Effects of aqueous crude extract ofEcheveria gibbifloraon mouse sperm function

Influence of Echeveria gibbiflora DC aqueous crude extract on mouse sperm energy metabolism and calcium-dependent channels

ETHNOPHARMACOLOGY RELEVANCE

In traditional Mexican medicine, Echeveria gibbiflora DC has been used as a vaginal post-coital rinse to prevent pregnancy. The aqueous crude extract (OBACE) induces sperm immobilization/agglutination and a hypotonic-like effect, likely attributed to the high concentration of calcium bis-(hydrogen-1-malate) hexahydrate [Ca²⁺ (C₄H₅O₅)₂•6H₂O]. Likewise, OBACE impedes the increase of [Ca²⁺]i during capacitation.

AIM OF THE STUDY

Evaluate the effect of OBACE on sperm energy metabolism and the underlying mechanism of action on sperm-specific channel.

MATERIAL AND METHODS

In vitro, we quantified the mouse sperm immobilization effect and the antifertility potential of OBACE. The energetic metabolism status was also evaluated by assessing the ATP levels, general mitochondrial activity, mitochondrial membrane potential, and enzymatic activity of three key enzymes of energy metabolism. Furthermore, the effect of the ion efflux of Cl^- and K⁺, as well as the pHi, were investigated in order to elucidate which channel is suitable to perform an in silico study.

RESULTS

Total and progressive motility notably decreased, as did fertility rates. ATP levels, mitochondrial activity and membrane potential were reduced. Furthermore, the activities of the three enzymes decreased. Neither Cl^- or K⁺ channels activities were affected at low concentrations of OBACE; nevertheless, pHi did not alkalinize. Finally, an in silico analysis was performed between the Catsper channel and calcium bis-(hydrogen-1-malate) hexahydrate, which showed a possible blockade of this sperm cation channel.

CONCLUSION

The results were useful to elucidate the effect of OBACE and to propose it as a future male contraceptive.

TMEM16A inhibition impedes capacitation and acquisition of hyperactivated motility in guinea pig sperm

Ca²⁺ -activated Cl^- channels (CaCCs) are anionic channels that regulate many important physiological functions associated with chloride and calcium flux in some somatic cells. The molecular identity of CaCCs was revealed to be TMEM16A and TMEM16B (also known as Anoctamin or ANO1 and ANO2, respectively) in all eukaryotes. A recent study suggests the presence of TMEM16A in human sperm and a relationship with the rhZP-induced acrosome reaction. However, to the best of our knowledge, little is known about the role of TMEM16A in other spermatic processes such as capacitation or motility. In this study, we evaluated the effects of two TMEM16A antagonists on capacitation, acrosome reaction, and motility in guinea pig sperm; these antagonists were T16Ainh-A01, belonging to a second generation of potent antagonists of TMEM16A, and niflumic acid (NFA), a well-known antagonist of TMEM16A (CaCCs). First of all, we confirmed that the absence of Cl^- in the capacitation medium changes motility parameters, capacitation, and the progesterone-induced acrosome reaction. Using a specific antibody, TMEM16A was found as a protein band of ∼120 kDa, which localization was in the apical crest of the acrosome and the middle piece of the flagellum. Inhibition of TMEM16A by T16Ainh-A01 affected sperm physiology by reducing capacitation, blocking the progesterone-induced acrosome reaction under optimal capacitation conditions, inhibiting progressive motility, and the acquisition of hyperactivated motility, diminishing [Ca²⁺ ]i, and increasing [Cl^- ]i. These changes in sperm kinematic parameters provide new evidence of the important role played by TMEM16A in the production of sperm capable of fertilizing oocytes.