Hypothalamic astrocytes respond to transforming growth factor-α with the secretion of neuroactive substances that stimulate the release of luteinizing hormone-releasing hormone

Ying J. Ma, Karin Berg-Von Der Emde, Florence Rage, William C. Wetsel, Sergio Ojeda

    Research output: Contribution to journalArticle

    122 Citations (Scopus)

    Abstract

    Previous studies demonstrated the involvement of transforming growth factor-α (TGFα), a member of the epidermal growth factor (EGF) family, in the developmental regulation of hypothalamic LHRH release. Although both TGFα and EGF stimulate LHRH release, they do not appear to act directly on LHRH neurons, as no EGF/TGFα receptors are detected on these cells in vivo. Instead, the stimulatory effect of TGFα on LHRH release seems to require a glial intermediacy. The present study identifies one of the glial molecules involved in this process. In vitro exposure of purified hypothalamic astrocytes to TGFα or EGF in a defined medium led to activation of the cyclooxygenase-mediated pathway of arachidonic acid metabolism, as indicated by an increase in PGE2 release, but failed to affect lipooxygenase-mediated metabolism, as assessed by the lack of increase in leukotriene C4 production; addition of TGFα- (T-CM) or EGF-conditioned medium to cultures of LHRH- producing GT1-1 cells stimulated LHRH release. In contrast, direct exposure of GT1-1 cells to the growth factors was ineffective. Incubation of the cells in medium conditioned by untreated astrocytes (CM) was also ineffective. Blockade of either EGF receptor signal transduction or cyclooxygenase activity in the astrocytic cultures prevented both TGFα-induced PGE2 formation in astrocytes and the stimulatory effect of T-CM on LHRH release. Immunoneutralization of PGE2 actions or selective removal of the PG from T- CM also prevented T-CM-induced LHRH release. Addition of exogenous PGE2 restored the effect. Thus, PGE2 is one of the glial molecules involved in mediating the stimulatory effect of TGFα on LHRH release. The effectiveness of PGE2 in eliciting LHRH release was, however, greatly reduced when PG was delivered to GT1-1 cells in astrocyte-defined medium instead of CM. Thus, astrocytes appear to produce a yet to be identified substance(s) that facilitates the stimulatory effect of PGE2 on LHRH output. We postulate that the ability of TGFα to enhance LHRH release depends on the potentiating interaction of PGE2 with these additional glial-derived molecules.

    Original languageEnglish (US)
    Pages (from-to)19-25
    Number of pages7
    JournalEndocrinology
    Volume138
    Issue number1
    DOIs
    StatePublished - 1997

    Fingerprint

    Transforming Growth Factors
    Gonadotropin-Releasing Hormone
    Astrocytes
    Dinoprostone
    Epidermal Growth Factor
    Neuroglia
    Prostaglandin-Endoperoxide Synthases
    Conditioned Culture Medium
    Leukotriene C4
    Growth Factor Receptors
    Epidermal Growth Factor Receptor
    Arachidonic Acid
    Signal Transduction
    Intercellular Signaling Peptides and Proteins
    Neurons

    ASJC Scopus subject areas

    • Endocrinology
    • Endocrinology, Diabetes and Metabolism

    Cite this

    Hypothalamic astrocytes respond to transforming growth factor-α with the secretion of neuroactive substances that stimulate the release of luteinizing hormone-releasing hormone. / Ma, Ying J.; Berg-Von Der Emde, Karin; Rage, Florence; Wetsel, William C.; Ojeda, Sergio.

    In: Endocrinology, Vol. 138, No. 1, 1997, p. 19-25.

    Research output: Contribution to journalArticle

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