The free-radical theory of male infertility suggests that reactive oxygen species produced by the spermatozoa themselves, are a leading cause of sperm dysfunction, including loss of sperm motility. However, the field is overshadowed on several fronts, primarily because: (i) the probes used to measure ROS are imprecise; and (ii) many reports suggesting that oxygen radicals are detrimental to sperm function add an exogenous source of ROS. Herein, we used a more reliable approach to measure superoxide anion production by human spermatozoa based on mass spectrometry analysis. Furthermore, we also investigated the formation of the lipid-peroxidation product 4-hydroxynonenal (4-HNE) during in vitro incubation using proteomics. Our data demonstrate that neither superoxide anion nor other free radicals that cause 4-HNE production are related to the loss of sperm motility during incubation. Interestingly, it appears that many of the 4-HNE adducted proteins, found within spermatozoa, originate from the prostate. A quantitative SWATH analysis demonstrated that these proteins transiently bind to sperm and are then shed during in vitro incubation. These proteomics-based findings propose a revised understanding of oxidative stress within the male reproductive tract. This article is protected by copyright. All rights reserved.
Proteomics. 2019 Dec 17 [Epub ahead of print]
J K Netherton, L Hetherington, R A Ogle, Mazloumi Mary, T Velkov, A I S B Villaverde, N Tanphaichitr, M A Baker
Department of Biological Science, University of Newcastle, Callaghan, Australia, 2308., Department of Pharmacology and Therapeutics, University of Melbourne, Parkville, Australia, 3010., Independent researcher, São Paulo, Brazil., Chronic Disease Program, Ottawa Hospital Research Institute, Department of Obstetrics and Gynaecology, and Department of Biochemistry, Microbiology, Immunology, University of Ottawa, Ottawa, Ontario, K1H 8L6, Canada.