The Roles of NO and HS in Sperm Biology: Recent Advances and New Perspectives

After being historically considered as noxious agents, nitric oxide (NO) and hydrogen sulfide (HS) are now listed as gasotransmitters, gaseous molecules that play a key role in a variety of cellular functions. Both NO and HS are endogenously produced, enzymatically or non-enzymatically, and interact with each other in a range of cells and tissues. In spite of the great advances achieved in recent decades in other biological systems, knowledge about HS function and interactions with NO in sperm biology is in its infancy. Here, we aim to provide an update on the importance of these molecules in the physiology of the male gamete. Special emphasis is given to the most recent advances in the metabolism, mechanisms of action, and effects (both physiological and pathophysiological) of these gasotransmitters. This manuscript also illustrates the physiological implications of NO and HS observed in other cell types, which might be important for sperm function. The relevance of these gasotransmitters to several signaling pathways within sperm cells highlights their potential use for the improvement and successful application of assisted reproductive technologies.