AMPK up-activation reduces motility and regulates other functions of boar spermatozoa

We recently demonstrated that AMPK inhibition in spermatozoa regulates motility, plasma membrane organization, acrosome integrity and mitochondrial membrane potential. As AMPK activity varies in different energy conditions induced by sperm environment, this work investigates the functional effects of AMPK activation in boar spermatozoa. Spermatozoa were incubated under non-stimulating (TBM) or Ca(2+) and [Formula: see text]-stimulating (TCM) media in the presence/absence of AMPK activator, A769662, for different times. AMPK activity, evaluated as Thr(172) phosphorylation by western blot, is effectively increased by A769662 in spermatozoa. AMPK activation significantly reduces the percentage of motile spermatozoa under Ca(2+) and/or [Formula: see text]-stimulating conditions. Moreover, AMPK activation in spermatozoa incubated in TBM or TCM significantly reduces curvilinear VCL, straight-line VSL and average VAP velocities, which subsequently lead to a significant decrease in the percentage of rapid spermatozoa (VAP > 80 μm/s). The effect of AMPK activation on motility is intensified by the absence of BSA in the incubation medium. AMPK activation for a short time prevents the decline in cell viability and in the sperm population displaying high mitochondrial membrane potential which is induced by Ca(2+) and [Formula: see text]. Sustained (24 h) AMPK activation under TBM or TCM significantly increases both lipid disorganization and phosphatidylserine externalization in the sperm plasma membrane, and diminishes the acrosome membrane integrity. In summary, AMPK activation modifies essential sperm processes such as motility, viability, mitochondrial membrane potential, acrosome membrane integrity, and organization and fluidity of plasma membrane. As these spermatozoa processes are required under different environmental conditions when transiting through the female reproductive tract to achieve fertilization, we conclude that balanced levels of AMPK activity are essential for regulating sperm function.