Antioxidant Enzyme Activity and Oxidative Stress in Bovine Oocyte In Vitro Maturation

Abstract

Reactive oxygen species (ROS) production is a normal process of cell metabolism. In vitro environments usually increase cell production of ROS, which has been implicated as a main cause of cell damage. Nevertheless, the role of ROS in oocyte in vitro maturation (IVM) is controversial. In most cells, enzymatic antioxidant systems can attenuate the effect of oxidative stress by scavenging ROS. The aim of this work was to determine whether: (1) standard conditions of bovine oocyte IVM are responsible for oxidative stress; (2) cumulus cells participate in protection against oxidative stress of the oocyte; and (3) enzymatic antioxidant activity is present in oocytes and cumulus cells. Cumulus-oocyte complexes (COCs) were matured in TCM-199 + 10% steer serum for 24 h at 39 degrees C in 5% CO2:95% humidified air. Oxidative stress was determined by the 2',7'-dichlorofluorescein diacetate assay. Superoxide dismutase (SOD), glutathione peroxidase, and catalase activities were measured spectrophotometrically. Under standard conditions of in vitro maturation, there was no increase in ROS production per COC (P > 0.05), but ROS level per cumulus cell diminished. There was no modification in ROS levels in oocytes matured in the presence versus the absence of their surrounding cumulus cells ( P > 0.05). To the best of our knowledge, the presence of SOD, glutathione peroxidase and catalase activities were detected in oocytes and cumulus cells for the first time. Enzymatic units were lower in denuded oocytes with respect to cumulus (P < 0.05), accounting for 37% for SOD, 25% for glutathione peroxidase, and 11% for catalase of the total COC units. Specific enzyme activity diminished in cumulus cells (P > 0.05) and increased in oocytes due to maturation (P > 0.05). The presence of activity of an enzymatic antioxidant system in the bovine oocyte would regulate in part ROS levels during IVM. Oocytes could be capable of controlling the increase in ROS because of the presence of their own enzymatic antioxidant system, SOD having the highest specific activity with respect to cumulus cells.

Selenium and Vitamin E Improve the <i>In Vitro</i> Maturation, Fertilization and Culture to Blastocyst of Porcine Oocytes

“…The oxidative modification of cell components due to the action of reactive oxygen species (ROS) is one of the most potentially damaging processes for proper cell function and may lead to cell death by necrosis or apoptosis [27,28]. During IVM of oocytes, ROS are produced [29][30][31], and it has been shown that cumulus cells play a major role in the antioxidant defense of oocytes using GPx and catalase activities. Since these enzymes are active in mature oocytes, it seems that oocytes also have their own capacity to control ROS production during maturation by their antioxidant system [29][30][31].…”

Effect of all-trans retinol on in vitro development of preimplantation buffalo embryos

“…Ligand-bound RARs and RXRs function as transcription factors by binding to cis-acting DNA sequences called retinoic acid response elements (RAREs), located within the transcriptional regulation of genes (Xiao et al, 1995). More over the role of retinoids in assisted reproductive technology has been demonstrated through their effect on cytoplasmic maturation and antioxidant property (Cetica et al, 2001;Ikeda et al, 2005). Hence, an attempt has been made to assess the role of all-trans retinol in in vitro production of buffalo embryos through its supplementation in maturation and embryo culture medium.…”

The Roles of Vitamin A for Cytoplasmic Maturation of Bovine Oocytes

“…Recently there has been increasing evidence of the impairment of oocyte cytoplasmic maturation by reactive oxygen species (ROS) during or at the peripheral period of maturation [62][63][64][65][66][67][68]. BC has been known to function as an antioxidant in lipid p h a s e s b y q u e n c h i n g s i n g l e t o x y g e n a n d scavenging the peroxyl radical [69].…”