Comparison between Inhibition of CatSper and KSper Channels with NNC 55-0396 and Quinidine on Human Sperm Function

Abstract

Background: Calcium enters human sperm through the “Cation Channel of Sperm” (CatSper), while potassium ions exit via the sperm potassium channel (KSper). These two channels regulate intracellular calcium concentration ([Ca2+]i) and membrane potential. Our study aims to investigate and compare the contributions of these channels in capacitated sperm function. Methods: This study was conducted at the Physiology Department of Shiraz Medical School in 2022. Thirty-six semen samples were washed, and the supernatants were discarded. Then, 0.5 mL of modified-supplemented Earle’s balanced salt solution (M-sEBSS) was added to the sediments. Samples were incubated at 37 ̊C and 5% CO2. The motile spermatozoa were aspirated after swimming up, and the samples were diluted with M-sEBSS to 10×106 spermatozoa per mL. The samples were divided into four groups: control, solvent (dimethyl-sulphoxide (DMSO), NNC55-0396 (NNC) (10 μM), and quinidine (100 μM) as CatSper and KSper blockers, respectively. Sperm kinematics were evaluated by a computer-assisted sperm analyzer. The samples were stained with Eosin-Y and FITC-PSA to assess sperm viability and acrosomal reaction. The [Ca2+]i was examined by flow cytometry using Fluo-3AM. The parametric and non-parametric data were analyzed using one-way ANOVA and Kruskal-Wallis test.Results: NNC and quinidine significantly decreased progressive sperm motility (P=0.001) and reduced sperm kinematics (P=0.001). NNC but not quinidine significantly decreased sperm survival (P=0.001), reduced [Ca2+]i in live spermatozoa (P=0.05), and induced the acrosomal reaction (P=0.012). Conclusion: Inhibition of KSper without effect on [Ca2+]i can inhibit sperm motility and increase mortality rate. It seems that the function of KSper is as vital as CatSper in human sperm physiology.

Keywords

• calcium channels
• potassium channels
• nnc 55-0396
• quinidine