Clinical microdose study of gossypol: effect on sperm motility and renal function

Reproductive toxicological effects of gossypol on male rabbits: semen characteristics and hormonal levels

The objective of this study was to evaluate the effects of two sublethal doses (4 and 20 mg/kg live weight (LW); every other day) of gossypol on semen and hormonal characteristics of male rabbits. The experiment lasted 16 weeks and included two periods: a treatment period (first 8 weeks) where the animals were given the test materials, and a recovery period (second 8 weeks) where drugs were withdrawn. Results showed that LW and respiration rate (RR) decreased ( P<0·05) among animals that received gossypol, while rectal temperature increased ( P<0·05). Animals in gossypol treatment groups had decreased ( P<0·05) blood plasma levels of tri-iodothyronine (T3) and testosterone. This was accompanied by reductions ( P<0·05) in sperm concentration, total sperm output, percentage incidence of forward motility, total functional sperm fraction and semen initial fructose concentration. Gossypol however increased ( P<0·05) reaction time (i.e. decreased libido), percentages of dead sperm and abnormal sperm (AbSp) and altered acrosomes. Estimated weights of testes and semen ejaculate volume increased ( P<0·05) possibly due to increased water retention. Values of LW, RR, AbSp, and blood plasma T3 and testosterone returned to control levels after withdrawal of gossypol, while the effect of this drug on other parameters continued during the recovery period.

Reversible inhibition of calcineurin by the polyphenolic aldehyde gossypol

The reversible inhibition of calcineurin (CaN), which is the only Ca(2+)/calmodulin-dependent protein Ser/Thr phosphatase, is thought to be a key functional event for most cyclosporin A (CsA)- and tacrolimus (FK506)-mediated biological effects. In addition to CaN inhibition, however, CsA and FK506 have multiple biochemical effects because of their action in a gain-of-function model that requires prior binding to immunophilic proteins. We screened a small molecule library for direct inhibitors of CaN using CaN-mediated dephosphorylation of (33)P-labeled 19-residue phosphopeptide substrate (RII phosphopeptide) as an assay and found the polyphenolic aldehyde gossypol to be a novel CaN inhibitor. Unlike CsA and FK506, gossypol does not require a matchmaker protein for reversible CaN inhibition with an IC(50) value of 15 microm. Gossypolone, a gossypol analog, showed improved inhibition of both RII phosphopeptide and p-nitrophenyl phosphate dephosphorylation with an IC(50) of 9 and 6 microm, respectively. In contrast, apogossypol hexaacetate was inactive. Gossypol acts noncompetitively, interfering with the binding site for the cyclophilin 18.CsA complex in CaN. In contrast to CsA and FK506, gossypol does not inactivate the peptidyl-prolyl-cis/trans-isomerase activity of immunophilins. Similar to CsA and FK506, T cell receptor signaling induced by phorbol 12-myristate 13-acetate/ionomycin is inhibited by gossypol in a dose-dependent manner, demonstrated by the inhibition of nuclear factor of activated T cell (NFAT) c1 translocation from the cytosol into the nucleus and suppression of NFAT-luciferase reporter gene activity.

Effect of refeeding diets containing cottonseed flour with traces of gossypol on rat liver and testis

The aim of the present work was to show that cottonseed flour introduced into rehabilitation diets is not nutritionally harmful. The cottonseed flour obtained from glandless seeds contains traces of gossypol. As gossypol is known to have pathological hepatic and testicular actions, the effects on hepatic variables and on the histological appearance of liver and testis of diets containing cottonseed flour were compared with those without cottonseed flour. Seventy growing male Wistar rats were divided into two groups. The control group (C) received a balanced diet (200 g casein + 3 g methionine/kg) for 78 d and the experimental group was fed on a low-protein diet (20 g casein + 3 g methionine/kg) for 29 d. After the period of protein deprivation, the depleted rats were divided into four groups and each group was refed with a different diet, for 49 d: a balanced diet (200 g casein + 3 g methionine/kg; rC), maize-soya-bean flour-milk (60:30:5, by wt; MSM), maize-cottonseed flour-milk (60:30:5, by wt; MCM) or rice-cottonseed flour-milk (60:30:5, by wt; RCM). Each diet was supplemented with a vitamin mixture (10 g/kg) and a salt mixture (40 g/kg). In the liver, protein, total lipid, fatty acid composition and nucleic acid contents were determined after 29 d of protein deprivation and after 2, 14, 29, 49 d of refeeding. The refeeding of rats with either diet MSM or RCM promoted a higher growth than that with diet MCM or diet rC. In all groups, a progressive decrease in relative liver weights with age was observed. The highest values were obtained with diets rC and MSM. After 49 d of refeeding, the lowest values for lipid, DNA and protein:RNA and the highest values for RNA and RNA:DNA were obtained with the cottonseed diets (MCM and RCM). Rats fed on the cottonseed-flour diets for a 49 d period after severe protein malnutrition showed no change in size or shape of their hepatocytes compared with those obtained with the control casein diet, and all stages of spermatogenesis occurred normally and spermatozoa were accurately formed. Therefore, our findings show that a low level of gossypol administrated during 49 d, even to an organism weakened by protein malnutrition, does not affect hepatic variables and the histological appearance of liver and testis.

Effects of gossypol on the motility of mammalian sperm

The effects of the male contraceptive gossypol on the motility of mammalian spermatozoa are reviewed. The role of sperm motility in the processes of fertilization and the effect of the drug on these processes determine its effectiveness as a contraceptive. The promising male contraceptive potential of gossypol is discussed in the context of the serious adverse effects of the agent.