Blocking of alpha 5 integrin stimulates production of TGF-beta and PAI-1 by human mesangial cells

Expression of integrin, which mediates cell-matrix interaction, is affected by several cytokines, in particular by transforming growth factor-beta (TGF-beta). However, it is unknown whether, in an opposite way, a specific integrin is involved in cytokine synthesis. We tested this hypothesis. Function-blocking anti-alpha 5 integrin (fibronectin receptor) antibody increased TGF-beta secretion in growth-arrested human mesangial cells (2.3-fold) compared with control IgG or anti-alpha v beta 3 integrin (receptor for several matrix proteins) antibody. It also increased the secretion of plasminogen activator inhibitor-1 (PAI-1), a protein associated with matrix increase, by 3.2-fold. The increase in PAI-1 secretion induced by anti-alpha 5 integrin antibody was not abrogated by anti-TGF-beta neutralizing antibody. These results indicate that function-blocking of anti-alpha 5 integrin stimulates TGF-beta as well as PAI-1 production, suggesting that alpha 5 integrin is involved in fibrotic process. Function-modulation of a specific integrin thus appears to play a role in glomerular remodeling.     

Smad3 mediates TGF-beta1 induction of VEGF production in lung fibroblasts

Transforming growth factor-beta1 (TGF-beta1) is a key factor in a variety of physiological and pathological processes. Vascular endothelial growth factor (VEGF) is a key angiogenic factor, and vascular change is one of the features of airway remodeling. We examined the effect of TGF-beta1 on VEGF production by fibroblasts from mice lacking expression of Smad2 or Smad3 as well as human lung fibroblasts treated with or without Smad2 or Smad3 siRNA. TGF-beta1 stimulated VEGF production by fibroblasts from Smad2 deficient animals and wildtype animals. In contrast, TGF-beta1 did not affect VEGF production by fibroblasts from Samd3 deficient mice. Similarly, TGF-beta1 failed to stimulate VEGF production by HFL-1 cells treated with Samd3 siRNA but significantly increased VEGF production by the cells treated with Smad2 siRNA. These result suggest that TGF-beta1 stimulation of VEGF production by fibroblasts is regulated by Smad3 but not by Smad2 signaling.     

Involvement of ERK1/2 pathway in TGF-beta1-induced VEGF secretion in normal human cytotrophoblast cells

Transforming growth factor-beta1 (TGF-beta1) plays a pivotal role in the angiogenesis during the development of placenta, but the intracellular signaling mechanism by which TGF-beta1 stimulates this process remains poorly understood. In this article, we demonstrated that exposure of normal human cytotrophoblast cells to TGF-beta1 stimulated the secretion of the VEGF gene encoding vascular endothelial growth factor, which is a key factor in angiogenesis. Meanwhile, treatment of normal human cytotrophoblast cells with TGF-beta1-induced expression of HIF-1a, the regulated subunit of hypoxia-inducible factor 1, a known transactivator of the VEGF gene. Our data indicated that TGF-beta1 induced extracellular signal- regulated kinase (ERK) 1/2 phosphorylation in normal human cytotrophoblast cells. Moreover, treating cells with PD98059, an inhibitor of ERK1/2 signaling, inhibited TGF-beta1 stimulation of VEGF secretion and HIF-1a protein expression. These data indicated that in normal human cytotrophoblast cells, TGF-beta1 induced HIF-1a-mediated VEGF secretion, and TGF-beta1-stimulated-ERK1/2 activation may be involved in this process.     

TGF-beta1 and HGF coordinately facilitate collagen turnover in subepithelial mesenchyme

Administration of tacrine (5 mg/kg ip), an anticholinesterase agent, in rats pretreated (24 h beforehand) with lithium chloride (LiCl; 12 mEq/kg ip) provides a useful experimental model to study limbic seizures and delayed hippocampal damage. Here we report Western blotting evidence demonstrating that in rat LiCl and tacrine enhance the expression of neuronal nitric oxide synthase (nNOS), but not eNOS, enzyme protein in the hippocampus during the preconvulsive period and this triggers seizures and hippocampal damage. In fact, systemic administration of 7-nitro indazole (7-NI; 50 mg/kg given ip 30 min before tacrine), a selective inhibitor of nNOS, prevented the expression of motor and electrocortical (ECoG) seizures and abolished neuronal cell death in the hippocampus. A lower dose (5 mg/kg ip) of 7-NI was ineffective. In conclusion, the present data support a role for abnormal nNOS expression in the mechanism which triggers limbic seizures and delayed excitotoxic damage in the hippocampus of rat.     

Opposing actions of Notch1 and VEGF in post-natal cardiac valve endothelial cells

The endothelium of the cardiac valves is unique compared the rest of the vasculature in its ability to undergo an endothelial-to-mesenchymal transformation (EMT) in vitro in response to transforming growth factor-β (TGF-β). EMT is a critical event during embryonic valve development, and both VEGF-A and Notch1 have been shown to function in this process. Here we investigate the effects of VEGF-A and Notch1 on EMT in clonal endothelial cell (EC) populations isolated from adult aortic valve leaflets. VEGF-A inhibited TGF-β-induced EMT. Endothelial growth, however, was not affected by VEGF-A or TGF-β. A positive role for Notch1 was revealed in three experiments: (1) TGF-β induced Notch1 mRNA in valve ECs, (2) a γ-secretase inhibitor of Notch1 signaling blocked EMT, and (3) overexpression of a ligand-independent form of Notch1 induced EMT. These results demonstrate, for the first time, that VEGF-A and Notch1 play opposing roles in regulating EMT in post-natal valve endothelium.     

Stimulation by glutamine and proline of HGF production in hepatic stellate cells

Amino acids regulate cellular functions in a variety of cell types. Most notably, leucine stimulates protein production through the mammalian target of rapamycin (mTOR)-dependent signaling pathway. We investigated the effect of amino acids on hepatocyte growth factor (HGF) production. Treatment with glutamine and proline, as well as leucine, increased HGF levels in the culture medium of a rat hepatic stellate cell clone in a dose-dependent manner. Up-regulation of phosphorylation of 70 kDa ribosomal protein S6 kinase and eukaryotic initiation factor 4E-binding protein 1 was not apparent in the cells after treatment with glutamine or proline. When rats received injections of glutamine or proline, hepatic and circulating HGF levels increased and peaked around 12 h after treatment. Glutamine and proline may have the potential to stimulate HGF production but the mechanism underlying this stimulation seems not to be through the mTOR-dependent signaling pathway.     

TGF-beta 1 prevents the noncognate maturation of human dendritic Langerhans cells

TGF-beta 1 is critical for differentiation of epithelial-associated dendritic Langerhans cells (LC). In accordance with the characteristics of in vivo LC, we show that LC obtained from human monocytes in vitro in the presence of TGF-beta 1 1) express almost exclusively intracellular class II Ags, low CD80, and no CD83 and CD86 Ags and 2) down-regulate TNF-RI (p55) and do not produce IL-10 after stimulation, in contrast to dermal dendritic cells and monocyte-derived dendritic cells. Surprisingly, while LC exhibit E-cadherin down-regulation upon exposure to TNF-alpha and IL-1, TGF-beta 1 prevents the final LC maturation in response to TNF-alpha, IL-1, and LPS with respect to Class II CD80, CD86, and CD83 Ag expression, loss of FITC-dextran uptake, production of IL-12, and Ag presentation. In sharp contrast, CD40 ligand cognate signal induces full maturation of LC and is not inhibited by TGF-beta 1. The presence of emigrated immature LCs in human reactive skin-draining lymph nodes provides in vivo evidence that LC migration and final maturation may be differentially regulated. Therefore, due to the effects of TGF-beta 1, inflammatory stimuli may not be sufficient to induce full maturation of LC, thus avoiding potentially harmful immune responses. We conclude that TGF-beta 1 appears to be responsible for both the acquisition of LC phenotype, cytokine production pattern, and prevention of noncognate maturation.     

Propolis and some of its constituents down-regulate DNA synthesis and inflammatory cytokine production but induce TGF-beta1 production of human immune cells

Propolis, the resinous product collected by honey bees from plants, is used as folk medicine since ancient time. Recently, immunoregulatory and anti-inflammatory properties of propolis have been published. The detailed mechanisms of actions of propolis and its components on immune cells, however, are still unknown. Therefore, we studied the effects of different propolis extracts, of the flavonoids hesperidin and quercetin as well as of caffeic acid phenethyl ester (CAPE) on basic human immune cell functions. In detail, we measured the effects on DNA synthesis and production of different types of cytokines, namely IL-1beta, IL-12, IL-2, IL-4, IL-10 and TGF-beta1, of mitogen-activated peripheral blood mononuclear cells (PBMC) as well as of purified T lymphocytes. Our data clearly show that propolis as well as its constituents studied are capable of dose-dependently suppressing phythemagglutinin (PHA)-induced DNA synthesis of PBMC and T cells. Moreover, cytokines produced by monocytes/macrophages (IL-1beta, IL-12), by Th1 type (IL-2) as well as Th2 type (IL-4) lymphocytes were found to be also suppressed, whereas the production of TGF-beta1 by T regulatory cells was ascertained to be increased. These data convincingly demonstrate that propolis has a direct regulatory effect on basic functional properties of immune cells which may be mediated by the Erk2 MAP-kinase signal pathway. Thus, the bee product propolis can be considered as a powerful natural anti-inflammatory medicine influencing different types of immune-responses probably via immunoregulatory T cells.     

TGF-beta1 on osteoimmunology and the bone component cells

TGF-β1 is an immunoregulatory cytokine that regulates immune cell proliferation, survival, differentiation, and migration. Compelling evidence has demonstrated a strong association between the immune and skeletal systems (so called Osteoimmunology), such as the critical role of TGF-β1 in the development and maintenance of the skeletal tissue. This review provides an overview of the mechanisms in which TGF-β1 interacts with bone component cells, such as osteoblasts, osteoclasts, chondrocytes, mesenchymal stem cells, and hematopoietic stem cells, in concert with other cytokines and hormones.     

Leucine stimulates HGF production by hepatic stellate cells through mTOR pathway

Branched chain amino acids modulate various cellular functions in addition to providing substrates for the production of proteins. We examined the mechanism underlying the stimulation by leucine of hepatocyte growth factor (HGF) production by hepatic stellate cells. Both p70 S6 kinase activity and phosphorylation of eukaryotic initiation factor 4E-binding protein 1 (4E-BP1) were up-regulated rapidly after leucine treatment of a rat hepatic stellate cell clone. No such activation was observed following treatment with valine or isoleucine. Rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), suppressed leucine-induced activation of p70 S6 kinase and 4E-BP1 and negated the stimulatory effect of leucine on HGF production. An mTOR-dependent signaling pathway mediates the stimulatory effect of leucine on the production of HGF by hepatic stellate cells.     

Fractalkine/CX3CL1 production by human airway smooth muscle cells: induction by IFN-gamma and TNF-alpha and regulation by TGF-beta and corticosteroids

Chemokine synthesis by airway smooth muscle cells (ASMC) may be an important process underlying inflammatory cell recruitment in airway inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD). Fractalkine (FKN) is a recently described CX(3)C chemokine that has dual functions, serving as both a cell adhesion molecule and a chemoattractant for monocytes and T cells, expressing its unique receptor, CX(3)CR1. We investigated FKN expression by human ASMC in response to the proinflammatory cytokines IL-1beta, TNF-alpha, and IFN-gamma, the T helper 2-type cytokines IL-4, IL-10, and IL-13, and the fibrogenic cytokine transforming growth factor (TGF)-beta. Neither of these cytokines alone had any significant effect on ASMC FKN production. Combined stimulation with IFN-gamma and TNF-alpha induced FKN mRNA and protein expression in a time- and concentration-dependent manner. TGF-beta had a significant inhibitory effect on cytokine-induced FKN mRNA and protein expression. Dexamethasone (10(-8)-10(-6) M) significantly upregulated cytokine-induced FKN mRNA and protein expression. Finally, we used selective inhibitors of the mitogen-activated protein kinases c-Jun NH(2)-terminal kinase (JNK) (SP-610025), p38 (SB-203580), and extracellular signal-regulated kinase (PD-98095) to investigate their role in FKN production. SP-610025 (25 microM) and SB-203580 (20 microM), but not PD-98095, significantly attenuated cytokine-induced FKN protein synthesis. IFN-gamma- and TNF-alpha-induced JNK phosphorylation remained unaltered in the presence of TGF-beta but was inhibited by dexamethasone, indicating that JNK is not involved in TGF-beta- or dexamethasone-mediated regulation of FKN production. In summary, FKN production by human ASMC in vitro is regulated by inflammatory and anti-inflammatory factors.     

Ganoderma lucidum suppresses angiogenesis through the inhibition of secretion of VEGF and TGF-beta1 from prostate cancer cells

Ganoderma lucidum (G. lucidum) is a popular medicinal mushroom that has been used as a home remedy for the general promotion of health and longevity in East Asia. The dried powder of G. lucidum, which was recommended as a cancer chemotherapy agent in traditional Chinese medicine, is currently popularly used worldwide in the form of dietary supplements. We have previously demonstrated that G. lucidum induces apoptosis, inhibits cell proliferation, and suppresses cell migration of highly invasive human prostate cancer cells PC-3. However, the molecular mechanism(s) responsible for the inhibitory effects of G. lucidum on the prostate cancer cells has not been fully elucidated. In the present study, we examined the effect of G. lucidum on angiogenesis related to prostate cancer. We found that G. lucidum inhibits the early event in angiogenesis, capillary morphogenesis of the human aortic endothelial cells. These effects are caused by the inhibition of constitutively active AP-1 in prostate cancer cells, resulting in the down-regulation of secretion of VEGF and TGF-beta1 from PC-3 cells. Thus, G. lucidum modulates the phosphorylation of Erk1/2 and Akt kinases in PC-3 cells, which in turn inhibits the activity of AP-1. In summary, our results suggest that G. lucidum inhibits prostate cancer-dependent angiogenesis by modulating MAPK and Akt signaling and could have potential therapeutic use for the treatment of prostate cancer.     

TGF-beta and IL-13 synergistically increase eotaxin-1 production in human airway fibroblasts

Chronic diseases may involve an "innate" response followed by an adaptive immune response, of a Th1 or Th2 variety. Little is known regarding the interactions of these responses. We hypothesized that TGF-beta1 (innate response factor associated with wound repair) in combination with IL-13 (Th2 factor) might augment inflammatory processes associated with asthma. Airway fibroblasts were cultured from asthmatic subjects and normal controls. These fibroblasts were exposed to TGF-beta1 and IL-13 alone or in combination, and eotaxin-1 expression and production were evaluated. At 48 h, eotaxin-1 production was markedly increased with the combination of TGF-beta1 and IL-13 (p < 0.0001) compared with either stimulus alone. mRNA increased slightly at 1 h with IL-13 or TGF-beta1 plus IL13, peaked, and became significantly increased over IL-13 alone at 24 h. Protein was measurable from 6 h with IL-13 and TGF-beta1 plus IL-13, but greater levels were measured over time with the combination. Actinomycin ablated the increase in mRNA and protein seen with IL-13 alone and with TGF-beta1 plus IL-13. Cycloheximide blocked the increase in mRNA at 6 h in both conditions, but also blocked the increase at 24 h with TGF-beta1 plus IL-13. STAT-6 was rapidly activated with both IL-13 and the combination, without difference. Finally, eotaxin-1-positive fibroblasts were identified in severe asthma biopsies in greater numbers than in normals. These results support the concept that interactions of innate and adaptive immune systems may be important in promoting the tissue eosinophilia of asthma, particularly in those with more severe disease.     

Regulation of TGF-beta1/MAPK-mediated PAI-1 gene expression by the actin cytoskeleton in human mesangial cells

The importance of transforming growth factor-beta1 (TGF-beta1) in plasminogen activator inhibitor-1 (PAI-1) gene expression has been established, but the precise intracellular mechanisms are not fully understood. Our hypothesis is that the actin cytoskeleton is involved in TGF-beta1/MAPK-mediated PAI-1 expression in human mesangial cells. Examination of the distributions of actin filaments (F-actin), alpha-actinin, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) by immunofluorescence and immunoprecipitation revealed that ERK and JNK associate with alpha-actinin along F-actin and that TGF-beta1 stimulation promote the dissociation of ERK and JNK with F-actin. Disassembly of the actin cytoskeleton inhibited phosphorylation of ERK and JNK and modulated PAI-1 expression and promoter activity under both basal and TGF-beta1-stimulated conditions. Stabilizing actin prevented dephosphorylation of ERK and JNK. ERK and JNK inhibitors and overexpressed dominant negative mutants antagonized the ability of TGF-beta1 to increase PAI-1 expression and promoter activity. Disassembly of F-actin also inhibited AP-1 DNA binding activity as determined by electrophoretic mobility shift assay using AP-1 consensus oligonucleotides derived from human PAI-1 promoter. F-actin stabilization prevented loss of AP-1 DNA binding activity. Therefore, changes in actin cytoskeleton modulate the ability of TGF-beta1 to stimulate PAI-1 expression through a mechanism dependent on the activation of MAPK/AP-1 pathways.     

Up-regulation of production of TGF-beta and IL-4 and down-regulation of IL-6 by apoptotic human bronchial epithelial cells

Human bronchial epithelial cells secrete cytokines that play a role in immune responses in the lung. However, the roles of these cytokines in regulating epithelial repair following acute lung injury are largely unknown. Responses to injury include hyperplasia of epithelial cells and squamous metaplasia. The resolution stage is characterized by discontinuation of hyperplasia. Apoptosis is considered to be the most efficient mechanism of removal of unwanted cells without causing inflammation. The presence of TGF-beta1 increases apoptosis, induces squamous metaplasia and inhibits proliferation of airway epithelial cells. Interleukin-4 increases the ability of macrophages to phagocytose epithelial cells and produce inflammatory cytokines. The purpose of this study was to investigate the hypothesis that apoptotic lung epithelial cells produce cytokines, which could act in an autocrine manner to control hyperplasia and induce squamous differentiation following acute lung injury. A bronchial epithelial cell line (16 HBE) was used as an in vitro model, to study the production of TGF-beta, IL-4 and IL-6 by lung epithelial cells undergoing apoptosis. Apoptotic and live cells were sorted on the basis of bright and negative staining with FITC-conjugated Annexin V, respectively. Intracellular IL-6, TGF-beta and IL-4 was measured using flow cytometric techniques. Electron microscopy, immunohistochemistry and ELISA were used as supportive techniques. Apoptotic cells produced significantly more TGF-beta and IL-4 (but less IL-6) than viable cells. Increased production of TGF-beta and IL-4 by epithelial cells undergoing apoptosis may contribute to the inhibition of proliferation, squamous metaplasia, and reduction of the inflammatory response in acute lung injury.     

Superoxide dismutase mimetic reduces hypoxia-induced O2*-, TGF-beta, and VEGF production by macrophages

Normal tissue injury poses a major limitation to the success of radiation therapy (RT) in the treatment of solid tumors. We propose that radiation-induced lung injury is a result of chronic oxidative stress propagated by hypoxia-induced macrophage activation and cytokine production. Therefore, the objective of our study was two-fold. First, in vivo studies were conducted to support our hypothesis suggesting radiation injury is characterized by chronic hypoxia associated with increased macrophage infiltration/activation and pro-fibrogenic/angiogenic cytokine production. Second, we investigated the proposed mechanism of radiation injury in vitro. We demonstrate that hypoxia (0.5% O2) elicits macrophages to produce higher levels of O2*-, TGF-beta, and VEGF than normoxia. Our hypothesis that O2*- is contributing to increased macrophage cytokine production was supported by a significant reduction in TGF-beta and VEGF when redox signaling was minimized using a small molecular weight metalloporphyrin antioxidant, MnTE-2-PyP5+ .