The role of mitochondrial transition pores on bovine oocyte competence after heat stress, as determined by effects of cyclosporin A

Abstract

This study was undertaken to investigate the effects on the nuclear maturation and subsequent embryonic development of bovine oocytes exposed to heat stress (HS) when treating bovine oocytes before in vitro maturation (IVM) with 1 µM cyclosporin A (CsA), an inhibitor of mitochondrial permeability transition pore opening. Mitochondrial activity, reactive oxygen species (ROS), and apoptosis levels of the oocytes were also assessed. Nuclear maturation rates of both the HS-exposed oocytes treated with or without CsA groups (HS + CsA or HS group) were significantly lower (P<0.05) than that of the control group, while the rate of the HS + CsA group was significantly higher (P<0.05) than that of the HS group. Furthermore, although the cleavage and blastocyst formation rates of the HS group were significantly lower than those of the control groups (P<0.05), both rates of the HS + CsA group recovered to the same level as those of the control group. The HS group showed a significantly higher ROS level, lower mitochondrial activity in the oocytes, and TUNEL-positive cumulus cells, but not oocytes, compared with those of the control group (P<0.05), whereas the TUNEL-positive and mitochondrial activity levels of the HS + CsA group recovered to those of the control group. These results indicate that 1 µM CsA treatment before IVM may mitigate reduced mitochondrial activity, increase number of apoptotic cumulus cells under HS, and improve the nuclear maturation and developmental competence of bovine oocytes.

Astaxanthin ameliorates heat stress-induced impairment of blastocyst development In Vitro: –astaxanthin colocalization with and action on mitochondria–

“…Although the Δ<m-promoting effect of Ax was previously shown in cultured HeLa cells [54], the present results show for the first time that the effect has an interaction with the heat-stress condition in preimplantation embryos. In contrast to the case of oocytes [29,44] and preimplantation embryos (present results), heat stress enhanced the Δ<m in some cases, including peripheral blood mononuclear cells [6] and skeletal muscles [3,28]. In these cases, heat-induced Δ<m elevation acts in a cell-protective manner against cell perturbation.…”

“…Several lines of investigation have suggested the possible associations of high-potential mitochondria with the ability of matured oocytes to be fertilized and the developmental competence of postfertilization embryos [9,49,51]. Furthermore, the influence of environmental insults, including heat stress, on mitochondrial function in mammalian oocytes has been documented previously [29,44]. Therefore, we further examined the effects of Ax in combination with heat stress on the membrane potential of mitochondria (Δ<m) of day 6 embryos (exclusively morula stage).…”

Aging-related Changes in <i>In Vitro</i>-matured Bovine Oocytes: Oxidative Stress, Mitochondrial Activity and ATP Content After Nuclear Maturation

“…JC-1 fluorescence has two emission peaks, with red fluorescence (JC-1 dimers) indicating high-polarized mitochondria (high membrane potential) and green fluorescence (JC-1 monomers) indicating low-polarized mitochondria (low membrane potential) [35]. Mitochondrial activity can be evaluated by the intensity of the red/green fluorescence [13, 17, 18]. …”

“…It has been reported that the aging of murine oocytes causes increased oxidative stress [12], mitochondrial dysfunction [13, 14] and decreased intracytoplasmic levels of ATP [15]. In in vitro- matured bovine oocytes, the changes in level of oxidative stress [16], mitochondrial activity [17, 18] and ATP content [19,20,21,22] during in vitro maturation (IVM) culture for less than 24 h have been determined, but there is little data on the changes in these parameters associated with bovine oocyte aging. Therefore, it is still unclear whether the extension of IVM duration in bovine oocytes causes the aging-related changes in oxidative stress, mitochondrial activity and ATP content.…”

Cathepsin B activity has a crucial role in the developmental competence of bovine cumulus–oocyte complexes exposed to heat shock during in vitro maturation

“…Heat shock during bovine oocyte maturation disrupts mitochondrial membrane permeability (Nabenishi et al 2012) and stimulates group II caspase activation (Roth & Hansen 2004a), which is probably key to apoptosis induction as evidenced by TUNEL-positive cells. However, the complete mechanism of heat shock-induced apoptosis through mitochondrial membrane damage and caspase activation in COCs is still unrevealed.…”