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C J De Jonge

Publications and source records attributed to C J De Jonge.

20 records · Page 2Linked to original sources
PubMedDate not supplied

Characterization of two second messenger pathways and their interactions in eliciting the human sperm acrosome reaction.

The human sperm acrosome reaction (AR) occurs via the activation of at least two signal transduction pathways. The purpose of this investigation was to characterize two of the pathways, the protein kinase A (PKA) and C (PKC) pathways, and determine whether pathway "crosstalk" occurs between them in eliciting the AR in capacitated spermatozoa. Stimulators of each pathway were tested in a dose-dependent manner. ARmax, ED50, and delta ARmax (%ARmax-%ARcontrol) values were calculated. The PKA pathway stimulators forskolin and dibutyryl cyclic AMP (dbcAMP) induced an ARmax at 1.0 microM and 1.0 mM, respectively. The ED50 and delta ARmax values were: 0.01 microM and 17% for forskolin and 0.069 mM and 13% for dbcAMP. Two stimulator types of the PKC pathway were tested: synthetic diacylglycerols (DG) and a phorbol diester. 1,2-dioleoyl-sn-glycerol and 1,2-dioctanoyl-sn-glycerol, analogues of the PKC-activating second messenger DG, each induced an ARmax at 50 microM. The ED50 and delta AR max values were: 33 microM and 24% for 1,2-dioleoyl and 34.8 microM and 34% for 1,2-dioctanoyl. 4 beta-Phorbol-12,13-didecanoate, a PKC stimulator, induced an ARmax at 0.1 microM. The ED50 and delta ARmax were 0.021 microM and 26%. An inhibitor of each kinase was added at the end of the capacitation period and prior to stimulation by inducers at their ARmax dose. KT5720, a PKA inhibitor, caused a dose-dependent reduction of the forskolin and dbcAMP-induced AR. Calphostin C, a PKC inhibitor, prevented stimulation of the AR by 1,2-dioleoyl and 4 beta-phorbol-12,13-didecanoate. To investigate pathway "crosstalk," the following experiments were conducted: (1) stimulators of each pathway were combined and tested at the ARmax and ED50 concentrations for each; (2) spermatozoa were pretreated with a kinase inhibitor and then stimulated using an alternative pathway stimulator; and (3) a PKA or PKC inhibitor and a combination of PKA and PKC stimulators, at ED50 concentrations, were tested. The results for (1) indicate an additive AR response of ED50 concentrations but not for ARmax doses. The results for (2) demonstrate that a kinase inhibitor for one pathway prevents induction of the AR by a stimulator of the alternative pathway. Finally, the results for (3) show that a kinase inhibitor for one pathway prevents induction of the AR by the combined use of separate pathway stimulators. When taken collectively, the present results suggest a convergent mechanism of crosstalk between the PKA and PKC pathways leading to the human sperm AR.

Acrosome↗
PubMedDate not supplied

Activation of coagulation factor X in human semen.

Tissue factor (TF) is an essential cofactor for factor VII (fVII) in initiating blood coagulation. Recently, TF was shown to be present in human semen and to be associated with prostasomes that originate from prostatic secretions. In the blood coagulation cascade, the complex of TF and activated factor VII (fVIIa) can activate both factor X and factor IX, by limited proteolysis. In the present study, we investigated the ability of semen to activate factor X. We also determined that factor X was activated predominantly by TF-fVIIa and that most of the TF was present in the seminal plasma, consistent with prostasome localization. No endogenous factor X was detected in semen, but activation of added factor X occurred in the absence of added fVIIa. Subsequent experiments showed that seminal plasma contains endogenous fVII-like activity, but the addition of more fVIIa increased factor X activation. Thus, while seminal plasma contains significant amounts of TF, its potential to activate factor X is limited by fVII availability and by the absence of endogenous factor X. Evaluation of semen specimens from infertility patients revealed a 16-fold variation in TF-fVII activity. No relationship between TF and number of days of abstinence, specimen pH, sperm count, or sperm motility was evident. Additional factor X-activating potential, independent of further TF activity, was generated in seminal plasma after treatment of semen with calcium and ionophore A23187. Production of this additional activity was blocked by the addition of anti-TF antibody during the activation. Since there is no factor X endogenous to semen, the additional activity stimulated by A23187 appears to be due to an endogenous, non-factor X substrate for TF-fVII in semen. This endogenous substrate may be either factor IX or a novel new substrate for TF-fVIIa. Future experiments will test these hypotheses.

Animals↗