Alzheimer's disease-related amyloid-β1-42 peptide induces the loss of human sperm function

Characteristically identified as the main component of senile plaques present in patients suffering from Alzheimer's disease, A beta has been detected in human testis and reproductive fluids, but its effect on spermatozoa has not been addressed. The present study evaluated whether the most toxic and aggregant amyloid precursor protein (APP)-proteolytic product, amyloid-beta(1-42) (A beta(1-42)), was capable of affecting sperm functionality. Normozoospermic samples were either exposed to different A beta(1-42) doses or to the untreated and scrambled controls for a maximum of 48 h at 37 A degrees C and 5%CO2, and motility, viability and mitochondrial status were evaluated. Additionally, tyrosine phosphorylation was analyzed by immunocytochemistry and acrosomal integrity through PSA-FITC. A shorter treatment period was used to monitor prompt Ca2+ responses. A beta(1-42) peptide decreased motility before inducing mitochondrial impairment (p < 0.05; n = 6). Both outcomes became more pronounced with time, reaching their maximal decrease at 48 h, where even 1 mu M produced undesirable effects (p < 0.05; n = 6). A beta(1-42) peptide also decreased cell survival (p < 0.05; n = 6). Furthermore, although no effects on tyrosine phosphorylation were observed (p > 0.05; n = 6), reduced acrosomal integrity was detected (p < 0.05; n = 7), which was not correlated with viability loss (p > 0.05). In parallel, all A beta(1-42) concentrations elicited a [Ca2+](i) rise but a significant difference was only observed at 20 mu M (p < 0.05; n = 7) and a tendency was obtained with 10 mu M (p = 0.053; n = 7). In conclusion, A beta(1-42) peptide oligomers impair sperm function in vitro, although further studies are required to determine the clinical relevance of these findings.