Chemical UV Filters Mimic the Effect of Progesterone on Ca Signaling in Human Sperm Cells.

Progesterone released by cumulus cells surrounding the egg induces a Ca influx into human sperm cells via the cationic channel of sperm (CatSper) Ca channel and controls multiple Ca-dependent responses essential for fertilization. We hypothesized that chemical UV filters may mimic the physiological action of progesterone on CatSper, thus affecting Ca signaling in human sperm cells. We examined 29 UV filters allowed in sunscreens in the United States and/or the European Union for their ability to induce Ca signals in human sperm by applying measurements of the intracellular free Ca concentration. We found that 13 UV filters induced a significant Ca signal at 10 μM. Nine UV filters induced Ca signals primarily by activating the CatSper channel. The UV filters 3-benzylidene camphor (3-BC) and benzylidene camphor sulfonic acid competitively inhibited progesterone-induced Ca signals. Dose-response relations for the UV filters showed that the Ca signal-inducing effects began in the nanomolar-micromolar range. Single-cell Ca measurements showed a Ca signal-inducing effect of the most potent UV filter, 3-BC, at 10 nM. Finally, we demonstrated that the 13 UV filters acted additively in low-dose mixtures to induce Ca signals. In conclusion, 13 of 29 examined UV filters (44%) induced Ca signals in human sperm. Nine UV filters primarily activated CatSper and thereby mimicked the effect of progesterone. The UV filters 3-BC and benzylidene camphor sulfonic acid competitively inhibited progesterone-induced Ca signals. In vivo exposure studies are needed to investigate whether UV filter exposure affects human fertility.