Deterioration of spermatozoal plasma membrane is associated with an increase of sperm lyso-phosphatidylcholines.
Spermatozoa with plasma membranes that lost their asymmetry or permeability for larger molecules can be identified by binding of annexin V to membrane phosphatidylserine (PS). Paramagnetic annexin-V-conjugated microbeads (AN-MB) can be used to eliminate these spermatozoa by magnetic activated cell sorting (MACS). Semen samples of six healthy volunteers with normal spermiogram parameters were divided into two sperm fractions by MACS as a function of bound AN-MB, and their individual lipid compositions were examined by matrix-assisted laser desorption and ionisation time-of-flight mass spectrometry (MALDI-TOF MS). As a model system, liposomes composed of phosphatidylcholines (PC) from egg yolk were digested by phospholipase A2 (PLA2). The MALDI-TOF mass spectra of organic extracts of both sperm subpopulations differed significantly. The ratio between lyso-phosphatidylcholine LPC 16 : 0 and PC 16 : 0/22 : 6 was approximately 2.5-4.7-fold higher (median 2.9) in the sperm group binding AN-MB than in spermatozoa with intact membrane unable to bind AN-MB. The ratio between LPC 22 : 6 and PC 16 : 0/22 : 6 was also enhanced in the spermatozoa with impaired membrane structure (factor in the range: 1.9-3.9; median 2.6). These alterations corresponded to the effects of PLA2 on artificial phospholipids. It is concluded that spermatozoa with deteriorated membrane and exposed PS are characterized by an increased lyso-phosphatidylcholine content that is likely generated by phospholipases.
Glander
H-J
HJ
Department of Dermatology/Andrology Unit, Faculty of Medicine, University of Leipzig, Leipzig, Germany. glah@medizin.uni-leipzig.de
Schiller
J
J
Süss
R
R
Paasch
U
U
Grunewald
S
S
Arnhold
J
J
D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D008244:Lysophosphatidylcholines / Q000378:metabolism*; D008297:Male; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013094:Spermatozoa / Q000378:metabolism*
D008244:Lysophosphatidylcholines