disease progresses to acute lung injury and an acute respiratory distress syndrome (ARDS)-like phenotype with high mortality. The pathophysiological mechanisms leading to decreased lung injury in children may involve the decreased expression of the mediators necessary for viral entry into the respiratory epithelium and differences in the immune system responses in children. Specifically, decreased expression of proteins, including angiotensin-converting enzyme 2 (ACE2) and Transmembrane Serine Protease 2 (TMPRSS2) in the airway epithelium in children may prevent viral entry. The immune system differences may include a relative preponderance of CD4+ T cells, decreased neutrophil infiltration, decreased production of proinflammatory cytokines, and increased production of immunomodulatory cytokines in children compared with adults. Notably, the developing lung in children may have a greater capacity to recover and repair after viral infection. Understanding the relative contributions of the above processes to the protective phenotype in the developing lung can guide the trial of the appropriate therapies in adults.

Recombinant Human Elafin Ameliorates Chronic Hyperoxia-Induced Lung Injury by Inhibiting Nuclear Factor-Kappa B Signaling in Neonatal Mice

The study aimed to investigate whether recombinant human elafin can prevent hyperoxia-induced pulmonary inflammation in newborn mice, and to explore the mechanism underlying the inhibitory effects of elafin on nuclear factor-kappa B (NF-κB) signaling pathway. Neonatal C57BL/6J mice were exposed to 85% O₂ for 1, 3, 7, 14, or 21 days. Then, elafin was administered daily for 20 days through intraperitoneal injection. After treatment, morphometric analysis, quantitative real-time polymerase chain reaction, terminal deoxynucleotidyl transferase dUTP nick end labeling staining, and Western blotting were carried out to determine the key markers involved in inflammatory process and the potential signaling pathways in hyperoxia-exposed newborn mice treated with elafin. In neonatal bronchopulmonary dysplasia (BPD) mice, hyperoxia induced apoptosis by increasing Bcl-2-associated X protein expression, and triggered inflammation by upregulating the expression levels of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α. Moreover, hyperoxia activated NF-κB signaling pathway by promoting the nuclear translocation of p65 in lung tissue. However, all these changes could be inhibited or reversed by elafin at least partially. Elafin reduced apoptosis, suppressed inflammation cytokines, and improved NF-κB p65 nuclear accumulation in hyperoxia-exposed neonatal mice, indicating that this recombinant protein can serve as a novel target for the treatment of BPD.

Blockade of interleukin-2-inducible T-cell kinase signaling attenuates acute lung injury in mice through adjustment of pulmonary Th17/Treg immune responses and reduction of oxidative stress

Acute lung injury (ALI) is linked with considerable morbidity and mortality. ALI can be caused by various agents, one of them being sepsis. ALI is characterized by injury to vascular endothelium and alveolar epithelium that results in edema, pulmonary immune cells infiltration and hypoxemia. Neutrophils and T cells particularly play a huge role in amplification of pulmonary inflammation through release of multiple inflammatory mediators. Recent reports suggest a strong involvement of Th17 cells and oxidative stress in initiation/amplification of pulmonary inflammation during ALI. Interleukin-2-inducible T-cell kinase (ITK) plays a key role in Th17 cell development through control of several transcription factors. Therefore, our study explored the role of ITK on airway inflammation (total/neutrophilic cell counts, myeloperoxidase activity, E-cadherin expression, histopathological analyses) and effect of its inhibition on various inflammatory/anti-inflammatory pathways during ALI [phosphorylated-ITK (p-ITK), NFATc1, IL-17A, STAT3, Foxp3, IL-10, iNOS, nitrotyrosine, lipid peroxides). ALI was associated with increased total/neutrophilic cell counts and myeloperoxidase activity, and decreased E-cadherin expression in airway epithelial cells (AECs) which was concurrent with upregulation of p-ITK, NFATc1, IL-17A, STAT3 in CD4+ T cells and iNOS/nitrotyrosine in AECs. Treatment with ITK inhibitor reversed ALI-induced changes in airway inflammation and Th17 cells/oxidative stress. Treatment with ITK inhibitor further expanded Treg cells in mice with ALI. In short, our study proposes that ITK signaling plays a significant role in sepsis-induced ALI through upregulation of Th17 cells and oxidative stress. Further, findings provide evidence that ITK blockade could be a potential treatment strategy to attenuate airway inflammation associated with ALI.

IL-1 promotes α-epithelial Sodium Channel (α-ENaC) expression in murine lung epithelial cells: involvement of NF-κB

Intra-amniotic exposure to proinflammatory cytokines such as interleukin-1 (IL-1) correlates with a decreased incidence of respiratory distress syndrome (RDS) in infants following premature birth. At birth, inadequate absorption of fluid from the fetal lung contributes to the onset RDS. Lung fluid clearance is coupled to Na⁺ transport via epithelial sodium channels (ENaC). In this study, we assessed the effects of IL-1 on the expression of ENaC, particularly the α-subunit which is critical for fetal lung fluid clearance at birth. Cultured mouse lung epithelial (MLE-12) cells were treated with either IL-1α or IL-1β to determine their effects on α-ENaC expression. Changes in IL-1-induced α-ENaC levels in the presence of IL-1 receptor antagonist (IL-1ra), cycloheximide, NF-κB inhibitor, and MAP kinase inhibitors were investigated. IL-1α and IL-1β independently induced a significant increase of α-ENaC mRNA and protein after 24 h compared to untreated cells. IL-1-dependent increases in α-ENaC protein were mitigated by IL-1ra and cycloheximide. IL-1 exposure induced NF-κB binding activity. Attenuation of IL-1-induced NF-κB activation by its inhibitor SN50 decreased α-ENaC protein abundance. Inhibition of ERK 1,2 MAPK significantly decreased both IL-1α and β-induced α-ENaC protein expression whereas inhibition of p38 MAPK only blocked IL-1β-induced α-ENaC protein levels. In contrast, IL-1-induced α-ENaC protein levels were unaffected by a c-Jun N-terminal kinase (JNK) inhibitor. Our results suggest that in MLE-12 cells, IL-1-induced elevation of α-ENaC is mediated via NF-κB activation and in part involves stimulation of the ERK 1,2 and p38 MAPK signaling pathways.

Developmentally Regulated Innate Immune NFκB Signaling Mediates IL-1α Expression in the Perinatal Murine Lung

Bronchopulmonary dysplasia (BPD) is the most common morbidity complicating premature birth. Importantly, preclinical models have demonstrated that IL-1 receptor antagonism prevents the lung injury and subsequent abnormal development that typically results following perinatal exposure to inflammatory stresses. This receptor is activated by two pro-inflammatory cytokines, IL-1α and IL-1β. While many studies have linked IL-1β to BPD development, IL-1α is relatively under-studied. The objective of our study was to determine whether systemic inflammatory stress induces IL-1α expression in the neonatal lung, and if so, whether this expression is mediated by innate immune NFκB signaling. We found that endotoxemia induced IL-1α expression during the saccular stage of neonatal lung development and was not present in the other neonatal organs or the adult lung. This IL-1α expression was dependent upon sustained pulmonary NFκB activation, which was specific to the neonatal lung. Using in vivo and in vitro approaches, we found that pharmacologic and genetic inhibition of NFκB signaling attenuated IL-1α expression. These findings demonstrate that innate immune regulation of IL-1α expression is developmentally regulated and occurs via an NFκB dependent mechanism. Importantly, the specific role of developmentally regulated pulmonary IL-1α expression remains unknown. Future studies must determine the effect of attenuating innate immune IL-1α expression in the developing lung before adopting broad IL-1 receptor antagonism as an approach to prevent neonatal lung injury.

Sex-differences in LPS-induced neonatal lung injury

Being of the male sex has been identified as a risk factor for multiple morbidities associated with preterm birth, including bronchopulmonary dysplasia (BPD). Exposure to inflammatory stress is a well-recognized risk factor for developing BPD. Whether there is a sex difference in pulmonary innate immune TLR4 signaling, lung injury and subsequent abnormal lung development is unknown. Neonatal (P0) male and female mice (ICR) were exposed to systemic LPS (5 mg/kg, IP) and innate immune signaling, and the transcriptional response were assessed (1 and 5 hours), along with lung development (P7). Male and female mice demonstrated a similar degree of impaired lung development with decreased radial alveolar counts, increased surface area, increased airspace area and increased mean linear intercept. We found no differences between male and female mice in the baseline pulmonary expression of key components of TLR4-NFκB signaling, or in the LPS-induced pulmonary expression of key mediators of neonatal lung injury. Finally, we found no difference in the kinetics of LPS-induced pulmonary NFκB activation between male and female mice. Together, these data support the conclusion that the innate immune response to early postnatal LPS exposure and resulting pulmonary sequelae is similar in male and female mice.

Lung development and emerging roles for type 2 immunity

Lung development is a complex process mediated through the interaction of multiple cell types, factors and mediators. In mice, it starts as early as embryonic day 9 and continues into early adulthood. The process can be separated into five different developmental stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar. Whilst lung bud formation and branching morphogenesis have been studied extensively, the mechanisms of alveolarisation are incompletely understood. Aberrant lung development can lead to deleterious consequences for respiratory health such as bronchopulmonary dysplasia (BPD), a disease primarily affecting preterm neonates, which is characterised by increased pulmonary inflammation and disturbed alveolarisation. While the deleterious effects of type 1-mediated inflammatory responses on lung development have been well established, the role of type 2 responses in postnatal lung development remains poorly understood. Recent studies indicate that type 2-associated immune cells, such as group 2 innate lymphoid cells and alveolar macrophages, are increased in number during postnatal alveolarisation. Here, we present the current state of understanding of the postnatal stages of lung development and the key cell types and mediators known to be involved. We also provide an overview of how stem cells are involved in lung development and regeneration, and the negative influences of respiratory infections. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Consequences of early postnatal lipopolysaccharide exposure on developing lungs in mice

Bronchopulmonary dysplasia (BPD) is a chronic lung disease of infants that is characterized by interrupted lung development. Postnatal sepsis causes BPD, yet the contributory mechanisms are unclear. To address this gap, studies have used lipopolysaccharide (LPS) during the alveolar phase of lung development. However, the lungs of infants who develop BPD are still in the saccular phase of development, and the effects of LPS during this phase are poorly characterized. We hypothesized that chronic LPS exposure during the saccular phase disrupts lung development by mechanisms that promote inflammation and prevent optimal lung development and repair. Wild-type C57BL6J mice were intraperitoneally administered 3, 6, or 10 mg/kg of LPS or a vehicle once daily on postnatal days (PNDs) 3-5. The lungs were collected for proteomic and genomic analyses and flow cytometric detection on PND6. The impact of LPS on lung development, cell proliferation, and apoptosis was determined on PND7. Finally, we determined differences in the LPS effects between the saccular and alveolar lungs. LPS decreased the survival and growth rate and lung development in a dose-dependent manner. These effects were associated with a decreased expression of proteins regulating cell proliferation and differentiation and increased expression of those mediating inflammation. While the lung macrophage population of LPS-treated mice increased, the T-regulatory cell population decreased. Furthermore, LPS-induced inflammatory and apoptotic response and interruption of cell proliferation and alveolarization was greater in alveolar than in saccular lungs. Collectively, the data support our hypothesis and reveal several potential therapeutic targets for sepsis-mediated BPD in infants.

Distinct roles for IκB kinases alpha and beta in regulating pulmonary endothelial angiogenic function during late lung development

Pulmonary angiogenesis is essential for alveolarization, the final stage of lung development that markedly increases gas exchange surface area. We recently demonstrated that activation of the nuclear factor kappa-B (NFκB) pathway promotes pulmonary angiogenesis during alveolarization. However, the mechanisms activating NFκB in the pulmonary endothelium, and its downstream targets are not known. In this study, we sought to delineate the specific roles for the NFκB activating kinases, IKKα and IKKβ, in promoting developmental pulmonary angiogenesis. Microarray analysis of primary pulmonary endothelial cells (PECs) after silencing IKKα or IKKβ demonstrated that the 2 kinases regulate unique panels of genes, with few shared targets. Although silencing IKKα induced mild impairments in angiogenic function, silencing IKKβ induced more severe angiogenic defects and decreased vascular cell adhesion molecule expression, an IKKβ regulated target essential for both PEC adhesion and migration. Taken together, these data show that IKKα and IKKβ regulate unique genes in PEC, resulting in differential effects on angiogenesis upon inhibition, and identify IKKβ as the predominant regulator of pulmonary angiogenesis during alveolarization. These data suggest that therapeutic strategies to specifically enhance IKKβ activity in the pulmonary endothelium may hold promise to enhance lung growth in diseases marked by altered alveolarization.

Developmental differences in focal adhesion kinase expression modulate pulmonary endothelial barrier function in response to inflammation

Compromised pulmonary endothelial cell (PEC) barrier function characterizes acute respiratory distress syndrome (ARDS), a cause of substantial morbidity and mortality. Survival from ARDS is greater in children compared with adults. Whether developmental differences intrinsic to PEC barrier function contribute to this survival advantage remains unknown. To test the hypothesis that PEC barrier function is more well-preserved in neonatal lungs compared with adult lungs in response to inflammation, we induced lung injury in neonatal and adult mice with systemic lipopolysaccharide (LPS). We assessed PEC barrier function in vivo and in vitro, evaluated changes in the expression of focal adhesion kinase 1 (FAK1) and phosphorylation in response to LPS, and determined the effect of FAK silencing and overexpression on PEC barrier function. We found that LPS induced a greater increase in lung permeability and PEC barrier disruption in the adult mice, despite similar degrees of inflammation and apoptosis. Although baseline expression was similar, LPS increased FAK1 expression in neonatal PEC but increased FAK1 phosphorylation and decreased FAK1 expression in adult PEC. Pharmacologic inhibition of FAK1 accentuated LPS-induced barrier disruption most in adult PEC. Finally, in response to LPS, FAK silencing markedly impaired neonatal PEC barrier function, whereas FAK overexpression preserved adult PEC barrier function. Thus, developmental differences in FAK expression during inflammatory injury serve to preserve neonatal pulmonary endothelial barrier function compared with that of adults and suggest that intrinsic differences in the immature versus pulmonary endothelium, especially relative to FAK1 phosphorylation, may contribute to the improved outcomes of children with ARDS.

Intrauterine growth restriction decreases NF-κB signaling in fetal pulmonary artery endothelial cells of fetal sheep

Intrauterine growth restriction (IUGR) in premature newborns increases the risk for bronchopulmonary dysplasia, a chronic lung disease characterized by disrupted pulmonary angiogenesis and alveolarization. We previously showed that experimental IUGR impairs angiogenesis; however, mechanisms that impair pulmonary artery endothelial cell (PAEC) function are uncertain. The NF-κB pathway promotes vascular growth in the developing mouse lung, and we hypothesized that IUGR disrupts NF-κB-regulated proangiogenic targets in fetal PAEC. PAECs were isolated from the lungs of control fetal sheep and sheep with experimental IUGR from an established model of chronic placental insufficiency. Microarray analysis identified suppression of NF-κB signaling and significant alterations in extracellular matrix (ECM) pathways in IUGR PAEC, including decreases in collagen 4α1 and laminin α4, components of the basement membrane and putative NF-κB targets. In comparison with controls, immunostaining of active NF-κB complexes, NF-κB-DNA binding, baseline expression of NF-κB subunits p65 and p50, and LPS-mediated inducible activation of NF-κB signaling were decreased in IUGR PAEC. Although pharmacological NF-κB inhibition did not affect angiogenic function in IUGR PAEC, angiogenic function of control PAEC was reduced to a similar degree as that observed in IUGR PAEC. These data identify reductions in endothelial NF-κB signaling as central to the disrupted angiogenesis observed in IUGR, likely by impairing both intrinsic PAEC angiogenic function and NF-κB-mediated regulation of ECM components necessary for vascular development. These data further suggest that strategies that preserve endothelial NF-κB activation may be useful in lung diseases marked by disrupted angiogenesis such as IUGR.

Inhibition of IκBβ/NFκB signaling prevents LPS-induced IL1β expression without increasing apoptosis in the developing mouse lung

BackgroundThe pro-inflammatory consequences of IL1β expression contribute to the pathogenesis of bronchopulmonary dysplasia. Selectively targeting Lipopolysaccharide (LPS)-induced IκBβ/NFκB signaling attenuates IL1β mRNA expression in macrophages. Whether targeting IκBβ/NFκB signaling affects the anti-apoptotic gene expression, a known consequence of global LPS-induced NFκB inhibition, is unknown.MethodsMacrophages (RAW 264.7, bone marrow-derived macrophage) were assessed for LPS-induced IL1β mRNA/protein expression, anti-apoptotic gene expression, cell viability (trypan blue exclusion), and activation of apoptosis (caspase-3 and PARP cleavage) following pharmacologic and genetic attenuation of IκBβ/NFκB signaling. Expressions of IL1β and anti-apoptotic genes were assessed in endotoxemic newborn mice (P0) with intact (WT), absent (IκBβ KO), and attenuated (IκBβ overexpressing) IκBβ/NFκB signaling.ResultsIn cultured macrophages, pharmacologic and genetic inhibition of LPS-induced IκBβ/NFκB signaling significantly attenuated IL1β mRNA and protein expression. Importantly, targeting IκBβ/NFκB signaling did not attenuate LPS-induced expression of anti-apoptotic genes or result in cell death. In endotoxemic neonatal mice, targeting LPS-induced IκBβ/NFκB signaling significantly attenuated pulmonary IL1β expression without affecting the anti-apoptotic gene expression.ConclusionTargeting IκBβ/NFκB signaling prevents LPS-induced IL1β expression without inducing apoptosis in cultured macrophages and in the lungs of endotoxemic newborn mice. Inhibiting this pathway may prevent inflammatory injury without affecting the protective role of NFκB activity in the developing lung.

Disassociating Lung Mechanics and Oxygenation in Pediatric Acute Respiratory Distress Syndrome

OBJECTIVES

Both oxygenation and peak inspiratory pressure are associated with mortality in pediatric acute respiratory distress syndrome. Since oxygenation and respiratory mechanics are linked, it is difficult to identify which variables, pressure or oxygenation, are independently associated with outcome. We aimed to determine whether respiratory mechanics (peak inspiratory pressure, positive end-expiratory pressure, ΔP [PIP minus PEEP], tidal volume, dynamic compliance [Cdyn]) or oxygenation (PaO2/FIO2) was associated with mortality.

DESIGN

Prospective, observational, cohort study.

SETTING

University affiliated PICU.

PATIENTS

Mechanically ventilated children with acute respiratory distress syndrome (Berlin).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Peak inspiratory pressure, positive end-expiratory pressure, ΔP, tidal volume, Cdyn, and PaO2/FIO2 were collected at acute respiratory distress syndrome onset and at 24 hours in 352 children between 2011 and 2016. At acute respiratory distress syndrome onset, neither mechanical variables nor PaO2/FIO2 were associated with mortality. At 24 hours, peak inspiratory pressure, positive end-expiratory pressure, ΔP were higher, and Cdyn and PaO2/FIO2 lower, in nonsurvivors. In multivariable logistic regression, PaO2/FIO2 at 24 hours and ΔPaO2/FIO2 (change in PaO2/FIO2 over the first 24 hr) were associated with mortality, whereas pressure variables were not. Both oxygenation and pressure variables were associated with duration of ventilation in multivariable competing risk regression.

CONCLUSIONS

Improvements in oxygenation, but not in respiratory mechanics, were associated with lower mortality in pediatric acute respiratory distress syndrome. Future trials of mechanical ventilation in children should focus on oxygenation (higher PaO2/FIO2) rather than lower peak inspiratory pressure or ΔP, as oxygenation was more consistently associated with outcome.

Early injury of the neonatal lung contributes to premature lung aging: a hypothesis

Chronic lung disease of the newborn, also known as bronchopulmonary dysplasia (BPD), is the most common chronic lung disease in early infancy and results in an increased risk for long-lasting pulmonary impairment in the adult. BPD develops upon injury of the immature lung by oxygen toxicity, mechanical ventilation, and infections which trigger sustained inflammatory immune responses and extensive remodeling of the extracellular matrix together with dysregulated growth factor signaling. Histopathologically, BPD is characterized by impaired alveolarization, disrupted vascular development, and saccular wall fibrosis. Here, we explore the hypothesis that development of BPD involves disturbance of conserved pathways of molecular aging that may contribute to premature aging of the lung and an increased susceptibility to chronic lung diseases in adulthood.

Perinatal Endotoxemia Induces Sustained Hepatic COX-2 Expression through an NFκB-Dependent Mechanism

BACKGROUND

Exposure to perinatal infection is associated with the multiple morbidities complicating preterm birth. How a relatively immature innate immune response contributes to this is unknown.

OBJECTIVE

We sought to determine if the perinatal innate immune response to endotoxemia induces a unique pattern of cyclooxygenase-2 (COX-2) expression via an NFκB-dependent mechanism.

METHODS

Hepatic and pulmonary COX-2 mRNA expression was assessed following perinatal (at embryonic days 15 and 19 and after birth) or adult endotoxemia. Hepatic NFκB activity was assessed by cytosolic inhibitory protein degradation and subunit nuclear translocation. Immunohistochemistry and isolated cell preparations determined hepatic macrophage COX-2 expression, and the effect of pharmacologic and genetic inhibition of NFκB activity was tested.

RESULTS

Perinatal endotoxemia induced sustained hepatic macrophage COX-2 expression and NFκB activity compared to in exposed adults. Isolated hepatic macrophages and immunohistochemistry demonstrated enriched LPS-induced COX-2 expression that was sensitive to pharmacologic and genetic approaches to attenuate NFκB activity. Finally, pharmacologic inhibition of endotoxemia-induced NFκB activity in neonatal mice prevented hepatic NFκB activity and attenuated COX-2 expression.

CONCLUSION

Our findings of sustained neonatal hepatic NFκB activity and COX-2 expression in response to endotoxemia support a robust perinatal innate immune response. This may represent a link between the innate immune response and the pathogenesis of diseases associated with preterm birth.

Combination therapy with nitric oxide and molecular hydrogen in a murine model of acute lung injury

Acute lung injury (ALI) is still a leading cause of morbidity and mortality in critically ill patients. Inhaled nitric oxide (NO) has been reported to ameliorate ALI. However, reactive nitrogen species produced by NO can cause lung injury. Because hydrogen gas (H2) is reported to eliminate peroxynitrite, it is expected to reduce the adverse effects of NO. Moreover, we have found that H2 inhalation can attenuate lung injury. Therefore, we hypothesized that combination therapy with NO and H2 might afford more potent therapeutic strategies for ALI. In the present study, a mouse model of ALI was induced by intratracheal administration of lipopolysaccharide (LPS). The animals were treated with inhaled NO (20 ppm), H2 (2%), or NO + H2, starting 5 min after LPS administration for 3 h. We found that LPS-challenged mice exhibited significant lung injury characterized by the deterioration of histopathology and histologic scores, wet-to-dry weight ratio, and oxygenation index (ratio of oxygen tension to inspired oxygen fraction [Pao2/Fio2]), as well as total protein in the bronchoalveolar lavage fluid (BALF), which was attenuated by NO or H2 treatment alone. Combination therapy with NO and H2 had a more beneficial effect with significant interaction between the two. While the nitrotyrosine level in lung tissue was prominent after NO inhalation alone, it was significantly eliminated after breathing a mixture of NO with H2. Furthermore, NO or H2 treatment alone markedly attenuated LPS-induced lung neutrophil recruitment and inflammation, as evidenced by downregulation of lung myeloperoxidase activity, total cells, and polymorphonuclear neutrophils in BALF, as well as proinflammatory cytokines (tumor necrosis factor α, interleukins 1β and 6, and high-mobility group box 1) and chemokines (keratinocyte-derived chemokine, macrophage inflammatory proteins 1α and 2, and monocyte chemoattractant protein 1) in BALF. Combination therapy with NO and H2 had a more beneficial effect against lung inflammatory response. Moreover, combination therapy with NO and H2 could more effectively inhibit LPS-induced pulmonary early and late nuclear factor κB activation as well as pulmonary cell apoptosis. In addition, combination treatment with inhaled NO and H2 could also significantly attenuate lung injury in polymicrobial sepsis. Combination therapy with subthreshold concentrations of NO and H2 still had a significantly beneficial effect against lung injury induced by LPS and polymicrobial sepsis. Collectively, these results demonstrate that combination therapy with NO and H2 provides enhanced therapeutic efficacy for ALI.

Understanding the Impact of Infection, Inflammation, and Their Persistence in the Pathogenesis of Bronchopulmonary Dysplasia

The concerted interaction of genetic and environmental factors acts on the preterm human immature lung with inflammation being the common denominator leading to the multifactorial origin of the most common chronic lung disease in infants – ­bronchopulmonary dysplasia (BPD). Adverse perinatal exposure to infection/inflammation with added insults like invasive mecha nical ventilation, exposure to hyperoxia, and sepsis causes persistent immune dysregulation. In this review article, we have attempted to analyze and consolidate current knowledge about the role played by persistent prenatal and postnatal inflammation in the pathogenesis of BPD. While some parameters of the early inflammatory response (neutrophils, cytokines, etc.) may not be detectable after days to weeks of exposure to noxious stimuli, they have already initiated the signaling pathways of the inflammatory process/immune cascade and have affected permanent defects structurally and functionally in the BPD lungs. Hence, translational research aimed at prevention/amelioration of BPD needs to focus on dampening the inflammatory response at an early stage to prevent the cascade of events leading to lung injury with impaired healing resulting in the pathologic pulmonary phenotype of alveolar simplification and dysregulated vascularization characteristic of BPD.

Myeloid differentiation protein 2 facilitates pollen- and cat dander-induced innate and allergic airway inflammation

BACKGROUND

The National Health and Nutrition Examination Survey identified several pollens and cat dander as among the most common allergens that induce allergic sensitization and allergic diseases. We recently reported that ragweed pollen extract (RWPE) requires Toll-like receptor 4 (TLR4) to stimulate CXCL-mediated innate neutrophilic inflammation, which in turn facilitates allergic sensitization and airway inflammation. Myeloid differentiation protein 2 (MD2) is a TLR4 coreceptor, but its role in pollen- and cat dander-induced innate and allergic inflammation has not been critically evaluated.

OBJECTIVE

We sought to elucidate the role of MD2 in inducing pollen- and cat dander-induced innate and allergic airway inflammation.

METHODS

TCM(Null) (TLR4(Null), CD14(Null), MD2(Null)), TLR4(Hi), and TCM(Hi) cells and human bronchial epithelial cells with small interfering RNA-induced downregulation of MD2 were stimulated with RWPE, other pollen allergic extracts, or cat dander extract (CDE), and activation of nuclear factor κB (NF-κB), secretion of the NF-κB-dependent CXCL8, or both were quantified. Wild-type mice or mice with small interfering RNA knockdown of lung MD2 were challenged intranasally with RWPE or CDE, and innate and allergic inflammation was quantified.

RESULTS

RWPE stimulated MD2-dependent NF-κB activation and CXCL secretion. Likewise, Bermuda, rye, timothy, pigweed, Russian thistle, cottonwood, walnut, and CDE stimulated MD2-dependent CXCL secretion. RWPE and CDE challenge induced MD2-dependent and CD14-independent innate neutrophil recruitment. RWPE induced MD2-dependent allergic sensitization and airway inflammation.

CONCLUSIONS

MD2 plays an important role in induction of allergic sensitization to cat dander and common pollens relevant to human allergic diseases.

Melatonin prevents lung injury induced by hepatic ischemia-reperfusion through anti-inflammatory and anti-apoptosis effects

Melatonin is a free radical scavenger and broad-spectrum antioxidant with immunomodulatory effects. The objective of the study is to investigate the effects of melatonin in hepatic ischemia/reperfusion (I/R) induced lung injury and explore its underlying mechanisms. Hepatic I/R injury was induced via portal vein and hepatic artery occlusion for 30min followed by 3-h reperfusion. Male Sprague-Dawley rats were divided into three groups: sham, I/R+ Vehicle and I/R+melatonin. Melatonin (10mg/kg) or vehicle was injected intravenously 15min before ischemia and 10min before reperfusion. The histology of the liver and lung, plasma aminotransferase and cytokine secretion, and apoptosis in the lung were evaluated. The phosphorylation of JNK, p38, and NF-ƙB and Nrf2 nuclear translocation in the lung was examined by Western blotting. We found that melatonin administration significantly attenuated hepatic I/R induced lung injury in rats. Melatonin inhibited the pro-inflammatory responses and enhanced antioxidative responses. Melatonin alleviated pathological changes of the lung and liver, and inhibited apoptosis of cells in the lung. Phosphorylation of JNK, p38 and NF-ƙB and Nrf2 nuclear translocation was increased significantly in the lung by hepatic I/R. Melatonin administration inhibited the activation of JNK, p38, and NF-ƙB, however, melatonin further enhanced Nrf2 activation. We conclude that melatonin exerts a protective effect in hepatic I/R induced lung injury by attenuating the pro-inflammatory responses, inhibiting cell apoptosis, which was mediated in part through JNK, p38 MAPK, NF-ƙB and Nrf2 signaling pathways. Melatonin may be a promising therapeutic strategy for hepatic I/R induced lung injury.

Activation of the nuclear factor-κB pathway during postnatal lung inflammation preserves alveolarization by suppressing macrophage inflammatory protein-2

A significant portion of lung development is completed postnatally during alveolarization, rendering the immature lung vulnerable to inflammatory stimuli that can disrupt lung structure and function. Although the NF-κB pathway has well-recognized pro-inflammatory functions, novel anti-inflammatory and developmental roles for NF-κB have recently been described. Thus, to determine how NF-κB modulates alveolarization during inflammation, we exposed postnatal day 6 mice to vehicle (PBS), systemic lipopolysaccharide (LPS), or the combination of LPS and the global NF-κB pathway inhibitor BAY 11-7082 (LPS + BAY). LPS impaired alveolarization, decreased lung cell proliferation, and reduced epithelial growth factor expression. BAY exaggerated these detrimental effects of LPS, further suppressing proliferation and disrupting pulmonary angiogenesis, an essential component of alveolarization. The more severe pathology induced by LPS + BAY was associated with marked increases in lung and plasma levels of macrophage inflammatory protein-2 (MIP-2). Experiments using primary neonatal pulmonary endothelial cells (PEC) demonstrated that MIP-2 directly impaired neonatal PEC migration in vitro; and neutralization of MIP-2 in vivo preserved lung cell proliferation and pulmonary angiogenesis and prevented the more severe alveolar disruption induced by the combined treatment of LPS + BAY. Taken together, these studies demonstrate a key anti-inflammatory function of the NF-κB pathway in the early alveolar lung that functions to mitigate the detrimental effects of inflammation on pulmonary angiogenesis and alveolarization. Furthermore, these data suggest that neutralization of MIP-2 may represent a novel therapeutic target that could be beneficial in preserving lung growth in premature infants exposed to inflammatory stress.

Pediatric acute respiratory distress syndrome: definition, incidence, and epidemiology: proceedings from the Pediatric Acute Lung Injury Consensus Conference

OBJECTIVES

Although there are similarities in the pathophysiology of acute respiratory distress syndrome in adults and children, pediatric-specific practice patterns, comorbidities, and differences in outcome necessitate a pediatric-specific definition. We sought to create such a definition.

DESIGN

A subgroup of pediatric acute respiratory distress syndrome investigators who drafted a pediatric-specific definition of acute respiratory distress syndrome based on consensus opinion and supported by detailed literature review tested elements of the definition with patient data from previously published investigations.

SETTINGS

International PICUs.

SUBJECTS

Children enrolled in published investigations of pediatric acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Several aspects of the proposed pediatric acute respiratory distress syndrome definition align with the Berlin Definition of acute respiratory distress syndrome in adults: timing of acute respiratory distress syndrome after a known risk factor, the potential for acute respiratory distress syndrome to coexist with left ventricular dysfunction, and the importance of identifying a group of patients at risk to develop acute respiratory distress syndrome. There are insufficient data to support any specific age for "adult" acute respiratory distress syndrome compared with "pediatric" acute respiratory distress syndrome. However, children with perinatal-related respiratory failure should be excluded from the definition of pediatric acute respiratory distress syndrome. Larger departures from the Berlin Definition surround 1) simplification of chest imaging criteria to eliminate bilateral infiltrates; 2) use of pulse oximetry-based criteria when PaO2 is unavailable; 3) inclusion of oxygenation index and oxygen saturation index instead of PaO2/FIO2 ratio with a minimum positive end-expiratory pressure level for invasively ventilated patients; 4) and specific inclusion of children with preexisting chronic lung disease or cyanotic congenital heart disease.

CONCLUSIONS

This pediatric-specific definition for acute respiratory distress syndrome builds on the adult-based Berlin Definition, but has been modified to account for differences between adults and children with acute respiratory distress syndrome. We propose using this definition for future investigations and clinical care of children with pediatric acute respiratory distress syndrome and encourage external validation with the hope for continued iterative refinement of the definition.

Pathobiology of acute respiratory distress syndrome

The unique characteristics of pulmonary circulation and alveolar-epithelial capillary-endothelial barrier allow for maintenance of the air-filled, fluid-free status of the alveoli essential for facilitating gas exchange, maintaining alveolar stability, and defending the lung against inhaled pathogens. The hallmark of pathophysiology in acute respiratory distress syndrome is the loss of the alveolar capillary permeability barrier and the presence of protein-rich edema fluid in the alveoli. This alteration in permeability and accumulation of fluid in the alveoli accompanies damage to the lung epithelium and vascular endothelium along with dysregulated inflammation and inappropriate activity of leukocytes and platelets. In addition, there is uncontrolled activation of coagulation along with suppression of fibrinolysis and loss of surfactant. These pathophysiological changes result in the clinical manifestations of acute respiratory distress syndrome, which include hypoxemia, radiographic opacities, decreased functional residual capacity, increased physiologic deadspace, and decreased lung compliance. Resolution of acute respiratory distress syndrome involves the migration of cells to the site of injury and re-establishment of the epithelium and endothelium with or without the development of fibrosis. Most of the data related to acute respiratory distress syndrome, however, originate from studies in adults or in mature animals with very few studies performed in children or juvenile animals. The lack of studies in children is particularly problematic because the lungs and immune system are still developing during childhood and consequently the pathophysiology of pediatric acute respiratory distress syndrome may differ in significant ways from that seen in acute respiratory distress syndrome in adults. This article describes what is known of the pathophysiologic processes of pediatric acute respiratory distress syndrome as we know it today while also presenting the much greater body of evidence on these processes as elucidated by adult and animal studies. It is also our expressed intent to generate enthusiasm for larger and more in-depth investigations of the mechanisms of disease and repair specific to children in the years to come.

Bronchopulmonary dysplasia - an overview about pathophysiologic concepts

Neonatal chronic lung disease in the preterm infant, i.e. bronchopulmonary dysplasia (BPD) is characterized by impaired pulmonary development with its effects persisting into adulthood. Triggered in the immature lung by infectious complications, oxygen toxicity and the impact of mechanical ventilation, a sustained inflammatory response, extensive remodeling of the extracellular matrix, increased apoptosis as well as altered growth factor signaling characterize the disease. The current review focuses on selected pathophysiologic processes and their interplay in disease development. Furthermore, the potential of both, acute and long-term changes to the pulmonary scaffold and the cellular interface in concert with dysregulated growth factor signaling to affect aging and repair processes in the adult lung is discussed.

Bronchopulmonary dysplasia early changes leading to long-term consequences

Neonatal chronic lung disease, i.e., bronchopulmonary dysplasia, is characterized by impaired pulmonary development resulting from the impact of different risk factors including infections, hyperoxia, and mechanical ventilation on the immature lung. Remodeling of the extracellular matrix, apoptosis as well as altered growth factor signaling characterize the disease. The immediate consequences of these early insults have been studied in different animal models supported by results from in vitro approaches leading to the successful application of some findings to the clinical setting in the past. Nonetheless, existing information about long-term consequences of the identified early and most likely sustained changes to the developing lung is limited. Interesting results point towards a tremendous impact of these early injuries on the pulmonary repair capacity as well as aging related processes in the adult lung.

Bacillus Calmette-Guerín vaccination: a novel therapeutic approach to preventing hyperoxic lung injury

OBJECTIVE

A growing body of evidence suggests that vaccinations play a role in the normal maturation of the immune system and in both the development and balance of immune regulatory pathways that can impact health later in life. This study aimed to evaluate the effects of Bacillus Calmette-Guerín (BCG) vaccine on the hyperoxia-induced neonatal rat lung injury.

METHODS

Four groups were defined as hyperoxia-exposed BCG-vaccinated, hyperoxia-exposed placebo, room air-exposed control and room air-exposed BCG-vaccinated group. The validity of the hyperoxia-induced lung injury model used in this study was confirmed by histological and immunohistochemical test. Gene expression related with cytokine and growth factor was evaluated by real-time reverse transcription polymerase chain reaction.

RESULT

The mean alveolar surface area and quantification of secondary crest formation in the oxygen-exposed placebo group was significantly lower than that of the oxygen-exposed BCG-vaccinated group. Compared to the oxygen-exposed placebo group, the oxygen-exposed BCG-vaccinated group showed a significantly decreased alveolar septal fibrosis and smooth muscle actin expression. The expression of genes VEGF, FGF-BP1, IL-13, and NFκB1 (p50) in the lungs of the hyperoxia-exposed BCG-vaccinated group was significantly higher than that of the hyperoxia-exposed placebo group.

CONCLUSION

Results suggest that BCG vaccination can protect against neonatal hyperoxic lung injury. These benefits may be interpreted to coincide with its immunomodulatory effects on pro-inflammatory and anti-inflammatory cytokine balance and expression of growth factors.

Alveolar NF-κB signaling regulates endotoxin-induced lung inflammation

PURPOSE/AIM

The alveolar epithelium participates in host defense through inflammatory pathways that activate NF-κB. Lung infections involving endotoxins trigger acute respiratory distress syndrome (ARDS) in adult and pediatric patients. The purpose of this study was to test the hypothesis that overexpression of NF-κB would worsen and conditional deletion of NF-κB signaling would improve endotoxin-induced lung inflammation using transgenic mouse models.

MATERIALS AND METHODS

Two previously described transgenic mouse models were used in which overexpression of the RelA/p65 subunit of NF-κB was targeted to the lung epithelium using an SPC promoter (SPC-RelA) and conditional deletion of the IKKβ molecule involved in NF-κB signaling was targeted to the lung epithelium using Nkx2.1(Cre) (Nkx2.1(Cre);IKKβ(F/F)). Adult transgenic and control mice were injected with intratracheal lipopolysaccharide (LPS) or saline followed by lung harvest at 48 h. Collected tissue included whole lungs from transgenic and control mice which was processed for analysis of BAL, lung histology, chemokine expression, and markers of cell apoptosis as well as collection of freshly isolated AECII cells from wild type mice for additional chemokine and apoptotic marker analysis.

RESULTS

SPC-RelA mice showed significant increases in lung inflammation and injury following LPS injection with increased neutrophil recruitment as compared to wild type and saline treated controls. In contrast, Nkx2.1(Cre); IKKβ(F/F) mice showed markedly decreased lung inflammation and injury with decreased neutrophil recruitment as compared to controls. In both models, lung inflammation was associated with increased cell apoptosis and these findings were confirmed in freshly isolated AECII cells in wild type mice following LPS injection.

CONCLUSIONS

Overexpression of NF-κB targeted to the lung epithelium worsened lung inflammation and injury in response to LPS exposure while conditional deletion of NF-κB signaling reduced lung inflammation. Lung inflammation and injury were associated with increased cell apoptosis.

Postnatal development and LPS responsiveness of pulmonary adenosine receptor expression and of adenosine-metabolizing enzymes in mice

BACKGROUND

Adenosine levels are regulated by ecto-5'-nucleotidase/CD73 and adenosine deaminase (ADA). Adenosine regulates endothelial permeability and anti-inflammatory responses via adenosine receptors. Here, the adenosine receptors and purine-converting enzymes were studied during postnatal development and inflammation.

METHODS

Newborn, 1-, 10-, 14-d-old and adult C57BL/6 mice were challenged intraperitoneally (i.p.) with lipopolysaccharide (LPS) for 6 h. The inflammatory response was evaluated by histochemistry. Expression levels of adenosine receptors (A1, A2A, A2B, and A3), CD73, and ADA were measured by quantitative reverse transcription polymerase chain reaction. A1 was studied by immunohistochemistry, and enzyme activities were analyzed by thin-layer chromatography.

RESULTS

LPS caused respiratory distress in newborns within 24 h. LPS induced neutrophils at the basal stage and alveolar congestion. Low activity and expression of CD73 increased after birth. Expression of ADA after LPS increased 16-fold in adults and 2-fold in newborns (P < 0.05). A1 expression was high in newborns and increased after LPS (P < 0.05). A1 was localized to endothelial membranes. A2A decreased after LPS in newborns and increased in adults (P < 0.05). The expression of A3 increased in newborns and adults after LPS.

CONCLUSION

Low pulmonary CD73 expression, LPS-induced suppression of A2A, LPS-induced increase of A1 expression, and severe respiratory distress were distinguishing responses in the newborns from those in the adults.

Ventilator-induced lung injury. Similarity and differences between children and adults

It is well established that mechanical ventilation can injure the lung, producing an entity known as ventilator-induced lung injury (VILI). There are various forms of VILI, including volutrauma (i.e., injury caused by overdistending the lung), atelectrauma (injury due to repeated opening/closing of lung units), and biotrauma (release of mediators that can induce lung injury or aggravate pre-existing injury, potentially leading to multiple organ failure). Experimental data in the pediatric context are in accord with the importance of VILI, and appear to show age-related susceptibility to VILI, although a conclusive link between use of large Vts and mortality has not been demonstrated in this population. The relevance of VILI in the pediatric intensive care unit population is thus unclear. Given the physiological and biological differences in the respiratory systems of infants, children, and adults, it is difficult to directly extrapolate clinical practice from adults to children. This Critical Care Perspective analyzes the relevance of VILI to the pediatric population, and addresses why pediatric patients might be less susceptible than adults to VILI.

Nuclear factor-kappa-B signaling in lung development and disease: one pathway, numerous functions

In contrast to other organs, the lung completes a significant portion of its development after term birth. During this stage of alveolarization, division of the alveolar ducts into alveolar sacs by secondary septation, and expansion of the pulmonary vasculature by means of angiogenesis markedly increase the gas exchange surface area of the lung. However, postnatal completion of growth renders the lung highly susceptible to environmental insults such as inflammation that disrupt this developmental program. This is particularly evident in the setting of preterm birth, where impairment of alveolarization causes bronchopulmonary dysplasia, a chronic lung disease associated with significant morbidity. The nuclear factor κ-B (NFκB) family of transcription factors are ubiquitously expressed, and function to regulate diverse cellular processes including proliferation, survival, and immunity. Extensive evidence suggests that activation of NFκB is important in the regulation of inflammation and in the control of angiogenesis. Therefore, NFκB-mediated downstream effects likely influence the lung response to injury and may also mediate normal alveolar development. This review summarizes the main biologic functions of NFκB, and highlights the regulatory mechanisms that allow for diversity and specificity in downstream gene activation. This is followed by a description of the pro and anti-inflammatory functions of NFκB in the lung, and of NFκB-mediated angiogenic effects. Finally, this review summarizes the clinical and experimental data that support a role for NFκB in mediating postnatal angiogenesis and alveolarization, and discusses the challenges that remain in developing therapies that can selectively block the detrimental functions of NFκB yet preserve the beneficial effects.

Pulmonary Hypertension in Preterm Infants with Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is a significant contributor to perinatal morbidity and mortality. Premature birth disrupts pulmonary vascular growth and initiates a cascade of events that result in impaired gas exchange, abnormal vasoreactivity, and pulmonary vascular remodeling that may ultimately lead to pulmonary hypertension (PH). Even infants who appear to have mild BPD suffer from varying degrees of pulmonary vascular disease (PVD). Although recent studies have enhanced our understanding of the pathobiology of PVD and PH in BPD, much remains unknown with respect to how PH should be properly defined, as well as the most accurate methods for the diagnosis and treatment of PH in infants with BPD. This article will provide neonatologists and primary care providers, as well as pediatric cardiologists and pulmonologists, with a review of the pathophysiology of PH in preterm infants with BPD and a summary of current clinical recommendations for managing PH in this population.

Postnatal inflammation in the pathogenesis of bronchopulmonary dysplasia

Exposure to hyperoxia, invasive mechanical ventilation, and systemic/local sepsis are important antecedents of postnatal inflammation in the pathogenesis of bronchopulmonary dysplasia (BPD). This review will summarize information obtained from animal (baboon, lamb/sheep, rat and mouse) models that pertain to the specific inflammatory agents and signaling molecules that predispose a premature infant to BPD.

Mechanisms of acute respiratory distress syndrome in children and adults: a review and suggestions for future research

OBJECTIVES

To provide a current overview of the epidemiology and pathophysiology of acute respiratory distress syndrome in adults and children, and to identify research questions that will address the differences between adults and children with acute respiratory distress syndrome.

DATA SOURCES

Narrative literature review and author-generated data.

DATA SELECTION

The epidemiology of acute respiratory distress syndrome in adults and children, lung morphogenesis, and postnatal lung growth and development are reviewed. The pathophysiology of acute respiratory distress syndrome is divided into eight categories: alveolar fluid transport, surfactant, innate immunity, apoptosis, coagulation, direct alveolar epithelial injury by bacterial products, ventilator-associated lung injury, and repair.

DATA EXTRACTION AND SYNTHESIS

Epidemiologic data suggest significant differences in the prevalence and mortality of acute respiratory distress syndrome between children and adults. Postnatal lung development continues through attainment of adult height, and there is overlap between the regulation of postnatal lung development and inflammatory, apoptotic, alveolar fluid clearance, and repair mechanisms. Therefore, there is a different biological baseline network of gene and protein expression in children as compared with adults.

CONCLUSIONS

There are significant obstacles to performing research on children with acute respiratory distress syndrome. However, epidemiologic, clinical, and animal studies suggest age-dependent differences in the pathophysiology of acute respiratory distress syndrome. In order to reduce the prevalence and improve the outcome of patients with acute respiratory distress syndrome, translational studies of inflammatory, apoptotic, alveolar fluid clearance, and repair mechanisms are needed. Understanding the differences in pathophysiologic mechanisms in acute respiratory distress syndrome between children and adults should facilitate identification of novel therapeutic interventions to prevent or modulate lung injury and improve lung repair.

Inhibition of pulmonary nuclear factor kappa-B decreases the severity of acute Escherichia coli pneumonia but worsens prolonged pneumonia

Introduction

Nuclear factor (NF)-κB is central to the pathogenesis of inflammation in acute lung injury, but also to inflammation resolution and repair. We wished to determine whether overexpression of the NF-κB inhibitor IκBα could modulate the severity of acute and prolonged pneumonia-induced lung injury in a series of prospective randomized animal studies.

Methods

Adult male Sprague-Dawley rats were randomized to undergo intratracheal instillation of (a) 5 × 10⁹ adenoassociated virus (AAV) vectors encoding the IκBα transgene (5 × 10⁹ AAV-IκBα); (b) 1 × 10¹⁰ AAV-IκBα; (c) 5 × 10¹⁰ AAV-IκBα; or (d) vehicle alone. After intratracheal inoculation with Escherichia coli, the severity of the lung injury was measured in one series over a 4-hour period (acute pneumonia), and in a second series after 72 hours (prolonged pneumonia). Additional experiments examined the effects of IκBα and null-gene overexpression on E. coli-induced and sham pneumonia.

Results

In acute pneumonia, IκBα dose-dependently decreased lung injury, improving arterial oxygenation and lung static compliance, reducing alveolar protein leak and histologic injury, and decreasing alveolar IL-1β concentrations. Benefit was maximal at the intermediate (1 × 10¹⁰) IκBα vector dose; however, efficacy was diminished at the higher (5 × 10¹⁰) IκBα vector dose. In contrast, IκBα worsened prolonged pneumonia-induced lung injury, increased lung bacterial load, decreased lung compliance, and delayed resolution of the acute inflammatory response.

Conclusions

Inhibition of pulmonary NF-κB activity reduces early pneumonia-induced injury, but worsens injury and bacterial load during prolonged pneumonia.

Lung microenvironment contributes to the resistance of alveolar macrophages to develop tolerance to endotoxin*

OBJECTIVE

Endotoxin tolerance corresponds to reprogramming of mononuclear phagocytes after iterative encounters with toll-like receptor agonists aimed to dampen the inflammatory response. We investigated why this phenomenon cannot be observed with murine alveolar macrophages.

DESIGN

Animal study.

SETTING

Research institution laboratory.

SUBJECTS

rag2-/-, rag2γc-/-, cd3ε-/-, µ-/-, il-15-/-, Jα18-/-, ifnγr-/-, il-18r-/-, and wild-type mice.

INTERVENTIONS

Alveolar macrophages were harvested from untreated mice or after injection of endotoxin. Alveolar macrophages were activated in vitro with endotoxin (lipopolysaccharide), and tumor necrosis factor production was monitored.

MEASUREMENTS AND MAIN RESULTS

In contrast to monocytes or peritoneal macrophages, alveolar macrophages did not display endotoxin tolerance in an ex vivo model after injection of endotoxin. An in vivo systemic inhibition of granulocyte-macrophage colony-stimulating factor or interferon-γ allowed the induction of alveolar macrophage endotoxin tolerance, which was also observed in interferon-γ receptor-deficient mice. Using mice missing different leukocyte subsets and adoptive cell transfers, we demonstrated the involvement of B lymphocytes in interferon-γ production within the lung microenvironment and in the prevention of alveolar macrophage endotoxin tolerance. Furthermore, we demonstrated the importance of interleukin-18 in preventing alveolar macrophage endotoxin tolerance through studies of interleukin-18 messenger RNA expression in il-18r-/- mice and injection of interleukin-18 in rag2-/- and µ-/- mice.

CONCLUSIONS

Our results support the conclusion that at homeostasis in the lungs, constitutive expression of granulocyte-macrophage colony-stimulating factor, interleukin-18, interferon-γ and possibly interleukin-15, and a cross-talk between B lymphocytes and alveolar macrophages create a microenvironment specific to the lungs that prevents alveolar macrophages from becoming tolerant to endotoxin.

Molecular hydrogen ameliorates lipopolysaccharide-induced acute lung injury in mice through reducing inflammation and apoptosis

Acute lung injury (ALI) is still a leading cause of morbidity and mortality in critically ill patients. Recently, our and other studies have found that hydrogen gas (H₂) treatment can ameliorate the lung injury induced by sepsis, ventilator, hyperoxia, and ischemia-reperfusion. However, the molecular mechanisms by which H₂ ameliorates lung injury remain unclear. In the current study, we investigated whether H₂ or hydrogen-rich saline (HS) could exert protective effects in a mouse model of ALI induced by intratracheal administration of lipopolysaccharide (LPS) via inhibiting the nuclear factor κB (NF-κB) signaling pathway-mediated inflammation and apoptosis. Two percent of H₂ was inhaled for 1 h beginning at 1 and 6 h after LPS administration, respectively. We found that LPS-challenged mice exhibited significant lung injury characterized by the deterioration of histopathology and histologic scores, wet-to-dry weight ratio, and oxygenation index (PaO₂/FIO₂), as well as total protein in the bronchoalveolar lavage fluid (BALF), which was attenuated by H₂ treatment. Hydrogen gas treatment inhibited LPS-induced pulmonary early and late NF-κB activation. Moreover, H₂ treatment dramatically prevented the LPS-induced pulmonary cell apoptosis in LPS-challenged mice, as reflected by the decrease in TUNEL (deoxynucleotidyl transferase dUTP nick end labeling) staining-positive cells and caspase 3 activity. Furthermore, H₂ treatment markedly attenuated LPS-induced lung neutrophil recruitment and inflammation, as evidenced by downregulation of lung myeloperoxidase activity, total cells, and polymorphonuclear neutrophils in BALF, as well as proinflammatory cytokines (tumor necrosis factor α, interleukin 1β, interleukin 6, and high-mobility group box 1) and chemokines (keratinocyte-derived chemokine, macrophage inflammatory protein [MIP] 1α, MIP-2, and monocyte chemoattractant protein 1) in BALF. In addition, i.p. injection of 10 mL/kg hydrogen-rich saline also significantly attenuated the LPS-induced ALI. Collectively, these results demonstrate that molecular hydrogen treatment ameliorates LPS-induced ALI through reducing lung inflammation and apoptosis, which may be associated with the decreased NF-κB activity. Hydrogen gas may be useful as a novel therapy to treat ALI. munosorbent assay; H₂-hydrogen gas; HMGB1-high-mobility group box 1; HS-hydrogen-rich saline; i.t.-intratracheal; KC-keratinocyte-derived chemokine; LPS-lipopolysaccharide; MCP-1-monocyte chemoattractant protein 1; MIP-1α-macrophage inflammatory protein 1α; MIP-2-macrophage inflammatory protein 2; MPO-myeloperoxidase; PBS-phosphate-buffered saline; PMNs-polymorphonuclear neutrophils; TUNEL-deoxynucleotidyl transferase dUTP nick end labeling; W/D-wet-to-dry.

The pulmonary endothelial glycocalyx regulates neutrophil adhesion and lung injury during experimental sepsis

Sepsis, a systemic inflammatory response to infection, commonly progresses to acute lung injury (ALI), an inflammatory lung disease with high morbidity. We postulated that sepsis-associated ALI is initiated by degradation of the pulmonary endothelial glycocalyx, leading to neutrophil adherence and inflammation. Using intravital microscopy, we found that endotoxemia in mice rapidly induced pulmonary microvascular glycocalyx degradation via tumor necrosis factor-α (TNF-α)-dependent mechanisms. Glycocalyx degradation involved the specific loss of heparan sulfate and coincided with activation of endothelial heparanase, a TNF-α-responsive, heparan sulfate-specific glucuronidase. Glycocalyx degradation increased the availability of endothelial surface adhesion molecules to circulating microspheres and contributed to neutrophil adhesion. Heparanase inhibition prevented endotoxemia-associated glycocalyx loss and neutrophil adhesion and, accordingly, attenuated sepsis-induced ALI and mortality in mice. These findings are potentially relevant to human disease, as sepsis-associated respiratory failure in humans was associated with higher plasma heparan sulfate degradation activity; moreover, heparanase content was higher in human lung biopsies showing diffuse alveolar damage than in normal human lung tissue.

Possible interventional therapies in severe sepsis or septic shock

For many years, basic research with relatively straightforward pathophysiologic approaches has driven clinical trials using molecules that supposedly interfere positively with inflammatory processes. However, most of these trials have failed to demonstrate any outcome benefit. Indeed, we need to revisit current paradigms and to think about the possibility that outcome may be predetermined in severe sepsis or septic shock. In addition, an early diagnosis of sepsis prior to the onset of clinical decline is also of particular interest to health practitioners because this information increases the possibilities for early and specific treatment of this life threatening condition. Indeed, the time to initiate therapy is thought to be crucial and the major determent factor in surviving sepsis. Despite substantial progress in sepsis therapy, the gap between the discovery of new effective medical molecules and their implementation in the daily clinical practice of the intensive care unit remains a major hurdle. Fortunately, ongoing research continues to provide new information on the management of sepsis, in particular, severe sepsis or septic shock. High quality and effective management tools are necessary to bring evidence-based therapy to the bedside. On this basis, new therapies could be tested to reduce mortality rates with respect to recently published studies.