Jie-Sen Zhou

Caveolin-1 Inhibits Expression of Antioxidant Enzymes through Direct Interaction with Nuclear Erythroid 2 p45-related Factor-2 (Nrf2)

Background: Caveolin-1 regulates cellular antioxidant capacity, but mechanisms remain unknown. Results: Caveolin-1 interacts with Nrf2 and suppresses its transcriptional activity and down-regulates cellular antioxidant enzymes. Conclusion: Caveolin-1 regulates cellular antioxidant capacity through interaction with Nrf2. Significance: Clarifying how caveolin-1 regulates cellular antioxidant capacity and identifying a novel target to establish the contribution of oxidative stress to human pathologies. The Nrf2 (nuclear erythroid 2 p45-related factor-2) signaling pathway is known to play a pivotal role in a variety of oxidative stress-related human disorders. It has been reported recently that the plasma membrane resident protein caveolin-1 (Cav-1) can regulate expression of certain antioxidant enzymes and involves in the pathogenesis of oxidative lung injury, but the detailed molecular mechanisms remain incompletely understood. Here, we demonstrated that Cav-1 inhibited the expression of antioxidant enzymes through direct interaction with Nrf2 and subsequent suppression of its transcriptional activity in lung epithelial Beas-2B cells. Cav-1 deficiency cells exhibited higher levels of antioxidant enzymes and were more resistant to oxidative stress induced cytotoxicity, whereas overexpression of Cav-1 suppressed the induction of these enzymes and further augmented the oxidative cell death. Cav-1 constitutively interacted with Nrf2 in both cytosol and nucleus. Stimulation of 4-hydroxynonenol increased the Cav-1-Nrf2 interaction in cytosol but disrupted their association in the nucleus. Knockdown of Cav-1 also disassociated the interaction between Nrf2 and its cytoplasmic inhibitor Keap1 (Kelch-like ECH-associated protein 1) and increased the Nrf2 transcription activity. Mutation of the resembling Cav-1 binding motif on Nrf2 effectively attenuated their interaction, which exhibited higher transcription activity and induced higher levels of antioxidant enzymes relative to the wild-type control. Altogether, these studies clearly demonstrate that Cav-1 inhibits cellular antioxidant capacity through direct interaction with Nrf2 and subsequent suppression of its activity, thereby implicating in certain oxidative stress-related human pathologies.

Interaction of caveolin-1 with ATG12-ATG5 system suppresses autophagy in lung epithelial cells

Autophagy plays a pivotal role in cellular homeostasis and adaptation to adverse environments, although the regulation of this process remains incompletely understood. We have recently observed that caveolin-1 (Cav-1), a major constituent of lipid rafts on plasma membrane, can regulate autophagy in cigarette smoking-induced injury of lung epithelium, although the underlying molecular mechanisms remain incompletely understood. In the present study we found that Cav-1 interacted with and regulated the expression of ATG12-ATG5, an ubiquitin-like conjugation system crucial for autophagosome formation, in lung epithelial Beas-2B cells. Deletion of Cav-1 increased basal and starvation-induced levels of ATG12-ATG5 and autophagy. Biochemical analyses revealed that Cav-1 interacted with ATG5, ATG12, and their active complex ATG12-ATG5. Overexpression of ATG5 or ATG12 increased their interactions with Cav-1, the formation of ATG12-ATG5 conjugate, and the subsequent basal levels of autophagy but resulted in decreased interactions between Cav-1 and another molecule. Knockdown of ATG12 enhanced the ATG5-Cav-1 interaction. Mutation of the Cav-1 binding motif on ATG12 disrupted their interaction and further augmented autophagy. Cav-1 also regulated the expression of ATG16L, another autophagy protein associating with the ATG12-ATG5 conjugate during autophagosome formation. Altogether these studies clearly demonstrate that Cav-1 competitively interacts with the ATG12-ATG5 system to suppress the formation and function of the latter in lung epithelial cells, thereby providing new insights into the molecular mechanisms by which Cav-1 regulates autophagy and suggesting the important function of Cav-1 in certain lung diseases via regulation of autophagy homeostasis.

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.

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.

Tc17 cells are associated with cigarette smoke-induced lung inflammation and emphysema.

Some types of T lymphocytes, especially cytotoxic T‐cells (Tc1) and T‐helper (Th17) cells, play a pivotal role in cigarette smoke‐induced lung diseases. However, whether Tc17 cells are involved remains largely unknown. We investigated Tc17 involvement using a cigarette smoke‐exposure model.

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.

HDAC2 Suppresses IL17A-Mediated Airway Remodeling in Human and Experimental Modeling of COPD

BACKGROUND: Although airway remodeling is a central feature of COPD, the mechanisms underlying its development have not been fully elucidated. The goal of this study was to determine whether histone deacetylase (HDAC) 2 protects against cigarette smoke (CS)‐induced airway remodeling through IL‐17A‐dependent mechanisms. METHODS: Sputum samples and lung tissue specimens were obtained from control subjects and patients with COPD. The relationships between HDAC2, IL‐17A, and airway remodeling were investigated. The effect of HDAC2 on IL‐17A‐mediated airway remodeling was assessed by using in vivo models of COPD induced by CS and in vitro culture of human bronchial epithelial cells and primary human fibroblasts exposed to CS extract, IL‐17A, or both. RESULTS: HDAC2 and IL‐17A expression in the sputum cells and lung tissue samples of patients with COPD were associated with bronchial wall thickening and collagen deposition. Il‐17a deficiency (Il‐17a–/–) resulted in attenuation of, whereas Hdac2 deficiency (Hdac2+/–) exacerbated, CS‐induced airway remodeling in mice. IL‐17A deletion also attenuated airway remodeling in CS‐exposed Hdac2+/– mice. HDAC2 regulated IL‐17A production partially through modulation of CD4+ T cells during T helper 17 cell differentiation and retinoid‐related orphan nuclear receptor &ggr;t in airway epithelial cells. In vitro, IL‐17A deficiency attenuated CS‐induced mouse fibroblast activation from Hdac2+/– mice. IL‐17A‐induced primary human fibroblast activation was at least partially mediated by autocrine production of transforming growth factor beta 1. CONCLUSIONS: These findings suggest that activation of HDAC2 and/or inhibition of IL‐17A production could prevent the development of airway remodeling by suppressing airway inflammation and modulating fibroblast activation in COPD.

MTOR Suppresses Cigarette Smoke–Induced Epithelial Cell Death and Airway Inflammation in Chronic Obstructive Pulmonary Disease

Airway epithelial cell death and inflammation are pathological features of chronic obstructive pulmonary disease (COPD). Mechanistic target of rapamycin (MTOR) is involved in inflammation and multiple cellular processes, e.g., autophagy and apoptosis, but little is known about its function in COPD pathogenesis. In this article, we illustrate how MTOR regulates cigarette smoke (CS)–induced cell death, airway inflammation, and emphysema. Expression of MTOR was significantly decreased and its suppressive signaling protein, tuberous sclerosis 2 (TSC2), was increased in the airway epithelium of human COPD and in mouse lungs with chronic CS exposure. In human bronchial epithelial cells, CS extract (CSE) activated TSC2, inhibited MTOR, and induced autophagy. The TSC2–MTOR axis orchestrated CSE-induced autophagy, apoptosis, and necroptosis in human bronchial epithelial cells; all of which cooperatively regulated CSE-induced inflammatory cytokines IL-6 and IL-8 through the NF-κB pathway. Mice with a specific knockdown of Mtor in bronchial or alveolar epithelial cells exhibited significantly augmented airway inflammation and airspace enlargement in response to CS exposure, accompanied with enhanced levels of autophagy, apoptosis, and necroptosis in the lungs. Taken together, these data demonstrate that MTOR suppresses CS-induced inflammation and emphysema—likely through modulation of autophagy, apoptosis, and necroptosis—and thus suggest that activation of MTOR may represent a novel therapeutic strategy for COPD.

Autophagy inhibitors suppress environmental particulate matter-induced airway inflammation

Particulate matter (PM) is a significant risk factor for airway injury. We have recently demonstrated a pivotal role of autophagy in mediating PM-induced airway injury. In the present study, we examined the possible effects of autophagy inhibitors spautin-1 and 3-Methyladenine (3-MA) in protection of PM-induced inflammatory responses. We observed that PM triggered autophagy in human bronchial epithelial (HBE) cells and in mouse airways. Spautin-1 or 3-MA inhibited PM-induced expression of inflammatory cytokines in HBE cells, and decreased the neutrophil influx and proinflammatory cytokines induced by PM in vivo. We further illustrated that autophagy inhibitors suppressed the inflammation responses via inhibition of the nuclear factor-кB (NF-кB) pathway. Thus, this study shows a paradigm that autophagy inhibitors effectively decrease the PM-induced airway inflammation via suppressing the NF-кB pathway, which may provide novel preventive and/or protective approaches for PM-related airway injury.

Early growth response factor 1 is essential for cigarette smoke-induced MUC5AC expression in human bronchial epithelial cells

Early growth response factor 1 (Egr-1) is a zinc finger transcription factor which responses rapidly to a variety of extracellular stimuli. Previous studies have suggested that Egr-1 exerts pathological functions in chronic obstructive pulmonary disease (COPD) by regulation of cigarette smoking-induced autophagy, cell death, and inflammation. However, little is known about the role of Egr-1 in regulation of mucus production in airway epithelium. In this study, we observed that cigarette smoke extract (CSE) induced a successive expression of Egr-1 and MUC5AC in human bronchial epithelial (HBE) cells. Knockdown of Egr-1 markedly attenuated CSE-induced MUC5AC production, and chromatin immunoprecipitation revealed that Egr-1 transcriptionally bound to MUC5AC promoter upon CSE stimulation. Concurrently, CSE increased the expression of c-Jun and c-Fos, two subunits of activator protein 1 (AP-1) which also critically regulates CSE-induced MUC5AC in HBE cells. CSE also induced a physical interaction of Egr-1 and AP-1, and knockdown of Egr-1 significantly decreased CSE-induced expression of c-Fos and c-Jun. Furthermore, knockdown of c-Fos remarkably attenuated the CSE-induced Egr-1 binding to MUC5AC promoter. These data taken together demonstrate that Egr-1 is essential for CSE-induced MUC5AC production in HBE cells likely through interaction with and modulation of AP-1, and re-emphasize targeting Egr-1 as a novel therapeutic strategy for COPD.