Proteolytic activation of latent TGF-beta precedes caspase-3 activation and enhances apoptotic death of lung epithelial cells

Suppression of the TGF-β signaling exacerbates degeneration of auditory neurons in kanamycin-induced ototoxicity in mice

Transforming growth factor-β (TGF-β) signaling plays a significant role in multiple biological processes, including inflammation, immunity, and cell death. However, its specific impact on the cochlea remains unclear. In this study, we aimed to investigate the effects of TGF-β signaling suppression on auditory function and cochlear pathology in mice with kanamycin-induced ototoxicity. Kanamycin and furosemide (KM-FS) were systemically administered to 8-week-old C57/BL6 mice, followed by immediate topical application of a TGF-β receptor inhibitor (TGF-βRI) onto the round window membrane. Results showed significant TGF-β receptor upregulation in spiral ganglion neurons (SGNs) after KM-FA ototoxicity, whereas expression levels in the TGF-βRI treated group remained unchanged. Interestingly, despite no significant change in cochlear TGF-β expression after KM-FS ototoxicity, TGF-βRI treatment resulted in a significant decrease in TGF-β signaling. Regarding auditory function, TGF-βRI treatment offered no therapeutic effects on hearing thresholds and hair cell survival following KM-FS ototoxicity. However, SGN loss and macrophage infiltration were significantly increased with TGF-βRI treatment. These results imply that inhibition of TGF-β signaling after KM-FS ototoxicity promotes cochlear inflammation and SGN degeneration.

Cyclosporine-A induces apoptosis in human prostate cancer cells PC3 and DU145 via downregulation of COX-2 and upregulation of TGFβ

Background

Potential targets for prostate cancer therapy are urgently needed for curative of patients. Cyclosporine-A (CsA), an immunosuppressive and a selective cyclooxygenase-2 (COX-2) inhibitor, exerts antitumor activity. However, the molecular effects of CsA is not fully understood in prostate cancer. In this research, we sought to determine role and mechanism of CsA in prostate cancer.

Materials and methods

PC3 and DU145 cells were treated with CsA time (12, 24, 48 h) and dose dependent (2.5, 10, 25 μM) and cell survival, migration, colony formation, expression of apoptosis related proteins/genes using MTT assay, scratch assay, Western blotting/qPCR. At the same time, cells treated with CsA to test on the effects of COX-2 promoter activity using luciferase reporter plasmid. Lastly, functional role in the CsA treatment prostate cancer cells were interrogated for relationship of TGFβ, Akt, caspases and COX-2.

Results

These study findings provided direct evidences that the CsA induced apoptosis and downregulated migration.

Conclusions

CsA downregulated Akt as well as COX-2 and upregulated TGFβ, resulting in the suppression of cell migration which was augmented a potential therapeutic of CsA in prostate cancer cells.

Bax-inhibiting peptide attenuates bleomycin-induced lung injury in mice

Bax is a pro-apoptotic member of the Bcl-2 family of proteins, and plays a central role in mitochondria-dependent apoptosis. Several lines of evidence have implied that Bax is involved in both epithelial apoptosis and fibroblast proliferation in idiopathic pulmonary fibrosis; however, the mechanisms remain unknown. Bax-inhibiting peptide V5 (BIP-V5) exhibits membrane permeability and inhibits the activation of Bax.

The purpose of this study was to investigate whether the control of Bax activity by BIP-V5 reduces the degree of bleomycin-induced lung injury. C57BL/6J mice were administered bleomycin and BIP-V5 intratracheally on day 0. Bronchoalveolar lavage fluid and lung tissue were obtained on day 7. Human pulmonary alveolar epithelial cells (A549 cells) and mouse pulmonary alveolar epithelial cells (LA-4 cells) were stimulated with bleomycin to induce apoptosis.

Administration of BIP-V5 improved the survival rate and degree of bleomycin-induced lung injury by suppressing Bax activation in mice. BIP-V5 treatment decreased bleomycin-induced apoptosis of alveolar epithelial cell lines (A549 cells and LA-4 cells) by suppressing Bax activation. These results indicate that administration of BIP-V5 may constitute a novel therapeutic strategy against lung injury.

Summary: The inhibiting peptide for Bax, a pro-apoptotic member of the Bcl-2 family of proteins, ameliorates bleomycin-induced lung injury in mice via apoptosis suppression in epithelial cells.

Alveolar epithelial disintegrity in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease characterized by progressive decline in lung function, resulting in significant morbidity and mortality. Current concepts of the pathogenesis of IPF primarily center on dysregulated epithelial cell repair and altered epithelial-mesenchymal communication and extracellular matrix deposition following chronic exposure to cigarette smoke or environmental toxins. In recent years, increasing attention has been directed toward the role of the intercellular junctional complex in determining the specific properties of epithelia in pulmonary diseases. Additionally, recent genomewide association studies suggest that specific genetic variants predictive of epithelial cell dysfunction may confer susceptibility to the development of sporadic idiopathic pulmonary fibrosis. A number of genetic disorders linked to pulmonary fibrosis and familial interstitial pneumonias are associated with loss of epithelial integrity. However, the potential links between extrapulmonary clinical syndromes associated with defects in epithelial cells and the development of pulmonary fibrosis are not well understood. Here, we report a case of hereditary mucoepithelial dysplasia that presented with pulmonary fibrosis and emphysema on high-resolution computed tomography. This case illustrates a more generalizable concept of epithelial disintegrity in the development of fibrotic lung diseases, which is explored in greater detail in this review article.

Effects of dietary concentrated mannan oligosaccharides supplementation on growth, gut mucosal immune system and liver lipid metabolism of European sea bass (Dicentrarchus labrax) juveniles

The study assesses the effects of dietary concentrated mannan oligosaccharides (cMOS) on fish performance, biochemical composition, tissue fatty acid profiles, liver and posterior gut morphology and gen expression of selected parameters involved on the intestinal immune response and liver lipid metabolism of European sea bass (Dicentrarchus labrax). For that purpose, specimens of 20 g were fed during 8 weeks at 0 and 1.6 g kg(-1) dietary cMOS of inclusion in a commercial sea bass diet. Dietary cMOS enhanced fish length, specific and relative growth without affecting tissue proximate composition. However, cMOS supplementation altered especially liver and muscle fatty acid profiles by reducing levels of those fatty acids that are preferential substrates for β-oxidation in spite of a preferential retention of long chain polyunsaturated fatty acids (LC-PUFA), such as 20:4n-6 or 22:5n-6, in relation to the down-regulation of delta 6/5 desaturase gene expression found in liver. Besides, dietary cMOS supplementation reduced posterior gut intestinal folds width and induced changes on the gene expression level of certain immune-related genes mainly by down regulating transforming growth factor β (TGFβ) and up-regulating immunoglobulin (Ig), major histocompatibility complex class II (MHCII), T cell receptor β (TCRβ) and Caspase 3 (Casp-3). Thus, dietary cMOS inclusion at 0.16% promoted European sea bass specific growth rate and length, stimulated selected cellular GALT-associated parameters and affected lipid metabolism in muscle and liver pointing to a higher LC-PUFA accumulation and promoted β-oxidation.

The epithelium in idiopathic pulmonary fibrosis: breaking the barrier

Idiopathic pulmonary fibrosis is a progressive disease of unknown etiology characterized by a dysregulated wound healing response that leads to fatal accumulation of fibroblasts and extracellular matrix (ECM) in the lung, which compromises tissue architecture and lung function capacity. Injury to type II alveolar epithelial cells is thought to be the key event for the initiation of the disease, and so far both genetic factors, such as mutations in telomerase and MUC5B genes as well as environmental components, like cigarette smoking, exposure to asbestos and viral infections have been implicated as potential initiating triggers. The injured epithelium then enters a state of senescence-associated secretory phenotype whereby it produces both pro-inflammatory and pro-fibrotic factors that contribute to the wound healing process in the lung. Immune cells, like macrophages and neutrophils as well as activated myofibroblasts then perpetuate this cascade of epithelial cell apoptosis and proliferation by release of pro-fibrotic transforming growth factor beta and continuous deposition of ECM stiffens the basement membrane, altogether having a deleterious impact on epithelial cell function. In this review, we describe the role of the epithelium as both a physical and immunological barrier between environment and self in the homeostatic versus diseased lung and explore the potential mechanisms of epithelial cell injury and the impact of loss of epithelial cell permeability and function on cytokine production, inflammation, and myofibroblast activation in the fibrotic lung.

Involvement of the Wnt/β-catenin signaling pathway in the cellular and molecular mechanisms of fibrosis in endometriosis

Background

During the development and progression of endometriotic lesions, excess fibrosis may lead to scarring, chronic pain, and altered tissue function. However, the cellular and molecular mechanisms of fibrosis in endometriosis remain to be clarified.

Objectives

The objective of the present study was to investigate whether the Wnt/β-catenin signaling pathway was involved in regulating the cellular and molecular mechanisms of fibrosis in endometriosis in vitro and to evaluate whether fibrosis could be prevented by targeting the Wnt/β-catenin pathway in a xenograft model of endometriosis in immunodeficient nude mice.

Methods

Seventy patients (40 with and 30 without endometriosis) with normal menstrual cycles were recruited. In vitro effects of small-molecule antagonists of the Tcf/β-catenin complex (PKF 115-584 and CGP049090) on fibrotic markers (alpha smooth muscle actin, type I collagen, connective tissue growth factor, fibronectin) and collagen gel contraction were evaluated in endometrial and endometriotic stromal cells from patients with endometriosis. In vitro effects of activation of the Wnt/β-catenin signaling pathway by treatment with recombinant Wnt3a on profibrotic responses were evaluated in endometrial stromal cells of patients without endometriosis. The effects of CGP049090 treatment on the fibrosis of endometriotic implants were evaluated in a xenograft model of endometriosis in immunodeficient nude mice.

Results

Treatment with PKF 115-584 and CGP049090 significantly decreased the expression of alpha smooth muscle actin, type I collagen, connective tissue growth factor and fibronectin mRNAs in both endometriotic and endometrial stromal cells with or without transforming growth factor-β1 stimulation. Both endometriotic and endometrial stromal cell-mediated contraction of collagen gels was significantly decreased by treatment with PKF 115-584 and CGP049090 as compared to that of untreated cells. The animal experiments showed that CGP049090 prevented the progression of fibrosis and reversed established fibrosis in endometriosis.

Conclusion

Aberrant activation of the Wnt/β-catenin pathway may be involved in mediating fibrogenesis in endometriosis.

Fibrosis of two: Epithelial cell-fibroblast interactions in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by the progressive and ultimately fatal accumulation of fibroblasts and extracellular matrix in the lung that distorts its architecture and compromises its function. IPF is now thought to result from wound-healing processes that, although initiated to protect the host from injurious environmental stimuli, lead to pathological fibrosis due to these processes becoming aberrant or over-exuberant. Although the environmental stimuli that trigger IPF remain to be identified, recent evidence suggests that they initially injure the alveolar epithelium. Repetitive cycles of epithelial injury and resultant alveolar epithelial cell death provoke the migration, proliferation, activation and myofibroblast differentiation of fibroblasts, causing the accumulation of these cells and the extracellular matrix that they synthesize. In turn, these activated fibroblasts induce further alveolar epithelial cell injury and death, thereby creating a vicious cycle of pro-fibrotic epithelial cell-fibroblast interactions. Though other cell types certainly make important contributions, we focus here on the "pas de deux" (steps of two), or perhaps more appropriate to IPF pathogenesis, the "folie à deux" (madness of two) of epithelial cells and fibroblasts that drives the progression of pulmonary fibrosis. We describe the signaling molecules that mediate the interactions of these cell types in their "fibrosis of two", including transforming growth factor-β, connective tissue growth factor, sonic hedgehog, prostaglandin E2, angiotensin II and reactive oxygen species. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Mutant surfactant A2 proteins associated with familial pulmonary fibrosis and lung cancer induce TGF-β1 secretion

Mutations in the genes encoding the lung surfactant proteins are found in patients with interstitial lung disease and lung cancer, but their pathologic mechanism is poorly understood. Here we show that bronchoalveolar lavage fluid from humans heterozygous for a missense mutation in the gene encoding surfactant protein (SP)-A2 (SFTPA2) contains more TGF-β1 than control samples. Expression of mutant SP-A2 in lung epithelial cells leads to secretion of latent TGF-β1, which is capable of autocrine and paracrine signaling. TGF-β1 secretion is not observed in lung epithelial cells expressing the common SP-A2 variants or other misfolded proteins capable of increasing cellular endoplasmic reticulum stress. Activation of the unfolded protein response is necessary for maximal TGF-β1 secretion because gene silencing of the unfolded protein response transducers leads to an ∼50% decrease in mutant SP-A2-mediated TGF-β1 secretion. Expression of the mutant SP-A2 proteins leads to the coordinated increase in gene expression of TGF-β1 and two TGF-β1-binding proteins, LTBP-1 and LTBP-4; expression of the latter is necessary for secretion of this cytokine. Inhibition of the TGF-β autocrine positive feedback loop by a pan-TGF-β-neutralizing antibody, a TGF-β receptor antagonist, or LTBP gene silencing results in the reversal of TGF-β-mediated epithelial-to-mesenchymal transition and cell death. Because secretion of latent TGF-β1 is induced specifically by mutant SP-A2 proteins, therapeutics targeted to block this pathway may be especially beneficial for this molecularly defined subgroup of patients.

Role of the lysophospholipid mediators lysophosphatidic acid and sphingosine 1-phosphate in lung fibrosis

Aberrant wound healing responses to lung injury are believed to contribute to fibrotic lung diseases, such as idiopathic pulmonary fibrosis (IPF). The lysophospholipids lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), by virtue of their ability to mediate many basic cellular functions, including survival, proliferation, migration, and contraction, can influence many of the biological processes involved in wound healing. Accordingly, recent investigations indicate that LPA and S1P may play critical roles in regulating the development of lung fibrosis. Here we review the evidence indicating that LPA and S1P regulate pulmonary fibrosis and the potential mechanisms through which these lysophospholipids may influence fibrogenesis induced by lung injury.

Angiotensin receptor blockade attenuates cigarette smoke-induced lung injury and rescues lung architecture in mice

Chronic obstructive pulmonary disease (COPD) is a prevalent smoking-related disease for which no disease-altering therapies currently exist. As dysregulated TGF-β signaling associates with lung pathology in patients with COPD and in animal models of lung injury induced by chronic exposure to cigarette smoke (CS), we postulated that inhibiting TGF-β signaling would protect against CS-induced lung injury. We first confirmed that TGF-β signaling was induced in the lungs of mice chronically exposed to CS as well as in COPD patient samples. Importantly, key pathological features of smoking-associated lung disease in patients, e.g., alveolar injury with overt emphysema and airway epithelial hyperplasia with fibrosis, accompanied CS-induced alveolar cell apoptosis caused by enhanced TGF-β signaling in CS-exposed mice. Systemic administration of a TGF-β-specific neutralizing antibody normalized TGF-β signaling and alveolar cell death, conferring improved lung architecture and lung mechanics in CS-exposed mice. Use of losartan, an angiotensin receptor type 1 blocker used widely in the clinic and known to antagonize TGF-β signaling, also improved oxidative stress, inflammation, metalloprotease activation and elastin remodeling. These data support our hypothesis that inhibition of TGF-β signaling through angiotensin receptor blockade can attenuate CS-induced lung injury in an established murine model. More importantly, our findings provide a preclinical platform for the development of other TGF-β-targeted therapies for patients with COPD.

The lysophosphatidic acid receptor LPA1 promotes epithelial cell apoptosis after lung injury

Increased epithelial cell apoptosis in response to lung injury has been implicated in the development of idiopathic pulmonary fibrosis (IPF), but the molecular pathways promoting epithelial cell apoptosis in this disease have yet to be fully identified. Lysophosphatidic acid (LPA), which we have previously demonstrated to mediate bleomycin lung injury-induced fibroblast recruitment and vascular leak in mice and fibroblast recruitment in patients with IPF, is an important regulator of survival and apoptosis in many cell types. We now show that LPA signaling through its receptor LPA(1) promotes epithelial cell apoptosis induced by bleomycin injury. The number of apoptotic cells present in the alveolar and bronchial epithelia of LPA(1)-deficient mice was significantly reduced compared with wild-type mice at Day 3 after bleomycin challenge, as was lung caspase-3 activity. Consistent with these in vivo results, we found that LPA signaling through LPA(1) induced apoptosis in normal human bronchial epithelial cells in culture. LPA-LPA(1) signaling appeared to specifically mediate anoikis, the apoptosis of anchorage-dependent cells induced by their detachment. Similarly, LPA negatively regulated attachment of R3/1 rat alveolar epithelial cell line cells. In contrast, LPA signaling through LPA(1) promoted the resistance of lung fibroblasts to apoptosis, which has also been implicated in IPF. The ability of LPA-LPA(1) signaling to promote epithelial cell apoptosis and fibroblast resistance to apoptosis may therefore contribute to the capacity of this signaling pathway to regulate the development of pulmonary fibrosis after lung injury.

Molecular imaging of TGFβ-induced Smad2/3 phosphorylation reveals a role for receptor tyrosine kinases in modulating TGFβ signaling

PURPOSE

The dual modality of TGFβ, both as a potent tumor suppressor and a stimulator of tumor progression, invasion, and metastasis, make it a critical target for therapeutic intervention in human cancers. The ability to carry out real-time, noninvasive imaging of TGFβ-activated Smad signaling in live cells and animal models would significantly improve our understanding of the regulation of this unique signaling cascade. To advance these efforts, we developed a highly sensitive molecular imaging tool that repetitively, noninvasively, and dynamically reports on TGFBR1 kinase activity.

EXPERIMENTAL DESIGN

The bioluminescent TGFβR1 reporter construct was developed using a split firefly luciferase gene containing a functional sensor of Smad2 phosphorylation, wherein inhibition of TGFβ receptor1 kinase activity leads to an increase in reporter signaling. The reporter was stably transfected into mammalian cells and used to image in vivo and in vitro bioluminescent activity as a surrogate for monitoring TGFBR1 kinase activity.

RESULTS

The reporter was successfully used to monitor direct and indirect inhibition of TGFβ-induced Smad2 and SMAD3 phosphorylation in live cells and tumor xenografts and adapted for high-throughput screening, to identify a role for receptor tyrosine kinase inhibitors as modulators of TGFβ signaling.

CONCLUSION

The reporter is a dynamic, noninvasive imaging modality for monitoring TGFβ-induced Smad2 signaling in live cells and tumor xenografts. It has immense potential for identifying novel effectors of R-Smad phosphorylation, for validating drug-target interaction, and for studying TGFβ signaling in different metastasis models.

Characterization of the transcriptional signature of C/EBPbeta isoforms (LAP/LIP) in Hep3B cells: implication of LIP in pro-survival functions

BACKGROUND & AIMS

C/EBPbeta is an important mediator of several cellular processes, such as differentiation, proliferation, and survival of hepatic cells. However, a complete catalog of the targets of C/EBPbeta or the mechanism by which this transcription factor regulates certain liver-dependent pathways has not been clearly determined. Two major natural isoforms of this transcription factor exist: the liver-enriched activating protein (LAP) and the liver-enriched inhibitory protein (LIP), a functional LAP antagonist. In this study, we used the opposing transcriptional effects driven by LAP and LIP to determine the genuine C/EBPbeta molecular signature in the Hep3B human hepatoma cell line. We subsequently investigated the role of each of the LAP and LIP isoforms in drug-induced Hep3B cell death.

METHODS

We engineered Hep3B cells with regulated LAP or LIP expression using the Tet-off expression system. The genes that showed inverse regulation by LAP and LIP were identified by cDNA array analysis. The cohort of direct-C/EBPbeta-targets was distinguished from indirect-targets by ChIP-on-chip analysis.

RESULTS

We characterized 676 genes by this approach. Among these genes, 39 are novel direct targets of C/EBPbeta. Eleven of these new direct targets are involved in cell survival, suggesting critical roles for LAP/LIP isoforms in this cellular process. Therefore, we examined the effects of LAP and LIP over-expression on cell survival. We show that LIP promotes survival in staurosporine- or taxol-induced Hep3B cell death.

CONCLUSIONS

Our study provides new molecular and cellular insights into the role of C/EBPbeta in cells of hepatic origin.

Suppression of latent transforming growth factor (TGF)-beta1 restores growth inhibitory TGF-beta signaling through microRNAs

Cancer cells secreting excess latent TGF-β are often resistant to TGF-β induced growth inhibition. We observed that RNAi against TGF-β1 led to apoptotic death in such cell lines with features that were, paradoxically, reminiscent of TGF-β signaling activity and that included transiently enhanced SMAD2 and AKT phosphorylation. A comprehensive search in Hela cells for potential microRNA drivers of this mechanism revealed that RNAi against TGF-β1 led to induction of pro-apoptotic miR-34a and to a globally decreased oncomir expression. The reduced levels of the oncomirs miR-18a and miR-24 accounted for the observed derepression of two TGF-β1 processing factors, thrombospondin-1, and furin, respectively. Our data suggest a novel mechanism in which latent TGF-β1, thrombospondin 1, and furin form a microRNA-mediated regulatory feedback loop. For cells with high levels of latent TGF-β, this provides a potentially widespread mechanism of escape from TGF-β-mediated growth arrest at the earliest point in the signaling pathway, TGF-β processing.

Transforming growth factor-β: activation by neuraminidase and role in highly pathogenic H5N1 influenza pathogenesis

Transforming growth factor-beta (TGF-β), a multifunctional cytokine regulating several immunologic processes, is expressed by virtually all cells as a biologically inactive molecule termed latent TGF-β (LTGF-β). We have previously shown that TGF-β activity increases during influenza virus infection in mice and suggested that the neuraminidase (NA) protein mediates this activation. In the current study, we determined the mechanism of activation of LTGF-β by NA from the influenza virus A/Gray Teal/Australia/2/1979 by mobility shift and enzyme inhibition assays. We also investigated whether exogenous TGF-β administered via a replication-deficient adenovirus vector provides protection from H5N1 influenza pathogenesis and whether depletion of TGF-β during virus infection increases morbidity in mice. We found that both the influenza and bacterial NA activate LTGF-β by removing sialic acid motifs from LTGF-β, each NA being specific for the sialic acid linkages cleaved. Further, NA likely activates LTGF-β primarily via its enzymatic activity, but proteases might also play a role in this process. Several influenza A virus subtypes (H1N1, H1N2, H3N2, H5N9, H6N1, and H7N3) except the highly pathogenic H5N1 strains activated LTGF-β in vitro and in vivo. Addition of exogenous TGF-β to H5N1 influenza virus-infected mice delayed mortality and reduced viral titers whereas neutralization of TGF-β during H5N1 and pandemic 2009 H1N1 infection increased morbidity. Together, these data show that microbe-associated NAs can directly activate LTGF-β and that TGF-β plays a pivotal role protecting the host from influenza pathogenesis.

Modulation of TGF-beta activity by latent TGF-beta-binding protein 1 in human malignant glioma cells

High biological activity of the transforming growth factor (TGF)-beta-Smad pathway characterizes the malignant phenotype of malignant gliomas and confers poor prognosis to glioma patients. Accordingly, TGF-beta has become a novel target for the experimental treatment of these tumors. TGF-beta is processed by furin-like proteases (FLP) and secreted from cells in a latent complex with its processed propeptide, the latency-associated peptide (LAP). Latent TGF-beta-binding protein 1 (LTBP-1) covalently binds to this small latent TGF-beta complex (SLC) and regulates its function, presumably via interaction with the extracellular matrix (ECM). We report here that the levels of LTBP-1 protein in vivo increase with the grade of malignancy in gliomas. LTBP-1 is associated with the ECM as well as secreted into the medium in cultured malignant glioma cells. The release of LTBP-1 into the medium is decreased by the inhibition of FLP activity. Gene-transfer mediated overexpression of LTBP-1 in glioma cell lines results in an increase inTGF-beta activity. Accordingly, Smad2 phosphorylation as an intracellular marker of TGF-beta activity is enhanced. Conversely, LTBP-1 gene silencing reduces TGF-beta activity and Smad2 phosphorylation without affecting TGF-beta protein levels. Collectively, we identify LTBP-1 as an important modulator of TGF-beta activation in glioma cells, which may contribute to the malignant phenotype of these tumors.

Physiology and molecular biology of petal senescence

Petal senescence is reviewed, with the main emphasis on gene expression in relation to physiological functions. Autophagy seems to be the major mechanism for large-scale degradation of macromolecules, but it is still unclear if it contributes to cell death. Depending on the species, petal senescence is controlled by ethylene or is independent of this hormone. EIN3-like (EIL) transcription factors are crucial in ethylene-regulated senescence. The presence of adequate sugar levels in the cell delays senescence and prevents an increase in the levels of EIL mRNA and the subsequent up-regulation of numerous senescence-associated genes. A range of other transcription factors and regulators are differentially expressed in ethylene-sensitive and ethylene-insensitive petal senescence. Ethylene-independent senescence is often delayed by cytokinins, but it is still unknown whether these are natural regulators. A role for caspase-like enzymes or metacaspases has as yet not been established in petal senescence, and a role for proteins released by organelles such as the mitochondrion has not been shown. The synthesis of sugars, amino acids, and fatty acids, and the degradation of nucleic acids, proteins, lipids, fatty acids, and cell wall components are discussed. It is claimed that there is not enough experimental support for the widely held view that a gradual increase in cell leakiness, resulting from gradual plasma membrane degradation, is an important event in petal senescence. Rather, rupture of the vacuolar membrane and subsequent rapid, complete degradation of the plasma membrane seems to occur. This review recommends that more detailed analysis be carried out at the level of cells and organelles rather than at that of whole petals.

Epithelial-mesenchymal interactions in pulmonary fibrosis

Pulmonary fibrosis represents the sequelae of a variety of acute and chronic lung injuries of known and unknown etiologies. Tissue specimens obtained from patients with pulmonary fibrosis, regardless of the etiology, consistently show evidence of an ongoing wound-repair response. Epithelial-mesenchymal interactions have critical roles in normal lung development, tissue repair processes, and fibrosis. Current hypotheses propose that dysregulated function of, and impaired communication between, epithelial and mesenchymal cells prevent resolution of the wound-repair response and contribute to the pathobiology of pulmonary fibrosis. This hypothesis is supported by abundant evidence from patients, animal models, and cell-culture studies demonstrating abnormalities in epithelial cell and mesenchymal cell activities including proliferation, differentiation, and survival. This article reviews the aberrant epithelial and mesenchymal cellular phenotypes found in the context of pulmonary fibrosis and discusses the mechanisms that perpetuate these cellular phenotypes.

Pirfenidone inhibits TGF-beta expression in malignant glioma cells

Due to its immunosuppressive properties, the cytokine transforming growth factor (TGF)-beta has become a promising target in the experimental treatment of human malignant gliomas. Here, we report that the antifibrotic drug 5-methyl-1-phenyl-2-(1H)-pyridone (pirfenidone, PFD) elicits growth-inhibitory effects and reduces TGF-beta2 protein levels in human glioma cell lines. This reduction in TGF-beta2 is biologically relevant since PFD treatment reduces the growth inhibition of TGF-beta-sensitive CCL-64 cells mediated by conditioned media of glioma cells. The downregulation of TGF-beta is mediated at multiple levels. PFD leads to a reduction of TGF-beta2 mRNA levels and of the mature TGF-beta2 protein due to decreased expression and direct inhibition of the TGF-beta pro-protein convertase furin. In addition, PFD reduces the protein levels of the matrix metalloproteinase (MMP)-11, a TGF-beta target gene and furin substrate involved in carcinogenesis. These data define PFD or PFD-related agents as promising agents for human cancers associated with enhanced TGF-beta activity.

Alveolar epithelial cell mesenchymal transition develops in vivo during pulmonary fibrosis and is regulated by the extracellular matrix

Mechanisms leading to fibroblast accumulation during pulmonary fibrogenesis remain unclear. Although there is in vitro evidence of lung alveolar epithelial-to-mesenchymal transition (EMT), whether EMT occurs within the lung is currently unknown. Biopsies from fibrotic human lungs demonstrate epithelial cells with mesenchymal features, suggesting EMT. To more definitively test the capacity of alveolar epithelial cells for EMT, mice expressing beta-galactosidase (beta-gal) exclusively in lung epithelial cells were generated, and their fates were followed in an established model of pulmonary fibrosis, overexpression of active TGF-beta1. beta-gal-positive cells expressing mesenchymal markers accumulated within 3 weeks of in vivo TGF-beta1 expression. The increase in vimentin-positive cells within injured lungs was nearly all beta-gal-positive, indicating epithelial cells as the main source of mesenchymal expansion in this model. Ex vivo, primary alveolar epithelial cells cultured on provisional matrix components, fibronectin or fibrin, undergo robust EMT via integrin-dependent activation of endogenous latent TGF-beta1. In contrast, primary cells cultured on laminin/collagen mixtures do not activate the TGF-beta1 pathway and, if exposed to active TGF-beta1, undergo apoptosis rather than EMT. These data reveal alveolar epithelial cells as progenitors for fibroblasts in vivo and implicate the provisional extracellular matrix as a key regulator of epithelial transdifferentiation during fibrogenesis.

ADAM10-mediated Release of Complement Membrane Cofactor Protein during Apoptosis of Epithelial Cells

Membrane cofactor protein CD46 controls complement activation on cells, is a receptor for several pathogens, and modulates immune responses by affecting CD8(+) T cells. Cells can release CD46 in an intact form on membrane vesicles and in a truncated form by a metalloproteolytic cleavage. The mechanism of shedding and its relationship to cell physiology has remained unclear. We have found using RNA interference analysis that a disintegrin and metalloproteinase (ADAM) 10 is responsible for the regulated shedding of the ectodomain of CD46 in apoptotic cells. The shedding of CD46 was initiated with staurosporine and UVB. Exposure of cell cultures to either UVB or staurosporine resulted in changes of cell morphology and detachment of cells from their matrices within 8-24 h. During this process CD46 was released both in apoptotic vesicles (vCD46) and proteolytically (sCD46) into the medium. Both the metalloproteinase inhibitor GM6001 and RNA interference of ADAM10 completely prevented the release of sCD46 and increased the expression of vCD46 on HaCaT cell vesicles, suggesting that ADAM10 releases sCD46 from the apoptotic vesicles. To explore whether the release of sCD46 is associated with apoptosis we analyzed the effects of caspase inhibitors. As expected, the inhibition of caspase activity attenuated the characteristic features of apoptosis and also decreased the release of sCD46. Our results reveal ADAM10 as an important regulator of CD46 expression during apoptosis. The ADAM10-mediated release of CD46 from apoptotic vesicles may represent a form of strategy to allow restricted complement activation to deal with modified self.