Alveolar macrophages contribute to alveolar barrier dysfunction in ventilator-induced lung injury

Harnessing pyroptosis for lung cancer therapy: The impact of NLRP3 inflammasome activation

Lung cancer is still a global health challenge in terms of high incidence, morbidity, and mortality. Recent scientific studies have determined that pyroptosis, a highly inflammatory form of programmed cell death, can be identified as a potential lung cancer therapeutic target. The NLRP3 inflammasome acts as a critical mediator in this process and, upon activation, activates multiprotein complex formation as well as caspase-1 activation. This process, triggered by a release of pro-inflammatory cytokines, results in pyroptotic cell death. Also, the relationship between the NLRP3 inflammasome and lung cancer was justified by its influence on tumour growth or metastasis. The molecular pathways produce progenitive mediators and remake the tissue. Finally, targeting NLRP3 inflammasome for pyroptosis induction and inhibition of its activation appears to be a promising lung cancer treatment approach. This technique makes cancer treatment more promising and personalized. This review explores the role of NLRP3 inflammasome activation and its possibilities in lung cancer treatment.

Epithelial CEBPD activates fibronectin and enhances macrophage adhesion in renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a cause of acute kidney injury in patients after renal transplantation and leads to high morbidity and mortality. Damaged kidney resident cells release cytokines and chemokines, which rapidly recruit leukocytes. Fibronectin (FN-1) contributes to immune cell migration, adhesion and growth in inflamed tissues. CCAAT/enhancer-binding protein delta is responsive to inflammatory cytokines and stresses and plays functional roles in cell motility, extracellular matrix production and immune responses. We found that the expression of CCAAT/enhancer-binding protein delta was increased in renal epithelial cells in IRI mice compared with sham mice. Following IRI, the colocalization of FN-1 with the macrophage marker F4/80 was increased in renal injury model wild-type mice but was significantly attenuated in Cebpd-deficient mice. Inactivation of CEBPD can repress hypoxia-induced FN-1 expression in HK-2 cells. Moreover, the inactivation of CEBPD and FN-1 also reduces macrophage accumulation in HK-2 cells. These findings suggest that the involvement of CEBPD in macrophage accumulation through the activation of FN-1 expression and the inhibition of CEBPD can protect against renal IRI.

Effect of antibody-mediated connective tissue growth factor neutralization on lung edema in ventilator-induced lung injury in rats

BACKGROUND

Acute respiratory distress syndrome (ARDS) is characterized by alveolar edema that can progress to septal fibrosis. Mechanical ventilation can augment lung injury, termed ventilator-induced lung injury (VILI). Connective tissue growth factor (CTGF), a mediator of fibrosis, is increased in ARDS patients. Blocking CTGF inhibits fibrosis and possibly vascular leakage. This study investigated whether neutralizing CTGF reduces pulmonary edema in VILI.

METHODS

Following LPS administration, rats were mechanically ventilated for 6 h with low (6 mL/kg; low VT) or moderate (10 mL/kg; mod VT) tidal volume and treated with a neutralizing CTGF antibody (FG-3154) or placebo lgG (vehicle). Control rats without LPS were ventilated for 6 h with low VT. Lung wet-to-dry weight ratio, FITC-labeled dextran permeability, histopathology, and soluble RAGE were determined.

RESULTS

VILI was characterized by reduced PaO2/FiO2 ratio (low VT: 540 [381-661] vs. control: 693 [620-754], p < 0.05), increased wet-to-dry weight ratio (low VT: 4.8 [4.6-4.9] vs. control: 4.5 [4.4-4.6], p < 0.05), pneumonia (low VT: 30 [0-58] vs. control: 0 [0-0]%, p < 0.05) and interstitial inflammation (low VT: 2 [1-3] vs. control: 1 [0-1], p < 0.05). FG-3154 did not affect wet-to-dry weight ratio (mod VT + FG-3154: 4.8 [4.7-5.0] vs. mod VT + vehicle: 4.8 [4.8-5.0], p > 0.99), extravasated dextrans (mod VT + FG-3154: 0.06 [0.04-0.09] vs. mod VT + vehicle: 0.04 [0.03-0.09] µg/mg tissue, p > 0.99), sRAGE (mod VT + FG-3154: 1865 [1628-2252] vs. mod VT + vehicle: 1885 [1695-2159] pg/mL, p > 0.99) or histopathology.

CONCLUSIONS

'Double hit' VILI was characterized by inflammation, impaired oxygenation, pulmonary edema and histopathological lung injury. Blocking CTGF does not improve oxygenation nor reduce pulmonary edema in rats with VILI.

Pulmonary inflammation decreases with ultra-protective ventilation in experimental ARDS under VV-ECMO: a positron emission tomography study

Background

Experimentally, ultra-protective ventilation (UPV, tidal volumes [VT] < 4 mL.kg-1) strategies in conjunction with veno-venous extracorporeal membrane oxygenation (VV-ECMO) are associated with lesser ventilator-induced lung injuries (VILI) during acute respiratory distress syndrome (ARDS). However, whether these strategies reduce lung inflammation more effectively than protective ventilation (PV) remains unclear. We aimed to demonstrate that a UPV strategy decreases acute lung inflammation in comparison with PV in an experimental swine model of ARDS.

Methods

ARDS was induced by tracheal instillation of chlorhydric acid in sedated and paralyzed animals under mechanical ventilation. Animals were randomized to receive either UPV (VT 1 mL.kg-1, positive end-expiration pressure [PEEP] set to obtain plateau pressure between 20 and 25 cmH2O and respiratory rate [RR] at 5 min-1 under VV-ECMO) or PV (VT 6 mL.kg-1, PEEP set to obtain plateau pressure between 28 and 30 cmH2O and RR at 25 min-1) during 4 h. After 4 h, a positron emission tomography with [11C](R)-PK11195 (ligand to TSPO-bearing macrophages) injection was realized, coupled with quantitative computerized tomography (CT). Pharmacokinetic multicompartment models were used to quantify regional [11C](R)-PK11195 lung uptake. [11C](R)-PK11195 lung uptake and CT-derived respiratory variables were studied regionally across eight lung regions distributed along the antero-posterior axis.

Results

Five pigs were randomized to each study group. Arterial O2 partial pressure to inspired O2 fraction were not significantly different between study groups after experimental ARDS induction (75 [68-80] mmHg in a PV group vs. 87 [69-133] mmHg in a UPV group, p = 0.20). Compared to PV animals, UPV animals exhibited a significant decrease in the regional non-aerated compartment in the posterior lung levels, in mechanical power, and in regional dynamic strain and no statistical difference in tidal hyperinflation after 4 h. UPV animals had a significantly lower [11C](R)-PK11195 uptake, compared to PV animals (non-displaceable binding potential 0.35 [IQR, 0.20-0.59] in UPV animals and 1.01 [IQR, 0.75-1.59] in PV animals, p = 0.01). Regional [11C](R)-PK11195 uptake was independently associated with the interaction of regional tidal hyperinflation and regional lung compliance.

Conclusion

In an experimental model of ARDS, 4 h of UPV strategy significantly decreased lung inflammation, in relation to the control of VT-derived determinants of VILI.

Circ-phkb promotes cell apoptosis and inflammation in LPS-induced alveolar macrophages via the TLR4/MyD88/NF-kB/CCL2 axis

BACKGROUND

Circular RNAs (CircRNAs) have been associated with acute lung injury (ALI), but their molecular mechanisms remain unclear.

METHODS

This study developed a rat model of lipopolysaccharide (LPS)-induced ALI and evaluated the modeling effect by hematoxylin and eosin staining, Masson's trichrome staining, lung wet-to-dry weight ratio, terminal deoxynucleotidyl transferase UTP nick end labeling (TUNEL), and enzyme-linked immunosorbent assay (ELISA) detection of inflammatory factors (interleukin-1β, tumor necrosis factor alpha, and interleukin-6). Using lung tissues from a rat model of LPS-induced ALI, we then conducted circRNA sequencing, mRNA sequencing, and bioinformatics analysis to obtain differential circRNA and mRNA expression profiles as well as potential ceRNA networks. Furthermore, we performed quantitative real-time polymerase chain reaction (qRT-PCR) assays to screen for circ-Phkb in ALI rat lung tissues, alveolar macrophages, and LPS-induced NR8383 cells. We conducted induction with or without LPS with circ-Phkb siRNA and overexpression lentivirus in NR8383. Cell Counting Kit-8, C5-Ethynyl-2'-deoxyuridine (Edu), TUNEL, and cytometry were used to identify proliferation and apoptosis, respectively. We detected inflammatory factors using ELISA. Finally, we used Western blot to detect the apoptosis-related proteins and TLR4/MyD88/NF-kB/CCL2 pathway activation.

RESULTS

Our results revealed that both circRNA and mRNA profiles are different from those of the Sham group. We observed a significant circ-Phkb upregulation in NR8383 cells and LPS-exposed rats. Apoptosis and inflammation were greatly reduced when circ-Phkb expression was reduced in NR8383 cells, cell proliferation was increased, and circ-Phkb overexpression was decreased.

CONCLUSIONS

In terms of mechanism, circ-Phkb suppression inhibits CCL2 expression via the TLR4/MyD88/NF-kB pathway in LPS-induced alveolar macrophages.

Acacetin protects against sepsis-induced acute lung injury by facilitating M2 macrophage polarization via TRAF6/NF-κB/COX2 axis

Acute lung injury (ALI) is the leading cause of death in patients with sepsis syndrome and without effective protective or therapeutic treatments. Acacetin, a natural dietary flavonoid, reportedly exerts several biological effects, such as anti-tumor, anti-inflammatory, and anti-oxidative effects. However, acacetin's effect and underlying mechanism on sepsis-induced ALI remain unclear. Here, the mouse model was established to explore the impact of acacetin on sepsis-induced ALI. Acacetin significantly increased ALI murine survival and attenuated lung injury in histological examinations. Additionally, acacetin down-regulated myeloperoxidase activity, protein concentration, and number of neutrophils and macrophages in bronchoalveolar lavage fluid. Subsequently, inflammatory cytokines, including TNF-α, IL-1β, and IL-6, were examined. Results showed that acacetin dramatically suppressed the production of TNF-α, IL-1β, and IL-6. These above results indicated that acacetin attenuated sepsis-induced ALI by inhibiting the inflammatory response. Moreover, acacetin inhibited the expression of markers for M1-type (iNOS, CD86) macrophages and promoted the expression of markers for M2-type (CD206, Arg1) macrophages by western blot. In addition, acacetin down-regulated the expression TRAF6, NF-κB, and Cyclooxygenase-2 (COX2) by western blot. The high concentration of acacetin had a better effect than the low concentration. Besides, over-expression of TRAF6 up-regulated the expression of COX2, CD86, and iNOS, and the ratio of p-NF-κB to NF-κB increased the mRNA levels of TNF-α, IL-1β, and IL-6, down-regulated the expression of CD206 and Arg1. The effects of TRAF6 were the opposite of acacetin. And TRAF6 could offset the impact of acacetin. This study demonstrated that acacetin could prevent sepsis-induced ALI by facilitating M2 macrophage polarization via TRAF6/NF-κB/COX2 axis.

Reactive Oxygen Species and Strategies for Antioxidant Intervention in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.

Multicompartmental analysis of the murine pulmonary immune response by spectral flow cytometry

Studies of pulmonary inflammation require unique considerations due to the complex structure and composition of the lungs. The lungs have multiple compartments and diverse immune cell populations, with inherently high autofluorescence, and are involved in the host response to pulmonary pathogens. We describe a protocol that accounts for these factors through a novel combination of methodologies-in vivo compartmental analysis and spectral flow cytometry with a broad panel of antibodies. In vivo compartmental analysis enables the precise localization of immune cells within the marginated vasculature, lung interstitium, nonlavageable airways, and lavageable airways of the lungs, as well as the pulmonary lymph nodes. Spectral flow cytometry with a broad panel of antibodies supports an unbiased exploratory approach to investigating diverse immune cell populations during pulmonary inflammation. Most importantly, spectral flow uses cellular autofluorescence to aid in the resolution and identification of immune cell populations. This methodology enables the acquisition of high-quality data compatible with informed gating and dimensionality reduction algorithms. In addition, our protocol emphasizes considerations for compartmentalization of the inflammatory response, spectral flow panel design, and autofluorescence spectra analysis. These methodologies are critical for increasing the rigor of pulmonary research. We apply this protocol for the precise characterization and localization of leukocytes in the pulmonary host response to influenza A virus in C57BL/6J mice. In particular, we demonstrate that this protocol improves the quantification and localization of alveolar macrophages within the airways. The methodology is modifiable and expandable to allow for further characterization of leukocyte populations of special interest.NEW & NOTEWORTHY We describe a novel combination of methodologies that incorporates dual in vivo compartmental analysis using intravascular and intratracheal CD45 labeling, a broad panel of antibodies for identifying lymphoid and nonlymphoid cells, and spectral flow cytometry that uses cellular autofluorescence to aid in resolving and identifying immune cell populations. This methodology allows precise localization of immune cells in the lavageable airways, nonlavageable airways, interstitial lung tissue, and marginated in the lung vasculature.

Pathogenetic role of alveolar surfactant depleted by phosgene: Biophysical mechanisms and peak inhalation exposure metrics

In contrast to water-soluble respiratory tract irritants in their gas phase, the physicochemical properties of 'hydrophilicity' vs. 'lipophilicity' are the preponderant factors that dictate the site of major retention of the gas at the portal of entry. The lipophilic physical properties of phosgene gas facilitate retention in the alveolar region lined with amphipathic pulmonary surfactant (PS). The relationship between exposure and adverse health outcomes is complex, may vary over time, and is dependent on the biokinetics, biophysics, and pool size of PS relative to the inhaled dose of phosgene. Kinetic PS depletion is hypothesized to occur as inhalation followed by inhaled dose-dependent PS depletion. A kinetic model was developed to better understand the variables characterizing the inhaled dose rates of phosgene vs. PS pool size reconstitution. Modeling and empirical data from published evidence revealed that phosgene gas unequivocally follows a concentration x exposure (C × t) metric, independent of the frequency of exposure. The modeled and empirical data support the hypothesis that the exposure standards of phosgene are described best by a C × t time-averaged metric. Modeled data favorably duplicate expert panel-derived standards. Peak exposures within a reasonable range are of no concern.

Sessile alveolar macrophage connexin-43 determines mechano-immunity in the lung

Although lung immunity is pathogen induced, the immunity can also be induced by mechanical distortion of the lung. The causal basis of the lung's mechanosensitive immunity remains unclear. Here, through live optical imaging of mouse lungs, we show that alveolar stretch due to hyperinflation induced prolonged cytosolic Ca2+ increases in sessile alveolar macrophages (AMs). Knockout studies revealed that the Ca2+ increases resulted from Ca2+ diffusion from the alveolar epithelium to sessile AMs through connexin 43 (Cx43)-containing gap junctions. Lung inflammation and injury in mice exposed to injurious mechanical ventilation were inhibited by AM-specific Cx43 knockout, or AM-specific delivery of a calcium inhibitor. We conclude, Cx43 gap junctions and calcium mobilization in sessile AMs determine the lung's mechanosensitive immunity, providing a therapeutic strategy against hyperinflation-induced lung injury.

Melatonin attenuates lipopolysaccharide-induced immune dysfunction in dendritic cells

Melatonin, a ubiquitous hormone, is principally secreted from pineal gland in mammals and possesses strong antioxidant and anti-inflammatory properties. However, its specific roles in the immune functions of dendritic cells (DCs) during acute lung injury (ALI) remain unknown. In this study, we found that melatonin restored the body weight, decreased the lung weight/body weight ratio, alleviated the histopathological lung injury, and decreased the levels of cytokines (tumor necrosis factor-α (TNF-α), interleukin (IL)-12p70, IL-17, and IL-10) in bronchoalveolar lavage fluid of the lipopolysaccharide (LPS)-induced ALI murine model. Moreover, melatonin inhibited the major histocompatibility complex II (MHCII) expression of lung CD11b⁺ DCs after LPS challenge in vivo. In vitro, melatonin reversed the shape index, promoted the endocytosis, and inhibited phenotypic expression of MHCII, CD40, CD80, and CD86 in LPS-activated DCs. Furthermore, melatonin decreased the expression of an activated marker, CD69, and the secretion of pro-inflammatory cytokines (TNF-α, IL-12p70, and IL-17) after LPS challenge. It hampered the LPS-activated DCs migration by downregulating the C-C chemokine receptor 7 (CCR7) expression, and then weakened the ability of LPS-induced DCs to stimulate allogeneic CD4⁺ T cell proliferation. Melatonin shaped the immune function of DCs in a nuclear factor erythroid-2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1) axis-dependent manner. These findings indicate that melatonin protects DCs from ALI-induced immunological stress and may be used to develop novel DC-targeting strategies for ALI therapy.

Peptide-guided delivery improves the therapeutic efficacy and safety of glucocorticoid drugs for treating acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening conditions with excessive inflammation in the lung. Glucocorticoids had been widely used for ALI/ARDS, but their clinical benefit remains unclear. Here, we tackled the problem by conjugating prednisolone (PSL) with a targeting peptide termed CRV. Systemically administered CRV selectively homes to the inflamed lung of a murine ALI model, but not healthy organs or the lung of healthy mice. The expression of the CRV receptor, retinoid X receptor β, was elevated in the lung of ALI mice and patients with interstitial lung diseases, which may be the basis of CRV targeting. We then covalently conjugated PSL and CRV with a reactive oxygen species (ROS)-responsive linker in the middle. While being intact in blood, the ROS linker was cleaved intracellularly to release PSL for action. In vitro, CRV-PSL showed an anti-inflammatory effect similar to that of PSL. In vivo, CRV conjugation increased the amount of PSL in the inflamed lung but reduced its accumulation in healthy organs. Accordingly, CRV-PSL significantly reduced lung injury and immune-related side effects elsewhere. Taken together, our peptide-based strategy for targeted delivery of glucocorticoids for ALI may have great potential for clinical translation.

Prone position decreases acute lung inflammation measured by [11C](R)-PK11195 positron emission tomography in experimental acute respiratory distress syndrome

Whether prone positioning (PP) modulates acute lung inflammation by the modulation of biomechanical forces of ventilator-induced lung injuries (VILIs) remains unclear. We aimed to demonstrate that PP decreases acute lung inflammation in animals with experimental acute respiratory distress syndrome (ARDS). Animals were under general anesthesia and protective ventilation (tidal volume 6 mL·kg^-1, PEEP 5 cmH₂O). ARDS was induced by intratracheal instillation of chlorohydric acid. Animals were then randomized to PP, or to supine position (SP). After 4 h, a positron emission tomography (PET) acquisition with [¹¹C](R)-PK11195 was performed coupled with computerized tomography (CT) acquisitions, allowing the CT quantification of VILI-associated parameters. [¹¹C](R)-PK11195 lung uptake was quantified using pharmacokinetic multicompartment models. Analyses were performed on eight lung sections distributed along the antero-posterior dimension. Six animals were randomized to PP, five to SP (median [Formula: see text]/[Formula: see text] [interquartile range]: 164 [102-269] mmHg). The normally aerated compartment was significantly redistributed to the posterior lung regions of animals in PP, compared with SP. Dynamic strain was significantly increased in posterior regions of SP animals, compared with PP. After 4 h, animals in PP had a significantly lower uptake of [¹¹C](R)-PK11195, compared with SP. [¹¹C](R)-PK11195 regional uptake was independently associated with the study group, dynamic strain, tidal hyperinflation, and regional respiratory system compliance in multivariate analysis. In an experimental model of ARDS, 4 h of PP significantly decreased acute lung inflammation assessed with PET. The beneficial impact of PP on acute lung inflammation was consecutive to the combination of decreased biomechanical forces and changes in the respiratory system mechanics.NEW & NOTEWORTHY Prone position decreases acute lung macrophage inflammation quantified in vivo with [¹¹C](R)-PK11195 positron emission tomography in an experimental acute respiratory distress syndrome. Regional macrophage inflammation is maximal in the most anterior and posterior lung section of supine animals, in relation with increased regional tidal strain and hyperinflation, and reduced regional lung compliance.

The roles of long noncoding RNA-mediated macrophage polarization in respiratory diseases

Macrophages play an essential role in maintaining the normal function of the innate and adaptive immune responses during host defence. Macrophages acquire diverse functional phenotypes in response to various microenvironmental stimuli, and are mainly classified into classically activated macrophages (M1) and alternatively activated macrophages (M2). Macrophage polarization participates in the inflammatory, fibrotic, and oncogenic processes of diverse respiratory diseases by changing phenotype and function. In recent decades, with the advent of broad-range profiling methods such as microarrays and next-generation sequencing, the discovery of RNA transcripts that do not encode proteins termed "noncoding RNAs (ncRNAs)" has become more easily accessible. As one major member of the regulatory ncRNA family, long noncoding RNAs (lncRNAs, transcripts >200 nucleotides) participate in multiple pathophysiological processes, including cell proliferation, differentiation, and apoptosis, and vary with different stimulants and cell types. Emerging evidence suggests that lncRNAs account for the regulation of macrophage polarization and subsequent effects on respiratory diseases. In this review, we summarize the current published literature from the PubMed database concerning lncRNAs relevant to macrophage polarization and the underlying molecular mechanisms during the occurrence and development of respiratory diseases. These differentially expressed lncRNAs are expected to be biomarkers and targets for the therapeutic regulation of macrophage polarization during disease development.

Regulation of CD18 stability by SIGIRR-modulated ubiquitination: new insights into the relationship between innate immune response and acute lung injury

Inappropriate accumulation of alveolar macrophages (AMs) and subsequent excessive production of immune responses play critical roles in the pathogenesis of acute lung injury (ALI), but the core negative regulators governing innate signalling in AMs are ill defined. We have previously shown that single immunoglobin IL-1 receptor-related protein (SIGIRR), a negative regulator of IL-1 receptor and Toll-like receptor signalling, inhibits lipopolysaccharide (LPS)-induced inflammatory responses in AMs. To address the biological relevance of SIGIRR in vivo, we generated a murine ALI model via intratracheal instillation of LPS. Intriguingly, SIGIRR expression was observed to be decreased in resident and recruited macrophages during ALI. This decrease was associated with parallel induction in CD18 protein levels in LPS-challenged lung tissues. Through intranasal injection of SIGIRR lentiviral particles studies, we showed that the overexpression of SIGIRR attenuated recruitment of macrophages and neutrophils, decreased production of inflammatory cytokines and ameliorated pathological changes in lungs. Whilst exploring the basis for this phenotype, SIGIRR was found to be coexpressed with CD18 in AMs, and SIGIRR potentiated the instability of CD18 protein via enhancement of its ubiquitination and proteasome degradation. Conversely, by using CD18^-/- mice, we further observed that CD18 deletion completely abolished the therapeutic effects of overexpression of SIGIRR on LPS-induced ALI. Mover, overexpression of CD18 in AMs promoted adhesion to ECM components, enhanced TLR4-mediated inflammasome activation and thereby potentiated IL-1β production. These data collectively identify SIGIRR/CD18 as a key negative regulatory circuit maintaining innate immune homeostasis in AMs along the pathogenesis of ALI.

Baseline plasma IL-18 may predict simvastatin treatment response in patients with ARDS: a secondary analysis of the HARP-2 randomised clinical trial

BACKGROUND

Interleukin (IL)-18 is a marker of inflammasome activation, and high baseline plasma IL-18 is associated with increased mortality in patients with sepsis-induced ARDS. The aim of this analysis was to determine if simvastatin was associated with benefit in patients with ARDS and high plasma IL-18.

METHODS

In this secondary analysis of the HARP-2 study, we compared 28-day mortality and response to simvastatin according to baseline plasma IL-18 using cox proportional hazards analysis. Separately, monocyte-derived macrophages from healthy volunteers were pre-incubated with simvastatin or rosuvastatin before stimulation with ATP and LPS, and the effect on secreted IL-18 and IL-1β compared.

RESULTS

511 patients from HARP-2 had available data. High baseline plasma IL-18 (≥ 800 pg/ml) was associated with increased 28-day mortality (high IL-18 30.6% vs. low IL-18 17.5%; HR 1.89 [95% CI 1.30-2.73]; p = 0.001). Allocation to simvastatin in patients with high baseline plasma IL-18 was associated with a lower probability of 28-day mortality compared with placebo (24.0% vs 36.8%; p = 0.01). Finally, simvastatin, but not rosuvastatin, reduced stimulated macrophage secretion of IL-18 and IL-1β.

CONCLUSION

In patients with high baseline plasma IL-18, simvastatin is associated with a higher probability of survival, and this effect may be due to reduced inflammasome activation. These data suggest that baseline plasma IL-18 may allow a personalised treatment approach by identifying patients with ARDS who could benefit from simvastatin therapy.

Protective effect and mechanism of loganin and morroniside on acute lung injury and pulmonary fibrosis

BACKGROUND

Loganin and morroniside are two iridoid glycosides with anti-inflammatory, antioxidant and anti-tumor effects. Whether they have effect on acute lung injury and pulmonary fibrosis are still unknown.

PURPOSE

To explore the potential effects of loganin and morroniside against acute lung cancer and pulmonary fibrosis, and the underlying molecular mechanism.

STUDY DESIGN AND METHODS

Cell and animal models of acute lung injury were established by the induction of LPS. After intervention with loganin and morroniside, the pathological symptom of lung tissue was assessed, pro-inflammatory factors in cells and lung tissues were detected, NF- κB/STAT3 signaling pathway related proteins were detected by western blotting. Mice pulmonary fibrosis model was induced by bleomycin, pathological symptom was assessed by HE and Masson staining. Fibrosis related indicators were detected by qPCR or western blot. CD4+/CD8+ was detected by flow cytometry.

RESULTS

Loganin and morroniside relieved the pathological symptom of lung tissue in acute lung injury, pro-inflammatory factors such as IL-6, IL-1β, TNF-α mRNA were inhibited. Expression of p-p65 and STAT3 in lung tissues were also downregulated. In addition, loganin and morroniside downregulated the expression of collagen fiber, hydroxyproline and TGF-β1, collagen I and α-SMA mRNA in lung tissues of pulmonary fibrosis model. This study proved that loganin and morroniside have protective effect on acute lung injury and pulmonary fibrosis, and may provide theoretical basis for the development of new clinical drugs.

Nicotinic acetylcholine receptor agonist reduces acute lung injury after renal ischemia-reperfusion injury by acting on splenic macrophages in mice

Acute kidney injury (AKI) contributes to development of acute lung injury (ALI) via proinflammatory responses. We hypothesized that activation of a nicotinic acetylcholine receptor (nAChR), which exerts cholinergic anti-inflammatory effects on macrophages, could reduce ALI after AKI. We aimed to determine: 1) whether nAChR agonists could reduce ALI after AKI and 2) which macrophages in the lung or spleen contribute to the improvement of ALI by nAChR agonists. We induced AKI in C57BL/6 male mice by unilateral ischemia-reperfusion injury (IRI) with contralateral nephrectomy and administered nAChR agonists in three experimental settings: 1) splenectomy, 2) splenic macrophage deletion via intravenous administration of clodronate liposomes, and 3) alveolar macrophage deletion via intratracheal administration of clodronate liposomes. Treatment with GTS-21, anα7nAChR selective agonist, significantly reduced the levels of circulating IL-6, a key proinflammatory cytokine and lung CXCL1 and CXCL2 and neutrophil infiltration and Evans blue dye vascular leakage increased after renal IRI. In splenectomized mice, GTS-21 did not reduce circulating IL-6 and lung CXCL1 and CXCL2levels and neutrophil infiltration, and Evans blue dye vascular leakage increased after renal IRI. In mice depleted of splenic macrophages, GTS-21 treatment did not reduce lung neutrophil infiltration, and Evans blue dye vascular leakage increased after renal IRI. In mice depleted of alveolar macrophages, GTS-21 treatment significantly reduced lung neutrophil infiltration, and Evans blue dye vascular leakage increased after renal IRI. Our findings show that nAChR agonist reduces circulating IL-6 levels and acute lung injury after renal IRI by acting on splenic macrophages.

c-Fos is a mechanosensor that regulates inflammatory responses and lung barrier dysfunction during ventilator-induced acute lung injury

Background

As one of the basic treatments performed in the intensive care unit, mechanical ventilation can cause ventilator-induced acute lung injury (VILI). The typical features of VILI are an uncontrolled inflammatory response and impaired lung barrier function; however, its pathogenesis is not fully understood, and c-Fos protein is activated under mechanical stress. c-Fos/activating protein-1 (AP-1) plays a role by binding to AP-1 within the promoter region, which promotes inflammation and apoptosis. T-5224 is a specific inhibitor of c-Fos/AP-1, that controls the gene expression of many proinflammatory cytokines. This study investigated whether T-5224 attenuates VILI in rats by inhibiting inflammation and apoptosis.

Methods

The SD rats were divided into six groups: a control group, low tidal volume group, high tidal volume group, DMSO group, T-5224 group (low concentration), and T-5224 group (high concentration). After 3 h, the pathological damage, c-Fos protein expression, inflammatory reaction and apoptosis degree of lung tissue in each group were detected.

Results

c-Fos protein expression was increased within the lung tissue of VILI rats, and the pathological damage degree, inflammatory reaction and apoptosis in the lung tissue of VILI rats were significantly increased; T-5224 inhibited c-Fos protein expression in lung tissues, and T-5224 inhibit the inflammatory reaction and apoptosis of lung tissue by regulating the Fas/Fasl pathway.

Conclusions

c-Fos is a regulatory factor during ventilator-induced acute lung injury, and the inhibition of its expression has a protective effect. Which is associated with the antiinflammatory and antiapoptotic effects of T-5224.

Norisoboldine Attenuates Sepsis-Induced Acute Lung Injury by Modulating Macrophage Polarization via PKM2/HIF-1α/PGC-1α Pathway

This study aimed to investigate the effect of norisopoldine (NOR) on acute lung injury in septic mice. Lipopolysaccharide (LPS) was used to establish sepsis induced acute lung injury (ALI) in mice. The dry and wet weight of mice lung was detected, and the pathological changes of lung were observed by hematoxylin and eosin (H&E) staining. Bronchoalveolar lavage fluid (BALF) was detected. Inflammatory factors in BALF were detected by enzyme-linked immunosorbent assay (ELISA). The polarization of macrophages in lung tissue was detected by flow cytometry. The markers of M1 and M2 macrophages were detected by RT-PCR. LPS induced RAW264.7 cells were treated with NOR. Inflammatory response, macrophage polarization, glycolysis, and M2 pyruvate kinase (PKM2)/hypoxia inducible factor-1α (HIF-1α)/peroxisome proliferator activated receptor-γ co-activator 1-α (PGC-1α) signaling pathway were detected. NOR could effectively alleviate sepsis induced ALI, and reduce the number of total cells, total protein concentration, neutrophils, macrophages in BALF. NOR decreased the level of inflammatory factors and promoted macrophages from M1 to M2 type in vivo and vitro. Moreover, NOR could activated PKM2, and inhibited PKM2 from cytoplasm to nuclear, attenuated HIF-1α expression, and increased PGC-1α and peroxisome proliferator-activated receptor (PPAR)-γ expression. In addition, NOR inhibited glycolysis and promoted oxidative phosphorylation in RAW264.7 cells. Furthermore, PKM2 inhibitors could reverse the effect of NOR on PKM2/HIF-1α/PGC-1α signaling pathway in RAW264.7 cells. NOR alleviated sepsis induced AIL in mice, inhibited the inflammatory response, promote M2 polarization of macrophages through regulating PKM2/HIF-1α/PGC-1α signaling pathway.

TLR4 is required for macrophage efferocytosis during resolution of ventilator-induced lung injury

Mechanical ventilation is a life-sustaining therapy for patients with respiratory failure but can cause further lung damage known as ventilator-induced lung injury (VILI). However, the intrinsic molecular mechanisms underlying recovery of VILI remain unknown. Phagocytosis of apoptotic cells (also known as efferocytosis) is a key mechanism orchestrating successful resolution of inflammation. Here we show the positive regulation of macrophage Toll-like receptor (TLR) 4 in efferocytosis and resolution of VILI. Mice were depleted of alveolar macrophages and then subjected to injurious ventilation (tidal volume, 20 mL/kg) for 4 h. On day 1 after mechanical ventilation, Tlr4^+/+ or Tlr4^-/- bone marrow-derived macrophages (BMDMs) were intratracheally administered to alveolar macrophage-depleted mice. We observed that mice depleted of alveolar macrophages exhibited defective resolution of neutrophilic inflammation, exuded protein, lung edema, and lung tissue injury after ventilation, whereas these delayed responses were reversed by administration of Tlr4^+/+ BMDMs. Importantly, these proresolving effects by Tlr4^+/+ BMDMs were abolished in mice receiving Tlr4^-/- BMDMs. The number of macrophages containing apoptotic cells or bodies in bronchoalveolar lavage fluid was much less in mice receiving Tlr4^-/- BMDMs than that in those receiving Tlr4^+/+ BMDMs. Macrophage TLR4 deletion facilitated a disintegrin and metalloprotease 17 maturation and enhanced Mer cleavage in response to mechanical ventilation. Heat shock protein 70 dramatically increased Mer tyrosine kinase surface expression, phagocytosis of apoptotic neutrophils, and rescued the inflammatory phenotype in alveolar macrophage-depleted mice receiving Tlr4^+/+ BMDMs, but not Tlr4^-/- BMDMs. Our results suggest that macrophage TLR4 promotes resolution of VILI via modulation of Mer-mediated efferocytosis.

Genetics of Acute Respiratory Distress Syndrome: Pathways to Precision

Clinical risk factors alone fail to fully explain acute respiratory distress syndrome (ARDS) risk or ARDS death, suggesting that individual risk factors contribute. The goals of genomic ARDS studies include better mechanistic understanding, identifying dysregulated pathways that may be amenable to pharmacologic targeting, using genomic causal inference techniques to find measurable traits with meaning, and deconvoluting ARDS heterogeneity by proving reproducible subpopulations that may share a unique biology. This article discusses the latest advances in ARDS genomics, provides historical perspective, and highlights some of the ways that the coronavirus disease 2019 (COVID-19) pandemic is accelerating genomic ARDS research.

Acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is an acute respiratory illness characterised by bilateral chest radiographical opacities with severe hypoxaemia due to non-cardiogenic pulmonary oedema. The COVID-19 pandemic has caused an increase in ARDS and highlighted challenges associated with this syndrome, including its unacceptably high mortality and the lack of effective pharmacotherapy. In this Seminar, we summarise current knowledge regarding ARDS epidemiology and risk factors, differential diagnosis, and evidence-based clinical management of both mechanical ventilation and supportive care, and discuss areas of controversy and ongoing research. Although the Seminar focuses on ARDS due to any cause, we also consider commonalities and distinctions of COVID-19-associated ARDS compared with ARDS from other causes.

The Role of Macrophages During Mammalian Tissue Remodeling and Regeneration Under Infectious and Non-Infectious Conditions

Several infectious pathologies in humans, such as tuberculosis or SARS-CoV-2, are responsible for tissue or lung damage, requiring regeneration. The regenerative capacity of adult mammals is limited to few organs. Critical injuries of non-regenerative organs trigger a repair process that leads to a definitive architectural and functional disruption, while superficial wounds result in scar formation. Tissue lesions in mammals, commonly studied under non-infectious conditions, trigger cell death at the site of the injury, as well as the production of danger signals favouring the massive recruitment of immune cells, particularly macrophages. Macrophages are also of paramount importance in infected injuries, characterized by the presence of pathogenic microorganisms, where they must respond to both infection and tissue damage. In this review, we compare the processes implicated in the tissue repair of non-infected versus infected injuries of two organs, the skeletal muscles and the lungs, focusing on the primary role of macrophages. We discuss also the negative impact of infection on the macrophage responses and the possible routes of investigation for new regenerative therapies to improve the recovery state as seen with COVID-19 patients.

Nanotherapeutics in the treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a form of oxygenation failure primarily characterized by rapid inflammation resulting from a direct pulmonary or indirect systemic insult. ARDS has been a major cause of death in the recent COVID-19 outbreak wherein asymptomatic respiratory tract infection progresses to ARDS from pneumonia have emphasized the need for a reliable therapy for the disease. The disease has a high mortality rate of approximately 30-50%. Despite the high mortality rate, a dearth of effective pharmacotherapy exists that demands extensive research in this area. The complex ARDS pathophysiology which remains to be understood completely and the multifactorial etiology of the disease has led to the poor diagnosis, impeded drug-delivery to the deeper pulmonary tissues, and delayed treatment of the ARDS patients. Besides, critically ill patients are unable to tolerate the off-target side effects. The vast domain of nanobiotechnology presents several drug delivery systems offering numerous benefits such as targeted delivery, prolonged drug release, and uniform drug-distribution. The present review presents a brief insight into the ARDS pathophysiology and summarizes conventional pharmacotherapies available to date. Furthermore, the review provides an updated report of major developments in the nanomedicinal approaches for the treatment of ARDS. We also discuss different nano-formulations studied extensively in the ARDS preclinical models along with underlining the advantages as well as challenges that need to be addressed in the future.

Effects of Ultrashort Wave Therapy on Inflammation and Macrophage Polarization after Acute Lung Injury in Rats

Acute lung injury (ALI) features dysregulated pulmonary inflammation. Ultrashort waves (USWs) exert anti-inflammatory effects but no studies have evaluated their activity in ALI. Herein, we used an in vivo lipopolysaccharide (LPS)-induced ALI model to investigate whether the anti-inflammatory activity of USWs is mediated by altering the polarization of M1 to M2 macrophages. Twenty-four male Sprague-Dawley rats were randomly divided into control, untreated ALI, and ALI treated with USW groups (n = 8 in each group). ALI was induced by intratracheal LPS instillation. Rats in the USW group were treated for 15 min at 0, 4, and 8 h after a single LPS intratracheal instillation. Histopathologic examination, wet/dry lung weight ratio, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, and western blot analyses were performed to evaluate the degree of lung injury and to determine macrophage phenotypes. Histopathologic examination disclosed attenuation of ALI, with reduced alveolar hemorrhage and neutrophilic infiltration in the USW group. Serum levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were significantly decreased after USW therapy. Moreover, the messenger RNA (mRNA) expressions of TNF-α and IL-1β were significantly decreased in the USW group, whereas the mRNA expression of Arginase 1 (Arg1) and the protein expression of mannose receptor significantly increased in comparison with the untreated ALI group. We conclude that USW therapy may attenuate inflammation in LPS-induced ALI through the modulation of macrophage polarization. © 2021 Bioelectromagnetics Society.

Paracoxib Alleviates Ventilator-Induced Lung Injury Through Functional Modulation of Lung-Recruited CD11bloLy6Chi Monocytes

OBJECTIVE

Lung-recruited Ly6Chi monocytes had been shown to be involved in ventilator-induced lung injury (VILI). Our present study aimed to investigate whether the cyclooxygenase-2 (COX-2) inhibition modulates the function of lung-recruited Ly6Chi monocytes in a mouse model of VILI.

METHODS

Mice were exposed to lipopolysaccharide (LPS; 20 ng) intraperitoneally prior to injurious mechanical ventilation (Vt = 30 mL/kg, PEEP = 0 cmH2O). A subgroup of mice was treated with intravenous parecoxib (30 mg/kg), a COX-2 inhibitor, 1 h prior to ventilation. Control mice received saline and were not ventilated. At the end of the experiment, blood gas analysis was performed and lung tissue was collected for histological assessment. Flow cytometry was employed to quantify the different populations of lung monocytes/macrophages and their function. Isolated Ly6Chi cells were used to measure the intracellular concentrations of reactive oxygen species (ROS) and nitric oxide (NO) by fluorescent probes, and cytokine production by cytometric bead array.

RESULTS

Exposure to LPS and injurious ventilation was associated with severe lung histological damage, oxygenation impairment, and pulmonary edema; all of which were largely attenuated following the treatment of parecoxib. Furthermore, flow cytometry analysis revealed that parecoxib caused a reduction in the number of the lung-recruited CD11bloLy6Chi monocytes while there was no effect on tissue-resident CD64+ alveolar macrophages. In addition, the production of oxidative stress products (ROS, NO), MHC-II expression, and inflammatory cytokines in response to LPS and VILI in CD11bloLy6Chi monocytes was ameliorated by parecoxib.

CONCLUSION

Parecoxib-induced alleviation of oxidative stress and inflammation in lung-recruited Ly6Chi monocytes may partly explain the beneficial action of COX-2 inhibition in VILI.

Nanoparticle delivery of microRNA-146a regulates mechanotransduction in lung macrophages and mitigates injury during mechanical ventilation

Mechanical ventilation generates injurious forces that exacerbate lung injury. These forces disrupt lung barrier integrity, trigger proinflammatory mediator release, and differentially regulate genes and non-coding oligonucleotides including microRNAs. In this study, we identify miR-146a as a mechanosensitive microRNA in alveolar macrophages that has therapeutic potential to mitigate lung injury during mechanical ventilation. We use humanized in-vitro systems, mouse models, and biospecimens from patients to elucidate the expression dynamics of miR-146a needed to decrease lung injury during mechanical ventilation. We find that the endogenous increase in miR-146a following injurious ventilation is not sufficient to prevent lung injury. However, when miR-146a is highly overexpressed using a nanoparticle delivery platform it is sufficient to prevent injury. These data indicate that the endogenous increase in microRNA-146a during mechanical ventilation is a compensatory response that partially limits injury and that nanoparticle delivery of miR-146a is an effective strategy for mitigating lung injury during mechanical ventilation.

Liver-lung interactions in acute respiratory distress syndrome

Patients with liver diseases are at high risk for the development of acute respiratory distress syndrome (ARDS). The liver is an important organ that regulates a complex network of mediators and modulates organ interactions during inflammatory disorders. Liver function is increasingly recognized as a critical determinant of the pathogenesis and resolution of ARDS, significantly influencing the prognosis of these patients. The liver plays a central role in the synthesis of proteins, metabolism of toxins and drugs, and in the modulation of immunity and host defense. However, the tools for assessing liver function are limited in the clinical setting, and patients with liver diseases are frequently excluded from clinical studies of ARDS. Therefore, the mechanisms by which the liver participates in the pathogenesis of acute lung injury are not totally understood. Several functions of the liver, including endotoxin and bacterial clearance, release and clearance of pro-inflammatory cytokines and eicosanoids, and synthesis of acute-phase proteins can modulate lung injury in the setting of sepsis and other severe inflammatory diseases. In this review, we summarized clinical and experimental support for the notion that the liver critically regulates systemic and pulmonary responses following inflammatory insults. Although promoting inflammation can be detrimental in the context of acute lung injury, the liver response to an inflammatory insult is also pro-defense and pro-survival. A better understanding of the liver–lung axis will provide valuable insights into new diagnostic targets and therapeutic strategies for clinical intervention in patients with or at risk for ARDS.

Antiplatelet Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a common and devastating syndrome that contributes to serious morbidities and mortality in critically ill patients. No known pharmacologic therapy is beneficial in the treatment of ARDS, and the only effective management is through a protective lung strategy. Platelets play a crucial role in the pathogenesis of ARDS, and antiplatelet therapy may be a potential medication for ARDS. In this review, we introduce the overall pathogenesis of ARDS, and then focus on platelet-related mechanisms underlying the development of ARDS, including platelet adhesion to the injured vessel wall, platelet-leukocyte-endothelium interactions, platelet-related lipid mediators, and neutrophil extracellular traps. We further summarize antiplatelet therapy, including aspirin, glycoprotein IIb/IIIa receptor antagonists, and P2Y12 inhibitors for ARDS in experimental and clinical studies and a meta-analysis. Novel aspirin-derived agents, aspirin-triggered lipoxin, and aspirin-triggered resolvin D1 are also described here. In this narrative review, we summarize the current knowledge of the role of platelets in the pathogenesis of ARDS, and the potential benefits of antiplatelet therapy for the prevention and treatment of ARDS.

Acute Hyperglycemia Aggravates Lung Injury via Activation of the SGK1-NKCC1 Pathway

Acute lung injury (ALI) is characterized by severe hypoxemia and has significantly high mortality rates. Acute hyperglycemia occurs in patients with conditions such as sepsis or trauma, among others, and it results in aggravated inflammation and induces damage in patients with ALI. Regulation of alveolar fluid is essential for the development and resolution of pulmonary edema in lung injury. Pulmonary sodium-potassium-chloride co-transporter 1 (NKCC1) regulates the net influx of ions and water into alveolar cells. The activation of with-no-lysine kinase 4 (WNK4), STE20/SPS1-related proline/alanine rich kinase (SPAK) and the NKCC1 pathway lead to an increase in the expression of NKCC1 and aggravation of ALI. Moreover, hyperglycemia is known to induce NKCC1 expression via the activation of the serum-glucocorticoid kinase 1 (SGK1)-NKCC1 pathway. We aim to evaluate the influence of acute hyperglycemia on the SGK1-NKCC1 pathway in ALI. ALI was induced using a high tidal volume for four hours in a rat model. Acute hyperglycemia was induced by injection with 0.5 mL of 40% glucose solution followed by continuous infusion at 2 mL/h. The animals were divided into sham, sham+ hyperglycemia, ALI, ALI + hyperglycemia, ALI + inhaled bumetanide (NKCC1 inhibitor) pretreatment, ALI + hyperglycemia + inhalational bumetanide pretreatment, and ALI + hyperglycemia + post-ALI inhalational bumetanide groups. Severe lung injury along with pulmonary edema, alveolar protein leakage, and lung inflammation was observed in ALI with hyperglycemia than in ALI without hyperglycemia. This was concurrent with the higher expression of pro-inflammatory cytokines, infiltration of neutrophils and alveolar macrophages (AM) 1, and NKCC1 expression. Inhalational NKCC1 inhibitor significantly inhibited the SGK1-NKCC1, and WNK4-SPAK-NKCC1 pathways. Additionally, it reduced pulmonary edema, inflammation, levels of pro-inflammatory cytokines, neutrophils and AM1 and increased AM2. Therefore, acute hyperglycemia aggravates lung injury via the further activation of the SGK1-NKCC1 pathway. The NKCC1 inhibitor can effectively attenuate lung injury aggravated by acute hyperglycemia.

Association Between Prior Aspirin Use and Acute Respiratory Distress Syndrome Incidence in At-Risk Patients: A Systematic Review and Meta-Analysis

Background

Recent studies have shown that prior antiplatelet drug use could ameliorate the risk and mortality of acute respiratory distress syndrome (ARDS). However, the connection between prior acetylsalicylic acid (aspirin) use and the risk of ARDS is unknown. Our primary objective was to perform a meta-analysis on the currently available studies to assess the association between aspirin use prior to ARDS onset and ARDS incidence in at-risk patients.

Methods

Two investigators separately searched four research databases: MEDLINE, EMBASE, Cochrane Library, and Web of Science for relevant articles from the earliest available data through to July 14, 2019. In this paper, we performed a meta-analysis of the fixed effects model using the inverse variance-weighted average method to calculate the pooled odds ratios (ORs) and 95% confidence intervals (CIs). The primary outcome was risk of ARDS, and the secondary outcome was the hospital mortality of at-risk patients.

Results

This article included seven studies altogether, enrolling 6,764 at-risk patients. Our meta-analysis revealed that, compared to non-aspirin use, prior aspirin use was linked with a significantly lower incidence of ARDS in at-risk patients (OR, 0.78; 95% CI, 0.64–0.96; P = 0.018) with low statistical heterogeneity (I² = 1.7%). Additionally, difference between prior aspirin use and non-aspirin use was not remarkable for hospital mortality in at-risk patients (OR, 0.88; 95% CI, 0.73–1.07; P = 0.204), and this analysis did not involve statistical heterogeneity (I² = 0%).

Conclusions

This article indicates an association between prior aspirin use and a lower incidence of ARDS in at-risk patients, suggesting that aspirin use could potentially lower the risk of ARDS, and the investigation of such an effect is an interesting area for future clinical studies.

LincRNA-p21 promotes classical macrophage activation in acute respiratory distress syndrome by activating NF-κB

Background: Previous studies have revealed the important role of alveolar macrophages (AMs) in the pathogenesis of acute respiratory distress syndrome (ARDS) and potential anti-inflammatory properties of lincRNA-p21. This study aims to study the association between lincRNA-p21 and active AMs to understand the molecular mechanisms of AMs-mediated inflammatory responses in ARDS.Methods: This study was mainly investigated in mice with the intratracheal instillation of lipopolysaccharide (LPS) or LPS-treated AMs. The expression of lincRNA-p21 and classical macrophage markers, IL-12β and iNOS, was detected by quantitative RT-PCR, while NF-κB p65 translocation was measured by western blotting analysis. And, NF-κB activity was analyzed through luciferase report assays. Gain- and loss-of-function studies were also performed for further investigations.Results: Elevated lincRNA-p21 levels were observed in both LPS-induced ARDS mice and LPS-treated AMs, with upregulated expression of IL-12β and iNOS, namely M1 activation, and p65 nuclear translocation. Further in vitro studies showed that LPS-induced M1 activation could be counteracted by both lincRNA-p21 inhibition and inhibited NF-κB activation. Moreover, both p65 nuclear translocation and NF-κB activity were promoted by lincRNA-p21 overexpression, while lincRNA-p21 inhibition showed a negative effect on LPS-induced p65 nuclear translocation and increase of NF-κB activity. Additionally, LPS-induced lung injuries could be attenuated by lincRNA-p21 inhibition in vivo.Conclusion: This study revealed elevated lincRNA-p21 levels in LPS-induced ARDS and investigated the potential role of lincRNA-p21 in LPS-induced pro-inflammatory response via NF-κB/p65 mediated pathways, suggesting the potential application of lincRNA-p21 for ADRS therapy.

Role of macrophage TRPV4 in inflammation

Transient receptor ion channels have emerged as immensely important channels/receptors in diverse physiological and pathological responses. Of particular interest is the transient receptor potential channel subfamily V member 4 (TRPV4), which is a polymodal, nonselective, calcium-permeant cation channel, and is activated by both endogenous and exogenous stimuli. Both neuronal and nonneuronal cells express functional TRPV4, which is responsive to a variety of biochemical and biomechanical stimuli. Emerging discoveries have advanced our understanding of the role of macrophage TRPV4 in numerous inflammatory diseases. In lung injury, TRPV4 mediates macrophage phagocytosis, secretion of pro-resolution cytokines, and generation of reactive oxygen species. TRPV4 regulates lipid-laden macrophage foam cell formation, the hallmark of atheroinflammatory conditions, in response to matrix stiffness and lipopolysaccharide stimulation. Accumulating data also point to a role of macrophage TRPV4 in the pathogenesis of the foreign body response, a chronic inflammatory condition, through the formation of foreign body giant cells. Deletion of TRPV4 in macrophages suppresses the allergic and nonallergic itch in a mouse model, suggesting a role of TRPV4 in skin disease. Here, we discuss the current understanding of the role of macrophage TRPV4 in various inflammatory conditions.

PKR suppress NLRP3-pyroptosis pathway in lipopolysaccharide-induced acute lung injury model of mice

To explore the effect of double-stranded RNA-dependent kinase (PKR) in acute lung injury (ALI) and resultant acute respiratory distress syndrome (ARDS). A mouse model of lipopolysaccharide (LPS)-induced ALI was used to evaluate the levels of phosphorylated (p)-PKR and NLRP3 in lung tissue, and the protective effects of a PKR inhibitor on lung injury. And in vitro, macrophages were incubated with LPS, with or without PKR inhibitor pre-treatment. It was observed that the levels of p-PKR protein and NLRP3 protein were significantly increased compared with those in control tissues after LPS administration. Meanwhile, treatment with PKR inhibitor decreased inflammation, injury score, wet/dry weight ratio, bronchoalveolar lavage fluid (BALF) protein levels, neutrophil count in BALF, myeloperoxidase activity and expression of high-mobility group box1(HMGB1) and interleukin(IL)-1β in the lungs of LPS-challenged mice. In vitro, we demonstrated that the levels of p-PKR and NLRP3, and cell mortality rate were increased in macrophages which were incubated with LPS compared with those without LPS administration, and PKR inhibitor significantly suppressed the level of NLRP3, caspase-1, HMGB1 and IL-1β. These results indicate that PKR plays a key role in ALI through NLRP3-pyrotosis pathway and pharmacological inhibition of PKR may have potential therapeutic effects in the treatment of patients with ALI and ARDS.

Noninvasive quantification of macrophagic lung recruitment during experimental ventilation-induced lung injury

Macrophagic lung infiltration is pivotal in the development of lung biotrauma because of ventilation-induced lung injury (VILI). We assessed the performance of [¹¹C](R)-PK11195, a positron emission tomography (PET) radiotracer binding the translocator protein, to quantify macrophage lung recruitment during experimental VILI. Pigs (n = 6) were mechanically ventilated under general anesthesia, using protective ventilation settings (baseline). Experimental VILI was performed by titrating tidal volume to reach a transpulmonary end-inspiratory pressure (∆P_L) of 35-40 cmH₂O. We acquired PET/computed tomography (CT) lung images at baseline and after 4 h of VILI. Lung macrophages were quantified in vivo by the standardized uptake value (SUV) of [¹¹C](R)-PK11195 measured in PET on the whole lung and in six lung regions and ex vivo on lung pathology at the end of experiment. Lung mechanics were extracted from CT images to assess their association with the PET signal. ∆P_L increased from 9 ± 1 cmH₂O under protective ventilation, to 36 ± 6 cmH₂O during experimental VILI. Compared with baseline, whole-lung [¹¹C](R)-PK11195 SUV significantly increased from 1.8 ± 0.5 to 2.9 ± 0.5 after experimental VILI. Regional [¹¹C](R)-PK11195 SUV was positively associated with the magnitude of macrophage recruitment in pathology (P = 0.03). Compared with baseline, whole-lung CT-derived dynamic strain and tidal hyperinflation increased significantly after experimental VILI, from 0.6 ± 0 to 2.0 ± 0.4, and 1 ± 1 to 43 ± 19%, respectively. On multivariate analysis, both were significantly associated with regional [¹¹C](R)-PK11195 SUV. [¹¹C](R)-PK11195 lung uptake (a proxy of lung inflammation) was increased by experimental VILI and was associated with the magnitude of dynamic strain and tidal hyperinflation.NEW & NOTEWORTHY We assessed the performance of [¹¹C](R)-PK11195, a translocator protein-specific positron emission tomography (PET) radiotracer, to quantify macrophage lung recruitment during experimental ventilation-induced lung injury (VILI). In this proof-of-concept study, we showed that the in vivo quantification of [¹¹C](R)-PK11195 lung uptake in PET reflected the magnitude of macrophage lung recruitment after VILI. Furthermore, increased [¹¹C](R)-PK11195 lung uptake was associated with harmful levels of dynamic strain and tidal hyperinflation applied to the lungs.

Cyclooxygenase-2 Activity Regulates Recruitment of VEGF-Secreting Ly6Chigh Monocytes in Ventilator-Induced Lung Injury

Mechanical ventilation is usually required for saving lives in critically ill patients; however, it can cause ventilator-induced lung injury (VILI). As VEGF-secreting Ly6C^high monocytes are involved in VILI pathogenesis, we investigated whether cyclooxygenase-2 (COX-2) activity regulates the recruitment of VEGF-secreting Ly6C^high monocytes during VILI. The clinically relevant two-hit mouse model of VILI, which involves the intravenous injection of lipopolysaccharide prior to high tidal volume (HTV)-mechanical ventilation, was used in this study. To investigate the role of COX-2 in the recruitment of VEGF-secreting Ly6C^high monocytes during VILI, celecoxib, which is a clinical COX-2 inhibitor, was administered 1 h prior to HTV-mechanical ventilation. Pulmonary vascular permeability and leakage, inflammatory leukocyte infiltration, and lung oxygenation levels were measured to assess the severity of VILI. HTV-mechanical ventilation significantly increased the recruitment of COX-2-expressing Ly6C^high, but not Ly6C^low, monocytes. Celecoxib significantly diminished the recruitment of Ly6C^high monocytes, attenuated the levels of VEGF and total protein in bronchoalveolar lavage fluid, and restored pulmonary oxygenation during VILI. Our findings demonstrate that COX-2 activity is important in the recruitment of VEGF-secreting Ly6C^high monocytes, which are involved in VILI pathogenesis, and indicate that the suppression of COX-2 activity might be a useful strategy in mitigating VILI.

Inflammatory Cellular Response to Mechanical Ventilation in Elastase-Induced Experimental Emphysema: Role of Preexisting Alveolar Macrophages Infiltration

An excessive pulmonary inflammatory response could explain the poor prognosis of chronic obstructive pulmonary disease (COPD) patients submitted to invasive mechanical ventilation. The aim of this study was to evaluate the response to normal tidal volume mechanical ventilation in an elastase-induced murine model of pulmonary emphysema. In this model, two time points, associated with different levels of lung inflammation but similar lung destruction, were analyzed. C57BL/6 mice received a tracheal instillation of 5 IU of porcine pancreatic elastase (Elastase mice) or the same volume of saline (Saline mice). Fourteen (D14) and 21 (D21) days after instillation, mice were anesthetized, intubated, and either mechanically ventilated (MV) or maintained on spontaneous ventilation (SV) during two hours. As compared with Saline mice, Elastase mice showed a similarly increased mean chord length and pulmonary compliance at D14 and D21, while bronchoalveolar lavage cellularity was comparable between groups. Lung mechanics was similarly altered during mechanical ventilation in Elastase and Saline mice. Activated alveolar macrophages CD11bmid were present in lung parenchyma in both Elastase SV mice and Elastase MV mice at D14 but were absent at D21 and in Saline mice, indicating an inflammatory state with elastase at D14 only. At D14, Elastase MV mice showed a significant increase in percentage of neutrophils in total lung, as compared with Elastase SV mice. Furthermore, alveolar macrophages of Elastase MV mice at D14 overexpressed Gr1, and monocytes showed a trend to overexpression of CD62L, compared with Elastase SV mice. In an elastase-induced model of pulmonary emphysema, normal tidal volume mechanical ventilation may produce an increase in the proportion of pulmonary neutrophils, and an activation of alveolar macrophages and pulmonary monocytes. This response seems to be observed only when the emphysema model shows an underlying inflammation (D14), reflected by the presence of activated alveolar macrophages CD11bmid.

The acute respiratory distress syndrome: pathophysiology, current clinical practice, and emerging therapies

INTRODUCTION

More than fifty years after the first description of acute respiratory distress syndrome (ARDS) by Ashbaugh and colleagues, no specific treatment of the underlying pathophysiological processes is available. The current therapeutic regime is comprised of supportive measures such as lung protective ventilation, restrictive fluid management, paralyzing drugs, and prone positioning. Although vast improvements have been made in ARDS-treatment during the last five decades, mortality among patients with severe ARDS remains at an unacceptable rate of 45%. Areas covered: This article reviews the evolution of the currently used definition, established pathophysiological mechanism, highlights the current best clinical practice to treat ARDS, gives a brief outlook on cutting edge trends in ARDS research and closes with an expert opinion on the subject. Expert commentary: Individualizing the provided measures to specific genotypes is the key challenge in ARDS research today. The ongoing digital revolution will help to individualize ARDS-treatment and will therefore presumably improve survival and quality of life.

Regulation of the NLRP3 inflammasome and macrophage pyroptosis by the p38 MAPK signaling pathway in a mouse model of acute lung injury

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) is characterized by uncontrolled progressive lung inflammation. Macrophages serve a key role in the pathogenesis of ALI/ARDS. Macrophage pyroptosis is a process of cell death releasing the proinflammatory cytokines interleukin (IL)‑1β and IL‑18. It was hypothesized that macrophage pyroptosis may partially account for the uncontrolled lung inflammation of ALI/ARDS. In the present study, greater macrophage pyroptosis in lipopolysaccharide (LPS)‑treated macrophages and the ALI/ARDS mouse model was observed. The expression of nucleotide‑binding domain, leucine‑rich‑containing family, pyrin domain‑containing (NLRP)3 and IL‑1β and cleavage of caspase‑1 were significantly elevated following LPS treatment accompanied by greater activation of p38 mitogen‑activated protein kinase (MAPK) signaling in vitro and in vivo. However, blocking p38 MAPK signaling through the inhibitor SB203580 significantly suppressed the acute lung injury and excessive lung inflammation in vivo, consistent with the reduced expression of the NLRP3 inflammasome and IL‑1β and cleavage of caspase‑1. Pretreatment of the rat NR8383 macrophage cell line with SB203580 significantly decreased the population of caspase‑1+PI+ pyroptotic cells and expression of NLRP3/IL‑1β. However, a larger population of Annexin V+PI‑ apoptotic cells was observed following blocking of the p38 MAPK signaling pathway. The results indicated that blockage of p38 MAPK signaling pathway skewed macrophage cell death from proinflammatory pyroptosis towards non‑inflammatory apoptosis. These effects may contribute to attenuated acute lung injury and excessive inflammation in the SB203580‑treated mice. The results may provide a novel therapeutic strategy for the treatment of uncontrolled lung inflammation in patients with ALI/ARDS.

Inflammation and Monocyte Recruitment due to Aging and Mechanical Stretch in Alveolar Epithelium are Inhibited by the Molecular Chaperone 4-phenylbutyrate

Introduction

Ventilator-Induced lung injury (VILI) is a form of acute lung injury that is initiated or exacerbated by mechanical ventilation. The aging lung is also more susceptible to injury. Harmful mechanical stretch of the alveolar epithelium is a recognized mechanism of VILI, yet little is known about how mechanical stretch affects aged epithelial cells. Disruption to Endoplasmic Reticulum (ER) homeostasis results in a condition known as ER stress that leads to disruption of cellular homeostasis, apoptosis, and inflammation. ER stress is increased with aging and other pathological stimuli. We hypothesized that age and mechanical stretch increase alveolar epithelial cells' proinflammatory responses that are mediated by ER stress. Furthermore, we believed that inhibition of this upstream mechanism with 4PBA, an ER stress reducer, alleviates subsequent inflammation and monocyte recruitment.

Methods

Type II alveolar epithelial cells (ATII) were harvested from C57Bl6/J mice 2 months (young) and 20 months (old) of age. The cells were cyclically stretched at 15% change in surface area for up to 24 hours. Prior to stretch, groups were administered 4PBA or vehicle as a control.

Results

Mechanical stretch and age upregulated ER stress and proinflammatory MCP-1/CCL2 and MIP-1β/CCL4 chemokine expression in ATIIs. Age-matched and mismatched monocyte recruitment by ATII conditioned media was also quantified.

Conclusions

Age increases susceptibility to stretch-induced ER stress and downstream inflammatory gene expression in a primary ATII epithelial cell model. Administration of 4PBA attenuated the increased ER stress and proinflammatory responses from stretch and/or age and significantly reduced monocyte migration to ATII conditioned media.

Pirfenidone ameliorates lipopolysaccharide-induced pulmonary inflammation and fibrosis by blocking NLRP3 inflammasome activation

Acute respiratory distress syndrome(ARDS)is a severe clinical disorder characterized by its acute onset, diffuse alveolar damage, intractable hypoxemia, and non-cardiogenic pulmonary edema. Acute lung injury(ALI) can trigger persistent lung inflammation and fibrosis through activation of the NLRP3 inflammasome and subsequent secretion of mature IL-1β, suggesting that the NLRP3 inflammasome is a potential therapeutic target for ALI, for which new therapeutic approaches are needed. Our present study aims to assess whether pirfenidone,with anti-fibrotic and anti-inflammatory properties, can improve LPS-induced inflammation and fibrosis by inhibiting NLRP3 inflammasome activation. Male C57BL/6 J mice were intratracheally injected with LPS to induce ALI. Mice were administered pirfenidone by oral gavage throughout the entire experimental course. The mouse macrophage cell line (J774 A.1) was incubated with LPS and ATP, with or without PFD pre-treatment. We demonstrated that PFD remarkably ameliorated LPS-induced pulmonary inflammation and fibrosis and reduced IL-1β and TGF-β1 levels in bronchoalveolar lavage fluid(BALF). Pirfenidone substantially reduced NLRP3 and ASC expression and inhibited caspase-1 activation and IL-1β maturation in lung tissues. In vitro, the experiments revealed that PFD significantly suppressed LPS/ATP-induced production of reactive oxygen species (ROS) and decreased caspase-1 activation and the level of IL-1β in J774 A.1 cells. Taken together, the administration of PFD reduced LPS-induced lung inflammation and fibrosis by blocking NLRP3 inflammasome activation and subsequent IL-1β secretion. These findings indicated that PFD can down-regulate NLRP3 inflammasome activation and that it may offer a promising therapeutic approach for ARDS patients.

The Role of Macrophages in the Pathogenesis of ALI/ARDS

Despite development in the understanding of the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), the underlying mechanism still needs to be elucidated. Apart from leukocytes and endothelial cells, macrophages are also essential for the process of the inflammatory response in ALI/ARDS. Notably, macrophages play a dual role of proinflammation and anti-inflammation based on the microenvironment in different pathological stages. In the acute phase of ALI/ARDS, resident alveolar macrophages, typically expressing the alternatively activated phenotype (M2), shift into the classically activated phenotype (M1) and release various potent proinflammatory mediators. In the later phase, the M1 phenotype of activated resident and recruited macrophages shifts back to the M2 phenotype for eliminating apoptotic cells and participating in fibrosis. In this review, we summarize the main subsets of macrophages and the associated signaling pathways in three different pathological phases of ALI/ARDS. According to the current literature, regulating the function of macrophages and monocytes might be a promising therapeutic strategy against ALI/ARDS.

TRPV4 inhibition attenuates stretch-induced inflammatory cellular responses and lung barrier dysfunction during mechanical ventilation

Mechanical ventilation is an important tool for supporting critically ill patients but may also exert pathological forces on lung cells leading to Ventilator-Induced Lung Injury (VILI). We hypothesised that inhibition of the force-sensitive transient receptor potential vanilloid (TRPV4) ion channel may attenuate the negative effects of mechanical ventilation. Mechanical stretch increased intracellular Ca²⁺ influx and induced release of pro-inflammatory cytokines in lung epithelial cells that was partially blocked by about 30% with the selective TRPV4 inhibitor GSK2193874, but nearly completely blocked with the pan-calcium channel blocker ruthenium red, suggesting the involvement of more than one calcium channel in the response to mechanical stress. Mechanical stretch also induced the release of pro-inflammatory cytokines from M1 macrophages, but in contrast this was entirely dependent upon TRPV4. In a murine ventilation model, TRPV4 inhibition attenuated both pulmonary barrier permeability increase and pro-inflammatory cytokines release due to high tidal volume ventilation. Taken together, these data suggest TRPV4 inhibitors may have utility as a prophylactic pharmacological treatment to improve the negative pathological stretch-response of lung cells during ventilation and potentially support patients receiving mechanical ventilation.

Protective mechanism of sulforaphane in Nrf2 and anti-lung injury in ARDS rabbits

The effect of sulforaphane on nuclear factor erythroid 2-related factor 2 (Nrf2) and its protective mechanism for lung injury in rabbits with acute respiratory distress syndrome (ARDS) were investigated. Thirty rabbits were randomly divided into control (n=10), model (n=10) and experimental groups (n=10). Rabbits in model group and experimental group were treated with femoral venous injection of oleic acid to establish the ARDS model, while those in control group were injected with the same volume of normal saline. The experimental group received intravenous injection of sulforaphane. Twelve hours after modeling, the clinical manifestations and deaths of rabbits in each group were recorded and compared, including blood gas indexes, lung index (LI), alveolar damage coefficient, serum Nrf2 expression, as well as messenger ribonucleic acid (mRNA) and protein expression of Nrf2 in lung tissues. Pink frothy sputum and death were observed in rabbits in model group and experimental group, but the number of such cases in experimental group was smaller than that in the model group (p<0.05). Compared with those in control group, LI and IQA in model group and experimental group were increased, but LI and IQA in the experimental group were significantly decreased compared with those in the model group. Compared with those in the model group, the blood gas indexes (PaO₂, PaCO₂ and SaO₂) in the experimental group were significantly increased (p<0.05). Nrf2 in serum and lung tissues of rabbits in experimental group was significantly increased compared with that in model group (p<0.05). Sulforaphane significantly inhibits ARDS in rabbits and plays a protective role in ARDS through upregulating Nrf2.

Mechanical ventilation promotes lung metastasis in experimental 4T1 breast cancer lung-metastasized models

BACKGROUND/PURPOSE

The aim of this study was to test the hypothesis that mechanical ventilation (MV) during cancer surgery induces lung stroma/tissue milieu changes, creating a favorable microenvironment for postoperative lung metastatic tumor establishment.

MATERIALS AND METHODS

In Protocol A, female BALB/c mice were divided into an MV group and a control (no MV) group, both of which were anesthetized and subjected to intravenous injection of green fluorescent protein (GFP)-labeled mouse mammary carcinoma cell line (4T1) cells. After 24 h, the lung tissue was removed and the number of GFP-labeled 4T1 cells was calculated. In Protocol B, the clinically relevant mouse model of spontaneous breast cancer lung metastasis was used with surgical resection of the primary tumor to investigate the MV event that dictates postoperative lung metastasis. Female BALB/c mice were inoculated in the mammary fat pad with 4T1 cells. After 14-d growth, mice were anesthetized and divided into an MV group and a control (no MV) group during surgical procedures (mastectomy). Metastatic tumor burden was assessed two weeks after mastectomy by both macroscopic metastatic nodule count, hematoxylin-eosin histology, immunohistochemistry for the macrophage marker (CD68), and epithelial cell adhesion molecule (EpCAM).

RESULTS

MV was associated with a significant increase in the number of circulating breast tumor cells (GFP-labeled 4T1 cells) remaining in the microvasculature of the lung (P<0.01). Immunohistochemical results showed increased infiltration of CD68-positive macrophages within injured lung parenchyma and metastatic tumor as well as increased expression of EpCAM in metastatic nodules. Postoperative metastases were more prevalent in the mechanically ventilated mice group compared to the non-ventilated group (P<0.05).

CONCLUSION

MV-induced lung metastasis occurs by attracting circulating tumor cells to the site of the lung injury and by accelerating the proliferation of preexisting micro-metastases in the lung. These observations indicate that the metastasis-enhancing effect of MV should be considered in general anesthesia during cancer surgery.