The cyclic AMP effector Epac integrates pro- and anti-fibrotic signals
2008
Yokoyama, Utako | Patel, Hemal H. | Lai, N Chin | Aroonsakool, Nakon | Roth, David M. | Insel, Paul A.
Scar formation occurs during the late stages of the inflammatory response but, when excessive, produces fibrosis that can lead to functional and structural damage of tissues. Here, we show that the profibrogenic agonist, transforming growth factor β1, transcriptionally decreases expression of Exchange protein activated by cAMP 1 (Epac1) in fibroblasts/fibroblast-like cells from multiple tissues (i.e., cardiac, lung, and skin fibroblasts and hepatic stellate cells). Overexpression of Epac1 inhibits transforming growth factor β1-induced collagen synthesis, indicating that a decrease of Epac1 expression appears to be necessary for the fibrogenic phenotype, an idea supported by evidence that Epac1 expression in cardiac fibroblasts is inhibited after myocardial infarction. Epac and protein kinase A, a second mediator of cAMP action, have opposite effects on migration but both inhibit synthesis of collagen and DNA by fibroblasts. Epac is preferentially activated by low concentrations of cAMP and stimulates migration via the small G protein Rap1 but inhibits collagen synthesis in a Rap1-independent manner. The regulation of Epac expression and activation thus appear to be critical for the integration of pro- and anti-fibrotic signals and for the regulation of fibroblast function.
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