Matrine inhibits mouse sperm function by reducing sperm [Ca2+]i and phospho-ERK1/2.

BACKGROUND Matrine is a bioactive alkaloid that has a variety of pharmacological effects and is widely used in Chinese medicine. However, its effects on male reproduction are not well known. In this study, we aimed to investigate the in vitro toxicity of matrine on mature mouse sperm. METHODS Mouse cauda epididymal sperm were exposed to matrine (10-200 µM) in vitro. The viability, motility, capacitation, acrosome reaction and fertilization ability of the mouse sperm were examined. Furthermore, the intracellular calcium concentration ([Ca(2+)]i), calcium (Catsper) and potassium (Ksper) currents, and phosphorylation of extracellular signal regulated kinases 1/2 (p-ERK1/2) of the sperm were analyzed. RESULTS After exposure to 100 µM or more of matrine, mouse cauda epididymal sperm exhibited a significant reduction in total motility, progressive motility, linear velocity and acrosome reaction rate induced by Ca(2+) ionophore A23187. As a result, the fertilization ability of mouse sperm was remarkably decreased by matrine. Our data further demonstrated that matrine significantly reduced sperm [Ca(2+)]i and [Ca(2+)]i-related p-ERK1/2; however, both the CatSper and KSper currents, which are thought to interactively regulate Ca(2+) influx in sperm, were not affected by matrine. CONCLUSION Our findings indicate that matrine inhibits mouse sperm function by reducing sperm [Ca(2+)]i and suppressing the phosphorylation of ERK1/2.