PARADOXICAL EFFECT OF REAGENTS FOR SULFHYDRYL AND DISULFIDE GROUPS ONHUMAN SPERM CAPACITATION AND SUPEROXIDE PRODUCTION

Spermatozoa must undergo capacitation prior to fertilization. In human s, this process appears regulated by oxidoreduction reactions. We inve stigated the possibility that these reactions involved the sulfhydryl- disulfide pair, which offers a reversible regulation of cellular proce sses. The effects of reagents targeted for sulfhydryl and disulfide gr oups on human sperm capacitation, superoxide (O-2(.-)) generation and protein tyrosine phosphorylation were evaluated. The sulfhydryl target ed agents, phenylarsine oxide (PAO), diamide, dithiopyridine (DTP), N- ethylmaleimide ((NEM), maleimidylpropionyl biocytin (MPB), p-chloromer curibenzoic acid (PCMB), and bromobimane analogs (mBBr and qBBr) trigg ered sperm capacitation to levels comparable to those observed with a biological inducer, fetal cord serum ultrafiltrate (FCSu). Capacitatio n induced by NEM, MPB, PCMB, and PAO was prevented by superoxide dismu tase (SOD) and associated with an increased sperm production of O2(.-) . However, SOD did not affect the increase in protein tyrosine phospho rylation of spermatozoa treated with NEM, PAO, or MPB. Disulfide reduc tants, dithiothreitol (DTT), thioredoxin (TRX), glutathione (GSH), tri s-(2-carboxyethyl) phosphine (TCEP), and tris-(2-cyanoethyl) phosphine (TCP) partially to totally inhibited FCSu-induced sperm capacitation and O2(.-) production. TCEP, DTT, and TRX decreased the capacitation-a ssociated tyrosine phosphorylation of sperm proteins. The strong time- dependent increase of sperm membrane sulfhydryl groups exposed to the extracellular space occurring during the 'first hour of capacitation c ould indicate an important rearrangement of sulfhydryl carrying protei ns during the initiation of capacitation. Therefore, protein sulfhydry l-disulfide status may be important for the regulation of human sperm capacitation and the mechanisms involved may be complex and multifacto rial. (C) 1998 Elsevier Science Inc.