Survival Role of Locally Produced Acetylcholine in the Bovine Corpus Luteum1

Abstract

The present study was conducted to explore the source of acetylcholine (ACH) in the corpus luteum (CL) and to test our hypothesis of an antiapoptotic role of ACH in the bovine CL and, further, to investigate whether nerve growth factor (NGF), insulin-like growth factor 1 (IGF1), and transforming growth factor beta1 (TGFB1) influence the expression of choline acetyltransferase (CHAT), the biosynthetic enzyme of ACH, in cultured bovine luteal cells. Protein expression and immunolocalization of CHAT were carried out at different stages throughout the luteal phase and in cultured luteal and endothelial cells. ACH was measured in luteal tissue at the different luteal stages and in luteal cells cultured for 8 and 24 h. Cell viability and TUNEL assays were performed on cultured midluteal cells treated with or without tumor necrosis factor alpha (TNF)/interferon gamma (IFNG) in the presence of ACH and its muscarinic (atropine) and nicotinic (mecamylamine) receptor antagonists. The CL was devoid of cholinergic nerve fibers. CHAT immunostaining was evident in luteal, endothelial, and stromal cells in luteal tissue sections and in cultured luteal and endothelial cells. CHAT protein was expressed throughout the cycle without any significant changes. ACH concentration in luteal tissue was not changed during the luteal stages but increased over time and with increased cell numbers in luteal cell cultures. ACH increased cell viability and prevented cell death induced by TNF/IFNG. Atropine significantly attenuated ACH action, whereas mecamylamine had no effect. TNF/IFNG treatment downregulated CHAT expression, whereas NGF, IGF1, and TGFB1 upregulated CHAT expression, in cultured luteal cells. The overall findings strongly suggest a nonneural source and antiapoptotic role of ACH in the bovine CL. Locally produced ACH appears to be regulated by NGF, IGF1, and TGFB1.

Seasonal changes in expression of nerve growth factor and its receptors TrkA and p75 in the ovary of wild ground squirrel (Citellus dauricus Brandt)

“…In pig, the increased NGF and TrkA protein levels in luteal cells were found during the estrous cycle [35]. These results shed light to the critical role of NGF in development and/or maintenance of luteal function, which is further supported by the findings that NGF can stimulate of progesterone and oxytocin release [40] and acetylcholine production [41] in bovine luteal cells as well as maintenance of luteal vasculature in rats [37]. In line with these aforementioned data, our present results indicated that NGF ligand and receptors might play a similar role in the development of corpora lutea in the wild seasonally-breeding rodent.…”

Pro-nerve growth factor in the ovary and human granulosa cells

“…EGR1 is regarded as a master transcription factor and is linked to differentiation and mitosis. Furthermore, a previous study showed that NGF increased levels of CHAT in bovine luteal cells [37]. This enzyme is important for the production of ACh from GCs and was also described in the human ovary and GCs [29, 38-40].…”

“…ACh in the ovary acts as a trophic molecule and regulates ion channel activity in human GCs [40]. In the bovine corpus luteum (CL) [37] it was also reported to exert anti-apoptotic actions. Thus NGF appears to be a trophic factor for human GCs.…”

The Interface of the Immune and Reproductive Systems in the Ovary: Lessons Learned from the Corpus Luteum of Domestic Animal Models

“…The effects of IFNG on luteal cells are potentiated in the presence of TNF, 66,72 probably because of TNF‐induced upregulation of IFNG receptors 74 . Induction of apoptosis by IFNG + TNF can be suppressed by IFNA or acetylcholine, 75,76 and progesterone may confer some protective effect against apoptosis in the CL 77 …”