Alpha-smooth Muscle Actin Gene Expression Research Articles

An essential role for CCAAT/enhancer binding protein β in bleomycin‐induced pulmonary fibrosis

Pulmonary fibrosis is characterized by inflammation, genesis of myofibroblasts, and abnormal tissue repair. Despite extensive research, its pathogenesis remains incompletely understood. Previously, the transcription factor CCAAT/enhancer binding protein beta (C/EBPbeta) was found to be a key regulator of myofibroblast differentiation in vitro, and to be involved in the acute phase and inflammatory responses. In an attempt to test the role of C/EBPbeta in the development of pulmonary fibrosis, experiments using C/EBPbeta null mice and their wild-type littermates were conducted. Our findings indicated that, compared to wild-type mice, animals deficient in C/EBPbeta showed significantly reduced fibrotic lesions and collagen deposition in the lung upon endotracheal injection of bleomycin. Further studies on the mechanisms by which C/EBPbeta regulates fibrosis indicated that knockout of C/EBPbeta attenuates inflammatory cytokine expression in bleomycin-treated mice. The reduced alpha-smooth muscle actin gene expression in either isolated lung fibroblasts or lung tissue from bleomycin or saline-treated C/EBPbeta deficient mice suggests that C/EBPbeta regulates myofibroblast differentiation during fibrosis. Consistent with this finding, cells from C/EBPbeta deficient mice exhibited higher proliferative rates than those from wild-type mice. These data suggest that C/EBPbeta plays an essential role in pulmonary fibrosis and that this role appears to be multifactorial with respect to cytokine expression, cell differentiation, and proliferation.

Curcumin blocks activation of pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis and inflammation. Inhibition of activation and cell functions of PSCs is a potential target for the treatment of pancreatic fibrosis and inflammation. The polyphenol compound curcumin is the yellow pigment in curry, and has anti-inflammatory and anti-fibrotic properties. We here evaluated the effects of curcumin on the activation and cell functions of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. The effects of curcumin on proliferation, alpha-smooth muscle actin gene expression, monocyte chemoattractant protein (MCP)-1 production, and collagen expression were examined. The effect of curcumin on the activation of freshly isolated cells in culture was also assessed. Curcumin inhibited platelet-derived growth factor (PDGF)-induced proliferation, alpha-smooth muscle actin gene expression, interleukin-1beta- and tumor necrosis factor (TNF)-alpha-induced MCP-1 production, type I collagen production, and expression of type I and type III collagen genes. Curcumin inhibited PDGF-BB-induced cyclin D1 expression and activation of extracellular signal-regulated kinase (ERK). Curcumin inhibited interleukin-1beta- and TNF-alpha-induced activation of activator protein-1 (AP-1) and mitogen-activated protein (MAP) kinases (ERK, c-Jun N-terminal kinase (JNK), and p38 MAP kinase), but not of nuclear factor-kappaB (NF-kappaB). In addition, curcumin inhibited transformation of freshly isolated cells to myofibroblast-like phenotype. In conclusion, curcumin inhibited key cell functions and activation of PSCs.

Inhibition of tendon cell migration by dexamethasone is correlated with reduced alpha-smooth muscle actin gene expression: a potential mechanism of delayed tendon healing

Local corticosteroid injection is commonly used to treat sports-related tendon injuries. However, isolated cases of tendon rupture following injection suggest that this treatment may impair the healing process. Tendon healing requires the migration of tendon cells to the repair site, followed by the proliferation and synthesis of the extracellular matrix. This study was designed to determine the effect of dexamethasone on the migration of tendon cells intrinsic to rat Achilles tendon at concentrations similar to those typically used for local injection treatment. Furthermore, the existence of a correlation between this effect and the expression of the contractile actin isoform, α-smooth muscle (SM) actin, which is associated with cell motility, was also examined. Using cultured tendon cells, migration was evaluated by counting the number of initial outgrowths from the tendon explants and by transwell filter migration assay. The distribution and assembly of α-SM actin were assessed by immunocytochemistry. The mRNA and protein expressions of α-SM actin were determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. Dose-dependent dexamethasone inhibition was demonstrated for both tendon cells outgrowth from the explants, ex vivo, and migration of tendon cells through the transwell filter, in vitro. Immunocytochemical staining revealed significant decreases in both the amount and assembly of α-SM actin in cells. Suppression of mRNA expression and protein level of α-SM actin was revealed from RT-PCR and Western blot analyses. In conclusion, dexamethasone inhibits tendon cell migration that is correlated with decreased gene expression of α-SM actin.

Cytokines and pulmonary fibrosis.

In the past several years, significant progress in many aspects of pulmonary fibrosis research has been made. Among them, the finding that a variety of cytokines play important roles in the complex process appears most intriguing. These cytokines include at least transforming growth factor-beta (TGF-beta), tumor necrosis factor-alpha (TNF-alpha), platelet-derived growth factor, fibroblast growth factors, (TGF-alpha), interleukin-1, monocyte chemoattractant protein-1 and macrophage inflammatory protein-1 alpha. These cytokines have been demonstrated to be produced at the sites of active fibrosis where they appear to be expressed by activated inflammatory cells, such as macrophages and eosinophils. More interestingly, other noninflammatory lung cells including mesenchymal cells, such as myofibroblasts, and epithelial cells, have been found to be significant sources as well, albeit in most instances at somewhat different time points than those by inflammatory cells. Study of the individual cytokines in vitro has revealed a variety of potential roles for these cytokines in the regulation of the fibrotic process in vivo, including chemoattractant, mitogenic activities for fibroblasts, stimulation of extracellular matrix and alpha-smooth muscle actin gene expression, alteration of the contractile phenotype of fibroblasts and regulation of diverse functions of lung inflammatory and epithelial cells which can further impact on the fibrotic process by autocrine and paracrine mechanisms. Of these cytokines, it appears that TGF-beta is probably the most important cytokine in terms of the direct stimulation of lung matrix expression which typifies fibrosis. Recently however, there is accumulating evidence to indicate that the situation is much more complex than any one single cytokine being solely responsible for the fibrotic response. The concept of complex lung cytokine networks, orchestrated by a few key cytokines, such as TNF-alpha, being responsible for this response has received strong support from recent studies. This means that it is the balance of positive (profibrogenic) and negative (antifibrogenic) forces generated from interaction among the various cytokines constituting these networks, which may finally determine the outcome of lung injury and inflammation. The importance of these cytokines also suggests new potential targets for designing new therapies for progressive pulmonary fibrosis, and perhaps their utility in prognostication as well.

Age-related changes in sarcoplasmic reticulum Ca(2+)-ATPase and alpha-smooth muscle actin gene expression in aortas of normotensive and spontaneously hypertensive rats.

The expression of the sarcoplasmic reticulum (SR) Ca(2+)-ATPase gene and the SR Ca2+ pump function were investigated in thoracic aortas of 5- and 17-week-old normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). The relative level of the two isoforms of SR Ca(2+)-ATPase mRNA expressed in the aorta (i.e., SERCA 2a and SERCA 2b) was determined by quantitative S1 nuclease protection analysis and normalized to the level of alpha-smooth muscle (alpha-Sm) actin mRNA. The level of alpha-Sm actin mRNA itself was normalized to the level of 18S ribosomal RNA using slot-blot hybridization assays. Total SR Ca2+ pump activity was estimated by measuring the rate of oxalate-supported Ca2+ uptake in homogenates. At 5 weeks, the amount of SERCA 2a and SERCA 2b mRNA, normalized to 18S ribosomal RNA, and the ratio of alpha-Sm actin mRNA to 18S RNA were identical in SHR and WKY rats. The Ca2+ pump activity was similar in the two strains of rats at 5 weeks. From 5 to 17 weeks, the amount of SERCA 2a mRNA increased in both strains while the level of SERCA 2b mRNA remained constant. The Ca2+ pump activity was unchanged in SHRs and tended to decrease in WKY rats. Accordingly, the change in the ratio of the SR Ca(2+)-ATPase mRNA isoforms does not appear to influence SR function. The level of alpha-Sm actin mRNA and SERCA 2a mRNA increased in parallel from 5 to 17 weeks in both strains.(ABSTRACT TRUNCATED AT 250 WORDS)