IL-32γ attenuates airway fibrosis by modulating the integrin-FAK signaling pathway in fibroblasts.

BACKGROUND: Fibrosis in severe asthma often leads to irreversible organ dysfunction. However, the mechanism that regulates fibrosis remains poorly understood. Interleukin (IL)-32 plays a role in several chronic inflammatory diseases, including severe asthma. In this study, we investigated whether IL-32 is involved in fibrosis progression in the lungs. METHODS: Murine models of chronic airway inflammation induced by ovalbumin and Aspergillus melleus protease and bleomycin-induced pulmonary fibrosis were employed. We evaluated the degree of tissue fibrosis after treatment with recombinant IL-32γ (rIL-32γ). Expression of fibronectin and α-smooth muscle actin (α-SMA) was examined and the transforming growth factor (TGF)-ß-related signaling pathways was evaluated in activated human lung fibroblasts (MRC-5 cells) treated with rIL-32γ. RESULTS: rIL-32γ significantly attenuated collagen deposition and α-SMA production in both mouse models. rIL-32γ inhibited the production of fibronectin and α-SMA in MRC-5 cells stimulated with TGF-ß. Additionally, rIL-32γ suppressed activation of the integrin-FAK-paxillin signaling axis but had no effect on the Smad and non-Smad signaling pathways. rIL-32γ localized outside of MRC-5 cells and inhibited the interaction between integrins and the extracellular matrix without directly binding to intracellular FAK and paxillin. CONCLUSIONS: These results demonstrate that IL-32γ has anti-fibrotic effects and is a novel target for preventing fibrosis.

Progranulin protects lung epithelial cells from cigarette smoking-induced apoptosis.

BACKGROUND AND OBJECTIVE: Emphysema is characterized by irreversible destruction of alveolar walls with distal air space enlargement. Cigarette smoke (CS) is considered a major risk factor for emphysematous changes in COPD. Progranulin (PGRN), a glycoprotein induced by CS, has been reported to participate in apoptosis. However, the precise role of PGRN in emphysema is currently unknown. This study aimed to evaluate the role of PGRN in human alveolar epithelial cells (AECs) in response to CS. METHODS: First, PGRN expression was assessed in a mouse model of CS-induced emphysema and in AECs after exposure to CS extract (CSE). Then, the effect of PGRN on CSE-mediated apoptosis was determined under PGRN silencing or overexpressing conditions. To investigate the functional mechanism of PGRN, endoplasmic reticulum (ER) stress markers and the mitogen-activated protein kinase (MAPK) pathway were also evaluated in the CSE-exposed cells. Finally, PGRN expression levels in sera and peripheral blood mononuclear cells (PBMCs) were measured and compared between patients with COPD and healthy subjects. RESULTS: Our results revealed that PGRN expression was elevated in CS-exposed mouse lungs and CSE-treated AECs. CSE-induced cellular apoptosis was significantly increased in PGRN-knockdown AECs and decreased in PGRN-overexpression cells. The activation of ER stress-associated molecules correlated with PGRN expression levels. Compared with healthy controls, COPD patients exhibited significantly lower PGRN serum levels and higher PBMC intracellular PGRN levels. CONCLUSION: PGRN in airway epithelial cells may regulate CS-induced AEC apoptosis and may be involved in the development of COPD.

hMSCs suppress neutrophil-dominant airway inflammation in a murine model of asthma.

Although chronic eosinophilic inflammation is a common feature in patients with asthma, some patients have neutrophil-dominant inflammation, which is known to be associated with severe asthma.Human mesenchymal stem cells (hMSCs) have shown promise in treating various refractory immunological diseases. Thus, hMSCs may represent an alternative therapeutic option for asthma patients with neutrophil-dominant inflammation, in whom current treatments are ineffective. BALB/c mice exposed to ovalbumin and polyinosinic:polycytidylic acid (Poly I:C) to induce neutrophilic airway inflammation were systemically treated with hMSCs to examine whether the hMSCs can modulate neutrophilic airway inflammation. In addition, cytokine production was evaluated in co-cultures of hMSCs with either anti-CD3/CD28-stimulated peripheral blood mononuclear cells (PBMCs) obtained from asthmatic patients or cells of the human bronchial epithelial cell line BEAS-2B to assess the response to hMSC treatment. The total number of immune cells in bronchoalveolar lavage fluid (BALF) showed a dramatic decrease in hMSC-treated asthmatic mice, and, in particular, neutrophilic infiltration was significantly attenuated. This phenomenon was accompanied by reduced CXCL15 production in the BALF. BEAS-2B cells co-cultured with hMSCs showed reduced secretion of IL-8. Moreover, decreased secretion of IL-4, IL-13 and IFN-γ was observed when human PBMCs were cultured with hMSCs, whereas IL-10 production was greatly enhanced. Our data imply that hMSCs may have a role in reducing neutrophilic airway inflammation by downregulating neutrophil chemokine production and modulating T-cell responses.

S-adenosylmethionine reduces airway inflammation and fibrosis in a murine model of chronic severe asthma via suppression of oxidative stress.

Increased oxidative stress has an important role in asthmatic airway inflammation and remodeling. A potent methyl donor, S-adenosylmethionine (SAMe), is known to protect against tissue injury and fibrosis through modulation of oxidative stress. The aim of this study was to evaluate the effect of SAMe on airway inflammation and remodeling in a murine model of chronic asthma. A mouse model was generated by repeated intranasal challenge with ovalbumin and Aspergillus fungal protease twice a week for 8 weeks. SAMe was orally administered every 24 h for 8 weeks. We performed bronchoalveolar lavage (BAL) fluid analysis and histopathological examination. The levels of various cytokines and 4-hydroxy-2-nonenal (HNE) were measured in the lung tissue. Cultured macrophages and fibroblasts were employed to evaluate the underlying anti-inflammatory and antifibrotic mechanisms of SAMe. The magnitude of airway inflammation and fibrosis, as well as the total BAL cell counts, were significantly suppressed in the SAMe-treated groups. A reduction in T helper type 2 pro-inflammatory cytokines and HNE levels was observed in mouse lung tissue after SAMe administration. Macrophages cultured with SAMe also showed reduced cellular oxidative stress and pro-inflammatory cytokine production. Moreover, SAMe treatment attenuated transforming growth factor-ß (TGF-ß)-induced fibronectin expression in cultured fibroblasts. SAMe had a suppressive effect on airway inflammation and fibrosis in a mouse model of chronic asthma, at least partially through the attenuation of oxidative stress and TGF-ß-induced fibronectin expression. The results of this study suggest a potential role for SAMe as a novel therapeutic agent in chronic asthma.

Clusterin Modulates Allergic Airway Inflammation by Attenuating CCL20-Mediated Dendritic Cell Recruitment.

Recruitment and activation of dendritic cells (DCs) in the lungs are critical for Th2 responses in asthma, and CCL20 secreted from bronchial epithelial cells (BECs) is known to influence the recruitment of DCs. Because asthma is a disease that is closely associated with oxidative stress, we hypothesized that clusterin, an oxidative stress regulatory molecule, may have a role in the development of allergic airway inflammation. The aim of this study was to examine whether clusterin regulates CCL20 production from the BECs and the subsequent DC recruitment in the lungs. To verify the idea, clusterin knockout (Clu(-/-)), clusterin heterogeneous (Clu(+/-)), and wild-type mice were exposed intranasally to house dust mite (HDM) extract to induce allergic airway inflammation. We found that the total number of immune cells in bronchoalveolar lavage fluid and the lung was increased in Clu(-/-) and Clu(+/-) mice. Of these immune cells, inflammatory DCs (CD11b(+)CD11c(+)) and Ly6C(high) monocyte populations in the lung were significantly increased, which was accompanied by increased levels of various chemokines, including CCL20 in bronchoalveolar lavage fluid, and increased oxidative stress markers in the lung. Moreover, HDM-stimulated human BECs with either up- or downregulated clusterin expression showed that CCL20 secretion was negatively associated with clusterin expression. Interestingly, clusterin also reduced the level of intracellular reactive oxygen species, which is related to induction of CCL20 expression after HDM stimulation. Thus, the antioxidant property of clusterin is suggested to regulate the expression of CCL20 in BECs and the subsequent recruitment of inflammatory DCs in the airway.

Serum progranulin as an indicator of neutrophilic airway inflammation and asthma severity.

BACKGROUND: Progranulin, a protein secreted from the airway epithelium, is known to attenuate the downstream cascade of neutrophilic inflammation in particular. We hypothesized that progranulin may have a role in inflammatory regulation in asthma. OBJECTIVE: To investigate the association between serum progranulin levels and various clinical features in patients with asthma. METHODS: Serum samples and clinical data of 475 patients with asthma and 35 healthy controls at a tertiary referral hospital and its affiliated health promotion center were collected. Serum progranulin levels were compared between patients with asthma and healthy controls and then were compared within the patients with asthma in terms of pulmonary function and measures of inflammatory status. Univariate and multivariate analyses were performed to identify factors associated with severity of asthma. RESULTS: Serum progranulin levels were significantly lower in the asthma group than in healthy group and were positively correlated with prebronchodilator forced expiratory volume in 1 second predicted within patients with asthma. We found a negative correlation between serum progranulin levels and blood neutrophil counts. Multivariate analysis revealed that higher serum progranulin levels were associated with a lower risk of severe asthma (odds ratio, 0.888; 95% confidence interval, 0.846-0.932; P < .001) after adjustment for other variables, such as age, sex, smoking status, blood neutrophil count, and current use of systemic corticosteroids. CONCLUSION: Although the exact mechanism of the anti-inflammatory action of progranulin remains unknown, we suggest that serum progranulin may be an indicator of severe asthma with airflow limitation. Future studies with comprehensive airway sampling strategies are warranted to clarify its role, particularly in neutrophilic asthma.

Senescence-Associated MCP-1 Secretion Is Dependent on a Decline in BMI1 in Human Mesenchymal Stromal Cells.

AIMS: Cellular senescence and its secretory phenotype (senescence-associated secretory phenotype [SASP]) develop after long-term expansion of mesenchymal stromal cells (MSCs). Further investigation of this phenotype is required to improve the therapeutic efficacy of MSC-based cell therapies. In this study, we show that positive feedback between SASP and inherent senescence processes plays a crucial role in the senescence of umbilical cord blood-derived MSCs (UCB-MSCs). RESULTS: We found that monocyte chemoattractant protein-1 (MCP-1) was secreted as a dominant component of the SASP during expansion of UCB-MSCs and reinforced senescence via its cognate receptor chemokine (c-c motif) receptor 2 (CCR2) by activating the ROS-p38-MAPK-p53/p21 signaling cascade in both an autocrine and paracrine manner. The activated p53 in turn increased MCP-1 secretion, completing a feed-forward loop that triggered the senescence program in UCB-MSCs. Accordingly, knockdown of CCR2 in UCB-MSCs significantly improved their therapeutic ability to alleviate airway inflammation in an experimental allergic asthma model. Moreover, BMI1, a polycomb protein, repressed the expression of MCP-1 by binding to its regulatory elements. The reduction in BMI1 levels during UCB-MSC senescence altered the epigenetic status of MCP-1, including the loss of H2AK119Ub, and resulted in derepression of MCP-1. INNOVATION: Our results provide the first evidence supporting the existence of the SASP as a causative contributor to UCB-MSC senescence and reveal a so far unappreciated link between epigenetic regulation and SASP for maintaining a stable senescent phenotype. CONCLUSION: Senescence of UCB-MSCs is orchestrated by MCP-1, which is secreted as a major component of the SASP and is epigenetically regulated by BMI1.

Interleukin-32γ suppresses allergic airway inflammation in mouse models of asthma.

Asthma is a chronic airway inflammatory disease typically associated with T helper cell type 2 (Th2) cytokines. IL-32, first reported as an inducer of tumor necrosis factor (TNF)-α, is an inflammatory cytokine involved in various autoinflammatory diseases, viral infection, and cancer-related inflammation. However, the role of IL-32γ in asthma has not been clearly elucidated. In this study, the levels of IL-32γ in sputum from patients with asthma were measured by ELISA, and IL-32γ function was investigated in murine models of asthma with human IL-32γ-overexpressed transgenic (IL-32γ TG) mice. The therapeutic effect of recombinant IL-32γ (rIL-32γ) on allergic inflammation was also evaluated through bronchoalveolar lavage fluid analysis and histopathologic examinations. Sputum IL-32γ levels from patients with asthma were lower than those from healthy control subjects. In an acute mouse model of asthma, IL-32γ TG mice exhibited significantly reduced airway inflammation compared with that in wild-type mice. The production of Th1 cytokines, such as TNF-α and IFN-γ, and Th2 cytokines, such as IL-4, IL-5, and IL-13, was decreased in the lungs of IL-32γTG mice. On the contrary, the expression of IL-10 and IL-10-producing CD11b(+) monocytic cells was significantly increased in the lungs of ovalbumin-sensitized IL-32γ TG mice. In addition, rIL-32γ treatment revealed a suppressive effect on the airway inflammation in a chronic mouse model of asthma. The results of this study suggest that IL-32γ may have a preventive role in the development of allergic airway inflammation and could be a potential novel therapeutic target for bronchial asthma.