TRPM8 in mouse sperm detects temperature changes and may influence the acrosome reaction

Abstract

Changes in the concentration of intracellular Ca2+ ([Ca2+]i) trigger and/or regulate principal sperm functions during fertilization, such as motility, capacitation, and the acrosome reaction (AR). Members of the large TRP channel family participate in a variety of Ca2+-dependent cell signaling processes. The eight TRPM channel members constitute one of the seven groups belonging to this family. Here we document using RT-PCR experiments the presence of Trpm2, 4, 7, and 8 in mouse spermatogenic cells. Trpm8 transcription is up-regulated after day 30. The localization of TRPM8 protein in mouse sperm was confirmed by immunocytochemistry and Western blots. Patch clamp recordings in testicular mouse sperm revealed TRPM8 agonist (menthol and icilin) activated currents sensitive to TRPM8 inhibitors N-(4-t-Butylphenyl)-4-(3-Chloropyridin-2-yl)tetrahydropyrazine-1(2H)-carboxamide (BCTC) and capsazepine. These findings are consistent with the presence of functional TRPM8 in mouse sperm. Furthermore, menthol induced a [Ca2+]i increase and the AR in these cells, that were inhibited by capsazepine (20 µM) and BCTC (1.6 µM). Notably, the progesterone and zona pellucida-induced AR was significantly (>40%) inhibited by BCTC and capsazepine, suggesting the possible participation of TRPM8 channels in this reaction. TRPM family members present in sperm could be involved in other important signaling events, such as thermotaxis, chemotaxis, and mechanosensory transduction.