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Regulation of sperm function by reactive oxygen species
1University of Bristol, Department of Clinical Sciences South Bristol (Obstetrics & Gynaecology), St Michael's Hospital, Southwell Street, Bristol BS2 8EG, UK. chris.ford@bristol.ac.uk
Human Reproduction Update
|June 26, 2004
Summary
Reactive oxygen species (ROS) influence sperm capacitation, but their production in human sperm is complex. While direct evidence for NADPH oxidase is lacking, other mechanisms may generate ROS, particularly in animal sperm.
Area of Science:
- Reproductive Biology
- Sperm Physiology
- Oxidative Stress
Background:
- Sperm capacitation, essential for fertilization, is modulated by reactive oxygen species (ROS).
- ROS can enhance sperm function, but their precise origin and role in human sperm remain debated.
- Antioxidants generally inhibit ROS-mediated effects on sperm.
Purpose of the Study:
- To investigate the role and production mechanisms of reactive oxygen species (ROS) in sperm capacitation.
- To critically evaluate the evidence for NADPH oxidase activity in human sperm.
Main Methods:
- Review of existing literature on ROS and sperm capacitation.
- Analysis of studies measuring ROS production in sperm using various techniques.
- Examination of evidence for NADPH oxidase components and activity in human and animal sperm.
Main Results:
- Exposure to ROS increases protein tyrosine phosphorylation, a key event in capacitation.
- Measurement of ROS in sperm is challenging due to potential contamination and artifactual signaling (e.g., lucigenin).
- Evidence for significant NADPH oxidase activity in mature human sperm is weak, contrary to earlier suggestions.
Conclusions:
- The hypothesis of NADPH oxidase as the primary ROS source in human sperm is undermined.
- Human sperm may still produce ROS through alternative pathways.
- Animal sperm show stronger evidence for ROS production, potentially of mitochondrial origin.