Yinfang Wu

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

The mammalian target of rapamycin (mTOR) is a central regulator of many major cellular processes including protein and lipid synthesis and autophagy, and is also implicated in an increasing number of pathological conditions. Emerging evidence suggests that both mTOR and autophagy are critically involved in the pathogenesis of pulmonary diseases including acute lung injury (ALI). However, the detailed mechanisms of these pathways in disease pathogenesis require further investigations. In certain cases within the same disease, the functions of mTOR and autophagy may vary from different cell types and pathogens. Here we review recent advances about the basic machinery of mTOR and autophagy, and their roles in ALI. We further discuss and propose the likelihood of cell type- and pathogen-dependent functions of these pathways in ALI pathogenesis.

Autophagy plays an essential role in cigarette smoke-induced expression of MUC5AC in airway epithelium

Mucus hypersecretion is a common pathological feature of chronic airway inflammatory diseases including chronic obstructive pulmonary disease (COPD). However, the molecular basis for this condition remains incompletely understood. We have previously demonstrated a critical role of autophagy in COPD pathogenesis through mediating apoptosis of lung epithelial cells. In this study, we aimed to investigate the function of autophagy as well as its upstream and downstream signals in cigarette smoke-induced mucus production in human bronchial epithelial (HBE) cells and in mouse airways. Cigarette smoke extract (CSE), as well as the classical autophagy inducers starvation or Torin-1, significantly triggered MUC5AC expression, and inhibition of autophagy markedly attenuated CSE-induced mucus production. The CSE-induced autophagy was mediated by mitochondrial reactive oxygen species (mitoROS), which regulated mucin expression through the JNK and activator protein-1 pathway. Epidermal growth factor receptor (EGFR) was also required for CSE-induced MUC5AC in HBE cells, but it exerted inconsiderable effects on the autophagy-JNK signaling cascade. Airways of mice with dysfunctional autophagy-related genes displayed a markedly reduced number of goblet cells and attenuated levels of Muc5ac in response to cigarette smoke exposure. These results altogether suggest that mitoROS-dependent autophagy is essential for cigarette smoke-induced mucus hyperproduction in airway epithelial cells, and reemphasize autophagy inhibition as a novel therapeutic strategy for chronic airway diseases.

P. aeruginosa Lipopolysaccharide-Induced MUC5AC and CLCA3 Expression Is Partly through Duox1 In Vitro and In Vivo

Background We have previously found that reactive oxygen species (ROS) are involved in Pseudomonas aeruginosa lipopolysaccharide (PA-LPS) induced MUC5AC in airway epithelial cells. Dual oxidase1 (Duox1), a member of NADPH oxidase(Nox), is known to be responsible for ROS production in respiratory tract epithelial cells. Our aim was to clarify whether Duox1 was also involved in the PA-LPS-induced MUC5AC and calcium dependent chloride channel 3(Clca3), another recognized marker of goblet cell hyperplasia and mucus hyper-production. Methods PA-LPS-induced Duox1 mRNA levels were examined in A549 cells, primary mouse tracheal epithelial cells (mTECS) and lung tissues of mice. Nox inhibitors diphenyleneiodonium chloride (DPI) and Duox1 siRNA were used to investigate whether Duox1 is involved in PA-LPS-induced MUC5AC and Clca3 expression both in vitro and in vivo. Results Duox1 is induced by PA-LPS in A549 cells, primary mTECs and lung tissues of mice. DPI significantly inhibited PA-LPS-induced up-regulation of Duox1, Muc5ac and Clca3 in primary mouse trachea epithelial cells and lung tissues of mice. Knockdown of Duox1 markedly inhibited PA-LPS-induced MUC5AC expression via a ROS-TGF-α cascade in A549 cells. Furthermore, DPI significantly inhibited PA-LPS-induced increases in inflammatory cells accumulated in mouse lungs. Conclusions We demonstrate for the first time that PA-LPS-induced MUC5AC and Clca3 expression is partly through Duox1, and provide supportive evidence for Duox1 as a potential target in treatments of mucin over-production diseases.

The effect of statins on chronic obstructive pulmonary disease exacerbation and mortality: a systematic review and meta-analysis of observational research

The objective of this study is to assess whether statin use is associated with beneficial effects on COPD outcomes. We conducted a systematic review and meta-analysis of all available studies describing the association between statin use and COPD mortality, exacerbations and cardiovascular events. Medline, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials were searched, with no restrictions. The hazard ratio (HR) with 95% confidence interval (CI) was estimated. Fifteen studies with a total of 238,459 patients were included. Nine articles provided data on all-cause mortality (124,543 participants), and they gave a HR of 0.62 (95% CI 0.52 to 0.73). Three studies provided data on cancer mortality (90,077 participants), HR 0.83 (0.65 to 1.08); four studies on COPD mortality (88,767 participants), HR 0.48 (0.23 to 0.99); and three studies on cardiovascular mortality (90,041 participants), HR 0.93 (0.50 to 1.72). Six articles provided data on COPD exacerbation with or without hospitalization (129,796 participants), HR 0.64 (0.55 to 0.75). Additionally, the use of statins was associated with a significant reduction risk of myocardial infarction, but not for stroke. Our systematic review showed a clear benefit of statins in patients with COPD.

Genetic Polymorphism of Matrix Metalloproteinase Family and Chronic Obstructive Pulmonary Disease Susceptibility: a Meta-analysis

Matrix metalloproteinase (MMP) family is considered to be associated with chronic obstructive pulmonary disease (COPD) pathogenesis, however, no consistent results have been provided by previous studies. In this report, we performed Meta analysis to investigate the association between four kinds of MMP single nucleotide polymorphisms (SNP, MMP1 -1607 1G/2G, MMP3 -1171 5A/6A, MMP9 -1562 C/T, MMP12 -82 A/G) and COPD risk from 21 studies including 4184 cases and 5716 controls. Both overall and subgroup association between SNP and COPD susceptibility were tested. There was no evident association between MMP polymorphisms and COPD susceptibility in general population. On the other hand, subgroup analysis suggested that MMP9 -1562 C/T polymorphism was related to COPD, as we found that C allele carriers were at lower risk in some subgroups stratified by lung function, age and genotype identification method, compared with TT homozygotes. Our results indicated the genotype TT might be one genetic risk factor of severe COPD.

Interleukin-13-induced MUC5AC expression is regulated by a PI3K-NFAT3 pathway in mouse tracheal epithelial cells.

Interleukin-13 (IL-13) plays a critical role in asthma mucus overproduction, while the mechanisms underlying this process are not fully elucidated. Previous studies showed that nuclear factor of activated T cells (NFAT) is involved in the pathogenesis of asthma, but whether it can directly regulate IL-13-induced mucus (particularly MUC5AC) production is still not clear. Here we showed that IL-13 specifically induced NFAT3 activation through promoting its dephosphorylation in air-liquid interface (ALI) cultures of mouse tracheal epithelial cells (mTECs). Furthermore, both Cyclosporin A (CsA, a specific NFAT inhibitor) and LY294002 (a Phosphoinositide 3-kinase (PI3K) inhibitor) significantly blocked IL-13-induced MUC5AC mRNA and protein production through the inhibition of NFAT3 activity. We also confirmed that CsA could not influence the forkhead Box A2 (Foxa2) and mouse calcium dependent chloride channel 3 (mClca3) expression in IL-13-induced MUC5AC production, which both are known to be important in IL-13-stimulated mucus expression. Our study is the first to demonstrate that the PI3K-NFAT3 pathway is positively involved in IL-13-induced mucus production, and provided novel insights into the molecular mechanism of asthma mucus hypersecretion.

Activating transcription factor 3 represses cigarette smoke-induced IL6 and IL8 expression via suppressing NF-κB activation

Airway and lung inflammation is a fundamental hallmark of chronic obstructive pulmonary disease (COPD). Activating transcription factor 3 (ATF3) has been reported to negatively regulate many pro-inflammatory cytokines and chemokines. However, little is known about the impact of ATF3 on the inflammatory response of COPD. Since cigarette smoke (CS) is considered to be the most important risk factor in the etiology of COPD, we attempted to investigate the effects and molecular mechanisms of ATF3 in CS-induced inflammation. We observed an increase in the expression of ATF3 in the lung tissues of CS-exposed mice and CS extract (CSE)-treated human bronchial epithelial (HBE) cells. In vitro results indicated that ATF3 inhibition significantly increased the expression of proinflammatory cytokines interleukin 6 (IL6) and interleukin 8 (IL8) in CSE-stimulated HBE cells. Furthermore, in vivo data verified that CS induced inflammatory cell recruitment around the bronchus. In addition, neutrophil infiltration in bronchoalveolar lavage fluid (BALF) of CS-exposed Atf3-/- mice was markedly higher than in stimulated WT mice. Finally, ATF3 deficiency increased the in vitro and in vivo expression and phosphorylation of nuclear factor-κB (NF-κB), a positive mediator of inflammation. Thus, this study shows that ATF3 plays an important role in the negative regulation of CS-induced pro-inflammatory gene expression through downregulating NF-κB phosphorylation.

Autophagy as a double-edged sword in pulmonary epithelial injury: a review and perspective

Pulmonary epithelial cells form the first line of defense of human airways against foreign irritants and also represent as the primary injury target of these pathogenic assaults. Autophagy is a revolutionary conserved ubiquitous process by which cytoplasmic materials are delivered to lysosomes for degradation when facing environmental and/or developmental changes, and emerging evidence suggests that autophagy plays pivotal but controversial roles in pulmonary epithelial injury. Here we review recent studies focusing on the roles of autophagy in regulating airway epithelial injury induced by various stimuli. Articles eligible for this purpose are divided into two groups according to the eventual roles of autophagy, either protective or deleterious. From the evidence summarized in this review, we draw several conclusions as follows: 1) in all cases when autophagy is decreased from its basal level, autophagy is protective; 2) when autophagy is deleterious, it is generally upregulated by stimulation; and 3) a plausible conclusion is that the endosomal/exosomal pathways may be associated with the deleterious function of autophagy in airway epithelial injury, although this needs to be clarified in future investigations.

Suhuang antitussive capsule at lower doses attenuates airway hyperresponsiveness, inflammation, and remodeling in a murine model of chronic asthma

Suhuang antitussive capsule (Suhuang), a traditional Chinese medication, is found effective in treating chronic cough and cough variant asthma (CVA). This study aimed to determine the possible effects and underlying mechanisms of Suhuang on chronic ovalbumin (OVA)-induced airway hyperresponsiveness (AHR), inflammation, and remodeling in mice. Mice were randomly assigned to six experimental groups: control, OVA model with or without Suhuang (low dose: 3.5 g/kg, middle dose: 7.0 g/kg, high dose: 14.0 g/kg), or dexamethasone (2.5 mg/kg). AHR, inflammatory cells, cytokines in bronchoalveolar lavage fluid (BALF), lung pathology, mucus production, and airway remodeling were examined. We found Suhuang treated at lower doses effectively inhibited OVA-induced AHR, airway inflammation, mucus production and collagen deposition around the airway. High dose of Suhuang reduced most of the inflammatory hallmarks while exerted inconsiderable effects on the number of macrophages in BALF and AHR. At all doses, Suhuang significantly reduced the levels of interlukin (IL) -13 and transforming growth factor (TGF)-β1, but had little effects on IL-4, IL-5, IL-17A and interferon (IFN)-γ. Thus, Suhuang administration alleviates the pathological changes of chronic asthma likely through inhibition of IL-13 and TGF-β1. Suhuang might be a promising therapy for patients with allergic asthma in the future.

TNF-α-308G/A Polymorphism Contributes to Obstructive Sleep Apnea Syndrome Risk: Evidence Based on 10 Case-Control Studies

Objective The aim of our study was to investigate the association between the TNF-α-308G/A polymorphism and obstructive sleep apnea syndrome (OSAS). Method The Medline, Web of Science, EMBASE, Chinese National Knowledge Infrastructure (CNKI), and Cochrane Central Register of Controlled Trials were searched. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to study TNF-α-308G/A polymorphism and risk of OSAS. Result 10 case-control studies were included in our meta-analysis. The results from our study showed that the TNF-α-308G/A polymorphism was significantly associated with risk of OSAS (A vs. G: OR = 1.67, 95% CI = 1.43–1.95). In the subgroup analysis by ethnicity, the statistical similar results were observed both in European (A vs. G: OR = 1.68, 95% CI = 1.35–2.08) and Asian population (A vs. G: OR = 2.02, 95% CI = 1.50–2.71). When stratified by age, a significantly increased risk was observed in adult carries A allele compared with G allele (OR = 1.79, 95% CI = 1.50–2.13), whereas no association was found in children (OR = 1.09, 95% CI = 0.70–1.69). Conclusion Our study suggested that the TNF-α- 308G/A polymorphism contributed to the susceptibility to the risk of OSAS. Additional well-designed large studies are needed to validate our findings.