Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ejaculated washed ram spermatozoa showed consistent increases in the intracellular concentration of cyclic 3', 5'-adenosine monophosphate (cAMP) after incubation for 15 minutes with the phosphodiesterase (PDE)-inhibitors, theophylline and caffeine. In vitro addition of cAMP or PDE-inhibitors to ram semen also stimulated and maintained sperm motility and enhanced the rate of fructose utilization. The same doses of cAMP or theophylline significantly stimulated the rate of protein synthesis by the washed spermatozoa, while the PDE-stimulator, imidazole, inhibited protein synthesis significantly. The stimulatory effect of cAMP on sperm protein synthesis was not affected by cycloheximide, but was abolished by the mitochondrial inhibitor, chloramphenicol. The present results indicate a positive correlation between the intracellular concentration of cAMP and the rates of progressive motility, fructose utilization, and protein synthesis by ram spermatozoa. The results suggest that the effect of cAMP is associated with the synthesis of mitochndrial proteins which may be involved with the observed enhancement of sperm motility and metabolism. The data also indicate that cAMP map act either as a first or a second messenger in mature spermatoza.
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PMID:Effect of cyclic AMP on fructose utilization, progressive motility and protein synthesis by ram spermatozoa. 1672 4

The aim of this review study is to elucidate the effects that phosphodiesterase 5 (PDE5) inhibitors exert on spermatozoa motility, capacitation process and on their ability to fertilize the oocyte. Second messenger systems such as the cAMP/adenylate cyclase (AC) system and the cGMP/guanylate cyclase (GC) system appear to regulate sperm functions. Increased levels of intracytosolic cAMP result in an enhancement of sperm motility and viability. The stimulation of GC by low doses of nitric oxide (NO) leads to an improvement or maintenance of sperm motility, whereas higher concentrations have an adverse effect on sperm parameters. Several in vivo and in vitro studies have been carried out in order to examine whether PDE5 inhibitors affect positively or negatively sperm parameters and sperm fertilizing capacity. The results of these studies are controversial. Some of these studies demonstrate no significant effects of PDE5 inhibitors on the motility, viability, and morphology of spermatozoa collected from men that have been treated with PDE5 inhibitors. On the other hand, several studies demonstrate a positive effect of PDE5 inhibitors on sperm motility both in vivo and in vitro. In vitro studies of sildenafil citrate demonstrate a stimulatory effect on sperm motility with an increase in intracellular cAMP suggesting an inhibitory action of sildenafil citrate on a PDE isoform other than the PDE5. On the other hand, tadalafil's actions appear to be associated with the inhibitory effect of this compound on PDE11. In vivo studies in men treated with vardenafil in a daily basis demonstrated a significantly larger total number of spermatozoa per ejaculate, quantitative sperm motility, and qualitative sperm motility; it has been suggested that vardenafil administration enhances the secretory function of the prostate and subsequently increases the qualitative and quantitative motility of spermatozoa. The effect that PDE5 inhibitors exert on sperm parameters may lead to the improvement of the outcome of assisted reproductive technology (ART) programs. In the future PDE5 inhibitors might serve as adjunct therapeutical agents for the alleviation of male infertility.
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PMID:Effects of phosphodiesterase-5 inhibitors on sperm parameters and fertilizing capacity. 1808 51

Unlike most other species, ram spermatozoa are difficult to capacitate in vitro. Bicarbonate and Ca(2+) are necessary, whereas bovine serum albumin does not appear to be obligatory. In the present investigation we have assessed (1) the ability of the cholesterol-sequestering agent, methyl-beta-cyclodextrin (M-beta-CD), to initiate protein tyrosine phosphorylation, and (2) the importance of phosphodiesterases (PDEs) in controlling the levels of cAMP. Results show that despite removing significant amounts of membrane cholesterol, as assessed by filipin staining, M-beta-CD treatment did not stimulate major increases in protein tyrosine phosphorylation. Addition of a cocktail of PDE inhibitors (theophylline and caffeine), a phosphatase inhibitor (okadaic acid) and dibutyryl-cAMP (db-cAMP), however, stimulated specific tyrosine phosphorylation of several proteins between 30 and 120 kDa. On their own, none of the above reagents were effective but a combination of db-cAMP + PDE inhibitors was sufficient to achieve a maximal response. H-89, a protein kinase-A inhibitor, suppressed tyrosine phosphorylation significantly. Immunofluorescence revealed that the newly-phosphorylated proteins localised mainly in the sperm tail. These findings suggest that in ram spermatozoa cAMP levels are too low to initiate tyrosine phosphorylation of flagellar proteins that are indicative of the capacitation state and that this is caused by unusually high levels of intracellular PDEs.
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PMID:Cyclic-AMP initiates protein tyrosine phosphorylation independent of cholesterol efflux during ram sperm capacitation. 1867 12

In rats, the success of in vitro fertilization (IVF) was reported 40 years ago. Although it has been demonstrated in papers that these IVF oocytes using sperm freshly collected from cauda epididymides can be developed to term via embryo transfer, successful IVF with cryopreserved rat sperm has never been reported to date. Here, we report establishment of a successful IVF system using frozen/thawed rat spermatozoa. Our data showed that intracellular cAMP and free cholesterol levels in frozen/thawed rat sperm were maintained low, suppressing capacitation-associated tyrosine phosphorylation. The treatment of methyl-beta-cyclodextrin improved removal of free cholesterol from the membrane in frozen/thawed sperm but not induction of capacitation-associated tyrosine phosphorylation in the sperm. Treatment with a phosphodiesterase inhibitor, 3-isobutyl-1-methyl-xanthin (IBMX), dramatically increased cAMP and tyrosine phosphorylation levels in frozen/thawed rat sperm. When the IBMX-treated frozen/thawed sperm were used for IVF, the proportions of pronuclear formation and blastocyst formation were significantly higher than those of frozen/thawed sperm treated without IBMX (P < 0.05). The embryos were developed to term at a high success rate equivalent to the rate obtained with IVF using fresh sperm. Thus, we established for the first time a successful IVF system in rats using cryopreserved spermatozoa.
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PMID:Generation of live rats produced by in vitro fertilization using cryopreserved spermatozoa. 1903 60

In the present study, the viability, intracellular pH (pHi), cAMP ([cAMP]i), calcium concentration and protein phosphotyrosine content were evaluated in relation to the acrosomal and capacitation status of freshly ejaculated bull spermatozoa. These parameters were evaluated before and after incubation with the capacitation inducer heparin, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), the phosphotyrosyl-protein phosphatase inhibitors phenylarsine oxide (PAO) and sodium orthovanadate, and hydrogen peroxide. The results obtained were integrated to address the physiological interactions between the different signalling events affecting sperm capacitation and acrosome reaction. As expected, heparin promoted the expression of the 'B' pattern of chlortetracycline binding, increased pHi, [cAMP]i and the phosphotyrosine content of sperm proteins. The effects of heparin were enhanced by IBMX. Both PAO and sodium orthovanadate stimulated protein phosphotyrosine content and acrosomal exocytosis, although only PAO affected pH, Ca2+ and cAMP levels. Intracellular pH was increased while both Ca2+ and [cAMP]i were decreased. Physiological concentrations of H2O2 increased [cAMP]i and promoted acrosomal exocytosis. A significant positive correlation was found between sperm capacitation, protein phosphotyrosine content and stored Ca2+ concentration, whereas the acrosome reaction was correlated with pHi and Ca2+ concentration. This study presents the first global analysis of the major elements individually described during sperm capacitation and acrosome reaction signalling pathways, supported by statistical correlations.
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PMID:Modulation of bovine sperm signalling pathways: correlation between intracellular parameters and sperm capacitation and acrosome exocytosis. 1938 58

Protein tyrosine phosphorylation is a key event accompanying sperm capacitation. Although this signaling cascade generates an array of tyrosine-phosphorylated polypeptides, their molecular characterization is still limited. It is necessary to differentiate the localization of the tyrosine-phosphorylated proteins in spermatozoa to understand the link between the different phosphorylated proteins and the corresponding regulated sperm function. cAMP plays a pivotal role in the regulation of tyrosine phosphorylation. The intracellular cAMP levels were raised in goat spermatozoa by the addition of the phosphodiesterase inhibitor, IBMX in conjugation with caffeine. Tyrosine phosphorylation was significantly up-regulated following treatment with these two reagents. Treatment of caudal spermatozoa with IBMX and caffeine, time dependent up-regulated phosphorylation of the protein of molecular weights 50 and 200 kDa was observed. Increased phosphorylation was observed with a combination of IBMX and caffeine treatment. Tyrosine phosphorylation in caput spermatozoa was not affected significantly under these conditions. The expression level of tyrosine kinase in sperm was examined with specific inhibitors and with anti-phosphotyrosine antibody. The indirect immunofluorescence staining was carried out on ethanol permeabilized sperm using anti-phosphotyrosine antibody. Western blot analysis was done using two separate PKA antibodies: anti-PKA catalytic and anti-PKA RIalpha. Almost no difference was found in the intracellular presence of the PKA RIalpha and RIIalpha subunits in caput and caudal epididymal spermatozoa. However, the catalytic subunit seemed to be present in higher amount in caudal spermatozoa. The results show that caprine sperm displays an enhancement of phosphorylation in the tyrosine residues of specific proteins under in vitro capacitation conditions.
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PMID:Regulation of tyrosine kinase activity during capacitation in goat sperm. 1980 24

We have previously shown that a cocktail-containing phosphodiesterase inhibitors (theophylline and caffeine), a phosphatase inhibitor (okadaic acid) and dibutyryl-cAMP promoted specific protein tyrosine phosphorylation in ram spermatozoa during incubation in capacitating conditions. Here, we show, for the first time, that this cocktail induced a progressive time-dependent increase in the capacitated-sperm subpopulation. The addition of either the analogue of adenosine, 2-chloro-2'-deoxyadenosine (Cl-Ado) or caffeine provided a significant increase in the proportion of capacitated spermatozoa and total tyrosine phosphorylation. Computer-assisted semen analysis was used to identify hyperactivated spermatozoa by setting maximum threshold for linearity (< or =45%) and minimum for amplitude of lateral head displacement (> or =3.5 microm). Our results showed that ram spermatozoa can be capacitated in vitro without displaying hyperactivated movement. Among the above-mentioned compounds, only caffeine was able to induce hyperactivation that achieved the maximal response at 8 min of incubation, with a significant increase in hyperactivated spermatozoa of 44.4 +/- 5.6% related to control samples. Flow cytometry analyses showed that caffeine induced a significant increase in the content of calcium in viable spermatozoa during the time-course of incubation in capacitating conditions. BAPTA-AM, a cell-permeable calcium chelator, did not suppress the caffeine-dependent hyperactivation. Quantitative analysis revealed that the addition of caffeine or Cl-Ado accounted for an increase in intracellular cAMP level. However, this increase in cAMP does not seem to be responsible for the caffeine-induced hyperactivation because the cAMP-elevating agents (cocktail) did not promote hyperactivation either, although they greatly induced capacitation and protein tyrosine phosphorylation. The inhibition of PKA with H89 reduced both capacitation and protein tyrosine phosphorylation although hyperactivation increased. These results suggest that calcium from internal stores would be enough to initiate the hyperactivated movement, and that protein tyrosine phosphorylation implicated in ram sperm hyperactivation would be regulated by calcium rather than by PKA-dependent cAMP.
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PMID:Caffeine induces ram sperm hyperactivation independent of cAMP-dependent protein kinase. 1984 99

The cAMP-dependent protein kinase (PKA), protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) pathways control most relevant functions in male germ cells including motility. Recently we demonstrated that phosphorylation state of glycogen synthase kinase-3alpha (GSK3A) is also a key event in the control of boar spermatozoa motility. However, the upstream regulators of GSK3A serine phosphorylation (inhibition) in male germ cells remain largely unknown. This work investigates the involvement of PKA, PKC and PI3K pathways in GSK3A phosphorylation in boar spermatozoa. A capacitating medium (TCM) or the phosphodiesterase-resistant cell permeable cAMP analogue 8Br-cAMP cause a significant increase in Ser21 GSK3A phosphorylation associated with a simultaneous significant increase in boar spermatozoa motility. These effects are blocked after preincubation of spermatozoa with PKA inhibitor H89 or PKC inhibitor Ro-32-0432. The PI3K inhibitor LY294002 increases both spermatozoa motility parameters and the basal GSK3A phosphorylation, but does not affect either TCM- or 8Br-cAMP-stimulated GSK3A phosphorylation. PI3K inhibition effects are mediated by an increase in intracellular cAMP levels in boar spermatozoa and are suppressed by PKA inhibitor H89. In summary, we demonstrate that PKA, PKC and PI3K pathways crosstalk in porcine male germ cells to crucially regulate GSK3A phosphorylation which subsequently controls cell motility. In addition, our results suggest that PI3K is upstream of PKA which lies upstream of PKC in this regulatory cascade(s). Our findings contribute to elucidate the molecular mechanisms underlying the regulation of one of the most relevant male germ cell functions, motility.
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PMID:Protein kinases A and C and phosphatidylinositol 3 kinase regulate glycogen synthase kinase-3A serine 21 phosphorylation in boar spermatozoa. 1991 76

The paper entitled "Expression of phosphodiesterase type 5A in human spermatozoa and influence of its inhibition on motility and functional sperm parameters" by C. Foresta et al, which was published online on 1 July 2010, has been withdrawn at the authors' request.
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PMID:Retraction: Expression of phosphodiesterase type 5A in human spermatozoa and influence of its inhibition on motility and functional sperm parameters. 2059 99

Seminal fluid inhibits sperm capacitation mainly because of its high cholesterol content. Prostasomes are the main source of cholesterol in seminal fluid. They are known to have numerous protective properties and are able to transfer proteins and lipids to spermatozoa, but their impact on capacitation and acrosome reaction (AR) is not yet well understood. The aim of this study was to determine the effects of prostasomes on human sperm capacitation and AR. After 80% Percoll selection, freshly ejaculated human spermatozoa were incubated for 3 h under capacitating conditions with prostasomes, phosphodiesterase inhibitor 3-iso-butyl-methylxantine (IBMX), or a combination of prostasomes and IBMX. Physiological concentration of prostasomes significantly decreased tyrosine phosphorylation levels of human sperm capacitation markers P110 and P80 (p < 0.01), and the proportions of capacitated (p < 0.05) and acrosome-reacted spermatozoa (p < 0.05). Prostasomes significantly increased the proportion of spermatozoa that did not incorporate propidium iodide and significantly attenuated the effect of IBMX on P110 tyrosine phosphorylation. Prostasomes had no effect on the pH(i) increase associated with capacitation. They significantly increased intracellular cAMP concentration ([cAMP](i)) and, when prostasomes and IBMX were present together, [cAMP](i) was further increased. To our knowledge, this is the first study to show clearly that prostasomes inhibit capacitation and spontaneous AR.
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PMID:Prostasomes: inhibitors of capacitation and modulators of cellular signalling in human sperm. 2102 15


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