Readthrough acetylcholinesterase (AChE-R) and regulated necrosis: pharmacological targets for the regulation of ovarian functions?

Abstract

Proliferation, differentiation and death of ovarian cells ensure orderly functioning of the female gonad during the reproductive phase, which ultimately ends with menopause in women. These processes are regulated by several mechanisms, including local signaling via neurotransmitters. Previous studies showed that ovarian non-neuronal endocrine cells produce acetylcholine (ACh), which likely acts as a trophic factor within the ovarian follicle and the corpus luteum via muscarinic ACh receptors. How its actions are restricted was unknown. We identified enzymatically active acetylcholinesterase (AChE) in human ovarian follicular fluid as a product of human granulosa cells. AChE breaks down ACh and thereby attenuates its trophic functions. Blockage of AChE by huperzine A increased the trophic actions as seen in granulosa cells studies. Among ovarian AChE variants, the readthrough isoform AChE-R was identified, which has further, non-enzymatic roles. AChE-R was found in follicular fluid, granulosa and theca cells, as well as luteal cells, implying that such functions occur in vivo. A synthetic AChE-R peptide (ARP) was used to explore such actions and induced in primary, cultured human granulosa cells a caspase-independent form of cell death with a distinct balloon-like morphology and the release of lactate dehydrogenase. The RIPK1 inhibitor necrostatin-1 and the MLKL-blocker necrosulfonamide significantly reduced this form of cell death. Thus a novel non-enzymatic function of AChE-R is to stimulate RIPK1/MLKL-dependent regulated necrosis (necroptosis). The latter complements a cholinergic system in the ovary, which determines life and death of ovarian cells. Necroptosis likely occurs in the primate ovary, as granulosa and luteal cells were immunopositive for phospho-MLKL, and hence necroptosis may contribute to follicular atresia and luteolysis. The results suggest that interference with the enzymatic activities of AChE and/or interference with necroptosis may be novel approaches to influence ovarian functions.

DHEA protects mitochondria against dual modes of apoptosis and necroptosis in human granulosa HO23 cells

“…Recently, necroptosis has been found to be involved in some pathological conditions. It not only contributes to ischemic injury in heart and kidney (Smith et al 2007, Linkermann et al 2012, but also accelerates ovarian follicle necroptosis during aging (Blohberger et al 2015).…”

Necrosis and necroptosis in germ cell depletion from mammalian ovary

“…The increased phosphorylated form of MLKL has been identified as a potent biomarker of necroptosis in mouse and human (He et al, 2016). The increased level of p-MLKL has been reported during granulosa cell necroptosis in the human ovary (Blohberger et al, 2015). This is supported by the observations that MLKL inhibitor necrosulfonamide (NSA) reduces necroptosis in human granulosa cells cultured in vitro (Blohberger et al, 2015;Du et al, 2018).…”

“…The presence of high level of cytokines may induce necroptosis in granulosa cells of cow and human ovary (Blohberger et al, ; Hojo et al, ; Moriwaki & Chan, ; Tsui et al, ). The granulosa cell necroptosis may induce oocyte susceptibility toward apoptosis (Blohberger et al, ; Tiwari et al, ). Indeed, bidirectional talk between granulosa cells and oocyte are important for the survival of both cell types (Barrette & Albertini, ; Tiwari et al, ).…”

“…The presence of high level of cytokines may induce necroptosis in granulosa cells of cow and human ovary (Blohberger et al, 2015;Hojo et al, 2016;Moriwaki & Chan, 2013;Tsui et al, 2017). The granulosa cell necroptosis may induce oocyte susceptibility toward apoptosis (Blohberger et al, 2015;Tiwari et al, 2017). Indeed, F I G U R E 1 A schematic diagram showing the possible mechanism of granulosa cell necroptosis.…”

Endoplasmic Reticulum Stress during Mammalian Follicular Atresia

“…Necroptosis contributes to follicular atresia and luteolysis [102]. The factors involved in granulosa cell necroptosis can be regulated by acetylcholinesterase (AChE), cytokines, starvation, and oxidative stress via TNFα [103].…”