David Danielpour

Regulation of alveolar macrophage transforming growth factor-beta secretion by corticosteroids in bleomycin-induced pulmonary inflammation in the rat.

In a model of pulmonary inflammation and fibrosis induced by the antineoplastic antibiotic, bleomycin, we previously demonstrated that TGF-beta was markedly elevated within 7 d of bleomycin administration. At the time of maximal TGF-beta production, TGF-beta 1 was localized by immunohistochemistry to be present almost exclusively in alveolar macrophages. In this study, we have demonstrated that alveolar macrophages stimulated by bleomycin-induced injury secrete large quantities of biologically active TGF-beta 1 when explanted into tissue culture. However, alveolar macrophages from normal saline-treated rats secrete small quantities of biologically inactive TGF-beta. In contrast, splenic macrophages secrete large quantities of inactive TGF-beta and are unaffected by the intratracheal bleomycin treatment. High doses of the corticosteroid methylprednisolone given intramuscularly before and concomitantly with bleomycin administration prevented the influx of alveolar macrophages into the lungs, diminishing both the number of macrophages present in the alveoli and the total lung content of TGF-beta. However, the rate of secretion of TGF-beta by alveolar macrophages recovered from the alveoli was unchanged after corticosteroid treatment. When activated alveolar macrophages were cultured in the presence of several concentrations of dexamethasone that completely suppressed IL-1 secretion, little effect on TGF-beta secretion was observed. The findings in this study demonstrate that during bleomycin-induced injury, alveolar macrophages not only secrete large quantities of active TGF-beta 1, but are a predominant source of the enhanced TGF-beta response seen in this model. Furthermore, the alveolar macrophage secretion of TGF-beta is not inhibited by the presence of high concentrations of corticosteroids.

Aberrant TGF-β Production and Regulation in Metastatic Malignancy

AbstractWe have examined the possible role of transforming growth factor-β (TGF-β) in metastatic malignancy by analyzing the production and activation of TGF-β, and -β2 and the regulation of TGF-β-responsive genes in oncogene-transformed metastatic fibrosarcomas. All transformed lines derived from either 10T1/2; or N1H 3T3 bv either H-ras or protein-kinase encoding oncogenes produced more TGF-β than parental cells. However, onlv highlv metastatic fibrosarcomas secreted activated TGF-β at rates that were greater than parental fibroblasts. Immunohistochemical staining for TGF-β, showed widespread intra- and extracellular distribution in metastatic lung nodules and adjacent tissue. Cells isolated from tumors successfully metastasizing to the lung had TGF-β1, mRNA levels which were increased 19-fold over in ritro controls. Despite the greatly enhanced rate of secretion of activated TGF-β, metastatic cells exhibited markedly altered responses of TGF-β1, and TGF-β2., being unable to either increase collagen sec...

The role of transforming growth factor-β1, -β2, and -β3 in androgen-responsive growth of NRP-152 rat prostatic epithelial cells

We have investigated the role of autocrine/paracrine TGF‐β secretion in the regulation of cell growth by androgens as demonstrated by its inhibition by two androgen response modifiers; the nonsteroidal antiandrogen hydroxyflutamide (OHF), believed to act by inhibiting androgen binding to androgen receptors, or finasteride, an inhibitor of 5α‐reductase, the enzyme necessary for the conversion of testosterone to 5α‐dihydrotestosterone (DHT), using the nontumorigenic rat prostatic epithelial cell line NRP‐152. Growth of these cells was stimulated three‐ to sixfold over control by either testosterone or DHT under serum‐free culture conditions. This was accompanied by a two‐ to threefold decrease in the secretion rate of TGF‐β1, ‐β2, and ‐β3. Finasteride reversed the ability of testosterone but not DHT to stimulate growth and downregulate expression of TGF‐β1, ‐β2, and ‐β3 in a dose‐dependent fashion, suggesting that this activity of testosterone required its conversion to DHT. OHF antagonized the stimulatory effects of DHT on NRP‐152 cell growth but could reverse the inhibitory effects of DHT only on TGF‐β2 and TGF‐β3 and not TGF‐β1 secretion. This suggests that either TGF‐β1 regulation by DHT or the androgen antagonism of OHF occurs independent of androgen receptor binding. Neutralizing antibodies to TGF‐β (pantropic and isoform‐specific) were able to block the ability of finasteride to antagonize the effects of testosterone nearly completely while only partially inhibiting the antiandrogenic effects of OHF. Thus, the ability of androgens to stimulate growth of NRP‐152 cells involves the downregulation of the production of TGF‐β1, ‐β2, and ‐β3 in addition to other growth‐stimulatory mechanisms. J. Cell. Physiol. 175:184–192, 1998. Published 1998 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.

Wound healing in the fetus. Possible role for inflammatory macrophages and transforming growth factor-beta isoforms.

Macrophages are believed to play a crucial role in wound healing by synthesizing and secreting numerous cytokines. Some of these cytokines, such as transforming growth factor‐β and tumor necrosis factor‐α, promote fibrosis and repair. We have shown that macrophages are recruited to sterile fetal wounds and have the potential to regulate repair by synthesizing transforming growth factor‐β1, transforming growth factor‐β2, and tumor necrosis factor‐α. Transforming growth factor‐β was present in fetal lamb wounds in higher amounts than in adult sheep wounds. Furthermore, the concentrations and ratios of the transforming growth factor‐β isoforms in wounds that healed without scarring were different from those in wounds that scarred; transforming growth factor‐β2 was highest in fetal wounds that did not scar and lowest in adult wounds. These data suggest that concentrations of transforming growth factor‐β isoforms rather than total transforming growth factor‐β concentration may be important in the regulation of fibrosis in prenatal and postnatal wound healing.

Regulation of Expression of Transforming Growth Factor-β2 by Transforming Growth Factor-β Isoforms is Dependent upon Cell Type

AbstractThe effect of three different isoforms of transforming growth factor-β (TGF-β) on the expression of TGF-β2 mRNA was studied in several continuous tumor cell lines. As previously reported for the mouse fibroblast cell line AKR-2B, the expression of TGF-β2 mRNA transcripts of 5.4, 4.7, 3.7 and 3.0 kb was decreased after a 24 hr treatment with 5ng/ml of TGF-β1, TGF-β2 or TGF-β3. In A549, HBL-100 and BSC-1 epithelial cell lines, five distinct TGF-β2 mRNA transcripts of 5.8, 5.1, 4.0, 3.8 and 2.8 kb were detected by Northern blot analysis. Treatment of these cells with TGF-β1, TGF-β2 or TGF-β3 for 24 hr resulted in a 2–3 fold increase in the 5.8, 4.0 and 3.8 kb transcripts, with little detectable change in abundance of the 5.1 and 2.8 kb transcripts. The effect of the TGF-β proteins was dose (5 ng/ml) and time (3–6 hr) dependent. A similar 2–3 fold increase in the level of secreted TGF-β2 was observed following treatment of A549 cells with TGF-β1. Basal level and induced expression of TGF-β2 mRNA in re...

Interleukin-2 suppresses activated macrophage intracellular killing activity by inducing macrophages to secrete TGF-β

Phorbol myristate acetate (PMA) treatment of an EL‐4 thymoma cell line (EL‐4farrar) induced secretion of a factor that inhibited intracellular killing of Leishmania major amastigotes by activated macrophages. Analysis of the cytokines produced by EL‐4 cells after PMA stimulation identified interleukin‐2 (IL‐2, 2500 U/ml), IL‐4 (1280 U/ml), interferon‐γ (IFN‐γ; 100 U/ml), and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF; 50 U/ml). Neither tumor necrosis factor nor transforming growth factor β (TGF‐β) was detected. Each of the cytokines present in EL‐4 fluids was assessed for capacity to activate macrophages for destruction of parasites or to suppress intracellular killing. IFN‐γ and GM‐CSF both activated macrophages to kill Leishmania; I L‐2 and IL‐4 had no activity for induction of this anti‐microbial effector function. IL‐2 and IL‐4 were tested for their capacity to inhibit lymphokine‐ or IFN‐γ‐induced destruction of L. major by macrophages: IL‐4 was ineffective, but IL‐2 markedly suppressed the activation of macrophages for intracellular killing. Addition of ≥ 10 U/ml of IL‐2 at the time of infection, or up to 4 h before, blocked up to 100% of the capacity of activated macrophages to kill intracellular amastigotes. Immunoaffinity treatment of EL‐4 fluids with anti‐IL‐2 antibody resulted in >80% reduction in suppression of intracellular killing. The suppressive effects of IL‐2 were not direct, but mediated by TGF‐β. IL‐2 induced resident peritoneal macrophages to secrete >5000 pg/ml TGF‐β1, a quantity that is > 500‐fold higher than constitutive background levels (20–40 pg/ml) and is sufficient to block intracellular killing activities. This increase in secretion of TGF‐β was not dependent increases in TGF‐β1 mRNA. Treatment of cultures with EL‐4 fluids or recombinant IL‐2 in the presence of antibody to TGF‐β1 blocked the suppressive activity of both. Thus, IL‐2 was the major suppressor factor in EL‐4 fluids, and it acted indirectly through the induction and autocrine action of TGF‐β. J. Leukoc. Biol. 55: 81–90; 1994.