Abstract
Postovulatory aging of the mammalian oocytes causes deterioration of oocytes through several factors including oxidative stress. Keeping that in mind, we aimed to investigate the potential of a well-known antioxidant, resveratrol (RV), to evaluate the adverse effects of postovulatory aging in porcine oocytes. After in vitro maturation (IVM), a group of (25–30) oocytes (in three replicates) were exposed to 0, 1, 2, and 4 μmol/L of RV, respectively. The results revealed that the first polar body (PB1) extrusion rate of the oocytes significantly increased when the RV concentration reached up to 2 μmol/L (p < 0.05). Considering optimum RV concentration of 2 μmol/L, the potential of RV was evaluated in oocytes aged for 24 and 48 h. We used fluorescence microscopy to detect the relative level of reactive oxygen species (ROS), while GHS contents were measured through the enzymatic method. Our results revealed that aged groups (24 h and 48 h) treated with RV (2 μmol/L) showed higher (p < 0.05) ROS fluorescence intensity than the control group, but lower (p < 0.05) than untreated aged groups. The GSH content in untreated aged groups (24 h and 48 h) was lower (p < 0.05) than RV-treated groups, but both groups showed higher levels than the control. Similarly, the relative expression of the genes involved in antioxidant activity (CAT, GPXGSH-Px, and SOD1) in RV-treated groups was lower (p < 0.05) as compared to the control group but higher than that of untreated aged groups. Moreover, the relative mRNA expression of caspase-3 and Bax in RV-treated groups was higher (p < 0.05) than the control group but lower than untreated groups. Furthermore, the expression of Bcl-2 in the RV-treated group was significantly lower than control but higher than untreated aged groups. Taken together, our findings revealed that the RV can increase the expression of antioxidant genes by decreasing the level of ROS, and its potent antiapoptotic effects resisted against the decline in mitochondrial membrane potential in aged oocytes.
Highlights
Our findings revealed that the RV can increase the expression of antioxidant genes by decreasing the level of reactive oxygen species (ROS), and its potent antiapoptotic effects resisted against the decline in mitochondrial membrane potential in aged oocytes
Being a prime source of ROS production, mitochondria are susceptible to ROS-induced damage [22], which results in the decreased ATP synthesis, altered mitochondrial membrane potential, oxidative stress, and early onset of apoptosis [23,24]
The results showed that the mRNA levels of Caspase-3 and Bax treated with 2 μmol/L RV were significantly higher than those in the control group but significantly lower than those in the 24 h and 48 h aged groups, while the expression of Bcl-2 was significantly lower
Summary
There are some major factors that mediate time dependent reduction in oocyte competence such as oxidative stress [9], chromosomal abnormalities [10], and modification of poly (A) tails (Deadenylation) of genes responsible for maternal effects [11] and epigenetic alteration [12,13]. Postovulatory aging is associated with excessive accumulation of ROS leading to oxidative stress, which predisposes aged oocytes to the apoptotic process [9,21]. Being a prime source of ROS production, mitochondria are susceptible to ROS-induced damage [22], which results in the decreased ATP synthesis, altered mitochondrial membrane potential, oxidative stress, and early onset of apoptosis [23,24]. The excessive accumulation of ROS can affect the permeability of mitochondrial membranes to open MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and promote the flow of calcium ions [25], which subsequently induces the release of cytochrome C and caspase
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