Effects of lithium and haloperidol on human sperm motility in-vitro

Phosphatidylinositol 3-kinase inhibition enhances human sperm motility

BACKGROUND

The number of spermatozoa with forward motility after capacitation procedures represents the limiting factor for application of IVF versus intracytoplasmatic sperm injection (ICSI) procedure in cases of oligoasthenozoospermia. The possibility of increasing this number may thus be of help to the patient. A complex array of signalling pathways is involved in the regulation of sperm motility and recent data pointed out an important role for kinase/phosphatase-regulated phosphorylation of proteins. Here, we investigated the role of phosphatidylinositol 3-kinase (PI3K), a lipid and protein kinase involved in the regulation of several biological aspects of somatic cells, on human sperm motility by using the specific PI3K inhibitor LY294002.

METHODS AND RESULTS

We demonstrated that in-vitro incubation of swim-up selected or unselected human spermatozoa with LY294002 determined an increase of percentage forward motility in all the treated samples. The effect was dose-dependent with an EC(50) of 1.09 +/- 0.54 micromol/l. LY294002 also increased sperm movement characteristics and hyperactivation as evaluated by computer-assisted motion analyser. The compound was also able to overcome the detrimental effect of hydrogen peroxide and lithium chloride on sperm motility.

CONCLUSIONS

Our results suggest a negative role for PI3K in the development and maintenance of sperm motility and suggest a possible use of PI3K inhibitors to enhance motility in cases of asthenozoospermia.

Adenosine stimulates human sperm motility via A2 receptors

The effects of adenosine and its analogues on human sperm motility were studied using a transmembrane migration method. Specific binding sites for adenosine in human sperm were also investigated. Adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) stimulated human sperm motility with similar efficacies and the maximal amplitudes of motility increases were both about 70%. 3,7-Dimethyl-1-propargylxanthine (DMPX), a potent A2 antagonist, competitively antagonized NECA-induced motility stimulation. Successively higher concentrations of DMPX shifted the dose-response curve of NECA to the right in a nearly parallel fashion. Dipyridamole, an inhibitor of adenosine uptake, does not reduce the ability of adenosine to stimulate human sperm motility. In radioligand-binding studies, adenosine A1 selective analogues, cyclopentyl-1,3-dipropylxanthine and 1-methyl-2-phenylethyl adenosine, have little competitive effect on [3H]NECA binding in human sperm membrane. These results provide evidence that adenosine enhances human sperm motility via adenosine A2 receptors on the surface of sperm membranes.

Identification of adenosine receptors in human spermatozoa

1. The effects of adenosine receptor agonists and antagonists on human sperm motility have been studied. Specific binding sites for adenosine and its analogues on human sperm were also investigated. 2. Agonists stimulated human sperm motility in a dose-dependent manner with a potency order of 5'-N-ethylcarboxamidoadenosine (NECA, EC50 = 0.3 mumol/L) > 2-[p-(carboxyethyl)phenylethylamino]-5'-N- ethylcarboxamidoadenosine (CGS-21680, EC50 = 10 mumol/L) > adenosine (EC50 = 100 mumol/L). 3. NECA-stimulated motility was competitively inhibited by various adenosine receptor antagonists. The potency order was 3,7-dimethyl-1-propargylxanthine > 8-(p-sulfophenyl) theophylline > xanthine amino congener. 4. The radioligand [3H]-NECA bound to sperm membrane in a saturable manner with a Bmax of 21.3 pmol/mg protein and equilibrium Kd of 4 mumol/L. Adenosine agonists and antagonists competed for [3H]-NECA binding with the same rank order of potency as for the stimulation of human sperm motility. 5. GTP gamma s inhibited 63% of specific [3H]-NECA binding with IC50 value of 11 nmol/L. This suggests that the [3H]-NECA binding sites may be coupled to one or more G proteins. 6. These results indicate the presence of adenosine A2 receptors on human sperm which are responsible for adenosine-mediated enhancement of sperm motility.