Signaling pathway of nitric oxide-induced acrosome reaction in human spermatozoa.
Nitric oxide (NO) has been recently shown to modulate in vitro motility, viability, the acrosome reaction (AR), and metabolism of spermatozoa in various mammalian species, but the mechanism or mechanisms through which it influences sperm functions has not been clarified. In human capacitated spermatozoa, both the intracellular cGMP level and the percentage of AR-positive cells were significantly increased after 4 h of incubation with the NO donor, sodium nitroprusside (SNP). SNP-induced AR was significantly reduced in the presence of the soluble guanylate cyclase (sGC) inhibitors, LY83583 and ODQ; this block was bypassed by adding 8-bromo-cGMP, a cell-permeating cGMP analogue, to the incubation medium. Finally, Rp-8-Br-cGMPS and Rp-8-pCPT-cGMPS, two inhibitors of the cGMP-dependent protein kinases (PKGs), inhibited the SNP-induced AR. Furthermore, SNP-induced AR did not occur in Ca2+ -free medium or in the presence of the protein kinase C (PKC) inhibitor, calphostin C. This study suggests that the AR-inducing effect of exogenous NO on capacitated human spermatozoa is accomplished via stimulation of an NO-sensitive sGC, cGMP synthesis, and PKG activation. In this effect the activation of PKC is also involved, and the presence of extracellular Ca2+ is required.
Revelli
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A
Department of Obstetrical and Gynecological Sciences, S. Anna Hospital, University of Torino, 10126 Torino, Italy. fertisave@yahoo.com
Costamagna
C
C
Moffa
F
F
Aldieri
E
E
Ochetti
S
S
Bosia
A
A
Massobrio
M
M
Lindblom
B
B
Ghigo
D
D
D020101:Acrosome Reaction / Q000187:drug effects*; D000634:Aminoquinolines / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D006801:Humans; D008297:Male; D009281:Naphthalenes / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D011810:Quinoxalines / Q000494:pharmacology; D015398:Signal Transduction; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000502:physiology*
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D000634:Aminoquinolines; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D020030:Nitric Oxide Donors; D010069:Oxadiazoles; D011810:Quinoxalines; D009599:Nitroprusside; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; C041715:6-anilino-5,8-quinolinedione; D011493:Protein Kinase C; D006162:Guanylate Cyclase; D006152:Cyclic GMP; C058819:calphostin C; D002118:Calcium