IGFBP-3 mediates TGF-beta1-induced cell growth in human airway smooth muscle cells

Gut microbiome, metabolome and alopecia areata

Alopecia areata (AA) is a type of dermatological disease characterized by rapid and non-scarring hair loss of the scalp or body skin that may be related to genetic, immunological and physiological factors. It is now believed that AA is associated with oxidative stress, autoimmune disease, neuropsychological factors, pathogens, immune checkpoint inhibitors and microecological imbalance under the premise of host genetic susceptibility. In recent years, studies have revealed the significant role of the gut microbiome or metabolome in many aspects of human health. Diverse studies have revealed that the gut microbiome and metabolome have an important influence on skin conditions. This review highlights the relationship between AA and the gut microbiome or metabolome to provide novel directions for the prevention, clinical diagnosis and treatment of AA.

Epithelial-Mesenchymal Transition Mechanisms in Chronic Airway Diseases: A Common Process to Target?

Epithelial-to-mesenchymal transition (EMT) is a reversible process, in which epithelial cells lose their epithelial traits and acquire a mesenchymal phenotype. This transformation has been described in different lung diseases, such as lung cancer, interstitial lung diseases, asthma, chronic obstructive pulmonary disease and other muco-obstructive lung diseases, such as cystic fibrosis and non-cystic fibrosis bronchiectasis. The exaggerated chronic inflammation typical of these pulmonary diseases can induce molecular reprogramming with subsequent self-sustaining aberrant and excessive profibrotic tissue repair. Over time this process leads to structural changes with progressive organ dysfunction and lung function impairment. Although having common signalling pathways, specific triggers and regulation mechanisms might be present in each disease. This review aims to describe the various mechanisms associated with fibrotic changes and airway remodelling involved in chronic airway diseases. Having better knowledge of the mechanisms underlying the EMT process may help us to identify specific targets and thus lead to the development of novel therapeutic strategies to prevent or limit the onset of irreversible structural changes.

Airway remodeling heterogeneity in asthma and its relationship to disease outcomes

Asthma affects an estimated 262 million people worldwide and caused over 461,000 deaths in 2019. The disease is characterized by chronic airway inflammation, reversible bronchoconstriction, and airway remodeling. Longitudinal studies have shown that current treatments for asthma (inhaled bronchodilators and corticosteroids) can reduce the frequency of exacerbations, but do not modify disease outcomes over time. Further, longitudinal studies in children to adulthood have shown that these treatments do not improve asthma severity or fixed airflow obstruction over time. In asthma, fixed airflow obstruction is caused by remodeling of the airway wall, but such airway remodeling also significantly contributes to airway closure during bronchoconstriction in acute asthmatic episodes. The goal of the current review is to understand what is known about the heterogeneity of airway remodeling in asthma and how this contributes to the disease process. We provide an overview of the existing knowledge on airway remodeling features observed in asthma, including loss of epithelial integrity, mucous cell metaplasia, extracellular matrix remodeling in both the airways and vessels, angiogenesis, and increased smooth muscle mass. While such studies have provided extensive knowledge on different aspects of airway remodeling, they have relied on biopsy sampling or pathological assessment of lungs from fatal asthma patients, which have limitations for understanding airway heterogeneity and the entire asthma syndrome. To further understand the heterogeneity of airway remodeling in asthma, we highlight the potential of in vivo imaging tools such as computed tomography and magnetic resonance imaging. Such volumetric imaging tools provide the opportunity to assess the heterogeneity of airway remodeling within the whole lung and have led to the novel identification of heterogenous gas trapping and mucus plugging as important predictors of patient outcomes. Lastly, we summarize the current knowledge of modification of airway remodeling with available asthma therapeutics to highlight the need for future studies that use in vivo imaging tools to assess airway remodeling outcomes.

The Utility of Resolving Asthma Molecular Signatures Using Tissue-Specific Transcriptome Data

An integrative analysis focused on multi-tissue transcriptomics has not been done for asthma. Tissue-specific DEGs remain undetected in many multi-tissue analyses, which influences identification of disease-relevant pathways and potential drug candidates. Transcriptome data from 609 cases and 196 controls, generated using airway epithelium, bronchial, nasal, airway macrophages, distal lung fibroblasts, proximal lung fibroblasts, CD4+ lymphocytes, CD8+ lymphocytes from whole blood and induced sputum samples, were retrieved from Gene Expression Omnibus (GEO). Differentially regulated asthma-relevant genes identified from each sample type were used to identify (a) tissue-specific and tissue-shared asthma pathways, (b) their connection to GWAS-identified disease genes to identify candidate tissue for functional studies, (c) to select surrogate sample for invasive tissues, and finally (d) to identify potential drug candidates via connectivity map analysis. We found that inter-tissue similarity in gene expression was more pronounced at pathway/functional level than at gene level with highest similarity between bronchial epithelial cells and lung fibroblasts, and lowest between airway epithelium and whole blood samples. Although public-domain gene expression data are limited by inadequately annotated per-sample demographic and clinical information which limited the analysis, our tissue-resolved analysis clearly demonstrated relative importance of unique and shared asthma pathways, At the pathway level, IL-1b signaling and ERK signaling were significant in many tissue types, while Insulin-like growth factor and TGF-beta signaling were relevant in only airway epithelial tissue. IL-12 (in macrophages) and Immunoglobulin signaling (in lymphocytes) and chemokines (in nasal epithelium) were the highest expressed pathways. Overall, the IL-1 signaling genes (inflammatory) were relevant in the airway compartment, while pro-Th2 genes including IL-13 and STAT6 were more relevant in fibroblasts, lymphocytes, macrophages and bronchial biopsies. These genes were also associated with asthma in the GWAS catalog. Support Vector Machine showed that DEGs based on macrophages and epithelial cells have the highest and lowest discriminatory accuracy, respectively. Drug (entinostat, BMS-345541) and genetic perturbagens (KLF6, BCL10, INFB1 and BAMBI) negatively connected to disease at multi-tissue level could potentially repurposed for treating asthma. Collectively, our study indicates that the DEGs, perturbagens and disease are connected differentially depending on tissue/cell types. While most of the existing literature describes asthma transcriptome data from individual sample types, the present work demonstrates the utility of multi-tissue transcriptome data. Future studies should focus on collecting transcriptomic data from multiple tissues, age and race groups, genetic background, disease subtypes and on the availability of better-annotated data in the public domain.

Insulin-Like Growth Factor-1 Signaling in Lung Development and Inflammatory Lung Diseases

Insulin-like growth factor-1 (IGF-1) was firstly identified as a hormone that mediates the biological effects of growth hormone. Accumulating data have indicated the role of IGF-1 signaling pathway in lung development and diseases such as congenital disorders, cancers, inflammation, and fibrosis. IGF-1 signaling modulates the development and differentiation of many types of lung cells, including airway basal cells, club cells, alveolar epithelial cells, and fibroblasts. IGF-1 signaling deficiency results in alveolar hyperplasia in humans and disrupted lung architecture in animal models. The components of IGF-1 signaling pathways are potentiated as biomarkers as they are dysregulated locally or systemically in lung diseases, whereas data may be inconsistent or even paradoxical among different studies. The usage of IGF-1-based therapeutic agents urges for more researches in developmental disorders and inflammatory lung diseases, as the majority of current data are collected from limited number of animal experiments and are generally less exuberant than those in lung cancer. Elucidation of these questions by further bench-to-bedside researches may provide us with rational clinical diagnostic approaches and agents concerning IGF-1 signaling in lung diseases.

SIRT7 regulates the TGF-β1-induced proliferation and migration of mouse airway smooth muscle cells by modulating the expression of TGF-β receptor I

Accumulating evidence shows that sirtuin 7 (SIRT7), a key mediator of many cellular activities, plays an important role in the pathogenesis of various diseases; however, little is known about the role of SIRT7 in asthma, which is characterized by airway remodeling. This study investigated the potential role of SIRT7 in regulating the proliferation and migration of airway smooth muscle (ASM) cells, which are critical events during airway remodeling in asthmatic conditions. The results demonstrated that SIRT7 expression was significantly upregulated in ASM cells treated with transforming growth factor-beta 1 (TGF-β1). Knockdown of SIRT7 inhibited the proliferation, promoted the apoptosis, and suppressed the migration of TGF-β1-treated ASM cells, while overexpression of SIRT7 had the opposite effect. Moreover, knockdown of SIRT7 inhibited protein expression of the TGF-β receptor I (TβRI), whilst overexpression of SIRT7 promoted the expression of TβRI. Importantly, knockdown of TβRI partially reversed the stimulatory effect of SIRT7 overexpression on the TGF-β1-induced proliferation and migration of ASM cells. Taken together, these results demonstrate that SIRT7 is involved in regulating TGF-β1-induced ASM cell proliferation and migration by regulating the expression of TβRI, thus indicating an important role of SIRT7 during airway remodeling in asthma.

Insulin-Like Growth Factor Binding Proteins in Autoimmune Diseases

Insulin-like growth factor binding proteins (IGFBPs) are a family of proteins binding to Insulin-like growth factors (IGFs), generally including IGFBP1, IGFBP2, IGFBP3, IGFBP4, IGFBP5, and IGFBP6. The biological functions of IGFBPs can be classified as IGFs-dependent actions and IGFs-independent effects. In this review, we will discuss the structure and function of various IGFBPs, particularly IGFBPs as potential emerging biomarkers and therapeutic targets in various autoimmune diseases, and the possible mechanisms by which IGFBPs act on the pathogenesis of autoimmune diseases.

Microvesicle-mediated delivery of miR-1343: impact on markers of fibrosis

Tissue fibrosis, the development of fibrous connective tissue as a result of injury or damage, is associated with many common diseases and cannot be treated effectively. The complex biological processes accompanying fibrosis often involve aberrant signaling through the transforming growth factor beta (TGF-β) pathway. In the search for mechanisms to repress this signaling, microRNAs have emerged as a novel class of molecules capable of targeting single members of the TGF-β pathway, or the pathway as a whole. We previously identified miR-1343 as a potent repressor of TGF-β signaling and fibrosis through the direct attenuation of both canonical TGF-β receptors. Here, we build upon our previous findings to better characterize the function of endogenous miR-1343 in normal biology and examine the potential role of exogenous miR-1343 as a repressor of TGF-β signaling. CRISPR/Cas9-mediated deletion of miR-1343 from A549 lung epithelial cells impacts several processes and genes implicated in fibrosis and known to be TGF-β pathway effectors. Moreover, the responses are opposite to those we observed previously when miR-1343 was overexpressed in the same cell type. We also show that miR-1343 can be shuttled into exosomes, a type of extracellular vesicle that are exported by cells into the surrounding medium and can be absorbed by distant target cells. miR-1343 delivered into primary lung fibroblasts by exosomes has a measurable function in reducing TGF-β signaling and markers of fibrosis. These results highlight a role for miR-1343 in fine-tuning the TGF-β pathway and suggest its use as a therapeutic in fibrotic disease.

Airway remodeling in asthma: what really matters

Airway remodeling is generally quite broadly defined as any change in composition, distribution, thickness, mass or volume and/or number of structural components observed in the airway wall of patients relative to healthy individuals. However, two types of airway remodeling should be distinguished more clearly: (1) physiological airway remodeling, which encompasses structural changes that occur regularly during normal lung development and growth leading to a normal mature airway wall or as an acute and transient response to injury and/or inflammation, which ultimately results in restoration of a normal airway structures; and (2) pathological airway remodeling, which comprises those structural alterations that occur as a result of either disturbed lung development or as a response to chronic injury and/or inflammation leading to persistently altered airway wall structures and function. This review will address a few major aspects: (1) what are reliable quantitative approaches to assess airway remodeling? (2) Are there any indications supporting the notion that airway remodeling can occur as a primary event, i.e., before any inflammatory process was initiated? (3) What is known about airway remodeling being a secondary event to inflammation? And (4), what can we learn from the different animal models ranging from invertebrate to primate models in the study of airway remodeling? Future studies are required addressing particularly pheno-/endotype-specific aspects of airway remodeling using both endotype-specific animal models and “endotyped” human asthmatics. Hopefully, novel in vivo imaging techniques will be further advanced to allow monitoring development, growth and inflammation of the airways already at a very early stage in life.

In vitro differentiation of mouse brown preadipocytes is enhanced by IGFBP-3 expression and reduced by IGFBP-3 silencing

OBJECTIVE

White adipocyte metabolism is regulated by insulin-like growth factor-binding protein (IGFBP)-3, but its effect on brown adipocytes is not known. This study investigated whether IGFBP-3 influences the proliferation and differentiation of brown preadipocytes in primary culture.

METHODS

In vitro growth and differentiation of brown preadipocytes from wild-type mice, transgenic mice overexpressing human IGFBP-3 (PGKBP3), or its non-IGF-binding Gly56/Gly80/Gly81-mutant (PGKmutBP3), and wild-type brown preadipocytes transfected with IGFBP-3 siRNA were studied by us. In addition to IGF-I and IGFBP-3 expression, brown preadipocyte growth and differentiation were assessed by antiproliferating cell nuclear antigen, oil red O, brown fat gene expression, and phosphorylation states of Akt and ERK.

RESULTS

Akt phosphorylation and IGF-I expression were paralleled by initial growth and differentiation and were slower for PGKBP3 brown preadipocytes than PGKmutBP3 and wild-type preadipocytes. Terminal adipocyte differentiation as assessed by lipid accumulation coincided with ERK inhibition and was greatest in PGKmutBP3 cells, followed by PGKBP3 cells and then wild-type cells, whereas adipocyte differentiation was poor after IGFBP-3 siRNA treatment. Thermogenic genes were increased by IGFBP-3 overexpression, but lower in differentiated PGKmutBP3 than PGKBP3 cells.

CONCLUSIONS

Brown adipocyte growth and differentiation in vitro were affected by the manipulation of IGFBP-3 expression, suggesting that IGFBP-3 is a factor regulating brown adipocyte fate.

Targeting Insulin-Like Growth Factor Binding Protein-3 Signaling in Triple-Negative Breast Cancer

Insulin-like growth factor binding protein-3 (IGFBP-3) is a key regulatory molecule of the IGF axis and can function in a tissue-specific way as both a tumor suppressor and promoter. Triple-negative breast cancer (TNBC) has high tumor expression of IGFBP-3 associated with markers of poor prognosis and, although accounting for 15-20% of all breast cancers, is responsible for disproportionate rates of morbidity and mortality. Because they lack estrogen and progesterone receptors and overexpression of HER2, TNBC are resistant to treatments that target these molecules, making the development of new therapies an important goal. In addition to frequent high expression of IGFBP-3, these tumors also express EGFR highly, but targeting EGFR signaling alone in TNBC has been of little success. Identification of a functional growth-stimulatory interaction between EGFR and IGFBP-3 signaling prompted investigation into cotargeting these pathways as a novel therapy for TNBC. This involves inhibition of both EGFR kinase activity and a mediator of IGFBP-3's stimulatory bioactivity, sphingosine kinase-1 (SphK1), and has shown promise in a preclinical setting. Functional interaction between EGFR and IGFBP-3 may also promote chemoresistance in TNBC, and delineating the mechanisms involved may identify additional targets for development of therapies in cancers that express both IGFBP-3 and EGFR.

Anti-CTGF single-chain variable fragment dimers inhibit human airway smooth muscle (ASM) cell proliferation by down-regulating p-Akt and p-mTOR levels

Connective tissue growth factor (CTGF) contributes to airway smooth muscle (ASM) cell hyperplasia in asthma. Humanized single-chain variable fragment antibody (scFv) was well characterized as a CTGF antagonist in the differentiation of fibroblast into myofibroblast and pulmonary fibrosis in our previous studies. To further improve the bioactivity of scFv, we constructed a plasmid to express scFv-linker-matrilin-6×His fusion proteins that could self-assemble into the scFv dimers by disulfide bonds in matrilin under non-reducing conditions. An immunoreactivity assay demonstrated that the scFv dimer could highly bind to CTGF in a concentration-dependent manner. The MTT and EdU assay results revealed that CTGF (≥10 ng/mL) promoted the proliferation of ASM cells, and this effect was inhibited when the cells were treated with anti-CTGF scFv dimer. The western blot analysis results showed that increased phosphorylation of Akt and mTOR induced by CTGF could be suppressed by this scFv dimer. Based on these findings, anti-CTGF scFv dimer may be a potential agent for the prevention of airway remodeling in asthma.

Inhibition of insulin-like growth factor-binding protein-3 signaling through sphingosine kinase-1 sensitizes triple-negative breast cancer cells to EGF receptor blockade

The type I EGF receptor (EGFR or ErbB1) and insulin-like growth factor-binding protein-3 (IGFBP-3) are highly expressed in triple-negative breast cancer (TNBC), a particularly aggressive disease that cannot be treated with conventional therapies targeting the estrogen or progesterone receptors (ER and PR), or HER2. We have shown previously in normal breast epithelial cells that IGFBP-3 potentiates growth-stimulatory signaling transduced by EGFR, and this is mediated by the sphingosine kinase-1 (SphK1)/sphingosine 1-phosphate (S1P) system. In this study, we investigated whether cotargeting the EGFR and SphK1/S1P pathways in TNBC cells results in greater growth inhibition compared with blocking either alone, and might therefore have novel therapeutic potential in TNBC. In four TNBC cell lines, exogenous IGFBP-3 enhanced ligand-stimulated EGFR activation, associated with increased SphK1 localization to the plasma membrane. The effect of exogenous IGFBP-3 on EGFR activation was blocked by pharmacologic inhibition or siRNA-mediated silencing of SphK1, and silencing of endogenous IGFBP-3 also suppressed EGF-stimulated EGFR activation. Real-time analysis of cell proliferation revealed a combined effect of EGFR inhibition by gefitinib and SphK1 inhibition using SKi-II. Growth of MDA-MB-468 xenograft tumors in mice was significantly inhibited by SKi-II and gefitinib when used in combination, but not as single agents. We conclude that IGFBP-3 promotes growth of TNBC cells by increasing EGFR signaling, that this is mediated by SphK1, and that combined inhibition of EGFR and SphK1 has potential as an anticancer therapy in TNBC in which EGFR and IGFBP-3 expression is high.

Megakaryocytes co-localise with hemopoietic stem cells and release cytokines that up-regulate stem cell proliferation

We report transplanted hemopoietic stem cells (HSC) preferentially lodge within two cells of mature megakaryocytes (MM). With both populations comprising ~0.2% of bone marrow cells, this strongly suggests a key functional interaction. HSC isolated from the endosteum (eLSKSLAM) showed significantly increased hemopoietic cell proliferation while in co-culture with MM. Furthermore, eLSKSLAM progeny retained HSC potential, maintaining long-term multi-lineage reconstitution capacity in lethally ablated recipients. Increased hemopoietic cell proliferation was not MM contact dependent and could be recapitulated with media supplemented with two factors identified in MM-conditioned media: insulin-like growth factor binding protein-3 (IGFBP-3) and insulin-like growth factor-1 (IGF-1). We demonstrate that HSC express the receptor for IGF-1 and that IGF-1/IGFBP-3 induced increased hemopoietic cell proliferation can be blocked by an anti-IGF-1 neutralising antibody. However, co-cultures of 8N, 16N or 32N MM with eLSKSLAM showed that MM of individual ploidy did not significantly increase hemopoietic cell proliferation. Our data suggests that MM are an important component of the HSC niche and regulate hemopoietic cell proliferation through cytokine release.

Airway smooth muscle in the pathophysiology and treatment of asthma

Airway smooth muscle (ASM) plays an integral part in the pathophysiology of asthma. It is responsible for acute bronchoconstriction, which is potentiated by constrictor hyperresponsiveness, impaired relaxation and length adaptation. ASM also contributes to airway remodeling and inflammation in asthma. In light of this, ASM is an important target in the treatment of asthma.

The effects of (±)-Praeruptorin A on airway inflammation, remodeling and transforming growth factor-β1/Smad signaling pathway in a murine model of allergic asthma

(±)-Praeruptorin A (PA) is a pair of coumarin enantiomers isolated from the root of Peucedanum praeruptorum Dunn (PPD), a common Chinese herbal medicine for the treatment of asthma. Considering its anti-inflammatory, anti-contractile and anti-hyperplasia activities, the effects of PA on airway inflammation and airway remodeling were investigated using a murine model of chronic asthma. Ovalbumin-sensitized BALB/c mice were challenged with ovalbumin to induce asthma every other day on eight successive weeks. PA was administered intragastrically before every ovalbumin challenge. Airway responsiveness was evaluated by a lung function analysis system 48 h after the last ovalbumin challenge. The total and differential leukocytes in bronchoalveolar lavage fluid (BALF) were counted using a hemocytometer and Diff-Quick-stained smears. Lung tissue samples were used for hematoxylin and eosin, periodic acid Schiff, Masson's trichrome and α-SMA immunohistochemistry staining. Levels of cytokines in BALF, immunoglobulin (Ig) E in serum as well as expression of TGF-β1 and Smad proteins in lung tissue were measured by enzyme-linked immunosorbent assay, immunohistochemistry or western blot analysis. Compared with the model group, PA suppressed airway inflammation, airway hyperresponsive and remodeling, reduced levels of IL-4 and IL-13 in BALF, and IgE in serum, inhibited expression of TGF-β1 and pSmad2/3, up-regulated the expression of Smad7 in lung tissue, and also increased the levels of INF-γ in BALF. These results suggested that PA significantly suppressed airway inflammation and airway remodeling induced by ovalbumin challenge, and is a potential candidate for the treatment of asthma.

Insulin-like growth factor binding proteins-3 and -5: central mediators of fibrosis and promising new therapeutic targets

Fibrosis involves an orchestrated cascade of events including activation of fibroblasts, increased production and deposition of extracellular matrix components, and differentiation of fibroblasts into myofibroblasts. Epithelial-mesenchymal cross-talk plays an important role in this process, and current hypotheses of organ fibrosis liken it to an aberrant wound healing response in which epithelial-mesenchymal transition (EMT) and cellular senescence may also contribute to disease pathogenesis. The fibrotic response is associated with altered expression of growth factors and cytokines, including increased levels of transforming growth factor-β1 (TGF-β1) and the more recent observation that increased levels of several insulin-like growth factor binding proteins (IGFBPs) are associated with a number of fibrotic conditions. IGFBPs have been implicated in virtually every cell type and process associated with the fibrotic response, making the IGFBPs attractive targets for the development of novel anti-fibrotic therapies. In this review, the current state of knowledge regarding the classical IGFBP family in organ fibrosis will be summarized and the clinical implications considered.

Localized expression of tenascin in systemic sclerosis-associated pulmonary fibrosis and its regulation by insulin-like growth factor binding protein 3

OBJECTIVE

To determine the role of insulin-like growth factor binding protein 3 (IGFBP-3) in mediating the effects of transforming growth factor β (TGFβ) on tenascin-C (TN-C) production and to assess the levels of TN-C in vivo in patients with systemic sclerosis (SSc)-associated pulmonary fibrosis.

METHODS

Human primary lung fibroblasts were stimulated with TGFβ or IGFBP-3 in the presence or absence of specific small interfering RNAs and chemical inhibitors of the signaling cascade. TN-C levels in lung tissue specimens obtained from patients with SSc-associated pulmonary fibrosis were assessed using immunohistochemical analysis and were compared with the levels in specimens obtained from normal donors. TN-C levels were quantified in sera from normal donors and patients with SSc with or without pulmonary fibrosis, using an enzyme-linked immunosorbent assay.

RESULTS

IGFBP-3 mediated the induction of TN-C by TGFβ. Direct induction of TN-C by IGFBP-3 occurred in a p38 MAP kinase-dependent manner. TN-C levels were abundant in lung tissues from patients with SSc and were localized to subepithelial layers of the distal airways. No TN-C was detectable around the proximal airways. Patients with SSc-associated pulmonary fibrosis had significantly higher levels of circulating TN-C compared with SSc patients without pulmonary fibrosis. Longitudinal samples obtained from patients with SSc before and after the onset of pulmonary fibrosis showed increased levels of TN-C after the onset of pulmonary fibrosis.

CONCLUSION

IGFBP-3, which is overexpressed in fibrotic lungs, induces production of TN-C by subepithelial fibroblasts. The increased lung tissue levels of TN-C parallel the levels detected in the sera of SSc patients with pulmonary fibrosis, suggesting that TN-C may be a useful biomarker for SSc-related pulmonary fibrosis.

How can microarrays unlock asthma?

Asthma is a complex disease regulated by the interplay of a large number of underlying mechanisms which contribute to the overall pathology. Despite various breakthroughs identifying genes related to asthma, our understanding of the importance of the genetic background remains limited. Although current therapies for asthma are relatively effective, subpopulations of asthmatics do not respond to these regimens. By unlocking the role of these underlying mechanisms, a source of novel and more effective treatments may be identified. In the new age of high-throughput technologies, gene-expression microarrays provide a quick and effective method of identifying novel genes and pathways, which would be impossible to discover using an individual gene screening approach. In this review we follow the history of expression microarray technologies and describe their contributions to advancing our current knowledge and understanding of asthma pathology.

Intrinsic, Pro-Apoptotic Effects of IGFBP-3 on Breast Cancer Cells are Reversible: Involvement of PKA, Rho, and Ceramide

We established previously that IGFBP-3 could exert positive or negative effects on cell function depending upon the extracellular matrix composition and by interacting with integrin signaling. To elicit its pro-apoptotic effects IGFBP-3 bound to caveolin-1 and the beta 1 integrin receptor and increased their association culminating in MAPK activation. Disruption of these complexes or blocking the beta 1 integrin receptor reversed these intrinsic actions of IGFBP-3. In this study we have examined the signaling pathway between integrin receptor binding and MAPK activation that mediates the intrinsic, pro-apoptotic actions of IGFBP-3. We found on inhibiting protein kinase A (PKA), Rho associated kinase (ROCK), and ceramide, the accentuating effects of IGFBP-3 on apoptotic triggers were reversed, such that IGFBP-3 then conferred cell survival. We established that IGFBP-3 activated Rho, the upstream regulator of ROCK and that beta1 integrin and PKA were upstream of Rho activation, whereas the involvement of ceramide was downstream. The beta 1 integrin, PKA, Rho, and ceramide were all upstream of MAPK activation. These data highlight key components involved in the pro-apoptotic effects of IGFBP-3 and that inhibiting them leads to a reversal in the action of IGFBP-3.

Transforming growth factor-beta1 in asthmatic airway smooth muscle enlargement: is fibroblast growth factor-2 required?

Enlargement of airway smooth muscle (ASM) tissue around the bronchi/bronchioles is a histopathological signature of asthmatic airway remodelling and has been suggested to play a critical role in the increased lung resistance and airway hyperresponsiveness seen in asthmatic patients. The pleiotropic cytokine, TGF-beta1, is believed to contribute to several aspects of asthmatic airway remodelling and is known to influence the growth of many cell types. Increased TGF-beta1 expression/signalling and ASM growth have been shown to occur concurrently in animal models of asthma. Abundant studies further substantiate this association by showing that therapeutic strategies that reduce or prevent TGF-beta1 overexpression/signalling lead to a parallel decrease or prevention of ASM enlargement. Finally, recent findings have supported a direct link of causality between TGF-beta1 overexpression/signalling and the overgrowth of ASM tissue. To follow-up on these in vivo studies, many investigators have pursued detailed investigation of ASM in cell culture conditions, assessing the direct role of TGF-beta1 on cellular proliferation and/or hypertrophy. Inconsistencies among the in vitro studies suggest that the effect of TGF-beta1 on ASM cell proliferation/hypertrophy is contextual. A hypothesis focusing on fibroblast growth factor-2 is presented at the end of this review, which could potentially reconcile the apparent discrepancy between the conflicting in vitro findings with the consistent in vivo finding that TGF-beta1 is required for ASM enlargement in asthma.

Human uterine leiomyoma-derived fibroblasts stimulate uterine leiomyoma cell proliferation and collagen type I production, and activate RTKs and TGF beta receptor signaling in coculture

Background

Uterine leiomyomas (fibroids) are benign smooth muscle tumors that often contain an excessive extracellular matrix (ECM). In the present study, we investigated the interactions between human uterine leiomyoma (UtLM) cells and uterine leiomyoma-derived fibroblasts (FB), and their importance in cell growth and ECM protein production using a coculture system.

Results

We found enhanced cell proliferation, and elevated levels of ECM collagen type I and insulin-like growth factor-binding protein-3 after coculturing. There was also increased secretion of vascular endothelial growth factor, epidermal growth factor, fibroblast growth factor-2, and platelet derived growth factor A and B in the media of UtLM cells cocultured with FB. Protein arrays revealed increased phosphorylated receptor tyrosine kinases (RTKs) of the above growth factor ligands, and immunoblots showed elevated levels of the RTK downstream effector, phospho-mitogen activated protein kinase 44/42 in cocultured UtLM cells. There was also increased secretion of transforming growth factor-beta 1 and 3, and immunoprecipitated transforming growth factor-beta receptor I from cocultured UtLM cells showed elevated phosphoserine expression. The downstream effectors phospho-small mothers against decapentaplegic -2 and -3 protein (SMAD) levels were also increased in cocultured UtLM cells. However, none of the above effects were seen in normal myometrial cells cocultured with FB. The soluble factors released by tumor-derived fibroblasts and/or UtLM cells, and activation of the growth factor receptors and their pathways stimulated the proliferation of UtLM cells and enhanced the production of ECM proteins.

Conclusions

These data support the importance of interactions between fibroid tumor cells and ECM fibroblasts in vivo, and the role of growth factors, and ECM proteins in the pathogenesis of uterine fibroids.

Abnormal expression of IGF-binding proteins, an initiating event in idiopathic pulmonary fibrosis?

For significant improvements to occur in the survival of patients with idiopathic pulmonary fibrosis (IPF), it is necessary to develop novel and more precisely targeted therapies. The selection of future appropriate regimens must critically depend on improved characterization of the molecules driving the pathogenesis of IPF. It is well defined that IPF is characterized by the expression of genes indicating an active tissue remodeling program, including extracellular matrix (ECM) and basement membrane components, as well as myofibroblast-associated and epithelial cell-related genes. A few recent advances are worth mentioning. Pulmonary research demonstrates abnormal expression of insulin-like growth factor (IGF) binding proteins (IGFBPs) in IPF, including human IPF bronchoalveolar lavage (BAL) cells and BAL fluids, human IPF fibroblasts, as well as fibrotic lung tissues of bleomycin-induced mice and IPF patients, analyzed by microarray, reverse transcription-polymerase chain reaction (RT-PCR), ribonuclease protection assay (RPA), Western blot, immunohistochemistry, or enzyme-linked immunosorbent assay (ELISA). Simultaneously, in vitro and in vivo studies indicate the involvement of IGFBPs in the initiation and development of the fibrosis process, including fibroblast activation and transdifferentiation to a myofibroblast phenotype, epithelial-mesenchymal transition (EMT), increased ECM production, and decreased ECM degradation, possibly contributing to the final lung fibrosis. These observations suggest that dysregulation of IGFBPs may be a key factor responsible for the initiation and perpetuation of IPF. Such efforts could lead to potential candidate molecules being exploited for therapeutic manipulation.

Insulin-like growth factor binding protein-3 has dual effects on gastrointestinal stromal tumor cell viability and sensitivity to the anti-tumor effects of imatinib mesylate in vitro

Background

Imatinib mesylate has significantly improved survival and quality of life of patients with gastrointestinal stromal tumors (GISTs). However, the molecular mechanism through which imatinib exerts its anti-tumor effects is not clear. Previously, we found up-regulation of insulin-like growth factor binding protein-3 (IGFBP3) expression in imatinib-responsive GIST cells and tumor samples. Because IGFBP3 regulates cell proliferation and survival and mediates the anti-tumor effects of a number of anti-cancer agents through both IGF-dependent and IGF-independent mechanisms, we hypothesized that IGFBP3 mediates GIST cell response to imatinib. To test this hypothesis, we manipulated IGFBP3 levels in two imatinib-responsive GIST cell lines and observed cell viability after drug treatment.

Results

In the GIST882 cell line, imatinib treatment induced endogenous IGFBP3 expression, and IGFBP3 down-modulation by neutralization or RNA interference resulted in partial resistance to imatinib. In contrast, IGFBP3 overexpression in GIST-T1, which had no detectable endogenous IGFBP3 expression after imatinib, had no effect on imatinib-induced loss of viability. Furthermore, both the loss of IGFBP3 in GIST882 cells and the overexpression of IGFBP3 in GIST-T1 cells was cytotoxic, demonstrating that IGFBP3 has opposing effects on GIST cell viability.

Conclusion

This data demonstrates that IGFBP3 has dual, opposing roles in modulating GIST cell viability and response to imatinib in vitro. These preliminary findings suggest that there may be some clinical benefits to IGFBP3 therapy in GIST patients, but further studies are needed to better characterize the functions of IGFBP3 in GIST.

Tissue and matrix influences on airway smooth muscle function

Asthma is characterized by structural changes in the airways - airway remodelling. These changes include an increase in the bulk of the airway smooth muscle (ASM) and alterations in the profile of extracellular matrix (ECM) proteins in the airway wall. The mechanisms leading to airway remodelling are not well understood. ASM cells have the potential to play a key role in these processes through the production and release of ECM proteins. The ASM cells and ECM proteins are each able to influence the behaviour and characteristics of the other. The modified ECM profile in the asthmatic airway may contribute to the altered behaviour of the ASM cells, such responses to ECM proteins are modulated through the cell surface expression of integrin receptors. ASM cells from asthmatic individuals express different levels of some integrin subunits compared to nonasthmatic ASM cells, which have the potential to further influence their responses to the ECM proteins in the airways. ECM homeostasis requires the presence and activation of matrix metalloproteinases and their tissue inhibitors, which in turn modulate the interaction of the ASM cells and the ECM proteins. Furthermore, the complex interactions of the ASM cells and the ECM in the asthmatic airways and the role played by external stimuli, such as viral infections, to modulate airway remodelling are currently unknown. This review summarises our current understanding of the influence of the ECM on ASM function.

NOX4 mediates hypoxia-induced proliferation of human pulmonary artery smooth muscle cells: the role of autocrine production of transforming growth factor-{beta}1 and insulin-like growth factor binding protein-3

Persistent hypoxia can cause pulmonary arterial hypertension that may be associated with significant remodeling of the pulmonary arteries, including smooth muscle cell proliferation and hypertrophy. We previously demonstrated that the NADPH oxidase homolog NOX4 mediates human pulmonary artery smooth muscle cell (HPASMC) proliferation by transforming growth factor-beta1 (TGF-beta1). We now show that hypoxia increases HPASMC proliferation in vitro, accompanied by increased reactive oxygen species generation and NOX4 gene expression, and is inhibited by antioxidants, the flavoenzyme inhibitor diphenyleneiodonium (DPI), and NOX4 gene silencing. HPASMC proliferation and NOX4 expression are also observed when media from hypoxic HPASMC are added to HPASMC grown in normoxic conditions, suggesting autocrine stimulation. TGF-beta1 and insulin-like growth factor binding protein-3 (IGFBP-3) are both increased in the media of hypoxic HPASMC, and increased IGFBP-3 gene expression is noted in hypoxic HPASMC. Treatment with anti-TGF-beta1 antibody attenuates NOX4 and IGFBP-3 gene expression, accumulation of IGFBP-3 protein in media, and proliferation. Inhibition of IGFBP-3 expression with small interfering RNA (siRNA) decreases NOX4 gene expression and hypoxic proliferation. Conversely, NOX4 silencing does not decrease hypoxic IGFBP-3 gene expression or secreted protein. Smad inhibition does not but the phosphatidylinositol 3-kinase (PI3K) signaling pathway inhibitor LY-294002 does inhibit NOX4 and IGFBP-3 gene expression, IGFBP-3 secretion, and cellular proliferation resulting from hypoxia. Immunoblots from hypoxic HPASMC reveal increased TGF-beta1-mediated phosphorylation of the serine/threonine kinase (Akt), consistent with hypoxia-induced activation of PI3K/Akt signaling pathways to promote proliferation. We conclude that hypoxic HPASMC produce TGF-beta1 that acts in an autocrine fashion to induce IGFBP-3 through PI3K/Akt. IGFBP-3 increases NOX4 gene expression, resulting in HPASMC proliferation. These observations add to our understanding hypoxic pulmonary vascular remodeling.

Mesodermal deletion of transforming growth factor-beta receptor II disrupts lung epithelial morphogenesis: cross-talk between TGF-beta and Sonic hedgehog pathways

In vertebrates, Sonic hedgehog (Shh) and transforming growth factor-beta (TGF-beta) signaling pathways occur in an overlapping manner in many morphogenetic processes. In vitro data indicate that the two pathways may interact. Whether such interactions occur during embryonic development remains unknown. Using embryonic lung morphogenesis as a model, we generated transgenic mice in which exon 2 of the TbetaRII gene, which encodes the type II TGF-beta receptor, was deleted via a mesodermal-specific Cre. Mesodermal-specific deletion of TbetaRII (TbetaRII(Delta/Delta)) resulted in embryonic lethality. The lungs showed abnormalities in both number and shape of cartilage in trachea and bronchi. In the lung parenchyma, where epithelial-mesenchymal interactions are critical for normal development, deletion of mesenchymal TbetaRII caused abnormalities in epithelial morphogenesis. Failure in normal epithelial branching morphogenesis in the TbetaRII(Delta/Delta) lungs caused cystic airway malformations. Interruption of the TbetaRII locus in the lung mesenchyme increased mRNA for Patched and Gli-1, two downstream targets of Shh signaling, without alterations in Shh ligand levels produced in the epithelium. Therefore, we conclude that TbetaRII-mediated signaling in the lung mesenchyme modulates transduction of Shh signaling that originates from the epithelium. To our knowledge, this is the first in vivo evidence for a reciprocal and novel mode of cross-communication between Shh and TGF-beta pathways during embryonic development.

Pharmacology of airway smooth muscle proliferation

Airway smooth muscle thickening is a pathological feature that contributes significantly to airflow limitation and airway hyperresponsiveness in asthma. Ongoing research efforts aimed at identifying the mechanisms responsible for the increased airway smooth muscle mass have indicated that hyperplasia of airway smooth muscle, due in part to airway myocyte proliferation, is likely a major factor. Airway smooth muscle proliferation has been studied extensively in culture and in animal models of asthma, and these studies have revealed that a variety of receptors and mediators contributes to this response. This review aims to provide an overview of the receptors and mediators that control airway smooth muscle cell proliferation, with emphasis on the intracellular signalling mechanisms involved.

Airway smooth muscle growth in asthma: proliferation, hypertrophy, and migration

Increased airway smooth muscle mass is present in fatal and non-fatal asthma. However, little information is available regarding the cellular mechanism (i.e., hyperplasia vs. hypertrophy). Even less information exists regarding the functional consequences of airway smooth muscle remodeling. It would appear that increased airway smooth muscle mass would tend to increase airway narrowing and airflow obstruction. However, the precise effects of increased airway smooth muscle mass on airway narrowing are not known. This review will consider the evidence for airway smooth muscle cell proliferation and hypertrophy in asthma, potential functional effects, and biochemical mechanisms.

Leukotriene D4-induced, epithelial cell-derived transforming growth factor beta1 in human bronchial smooth muscle cell proliferation

BACKGROUND

Cysteinyl-leukotrienes (cys-LTs) orchestrate many pathognomonic features of asthma in animal models of allergic airway inflammation, including bronchial smooth muscle cell (BSMC) hyperplasia. However, because cys-LTs alone do not induce mitogenesis in monocultures of human BSMC, the effect observed in vivo seemingly involves indirect mechanisms, which are still undefined.

OBJECTIVE

This study aims to investigate the regulatory role of leukotriene (LT)D(4) on TGF-beta1 expression in airway epithelial cells and the consequence of this interplay on BSMC proliferation.

METHODS

HEK293 cells stably transfected with cys-LT receptor 1 (CysLT1) (293LT1) were stimulated with LTD(4) and TGF-beta1 mRNA and protein expression was measured using Northern blot and ELISA, respectively. Conditioned medium (CM) harvested from LTD(4)-treated cells was then assayed for its proliferative effect on primary human BSMC. TGF-beta1 mRNA expression was also determined in tumoural type II pneumocytes A549 and in normal human bronchial epithelial cells (NHBE) following LTD(4) stimulation.

RESULTS

The results demonstrated that LTD(4)-induced TGF-beta1 mRNA production in a time- and concentration-dependent manner in 293LT1. TGF-beta1 secretion was also up-regulated and CM from LTD(4)-treated 293LT1 was shown to increase BSMC proliferation in a TGF-beta1-dependent manner. The increased expression of TGF-beta1 mRNA by LTD(4) also occured in A549 and NHBE cells via a CysLT1-dependent mechanism.

CONCLUSION

In conclusion, elevated expression of cys-LTs in asthmatic airways might contribute to BSMC hyperplasia and concomitant clinical features of asthma such as airway hyperresponsiveness via a paracrine loop involving TGF-beta1 production by airway epithelial cells.

Localization of insulin-like growth factor (IGFBP)-3 in cultured porcine embryonic myogenic cells before and after TGF-beta1 treatment

Insulin-like growth factor binding protein (IGFBP)-3 binds IGFs with high affinity and affects their biological activity. IGFBP-3 that is not bound to IGF also affects cells via mechanisms involving binding to specific cell surface receptors and/or transport into the cell. IGFBP-3 is produced by porcine embryonic myogenic cell (PEMC) cultures. Additionally, IGFBP-3 facilitates the proliferation-suppressing actions of TGF-beta(1) and myostatin in PEMC cultures via mechanisms that do not involve IGF binding. Moreover, these mechanisms do not involve preventing myostatin or TGF-beta(1)-induced increases in phosphosmad2 or phosphosmad3 level. Consequently, the mechanism(s) by which IGFBP-3 facilitates the proliferation-suppressing actions of TGF-beta(1) and myostatin in PEMC is unclear. Since IGFBP-3 reportedly interacts with nuclear proteins that regulate transcription, TGF-beta(1) or myostatin-induced translocation of IGFBP-3 into the nucleus may facilitate the proliferation-suppressing actions of these cytokines. Here, we show that IGFBP-3 is localized in cells containing the muscle specific protein desmin, thus establishing the presence of this IGFBP in myogenic cells. IGFBP-3 is present in the cytoplasm of all myogenic cells and approximately 50% of the nuclei of proliferating PEMC. IGFBP-3 is also detectable in fused myotubes. IGFBP-3 suppresses IGF-I-stimulated differentiation of PEMC but has no affect on Long-R3-IGF-I-stimulated differentiation of PEMC. Treatment of PEMC for 24h with TGF-beta(1) (20 ng/ml) results in a 78% (p<0.01) increase in the number of nuclei that contain detectable IGFBP-3. These results suggest that translocation of IGFBP-3 into the nucleus of PEMC could play a role in mediating the proliferation-suppressing action of TGF-beta(1).

Role of mast cells in airway remodeling

The extent of airway remodeling correlates with severity of asthma. Persistent airway hyperresponsiveness (AHR) is associated with airway remodeling, but not with inflammation. The increase in ASM mass is recognized as one of the most important factors related to AHR and to the severity of asthma. The infiltration of ASM by mast cells (MCs) is associated with the disordered airway function. The mediators such as tryptase and cytokines from MCs can modulate ASM cell function and induce goblet cell hyperplasia. MCs were found to contribute to the development of multiple features of chronic asthma in MC-deficient mice. Therefore, MCs play an important role not only in immediate hypersensitivity and late phase inflammation but also in tissue remodeling in the airway.

Mechanisms of induction of airway smooth muscle hyperplasia by transforming growth factor-beta

Airway smooth muscle (ASM) hyperplasia is a characteristic feature of the asthmatic airway, but the underlying mechanisms that induce ASM hyperplasia remain unknown. Because transforming growth factor (TGF)-beta is a potent regulator of ASM cell proliferation, we determined its expression and mitogenic signaling pathways in ASM cells. We obtained ASM cells by laser capture microdissection of bronchial biopsies and found that ASM cells from asthmatic patients expressed TGF-beta1 mRNA and protein to a greater extent than nonasthmatic individuals using real-time RT-PCR and immunohistochemistry, respectively. TGF-beta1 stimulated the growth of nonconfluent and confluent ASM cells either in the presence or absence of serum in a time- and concentration-dependent manner. The mitogenic activity of TGF-beta1 on ASM cells was inhibited by selective inhibitors of TGF-beta receptor I kinase (SD-208), phosphatidylinositol 3-kinase (PI3K, LY-294002), ERK (PD-98059), JNK (SP-600125), and NF-kappaB (AS-602868). On the other hand, p38 MAPK inhibitor (SB-203580) augmented TGF-beta1-induced proliferation. To study role of the Smads, we transduced ASM cells with an adenovirus vector-expressing Smad4, Smad7, or dominant-negative Smad3 and found no involvement of these Smads in TGF-beta1-induced proliferation. Dexamethasone caused a dose-dependent inhibition in TGF-beta1-induced proliferation. Our findings suggest that TGF-beta1 may act in an autocrine fashion to induce ASM hyperplasia, mediated by its receptor and several kinases including PI3K, ERK, and JNK, whereas p38 MAPK is a negative regulator. NF-kappaB is also involved in the TGF-beta1 mitogenic signaling, but Smad pathway does not appear important.

Nox4 mediates TGF-beta1-induced retinoblastoma protein phosphorylation, proliferation, and hypertrophy in human airway smooth muscle cells

Transforming growth factor-beta1 (TGF-beta1) plays a pivotal role in increasing airway smooth muscle mass in severe asthma by inducing proliferation and hypertrophy of human airway smooth muscle. The mechanism(s) for these effects of TGF-beta1 have not been fully elucidated. In this study, we demonstrate that TGF-beta1 is a potent inducer of expression of the nonphagocyte NAD(P)H oxidase catalytic homolog Nox4, diphenylene iodonium-inhibitable reactive oxygen species production, proliferation, and hypertrophy in cultured human airway smooth muscle cells. By confocal microscopy, TGF-beta1-induced Nox4 was localized with the endoplasmic reticulum and the nucleus, implying a role for Nox4 in regulation of both the cell cycle and protein synthesis. Consistent with this hypothesis, TGF-beta1 increased retinoblastoma protein phosphorylation at both Ser807/811 and Ser780. Silencing Nox4 prevented TGF-beta1-mediated retinoblastoma protein phosphorylation, proliferation, and cell hypertrophy. TGF-beta1 also increased phosphorylation of eukaryotic translation initiation factor 4E binding protein-1 at Thr37/46, and this was likewise blocked by silencing Nox4. This is the first report to suggest a functional role for Nox4 in cell cycle transition and to demonstrate that Nox4 influences the pathobiochemistry of asthma by generating reactive oxygen species that promote TGF-beta1-induced proliferation and hypertrophy of human airway smooth muscle.

The insulin-like growth factor system in multiple sclerosis

Multiple sclerosis (MS) is a chronic disorder of the central nervous system characterized by inflammation, demyelination, and axonal degeneration. Present therapeutic strategies for MS reduce inflammation and its destructive consequences, but are not effective in the progressive phase of the disease. There is a need for neuroprotective and restorative therapies in MS. Insulin-like growth factor-1 (IGF-1) is of considerable interest because it is not only a potent neuroprotective trophic factor but also a survival factor for cells of the oligodendrocyte lineage and possesses a potent myelinogenic capacity. However, the IGF system is complex and includes not only IGF-1 and IGF-2 and their receptors but also modulating IGF-binding proteins (IGFBPs), of which six have been identified. This chapter provides an overview of the role of the IGF system in the pathophysiology of MS, relevant findings in preclinical models, and discusses the possible use of IGF-1 as a therapeutic agent for MS.

Fibroblast growth factor 2 and transforming growth factor beta1 synergism in human bronchial smooth muscle cell proliferation

Bronchial smooth muscle cell (BSMC) hyperplasia is a typical feature of airway remodeling and contributes to airway obstruction and hyperresponsiveness in asthma. Fibroblast growth factor 2 (FGF-2) and transforming growth factor beta1 (TGF-beta1) are sequentially upregulated in asthmatic airways after allergic challenge. Whereas FGF-2 induces BSMC proliferation, the mitogenic effect of TGF-beta1 remains controversial, and the effect of sequential FGF-2 and TGF-beta1 co-stimulation on BSMC proliferation is unknown. This study aimed to assess the individual and sequential cooperative effects of FGF-2 and TGF-beta1 on human BSMC proliferation and define the underlying mechanisms. Mitogenic response was measured using crystal violet staining and [3H]-thymidine incorporation. Steady-state mRNA and protein levels were measured by semiquantitative RT-PCR, Western blot, and ELISA, respectively. TGF-beta1 (0.1-20 ng/ml) alone had no effect on BSMC proliferation, but increased the proliferative effect of FGF-2 (2 ng/ml) in a concentration-dependent manner (up to 6-fold). Two distinct platelet-derived growth factor receptor (PDGFR) inhibitors, AG1296 and Inhibitor III, as well as a neutralizing Ab against PDGFRalpha, partially blocked the synergism between these two growth factors. In this regard, TGF-beta1 increased PDGF-A and PDGF-C mRNA expression as well as PDGF-AA protein expression. Moreover, FGF-2 pretreatment increased the mRNA and protein expression of PDGFRalpha and the proliferative effect of exogenous PDGF-AA (140%). Our data suggest that FGF-2 and TGF-beta1 synergize in BSMC proliferation and that this synergism is partially mediated by a PDGF loop, where FGF-2 and TGF-beta1 upregulate the receptor (PDGFRalpha) and the ligands (PDGF-AA and PDGF-CC), respectively. This powerful synergistic effect may thus contribute to the hyperplastic phenotype of BSMC in remodeled asthmatic airways.

TGF-beta1 increases proliferation of airway smooth muscle cells by phosphorylation of map kinases

BACKGROUND

Airway remodeling in asthma is the result of increased expression of connective tissue proteins, airway smooth muscle cell (ASMC) hyperplasia and hypertrophy. TGF-beta1 has been found to increase ASMC proliferation. The activation of mitogen-activated protein kinases (MAPKs), p38, ERK, and JNK, is critical to the signal transduction associated with cell proliferation. In the present study, we determined the role of phosphorylated MAPKs in TGF-beta1 induced ASMC proliferation.

METHODS

Confluent and growth-arrested bovine ASMCs were treated with TGF-beta1. Proliferation was measured by [3H]-thymidine incorporation and cell counting. Expressions of phosphorylated p38, ERK1/2, and JNK were determined by Western analysis.

RESULTS

In a concentration-dependent manner, TGF-beta1 increased [3H]-thymidine incorporation and cell number of ASMCs. TGF-beta1 also enhanced serum-induced ASMC proliferation. Although ASMCs cultured with TGF-beta1 had a significant increase in phosphorylated p38, ERK1/2, and JNK, the maximal phosphorylation of each MAPK had a varied onset after incubation with TGF-beta1. TGF-beta1 induced DNA synthesis was inhibited by SB 203580 or PD 98059, selective inhibitors of p38 and MAP kinase kinase (MEK), respectively. Antibodies against EGF, FGF-2, IGF-I, and PDGF did not inhibit the TGF-beta1 induced DNA synthesis.

CONCLUSION

Our data indicate that ASMCs proliferate in response to TGF-beta1, which is mediated by phosphorylation of p38 and ERK1/2. These findings suggest that TGF-beta1 which is expressed in airways of asthmatics may contribute to irreversible airway remodeling by enhancing ASMC proliferation.

Insulin-like growth factor polymorphisms and colorectal cancer risk

Several modifiable lifestyle factors, such as physical activity, obesity, and postmenopausal hormone use, have been associated with colorectal cancer risk. It has been hypothesized that some or all of these factors may mediate their effects through alterations in insulin-like growth factor-1 (IGF-1) and its binding proteins (IGFBP). To evaluate the role of IGFs in colorectal cancer, we examined the relationship of two common genetic polymorphisms in IGF-1 (a cytosine-adenosine dinucleotide repeat) and IGFBP-3 (a G --> C single nucleotide polymorphism) with colorectal cancer risk, as well as their potential modification by physical activity, body mass index (BMI), and postmenopausal hormone use. Subjects included 782 male and female colorectal cancer cases diagnosed between 1998 and 2002 and reported to the statewide registry in the metropolitan Seattle area, and 503 age- and sex-matched cancer-free population controls. Colorectal cancer was modestly associated with having an IGF-1 genotype other than homozygous for 19 repeats (odds ratio, 1.3; 95% confidence interval, 1.0-1.6) and having the GG IGFBP-3 genotype (odds ratio, 1.3; 95% confidence interval, 1.0-1.8). There was evidence that IGF-1 genotype modified the relationship between BMI and colorectal cancer among women, such that high BMI increased risk of colorectal cancer only among those with the 19/19 genotype (P(interaction) = 0.02). IGFBP-3 genotype was also a significant effect modifier of the relationship between risk factors and colorectal cancer: The positive association between BMI and colorectal cancer was observed only among men (P(interaction) < 0.01) and women (P(interaction) = 0.06) with the GG genotype; the inverse association between postmenopausal hormone use and colorectal cancer was observed only among women with the GG genotype (P = 0.01) and the inverse association between physical activity and colorectal cancer was observed only among men who carried the C allele (P < 0.01). The current study provides some support for a role of IGFs in colorectal cancer etiology, particularly in mediating the relationship of common risk factors (physical activity, BMI, and postmenopausal hormone use).

Role of insulin-like growth factor-I in allergen-induced airway inflammation and remodeling

Insulin-like growth factor (IGF)-I is known to act on fibroblasts as a progression factor to push cells toward proliferation and activation to synthesize collagen. Subepithelial fibrosis, collagen deposition at the lamina reticularis, is part of the process of so-called remodeling and is a characteristic finding in the asthmatic airway. To study the role of IGF in the evolution of asthma, we used a model that involved immunization of mice with ovalbumin and alum, followed by an inhaled challenge of ovalbumin. IGF-I neutralizing antibody was continuously infused with an osmotic pump. Pulmonary function was analyzed using whole-body plethysmography before and after acetylcholine administration. It was found that OVA inhalation induced IGF-I expression at the site of the airway. IGF-I neutralizing Ab inhibited the elevation of airway resistance, airway inflammation, and an increase in airway wall thickening. The depression of ICAM-1 expression was accompanied by a diminution in airway inflammation. In conclusion, these results suggest that IGF-I is likely to be an important mediator of inflammation and remodeling in the asthmatic airway.

Effects of interleukin-1beta, interleukin-13 and transforming growth factor-beta on gene expression in human airway smooth muscle using gene microarrays

Inflammatory gene expression in airway smooth muscle may be influenced by its inflammatory milieu. We analysed the gene expression profile of airway smooth muscle cells cultured from human airways exposed to a pro-inflammatory cytokine, interleukin-1beta, a T helper-2 cytokine, interleukin-13, and to a growth factor, transforming growth factor (TGF)beta1 (10 ng/ml each) after 4 and 24 h using the Affymetrix GeneChip 95A array which detects approximately 12,500 genes and expression sequence tags (ESTs). Airway smooth muscle cells were responsive to each cytokine with distinctive patterns of gene expression for cytokines, chemokines, adhesion and signalling proteins, and transcription factors. Interleukin-1beta induced the highest number of genes such as cytokines/chemokines including interleukin-8, growth-related oncogene (GRO)-alpha, -beta and -gamma, epithelial neutrophil activating protein (ENA)-78, monocyte chemotactic protein (MCP)-1, -2 and -3 and eotaxin. Using quantitative real-time reverse transcription-polymerase chain reaction, the expression of GRO-alpha, -beta and -gamma, interleukin-8 and eotaxin by interleukin-1beta was confirmed, with good correlation with microarray data. Transforming growth factor (TGF)beta1 induced other growth factors such as connective tissue growth factor (CTGF), vascular endothelial growth factor (VEGF), insulin growth factor (IGF) and many structural and extracellular matrix proteins. Interleukin-13 was the weakest inducer, with stimulation of eotaxin and genes of unknown function. While many genes were co-regulated at 4 and 24 h, there were also differences in expression patterns. Interleukin-1beta induces a predominantly pro-inflammatory profile while TGFbeta1 can be linked to proliferative and matrix changes. The rich profile of mediators, growth factors and signalling molecules released from airway smooth muscle depends on the inflammatory milieu.

The role of airway smooth muscle in the pathogenesis of airway wall remodeling in chronic obstructive pulmonary disease

Airway wall remodeling processes are present in the small airways of patients with chronic obstructive pulmonary disease, consisting of tissue repair and epithelial metaplasia that contribute to airway wall thickening and airflow obstruction. With increasing disease severity, there is also increased mucous metaplasia and submucosal gland hypertrophy, peribronchial fibrosis, and an increase in airway smooth muscle mass. Apart from its contractile properties, airway smooth muscle produces inflammatory cytokines, proteases, and growth factors, which may contribute to the remodeling process and induce phenotypic changes of the muscle. Airflow limitation responds minimally to beta-agonists and corticosteroid therapy, unlike asthma, perhaps because of alterations in beta-receptor or glucocorticoid receptor numbers, alterations in receptor signaling, or the constrictive limitation imposed by peribronchial fibrosis. Better response is observed with the combination of inhaled long-acting beta-agonists and corticosteroids. This could result from effects at the level of airway smooth muscle. Airway wall remodeling may involve the release of growth factors from inflammatory or resident cells. The influence of smoking cessation or of current therapies on airway wall remodeling is unknown. Specific therapies for airway wall remodeling may be necessary, together with noninvasive methods of imaging small airway wall remodeling to assess responses.

Regulation of TGF-beta 1-induced connective tissue growth factor expression in airway smooth muscle cells

Transforming growth factor (TGF)-beta may play an important role in airway remodeling, and the fibrogenic effect of TGF-beta may be mediated through connective tissue growth factor (CTGF) release. We investigated the role of MAPKs and phosphatidylinositol 3-kinase (PI3K) and the effects of inflammatory cytokines on TGF-beta-induced CTGF expression in human airway smooth muscle cells (ASMC). We examined whether Smad signal was involved in the regulatory mechanisms. TGF-beta 1 induced a time- and concentration-dependent expression of CTGF gene and protein as analyzed by real-time RT-PCR and Western blot. Inhibition of ERK and c-jun NH(2)-terminal kinase (JNK), but not of p38 MAPK and PI3K, blocked the effect of TGF-beta 1 on CTGF mRNA and protein expression and on Smad2/3 phosphorylation. T helper lymphocyte 2-derived cytokines, IL-4 and IL-13, attenuated TGF-beta 1-stimulated mRNA and protein expression of CTGF and inhibited TGF-beta 1-stimulated ERK1/2 and Smad2/3 activation in ASMC. The proinflammatory cytokines tumor necrosis factor-alpha and IL-1 beta reduced TGF-beta 1-stimulated mRNA expression of CTGF but did not inhibit TGF-beta-induced Smad2/3 phosphorylation. TGF-beta 1-stimulated CTGF expression is mediated by mechanisms involving ERK and JNK pathways and is downregulated by IL-4 and IL-13 through modulation of Smad and ERK signals.

Synthetic responses in airway smooth muscle

Human airway smooth muscle (ASM) has several properties and functions that contribute to asthma pathogenesis, and increasing attention is being paid to its synthetic capabilities. ASM can promote the formation of the interstitial extracellular matrix, and in this respect, ASM from asthmatic subjects compared with normal subjects responds differently, both qualitatively and quantitatively. Thus, ASM cells are important regulating cells that potentially contribute to the known alterations within the extracellular matrix in asthma. In addition, through integrin-directed signaling, extracellular matrix components can alter the proliferative, survival, and cytoskeletal synthetic function of ASM cells. ASM also functions as a rich source of biologically active chemokines and cytokines that are capable of perpetuating airway inflammation in asthma and chronic obstructive pulmonary disease by promoting recruitment, activation, and trafficking of inflammatory cells in the airway milieu. Emerging evidence shows that airway remodeling may also be a result of the autocrine action of secreted inflammatory mediators, including T(H)2 cytokines, growth factors, and COX-2-dependent prostanoids. Finally, ASM cells contain both beta(2)-adrenergic receptors and glucocorticoid receptors and may represent a key target for beta(2)-adrenergic receptor agonist/corticosteroid interactions. Combinations of long-acting beta(2)-agonists and corticosteroids appear to have additive and/or synergistic effects in inhibiting inflammatory mediator release and the migration and proliferation of ASM cells.

Dual effects of IGFBP-3 on endothelial cell apoptosis and survival: involvement of the sphingolipid signaling pathways

Insulin-like growth factor binding protein (IGFBP)-3 has both growth-inhibiting and growth-promoting effects at the cellular level. The cytotoxic action of several anticancer drugs is linked to increased ceramide generation through sphingomyelin hydrolysis or de novo biosynthesis. Herein, we investigated the role of IGFBP-3 on apoptosis of human umbilical vein endothelial cells (HUVEC) and its relationship with ceramide levels. We report that IGFBP-3 exerts dual effects on HUVEC, potentiating doxorubicin-induced apoptosis but enhancing survival in serum-starved conditions. Ceramide was increased by IGFBP-3 in the presence of doxorubicin and decreased when IGFBP-3 was added alone to cells cultured in serum-free medium. The protection exerted by the ceramide synthase inhibitor fumonisin B1 over doxorubicin-induced apoptosis was enhanced by IGFBP-3 with concomitant reduction of ceramide levels. IGFBP-3 alone activated sphingosine kinase (SK) and increased SK1 mRNA; the SK inhibitor N,N-dimethylsphingosine (DMS) blocked IGFBP-3 antiapoptotic effect. Moreover, IGFBP-3 increased IGF-I mRNA and dramatically enhanced IGF-I release. IGF-I receptor (IGF-IR) and its downstream signaling pathways Akt and ERK were phosphorylated by IGFBP-3, whereas inhibition of IGF-IR phosphorylation with tyrphostin AG1024 suppressed the antiapopoptic effect of IGFBP-3. Finally, IGFBP-3 increased endothelial cell motility in all experimental conditions. These findings provide evidence that IGFBP-3 differentially regulates endothelial cell apoptosis by involvement of the sphingolipid signaling pathways. Moreover, the survival effect of IGFBP-3 seems to be mediated by the IGF-IR.

1alpha,25-dihydroxyvitamin D3 induced growth inhibition of PC-3 prostate cancer cells requires an active transforming growth factor beta signaling pathway

BACKGROUND

Prostate cancer growth inhibition by 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) is best characterized in the androgen dependent LNCaP cell line, where treatment with this hormone causes cell cycle arrest and apoptosis. 1,25(OH)2D3 also inhibits the growth of PC-3 prostate cancer cells, but not through the induction of G1 arrest or apoptosis. In this study, we have sought to elucidate the mechanism/s involved in PC-3 cell growth inhibition by 1,25(OH)2D3.

EXPERIMENTAL METHODS

We determined the effect of transforming growth factor beta (TGFbeta) blocking antibodies on 1,25(OH)2D3 mediated growth inhibition of PC-3 cells. In addition, we also studied the effects of 1,25(OH)2D3 on TGFbeta signaling and receptor expression. Finally, we assessed the role of TGFbeta signaling in the induction of the growth inhibitory protein, insulin like growth factor binding protein 3 (IGFBP-3), by 1,25(OH)2D3.

RESULTS

We find that 1,25(OH)2D3 action in PC-3 cells is mediated through at least two distinct pathways, the TGFbeta pathway and the IGFBP-3 pathway. We show that 1,25(OH)2D3 treatment elevates TGFbeta production and signaling, as well as receptor levels, in PC-3 cells. Further, using a blocking antibody against TGFbeta substantially reduces 1,25(OH)2D3 mediated growth inhibition without affecting IGFBP-3 induction, suggesting that IGFBP-3, alone, is insufficient to inhibit the growth of PC-3 cells.

Insulin-like growth factor binding protein-3 antagonizes the effects of retinoids in myeloid leukemia cells

Insulin-like growth factor binding protein-3 (IGFBP-3) can cause growth suppressive and proapoptotic effects on retinoids in many types of cancer cells. However, the expression and effects of IGFBP-3 in myeloid leukemia cells have not been elucidated. In this study, we found no IGFBP-3 expression in the human myeloid leukemia cell lines either at baseline or after stimulation with all-trans retinoic acid (ATRA). Human recombinant IGFBP-3 induced growth arrest and apoptosis of HL-60 and NB4 cells. We have previously identified RXR alpha as a nuclear receptor for IGFBP-3 and have proceeded to examine further the role of this interaction in leukemia cell lines. In signaling assays, IGFBP-3 potently suppressed RAR- and VDR-mediated signaling while enhancing RXR signaling. Interestingly, when IGFBP-3 was administered to these cells in combination with an RAR-selective ligand, the ability of these retinoids to induce differentiation was blunted. On the other hand, IGFBP-3 enhanced the effect of an RXR-selective ligand to induce differentiation of HL-60 and NB4 cells. Further studies showed that IGFBP-3 down-regulated (at the transcriptional level) the retinoid-induced expression of C/EBP epsilon in NB4 cells. Taken together, these results indicate that IGFBP-3 has antiproliferative activity against myeloid leukemia cells; while it enhances signaling through RXR/RXR, it blunts signaling by activated RAR/RXR.

Inhibitory effects of interferon-gamma on the heterologous desensitization of beta-adrenoceptors by transforming growth factor-beta 1 in tracheal smooth muscle

BACKGROUND

Transforming growth factor-beta1 (TGF-beta 1) is generally considered to play an important role in the pathogenesis of chronic inflammation and fibrosis.

OBJECTIVE AND METHODS

This study was designed to determine mechanisms of reduced responsiveness of guinea-pig tracheal smooth muscle to beta-adrenoceptor agonists by TGF-beta 1, using isometric tension records and tissue cAMP measurement. Moreover, we examined the involvement of the signal transduction processes of TGF-beta superfamily in the desensitization of beta-adrenoceptors.

RESULTS

After exposure to 0.2-2000 pm TGF-beta 1 for 4-8 h, the inhibitory effects of 1 microm isoprenaline (ISO) and 10 microm forskolin on 1 microm MCh-induced contraction were markedly reduced in a concentration-dependent fashion. The desensitization by TGF-beta 1 was greater against ISO than for forskolin. The values of EC75 for the curves for ISO after exposure to the normal bathing solution and TGF-beta 1 were 0.039 +/- 0.02 and 0.38 +/- 0.28 microm, respectively. The values of EC50 for the curves for forskolin under these conditions were 0.50 +/- 0.12 and 0.89 +/- 0.21 microm, respectively. On the other hand, the inhibitory effects of phosphodiesterase inhibitors such as theophylline and rolipram were not attenuated after exposure to TGF-beta 1. Concentration-inhibition curve for ISO was shifted to the right after exposure to 2000 pm TGF-beta 1 for 8 h more than that curve for forskolin. In contrast, the curve for theophylline was not shifted to the right by TGF-beta 1. When the tissues were incubated with TGF-beta 1 in the presence of IFN-gamma, an intracellular antagonist of TGF-beta signalling, IFN-gamma inhibited the reduced response to ISO and forskolin after exposure to TGF-beta 1 in a concentration-dependent fashion. After exposure to TGF-beta 1, the effects of cAMP accumulation of ISO was significantly reduced, however, neither forskolin-nor theophylline-induced cAMP accumulation was affected. IFN-gamma had no significant effect on cAMP accumulation either to ISO or forskolin.

CONCLUSIONS

Impairment of the beta-adrenoceptors/adenylyl cyclase pathway are involved in heterologous desensitization of beta-adrenoceptors induced by TGF-beta 1 in airway smooth muscle. IFN-gamma functionally suppresses this phenomenon via cAMP-independent processes. Phosphodiesterase is still intact under this condition.

CysLT1 receptor upregulation by TGF-beta and IL-13 is associated with bronchial smooth muscle cell proliferation in response to LTD4

BACKGROUND

Airway remodeling is a feature of chronic asthma. It involves a number of structural changes, including bronchial smooth muscle cell (BSMC) hyperplasia and hypertrophy. Cysteinyl leukotrienes (cysLTs) have been suggested to play a role in airway remodeling in addition to their numerous other physiopathologic effects.

OBJECTIVES

This work was aimed at characterizing the potential modulation of CysLT1 receptor expression by cytokines and the eventual functional relevance of this modulation.

METHODS

Expression of CysLT1 receptor was measured by flow cytometry and immunofluorescence microscopy. Transcripts were measured by RT-PCR and BSMC proliferation by crystal violet staining.

RESULTS

When human BSMC were exposed to transforming growth factor (TGF)-beta, IL-13, or IFN-gamma, their expression of CysLT1 receptor was significantly augmented in a time- and concentration-dependent manner. Interestingly, IL-4 had no significant effect on CysLT1 receptor expression in BSMC. Moreover, IL-13 and IFN-gamma but not TGF-beta were able to increase CysLT1 mRNA levels. Finally, when BSMC were pretreated with TGF-beta or IL-13 but not IFN-gamma, their responsiveness to LTD(4) was markedly enhanced in terms of BSMC proliferation. Whereas TGF-beta, IL-13, or LTD(4) alone had little effect on BSMC proliferation, preexposure of the cells to TGF-beta or IL-13 for 24 hours resulted in a significant increase in proliferation in response to LTD(4). The enhanced proliferation was totally prevented by pretreating the cytokine-primed BSMC with the selective CysLT1 receptor antagonist Montelukast.

CONCLUSIONS

Taken together, our findings indicate a synergy between certain cytokines and cysLTs, mediated by the augmented expression of the CysLT1 receptor and subsequent LTD(4)-triggered BSMC proliferation. These findings support a role for cysLTs in the airway remodeling observed in asthmatic patients and may provide a rationale for preventive and therapeutic intervention.

Expression of connective tissue growth factor in asthmatic airway smooth muscle cells

There is strong evidence to implicate transforming growth factor-beta in the remodeling that occurs in asthma, as levels are increased in bronchial lavage fluid and gene expression is increased in bronchial tissue. Transforming growth factor-beta is also known to increase the release of collagen from airway smooth muscle. Here we identify for the first time a possible mechanism for the effects of transforming growth factor-beta. Transforming growth factor-beta specifically induces mRNA and protein for connective tissue growth factor in airway smooth muscle, and moreover, we report that the connective tissue growth factor response is greater in airway smooth muscle cultured from patients with asthma compared with patients without asthma. This occurs at both the level of mRNA (37.53 +/- 11.62- and 13.59 +/- 3.12-fold increase at 24 hours compared with time 0, respectively, p < 0.02) and protein production (67.57 +/- 27.80- and 3.58 +/- 0.6-fold increase at 24 hours compared with time 0, respectively, p < 0.03). The differential connective tissue growth factor response to transforming growth factor-beta in asthmatic airway smooth muscle identifies a potential role for connective tissue growth factor in the remodeling that is characteristic of severe persistent asthma.