Alveolar Epithelial Cell Damage Research Articles

Revisiting the role of MicroRNAs in the pathogenesis of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a prevalent chronic pulmonary fibrosis disease characterized by alveolar epithelial cell damage, fibroblast proliferation and activation, excessive extracellular matrix deposition, and abnormal epithelial-mesenchymal transition (EMT), resulting in tissue remodeling and irreversible structural distortion. The mortality rate of IPF is very high, with a median survival time of 2-3years after diagnosis. The exact cause of IPF remains unknown, but increasing evidence supports the central role of epigenetic changes, particularly microRNA (miRNA), in IPF. Approximately 10% of miRNAs in IPF lung tissue exhibit differential expression compared to normal lung tissue. Diverse miRNA phenotypes exert either a pro-fibrotic or anti-fibrotic influence on the progression of IPF. In the context of IPF, epigenetic factors such as DNA methylation and long non-coding RNAs (lncRNAs) regulate differentially expressed miRNAs, which in turn modulate various signaling pathways implicated in this process, including transforming growth factor-β1 (TGF-β1)/Smad, mitogen-activated protein kinase (MAPK), and phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) pathways. Therefore, this review presents the epidemiology of IPF, discusses the multifaceted regulatory roles of miRNAs in IPF, and explores the impact of miRNAs on IPF through various pathways, particularly the TGF-β1/Smad pathway and its constituent structures. Consequently, we investigate the potential for targeting miRNAs as a treatment for IPF, thereby contributing to advancements in IPF research.

SiTGF-β1 and pirfenidone contained Ionizable-Liposomal nanodrug for enhanced treatment of Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a challenging interstitial lung disease characterized by heterogeneous manifestations and significant mortality. Due to the relative complexity of IPF pathogenesis, currently approved clinical drugs mainly for anti-inflammatory or anti-fibrotic present limited disease containment and insufficient damage repair, falling far short of previous expectations. To address this limitation, we developed an ionizable liposome nanodrug (named as TPNPs) co-loaded with small interfering RNA targeting TGF-β1 (siTGF-β1) and pirfenidone (PFD) for enhanced IPF therapy. The siTGF-β1 (blocking TGF-β signaling pathway) and PFD were carefully selected and integrated in consideration of their crucial roles in endothelial mesenchymal transition, alveolar epithelial cell apoptosis, and fibroblast differentiation and migration, which are closely related to IPF development. As a result, TPNPs exhibited synergistic enhancement effects against the damage of alveolar epithelial cells and fibroblasts in vitro. Notably, repeated administration of TPNPs mitigated the injury to alveolar epithelium, inhibited the excessive accumulation of extracellular matrix (ECM), and alleviated the destruction of lung, thereby synergistically ameliorating the lung function in a bleomycin (BLM)-induced murine model. This work provides a promising therapeutic strategy that combines nucleic acid with small molecule for enhanced treatment of IPF.

Biomechanical Properties and Cellular Responses in Pulmonary Fibrosis.

Pulmonary fibrosis is a fatal lung disease affecting approximately 5 million people worldwide, with a 5-year survival rate of less than 50%. Currently, the only available treatments are palliative care and lung transplantation, as there is no curative drug for this condition. The disease involves the excessive synthesis of the extracellular matrix (ECM) due to alveolar epithelial cell damage, leading to scarring and stiffening of the lung tissue and ultimately causing respiratory failure. Although multiple factors contribute to the disease, the exact causes remain unclear. The mechanical properties of lung tissue, including elasticity, viscoelasticity, and surface tension, are not only affected by fibrosis but also contribute to its progression. This paper reviews the alteration in these mechanical properties as pulmonary fibrosis progresses and how cells in the lung, including alveolar epithelial cells, fibroblasts, and macrophages, respond to these changes, contributing to disease exacerbation. Furthermore, it highlights the importance of developing advanced in vitro models, based on hydrogels and 3D bioprinting, which can accurately replicate the mechanical and structural properties of fibrotic lungs and are conducive to studying the effects of mechanical stimuli on cellular responses. This review aims to summarize the current understanding of the interaction between the progression of pulmonary fibrosis and the alterations in mechanical properties, which could aid in the development of novel therapeutic strategies for the disease.

KLF13 Attenuates Lipopolysaccharide-Induced Alveolar Epithelial Cell Damage by Regulating Mitochondrial Quality Control via Binding PGC-1α.

Sepsis is a clinically life-threatening syndrome, and acute lung injury is the earliest and most serious complication. We aimed to assess the role of kruppel-like factor 13 (KLF13) in lipopolysaccharide (LPS)-induced human alveolar type II epithelial cell damage and to reveal the possible mechanism related to peroxisome proliferator-activated receptor-γ co-activator 1-α (PGC-1α). In LPS-treated A549 cells with or without KLF13 overexpression or PGC-1α knockdown, cell viability was measured by a cell counting kit-8 assay. Enzyme-linked immunosorbent assay kits detected the levels of inflammatory factors, and terminal deoxynucleotidyl transferase dUTP nick-end labeling staining measured cell apoptosis. Besides, mitochondrial reactive oxygen species (MitoSOX) and mitochondrial membrane potential were detected using MitoSOX red- and JC-1 staining. Expression of proteins related to mitochondrial quality control (MQC) was evaluated by western blot. Co-immunoprecipitation (Co-IP) assay was used to analyze the interaction between KLF13 and PGC-1α. Results indicated that KLF13 was highly expressed in LPS-treated A549 cells. KLF13 upregulation elevated the viability and reduced the levels of inflammatory factors in A549 cells exposed to LPS. Moreover, KLF13 gain-of-function inhibited LPS-induced apoptosis of A549 cells, accompanied by upregulated BCL2 expression and downregulated Bax and cleaved caspase3 expression. Furthermore, MQC was improved by KLF13 overexpression, as evidenced by decreased MitoSOX, JC-1 monomers and increased JC-1 aggregates, coupled with the changes of proteins related to MQC. In addition, Co-IP assay confirmed the interaction between KLF13 and PGC-1α. PGC-1α deficiency restored the impacts of KLF13 upregulation on the inflammation, apoptosis, and MQC in LPS-treated A549 cells. In conclusion, KLF13 attenuated LPS-induced alveolar epithelial cell inflammation and apoptosis by regulating MQC via binding PGC-1α.

Modulating in vitro lung fibroblast activation via senolysis of senescent human alveolar epithelial cells.

Idiopathic pulmonary fibrosis (IPF) is an age-related disease with poor prognosis and limited therapeutic options. Activation of lung fibroblasts and differentiation to myofibroblasts are the principal effectors of disease pathology, but damage and senescence of alveolar epithelial cells, specifically type II (ATII) cells, has recently been identified as a potential trigger event for the progressive disease cycle. Targeting ATII senescence and the senescence-associated secretory phenotype (SASP) is an attractive therapeutic strategy; however, translatable primary human cell models that enable mechanistic studies and drug development are lacking. Here, we describe a novel system of conditioned medium (CM) transfer from bleomycin-induced senescent primary alveolar epithelial cells (AEC) onto normal human lung fibroblasts (NHLF) that demonstrates an enhanced fibrotic transcriptional and secretory phenotype compared to non-senescent AEC CM treatment or direct bleomycin damage of the NHLFs. In this system, the bleomycin-treated AECs exhibit classical hallmarks of cellular senescence, including SASP and a gene expression profile that resembles aberrant epithelial cells of the IPF lung. Fibroblast activation by CM transfer is attenuated by pre-treatment of senescent AECs with the senolytic Navitoclax and AD80, but not with the standard of care agent Nintedanib or senomorphic JAK-targeting drugs (e.g., ABT-317, ruxolitinib). This model provides a relevant human system for profiling novel senescence-targeting therapeutics for IPF drug development.

Glutamine maintains the stability of alveolar structure and function after lung transplantation by inhibiting autophagy

Excessive autophagy may lead to degradation and damage of alveolar epithelial cells after lung transplantation, eventually leading to alveolar epithelial cell loss, affecting the structural integrity and function of alveoli. Glutamine (Gln), a nutritional supplement, regulates autophagy through multiple signaling pathways. In this study, we explored the protective role of Gln on alveolar epithelial cells by inhibiting autophagy. In vivo, a rat orthotopic lung transplant model was carried out to evaluate the therapeutic effect of glutamine. Ischemia/reperfusion (I/R) induced alveolar collapse, edema, epithelial cell apoptosis, and inflammation, which led to a reduction of alveolar physiological function, such as an increase in peak airway pressure, and a decrease in lung compliance and oxygenation index. In comparison, Gln preserved alveolar structure and function by reducing alveolar apoptosis, inflammation, and edema. In vitro, a hypoxia/reoxygenation (H/R) cell model was performed to simulate IR injury on mouse lung epithelial (MLE) cells and human lung bronchus epithelial (Beas-2B) cells. H/R impaired the proliferation of epithelial cells and triggered cell apoptosis. In contrast, Gln normalized cell proliferation and suppressed I/R-induced cell apoptosis. The activation of mTOR and the downregulation of autophagy-related proteins (LC3, Atg5, Beclin1) were observed in Gln-treated lung tissues and alveolar epithelial cells. Both in vivo and in vitro, rapamycin, a classical mTOR inhibitor, reversed the beneficial effects of Gln on alveolar structure and function. Taken together, Glnpreserved alveolar structure and function after lung transplantation by inhibiting autophagy.

The Mitochondrial-Derived Peptide MOTS-c Alleviates Radiation Pneumonitis via an Nrf2-Dependent Mechanism.

Radiation pneumonitis (RP) is a prevalent and fatal complication of thoracic radiotherapy due to the lack of effective treatment options. RP primarily arises from mitochondrial injury in lung epithelial cells. The mitochondrial-derived peptide MOTS-c has demonstrated protective effects against various diseases by mitigating mitochondrial injury. C57BL/6 mice were exposed to 20 Gy of lung irradiation (IR) and received daily intraperitoneal injections of MOTS-c for 2 weeks. MOTS-c significantly ameliorated lung tissue damage, inflammation, and oxidative stress caused by radiation. Meanwhile, MOTS-c reversed the apoptosis and mitochondrial damage of alveolar epithelial cells in RP mice. Furthermore, MOTS-c significantly inhibited oxidative stress and mitochondrial damage in MLE-12 cells and primary mouse lung epithelial cells. Mechanistically, MOTS-c increased the nuclear factor erythroid 2-related factor (Nrf2) level and promoted its nuclear translocation. Notably, Nrf2 deficiency abolished the protective function of MOTS-c in mice with RP. In conclusion, MOTS-c alleviates RP by protecting mitochondrial function through an Nrf2-dependent mechanism, indicating that MOTS-c may be a novel potential protective agent against RP.

Effects of nanoparticles on sensitivity to injury and role of autophagy in alveolar epithelial cells

Autophagy, a housekeeping mechanism, is crucial in the maintenance of normal cellular function. Although the involvement of autophagic processes is recognized in numerous diseases, it is unknown how cellular homeostasis might be affected by alterations in available autophagic activity and/or autophagic capacity. In this study, we measured autophagic flux and cellular damage in primary cultured monolayers of rat alveolar epithelial cells (AEC) exposed separately and sequentially to two different autophagy inducers. Rat AEC monolayers were exposed apically for 24 hrs to (1) polystyrene nanoparticles (PNP, 20 nm, carboxylated, near-infrared dye-labeled), (2) tunicamycin (TN, a disruptor of protein synthesis and inducer of the unfolded protein response, at 1-15 μg/mL), or (3) TN (1-15 μg/mL) after 12 hrs of PNP pre-incubation. Release of the cytoplasmic enzyme lactate dehydrogenase (LDH) was used as an indicator of cellular damage and quantified by an LDH assay from Dojindo (Rockville, MD). Autophagic flux was assessed by live cell imaging using confocal microscopy and 0.1 μM DAPRed (Dojindo; Rockville, MD) in the presence (for 1 hr) and absence of 40 μM chloroquine. Serial z sections were collected over the entire cell volume of live single cells to detect DAPRed (autophagosome) fluorescence. PNP were taken up into AEC, where their cytosolic presence induced a gradually increased autophagic flux, reaching a steady state at ~10-24 hrs. When AEC were exposed to TN alone for 24 hrs, autophagy was also activated. Cellular damage in the presence of TN, determined by increased LDH release, revealed dose-dependent injury with LD50 of 8.12 μg/mL over 24 hr TN exposure. When AEC were pre-exposed to PNP for 12 hrs and subsequently exposed to TN, increased LDH release was seen with LD50 of 3.95 μg/mL. In summary, the intracellular presence of PNP taken up from apical fluid of rat AEC monolayers activated autophagy. When cellular protein synthesis was disrupted with TN alone, autophagy was also activated. Furthermore, TN induced dose-dependent cellular damage in AEC. However, after pre-exposure to PNP, TN induced greater cellular damage observed as increased LDH release. These results suggest that autophagic capacity is limited and that pre-induction of autophagy by inhaled PNP makes AEC more susceptible to secondary injury by TN. These findings are consistent with the hypothesis that environmental stressors (e.g., ambient air nanoparticles) exert their harmful effects, at least in part, by reducing available autophagic activity/capacity, thereby causing nanoparticle-exposed AEC to be more susceptible to secondary injury. Funding: NIH; WRMPPF. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Bleomycin induces senescence and repression of DNA repair via downregulation of Rad51

BackgroundBleomycin, a potent antitumor agent, is limited in clinical use due to the potential for fatal pulmonary toxicity. The accelerated DNA damage and senescence in alveolar epithelial cells (AECs) is considered a key factor in the development of lung pathology. Understanding the mechanisms for bleomycin-induced lung injury is crucial for mitigating its adverse effects.MethodsHuman lung epithelial (A549) cells were exposed to bleomycin and subsequently assessed for cellular senescence, DNA damage, and double-strand break (DSB) repair. The impact of Rad51 overexpression on DSB repair and senescence in AECs was evaluated in vitro. Additionally, bleomycin was intratracheally administered in C57BL/6 mice to establish a pulmonary fibrosis model.ResultsBleomycin exposure induced dose- and time-dependent accumulation of senescence hallmarks and DNA lesions in AECs. These effects are probably due to the inhibition of Rad51 expression, consequently suppressing homologous recombination (HR) repair. Mechanistic studies revealed that bleomycin-mediated transcriptional inhibition of Rad51 might primarily result from E2F1 depletion. Furthermore, the genetic supplement of Rad51 substantially mitigated bleomycin-mediated effects on DSB repair and senescence in AECs. Notably, decreased Rad51 expression was also observed in the bleomycin‐induced mouse pulmonary fibrosis model.ConclusionsOur works suggest that the inhibition of Rad51 plays a pivotal role in bleomycin-induced AECs senescence and lung injury, offering potential strategies to alleviate the pulmonary toxicity of bleomycin.

Serum VEGF-A levels on admission in COVID-19 patients correlate with SP-D and neutrophils, reflecting disease severity: A prospective study

Background and objectiveThe coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in significant global morbidity and mortality. This study aimed to investigate the clinical significance of serum vascular endothelial growth factor A (VEGF-A) in COVID-19 patients and its association with disease severity and pulmonary injury. MethodsWe prospectively collected data from 71 hospitalized COVID-19 patients between June 2020 and January 2021. Patients were classified as either mild or severe based on their oxygen requirements during hospitalization. Serum VEGF-A levels were measured using an ELISA kit. ResultsIn comparison to mild cases, significantly elevated serum VEGF-A levels were observed in severe COVID-19 patients. Furthermore, VEGF-A levels exhibited a positive correlation with white blood cell count, neutrophil count, and lymphocyte count. Notably, serum surfactant protein-D (SP-D), an indicator of alveolar epithelial cell damage, was significantly higher in patients with elevated VEGF-A levels. ConclusionThese results suggest that elevated serum VEGF-A levels could serve as a prognostic biomarker for COVID-19 as it is indicative of alveolar epithelial cell injury caused by SARS-CoV-2 infection. Additionally, we observed a correlation between VEGF-A and neutrophil activation, which plays a role in the immune response during endothelial cell injury, indicating a potential involvement of angiogenesis in disease progression. Further research is needed to elucidate the underlying mechanisms of VEGF-A elevation in COVID-19.

The Role of MicroRNAs in Mesenchymal Stem Cell-Based Modulation of Pulmonary Fibrosis.

Pulmonary fibrosis is a complex and multifactorial condition that involves a cascade of events, including lung injury, damage of alveolar epithelial cells (AECs), generation of immune cell-driven inflammation, and activation of fibroblasts and their differentiation into myofibroblasts, resulting in the excessive production and deposition of collagen and progressive scarring and fibrosis of the lung tissue. As lung fibrosis advances, the scarring and stiffening of lung tissue can significantly hinder the exchange of oxygen and carbon dioxide, potentially leading to respiratory failure that can be life-threatening. Anti-inflammatory and immunosuppressive drugs are used to slow down the progression of the disease, manage symptoms, and enhance the patient's quality of life. However, prolonged immunosuppression could increase the susceptibility to severe bacterial, viral, or fungal pneumonia in lung-transplant recipients. Therefore, there is an urgent need for new therapeutic agents that can effectively reduce lung inflammation and fibrosis without compromising the protective immune response in patients with severe lung fibrosis. Results obtained in recently published studies demonstrated that mesenchymal stem/stromal cell-derived microRNAs (MSC-miRNAs) could attenuate detrimental immune response in injured lungs and prevent progression of lung fibrosis. Through the post-transcriptional regulation of target mRNA, MSC-miRNAs modulate protein synthesis and affect viability, proliferation, and cytokine production in AECs, fibroblasts, and lung-infiltrated immune cells. In order to delineate molecular mechanisms responsible for beneficial effects of MSC-miRNAs in the treatment of lung fibrosis, in this review article, we summarized current knowledge related to anti-fibrotic and anti-inflammatory pathways elicited in immune cells, AECs, and myofibroblasts by MSC-miRNAs.

Vitamin D3 improved hypoxia-induced lung injury by inhibiting the complement and coagulation cascade and autophagy pathway

BackgroundPulmonary metabolic dysfunction can cause lung tissue injury. There is still no ideal drug to protect against hypoxia-induced lung injury, therefore, the development of new drugs to prevent and treat hypoxia-induced lung injury is urgently needed. We aimed to explore the ameliorative effects and molecular mechanisms of vitamin D3 (VD3) on hypoxia-induced lung tissue injury.MethodsSprague–Dawley (SD) rats were randomly divided into three groups: normoxia, hypoxia, and hypoxia + VD3. The rat model of hypoxia was established by placing the rats in a hypobaric chamber. The degree of lung injury was determined using hematoxylin and eosin (H&E) staining, lung water content, and lung permeability index. Transcriptome data were subjected to differential gene expression and pathway analyses. In vitro, type II alveolar epithelial cells were co-cultured with hepatocytes and then exposed to hypoxic conditions for 24 h. For VD3 treatment, the cells were treated with low and high concentrations of VD3.ResultsTranscriptome and KEGG analyses revealed that VD3 affects the complement and coagulation cascade pathways in hypoxia-induced rats, and the genes enriched in this pathway were Fgb/Fga/LOC100910418. Hypoxia can cause increases in lung edema, inflammation, and lung permeability disruption, which are attenuated by VD3 treatment. VD3 weakened the complement and coagulation cascade in the lung and liver of hypoxia-induced rats, characterized by lower expression of fibrinogen alpha chain (Fga), fibrinogen beta chain (Fgb), protease-activated receptor 1 (PAR1), protease-activated receptor 3 (PAR3), protease-activated receptor 4 (PAR4), complement (C) 3, C3a, and C5. In addition, VD3 improved hypoxic-induced type II alveolar epithelial cell damage and inflammation by inhibiting the complement and coagulation cascades. Furthermore, VD3 inhibited hypoxia-induced autophagy in vivo and in vitro, which was abolished by the mitophagy inducer, carbonyl cyanide-m-chlorophenylhydrazone (CCCP).ConclusionVD3 alleviated hypoxia-induced pulmonary edema by inhibiting the complement and coagulation cascades and autophagy pathways.

Role of Lipopolysaccharides in the Inflammation and Pyroptosis of Alveolar Epithelial Cells in Acute Lung Injury and Acute Respiratory Distress Syndrome.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) represent a spectrum of common critical respiratory conditions characterized by damage and death of alveolar epithelial cells (AECs). Pyroptosis is a form of programmed cell death with inflammatory characteristics, and activation of pyroptosis markers has been observed in AECs of patients with ALI/ARDS. Lipopolysaccharides (LPS) possess strong pro-inflammatory effects and are a crucial pathological factor leading to ALI in patients and animals. In LPS-induced ALI models, AECs undergo pyroptosis. However, physiologically and pathologically relevant concentrations of LPS lead to minor effects on AEC cell viability and minimal induction of cytokine release in vitro and do not induce classical pyroptosis. Nevertheless, LPS can enter the cytoplasm directly and induce non-classical pyroptosis in AECs when assisted by extracellular vesicles from bacteria, HMGB1, and pathogens. In this review, we have explored the effects of LPS on AECs concerning inflammation, cell viability, and pyroptosis, analyzing key factors that influence LPS actions. Notably, we highlight the intricate response of AECs to LPS within the framework of ALI and ARDS, emphasizing the variable induction of pyroptosis. Despite the minimal effects of LPS on AEC viability and cytokine release in vitro, LPS can induce non-classical pyroptosis under specific conditions, presenting potential pathways for therapeutic intervention. Collectively, understanding these mechanisms is crucial for the development of targeted treatments that mitigate the inflammatory responses in ALI/ARDS, thereby enhancing patient outcomes in these severe respiratory conditions.

Potential mechanisms of lung injury and repair after hexavalent chromium [Cr(VI)] aerosol whole-body dynamic exposure

Hexavalent chromium [Cr(VI)], known as "Top Hazardous Substances", poses a significant threat to the respiratory system. Nevertheless, the potential mechanisms of toxicity and the lung's repair ability after injury remain incompletely understood. In this study, Cr(VI) aerosol whole-body dynamic exposure system simulating real exposure scenarios of chromate workers was constructed to evaluate the lung injury and repair effects. Subsequently, miRNA sequencing, mRNA sequencing and metabolomics analyses on lung tissue were performed to explore the underlying mechanisms. Our results revealed that Cr(VI) exposure led to an increase in lactic dehydrogenase activity and a time-dependent decline in lung function. Notably, after 13 w of Cr(VI) exposure, alveolar hemorrhage, thickening of alveolar walls, emphysema-like changes, mitochondrial damage of alveolar epithelial cells and macrophage polarization changes were observed. Remarkably, a two-week repair intervention effectively ameliorated lung function decline and pulmonary injury. Furthermore, significant disruptions in the expressions of miRNAs and mRNAs involved in oxidative phosphorylation, glycerophospholipid metabolism and inflammatory signaling pathways were found. The two-week repair period resulted in the reversal of expression of oxidative phosphorylation related genes, and inhibited the inflammatory signaling pathways. This study concluded that the inhibition of the mitochondrial oxidative phosphorylation pathway and the subsequent enhancement of inflammatory response might be key mechanisms underlying Cr(VI) pulmonary toxicity, and timely cessation of exposure could effectively alleviate the pulmonary injury. These findings shed light on the potential mechanisms of Cr(VI) toxicity and provide crucial insights into the health protection for occupational populations exposed to Cr(VI).

Acute respiratory distress syndrome heterogeneity and the septic ARDS subgroup.

Acute respiratory distress syndrome (ARDS) is an acute diffuse inflammatory lung injury characterized by the damage of alveolar epithelial cells and pulmonary capillary endothelial cells. It is mainly manifested by non-cardiogenic pulmonary edema, resulting from intrapulmonary and extrapulmonary risk factors. ARDS is often accompanied by immune system disturbance, both locally in the lungs and systemically. As a common heterogeneous disease in critical care medicine, researchers are often faced with the failure of clinical trials. Latent class analysis had been used to compensate for poor outcomes and found that targeted treatment after subgrouping contribute to ARDS therapy. The subphenotype of ARDS caused by sepsis has garnered attention due to its refractory nature and detrimental consequences. Sepsis stands as the most predominant extrapulmonary cause of ARDS, accounting for approximately 32% of ARDS cases. Studies indicate that sepsis-induced ARDS tends to be more severe than ARDS caused by other factors, leading to poorer prognosis and higher mortality rate. This comprehensive review delves into the immunological mechanisms of sepsis-ARDS, the heterogeneity of ARDS and existing research on targeted treatments, aiming to providing mechanism understanding and exploring ideas for accurate treatment of ARDS or sepsis-ARDS.

Pathological and immunohistochemical findings of lungs, heart, liver, and kidneys, and unexpected findings of fungi and parasites in lungs of deceased COVID-19 patients: A case series

Objective: To define histopathologic and immunohistochemical features of the lungs, heart, liver, and kidneys in patients who died from coronavirus disease 2019 (COVID-19), and to determine the presence of SARS-CoV-2 in all tissues, as well as the presence of fungi and parasites in lung tissues. Methods: This retrospective case study was conducted in the intensive care units of Dokuz Eylül University Hospital, and patients (≥18 years) who died due to COVID-19 between October 2020 and April 2021 were included. The biopsy samples of the patient's lung, heart, liver, and kidney tissues were studied. Results: In the study, we enrolled 12 patients (mean age: 70 years; 50% male). Alveolar epithelial cell damage and diffuse alveolar damage were predominant in lung tissues. Lobular lymphocyte infiltration, centrilobular sinusoidal dilatation, and microvesicular steatosis in the liver, together with pigmented cast, non-isometric vacuolar degeneration, and capillary plugging in the kidneys, were commonly found among the patients. SARS-CoV-2 nucleocapsid protein antibodies were detected in three lung and two kidney tissues, and so did angiotensin-converting enzyme 2 receptor positivity in one lung and more than half of the kidney tissues. The RT-PCR tests were positive in three lungs and one kidney tissue. After DNA isolation from lung tissues, Pneumocystis jirovecii was detected in nine patients, Aspergillus fumigatus in two, Microsporidia in three, and Cryptosporidium in two. Conclusions: SARS-CoV-2 is a multisystemic disease. Fungi and parasites should be investigated in critically ill COVID-19 patients prescribed corticosteroids.

Attenuation of PM2.5-induced alveolar epithelial cells and lung injury through regulation of mitochondrial fission and fusion

BackgroundExposure to particulate matter (PM) with an aerodynamic diameter less than 2.5 μm (PM2.5) is a risk factor for developing pulmonary diseases and the worsening of ongoing disease. Mitochondrial fission and fusion are essential processes underlying mitochondrial homeostasis in health and disease. We examined the role of mitochondrial fission and fusion in PM2.5-induced alveolar epithelial cell damage and lung injury. Key genes in these processes include dystrophin-related protein 1 (DRP1) and optic atrophy 1 (OPA1) respectively.MethodsAlveolar epithelial (A549) cells were treated with PM2.5 (32 µg/ml) in the presence and absence of Mdivi-1 (10µM, a DRP1 inhibitor) or BGP-15 (10µM, an OPA1 activator). Results were validated using DRP1-knockdown (KD) and OPA1-overexpression (OE). Mice were injected intraperitoneally with Mdivi-1 (20 mg/kg), BGP-15 (20 mg/kg) or distilled water (control) one hour before intranasal instillation of PM2.5 (7.8 mg/kg) or distilled water for two consecutive days.ResultsPM2.5 exposure of A549 cells caused oxidative stress, enhanced inflammation, necroptosis, mitophagy and mitochondrial dysfunction indicated by abnormal mitochondrial morphology, decreased mitochondrial membrane potential (ΔΨm), reduced mitochondrial respiration and disrupted mitochondrial fission and fusion. Regulating mitochondrial fission and fusion pharmacologically using Mdivi-1 and BGP-15 and genetically using DRP1-KD and OPA1-OE prevented PM2.5-induced celluar damage in A549 cells. Mdivi-1 and BGP-15 attenuated PM2.5-induced acute lung injury in mice.ConclusionIncreased mitochondrial fission and decreased mitochondrial fusion may underlie PM2.5-induced alveolar epithelial cell damage in vitro and lung injury in vivo.

Long non-coding RNA PFI inhibits apoptosis of alveolar epithelial cells to alleviate lung injury via miR-328-3p/Creb1 axis

Acute lung injury (ALI), a common clinical type of critical illness, is an acute hypoxic respiratory insufficiency caused by the damage of alveolar epithelial cells and capillary endothelial cells. In a previous study, we reported a novel lncRNA, lncRNA PFI, which could protect against pulmonary fibrosis in pulmonary fibroblasts. The present study demonstrated that lncRNA PFI was downregulated in alveolar epithelial cell of mice injury lung tissues, and further investigated the role of lncRNA PFI in regulating inflammation-induced alveolar epithelial cell apoptosis. Overexpression of lncRNA PFI could partially abrogated bleomycin induced type II AECs injured. Subsequently, bioinformatic prediction revealed that lncRNA PFI might directly bind to miR-328-3p, and further AGO-2 RNA binding protein immunoprecipitation (RIP) assay confirmed their binding relationship. Furthermore, miR-328-3p promoted apoptosis in MLE-12 cells by limiting the activation of the Creb1, a protein correlated with cell apoptosis, whereas AMO-328-3p ablated the pro-apoptosis effect of silencing lncRNA PFI in MLE-12 cells. While miR-328-3p could also ablate the function of lncRNA PFI in bleomycin treated human lung epithelial cells. Enhanced expression of lncRNA PFI reversed the LPS-induced lung injury in mice. Overall, these data reveal that lncRNA PFI mitigated acute lung injury through miR-328-3p/Creb1 pathway in alveolar epithelial cells.

SIRT3 improves alveolar epithelial cell damage caused by bronchopulmonary dysplasia through deacetylation of FOXO1.

Bronchopulmonary dysplasia (BPD) is a serious and long-term lung condition commonly observed in premature babies. Sirtuin 3 (SIRT3) has been reported to reduce pulmonary injury and pulmonary fibrosis. The present study investigated the specific role of SIRT3 in BPD by establishing hyperoxia-induced BPD rat and cell models. Hematoxylin and eosin staining was used to observe pathological changes in lung tissues. The expression levels of SIRT3 and forkhead box protein O1 (FOXO1), as well as its acetylation levels, were detected in hyperoxia-induced lung tissues and cells by Western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Levels of reactive oxygen species, superoxide dismutase, and malondialdehyde were assessed by using biochemical kits. Following SIRT3 overexpression, the levels of inflammatory cytokines were assessed by RT-qPCR. Apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nickend labeling (TUNEL) and Western blot analysis. Upon FOXO1 knockout, cell inflammation, oxidative stress and apoptosis were evaluated again. Compared to the control group, the SIRT3 and FOXO1 expression levels were decreased and the FOXO1 acetylation levels were increased in hyperoxia-induced lung tissues and cells. In addition, SIRT3 reduced hyperoxia-induced inflammation, oxidative stress, and apoptosis in A549 cells, and inhibited FOXO1 acetylation to activate FOXO1. However, FOXO1 knockdown reversed the effects of SIRT3 overexpression in hyperoxia-induced A549 cells. SIRT3 relieved alveolar epithelial cell damage caused by BPD via deacetylation of FOXO1, suggesting that SIRT3 could be a therapeutic target in BPD.

Necrostatin-1 Alleviates Diffuse Pulmonary Haemorrhage by Preventing the Release of NETs via Inhibiting NE/GSDMD Activation in Murine Lupus.

Diffuse alveolar haemorrhage (DAH) is a rapidly developing condition owing to a lack of effective treatment and resulting in a high mortality rate in systemic lupus erythematosus (SLE). Neutrophil extracellular traps (NETs) contain numerous antigens and proinflammatory substances that directly damage the vascular endothelium and aggravate vascular inflammation, which is considered an important pathogenic factor of DAH in SLE. Therefore, blocking the release of NETs from neutrophils is an important target for the treatment of DAH in SLE. In this study, we investigated whether the inhibition of neutrophils releasing NETs could relieve DAH in SLE. Necrostatin-1 (Nec-1), a small molecule, has been reported to inhibit the release of NETs by neutrophils. In vitro experiments revealed that Nec-1 inhibited alveolar epithelial cell damage by preventing the release of NETs. Furthermore, vivo studies showed that Nec-1 alleviated lupus pulmonary haemorrhage in mice by reducing lung pathology severity, body weight, and serum inflammatory cytokine levels. Mechanistically, Nec-1 prevented NET release by inhibiting neutrophil elastase (NE) activation and N-Gasdermin D (N-GSDMD) expression. Additionally, immunohistochemistry and immunofluorescence findings showed that Nec-1 decreased NE expression in the lung tissues of mice with lupus pulmonary haemorrhage. Thus, NETs released by neutrophils contributed to the pathogenesis of DAH in SLE, and Nec-1 showed protective effects by the inhibition of NET production via the reduction of NE activation and N-GSDMD expression.