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Lookup NU author(s): Professor James Gillespie
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Little is known about the mechanisms controlling the expression of key proteins that regulate excitability and contractility in the human myometrium at term. However, evidence is accumulating to suggest that the cytokine transforming growth factor (TGF)β may play a central role. TGFβ1 and TGFβ receptors are present in the myometrial cells, indicative of an autocrine signaling system. Furthermore, the levels of TGFβ1 and the expression of its receptors increase in the myometrium at term suggesting that they are, in turn, regulated and form part of a physiological cascade of events involving a number of autocrine signaling associated proteins. The present experiments were done to identify factors that regulate the expression of TGFβ1 and TGFβ receptors and may form other elements of this cascade. Because IL-1 and IL-8 are found in the myometrium at term and have been implicated in the etiology in premature labor we focus on this cytokines. Receptors for IL-1 and IL-8 were detected in the myometrial cells. Using Western blot analysis, the levels of expression were found to vary. The expression of IL-1 receptor type I was highest in the nonpregnant tissue with lower levels in nonlaboring myometrium with a further reduction in the spontaneously laboring tissue. In contrast, the expression of IL-8 receptor type B was highest in the pregnant nonlaboring tissue with a lower level in the spontaneously laboring tissue. Using an in vitro model, TGFβ1 and TGFβ receptor expression was up-regulated by IL-8, IL-1, and TGFβ1 itself. However, IL-8 receptor expression was decreased by IL-8 and TGFβ1. This suggests that in a cascade IL-8 would feed forward to promote the TGFβ system, whereas TGFβ1 feeds back to inhibit responsiveness to IL-8. Estrogen and progesterone increased the release of TGFβ1. However, at high concentrations, estrogen and progesterone (100 nM 17β-estradiol or 200 nM progesterone) decreased the level of TGFβ receptor expression. Thus, the progressive rise of steroid levels in vivo might account for the observed changes in TGFβ1 and TGFβ receptor expression in vivo. Taken together, these observations support the idea that there is a cascade of autocrine signals that may play a major role in the physiological processes preparing the myometrium for parturition at term.
Author(s): Gillespie JI; Hatthachote P
Publication type: Article
Publication status: Published
Print publication date: 01/06/1999
ISSN (print): 0013-7227
ISSN (electronic): 1945-7170
Publisher: The Endocrine Society
PubMed id: 10342839
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