Opposite and independent actions of cyclic AMP and transforming growth factor β in the regulation of type 1 plasminogen activator inhibitor expression

Abstract

We have investigated the mechanisms by which type 1 plasminogen activator inhibitor (PAI-1) is regulated by transforming growth factor beta (TGF-beta) and by epidermal growth factor (EGF) in CCL64 mink lung epithelial cells, BSC-1 monkey kidney epithelial cells, mouse embryo fibroblast (AKR-2B 84A) cells and normal rat kidney fibroblasts (NRK). TGF-beta increases PAI-1 expression in all four cell lines, and EGF acts synergistically with TGF-beta to increase PAI-1 expression in CCL64 cells but not in the other three cell lines. Here we show that PAI-1 expression can be regulated independently through two different signal transduction pathways. One pathway involves protein kinase C and is stimulated by the tumour promoter phorbol myristate acetate (PMA). Whereas preincubation with PMA completely eliminated PMA-induced PAI-1 synthesis and secretion in both CCL64 and BSC-1 cells, this treatment had no effect on TGF-beta- and EGF-induced PAI-1 levels. Therefore we conclude that protein kinase C does not mediate the effects of either EGF or TGF-beta on PAI-1 expression. The expression of PAI-1 was decreased by agents increasing intracellular cyclic AMP: (cAMP) cholera toxin, forskolin and dibutyryl cAMP lowered both the basal level and the TGF-beta- and PMA-induced levels of PAI-1 expression. These effects of cAMP-elevating agents and of TGF-beta on PAI-1 protein synthesis were also reflected in changes in TGF-beta-induced PAI-1 gene transcription, as measured by nuclear run-on. These results show that PAI-1 gene expression is sensitive to high levels of intracellular cAMP and that this effect occurs at the transcriptional level. Although increased intracellular cAMP concentrations decrease the absolute level of PAI-1 expression, the ability of TGF-beta and EGF to induce PAI-1 gene expression is unchanged. These results are discussed in relation to the observation that sensitivity to cAMP is a common feature of TGF-beta-regulated genes.

Role of hypoxia and cAMP in the transdifferentiation of human fetal cardiac fibroblasts: Implications for progression to scarring in autoimmune‐associated congenital heart block

“…The latter finding was of particular interest and unexpected, because adrenomedullin is known to raise the levels of cAMP and has been reported to serve as an inhibitor of matrix synthesis (19)(20)(21)(22).…”

A common response element mediates differential effects of phorbol esters and forskolin on type‐1 plasminogen activator inhibitor gene expression in human breast carcinoma cells

“…PMA induction of PAI-1 gene transcription and mRNA level has been demonstrated in the cell lines RD, HepG2, HT-1080 and NRK, and in synovial fibroblast cells (Mayer et al, 1988;Bosma and Kooistra, 1991;Uhl et al, 1991;Bergonzelli et al, 1992 ;Thalacker and Nilsen-Hamilton, 1992). Hormones acting with cAMP as a second messenger have been found to have a suppressive effect on PAI-1 gene expression (see reviews by Andreasen et al, 1990;Loskutoff et al, 1991).…”

“…CAMP down-regulates PAI-1 gene transcription and the mRNA level in the cell lines HTC, HT-1080 andNRK (Heaton andGeorg et al, 1990;Bergonzelli et al, 1992;Heaton et al, 1992;Thalacker and Nilsen-Hamilton, 1992). Moreover, cAMP inhibits the PMA-induced increase in PAI-1 gene transcription in HT-1080 and NRK cells (Bergonzelli et al, 1992;Thalacker and Nilsen-Hamilton, 1992). An exception is primary cultures of rat hepatocytes, in which cAMP induces PAI-1 (Heaton et al, 1989).…”

“…Hormones acting with cAMP as a second messenger have been found to have a suppressive effect on PAI-1 gene expression (see reviews by Andreasen et al, 1990;Loskutoff et al, 1991). CAMP down-regulates PAI-1 gene transcription and the mRNA level in the cell lines HTC, HT-1080 andNRK (Heaton andGeorg et al, 1990;Bergonzelli et al, 1992;Heaton et al, 1992;Thalacker and Nilsen-Hamilton, 1992). Moreover, cAMP inhibits the PMA-induced increase in PAI-1 gene transcription in HT-1080 and NRK cells (Bergonzelli et al, 1992;Thalacker and Nilsen-Hamilton, 1992).…”

Synergistic and Multidimensional Regulation of Plasminogen Activator Inhibitor Type 1 Expression by Transforming Growth Factor Type β and Epidermal Growth Factor

“…The need for tight regulation of PAI-1 expression levels and time of production is reflected in the many hormones, cytokines, and growth factors that regulate it, including insulin, transforming growth factor type ␤ (TGF␤), epidermal growth factor (EGF), basic fibroblast growth factor (FGF-2), insulinlike growth factor I (IGF-1), and tumor necrosis factor ␣ (TNF␣) (7)(8)(9)(10)(11)(12). TGF␤ and EGF cooperatively regulate PAI-1 expression (9,13).…”