L-Proline improves the cytoplasmic maturation of mouse oocyte by regulating glutathione-related redox homeostasis

Recent studies have shown that L-proline (proline) is an antioxidant to protect cells from oxidative stress in vivo and in vitro. Glutathione (GSH) is a major cellular redox regulator involved in controlling redox balance and is regarded as one of the key indices to predict the cytoplasmic maturation of oocytes. The objectives of this study are to investigate the effect of proline on the developmental potential of mouse oocytes and to determine the role of gap junctional communication (GJC) on intraoocyte GSH concentration during in vitro maturation (IVM). Compared with control (0 mmol/L), 0.5 mmol/L proline supplementation enhanced rates of activated oocytes, 2-cell and 4-cell embryos, and blastocysts. Furthermore, 0.25 and 0.5 mmol/L proline supplementation markedly upregulated mRNA expression of glutamate-cysteine ligase catalytic subunit (GCLC) and glutamate-cysteine ligase modifier subunit (GCLM) in oocytes and cumulus cells, enhanced GSH concentration in oocytes, and reduced reactive oxygen species (ROS) level in oocytes. Interestingly, carbenoxolone disodium salt (CBX) treatment reduced GSH concentration in oocytes and the rate of early embryo development without proline incubation. Notably, CBX-triggered reduction in the rates of the number of 2-cell and 4-cell embryos and blastocysts were rescued by 0.5 mmol/L proline supplementation. Collectively, these results indicate a novel functional role of proline in oocyte cytoplasmic maturation and regulation of glutathione-related redox homeostasis. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

Recent studies have shown that L-proline acts as an antioxidant to protect cells from oxidative stress. This study investigates the effect of proline on the developmental potential of mouse oocytes and its role in regulating glutathione-related redox homeostasis. The results demonstrate that proline supplementation enhances oocyte and embryo development, upregulates mRNA expression of key enzymes, increases glutathione concentration, and reduces reactive oxygen species levels in oocytes. Gap junctional communication and proline supplementation play important roles in maintaining redox balance and promoting embryo development.