ELOVL6 deficiency aggravates allergic airway inflammation through the ceramide-S1P pathway in mice.

BACKGROUND: Elongation of very-long-chain fatty acids protein 6 (ELOVL6), an enzyme regulating elongation of saturated and monounsaturated fatty acids with C12 to C16 to those with C18, has been recently indicated to affect various immune and inflammatory responses; however, the precise process by which ELOVL6-related lipid dysregulation affects allergic airway inflammation is unclear. OBJECTIVES: This study sought to evaluate the biological roles of ELOVL6 in allergic airway responses and investigate whether regulating lipid composition in the airways could be an alternative treatment for asthma. METHODS: Expressions of ELOVL6 and other isoforms were examined in the airways of patients who are severely asthmatic and in mouse models of asthma. Wild-type and ELOVL6-deficient (Elovl6-/-) mice were analyzed for ovalbumin-induced, and also for house dust mite-induced, allergic airway inflammation by cell biological and biochemical approaches. RESULTS: ELOVL6 expression was downregulated in the bronchial epithelium of patients who are severely asthmatic compared with controls. In asthmatic mice, ELOVL6 deficiency led to enhanced airway inflammation in which lymphocyte egress from lymph nodes was increased, and both type 2 and non-type 2 immune responses were upregulated. Lipidomic profiling revealed that the levels of palmitic acid, ceramides, and sphingosine-1-phosphate were higher in the lungs of ovalbumin-immunized Elovl6-/- mice compared with those of wild-type mice, while the aggravated airway inflammation was ameliorated by treatment with fumonisin B1 or DL-threo-dihydrosphingosine, inhibitors of ceramide synthase and sphingosine kinase, respectively. CONCLUSIONS: This study illustrates a crucial role for ELOVL6 in controlling allergic airway inflammation via regulation of fatty acid composition and ceramide-sphingosine-1-phosphate biosynthesis and indicates that ELOVL6 may be a novel therapeutic target for asthma.

Transcriptome genetic differences between responders and non-responders before bronchial thermoplasty.

BACKGROUND: Bronchial thermoplasty (BT) is an endoscopic therapy used for the treatment of refractory asthma. Some predictive factors, for example the number of activations and severity of disease at baseline, have been used to determine the effectiveness of BT in treating patients with asthma. The aim of the present study was to comprehensively analyze RNA samples from the airway bronchial tissues of patients with severe asthma treated by BT, and to characterize each patient as a BT responder or non-responder. METHODS: Eight patients with severe asthma scheduled to undergo BT and bronchus biopsies were recruited before the procedures were conducted. Extracted RNA samples from bronchial tissues were sequenced and differential gene expression analysis was carried out.Results/discussion: Subjects with Asthma Quality of Life Questionnaire score changes ≥0.5 for a period of 12 months were considered BT responders. Non-responders had score changes <0.5 for 12 months. Histopathology findings were similar to those reported previously, and no significant differences in the expression of α-smooth muscle actin and protein gene product 9.5 were observed between responders and non-responders. Transcriptome analysis at baseline identified 67 genes that were differentially expressed between responders and non-responders, including SLPI, MMP3, and MUC19, which were upregulated in responders. Although the differentially expressed gene products may have conflicting effects, genes in the airway epithelium and extracellular matrix of patients with severe asthma may determine the BT response. Our results identified possible transcriptomic changes that could be used to identify BT responders.

Transcription Factor T-bet Attenuates the Development of Elastase-induced Emphysema in Mice.

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease characterized by peripheral airways inflammation and emphysema. Emerging evidence indicates a contribution of both innate and adaptive immune cells to the development of COPD. Transcription factor T-bet modulates the function of immune cells and therefore might be involved in the pathogenesis of COPD. To elucidate the role for T-bet in elastase-induced emphysema, pathological phenotypes were compared between wild-type and T-bet-/- mice. T-bet-/- mice demonstrated enhanced emphysema development on histological analyses, with higher values of mean linear intercept and dynamic compliance relative to wild-type mice. The number of neutrophils in BAL fluids, lung IL-6 and IL-17 expression, and the proportion of CD4+ T cells positive for IL-17 or retinoic acid receptor-related orphan receptor-γt were higher in T-bet-/- mice than in wild-type mice. Although T-bet downregulates cytokine expression in bone marrow-derived macrophages and MH-S cells, a murine alveolar cell line, depending on the surrounding environment, IL-6 expression in alveolar macrophages isolated from elastase-treated mice was not dependent on T-bet. Coculture of bone marrow-derived macrophages and CD4+ T cells revealed that T-bet regulation of IL-17 expression was dependent on CD4+ T cells. Neutralizing antibodies against IL-6R or IL-17 ameliorated the development of emphysema in T-bet-/- mice. In conclusion, we demonstrate that T-bet ameliorates elastase-induced emphysema formation by modulating the host immune response in the lungs.

Transcription Elongation Factor P-TEFb Is Involved in IL-17F Signaling in Airway Smooth Muscle Cells.

BACKGROUND: IL-17F is involved in the pathogenesis of several inflammatory diseases, including asthma and COPD. However, the effects of steroids on the function of IL-17F signaling mechanisms are largely unknown. One of the transcription elongation factors, positive transcription elongation factor b (P-TEFb) composed of cyclin T1 and cyclin-dependent kinase 9 (CDK9), is known as a novel checkpoint regulator of gene expression via bromodomain-containing protein 4 (Brd4). METHODS: Human airway smooth muscle cells were stimulated with IL-17F and the expression of IL-8 was evaluated by real-time PCR and ELISA. Next, the phosphorylation of CDK9 was determined by Western blotting. The CDK9 inhibitor and short interfering RNAs (siRNAs) targeting Brd4, cyclin T1, and CDK9 were used to identify the effect on IL-17F-induced IL-8 expression. Finally, the effect of steroids and its signaling were evaluated. RESULTS: IL-17F markedly induced the transcription of the IL-8 gene and the expression of the protein. Pretreatment of CDK9 inhibitor and transfection of siRNAs targeting CDK9 markedly abrogated IL-17F-induced IL-8 production. Transfection of siRNAs targeting Brd4 and cyclin T1 diminished IL-17F-induced phosphorylation of CDK9 and IL-8 production. Moreover, budesonide decreased CDK9 phosphorylation and markedly inhibited IL-17F-induced IL-8 production. CONCLUSIONS: This is the first report that P-TEFb is involved in IL-17F-induced IL-8 expression and that steroids diminish it via the inhibition of CDK9 phosphorylation. IL-17F and P-TEFb might be novel therapeutic targets for airway inflammatory diseases.

Activation of murine invariant NKT cells promotes susceptibility to candidiasis by IL-10 induced modulation of phagocyte antifungal activity.

Invariant NKT (iNKT) cells play an important role in a variety of antimicrobial immune responses due to their ability to produce high levels of immune-modulating cytokines. Here, we investigated the role of iNKT cells in host defense against candidiasis using Jα18-deficient mice (Jα18(-/-) ), which lack iNKT cells. Jα18(-/-) mice were more resistant to the development of lethal candidiasis than wild-type (WT) mice. In contrast, treatment of WT mice with the iNKT cell activating ligand α-galactosylceramide markedly enhanced their mortality after infection with Candida albicans. Serum IL-10 levels were significantly elevated in WT mice in response to infection with C. albicans. Futhermore, IL-10 production increased after in vitro coculture of peritoneal macrophages with iNKT cells and C. albicans. The numbers of peritoneal macrophages, the production of IL-1ß and IL-18, and caspase-1 activity were also significantly elevated in Jα18(-/-) mice after infection with C. albicans. The adoptive transfer of iNKT cells or exogenous administration of IL-10 into Jα18(-/-) reversed susceptibility to candidiasis to the level of WT mice. These results suggest that activation of iNKT cells increases the initial severity of C. albicans infection, most likely mediated by IL-10 induced modulation of macrophage antifungal activity.

T-cell-restricted T-bet overexpression induces aberrant hematopoiesis of myeloid cells and impairs function of macrophages in the lung.

Although overexpression of T-bet, a master transcription factor in type-1 helper T lymphocytes, has been reported in several hematologic and immune diseases, its role in their pathogenesis is not fully understood. In the present study, we used transgenic model mice (T-bet(tg/wt) and T-bet(tg/tg)) to investigate the effects of T-bet overexpression selectively in T lymphocytes on the development of hematologic and immune diseases. The results showed that T-bet overexpression in T cells spontaneously induced maturation arrest in the mononuclear phagocyte lineage, as well as spontaneous dermatitis and pulmonary alveolar proteinosis (PAP)-like disease in T-bet(tg/wt) and T-bet(tg/tg) mice, respectively. T-bet(tg/tg) alveoli with the PAP phenotype showed remarkable reorganization of alveolar mononuclear phagocyte subpopulations and impaired function, in addition to augmented T-cell infiltration. In addition, PAP development in T-bet(tg/tg) mice was found to be associated with increased migration of myeloid cells from the bone marrow into the peripheral blood. These findings reveal an unexpected link between T-bet overexpression in T lymphocytes and the development of PAP caused by reorganization of mononuclear phagocytes in the lung, and provide new insight into the molecular pathogenesis of secondary PAP accompanied by hematologic disorders.

Role of Th1/Th17 balance regulated by T-bet in a mouse model of Mycobacterium avium complex disease.

Th1 immune responses are thought to be important in protection against intracellular pathogens. T-bet is a critical regulator for Th1 cell differentiation and Th1 cytokine production. The aim of this study was to determine the role of T-bet in host defense against Mycobacterium avium complex (MAC) infection. Wild-type mice, T-bet-deficient mice, and T-bet-overexpressing mice were infected with MAC via intratracheal inoculation. Macrophages and dendritic cells obtained from these mice were incubated with MAC. T-bet-deficient mice were highly susceptible to MAC, compared with wild-type mice and T-bet-overexpressing mice. Neutrophilic pulmonary inflammation was also enhanced in T-bet-deficient mice, but attenuated in T-bet-overexpressing mice, following MAC infection. Cytokine expression shifted toward Th1 in the lung and spleen of T-bet-overexpressing mice, but toward Th17 in T-bet-deficient mice. IFN-γ supplementation to T-bet-deficient mice reduced systemic MAC growth but did not reduce pulmonary inflammation. In contrast, neutralization of IL-17 in T-bet-deficient mice reduced pulmonary inflammation but did not affect mycobacterial growth in any organs tested. T-bet-deficient T cells tended to differentiate toward Th17 cells in vitro following exposure to MAC. Treatment with NO donor suppressed MAC-induced Th17 cell differentiation of T-bet-deficient T cells. This study identified that the fine balance between Th1 and Th17 responses is essential in defining the outcome of MAC disease. T-bet functions as a regulator for Th1/Th17 balance and is a critical determinant for host resistance to MAC infection by controlling cytokine and NO levels.

SQSTM1/p62/A170 regulates the severity of Legionella pneumophila pneumonia by modulating inflammasome activity.

Sequestosome1/A170/p62 (SQSTM1) is a scaffold multifunctional protein involved in several cellular events, such as signal transduction, cell survival, cell death, and inflammation. SQSTM1 expression by macrophages is induced in response to environmental stresses; however, its role in macrophage-mediated host responses to environmental stimuli, such as infectious pathogens, remains unclear. In this study, we investigated the role of SQSTM1 in host responses to Legionella pneumophila, an intra-cellular pathogen that infects macrophages, in both an SQSTM1-deficient (SQSTM1(-/-) ) mouse model and macrophages from these mice. Compared with wild-type (WT) macrophages, the production and secretion of the proinflammatory cytokine IL-1ß was significantly enhanced in SQSTM1(-/-) macrophages after infection with L. pneumophila. Inflammasome activity, indicated by the level of IL-18 and caspase-1 activity, was also elevated in SQSTM1(-/-) macrophages after infection with L. pneumophila. SQSTM1 may interact with nucleotide-binding oligomerization domain-like receptor family, caspase recruitment domain-containing 4 and nucleotide-binding oligomerization domain like receptor family, pyrin domain containing 3 proteins to inhibit their self-dimerization. Acute pulmonary inflammation induced by L. pneumophila and silica was enhanced in SQSTM1(-/-) mice with an increase in IL-1ß levels in the bronchoalveolar lavage fluids. These findings suggest that SQSTM1 is a negative regulator of acute pulmonary inflammation, possibly by regulating inflammasome activity and subsequent proinflammatory cytokine production.

Transcription factors GATA-3 and RORγt are important for determining the phenotype of allergic airway inflammation in a murine model of asthma.

In refractory asthma, neutrophils, rather than eosinophils, often predominate in the airways. Neutrophilic airway inflammation appears to be resistant to steroids and may be related to the Th17, rather than the Th2, cytokine milieu. However, the role of GATA-3 and RORγt, transcription factors for Th2 and Th17 cell differentiation, respectively, in the pathogenesis of steroid-insensitive asthma remains unclear. To examine the effect of GATA-3- and RORγt-overexpression backgrounds on airway inflammation and steroid sensitivity, we generated two strains of transgenic mice overexpressing GATA-3 or RORγt. Mice were sensitized and challenged with OVA. Some OVA-sensitized/challenged mice were treated with dexamethasone, anti-IL-17 Ab, CXCR2 antagonist, or anti-IL-6R Ab to demonstrate their therapeutic effects on airway inflammation. Although Ag-specific airway inflammation and hyperresponsiveness were induced in each mouse, the phenotype of inflammation showed a distinct difference that was dependent upon the genotype. GATA-3-overexpressing mice exhibited steroid-sensitive eosinophilic inflammation with goblet cell hyperplasia and mucus hyperproduction under Th2-biased conditions, and RORγt-overexpressing mice developed steroid-insensitive neutrophilic inflammation under Th17-biased conditions. The levels of keratinocyte-derived chemokine, MIP-2, IL-6, and other neutrophil chemotaxis-related mediators were significantly elevated in OVA-exposed RORγt-overexpressing mice compared with wild-type mice. Interestingly, airway hyperresponsiveness accompanied by neutrophilic airway inflammation in RORγt-overexpressing mice was effectively suppressed by anti-IL-17 Ab, CXCR2 antagonist, or anti-IL-6R Ab administration. In conclusion, our results suggest that the expression levels of GATA-3 and RORγt may be important for determining the phenotype of asthmatic airway inflammation. Furthermore, blockade of the Th17-signaling pathway may be a treatment option for steroid-insensitive asthma.

Synthetic double-stranded RNA induces interleukin-32 in bronchial epithelial cells.

OBJECTIVE: Interleukin (IL)-32 is a novel cytokine and is involved in the pathogenesis of various inflammatory diseases, including asthma and COPD. However, the regulatory mechanisms of IL-32 expression and its precise pathogenic role remain to be defined. Given that viral infections are known to potentially cause and exacerbate airway inflammation, in this study, we investigated the expression of IL-32 induced by synthetic double-stranded (ds) RNA, and its signaling mechanisms involved. METHODS: Bronchial epithelial cells were stimulated with synthetic dsRNA poly I:C. The levels of IL-32 expression were analyzed using real-time PCR and ELISA. The involvement of transforming growth factor ß-activated kinase 1 (TAK1) and a subunit of nuclear factor-κB (NF-κB), p65 was determined by western blot analyses. TAK1 inhibitor, 5Z-7-Oxozeaenol and NF-κB inhibitor, BAY 11-7082 were added to the culture to identify key signaling events leading to the expression of IL-32. Finally, the effect of short interfering RNAs (siRNAs) targeting TAK1 and p65 was investigated. RESULTS: dsRNA significantly induced IL-32 gene and protein expression, concomitant with activation of TAK1 and p65. Pretreatment of 5Z-7-Oxozeaenol diminished dsRNA-induced phosphorylation of NF-κB. Both 5Z-7-Oxozeaenol and BAY 11-7082 significantly abrogated dsRNA-induced IL-32 production. Moreover, transfection of the cells with siRNAs targeting TAK1 and p65 inhibited the expression of IL-32. CONCLUSIONS: The expression of IL-32 is induced by dsRNA via the TAK1-NF-κB signaling pathway in bronchial epithelial cells. IL-32 is involved in the pathogenesis of airway inflammation, and may be a novel therapeutic target for airway inflammatory diseases.

Carbocisteine reduces virus-induced pulmonary inflammation in mice exposed to cigarette smoke.

Carbocisteine (S-CMC) inhibits viral infection and prevents acute exacerbation of chronic obstructive pulmonary disease. We recently demonstrated the protective effects of NF-E2-related factor (Nrf) 2 against influenza virus (FluV)-induced pulmonary inflammation in mice exposed to cigarette smoke (CS). In our current study, we investigated the effects of S-CMC on Nrf2 activation in cultured macrophages, and in mice infected with influenza after exposure to CS. Nuclear translocation of Nrf2 and the expression of Nrf2-targeted antioxidant genes, such as heavy and light subunits of γ glutamyl cysteine synthetase and heme oxigenase-1, were enhanced in a dose-dependent manner after treatment with S-CMC in peritoneal and alveolar macrophages of wild-type mice, but not in those of Nrf2-deficient mice. Nuclear translocation of Nrf2 in macrophages was inhibited by the phosphatidylinositol 3-kinase inhibitor, LY294002. Phosphorylated Akt, Nrf2, and heme oxigenase-1 were induced in the alveolar macrophages of the lungs in wild-type mice after S-CMC administration. The extent of oxidative stress, inflammatory cell infiltration, pulmonary edema, and goblet cell hyperplasia was suppressed by S-CMC administration in the lungs of wild-type mice after exposure to both CS and FluV. Our findings suggest that S-CMC reduces pulmonary inflammation and mucus overproduction in mice exposed to CS after infection with FluV via the activation of Nrf2.

Abnormal saturated fatty acids and sphingolipids metabolism in asthma.

Recent advances in fatty acid analysis have highlighted the links between lipid disruption and disease development. Lipid abnormalities are well-established risk factors for many of the most common chronic illnesses, and their involvement in asthma is also becoming clear. Here, we review research demonstrating the role of abnormal lipid metabolism in asthma, with a focus on saturated fatty acids and sphingolipids. High levels of palmitic acid, the most abundant saturated fatty acid in the human body, have been found in the airways of asthmatic patients with obesity, and were shown to worsen eosinophilic airway inflammation in asthma model mice on a high-fat diet. Aside from being a building block of longer-chain fatty acids, palmitic acid is also the starting point for de novo synthesis of ceramides, a class of sphingolipids. We outline the three main pathways for the synthesis of ceramides, which have been linked to the severity of asthma and act as precursors for the dynamic lipid mediator sphingosine 1-phosphate (S1P). S1P signaling is involved in allergen-induced eosinophilic inflammation, airway hyperresponsiveness, and immune-cell trafficking. A recent study of mice with mutations for the elongation of very long-chain fatty acid family member 6 (Elovl6), an enzyme that elongates fatty acid chains, has highlighted the potential role of palmitic acid composition, and thus lipid balance, in the pathophysiology of allergic airway inflammation. Elovl6 may be a potential therapeutic target in severe asthma.

Overexpression of RORγt under control of the CD2 promoter induces polyclonal plasmacytosis and autoantibody production in transgenic mice.

Retinoic acid related orphan receptor gamma-t (RORγt) is known to be a master regulator of Th17-cell development. In this study, we generated RORγt-overexpressing transgenic (RORγt Tg) mice in which transgene expression was driven by the CD2 promoter, and found that these mice developed polyclonal plasmacytosis and autoantibody production. RORγt Tg mice were generated on a C57BL/6 background, and also were intercrossed with BALB/c mice. BALB/c F1 (BALB/F1) RORγt Tg mice developed massive polyclonal plasma-cytosis, and had shorter life spans. Splenomegaly and infiltration of plasma cells into the lung were observed. Hyperglobulinemia, anti-double-stranded DNA antibodies, anti-erythrocyte antibodies, and anti-platelet antibodies were detected in BALB/F1 RORγt Tg mice. In the present study, polyclonal plasmacytosis in BALB/F1 RORγt Tg mice appeared to be due to the induction of excessive IL-6 production by IL-17. We detected increased numbers of CD11b(+) cells that produced IL-6. We also generatedIL-6-deficient RORγt Tg BALB/F1 background mice, which displayed high levels of serum IL-17, but did not develop severe hyperglobulinemia. Excessive IL-6 production by several cell types, including macrophages, in BALB/F1 RORγt Tg mice, might effect the development of plasma-cytosis. These results suggest that RORγt plays important roles in the development of plasmacytosis and autoantibody production.

Th17-associated cytokines as a therapeutic target for steroid-insensitive asthma.

Steroid-insensitive asthma is an infrequent but problematic airway disease that presents with persistent symptoms, airflow limitation, or recurrent exacerbations even when treated with steroid-based therapies. Because of unsatisfactory results obtained from currently available therapies for steroid-insensitive asthma, a better understanding of its pathogenesis and the development of new targeted molecular therapies are warranted. Recent studies indicated that levels of interleukin (IL)-17 are increased and both eosinophils and neutrophils infiltrate the airways of severe asthmatics. IL-17 is a proinflammatory cytokine mainly secreted from helper T (Th) 17 cells and is important for the induction of neutrophil recruitment and migration at sites of inflammation. This review focuses on the pathogenetic role of Th17 cells and their associated cytokines in steroid-insensitive asthma and discusses the prospects of novel therapeutic options targeting the Th17 signaling pathway.

A case of epidermal growth factor receptor tyrosine kinase inhibitor effectiveness in epidermal growth factor receptor mutation-positive squamous cell carcinoma.

A 71-year-old non-smoker woman was admitted to our hospital because of left front chest pain. A computed tomography scan showed a large mass of >7.0 cm in the lower left part of the lung and multiple organ metastases in the liver, brain, bone, and left adrenal gland. Pathological analysis of a resected specimen obtained by bronchoscopy revealed keratinization. In addition, p40 was positive and thyroid transcription factor-1, synaptophysin, CD56, and chromogranin A were negative by immunohistochemistry. Programmed cell death ligand 1 expression was 1%-10%, and exon 19 deletion was detected. We diagnosed the patient with stage IVB lung squamous cell carcinoma and administered osimertinib. Osimertinib was later replaced with afatinib because of grade 3 skin rash. Overall, the size of the cancer was decreased. Furthermore, her symptoms, laboratory data, and computer tomographic findings markedly improved. In summary, we experienced a case of epidermal growth factor receptor-positive lung squamous cell carcinoma that was responsive to epidermal growth factor receptor tyrosine kinase inhibitors.

Role of Nrf2 in host defense against influenza virus in cigarette smoke-exposed mice.

Influenza virus is a common respiratory tract viral infection. Although influenza can be fatal in patients with chronic pulmonary diseases such as chronic obstructive pulmonary disease, its pathogenesis is not fully understood. The Nrf2-mediated antioxidant system is essential to protect the lungs from oxidative injury and inflammation. In the present study, we investigated the role of Nrf2 in protection against influenza virus-induced pulmonary inflammation after cigarette smoke exposure with both in vitro and in vivo approaches. For in vitro analyses, peritoneal macrophages isolated from wild-type and Nrf2-deficient mice were treated with poly(I:C) and/or cigarette smoke extract. For in vivo analysis, these mice were infected with influenza A virus with or without exposure to cigarette smoke. In Nrf2-deficient macrophages, NF-κB activation and the induction of its target inflammatory genes were enhanced after costimulation with cigarette smoke extract and poly(I:C) compared with wild-type macrophages. The induction of antioxidant genes was observed for the lungs of wild-type mice but not those of Nrf2-deficient mice after cigarette smoke exposure. Cigarette smoke-exposed Nrf2-deficient mice showed higher rates of mortality than did wild-type mice after influenza virus infection, with enhanced peribronchial inflammation, lung permeability damage, and mucus hypersecretion. Lung oxidant levels and NF-κB-mediated inflammatory gene expression in the lungs were also enhanced in Nrf2-deficient mice. Our data indicate that the antioxidant pathway controlled by Nrf2 is pivotal for protection against the development of influenza virus-induced pulmonary inflammation and injury under oxidative conditions.