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 20×10^6 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 eosiny. 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.