Adenovirus-delivered angiopoietin-1 treatment for phosgene-induced acute lung injury

New Insights into Clinical and Mechanistic Heterogeneity of the Acute Respiratory Distress Syndrome: Summary of the Aspen Lung Conference 2021

Clinical and molecular heterogeneity are common features of human disease. Understanding the basis for heterogeneity has led to major advances in therapy for many cancers and pulmonary diseases such as cystic fibrosis and asthma. Although heterogeneity of risk factors, disease severity, and outcomes in survivors are common features of the acute respiratory distress syndrome (ARDS), many challenges exist in understanding the clinical and molecular basis for disease heterogeneity and using heterogeneity to tailor therapy for individual patients. This report summarizes the proceedings of the 2021 Aspen Lung Conference, which was organized to review key issues related to understanding clinical and molecular heterogeneity in ARDS. The goals were to review new information about ARDS phenotypes, to explore multicellular and multisystem mechanisms responsible for heterogeneity, and to review how best to account for clinical and molecular heterogeneity in clinical trial design and assessment of outcomes. The report concludes with recommendations for future research to understand the clinical and basic mechanisms underlying heterogeneity in ARDS to advance the development of new treatments for this life-threatening critical illness.

Phosgene-Induced acute lung injury: Approaches for mechanism-based treatment strategies

Phosgene (COCl2) gas is a chemical intermediate of high-volume production with numerous industrial applications worldwide. Due to its high toxicity, accidental exposure to phosgene leads to various chemical injuries, primarily resulting in chemical-induced lung injury due to inhalation. Initially, the illness is mild and presents as coughing, chest tightness, and wheezing; however, within a few hours, symptoms progress to chronic respiratory depression, refractory pulmonary edema, dyspnea, and hypoxemia, which may contribute to acute respiratory distress syndrome or even death in severe cases. Despite rapid advances in medicine, effective treatments for phosgene-inhaled poisoning are lacking. Elucidating the pathophysiology and pathogenesis of acute inhalation toxicity caused by phosgene is necessary for the development of appropriate therapeutics. In this review, we discuss extant literature on relevant mechanisms and therapeutic strategies to highlight novel ideas for the treatment of phosgene-induced acute lung injury.

NEDD4 attenuates phosgene-induced acute lung injury through the inhibition of Notch1 activation

Phosgene gas leakage can cause life-threatening acute lung injury (ALI), which is characterized by inflammation, increased vascular permeability, pulmonary oedema and oxidative stress. Although the downregulation of neuronal precursor cell-expressed developmentally downregulated 4 (NEDD4) is known to be associated with inflammation and oxidative damage, its functions in phosgene-induced ALI remain unclear. In this study, rats with phosgene-induced ALI were intravenously injected with NEDD4-overexpressing lentiviruses to determine the functions of NEDD4 in this inflammatory condition. NEDD4 expression was decreased in the lung parenchyma of phosgene-exposed control rats, whereas its expression level was high in the NEDD4-overexpressing rats. Phosgene exposure increased the wet-to-dry lung weight ratio, but NEDD4 abrogated this effect. NEDD4 overexpression attenuated phosgene-induced lung inflammation, lowering the high lung injury score (based on total protein, inflammatory cells and inflammatory factors in bronchoalveolar lavage fluid) and also reduced phosgene-induced oxidative stress and cell apoptosis. Finally, NEDD4 was found to interact with Notch1, enhancing its ubiquitination and thereby its degradation, thus attenuating the inflammatory responses to ALI. Therefore, we demonstrated that NEDD4 plays a protective role in alleviating phosgene-induced ALI, suggesting that enhancing the effect of NEDD4 may be a new approach for treating phosgene-induced ALI.

Mechanism of Phosgene-Induced Acute Lung Injury and Treatment Strategy

Phosgene (COCl₂) was once used as a classic suffocation poison and currently plays an essential role in industrial production. Due to its high toxicity, the problem of poisoning caused by leakage during production, storage, and use cannot be ignored. Phosgene mainly acts on the lungs, causing long-lasting respiratory depression, refractory pulmonary edema, and other related lung injuries, which may cause acute respiratory distress syndrome or even death in severe cases. Due to the high mortality, poor prognosis, and frequent sequelae, targeted therapies for phosgene exposure are needed. However, there is currently no specific antidote for phosgene poisoning. This paper reviews the literature on the mechanism and treatment strategies to explore new ideas for the treatment of phosgene poisoning.

Lung-derived exosomes regulate the function of mesenchymal stem cells and alleviate phosgene-induced lung injury via miR-34c-3p

Phosgene may induce acute lung injury (ALI) when a person is exposed to it. Mesenchymal stem cells (MSCs) were affirmed to have therapeutic effects on phosgene-induced ALI. In a previous study, ALI exosomes have been confirmed to promote the proliferation and migration of MSCs. However, the mechanism of this phenomenon is still unclear. MicroRNAs (miRNAs) are essential in the physiological process of cells. In this study, lung-derived exosomes were isolated from phosgene-exposed and normal rats, respectively, through ultracentrifugation and cultured MSCs with these exosomes. We found that rno-miR-34c-3p was downregulated in MSCs cocultured with ALI exosomes. MiR-34c-3p inhibitor promoted the proliferation and migration of MSCs. Moreover, the dual-luciferase reporter assay demonstrated that miR-34c-3p regulated Janus kinase 1 (JAK1) expression. The miR-34c-3p inhibitor also significantly activated the JAK1/signal transducer and activator of transcription 3 (STAT3) signaling pathway. In conclusion, ALI exosomes decrease the miR-34c-3p expression levels, influencing MSCs via the JAK1/STAT3 signaling pathway.

Comprehensive Analysis of the Profiles of Differentially Expressed mRNAs, lncRNAs, and circRNAs in Phosgene-Induced Acute Lung Injury

Phosgene exposure can cause acute lung injury (ALI), for which there is no currently available effective treatment. Mesenchymal stem cells (MSCs) which have been proven to have therapeutic potential and be helpful in the treatment of various diseases, but the mechanisms underlying the function of MSCs against phosgene-induced ALI are still poorly explored. In this study, we compared the expression profiles of mRNAs, lncRNAs, and circRNAs in the lung tissues from rats of three groups—air control (group A), phosgene-exposed (group B), and phosgene + MSCs (group C). The results showed that 389 mRNAs, 198 lncRNAs, and 56 circRNAs were differently expressed between groups A and B; 130 mRNAs, 107 lncRNAs, and 35 circRNAs between groups A and C; and 41 mRNAs, 88 lncRNAs, and 18 circRNAs between groups B and C. GO and KEGG analyses indicated that the differentially expressed RNAs were mainly involved in signal transduction, immune system processes, and cancers. In addition, we used a database to predict target microRNAs (miRNAs) interacting with circRNAs and the R network software package to construct a circRNA-targeted miRNA gene network map. Our study showed new insights into changes in the RNA expression in ALI, contributing to explore the mechanisms underlying the therapeutic potential of MSCs in phosgene-induced ALI.

NLRP3 gene silencing ameliorates phosgene-induced acute lung injury in rats by inhibiting NLRP3 inflammasome and proinflammatory factors, but not anti-inflammatory factors

NOD-like receptor protein 3 (NLRP3) is involved in acute lung injury (ALI), but its exact role in phosgene-induced ALI is not clearly understood. The aim of the study is to explore the potential therapeutic effect of NLRP3 inflammasome modulation in the management of phosgene-induced ALI. ALI was induced in rats by phosgene exposure at 8.33 g/m³ for 5 min, 30 hr before intravenous injection of adenovirus-NLRP3 shRNA (Ad/NLRP3-shRNA). The histological changes in the lung were evaluated. Bronchoalveolar lavage fluid (BALF) neutrophils were counted (smear), and protein content was measured using the BCA assay. The wet/dry ratio of lung tissue (W/D) was measured. TUNEL staining for DNA damage was used to indirectly assess pyroptosis. NLRP3 inflammasome was assessed by immunohistochemistry, RT-PCR, western blotting. Cytokines were measured by ELISA. Histological analyses revealed reduced severity in phosgene-induced ALI with Ad/NLRP3-shRNA pretreatment. TUNEL staining indicated decreased pyroptosis in Psg-Ad/NLRP3-shRNA rats. Decreased mRNA and protein levels of NLRP3 and caspase-1 (all P < 0.05), but not ASC (P > 0.05), were found in Psg-Ad/NLRP3-shRNA rats. Immunohistochemistry revealed that Ad/NLRP3-shRNA pretreatment inhibited NLRP3 inflammasome activation. Reduced level of pro-inflammatory interleukin (IL)-1β, IL-18, IL-33, and tumor necrosis factor (TNF)-α (all P < 0.05), but not of anti-inflammatory IL-4 and IL-10 (all P > 0.05), were found in serum and BALF from Ad/NLRP3-shRNA rats. NLRP3 gene silencing exerts beneficial effects on phosgene-induced lung injury by inhibiting NLRP3 inflammasome activation and pro-inflammatory factors, but not anti-inflammatory factors. Disruption of NLRP3 inflammasome activation might be used as a therapeutic modality for the treatment of phosgene-induced ALI.

The Angiopoietin-Tie2 Pathway in Critical Illness

Lethal features of sepsis and acute respiratory distress syndrome (ARDS) relate to the health of small blood vessels. For example, alveolar infiltration with proteinaceous fluid is often driven by breach of the microvascular barrier. Spontaneous thrombus formation within inflamed microvessels exacerbates organ ischemia, and in its final stages, erupts into overt disseminated intravascular coagulation. Disruption of an endothelial signaling axis, the Angiopoietin-Tie2 pathway, may mediate the abrupt transition from microvascular integrity to pathologic disruption. This review summarizes preclinical and clinical results that implicate the Tie2 pathway as a promising target to restore microvascular health in sepsis and ARDS.

Lung-derived exosomes in phosgene-induced acute lung injury regulate the functions of mesenchymal stem cells partially via miR-28-5p

Accidental phosgene exposure can result in acute lung injury (ALI). Mesenchymal stem cells (MSCs) have been found to alleviate phosgene-induced ALI. However, the mechanism of MSCs underlying such protective effect remains largely unexplored. Exosomes, important components of microenvironment, are closely associated with intercellular information transfer. In the present study, we isolated lung exosomes in rats after phosgene exposure by ultracentrifugation and explored their effects on MSCs in vitro. ALI exosomes were elliptical in shape and 50-200 nm in size. ALI exosomes could promote proliferation and migration of MSCs. Moreover, ALI exosomes increased the secretion of IL-10, leading to enhanced immunoregulatory properties of MSCs. The paracrine factors, VEGF, HGF, LL-37 and Ang-1, were also augmented by ALI exosomes. However, ALI exosomes had no effect on differentiation of MSCs towards lung alveolar cells. To identify the effective miRNAs in ALI exosomes, we performed miRNA profile analysis. MiR-28-5p was considered as a possible effective molecule. We further studied the effect of miR-28-5p on MSCs. MiR-28-5p mimic promoted proliferation, migration, immunomodulation of MSCs. MiR-28-5p mimic promoted the paracrine of VEGF, HGF, LL-37 and Ang-1. Besides, we explored molecular mechanism of miR-28-5p in MSCs. PI3K/Akt signaling pathway was found significantly augmented by miR-28-5p mimic, indicating the activation in this process. Taken together, our findings could help identify the effects of lung-derived exosomes on MSCs, and the effective molecule in exosomes, miR-28-5p, activated MSCs through PI3K/Akt signaling pathway.

Adenovirus-delivered angiopoietin-1 ameliorates phosgene-induced acute lung injury via inhibition of NLRP3 inflammasome activation

OBJECTIVE

Angiopoietin-1 (Ang1) is reported to have the ability to attenuate endothelial permeability and inflammation during the stress condition and is considered to play a critical role in vascular stabilization. The aim of this study was to investigate the mechanisms involved in the protective effects of adenovirus-delivered Ang1 in phosgene-induced acute lung injury (ALI).

METHODS

ALI was induced in rats by phosgene exposure at 8.33 g/m³ for 5 min, followed by an intravenous injection of adenovirus-Ang1 (Ad/Ang1). The histologic changes of the lung were evaluated with H&E staining. The levels of cytokines in the serum and bronchoalveolar lavage fluid (BALF) were determined by ELISA. NLRP3 inflammasome activation was assessed with immunohistochemistry, RT-PCR, Western blotting and TUNEL staining.

RESULTS

Histologic analyses suggested that reduced severity in phosgene-induced ALI with Ad/Ang1 treatment. Reduced levels of IL-1β, IL-18 and IL-33 were found in both serum and BALF samples from Ad/Ang1-treated ALI rats induced by phosgene. Moreover, immunohistochemistry analysis revealed that Ad/Ang1 treatment inhibited the NLRP3 inflammasome activation. Decreased mRNA and protein levels of NLRP3 and caspase-1 were found in phosgene-exposed rats treated with Ad/Ang1. In addition, TUNEL staining indicated a decrease in pyroptosis in phosgene-exposed rats treated with Ad/Ang1.

CONCLUSIONS

Ang1 exerts beneficial effects on phosgene-induced lung injury via inhibition of NLRP3 inflammasome activation. Disruption of NLRP3 inflammasome activation might be served as therapeutic modality for the treatment of phosgene-induced ALI.

Overexpression of CXCR7 promotes mesenchymal stem cells to repair phosgene-induced acute lung injury in rats

Phosgene exposure may result in acute lung injury (ALI) with high mortality. Emerging evidence suggests that mesenchymal stem cells (MSCs) have a therapeutic potential against ALI. CXC chemokine receptor 7 (CXCR7) has been identified as a receptor of stromal-cell-derived factor 1 (SDF1) involved in MSC migration and may be an important mediator of the therapeutic effects of MSCs on ALI. In our study, we initially constructed a lentiviral vector overexpressing CXCR7 and then successfully transduced it into rat bone marrow-derived MSCs (resulting in MSCs-CXCR7). We found that ALI and the wet-to-dry ratio significantly decreased in the phosgene-exposed rats after administration of MSCs-CXCR7 or MSCs-GFP. Indeed, treatment with MSCs-CXCR7 caused further improvement. Moreover, injection of MSCs-CXCR7 significantly facilitated MSC homing to injured lung tissue. Meanwhile, overexpression of CXCR7 promoted differentiation of MSCs into type II alveolar epithelial (AT II) cells and enhanced the ability of MSCs to modulate the inflammatory response in phosgene-induced ALI. Taken together, our findings suggest that CXCR7-overexpressing MSCs may markedly facilitate treatment of phosgene-induced ALI (P-ALI) in rats.

Mesenchymal stem cells overexpressing Ang1 attenuates phosgene-induced acute lung injury in rats

Phosgene-induced acute lung injury (P-ALI) is characterized by inflammation and effective treatments are lacking. Angiopoietin-1 (Ang1) has the beneficial effects on P-ALI. Mesenchymal stem cells (MSCs) have the potential for re-epithelization and recovery in lung injury. Thus, we hypothesized that Ang1 expressing MSCs would have beneficial effects on P-ALI. Here, an Ang1 expressing lentiviral vector was constructed and infected into rat bone marrow MSCs. Histological analyses revealed significant pathological improvements especially after treatment with MSCs in the rats exposed to phosgene. Ang1 facilitated the homing of MSCs to injured lung tissue and significantly increased expression of both epithelial cell marker Aquaporin-5 (AQP5) and surfactant protein-C (SPC) in the lung tissues. Moreover, MSCs-Ang1 reduced level of pro-inflammatory cytokines TGF-β1 and IL-1β and increased the expression of the anti-inflammatory cytokine IL-10 in the serum and bronchoalveolar lavage fluid (BALF) of P-ALI rats. In conclusion, our results suggest that Ang1 may improve the therapeutic potential of MSCs for P-ALI treatment.

Proliferation and functionality of human umbilical vein endothelial cells on angiopoietin-1 immobilized 316L stainless steel

An angiopoietin-1 functionalized surface was establishedviapolydopamine coating and regulated HUVECs survival, proliferation and function.

Adenovirus-delivered angiopoietin-1 suppresses NF-κB and p38 MAPK and attenuates inflammatory responses in phosgene-induced acute lung injury

Animals exposed to phosgene (Psg) result in acute lung injury (ALI). We have recently reported that angiopoietin-1 (Ang1) reduces inflammation and vascular hyperpermeability in ALI animals. In this study, we examined whether the beneficial effects of adenovirus-delivered Ang1 (Ad/Ang1) on inflammatory responses in Psg-induced ALI rats are due to the suppression of the nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) pathways, which play crucial roles in inflammatory responses in ALI. We demonstrated that Psg increased Ang2 and inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-4 (IL-4), IL-6, IL-8, and IL-10, in the serum and bronchoalveolar lavage fluid of ALI rats, determined by ELISA. Ang1 inhibits pro-inflammatory mediators (TNF-α, IL-6 and IL-8) and has no effect on anti-inflammatory mediators (IL-4 and IL-10). Furthermore, the inhibitory action of Ang1 was mediated by the suppression of the NF-κB and p38 MAPK pathways, leading to the attenuation of inflammatory responses of ALI. Thus, Ad/Ang1 may provide a useful tool for the effective treatment in Psg-induced ALI.