Inhibition of rat testis LDH-X activity by gossypol

In vitro gossypol induced spermatozoa motility alterations in rabbits

The objectives of the present study were to: (i) examine the in vitro dose response of rabbit spermatozoa motility to the antifertility agent gossypol (GOS) and (ii) determine whether filtered (FIL) and unfiltered (UNFIL) GOS differ in their magnitude of effect. Rabbit semen belonging to adult males (n = 5; 12-14 months) were cultured with UNFIL GOS and FIL GOS (5% solution) and subsequently diluted (1:1-7) for analysis using a Computer Assisted Semen Analyzer (CASA) system in 5 time periods (0, 60, 120, 180 and 360 minutes). At Time 0, no significant change in rabbit spermatozoa motility (MOT) and progressive motility (PROG) with GOS FIL was noted, while increases were observed with GOS UNFIL. At Time 60, weak changes were noted for MOT and PROG. After 120 minutes of culture with both GOS FIL and GOS UNFIL, MOT and PROG decreased significantly in some experimental groups. However, no differences were recorded for both the parameters at Times 180 and 360, with the exception of PROG in the GOS UNFIL category (groups A, B, E, F and G), where a significant decrease was noticed. Detailed evaluation of the distance and velocity parameters revealed reduction in all these studied markers after 60 and 120 minutes of in vitro culture with both GOS FIL and GOS UNFIL, indirectly confirming the PROG decrease. Straightness (STR), linearity (LIN), wobble (WOB), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF) mostly remained unaltered at all time periods for GOS FIL, where as some minor alterations were noticed in GOS UNFIL category for STR, LIN, WOB, ALH and BCF parameters at Time 0, 60 and 120. The present study confirms the dose and time dependent alterations of rabbit spermatozoa motility parameters by GOS. The GOS dynamics in our experiment shows that rabbit spermatozoa as a biological material can indicate a GOS inhibition of motility. Obtained data for the first time indicates a higher immobilizing potential of unfiltered GOS in comparison to filtered GOS in its inhibitory action of spermatozoa motility parameters in rabbits.

The inhibitory effects of gossypol on human sperm motility characteristics: possible modes of reversibility of those effects

Gossypol (GOS) is a polyphenolic compound derived mainly from cottonseed oil, which has been found to have anti-fertility effects in males. It has been reported to induce disturbances of the hypothalamicpituitary axis, disruption of spermatogenesis in the testes, and inhibition of postejaculatory spermatozoa motility. The inhibition of human sperm motility by GOS has been documented both in vivo and in vitro, although the exact mechanism and possible reversibility of such inhibition is unknown. The objectives of the present study were 1) to examine the in vitro dose response of human sperm motility to GOS, and 2) to determine if the motility inhibition of GOS was reversible, using agents which alter the second messenger cyclic adenosine monophosphate (cAMP), such as, 8-bromo-cAMP (8-Br-cAMP), and forskolin, and adenylate cyclase stimulator. Fresh spermatozoa were obtained from males of known fertility. Motile spermatozoa were recovered via the SpermPrep (SP) method and used further in all experiments. Quantitative and qualitative sperm parameters were recorded at collection, post-SP filtration and post-treatment. Motile spermatozoa were resuspended in either media (SP), or in increasing concentrations of GOS (10, 20, 30 and 50 micrograms/ml) as gossypol acetic acid in media. To study the possible reversibility of the GOS effects, spematozoa already exposed to GOS for 2 hr (at the concentrations mentioned above) were centrifuged and reconstituted in media containing either 10 mM 8-Br-cAMP or 100 microM forskolin and measurements of percent motility and grade of motility (0-4) were taken at 0 time and at 30 min intervals for a total of 2 hr. Each experiment was replicated 8 times. The results obtained in this study showed that GOS inhibited sperm motility in a dose and time dependent manner. The motility characteristics of the 50 micrograms/ml GOS group were lower than all other groups (p < 0.001) and the spermatozoa were completely immobilized within 60 min. Cyclic AMP somewhat rescued the GOS-treated sperm, whereas exposure of GOS-treated sperm to forskolin had no such effects. The data generated in the present study suggest that GOS inhibits cAMP formation, which subsequently decreases sperm motility characteristics. At low concentrations (up to 20 micrograms/ml for 30 min), GOS inhibition is reversibile and compounds that act to increase cAMP seem to be partially responsible for the reversal of GOS inhibition. However, GOS inhibitory effects at levels higher than 20 micrograms/ml (exposed for 30 min) were impossible to reverse, which suggest that GOS at those levels could be an effective agent for vaginal contraception.

The effects of cyclic adenosine monophosphate, forskolin, and theophylline on motility parameters in gossypol-treated human sperm

OBJECTIVE

To examine the effect of gossypol on human sperm in vitro and the mechanism for the effect.

DESIGN

Fresh sperm ejaculates obtained from normal donors to the University of Kentucky Andrology Donor Program were exposed to gossypol. Motility was studied manually and using computer-assisted sperm analysis. In subsequent experiments, the effects of forskolin, theophylline, and cyclic adenosine monophosphate (cAMP) on sperm motion were measured.

SETTING

University of Kentucky Department of Obstetrics and Gynecology Andrology Laboratory.

MAIN OUTCOME MEASURES

Manual and computer-assisted measurements of sperm motility and motion characteristics.

RESULTS

Gossypol inhibited sperm motility, which could be reversed partially by increasing cAMP.

CONCLUSION

Gossypol exposure in vitro adversely affects sperm motility in a dose- and time-dependent manner by a cAMP-dependent mechanism.

Taenia taeniaeformis: inactivation of metacestodes by gossypol in vitro

Gossypol, a natural biphenyl compound inhibits Taenia taeniaeformis metacestode development in vivo. In this paper, the direct effect of gossypol on metacestodes was examined. Within 24 hr of incubation at 37 degrees C in greater than or equal to 10(-5) M gossypol, shedding of the tegument from the surface of the metacestodes was observed. There was a significant decrease in [3H]thymidine uptake by T. taeniaeformis in greater than or equal to 10(-5)M gossypol. In addition, NADH lactate dehydrogenase activity of metacestodes was significantly inhibited in greater than or equal to 10(-5) M gossypol. Thus, gossypol has a direct inhibitory effect on T. taeniaeformis metacestodes in vitro.

Developmental changes in lactate dehydrogenase-X activity in young jaundiced male rats

This study was designed to examine the testicular maturation in both jaundiced (jj) and nonjaundiced (Jj) male Gunn rats as indicated by the activity of a testis and sperm-specific enzyme, lactate dehydrogenase-X (LDH-X), and serum testosterone levels. Testicular cytosolic LDH-X activity was determined by oxidation of reduced nicotinamide adenine dinucleotide (NADH). Serum testosterone levels were measured by radioimmunoassay (RIA). Testicular LDH-X activity increased rapidly between 30 and 50 days of age in both Jj and jj Gunn rats. LDH-X activity was significantly lower in the jj Gunn rats at 50 and 60 days of age. Testosterone level was significantly lower in the jj Gunn rats at 50 days of age. LDH-X activity and serum testosterone levels were similar for both genotypes at 180 days of age. The delay of testicular maturation in the jaundiced males seems to be due to lower LDH-X activity and serum testosterone levels.

Biochemical effects of gossypol in isolated mitochondria: monovalent cations and ATPase activity

1. The effect of gossypol acetic acid upon the energy-producing system of isolated liver mitochondria was studied. Gossypol was found to exert an uncoupling effect. 2. Oxygen consumption and ATPase activity were stimulated only when a monovalent alkali metal cations was present. 3. The mitochondrial proton gradient, produced by the enzymatic hydrolysis of ATP, was lower in the gossypol-treated mitochondria than in the control experiments. 4. It is proposed that gossypol stimulates oxygen consumption and the ATPase activity in mitochondria by a protonophoretic effect and a cation translocation process.

Effect of gossypol on spermatozoal lactate dehydrogenase-X (LDH-X) in male rats

The studies in this report evaluate the inhibitory effects of long-term gossypol acetic acid (gossypol) administration on spermatozoal lactate dehydrogenase (LDH-X) activity, fertility and reversibility. Gossypol at 20 mg/kg/day or vehicle only was administered orally to adult male rats for 5 consecutive weeks. Groups of control and gossypol-treated rats were sacrificed at 2-, 4-, and 5-week intervals when LDH-X analysis of spermatozoa were prepared from the tail of the epididymis. An additional group of control and gossypol-treated rats were allowed to recover for up to 8 weeks after withdrawal of the treatment. In the gossypol-treated rats, the spermatozoal LDH-X activity was depressed by 80% of control level after a 5-week treatment period. There was no significant difference in spermatozoal LDH-X activity between the control and treated animals at 2 and 4 weeks. However, the number of ejaculated sperm estimated from the vaginal smear preparations after each mating was significantly less than the control values after 2, 4 and 5 weeks of treatment. At 5 weeks after the cessation of gossypol treatment, the spermatozoal LDH-X activity had only partially recovered but the fertility (number of ejaculated sperm, embryo implantation sites and pups born) had recovered to a level comparable to the control values 5 weeks after the cessation of gossypol treatment. The inconsistencies in the response of spermatozoal LDH-X activity, sperm number and fertility to gossypol may suggest that the antifertility action of gossypol and spermatozoal LDH-X activity in adult male rats may not be directly related as suggested by the results generated from the in vitro studies.

Inhibition of lactate dehydrogenase-X by imino-derivatives of gossypol:structure activity relationship

Six imino-derivatives (II, III, IV, V, VI, VII) of gossypol (I) have been synthesized, and their effects were evaluated on the purified mouse lactate dehydrogenase-X. Three of these derivatives (V, VI, VII) with aldehyde groups substituted with hydrophobic functionalities showed equivalent or more inhibitory effects on lactate dehydrogenase-X than gossypol, whereas three other derivatives (II, III, IV) with aldehyde groups substituted with hydrophilic functional groups lost the ability to inhibit lactate dehydrogenase-X. It is suggested that two aldehyde groups of gossypol are not essential to inhibit lactate dehydrogenase-X. Furthermore, the hydrophobic property of the gossypol molecule seems to play a more important role in inhibiting lactate dehydrogenase-X. Therefore, lactate dehydrogenase-X inhibition by gossypol may not be associated with its antifertility mechanism, because the aldehyde group of gossypol is known to be required for its antifertility effect.

Dose and time related changes in LDH-X activity, epididymal carnitine levels and fertility, in gossypol-treated male rats

Gossypol acetic acid could induce total infertility in male Wistar/NIN strain rats at a dose of 30 mg per kg body weight per day, for 52 days. 20 mg for 52 days and 30 mg for 38 days produced partial infertility. Highly significant correlation between parameters of infertility like reduced cauda sperm count, and implantation sites, and reduction in LDH-X activity of cauda epididymal sperm and carnitine levels in cauda epididymal fluid were observed. Testis remained unaffected.

Kinetic characterization of the inhibition of purified cynomolgus monkey lactate dehydrogenase isozymes by gossypol

This report describes the results of the first step in a sequence of experiments designed to test the hypothesis that the sperm-specific isozyme of lactate dehydrogenase (LDH-C4), is a site of action of the potential male contraceptive agent gossypol. Cynomolgus monkey LDH-A4, LDH-B4 and LDH-C4 were purified and kinetically characterized. LDH-A4 and LDH-B4 exhibited "linear mixed-type" inhibition by gossypol with both lactate and pyruvate as variable substrates. LDH-C4 also exhibited "linear mixed-type" inhibition with lactate as substrate. However, the C4 isozyme exhibited "parabolic mixed-type" inhibition by gossypol and substrate inhibition with pyruvate as substrate, the latter due to abortive complex formation. Of the three isozymes, LDH-C4 exhibited the lowest apparent Km for pyruvate and the highest apparent Km for lactate. The LDH-C4 form was found to be the most sensitive isozyme to gossypol inhibition, since it had the lowest apparent Ki values for gossypol inhibition. The effect of gossypol on coenzyme binding to LDH-C4 was examined and gossypol binding was found to inhibit binding and release of NADH but not NAD+, an effect possibly due to its interaction with the more hydrophobic loop region of LDH-C4.

Inhibition of liquefaction and protein degradation in human semen by gossypol

The liquefaction of freshly ejaculated human semen was delayed by gossypol. Liquefaction is normally accompanied by an autolytic degradation of semen proteins, and prior incubation with gossypol can inhibit factors (presumably proteinases) present in seminal plasma that degrade semen proteins. The possible consequences of this inhibition are discussed in relation to the proposed use of gossypol as a vaginal contraceptive.

Inhibition of LDH-X by gossypol optical isomers

Racemic gossypol is an effective male antifertility agent in several mammalian species. However, (+)-gossypol is not an effective male antifertility agent in the rat or the hamster. Previous studies have demonstrated the ability of racemic gossypol to inhibit the testis-specific LDH-X enzyme derived from various mammalian species and have suggested LDH-X as the potential site of gossypol antifertility action. In the present study, the effects of racemic gossypol and the (+) and (-) optical isomers of gossypol on LDH-X derived from rat and hamster testicular cytosol are compared to determine if there is any correlation between the in vitro inhibition of the LDH-X enzyme and in vivo antifertility effects. Both optical isomers of gossypol as well as racemic gossypol inhibit rat and hamster testicular cytosolic LDH-X activity. Inhibition of hamster testicular cytosolic LDH-X activity by (-)-gossypol was less than by either racemic gossypol or (+)-gossypol. Based on the previous reports of racemic gossypol inhibition of LDH-X, therefore, it cannot be simply concluded that LDH-X is the specific site of antifertility action of gossypol since, in the present study, (+)-gossypol, which is not an effective male antifertility agent, also inhibited rat and hamster testicular cytosolic LDH-X.

Reversible changes in rat spermatogenesis induced by an antifertility substance (Gossypol). A histochemical report

Male rats received Gossypol 30 mg/kg body mass daily through intubation for 30 and 60 d. The testes were processed for histological and histochemical lipid staining, thiamine pyrophosphatase (TPPase), and alpha-glycerophosphate dehydrogenase (alpha-GPDH)--examinations. Gossypol induced effects were: various types of deformations of elongated spermatids, and their loss of orientation towards the lamina propria during the maturation phase; displacement of germ cells and occasionally also of Sertoli cells towards the lumen of the seminiferous tubule in form of a "puff". TPPase was observed in the supranuclear region of dislocated round spermatids and pachytene spermatocytes. alpha-GPDH was observed in the split pieces of mid- and tail pieces of elongated spermatids enclosed in the "puff". The induced effects were reversible.

In vivo study of LDH isoenzyme activities in heart, liver and testis cytosols of gossypol-treated rats

LDH isoenzyme activities of heart, liver and testis homogenates were measured in rats treated for 15 or 30 days with 30 mg gossypol acetic acid/kg body weight daily, a dose which severely suppressed sperm motility. No differences in LDH activities of the examined organs were found in comparison with control animals. LDH-X, the main LDH isoenzyme in spermatozoa and testicular germ cells from primary spermatocytes onwards was also unaffected. These results contrast with in vitro experiments on human, rabbit, and boar spermatozoa, purified bovine LDH-X and rat testis homogenate which show dose-dependent inhibition of LDH-X after incubation with gossypol. Our results therefore suggest that inhibition of LDH by gossypol is not the primary cause of sperm immotility.