Exosomal MicroRNA-328 from Bone Marrow Mesenchymal Stem Cells (BMSCs) Alleviates Acute Lung Injury Through Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase (MAPK/ERK) Pathway

To elucidate the communication between exosomes (exo) derived from BMSCs and injured lung cells. BMSC-exo was isolated and characterized. Lung epithelial cells A549 were incubated with BMSC-exo, and treated by LPS to induce cell damage. CCK-8 assay was carried out to test cell proliferation, flow cytometry was adopted to analyze cell apoptosis, and RT-qPCR as well as Western blot analysis were selected to assess expression of apoptosis- and anti-apoptosis related proteins. Functional experiment was performed to identify the role of microRNA (miRNA)-328 in lung injury. LPS treatment significantly inhibited the viability of A549 cells, induced apoptosis of A549 cells by increasing Bax and casepase-3 levels and reducing Bcl-2 expression, whilst declined expression of miR-328 and suppressed the phosphorylation activation of the MAPK/ERK pathway. Meanwhile, the amount of IL-6, IL-1β and TNF-α were elevated in injured cells, but, the presence of BMSC-exo eliminated the elevation of the contents. Importantly, treatment with BMSC-exo increased miR-328 expression, activated MAPK MAPK/ERK pathway, inhibited apoptosis, and enhanced cell proliferation. However, the effect of BMSC-exo was attenuated when the cells were silenced for miR-328 expression. Collectively, BMSC-exo enriched miR-328 could relieve acute lung injury through MAPK/ERK pathway.

Activated Platelets Autocrine 5-Hydroxytryptophan Aggravates Sepsis-Induced Acute Lung Injury by Promoting Neutrophils Extracellular Traps Formation

Excessive neutrophil extracellular trap (NET) formation is an important contributor to sepsis-induced acute lung injury (ALI). Recent reports indicate that platelets can induce neutrophil extracellular trap formation. However, the specific mechanism remains unclear. Tph1 gene, which encodes the rate-limiting enzyme for peripheral 5-hydroxytryptophan (5-HT) synthesis, was knocked out in mice to simulate peripheral 5-HT deficiency. Cecal ligation and puncture (CLP) surgery was performed to induce sepsis. We found that peripheral 5-HT deficiency reduced NET formation in lung tissues, alleviated sepsis-induced lung inflammatory injury, and reduced the mortality rate of CLP mice. In addition, peripheral 5-HT deficiency was shown to reduce the accumulation of platelets and NETs in the lung of septic mice. We found that platelets from wild-type (WT), but not Tph1 knockout (Tph1−/−), mice promote lipopolysaccharide (LPS)-induced NET formation. Exogenous 5-HT intervention increased LPS-induced NET formation when Tph1−/− platelets were co-cultured with WT neutrophils. Therefore, our study uncovers a mechanism by which peripheral 5-HT aggravated sepsis-induced ALI by promoting NET formation in the lung of septic mice.

TGF-β-R2 is required for HBP induced acute lung injury and vascular leakage for TGF-[beta]/Smad/Rho signaling pathway activation

Heparin-binding protein (HBP), as a granule protein secreted by polymorphonuclear neutrophils (PMNs) participates in the pathophysiological process of sepsis. It has been reported that HBP is a biomarker of sepsis, which is related to the severity of septic shock and organ dysfunction. HBP binds to vascular endothelial cells as one of the primary target sites. However, it is still unclear whether HBP-binding protein receptors exist on the surface of ECs. The effect of HBP on vascular permeability in sepsis and its mechanism needs to be explored. We conducted in vivo and in vitro study. We demonstrated that HBP bound to transforming growth factor-β receptor type 2 (TGF-β-R2) as a ligand. GST pull-down analysis reveals that HBP mainly interacts with the extracellular domain of TGF-β-R2. HBP induced acute lung injury (ALI) and vascular leakage via activation of TGF-β/SMAD2/3 signaling pathway. Permeability assay suggests TGF-β-R2 is necessary for HBP-induced increased permeability. We also defined the role of HBP and its potential membrane receptor TGF-β-R2 in the blood-gas barrier in the pathogenesis of HBP-related ALI.

Lung protective effect of Punicalagin on LPS-induced acute lung injury in mice

Background: Punicalagin (Pun) is one of the main bioactive compounds in pomegranate peel, it possesses many properties, including antioxidant, anti-inflammation, and immunosuppressive activities. The study was aimed to investigate the protective effect and mechanisms of Pun on lipopolysaccharide (LPS) induced acute lung injury (ALI) in mice. Methods and Results: Forty-eight BALB/c male mice were used to establish ALI by intratracheal-instilled 2.4 mg/kg LPS, the mice were randomly divided into model and Pun (10, 20, 40 mg/kg) groups. The other twelve mice were intratracheal-instilled same volume of water as control. After 2 h of receiving LPS, mice were administrated drug through intraperitoneal injection. Lung index, histopathological changes, white blood cells and biomarkers in bronchoalveolar lavage fluid (BALF) were analyzed. The protein expression of total and phosphor p65, IκBα, ERK1/2, JNK and p38 in lung tissue was detected. The result showed that Pun could reduce the lung index and wet/dry weight ratio, improve lung histopathological injury. In addition, Pun decreased the inflammation cells and regulated the biomarkers in BALF. Furthermore, Pun dose-dependently reduced the phosphor protein levels of p65, IκBα, ERK1/2, JNK and p38 in lung tissue, which exhibited that the effect of Pun related to MAPKs pathway. More importantly, there is no toxicity was observed in the acute toxicity study of Pun. Conclusion: Pun improves LPS-induced ALI mainly through its anti-inflammatory properties, which is associated with NF-κB and MAPKs signaling pathways. The study implied that Pun maybe a potent agent against ALI in future clinic.

Methionine Restriction Prevents Lipopolysaccharide-Induced Acute Lung Injury via Modulating CSE/H2S Pathway

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) result in high mortality, whereas effective treatments are limited. Methionine restriction (MR) has been reported to offer various benefits against multiple pathological processes of organ injuries. However, it remains unknown whether MR has any potential therapeutic value for ALI/ARDS. The current study was set to investigate the therapeutic potential of MR on lipopolysaccharide (LPS)-induced ALI and its underlying mechanisms. We found that MR attenuated LPS-induced pulmonary edema, hemorrhage, atelectasis, and alveolar epithelial cell injuries in mice. MR upregulated cystathionine-gamma-lyase (CSE) expression and enhanced the production of hydrogen sulfide (H2S). MR also inhibited the activation of Toll-like receptors 4 (TLR4)/NF-κB/NOD-like receptor protein 3 (NLRP3), then reduced IL-1β, IL-6, and TNF-α release and immune cell infiltration. Moreover, the protective effects of MR on LPS-induced ALI were abrogated by inhibiting CSE, whereas exogenous H2S treatment alone mimicked the protective effects of MR in Cse−/− mice after LPS administration. In conclusion, our findings showed that MR attenuated LPS-induced lung injury through CSE and H2S modulation. This work suggests that developing MR towards clinical use for ALI/ARDS patients may be a valuable strategy.

LTB4 Promotes Acute Lung Injury via Upregulating the PLCε-1/TLR4/NF-κB Pathway in One-Lung Ventilation

Background. Mechanical ventilation (MV) can provoke acute lung injury (ALI) by increasing inflammation activation and disrupting the barrier in lung tissues even causing death. However, the inflammation-related molecules and pathways in MV-induced ALI remain largely unknown. Hence, the purposes of this study are to examine the role and mechanism of a novel inflammation-related molecule, leukotriene B4 (LTB4), in ALI. Methods. The functions of LTB4 in one-lung ventilation (OLV) model were detected by the loss-of-function experiments. H&E staining was used to examine the pathologic changes of lung tissues. Functionally, PLCε-1 knockdown and Toll-like receptor 4 (TLR4)/NF-κB pathway inhibitor were used to detect the regulatory effects of LTB4 on the phospholipase Cε (PLCε-1)/TLR4/nuclear factor-kappa B (NF-κB) pathway. The levels of genes and proteins were determined by RT-qPCR and western blotting assay. The levels of inflammation cytokines and chemokines were measured by ELISA. Results. Here, we found LTA4H, leukotriene B (4) receptor 1 (BLT1), LTB4, and PLCε-1 upregulated in OLV rats and associated with inflammatory activation and lung permeability changes of lung tissues. Inhibition of LTB4 alleviated the OLV-induced ALI by inhibiting inflammatory activation and lung permeability changes of lung tissues. For mechanism analyses, LTB4 promoted OLV-induced ALI by activating the PLCε-1/TLR4/NF-κB pathway. Conclusion. LTB4 induced ALI in OLV rats by activating the PLCε-1/TLR4/NF-κB pathway. Our findings might supply a new potential therapeutic for OLV-induced ALI.

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.

Incidence Rate of ALI in COVID-19 Patients

Background: With the outbreak of COVID19, acute lung injury has been detected as the main etiology for intensive care admission and high mortality rate. Among the infected population, there is some percentage of those who tend to develop acute respiratory distress syndrome and respiratory failure. Thus, the intensivist and anesthesiologist must be aware of the of incidence rate of ARDS, risk factors, and try to take measures to reduce its incidence. To define the rate of incidence of acute lung injury and ARDS among COVID 19 patient. Methods: We performed a narrative review via searching in three databases PubMed, Google Scholar and Embase for all studies that mentioned the incidence of acute lung injury among infected patients with COVID19, manual searching also completed. All the selected reviews were limited to the English language and data also. Results: Five searches referred to the exact number of patients and the percentage rate of incidence of ARDS related to COVID 19 infection, other articles are merely reviews and case reports. Conclusion: Incidence of acute lung injury among COVID19 patient was highly reported, and some percentage of these cases tend to develop ARDS especially in those who have preexisting diseases and obesity.