Autophagy is central to the maintenance of organismal homeostasis in both physiological and pathological situations Accordingly, alterations in autophagy have been linked to clinically relevant conditions as diverse as cancer, neurodegeneration and cardiac disorders Throughout the past decade, autophagy has attracted considerable attention as a target for the development of novel therapeutics However, such efforts have not yet generated clinically viable interventions In this Review, we discuss the therapeutic potential of autophagy modulators, analyse the obstacles that have limited their development and propose strategies that may unlock the full therapeutic potential of autophagy modulation in the clinic

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Pharmacological modulation of autophagy: therapeutic potential and persisting obstacles.

The enhancement of immune responses upon treatment with immune checkpoint inhibitors can have the desired outcome of reinvigorating antitumour immune surveillance, but often at the expense of immune-related adverse events (irAEs). This novel disease entity often prompts comparisons with, and extrapolation of treatment approaches from, primary autoimmune disorders. Accordingly, current treatment guidelines for irAEs make generic recommendations adapted from the literature describing primary autoimmune diseases, without taking into consideration the substantial disparity of the immunohistopathological findings within each organ affected by an irAE. The treatment modalities themselves are complex and have many potential drawbacks, such as serious and rarely fatal infections, drug toxicities overlapping with irAEs and the risk of compromising cancer immune surveillance. Herein, we provide an overview of key cellular and soluble immunological factors mediating irAEs and propose a model integrating this knowledge with the immunohistopathological findings of the affected organs for a personalized decision-making process for each patient. The treatment of immune-related adverse events (irAEs) in patients receiving immune checkpoint inhibitors has mostly been based on adapting therapeutic approaches used in the management of primary autoimmune diseases. The authors of this Review provide an overview of the different cellular and soluble immune factors involved in the pathogenesis of irAEs in order to help clinicians deliver personalized immunopathologically guided treatment to manage these adverse events.

Moving towards personalized treatments of immune-related adverse events.

Environmental ultrafine particulate matter (PM) is capable of inducing airway injury, while the detailed molecular mechanisms remain largely unclear. Here, we demonstrate pivotal roles of autophagy in regulation of inflammation and mucus hyperproduction induced by PM containing environmentally persistent free radicals in human bronchial epithelial (HBE) cells and in mouse airways. PM was endocytosed by HBE cells and simultaneously triggered autophagosomes, which then engulfed the invading particles to form amphisomes and subsequent autolysosomes. Genetic blockage of autophagy markedly reduced PM-induced expression of inflammatory cytokines, e.g. IL8 and IL6, and MUC5AC in HBE cells. Mice with impaired autophagy due to knockdown of autophagy-related gene Becn1 or Lc3b displayed significantly reduced airway inflammation and mucus hyperproduction in response to PM exposure in vivo. Interference of the autophagic flux by lysosomal inhibition resulted in accumulated autophagosomes/amphisomes, and intriguingly, this process significantly aggravated the IL8 production through NFKB1, and markedly attenuated MUC5AC expression via activator protein 1. These data indicate that autophagy is required for PM-induced airway epithelial injury, and that inhibition of autophagy exerts therapeutic benefits for PM-induced airway inflammation and mucus hyperproduction, although they are differentially orchestrated by the autophagic flux.

https://www.tandfonline.com/doi/pdf/10.1080/15548627.2015.1124224

Autophagy is essential for ultrafine particle-induced inflammation and mucus hyperproduction in airway epithelium

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the severe lung damage and respiratory failure without effective therapy. However, there was a lack of understanding of the mechanism by which exosomes regulate autophagy during ALI/ARDS. Here, we found lipopolysaccharide (LPS) significantly increased inflammatory factors, administration of exosomes released by human umbilical cord mesenchymal stem cells (hucMSCs) successfully improved lung morphometry. Further studies showed that miR-377-3p in the exosomes played a pivotal role in regulating autophagy, leading to protect LPS induced ALI. Compared to exosomes released by human fetal lung fibroblast cells (HFL-1), hucMSCs-exosomes overexpressing miR-377-3p more effectively suppressed the bronchoalveolar lavage (BALF) and inflammatory factors and induced autophagy, causing recoveration of ALI. Administration of miR-377-3p expressing hucMSCs-exosomes or its target regulatory-associated protein of mTOR (RPTOR) knockdown significantly reduced ALI. In summary, miR-377-3p released by hucMSCs-exosomes ameliorated Lipopolysaccharide-induced acute lung injury by targeting RPTOR to induce autophagy in vivo and in vitro.

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MicroRNA-377-3p released by mesenchymal stem cell exosomes ameliorates lipopolysaccharide-induced acute lung injury by targeting RPTOR to induce autophagy

MTOR (mechanistic target of rapamycin [serine/threonine kinase]) plays a crucial role in many major cellular processes including metabolism, proliferation and macroautophagy/autophagy induction, and is also implicated in a growing number of proliferative and metabolic diseases. Both MTOR and autophagy have been suggested to be involved in lung disorders, however, little is known about the role of MTOR and autophagy in pulmonary epithelium in the context of acute lung injury (ALI). In the present study, we observed that lipopolysaccharide (LPS) stimulation induced MTOR phosphorylation and decreased the expression of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 β)-II, a hallmark of autophagy, in mouse lung epithelium and in human bronchial epithelial (HBE) cells. The activation of MTOR in HBE cells was mediated by TLR4 (toll-like receptor 4) signaling. Genetic knockdown of MTOR or overexpression of autophagy-related proteins significantly attenuated, whereas inhibition of autophagy ...

https://www.tandfonline.com/doi/pdf/10.1080/15548627.2016.1230584

Activation of MTOR in pulmonary epithelium promotes LPS-induced acute lung injury.

Background Asthmatic inflammation is dominated by accumulation of either eosinophils, neutrophils, or both in the airways. Disposal of these inflammatory cells is the key to disease control. Eosinophilic airway inflammation is responsive to corticosteroid treatment, whereas neutrophilic inflammation is resistant and increases the burden of global health care. Corticosteroid-resistant neutrophilic asthma remains mechanistically poorly understood and requires novel effective therapeutic strategies. Objective We sought to explore the underlying mechanisms of airway inflammation persistence, as well as corticosteroid resistance, and to investigate a new strategy of effective treatment against corticosteroid-insensitive neutrophilic asthma. Methods Mouse models of either eosinophil-dominated or neutrophil-dominated airway inflammation were used in this study to test corticosteroid sensitivity in vivo and in vitro . We also used vav–Bcl-2 transgenic mice to confirm the importance of granulocytes apoptosis in the clearance of airway inflammation. Finally, the Bcl-2 inhibitors ABT-737 or ABT-199 were tested for their therapeutic effects against eosinophilic or neutrophilic airway inflammation and airway hyperresponsiveness. Results Overexpression of Bcl-2 protein was found to be responsible for persistence of granulocytes in bronchoalveolar lavage fluid after allergic challenge. This was important because allergen-induced airway inflammation aggravated and persisted in vav–Bcl-2 transgenic mice, in which nucleated hematopoietic cells were overexpressed with Bcl-2 and resistant to apoptosis. The Bcl-2 inhibitors ABT-737 or ABT-199 play efficient roles in alleviation of either eosinophilic or corticosteroid-resistant neutrophilic airway inflammation by inducing apoptosis of immune cells, such as eosinophils, neutrophils, T H 2 cells, T H 17 cells, and dendritic cells. Moreover, these inhibitors were found to be more efficient than steroids to induce granulocyte apoptosis ex vivo from patients with severe asthma. Conclusion Apoptosis of inflammatory cells is essential for clearance of allergen-induced airway inflammation. The Bcl-2 inhibitors ABT-737 or ABT-199 might be promising drugs for the treatment of airway inflammation, especially for corticosteroid-insensitive neutrophilic airway inflammation.

Bcl-2 Inhibitors Reduce Steroid-insensitive Airway Inflammation.

mTOR and autophagy in regulation of acute lung injury: a review and perspective

Eosinophil infiltration is considered a hallmark in allergic airway inflammation, and the blockade of eosinophil differentiation may be an effective approach for treating eosinophil-related disorders. Mammalian target of rapamycin (mTOR) is a vital modulator in cell growth control and related diseases, and we have recently demonstrated that rapamycin can suppress eosinophil differentiation in allergic airway inflammation. Considering its critical role in haematopoiesis, we further investigated the role of mTOR in eosinophil differentiation in the context of asthmatic pathogenesis. Intriguingly, the inhibition of mTOR, either by genetic deletion or by another pharmacological inhibitor torin-1, accelerated the eosinophil development in the presence of IL-5. However, this was not observed to have any considerable effect on eosinophil apoptosis. The effect of mTOR in eosinophil differentiation was mediated by Erk signalling. Moreover, myeloid specific knockout of mTOR or Rheb further augmented allergic airway inflammation in mice after allergen exposure. Ablation of mTOR in myeloid cells also resulted in an increased number of eosinophil lineage-committed progenitors (Eops) in allergic mice. Collectively, our data uncovered the differential effects of mTOR in the regulation of eosinophil development, likely due to the distinct functions of mTOR complex 1 or 2, which thus exerts a pivotal implication in eosinophil-associated diseases.

mTOR complexes differentially orchestrates eosinophil development in allergy.

Mechanistic target of rapamycin (MTOR) plays a crucial role in many major cellular processes includingmetabolism, proliferation and autophagy induction, and is also implicated in a growing number of proliferative and metabolic diseases. Both MTOR and autophagy have been suggested to be involved in lung disorders, however, little is known about the role of MTOR and autophagy in pulmonary epithelium in the context of acute lung injury (ALI).In the present study, we observed that LPS stimulation induced MTORphosphorylation and decreased the expression of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3β)-II, a hallmark of autophagy, in mouse lung epithelium and in human bronchial epithelial (HBE) cells. The activation of MTOR in HBE cells was mediated by the toll-like receptor 4 signaling. Genetic knockdown of MTOR or overexpression of autophagy-related proteins significantly attenuated, while inhibition of autophagy further augmented LPS-induced expression of interleukin 6 (IL6) and IL8, through NFKB signaling in HBE cells. Mice with specific knockdown of Mtor in bronchial or alveolar epithelial cells exhibited significantly attenuated airway inflammation, barrier disruption, and lung edema, and displayed prolonged survival in response to LPS exposure.Taken together, our results demonstrate that activation of MTOR in the epithelium promotes LPS-induced ALI, likely through down-regulation of autophagy and its subsequent activation of NFKB. Thus,inhibition of MTOR in pulmonary epithelial cells may represent a novel therapeutic strategy for preventing ALI induced by certain bacteria.

Yuan-Yuan Mao

Papers

Activation of MTOR in pulmonary epithelium promotes LPS-induced acute lung injury.

Bcl-2 Inhibitors Reduce Steroid-insensitive Airway Inflammation.

mTOR and autophagy in regulation of acute lung injury: a review and perspective

mTOR complexes differentially orchestrates eosinophil development in allergy.

LATE-BREAKING ABSTRACT: Activation of MTOR in pulmonary epithelium promotes LPS-induced acute lung injury