N-thiocarboxyanhydrides, amino acid-derived enzyme-activated H2S donors, enhance sperm mitochondrial activity in presence and absence of oxidative stress

Background Hydrogen sulfide (H2S) donors are crucial tools not only for understanding the role of H2S in cellular function but also as promising therapeutic agents for oxidative stress-related diseases. This study aimed to explore the effect of amino acid-derived N-thiocarboxyanhydrides (NTAs), which release physiological H2S levels in the presence of carbonic anhydrase, on porcine sperm function during short-term incubation with and without induced oxidative stress. For this purpose, we employed two H2S-releasing NTAs with release half-lives (t1/2) in the range of hours that derived from the amino acids glycine (Gly-NTA) or leucine (Leu-NTA). Because carbonic anhydrase is crucial for H2S release from NTAs, we first measured the activity of this enzyme in the porcine ejaculate. Then, we tested the effect of Gly- and Leu-NTAs at 10 and 1 nM on sperm mitochondrial activity, plasma membrane integrity, acrosomal status, motility, motile subpopulations, and redox balance during short-term incubation at 38 °C with and without a reactive oxygen species (ROS)-generating system.

            Results
            Our results show that carbonic anhydrase is found both in spermatozoa and seminal plasma, with activity notably higher in the latter. Both Gly- and Leu-NTAs did not exert any noxious effects, but they enhanced sperm mitochondrial activity in the presence and absence of oxidative stress. Moreover, NTAs (except for Leu-NTA 10 nM) tended to preserve the sperm redox balance against the injuries provoked by oxidative stress, which provide further support to the antioxidant effect of H2S on sperm function. Both compounds also increased progressive motility over short-term incubation, which may translate into prolonged sperm survival.

            Conclusions
            The presence of carbonic anhydrase activity in mammalian spermatozoa makes NTAs promising molecules to investigate the role of H2S in sperm biology. For the first time, beneficial effects of NTAs on mitochondrial activity have been found in mammalian cells in the presence and absence of oxidative stress. NTAs are interesting compounds to investigate the role of H2S in sperm mitochondria-dependent events and to develop H2S-related therapeutic protocols against oxidative stress in assisted reproductive technologies.