cGnRH II involvement in pyriform cell apoptosis

Abstract

We have investigated whether gonadotrophin-releasing hormone (GnRH) is involved in triggering the apoptotic death of pyriforms, the nurse cells that cooperate in oocyte growth during mid- to late previtellogenesis in the lizard Podarcis sicula. Our immunocytochemical analyses demonstrate that pyriforms express GnRH receptors and that, in late previtellogenesis, they are up-regulated by cGnRH II. The hormone however does not trigger receptor synthesis and activation, events that therefore must be under the control of other regulatory factors. Our results also indicate that in vitro treatment of pyriforms with cGnRH II induces DNAse I activation and DNA laddering, clear cytological evidence of apoptosis, but not Fas/Fas-L synthesis or caspase activation. We conclude that cGnRH II is pro-apoptotic to pyriform cells and that it exerts its effects by activating an alternative cell death pathway, probably involving calcium as first messenger and DNase I as first executioner.

Sex steroid receptors in the ovarian follicles of the lizard Sceloporus torquatus

“…Recent research on lizard reproductive biology has evaluated changes in sex steroid concentration and the molecular components involved in these processes (Motta et al, 2004(Motta et al, , 2020Tammaro et al, 2008;Tripathy and Rai, 2017). However, most of the studies involve oviparous species.…”

Glyphosate Interference in Follicular Organization in the Wall Lizard Podarcis siculus

“…The most striking is the induction of apoptosis at a stage, the early previtellogenesis, in which apoptosis should be completely absent. Pyriforms are nurse cells [ 28 ], committed to apoptosis [ 44 ], but the process begins at the end of previtellogenesis when follicles reach about 1500 µm in diameter and pyriform cells expose GnRH receptors [ 45 ]. In addition, regression is asynchronous and only a few apoptotic cells are visible at a time in sections obtained from control animals [ 46 ].…”

“…Significantly, recruitment is not accompanied by oogonial proliferation or the appearance of new leptotene oocytes; therefore, more than true recruitment, it appears that glyphosate has anticipated differentiation, an effect parallel to the anticipated apoptosis in the follicular epithelium. A check for an anticipated exposure of GnRH receptors might prove that this is the case [ 45 ].…”

Immunolocalization of activin and inhibin at different stages of follicular development in the lizard Sceloporus torquatus

“…In the vitellogenic follicles, when the granulosa layers were reduced, we found invaginations of the follicular layer filled with small cells, as reported previously in P. sicula [ 33 ]. These invaginations may be related to granulosa cell reduction and flattening rather than proliferative properties [ [34] , [35] , [36] , [37] , [38] , [39] ]. Future studies should focus on the role of these invaginations in remodeling the follicular epithelium in lizards and determine the role of each cell type during oocyte maturation.…”

“…We found Act immunoreactivity at the stage of vitellogenesis when pyriform cells regressed. We suggest this factor might be acting synergistically with other factors such as GnRH and their receptors via DNAse activation to induce their apoptosis [ 39 , 51 ] and the transition to the vitellogenic state [ 14 ]. In the preovulatory phase, the small cells, cortex, and blood vessels showed marks that may reflect their role in steroidogenesis [ 10 , 52 ].…”