Apoptosis in lung injury and remodeling

Meconium aspiration syndrome: from pathophysiology to treatment

Meconium aspiration syndrome (MAS) is a clinical condition characterized by respiratory distress in neonates born through meconium-stained amniotic fluid (MSAF). Despite advances in obstetric practices and perinatal care, MAS remains an important cause of morbidity and mortality in term and post-term newborns. Since the 1960s, there have been significant changes in the perinatal and postnatal management of infants born through MSAF. Routine endotracheal suctioning is no longer recommended in both vigorous and non-vigorous neonates with MSAF. Supportive care along with new treatments such as surfactant, inhaled nitric oxide, and high-frequency ventilation has significantly improved the outcome of MAS patients. However, determining the most appropriate approach for this condition continues to be a topic of debate. This review offers an updated overview of the epidemiology, etiopathogenesis, diagnosis, management, and prognosis of infants with MAS.

Unmasking the complex roles of hypocalcemia in cancer, COVID-19, and sepsis: Engineered nanodelivery and diagnosis

Calcium (Ca2+) homeostasis is essential for maintaining physiological processes in the body. Disruptions in Ca2+ signaling can lead to various pathological conditions including inflammation, fibrosis, impaired immune function, and accelerated senescence. Hypocalcemia, a common symptom in diseases such as acute respiratory distress syndrome (ARDS), cancer, septic shock, and COVID-19, can have both potential protective and detrimental effects. This article explores the multifaceted role of Ca2+ dysregulation in inflammation, fibrosis, impaired immune function, and accelerated senescence, contributing to disease severity. Targeting Ca2+ signaling pathways may provide opportunities to develop novel therapeutics for age-related diseases and combat viral infections. However, the role of Ca2+ in viral infections is complex, and evidence suggests that hypocalcemia may have a protective effect against certain viruses, while changes in Ca2+ homeostasis can influence susceptibility to viral infections. The effectiveness and safety of Ca2+ supplements in COVID-19 patients remain a subject of ongoing research and debate. Further investigations are needed to understand the intricate interplay between Ca2+ signaling and disease pathogenesis.

THE CRITICAL ROLE OF THE HISTONE MODIFICATION ENZYME SETDB2 IN THE PATHOGENESIS OF ACUTE RESPIRATORY DISTRESS SYNDROME

ABSTRACT

Introduction: Acute respiratory distress syndrome (ARDS) is a severe hypoxemic respiratory failure with a high in-hospital mortality. However, the molecular mechanisms underlying ARDS remain unclear. Recent findings have indicated that the onset of severe inflammatory diseases, such as sepsis, is regulated by epigenetic changes. We investigated the role of epigenetic changes in ARDS pathogenesis using mouse models and human samples. Methods: Acute respiratory distress syndrome was induced in a mouse model (C57BL/6 mice, myeloid cell or vascular endothelial cell [VEC]-specific SET domain bifurcated 2 [Setdb2]-deficient mice [Setdb2 ff Lyz2 Cre+ or Setdb2 ff Tie2 Cre+ ], and Cre - littermates) by intratracheal administration of lipopolysaccharide (LPS). Analyses were performed at 6 and 72 h after LPS administration. Sera and lung autopsy specimens from ARDS patients were examined. Results: In the murine ARDS model, we observed high expression of the histone modification enzyme SET domain bifurcated 2 ( Setdb2 ) in the lungs. In situ hybridization examination of the lungs revealed Setdb2 expression in macrophages and VECs. The histological score and albumin level of bronchoalveolar lavage fluid were significantly increased in Setdb2 ff Tie2 Cre+ mice following LPS administration compared with Setdb2 ff Tie2 Cre- mice, whereas there was no significant difference between the control and Setdb2 ff Lyz2 Cre+ mice. Apoptosis of VECs was enhanced in Setdb2 ff Tie2 Cre+ mice. Among the 84 apoptosis-related genes, the expression of TNF receptor superfamily member 10b ( Tnfrsf10b ) was significantly higher in Setdb2 ff Tie2 Cre+ mice than in control mice. Acute respiratory distress syndrome patients' serum showed higher SETDB2 levels than those of healthy volunteers. SETDB2 levels were negatively correlated with the partial pressure of oxygen in arterial blood/fraction of inspiratory oxygen concentration ratio. Conclusion: Acute respiratory distress syndrome elevates Setdb2 , apoptosis of VECs, and vascular permeability. Elevation of histone methyltransferase Setdb2 suggests the possibility to histone change and epigenetic modification. Thus, Setdb2 may be a novel therapeutic target for controlling the pathogenesis of ARDS.

Targeting ATP12A, a Nongastric Proton Pump α Subunit, for Idiopathic Pulmonary Fibrosis Treatment

Idiopathic pulmonary fibrosis (IPF) is a pathological condition of unknown etiology that results from injury to the lung and an ensuing fibrotic response that leads to the thickening of the alveolar walls and obliteration of the alveolar space. The pathogenesis is not clear, and there are currently no effective therapies for IPF. Small airway disease and mucus accumulation are prominent features in IPF lungs, similar to cystic fibrosis lung disease. The ATP12A gene encodes the α-subunit of the nongastric H+, K+-ATPase, which functions to acidify the airway surface fluid and impairs mucociliary transport function in patients with cystic fibrosis. It is hypothesized that the ATP12A protein may play a role in the pathogenesis of IPF. The authors' studies demonstrate that ATP12A protein is overexpressed in distal small airways from the lungs of patients with IPF compared with normal human lungs. In addition, overexpression of the ATP12A protein in mouse lungs worsened bleomycin induced experimental pulmonary fibrosis. This was prevented by a potassium competitive proton pump blocker, vonoprazan. These data support the concept that the ATP12A protein plays an important role in the pathogenesis of lung fibrosis. Inhibition of the ATP12A protein has potential as a novel therapeutic strategy in IPF treatment.

Idiopathic subglottic stenosis arises at the epithelial interface of host and pathogen

Background

Idiopathic subglottic stenosis (iSGS) is a rare fibrotic disease of the proximal airway affecting adult Caucasian women nearly exclusively. Life-threatening ventilatory obstruction occurs secondary to pernicious subglottic mucosal scar. Disease rarity and wide geographic patient distribution has previously limited substantive mechanistic investigation into iSGS pathogenesis.

Result

By harnessing pathogenic mucosa from an international iSGS patient cohort and single-cell RNA sequencing, we unbiasedly characterize the cell subsets in the proximal airway scar and detail their molecular phenotypes. Results show that the airway epithelium in iSGS patients is depleted of basal progenitor cells, and the residual epithelial cells acquire a mesenchymal phenotype. Observed displacement of bacteria beneath the lamina propria provides functional support for the molecular evidence of epithelial dysfunction. Matched tissue microbiomes support displacement of the native microbiome into the lamina propria of iSGS patients rather than disrupted bacterial community structure. However, animal models confirm that bacteria are necessary for pathologic proximal airway fibrosis and suggest an equally essential role for host adaptive immunity. Human samples from iSGS airway scar demonstrate adaptive immune activation in response to the proximal airway microbiome of both matched iSGS patients and healthy controls. Clinical outcome data from iSGS patients suggests surgical extirpation of airway scar and reconstitution with unaffected tracheal mucosa halts the progressive fibrosis.

Conclusion

Our data support an iSGS disease model where epithelial alterations facilitate microbiome displacement, dysregulated immune activation, and localized fibrosis. These results refine our understanding of iSGS and implicate shared pathogenic mechanisms with distal airway fibrotic diseases.

Oxymatrine inhibits TGF‑β1‑mediated mitochondrial apoptotic signaling in alveolar epithelial cells via activation of PI3K/AKT signaling

Although pulmonary fibrosis (PF) causes respiratory failure and death, effective therapies for PF have not been developed. Oxymatrine (OMT), an active ingredient in the Chinese herb Sophora flavescens, exerts antifibrotic effects; however, its effect on PF remains unclear. The present study aimed to determine whether OMT decreases transforming growth factor-β1 (TGF-β1)-induced PF in human lung cancer A549 cells by inhibiting apoptosis and targeting the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway. To construct a PF cell model, A549 cells were stimulated with TGF-β1. The experimental groups were as follows: control (untreated cells grown in complete medium), TGF-β1 (cells treated with 5 ng/ml TGF-β1), OMT (cells treated with 5 ng/ml TGF-β1 and 0.25, 0.50, or 1.00 mg/ml OMT), and OMT + LY294002 (cells treated with 5 ng/ml TGF-β1, 1.0 mg/ml OMT. and 25 µmol/l LY294002). The effects of OMT on cell morphology (via electron microscopy), apoptosis (via Annexin V-PI staining), mitochondrial apoptosis signaling [using JC-1 method to analyze mitochondrial membrane potential (MMP)], and Bcl-2, as well as Bax expression (via western blotting and reverse transcription-quantitative polymerase chain reaction), were analyzed. OMT significantly protected cells against TGF-β1-induced PF by inhibiting apoptosis. The specific manifestations were cell injury, as evidenced by morphological changes and decreased MMP. Following OMT treatment, the expression of the pro-apoptotic protein Bax increased, whereas that of the anti-apoptotic protein Bcl-2 decreased. The PI3K/AKT-specific inhibitor LY294002 significantly inhibited the ameliorative effects of OMT on TGF-β1-induced apoptosis. Collectively, OMT attenuated TGF-β1-mediated mitochondrial apoptosis of alveolar epithelial cells by activating the PI3K/AKT signaling pathway. Therefore, OMT may be a promising drug for PF treatment.

Extracellular vesicles in respiratory disease

Extracellular vesicles (EVs) are membranous nanoparticles secreted by nearly all cell types and play a critical role in cell-to-cell crosstalk. EVs can be categorized based on their size, surface markers, or the cell type from which they originate. EVs carry "cargo," including but not limited to, RNA, DNA, proteins, and small signaling molecules. To date, many methods have been developed to isolate EVs from biological fluids, such as blood plasma, urine, bronchoalveolar lavage fluid, and urine. Once isolated, EVs can be characterized by dynamic light scattering, nanotracking analysis, nanoscale flow cytometry, and transmission electron microscopy. Given the ability of EVs to transport cargo between cells, research has recently focused on understanding their role in various human diseases. As understanding of their significance to disease processes grows, insight into the mechanisms behind the physiological role of their cargo in target cells can facilitate the development of a new type of biomarker and therapeutic target for diseases in future. In addition, their ability to deliver their cargo selectively to target cells within the human body means that they could serve as therapeutic agents or methods of drug delivery. In this review, we will first introduce EVs and the cargo they carry, outline current methods for EV isolation and characterization, and discuss their potential use as biomarkers and therapeutic agents in the near future.

Targeting PI3K/AKT signaling for treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic interstitial pneumonia with unknown causes. The incidence rate increases year by year and the prognosis is poor without cure. Recently, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) signaling pathway can be considered as a master regulator for IPF. The contribution of the PI3K/AKT in fibrotic processes is increasingly prominent, with PI3K/AKT inhibitors currently under clinical evaluation in IPF. Therefore, PI3K/AKT represents a critical signaling node during fibrogenesis with potential implications for the development of novel anti-fibrotic strategies. This review epitomizes the progress that is being made in understanding the complex interpretation of the cause of IPF, and demonstrates that PI3K/AKT can directly participate to the greatest extent in the formation of IPF or cooperate with other pathways to promote the development of fibrosis. We further summarize promising PI3K/AKT inhibitors with IPF treatment benefits, including inhibitors in clinical trials and pre-clinical studies and natural products, and discuss how these inhibitors mitigate fibrotic progression to explore possible potential agents, which will help to develop effective treatment strategies for IPF in the near future.

Pivotal role of endothelial cell autophagy in sepsis

Sepsis is a fatal organ dysfunction resulting from a disordered host response to infection. Endothelial cells (ECs) are usually the primary targets of inflammatory mediators in sepsis; damage to ECs plays a pivotal part in vital organ failure. In recent studies, autophagy was suggested to play a critical role in the ECs injury although the mechanisms by which ECs are injured in sepsis are not well elucidated. Autophagy is a highly conserved catabolic process that includes sequestrating plasma contents and transporting cargo to lysosomes for recycling the vital substrates required for metabolism. This pathway also counteracts microbial invasion to balance and retain homeostasis, especially during sepsis. Increasing evidence indicates that autophagy is closely associated with endothelial function. The role of autophagy in sepsis may or may not be favorable depending upon conditions. In the present review, the current knowledge of autophagy in the process of sepsis and its influence on ECs was evaluated. In addition, the potential of targeting EC autophagy for clinical treatment of sepsis was discussed.

Emerging role of extracellular vesicles in the respiratory system

Extracellular vesicles (EVs) present numerous biomedical ways of studying disease and pathology. They function as protective packaging for the delivery of controlled concentrations of miRNAs and effector molecules, including cytokines, chemokines, genetic material, and small signaling molecules. Previous studies of EVs have yielded valuable insights into pathways of intercellular communication that affect a variety of biological processes and disease responses. The roles of EVs, specifically microRNA-containing EVs (EV-miRNAs), in either mitigating or exacerbating pulmonary disease symptoms are numerous and show promise in helping us understand pulmonary disease pathology. Because of their well-documented involvement in pulmonary diseases, EVs show promise both as possible diagnostic biomarkers and as therapeutic agents. This review surveys the physiological functions of EVs in the respiratory system and outlines the pulmonary disease states in which EVs are involved in intercellular crosstalk. This review also discusses the potential clinical applications of EV-miRNAs in pulmonary diseases.

Studies of tiny membrane-bound sacs called extracellular vesicles (EVs), which bud from cells naturally but are also implicated in disease, offer insights into respiratory health and disease, and could be used to deliver therapies into respiratory system cells. Joshua Holtzman at Oberlin College, Ohio, USA, and Heedoo Lee at Changwon National University in South Korea review current understanding of the role of EVs in the respiratory system and their potential uses in treatment. Researchers are discovering how EVs deliver signaling molecules to promote respiratory health, and how they can be involved in cancer, autoimmunity, asthma and other diseases. Early trials using EVs to deliver conventional drugs, and small RNA molecules that can control gene activity suggest great potential for treating a range of serious respiratory conditions. Analysis of EVs may also assist in diagnosis.

Ruscogenin alleviates LPS-induced pulmonary endothelial cell apoptosis by suppressing TLR4 signaling

Acute lung injury (ALI) or its most advanced form, acute respiratory distress syndrome (ARDS) is a severe inflammatory pulmonary process triggered by varieties of pathophysiological factors, among which apoptosis of pulmonary endothelial cells plays a critical role in the progression of ALI/ARDS. Ruscogenin (RUS) has been found to exert significant protective effect on ALI induced by lipopolysaccharides (LPS), but there is little information about its role in LPS-induced pulmonary endothelial cell apoptosis. The aim of the present study was to investigate the underlying mechanism in which RUS attenuates LPS-induced pulmonary endothelial cell apoptosis. Mice were challenged with LPS (5 mg/kg) by intratracheal instillation for 24 h to induce apoptosis of pulmonary endothelial cells in model group. RUS (three doses: 0.1, 0.3, and 1 mg/kg) was administrated orally 1 h prior to LPS challenge. The results showed that RUS could attenuate LPS-induced lung injury and pulmonary endothelial apoptosis significantly. And we observed that RUS inhibited the activation of TLR4/MYD88/NF-κB pathway in pulmonary endothelium after LPS treatment. In murine lung vascular endothelial cells (MLECs) we further confirmed that RUS (1 μmol/L) markedly ameliorated MLECs apoptosis by suppressing TLR4 signaling. By using TLR4 knockout mice we found that TLR4 was essential for the RUS-mediated eff ;ect on LPS-stimulated pulmonary endothelial apoptosis. Collectively, our results indicate that RUS plays a protective role against LPS-induced endothelial cell apoptosis via regulating TLR4 signaling, and may be a promising agent in the management of ALI.

Acute Lung Injury: IL-17A-Mediated Inflammatory Pathway and Its Regulation by Curcumin

Acute lung injury (ALI) is characterized by acute inflammation and tissue injury results in dysfunction of the alveolar epithelial membrane. If the epithelial injury is severe, a fibroproliferative phase of ALI can develop. During this phase, the activated fibroblast and myofibroblasts synthesize excessive collagenous extracellular matrix that leads to a condition called pulmonary fibrosis. Lung injury can be caused by several ways; however, the present review focus on bleomycin (BLM)-mediated changes in the pathology of lungs. BLM is a chemotherapeutic agent and has toxic effects on lungs, which leads to oxidative damage and elaboration of inflammatory cytokines. In response to the injury, the inflammatory cytokines will be activated to defend the system from injury. These cytokines along with growth factors stimulate the proliferation of myofibroblasts and secretion of pathologic extracellular matrix. During BLM injury, the pro-inflammatory cytokine such as IL-17A will be up-regulated and mediates the inflammation in the alveolar epithelial cell and also brings about recruitment of certain inflammatory cells in the alveolar surface. These cytokines probably help in up-regulating the expression of p53 and fibrinolytic system molecules during the alveolar epithelial cells apoptosis. Here, our key concern is to provide the adequate knowledge about IL-17A-mediated p53 fibrinolytic system and their pathogenic progression to pulmonary fibrosis. The present review focuses mainly on IL-17A-mediated p53-fibrinolytic aspects and how curcumin is involved in the regulation of pathogenic progression of ALI and pulmonary fibrosis.

Supplementation of Adiantum capillus-veneris Modulates Alveolar Apoptosis under Hypoxia Condition in Wistar Rats Exposed to Exercise

Background and Objectives: Several studies have reported that some conditions such as exercise and hypoxia induce DNA damage and dysfunction and apoptosis. Some plant foods contain numerous bioactive compounds and anti-inflammatory properties that can help fight DNA damage. Therefore, the current study evaluated the effect of supplementation of Adiantum capillus-veneris (ACV) extract on Bax/B-cell lymphoma 2 (Bcl-2) ratio apoptotic index and remodeling of pulmonary alveolar epithelial cells in lung tissue of healthy Wistar rats during stressful conditions (hypoxia). Materials and Methods: Twenty-seven Wistar male rats (four-week old, 72 ± 9 g) were randomly assigned into three groups: normoxic, sedentary, and not-supplemented (NG, n = 9); exercise and hypoxia and not-supplemented (HE, n = 9); and exercise and hypoxia and supplemented group (HS, n = 9). The NG remained sedentary in the normoxia environment for nine weeks. The HE group participated in a high-intensity (IT) program for six weeks, then remained sedentary in the hypoxia environment for three weeks. The low-pressure chamber simulated a ~2800 M altitude 24 h/d. HS participated in IT, then entered and remained sedentary in the hypoxia environment for three weeks, and they consumed 500 mg per kg of body weight ACV extract. Results: The Bax/Bcl-2 ratio of the HE group increased significantly (+50.27%, p ≤ 0.05), the average number of type I pneumocytes was reduced significantly (−18.85%, p ≤ 0.05), and the average number of type II pneumocytes was increased significantly (+14.69%, p ≤ 0.05). Also, after three weeks of consuming the ACV extract, the HS group in comparison with the HE group had their Bax/Bcl-2 ratio reduced significantly (−24.27%, p ≤ 0.05), the average number of type I pneumocytes increased significantly (+10.15%, p ≤ 0.05), and the average number of type II pneumocytes reduced significantly (−7.18%, p ≤ 0.05). Conclusion: The findings show that after three weeks of hypoxia following six weeks of high-intensity interval training in Wistar rats, the Bax/Bcl-2 ratio and the number of type II pneumocytes were increased and the number of type I pneumocytes was reduced significantly. These results strongly suggest that an apoptosis state was induced in the lung parenchyma, and consuming ACV extract modulated this state.

Piezo1 induced apoptosis of type II pneumocytes during ARDS

OBJECTIVE

The mechanisms of lung injury in acute respiratory distress syndrome (ARDS) are not well understood.Piezo1 was recently identified as a mechanotransduction protein. The present study found the expression of Piezo1 in type II pneumocytes and investigated its role in mediating ARDS-related lung injury.

METHODS

Sprague-Dawley rats were used to establish an ARDS model, the expression of Piezo1,lung injuries, apoptosis as well as calcium influx were assessed.

RESULTS

Piezo1 was expressed in type II pneumocytes as shown by immunofluorescence staining and expression was increased in the ARDS model. Knockdown of Piezo1 reduced apoptosis which was related to the elevation of Bcl-2.Calcium influx played a vital role in Piezo1-induced apoptosis.

CONCLUSION

Piezo1 was expressed in type II pneumocytes. Mechanical stretch of alveoli during ARDS induced activation of the Piezo1 channel,which resulted in calcium influx. The increased intracellular Ca2+ induced the apoptosis of type II pneumocytes, which may be related to the Bcl-2 pathway.

Differential roles of p38 MAPK and ERK1/2 in angiopoietin-2-mediated rat pulmonary microvascular endothelial cell apoptosis induced by lipopolysaccharide

Angiopoietin-2 (Ang-2) is a Tie-2 ligand that destabilizes vascular structures, enhances vascular permeability and induces vascular regression and endothelial cell apoptosis. Although there is evidence for the involvement of the Ang/Tie2 axis in acute lung injury (ALI), the underlying mechanisms involved in Ang-2-induced cell apoptosis are not well understood. In this study, whether Ang-2 contributes to microvascular endothelial cell injury and mediates lipopolysaccharide (LPS)-induced endothelial cell apoptosis and its associated signaling pathways was investigated. Exposure of rat pulmonary microvascular endothelial cells (RPMVECs) to LPS, Ang-2 and related inhibitors was performed to measure the expression levels of Ang-2, the activation of mitogen-activated protein kinases (MAPKs), the phosphorylation of extracellular signal-regulated kinase (ERK)1/2, and expression of the apoptosis-related proteins Bax and Bcl-2 using western blotting, reverse transcription-quantitative polymerase chain reaction, flow cytometry and fluorescence microscopy. The expression of Ang-2 in the RPMVECs was increased by LPS independent of time. The phosphorylation of p38 MAPK and ERK1/2 was significantly upregulated and the activation of apoptosis-related proteins Bax and Bcl was mediated by Ang-2. In addition, inhibition of the p38 pathway by SB203580 attenuated the Ang-2-mediated cell apoptosis, but inhibition of the ERK1/2 pathway by PD98059 exerted an anti-apoptotic effect against Ang-2. In conclusion, LPS-induced apoptosis is partly mediated via stimulation of p38 and ERK1/2 signaling pathways, where Ang-2 acts an inflammation-related factor to participate in the course of cell apoptosis in RPMVECs.

Evaluating the Remote Control of Programmed Cell Death, with or without a Compensatory Cell Proliferation

Organisms and their different component levels, whether organelle, cellular or other, come by birth and go by death, and the deaths are often balanced by new births. Evolution on the one hand has built demise program(s) in cells of organisms but on the other hand has established external controls on the program(s). For instance, evolution has established death program(s) in animal cells so that the cells can, when it is needed, commit apoptosis or senescent death (SD) in physiological situations and stress-induced cell death (SICD) in pathological situations. However, these programmed cell deaths are not predominantly regulated by the cells that do the dying but, instead, are controlled externally and remotely by the cells' superior(s), i.e. their host tissue or organ or even the animal's body. Currently, it is still unclear whether a cell has only one death program or has several programs respectively controlling SD, apoptosis and SICD. In animals, apoptosis exterminates, in a physiological manner, healthy but no-longer needed cells to avoid cell redundancy, whereas suicidal SD and SICD, like homicidal necrosis, terminate ill but useful cells, which may be followed by regeneration of the live cells and by scar formation to heal the damaged organ or tissue. Therefore, “who dies” clearly differentiates apoptosis from SD, SICD and necrosis. In animals, apoptosis can occur only in those cell types that retain a lifelong ability of proliferation and never occurs in those cell types that can no longer replicate in adulthood. In cancer cells, SICD is strengthened, apoptosis is dramatically weakened while SD has been lost. Most published studies professed to be about apoptosis are actually about SICD, which has four basic and well-articulated pathways involving caspases or involving pathological alterations in the mitochondria, endoplasmic reticula, or lysosomes.

Heat stress prevents lipopolysaccharide-induced apoptosis in pulmonary microvascular endothelial cells by blocking calpain/p38 MAPK signalling

Pulmonary microvascular endothelial cells (PMECs) injury including apoptosis plays an important role in the pathogenesis of acute lung injury during sepsis. Our recent study has demonstrated that calpain activation contributes to apoptosis in PMECs under septic conditions. This study investigated how calpain activation mediated apoptosis and whether heat stress regulated calpain activation in lipopolysaccharides (LPS)-stimulated PMECs. In cultured mouse primary PMECs, incubation with LPS (1 μg/ml, 24 h) increased active caspase-3 fragments and DNA fragmentation, indicative of apoptosis. These effects of LPS were abrogated by pre-treatment with heat stress (43 °C for 2 h). LPS also induced calpain activation and increased phosphorylation of p38 MAPK. Inhibition of calpain and p38 MAPK prevented apoptosis induced by LPS. Furthermore, inhibition of calpain blocked p38 MAPK phosphorylation in LPS-stimulated PMECs. Notably, heat stress decreased the protein levels of calpain-1/2 and calpain activities, and blocked p38 MAPK phosphorylation in response to LPS. Additionally, forced up-regulation of calpain-1 or calpain-2 sufficiently induced p38 MAPK phosphorylation and apoptosis in PMECs, both of which were inhibited by heat stress. In conclusion, heat stress prevents LPS-induced apoptosis in PMECs. This effect of heat stress is associated with down-regulation of calpain expression and activation, and subsequent blockage of p38 MAPK activation in response to LPS. Thus, blocking calpain/p38 MAPK pathway may be a novel mechanism underlying heat stress-mediated inhibition of apoptosis in LPS-stimulated endothelial cells.

Lung Epithelial Cell-Derived Microvesicles Regulate Macrophage Migration via MicroRNA-17/221-Induced Integrin β1 Recycling

Robust lung inflammation is one of the prominent features in the pathogenesis of acute lung injury (ALI). Macrophage migration and recruitment are often seen at the early stage of lung inflammatory responses to noxious stimuli. Using an acid inhalation-induced lung injury model, we explored the mechanisms by which acid exposure initiates macrophage recruitment and migration during development of ALI. The lung epithelium comprises a large surface area and functions as a first-line defense against noxious insults. We found that acid exposure induced a remarkable microvesicle (MV) release from lung epithelium as detected in bronchoalveolar lavage fluid. Significantly elevated RNA, rather than protein, was found in these epithelium-derived MVs after acid and included several highly elevated microRNAs, including microRNA (miR)-17 and miR-221. Acid-induced epithelial MV release promoted macrophage migration in vitro and recruitment into the lung in vivo and required, in part, MV shuttling of miR-17 and/or miR-221. Mechanistically, acid-induced epithelial MV miR-17/221 promoted β₁ integrin recycling and presentation back onto the surface of macrophages, in part via a Rab11-mediated pathway. Integrin β₁ is known to play an essential role in regulating macrophage migration. Taken together, acid-induced ALI results in epithelial MV shuttling of miR-17/221 that in turn modulates macrophage β₁ integrin recycling, promoting macrophage recruitment and ultimately contributing to lung inflammation.

The unfolded protein response controls ER stress-induced apoptosis of lung epithelial cells through angiotensin generation

Recent work from this laboratory showed that endoplasmic reticulum (ER) stress-induced apoptosis of alveolar epithelial cells (AECs) is regulated by the autocrine angiotensin (ANG)II/ANG1-7 system. The proteasome inhibitor MG132 or surfactant protein C (SP-C) BRICHOS domain mutation G100S induced apoptosis in human AECs by activating the proapoptotic cathepsin D and reducing antiapoptotic angiotensin converting enzyme-2 (ACE-2). This study tested the hypothesis that ER stress-induced apoptosis of human AECs might be mediated by influence of the unfolded protein response (UPR) on the autocrine ANGII/ANG1-7 system. A549 cells were challenged with MG132 or SP-C BRICHOS domain mutant G100S to induce ER stress and activation of UPR pathways. The results showed that either MG132 or G100S SP-C mutation activated all three canonical pathways of the UPR (IRE1/XBP1, ATF6, and PERK/eIF2α), which led to a significant increase in cathepsin D or in TACE (an ACE-2 ectodomain shedding enzyme) and eventually caused AEC apoptosis. However, ER stress-induced AEC apoptosis could be prevented by chemical chaperone or by UPR blockers. It is also suggested that ATF6 and IRE1 pathways might play important role in regulation of angiotensin system. These data demonstrate that ER stress induces apoptosis in human AECs through mediation of UPR pathways, which in turn regulate the autocrine ANGII/ANG1-7 system. They also demonstrated that ER stress-induced AEC apoptosis can be blocked by inhibition of UPR signaling pathways.

Epithelial cell-derived microvesicles activate macrophages and promote inflammation via microvesicle-containing microRNAs

Intercellular communications between lung epithelial cells and alveolar macrophages play an essential role in host defense against acute lung injury. Hyperoxia-induced oxidative stress is an established model to mimic human lung injury. We show that after hyperoxia-associated oxidative stress, a large amount of extracellular vesicles (EVs) are detectable in bronchoalveolar lavage fluid (BALF) and culture medium of lung epithelial cells. Microvesicles (MVs), but not exosomes (Exos) or apoptotic bodies (Abs), are the main type of EVs found in the early stages after hyperoxia. Among all the MV compositions, small RNAs are altered the most significantly after hyperoxia-associated oxidative stress. We further confirmed that hyperoxia up-regulates the levels of certain specific miRNAs in the epithelial cell-derived MVs, such as the miR-320a and miR-221. Functionally, the hyperoxia-induced epithelial MVs promote macrophage activation in vitro and facilitate the recruitment of immunomodulatory cells in vivo detected in BALF. Using MV as a cargo, delivery of the specific miRNA-enriched epithelial MVs (miR-221 and/or miR-320a) also triggers macrophage-mediated pro-inflammatory effects. Collectively, epithelial cell-derived MVs promote macrophage-regulated lung inflammatory responses via MV-shuttling miRNAs.

MiR-15a/16 Regulates Apoptosis of Lung Epithelial Cells after Oxidative Stress

Lung epithelial cell apoptosis is an important feature of hyperoxia-induced lung injury. Death receptor-associated extrinsic pathway and mitochondria-associated intrinsic pathway both mediate the development of lung epithelial cell apoptosis. Despite decades of research, molecular mechanisms of hyperoxia-induced epithelial cell apoptosis remain incompletely understood. Here we report a novel regulatory paradigm in response to hyperoxia-associated oxidative stress. Hyperoxia markedly up-regulated miR-15a/16 levels in lung epithelial cells, broncho-alveolar lavage fluid (BALF) and lung tissue. This effect was mediated by hyperoxia-induced reactive oxygen species (ROS). Functionally, miR-15a/16 inhibitors induced caspase 3-mediated lung epithelial cell apoptosis, in the presence of hyperoxia. MiR-15a/16 inhibitors robustly enhanced FADD level and down-regulated Bcl-2 expression. Consistently, cleaved caspase 8 and 9 were highly induced in the miR-15a/16 deficient cells, after hyperoxia. Using airway epithelial cell specific, miR-15a/16^-/- mice, we found that Bcl-2 significantly reduced in lung epithelial cells in vivo after hyperoxia. In contrast, caspase 3, 8 and Bcl-2 associated death promoter (BAD) were highly elevated in the miR-15a/16^-/- epithelial cells in vivo. Interestingly, in lung epithelial malignant cells, rather than benign cells, deletion of miR-15a/16 prevented apoptosis. Furthermore, deletion of miR-15a/16 in macrophages also prohibited apoptosis, opposite to what we have found in normal lung epithelial cells. Taken together, our data suggested that miR-15a/16 may exert differential roles in different cell types. MiR-15a/16 deficiency result in lung epithelial cell apoptosis in response to hyperoxia, via modulating both intrinsic and extrinsic apoptosis pathways.

Adh enhances Actinobacillus pleuropneumoniae pathogenicity by binding to OR5M11 and activating p38 which induces apoptosis of PAMs and IL-8 release

Members of the Trimeric Autotransporter Adhesin (TAA) family play a crucial role in the adhesion of Gram-negative pathogens to host cells, but the immunopathogenesis of TAAs remains unknown. Our previous studies demonstrated that Adh from Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is required for full bacterial pathogenicity. Alveolar macrophages are the first line of defense against respiratory infections. This study compared the interactions between porcine alveolar macrophages (PAMs) and wild-type A. pleuropneumoniae (5b WT) or an Adh-deletion strain (5b ΔAdh) via gene microarray, immunoprecipitation and other technologies. We found that Adh was shown to interact with the PAMs membrane protein OR5M11, an olfactory receptor, resulting in the high-level secretion of IL-8 by activation of p38 MAPK signaling pathway. Subsequently, PAMs apoptosis via the activation of the Fax and Bax signaling pathways was observed, followed by activation of caspases 8, 9, and 3. The immunological pathogenic roles of Adh were also confirmed in both murine and piglets infectious models in vivo. These results identify a novel immunological strategy for TAAs to boost the pathogenicity of A. pleuropneumoniae. Together, these datas reveal the high versatility of the Adh protein as a virulence factor and provide novel insight into the immunological pathogenic role of TAAs.

Angiotensin-(1-7)/mas inhibits apoptosis in alveolar epithelial cells through upregulation of MAP kinase phosphatase-2

Earlier work from this laboratory showed that autocrine generation of angiotensin II and c-Jun-NH2-terminal kinase phosphorylation (p-JNK) are both required events in alveolar epithelial cell (AEC) apoptosis. Although earlier data showed that angiotensin-(1-7) [ANG-(1-7)] protects against AEC apoptosis, the pathways by which ANG-(1-7)/mas activation prevent JNK phosphorylation and apoptosis are poorly understood. Therefore, in the current study, it was theorized that ANG-(1-7) activates a mitogen-activated protein kinase phosphatase (MKP) and thereby reduces JNK phosphorylation to inhibit apoptosis and promote cell survival. This hypothesis was evaluated in the human A549 and mouse MLE12 AEC lines and primary cultures of human AECs. Cells were transfected with small-interfering RNAs, antisense oligonucleotides, or inhibitors specific for MKP-2 or mas, and were then assayed for phospho-JNK, caspase-9, loss of mitochondrial membrane potential, and nuclear fragmentation. Silencing of MKP-2 significantly prevented the blockade of all apoptotic markers by ANG-(1-7). Knockdown or blockade of mas receptor by antisense oligonucleotides or by the receptor antagonist A779, respectively, caused significant decreases in MKP-2, and simultaneously increased the apoptotic markers of caspase-9 activation and nuclear fragmentation. These data show that the ANG-(1-7)/mas pathway constitutively prevents JNK phosphorylation and apoptosis of AECs by maintaining activation of the JNK-selective phosphatase MKP-2, and further demonstrate the critical role of the ANG-(1-7) receptor mas in AEC survival.

Lung epithelial cell-derived extracellular vesicles activate macrophage-mediated inflammatory responses via ROCK1 pathway

Despite decades of research, the pathogenesis of acute respiratory distress syndrome (ARDS) remains poorly understood, thus impeding the development of effective treatment. Diffuse alveolar damage (DAD) and lung epithelial cell death are prominent features of ARDS. Lung epithelial cells are the first line of defense after inhaled stimuli, such as in the case of hyperoxia. We hypothesized that lung epithelial cells release 'messenger' or signaling molecules to adjacent or distant macrophages, thereby initiating or propagating inflammatory responses after noxious insult. We found that, after hyperoxia, a large amount of extracellular vesicles (EVs) were generated and released into bronchoalveolar lavage fluid (BALF). These hyperoxia-induced EVs were mainly derived from live lung epithelial cells as the result of hyperoxia-associated endoplasmic reticulum (ER) stress. These EVs were remarkably different from epithelial 'apoptotic bodies', as reflected by the significantly smaller size and differentially expressed protein markers. These EVs fall mainly in the size range of the exosomes and smaller microvesicles (MVs) (50-120 nm). The commonly featured protein markers of apoptotic bodies were not found in these EVs. Treating alveolar macrophages with hyperoxia-induced, epithelial cell-derived EVs led to an increased secretion of pro-inflammatory cytokines and macrophage inflammatory protein 2 (MIP-2). Robustly increased macrophage and neutrophil influx was found in the lung tissue of the mice intranasally treated with hyperoxia-induced EVs. It was determined that EV-encapsulated caspase-3 was largely responsible for the alveolar macrophage activation via the ROCK1 pathway. Caspase-3-deficient EVs induced less cytokine/MIP-2 release, reduced cell counts in BALF, less neutrophil infiltration and less inflammation in lung parenchyma, both in vitro and in vivo. Furthermore, the serum circulating EVs were increased and mainly derived from lung epithelial cells after hyperoxia exposure. These circulating EVs also activated systemic macrophages other than the alveolar ones. Collectively, the results show that hyperoxia-induced, lung epithelial cell-derived and caspase-3 enriched EVs activate macrophages and mediate the inflammatory lung responses involved in lung injury.

Effect of lipopolysaccharide on angiotensin II type 1 receptor expression and function in human pulmonary microvascular endothelial cells

Lipopolysaccharides (LPSs) are an important initiation factor in acute respiratory distress syndrome. The aim of the present study was to investigate the effect of LPSs on the regulation of angiotensin II (Ang II) receptors in human pulmonary microvascular endothelial cells (HPMECs). HPMECs were treated with 0, 50, 100 or 200 ng/ml LPS and incubated for 4, 8, 12 or 16 h. The expression of Ang II type 1 receptor (AT1R) and Ang II type 2 receptor (AT2R) was determined using reverse transcription‑polymerase chain reaction and western blot analysis. The affinity to Ang II was measured using a radioligand binding assay. No AT2R expression was detected with or without LPS administration in HPMECs, and LPS treatment increased the expression level of AT1R. A time‑dependent increase of AT1R transcription was observed in the 50 ng/ml group, while in the 100 and 200 ng/ml groups, the AT1R mRNA levels reached peak values at 4 h and remained unchanged. The protein level of AT1R increased significantly in a dose‑dependent manner for each incubation time period. A time‑dependent increase in the protein level was observed in the 50 and 100 ng/ml groups. As for the 200 ng/ml group, the level of AT1R reached a peak value at 8 h. Maximal binding (Bmax) significantly increased following LPS treatment and Bmax of the 50 ng/ml group exhibited a time‑dependent increase. The Bmax of the 100 and 200 ng/ml groups reached peak values at 12 and 8 h, respectively, and decreased thereafter. The dissociation constant remained unchanged following LPS treatment. Thus, treatment with LPS increased AT1R expression and its Bmax to Ang II in HPMECs, however, did not alter the affinity of AT1R to Ang II.

Paracrine factors from mesenchymal stem cells attenuate epithelial injury and lung fibrosis

Paracrine factors are currently considered to be the major mechanism through which mesenchymal stem cells (MSCs) exert their actions. The aim of this study was to investigate the protective effects of conditioned medium (CM) from bone marrow mesenchymal stem cells (MSC) on bleomycin (BLM)‑induced lung injury and fibrosis, both in vitro and in vivo. A549 human non‑small cell lung cancer epithelial cells were cultured in serum‑free medium, or MSC‑CM, both with or without BLM. The protective effects of MSC‑CM was determined by MTT assay to assess cell viability and Annexin V‑PE to assess apoptosis. Rats were intratracheally injected with MSC‑CM, saline, or conditioned medium from fibroblasts on day 0 and day 3 after intratracheal administration of BLM, and were sacrificed on day 28. Lung injury and fibrosis were assessed by histological assessment, Ashcroft score, and hydroxyproline assay; lung cell apoptosis was detected using terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In comparison to the control group (0.17±0.01), 8 and 16% MSC‑CM had a significant stimulatory effect on A549 cellular proliferation (0.24±0.03 and 0.24±0.04, respectively, P<0.01). A549 cells cultured with MSC‑CM were protected from BLM‑induced apoptosis, 23.43±3.76% vs. 38.06±4.32%; (P<0.05). In the BLM‑challenged rats, MSC‑CM was shown to protect against lung fibrosis in terms of lung inflammation, fibrotic scores, collagen deposition, and cell apoptosis. This data suggests that MSCs are capable of protecting against lung injury and fibrosis both in vitro and in vivo through a paracrine anti‑inflammatory mechanism. MSC‑CM may provide a novel approach for the treatment of lung fibrosis.

Epithelium-dependent profibrotic milieu in the pathogenesis of idiopathic pulmonary fibrosis: current status and future directions

BACKGROUND AND AIM

Idiopathic pulmonary fibrosis (IPF) is characterized by hyperplasia of type II alveolar epithelial cells, aggregation of activated (myo)fibroblasts and excessive deposition of extracellular matrix, which will ultimately lead to lung architecture destruction with no proven effective therapies. Despite a significant increase in our understanding on the etiology and pathogenesis of IPF, the real triggers that initiate epithelial cell injury and promote fibrosis evolution are still elusive. We wanted to discuss the evolution of hypothesis on IPF pathogenesis and to suggest some new directions which need to be further elucidated.

METHODS

We have done a literature search in PubMed database by using the term 'idiopathic pulmonary fibrosis' AND (pathogenesis OR inflammation OR wound healing OR apoptosis OR extracellular matrix OR animal model).

RESULTS

Inflammatory hypothesis had been the dominant idea for several decades which suggests that chronic inflammation drives the onset and advance of the fibrotic process. However, it is seriously challenged nowadays because lung tissues from IPF patients exhibit little inflammatory lesions. Also, anti-inflammation therapy failed to exert a beneficial effect to IPF patients. Furthermore, experimental lung fibrosis can be realized independent of inflammation. Today, modern paradigm suggests that IPF is mainly driven by the profibtic milieu formed by epithelial injury/ disability and dysregulated epithelial mesenchymal interaction.

CONCLUSIONS

Epithelium-dependent profibrotic milieu formation and mesenchymal activation is the current view on the pathogenesis of IPF. New evidence from more analogous animal models may emerge and shift our thinking to a new and more faithful concept in the future.

Histone deacetylase inhibition downregulates collagen 3A1 in fibrotic lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a deadly disease characterized by chronic inflammation and excessive collagen accumulation in the lung. Myofibroblasts are the primary collagen-producing cells in pulmonary fibrosis. Histone deacetylase inhibitor (HDACi) can affect gene expression, and some, such as suberoylanilide hydroxamic acid (SAHA), are US FDA approved for cancer treatment. In this study, we investigated SAHA’s effects on the expression of collagen III alpha 1 (COL3A1) in primary human IPF fibroblasts and in a murine model of pulmonary fibrosis. We observed that increased COL3A1 expression in IPF fibroblasts can be substantially reduced by SAHA treatment at the level of transcription as detected by RT-PCR; collagen III protein level was also reduced, as detected by Western blots and immunofluorescence. The deacetylation inhibitor effect of SAHA was verified by observing higher acetylation levels of both histone H3 and H4 in treated IPF cells. Chromatin immunoprecipitation (ChIP) experiments demonstrated that the reduced expression of COL3A1 by SAHA is with increased association of the repressive chromatin marker, H3K27Me3, and decreased association of the active chromatin marker, H3K9Ac. In our murine model of bleomycin-induced pulmonary fibrosis, the SAHA treated group demonstrated significantly less collagen III, as detected by immunohistochemistry. Our data indicate that the HDACi SAHA alters the chromatin associated with COL3A1, resulting in its decreased expression.

Intersectin-1s: an important regulator of cellular and molecular pathways in lung injury

Abstract Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe syndromes resulting from the diffuse damage of the pulmonary parenchyma. ALI and ARDS are induced by a plethora of local or systemic insults, leading to the activation of multiple pathways responsible for injury, resolution, and repair or scarring of the lungs. Despite the large efforts aimed at exploring the roles of different pathways in humans and animal models and the great strides made in understanding the pathogenesis of ALI/ARDS, the only viable treatment options are still dependent on ventilator and cardiovascular support. Investigation of the pathophysiological mechanisms responsible for initiation and resolution or advancement toward lung scarring in ALI/ARDS animal models led to a better understanding of the disease's complexity and helped in elucidating the links between ALI and systemic multiorgan failure. Although animal models of ALI/ARDS have pointed out a variety of new ideas for study, there are still limited data regarding the initiating factors, the critical steps in the progression of the disease, and the central mechanisms dictating its resolution or progression to lung scarring. Recent studies link deficiency of intersectin-1s (ITSN-1s), a prosurvival protein of lung endothelial cells, to endothelial barrier dysfunction and pulmonary edema as well as to the repair/recovery from ALI. This review discusses the effects of ITSN-1s deficiency on pulmonary endothelium and its significance in the pathology of ALI/ARDS.

β-catenin in the alveolar epithelium protects from lung fibrosis after intratracheal bleomycin

RATIONALE

Alveolar epithelial cells (AECs) play central roles in the response to lung injury and the pathogenesis of pulmonary fibrosis.

OBJECTIVES

We aimed to determine the role of β-catenin in alveolar epithelium during bleomycin-induced lung fibrosis.

METHODS

Genetically modified mice were developed to selectively delete β-catenin in AECs and were crossed to cell fate reporter mice that express β-galactosidase (βgal) in cells of AEC lineage. Mice were given intratracheal bleomycin (0.04 units) and assessed for AEC death, inflammation, lung injury, and fibrotic remodeling. Mouse lung epithelial cells (MLE12) with small interfering RNA knockdown of β-catenin underwent evaluation for wound closure, proliferation, and bleomycin-induced cytotoxicity.

MEASUREMENTS AND MAIN RESULTS

Increased β-catenin expression was noted in lung parenchyma after bleomycin. Mice with selective deletion of β-catenin in AECs had greater AEC death at 1 week after bleomycin, followed by increased numbers of fibroblasts and enhanced lung fibrosis as determined by semiquantitative histological scoring and total collagen content. However, no differences in lung inflammation or protein levels in bronchoalveolar lavage were noted. In vitro, β-catenin-deficient AECs showed increased bleomycin-induced cytotoxicity as well as reduced proliferation and impaired wound closure. Consistent with these findings, mice with AEC β-catenin deficiency showed delayed recovery after bleomycin.

CONCLUSIONS

β-Catenin in the alveolar epithelium protects against bleomycin-induced fibrosis. Our studies suggest that AEC survival and wound healing are enhanced through β-catenin-dependent mechanisms. Activation of the developmentally important β-catenin pathway in AECs appears to contribute to epithelial repair after epithelial injury.

Role of mechanical stretching and lipopolysaccharide in early apoptosis and IL-8 of alveolar epithelial type II cells A549

OBJECTIVE

To investigate the effects of mechanical stretching and lipopolysaccharide (LPS) on the early apoptosis and IL-8 production of alveolar epithelial type II cells A549.

METHODS

The experimental matrix consisted of three integrated studies. In the first study, A549 cells were subjected to different stretching strain frequency and duration time to see the effects on the early apoptosis. In the second study, A549 cells were subjected to mechanical stretch (15% 4 h, 0.5 Hz) and LPS (1 or 100 ng/mL) to see whether mechanical strain and LPS also have an addictive effect on the early apoptosis. In the third study to investigate whether this addictive effect could be induced by LPS and mechanical stretch on IL-8 production, A549 cells were subjected to LPS (100 ng/mL) and mechanical strain (15%, 0.5 Hz, 4 h). Real time PCR and enzyme linked immunosorbent assay were used to measure mRNA and protein level of IL-8. The early apoptosis was detected by flow cytometry.

RESULTS

Mechanical stretch induced the early apoptosis in a force and frequency and time-dependent manner. In the presence of LPS, mechanical stretch enhanced LPS-induced early apoptosis, especially in 100 ng/mL LPS group compared with 1 ng/mL LPS and the control group. Mechanical stretch increased IL-8 production and enhanced LPS-induced IL-8 screation both in mRNA and protein levels.

CONCLUSIONS

Mechanical stretch can induce the early apoptosis and IL-8 secretion. Mechanical stretch and LPS have an addictive effect on the early apoptosis and IL-8 production in alveolar type 2 cells, which is one of the mechanisms of ventilator-induced lung injury.

Long-lasting oxidative pulmonary insult in rat after intratracheal instillation of silica nanoparticles doped with cadmium

Silica/cadmium containing nanomaterials are now produced on industrial scale due to their potential for a variety of technological applications. Nevertheless, information on toxicity, exposure and health impact of these nanomaterials is still limited. In this study, in vivo effects of silica nanoparticles (SiNPs) doped with Cd (SiNPs-Cd, 1mg/rat), soluble CdCl(2) (400 μg/rat), or SiNPs (600 μg/rat) have been investigated by evaluating F(2)-isoprostanes (F(2)-IsoPs), superoxide dismutase (SOD1), inducible nitric oxide synthase (iNOS) and cyclooxygenase type 2 (COX-2) enzymes, as markers of oxidative stress, 24h, 7 and 30 days after intra-tracheal (i.t.) instillation to rats. Free and esterified F(2)-IsoPs were evaluated in lung and plasma samples by GC/NICI-MS/MS analysis, and SOD1, iNOS and COX-2 expression in pulmonary tissue by immunocytochemistry. Thirty days after exposure, pulmonary total F(2)-IsoPs were increased by 56% and 43% in CdCl(2) and SiNPs-Cd groups, respectively, compared to controls (32.8 ± 7.8 ng/g). Parallel elevation of free F(2)-IsoPs was observed in plasma samples (by 113% and 95% in CdCl(2) and SiNPs-Cd groups, respectively), compared to controls (28 ± 8 pg/ml). These effects were already detectable at day 7 and lasted until day 30 post-exposure. Pulmonary SOD1-, iNOS-, and COX-2-immunoreactivity was significantly enhanced in a time-dependent manner (7 days <30 days) after both CdCl(2) and SiNPs-Cd treatments. SiNPs did not influence any of the evaluated endpoints. The results indicate the capacity of engineered SiNPs-Cd to cause long-lasting oxidative tissue injury following pulmonary exposure in rat.

Lung epithelial cell death induced by oil-dispersant mixtures

The dispersants used in oil spill disasters are claimed to be safe, but increased solubility of high-molecular-weight components in crude oil is of public health concern. The water-accommodated fractions (WAF) of crude oil mixed with dispersants may become airborne and cause lung epithelial damage when inhaled. This study was designed to examine the cell death and related death pathways of lung epithelial cells in response to WAF. Cultured A549 cells were treated for 2 or 24h with different concentrations of WAF. The WAF was prepared by mixing each of the dispersants (Corexit EC9527A, Corexit EC9500A and Corexit EC9580A) with crude oil for extraction with PBS. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay, lactate dehydrogenase assay, morphology and cleaved caspase 9 protein, and microtubule-associated protein 1 light chain 3 were all used to measure cell viability, necrosis, apoptosis and autophagy quantitation, respectively. Results showed that the WAF of oil-dispersant mixtures caused cell death in the lung epithelial cells, in a dose-dependent manner, with the major cellular pathways of necrosis and apoptosis involved. Autophagy also occurred in cells exposed to WAF mixtures at lower concentrations before any detectable cell death, indicating greater sensitivity to WAF exposure. The three types of cell behavior, namely necrosis, apoptosis and autophagy, may play different roles in oil spill-related respiratory disorders.

Angiotensin signalling in pulmonary fibrosis

A large body of evidence demonstrates that angiotensin II and angiotensin receptors are required for the pathogenesis of experimental lung fibrosis. Angiotensin has a number of profibrotic effects on lung parenchymal cells that include the induction of growth factors for mesenchymal cells, extracellular matrix molecules, cytokines and increased motility of lung fibroblasts. Angiotensin is also proapoptotic for lung epithelial cells, and is synthesized by a local system (i.e., entirely within the lung tissue) after lung injury by a variety of agents of both xenobiotic and endogenous origins. Recent evidence shows that the counterregulatory molecule angiotensin 1-7, the product of the enzyme ACE-2, inhibits epithelial cell apoptosis and thus acts as an antifibrotic epithelial survival factor. This manuscript reviews the evidence supporting a role for angiotensin in lung fibrogenesis and discusses the signalling mechanisms underlying its action on lung parenchymal cells important in the pathogenesis of pulmonary fibrosis.

Enhanced Hsp70 expression protects against acute lung injury by modulating apoptotic pathways

The Acute respiratory distress syndrome (ARDS) is a highly lethal inflammatory lung disorder. Apoptosis plays a key role in its pathogenesis. We showed that an adenovirus expressing the 70 kDa heat shock protein Hsp70 (AdHSP) protected against sepsis-induced lung injury. In this study we tested the hypothesis that AdHSP attenuates apoptosis in sepsis-induced lung injury.

Sepsis was induced in rats via cecal ligation and double puncture (2CLP). At the time of 2CLP PBS, AdHSP or AdGFP (an adenoviral vector expressing green fluorescent protein) were injected into the tracheas of septic rats. 48 hours later, lungs were isolated. One lung was fixed for TUNEL staining and immunohistochemistry. The other was homogenized to isolate cytosolic and nuclear protein. Immunoblotting, gel filtration and co-immunoprecipitation were performed in these extracts. In separate experiments MLE-12 cells were incubated with medium, AdHSP or AdGFP. Cells were stimulated with TNFα. Cytosolic and nuclear proteins were isolated. These were subjected to immunoblotting, co- immunoprecipitation and a caspase-3 activity assay.

TUNEL assay demonstrated that AdHSP reduced alveolar cell apoptosis. This was confirmed by immunohistochemical detection of caspase 3 abundance. In lung isolated from septic animals, immunoblotting, co-immunoprecipitation and gel filtration studies revealed an increase in cytoplasmic complexes containing caspases 3, 8 and 9. AdHSP disrupted these complexes.

We propose that Hsp70 impairs apoptotic cellular pathways via interactions with caspases. Disruption of large complexes resulted in stabilization of lower molecular weight complexes, thereby, reducing nuclear caspase-3. Prevention of apoptosis in lung injury may preserve alveolar cells and aid in recovery.

Idiopathic pulmonary fibrosis: a disorder of epithelial cell dysfunction

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive dyspnea, interstitial infiltrates in lung parenchyma and restriction on pulmonary function testing. IPF is the most common and severe of the idiopathic interstitial pneumonias, with most individuals progressing to respiratory failure. Multiple lines of evidence reveal prominent roles for alveolar epithelial cells (AECs) in disease. The current disease paradigm is that ongoing or repetitive injurious stimuli in the presence of a genetic or acquired dysfunctional type II AEC phenotype results in increased AEC injury/apoptosis, deficiencies in regeneration of normal alveolar structure and aberrant lung repair and fibroblast activation, leading to progressive fibrosis. Although the nature of injurious events and processes involved in aberrant repair of the alveolar epithelium are not well understood, ongoing investigations provide hope to better understand mechanisms by which AECs maintain homeostasis or contribute to fibrosis. These strategies may hold promise for developing novel treatment approaches for IPF.

Nonresolving fibrotic disorders: idiopathic pulmonary fibrosis as a paradigm of impaired tissue regeneration

The pathogenesis idiopathic pulmonary of fibrosis and related fibrosis lung disorders are complex and poorly understood. This likely involves cellular mechanisms that result in loss of cellular homeostasis leading to aberrant alveolar wall remodeling through the excessive deposition of connective tissue matrices. Impaired tissue regeneration and dysregulation of cell death in lung fibroblasts and epithelial cells appear to be important in the initiation and progression of these disorders. This review summarizes current understanding in this area to stimulate research into the development of novel therapeutic strategies that prevent, halt or reverse the progression of lung fibrosis.

TGFβ signaling in lung epithelium regulates bleomycin-induced alveolar injury and fibroblast recruitment

The response of alveolar epithelial cells (AECs) to lung injury plays a central role in the pathogenesis of pulmonary fibrosis, but the mechanisms by which AECs regulate fibrotic processes are not well defined. We aimed to elucidate how transforming growth factor-β (TGFβ) signaling in lung epithelium impacts lung fibrosis in the intratracheal bleomycin model. Mice with selective deficiency of TGFβ receptor 2 (TGFβR2) in lung epithelium were generated and crossed to cell fate reporter mice that express β-galactosidase (β-gal) in cells of lung epithelial lineage. Mice were given intratracheal bleomycin (0.08 U), and the following parameters were assessed: AEC death by terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling assay, inflammation by total and differential cell counts from bronchoalveolar lavage, fibrosis by scoring of trichrome-stained lung sections, and total lung collagen content. Mice with lung epithelial deficiency of TGFβR2 had improved AEC survival, despite greater lung inflammation, after bleomycin administration. At 3 wk after bleomycin administration, mice with epithelial TGFβR2 deficiency showed a significantly attenuated fibrotic response in the lungs, as determined by semiquantitatve scoring and total collagen content. The reduction in lung fibrosis in these mice was associated with a marked decrease in the lung fibroblast population, both total lung fibroblasts and epithelial-to-mesenchymal transition-derived (S100A4(+)/β-gal(+)) fibroblasts. Attenuation of TGFβ signaling in lung epithelium provides protection from bleomycin-induced fibrosis, indicating a critical role for the epithelium in transducing the profibrotic effects of this cytokine.

Repetitive intratracheal bleomycin models several features of idiopathic pulmonary fibrosis

Single-dose intratracheal bleomycin has been instrumental for understanding fibrotic lung remodeling, but fails to recapitulate several features of idiopathic pulmonary fibrosis (IPF). Since IPF is thought to result from recurrent alveolar injury, we aimed to develop a repetitive bleomycin model that results in lung fibrosis with key characteristics of human disease, including alveolar epithelial cell (AEC) hyperplasia. Wild-type and cell fate reporter mice expressing β-galactosidase in cells of lung epithelial lineage were given intratracheal bleomycin after intubation, and lungs were harvested 2 wk after a single or eighth biweekly dose. Lungs were evaluated for fibrosis and collagen content. Bronchoalveolar lavage (BAL) was performed for cell counts. TUNEL staining and immunohistochemistry were performed for pro-surfactant protein C (pro-SP-C), Clara cell 10 (CC-10), β-galactosidase, S100A4, and α-smooth muscle actin. Lungs from repetitive bleomycin mice had marked fibrosis with prominent AEC hyperplasia, similar to usual interstitial pneumonia (UIP). Compared with single dosing, repetitive bleomycin mice had greater fibrosis by scoring, morphometry, and collagen content; increased TUNEL+ AECs; and reduced inflammatory cells in BAL. Sixty-four percent of pro-SP-C+ cells in areas of fibrosis expressed CC-10 in the repetitive model, suggesting expansion of a bronchoalveolar stem cell-like population. In reporter mice, 50% of S100A4+ lung fibroblasts were derived from epithelial mesenchymal transition compared with 33% in the single-dose model. With repetitive bleomycin, fibrotic remodeling persisted 10 wk after the eighth dose. Repetitive intratracheal bleomycin results in marked lung fibrosis with prominent AEC hyperplasia, features reminiscent of UIP.

Differential role of the Fas/Fas ligand apoptotic pathway in inflammation and lung fibrosis associated with reovirus 1/L-induced bronchiolitis obliterans organizing pneumonia and acute respiratory distress syndrome

Bronchiolitis obliterans organizing pneumonia (BOOP) and acute respiratory distress syndrome (ARDS) are two clinically and histologically distinct syndromes sharing the presence of an inflammatory and fibrotic component. Apoptosis via the Fas/Fas ligand (FasL) pathway plays an important role in the development of acute lung injury and fibrosis characteristic of these and other pulmonary inflammatory and fibrotic syndromes. We evaluated the role of apoptosis via the Fas/FasL pathway in the development of pulmonary inflammation and fibrosis in reovirus 1/L-induced BOOP and ARDS. CBA/J mice were intranasally inoculated with saline, 1 x 10(6) (BOOP), or 1 x 10(7) (ARDS) PFU reovirus 1/L, and evaluated at various days postinoculation for in situ apoptosis by TUNEL analysis and Fas/FasL expression. Our results demonstrate the presence of apoptotic cells and up-regulation of Fas/FasL expression in alveolar epithelium and in infiltrating cells during the inflammatory and fibrotic stages of both reovirus 1/L-induced ARDS and BOOP. Treatment of mice with the caspase 8 inhibitor, zIETD-fmk, inhibited apoptosis, inflammation, and fibrotic lesion development in reovirus 1/L-induced BOOP and ARDS. However, CBA/KlJms-Fas(lpr-cg)/J mice, which carry a point mutation in the Fas cytoplasmic region that abolishes the ability of Fas to transduce an apoptotic signal, do not develop pulmonary inflammation and fibrotic lesions associated with reovirus 1/L-induced BOOP, but still develop inflammation and fibrotic lesions associated with reovirus 1/L-induced ARDS. These results suggest a differential role for the Fas/FasL apoptotic pathway in the development of inflammation and fibrotic lesions associated with BOOP and ARDS.

Transepithelial migration of neutrophils: mechanisms and implications for acute lung injury

The primary function of neutrophils in host defense is to contain and eradicate invading microbial pathogens. This is achieved through a series of swift and highly coordinated responses culminating in ingestion (phagocytosis) and killing of invading microbes. While these tasks are usually performed without injury to host tissues, in pathologic circumstances such as sepsis, potent antimicrobial compounds can be released extracellularly, inducing a spectrum of responses in host cells ranging from activation to injury and death. In the lung, such inflammatory damage is believed to contribute to the pathogenesis of diverse lung diseases, including acute lung injury and the acute respiratory distress syndrome, chronic obstructive lung disease, and cystic fibrosis. In these disorders, epithelial cells are targets of leukocyte-derived antimicrobial products, including proteinases and oxidants. Herein, we review the mechanisms involved in the physiologic process of neutrophil transepithelial migration, including the role of specific adhesion molecules on the leukocyte and epithelial cells. We examine the responses of the epithelial cells to the itinerant leukocytes and their cytotoxic products and the consequences of this for lung injury and repair. This paradigm has important clinical implications because of the potential for selective blockade of these pathways to prevent or attenuate lung injury.