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

ABSTRACT: 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 ?)-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 further augmented, LPS-induced expression of IL6 (interleukin 6) 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 downregulation of autophagy and the 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.

SUBMITTER: Hu Y

PROVIDER: S-EPMC5173285 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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

Hu Yue Y Lou Jian J Mao Yuan-Yuan YY Lai Tian-Wen TW Liu Li-Yao LY Zhu Chen C Zhang Chao C Liu Juan J Li Yu-Yan YY Zhang Fan F Li Wen W Ying Song-Min SM Chen Zhi-Hua ZH Shen Hua-Hao HH

Autophagy 20160922 12

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 ...[more]

PMID: 27658023

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Project description:BackgroundAcute lung injury/acute respiratory distress syndrome (ALI/ARDS) are clinical syndromes characterized by acute lung inflammation, pulmonary edema and hypoxemia, with up to 50% mortality rate without effective pharmacological therapy. Following the acute inflammation, repair and remodeling occurs which in some cases resulting in lung fibrosis. The pathophysiology of ALI/ARDS remains incompletely understood. Lipopolysaccharide (LPS)-induced ALI in mice have been widely used as a model to study human ALI/ARDS. Isthmin 1 (ISM1) is a secreted protein highly abundant in mouse lung. We have previously reported that upon intratracheal LPS instillation, ISM1 expression in the lung is further upregulated. Recently, we also reported that ISM1 is an anti-inflammatory protein in the lung with Ism1-/- mice presenting spontaneous chronic low-grade lung inflammation and obvious emphysema at young adult stage. However, what role ISM1 plays in ALI/ARDS and lung fibrosis remain unclear.MethodsUsing Ism1-/- mice and intratracheal LPS-induced ALI, and local delivery of recombinant ISM1 (rISM1), we investigated the role ISM1 plays in ALI and post-ALI lung fibrosis using flow cytometry, Western blot, antibody array, immunohistochemistry (IHC), immunofluorescent and other histological staining.ResultsWe reveal that ISM1 deficiency in mice led to an intensified acute lung inflammation upon intratracheal LPS challenge, with a heightened leukocyte infiltration including neutrophils and monocyte-derived alveolar macrophages, as well as upregulation of multiple pro-inflammatory cytokines/chemokines including tumor necrosis factor α (TNF-α). Although innate immune cells largely subsided to the baseline by day 7 post-LPS challenge in both wild-type and Ism1-/- mice, Ism1-/- lung showed increased post-ALI fibrosis from day 9 post-LPS treatment with increased myofibroblasts, excessive collagen accumulation and TGF-β upregulation. The heightened lung fibrosis remained on day 28 post-LPS. Moreover, intranasal delivered recombinant ISM1 (rISM1) effectively suppressed LPS-induced acute lung inflammation and ALI, and rISM1 suppressed LPS-induced NF-κB activation in cultured mouse alveolar macrophages.ConclusionTogether with our previous report, this work further established ISM1 as an endogenous anti-inflammation protein in the lung, restraining excessive host inflammatory response to LPS-triggered ALI and suppressing post-ALI lung fibrosis likely through suppressing NF-κB activation and pro-inflammatory cytokine/chemokine production.

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

Publications

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

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