Inhibition of the CatSper Channel and NOX5 Enzyme Activity Affects the Functions of the Progesterone-Stimulated Human Sperm

Background Low levels of reactive oxygen species (ROS) and calcium are necessary for sperm function. NADPH oxidase 5 (NOX5) is a membrane enzyme which produces ROS. This enzyme is dependent on calcium for its activity. We investigated the importance of NOX5 and an important calcium channel (CatSper) on sperm function. Methods This laboratory in-vitro study was done in Shiraz, Iran, 2016. Normal semen samples (n=24) were washed and diluted to 20×106 sperm/mL. The diluted samples were divided into 8 groups, containing Ham's F-10 (control group), 2 µM of NNC (CatSper channel inhibitor), 1 µM DPI (NOX5 inhibitor), and NNC+DPI. The other 4 groups were the same as the 1st ones, except that they contained 1 µM of progesterone. Motility assessment was done by VT-Sperm 3.1. Acrosome status was monitored with acrosome-specific FITC-PSA using fluorescent microscopy. Sperm viability was assessed by Eosin Y. Statistical analysis was performed using SPSS 16 software. The comparison between the groups was done using the one-way ANOVA, followed by Tukey. A P<0.05 was considered significant. Results The percentage of motile sperm, sperm velocity, and viability decreased significantly in the groups containing NNC. DPI reduced sperm progressive motility only in the progesterone-stimulated condition. Progesterone induced acrosome reaction, but this effect was inhibited by NNC and DPI. Conclusion CatSper had a prominent role in the motility, acrosome reaction, and viability of the human sperm. The function of NOX5 was important only in the stimulated sperm. We conclude that CatSper has a more prominent role than NOX5 activity. The functional relation between NOX5 and CatSper is not clear but is very probable.