Spirulina polysaccharides improve postthaw sperm quality in bulls by inhibiting the activation of pathways related to protein kinase A.

Sperm cryopreservation is widely used in assisted reproductive technology (ART) and livestock breeding. Although sperm cryopreservation accelerates breeding, the quality of cryopreserved sperm tends to be decreased. Improving the quality of frozen sperm is a hot topic, and spirulina polysaccharide, known for its immunomodulatory and antioxidant properties, is considered a promising natural extract for extensive studies. In this study, a pectic polysaccharide was extracted from spirulina (PSP), and its effects on postthaw bovine sperm viability were evaluated. Phosphoproteomic analysis based on TMT labelling and LC-MS/MS was employed. The results revealed that 10 mg/L PSP had significant protective effects on postthaw sperm viability, plasma membrane integrity, acrosomal integrity, and mitochondrial membrane integrity. Moreover, PSP increased the antioxidant capacity by activating antioxidant enzymes such as SOD, CAT, and GSH-PX and reduced apoptosis, ROS release and MDA levels. In addition, PSP resulted in decreased phosphorylation levels of proteins related to the acrosome, flagellum, metabolism, energy acquisition, and apoptosis. This protective effect of PSP on frozen sperm was achieved by inhibiting the activation of protein kinase A(PKA) protein-related pathways.