Giovanna Zolese

N-acylethanolamides (NAEs) are naturally occurring signaling lipids consisting of amides and esters of long-chain polyunsaturated fatty acids. Usually they are present in a very small amounts in many mammalian tissues and cells, including human reproductive tracts and fluids. Recently, the presence of N-arachidonoylethanolamide (anandamide, AEA), the most characterised member of endocannabinoids, and its congeners palmitoylethanolamide (PEA) and oleylethanolamide (OEA) in seminal plasma, oviductal fluid, and follicular fluids was demonstrated. AEA has been shown to bind not only type-1 (CB1) and type-2 (CB2) cannabinoid receptors, but also type-1 vanilloid receptor (TRPV1), while PEA and OEA are inactive with respect to classical cannabinoid CB1 and CB2 but activate TRPV1 or peroxisome proliferator activate receptors (PPARs). This review concerns the most recent experimental data on PEA and OEA, endocannabinoid-like molecules which appear to exert their action exclusively on sperm cells with altered features, such as membrane characteristics and kinematic parameters. Their beneficial effects on these cells could suggest a possible pharmacological use of PEA and OEA on patients affected by some forms of idiopathic infertility.

The goal of this study was to examine the effect of palmitoylethanolamide (PEA) on the capacitation process and hyperactivated motility (HA) in idiopathic infertile men. Our data show the effect of PEA on the kinematic parameters of sperm cells from idiopathic infertile men during the capacitation of spermatozoa in vitro, both in the presence and absence of 2.5 nM PEA, a molecule physiologically present in human reproductive tracts. Two groups of sperm cells were identified. In group I (36 ± 14 × 10⁶ cells/mL), PEA significantly increased some motility parameters and HA during capacitation. In group II (58 ± 18 × 10⁶ cells/mL), PEA did not significantly modify motility parameters and HA. Fura 2 AM (acetoxymethyl ester derivative of fura 2) measurements demonstrated that PEA increased external Ca²⁺ influx (which modulates HA) in group I, while no change was measured in group II. In conclusion, our data indicated that PEA modulated certain physiological sperm functions that are involved in fertilization; in particular, we showed that PEA modulated for HA in men with low sperm kinematic parameters.