Platelet-activating factor contributes to acute lung leak in rats given interleukin-1 intratracheally

Secondary Streptococcus pneumoniae infection increases morbidity and mortality during murine cryptococcosis

Microorganisms that cause pneumonia and translocate to the central nervous system (CNS) are responsible for high mortality worldwide. The fungus Cryptococcus gattii (Cg) and the bacteria Streptococcus pneumoniae (Sp) target the same infection organs. This study aimed to investigate the consequences of secondary Sp infection during murine cryptococcosis. Mice infected with Sp after Cg showed significantly increased lethality and a drop in scores of motor behaviour, neuropsychiatric status and autonomous function. Previous Cg infection favoured Sp multiplication in the lungs, causing intense inflammation and necrosis, with further increased bacterial translocation to the spleen, liver and brain. This phenotype was associated with increased platelet-activating factor receptor (Pafr) gene expression, reduced M1 macrophage recruitment, and high levels of proinflammatory mediators. Strategies to overcome early mortality (i.e., infection of Pafr-/- mice, treatment with IL-1 inhibitor or corticoid) were insufficient to revert this phenotype. These results suggest that Cg infection makes the lung microenvironment favourable for Sp colonization and dissemination. Altogether, it leads to an exacerbated and ineffective inflammatory response, decisive for the increased morbidity and mortality during coinfection. In conclusion, our results highlight the importance of more studies addressing coinfections and their consequences in the host, aiming to establish more effective therapeutical strategies.

NMDARs antagonist MK801 suppresses LPS-induced apoptosis and mitochondrial dysfunction by regulating subunits of NMDARs via the CaM/CaMKII/ERK pathway

Lipopolysaccharide (LPS) displays a robust immunostimulatory ability upon Toll-like receptor 4 (TLR4) recognition. N-methyl-D-aspartate receptors (NMDARs) are highly compartmentalized in most cells and implicated in various inflammatory disorders. However, the relationship between TLR4 and NMDARs has not been explored deeply. This study aimed to examine the role of NMDARs and its specific inhibitor MK801 in LPS-treated endothelial cell dysfunction and the related mechanism in vivo and in vitro. The results showed that pre-treatment with MK801 significantly decreased LPS-induced cell death, cellular Ca²⁺, cellular reactive oxygen species, and glutamate efflux. Moreover, MK801 restrained LPS-induced mitochondrial dysfunction by regulating mitochondrial membrane potential and mitochondrial Ca²⁺ uptake. The oxygen consumption, basal and maximal respiration rate, and ATP production in LPS-treated HUVECs were reversed by MK801 via regulating ATP synthesis-related protein SDHB2, MTCO1, and ATP5A. The molecular pathway involved in MK801-regulated LPS injury was mediated by phosphorylation of CaMKII and ERK and the expression of MCU, MCUR1, and TLR4. LPS-decreased permeability in HUVECs was improved by MK801 via the Erk/ZO-1/occluding/Cx43 axis. Co-immunoprecipitation assay and western blotting showed three subtypes of NMDARs, NMDAζ1, NMDAε2, and NMDAε4 were bound explicitly to TLR4, suppressed by LPS, and promoted by MK801. Deficiency of NMDAζ1, NMDAε2, or NMDAε4 induced cell apoptosis, Ca²⁺ uptake, ROS production, and decreased basal and maximal respiration rate, and ATP production, suggesting that NMDARs integrity is vital for cell and mitochondrial function. In vivo investigation showed MK801 improved impairment of vascular permeability, especially in the lung and mesentery in LPS-injured mice. Our study displayed a novel mechanism and utilization of MK801 in LPS-induced ECs injury and permeability.

Fatty Acid Amide Hydrolase (FAAH) Inhibition Plays a Key Role in Counteracting Acute Lung Injury

Acute lung injury (ALI) is a group of lung illnesses characterized by severe inflammation, with no treatment. The fatty acid amide hydrolase (FAAH) enzyme is an integral membrane protein responsible for the hydrolysis of the main endocannabinoids, such as anandamide (AEA). In pre-clinical pain and inflammation models, increasing the endogenous levels of AEA and other bioactive fatty acid amides (FAAs) via genetic deletion or the pharmacological inhibition of FAAH produces many analgesic benefits in several different experimental models. To date, nobody has investigated the role of FAAH inhibition on an ALI mouse model. Mice were subjected to a carrageenan injection and treated orally 1 h after with the FAAH inhibitor URB878 dissolved in a vehicle consisting of 10% PEG-400, 10% Tween-80 and 80% saline at different doses: The inhibition of FAAH activity was able to counteract not only the CAR-induced histological alteration, but also the cascade of related inflammatory events. URB878 clears the way for further studies based on FAAH inhibition in acute lung pathologies.

Unique inflammatory profile is associated with higher SARS-CoV-2 acute respiratory distress syndrome (ARDS) mortality

The COVID19 pandemic has caused more than a million of deaths worldwide, primarily due to complications from COVID19-associated acute respiratory distress syndrome (ARDS). Controversy surrounds the circulating cytokine/chemokine profile of COVID19-associated ARDS, with some groups suggesting that it is similar to patients without COVID19 ARDS and others observing substantial differences. Moreover, although a hyperinflammatory phenotype associates with higher mortality in non-COVID19 ARDS, there is little information on the inflammatory landscape's association with mortality in patients with COVID19 ARDS. Even though the circulating leukocytes' transcriptomic signature has been associated with distinct phenotypes and outcomes in critical illness including ARDS, it is unclear whether the mortality-associated inflammatory mediators from patients with COVID19 are transcriptionally regulated in the leukocyte compartment. Here, we conducted a prospective cohort study of 41 mechanically ventilated patients with COVID19 infection using highly calibrated methods to define the levels of plasma cytokines/chemokines and their gene expressions in circulating leukocytes. Plasma IL1RA and IL8 were found positively associated with mortality, whereas RANTES and EGF negatively associated with that outcome. However, the leukocyte gene expression of these proteins had no statistically significant correlation with mortality. These data suggest a unique inflammatory signature associated with severe COVID19.

Diammonium glycyrrhizinate lipid ligand ameliorates lipopolysaccharide-induced acute lung injury by modulating vascular endothelial barrier function

The aim of the present study was to investigate the effects of diammonium glycyrrhizinate lipid ligand (DGLL) treatment on acute lung injury (ALI) and pulmonary edema induced by lipopolysaccharide (LPS) in Sprague-Dawley rats. Rats orally received 30, 60 and 120 mg/kg DGLL. After 1 h, the rat ALI model was established by LPS (10 mg/kg) intraperitoneal injection. After 6 h, lung injury was evaluated using hematoxylin and eosin staining techniques. Pulmonary edema was evaluated using lung wet-dry weight ratio, protein concentrations in the bronchoalveolar lavage fluid (BALF) and Evans blue (EB) extravasation in lung tissue. The expression levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in lung tissues were measured using ELISA. Myeloperoxidase (MPO) expression levels were detected by immunohistochemical staining. Western blotting was used to measure the expression level changes of intercellular adhesion molecule (ICAM)-1, as well as adherent and tight junction proteins, including vascular endothelial (VE)-cadherin, zonula occludens (ZO)-1, occludin and junctional adhesion molecule (JAM)-1 that were associated with pulmonary inflammation and microvascular permeability. DGLL treatment significantly alleviated ALI induced by LPS, which was demonstrated by reduction of MPO-positive cells and expression levels of TNF-α, IL-1β and ICAM-1 in rat lung tissues. In addition, DGLL abrogated LPS-induced pulmonary edema, decreased the protein concentration in BALF and reduced EB extravasation. DGLL also reversed the reduced expression of VE-cadherin and tight junction proteins, including ZO-1, occludin and JAM-1 in the lung tissues caused by LPS. In conclusion, DGLL exhibits a protective effect on LPS-induced rat ALI, which is associated with the inhibition of inflammatory cell infiltration and microvascular barrier disruption. The present results provide a theoretical basis for the application of DGLL for the potential clinical treatment of ALI.

PAF-R on activated T cells: Role in the IL-23/Th17 pathway and relevance to multiple sclerosis

IL-23 is a potent stimulus for Th17 cells. These cells have a distinct developmental pathway from Th1 cells induced by IL-12 and are implicated in autoimmune and inflammatory disorders including multiple sclerosis (MS). TGF-β, IL-6, and IL-1, the transcriptional regulator RORγt (RORC) and IL-23 are implicated in Th17 development and maintenance. In human polyclonally activated T cells, IL-23 enhances IL-17 production. The aims of our study were: 1). To validate microarray results showing preferential expression of platelet activating factor receptor (PAF-R) on IL-23 stimulated T cells. 2). To determine whether PAF-R on activated T cells is functional, whether it is co-regulated with Th17-associated molecules, and whether it is implicated in Th17 function. 3). To determine PAF-R expression in MS. We show that PAF-R is expressed on activated T cells, and is inducible by IL-23 and IL-17, which in turn are induced by PAF binding to PAF-R. PAF-R is co-expressed with IL-17 and regulated similarly with Th17 markers IL-17A, IL-17F, IL-22 and RORC. PAF-R is upregulated on PBMC and T cells of MS patients, and levels correlate with IL-17 and with MS disability scores. Our results show that PAF-R on T cells is associated with the Th17 phenotype and function. Clinical Implications Targeting PAF-R may interfere with Th17 function and offer therapeutic intervention in Th17-associated conditions, including MS.

Unique inflammatory profile is associated with higher SARS-CoV-2 acute respiratory distress syndrome (ARDS) mortality

The COVID19 pandemic is likely to cause more than a million of deaths worldwide, primarily due to complications from COVID19-associated acute respiratory distress syndrome (ARDS). Controversy surrounds the circulating cytokine/chemokine profile of COVID19-associated ARDS, with some groups suggesting that it is similar to non-COVID19 ARDS patients and others observing substantial differences. Moreover, while a hyperinflammatory phenotype associates with higher mortality in non-COVID19 ARDS, there is little information on the inflammatory landscape's association with mortality in COVID19 ARDS patients. Even though the circulating leukocytes' transcriptomic signature has been associated with distinct phenotypes and outcomes in critical illness including ARDS, it is unclear whether the mortality-associated inflammatory mediators from COVID19 patients are transcriptionally regulated in the leukocyte compartment. Here, we conducted a prospective cohort study of 41 mechanically ventilated patients with COVID19 infection using highly calibrated methods to define the levels of plasma cytokines/chemokines and their gene expressions in circulating leukocytes. Plasma IL1RA and IL8 were found positively associated with mortality while RANTES and EGF negatively associated with that outcome. However, the leukocyte gene expression of these proteins had no statistically significant correlation with mortality. These data suggest a unique inflammatory signature associated with severe COVID19.

IL-1β dysregulates cGMP signaling in the newborn lung

Cyclic guanosine monophosphate (cGMP) signaling is an important regulator of newborn lung function and development. Although cGMP signaling is decreased in many models of newborn lung injury, the mechanisms are poorly understood. We determined how IL-1β regulates the expression of the α1-subunit of soluble guanylate cyclase (sGCα1), a prime effector of pulmonary cGMP signaling. Physiologic levels of IL-1β were discovered to rapidly decrease sGCα1 mRNA expression in a human fetal lung fibroblast cell line (IMR-90 cells) and protein levels in primary mouse pup lung fibroblasts. This sGCα1 expression inhibition appeared to be at a transcriptional level; IL-1β treatment did not alter sGCα1 mRNA stability although it reduced sGCα1 promoter activity. TGFβ-activated kinase 1 (TAK1) was determined to be required for IL-1β's regulation of sGCα1 expression; TAK1 knockdown protected sGCα1 mRNA expression in IL-1β-treated IMR-90 cells. Moreover, heterologously expressed TAK1 was sufficient to decrease sGCα1 mRNA levels in those cells. Nuclear factor-kappaB (NF-κB) signaling played a critical role in the IL-1β-TAK1-sGCα1 regulatory pathway; chromatin immunoprecipitation studies demonstrated enhanced activated NF-kB subunit (RelA) binding to the sGCα1 promoter after IL-1β treatment unless were treated with an IκB kinase2 inhibitor. Also, this NF-kB signaling inhibition protected sGCα1 expression in IL-1β-treated fibroblasts. Lastly, using transgenic mice in which active IL-1β was conditionally expressed in lung epithelial cells, we established that IL-1β expression is sufficient to stimulate TAK1 and decrease sGCα1 protein expression in the newborn lung. Together these results detail the role and mechanisms by which IL-1β inhibits cGMP signaling in the newborn lung.

Protective Effects of Chymostatin on Paraquat-Induced Acute Lung Injury in Mice

This study aims to evaluate the role of chymostatin in paraquat-induced acute lung injury. Institute of Cancer Research mice were randomly distributed into the NS, DMSO, chymostatin, paraquat or chymostatin treatment groups. Six mice from each group were intraperitoneally injected with chloral hydrate at 0, 1, 2, 4, 8, 12, 24 and 48 h after treatment administration. Blood samples were collected through cardiac puncture. Lung tissues were stained with haematoxylin and eosin for the observation of lung histology. The degree of pulmonary oedema was determined on the basis of lung wet-to-dry ratio (W/D). The serum activity of cathepsin G was determined through substrate fluorescence assay. The serum levels of endothelial cell-specific molecule-1 (endocan), tumour necrosis factor-a (TNF-a), interleukin-1β (IL-1β), IL-6 and high-mobility group box protein 1 (HMGB1) were determined through enzyme-linked immunosorbent assay. The expression levels of endocan and nuclear NF-κBp65 in the lung were quantified through Western blot. Chymostatin alleviated the pathological changes associated with acute alveolitis in mice; decreased the lung W/D ratio, the activity of cathepsin G and the serum concentrations of TNF-a, IL-1β, IL-6 and HMGB1; and increased the serum concentration of endocan. Western blot results revealed that chymostatin up-regulated endocan expression and down-regulated nuclear NF-κBp65 expression in the lung. Chymostatin reversed the inflammatory effects of paraquat-induced lung injury by inhibiting cathepsin G activity to up-regulate endocan expression and indirectly inhibit NF-κBp65 activity.

SOCS-1 rescues IL-1β-mediated suppression of epithelial sodium channel in mouse lung epithelial cells via ASK-1

Background

Acute lung injury (ALI) is characterized by alveolar damage, increased levels of pro-inflammatory cytokines and impaired alveolar fluid clearance. Recently, we showed that the deletion of Apoptosis signal-regulating kinase 1 (ASK1) protects against hyperoxia-induced acute lung injury (HALI) by suppressing IL-1β and TNF-α. Previously, our data revealed that the suppressor of cytokine signaling-1 (SOCS-1) overexpression restores alveolar fluid clearance in HALI by inhibiting ASK-1 and suppressing IL-1β levels. Furthermore, IL-1β is known to inhibit the expression of epithelial sodium channel α-subunit (ENaC) via a p38 MAPK signaling pathway.

Objective

To determine whether SOCS-1 overexpression in MLE-12 cells would protect against IL-1β-mediated depletion of αENaC by suppressing ASK-1 expression.

Methods

We co-transfected MLE-12 cells with SOCS-1 overexpressing plasmid with or without IL-1β in the presence or absence of sodium channel inhibitor, amiloride. We measured potential difference, transepithelial current, resistance, and sodium uptake levels across MLE-12 cells. We studied the effect of ASK-1 depletion, as well as ASK-1 and SOCS-1 overexpression on αENaC expression.

Results

SOCS-1 overexpression sufficiently restored transepithelial current and resistance in MLE-12 cells treated with either IL-1β or amiloride. The αENaC mRNA levels and sodium transport were increased in SOCS-1 overexpressing MLE-12 cells exposed to IL-1β. Depletion of ASK-1 in MLE-12 cells increased αENaC mRNA levels. Interestingly, SOCS-1 overexpression restored αENaC expression in MLE-12 cells in the presence of ASK-1 overexpression.

Conclusion

Collectively, these findings suggest that SOCS-1 may exert its protective effect by rescuing αENaC expression via suppression of ASK-1.

Cytokine-Ion Channel Interactions in Pulmonary Inflammation

The lungs conceptually represent a sponge that is interposed in series in the bodies’ systemic circulation to take up oxygen and eliminate carbon dioxide. As such, it matches the huge surface areas of the alveolar epithelium to the pulmonary blood capillaries. The lung’s constant exposure to the exterior necessitates a competent immune system, as evidenced by the association of clinical immunodeficiencies with pulmonary infections. From the in utero to the postnatal and adult situation, there is an inherent vital need to manage alveolar fluid reabsorption, be it postnatally, or in case of hydrostatic or permeability edema. Whereas a wealth of literature exists on the physiological basis of fluid and solute reabsorption by ion channels and water pores, only sparse knowledge is available so far on pathological situations, such as in microbial infection, acute lung injury or acute respiratory distress syndrome, and in the pulmonary reimplantation response in transplanted lungs. The aim of this review is to discuss alveolar liquid clearance in a selection of lung injury models, thereby especially focusing on cytokines and mediators that modulate ion channels. Inflammation is characterized by complex and probably time-dependent co-signaling, interactions between the involved cell types, as well as by cell demise and barrier dysfunction, which may not uniquely determine a clinical picture. This review, therefore, aims to give integrative thoughts and wants to foster the unraveling of unmet needs in future research.

Regulation of Lung Epithelial Sodium Channels by Cytokines and Chemokines

Acute lung injury leading to acute respiratory distress (ARDS) is a global health concern. ARDS patients have significant pulmonary inflammation leading to flooding of the pulmonary alveoli. This prevents normal gas exchange with consequent hypoxemia and causes mortality. A thin fluid layer in the alveoli is normal. The maintenance of this thin layer results from fluid movement out of the pulmonary capillaries into the alveolar interstitium driven by vascular hydrostatic pressure and then through alveolar tight junctions. This is then balanced by fluid reabsorption from the alveolar space mediated by transepithelial salt and water transport through alveolar cells. Reabsorption is a two-step process: first, sodium enters via sodium-permeable channels in the apical membranes of alveolar type 1 and 2 cells followed by active extrusion of sodium into the interstitium by the basolateral Na⁺, K⁺-ATPase. Anions follow the cationic charge gradient and water follows the salt-induced osmotic gradient. The proximate cause of alveolar flooding is the result of a failure to reabsorb sufficient salt and water or a failure of the tight junctions to prevent excessive movement of fluid from the interstitium to alveolar lumen. Cytokine- and chemokine-induced inflammation can have a particularly profound effect on lung sodium transport since they can alter both ion channel and barrier function. Cytokines and chemokines affect alveolar amiloride-sensitive epithelial sodium channels (ENaCs), which play a crucial role in sodium transport and fluid reabsorption in the lung. This review discusses the regulation of ENaC via local and systemic cytokines during inflammatory disease and the effect on lung fluid balance.

Inflammatory Responses Regulating Alveolar Ion Transport during Pulmonary Infections

The respiratory epithelium is lined by a tightly balanced fluid layer that allows normal O₂ and CO₂ exchange and maintains surface tension and host defense. To maintain alveolar fluid homeostasis, both the integrity of the alveolar–capillary barrier and the expression of epithelial ion channels and pumps are necessary to establish a vectorial ion gradient. However, during pulmonary infection, auto- and/or paracrine-acting mediators induce pathophysiological changes of the alveolar–capillary barrier, altered expression of epithelial Na,K-ATPase and of epithelial ion channels including epithelial sodium channel and cystic fibrosis membrane conductance regulator, leading to the accumulation of edema and impaired alveolar fluid clearance. These mediators include classical pro-inflammatory cytokines such as TGF-β, TNF-α, interferons, or IL-1β that are released upon bacterial challenge with Streptococcus pneumoniae, Klebsiella pneumoniae, or Mycoplasma pneumoniae as well as in viral infection with influenza A virus, pathogenic coronaviruses, or respiratory syncytial virus. Moreover, the pro-apoptotic mediator TNF-related apoptosis-inducing ligand, extracellular nucleotides, or reactive oxygen species impair epithelial ion channel expression and function. Interestingly, during bacterial infection, alterations of ion transport function may serve as an additional feedback loop on the respiratory inflammatory profile, further aggravating disease progression. These changes lead to edema formation and impair edema clearance which results in suboptimal gas exchange causing hypoxemia and hypercapnia. Recent preclinical studies suggest that modulation of the alveolar–capillary fluid homeostasis could represent novel therapeutic approaches to improve outcomes in infection-induced lung injury.

Cecal ligation and puncture accelerates development of ventilator-induced lung injury

Sepsis is a leading cause of respiratory failure requiring mechanical ventilation, but the interaction between sepsis and ventilation is unclear. While prior studies demonstrated a priming role with endotoxin, actual septic animal models have yielded conflicting results regarding the role of preceding sepsis on development of subsequent ventilator-induced lung injury (VILI). Using a rat cecal ligation and puncture (CLP) model of sepsis and subsequent injurious ventilation, we sought to determine if sepsis affects development of VILI. Adult male Sprague-Dawley rats were subject to CLP or sham operation and, after 12 h, underwent injurious mechanical ventilation (tidal volume 30 ml/kg, positive end-expiratory pressure 0 cmH2O) for either 0, 60, or 120 min. Biochemical and physiological measurements, as well as computed tomography, were used to assess injury at 0, 60, and 120 min of ventilation. Before ventilation, CLP rats had higher levels of alveolar neutrophils and interleukin-1β. After 60 min of ventilation, CLP rats had worse injury as evidenced by increased alveolar inflammation, permeability, respiratory static compliance, edema, oxygenation, and computed tomography. By 120 min, CLP and sham rats had comparable levels of lung injury as assessed by many, but not all, of these metrics. CLP rats had an accelerated and worse loss of end-expiratory lung volume relative to sham, and consistently higher levels of alveolar interleukin-1β. Loss of aeration and progression of edema was more pronounced in dependent lung regions. We conclude that CLP initiated pulmonary inflammation in rats, and accelerated the development of subsequent VILI.

CB2 receptor activation ameliorates the proinflammatory activity in acute lung injury induced by paraquat

Paraquat, a widely used herbicide, is well known to exhibit oxidative stress and lung injury. In the present study, we investigated the possible underlying mechanisms of cannabinoid receptor-2 (CB2) activation to ameliorate the proinflammatory activity induced by PQ in rats. JWH133, a CB2 agonist, was administered by intraperitoneal injection 1 h prior to PQ exposure. After PQ exposure for 4, 8, 24, and 72 h, the bronchoalveolar lavage fluid was collected to determine levels of TNF-α and IL-1β, and the arterial blood samples were collected for detection of PaO₂ level. At 72 h after PQ exposure, lung tissues were collected to determine the lung wet-to-dry weight ratios, myeloperoxidase activity, lung histopathology, the protein expression level of CB2, MAPKs (ERK1/2, p38MAPK, and JNK1/2), and NF-κBp65. After rats were pretreated with JWH133, PQ-induced lung edema and lung histopathological changes were significantly attenuated. PQ-induced TNF-α and IL-1β secretion in BALF, increases of PaO₂ in arterial blood, and MPO levels in the lung tissue were significantly reduced. JWH133 could efficiently activate CB2, while inhibiting MAPKs and NF-κB activation. The results suggested that activating CB2 receptor exerted protective activity against PQ-induced ALI, and it potentially contributed to the suppression of the activation of MAPKs and NF-κB pathways.

Inhibitory effects of rosiglitazone on paraquat-induced acute lung injury in rats

AIM

To investigate the effects of the PPAR-γ agonist rosiglitazone on acute lung injury induced by the herbicide paraquat (PQ) and the underlying mechanisms of action.

METHODS

Male Sprague-Dawley rats were injected with PQ (20 mg/kg, ip). Rosiglitazone (3 or 10 mg/kg, ip) was administered 1 h before PQ exposure. Peripheral blood was collected at 4, 8, 24 and 72 h after PQ exposure for measuring the levels of MDA, TNF-α and IL-1β, and the SOD activity. Lung tissues were collected at 72 h after PQ exposure to determine the wet-to-dry (W/D) ratios and lung injury scores, as well as the protein levels of NF-κBp65, PPAR-γ, Nrf2, IκBα and pIκBα.

RESULTS

At 72 h after PQ exposure, the untreated rats showed a 100% cumulative mortality, whereas no death was observed in rosiglitazone-pretreated rats. Moreover, rosiglitazone pretreatment dose-dependently attenuated PQ-induced lung edema and lung histopathological changes. The pretreatment significantly reduced the levels of TNF-α, IL-1β and MDA, increased SOD activity in the peripheral blood of PQ-treated rats. The pretreatment also efficiently activated PPAR-γ, induced Nrf2 expression and inhibited NF-κB activation in the lung tissues of PQ-treated rats. Furthermore, the pretreatment dose-dependently inhibited IκB-α degradation and phosphorylation, thus inhibiting NF-κB activation.

CONCLUSION

Pretreatment with rosiglitazone protects rats against PQ-induced acute lung injury by activating PPAR-γ, inducing Nrf2 expression and inhibiting NF-κB activation.

IL1RN coding variant is associated with lower risk of acute respiratory distress syndrome and increased plasma IL-1 receptor antagonist

RATIONALE

Acute respiratory distress syndrome (ARDS) behaves as a complex genetic trait, yet knowledge of genetic susceptibility factors remains incomplete.

OBJECTIVES

To identify genetic risk variants for ARDS using large scale genotyping.

METHODS

A multistage genetic association study was conducted of three critically ill populations phenotyped for ARDS. Stage I, a trauma cohort study (n = 224), was genotyped with a 50K gene-centric single-nucleotide polymorphism (SNP) array. We tested SNPs associated with ARDS at P < 5 × 10(-4) for replication in stage II, a trauma case-control population (n = 778). SNPs replicating their association in stage II (P < 0.005) were tested in a stage III nested case-control population of mixed subjects in the intensive care unit (n = 2,063). Logistic regression was used to adjust for potential clinical confounders. We performed ELISA to test for an association between ARDS-associated genotype and plasma protein levels.

MEASUREMENTS AND MAIN RESULTS

A total of 12 SNPs met the stage I threshold for an association with ARDS. rs315952 in the IL1RN gene encoding IL-1 receptor antagonist (IL1RA) replicated its association with reduced ARDS risk in stages II (P < 0.004) and III (P < 0.02), and was robust to clinical adjustment (combined odds ratio = 0.81; P = 4.2 × 10(-5)). Plasma IL1RA level was associated with rs315952C in a subset of critically ill subjects. The effect of rs315952 was independent from the tandem repeat variant in IL1RN.

CONCLUSIONS

The IL1RN SNP rs315952C is associated with decreased risk of ARDS in three populations with heterogeneous ARDS risk factors, and with increased plasma IL1RA response. IL1RA may attenuate ARDS risk.

Death receptors mediate the adverse effects of febrile-range hyperthermia on the outcome of lipopolysaccharide-induced lung injury

We have shown that febrile-range hyperthermia enhances lung injury and mortality in mice exposed to inhaled LPS and is associated with increased TNF-α receptor activity, suppression of NF-κB activity in vitro, and increased apoptosis of alveolar epithelial cells in vivo. We hypothesized that hyperthermia enhances lung injury and mortality in vivo by a mechanism dependent on TNF receptor signaling. To test this, we exposed mice lacking the TNF-receptor family members TNFR1/R2 or Fas (TNFR1/R2(-/-) and lpr) to inhaled LPS with or without febrile-range hyperthermia. For comparison, we studied mice lacking IL-1 receptor activity (IL-1R(-/-)) to determine the role of inflammation on the effect of hyperthermia in vivo. TNFR1/R2(-/-) and lpr mice were protected from augmented alveolar permeability and mortality associated with hyperthermia, whereas IL-1R(-/-) mice were susceptible to augmented alveolar permeability but protected from mortality associated with hyperthermia. Hyperthermia decreased pulmonary concentrations of TNF-α and keratinocyte-derived chemokine after LPS in C57BL/6 mice and did not affect pulmonary inflammation but enhanced circulating markers of oxidative injury and nitric oxide metabolites. The data suggest that hyperthermia enhances lung injury by a mechanism that requires death receptor activity and is not directly associated with changes in inflammation mediated by hyperthermia. In addition, hyperthermia appears to enhance mortality by generating a systemic inflammatory response and not by a mechanism directly associated with respiratory failure. Finally, we observed that exposure to febrile-range hyperthermia converts a modest, survivable model of lung injury into a fatal syndrome associated with oxidative and nitrosative stress, similar to the systemic inflammatory response syndrome.

TLR4 is a negative regulator in noninfectious lung inflammation

Low m.w. hyaluronan (LMW HA) has been shown to elicit the expression of proinflammatory cytokines and chemokines in various cells in vitro. However, the effects of this molecule in vivo are unknown. In this study, we report that intratracheal administration of LMW HA (200 kDa) causes inflammation in mouse lung. A lack of TLR4 is associated with even stronger inflammatory response in the lung as shown by increased neutrophil counts and elevated cytokine and chemokine concentrations. We also demonstrate that TLR4 anti-inflammatory signaling is dependent upon a MyD88-independent pathway. TLR4-mediated IL-1R antagonist production plays a negative regulatory role in LMW HA (200 kDa) induced lung inflammation. These data provide a molecular level explanation for the function of TLR4 in LMW HA (200 kDa)-induced lung inflammation, as inhibition of the beta form of pro-IL-1 promotes an anti-inflammatory response.

Common pathways for activation of proinflammatory gene expression by G protein-coupled receptors in primary lung epithelial and endothelial cells

Acute lung injury is associated with an inflammatory response resulting from the action of multiple mediators. Many proinflammatory mediators released during lung injury exert effects by binding to G protein-coupled receptors (GPCRs). The authors' earlier studies showed that substance P (SP), a ligand for the tachykinin 1 receptor, induced nuclear factor (NF)-kappa B activation and interleukin (IL)-8 up-regulation through a G(q)-dependent pathway. Here the authors extend these findings by examining effects of multiple ligands for G(q)-coupled GPCRs in primary human small airway epithelial cells (SAECs) and rat lung microvessel endothelial cells (RLMVECs). SP, bradykinin, protease activated receptor 2 agonist, and platelet-activating factor (PAF) stimulated IL-8 production in SAECs, whereas only SP and PAF up-regulated CINC-1 (a rat IL-8 homolog) in RLMVECs. Using signaling inhibitors, the authors investigated PAF-induced IL-8 expression and SP-induced CINC-1 expression in primary cells. Signaling cascades were similar in SAECs and RLMVECs and involved phospholipase C/calcium/protein kinase C (PKC) and Ras/Raf/Erk pathways. In addition, the tyrosine kinase inhibitor AG 17 and the proteasome inhibitor MG132 significantly reduced IL-8 and CINC-1 expression induced by GPCR ligands. The results demonstrate a common signaling pathway in primary lung epithelial and endothelial cells, suggesting a generalized mechanism for the induction of proinflammatory gene expression by G(q)-coupled GPCRs following lung injury.

ACUTE BRONCHIAL OBSTRUCTION IN SHEEP: HISTOPATHOLOGY AND GLAND CYTOKINE EXPRESSION

An ovine model of smoke inhalation and burn (S+B) injury models the pathophysiology of these injuries in humans. This study examines the degree of airway obstruction, associated histopathology, and bronchial gland cell expression of cytokines during the first 24 hours after S+B injury in sheep. Changes in the mean degree of obstruction were limited to the bronchial airways, showing significant increases in obstruction with time, P<.05. At 4 hours after injury, the obstructive material was predominantly mucus, with neutrophils clustered around and within gland acini. At 8 to 24 hours, bronchial obstruction was characterized by increased inflammatory cell accumulation. Immunohistochemical results showed that gland cells constitutively express and secrete interleukin (IL)-1beta, and that after injury there is an increase in the percentage of gland cells staining for IL-1alpha, IL-8, and tumor necrosis factor (TNF)-alpha, P<.05.

Inhibitory effects of flavonoids extracted from licorice on lipopolysaccharide-induced acute pulmonary inflammation in mice

Airway inflammation plays important roles in the pathogenesis of acute respiratory distress syndrome (ARDS), asthma and chronic obstructive pulmonary disease (COPD), and anti-inflammatory treatment effectively improves the symptoms of these diseases. To develop the potentially therapeutic compounds for the treatment of pulmonary inflammation, we investigated the effects of licorice flavonoids (LF) extracted from the roots of Glycyrrhiza uralensis (licorice) on lipopolysaccharide (LPS)-induced acute pulmonary inflammation in mice. Acute pulmonary inflammation was induced by intracheal instillation with LPS, treatment with LF at dosages of 3, 10 and 30 mg/kg significantly reduced the LPS-induced inflammatory cells, including neutrophils, macrophages and lymphocytes accumulation in bronchoalveolar lavage fluids (BALF), among these inflammatory cells, LF predominately inhibited neutrophil infiltration, and the maximal effect (30 mg/kg) was as comparable as dexamethasone treatment at 1 mg/kg. Consistent with its effects on neutrophil infiltration, LF treatment significantly increased LPS-induced BALF superoxide dismutase activity, and significantly decreased lung myeloperoxidase activity as well. Furthermore, treatment with LF at 30 mg/kg significantly reduced LPS-induced lung TNFalpha and IL-1beta mRNA expression at 6 h and 24 h after LPS instillation, respectively. Finally, LF at different dosages not only significantly decreased the elevation of lung water content, but also markedly attenuated LPS-induced histological alteration. Therefore, we suggest that LF effectively attenuates LPS-induced pulmonary inflammation through inhibition of inflammatory cells infiltration and inflammatory mediator release which subsequently reduces neutrophil recruitment into lung and neutrophil-mediated oxidative injury, and this study provides with the potential rationale for development of anti-inflammatory compounds from flavonoid extracts of licorice.

Interleukin-1beta causes acute lung injury via alphavbeta5 and alphavbeta6 integrin-dependent mechanisms

Interleukin (IL)-1beta has previously been shown to be among the most biologically active cytokines in the lungs of patients with acute lung injury (ALI). Furthermore, there is experimental evidence that lung vascular permeability increases after short-term exposure to IL-1 protein, although the exact mechanism is unknown. Therefore, the objective of this study was to determine the mechanisms of IL-1beta-mediated increase in lung vascular permeability and pulmonary edema following transient overexpression of this cytokine in the lungs by adenoviral gene transfer. Lung vascular permeability increased with intrapulmonary IL-1beta production with a maximal effect 7 days after instillation of the adenovirus. Furthermore, inhibition of the alphavbeta6 integrin and/or transforming growth factor-beta attenuated the IL-1beta-induced ALI. The results of in vitro studies indicated that IL-1beta caused the activation of transforming growth factor-beta via RhoA/alphavbeta6 integrin-dependent mechanisms and the inhibition of the alphavbeta6 integrin and/or transforming growth factor-beta signaling completely blocked the IL-1beta-mediated protein permeability across alveolar epithelial cell monolayers. In addition, IL-1beta increased protein permeability across lung endothelial cell monolayers via RhoA- and alphavbeta5 integrin-dependent mechanisms. The final series of in vivo experiments demonstrated that pretreatment with blocking antibodies to both the alphavbeta5 and alphavbeta6 integrins had an additive protective effect against IL-1beta-induced ALI. In summary, these results demonstrate a critical role for the alphavbeta5/beta6 integrins in mediating the IL-1beta-induced ALI and indicate that these integrins could be a potentially attractive therapeutic target in ALI.

Interleukin 1 receptor antagonist mediates the antiinflammatory and antifibrotic effect of mesenchymal stem cells during lung injury

Mesenchymal stem cells (MSCs) have been exploited as cellular vectors to treat a wide array of diseases but the mechanisms responsible for their therapeutic effect remain indeterminate. Previously, we reported that MSCs inhibit bleomycin (BLM)-induced inflammation and fibrosis within the lungs of mice. Interrogation of the MSC transcriptome identified interleukin 1 receptor antagonist (IL1RN) as a potential mediator of this effect. Fractionation studies indicated that MSCs are the principal source of IL1RN in murine bone marrow and that its expression is restricted to a unique subpopulation of cells. Moreover, MSC-conditioned media was shown to block proliferation of an IL-1alpha-dependent T cell line and inhibit production of TNF-alpha by activated macrophages in vitro. Studies conducted in mice revealed that MSC administration was more effective than recombinant IL1RN delivered via adenoviral infection or osmotic pumps in inhibiting BLM-induced increases in TNF-alpha, IL-1alpha, and IL1RN mRNA in lung, IL1RN protein in bronchoalveolar lavage (BAL) fluid, and trafficking of lymphocytes and neutrophils into the lung. Therefore, MSCs protect lung tissue from BLM-induced injury by blocking TNF-alpha and IL-1, two fundamental proinflammatory cytokines in lung. Identification of IL1RN-expressing human MSC subpopulations may provide a novel cellular vector for treating chronic inflammatory diseases in humans.

Adenovirus expressing interleukin-1 receptor antagonist alleviates allergic airway inflammation in a murine model of asthma

Interleukin-1 (IL-1) is a proinflammatory cytokine and IL-1 receptor antagonist (IL-1ra) is a natural inhibitor that binds to IL-1 receptor type I without inducing signal transduction. It is suggested that IL-1 is required for allergen-specific T helper type 2 cell activation and the development of airway hyper-responsiveness (AHR), but the immunologic effect of exogenous IL-1ra in allergic asthma remains unclear. To examine the effect of IL-1ra on airway inflammation and immunoeffector cells in allergic asthma, recombinant adenovirus expressing human IL-1ra (Ad-hIL-1ra) was delivered intranasally into ovalbumin (OVA)-immunized mice. Single intranasal administration of Ad-hIL-1ra before airway antigen challenge in OVA-immunized mice significantly decreased the severity of AHR and reduced pulmonary infiltration of eosinophils and neutrophils. Suppression of IL-5 and eotaxin with concomitant enhancement of interferon gamma in bronchoalveolar lavage fluid was also noted in OVA-immunized mice by administration of Ad-hIL-1ra. In addition, histological studies showed that Ad-hIL-1ra was able to decrease OVA-induced peribronchial inflammation. Taken together, our results indicated that administration of Ad-hIL-1ra may have therapeutic potential for the immunomodulatory treatment of allergic asthma.

The influence of hydrogen peroxide and histamine on lung permeability and translocation of iridium nanoparticles in the isolated perfused rat lung

Background

Translocation of ultrafine particles (UFP) into the blood that returns from the lungs to the heart has been forwarded as a mechanism for particle-induced cardiovascular effects. The objective of this study was to evaluate the role of the endothelial barrier in the translocation of inhaled UFP from the lung into circulation.

Methods

The isolated perfused rat lung (IPRL) was used under negative pressure ventilation, and radioactive iridium particles (18 nm, CMD, ¹⁹²Ir-UFP) were inhaled during 60 minutes to achieve a lung burden of 100 – 200 μg. Particle inhalation was done under following treatments: i) control perfusion, ii) histamine (1 μM in perfusate, iii) luminal histamine instillation (1 mM), and iv) luminal instillation of H₂O₂. Particle translocation to the perfusate was assessed by the radioactivity of ¹⁹²Ir isotope. Lung permeability by the use of Tc^99m-labeled diethylene triamine pentaacetic acid (DTPA). In addition to light microscopic morphological evaluation of fixed lungs, alkaline phosphatase (AKP) and angiotensin converting enzyme (ACE) in perfusate were measured to assess epithelial and endothelial integrity.

Results

Particle distribution in the lung was homogenous and similar to in vivo conditions. No translocation of Ir particles at negative pressure inhalation was detected in control IPL, but lungs pretreated with histamine (1 μM) in the perfusate or with luminal H₂O₂ (0.5 mM) showed small amounts of radioactivity (2–3 % dose) in the single pass perfusate starting at 60 min of perfusion. Although the kinetics of particle translocation were different from permeability for ^99mTc-DTPA, the pretreatments (H₂O₂, vascular histamine) caused similar changes in the translocation of particles and soluble mediator. Increased translocation through epithelium and endothelium with a lag time of one hour occurred in the absence of epithelial and endothelial damage.

Conclusion

Permeability of the lung barrier to UFP or nanoparticles is controlled both at the epithelial and endothelial level. Conditions that affect this barrier function such as inflammation may affect translocation of NP.

Serum ferritin increases in hemorrhaged rats that develop acute lung injury: effect of an iron-deficient diet

For unknown reasons, serum ferritin levels increase in patients at risk for and with acute lung injury (ALI). To improve understanding of the relationship between serum ferritin alterations and the development of ALI, we investigated the effect of iron deficiency on the serum ferritin response of rats subjected to hemorrhage. We found that rats fed an iron-deficient diet for 6 weeks had decreased hemoglobin, hematocrit, liver total iron, liver total iron-binding capacity, and liver ferritin concentrations but the same serum ferritin concentrations as rats fed a control diet. Following hemorrhage, serum ferritin concentrations increased rapidly and progressively in rats fed a control diet. Along with increases in serum ferritin concentrations, control diet rats subjected to hemorrhage also had increased lung lavage leukocyte numbers, lung myeloperoxidase activities (lung inflammation), and lung lavage protein concentrations (lung leak) compared to control diet fed rats subjected to sham treatment. By comparison, the serum ferritin concentrations, lung inflammation, and lung leak of hemorrhaged rats fed an iron-deficient diet were decreased compared to hemorrhaged rats fed a control diet. These findings indicate that serum ferritin concentrations increase and acute lung injury develops following hemorrhage in rats fed a control, but not an iron-deficient, diet. A relatively brief exposure to an iron-deficient diet reduces hemorrhage-induced ALI.

Interleukin-1 receptor antagonist attenuates airway hyperresponsiveness following exposure to ozone

The role of an interleukin (IL)-1 receptor antagonist (IL-1Ra) on the development of airway hyperresponsiveness (AHR) and airway inflammation following acute O(3) exposure in mice was investigated. Exposure of C57/BL6 mice to O(3) at a concentration of 2.0 ppm or filtered air for 3 h resulted in increases in airway responsiveness to inhaled methacholine (MCh) 8 and 16 h after the exposure, and an increase in neutrophils in the bronchoalveolar lavage (BAL) fluid. IL-1beta expression, assessed by gene microarray, was increased 2-fold 4 h after O(3) exposure, and returned to baseline levels by 24 h. Levels of IL-1beta in lung homogenates were also increased 8 h after O(3) exposure. Administration of (human) IL-1Ra before and after O(3) exposure prevented development of AHR and decreased BAL fluid neutrophilia. Increases in chemokine levels in lung homogenates, tumor necrosis factor-alpha, MIP-2, and keratinocyte chemoattractant following O(3) exposure were prevented by IL-1Ra. Inhalation of dexamethasone, an inhibitor of IL-1 production, blocked the development of AHR, BAL fluid neutrophilia, and decreased levels of IL-1 following O(3) exposure. In summary, acute exposure to O(3) induces AHR, neutrophilic inflammation, epithelial damage, and IL-1. An IL-1Ra effectively prevents the development of altered airway function, inflammation, and structural damage.

Platelet-activating factor induces lung inflammation and leak in rats: hydrogen peroxide production along neutrophil-lung endothelial cell interfaces

Interleukin-1 (IL-1) levels and neutrophils are increased in the lung-lavage fluid of patients with acute lung injury (ALI), and instilling IL-1 intratracheally into rats causes rapid lung-neutrophil influx and neutrophil-dependent lung leakage. IL-1 insufflation also increases platelet-activating factor (PAF) activity in rat lung, and PAF is increased in the lung-lavage fluid of ALI patients. To assess the direct effects of PAF on the lung, we administered PAF intratracheally in rats. We found that rats given PAF (5 microg) intratracheally had increased lung nuclear factor-kappaB activation, myeloperoxidase activity, numbers of lavage neutrophils, lavage neutrophil nitroblue tetrazolium reduction, and leakage compared with sham-treated rats administered saline solution intratracheally. Electron microscopic examination also indicated that lungs from rats given PAF intratracheally had increased neutrophil infiltration, cell damage, and neutrophil-endothelial cell interface cerium chloride staining - a marker of hydrogen peroxide production - compared with sham-treated rats. Simultaneous treatment with a PAF receptor-antagonist, WEB 2086, decreased the aforementioned changes observed after intratracheal administration of PAF.

Transient expression of IL-1beta induces acute lung injury and chronic repair leading to pulmonary fibrosis

IL-1beta is one of a family of proinflammatory cytokines thought to be involved in many acute and chronic diseases. Although it is considered to participate in wound repair, no major role has been attributed to IL-1beta in tissue fibrosis. We used adenoviral gene transfer to transiently overexpress IL-1beta in rat lungs after intratracheal administration. The high expression of IL-1beta in the first week after injection was accompanied by local increase of the proinflammatory cytokines IL-6 and TNF-alpha and a vigorous acute inflammatory tissue response with evidence of tissue injury. The profibrotic cytokines PDGF and TGF-beta1 were increased in lung fluid samples 1 week after peak expression of IL-1beta. Although PDGF returned to baseline in the third week, TGF-beta1 showed increased concentrations in bronchoalveolar lavage fluid for up to 60 days. This was associated with severe progressive tissue fibrosis in the lung, as shown by the presence of myofibroblasts, fibroblast foci, and significant extracellular accumulations of collagen and fibronectin. These data directly demonstrate how acute tissue injury in the lung, initiated by a highly proinflammatory cytokine, IL-1beta, converts to progressive fibrotic changes. IL-1beta should be considered a valid target for therapeutic intervention in diseases associated with fibrosis and tissue remodeling.

Acute lung injury: cellular mechanisms and derangements

The clinical course of acute lung injury (ALI) is a complex and variable process accompanied by severe lung dysfunction, which persists for a long period of time with variable recovery of pulmonary function. The extent and severity of the lung disease associated with ALI varies with those patients having the most severe manifestations of lung disease being grouped as acute respiratory distress syndrome (ARDS). The pathological injury associated with this disease process, termed diffuse alveolar damage (DAD), has three overlapping phases (exudative, proliferative and fibrotic) which are the consequences of severe injury to the alveolar-capillary unit. There is no uniformity to the progression and length of each stage. This review explores those cellular mechanisms and derangements involved in the progression of ARDS. Those areas that demonstrate the major advances within the field are highlighted because of the diverse and vast nature of the cellular components involved in the process of ALI. We are beginning to identify those processes that contribute to the cellular derangements which are the hallmark of ALI. By expanding our understanding of those factors, we should in the future be able to construct therapeutic interventions that address the aetiology of ALI.