Mitochondrial uncouplers impair human sperm motility without altering ATP content†

Will M. Skinner, Natalie T. Petersen, Bret Unger, Shaogeng Tang, Emiliano Tabarsi, Julianna Lamm, Liza Jalalian, James Smith, Ambre M. Bertholet, Ke Xu, Yuriy Kirichok, Polina V. Lishko

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


In human spermatozoa, the electrochemical potentials across the mitochondrial and plasma membranes are related to sperm functionality and fertility, but the exact role of each potential has yet to be clarified. Impairing sperm mitochondrial function has been considered as an approach to creating male or unisex contraceptives, but it has yet to be shown whether this approach would ultimately block the ability of sperm to reach or fertilize an egg. To investigate whether the mitochondrial and plasma membrane potentials are necessary for sperm fertility, human sperm were treated with two small-molecule mitochondrial uncouplers (niclosamide ethanolamine and BAM15) that depolarize membranes by inducing passive proton flow, and evaluated the effects on a variety of sperm physiological processes. BAM15 specifically uncoupled human sperm mitochondria while niclosamide ethanolamine induced proton current in the plasma membrane in addition to depolarizing the mitochondria. In addition, both compounds significantly decreased sperm progressive motility with niclosamide ethanolamine having a more robust effect. However, these uncouplers did not reduce sperm adenosine triphosphate (ATP) content or impair other physiological processes, suggesting that human sperm can rely on glycolysis for ATP production if mitochondria are impaired. Thus, systemically delivered contraceptives that target sperm mitochondria to reduce their ATP production would likely need to be paired with sperm-specific glycolysis inhibitors. However, since niclosamide ethanolamine impairs sperm motility through an ATP-independent mechanism, and niclosamide is FDA approved and not absorbed through mucosal membranes, it could be a useful ingredient in on-demand, vaginally applied contraceptives.

Original languageEnglish
Pages (from-to)192-203
Number of pages12
JournalBiology of reproduction
Issue number2
StatePublished - Aug 10 2023


  • contraception
  • mitochondrial uncouplers
  • sperm metabolism
  • sperm motility


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