Low levels of tissue factor lead to alveolar haemorrhage, potentiating murine acute lung injury and oxidative stress

MEK1/2 and ERK1/2 mediated lung endothelial injury and altered hemostasis promote diffuse alveolar hemorrhage in murine lupus

Objective

About 3% of lupus patients develop severe diffuse alveolar hemorrhage (DAH) with pulmonary vasculitis. B6 mice with pristane-induced lupus also develop DAH, but BALB/c mice are resistant. DAH is independent of TLR signaling and other inflammatory pathways. This study examined the role of the mitogen-activated protein kinase pathway (MEK1/2-ERK1/2, JNK, p38).

Methods

B6 and BALB/c mice were treated with pristane ± inhibitors of MEK1/2 (trametinib/GSK1120212, "GSK"), ERK1/2 (SCH772984, "SCH"), JNK, or p38. Effects on lung hemorrhage and hemostasis were determined.

Results

GSK and SCH abolished DAH, whereas JNK and p38 inhibitors were ineffective. Apoptotic cells were present in lung from pristane-treated mice, but not mice receiving pristane+GSK and endothelial dysfunction was normalized. Expression of the ERK1/2-regulated transcription factor Egr1 increased in pristane-treated B6, but not BALB/c, mice and was normalized by GSK. Pristane also increased expression of the anticoagulant genes Tfpi (tissue factor pathway inhibitor) and Thbd (thrombomodulin) in B6 mice. The ratio of tissue factor ( F3 ) to Tfpi increased in B6 (but not BALB/c) mice and was normalized by GSK. Circulating Thbd protein increased in B6 mice and returned to normal after GSK treatment. Consistent with augmented endothelial anticoagulant activity, pristane treatment increased tail bleeding in B6 mice.

Conclusion

Pristane treatment promotes lung endothelial injury and DAH in B6 mice by activating the MEK1/2-ERK1/2 pathway and impairing hemostasis. The hereditary factors determining susceptibility to lung injury and bleeding in pristane-induced lupus are relevant to the pathophysiology of life-threatening DAH in SLE and may help to optimize therapy.

Cell-free hemoglobin triggers macrophage cytokine production via TLR4 and MyD88

Cell-free hemoglobin (CFH) is elevated in the airspace of patients with acute respiratory distress syndrome (ARDS) and is sufficient to cause acute lung injury in a murine model. However, the pathways through which CFH causes lung injury are not well understood. Toll-like receptor 4 (TLR4) is a mediator of inflammation after detection of damage- and pathogen-associated molecular patterns. We hypothesized that TLR4 signaling mediates the proinflammatory effects of CFH in the airspace. After intratracheal CFH, BALBc mice deficient in TLR4 had reduced inflammatory cell influx into the airspace [bronchoalveolar lavage (BAL) cell counts, median TLR4 knockout (KO): 0.8 × 104/mL [IQR 0.4-1.2 × 104/mL], wild-type (WT): 3.0 × 104/mL [2.2-4.0 × 104/mL], P < 0.001] and attenuated lung permeability (BAL protein, TLR4KO: 289 µg/mL [236-320], WT: 488 µg/mL [422-536], P < 0.001). These mice also had attenuated production of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in the airspace. C57Bl/6 mice lacking TLR4 on myeloid cells only (LysM.Cre+/-TLR4fl/fl) had reduced cytokine production in the airspace after CFH, without attenuation of lung permeability. In vitro studies confirm that WT primary murine alveolar macrophages exposed to CFH (0.01-1 mg/mL) had dose-dependent increases in IL-6, IL-1 β, CXC motif chemokine ligand 1 (CXCL-1), TNF-α, and IL-10 (P < 0.001). Murine MH-S alveolar-like macrophages show TLR4-dependent expression of IL-1β, IL-6, and CXCL-1 in response to CFH. Primary alveolar macrophages from mice lacking TLR4 adaptor proteins myeloid differentiation primary response 88 (MyD88) or TIR-domain-containing adapter-inducing interferon-β (TRIF) revealed that MyD88KO macrophages had 71-96% reduction in CFH-dependent proinflammatory cytokine production (P < 0.001), whereas macrophages from TRIFKO mice had variable changes in cytokine responses. These data demonstrate that myeloid TLR4 signaling through MyD88 is a key regulator of airspace inflammation in response to CFH.NEW & NOTEWORTHY Cell-free hemoglobin (CFH) is elevated in the airspace of most patients with acute respiratory distress syndrome and causes severe inflammation. Here, we identify that CFH contributes to macrophage-induced cytokine production via Toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) signaling. These data increase our knowledge of the mechanisms through which CFH contributes to lung injury and may inform development of targeted therapeutics to attenuate inflammation.

Regulation of von Willebrand factor by ADAMTS13 ameliorates lipopolysaccharide-induced lung injury in mice

The relationship between von Willebrand factor (VWF) and inflammation has attracted considerable attention in recent years. VWF, which is stored in the Weibel-Palade bodies (WPBs) of endothelial cells (ECs), is released from WPBs in response to inflammatory stimuli and is thought to contribute to inflammation by promoting leukocyte extravasation. In this study, lung injury model mice were produced by intratracheal injection with lipopolysaccharides. The severity of lung inflammation was evaluated in mice with different genotypes (wild-type, Vwf-/-, Adamts13-/-) and mice treated with drugs that inhibit VWF function. Lung inflammation was significantly ameliorated in Vwf-/- mice compared with wild-type mice. Furthermore, inflammation was significantly suppressed in wild-type mice treated with anti-VWF A1 antibody or recombinant human ADAMTS13 compared with the untreated control group. The underlying mechanism appears to be an increased VWF/ADAMTS13 ratio at the site of inflammation and the interaction between blood cell components, such as leukocytes and platelets, and the VWF A1 domain, which promotes leukocyte infiltration into the lung. This study suggested that ADAMTS13 protein and other VWF-targeting agents may be a novel therapeutic option for treatment of pulmonary inflammatory diseases.

Liraglutide pretreatment attenuates sepsis-induced acute lung injury

There are no effective targeted therapies to treat acute respiratory distress syndrome (ARDS). Recently, the commonly used diabetes and obesity medications, glucagon-like peptide-1 (GLP-1) receptor agonists, have been found to have anti-inflammatory properties. We, therefore, hypothesized that liraglutide pretreatment would attenuate murine sepsis-induced acute lung injury (ALI). We used a two-hit model of ALI (sepsis+hyperoxia). Sepsis was induced by intraperitoneal injection of cecal slurry (CS; 2.4 mg/g) or 5% dextrose (control) followed by hyperoxia [HO; fraction of inspired oxygen ([Formula: see text]) = 0.95] or room air (control; [Formula: see text] = 0.21). Mice were pretreated twice daily with subcutaneous injections of liraglutide (0.1 mg/kg) or saline for 3 days before initiation of CS+HO. At 24-h post CS+HO, physiological dysfunction was measured by weight loss, severity of illness score, and survival. Animals were euthanized, and bronchoalveolar lavage (BAL) fluid, lung, and spleen tissues were collected. Bacterial burden was assessed in the lung and spleen. Lung inflammation was assessed by BAL inflammatory cell numbers, cytokine concentrations, lung tissue myeloperoxidase activity, and cytokine expression. Disruption of the alveolar-capillary barrier was measured by lung wet-to-dry weight ratios, BAL protein, and epithelial injury markers (receptor for advanced glycation end products and sulfated glycosaminoglycans). Histological evidence of lung injury was quantified using a five-point score with four parameters: inflammation, edema, septal thickening, and red blood cells (RBCs) in the alveolar space. Compared with saline treatment, liraglutide improved sepsis-induced physiological dysfunction and reduced lung inflammation, alveolar-capillary barrier disruption, and lung injury. GLP-1 receptor activation may hold promise as a novel treatment strategy for sepsis-induced ARDS. Additional studies are needed to better elucidate its mechanism of action.NEW & NOTEWORTHY In this study, pretreatment with liraglutide, a commonly used diabetes medication and glucagon-like peptide-1 (GLP-1) receptor agonist, attenuated sepsis-induced acute lung injury in a two-hit mouse model (sepsis + hyperoxia). Septic mice who received the drug were less sick, lived longer, and displayed reduced lung inflammation, edema, and injury. These therapeutic effects were not dependent on weight loss. GLP-1 receptor activation may hold promise as a new treatment strategy for sepsis-induced acute respiratory distress syndrome.

Procoagulant Activity of Blood and Microvesicles Is Disturbed by Pneumococcal Pneumolysin, Which Interacts with Coagulation Factors

The coagulation and contact systems are parts of the innate immune system as they prevent bleeding and dissemination of pathogens and also contribute to microbial killing by inflammatory reactions and the release of antimicrobial peptides. Here, we investigated the influence of Streptococcus pneumoniae on the coagulation and contact system. S. pneumoniae (pneumococci), but no other investigated streptococcal species, impairs coagulation of blood by autolysis and release of pneumolysin. Defective blood coagulation results from the lysis of tissue factor-producing mononuclear cells and their procoagulant microvesicles, which are the main trigger for blood coagulation during sepsis. In addition, pneumolysin binds coagulation and contact system factors, but this does not result in activation. Thus, pneumococci modulate activation of the coagulation system by releasing pneumolysin, which could potentiate lung injury during pneumonia.

Mesencephalic astrocyte-derived neurotrophic factor attenuates acute lung injury via inhibiting macrophages' activation

Acute lung injury (ALI) is an urgent respiratory disease without effective treatment. Mesencephalic astrocyte-derived neurotrophic factor (MANF)has been demonstrated to play a suppressive role in some inflammatory conditions. However, the effect of MANF on ALI has not yet been reported. In this study, we collected bronchoalveolar lavage fluid (BALF) from the patients with or without pulmonary inflammation, and used lipopolysaccharide (LPS) to induce mice ALI model. Mono-macrophage-specific MANF knockout (MKO) mice were constructed and recombinant human MANF protein was used to ALI mice. We found that the endogenous MANF protein in both human BALF and mice lung tissues was increased in inflammatory conditions. MANF level in the macrophages of inflammatory lung was higher than that in normal controls in both human and mice. MANF deficiency in macrophages induced lung inflammation and aggravated LPS-induced lung injury. MANF lowered LPS-induced lung injury, inhibited macrophage polarization to M1 functional type. Meanwhile, MANF inhibited-LPS induced activation of NF-κB signal pathway by down regulating phosphorylated p65in lung tissue and macrophages. These results indicate that MANF acts as a suppressor in ALI via negatively regulating NF-κB activation and macrophages polarization, which may be a novel potential target and shed light on ALI therapy.

A two-hit model of sepsis plus hyperoxia causes lung permeability and inflammation

Mouse models of acute lung injury (ALI) have been instrumental for studies of the biological underpinnings of lung inflammation and permeability, but murine models of sepsis generate minimal lung injury. Our goal was to create a murine sepsis model of ALI that reflects the inflammation, lung edema, histological abnormalities, and physiological dysfunction that characterize ALI. Using a cecal slurry (CS) model of polymicrobial abdominal sepsis and exposure to hyperoxia (95%), we systematically varied the timing and dose of the CS injection, fluids and antibiotics, and dose of hyperoxia. We found that CS alone had a high mortality rate that was improved with the addition of antibiotics and fluids. Despite this, we did not see evidence of ALI as measured by bronchoalveolar lavage (BAL) cell count, total protein, C-X-C motif chemokine ligand 1 (CXCL-1) or by lung wet:dry weight ratio. Addition of hyperoxia [95% fraction of inspired oxygen ([Formula: see text])] to CS immediately after CS injection increased BAL cell counts, CXCL-1, and lung wet:dry weight ratio but was associated with 40% mortality. Splitting the hyperoxia treatment into two 12-h exposures (0-12 h and 24-36 h) after CS injection increased survival to 75% and caused significant lung injury compared with CS alone as measured by increased BAL total cell count (92,500 vs. 240,000, P = 0.0004), BAL protein (71 vs. 103 µg/mL, P = 0.0030), and lung wet:dry weight ratio (4.5 vs. 5.5, P = 0.0005), and compared with sham as measured by increased BAL CXCL-1 (20 vs. 2,372 pg/mL, P < 0.0001) and histological lung injury score (1.9 vs. 4.2, P = 0.0077). In addition, our final model showed evidence of lung epithelial [increased BAL and plasma receptor for advanced glycation end products (RAGE)] and endothelial (increased Syndecan-1 and sulfated glycosaminoglycans) injury. In conclusion, we have developed a clinically relevant mouse model of sepsis-induced ALI using intraperitoneal injection of CS, antibiotics and fluids, and hyperoxia. This clinically relevant model can be used for future studies of sepsis-induced ALI.

Friend or Foe? The Roles of Antioxidants in Acute Lung Injury

Acute lung injury (ALI) is an acute hypoxic respiratory insufficiency caused by various intra- and extra-pulmonary injury factors. The oxidative stress caused by excessive reactive oxygen species (ROS) produced in the lungs plays an important role in the pathogenesis of ALI. ROS is a "double-edged sword", which is widely involved in signal transduction and the life process of cells at a physiological concentration. However, excessive ROS can cause mitochondrial oxidative stress, leading to the occurrence of various diseases. It is well-known that antioxidants can alleviate ALI by scavenging ROS. Nevertheless, more and more studies found that antioxidants have no significant effect on severe organ injury, and may even aggravate organ injury and reduce the survival rate of patients. Our study introduces the application of antioxidants in ALI, and explore the mechanisms of antioxidants failure in various diseases including it.

BAY11-7082 inhibits the expression of tissue factor and plasminogen activator inhibitor-1 in type-II alveolar epithelial cells following TNF-α stimulation via the NF-κB pathway

Pulmonary inflammation strongly promotes alveolar hypercoagulation and fibrinolytic inhibition. NF-κB signaling regulates the expression of molecules associated with coagulation and fibrinolytic inhibition in type-II alveolar epithelial cells (AECII) stimulated by lipopolysaccharide. However, whether TNF-α-induced alveolar hypercoagulation and fibrinolysis inhibition is also associated with the NF-κB pathway remains to be determined. The aim of the present study was to determine whether BAY11-7082, an inhibitor of the NF-κB pathway, inhibits the expressions of tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) in AECⅡ in response to TNF-α. Rat AECII were treated with BAY11-7082 for 24 h and stimulated with TNF-α for 1 h. The expression of TF and PAI-1 were determined using western blotting and reverse transcription-quantitative PCR. The concentrations of TF and PAI-1 in culture supernatant were also measured by ELISA. Moreover, levels of NF-κB p65 (p65), phosphorylated (p)-p65 (p-p65), inhibitor of NF-κB α (IκBα) and p-IκBα were also evaluated. Immunofluorescence was used to detect p65 levels in cell nuclei. TNF-α significantly promoted TF and PAI-1 expression either at the mRNA or protein level in AECII cells. Concentrations of TF and PAI-1 in supernatant also significantly increased upon TNF-α stimulation. Furthermore, TNF-α upregulated the levels of p-IκBα, p65, and p-p65 in the cytoplasm. Immunofluorescence analysis indicated that TNF-α increased p65 translocation from the cytoplasm to the nucleus. However, AECII pre-treated with BAY11-7082 expressed lower levels of TF and PAI-1 following TNF-α treatment. Levels of p-IκBα, p65 and p-p65 in the cytoplasm also decreased, and translocation of p65 from cytoplasm into the nucleus was inhibited by BAY11-7082 pretreatment. These findings suggest that BAY11-7082 improves the hypercoagulation and fibrinolytic inhibition induced by TNF-α in alveolar epithelial cells via the NF-κB signaling pathway. BAY11-7082 might represent a therapeutic option for alveolar hypercoagulation and fibrinolytic inhibition in acute respiratory distress syndrome.

The NLRP3 inflammasome in macrophages is stimulated by cell-free hemoglobin

Cell‐free hemoglobin (CFH) is associated with severe lung injury in human patients and is sufficient to induce airspace inflammation and alveolar–capillary barrier dysfunction in an experimental model of acute lung injury. The mechanisms through which this occurs are unknown. One key pathway which regulates inflammation during acute lung injury is the NLRP3 inflammasome. Because CFH can act as a damage‐associated molecular pattern, we hypothesized that CFH may activate the NLRP3 inflammasome during acute lung injury. Primary mouse alveolar macrophages and cultured murine macrophages exposed to CFH (0–1 mg/ml) for 24 hr demonstrated robust upregulation of the NLRP3 inflammasome components NLRP3, caspase‐1, and caspase‐11. Maximal induction of the NLRP3 inflammasome by CFH required TLR4. Compared to wild‐type controls, mice lacking NLRP3 developed less airspace inflammation (2.7 × 10⁵ cells/ml in bronchoalveolar lavage fluid versus. 1.1 × 10⁵/ml, p = .006) after exposure to intratracheal CFH. Together, these data demonstrate that CFH can stimulate the NLRP3 inflammasome in macrophages and that this pathway may be important in the pathogenesis of CFH‐induced acute lung injury.

Murine tissue factor disulfide mutation causes a bleeding phenotype with sex specific organ pathology and lethality

Tissue factor is highly expressed in sub-endothelial tissue. The extracellular allosteric disulfide bond Cys186-Cys209 of human tissue factor shows high evolutionary conservation and in vitro evidence suggests that it significantly contributes to tissue factor procoagulant activity. To investigate the role of this allosteric disulfide bond in vivo, we generated a C213G mutant tissue factor mouse by replacing Cys213 of the corresponding disulfide Cys190-Cys213 in murine tissue factor. A bleeding phenotype was prominent in homozygous C213G tissue factor mice. Pre-natal lethality of 1/3rd of homozygous offspring was observed between E9.5 and E14.5 associated with placental hemorrhages. After birth, homozygous mice suffered from bleedings in different organs and reduced survival. Homozygous C213G tissue factor male mice showed higher incidence of lung bleedings and lower survival rates than females. In both sexes, C213G mutation evoked a reduced protein expression (about 10-fold) and severely reduced pro-coagulant activity (about 1000-fold). Protein glycosylation was impaired and cell membrane exposure decreased in macrophages in vivo. Single housing of homozygous C213G tissue factor males reduced the occurrence of severe bleeding and significantly improved survival, suggesting that inter-male aggressiveness might significantly account for the sex differences. These experiments show that the tissue factor allosteric disulfide bond is of crucial importance for normal in vivo expression, post-translational processing and activity of murine tissue factor. Although C213G tissue factor mice do not display the severe embryonic lethality of tissue factor knock-out mice, their postnatal bleeding phenotype emphasizes the importance of fully functional tissue factor for hemostasis.

Heparin as a therapy for COVID-19: current evidence and future possibilities

Coronavirus disease 2019 (COVID-19), the clinical syndrome associated with infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has impacted nearly every country in the world. Despite an unprecedented focus of scientific investigation, there is a paucity of evidence-based pharmacotherapies against this disease. Because of this lack of data-driven treatment strategies, broad variations in practice patterns have emerged. Observed hypercoagulability in patients with COVID-19 has created debate within the critical care community on the therapeutic utility of heparin. We seek to provide an overview of the data supporting the therapeutic use of heparin, both unfractionated and low molecular weight, as an anticoagulant for the treatment of SARS-CoV-2 infection. Additionally, we review preclinical evidence establishing biological plausibility for heparin and synthetic heparin-like drugs as therapies for COVID-19 through antiviral and anti-inflammatory effects. Finally, we discuss known adverse effects and theoretical off-target effects that may temper enthusiasm for the adoption of heparin as a therapy in COVID-19 without confirmatory prospective randomized controlled trials. Despite previous failures of anticoagulants in critical illness, plausibility of heparin for COVID-19 is sufficiently robust to justify urgent randomized controlled trials to determine the safety and effectiveness of this therapy.

Targeting the Heme-Heme Oxygenase System to Prevent Severe Complications Following COVID-19 Infections

SARS-CoV-2 is causing a pandemic resulting in high morbidity and mortality. COVID-19 patients suffering from acute respiratory distress syndrome (ARDS) are often critically ill and show lung injury and hemolysis. Heme is a prosthetic moiety crucial for the function of a wide variety of heme-proteins, including hemoglobin and cytochromes. However, injury-derived free heme promotes adhesion molecule expression, leukocyte recruitment, vascular permeabilization, platelet activation, complement activation, thrombosis, and fibrosis. Heme can be degraded by the anti-inflammatory enzyme heme oxygenase (HO) generating biliverdin/bilirubin, iron/ferritin, and carbon monoxide. We therefore postulate that free heme contributes to many of the inflammatory phenomena witnessed in critically ill COVID-19 patients, whilst induction of HO-1 or harnessing heme may provide protection. HO-activity not only degrades injurious heme, but its effector molecules possess also potent salutary anti-oxidative and anti-inflammatory properties. Until a vaccine against SARS-CoV-2 becomes available, we need to explore novel strategies to attenuate the pro-inflammatory, pro-thrombotic, and pro-fibrotic consequences of SARS-CoV-2 leading to morbidity and mortality. The heme-HO system represents an interesting target for novel "proof of concept" studies in the context of COVID-19.

Knockdown of TFPI-Anchored Endothelial Cells Exacerbates Lipopolysaccharide-Induced Acute Lung Injury Via NF-κB Signaling Pathway

As activation of the coagulation system is both a consequence and contributor to acute lung injury (ALI), pulmonary coagulopathy has become a potential target for therapeutic intervention in ALI patients. We investigated the effects and possible mechanisms of endothelial cell (EC)-anchored tissue factor pathway inhibitor (TFPI) on lipopolysaccharide (LPS)-induced ALI in mice. To assess the effect of EC-anchored TFPI deletion on ALI indices, TFPI knockout (cKO) mice were generated. Mice were instilled by direct intratracheal injection LPS for the preparation of an ALI model. Evans blue dye (EBD) was injected intravenously 2 h prior to animal sacrifice (48 h post-LPS). Lungs were fixed for histopathology and the prepared tissue was homogenized or used to extract bronchoalveolar lavage fluid (BALF) or detect EBD concentration. TFPI knockdown mice with ALI were compared to wild-type (WT) mice with ALI to assess the effect of TFPI on endothelial barrier function and inflammation. TFPI deletion markedly exacerbated LPS histopathological changes in lung, and the LPS changes in protein, EBD extravasation, proinflammatory cytokines TNF-α, IL-1β, and IL-6 in BALF in lung. The number and infiltration of white blood cells (WBCs) from BALF and lung tissue of TFPI cKO mice with LPS-challenged ALI was increased compared to WT mice with LPS-challenged ALI. We also found further increased toll-like receptor 4 and nuclear factor kappa-light-chain-enhancer of activated B cells activation and additional expression of vascular cell adhesion molecule 1 and reduction of angiotensin converting enzyme 2 expression in TFPI cKO+LPS mice compared with WT+LPS mice. Endothelial-specific TFPI deficiency promoted LPS-induced pulmonary inflammation and endothelial barrier permeability possibly via toll-like receptor 4-mediated nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway activation.

Effects of nebulized antithrombin and heparin on inflammatory and coagulation alterations in an acute lung injury model in rats

BACKGROUND

During acute respiratory distress syndrome, proinflammatory mediators inhibit natural anticoagulant factors, which alter the normal balance between coagulation and fibrinolysis leading to a procoagulant state. We hypothesize that pulmonary administration of anticoagulants might be beneficial to treat acute respiratory distress syndrome for their anticoagulant and antiinflammatory effects and reduce the risk of systemic bleeding.

OBJECTIVES

Our aim is to study the effects of nebulized antithrombin (AT) and combined AT and heparin in an animal model of acute lung injury.

METHODS

Acute lung injury was induced in rats by the intratracheal administration of hydrochloric acid and lipopolysaccharide. AT alone (500 IU/kg body weight) or combined with heparin (1000 IU/kg body weight) were nebulized after the injury. Control groups received saline instead. Blood, lung tissue, bronchoalveolar lavage, and alveolar macrophages (AM) isolated from bronchoalveolar lavage were collected after 48 hours and analyzed.

RESULTS

Nebulized anticoagulant treatments reduced protein concentration in the lungs and decreased injury-mediated coagulation factors (tissue factor, plasminogen activator inhibitor-1, plasminogen, and fibrinogen degradation product) and inflammation (tumor necrosis factor α and interleukin 1β) in the alveolar space without affecting systemic coagulation and no bleeding. AT alone reduced fibrin deposition and edema in the lungs. Heparin did not potentiate AT coagulant effect but promoted the reduction of macrophages infiltration into the alveolar compartment. Anticoagulants reduced nuclear factor-kB downstream effectors in AM.

CONCLUSIONS

Nebulized AT and heparin attenuate lung injury through decreasing coagulation and inflammation without altering systemic coagulation and no bleeding. However, combined AT and heparin did not produce a synergistic effect.

Cell-free hemoglobin increases inflammation, lung apoptosis, and microvascular permeability in murine polymicrobial sepsis

Increased endothelial permeability is central to the pathogenesis of sepsis and leads to organ dysfunction and death but the endogenous mechanisms that drive increased endothelial permeability are not completely understood. We previously reported that cell-free hemoglobin (CFH), elevated in 80% of patients with sepsis, increases lung microvascular permeability in an ex vivo human lung model and cultured endothelial cells. In this study, we augmented a murine model of polymicrobial sepsis with elevated circulating CFH to test the hypothesis that CFH increases microvascular endothelial permeability by inducing endothelial apoptosis. Mice were treated with an intraperitoneal injection of cecal slurry with or without a single intravenous injection of CFH. Severity of illness, mortality, systemic and lung inflammation, endothelial injury and dysfunction and lung apoptosis were measured at selected time points. We found that CFH added to CS increased sepsis mortality, plasma inflammatory cytokines as well as lung apoptosis, edema and inflammation without affecting large vessel reactivity or vascular injury marker concentrations. These results suggest that CFH is an endogenous mediator of increased endothelial permeability and apoptosis in sepsis and may be a promising therapeutic target.

Haptoglobin-2 variant increases susceptibility to acute respiratory distress syndrome during sepsis

Acute respiratory distress syndrome (ARDS) is an inflammatory lung disorder that frequently complicates critical illness and commonly occurs in sepsis. Although numerous clinical and environmental risk factors exist, not all patients with risk factors develop ARDS, raising the possibility of genetic underpinnings for ARDS susceptibility. We have previously reported that circulating cell-free hemoglobin (CFH) is elevated during sepsis, and higher levels predict worse outcomes. Excess CFH is rapidly scavenged by haptoglobin (Hp). A common HP genetic variant, HP2, is unique to humans and is common in many populations worldwide. HP2 haptoglobin has reduced ability to inhibit CFH-mediated inflammation and oxidative stress compared with the alternative HP1. We hypothesized that HP2 increases ARDS susceptibility during sepsis when plasma CFH levels are elevated. In a murine model of sepsis with elevated CFH, transgenic mice homozygous for Hp2 had increased lung inflammation, pulmonary vascular permeability, lung apoptosis, and mortality compared with wild-type mice. We then tested the clinical relevance of our findings in 496 septic critically ill adults, finding that HP2 increased ARDS susceptibility after controlling for clinical risk factors and plasma CFH. These observations identify HP2 as a potentially novel genetic ARDS risk factor during sepsis and may have important implications in the study and treatment of ARDS.

USP9X promotes LPS-induced pulmonary epithelial barrier breakdown and hyperpermeability by activating an NF-κBp65 feedback loop

NF-κB is a central regulator of inflammatory and immune responses and has been shown to regulate transcription of several inflammatory factors as well as promote acute lung injury. However, the regulation of NF-κB signaling in acute lung injury has yet to be investigated. Human pulmonary alveolar epithelial cells (HPAEpiC) were treated with LPS to establish an acute lung injury model in vitro in which LPS stimulation resulted in pulmonary epithelial barrier breakdown and hyperpermeability. Cell viability was measured by CCK-8, and the transepithelial permeability was examined by measurement of transepithelial electrical resistance (TEER) and the transepithelial flux. Expression of ubiquitin-specific peptidase 9 X-linked (USP9X), zonula occludens (ZO-1), occludin and NF-κBp65, and the secretion of TNF-α and IL-1β were measured by Western blotting and ELISA, respectively. For in vivo studies, mice were intraperitoneally injected with LPS and/or NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). Lung tissues were harvested for hematoxylin-eosin staining and Western blotting, and bronchoalveolar lavage fluid (BALF) was harvested for ELISA. We found that treatment with LPS in HPAEpiC inhibited cell viability and induced the expression of USP9X. Interestingly, knockdown of USP9X and treatment with PDTC suppressed LPS-induced HPAEpiC injury. USP9X overexpression promoted NF-κB activation, while NF-κB inactivation inhibited USP9X transcription and HPAEpiC injury induced by USP9X overexpression. Furthermore, LPS also induced the expression of USP9X in lungs, which was inhibited by PDTC. Taken together, these results demonstrate a critical role of USP9X-NF-κBp65 loop in mediating LPS-induced acute lung injury and may serve as a potential therapeutic target in acute lung injury.

Endothelial cell-specific anticoagulation reduces inflammation in a mouse model of acute lung injury

Tissue factor (TF)-dependent coagulation contributes to lung inflammation and the pathogenesis of acute lung injury (ALI). In this study, we explored the roles of targeted endothelial anticoagulation in ALI using two strains of transgenic mice expressing either a membrane-tethered human tissue factor pathway inhibitor (hTFPI) or hirudin fusion protein on CD31⁺ cells, including vascular endothelial cells (ECs). ALI was induced by intratracheal injection of LPS, and after 24 h the expression of TF and protease-activated receptors (PARs) on EC in lungs were assessed, alongside the extent of inflammation and injury. The expression of TF and PARs on the EC in lungs was upregulated after ALI. In the two strains of transgenic mice, expression of either of hTFPI or hirudin by EC was associated with significant reduction of inflammation, as assessed by the extent of leukocyte infiltration or the levels of proinflammatory cytokines, and promoted survival after LPS-induced ALI. The beneficial outcomes were associated with inhibition of the expression of chemokine CCL2 in lung tissues. The protection observed in the CD31-TFPI-transgenic strain was abolished by injection of an anti-hTFPI antibody, but not by prior engraftment of the transgenic strains with WT bone marrow, confirming that the changes observed were a specific transgenic expression of anticoagulants by EC. These results demonstrate that the inflammation in ALI is TF and thrombin dependent, and that expression of anticoagulants by EC significantly inhibits the development of ALI via repression of leukocyte infiltration, most likely via inhibition of chemokine gradients. These data enhance our understanding of the pathology of ALI and suggest a novel therapeutic strategy for treatment.

Role of TLR4-p38 MAPK-Hsp27 signal pathway in LPS-induced pulmonary epithelial hyperpermeability

Background

The breakdown of alveolar barrier dysfunction contributes to Lipopolysaccharide stimulated pulmonary edema and acute lung injury. Actin cytoskeleton has been implicated to be critical in regulation of epithelial barrier. Here, we performed in vivo and in vitro study to investigate role of TLR4-p38 MAPK-Hsp27 signal pathway in LPS-induced ALI.

Methods

For in vivo studies, 6–8-week-old C57 mice were used, Bronchoalveolar lavage Fluid /Blood fluorescent ratio, wet-to-dry lung weight ratio, as well as protein concentrations and neutrophil cell counts in BALF were detected as either directly or indirectly indicators of pulmonary alveolar barrier dysfunction. And hematoxylin and eosin staining was performed to estimate pulmonary injury. The in vitro explorations of transepithelial permeability were achieved through transepithelial electrical resistance measurement and testing of FITC-Dextran transepithelial flux in A549. In addition, cytoskeletal rearrangement was tested through F-actin immunostaining. And SB203580 was used to inhibit p38 MAPK activation, while siRNA was administered to genetically knockdown specific protein.

Results

We showed that LPS triggered activation of p38 MAPK, rearrangement of cytoskeleton which resulted in severe epithelial hyperpermeability and lung edema. A549 pretreated with TLR4 siRNA、p38 MAPK siRNA and its inhibitor SB203580 displayed a lower permeability and fewer stress fibers formation after LPS stimulation, accompanied with lower phosphorylation level of p38 MAPK and Hsp27, which verified the involvement of TLR4-p38 MAPK-Hsp27 in LPS-evoked alveolar epithelial injury. Inhibition of p38 MAPK activity with SB203580 in vivo attenuated pulmonary edema formation and hyperpermeability in response to LPS.

Conclusions

Our study demonstrated that LPS increased alveolar epithelial permeability both in vitro and in vivo and that TLR4- p38 MAPK- Hsp27 signal pathway dependent actin remolding was involved in this process.

The coagulation system in host defense

The blood coagulation system and immune system of higher organisms are thought to have a common ancestral origin. During infections, the blood coagulation system is activated and components of the hemostatic system are directly involved in the immune response and immune system modulations. The current view is that the activation of coagulation is beneficial for infections with bacteria and viruses. It limits pathogen dissemination and supports pathogen killing and tissue repair. On the other hand, over-activation can lead to thrombosis with subsequent depletion of hemostatic factors and secondary bleeding. This review will summarize the current knowledge on blood coagulation and pathogen infection with focus on most recent studies of the role of the different parts of the blood coagulation system in selected bacterial and viral infections.

Hydrogen protects lung from hypoxia/re-oxygenation injury by reducing hydroxyl radical production and inhibiting inflammatory responses

Here we investigated whether hydrogen can protect the lung from chronic injury induced by hypoxia/re-oxygenation (H/R). We developed a mouse model in which H/R exposure triggered clinically typical lung injury, involving increased alveolar wall thickening, infiltration by neutrophils, consolidation, alveolar hemorrhage, increased levels of inflammatory factors and recruitment of M1 macrophages. All these processes were attenuated in the presence of H₂. We found that H/R-induced injury in our mouse model was associated with production of hydroxyl radicals as well as increased levels of colony-stimulating factors and circulating leukocytes. H₂ attenuated H/R-induced production of hydroxyl radicals, up-regulation of colony-stimulating factors, and recruitment of neutrophils and M1 macrophages to lung tissues. However, H₂ did not substantially affect the H/R-induced increase in erythropoietin or pulmonary artery remodeling. Our results suggest that H₂ ameliorates H/R-induced lung injury by inhibiting hydroxyl radical production and inflammation in lungs. It may also prevent colony-stimulating factors from mobilizing progenitors in response to H/R-induced injury.

GBT1118, a compound that increases the oxygen affinity of hemoglobin, improves survival in murine hypoxic acute lung injury

Acute respiratory distress syndrome (ARDS) is characterized by lung inflammation and pulmonary edema, leading to arterial hypoxemia and death if the hypoxemia is severe. Strategies to correct hypoxemia have the potential to improve clinical outcomes in ARDS. The goal of this study was to evaluate the potential of hemoglobin modification as a novel therapy for ARDS-induced hypoxemia. The therapeutic effect of two different doses of GBT1118, a compound that increases the oxygen affinity of hemoglobin, was evaluated in a murine model of acute lung injury induced by intratracheal LPS instillation 24 h before exposure to 5% or 10% hypoxia ( n = 8-15 per group). As expected, administration of GBT1118 to mice significantly increased the oxygen affinity of hemoglobin. Compared with mice receiving vehicle control, mice treated with GBT1118 had significantly lower mortality after LPS + 5% hypoxia (47% with vehicle vs. 22% with low-dose GBT1118, 13% with high-dose GBT1118, P = 0.032 by log rank) and had reduced severity of illness. Mice treated with GBT1118 showed a sustained significant increase in SpO₂ over 4 h of hypoxia exposure. Treatment with GBT1118 did not alter alveolar-capillary permeability, bronchoalveolar lavage (BAL) inflammatory cell counts, or BAL concentrations of IL-1β, TNF-α, or macrophage inflammatory protein-1α. High-dose GBT1118 did not affect histological lung injury but did decrease tissue hypoxia as measured intensity of pimonidazole (Hypoxyprobe) staining in liver ( P = 0.043) and kidney ( P = 0.043). We concluded that increasing the oxygen affinity of hemoglobin using GBT1118 may be a novel therapy for treating hypoxemia associated with acute lung injury. NEW & NOTEWORTHY In this study, we show that GBT1118, a compound that increases hemoglobin affinity for oxygen, improves survival and oxygen saturation in a two-hit lung injury model of intratracheal LPS without causing tissue hypoxia. Modulation of hemoglobin oxygen affinity represents a novel therapeutic approach to treatment of acute lung injury and acute respiratory distress syndrome, conditions characterized by hypoxemia.

Tissue Factor: An Essential Mediator of Hemostasis and Trigger of Thrombosis

Tissue factor (TF) is the high-affinity receptor and cofactor for factor (F)VII/VIIa. The TF-FVIIa complex is the primary initiator of blood coagulation and plays an essential role in hemostasis. TF is expressed on perivascular cells and epithelial cells at organ and body surfaces where it forms a hemostatic barrier. TF also provides additional hemostatic protection to vital organs, such as the brain, lung, and heart. Under pathological conditions, TF can trigger both arterial and venous thrombosis. For instance, atherosclerotic plaques contain high levels of TF on macrophage foam cells and microvesicles that drives thrombus formation after plaque rupture. In sepsis, inducible TF expression on monocytes leads to disseminated intravascular coagulation. In cancer patients, tumors release TF-positive microvesicles into the circulation that may contribute to venous thrombosis. TF also has nonhemostatic roles. For instance, TF-dependent activation of the coagulation cascade generates coagulation proteases, such as FVIIa, FXa, and thrombin, which induce signaling in a variety of cells by cleavage of protease-activated receptors. This review will focus on the roles of TF in protective hemostasis and pathological thrombosis.

Cell-free hemoglobin promotes primary graft dysfunction through oxidative lung endothelial injury

Primary graft dysfunction (PGD) is acute lung injury within 72 hours of lung transplantation. We hypothesized that cell-free hemoglobin (CFH) contributes to PGD by increasing lung microvascular permeability and tested this in patients, ex vivo human lungs, and cultured human lung microvascular endothelial cells. In a nested case control study of 40 patients with severe PGD at 72 hours and 80 matched controls without PGD, elevated preoperative CFH was independently associated with increased PGD risk (odds ratio [OR] 2.75, 95%CI, 1.23-6.16, P = 0.014). The effect of CFH on PGD was magnified by reperfusion fraction of inspired oxygen (FiO2) ≥ 0.40 (OR 3.41, P = 0.031). Isolated perfused human lungs exposed to intravascular CFH (100 mg/dl) developed increased vascular permeability as measured by lung weight (CFH 14.4% vs. control 0.65%, P = 0.047) and extravasation of Evans blue-labeled albumin dye (EBD) into the airspace (P = 0.027). CFH (1 mg/dl) also increased paracellular permeability of human pulmonary microvascular endothelial cell monolayers (hPMVECs). Hyperoxia (FiO2 = 0.95) increased human lung and hPMVEC permeability compared with normoxia (FiO2 = 0.21). Treatment with acetaminophen (15 μg/ml), a specific hemoprotein reductant, prevented CFH-dependent permeability in human lungs (P = 0.046) and hPMVECs (P = 0.037). In summary, CFH may mediate PGD through oxidative effects on microvascular permeability, which are augmented by hyperoxia and abrogated by acetaminophen.

Anticoagulant therapy in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) presents a complex pathophysiology characterized by pulmonary activated coagulation and reduced fibrinolysis. Despite advances in supportive care of this syndrome, morbidity and mortality remains high, leading to the need of novel therapies to combat this disease. Focus these therapies in the inhibition of ARDS development pathophysiology is essential. Beneficial effects of anticoagulants in ARDS have been proved in preclinical and clinical trials, thanks to its anticoagulant and anti-inflammatory properties. Moreover, local administration by nebulization in the alveolar compartment increases local efficacy and does not produce systemic bleeding. In this review the coagulation and fibrinolytic pathway and its pharmacological targets to treat ARDS are summarized.

Molecular and Immune Biomarkers in Acute Respiratory Distress Syndrome: A Perspective From Members of the Pulmonary Pathology Society

Acute respiratory distress syndrome (ARDS) is a multifactorial syndrome with high morbidity and mortality rates, characterized by deficiency in gas exchange and lung mechanics that lead to hypoxemia, dyspnea, and respiratory failure. Histologically, ARDS is characterized by an acute, exudative phase, combining diffuse alveolar damage and noncardiogenic edema, followed by a later fibroproliferative phase. Despite an enhanced understanding of ARDS pathogenesis, the capacity to predict the development of ARDS and to risk-stratify patients with the disease remains limited. Biomarkers may help to identify patients at the greatest risk of developing ARDS, to evaluate response to therapy, to predict outcome, and to improve clinical trials. The ARDS pathogenesis is presented in this article, as well as concepts and information on biomarkers that are currently used clinically or are available for laboratory use by academic and practicing pathologists and the developing and validating of new assays, focusing on the assays' major biologic roles in lung injury and/or repair and to ultimately suggest innovative, therapeutic approaches.

Role of biomarkers in acute traumatic lung injury

In severely injured patients severe thoracic trauma is common and can significantly influence the outcome of these critically ill patients by increased rates of mainly pulmonary complications. Furthermore, patients who sustained thoracic trauma are at increased risk for Acute Lung Injury (ALI) or Adult Respiratory Distress Syndrome (ARDS). Therapeutic options are limited, basically consisting of prophylactic antibiotic therapy and changing patient's positions. It is known, that ALI and ARDS differ clinically and pathobiologically from ALI/ARDS caused by other reasons, but the exact pathology remains elusive. Due to that no reliable predictive or surveillance biomarkers could be established for clinical diagnosis and identification of patients at high risk for acute traumatic lung injury. Nevertheless, there are plenty of promising markers that need to be further elucidated in larger case numbers and multicenter studies. This article sums up the recent status of those promising clinical biomarkers.

Myeloid but not epithelial tissue factor exerts protective anti-inflammatory effects in acid aspiration-induced acute lung injury

Essentials Tissue factor (TF) represents a central link between hemostasis and inflammation. We studied the roles of myeloid and airway epithelial TF in acid-caused acute lung injury (ALI). TF on myeloid cells displays a non-coagulatory role regulating the inflammatory response in ALI. Airway epithelial TF contributes to hemostatic functions, but is dispensable in ALI pathogenesis.

SUMMARY

Introduction Acute lung injury (ALI) is a life-threatening condition characterized by damaged alveolar-capillary structures and activation of inflammatory and hemostatic processes. Tissue factor (TF) represents a crucial link between inflammation and coagulation, as inflammatory mediators induce myeloid TF expression, and TF initiates extrinsic coagulation. Objective As pulmonary inflammation stimulates TF expression and TF modulates immune responses, we aimed to elucidate its impact on ALI. In particular, we wanted to distinguish the contributions of TF expressed on airway epithelial cells and TF expressed on myeloid cells. Methods Mice with different cell type-specific TF deficiency and wild-type littermates were intratracheally treated with hydrochloric acid, and leukocyte recruitment, cytokine levels, thrombin-antithrombin (TAT) complexes and pulmonary protein-rich infiltrates were analyzed. Results Our data demonstrate that a lack of epithelial TF did not influence acute responses, as bronchoalveolar neutrophil accumulation 8 h after ALI induction was unaltered. However, it led to mild, prolonged inflammation, as pulmonary leukocyte and erythrocyte numbers were still increased after 24 h, whereas those in wild-type mice had returned to basal levels. In contrast, myeloid TF was primarily involved in regulating the acute phase of ALI without affecting local coagulation, as indicated by increased bronchoalveolar neutrophil infiltration, pulmonary interleukin-6 levels, and edema formation, but equal TAT complex formation, 8 h after ALI induction. This augmented inflammatory response associated with myeloid TF deficiency was confirmed in vitro, as lipopolysaccharide-stimulated TF-deficient alveolar macrophages released increased levels of chemokine (C-X-C motif) ligand 1 and tumor necrosis factor-α as compared with wild-type macrophages. Conclusion We conclude that myeloid TF dampens inflammation in acid-induced ALI.

Circulating microparticle levels are reduced in patients with ARDS

BACKGROUND

It is unclear how to identify which patients at risk for acute respiratory distress syndrome (ARDS) will develop this condition during critical illness. Elevated microparticle (MP) concentrations in the airspace during ARDS are associated with activation of coagulation and in vitro studies have demonstrated that MPs contribute to acute lung injury, but the significance of MPs in the circulation during ARDS has not been well studied. The goal of the present study was to test the hypothesis that elevated levels of circulating MPs could prospectively identify critically ill patients who will develop ARDS and that elevated circulating MPs are associated with poor clinical outcomes.

METHODS

A total of 280 patients with platelet-poor plasma samples from the prospective Validating Acute Lung Injury biomarkers for Diagnosis (VALID) cohort study were selected for this analysis. Demographics and clinical data were obtained by chart review. MP concentrations in plasma were measured at study enrollment on intensive care unit (ICU) day 2 and on ICU day 4 by MP capture assay. Activation of coagulation was measured by plasma recalcification (clot) times.

RESULTS

ARDS developed in 90 of 280 patients (32%) in the study. Elevated plasma MP concentrations were associated with reduced risk of developing ARDS (odds ratio (OR) 0.70 per 10 μM increase in MP concentration, 95% CI 0.50-0.98, p = 0.042), but had no significant effect on hospital mortality. MP concentration was greatest in patients with sepsis, pneumonia, or aspiration as compared with those with trauma or receiving multiple blood transfusions. MP levels did not significantly change over time. The inverse association of MP levels with ARDS development was most striking in patients with sepsis. After controlling for age, presence of sepsis, and severity of illness, higher MP concentrations were independently associated with a reduced risk of developing ARDS (OR 0.69, 95% CI 0.49-0.98, p = 0.038). MP concentration was associated with reduced plasma recalcification time.

CONCLUSIONS

Elevated levels of circulating MPs are independently associated with a reduced risk of ARDS in critically ill patients. Whether this is due to MP effects on systemic coagulation warrants further investigation.

Impact of thrombosis on pulmonary endothelial injury and repair following sepsis

The prevailing morbidity and mortality in sepsis are largely due to multiple organ dysfunction (MOD), most commonly lung injury, as well as renal and cardiac dysfunction. Despite recent advances in defining many aspects of the pathogenesis of sepsis-related MOD, including acute respiratory distress syndrome (ARDS), there are currently no effective pharmacological or cell-based treatments for the disease. Human and animal studies have shown that pulmonary thrombosis is common in sepsis-induced ARDS, and preclinical studies have shown that anticoagulation may improve outcome following sepsis challenge. The potential beneficial effect of anticoagulation on outcome is unconvincing in clinical studies, however, and these discrepancies may arise from the multiple and sometimes opposing actions of thrombosis on the pulmonary endothelium following sepsis. It has been suggested, for example, that mild pulmonary thrombosis prevents escape of bacterial infection into the circulation, while severe thrombosis causes hypoxia and results in pulmonary endothelial damage. Evidence from both human and animal studies has demonstrated the key role of microvascular leakage in determining the outcome of sepsis. In this review, we describe thrombosis-dependent mechanisms that regulate pulmonary endothelial injury and repair following sepsis, including activation of the coagulation cascade by tissue factor and stimulation of vascular repair by hypoxia-inducible factors. Targeting such mechanisms through anticoagulant, anti-inflammatory, and reparative methods may represent a novel approach for the treatment of septic patients.

Purified and Recombinant Hemopexin: Protease Activity and Effect on Neutrophil Chemotaxis

Infusion of the heme-binding protein hemopexin has been proposed as a novel approach to decrease heme-induced inflammation in settings of red blood cell breakdown, but questions have been raised as to possible side effects related to protease activity and inhibition of chemotaxis. We evaluated protease activity and effects on chemotaxis of purified plasma hemopexin obtained from multiple sources as well as a novel recombinant fusion protein Fc-hemopexin. Amidolytic assay was performed to measure the protease activity of several plasma-derived hemopexin and recombinant Fc-hemopexin. Hemopexin was added to the human monocyte culture in the presence of lipopolysaccharides (LPS), and also injected into mice intravenously (i.v.) 30 min before inducing neutrophil migration via intraperitoneal (i.p.) injection of thioglycolate. Control groups received the same amount of albumin. Protease activity varied widely between hemopexins. Recombinant Fc-hemopexin bound heme, inhibited the synergy of heme with LPS on tumor necrosis factor (TNF) production from monocytes, and had minor but detectable protease activity. There was no effect of any hemopexin preparation on chemotaxis, and purified hemopexin did not alter the migration of neutrophils into the peritoneal cavity of mice. Heme and LPS synergistically induced the release of LTB4 from human monocytes, and hemopexin blocked this release, as well as chemotaxis of neutrophils in response to activated monocyte supernatants. These results suggest that hemopexin does not directly affect chemotaxis through protease activity, but may decrease heme-driven chemotaxis and secondary inflammation by attenuating the induction of chemoattractants from monocytes. This property could be beneficial in some settings to control potentially damaging inflammation induced by heme.

The novelty of phytofurans, isofurans, dihomo-isofurans and neurofurans: Discovery, synthesis and potential application

Polyunsaturated fatty acids (PUFA) are oxidized in vivo under oxidative stress through free radical pathway and release cyclic oxygenated metabolites, which are commonly classified as isoprostanes and isofurans. The discovery of isoprostanes goes back twenty-five years compared to fifteen years for isofurans, and great many are discovered. The biosynthesis, the nomenclature, the chemical synthesis of furanoids from α-linolenic acid (ALA, C18:3 n-3), arachidonic acid (AA, C20:4 n-6), adrenic acid (AdA, 22:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) as well as their identification and implication in biological systems are highlighted in this review.

Tissue factor deficiency increases alveolar hemorrhage and death in influenza A virus-infected mice

Essentials H1N1 Influenza A virus (IAV) infection is a hemostatic challenge for the lung. Tissue factor (TF) on lung epithelial cells maintains lung hemostasis after IAV infection. Reduced TF-dependent activation of coagulation leads to alveolar hemorrhage. Anticoagulation might increase the risk for hemorrhages into the lung during severe IAV infection.

SUMMARY

Background Influenza A virus (IAV) infection is a common respiratory tract infection that causes considerable morbidity and mortality worldwide. Objective To investigate the effect of genetic deficiency of tissue factor (TF) in a mouse model of IAV infection. Methods Wild-type mice, low-TF (LTF) mice and mice with the TF gene deleted in different cell types were infected with a mouse-adapted A/Puerto Rico/8/34 H1N1 strain of IAV. TF expression was measured in the lungs, and bronchoalveolar lavage fluid (BALF) was collected to measure extracellular vesicle TF, activation of coagulation, alveolar hemorrhage, and inflammation. Results IAV infection of wild-type mice increased lung TF expression, activation of coagulation and inflammation in BALF, but also led to alveolar hemorrhage. LTF mice and mice with selective deficiency of TF in lung epithelial cells had low basal levels of TF and failed to increase TF expression after infection; these two strains of mice had more alveolar hemorrhage and death than controls. In contrast, deletion of TF in either myeloid cells or endothelial cells and hematopoietic cells did not increase alveolar hemorrhage or death after IAV infection. These results indicate that TF expression in the lung, particularly in epithelial cells, is required to maintain alveolar hemostasis after IAV infection. Conclusion Our study indicates that TF-dependent activation of coagulation is required to limit alveolar hemorrhage and death after IAV infection.

Cell-free hemoglobin: a novel mediator of acute lung injury

Patients with the acute respiratory distress syndrome (ARDS) have elevated levels of cell-free hemoglobin (CFH) in the air space, but the contribution of CFH to the pathogenesis of acute lung injury is unknown. In the present study, we demonstrate that levels of CFH in the air space correlate with measures of alveolar-capillary barrier dysfunction in humans with ARDS (r = 0.89, P < 0.001) and in mice with ventilator-induced acute lung injury (r = 0.89, P < 0.001). To investigate the specific contribution of CFH to ARDS, we studied the impact of purified CFH in the mouse lung and on cultured mouse lung epithelial (MLE-12) cells. Intratracheal delivery of CFH in mice causes acute lung injury with air space inflammation and alveolar-capillary barrier disruption. Similarly, in MLE-12 cells, CFH increases proinflammatory cytokine expression and increases paracellular permeability as measured by electrical cell-substrate impedance sensing. Next, to determine whether these effects are mediated by the iron-containing heme moiety of CFH, we treated mice with intratracheal hemin, the chloride salt of heme, and found that hemin was sufficient to increase alveolar permeability but failed to induce proinflammatory cytokine expression or epithelial cell injury. Together, these data identify CFH in the air space as a previously unrecognized driver of lung epithelial injury in human and experimental ARDS and suggest that CFH and hemin may contribute to ARDS through different mechanisms. Interventions targeting CFH and heme in the air space could provide a new therapeutic approach for ARDS.

Myeloid tissue factor does not modulate lung inflammation or permeability during experimental acute lung injury

Tissue factor (TF) is a critical mediator of direct acute lung injury (ALI) with global TF deficiency resulting in increased airspace inflammation, alveolar-capillary permeability, and alveolar hemorrhage after intra-tracheal lipopolysaccharide (LPS). In the lung, TF is expressed diffusely on the lung epithelium and intensely on cells of the myeloid lineage. We recently reported that TF on the lung epithelium, but not on myeloid cells, was the major source of TF during intra-tracheal LPS-induced ALI. Because of a growing body of literature demonstrating important pathophysiologic differences between ALI caused by different etiologies, we hypothesized that TF on myeloid cells may have distinct contributions to airspace inflammation and permeability between direct and indirect causes of ALI. To test this, we compared mice lacking TF on myeloid cells (TF^∆mye, LysM.Cre^+/−TF^flox/flox) to littermate controls during direct (bacterial pneumonia, ventilator-induced ALI, bleomycin-induced ALI) and indirect ALI (systemic LPS, cecal ligation and puncture). ALI was quantified by weight loss, bronchoalveolar lavage (BAL) inflammatory cell number, cytokine concentration, protein concentration, and BAL procoagulant activity. There was no significant contribution of TF on myeloid cells in multiple models of experimental ALI, leading to the conclusion that TF in myeloid cells is not a major contributor to experimental ALI.

A Pathophysiologic Approach to Biomarkers in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is an acute-onset hypoxic condition with radiographic bilateral lung infiltration. It is characterized by an acute exudative phase combining diffuse alveolar damage and lung edema followed by a later fibroproliferative phase. Despite an improved understanding of ARDS pathobiology, our ability to predict the development of ARDS and risk-stratify patients with the disease remains limited. Biomarkers may help to identify patients at the highest risk of developing ARDS, assess response to therapy, predict outcome, and optimize enrollment in clinical trials. After a short description of ARDS pathobiology, here, we review the scientific evidence that supports the value of various ARDS biomarkers with regard to their major biological roles in ARDS-associated lung injury and/or repair. Ongoing research aims at identifying and characterizing novel biomarkers, in order to highlight relevant mechanistic explorations of lung injury and repair, and to ultimately develop innovative therapeutic approaches for ARDS patients. This review will focus on the pathophysiologic, diagnostic, and therapeutic implications of biomarkers in ARDS and on their utility to ultimately improve patient care.

Regulation of alveolar procoagulant activity and permeability in direct acute lung injury by lung epithelial tissue factor

Tissue factor (TF) initiates the extrinsic coagulation cascade in response to tissue injury, leading to local fibrin deposition. Low levels of TF in mice are associated with increased severity of acute lung injury (ALI) after intratracheal LPS administration. However, the cellular sources of the TF required for protection from LPS-induced ALI remain unknown. In the current study, transgenic mice with cell-specific deletions of TF in the lung epithelium or myeloid cells were treated with intratracheal LPS to determine the cellular sources of TF important in direct ALI. Cell-specific deletion of TF in the lung epithelium reduced total lung TF expression to 39% of wild-type (WT) levels at baseline and to 29% of WT levels after intratracheal LPS. In contrast, there was no reduction of TF with myeloid cell TF deletion. Mice lacking myeloid cell TF did not differ from WT mice in coagulation, inflammation, permeability, or hemorrhage. However, mice lacking lung epithelial TF had increased tissue injury, impaired activation of coagulation in the airspace, disrupted alveolar permeability, and increased alveolar hemorrhage after intratracheal LPS. Deletion of epithelial TF did not affect alveolar permeability in an indirect model of ALI caused by systemic LPS infusion. These studies demonstrate that the lung epithelium is the primary source of TF in the lung, contributing 60-70% of total lung TF, and that lung epithelial, but not myeloid, TF may be protective in direct ALI.

Kinetics of lung tissue factor expression and procoagulant activity in bleomycin induced acute lung injury

Background

Activation of coagulation by expression of tissue factor (TF) in the airspace is a hallmark of acute lung injury (ALI) but the timing of TF activation in relationship to increases in lung permeability and inflammation are unknown.

Methods

To test the hypothesis that TF is upregulated early in the course of acute bleomycin lung injury and precedes increased permeability and inflammation we studied the early course of bleomycin-induced ALI in mice. Mice were treated with 0.04U intratracheal bleomycin or vehicle control and bronchoalveolar lavage (BAL) and lung tissue were collected daily for 7 days. Whole lung TF mRNA was determined by QT-PCR. TF protein was assessed by ELISA and immunostaining. BAL procoagulant activity was measured by BAL clot time and thrombin-antithrombin complexes. Inflammation was assessed by BAL cell count, differentials and CXCL1/KC concentration. Lung permeability was assessed by BAL protein and lung wet to dry weight ratio.

Results

Expression of CXCL1 occurred by day 1. BAL protein and lung wet-to-dry weight ratio increased significantly by day 3. TF mRNA and BAL procoagulant activity peaked on day 4 while whole lung TF protein peaked on day 6. Changes in permeability and procoagulant activity preceded inflammatory cell influx which was maximal at day 6 while whole lung TF protein peaked along with inflammation.

Conclusion

These data demonstrate that cytokine upregulation is the earliest response to bleomycin administration, followed by increased lung permeability, upregulation of TF, and recruitment of inflammatory cells.

The role of red blood cells and cell-free hemoglobin in the pathogenesis of ARDS

The primary focus of research into the pathophysiology of the acute respiratory distress syndrome (ARDS) has been on the interaction between the lung, underlying causes of ARDS, and the role of white blood cells and platelets in contributing to lung injury. Given a lack of specific therapies for this common complication of critical illness, further insight into the pathophysiology of this syndrome is greatly needed to develop targeted interventions. The red blood cell (RBC) has been reported to undergo deleterious changes in critical illness and be present in the alveoli of patients with ARDS. Release of RBC contents is known to be injurious in other conditions but has only recently been studied in critical illness and ARDS. The contribution of the RBC to ARDS represents a new avenue of research that may produce new, targeted therapies for this deadly syndrome.

Feasibility and Safety of Local Treatment with Recombinant Human Tissue Factor Pathway Inhibitor in a Rat Model of Streptococcus pneumoniae Pneumonia

Pulmonary coagulopathy is intrinsic to pulmonary injury including pneumonia. Anticoagulant strategies could benefit patients with pneumonia, but systemic administration of anticoagulant agents may lead to suboptimal local levels and may cause systemic hemorrhage. We hypothesized nebulization to provide a safer and more effective route for local administration of anticoagulants. Therefore, we aimed to examine feasibility and safety of nebulization of recombinant human tissue factor pathway inhibitor (rh-TFPI) in a well-established rat model of Streptococcus (S.) pneumoniae pneumonia. Thirty minutes before and every 6 hours after intratracheal instillation of S. pneumonia causing pneumonia, rats were subjected to local treatment with rh-TFPI or placebo, and sacrificed after 42 hours. Pneumonia was associated with local as well as systemic activation of coagulation. Nebulization of rh-TFPI resulted in high levels of rh-TFPI in bronchoalveolar lavage fluid, which was accompanied by an attenuation of pulmonary coagulation. Systemic rh-TFPI levels remained undetectable, and systemic TFPI activity and systemic coagulation were not affected. Histopathology revealed no bleeding in the lungs. We conclude that nebulization of rh-TFPI seems feasible and safe; local anticoagulant treatment with rh-TFPI attenuates pulmonary coagulation, while not affecting systemic coagulation in a rat model of S. pneumoniae pneumonia.

Regulation of neutrophilic inflammation by proteinase-activated receptor 1 during bacterial pulmonary infection

Neutrophils are key effector cells of the innate immune response to pathogenic bacteria, but excessive neutrophilic inflammation can be associated with bystander tissue damage. The mechanisms responsible for neutrophil recruitment to the lungs during bacterial pneumonia are poorly defined. In this study, we focus on the potential role of the major high-affinity thrombin receptor, proteinase-activated receptor 1 (PAR-1), during the development of pneumonia to the common lung pathogen Streptococcus pneumoniae. Our studies demonstrate that neutrophils were indispensable for controlling S. pneumoniae outgrowth but contributed to alveolar barrier disruption. We further report that intra-alveolar coagulation (bronchoalveolar lavage fluid thrombin-antithrombin complex levels) and PAR-1 immunostaining were increased in this model of bacterial lung infection. Functional studies using the most clinically advanced PAR-1 antagonist, SCH530348, revealed a key contribution for PAR-1 signaling in influencing neutrophil recruitment to lung airspaces in response to both an invasive and noninvasive strain of S. pneumoniae (D39 and EF3030) but that PAR-1 antagonism did not impair the ability of the host to control bacterial outgrowth. PAR-1 antagonist treatment significantly decreased pulmonary levels of IL-1β, CXCL1, CCL2, and CCL7 and attenuated alveolar leak. Ab neutralization studies further demonstrated a nonredundant role for IL-1β, CXCL1, and CCL7 in mediating neutrophil recruitment in response to S. pneumoniae infection. Taken together, these data demonstrate a key role for PAR-1 during S. pneumoniae lung infection that is mediated, at least in part, by influencing multiple downstream inflammatory mediators.

Chard (Beta vulgaris var. cicla) extract improved hyperglycemia-induced oxidative stress and surfactant-associated protein alterations in rat lungs

CONTEXT

Chard is used as an antidiabetic agent by the diabetic patients in Turkey.

OBJECTIVE

The effect of chard extract [Beta vulgaris L. var. cicla (Chenopodiaceae)] on the antioxidant system and the expression of surfactant-associated proteins (SP) in the lungs of hyperglycemic rats were examined.

MATERIALS AND METHODS

Hyperglycemia was induced by a single dose of streptozotocin (60 mg/kg) provided intraperitoneally. Fourteen days after the rats were rendered hyperglycemic, the chard (2 g/kg/d), insulin (6 U/kg/d), and chard plus insulin (as mentioned above) were administered to rats for 45 d. On day 60, rats' lungs were removed. Oxidative stress parameters and SP expression were assayed.

RESULTS

The lungs of hyperglycemic rats were characterized by the induced lipid and protein oxidation, elevated myeloperoxidase and xanthine oxidase activities, decreased glutathione levels, and reduced tissue factor and antioxidant enzymes activities (catalase, superoxide dismutase, glutathione peroxidase, and glutathione-S-transferase). Chard treatment alone and chard treatment combined with insulin were capable of achieving a regression of pulmonary oxidative stress, by inhibiting lipid and protein oxidation, and restoring the antioxidant system of hyperglycemic rats. SP-A expressions were significantly unchanged in all groups, whereas pro-SP-C and SP-D expressions were reduced in hyperglycemic rats. Pro-SP-C and SP-D levels were increased by chard and insulin administrations alone and combined in hyperglycemic rats.

DISCUSSION AND CONCLUSION

All treatments have a positive effect on the surfactant and antioxidant systems of the lungs of hyperglycemic rats. The best therapeutic effect was provided by treatment with chard extract alone in the compensation of hyperglycemic symptoms.

Hemopexin in severe inflammation and infection: mouse models and human diseases

Introduction

Cell-free plasma hemoglobin is associated with poor outcome in patients with sepsis. Extracellular hemoglobin and secondarily released heme amplify inflammation in the presence of microbial TLR ligands and/or endogenous mediators. Hemopexin, a plasma protein that binds heme with extraordinary affinity, blocks these effects and has been proposed as a possible treatment approach to decrease inflammation in critically ill patients.

Methods

We studied mouse models of endotoxemia, burn wound infections and peritonitis in order to assess if a repletion strategy for hemopexin might be reasonable. We also measured hemopexin in small numbers of three patient populations that might be logical groups for hemopexin therapy: patients with sepsis and ARDS, patients with severe burns, and premature infants.

Results

Despite severe disease, mean plasma hemopexin levels were increased above baseline in each murine model. However, plasma hemopexin levels were decreased or markedly decreased in many patients in each of the three patient populations.

Conclusions

Potentially different behavior of hemopexin in mice and humans may be important to consider when utilizing murine models to represent acute human inflammatory diseases in which heme plays a role. The findings raise the possibility that decreased hemopexin could result in insufficiently neutralized or cleared heme in some patients with ARDS, burns, or in premature infants who might be candidates to benefit from hemopexin administration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0885-x) contains supplementary material, which is available to authorized users.

Xuebijing exerts protective effects on lung permeability leakage and lung injury by upregulating Toll-interacting protein expression in rats with sepsis

Xuebijing (XBJ) is a type of traditional Tibetan medicine, and previous pharmacological studies have shown that the ethanol extract is derived from Chuanxiong, Chishao, Danshen and Honghua. Chuanxiong, Chishao, Danshen and Honghua possesses potent anti-inflammatory activity, and has been used in the treatment of inflammatory infectious diseases. In the present study, we investigated the effects of XBJ on pulmonary permeability and lung injury in cecal ligation and puncture (CLP)-induced sepsis in rats. A CLP sepsis model was established for the control and treatment groups, respectively. Approximately 2 h prior to surgery, an amount of 100 mg/kg XBJ injection was administered to the treatment group. Reverse transcription polymerase chain reaction (PT-PCR) and western blot analysis were used to examine the expression of Toll-interacting protein (Tollip), interleukin-1 receptor-associated kinase 1 (IRAK1), Toll-like receptor 4 (TLR4), nuclear factor-κB65 (NF-κB65) and TNF receptor-associated factor 6 (TRAF6) in lung tissue. ELISA was applied to detect changes of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1 (IL-1), interleukin-4 (IL-4) and interleukin-10 (IL-10) levels in bronchoalveolar lavage (BAL) fluid, and intercellular adhesion molecule 1 (ICAM-1) and von Willebrand factor (vWF) in serum. The number of neutrophils, albumin and total cells in the BAL fluid were measured. For histological analysis, hematoxylin and eosin (H&E) stains were evaluated. Lung permeability, the wet/dry weight ratio (W/D) and the lung pathology score were determined following the induction of ALI by CLP for 24 h. The results demonstrated that XBJ upregulated Tollip expression and blocked the activity of IRAK1, TLR4, NF-κβ65 and TRAF6. Additionally, the number of neutrophils and total cells were significantly decreased in the XBJ group compared to that in the control group. Lung permeability, the wet/dry weight ratio (W/D) and the lung pathology score were significantly decreased in the XBJ group. The histological results also demonstrated the attenuation effect of XBJ on CLP-induced lung inflammation. The results of the present study indicated that XBJ has a significantly reduced CLP-induced lung permeability by upregulating Tollip expression. The protective effects of XBJ suggest its therapeutic potential in CLP-induced acute lung injury treatment.

Validation of a multiplex electrochemiluminescent immunoassay platform in human and mouse samples

BACKGROUND

Despite the widespread use of multiplex immunoassays, there are very few scientific reports that test the accuracy and reliability of a platform prior to publication of experimental data. Our laboratory has previously demonstrated the need for new assay platform validation prior to use of biologic samples from large studies in order to optimize sample handling and assay performance.

METHODS

In this study, our goal was to test the accuracy and reproducibility of an electrochemiluminescent multiplex immunoassay platform (Meso Scale Discovery, MSD®) and compare this platform to validated, singleplex immunoassays (R&D Systems®) using actual study subject (human plasma and mouse bronchoalveolar lavage fluid (BAL) and plasma) samples.

RESULTS

We found that the MSD platform performed well on intra- and inter-assay comparisons, spike and recovery and cross-platform comparisons. The mean intra-assay CV% and range for MSD were 3.49 (0.0-10.4) for IL-6 and 2.04 (0.1-7.9) for IL-8. The correlation between values for identical samples measured on both MSD and R&D was R=0.97 for both analytes. The mouse MSD assay had a broader range of CV% with means ranging from 9.5 to 28.5 depending on the analyte. The range of mean CV% was similar for single plex ELISAs at 4.3-23.7 depending on the analyte. Regardless of species or sample type, CV% was more variable at lower protein concentrations.

CONCLUSIONS

In conclusion, we validated a multiplex electrochemiluminescent assay system and found that it has superior test characteristics in human plasma compared to mouse BALF and plasma. Both human and MSD assays compared favorably to well-validated singleplex ELISAs.

Methemoglobin-induced signaling and chemokine responses in human alveolar epithelial cells

Diffuse alveolar hemorrhage is characterized by the presence of red blood cells and free hemoglobin in the alveoli and complicates a number of serious medical and surgical lung conditions including the pulmonary vasculitides and acute respiratory distress syndrome. In this study we investigated the hypothesis that exposure of human alveolar epithelial cells to hemoglobin and its breakdown products regulates chemokine release via iron- and oxidant-mediated activation of the transcription factor NF-κB. Methemoglobin alone stimulated the release of IL-8 and MCP-1 from A549 cells via activation of the NF-κB pathway; additionally, IL-8 required ERK activation and MCP-1 required JNK activation. Neither antioxidants nor iron chelators and knockdown of ferritin heavy and light chains affected these responses, indicating that iron and reactive oxygen species are not involved in the response of alveolar epithelial cells to methemoglobin. Incubation of primary cultures of human alveolar type 2 cells with methemoglobin resulted in a similar pattern of chemokine release and signaling pathway activation. In summary, we have shown for the first time that methemoglobin induced chemokine release from human lung epithelial cells independent of iron- and redox-mediated signaling involving the activation of the NF-κB and MAPK pathways. Decompartmentalization of hemoglobin may be a significant proinflammatory stimulus in a variety of lung diseases.