Human airway smooth muscle cells from asthmatic individuals have CXCL8 hypersecretion due to increased NF-kappa B p65, C/EBP beta, and RNA polymerase II binding to the CXCL8 promoter

Airway hyperresponsiveness in asthma: The role of the epithelium

Airway hyperresponsiveness (AHR) is a key clinical feature of asthma. The presence of AHR in people with asthma provides the substrate for bronchoconstriction in response to numerous diverse stimuli, contributing to airflow limitation and symptoms including breathlessness, wheeze, and chest tightness. Dysfunctional airway smooth muscle significantly contributes to AHR and is displayed as increased sensitivity to direct pharmacologic bronchoconstrictor stimuli, such as inhaled histamine and methacholine (direct AHR), or to endogenous mediators released by activated airway cells such as mast cells (indirect AHR). Research in in vivo human models has shown that the disrupted airway epithelium plays an important role in driving inflammation that mediates indirect AHR in asthma through the release of cytokines such as thymic stromal lymphopoietin and IL-33. These cytokines upregulate type 2 cytokines promoting airway eosinophilia and induce the release of bronchoconstrictor mediators from mast cells such as histamine, prostaglandin D2, and cysteinyl leukotrienes. While bronchoconstriction is largely due to airway smooth muscle contraction, airway structural changes known as remodeling, likely mediated in part by epithelial-derived mediators, also lead to airflow obstruction and may enhance AHR. In this review, we outline the current knowledge of the role of the airway epithelium in AHR in asthma and its implications on the wider disease. Increased understanding of airway epithelial biology may contribute to better treatment options, particularly in precision medicine.

BRD4 as a Therapeutic Target in Pulmonary Diseases

Bromodomain and extra-terminal domain (BET) proteins are epigenetic modulators that regulate gene transcription through interacting with acetylated lysine residues of histone proteins. BET proteins have multiple roles in regulating key cellular functions such as cell proliferation, differentiation, inflammation, oxidative and redox balance, and immune responses. As a result, BET proteins have been found to be actively involved in a broad range of human lung diseases including acute lung inflammation, asthma, pulmonary arterial hypertension, pulmonary fibrosis, and chronic obstructive pulmonary disease (COPD). Due to the identification of specific small molecular inhibitors of BET proteins, targeting BET in these lung diseases has become an area of increasing interest. Emerging evidence has demonstrated the beneficial effects of BET inhibitors in preclinical models of various human lung diseases. This is, in general, largely related to the ability of BET proteins to bind to promoters of genes that are critical for inflammation, differentiation, and beyond. By modulating these critical genes, BET proteins are integrated into the pathogenesis of disease progression. The intrinsic histone acetyltransferase activity of bromodomain-containing protein 4 (BRD4) is of particular interest, seems to act independently of its bromodomain binding activity, and has implication in some contexts. In this review, we provide a brief overview of the research on BET proteins with a focus on BRD4 in several major human lung diseases, the underlying molecular mechanisms, as well as findings of targeting BET proteins using pharmaceutical inhibitors in different lung diseases preclinically.

Pathogenesis of allergic diseases and implications for therapeutic interventions

Allergic diseases such as allergic rhinitis (AR), allergic asthma (AAS), atopic dermatitis (AD), food allergy (FA), and eczema are systemic diseases caused by an impaired immune system. Accompanied by high recurrence rates, the steadily rising incidence rates of these diseases are attracting increasing attention. The pathogenesis of allergic diseases is complex and involves many factors, including maternal-fetal environment, living environment, genetics, epigenetics, and the body's immune status. The pathogenesis of allergic diseases exhibits a marked heterogeneity, with phenotype and endotype defining visible features and associated molecular mechanisms, respectively. With the rapid development of immunology, molecular biology, and biotechnology, many new biological drugs have been designed for the treatment of allergic diseases, including anti-immunoglobulin E (IgE), anti-interleukin (IL)-5, and anti-thymic stromal lymphopoietin (TSLP)/IL-4, to control symptoms. For doctors and scientists, it is becoming more and more important to understand the influencing factors, pathogenesis, and treatment progress of allergic diseases. This review aimed to assess the epidemiology, pathogenesis, and therapeutic interventions of allergic diseases, including AR, AAS, AD, and FA. We hope to help doctors and scientists understand allergic diseases systematically.

Role of Ezrin in Asthma-Related Airway Inflammation and Remodeling

Ezrin is an actin binding protein connecting the cell membrane and the cytoskeleton, which is crucial to maintaining cell morphology, intercellular adhesion, and cytoskeleton remodeling. Asthma involves dysfunction of inflammatory cells, cytokines, and airway structural cells. Recent studies have shown that ezrin, whose function is affected by extensive phosphorylation and protein interactions, is closely associated with asthma, may be a therapeutic target for asthma treatment. In this review, we summarize studies on ezrin and discuss its role in asthma-related airway inflammation and remodeling.

Stressed out - The role of oxidative stress in airway smooth muscle dysfunction in asthma and COPD

The airway smooth muscle (ASM) surrounding the airways is dysfunctional in both asthma and chronic obstructive pulmonary disease (COPD), exhibiting; increased contraction, increased mass, increased inflammatory mediator release and decreased corticosteroid responsiveness. Due to this dysfunction, ASM is a key contributor to symptoms in patients that remain symptomatic despite optimal provision of currently available treatments. There is a significant body of research investigating the effects of oxidative stress/ROS on ASM behaviour, falling into the following categories; cigarette smoke and associated compounds, air pollutants, aero-allergens, asthma and COPD relevant mediators, and the anti-oxidant Nrf2/HO-1 signalling pathway. However, despite a number of recent reviews addressing the role of oxidative stress/ROS in asthma and COPD, the potential contribution of oxidative stress/ROS-related ASM dysfunction to asthma and COPD pathophysiology has not been comprehensively reviewed. We provide a thorough review of studies that have used primary airway, bronchial or tracheal smooth muscle cells to investigate the role of oxidative stress/ROS in ASM dysfunction and consider how they could contribute to the pathophysiology of asthma and COPD. We summarise the current state of play with regards to clinical trials/development of agents targeting oxidative stress and associated limitations, and the adverse effects of oxidative stress on the efficacy of current therapies, with reference to ASM related studies where appropriate. We also identify limitations in the current knowledge of the role of oxidative stress/ROS in ASM dysfunction and identify areas for future research.

Pathobiology of Airway Remodeling in Asthma: The Emerging Role of Integrins

Airway remodeling is a complex clinical feature of asthma that involves long-term disruption and modification of airway architecture, which contributes significantly to airway hyperresponsiveness (AHR) and lung function decline. It is characterized by thickening of the airway smooth muscle layer, deposition of a matrix below the airway epithelium, resulting in subepithelial fibrosis, changes within the airway epithelium, leading to disruption of the barrier, and excessive mucous production and angiogenesis within the airway wall. Airway remodeling contributes to stiffer and less compliant airways in asthma and leads to persistent, irreversible airflow obstruction. Current asthma treatments aim to reduce airway inflammation and exacerbations but none are targeted towards airway remodeling. Inhibiting the development of airway remodeling or reversing established remodeling has the potential to dramatically improve symptoms and disease burden in asthmatic patients. Integrins are a family of transmembrane heterodimeric proteins that serve as the primary receptors for extracellular matrix (ECM) components, mediating cell-cell and cell-ECM interactions to initiate intracellular signaling cascades. Cells present within the lungs, including structural and inflammatory cells, express a wide and varying range of integrin heterodimer combinations and permutations. Integrins are emerging as an important regulator of inflammation, repair, remodeling, and fibrosis in the lung, particularly in chronic lung diseases such as asthma. Here, we provide a comprehensive summary of the current state of knowledge on integrins in the asthmatic airway and how these integrins promote the remodeling process, and emphasize their potential involvement in airway disease.

Psychological Stress, Mast Cells, and Psoriasis-Is There Any Relationship?

Psoriasis vulgaris is a common inflammatory skin disease with still unknown pathogenesis. In recent years, genetic and environmental factors have been mentioned as the main causes. Among environmental factors, many researchers are trying to investigate the role of mental health and its importance in the development of many diseases. In the pathophysiology of psoriasis, the role of the interaction between the nervous, endocrine, and immune systems are often emphasized. So far, no one has clearly indicated where the pathological process begins. One of the hypotheses is that chronic stress influences the formation of hormonal changes (lowering the systemic cortisol level), which favors the processes of autoimmunity. In inflammatory skin conditions, mast cells (MCs) are localized close to blood vessels and peripheral nerves, where they probably play an important role in the response to environmental stimuli and emotional stress. They are usually connected with a fast immune response, not only in allergies but also a protective response to microbial antigens. Among many cells of the immune system, MCs have receptors for the hormones of the hypothalamic-pituitary-adrenal (HPA) axis on their surface. In this review, we will try to take a closer look at the role of MCs in the pathophysiology of psoriasis. This knowledge may give the opportunity to search for therapeutic solutions.

A review of epigenetic changes in asthma: methylation and acetylation

Several studies show that childhood and adulthood asthma and its symptoms can be modulated through epigenetic modifications. Epigenetic changes are inheritable modifications that can modify the gene expression without changing the DNA sequence. The most common epigenetic alternations consist of DNA methylation and histone modifications. How these changes lead to asthmatic phenotype or promote the asthma features, in particular by immune pathways regulation, is an understudied topic. Since external effects, like exposure to tobacco smoke, air pollution, and drugs, influence both asthma development and the epigenome, elucidating the role of epigenetic changes in asthma is of great importance. This review presents available evidence on the epigenetic process that drives asthma genes and pathways, with a particular focus on DNA methylation, histone methylation, and acetylation. We gathered and assessed studies conducted in this field over the past two decades. Our study examined asthma in different aspects and also shed light on the limitations and the important factors involved in the outcomes of the studies. To date, most of the studies in this area have been carried out on DNA methylation. Therefore, the need for diagnostic and therapeutic applications through this molecular process calls for more research on the histone modifications in this disease.

Second-hand smoke and NFE2L2 genotype interaction increases paediatric asthma risk and severity

BACKGROUND

Second-hand smoke (SHS) exposure is associated with paediatric asthma, and oxidative stress is believed to play a role in mediating this association. The nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) is important for the defence against oxidative stress.

OBJECTIVE

To explore interactions between NFE2L2 genotype and SHS exposure in paediatric asthma risk.

METHODS

We used a genotyped subset of patients of European ancestry (N = 669, median age at enrolment = 6.8 years) enrolled in the clinical cohort Greater Cincinnati Pediatric Clinic Repository as the study population, and a population-based paediatric cohort (N = 791) to replicate our findings. History of asthma diagnosis was obtained from medical records, and SHS exposure was obtained from questionnaires. Four NFE2L2 tagging SNPs were included in the analysis, and interactions between SHS and NFE2L2 genotype were evaluated using logistic regression.

RESULTS

Three of the analysed SNPs, rs10183914, rs1806649 and rs2886161, interacted significantly with SHS exposure to increase asthma risk (p ≤ .02). The interaction was replicated in an independent cohort for rs10183914 (p = .04). Interactions between SHS exposure and NFE2L2 genotype were also associated with an increased risk of hospitalization (p = .016). In stratified analyses, NFE2L2 genotype was associated with daily asthma symptoms in children with SHS exposure (OR = 3.1; p = .048). No association was found in children without SHS exposure. Examination of publicly available chromatin immunoprecipitation followed by sequencing (ChIP-seq) data sets confirmed the presence of active histone marks and binding sites for particular transcription factors overlapping the coordinates for the significantly associated SNPs.

CONCLUSIONS AND CLINICAL RELEVANCE

Our study provides evidence that NFE2L2 genotype interacts with SHS exposure to affect both asthma risk and severity in children and identifies a population of children at increased risk of asthma development.

Mammalian target of rapamycin and p70S6K mediate thrombin-induced nuclear factor-κB activation and IL-8/CXCL8 release in human lung epithelial cells

Thrombin plays a crucial role in lung inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD). Thrombin induces the release of interleukin-8 (IL-8)/CXCL8 by lung epithelial cells, and this phenomenon plays a vital role in lung inflammation. Our previous studies have indicated that thrombin stimulates IL-8/CXCL8 expression through PI3K/Akt/IκB kinase (IKK)α/β/nuclear factor-κB (NF-κB) and p300 pathways in human lung epithelial cells. In the present study, we explored the roles of mammalian target of rapamycin (mTOR) and p70S6 kinase (p70S6K) in thrombin-induced NF-κB activation and IL-8/CXCL8 release in human lung epithelial cells. In this study, we found that rapamycin (an mTOR inhibitor) and p70S6K siRNA diminished thrombin-induced IL-8/CXCL8 release. Thrombin induced mTOR Ser2448 phosphorylation and p70S6K Thr389 phosphorylation in a time-dependent manner. Moreover, rapamycin attenuated thrombin-stimulated p70S6K phosphorylation. We also found that transfection of cells with the dominant negative mutant of Akt (Akt DN) reduced the thrombin-induced increase in mTOR phosphorylation and p70S6K phosphorylation. Moreover, thrombin-stimulated p300 phosphorylation was attenuated by Akt DN, rapamycin, and p70S6K siRNA. Thrombin triggered p70S6K translocation from the cytosol to the nucleus in a time-dependent manner. Thrombin induced the complex formation of p70S6K, p300, and p65; acetylation of p65 Lys310, and recruitment of p70S6K, p300, and p65 to the κB-binding site of the IL-8/CXCL8 promoter region. In conclusion, these results indicate that thrombin initiates the Akt-dependent mTOR/p70S6K signaling pathway to promote p300 phosphorylation and NF-κB activation and finally induces IL-8/CXCL8 release in human lung epithelial cells.

Specificity of NHERF1 regulation of GPCR signaling and function in human airway smooth muscle

Na+/H+ exchanger regulatory factor 1 (NHERF1; also known as ezrin-radixin-moesin-binding phosphoprotein 50) is a PSD-95, disc large, zona occludens-1 adapter that acts as a scaffold for signaling complexes and cytoskeletal-plasma membrane interactions. NHERF1 is crucial to β-2-adrenoceptor (β2AR)-mediated activation of cystic fibrosis transmembrane conductance regulator (CFTR) in epithelial cells, and NHERF1 has been proposed to mediate the recycling of internalized β2AR back to the cell membrane. In the current study, we assessed the role of NHERF1 in regulating cAMP-mediated signaling and immunomodulatory functions in airway smooth muscle (ASM). NHERF1 knockdown attenuated the induction of (protein kinase A) phospho-vasodilator-stimulated phosphoprotein (p-VASP) by isoproterenol (ISO), prostaglandin E2 (PGE2), or forskolin (FSK) as well as the induction of p-heat shock protein 20 after 4 h of stimulation with ISO and FSK. NHERF1 knockdown fully abrogated the ISO-, PGE2-, and FSK-induced IL-6 gene expression and cytokine production without affecting cAMP-mediated phosphodiesterase 4D (PDE4D) gene expression, phospho-cAMP response element-binding protein (p-CREB), and cAMP response element (CRE)-Luc, or PDGF-induced cyclin D1 expression. Interestingly, NHERF1 knockdown prevented ISO-induced chromatin-binding of the transcription factor CCAAT-enhancer-binding protein-β (c/EBPβ). c/EBPβ knockdown almost completely abrogated the cAMP-mediated IL-6 but not PDE4D gene expression. The differential regulation of cAMP-induced signaling and gene expression in our study indicates a role for NHERF1 in the compartmentalization of cAMP signaling in ASM.-Pera, T., Tompkins, E., Katz, M., Wang, B., Deshpande, D. A., Weinman, E. J., Penn, R. B. Specificity of NHERF1 regulation of GPCR signaling and function in human airway smooth muscle.

Role of Protein Tyrosine Phosphatase Epsilon (PTPε) in Leukotriene D4-Induced CXCL8 Expression

Phosphorylation on tyrosine residues is recognized as an important mechanism for connecting extracellular stimuli to cellular events and defines a variety of physiologic responses downstream of G protein-coupled receptor (GPCR) activation. To date, few protein tyrosine phosphatases (PTPs) have been shown to associate with GPCRs, and little is known about their role in GPCR signaling. To discover potential cysteinyl-leukotriene receptor (CysLT₁R)-interacting proteins, we identified protein tyrosine phosphatase ε (PTPε) in a yeast two-hybrid assay. Since both proteins are closely linked to asthma, we further investigated their association. Using a human embryonic kidney cell line 293 (HEK-293) cell line stably transfected with the receptor (HEK-LT1), as well as human primary monocytes, we found that PTPε colocalized with CysLT₁R in both resting and leukotriene D4 (LTD₄)-stimulated cells. Cotransfection of HEK-LT1 with PTPε had no effect on CysLT₁R expression or LTD₄-induced internalization, but it inhibited LTD₄-induced CXC chemokine 8 (CXCL8) promoter transactivation, protein expression, and secretion. Moreover, reduced phosphorylation of extracellular signal regulated kinase 1/2 (ERK1/2), but not of p38 or c-Jun-N-terminal kinase 1 or 2 mitogen-activated protein kinases (MAPKs), was observed upon LTD₄ stimulation of HEK-LT1 coexpressing cytosolic (cyt-) PTPε, but not receptor (R) PTPε The increased interaction of cyt-PTPε and ERK1/2 after LTD₄ stimulation was shown by coimmunoprecipitation. In addition, enhanced ERK1/2 phosphorylation and CXCL8 secretion were found in LTD₄-stimulated human monocytes transfected with PTPε-specific siRNAs, adding support to a regulatory/inhibitory role of PTPε in CysLT₁R signaling. Given that the prevalence of severe asthma is increasing, the identification of PTPε as a new potential therapeutic target may be of interest.

A Randomized Controlled Trial of Chuanhutongfeng Mixture for the Treatment of Chronic Gouty Arthritis by Regulating miRNAs

Background

We investigated whether Chuanhutongfeng mixture has actions on chronic gouty arthritis (CGA) by regulating miRNAs.

Methods

A total of 255 patients with CGA and 30 controls were enrolled. miRNA expression profiles and cluster analysis were preformed; RT-qPCR was used to detect miRNAs associated with CGA. Patients were allocated into Chuanhutongfeng mixture, allopurinol (positive control), and control (etoricoxib) groups. Expression of plasma miRNAs was measured before and after treatments; expression of chemokine 2 (CCL2) and interleukin 8 (CXCL8) was determined by ELISA.

Results

48 miRNAs were differentially expressed and compared to controls. 36 miRNAs expression levels were > 1.5 times and 12 miRNAs < 1.5 times compared to the controls. miR-339-5p, miR-486-5p, and miR-361-5p levels in patients with CGA were lower than in controls (P < 0.05). This trial showed that the Chuanhutongfeng mixture and allopurinol groups had upregulated the expressions of miR-486-5, miR-339-5p, and miR-361-5p and decreased levels of CCL2 and CXCL8 proteins. After 8 weeks of treatment, Chuanhutongfeng mixture decreased serum uric acid levels more than allopurinol (P < 0.05) and reduced levels of CCL2 and CXCL8 protein significantly more than in the allopurinol and control groups.

Conclusions

The therapeutic actions of Chuanhutongfeng mixture inhibit the expression of proteins CCL2 and CXCL8 in plasma and upregulated the expressions of three miRNAs (miR-486-5p, miR-339-5p, and miR-361-5p).

CD38/cADPR Signaling Pathway in Airway Disease: Regulatory Mechanisms

Asthma is an inflammatory disease in which proinflammatory cytokines have a role in inducing abnormalities of airway smooth muscle function and in the development of airway hyperresponsiveness. Inflammatory cytokines alter calcium (Ca²⁺) signaling and contractility of airway smooth muscle, which results in nonspecific airway hyperresponsiveness to agonists. In this context, Ca²⁺ regulatory mechanisms in airway smooth muscle and changes in these regulatory mechanisms encompass a major component of airway hyperresponsiveness. Although dynamic Ca²⁺ regulation is complex, phospholipase C/inositol tris-phosphate (PLC/IP3) and CD38-cyclic ADP-ribose (CD38/cADPR) are two major pathways mediating agonist-induced Ca²⁺ regulation in airway smooth muscle. Altered CD38 expression or enhanced cyclic ADP-ribosyl cyclase activity associated with CD38 contributes to human pathologies such as asthma, neoplasia, and neuroimmune diseases. This review is focused on investigations on the role of CD38-cyclic ADP-ribose signaling in airway smooth muscle in the context of transcriptional and posttranscriptional regulation of CD38 expression. The specific roles of transcription factors NF-kB and AP-1 in the transcriptional regulation of CD38 expression and of miRNAs miR-140-3p and miR-708 in the posttranscriptional regulation and the underlying mechanisms of such regulation are discussed.

SDS-Polyacrylamide Electrophoresis and Western Blotting Applied to the Study of Asthma

Western blotting is used to analyze proteins after being separated by electrophoresis and subsequently electro-transferred to a membrane. Once immobilized, a specific protein can be identified through its reaction with a labeled antibody or antigen. It is a methodology commonly used in biomedical research such as asthma studies, to assess the pathways of inflammatory mediators involved in the disease.Here, we describe an example of western blotting to determine the factors involved in asthma. In this chapter, the methodology of western blotting is reviewed, paying attention on potential problems and giving interesting recommendations.

CD38 in the pathogenesis of allergic airway disease: Potential therapeutic targets

CD38 is an ectoenzyme that catalyzes the conversion of β-nicotinamide adenine dinucleotide (β-NAD) to cyclic adenosine diphosphoribose (cADPR) and adenosine diphosphoribose (ADPR) and NADP to nicotinic acid adenine dinucleotide phosphate (NAADP) and adenosine diphosphoribose-2'-phosphate (ADPR-P). The metabolites of NAD and NADP have roles in calcium signaling in different cell types including airway smooth muscle (ASM) cells. In ASM cells, inflammatory cytokines augment CD38 expression and to a greater magnitude in cells from asthmatics, indicating a greater capacity for the generation of cADPR and ADPR in ASM from asthmatics. CD38 deficient mice develop attenuated airway responsiveness to inhaled methacholine following allergen sensitization and challenge compared to wild-type mice indicating its potential role in asthma. Regulation of CD38 expression in ASM cells is achieved by mitogen activated protein kinases, specific isoforms of PI3 kinases, the transcription factors NF-κB and AP-1, and post-transcriptionally by microRNAs. This review will focus on the role of CD38 in intracellular calcium regulation in ASM, contribution to airway inflammation and airway hyperresponsiveness in mouse models of allergic airway inflammation, the transcriptional and post-transcriptional mechanisms of regulation of expression, and outline approaches to inhibit its expression and activity.

Inundation of asthma target research: Untangling asthma riddles

Asthma is an inveterate inflammatory disorder, delineated by the airway inflammation, bronchial hyperresponsiveness (BHR) and airway wall remodeling. Although, asthma is a vague term, and is recognized as heterogenous entity encompassing different phenotypes. Targeting single mediator or receptor did not prove much clinical significant, as asthma is complex disease involving myriad inflammatory mediators. Asthma may probably involve a large number of different types of molecular and cellular components interacting through complex pathophysiological pathways. This review covers the past, present, and future therapeutic approaches and pathophysiological mechanisms of asthma. Furthermore, review describe importance of targeting several mediators/modulators and receptor antagonists involved in the physiopathology of asthma. Novel targets for asthma research include Galectins, Immunological targets, K ⁺ Channels, Kinases and Transcription Factors, Toll-like receptors, Selectins and Transient receptor potential channels. But recent developments in asthma research are very promising, these include Bitter taste receptors (TAS2R) abated airway obstruction in mouse model of asthma and Calcium-sensing receptor obliterate inflammation and in bronchial hyperresponsiveness allergic asthma. All these progresses in asthma targets, and asthma phenotypes exploration are auspicious in untangling of asthma riddles.

Inhibition of PI3K promotes dilation of human small airways in a rho kinase-dependent manner

Background and Purpose

Asthma manifests as a heterogeneous syndrome characterized by airway obstruction, inflammation and hyperresponsiveness (AHR). Although the molecular mechanisms remain unclear, activation of specific PI3K isoforms mediate inflammation and AHR. We aimed to determine whether inhibition of PI3Kδ evokes dilation of airways and to elucidate potential mechanisms.

Experimental Approach

Human precision cut lung slices from non‐asthma donors and primary human airway smooth muscle (HASM) cells from both non‐asthma and asthma donors were utilized. Phosphorylation of Akt, myosin phosphatase target subunit 1 (MYPT1) and myosin light chain (MLC) were assessed in HASM cells following either PI3K inhibitor or siRNA treatment. HASM relaxation was assessed by micro‐pattern deformation. Reversal of constriction of airways was assessed following stimulation with PI3K or ROCK inhibitors.

Key Results

Soluble inhibitors or PI3Kδ knockdown reversed carbachol‐induced constriction of human airways, relaxed agonist‐contracted HASM and inhibited pAkt, pMYPT1 and pMLC in HASM. Similarly, inhibition of Rho kinase also dilated human PCLS airways and suppressed pMYPT1 and pMLC. Baseline pMYPT1 was significantly elevated in HASM cells derived from asthma donors in comparison with non‐asthma donors. After desensitization of the β₂‐adrenoceptors, a PI3Kδ inhibitor remained an effective dilator. In the presence of IL‐13, dilation by a β agonist, but not PI3K inhibitor, was attenuated.

Conclusion and Implications

PI3Kδ inhibitors act as dilators of human small airways. Taken together, these findings provide alternative approaches to the clinical management of airway obstruction in asthma.

Glucocorticoid and TNF signaling converge at A20 (TNFAIP3) to repress airway smooth muscle cytokine expression

Airway smooth muscle is a major target tissue for glucocorticoid (GC)-based asthma therapies, however, molecular mechanisms through which the GC receptor (GR) exerts therapeutic effects in this key airway cell type have not been fully elucidated. We previously identified the nuclear factor-κB (NF-κB) inhibitor, A20 (TNFAIP3), as a mediator of cytokine repression by glucocorticoids (GCs) in airway epithelial cells and defined cooperative regulation of anti-inflammatory genes by GR and NF-κB as a key mechanistic underpinning of airway epithelial GR function. Here, we expand on these findings to determine whether a similar mechanism is operational in human airway smooth muscle (HASM). Using HASM cells derived from normal and fatal asthma samples as an in vitro model, we demonstrate that GCs spare or augment TNF-mediated induction of A20 (TNFAIP3), TNIP1, and NFKBIA, all implicated in negative feedback control of NF-κB-driven inflammatory processes. We applied chromatin immunoprecipitation and reporter analysis to show that GR and NF-κB directly regulate A20 expression in HASM through cooperative induction of an intronic enhancer. Using overexpression, we show for the first time that A20 and its interacting partner, TNIP1, repress TNF signaling in HASM cells. Moreover, we applied small interfering RNA-based gene knockdown to demonstrate that A20 is required for maximal cytokine repression by GCs in HASM. Taken together, our data suggest that inductive regulation of A20 by GR and NF-κB contributes to cytokine repression in HASM.

Epigenetic dysregulation of interleukin 8 (CXCL8) hypersecretion in cystic fibrosis airway epithelial cells

Airway epithelial cells in cystic fibrosis (CF) overexpress Interleukin 8 (CXCL8) through poorly defined mechanisms. CXCL8 transcription is dependent on coordinated binding of CCAAT/enhancer binding protein (C/EBP)β, nuclear factor (NF)-κB, and activator protein (AP)-1 to the promoter. Here we show abnormal epigenetic regulation is responsible for CXCL8 overexpression in CF cells. Under basal conditions CF cells had increased bromodomain (Brd)3 and Brd4 recruitment and enhanced NF-κB and C/EBPβ binding to the CXCL8 promoter compared to non-CF cells due to trimethylation of histone H3 at lysine 4 (H3K4me3) and DNA hypomethylation at CpG6. IL-1β increased NF-κB, C/EBPβ and Brd4 binding. Furthermore, inhibitors of bromodomain and extra-terminal domain family (BET) proteins reduced CXCL8 production in CF cells suggesting a therapeutic target for the BET pathway.

Differential Regulation of CXCL8 Production by Different G Protein Subunits with Synergistic Stimulation by Gi- and Gq-Regulated Pathways

CXCL8 (also known as interleukin-8 or IL-8) is a proinflammatory chemokine that not only modulates the inflammatory and immune responses, but whose upregulation is often associated with diseases including various types of cancer. Although numerous ligands for G protein-coupled receptors (GPCRs) have been shown to stimulate the production of CXCL8, the specificity of the G protein signal remains undefined. By expressing the constitutively active Gα subunits in HEK293 cells, CXCL8 production was herein demonstrated to be most effectively stimulated by Gαq family members, while those of Gαs and Gα12 elicited much weaker activities, and Gαi being totally ineffective. However, in cell lines such as HepG2, HeLa, and MCF-7 that endogenously express Gβγ-responsive phospholipase Cβ isoforms (PLCβ2/3), activation of the Gi-coupled α2-adrenoceptor significantly stimulated CXCL8 production. This Gi-induced CXCL8 production was apparently mediated via specific Gβγ dimers and required the presence of PLCβ2/3. Co-activation of Gi-coupled α2-adrenoceptor and Gq-coupled bradykinin receptor resulted in a synergistic CXCL8 production, with Gβγ-responsive PLCβ2/3, Src, ERK, and STAT3 serving as critical signaling intermediates. The treatment of HepG2 and B-10 endothelial cells with bradykinin stimulated CXCL8 production and cell proliferation. Interestingly, the latter response was driven by CXCL8 autocrine signaling because it was abolished by SB225002, an antagonist that prevents CXCL8 from binding to CXCR2. Collectively, our results provide a mechanistic basis for various G protein subfamilies to regulate the production of CXCL8, which may then lead to paracrine and/or autocrine signaling with major implications in both normal physiology and pathophysiological conditions.

MicroRNA Mediated Chemokine Responses in Human Airway Smooth Muscle Cells

Airway smooth muscle (ASM) cells play a critical role in the pathophysiology of asthma due to their hypercontractility and their ability to proliferate and secrete inflammatory mediators. microRNAs (miRNAs) are gene regulators that control many signaling pathways and thus serve as potential therapeutic alternatives for many diseases. We have previously shown that miR-708 and miR-140-3p regulate the MAPK and PI3K signaling pathways in human ASM (HASM) cells following TNF-α exposure. In this study, we investigated the regulatory effect of these miRNAs on other asthma-related genes. Microarray analysis using the Illumina platform was performed with total RNA extracted from miR-708 (or control miR)-transfected HASM cells. Inhibition of candidate inflammation-associated gene expression was further validated by qPCR and ELISA. The most significant biologic functions for the differentially expressed gene set included decreased inflammatory response, cytokine expression and signaling. qPCR revealed inhibition of expression of CCL11, CXCL10, CCL2 and CXCL8, while the release of CCL11 was inhibited in miR-708-transfected cells. Transfection of cells with miR-140-3p resulted in inhibition of expression of CCL11, CXCL12, CXCL10, CCL5 and CXCL8 and of TNF-α-induced CXCL12 release. In addition, expression of RARRES2, CD44 and ADAM33, genes known to contribute to the pathophysiology of asthma, were found to be inhibited in miR-708-transfected cells. These results demonstrate that miR-708 and miR-140-3p exert distinct effects on inflammation-associated gene expression and biological function of ASM cells. Targeting these miRNA networks may provide a novel therapeutic mechanism to down-regulate airway inflammation and ASM proliferation in asthma.

Cyclooxygenase-2 and microRNA-155 expression are elevated in asthmatic airway smooth muscle cells

Cyclooxygenase-2 (COX-2) expression and PGE2 secretion from human airway smooth muscle cells (hASMCs) may contribute to β2-adrenoceptor hyporesponsiveness, a clinical feature observed in some patients with asthma. hASMCs from patients with asthma exhibit elevated expression of cytokine-responsive genes, and in some instances this is attributable to an altered histone code and/or microRNA expression. We hypothesized that COX-2 expression and PGE2 secretion might be elevated in asthmatic hASMCs in response to proinflammatory signals in part due to altered histone acetylation and/or microRNA expression. hASMCs obtained from nonasthmatic and asthmatic human subjects were treated with cytomix (IL-1β, TNF-α, and IFN-γ). A greater elevation of COX-2 mRNA, COX-2 protein, and PGE2 secretion was observed in the asthmatic cells. We investigated histone H3/H4-acetylation, transcription factor binding, mRNA stability, p38 mitogen-activated protein kinase signaling, and microRNA (miR)-155 expression as potential mechanisms responsible for the differential elevation of COX-2 expression. We found that histone H3/H4-acetylation and transcription factor binding to the COX-2 promoter were similar in both groups, and histone H3/H4-acetylation did not increase after cytomix treatment. Cytomix treatment elevated NF-κB and RNA polymerase II binding to similar levels in both groups. COX-2 mRNA stability was increased in asthmatic cells. MiR-155 expression was higher in cytomix-treated asthmatic cells, and we show it enhances COX-2 expression and PGE2 secretion in asthmatic and nonasthmatic hASMCs. Thus, miR-155 expression positively correlates with COX-2 expression in the asthmatic hASMCs and may contribute to the elevated expression observed in these cells. These findings may explain, at least in part, β2-adrenoceptor hyporesponsiveness in patients with asthma.

Mechanisms of airway hyper-responsiveness in asthma: the past, present and yet to come

Airway hyper-responsiveness (AHR) has long been considered a cardinal feature of asthma. The development of the measurement of AHR 40 years ago initiated many important contributions to our understanding of asthma and other airway diseases. However, our understanding of AHR in asthma remains complicated by the multitude of potential underlying mechanisms which in reality are likely to have different contributions amongst individual patients. Therefore, the present review will discuss the current state of understanding of the major mechanisms proposed to contribute to AHR and highlight the way in which AHR testing is beginning to highlight distinct abnormalities associated with clinically relevant patient populations. In doing so we aim to provide a foundation by which future research can begin to ascribe certain mechanisms to specific patterns of bronchoconstriction and subsequently match phenotypes of bronchoconstriction with clinical phenotypes. We believe that this approach is not only within our grasp but will lead to improved mechanistic understanding of asthma phenotypes and we hoped to better inform the development of phenotype-targeted therapy.

MicroRNA Regulation of Airway Inflammation and Airway Smooth Muscle Function: Relevance to Asthma

Genetic and environmental factors contribute to the onset and severity of asthma. Molecular pathogenesis of asthma involves changes in gene expression by a variety of inflammatory mediators acting in autocrine and paracrine fashion on effector cells of the airways. Transcriptional regulation of gene expression in resident airway cells has been studied extensively. However, protein function in a target cell can be regulated at multiple levels starting from transcription followed by post-transcription, translation, and post-translation steps. In this context, small noncoding RNAs known as microRNAs (miRNAs) have evolved as one of the key regulators of gene expression post-transcriptionally. Most importantly, miRNA expression is dynamic in nature and can be regulated by a variety of external stimuli. Altered expression of individual or a group of miRNAs is thought to contribute to human diseases. Recent studies have implicated differential expression of miRNAs in the lungs during inflammation. Most importantly, advanced biochemical and molecular tools could be used to manipulate miRNA expression thereby effecting functional changes in target cells and organ systems. This review summarizes the current understanding of miRNA in the regulation of airway function in health and disease, and highlights the potential clinical utility of mRNAs as biomarkers of airway diseases and as potential therapeutic targets.

NF-kappaB Signaling in Chronic Inflammatory Airway Disease

Asthma and chronic obstructive pulmonary disease (COPD) are obstructive airway disorders which differ in their underlying causes and phenotypes but overlap in patterns of pharmacological treatments. In both asthma and COPD, oxidative stress contributes to airway inflammation by inducing inflammatory gene expression. The redox-sensitive transcription factor, nuclear factor (NF)-kappaB (NF-κB), is an important participant in a broad spectrum of inflammatory networks that regulate cytokine activity in airway pathology. The anti-inflammatory actions of glucocorticoids (GCs), a mainstay treatment for asthma, involve inhibition of NF-κB induced gene transcription. Ligand bound GC receptors (GRs) bind NF-κB to suppress the transcription of NF-κB responsive genes (i.e., transrepression). However, in severe asthma and COPD, the transrepression of NF-κB by GCs is negated as a consequence of post-translational changes to GR and histones involved in chromatin remodeling. Therapeutics which target NF-κB activation, including inhibitors of IκB kinases (IKKs) are potential treatments for asthma and COPD. Furthermore, reversing GR/histone acetylation shows promise as a strategy to treat steroid refractory airway disease by augmenting NF-κB transrepression. This review examines NF-κB signaling in airway inflammation and its potential as target for treatment of asthma and COPD.

CXCL8 histone H3 acetylation is dysfunctional in airway smooth muscle in asthma: regulation by BET

Asthma is characterized by airway inflammation and remodeling and CXCL8 is a CXC chemokine that drives steroid-resistant neutrophilic airway inflammation. We have shown that airway smooth muscle (ASM) cells isolated from asthmatic individuals secrete more CXCL8 than cells from nonasthmatic individuals. Here we investigated chromatin modifications at the CXCL8 promoter in ASM cells from nonasthmatic and asthmatic donors to further understand how CXCL8 is dysregulated in asthma. ASM cells from asthmatic donors had increased histone H3 acetylation, specifically histone H3K18 acetylation, and increased binding of histone acetyltransferase p300 compared with nonasthmatic donors but no differences in CXCL8 DNA methylation. The acetylation reader proteins Brd3 and Brd4 were bound to the CXCL8 promoter and Brd inhibitors inhibited CXCL8 secretion from ASM cells by disrupting Brd4 and RNA polymerase II binding to the CXCL8 promoter. Our results show a novel dysregulation of CXCL8 transcriptional regulation in asthma characterized by a promoter complex that is abnormal in ASM cells isolated from asthmatic donors and can be modulated by Brd inhibitors. Brd inhibitors may provide a new therapeutic strategy for steroid-resistant inflammation.

Airway responsiveness in CD38-deficient mice in allergic airway disease: studies with bone marrow chimeras

CD38 is a cell-surface protein involved in calcium signaling and contractility of airway smooth muscle. It has a role in normal airway responsiveness and in airway hyperresponsiveness (AHR) developed following airway exposure to IL-13 and TNF-α but appears not to be critical to airway inflammation in response to the cytokines. CD38 is also involved in T cell-mediated immune response to protein antigens. In this study, we assessed the contribution of CD38 to AHR and inflammation to two distinct allergens, ovalbumin and the epidemiologically relevant environmental fungus Alternaria. We also generated bone marrow chimeras to assess whether Cd38(+/+) inflammatory cells would restore AHR in the CD38-deficient (Cd38(-/-)) hosts following ovalbumin challenge. Results show that wild-type (WT) mice develop greater AHR to inhaled methacholine than Cd38(-/-) mice following challenge with either allergen, with comparable airway inflammation. Reciprocal bone marrow transfers did not change the native airway phenotypic differences between WT and Cd38(-/-) mice, indicating that the lower airway reactivity of Cd38(-/-) mice stems from Cd38(-/-) lung parenchymal cells. Following bone marrow transfer from either source and ovalbumin challenge, the phenotype of Cd38(-/-) hosts was partially reversed, whereas the airway phenotype of the WT hosts was preserved. Airway inflammation was similar in Cd38(-/-) and WT chimeras. These results indicate that loss of CD38 on hematopoietic cells is not sufficient to prevent AHR and that the magnitude of airway inflammation is not the predominant underlying determinant of AHR in mice.

Epigenetic targets for novel therapies of lung diseases

In spite of substantial advances in defining the immunobiology and function of structural cells in lung diseases there is still insufficient knowledge to develop fundamentally new classes of drugs to treat many lung diseases. For example, there is a compelling need for new therapeutic approaches to address severe persistent asthma that is insensitive to inhaled corticosteroids. Although the prevalence of steroid-resistant asthma is 5-10%, severe asthmatics require a disproportionate level of health care spending and constitute a majority of fatal asthma episodes. None of the established drug therapies including long-acting beta agonists or inhaled corticosteroids reverse established airway remodeling. Obstructive airways remodeling in patients with chronic obstructive pulmonary disease (COPD), restrictive remodeling in idiopathic pulmonary fibrosis (IPF) and occlusive vascular remodeling in pulmonary hypertension are similarly unresponsive to current drug therapy. Therefore, drugs are needed to achieve long-acting suppression and reversal of pathological airway and vascular remodeling. Novel drug classes are emerging from advances in epigenetics. Novel mechanisms are emerging by which cells adapt to environmental cues, which include changes in DNA methylation, histone modifications and regulation of transcription and translation by noncoding RNAs. In this review we will summarize current epigenetic approaches being applied to preclinical drug development addressing important therapeutic challenges in lung diseases. These challenges are being addressed by advances in lung delivery of oligonucleotides and small molecules that modify the histone code, DNA methylation patterns and miRNA function.

MicroRNA-146a and microRNA-146b expression and anti-inflammatory function in human airway smooth muscle

MicroRNA (miR)-146a and miR-146b are negative regulators of inflammatory gene expression in lung fibroblasts, epithelial cells, monocytes, and endothelial cells. The abundance of cyclooxygenase-2 (COX-2) and IL-1β is negatively regulated by the miR-146 family, suggesting miR-146a and/or miR-146b might modulate inflammatory mediator expression in airway smooth muscle thereby contributing to pathogenesis of asthma. To test this idea we compared miR-146a and miR-146b expression in human airway smooth muscle cells (hASMCs) from nonasthmatic and asthmatic subjects treated with cytomix (IL-1β, TNF-α, and IFNγ) and examined the miRNAs' effects on COX-2 and IL-1β expression. We found that cytomix treatment elevated miR-146a and miR-146b abundance. Induction with cytomix was greater than induction with individual cytokines, and asthmatic cells exhibited higher levels of miR-146a expression following cytomix treatment than nonasthmatic cells. Transfection of miR-146a or miR-146b mimics reduced COX-2 and IL-1β expression. A miR-146a inhibitor increased COX-2 and IL-1β expression, but a miR-146b inhibitor was ineffective. Repression of COX-2 and IL-1β expression by miR-146a correlated with reduced abundance of the RNA-binding protein human antigen R. These results demonstrate that miR-146a and miR-146b expression is inducible in hASMCs by proinflammatory cytokines and that miR-146a expression is greater in asthmatic cells. Both miR-146a and miR-146b can negatively regulate COX-2 and IL-1β expression at pharmacological levels, but loss-of-function studies showed that only miR-146a is an endogenous negative regulator in hASMCs. The results suggest miR-146 mimics may be an attractive candidate for further preclinical studies as an anti-inflammatory treatment of asthma.

Airway smooth muscle hyperproliferation is regulated by microRNA-221 in severe asthma

Increased airway smooth muscle (ASM) mass is a feature of asthmatic airways, and could result from augmented proliferation. We determined whether proliferation and IL-6 release are abnormal in ASM cells (ASMCs) from patients with severe asthma, and whether these features could be mediated by microRNA-221 and microRNA-222, through modulation of the cyclin-dependent kinase inhibitors, p21(WAF1) and p27(kip1). ASMCs cultured from bronchial biopsies of healthy subjects and patients with nonsevere or severe asthma were studied. Proliferation was measured by the incorporation of bromodeoxyuridine and IL-6 by ELISA. FCS and transforming growth factor (TGF)-β caused greater proliferation and IL-6 release in patients with severe compared with nonsevere asthma and normal subjects. FCS + TGF-β inhibited p21(WAF1) and p27(kip1) expression, and increased microRNA-221 (miR-221) expression in ASMCs from individuals with severe asthma. miR-221, and not miR-222, mimics the increased proliferation and IL-6 release induced by FCS + TGF in healthy ASM, whereas in patients with severe asthma, the inhibition of miR-221, but not miR-222, inhibited proliferation and IL-6 release. miR-221 inhibition led to the increased expression of FCS + TGF-β-induced p21(WAF1) and p27(kip1). Dexamethasone suppressed proliferation in healthy subjects, but not in subjects with asthma. IL-6 was less suppressible by dexamethasone in patients with nonsevere and severe asthma, compared with healthy subjects. miR-221 did not influence the effects of dexamethasone. ASM from patients with severe asthma shows greater proliferation and IL-6 release than in patients with nonsevere asthma, but both groups show corticosteroid insensitivity. miR-221 regulates p21(WAF1) and p27(kip1) expression levels. Furthermore, miR-221 regulates the hyperproliferation and IL-6 release of ASMCs from patients with severe asthma, but does not regulate corticosteroid insensitivity.

Regulation of pulmonary inflammation by mesenchymal cells

Pulmonary inflammation and tissue remodelling are common elements of chronic respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and pulmonary hypertension (PH). In disease, pulmonary mesenchymal cells not only contribute to tissue remodelling, but also have an important role in pulmonary inflammation. This review will describe the immunomodulatory functions of pulmonary mesenchymal cells, such as airway smooth muscle (ASM) cells and lung fibroblasts, in chronic respiratory disease. An important theme of the review is that pulmonary mesenchymal cells not only respond to inflammatory mediators, but also produce their own mediators, whether pro-inflammatory or pro-resolving, which influence the quantity and quality of the lung immune response. The notion that defective pro-inflammatory or pro-resolving signalling in these cells potentially contributes to disease progression is also discussed. Finally, the concept of specifically targeting pulmonary mesenchymal cell immunomodulatory function to improve therapeutic control of chronic respiratory disease is considered.

Direct, interferon-independent activation of the CXCL10 promoter by NF-κB and interferon regulatory factor 3 during hepatitis C virus infection

Hepatitis C virus (HCV) infection of hepatocytes leads to transcriptional induction of the chemokine CXCL10, which is considered an interferon (IFN)-stimulated gene. However, we have recently shown that IFNs are not required for CXCL10 induction in hepatocytes during acute HCV infection. Since the CXCL10 promoter contains binding sites for several proinflammatory transcription factors, we investigated the contribution of these factors to CXCL10 transcriptional induction during HCV infection in vitro. Wild-type and mutant CXCL10 promoter-luciferase reporter constructs were used to identify critical sites of transcriptional regulation. The proximal IFN-stimulated response element (ISRE) and NF-κB binding sites positively regulated CXCL10 transcription during HCV infection as well as following exposure to poly(I·C) (a Toll-like receptor 3 [TLR3] stimulus) and 5' poly(U) HCV RNA (a retinoic acid-inducible gene I [RIG-I] stimulus) from two viral genotypes. Conversely, binding sites for AP-1 and CCAAT/enhancer-binding protein β (C/EBP-β) negatively regulated CXCL10 induction in response to TLR3 and RIG-I stimuli, while only C/EBP-β negatively regulated CXCL10 during HCV infection. We also demonstrated that interferon-regulatory factor 3 (IRF3) is transiently recruited to the proximal ISRE during HCV infection and localizes to the nucleus in HCV-infected primary human hepatocytes. Furthermore, IRF3 activated the CXCL10 promoter independently of type I or type III IFN signaling. The data indicate that sensing of HCV infection by RIG-I and TLR3 leads to direct recruitment of NF-κB and IRF3 to the CXCL10 promoter. Our study expands upon current knowledge regarding the mechanisms of CXCL10 induction in hepatocytes and lays the foundation for additional mechanistic studies that further elucidate the combinatorial and synergistic aspects of immune signaling pathways.

Modulation of IL-8 boosted by Mycoplasma pneumoniae lysate in human airway epithelial cells

Mycoplasma pneumoniae, a major cause of community-acquired pneumonia, has been recognized as a trigger for asthma inception and exacerbation. The epithelial cells on the respiratory tract parasitized by M. pneumoniae exhibit a number of cytopathic effects as a result of local inflammation and stimulated host immune response. We investigated the interactions of signaling molecules regulating the release of IL-8 by the direct stimulation of M. pneumoniae lysate (MPL) in human airway epithelial cells. In human airway epithelial cells, MPL-induced IL-8 proteins were decreased by monoclonal anti-TLR2 antibody in a dose-dependent fashion, and significantly blocked by siRNA TLR2. The pharmacologic inhibitors of ERK, U0126 and PD98059, effectively reduced IL-8 expression and the active forms of ERK signaling molecules, as detected by anti-phosphorylated p44/42 antibody. The region spanning from -132 to +41 in the IL-8 promoter demonstrated the highest luciferase activity against MPL and the mutations of NF-κB and NF-IL6 entirely diminished the activity. After investigating transfections of the NF-κB and NF-IL6 reporter vectors, NF-IL6 activation was significantly induced by MPL stimulation, which was considerably decreased by U0126 and monoclonal anti-TLR2 antibody. These results indicate that MPL-induced IL-8 increase is transcriptionally regulated by NF-IL6 more than by NF-κB. Additionally, the activation of NF-IL6 is influenced by TLR2 and ERK signaling pathways in airway epithelial cells.

A NF-κB-dependent dual promoter-enhancer initiates the lipopolysaccharide-mediated transcriptional activation of the chicken lysozyme in macrophages

The transcriptional activation of the chicken lysozyme gene (cLys) by lipopolysaccharide (LPS) in macrophages is dependent on transcription of a LPS-Inducible Non-Coding RNA (LINoCR) triggering eviction of the CCCTC-binding factor (CTCF) from a negative regulatory element upstream of the lysozyme transcription start site. LINoCR is transcribed from a promoter originally characterized as a hormone response enhancer in the oviduct. Herein, we report the characterization of this cis-regulatory element (CRE). In activated macrophages, a 60 bp region bound by NF-κB, AP1 and C/EBPβ controls this CRE, which is strictly dependent on NF-κB binding for its activity in luciferase assays. Moreover, the serine/threonine kinase IKKα, known to be recruited by NF-κB to NF-κB-dependent genes is found at the CRE and within the transcribing regions of both cLys and LINoCR. Such repartition suggests a simultaneous promoter and enhancer activity of this CRE, initiating cLys transcriptional activation and driving CTCF eviction. This recruitment was transient despite persistence of both cLys transcription and NF-κB binding to the CRE. Finally, comparing cLys with other LPS-inducible genes indicates that IKKα detection within transcribing regions can be correlated with the presence of the elongating form of RNA polymerase II or concentrated in the 3′ end of the gene.

Role of transcription factors in the pathogenesis of asthma and COPD

Inflammation is a central feature of asthma and chronic obstructive pulmonary disease (COPD). Despite recent advances in the knowledge of the pathogenesis of asthma and COPD, much more research on the molecular mechanisms of asthma and COPD are needed to aid the logical development of new therapies for these common and important diseases, particularly in COPD where no effective treatments currently exist. In the future the role of the activation/repression of different transcription factors and the genetic regulation of their expression in asthma and COPD may be an increasingly important aspect of research, as this may be one of the critical mechanisms regulating the expression of different clinical phenotypes and their responsiveness to therapy, particularly to anti-inflammatory drugs.

Cytokines in chronic respiratory diseases

Cytokines are small, secreted proteins that control immune responses. Within the lung, they can control host responses to injuries or infection, resulting in clearance of the insult, repair of lung tissue, and return to homeostasis. Problems can arise when this response is over exuberant and/or cytokine production becomes dysregulated. In such cases, chronic and repeated inflammatory reactions and cytokine production can be established, leading to airway remodeling and fibrosis with unintended, maladaptive consequences. In this report, we describe the cytokines and molecular mechanisms behind the pathology observed in three major chronic diseases of the lung: asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. Overlapping mechanisms are presented as potential sites for therapeutic intervention.

Epigenetics and miRNA emerge as key regulators of smooth muscle cell phenotype and function

Regulation of phenotypic plasticity in smooth muscle requires an understanding of the mechanisms regulating phenotype-specific genes and the processes dysregulated during pathogenesis. Decades of study in airway smooth muscle has provided extensive knowledge of the gene expression patterns and signaling pathways necessary to maintain and alter smooth muscle cell phenotype. With this solid foundation, the importance and complexity of inheritable epigenetic modifications and mechanisms silencing gene expression have now emerged as fundamental components regulating aspects of inflammation, proliferation and remodeling.

Molecular pathways: hepatitis C virus, CXCL10, and the inflammatory road to liver cancer

An estimated 170 million people worldwide are chronically infected with the hepatitis C virus (HCV), which is characterized histologically by a persistent immune and inflammatory response that fails to clear HCV from hepatocytes. This response is recruited to the liver, in part, by the chemokine CXCL10, the serum and intrahepatic levels of which have been inversely linked to the outcome of interferon-based therapies for hepatitis C. Bystander tissue damage from this ineffective response is thought to lead to increased hepatocyte turnover and the development of fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). However, CXCL10 is traditionally viewed as an orchestrator of the angiostatic and antitumor immune response. In this review, we will explore this duality and the pathways by which CXCL10 is produced by hepatocytes during HCV infection, its effects on resident and infiltrating immune cells, and how deregulation of these cell populations within the liver may lead to chronic liver inflammation. We will also discuss potential host-directed therapies to slow or reverse HCV-induced inflammation that leads to fibrosis, cirrhosis, and HCCs.

Regulation of interleukin-6 secretion by the two-pore-domain potassium channel Trek-1 in alveolar epithelial cells

We recently proposed a role for the two-pore-domain K(+) (K2P) channel Trek-1 in the regulation of cytokine release from mouse alveolar epithelial cells (AECs) by demonstrating decreased interleukin-6 (IL-6) secretion from Trek-1-deficient cells, but the underlying mechanisms remained unknown. This study was designed to investigate the mechanisms by which Trek-1 decreases IL-6 secretion. We hypothesized that Trek-1 regulates tumor necrosis factor-α (TNF-α)-induced IL-6 release via NF-κB-, p38-, and PKC-dependent pathways. We found that Trek-1 deficiency decreased IL-6 secretion from mouse and human AECs at both transcriptional and translational levels. While NF-κB/p65 phosphorylation was unchanged, p38 phosphorylation was decreased in Trek-1-deficient cells, and pharmacological inhibition of p38 decreased IL-6 secretion in control but not Trek-1-deficient cells. Similarly, pharmacological inhibition of PKC also decreased IL-6 release, and we found decreased phosphorylation of the isoforms PKC/PKDμ (Ser(744/748)), PKCθ, PKCδ, PKCα/βII, and PKCζ/λ, but not PKC/PKDμ (Ser(916)) in Trek-1-deficient AECs. Phosphorylation of PKCθ, a Ca(2+)-independent isoform, was intact in control cells but impaired in Trek-1-deficient cells. Furthermore, TNF-α did not elevate the intracellular Ca(2+) concentration in control or Trek-1-deficient cells, and removal of extracellular Ca(2+) did not impair IL-6 release. In summary, we report the expression of Trek-1 in human AECs and propose that Trek-1 deficiency may alter both IL-6 translation and transcription in AECs without affecting Ca(2+) signaling. The results of this study identify Trek-1 as a new potential target for the development of novel treatment strategies against acute lung injury.

YKL-40 induces IL-8 expression from bronchial epithelium via MAPK (JNK and ERK) and NF-κB pathways, causing bronchial smooth muscle proliferation and migration

Recently, the serum levels of YKL-40, a chitinase-like glycoprotein, have been shown to be significantly elevated in asthmatics and are associated with asthma severity. Although these studies raise the possibility that YKL-40 may influence asthma, the mechanisms remain unknown. This study firstly investigated the mechanisms involved in YKL-40-mediated inflammation in human bronchial epithelial cells (HBECs) and analyzed the soluble factors secreted by bronchial epithelial cells exposed to YKL-40 that were responsible for increasing proliferation and migration of primary normal human bronchial smooth muscle cells (BSMCs). YKL-40-induced inflammation was assayed in two HBECs (BEAS-2B cell line and primary HBECs). In addition, we treated BEAS-2B cells and HBECs with YKL-40 and added the conditioned culture media to BSMCs. The proliferation and migration of BSMCs were determined by premixed WST-1 cell proliferation reagent (Clontech Laboratories) and QCM chemotaxis migration assay (Millipore), respectively. Bronchial epithelial cells treated with YKL-40 resulted in a significant increase of IL-8 production, which was dependent on MAPK (JNK and ERK) and NF-κB pathways activation. YKL-40-induced IL-8 was found to further stimulate proliferation and migration of BSMCs, and the effects were inhibited after neutralizing IL-8. Through investigating the interaction of airway epithelium and smooth muscle, our findings implicate that YKL-40 may be involved in the inflammation of asthma by induction of IL-8 from epithelium, subsequently contributing to BSMC proliferation and migration. Moreover, inhibition of IL-8 signaling is a potential therapeutic target for YKL-40-induced inflammation and remodeling of asthma.

CXC chemokine ligand 12/stromal cell-derived factor-1 regulates cell adhesion in human colon cancer cells by induction of intercellular adhesion molecule-1

Background

The CXC chemokine ligand 12 (CXCL12)/stromal cell-derived factor-1 (SDF-1) and CXC receptor 4 (CXCR4) axis is involved in human colorectal cancer (CRC) carcinogenesis and can promote the progression of CRC. Interaction between CRC cells and endothelium is a key event in tumor progression. The aim of this study was to investigate the effect of SDF-1 on the adhesion of CRC cells.

Methods

Human CRC DLD-1 cells were used to study the effect of SDF-1 on intercellular adhesion molecule-1 (ICAM-1) expression and cell adhesion to endothelium.

Results

SDF-1 treatment induced adhesion of DLD-1 cells to the endothelium and increased the expression level of the ICAM-1. Inhibition of ICAM-1 by small interfering RNA (siRNA) and neutralizing antibody inhibited SDF-1-induced cell adhesion. By using specific inhibitors and short hairpin RNA (shRNA), we demonstrated that the activation of ERK, JNK and p38 pathways is critical for SDF-1-induced ICAM-1 expression and cell adhesion. Promoter activity and transcription factor ELISA assays showed that SDF-1 increased Sp1-, C/EBP-β- and NF-κB-DNA binding activities in DLD-1 cells. Inhibition of Sp1, C/EBP-β and NF-κB activations by specific siRNA blocked the SDF-1-induced ICAM-1 promoter activity and expression. The effect of SDF-1 on cell adhesion was mediated by the CXCR4.

Conclusion

Our findings support the hypothesis that ICAM-1 up-regulation stimulated by SDF-1 may play an active role in CRC cell adhesion.

Corticosteroid insensitivity of chemokine expression in airway smooth muscle of patients with severe asthma

BACKGROUND

Patients with severe asthma are less responsive to the beneficial effects of corticosteroid therapy.

OBJECTIVE

We investigated whether corticosteroid insensitivity was present in airway smooth muscle cells (ASMCs) of patients with severe asthma.

METHODS

ASMCs cultured from bronchial biopsy specimens of nonasthmatic control subjects (n = 12) and patients with nonsevere (n = 10) or severe (n = 10) asthma were compared for the effect of dexamethasone on suppression of TNF-α- and IFN-γ-induced CCL11 (eotaxin), CXCL8 (IL-8), and CX3CL1 (fractalkine) expression. The mechanisms of corticosteroid insensitivity are also determined.

RESULTS

CCL11 release was higher in ASMCs of patients with nonsevere but not severe asthma and nonasthmatic control subjects; CXCL8 and CX3CL1 release were similar in all groups. In patients with severe asthma, dexamethasone caused less suppression of CCL11 and CXCL8 release induced by TNF-α. Dexamethasone potentiated TNF-α- and IFN-γ-induced CX3CL1 release equally in all 3 groups. TNF-α-induced phosphorylated p38 mitogen-activated protein kinase levels were increased in ASMCs from patients with severe asthma compared with those from patients with nonsevere asthma and nonasthmatic subjects, whereas TNF-α-induced phosphorylated c-Jun N-terminal kinase and phosphorylated extracellular signal-related kinase levels were increased in all asthmatic groups. A p38 inhibitor increased the inhibitory effect of dexamethasone.

CONCLUSIONS

ASMCs of patients with severe asthma are corticosteroid insensitive; this might be secondary to heightened p38 mitogen-activated protein kinase levels.

Asthmatic airway smooth muscle CXCL10 production: mitogen-activated protein kinase JNK involvement

CXCL10 (IP10) is involved in mast cell migration to airway smooth muscle (ASM) bundles in asthma. We aimed to investigate the role of cytokine-induced MAPK activation in CXCL10 production by ASM cells from people with and without asthma. Confluent growth-arrested ASM cells were treated with inhibitors of the MAPKs ERK, p38, and JNK and transcription factor NF-κB, or vehicle, and stimulated with IL-1β, TNF-α, or IFN-γ, alone or combined (cytomix). CXCL10 mRNA and protein, JNK, NF-κB p65 phosphorylation, and Iκ-Bα protein degradation were assessed using real-time PCR, ELISA, and immunoblotting, respectively. Cytomix, IL-1β, and TNF-α induced CXCL10 mRNA expression more rapidly in asthmatic than nonasthmatic ASM cells. IL-1β and/or TNF-α combined with IFN-γ synergistically increased asthmatic ASM cell CXCL10 release. Inhibitor effects were similar in asthmatic and nonasthmatic cells, but cytomix-induced release was least affected, with only JNK and NF-κB inhibitors halving it. Notably, JNK phosphorylation was markedly less in asthmatic compared with nonasthmatic cells. However, in both, the JNK inhibitor SP600125 reduced JNK phosphorylation and CXCL10 mRNA levels but did not affect CXCL10 mRNA stability or Iκ-Bα degradation. Together, the JNK and NF-κB inhibitors completely inhibited their CXCL10 release. We concluded that, in asthmatic compared with nonasthmatic ASM cells, JNK activation was reduced and CXCL10 gene expression was more rapid following cytomix stimulation. However, in both, JNK activation did not regulate early events leading to NF-κB activation. Thus JNK and NF-κB provide independent therapeutic targets for limiting CXCL10 production and mast cell migration to the ASM in asthma.

Regulator of G-protein signaling-5 inhibits bronchial smooth muscle contraction in severe asthma

Severe asthma is associated with fixed airway obstruction attributable to inflammation, copious luminal mucus, and increased airway smooth muscle (ASM) mass. Paradoxically, studies demonstrated that the hypertrophic and hyperplastic ASM characteristic of severe asthma has reduced contractile capacity. We compared the G-protein-coupled receptor (GPCR)-induced Ca(2+) mobilization and expression of GPCRs and signaling proteins related to procontractile signaling in ASM derived postmortem from subjects who died of nonrespiratory causes, with cells from subjects who died of asthma. Despite the increased or comparable expression of contraction-promoting GPCRs (bradykinin B2 or histamine H1 and protease-activated receptor 1, respectively) in asthmatic ASM cells relative to cells from healthy donors, asthmatic ASM cells exhibited reduced histamine-induced Ca(2+) mobilization and comparable responses to bradykinin and thrombin, suggesting a postreceptor signaling defect. Accordingly, the expression of regulator of G-protein signaling-5 (RGS5), an inhibitor of ASM contraction, was increased in cultured, asthmatic ASM cells and in bronchial smooth muscle bundles of both human subjects with asthma and allergen-challenged mice, relative to those of healthy human subjects or naive mice. The overexpression of RGS5 impaired the release of Ca(2+) to thrombin, histamine, and carbachol, and reduced the contraction of precision-cut lung slices to carbachol. These results suggest that increased RGS5 expression contributes to decreased myocyte shortening in severe and fatal asthma.