MicroRNA-19b Mediates Lung Epithelial-Mesenchymal Transition via Phosphatidylinositol-3,4,5-Trisphosphate 3-Phosphatase in Response to Mechanical Stretch

Epithelial damage and ageing: the perfect storm

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a progressive disease of lung parenchymal scarring that is triggered by repeated microinjury to a vulnerable alveolar epithelium. It is increasingly recognised that cellular ageing, whether physiological or accelerated due to telomere dysfunction, renders the epithelium less able to cope with injury and triggers changes in epithelial behaviour that ultimately lead to the development of disease.

AIMS

This review aims to highlight how, with increasing age, the alveolar epithelium becomes vulnerable to exogenous insults. We discuss the downstream consequences of alveolar epithelial dysfunction on epithelial phenotype, alveolar repair and pro-pathogenic interactions with other alveolar niche-resident cell types which drive IPF pathogenesis.

NARRATIVE

We highlight how a wide array of cellular mechanisms that maintain cellular homeostasis become dysfunctional with ageing. Waning replicative capacity, genomic stability, mitochondrial function, proteostasis and metabolic function all contribute to a phenotype of vulnerability to 'second hits'. We discuss how in IPF the alveolar epithelium becomes dysfunctional, highlighting changes in repair capacity and fundamental cellular phenotype and how interactions between abnormal epithelium and other alveolar niche-resident cell types perpetuate disease.

CONCLUSIONS

The ageing epithelium is a vulnerable epithelium which, with the cumulative effects of environmental exposures, fundamentally changes its behaviour towards stalled differentiation, failed repair and profibrotic signalling. Further dissection of aberrant epithelial behaviour, and its impact on other alveolar cell types, will allow identification of novel therapeutic targets aimed at earlier pathogenic events.

Mechanical Stretch Control of Adipocyte AKT Signaling and the Role of FAK and ROCK Mechanosensors

Adipose tissue in vivo is physiologically exposed to compound mechanical loading due to bodyweight bearing, posture, and motion. The capability of adipocytes to sense and respond to mechanical loading milieus to influence metabolic functions may provide a new insight into obesity and metabolic diseases such as type 2 diabetes (T2D). Here, we evidenced physiological mechanical loading control of adipocyte insulin signaling cascades. We exposed differentiated 3T3-L1 adipocytes to mechanical stretching and assessed key markers of insulin signaling, AKT activation, and GLUT4 translocation, required for glucose uptake. We showed that cyclic stretch loading at 5% strain and 1 Hz frequency increases AKT phosphorylation and GLUT4 translocation to the plasma membrane by approximately two-fold increases compared to unstretched controls for both markers as assessed by immunoblotting (p < 0.05). These results indicate that cyclic stretching activates insulin signaling and GLUT4 trafficking in adipocytes. In the mechanosensing mechanism study, focal adhesion kinase (FAK) inhibitor (FAK14) and RhoA kinase (ROCK) inhibitor (Y-27632) impaired actin cytoskeleton structural formation and significantly suppressed the stretch induction of AKT phosphorylation in adipocytes (p < 0.001). This suggests the regulatory role of focal adhesion and cytoskeletal mechanosensing in adipocyte insulin signaling under stretch loading. Our finding on the impact of mechanical stretch loading on key insulin signaling effectors in differentiated adipocytes and the mediatory role of focal adhesion and cytoskeleton mechanosensors is the first of its kind to our knowledge. This may suggest a therapeutic potential of mechanical loading cue in improving conditions of obesity and T2D. For instance, cyclic mechanical stretch loading of adipose tissue could be explored as a tool to improve insulin sensitivity in patients with obesity and T2D, and the mediatory mechanosensors such as FAK and ROCK may be targeted to further invigorate stretch-induced insulin signaling activation.

PTEN Regulates Myofibroblast Activation in Valvular Interstitial Cells based on Subcellular Localization

Aortic valve stenosis (AVS) is characterized by altered mechanics of the valve leaflets, which disrupts blood flow through the aorta and can cause left ventricle hypotrophy. These changes in the valve tissue result in activation of resident valvular interstitial cells (VICs) into myofibroblasts, which have increased levels of αSMA in their stress fibers. The persistence of VIC myofibroblast activation is a hallmark of AVS. In recent years, the tumor suppressor gene phosphatase and tensin homolog (PTEN) has emerged as an important player in the regulation of fibrosis in various tissues (e.g., lung, skin), which motivated us to investigate PTEN as a potential protective factor against matrix-induced myofibroblast activation in VICs. In aortic valve samples from humans, we found high levels of PTEN in healthy tissue and low levels of PTEN in diseased tissue. Then, using pharmacological inducers to treat VIC cultures, we observed PTEN overexpression prevented stiffness-induced myofibroblast activation, whereas genetic and pharmacological inhibition of PTEN further activated myofibroblasts. We also observed increased nuclear PTEN localization in VICs cultured on stiff matrices, and nuclear PTEN also correlated with smaller nuclei, altered expression of histones and a quiescent fibroblast phenotype. Together, these results suggest that PTEN not only suppresses VIC activation, but functions to promote quiescence, and could serve as a potential pharmacological target for the treatment of AVS.

Mechanisms of mechanical stimulation in the development of respiratory system diseases

During respiration, mechanical stress can initiate biological responses that impact the respiratory system. Mechanical stress plays a crucial role in the development of the respiratory system. However, pathological mechanical stress can impact the onset and progression of respiratory diseases by influencing the extracellular matrix and cell transduction processes. In this article, we explore the mechanisms by which mechanical forces communicate with and influence cells. We outline the basic knowledge of respiratory mechanics, elucidating the important role of mechanical stimulation in influencing respiratory system development and differentiation from a microscopic perspective. We also explore the potential mechanisms of mechanical transduction in the pathogenesis and development of respiratory diseases such as asthma, lung injury, pulmonary fibrosis, and lung cancer. Finally, we look forward to new research directions in cellular mechanotransduction, aiming to provide fresh insights for future therapeutic research on respiratory diseases.

Mechanosensitive ion channel Piezo1 mediates mechanical ventilation-exacerbated ARDS-associated pulmonary fibrosis

INTRODUCTION

Pulmonary fibrosis is a major cause of the poor prognosis of acute respiratory distress syndrome (ARDS). While mechanical ventilation (MV) is an indispensable life-saving intervention for ARDS, it may cause the remodeling process in lung epithelial cells to become disorganized and exacerbate ARDS-associated pulmonary fibrosis. Piezo1 is a mechanosensitive ion channel that is known to play a role in regulating diverse physiological processes, but whether Piezo1 is necessary for MV-exacerbated ARDS-associated pulmonary fibrosis remains unknown.

OBJECTIVES

This study aimed to explore the role of Piezo1 in MV-exacerbated ARDS-associated pulmonary fibrosis.

METHODS

Human lung epithelial cells were stimulated with hydrochloric acid (HCl) followed by mechanical stretch for 48 h. A two-hitmodel of MV afteracidaspiration-inducedlunginjuryin mice was used. Mice were sacrificed after 14 days of MV. Pharmacological inhibition and knockout of Piezo1 were used to delineate the role of Piezo1 in MV-exacerbated ARDS-associated pulmonary fibrosis. In some experiments, ATP or the ATP-hydrolyzing enzyme apyrase was administered.

RESULTS

The stimulation of human lung epithelial cells to HCl resulted in phenotypes of epithelial-mesenchymal transition (EMT), which were enhanced by mechanical stretching. MV exacerbated pulmonary fibrosis in mice exposed to HCl. Pharmacologicalinhibitionorknockout of Piezo1 attenuated the MV-exacerbated EMT process and lung fibrosis in vivo and in vitro. Mechanistically, the observed effects were mediated by Piezo1-dependent Ca2+ influx and ATP release in lung epithelial cells.

CONCLUSIONS

Our findings identify a key role for Piezo1 in MV-exacerbated ARDS-associated pulmonary fibrosis that is mediated by increased ATP release in lung epithelial cells. Inhibiting Piezo1 may constitute a novelstrategyfor the treatment of MV-exacerbated ARDS-associated pulmonary fibrosis.

Reduction of TRPC1/TRPC3 mediated Ca2+-signaling protects oxidative stress-induced COPD

Oxidative stress is a predisposing factor in Chronic Obstructive Pulmonary Disease (COPD). Specifically, pulmonary epithelial (PE) cells reduce antioxidant capacity during COPD because of the continuous production of reactive oxygen species (ROS). However, the molecular pathogenesis that governs such ROS activity is unclear. Here we show that the dysregulation of intracellular calcium concentration ([Ca2+]i) in PE cells from COPD patients, compared to the healthy PE cells, is associated with the robust functional expressions of Transient Receptor Potential Canonical (TRPC)1 and TRPC3 channels, and Ca2+ entry (SOCE) components, Stromal Interaction Molecule 1 (STIM1) and ORAI1 channels. Additionally, the elevated expression levels of fibrotic, inflammatory, oxidative, and apoptotic markers in cells from COPD patients suggest detrimental pathway activation, thereby reducing the ability of lung remodeling. To further delineate the mechanism, we used human lung epithelial cell line, A549, since the behavior of SOCE and the expression patterns of TRPC1/C3, STIM1, and ORAI1 were much like PE cells. Notably, the knockdown of TRPC1/C3 in A549 cells substantially reduced the SOCE-induced [Ca2+]i rise, and reversed the ROS-mediated oxidative, fibrotic, inflammatory, and apoptotic responses, thus confirming the role of TRPC1/C3 in SOCE driven COPD-like condition. Higher TRPC1/C3, STIM1, and ORAI1 expressions, along with a greater Ca2+ entry, via SOCE in ROS-induced A549 cells, led to the rise in oxidative, fibrotic, inflammatory, and apoptotic gene expression, specifically through the extracellular signal-regulated kinase (ERK) pathway. Abatement of TRPC1 and/or TRPC3 reduced the mobilization of [Ca2+]i and reversed apoptotic gene expression and ERK activation, signifying the involvement of TRPC1/C3. Together these data suggest that TRPC1/C3 and SOCE facilitate the COPD condition through ROS-mediated cell death, thus implicating their likely roles as potential therapeutic targets for COPD. SUMMARY: Alterations in Ca2+ signaling modalities in normal pulmonary epithelial cells exhibit COPD through oxidative stress and cellular injury, compromising repair, which was alleviated through inhibition of store-operated calcium entry. SUBJECT AREA: Calcium, ROS, Cellular signaling, lung disease.

PTEN: An Emerging Potential Target for Therapeutic Intervention in Respiratory Diseases

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a potent tumor suppressor that regulates several key cellular processes, including proliferation, survival, genomic integrity, migration, and invasion, via PI3K-dependent and independent mechanisms. A subtle decrease in PTEN levels or catalytic activity is implicated not only in cancer but also in a wide spectrum of other diseases, including various respiratory diseases. A systemic overview of the advances in the molecular and cellular mechanisms of PTEN involved in the initiation and progression of respiratory diseases may offer novel targets for the development of effective therapeutics for the treatment of respiratory diseases. In the present review, we highlight the novel findings emerging from current research on the role of PTEN expression and regulation in airway pathological conditions such as asthma/allergic airway inflammation, pulmonary hypertension (PAH), chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and other acute lung injuries (ALI). Moreover, we discuss the clinical implications of PTEN alteration and recently suggested therapeutic possibilities for restoration of PTEN expression and function in respiratory diseases.

Focusing on Mechanoregulation Axis in Fibrosis: Sensing, Transduction and Effecting

Fibrosis, a pathologic process featured by the excessive deposition of connective tissue components, can affect virtually every organ and has no satisfactory therapy yet. Fibrotic diseases are often associated with organ dysfunction which leads to high morbidity and mortality. Biomechanical stmuli and the corresponding cellular response havebeen identified in fibrogenesis, as the fibrotic remodeling could be seen as the incapacity to reestablish mechanical homeostasis: along with extracellular matrix accumulating, the physical property became more “stiff” and could in turn induce fibrosis. In this review, we provide a comprehensive overview of mechanoregulation in fibrosis, from initialing cellular mechanosensing to intracellular mechanotransduction and processing, and ends up in mechanoeffecting. Our contents are not limited to the cellular mechanism, but further expand to the disorders involved and current clinical trials, providing an insight into the disease and hopefully inspiring new approaches for the treatment of tissue fibrosis.

Mechanotransduction Regulates the Interplays Between Alveolar Epithelial and Vascular Endothelial Cells in Lung

Mechanical stress plays a critical role among development, functional maturation, and pathogenesis of pulmonary tissues, especially for the alveolar epithelial cells and vascular endothelial cells located in the microenvironment established with vascular network and bronchial-alveolar network. Alveolar epithelial cells are mainly loaded by cyclic strain and air pressure tension. While vascular endothelial cells are exposed to shear stress and cyclic strain. Currently, the emerging evidences demonstrated that non-physiological mechanical forces would lead to several pulmonary diseases, including pulmonary hypertension, fibrosis, and ventilation induced lung injury. Furthermore, a series of intracellular signaling had been identified to be involved in mechanotransduction and participated in regulating the physiological homeostasis and pathophysiological process. Besides, the communications between alveolar epithelium and vascular endothelium under non-physiological stress contribute to the remodeling of the pulmonary micro-environment in collaboration, including hypoxia induced injuries, endothelial permeability impairment, extracellular matrix stiffness elevation, metabolic alternation, and inflammation activation. In this review, we aim to summarize the current understandings of mechanotransduction on the relation between mechanical forces acting on the lung and biological response in mechanical overloading related diseases. We also would like to emphasize the interplays between alveolar epithelium and vascular endothelium, providing new insights into pulmonary diseases pathogenesis, and potential targets for therapy.

Inhibition of MicroRNA-214 Alleviates Lung Injury and Inflammation via Increasing FGFR1 Expression in Ventilator-Induced Lung Injury

PURPOSE

Ventilator-induced lung injury (VILI) is an additional inflammatory injury caused by mechanical ventilation (MV). This study aimed to determine the effects of microRNA-214 (miR-214) on VILI and its underlying mechanism of action.

METHODS

To develop a VILI mouse model, mice were subjected to MV. The expression of miR-214 was detected by qRT-PCR. The macrophages, fibroblasts, epithelial cells, and endothelial cells were isolated from lung tissues by fluorescence-activated cell sorting. The histopathological changes of lung, lung wet/dry weight (W/D) ratio, and myeloperoxidase (MPO) activity were used to evaluate the degree of lung injury. The levels of pro-inflammatory cytokines in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA). Dual-luciferase reporter assay was performed to determine the interactions between miR-214 and FGFR1. Western blot was used to detect the protein expression of FGFR1, p-AKT, and p-PI3K.

RESULTS

The expression of miR-214 was increased in lung tissues and macrophages, fibroblasts, epithelial cells, and endothelial cells isolated from lung tissues in VILI mice. MiR-214 inhibition decreased the histopathological changes of lung, lung W/D ratio, MPO activity, and pro-inflammatory cytokines levels in BALF in VILI mice. FGFR1 was targeted by miR-214. The protein expression of FGFR1 was decreased in VILI mice. Ponatinib (FGFR1 inhibitor) reversed the suppressive effects of miR-214 inhibition on lung injury and inflammation of VILI mice. MiR-214 increased the activity of PI3K/AKT pathway by regulating FGFR1.

CONCLUSIONS

Inhibition of miR-214 attenuated lung injury and inflammation in VILI mice by increasing FGFR1 expression, providing a novel therapeutic target for VILI.

Alveolar cells under mechanical stressed niche: critical contributors to pulmonary fibrosis

Pulmonary fibrosis arises from the repeated epithelial mild injuries and insufficient repair lead to over activation of fibroblasts and excessive deposition of extracellular matrix, which result in a mechanical stretched niche. However, increasing mechanical stress likely exists before the establishment of fibrosis since early micro injuries increase local vascular permeability and prompt cytoskeletal remodeling which alter cellular mechanical forces. It is noteworthy that COVID-19 patients with severe hypoxemia will receive mechanical ventilation as supportive treatment and subsequent pathology studies indicate lung fibrosis pattern. At advanced stages, mechanical stress originates mainly from the stiff matrix since boundaries between stiff and compliant parts of the tissue could generate mechanical stress. Therefore, mechanical stress has a significant role in the whole development process of pulmonary fibrosis. The alveoli are covered by abundant capillaries and function as the main gas exchange unit. Constantly subject to variety of damages, the alveolar epithelium injuries were recently recognized to play a vital role in the onset and development of idiopathic pulmonary fibrosis. In this review, we summarize the literature regarding the effects of mechanical stress on the fundamental cells constituting the alveoli in the process of pulmonary fibrosis, particularly on epithelial cells, capillary endothelial cells, fibroblasts, mast cells, macrophages and stem cells. Finally, we briefly review this issue from a more comprehensive perspective: the metabolic and epigenetic regulation.

Strategies to Modulate MicroRNA Functions for the Treatment of Cancer or Organ Injury

Cancer and organ injury-such as that occurring in the perioperative period, including acute lung injury, myocardial infarction, and acute gut injury-are among the leading causes of death in the United States and impose a significant impact on quality of life. MicroRNAs (miRNAs) have been studied extensively during the last two decades for their role as regulators of gene expression, their translational application as diagnostic markers, and their potential as therapeutic targets for disease treatment. Despite promising preclinical outcomes implicating miRNA targets in disease treatment, only a few miRNAs have reached clinical trials. This likely relates to difficulties in the delivery of miRNA drugs to their targets to achieve efficient inhibition or overexpression. Therefore, understanding how to efficiently deliver miRNAs into diseased tissues and specific cell types in patients is critical. This review summarizes current knowledge on various approaches to deliver therapeutic miRNAs or miRNA inhibitors and highlights current progress in miRNA-based disease therapy that has reached clinical trials. Based on ongoing advances in miRNA delivery, we believe that additional therapeutic approaches to modulate miRNA function will soon enter routine medical treatment of human disease, particularly for cancer or perioperative organ injury. SIGNIFICANCE STATEMENT: MicroRNAs have been studied extensively during the last two decades in cancer and organ injury, including acute lung injury, myocardial infarction, and acute gut injury, for their regulation of gene expression, application as diagnostic markers, and therapeutic potentials. In this review, we specifically emphasize the pros and cons of different delivery approaches to modulate microRNAs, as well as the most recent exciting progress in the field of therapeutic targeting of microRNAs for disease treatment in patients.

Transient receptor potential canonical 1 channel mediates the mechanical stress‑induced epithelial‑mesenchymal transition of human bronchial epithelial (16HBE) cells

Airway remodeling is a central event in the pathology of chronic obstructive pulmonary disease (COPD) that leads to airway narrowing and subsequently, to increased mechanical pressure. High mechanical pressure can exacerbate airway remodeling. Thus, a treatment regimen aimed at disrupting this high‑pressure airway remodeling vicious cycle may improve the prognosis of patients with COPD. Recent studies have demonstrated that mechanical stress induces lung epithelial‑mesenchymal transition (EMT), which is commonly present in airway epithelial cells of patients with COPD. As TRPC1 functions as a mechanosensitive channel that mediates non‑selective cation entry in response to increased membrane stretch, the present study investigated the role of TRPC1 in the occurrence of EMT induced by mechanical stress. In the present study, the expression of TRPC1 in the bronchial epithelium was examined in vivo by immunohistochemistry. In vitro, human bronchial epithelial (16HBE) cells were subjected to mechanical stretching for up to 48 h, and TRPC1 expression was then examined by RT‑qPCR and western blot analysis. In addition, TRPC1 receptor function was assessed by Ca2+ imaging and siRNA transfection. EMT was identified using immunofluorescence, western blot analysis and RT‑qPCR. It was found that TRPC1 expression was upregulated in patients with COPD and in 16HBE cells subjected to mechanical stretch. The mechanical stress‑induced activation of TRPC1 in 16HBE cells increased the intracellular calcium concentration and subsequently decreased the expression of cytokeratin 8 and E‑cadherin, and increased the expression of α‑smooth muscle actin, indicating the occurrence of EMT. On the whole, the findings of the present study demonstrate that TRPC1 plays a key role in the occurrence of EMT in human lung epithelial cells in response to mechanical stretch; thus, this protein may serve as a novel therapeutic target for progressive airway remodeling in COPD.

Alveolar Dynamics and Beyond - The Importance of Surfactant Protein C and Cholesterol in Lung Homeostasis and Fibrosis

Surfactant protein C (SP-C) is an important player in enhancing the interfacial adsorption of lung surfactant lipid films to the alveolar air-liquid interface. Doing so, surface tension drops down enough to stabilize alveoli and the lung, reducing the work of breathing. In addition, it has been shown that SP-C counteracts the deleterious effect of high amounts of cholesterol in the surfactant lipid films. On its side, cholesterol is a well-known modulator of the biophysical properties of biological membranes and it has been proven that it activates the inflammasome pathways in the lung. Even though the molecular mechanism is not known, there are evidences suggesting that these two molecules may interplay with each other in order to keep the proper function of the lung. This review focuses in the role of SP-C and cholesterol in the development of lung fibrosis and the potential pathways in which impairment of both molecules leads to aberrant lung repair, and therefore impaired alveolar dynamics. From molecular to cellular mechanisms to evidences in animal models and human diseases. The evidences revised here highlight a potential SP-C/cholesterol axis as target for the treatment of lung fibrosis.

Role of AKT and mTOR signaling pathways in the induction of epithelial-mesenchymal transition (EMT) process

Epithelial-mesenchymal transition (EMT) is a critical process in the development of many tissues and organs in multicellular organisms that its important role in the pathogenesis of metastasis and tumor cell migration has been firmly established. Decreased adhesive capacity, cytoskeletal reorganization, and increased mobility are hallmarks of the EMT. Several molecular mechanisms promote EMT, Including regulation of the levels of specific cell-surface proteins, ECM-degrading enzymes, and altering the expression of certain transcription factors and microRNAs. EMT process is modulated through multiple signaling pathways including the AKT/mTOR pathway. AKT is a key component in numerous processes which was recently shown to regulate the EMT through suppression of the expression of E-cadherin via EMT transcription factors. On the other hand, mTOR complexes can also regulate the EMT through the regulation of cell's actin cytoskeleton by altering the PKC phosphorylation state and direct phosphorylation and activation of Akt. Here we review the effect of AKT and mTOR on EMT and consequently metastasis and cell motility.

High amplitude stretching of ATII cells and fibroblasts results in profibrotic effects

Background: Inappropriate mechanical forces act on alveolar epithelial cells during mechanical ventilation e.g. in ARDS and possibly in patients with pulmonary fibrosis. These forces can cause lung injury and may contribute to the development or aggravation of pulmonary fibrosis. Aim of the study: We investigated the hypothesis that high amplitude mechanical stretching of alveolar type II (ATII) cells and lung fibroblasts promotes profibrotic processes. Material and Methods: ATII cells and fibroblasts were stretched on elastic membranes using a pattern of higher amplitudes ("unphysiological"). The production of profibrotic cytokines and extra cellular matrix (ECM) proteins were investigated in supernatants. In addition, we determined the expression of relevant microRNAs (miRNA) and the process of epithelial-mesenchymal transition (EMT) in ATII cells. Results: Unphysiological stretch of ATII cells led to increased release of TGF-β1 into supernatants. We also found elevated protein levels of collagen I and IV in supernatants of stretched cells. By contrast, stretching of fibroblasts changed neither the expression of fibrosis-modulating factors nor ECM-proteins. However, fibroblasts significantly withstood stretch-induced cell injury and seemed to have a survival benefit. Further, stretched ATII cells exhibited a higher expression of miRNAs (miR-15b, miR-25, let-7d) relevant to EMT. The process of EMT, which is characterized by an increase of vimentin and a decrease of cytokeratin expression, was significantly accelerated due to stretching of ATII cells. Conclusion: These data provide evidence that unphysiological mechanical stretching of lung cells induced several profibrotic effects and accelerated EMT, which may have critical implications in terms of development or aggravation of pulmonary fibrosis in the clinical context.

CD103-positive CSC exosome promotes EMT of clear cell renal cell carcinoma: role of remote MiR-19b-3p

Background

Clear cell renal cell carcinoma (CCRCC) is characterized by a highly metastatic potential. The stromal communication between stem cells and cancer cells critically influences metastatic dissemination of cancer cells.

Methods

The effect of exosomes isolated from cancer stem cells (CSCs) of CCRCC patients on the progress of epithelial-mesenchymal transition (EMT) and lung metastasis of CCRCC cells were examined.

Results

CSCs exosomes promoted proliferation of CCRCC cells and accelerated the progress of EMT. Bioactive miR-19b-3p transmitted to cancer cells by CSC exosomes induced EMT via repressing the expression of PTEN. CSCs exosomes derived from CCRCC patients with lung metastasis produced the strongest promoting effect on EMT. Notably, CD103⁺ CSC exosomes were enriched in tumor cells and in lung as well, highlighting the organotropism conferred by CD103. In addition, CD103⁺ exosomes were increased in blood samples from CCRCC patients with lung metastasis.

Conclusions

CSC exosomes transported miR-19b-3p into CCRCC cells and initiated EMT promoting metastasis. CD103⁺ acted to guide CSC exosomes to target cancer cells and organs, conferring the higher metastatic capacity of CCRCC to lungs, suggesting CD103⁺ exosomes as a potential metastatic diagnostic biomarker.

Graphical abstract

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Electronic supplementary material

The online version of this article (10.1186/s12943-019-0997-z) contains supplementary material, which is available to authorized users.

Hydrogen Sulfide Prevents Formation of Reactive Oxygen Species through PI3K/Akt Signaling and Limits Ventilator-Induced Lung Injury

The development of ventilator-induced lung injury (VILI) is still a major problem in mechanically ventilated patients. Low dose inhalation of hydrogen sulfide (H₂S) during mechanical ventilation has been proven to prevent lung damage by limiting inflammatory responses in rodent models. However, the capacity of H₂S to affect oxidative processes in VILI and its underlying molecular signaling pathways remains elusive. In the present study we show that ventilation with moderate tidal volumes of 12 ml/kg for 6 h led to an excessive formation of reactive oxygen species (ROS) in mice lungs which was prevented by supplemental inhalation of 80 parts per million of H₂S. In addition, phosphorylation of the signaling protein Akt was induced by H₂S. In contrast, inhibition of Akt by LY294002 during ventilation reestablished lung damage, neutrophil influx, and proinflammatory cytokine release despite the presence of H₂S. Moreover, the ability of H₂S to induce the antioxidant glutathione and to prevent ROS production was reversed in the presence of the Akt inhibitor. Here, we provide the first evidence that H₂S-mediated Akt activation is a key step in protection against VILI, suggesting that Akt signaling limits not only inflammatory but also detrimental oxidative processes that promote the development of lung injury.