Pyrroroquinoline Quinone (PQQ) Improves the Quality of Holstein Bull Semen during Cryopreservation

Cryopreserved semen is extensively utilized in the artificial insemination (AI) of domestic animals; however, suboptimal conception rates due to oxidative damage following AI continue to pose a challenge. The present study investigated the effects of Pyrroroquinoline Quinone (PQQ), a novel antioxidant, on the semen quality of Holstein bulls during cryopreservation, as well as its potential molecular mechanisms. Semen samples were diluted with varying concentrations of PQQ (0, 50 μmol/L, 100 μmol/L, 150 μmol/L) prior to cryopreservation. Following the freeze-thaw process, a comprehensive evaluation was conducted to assess sperm motility, plasma membrane integrity, acrosome integrity, and the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and adenosine triphosphate (ATP). Western blot analysis was employed to examine the levels of proteins including PGAM2, CAPZB, CAT, SOD1, and GPX1. Notably, the inclusion of 100 μmol/L PQQ significantly enhanced sperm motility, membrane integrity, and acrosome integrity post freeze-thawing (<i>p</i> < 0.05). Furthermore, the group treated with 100 μmol/L PQQ exhibited reduced levels of MDA and ROS (<i>p</i> < 0.05), while ATP levels were significantly elevated (<i>p</i> < 0.05). Interestingly, treatment with 100 μmol/L PQQ resulted in decreased consumption of PGAM2, CAPZB, CAT, SOD1, and GPX1 proteins in sperm after freeze-thawing, compared to the control group (<i>p</i> < 0.05). These findings indicate that PQQ treatment enhances the quality of bull semen, mitigates oxidative stress damage, and ultimately improves the efficacy of sperm cryopreservation.