Involvement of calcium in the caffeine stimulation of human sperm motility

L-carnitine is a calcium chelator: a reason for its useful and toxic effects in biological systems

BACKGROUND

Investigation of the direct link between l-carnitine (LC), a quaternary ammonium compound that facilitates the passage of unsaturated fatty acids into the mitochondrial matrix, and free calcium (Ca2+) is needed to explain a number of varying results obtained from different in vitro and in vivo studies of LC as a supplement.

METHODS

The chemical structure of LC, which contains oxygen ligand atoms, prompted to measure its activity asa Ca2+ chelator. The measurement was carried out spectrophotometri cally by measuring the reduction in the formation of Ca2+-o-cresolphthalein complexone (Ca-CPC) in the presence of different doses of LC (0.075, 0.75, and 7.5 mM) compared to the control (0.0 mM LC).

RESULTS

The effect of LC was measured as a free entity in solution and when added to human serum. Our results showed a significant decrease (p < 0.05) in the average absorbance of Ca-CPC in the presence of LC compared to the control.

CONCLUSIONS

In conclusion, LC exhibits a significant Ca2+ chelating activity. As Ca2+ is vital in the biochemical and physiological processes of living cells, LC could be affecting the calcium-dependent biological systems by limiting the levels of free Ca2+. Examples include decelerating the blood clotting process, amplifying the effect of anticoagulants, reducing nitric oxide synthase activity, inhibiting

Macaque sperm release ESP13.2 and PSP94 during capacitation: the absence of ESP13.2 is linked to sperm-zona recognition and binding

ESP13.2 coats the entire surface of macaque sperm and remains until sperm become capacitated (Yudin et al., 2003: Biol Reprod 69: 1118-1128). Capacitation of macaque sperm is synchronized by treatment with dibutyrl cAMP (dbcAMP) and caffeine. ESP13.2 and PSP94 constituted approximately 95% of the proteins released from the sperm surface following treatment with caffeine + dbcAMP. Caffeine and dbcAMP alone induce different patterns of ESP13.2 release. As determined by ELISAs of supernatants and immuno-fluorescent labeling of sperm heads, caffeine alone and caffeine + dbcAMP induced comparable release of ESP13.2, while dbcAMP-treated sperm did not differ from controls. Sperm treated with caffeine + dbcAMP showed a reduction of ESP13.2 from the entire surface, while caffeine treatment alone induced removal of ESP13.2 from the sperm head and midpiece. As confirmed with immunofluorescence, ESP13.2 could be added back to the surfaces of sperm that had been previously exposed to caffeine. Treatment with caffeine significantly increased the number of sperm that bound tightly to the zona pellucida as compared with controls (42 +/- 9 and 13 +/- 3 sperm/zona, respectively; P < or = 0.01). This increase in binding was inhibited by "adding back" ESP13.2 to the sperm surface (12.8 +/- 3; P < or = 0.01). Alexa-conjugated anti-ESP13.2 Ig labeling of live sperm showed that only sperm lacking ESP13.2 over the head were capable of tight binding to the zona. Our results suggest that ESP13.2 masks zona pellucida ligands on the sperm surface and its release, as part of capacitation, is required for sperm-zona interaction.

The decline of porcine sperm motility by geldanamycin, a specific inhibitor of heat-shock protein 90 (HSP90)

Sperm motility is an important parameter for fertility. The molecular mechanisms of mammalian sperm motility are still largely undefined. Our previous observations suggested that heat shock protein 90 (HSP90) may be associated with porcine sperm motility. The aim of the present study was to further characterize the plausible novel function of HSP90 on sperm motility. Semen from normal, sexually mature boars with sperm motility higher than 80% was used. An HSP90-specific inhibitor, geldanamycin (GA), was added to diluted semen at 0.5, 1.0, 2.5 or 5.0 microg/mL and the semen was then incubated at 37 degrees C for 15, 30, 45 or 60 min. Sperm motility was determined by using computer-assisted semen analyzer at the end of incubation. The results indicated that GA significantly reduced sperm motility in a dose and time dependent manner. Moreover, incubation of semen with 5.0 microg/mL GA for 15 min completely stopped sperm motility. To test the reversibility of the GA effect on sperm motility, GA was removed after 30 min incubation and was replaced with fresh extender alone or with extender plus 5 mM caffeine, then incubated for another 15, 30, 45 or 60 min. The results showed that simply removing GA did not reverse the inhibitory effect on sperm motility, while adding caffeine partially reversed this inhibitory effect. However, the effect of 2.5 or 5.0 microg/mL GA was not reversed by caffeine. Considering the specificity of GA targeting to HSP90, the above observations suggested that HSP90 may play a crucial role in regulating porcine sperm motility.

Pentoxifylline stimulates various sperm motion parameters and cervical mucus penetrability in patients with asthenozoospermia

Pentoxifylline (PTX) was incubated in vitro with human spermatozoa to examine its effects on sperm motility characteristics and bovine cervical mucus penetrability (BCMP). Sperm motion parameters were assessed by computer-assisted motion analysis (CASA) using HTM-IVOS and BCMP was evaluated using the Penetrak kit. In vitro incubation with PTX (1 mg ml-1; 3.6 mM, 30 min) did not significantly change percentage motility, average path velocity (VAP), straight-line velocity (VSL) or beat cross frequency (BCF) of spermatozoa from normozoospermic or asthenozoospermic samples. However, it significantly increased curvilinear velocity (VCL), amplitude of lateral head displacement (ALH) and hyperactivated motility (HA), and significantly decreased linearity (LIN) of spermatozoa from both samples. Pentoxifylline was found to increase BCMP scores for spermatozoa from asthenozoospermic samples, but did not affect scores for spermatozoa from normozoospermic samples. Bovine cervical mucus penetrability (BCMP) was found to be positively and significantly correlated with the percentage motility of both non-PTX-treated and PTX-treated spermatozoa for asthenozoospermic samples. These results demonstrated that PTX enhanced several motion sperm parameters as well as BCMP in asthenozoospermic samples and suggest a potential use of the methylxanthine in infertile patients with motility defects undergoing artificial insemination.

Increase of intracellular calcium is not a cause of pentoxifylline-induced hyperactivated motility or acrosome reaction in human sperm

OBJECTIVE

To investigate the effects of the phosphodiesterase inhibitor pentoxifylline on hyperactivated motility and acrosome reaction in human sperm and to determine whether its stimulatory effects occur via increased intracellular calcium levels.

DESIGN

Prospective study.

SETTING

Academic tertiary care facility.

PARTICIPANT(S)

Healthy male donors.

INTERVENTION(S)

The effects of pentoxifylline on hyperactivated motility, acrosome reaction, and intracellular calcium were studied and compared with the effects of progesterone. Thapsigargin, a known mobilizer of intracellular calcium, also was used as positive control.

MAIN OUTCOME MEASURE(S)

Hyperactivated motility was assessed by computer-assisted sperm motion analysis using the HTM-IVOS, acrosome reaction was evaluated with the fluorescent probe fluorescein isothiocyanate-labeled Pisum sativum agglutinin, and intracellular calcium was determined by fura-2 using spectrofluorometry.

RESULT(S)

Pentoxifylline significantly increased both hyperactivated motility and acrosome reaction. Enhancement of hyperactivated motility by pentoxifylline in the capacitation medium persisted for up to 5 hours after pentoxifylline was washed from the medium. It also enhanced the percentage of acrosome-reacted spermatozoa after 4 hours of incubation. These effects occurred in the presence of a marginally significant decrease in intracellular calcium.

CONCLUSION(S)

Pentoxifylline stimulates hyperactivated motility and acrosome reaction in spermatozoa from fertile men. Its stimulatory effects occur through mechanism(s) other than increase in intracellular calcium.

Review: in vitro spermicidal tests

This review analyzes in vitro spermicidal tests that have been used to evaluate the spermicidal activity of contraceptive products. Special requirements and processes in numerous technologies were also reviewed. Nonoxynol-9 (N-9) was used as an example of a vaginally delivered spermicidal agent, and its spermicidal potency was compared by various spermicidal tests, such as Sander-Cramer, computer-assisted semen analysis, hypoosmotic swelling test, cervical mucus penetration test, and flow cytometry, and advantages and disadvantages of each test were specified. This provides an insight into the different aspects of sperm functionality on which each spermicidal agent exerts its activity. A rationale of the best combination of in vitro spermicidal tests, with particular emphasis on a simple and efficient strategy that targets the complete fertility control, was explained.

Characterization of in-vitro spermicidal activity of chelating agent against human sperm

The effect of ethylenediaminetetraacetic acid (EDTA), a cationic chelating agent, on sperm motility and sperm penetration through cervical mucus was evaluated. EDTA exerted a relatively mild dose-dependent effect on sperm motility. Total loss of sperm motility (EC100) was achieved at a concentration of about 5.0 mg/mL of EDTA, which is much greater than the 200 micrograms/mL concentration of Nonoxynol-9 (N-9). EDTA salts, such as EDTA-Na2 and EDTA-Na4, showed weak spermicidal activity, while EDTA-K2 and EDTA-Ca had no spermicidal activity at concentrations up to 5.0 mg/mL. EDTA appeared to decrease the in vitro percentage of motile sperm as a function of exposure time. EDTA completely impeded the penetration of sperm into cervical mucus at a concentration much lower than that for 100% inhibition of sperm motility in semen. In the presence of 500-3200 micrograms/mL extra calcium, the first-order rate constant for sperm immobilization, which was derived from the slopes of a relative sperm motility curve, was reduced by 38.9--55.6% of the control and was inversely proportional to calcium concentration. After exposure to EDTA, the calcium ion concentration in semen was reduced as a function of EDTA concentration, which yielded a linear reduction of sperm motility. A decrease of approximately 65% in calcium ion concentration in semen seemed to be the threshold at which total loss of sperm motility occurred. Calcium ion was shown to play an essential role in regulating sperm molitility in semen, and EDTA was demonstrated to exert spermicidal activity by modulating calcium ion concentration in semen.

In vitro fertilization in couples with previous fertilization failure using sperm incubated with pentoxifylline and 2-deoxyadenosine

OBJECTIVE

To evaluate whether incubation of spermatozoa with both pentoxifylline and 2-deoxyadenosine would improve fertilization rates in couples with previous IVF failure.

DESIGN

Autocontrolled design in which sibling oocytes were inseminated at random in vitro with spermatozoa treated or not treated by pentoxifylline and 2-deoxyadenosine.

MEAN OUTCOME MEASURES

Oocyte quality, sperm motility, fertilization in vitro, and embryo quality.

RESULTS

Sperm motility was found optimized by metabolic stimulation using pentoxifylline and 2-deoxyadenosine. The mean fertilization rate per patient was 33.1% in the treatment group compared with 37.0% in the control group. The mean cleavage rate per patient was 79.6% for treatment versus 68.7% for control embryos. No differences in embryo quality were noted.

CONCLUSION

The results of this study demonstrate that an indiscriminate use of pentoxifylline and 2-deoxyadenosine is not beneficial to fertilization in couples with previous IVF failure. Further prospective research may be needed to assess the benefit of pentoxifylline and 2-deoxyadenosine in patients selected by preliminary functional in vitro tests.

The influence of pentoxifylline on motility and viability of spermatozoa from normozoospermic semen samples

In order to evaluate the effects of pentoxifylline on sperm motility and longevity, a controlled in-vitro study was conducted on normozoospermic donor semen samples using the Cellsoft automated system for sperm motility analysis. After incubation and selection, pentoxifylline was found to improve the recovery of spermatozoa and to increase their velocity. In the subgroup of progressively motile spermatozoa, curvilinear velocity was also enhanced. It is concluded that pentoxifylline has an effect on the vigour, but not on the pattern, of sperm motion. Pentoxifylline did not improve the motility characteristics of senescent spermatozoa in normozoospermic sperm samples. Sperm survival, as shown by supra-vital staining, and motility longevity both decreased with time after pentoxifylline treatment.

Human follicular fluid stimulates motility and velocity of washed human sperm in vitro

Human follicular fluid collected by laparoscopic oocyte pick-up during IVF was studied with a computer-assisted semen analyser to evaluate the effect of hFF on human sperm motility and velocity. Freshly ejaculated human sperm were washed with phosphate buffered saline and mixed with either PBS or hFF. At various incubation periods of time, hFF increased both sperm motility and velocity as compared with control (P less than 0.01). After incubation of sperm with hFF at 37 degrees C and 5% CO2 in air for 0, 1, 3, 6, and 12 h, the amplitude increase of motility were 49%, 77%, 330%, 2020%, and 3340% when individual control motility was considered to be 100%. The amplitude increase of curvilinear velocity were 43%, 51%, 67%, 152%, 278%, respectively. Comparison of the motility and velocity of the sperm treated with hFF between 0 and 12 h, showed that hFF preserved both motility and velocity in vitro (P less than 0.01). The stimulatory effect of hFF was retained after boiling at 100 degrees C for 30 min, or after being filtered through Amicon membrane cones, but it disappeared if the hFF had been pre-treated with chymotrypsin. However, hFF did not stimulate the motility and velocity of unwashed sperm in freshly ejaculated human semen. A non-dialyzable and heat-stable factor(s) with a molecular weight below 50,000 in hFF may improve and maintain the motility and velocity of washed human sperm. Whether this factor could be used to improve pregnancy rate in assisted reproduction awaits further investigation.

Pentoxifylline stimulates human sperm motility both in vitro and after oral therapy

Pentoxifylline is a haemorrheologic agent often used in the treatment of peripheral vascular disorders. In this study, we measured sperm motility with a trans-membrane migration method and investigated the effect of this drug in the treatment of male infertility. We found that pentoxifylline increased motility of ejaculated spermatozoa in vitro from both normal and asthenozoospermic samples. After giving pentoxifylline to patients with asthenozoospermia for 3 months, sperm motility significantly increased, but sperm concentration did not increase. From the above results, it can be concluded that pentoxifylline is a useful drug in the treatment of normogonadotropic asthenozoospermia.

Human follicular fluid stimulates the motility of washed human sperm

Human follicular fluid (hFF) was collected by laparoscopic oocyte pickup during IVF to evaluate the effect of hFF on human sperm motility with a transmembrane migration method. Freshly ejaculated human sperm were washed with phosphate buffered saline (PBS) and mixed with either PBS or hFF. Amplitude of motility increases were 38% and 72% in washed fertile sperm and washed asthenozoospermic sperm when individual control motility was considered to be 100%. The stimulatory effect of hFF was lost when preheated at 100 degrees C for 30 minutes. hFF collected from mature follicles stimulated sperm motility better than that collected from intermediate or immature follicles. hFF did not stimulate the motility of unwashed sperm in freshly ejaculated human semen. A heat labile factor(s) in hFF may stimulate the motility of washed human sperm. Whether this factor could be used to improve the success rate of IVF and artificial insemination awaits further investigation.

Effects of propranolol and caffeine on movement characteristics of human sperm

Human sperm, separated on Percoll gradients and transferred to cell culture medium, were exposed to various concentrations of propranolol (0.8-800 microM) or caffeine (3 microM-17 mM) for 4 h. Their motility pattern was analysed after 5 min and 4 h, employing the computerized Cellsoft system. Curvilinear velocity (VCL), percentage motile sperm, linearity (LIN), mean amplitude of lateral head displacement (ALHMEAN) and beat cross-frequency (BCF) were assessed. Both drugs had a practically immediate effect on the sperm. Propranolol concentrations greater than 80 microM had a negative effect on all movement variables, except VCL and ALHMEAN, which showed a slight, non-significant, initial increase. LIN and the percentage motile sperm appeared to be somewhat negatively affected at lower concentrations (80 microM) than the other variables, and were reduced further at higher concentrations and with time. The presence of 800 microM propranolol immobilized all sperm within 4 h. Caffeine at 1.7 and 5 mM, increased VCL and ALHMEAN. In contrast, the highest caffeine concentration tested (17 mM) had a negative effect on all variables at 4 h after addition.

The effects of drugs on sperm

Spermatogenesis is a complex process which takes about 70 days in the human. Its endocrine control may be affected by various hormones, antihormones or psychotrophic drugs. Cytotoxic agents, or industrial chemicals such as dibromochloropropane, directly affect the germinal epithelium. Sperm maturation may be impaired by alpha-chlorohydrin, antiandrogens, or sulphasalazine, and sperm motility in the female genital tract can be inhibited by vaginal spermicides such as nonoxynol-9 and by propranolol. Drug treatment of idiopathic oligozoospermia is disappointing, though gonadotrophins or their releasing hormone are useful in treating gonadotrophin deficiency. As far as contraception is concerned, there is still no suitable 'male pill': combinations of hormonal steroids are not sufficiently effective and gossypol appears to be too toxic.