HFPO homologue exposure impairs human sperm function via calcium dyshomeostasis and mitochondrial dysfunction

Hexafluoropropylene oxide homologues (HFPOs), developed as alternatives to the banned perfluorooctanoic acid (PFOA), are environmentally persistent and increasingly detected. However, despite some evidence of reproductive toxicity, their direct impact on human sperm function has not been characterized.

This study investigated the reproductive toxicity of three prevalent HFPOs (hexafluoropropylene oxide dimer acid, HFPO-DA; hexafluoropropylene oxide trimer acid, HFPO-TA; and hexafluoropropylene oxide tetramer acid, HFPO-TeA) using an in vitro human spermatozoa exposure model, and further explored the underlying mechanisms.

In vitro assays were conducted using human spermatozoa to assess reproductive toxicity upon exposure to three prevalent HFPOs. Sperm motility, viability, and fertilization potential were assessed. Mitochondrial integrity and function, reactive oxygen species (ROS) generation, calcium homeostasis, and metabolic and proteomic profiles were evaluated. The CatSper channel blocker NNC 55-0396 was used to examine calcium influx. Progesterone-mediated acrosome reaction, sperm penetration capability, and calcium signaling were determined. The mitochondria-targeted antioxidant mitoquinone was applied to evaluate protection against HFPO-induced toxicity.

HFPO exposure, particularly HFPO-TeA and HFPO-TA, significantly impaired mitochondrial integrity and function, elevated ROS generation, disrupted calcium homeostasis, and perturbed metabolic and proteomic profiles. These effects culminated in compromised sperm motility, viability, and fertilization potential. Notably, the CatSper channel blocker NNC 55-0396 markedly inhibited HFPO-induced calcium influx. Furthermore, HFPOs significantly suppressed progesterone-mediated acrosome reaction, as well as sperm penetration capability and calcium signaling. Conversely, the mitochondria-targeted antioxidant mitoquinone significantly attenuated HFPO-caused toxicity to human sperm.

These findings identify HFPOs as reproductive toxicants that compromise male fertility through disruption of calcium signaling and mitochondrial function. Our results underscore the urgent need for risk assessment and regulatory measures to address these emerging contaminants.