The proliferative responses of porcine thyroid follicular cells to epidermal growth factor and thyrotrophin reflect the autocrine production of transforming growth factor-β1

1996 ◽  
Vol 148 (1) ◽  
pp. 87-94 ◽  
Author(s):  
A J Cowin ◽  
E L Heaton ◽  
S H Cheshire ◽  
S P Bidey
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Transforming Growth Factor ◽  
Thymidine Incorporation ◽  
Transforming Growth Factor Β1 ◽  
Follicular Cells ◽  
Stimulatory Action ◽  
Thyroid Follicular Cells ◽  
Epidermal Growth ◽  
Tgf Β1

Abstract The present study has investigated an involvement of autocrine transforming growth factor-β1 (TGF-β1) in regulating the proliferative response of porcine thyroid follicular cells (TFCs) to epidermal growth factor (EGF) and TSH. Primary monolayer TFC cultures exposed to EGF over the range 0–0·4 nmol/l showed a dose-dependent increase in [methyl-3H]thymidine incorporation, whereas higher EGF doses were associated with a reduction in the level of [methyl-3 H]thymidine incorporation. TGF-β immunoneutralisation had little effect on the stimulatory action of low EGF doses, but led to an increase in [methyl-3H]thymidine incorporation at higher EGF levels. In TFC cultures exposed to TSH, the level of [methyl-3H]thymidine incorporation attained at a dose of 1 U TSH/1 was enhanced in the presence of TGF-β1 antiserum, although the similar stimulatory effect of 8-bromo cAMP was unaffected. Treatment of TFCs with phorbol 12-myristate 13-acetate (8 nmol/l) to activate protein kinase C (PKC) led to an enhanced incorporation of [methyl-3H]thymidine which was increased further after neutralisation of endogenous TGF-β1. While confirming, therefore, a role for autocrine TGF-β1 in maintaining control of TFC DNA synthesis in vitro, these findings provide evidence that an increase in the availability of autocrine TGF-β1 effected by EGF and TSH may play an instrumental role in limiting the cellular hyperplasia induced by these factors within the thyroid follicular microenvironment. Moreover, the present data also suggest that the availability of active autocrine TGF-β1 to TFCs under such conditions may be dependent upon a PKC-mediated mechanism. Journal of Endocrinology (1996) 148, 87–94

Porcine thyroid follicular cells in monolayer culture activate the iodide-responsive precursor form of transforming growth factor-β1

1995 ◽  
Vol 144 (1) ◽  
pp. 67-73 ◽  
Author(s):  
A J Cowin ◽  
S P Bidey
Keyword(s):  
Growth Factor ◽  
Monolayer Culture ◽  
Transforming Growth Factor ◽  
Thymidine Incorporation ◽  
Active Form ◽  
Transforming Growth Factor Β1 ◽  
Biologically Active ◽  
Follicular Cells ◽  
Thyroid Follicular Cells ◽  
Tgf Β1

Abstract The release of latent transforming growth factor-β1 (TGFβ1), and conversion to the biologically active peptide, has been investigated in porcine thyroid follicular cells maintained in primary monolayer culture. Analysis by radioreceptor assay of medium conditioned for 72 h by subconfluent thyroid monolayers showed that a high proportion of the expressed TGF-β1 peptide was in the active form. Medium conditioned by iodide (10 aμmol/l)treated follicular cells contained higher levels of both active and total TGF-β1 than were present in medium conditioned by untreated cells. Exposure of cells to iodide also led to a marked decrease in [methyl-3H]thymidine incorporation that was relieved by immunoadsorption with a neutralizing antiserum against the active form of TGFβ1. Inclusion of a low dose (80 units/l) of porcine plasmin led to a small increase in incorporation of [methyl3H]thymidine, while higher doses of plasmin (1250–5000 units/l) or plasminogen (100 mg/l) significantly reduced [methyl-3H]thymidine incorporation. This inhibition was effectively reversed by immunoadsorption of TGF-β1 from the medium during the test incubations. The study therefore provides direct evidence for a stimulatory role of thyroidal iodide in enhancing the release of latent TGF-β1 peptide, and suggests that in normal thyroid follicular cells, as in other TGF-β1 producing epithelia, post-secretory processing to the biologically active molecule occurs through an endogenous cellular mechanism. It appears likely that plasmin, generated locally within the thyroid follicular microenvironment, may play a fundamental role in effecting this conversion. Journal of Endocrinology (1995) 144, 67–73

Transforming growth factor-β1 production in porcine thyroid follicular cells: regulation by intrathyroidal organic iodine

1992 ◽  
Vol 9 (3) ◽  
pp. 197-205 ◽  
Author(s):  
A. J. Cowin ◽  
J. R. E. Davis ◽  
S. P. Bidey
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
Thymidine Incorporation ◽  
Control Level ◽  
Cdna Probe ◽  
Transforming Growth Factor Β1 ◽  
Follicular Cells ◽  
Thyroid Follicular Cells ◽  
Tgf Β1

ABSTRACT The present studies have demonstrated the production of transforming growth factor-β1 (TGF-β1) by porcine thyroid follicular cells (TFCs) maintained in vitro as subconfluent monolayers, and have confirmed a stimulatory effect of iodide on thyroidal TGF-β1 mRNA and peptide release. RNA extracted from TFCs maintained in the absence of iodide contained a 2·5 kb transcript which hybridized specifically with a cDNA probe for human TGF-β1, and which showed an approximate doubling in intensity in cells exposed to 10 μmol NaI/l. In the presence of the anti-thyroid thionamide drug methimazole (MMI; 1 mmol/l), the action of iodide on TGF-β1 mRNA was attenuated, although MMI alone had no effect on the control level of TGF-β1 mRNA. The TGF-β1 peptide content of TFC-conditioned media (TFC-CM) was assessed using the fetal mink lung cell line Mv1 Lu, in which activated TGF-β1 specifically suppresses trichloroacetic acid-precipitable [methyl-3H]thymidine incorporation. Newly conditioned TFC-CM stimulated [methyl-3H]thymidine incorporation into Mv1Lu cells, but after heat treatment to inactivate growth stimulators and activate the latent TGF-β1 component this medium inhibited [methyl-3H]thymidine incorporation. This inhibitory effect was prevented by immunoadsorption of TFC-CM with a TGF-β1-neutralizing antiserum, confirming the specificity of the inhibitory response. The inhibitory activity of TFC-CM was increased when the TFCs were preincubated with 10 μmol NaI/l, and lost when TFCs were exposed to MMI. In conclusion, TFCs produce TGF-β1 mRNA and TGF-β1 peptide, which are both increased by iodide treatment in vitro. The anti-thyroid effects of MMI may, at least in part, be mediated by a decrease in TFC-derived TGF-β1 production.

Transforming growth factor-β1 synthesis in human thyroid follicular cells: differential effects of iodide and plasminogen on the production of latent and active peptide forms

1994 ◽  
Vol 141 (1) ◽  
pp. 183-190 ◽  
Author(s):  
A J Cowin ◽  
S P Bidey
Keyword(s):  
Growth Factor ◽  
Dna Synthesis ◽  
Conditioned Medium ◽  
Transforming Growth Factor ◽  
Thymidine Incorporation ◽  
Transforming Growth Factor Β1 ◽  
Human Thyroid ◽  
Follicular Cells ◽  
Thyroid Follicular Cells ◽  
Tgf Β1

Abstract The present study has investigated the relative levels and interconversion of latent and active forms of transforming growth factor-β1 (TGF-β1) in human thyroid follicular cell cultures derived from sporadic non-toxic goitres. Northern blotting of RNA extracted from 72-h cultures revealed a 2·5 kb mRNA transcript hybridizing with a cDNA probe for latent TGF-β1, the intensity of which was doubled in cells exposed to Nal (10 μmol/l). Radioreceptor assay of follicular cell-conditioned medium for TGF-β1 content confirmed a similar enhancing effect of iodide. The endogenous active component of TGF-β1 present in conditioned medium represented only a minor fraction of the total TGF-β1 content, this fraction was not enhanced by exposure of follicular cells to iodide. The low level of endogenous active TGF-β1 in medium conditioned by either control or iodide-treated cells was confirmed by immunoadsorption with a precipitating antiserum against active TGF-β1, when such cells failed to show a reversal of the iodide-induced decrease in [methyl-3H]thymidine incorporation into trichloroacetic acid-precipitable material. In contrast to the inhibitory effect of iodide on de novo DNA synthesis, which appeared not to reflect an increase in active TGF-β1, the inhibitory effects of plasminogen (100 mg/l) or plasmin (2000 U/l) on [methyl-3H]thymidine incorporation into thyroid cells were reversible by TGF-β1 immunoadsorption. This provides evidence that the plasmin-mediated inhibition of DNA synthesis in thyroid follicular cells may be attributed to the growth-regulating action of an increased level of activated TGF-β1. The findings of this study therefore provide evidence that (i) human thyroid follicular cells are potentially capable of activating locally derived latent TGF-β1, (ii) an increase in thyroidal TGF-β1 mRNA and latent TGF-β1 peptide availability, following exposure of cells to iodide, is not accompanied by a corresponding increase in active TGF-β1, and (iii) within the thyroid gland, as in other epithelial tissues, activation of endogenous TGF-β1 may be dependent upon the proteolytic actions of plasmin. Journal of Endocrinology (1994) 141, 183–190

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