Involvement of PINK1/Parkin-mediated mitophagy in mitochondrial functional disruption under oxidative stress in vitrified porcine oocytes

Abstract

Vitrification is an effective technique for fertility preservation, but is known to lead to mitochondrial dysfunction in porcine oocytes. Mitophagy is induced to rebalance mitochondrial function, a process in which reactive oxygen species (ROS) plays a role. In this study, vitrified-warmed porcine oocytes were incubated for 4 h with the oxidant AAPH or antioxidant α-tocopherol to alter ROS levels. A series of tests suggested that vitrification damaged mitochondrial structure and caused dysfunction, including blurred mitochondrial cristae, decreased mitochondrial membrane potential, decreased mtDNA copy number and increased ROS generation. This dysfunction resulted in mitophagy and the loss of embryonic developmental potential. Incubation with AAPH or α-tocopherol altered mitochondrial function and mitophagy flux status in vitrified oocytes. The PINK1/Parkin pathway was involved in oxidative stress regulation in vitrified oocytes. Under AAPH-induced oxidative stress, increased fluorescence intensity of Parkin, increased expression of PINK1, Parkin, and LC3B-II, and decreased expression of MFN2 and p62 were observed, whereas the opposite effects were induced under α-tocopherol treatment. The inhibition of ROS by α-tocopherol benefitted mitochondrial homeostasis and alleviated PINK1/Parkin-mediated mitophagy, resulting in the recovery of embryonic developmental potential in vitrified porcine oocytes. Therefore, this study provides a new mechanism for the application of antioxidants to aid the cryopreservation of porcine oocytes.

Keywords: Mitophagy; Oxidative stress; PINK1/Parkin; Porcine oocyte; Vitrification.