Expression of apelin and apelin receptor (APJ) in porcine ovarian follicles and in vitro effect of apelin on steroidogenesis and proliferation through APJ activation and different signaling pathways

Apelin was thought to be an adipocyte-specific hormone, but recent studies indicate a link between apelin and female reproductive function. Using real-time PCR, immunoblotting, immunohistochemistry and ELISA, we demonstrated expression of apelin and its receptor (APJ) in ovarian follicles of differe...

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Bibliographic Details
Published in:Theriogenology 2017-07, Vol.96, p.126-135
Main Authors: Rak, A., Drwal, E., Rame, Ch, Knapczyk-Stwora, K., Słomczyńska, M., Dupont, J., Gregoraszczuk, E.L.
Format: Article
Language:English
Subjects:
Animals
Apelin
Apelin - genetics
Apelin - metabolism
Apelin - pharmacology
Apelin Receptors - genetics
Apelin Receptors - metabolism
APJ
Cell Proliferation
Female
Follicle Stimulating Hormone - pharmacology
Gene Expression Regulation - drug effects
Gene Expression Regulation - physiology
Granulosa Cells - drug effects
Granulosa Cells - physiology
Humans
Insulin-Like Growth Factor I - pharmacology
Life Sciences
Other
Ovarian follicle
Ovarian Follicle - metabolism
Proliferation
Recombinant Proteins
Reproductive Biology
RNA, Messenger
Signal Transduction - physiology
Steroidogenesis
Steroids - biosynthesis
Swine - physiology
Theca Cells - drug effects
Theca Cells - physiology
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Summary:Apelin was thought to be an adipocyte-specific hormone, but recent studies indicate a link between apelin and female reproductive function. Using real-time PCR, immunoblotting, immunohistochemistry and ELISA, we demonstrated expression of apelin and its receptor (APJ) in ovarian follicles of different sizes from mature pigs. Apelin concentration in the follicular fluid, and expression of both apelin and APJ, increased with follicular growth; greatest values were found in large follicles. Immunohistochemistry revealed the positive staining for apelin and APJ in membranes of granulosa, than theca cells. Furthermore, we observed strong expression of apelin in oocytes and APJ in the zona pellucida. The effect of apelin (0.02, 0.2, 2 and 20 ng/ml) on basal and IGF1- and FSH-induced steroid hormone (progesterone [P4], and estradiol [E2]) secretion, steroidogenic enzyme (3βHSD and CYP19A1) expression and cell proliferation (Alamar blue) was determined. Apelin was found to increase basal steroid secretion, but decrease IGF1- and FSH-induced steroid secretion, and 3βHSD and CYP19 expression. Apelin also increased cell proliferation and the phosphorylation level of 5′-monophosphate-activated protein kinase (AMPK), phosphatidyl inositol 3′ kinase/Akt (Akt) and extracellular signal-regulated kinases (ERK1/2). AMPKα was involved in the action of apelin in P4 production, and MAPK/ERK and Akt/PI3 mediated the proliferative effect of apelin. However, these effects on steroid secretion and cell proliferation were abolished when cultured in the presence of ML221, an APJ antagonist. In conclusion, apelin appears to regulate ovarian follicular functions such as steroidogenesis and proliferation via APJ activation and different signaling pathways. •Expression of apelin and APJ increased with ovarian follicular growth.•Apelin stimulation basal, but decrease IGF1- and FSH-induced steroidogenesis.•Apelin increased cell proliferation and AMPK, Akt and ERK1/2 activation.
ISSN:0093-691X
1879-3231
DOI:10.1016/j.theriogenology.2017.04.014