Laila Al-Alwan

Th17-associated cytokines promote human airway smooth muscle cell proliferation

Increased airway smooth muscle (ASM) mass is a hallmark of airway remodeling in severe asthma. Th17‐associated cytokines, particularly IL‐17A, IL‐17F, and IL‐22, have been postulated to play a role in the pathogenesis of asthma. To investigate the in vitro effect of Th17 cytokines on the proliferation and survival of airway smooth muscle cells (ASMCs), human ASMCs from asthmatic and nonasthmatic subjects were incubated with IL‐17A, IL‐17F, or IL‐22. The aforementioned cytokines demonstrated an ability to promote proliferation and survival of ASMCs from asthmatic and nonasthmatic subjects, which were mediated by selective activation of their corresponding receptors on ASMCs, including IL‐17RA, IL‐17RC, or IL‐22R1, respectively. IL‐17A and IL‐17F‐induced proliferation of ASMCs was dependent on ERK1/2 MAPK pathway, while IL‐22‐induced proliferation involved both ERK1/2 MAPK and NF‐κB pathways. The involvement of signaling pathways was further confirmed by the inhibition of proliferation by knockdown of ERK1/2 MAPK or NF‐κB p65 expression with pathway‐specific siRNA. Together, our results show that Th17‐associated cytokines promote proliferation and reduce the apoptotic rate of human ASMCs, raising the possibility that Th17 cytokines may contribute to increasing airway smooth muscle mass and airway remodeling in asthma.—Chang, Y., Al‐Alwan, L., Risse, P.‐A., Halayko, A. J., Martin, J. G., Baglole, C. J., Eidelman, D. H., Hamid, Q. Th17‐associated cytokines promote human airway smooth muscle cell proliferation. FASEB J. 26, 5152–5160 (2012). www.fasebj.org

TH17 cytokines induce human airway smooth muscle cell migration

BACKGROUND Migration of airway smooth muscle cells (ASMCs) might contribute to increased airway smooth muscle mass in asthma. T(H)17 cells and T(H)17-associated cytokines are involved in the pathogenesis of asthma and might also contribute to airway remodeling. OBJECTIVE We sought to explore the possibility that migration of ASMCs might contribute to airway remodeling through the action of T(H)17-related cytokines. METHODS The effect of exogenous T(H)17 cytokines on ex vivo human ASMC migration was investigated by using a chemotaxis assay. The involvement of signaling pathways, including p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 MAPK, nuclear factor κB, and phosphoinositide 3-kinase, was also examined. RESULTS We demonstrated that IL-17A, IL-17F, and IL-22 promote migration in a dose-dependent manner. We further demonstrated that ASMCs express receptors for IL-17RA, IL-17RC, and IL-22R1. Using mAbs directed against these receptors, we confirmed that T(H)17-associated cytokine-induced migration was dependent on selective receptor activation. Moreover, IL-17A and IL-17F exert their effects through signaling pathways that are distinct from those used by IL-22. The p38 MAPK inhibitor BIRB0796 inhibited the migration induced by IL-17A and IL-17F. PS1145, an inhibitor of nuclear factor κB, abolished the IL-22-induced migration. CONCLUSION These data raise the possibility that T(H)17-associated cytokines promote human ASMC migration in vivo and suggest an important new mechanism for the promotion of airway remodeling in asthma.

Histamine may induce airway remodeling through release of epidermal growth factor receptor ligands from bronchial epithelial cells.

Asthma is a chronic inflammatory disease that is associated with airway remodeling, including hyperplasia of airway epithelial cells and airway smooth muscle cells, and goblet cell differentiation. We wished to address the potential role of histamine, a key biogenic amine involved in allergic reactions, in airway remodeling through the epidermal growth factor receptor (EGFR) pathway. Here, we demonstrate that histamine releases 2 EGFR ligands, amphiregulin and heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF), from airway epithelial cells. Amphiregulin and HB‐EGF were expressed in airway epithelium of patients with asthma. Histamine up‐regulated their mRNA expression (amphiregulin 3.2‐fold, P< 0.001; HB‐EGF 2.3‐fold, P<0.05) and triggered their release (amphiregulin EC50 0.50 μM, 31.2±2.7 pg/ml with 10 μM histamine, P<0.01; HB‐EGF EC50 0.54 μM, 78.5±1.8 pg/ml with 10 μM histamine, P<0.001) compared to vehicle control (amphiregulin 19.3±0.9 pg/ ml; HB‐EGF 60.2± 1.0 pg/ml), in airway epithelial cells. Histamine increased EGFR phosphorylation (2.1‐fold by Western blot analysis) and induced goblet cell differentiation (CLCA1 up‐regulation by real‐time qPCR) in normal human bronchial epithelial (NHBE) cells. Moreover, amphiregulin and HB‐EGF caused proliferation and migration of both NHBE cells and human airway smooth muscle cells. These results suggest that histamine may induce airway remodeling via the epithelial‐derived EGFR ligands amphiregulin and HB‐EGF.—Hirota, N., Risse, P.‐A., Novali, M., McGovern, T., Al‐Alwan, L., McCuaig, S., Proud, D., Hayden, P., Hamid, Q., Martin, J. G. Histamine may induce airway remodeling through release of epidermal growth factor receptor ligands from bronchial epithelial cells. FASEB J. 26, 1704‐1716 (2012). www.fasebj.org

Genetic deletion of IL-17A reduces cigarette smoke-induced inflammation and alveolar type II cell apoptosis

Chronic obstructive pulmonary disease (COPD) is an inflammatory disorder marked by relative resistance to steroids. Inflammation and apoptosis have been suggested to be important mechanisms for COPD. Interleukin (IL)-17 superfamily has been associated with chronic inflammation and diminished responses to steroids. It is reasonable to consider that IL-17 may play a role in the pathogenesis of COPD. In this study, we examined IL-17 expression in mice exposed to cigarette smoke (CS) and investigated the contribution of IL-17 to CS-induced inflammation and alveolar cell apoptosis in IL-17(-/-) mice. After exposing wild-type and IL-17(-/-) mice to mainstream CS for 4 wk, IL-17A, but not IL-17F, expression was increased in mice upon CS exposure. Neutrophil infiltration in the lungs of IL-17(-/-) mice was significantly decreased. In IL-17(-/-) mice, there is reduced expression of IL-6, macrophage inflammatory protein-2, and matrix metalloproteinase-12 compared with wild-type mice after CS exposure. The number of apoptotic type II alveolar cells was significantly increased in CS-exposed wild-type mice but not in IL-17(-/-) mice. The effect of IL-17A on type II alveolar cell apoptosis was confirmed in vitro through either addition of IL-17A or transient knockdown of IL-17A by small-interfering RNA transfection in type II alveolar cells. These findings suggest that IL-17A plays an important role in the inflammatory response to CS exposure through increased multiple inflammatory mediators. Moreover, IL-17 may also contribute to type II alveolar cell apoptosis. This study opens a new option in targeting IL-17A to modulate inflammatory response to CS and may be the bases for new therapy for COPD.

Differential Roles of CXCL2 and CXCL3 and Their Receptors in Regulating Normal and Asthmatic Airway Smooth Muscle Cell Migration

Structural cell migration plays a central role in the pathophysiology of several diseases, including asthma. Previously, we established that IL-17–induced (CXCL1, CXCL2, and CXCL3) production promoted airway smooth muscle cell (ASMC) migration, and consequently we sought to investigate the molecular mechanism of CXC-induced ASMC migration. Recombinant human CXCL1, CXCL2, and CXCL3 were used to assess migration of human primary ASMCs from normal and asthmatic subjects using a modified Boyden chamber. Neutralizing Abs or small interfering RNA (siRNA) knockdown and pharmacological inhibitors of PI3K, ERK1/2, and p38 MAPK pathways were used to investigate the receptors and the signaling pathways involved in CXC-induced ASMC migration, respectively. We established the ability of CXCL2 and CXCL3, but not CXCL1, to induce ASMC migration at the tested concentrations using normal ASMCs. We found CXCL2-induced ASMC migration to be dependent on p38 MAPK and CXCR2, whereas CXCL3-induced migration was dependent on p38 and ERK1/2 MAPK pathways via CXCR1 and CXCR2. While investigating the effect of CXCL2 and CXCL3 on asthmatic ASMC migration, we found that they induced greater migration of asthmatic ASMCs compared with normal ones. Interestingly, unlike normal ASMCs, CXCL2- and CXCL3-induced asthmatic ASMC migration was mainly mediated by the PI3K pathway through CXCR1. In conclusion, our results establish a new role of CXCR1 in ASMC migration and demonstrate the diverse mechanisms by which CXCL2 and CXCL3 mediate normal and asthmatic ASMC migration, suggesting that they may play a role in the pathogenesis of airway remodeling in asthma.

Pro-inflammatory and immunomodulatory functions of airway smooth muscle: Emerging concepts

Airway smooth muscle (ASM) is the main regulator of bronchomotor tone. Extensive studies show that in addition to their physical property, human airway smooth muscle (ASM) cells can participate in inflammatory processes modulating the initiation, perpetuation, amplification, and perhaps resolution of airway inflammation. Upon stimulation or interaction with immune cells, ASM cells produce and secrete a variety of inflammatory cytokines and chemokines, cell adhesion molecules, and extracellular matrix (ECM) proteins. These released mediators can, in turn, contribute to the inflammatory state, airway hyperresponsiveness, and airway remodeling present in asthma. As our knowledge of ASM myocyte biology improves, novel bioactive factors are emerging as potentially important regulators of inflammation. This review provides an overview of our understanding of some of these molecules, identifies rising questions, and proposes future studies to better define their role in ASM cell modulation of inflammation and immunity in the lung and respiratory diseases.

Autocrine-regulated airway smooth muscle cell migration is dependent on IL-17–induced growth-related oncogenes

BACKGROUND Airway smooth muscle cell (ASMC) migration is one of the proposed mechanisms underlying the increased airway smooth muscle mass seen in airway remodeling of patients with severe asthma. IL-17-related cytokines are a new subgroup of inflammatory mediators that have been suggested to play a role in regulating smooth muscle function. We hypothesized that IL-17-induced chemokine production from smooth muscle cells can contribute to migration of additional smooth muscle cells in the airways of asthmatic patients. OBJECTIVE We sought to investigate the effect of IL-17 on smooth muscle-derived chemokines and to examine the mechanisms involved in their production and contribution to the increase in airway smooth muscle migration. METHODS The effect of IL-17-induced supernatants on human ASMC migration was investigated. IL-17-induced growth-related oncogene (GRO) production and mRNA expression was assessed by using ELISA and RT-PCR, respectively. The direct effect of GROs on ASMC migration and the involvement of the CXCR2 receptor were also examined. RESULTS IL-17-induced supernatants promoted ASMC migration. After IL-17 stimulation, GROs were the most abundant chemokines produced from ASMCs, and blocking their effect by using neutralizing antibodies significantly inhibited ASMC migration. In addition, a combination of recombinant human GRO-α, GRO-β, and GRO-γ was able to promote significant migration of ASMCs that was mediated through the CXCR2 receptor. CONCLUSION These findings suggest that IL-17-induced GROs can be an important mediator of ASMC migration and therefore might contribute to the pathogenesis of airway remodeling in asthmatic patients.

Emerging mediators of airway smooth muscle dysfunction in asthma.

Phenotypic changes in airway smooth muscle are integral to the pathophysiological changes that constitute asthma - namely inflammation, airway wall remodelling and bronchial hyperresponsiveness. In vitro and in vivo studies have shown that the proliferative, secretory and contractile functions of airway smooth muscle are dysfunctional in asthma. These functions can be modulated by various mediators whose levels are altered in asthma, derived from inflammatory cells or produced by airway smooth muscle itself. In this review, we describe the emerging roles of the CXC chemokines (GROs, IP-10), Th17-derived cytokines (IL-17, IL-22) and semaphorins, as well as the influence of viral infection on airway smooth muscle function, with a view to identifying new opportunities for therapeutic intervention in asthma.

Monocyte‐derived fibrocytes induce an inflammatory phenotype in airway smooth muscle cells

Infiltration of fibrocytes (FC) in the airway smooth muscle is a feature of asthma, but the pathological significance is unknown.

CXCL1 Inhibits Airway Smooth Muscle Cell Migration through the Decoy Receptor Duffy Antigen Receptor for Chemokines

Airway smooth muscle cell (ASMC) migration is an important mechanism postulated to play a role in airway remodeling in asthma. CXCL1 chemokine has been linked to tissue growth and metastasis. In this study, we present a detailed examination of the inhibitory effect of CXCL1 on human primary ASMC migration and the role of the decoy receptor, Duffy AgR for chemokines (DARC), in this inhibition. Western blots and pathway inhibitors showed that this phenomenon was mediated by activation of the ERK-1/2 MAPK pathway, but not p38 MAPK or PI3K, suggesting a biased selection in the signaling mechanism. Despite being known as a nonsignaling receptor, small interference RNA knockdown of DARC showed that ERK-1/2 MAPK activation was significantly dependent on DARC functionality, which, in turn, was dependent on the presence of heat shock protein 90 subunit α. Interestingly, DARC- or heat shock protein 90 subunit α–deficient ASMCs responded to CXCL1 stimulation by enhancing p38 MAPK activation and ASMC migration through the CXCR2 receptor. In conclusion, we demonstrated DARC’s ability to facilitate CXCL1 inhibition of ASMC migration through modulation of the ERK-1/2 MAPK–signaling pathway.