An intact hypothalamic-pituitary-adrenal axis responds to stress in mammals. Mediation of the response takes place by secretion of cortocotropin-releasing hormone (CRH) by the paraventricular nucleus of the hypothalamus. CRH is a 41-amino acid peptide derived by enzymatic cleavage from a 191-amino acid preprohormone. Shibahara et al. (1983)cloned and sequenced the human CRH gene. Arbiser et al. (1988) assigned the gene for CRH to 8q13 by somatic cell hybrid and in situ hybridization studies. The absence of secondary hybridization strongly suggested that hypothalamic and placental CRH are transcribed from the same gene. Knapp et al. (1993) showed that the homologous gene is located on mouse chromosome 3.
Corticotropin-releasing hormone (CRH) is a 41-amino acid peptide derived from a 191-amino acid preprohormone. CRH is secreted by the paraventricular nucleus (PVN) of the hypothalamus in response to stress. Marked reduction in CRH has been observed in association with Alzheimer disease and autosomal recessive hypothalamic corticotropin dificiency has multiple and potentially fatal metabolic consequences including hypoglycemia and hepatitis. In addition to production in the hypothalamus, CRH is also synthesized in peripheral tissues, such as T lymphocytes and is highly expressed in the placenta. In the placenta CRH is a marker that determines the length of gestation and the timing of parturition and delivery. A rapid increase in circulating levels of CRH occurs at the onset of parturition, suggesting that, in addition to its metabolic functions, CRH may act as a trigger for parturition.
The Effect of CRH and Its Inhibitor, Antalarmin, on in Vitro Growth of Preantral Mouse Follicles, Early Embryo Development, and Steroidogenesis. Dinopoulou V et al. In vitro growth systems of preantral follicles allow studying the effect of various endocrine, paracrine, and autocrine factors on follicular growth and oocyte maturation. CRH is a 41-amino-acid neuropeptide responsible for endocrine, autonomic, immunological, and behavioral responses of mammals to stress and has two receptors, CRH receptor type 1 (CRH-R1) and CRH-R2. Antalarmin, a CRH-R1 antagonist, has been used to elucidate the role of CRH in stress, inflammation, and reproduction. The present study describes in vitro growth of mouse preantral follicles, early embryo development, and steroidogenesis in the presence of CRH and its antagonist antalarmin. We cultured 732 follicles in control media, 1306 in CRH 10(-7) mol/liter, and 1202 in CRH 10(-7) plus antalarmin 10(-6) mol/liter. The culture medium was assayed on alternate days for 17ß-estradiol, progesterone, and ß-human chorionic gonadotropin. Total RNA was extracted from preantral follicles as well as early preimplantation embryos and was assessed by real-time RT-PCR for the expression of CRH-R1 and CRH-R2 mRNAs. Hormone analysis showed that the CRH group had lower levels of 17ß-estradiol, progesterone, and ß-human chorionic gonadotropin as the culture progressed, in comparison with the other two groups. RT-PCR demonstrated the presence of CRH-R1 and CRH-R2 in all stages of preantral follicle culture. Morula/blastocyst-stage embryos expressed only CRH-R1. In conclusion, CRH has an inhibitory effect on in vitro fertilized oocytes, resulting from cultured preantral follicles at all stages of preimplantation embryo development. Furthermore, the presence of CRH in the culture medium inhibits steroidogenesis by preantral mouse follicles cultured in vitro.
Corticotropin-releasing hormone inhibits in vitro oocyte maturation in mice. Kiapekou E et al. The expression of corticotropin-releasing hormone (CRH) receptor 1 messenger RNA in stages of follicle growth was examined by reverse transcriptase-polymerase chain reaction in long-term cultures of early preantral mouse follicles with and without CRH addition. Corticotropin-releasing hormone receptor 1 is present in stages of mouse follicle growth, whereas 10(-9), 10(-7), and 10(-6) mol/L CRH inhibits oocyte maturation in vitro, an effect reversed by antalarmin addition.
Ghizzoni et al. (1997) found that CRH exerts a CRH- and IL-1 receptor-mediated inhibitory effect on ovarian steroidogenesis and might be actively involved in the still enigmatic processes of follicular atresia and luteolysis. Ghizzoni L, et al 1997 reported that corticotropin-releasing hormone (CRH) inhibits steroid biosynthesis by cultured human granulosa-lutein cells in a CRH
and interleukin-1 receptor-mediated fashion. The
effects of graded doses of ovine CRH were evaluated in the
conditioned medium obtained after 24 h incubation of the cells. All CRH
concentrations employed except for the lowest one caused a
significant decrease of media E2 and P4 levels. The alpha-helical
CRH9-41 antagonist blocked the suppressive effect
of 10(-9) mol/liter CRH on both E2 and P4 secretion, while it had no effect when
added to the culture media without CRH. Since interleukin (IL-1)-1 mediates
certain actions of CRH on leukocytes, they examined whether the CRH effect on
ovarian steroidogenesis was IL-1-mediated. Interleukin-1 receptor antagonist at
10(-7) and 10(-6) mol/liter blocked the inhibitory effects of CRH on E2 and P4
secretion, while it had no effect in the absence of CRH. In conclusion, CRH exerts
a CRH- and IL-1 receptor-mediated inhibitory effect on ovarian steroidogenesis
and might be actively involved in the still enigmatic processes of follicular atresia
Calogero AE, et al 1996 reported the effects of corticotropin-releasing hormone on ovarian estrogen production in vitro.
CRH inhibited FSH-stimulated estrogen production from rat
granulosa cells in a dose-dependent fashion. The maximal effect was achieved at
a concentration of 10(-8) M, which suppressed estrogen production by about 30%. Low concentrations of CRH (10(-10) M), incapable of modulating maximal
estrogen production in response to FSH, provoked a right-ward shift of the
estrogen dose-response curve to FSH. CRH (10(-8) M) suppressed the production
of tritiated water (equivalent to estrogen production) from homogenates of rat
granulosa cells incubated with a half-maximal concentration of FSH. Basal
estrogen production by human granulosa-luteal cells was also inhibited by CRH at
a concentration of 10(-10) M. The maximal effect was achieved with a
concentration of 10(-8) M, which lowered estrogen production by 25%. The CRH
receptor antagonist alpha-helical CRH-(9-41) antagonized the inhibitory effect of CRH on estrogen production from rat granulosa and human granulosa-luteal cells,
whereas alone it had no effect. CRH did not have any effect on the intracellular
cAMP content of rat granulosa and human granulosa-luteal cells. Calogero AE, et al reported that Corticotrophin-releasing hormone inhibits insulin-like growth
factor-I release from primary cultures of rat granulosa cells.
Expression regulated by
Theca, Luteal cells, Stromal cells
Ghizzoni et al. (1997) determined that CRH immunoreactivity was localized by immunohistochemistry in the cytoplasm of thecal cells surrounding the ovarian follicles, in luteinized cells of the stroma, and in large granulosa-derived luteinized cells of developing corpora lutea. Mastorakos G, et al 1993 reported immunoreactive corticotropin-releasing hormone and its binding
sites in the rat ovary.
detected cytoplasmic immunoreactive CRH (IrCRH) in theca and stromal cells
and in cells within the corpora lutea, at all phases of the estrous cycle. Using a
specific radioimmunoassay, they measured IrCRH in extracts of rat ovaries
(0.042-0.126 pmol/g wet tissue). The mobility of the ovarian IrCRH molecule
was similar to that of rat/human CRH by reverse phase HPLC.
Mastorakos G, et al 1994 reported the presence of immunoreactive corticotropin-releasing hormone in
normal and polycystic human ovaries.
Immunoreactivity was intense in the cytoplasm of
thecal cells surrounding the ovarian follicles, in luteinized cells of the stroma, and in a subpopulation of cells within the corpora lutea. No IrCRH was present in
oocytes of primordial follicles. Polycystic ovaries also had IrCRH in thecal cells;
however, CRH immunostaining was less prominent or completely absent from the stroma or the sparsely present corpora lutea and was clearly detected in oocytes of primordial follicles.
Species: mouse -
type: null mutation fertility: fertile Comment: To find the importance of CRH in the response of the hypothalamic-pituitary-adrenal axis to stress and its role in fetal development, Muglia et al. (1995) constructed a mouse model of CRH deficiency by targeted mutation in embryonic stem cells. They reported that CRH-deficient mice reveal a fetal glucocorticoid requirement for lung maturation. Postnatally, however, despite marked glucocorticoid deficiency, the mice exhibited normal growth, fertility, and longevity, suggesting that the major role of glucocorticoid occurs during fetal, rather than postnatal, life.