High Prolactin Concentration Induces Ovarian Granulosa Cell Oxidative Stress, Leading to Apoptosis Mediated by L-PRLR and S-PRLR

High prolactin (PRL) concentration has been shown to induce the apoptosis of ovine ovarian granulosa cells (GCs), but the underlying mechanisms are unclear. This study aimed to investigate the mechanism of apoptosis induced by high PRL concentration in GCs. Trial 1: The optimal concentration of glutathion was determined according to the detected cell proliferation. The results showed that the optimal glutathione concentration was 5 μmol/mL. Trial 2: 500 ng/mL PRL was chosen as the high PRL concentration. The GCs were treated with 0 ng/mL PRL (C group), 500 ng/mL PRL (P group) or 500 ng/mL PRL, and 5 μmol/mL glutathione (P-GSH group). The results indicated that the mitochondrial respiratory chain complex (MRCC) I–V, ATP production, total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and thioredoxin peroxidase (TPx) in the C group were higher than those in the P group (p < 0.05), while they were lower than those in the P-GSH group (p < 0.05). Compared to the C group, the P group exhibited elevated levels of reactive oxygen species (ROS) and apoptosis (p < 0.05) and increased expression of ATG7 and ATG5 (p < 0.05). However, MRCC I–V, ATP, SOD, A-TOC, TPx, ROS, and apoptosis were decreased after the addition of glutathione (p < 0.05). The knockdown of either L-PRLR or S-PRLR in P group GCs resulted in a significant reduction (p < 0.05) in MRCC I–V, ATP, T-AOC, SOD and TPx, while the overexpression of either receptor showed an opposite trend (p < 0.05). Our findings suggest that high PRL concentrations induce apoptotic cell death in ovine ovarian GCs by downregulating L-PRLR and S-PRLR, activating oxidative stress and autophagic pathways.