Xing Yu; Xinyue Lin; Wenyan Wang; Guojun Zhang; Xingquan Xia; Liuwang Nie & Xingjiang Bu
Most reptiles can store sperm for subsequent use. After mating, sperm stored in the female reproductive tract experience oxidative stress due to limited cytoplasmic volume, which restricts antioxidant enzyme storage, and sperm are sensitive to reactive oxygen species (ROS), potentially activating the nuclear factor erythrocyte 2 related factor 2 (NRF2) pathway in response. This study aimed to investigate the role of the NRF2 pathway during oxidative stress in the oviduct of Mauremys reevesii. We evaluated the expression of NRF2-related genes (NRF2, HO1, NQO1, CAT, SOD1, SOD2, SOD3, GPX1, GPX3, GPX4), the activities of antioxidant enzymes Catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD), and the localization of the NRF2 protein by fluorescence quantification, enzyme assays, and immunofluorescence. Hematoxylin-eosin staining revealed an amount of sperm in the uterus and isthmus, and only a little sperm in the vagina. qRT-PCR indicated that after fertilization (P<0.05), NRF2 and its downstream genes showed reduced expression except for SOD3 and GPX3 on day one, with increased expression on day seven, and after one month. Enzyme activity assays indicated that after fertilization (P<0.05), one day the activities of SOD, CAT, and GPX were markedly reduced; seven days the activities of CAT and GPX were significantly reduced; were inconsistent with mRNA; one month all of the enzyme activities were increased. Immunofluorescence revealed increased NRF2 protein intensity in fertilized turtles. These results suggest that activation of the NRF2 pathway enhances the expression of NRF2-related genes in the oviduct, resulting in a protective effect on sperm storage in M. reevessii.
KEY WORDS: Mauremys reevesii; Oviduct; Sperm storage; Antioxidant pathway; Nuclear factor-erythroid 2-related factor 2.
YU, X.; LIN, X.; WANG, W.; ZHANG, G.; XIA, X.; NIE, L. & BU, X. Oviductal sperm storage activates the NRF2 antioxidant pathway in Mauremys reevesii. Int. J. Morphol., 43(3):968-977, 2025.
