Reproduction Abstracts

Introduction: Phosphoinositide 3-kinase (PI3K) activity has been reported to be critical to sperm motility and mitochondrial ROS generation while mitochondrial membrane protein Prohibitin (PHB) controls PI3K/AKT pathway in somatic cells by regulating mitochondrial function. Our recent findings showed that sperm PHB expression is significantly decreased in infertile men with poor sperm quality by regulating mitochondrial morphology and function. The objective of this study is to test if PHB expression in sperm is associated with the PI3K/AKT pathway.

Methods: Semen samples from 101 male subjects between 30 and 40 years old attempting ICSI/IVF were collected and then assayed by semen analysis according to 2010 WHO standards. Contaminating leucocytes are removed from all samples by using magnetic Dynabeads coated with a monoclonal antibody against CD45 and confirmed using a zymosan provocation assay. After then, the level of phosphorylation of PI3K/AKT pathway in sperm was detected using SDS–PAGE and Western blot in infertile men with poor sperm motility (asthenospermia, A) and/or low sperm concentrations (oligoasthenospermia, OA).

Results and discussion: Our results demonstrate a significantly lower expression of P110 catalytic subunit but a higher P85 regulatory subunit of PI3K in sperm from A and OA subjects than that from normospermic (N) subjects. However, the findings of significantly lower level of phosphorylation of P85 regulatory subunit of PI3K may result from the significantly lower level of phosphorylation of PTEN in sperm from A and OA subjects. Consequently, the significantly downregulated phosphorylation of AKT (pSer⁴⁷³ and pThr³⁰⁸) shown in sperm from A and OA subjects, may result from dephosphorylation in sperm with a higher level of mitochondrial ROS as reported previously. Collectively, our observations suggest that downregulated PI3K/AKT pathway shown in infertile men with poor sperm motility may be associated with decreased PHB expression. (This project was supported by National Natural Science Foundation of China, grant number 81270738).