Glucocorticoid-induced contractility and F-actin content of human lung fibroblasts in three-dimensional culture

Glucocorticoid therapy in respiratory illness: bench to bedside

Each year, hundreds of millions of individuals are affected by respiratory disease leading to approximately 4 million deaths. Most respiratory pathologies involve substantially dysregulated immune processes that either fail to resolve the underlying process or actively exacerbate the disease. Therefore, clinicians have long considered immune-modulating corticosteroids (CSs), particularly glucocorticoids (GCs), as a critical tool for management of a wide spectrum of respiratory conditions. However, the complex interplay between effectiveness, risks and side effects can lead to different results, depending on the disease in consideration. In this comprehensive review, we present a summary of the bench and the bedside evidence regarding GC treatment in a spectrum of respiratory illnesses. We first describe here the experimental evidence of GC effects in the distal airways and/or parenchyma, both in vitro and in disease-specific animal studies, then we evaluate the recent clinical evidence regarding GC treatment in over 20 respiratory pathologies. Overall, CS remain a critical tool in the management of respiratory illness, but their benefits are dependent on the underlying pathology and should be weighed against patient-specific risks.

The effect of the pro-inflammatory cytokine tumor necrosis factor-alpha on human joint capsule myofibroblasts

Introduction

Previous studies have shown that the number of myoblastically differentiated fibroblasts known as myofibroblasts (MFs) is significantly increased in stiff joint capsules, indicating their crucial role in the pathogenesis of post-traumatic joint stiffness. Although the mode of MFs' function has been well defined for different diseases associated with tissue fibrosis, the underlying mechanisms of their regulation in the pathogenesis of post-traumatic joint capsule contracture are largely unknown.

Methods

In this study, we examined the impact of the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-α) on cellular functions of human joint capsule MFs. MFs were challenged with different concentrations of TNF-α with or without both its specifically inactivating antibody infliximab (IFX) and cyclooxygenase-2 (COX2) inhibitor diclofenac. Cell proliferation, gene expression of both alpha-smooth muscle actin (α-SMA) and collagen type I, the synthesis of prostaglandin derivates E₂, F_1A, and F_2A, as well as the ability to contract the extracellular matrix were assayed in monolayers and in a three-dimensional collagen gel contraction model. The α-SMA and COX2 protein expressions were evaluated by immunofluorescence staining and Western blot analysis.

Results

The results indicate that TNF-α promotes cell viability and proliferation of MFs, but significantly inhibits the contraction of the extracellular matrix in a dose-dependent manner. This effect was associated with downregulation of α-SMA and collagen type I by TNF-α application. Furthermore, we found a significant time-dependent upregulation of prostaglandin E₂ synthesis upon TNF-α treatment. The effect of TNF-α on COX2-positive MFs could be specifically prevented by IFX and partially reduced by the COX2 inhibitor diclofenac.

Conclusions

Our results provide evidence that TNF-α specifically modulates the function of MFs through regulation of prostaglandin E₂ synthesis and therefore may play a crucial role in the pathogenesis of joint capsule contractures.

Control of thrombin signaling through PI3K is a mechanism underlying plasticity between hair follicle dermal sheath and papilla cells

In hair follicles, dermal papilla (DP) and dermal sheath (DS) cells exhibit striking levels of plasticity, as each can regenerate both cell types. Here, we show that thrombin induces a phosphoinositide 3-kinase (PI3K)-Akt pathway-dependent acquisition of DS-like properties by DP cells in vitro, involving increased proliferation rate, acquisition of `myofibroblastic' contractile properties and a decreased capacity to sustain growth and survival of keratinocytes. The thrombin inhibitor protease nexin 1 [PN-1, also known as SERPINE2) regulates all those effects in vitro. Accordingly, the PI3K-Akt pathway is constitutively activated and expression of myofibroblastic marker smooth-muscle actin is enhanced in vivo in hair follicle dermal cells from PN-1–/– mice. Furthermore, physiological PN-1 disappearance and upregulation of the thrombin receptor PAR-1 (also known as F2R) during follicular regression in wild-type mice also correlate with such changes in DP cell characteristics. Our results indicate that control of thrombin signaling interferes with hair follicle dermal cells plasticity to regulate their function.

Comparison of gel contraction mediated by airway smooth muscle cells from patients with and without asthma

BACKGROUND

Exaggerated bronchial constriction is the most significant and life threatening response of patients with asthma to inhaled stimuli. However, few studies have investigated the contractility of airway smooth muscle (ASM) from these patients. The purpose of this study was to establish a method to measure contraction of ASM cells by embedding them into a collagen gel, and to compare the contraction between subjects with and without asthma.

METHODS

Gel contraction to histamine was examined in floating gels containing cultured ASM cells from subjects with and without asthma following overnight incubation while unattached (method 1) or attached (method 2) to casting plates. Smooth muscle myosin light chain kinase protein levels were also examined.

RESULTS

Collagen gels containing ASM cells reduced in size when stimulated with histamine in a concentration-dependent manner and reached a maximum at a mean (SE) of 15.7 (1.2) min. This gel contraction was decreased by inhibitors for phospholipase C (U73122), myosin light chain kinase (ML-7) and Rho kinase (Y27632). When comparing the two patient groups, the maximal decreased area of gels containing ASM cells from patients with asthma was 19 (2)% (n = 8) using method 1 and 22 (3)% (n = 6) using method 2, both of which were greater than that of cells from patients without asthma: 13 (2)% (n = 9, p = 0.05) and 10 (4)% (n = 5, p = 0.024), respectively. Smooth muscle myosin light chain kinase levels were not different between the two groups.

CONCLUSION

The increased contraction of asthmatic ASM cells may be responsible for exaggerated bronchial constriction in asthma.

The β2-adrenergic receptor activates pro-migratory and pro-proliferative pathways in dermal fibroblasts via divergent mechanisms

Dermal fibroblasts are required for skin wound repair; they migrate into the wound bed, proliferate, synthesize extracellular matrix components and contract the wound. Although fibroblasts express β2-adrenergic receptors (β2-AR) and cutaneous keratinocytes can synthesize β-AR agonists (catecholamines), the functional significance of this hormonal mediator network in the skin has not been addressed. Emerging studies from our laboratory demonstrate that β2-AR activation modulates keratinocyte migration, essential for wound re-epithelialization. Here we describe an investigation of the effects of β2-AR activation on the dermal component of wound healing. We examined β2-AR-mediated regulation of biological processes in dermal fibroblasts that are critical for wound repair: migration, proliferation, contractile ability and cytoskeletal conformation.

We provide evidence for the activation of at least two divergent β2-AR-mediated signaling pathways in dermal fibroblasts, a Src-dependent pro-migratory pathway, transduced through the epidermal growth factor receptor and extracellular signal-regulated kinase, and a PKA-dependent pro-proliferative pathway. β2-AR activation attenuates collagen gel contraction and alters the actin cytoskeleton and focal adhesion distribution through PKA-dependent mechanisms. Our work uncovers a previously unrecognized role for the adrenergic hormonal mediator network in the cutaneous wound repair process. Exploiting these divergent β2-AR agonist responses in cutaneous cells may generate novel therapeutic approaches for the control of wound healing.

Expression and differential effects of the activation of glucocorticoid receptors in mouse gonadotropin-releasing hormone neurons

Prenatal exposure of rodents to glucocorticoids (Gc) affects the sexual development of the offspring, possibly interfering with the differentiation of the hypothalamic-pituitary-gonadal axis. Glucocorticoid receptors (GR) are present on gonadotropin-releasing hormone (GnRH) neurons in the rat hypothalamus, suggesting a direct effect of Gc in the control of the synthesis and/or release of the hormone. In this study, we demonstrate the colocalization of immunoreactive GR with GnRH in a subpopulation of mouse hypothalamic GnRH neurons, confirming the possible involvement of Gc in mouse GnRH neuronal physiology. Receptor-binding assay, RT-PCR, immunocytochemistry, and immunoblotting experiments carried out in GN11 immortalized GnRH neurons show the presence of GR even in the more immature mouse GnRH neurons and confirm the expression of GR in GT1-7 mature GnRH cells. In GN11 cells, the activation of GR with dexamethasone produces nuclear translocation, but does not lead to the inhibition of GnRH gene expression already reported in GT1-7 cells. Long-term exposure of GN11 cells to dexamethasone induces an epithelial-like phenotype with a reorganization of F-actin in stress fibers. Finally, we found that Gc treatment significantly decreases the migratory activity in vitro and the levels of phosphorylated focal adhesion kinase of GN11 immature neurons. In conclusion, these data indicate that GR are expressed in mouse hypothalamic GnRH neurons in vivo as well as in the immature GN11 GnRH neurons in vitro. Moreover, the effects of the GR activation in GN11 and in GT1-7 cells may be related to the neuronal maturational stage of the two cell lines, suggesting a differential role of Gc in neuronal development.

The fibroblast-populated collagen matrix as a model of wound healing: a review of the evidence

The fibroblast-populated collagen matrix (FPCM) has been utilized as an in vitro model of wound healing for more than 2 decades. It offers a reasonable approximation of the healing wound during the phases of established granulation tissue and early scar. The gross and microscopic morphology of the FPCM and the healing wound are similar at analogous phases. The processes of proliferation, survival/apoptosis, protein synthesis, and contraction act in similar directions in these two models, and the response to exogenous agents also is consistent between them. If its limitations are respected, then the FPCM can be used as a model of the healing wound.

An in vitro model of pericardial tissue healing

INTRODUCTION

A previous study in our laboratory showed that a flap of fresh autologous pericardium bisecting the aorta of sheep retracted and became fibrotic. Histologic analyses suggested that activated cells within the pericardium contributed to the retraction of the implant. Here we report the development of an in vitro model to investigate the effects of serum on cellular proliferation and cell-mediated tissue contraction.

METHODS

Sections of living and ethanol-treated sheep pericardium were incubated with 0.5%, 5%, 10%, 20%, and 50% serum in medium for up to 8 days and evaluated for cellular proliferation and tissue contraction. These serum-stimulated events were further evaluated in the presence of Mitomycin C, Cytochalasin B and D, Aphidicolin, AraC, and Cycloheximide.

RESULTS

Cellular proliferation and cell-mediated tissue contraction were induced by serum in a dose-dependent manner. Expression of PCNA was suppressed in the presence of Cytochalasin B, Cytochalasin D, Aphidicolin, and AraC. Tissue contraction was prevented by Cycloheximide. Mitomycin C inhibited both proliferation and tissue contraction. Ethanol-treated tissue, which was absent of living cells, did not respond to stimulation with serum.

CONCLUSIONS

An in vitro model was developed to study the responses of cells within pericardial tissues to stimulation by serum. In this model, serum induced cellular proliferation and tissue contraction. Different chemical inhibitors independently modulated these serum-stimulated events. Pre-existing cells within pericardial tissues might respond to stimulus through differential pathways. This model may help to develop methods to make autologous pericardium a clinically useful biomaterial.

Fibroblast contractility: usual interstitial pneumonia and nonspecific interstitial pneumonia

The aim of this study was to compare the function of lung fibroblasts obtained from surgically biopsied specimens of patients with idiopathic pulmonary fibrosis/usual interstitial pneumonia (UIP; n = 5), nonspecific interstitial pneumonia (NSIP; n = 5), and normal parts of surgically resected lungs (control; n = 5). The results showed that (1) fibroblasts obtained from UIP showed increased contractility compared with those obtained from NSIP or controls (UIP, 72.7 +/- 6.21%; NSIP, 32.8 +/- 5.46; controls, 28.5 +/- 3.51, p < 0.01 in UIP versus NSIP or control); (2) this increase in contractility was consistent with enhanced F-actin content in fibroblasts; (3) conditioned media from UIP fibroblast cultures enhanced control fibroblast contractility, whereas those obtained from NSIP or controls did not; (4) the 180 and 25 kD products representing the contractility in conditioned media were identified as fibronectin (ED-A domain) and TGF-beta1 by immunoblots, respectively; (5) the UIP-conditioned media contained higher amounts of fibronectin or TGF-beta 1 (fibronectin: UIP 289 +/- 47.1 ng/ml, NSIP 121 +/- 23.0, control 118 +/- 16.0; TGF-beta1: UIP 798 +/- 119 pg/ml, NSIP 246 +/- 69.1, control 247 +/- 53.6, p < 0.01 in UIP versus NSIP or control); () the contractility positively correlated with the amount of either fibronectin (r = 0.867, p < 0.001, n = 15) or TGF-beta 1 (r = 0.939, p < 0.001, n = 15), respectively. Thus, UIP fibroblasts showed greater contractility than did NSIP fibroblasts and up-regulated control fibroblasts.