Caspase-3 Is a Pivotal Mediator of Apoptosis during Regression of the Ovarian Corpus Luteum

Abstract

Because caspase-3 is considered a primary executioner of apoptosis and has been implicated as a mediator of luteal regression, we hypothesized that corpora lutea (CL) derived from caspase-3 null mice would exhibit a delayed onset of apoptosis during luteal regression, when compared with CL derived from wild-type (WT) mice. To test this hypothesis, ovulation was synchronized in immature (postpartum d 24-27) WT and caspase-3-deficient female littermates by exogenous gonadotropins. Individual CL were isolated by manual dissection, 30 h after ovulation, and placed in organ culture dishes in the absence of serum and growth factors. At the time of isolation (0 h) and after 24, 48, and 72 h in culture, the CL were removed and assessed for the presence of processed (active) caspase-3 enzyme and for apoptosis by multiple criteria. There was no evidence of active caspase-3 enzyme or apoptosis in either WT or caspase-3-deficient CL before culture. However, CL derived from the WT mice exhibited a time-dependent increase in the level of active caspase-3 and apoptosis during culture. By comparison, CL derived from caspase-3-deficient mice, cultured in parallel, failed to exhibit any detectable active caspase-3 and showed attenuated rates of apoptosis. To extend these findings derived from ex vivo culture experiments, ovaries were collected from WT and caspase-3 null female littermates at 2, 4, or 6 d post ovulation, and the occurrence of apoptosis within the CL was analyzed. Whereas ovaries of WT mice had only residual luteal tissue at d 6 post ovulation, ovaries collected from caspase-3-deficient mice retained many CL, at d 6 post ovulation, that were similar in size to those observed in the early luteal phase of WT mice. Importantly, there was no dramatic increase in apoptosis in CL of caspase-3-deficient mice at any time point examined post ovulation, indicating that the involution process had indeed been delayed. In contrast, the levels of progesterone declined regardless of genotype. These data provide the first direct evidence that caspase-3 is functionally required for apoptosis to proceed normally during luteal regression. However, caspase-3 is not a direct mediator of the decrease in steroidogenesis associated with luteolysis.

Early pregnancy modulates survival and apoptosis pathways in the corpus luteum in sheep

“…Immunohistochemistry data demonstrate that most of these proteomic changes are evident in both LLC and SLC on day 16 of the estrous cycle or pregnancy. Previous studies clearly indicate a role for caspase-3 in luteal cell apoptosis in various species (Carambula et al 2002, Davis & Rueda 2002, Peluffo et al 2005, Yadav et al 2005, Slot et al 2006. Together, present results along with previous findings suggest that activation of caspase-3 dependent as well as independent apoptosis pathways are required for natural luteolysis; whereas, these pathways need to be inhibited or suppressed to maintain the survival of the CL during establishment of pregnancy in sheep.…”

“…By contrast, interactions between pro-apoptotic and anti-apoptotic signaling pathways and activation of caspases-3 dependent or independent intrinsic apoptosis pathways determine the death of cells (Adams & Cory 1998, Jiang & Wang 2004. Previous studies have shown that administration PGF 2a regulates genes or protein associated with cell survival and apoptosis in cows (Davis & Rueda 2002, Hou et al 2008, Arvisais et al 2010, Atli et al 2012, sheep (Romero et al 2013), pigs (Diaz et al 2013), rodents (Carambula et al 2002, Slot et al 2006, and primates (Peluffo et al 2005, Yadav et al 2005 during induced luteolysis in vivo and in vitro models. Although there is a large body of information available on induced luteolysis in various species, temporal regulations of cell survival and apoptosis signaling protein machinery in the CL during natural luteolysis and establishment of pregnancy in ruminants are largely unknown.…”

Cell-type-specific expression of murine multifunctional galectin-3 and its association with follicular atresia/luteolysis in contrast to pro-apoptotic galectins-1 and -7

“…This protease is an indispensable eVector in luteolysis (Carambula et al 2002). Obviously, galectin-3 is in this case not involved in modulation of regulatory events at the level of mediators of caspase-3 activation such as Bcl-2 or Bax, both proteins proven to be operative in luteolysis (Ratts et al 1995;Hsu et al 1996;Perez et al 1999;MatsudaMinehata et al 2006).…”

Progesterone Is a Suppressor of Apoptosis in Bovine Luteal Cells1

“…Moreover, Rueda et al [3] showed that the increase of apoptosis in the regressed bovine CL was associated with a significant increase of bax mRNA expression as compared with that in the functional CL. Caspases, a family of aspartic acid-specific cysteine proteases, are pivotal mediators of apoptosis during regression of the CL [16,18]. Of the 14 identified caspase family members, caspase-3 is the best-characterized enzyme [18].…”

“…Caspases, a family of aspartic acid-specific cysteine proteases, are pivotal mediators of apoptosis during regression of the CL [16,18]. Of the 14 identified caspase family members, caspase-3 is the best-characterized enzyme [18]. Rueda et al [19] showed that the levels of caspase-3 mRNA were 3-fold higher in the CL at 12 and 24 h after induction of luteolysis by PGF 2␣ treatment in comparison to the levels measured in matched CL from untreated ewes.…”