Adverse Effects of Single Neutrophil Extracellular Trap-Derived Components on Bovine Sperm Function

Simple Summary Neutrophil extracellular traps (NETs) play a key role in fertilisation by eliminating microorganisms and entrapping spermatozoa in the female reproductive tract. However, the individual exposure of bull spermatozoa to NET-derived components has not yet been explored. The aim of this study was to evaluate the individual effects of the main NET-derived proteins on sperm parameters. Sperm were selected and incubated for 4 h with different NET-derived proteins. Membrane and acrosome integrity, lipoperoxidation, and membrane phospholipid disorders were also evaluated. All NET-derived proteins/enzymes showed cytotoxic effects on bull sperm, and this effect should be considered in future investigations on the uterine microenvironment and advancement of spermatozoa in the female reproductive tract. Neutrophil extracellular traps (NETs) play a key role in fertilisation by eliminating microorganisms and entrapping spermatozoa in the female reproductive tract (FRT). The deleterious effects of NETs on spermatozoa have been previously described; however, individual exposure to NET-derived components in bull spermatozoa has not been explored. The aim of this study was to evaluate the effects of the main NET-derived proteins, histone 2A (H2A), neutrophil elastase (ELA), myeloperoxidase (MPO), pentraxin 3 (PTX), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), at concentrations of 1, 10, and 30 mu g/mL, on sperm parameters. Sperm were selected and incubated with different NET-derived proteins for 4 h. Membrane and acrosome integrity, lipoperoxidation, and membrane phospholipid disorders were also evaluated. Bovine polymorphonuclear neutrophil (PMN)/sperm co-cultures were evaluated by scanning electron microscopy and immunofluorescence. All NET-derived proteins/enzymes resulted in a reduction in membrane integrity, acrosome integrity, and lipoperoxidation at a concentration of 30 mu g/mL. Bovine PMN/sperm co-cultures showed marked NET formation in the second hour. In conclusion, all NET-derived proteins/enzymes exerted cytotoxic effects on bull sperm, and this effect should be considered in future investigations on the uterine microenvironment and the advancement of spermatozoa in the FRT.