Effects of human follicular fluid and high-density lipoproteins on early spermatozoa hyperactivation and cholesterol efflux

Safouane M Hamdi,Gérard Vieitez,Béatrice Jaspard,Ronald Barbaras,Bertrand Perret,Roget Mieusset,Jean Parinaud,Xavier Collet

doi:10.1194/jlr.m000679

Abstract

The preovulatory human follicular fluid contains only HDLs as a lipoprotein class with a typically high proportion of prebeta HDL. We first examined the role of follicular fluid and HDL subfractions on human spermatozoa capacitation, a process characterized by a hyperactivation of the flagellar movement and a depletion of plasma membrane cholesterol. Whole follicular fluid and isolated HDL, used at constant free cholesterol concentration, were both able to promote an early flagellar hyperactivation. Moreover, incubation of [(3)H]cholesterol-labeled spermatozoa with follicular fluid induced a rapid cholesterol efflux from spermatozoa that was confirmed by mass measurements of cholesterol transfer. Using isolated HDL, the cholesterol efflux had a similar time course and represented 70% of that mediated by whole follicular fluid. We then analyzed the time course of radioactive labeling of HDL subfractions. In the first minute of incubation, we found that the prebeta HDL fraction incorporated the main part of the radioactivity (60%), with the rest being found in alpha-HDL, but strikingly, the labeling of alpha-HDL increased with time at the expense of prebeta HDL.Thus, our results indicate that HDLs are involved in both spermatozoa hyperactivation and cholesterol effl ux and suggest the role of prebeta-HDL particles as fi rst cellular cholesterol acceptors.

Highlights

The preovulatory human follicular fluid contains only HDLs as a lipoprotein class with a typically high proportion of pre␤ HDL
Of interest, when HDL isolated from follicular fluid (FF) were used at the same free cholesterol concentration than that of the 20%-FF dilution (i.e., 13.6 μmol/l of HDL-free cholesterol), level and kinetics of spermatozoa hyperactivation were in the same range (14 ± 2% at 5 min)
We evidenced that HDL is the single class of lipoprotein during the preovulatory period [13] and that pre␤ HDLs represent about 18% of total HDL of the FF [14]

Summary

Introduction

The preovulatory human follicular fluid contains only HDLs as a lipoprotein class with a typically high proportion of pre␤ HDL. We first examined the role of follicular fluid and HDL subfractions on human spermatozoa capacitation, a process characterized by a hyperactivation of the flagellar movement and a depletion of plasma membrane cholesterol. Using isolated HDL, the cholesterol efflux had a similar time course and represented 70% of that mediated by whole follicular fluid. Effects of human follicular fluid and high-density lipoproteins on early spermatozoa hyperactivation and cholesterol efflux. Human follicular fluid (FF) is an efficient capacitating agent [8, 9] It acts, at least in part, by inducing an efflux of cholesterol from spermatozoa to different acceptors like HDL, albumin [10], or lipid transfer protein-I [11, 12]. We revealed the distinctive role of pre␤ HDL particles

Methods

Results

Conclusion