Initiation of LPS-induced pulmonary dysfunction and its recovery occur independent of T cells

Lung-delivered IL-10 therapy elicits beneficial effects via immune modulation in organic dust exposure-induced lung inflammation

Efficacious therapeutic options capable of resolving inflammatory lung disease associated with environmental and occupational exposures are lacking. This study sought to determine the preclinical therapeutic potential of lung-delivered recombinant interleukin (IL)-10 therapy following acute organic dust exposure in mice. Here, C57BL/6J mice were intratracheally instilled with swine confinement organic dust extract (ODE) (12.5%, 25%, 50% concentrations) with IL-10 (1 μg) treatment or vehicle control intratracheally-administered three times: 5 hr post-exposure and then daily for 2 days. The results showed that IL-10 treatment reduced ODE (25%)-induced weight loss by 66% and 46% at Day 1 and Day 2 post-exposure, respectively. IL-10 treatment reduced ODE (25%, 50%)-induced lung levels of TNFα (-76%, -83% [reduction], respectively), neutrophil chemoattractant CXCL1 (-51%, -60%), and lavage fluid IL-6 (-84%, -89%). IL-10 treatment reduced ODE (25%, 50%)-induced lung neutrophils (-49%, -70%) and recruited CD11cintCD11b+ monocyte-macrophages (-49%, -70%). IL-10 therapy reduced ODE-associated expression of antigen presentation (MHC Class II, CD80, CD86) and inflammatory (Ly6C) markers and increased anti-inflammatory CD206 expression on CD11cintCD11b+ cells. ODE (12.5%, 25%)-induced lung pathology was also reduced with IL-10 therapy. In conclusion, the studies here showed that short-term, lung-delivered IL-10 treatment induced a beneficial response in reducing inflammatory consequences (that were also associated with striking reduction in recruited monocyte-macrophages) following acute complex organic dust exposure.

Physiologically based pharmacokinetic model for predicting the biodistribution of albumin nanoparticles after induction and recovery from acute lung injury

The application of nanomedicine in the treatment of acute lung injury (ALI) has great potential for the development of new therapeutic strategies. To gain insight into the kinetics of nanocarrier distribution upon time-dependent changes in tissue permeability after ALI induction in mice, we developed a physiologically based pharmacokinetic model for albumin nanoparticles (ANP). The model was calibrated using data from mice treated with intraperitoneal LPS (6 mg/kg), followed by intravenous ANP (0.5 mg/mouse or about 20.8 mg/kg) at 0.5, 6, and 24 h. The simulation results reproduced the experimental observations and indicated that the accumulation of ANP in the lungs increased, reaching a peak 6 h after LPS injury, whereas it decreased in the liver, kidney, and spleen. The model predicted that LPS caused an immediate (within the first 30 min) dramatic increase in lung and kidney tissue permeability, whereas splenic tissue permeability gradually increased over 24 h after LPS injection. This information can be used to design new therapies targeting specific organs affected by bacterial infections and potentially by other inflammatory insults.

A 'one stone, two birds' approach with mesenchymal stem cells for acute respiratory distress syndrome and Type II diabetes mellitus

This review explores the intricate relationship between acute respiratory distress syndrome (ARDS) and Type II diabetes mellitus (T2DM). It covers ARDS epidemiology, etiology and pathophysiology, along with current treatment trends and challenges. The lipopolysaccharides (LPS) role in ARDS and its association between non-communicable diseases and COVID-19 are discussed. The review highlights the therapeutic potential of human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) for ARDS and T2DM, emphasizing their immunomodulatory effects. This review also underlines how T2DM exacerbates ARDS pathophysiology and discusses the potential of hUC-MSCs in modulating immune responses. In conclusion, the review highlights the multidisciplinary approach to managing ARDS and T2DM, focusing on inflammation, oxidative stress and potential therapy of hUC-MSCs in the future.

Protective effect of β-glucan on Poly(I:C)-induced acute lung injury/inflammation: Therapeutic implications of viral infections in the respiratory system

AIMS

Acute lung inflammation, particularly acute respiratory distress syndrome (ARDS), is caused by a variety of pathogens including bacteria and viruses. β-Glucans have been reported to possess both anti-inflammatory and immunomodulatory properties. The current study evaluated the therapeutic effect of β-glucans on polyinosinic:polycytidylic acid (Poly(I:C)) induced lung inflammation in both hamster and mice models.

MAIN METHODS

Poly(I:C)-induced ALI/inflammation models were developed in hamsters (2.5 mg/kg) and mice (2 mg/kg) by delivering the Poly(I:C) intratracheally, and followed with and without β-glucan administration. After treatment, lung mechanics were assessed and lung tissues were isolated and analyzed for mRNA/protein expression, and histopathological examinations.

KEY FINDINGS

Poly(I:C) administration, caused a significant elevation of inflammatory marker's expression in lung tissues and showed abnormal lung mechanics in mice and hamsters. Interestingly, treatment with β-glucan significantly (p < 0.001) reversed the Poly(I:C)-induced inflammatory events and inflammatory markers expression in both mRNA (IL-6, IL-1β, TNF-α, CCL2 and CCL7) and protein levels (TNF-α, CD68, myeloperoxidase, neutrophil elastase, MUC-5Ac and iNOS). Lung functional assays revealed that β-glucan treatment significantly improved lung mechanics. Histopathological analysis showed that β-glucan treatment significantly attenuated the Poly(I:C) induced inflammatory cell infiltration, injury and goblet cell population in lung tissues. Consistent with these findings, β-glucan treatment markedly reduced the number of neutrophils and macrophages in lung tissues. Our findings further demonstrated that β-glucan could reduce inflammation by suppressing the MAPK pathway.

SIGNIFICANCE

These results suggested that β-glucan may attenuate the pathogenic effects of Poly(I:C)-induced ALI/ARDS via modulating the MAPK pathway, indicating β-glucan as a possible therapeutic agent for the treatment of viral-pulmonary inflammation/injury.

YAP-regulated type II alveolar epithelial cell differentiation mediated by human umbilical cord-derived mesenchymal stem cells in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) contributes to higher mortality worldwide. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have immunomodulatory and regenerative potential. However, the effects of hUC-MSCs as an ARDS treatment remain unclear. We investigated the role of hUC-MSCs in the differentiation of type II alveolar epithelial cells (AECII) by regulating Yes-associated protein (YAP) in ARDS. Male C57BL/6JNarl mice were intratracheally (i.t.) administered lipopolysaccharide (LPS) to induce an ARDS model, followed by a single intravenous (i.v.) dose of hUC-MSCs. hUC-MSCs improved pulmonary function, decreased inflammation on day 3, and mitigated lung injury by reducing the lung injury score and increasing lung aeration (%) in mice on day 7 (p < 0.05). hUC-MSCs inactivated YAP on AECII and facilitated cell differentiation by decreasing Pro-surfactant protein C (Pro-SPC) and galectin 3 (LGALS3) while increasing podoplanin (T1α) in lungs of mice (p < 0.05). In AECII MLE-12 cells, both coculture with hUC-MSCs after LPS exposure and the YAP inhibitor, verteporfin, reduced Pro-SPC and LGALS3, whereas the YAP inhibitor increased T1α expression (p < 0.05). In conclusion, hUC-MSCs ameliorated lung injury of ARDS and regulated YAP to facilitate AECII differentiation.

IFN- Is Protective in Cytokine Release Syndrome-associated Extrapulmonary Acute Lung Injury

The mechanisms by which excessive systemic activation of adaptive T lymphocytes, as in cytokine release syndrome (CRS), leads to innate immune cell-mediated acute lung injury (ALI) or acute respiratory distress syndrome, often in the absence of any infection, remains unknown. Here, we investigated the roles of IFN-γ and IL-17A, key T-cell cytokines significantly elevated in patients with CRS, in the immunopathogenesis of CRS-induced extrapulmonary ALI. CRS was induced in wild-type (WT), IL-17A- and IFN-γ knockout (KO) human leukocyte antigen-DR3 transgenic mice with 10 μg of the superantigen, staphylococcal enterotoxin B, given intraperitoneally. Several ALI parameters, including gene expression profiling in the lungs, were studied 4, 24, or 48 hours later. Systemic T-cell activation with staphylococcal enterotoxin B resulted in robust upregulation of several chemokines, S100A8/A9, matrix metalloproteases, and other molecules implicated in tissue damage, granulocyte as well as agranulocyte adhesion, and diapedesis in the lungs as early as 4 hours, which was accompanied by subsequent neutrophil/eosinophil lung infiltration and severe ALI in IFN-γ KO mice. These pathways were significantly underexpressed in IL-17A KO mice, which manifested mildest ALI and intermediate in WT mice. Neutralization of IFN-γ worsened ALI in WT and IL-17A KO mice, whereas neutralizing IL-17A did not mitigate lung injury in IFN-γ KO mice, suggesting a dominant protective role for IFN-γ in ALI and that IL-17A is dispensable. Ruxolitinib, a Janus kinase inhibitor, increased ALI severity in WT mice. Thus, our study identified novel mechanisms of ALI in CRS and its differential modulation by IFN-γ and IL-17A.

Post-endotoxin exposure-induced lung inflammation and resolution consequences beneficially impacted by lung-delivered IL-10 therapy

Although lung diseases typically result from long-term exposures, even a robust, one-time exposure can result in long-lasting consequences. Endotoxin is a ubiquitous environmental/occupational inflammatory agent often used to model airway inflammation. Using a murine model, the return to lung homeostasis following high dose inhalant lipopolysaccharide (LPS, 10-100 μg) exposure were delineated over 2 weeks. LPS-induced rapid weight loss, release of proinflammatory mediators, and inflammatory cell influx with prolonged persistence of activated macrophages CD11c⁺CD11b⁺ and recruited/transitioning CD11c^intCD11b⁺ monocyte-macrophages out to 2 weeks. Next, lung-delivered recombinant (r) interleukin (IL)-10 was intratracheally administered for 3 doses initiated 5 h following LPS (10 μg) exposure for 2 days. IL-10 therapy reduced LPS-induced weight loss and increased blood glucose levels. Whereas there was no difference in LPS-induced bronchoalveolar lavage airway fluid cellular influx, total lung cell infiltrates were reduced (37%) with rIL-10 treatment. Post-LPS exposure treatment with rIL-10 strikingly reduced lavage fluid and lung homogenate levels of tumor necrosis factor-α (88% and 93% reduction, respectively), IL-6 (98% and 94% reduction), CXCL1 (66% and 75% reduction), and CXCL2 (47% and 67% reduction). LPS-induced recruited monocyte-macrophages (CD11c^intCD11b⁺) were reduced (68%) with rIL-10. Correspondingly, LPS-induced lung tissue CCR2⁺ inflammatory monocyte-macrophage were reduced with rIL-10. There were also reductions in LPS-induced lung neutrophils, lymphocyte subpopulations, collagen content, and vimentin expression. These findings support the importance of studying resolution processes for the development of treatment after unintended environmental/occupational biohazard exposures. Short-term, lung-delivered rIL-10 favorably hastened inflammatory recovery processes following acute, high dose inhalant LPS exposure.

A novel pulmonary fibrosis murine model with immune-related liver injury

Idiopathic pulmonary fibrosis (IPF), characterized by aggravated alveolar destruction and fibrotic matrix deposition, tendentiously experiences the stage called acute exacerbation IPF (AE-IPF) and progresses to multiple organ damage, especially liver injury. Recent studies have found a variety of immune microenvironment disorders associated with elevated IPF risk and secondary organ injury, whereas current animal models induced with bleomycin (BLM) could not completely reflect the pathological manifestations of AE-IPF patients in clinic, and the exact underlying mechanisms are not yet fully explored. In the current study, we established an AE-IPF model by tracheal administration of a single dose of BLM and then repeated administrations of lipopolysaccharide in mice. This mouse model successfully recapitulated the clinical features of AE-IPF, including excessive intrapulmonary inflammation and fibrosis and extrapulmonary manifestations, as indicated by significant upregulation of Il6, Tnfa, Il1b, Tgfb, fibronectin, and Col1a1 in both lungs and liver and elevated serum aspartate transaminase and alanine transaminase levels. These effects might be attributed to the regulation of Th17 cells. By sharing this novel murine model, we expect to provide an appropriate experimental platform to investigate the pathogenesis of AE-IPF coupled with liver injury and contribute to the discovery and development of targeted interventions.

Effects of SPA4 peptide on lipopolysaccharide-disrupted lung epithelial barrier, injury, and function in a human cell system and mouse model of lung injury

Disrupted epithelial barrier, fluid accumulation, inflammation, and compromised physiology are hallmarks of lung injury. Here we investigated the structural stability of the Toll-like receptor-4 (TLR4)-interacting SPA4 peptide, its effect on Pseudomonas aeruginosa lipopolysaccharide (LPS)-disrupted epithelial barrier in a human cell system, and lung injury markers in a mouse model of LPS-induced lung inflammation. The structural properties of SPA4 peptide were investigated using circular dichroism and UV-VIS spectroscopy. The transepithelial electrical resistance (TEER), an indicator of barrier function, was measured after the cells were challenged with 1 μg/ml LPS and treated with 10 or 100 μM SPA4 peptide. The expression and localization of tight junction proteins were studied by immunoblotting and immunocytochemistry, respectively. Mice were intratracheally challenged with 5 μg LPS per g body weight and treated with 50 μg SPA4 peptide. The lung wet/dry weight ratios or edema, surfactant protein-D (SP-D) levels in serum, lung function, tissue injury, body weights, and temperature, and survival were determined as study parameters. The spectroscopy results demonstrated that the structure was maintained among different batches of SPA4 peptide throughout the study. Treatment with 100 μM SPA4 peptide restored the LPS-disrupted epithelial barrier, which correlated with the localization pattern of Zonula Occludens (ZO)-1 and occludin proteins. Correspondingly, SPA4 peptide treatment helped suppress the lung edema and levels of serum SP-D, improved some of the lung function parameters, and reduced the mortality risk against LPS challenge. Our results suggest that the anti-inflammatory activity of the SPA4 peptide facilitates the resolution of lung pathology.

Lipopolysaccharide-induced murine lung injury results in long-term pulmonary changes and downregulation of angiogenic pathways

Acute respiratory distress syndrome is the most severe form of acute lung injury (ALI) and is associated with significant mortality. Lipopolysaccharide (LPS)-induced injury is a valuable murine model of ALI but there is a paucity of data on lung regeneration and the role of angiogenic signaling involving vascular endothelial growth factor (VEGF). Eight-week-old male C57BL/6J mice were randomized to receive intratracheal instillation of either LPS or isovolumetric phosphate buffered saline as a vehicle control. Mice were observed at a single follow-up time-point that was either short-term (24 h or 4 days) or long-term (7 days or 4 weeks). On pulmonary function testing, LPS-treated mice had increased compliance at 4 weeks post-instillation, which correlated with decreased vascularization and with time-dependent, progressive decrease in alveolarization. Treadmill exercise tolerance testing demonstrated impaired performance at 24 h, 4 days and 4 weeks following LPS exposure. On lung protein analysis, LPS instillation decreased VEGF expression at up to 4 weeks, and decreased activation of its key receptor, VEGFR2 at 7 days and 4 weeks post-instillation. Together, these data provide insight on long-term pulmonary functional outcomes 4 weeks after ALI and identify angiogenic proteins as possible therapeutic targets following lung injury.

Sensitive physiological readouts to evaluate countermeasures for lipopolysaccharide-induced lung alterations in mice

Despite decades of research, studies investigating the physiological alterations caused by an acute bout of inflammation induced by exposing the lung to lipopolysaccharide have yielded inconsistent results. This can be attributed to small effects and/or a lack of fitted physiological testing. Herein, a comprehensive investigation of lung mechanics was conducted in 270 male C57BL/6 mice at 24, 48 or 96 h after an intranasal exposure to saline or lipopolysaccharide at either 1 or 3 mg/kg (30 mice per group). Traditional techniques that probe the lung using small-amplitude perturbations (i.e., oscillometry) were used, together with less conventional and new techniques that probe the lung using maneuvers of large amplitudes. The latter include a partial and a full-range pressure-volume maneuvers to measure quasi-static elastance, compliance, total lung volume, vital capacity and residual volume. The results demonstrate that lung mechanics assessed by oscillometry was only slightly affected by lipopolysaccharide, confirming previous findings. In contradistinction, lipopolysaccharide markedly altered mechanics when the lung was probed with maneuvers of large amplitudes. With the dose of 3 mg/kg at the peak of inflammation (48 h post-exposure), lipopolysaccharide increased quasi-static elastance by 26.7% (p<0.0001), and decreased compliance by 34.5% (p<0.0001). It also decreased lung volumes, including total lung capacity, vital capacity and residual volume by 33.3%, 30.5% and 43.3%, respectively (all p<0.0001). These newly reported physiological alterations represent sensitive outcomes to efficiently evaluate countermeasures (e.g., drugs) in the context of several lung diseases.

Therapeutic hypothermia attenuates physiologic, histologic, and metabolomic markers of injury in a porcine model of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a lung injury characterized by noncardiogenic pulmonary edema and hypoxic respiratory failure. The purpose of this study was to investigate the effects of therapeutic hypothermia on short-term experimental ARDS. Twenty adult female Yorkshire pigs were divided into four groups (n = 5 each): normothermic control (C), normothermic injured (I), hypothermic control (HC), and hypothermic injured (HI). Acute respiratory distress syndrome was induced experimentally via intrapulmonary injection of oleic acid. Target core temperature was achieved in the HI group within 1 h of injury induction. Cardiorespiratory, histologic, cytokine, and metabolomic data were collected on all animals prior to and following injury/sham. All data were collected for approximately 12 h from the beginning of the study until euthanasia. Therapeutic hypothermia reduced injury in the HI compared to the I group (histological injury score = 0.51 ± 0.18 vs. 0.76 ± 0.06; p = 0.02) with no change in gas exchange. All groups expressed distinct phenotypes, with a reduction in pro-inflammatory metabolites, an increase in anti-inflammatory metabolites, and a reduction in inflammatory cytokines observed in the HI group compared to the I group. Changes to respiratory system mechanics in the injured groups were due to increases in lung elastance (E) and resistance (R) (ΔE from pre-injury = 46 ± 14 cmH₂ O L^-1 , p < 0.0001; ΔR from pre-injury: 3 ± 2 cmH₂ O L^-1  s^- , p = 0.30) rather than changes to the chest wall (ΔE from pre-injury: 0.7 ± 1.6 cmH₂ O L^-1 , p = 0.99; ΔR from pre-injury: 0.6 ± 0.1 cmH₂ O L^-1  s^- , p = 0.01). Both control groups had no change in respiratory mechanics. In conclusion, therapeutic hypothermia can reduce markers of injury and inflammation associated with experimentally induced short-term ARDS.

An activation specific anti-Mac-1 designed ankyrin repeat protein improves survival in a mouse model of acute lung injury

The acute respiratory distress syndrome (ARDS) is a life-threatening clinical condition. The number of ARDS cases has risen dramatically recently but specific treatment options are limited. ARDS is associated with an overshooting inflammatory response and neutrophils play a central role in its pathogenesis. Neutrophils express the integrin Mac-1 on their surface which adopts a resting and activated conformation depending on leukocyte activation. The aim of this study was to investigate the anti-inflammatory effects of the unique activation-specific anti-Mac-1 DARPin 'F7' in a mouse model of ARDS. ARDS was induced by intratracheal lipopolysaccharide (LPS) instillation and the acute (day 1-4) and chronic phase (day 5-10) were studied. After expression and purification, F7, a control DARPin and PBS, were applied daily via the intraperitoneal route. Survival and weight loss were recorded. Histological analysis of lung sections, flow cytometric leukocyte analysis of blood and bronchioalveolar lavage (BALF) were performed. Moreover, protein concentration and cytokine levels were determined in the BALF. Treatment with F7 improved survival and reduced weight loss significantly compared to treatment with the control DARPin or PBS. Neutrophil count in the BALF and peripheral blood were significantly reduced in mice treated with F7. Histology revealed significantly reduced pulmonary inflammation in the F7 treated group. Treatment with DARPin F7 inhibited neutrophil accumulation, reduced signs of local and systemic inflammation and improved survival in a mouse model of ARDS. F7 may be a novel anti-inflammatory drug candidate for the treatment of severe ARDS.

Inhalation of nebulized omega-3 fatty acids mitigate LPS-induced acute lung inflammation in rats: Implications for treatment of COPD and COVID-19

Many current treatment options for lung inflammation and thrombosis come with unwanted side effects. The natural omega-3 fatty acids (O3FA) are generally anti-inflammatory and antithrombotic. O3FA are always administered orally and occasionally by intravenous (IV) infusion. The main goal of this study is to determine if O3FA administered by inhalation of a nebulized formulation mitigates LPS-induced acute lung inflammation in male Wistar rats. Inflammation was triggered by intraperitoneal injection of LPS once a day for 14 days. One hour post-injection, rats received nebulized treatments consisting of egg lecithin emulsified O3, Budesonide and Montelukast, and blends of O3 and Melatonin or Montelukast or Cannabidiol; O3 was in the form of free fatty acids for all groups except one group with ethyl esters. Lung histology and cytokines were determined in n = 3 rats per group at day 8 and day 15. All groups had alveolar histiocytosis severity scores half or less than that of the disease control (Cd) treated with LPS and saline only inhalation. IL-6, TNF-α, TGF-β, and IL-10 were attenuated in all O3FA groups. IL-1β was attenuated in most but not all O3 groups. O3 administered as ethyl ester was overall most effective in mitigating LPS effects. No evidence of lipid pneumonia or other chronic distress was observed. These preclinical data suggest that O3FA formulations should be further investigated as treatments in lung inflammation and thrombosis related lung disorders, including asthma, chronic obstructive pulmonary disease, lung cancer and acute respiratory distress such as COVID-19.

Differential effects of the Src family tyrosine kinases Yes and Fyn on lipopolysaccharide-induced lung injury in ice

Endothelial cell apoptosis is an early event in the development of acute lung injury (ALI). We have previously found that the Src family tyrosine kinase (STK) Yes activates caspase-3, whereas the STK Fyn inhibits caspase-3 activation in cultured pulmonary endothelial cells. We hypothesized that deficiency in Yes or Fyn in mice would have differential effects on lipopolysaccharide (LPS)-induced ALI. Mice were treated with LPS (10 mg/kg ip) for 24 h. Histological evidence of lung injury was greater in LPS-treated wild-type mice than in vehicle-treated wild-type mice, and the LPS-induced histological evidence of lung injury was attenuated in yes^-/- mice and enhanced in fyn^-/- mice. In wild-type or fyn^-/- mice, LPS resulted in greater lung wet-to-dry weight ratios than in controls, whereas in yes^-/- mice lung, wet-to-dry weight was similar between LPS and controls. LPS-exposed fyn^-/- mice had greater respiratory system resistance and lower respiratory system compliance than did LPS-exposed wild-type mice. TUNEL positive cells in the lung following LPS treatment were greater in the fyn^-/- mice and lower in the yes^-/- mice compared with that in the wild-type mice. Following LPS treatment lung protein levels of PECAM-1 were lower in fyn^-/- mice than in controls or yes^-/- mice. LPS treatment increased cleaved caspase-3 protein levels in wild-type mice, whereas LPS-induced caspase-3 activation was attenuated in yes^-/- mice and enhanced in fyn^-/- mice. These results indicate that LPS-induced ALI is positively mediated via Yes-related mechanisms and negatively mediated by Fyn-related mechanisms.

MCTR3 reduces LPS-induced acute lung injury in mice via the ALX/PINK1 signaling pathway

Acute lung injury (ALI), a common respiratory distress syndrome in the intensive care unit (ICU), is mainly caused by severe infection and shock. Epithelial and capillary endothelial cell injury, interstitial edema and inflammatory cell infiltration are the main pathological changes observed in ALI animal models. Maresin conjugates in tissue regeneration (MCTR) are a new family of anti-inflammatory proteins. MCTR3 is a key enhancer of the host response, that promotes tissue regeneration and reduces infection; however, its role and mechanism in ALI are still unclear. The purpose of our research was to assess the protective effects of MCTR3 against ALI and its underlying mechanism. The work in this study was conducted in a murine model and the pulmonary epithelial cell line MLE-12. In vivo, MCTR3 (2 ng/g) was given 2 h after lipopolysaccharide (LPS) injection. We found that the treatment of mice with LPS-induced ALI with MCTR3 significantly reduced the cell number and protein levels in the bronchoalveolar lavage fluid (BALF); decreased the production of inflammatory cytokines; alleviated oxidative stress and cell apoptosis, consequently decreased lung injury; and restored pulmonary function. These protective effects of MCTR3 were dependent on down-regulation of the PTEN-induced putative kinase 1 (PINK1) pathway. Additionally, in MLE-12 cells stimulated with LPS, MCTR3 inhibited cell death, inflammatory cytokine levels and oxidative stress via the ALX/PINK1 signaling pathway. Thus, we conclude that MCTR3 protected against LPS-induced ALI partly through inactivation of the ALX/PINK1 mediated mitophagy pathway.

Insights into pathogenesis of fatal COVID-19 pneumonia from histopathology with immunohistochemical and viral RNA studies

Introduction

We describe post‐mortem pulmonary histopathologic findings of COVID‐19 pneumonia in patients with a spectrum of disease course, from rapid demise to prolonged hospitalisation.

Methods and results

Histopathologic findings in post‐mortem lung tissue from eight patients who died from COVID‐19 pneumonia were reviewed. Immunohistochemistry (IHC) and next‐generation sequencing (NGS) were performed to detect virus. Diffuse alveolar damage (DAD) was seen in all cases with a spectrum of acute phase and/or organising phase. IHC with monoclonal antibodies against SARS‐CoV‐2 viral nucleoprotein and spike protein detected virus in areas of acute but not organising DAD, with intracellular viral antigen and RNA expression seen predominantly in patients with duration of illness less than 10 days. Major vascular findings included thrombi in medium‐ and large‐calibre vessels, platelet microthrombi detected by CD61 IHC and fibrin microthrombi.

Conclusions

Presence of SARS‐CoV‐2 viral RNA by NGS early in the disease course and expression of viral antigen by IHC exclusively in the acute, but not in the organising phase of DAD, suggests that the virus may play a major role in initiating the acute lung injury of DAD, but when DAD progresses to the organising phase the virus may have been cleared from the lung by the patient's immune response. These findings suggest the possibility of a major change during the disease course of COVID‐19 pneumonia that may have therapeutic implications. Frequent thrombi and microthrombi may also present potential targets for therapeutic intervention.

Effects of long term normobaric hyperoxia exposure on lipopolysaccharide-induced lung injury

Purpose/Aim of the study: Prolonged exposure to hyperoxia can cause injury to normal lung tissue. However, patients with acute hypoxic respiratory failure are frequently exposed to very high oxygen levels. This study investigated the effects of long term normobaric hyperoxia exposure in a mouse model of acute severe lung injury (SLI).Meterials and Methods: C57BL/6J mice were injected intratracheally with lipopolysaccharide (LPS, 4 mg/kg) to induce acute lung injury. After 2 h, mice were divided into two groups, and then exposed to room air or hyperoxic conditions for 48 h. Animals in the hyperoxia group were placed within their cages in a Plexiglass chamber with an atmosphere of 95% O₂ maintained constant using an oxygen analyzer. After exposure to normoxia (N) or hyperoxia (H) for 48 h, the left lungs were collected for tissue paraffin block or oxidative stress assay. One lobe of the right lung was collected for lung/body weight ratio. The lung injury score and the mean linear intercept were evaluated in hematoxylin and eosin -stained lungs. The biochemical tests were performed by using ELISA assay.Results: Lung injury scoring, lung/body weight, and mean linear intercept were not significantly different between the N + LPS (NLPS) and H + LPS (HLPS) groups. Similar trends were observed in hydroxyproline and transforming growth factor-β (TGF-β) levels. Total cell and neutrophil counts in bronchoalveolar lavage fluid showed no significant differences between NLPS and HLPS groups. Histological analyses demonstrated more severe lung injury and fibrosis in the NLPS group than in the HLPS group. In addition, interleukin (IL)-1β was significantly decreased in the HLPS group compared to the NLPS group. Other inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and IL-6, showed similar trends. The malondialdehyde (MDA) level was significantly lower in the HLPS group than in the NLPS group.Conclusions: Exposure to hyperoxia did not augment lung injury in the LPS-induced lung injury model, and some indicators even showed better outcomes. These results suggest that long-term high-oxygen therapy in patients with SLI has low risk of lung injury.

MCTR1 alleviates lipopolysaccharide-induced acute lung injury by protecting lung endothelial glycocalyx

Endothelial glycocalyx degradation, critical for increased pulmonary vascular permeability, is thought to facilitate the development of sepsis into the multiple organ failure. Maresin conjugates in tissue regeneration 1 (MCTR1), a macrophage-derived lipid mediator, which exhibits potentially beneficial effects via the regulation of bacterial phagocytosis, promotion of inflammation resolution, and regeneration of tissue. In this study, we show that MCTR1 (100 ng/mouse) enhances the survival of mice with lipopolysaccharide (LPS)-induced (15 mg/kg) sepsis. MCTR1 alleviates LPS (10 mg/kg)-induced lung dysfunction and lung tissue inflammatory response by decreasing inflammatory cytokines (tumor necrosis factor-α, interleukin-1β [IL-1β], and IL-6) expression in serum and reducing the serum levels of heparan sulfate (HS) and syndecan-1. In human umbilical vein endothelial cells (HUVECs) experiments, MCTR1 (100 nM) was added to the culture medium with LPS for 6 hr. MCTR1 treatment markedly inhibited HS degradation by downregulating heparanase (HPA) protein expression in vivo and in vitro. Further analyses indicated that MCTR1 upregulates sirtuin 1 (SIRT1) expression and decreases NF-κB p65 phosphorylation. In the presence of BOC-2 or EX527, the above effects of MCTR1 were abolished. These results suggest that MCTR1 protects against LPS-induced sepsis in mice by attenuating pulmonary endothelial glycocalyx injury via the ALX/SIRT1/NF-κB/HPA pathway.