Potassium leakage: not the cause of gossypol induced anti-motility in spermatozoa

The potential roles of gossypol as anticancer agent: advances and future directions

Gossypol, a polyphenolic aldehyde derived from cottonseed plants, has seen a transformation in its pharmaceutical application from a male contraceptive to a candidate for cancer therapy. This shift is supported by its recognized antitumor properties, which have prompted its investigation in the treatment of various cancers and related inflammatory conditions. This review synthesizes the current understanding of gossypol as an anticancer agent, focusing on its pharmacological mechanisms, strategies to enhance its clinical efficacy, and the status of ongoing clinical evaluations.The methodological approach to this review involved a systematic search across several scientific databases including the National Center for Biotechnology Information (NCBI), PubMed/MedLine, Google Scholar, Scopus, and TRIP. Studies were meticulously chosen to cover various aspects of gossypol, from its chemical structure and natural sources to its pharmacokinetics and confirmed anticancer efficacy. Specific MeSH terms and keywords related to gossypol's antineoplastic applications guided the search strategy.Results from selected pharmacological studies indicate that gossypol inhibits the Bcl-2 family of anti-apoptotic proteins, promoting apoptosis in tumor cells. Clinical trials, particularly phase I and II, reveal gossypol's promise as an anticancer agent, demonstrating efficacy and manageable toxicity profiles. The review identifies the development of gossypol derivatives and novel carriers as avenues to enhance therapeutic outcomes and mitigate adverse effects.Conclusively, gossypol represents a promising anticancer agent with considerable therapeutic potential. However, further research is needed to refine gossypol-based therapies, explore combination treatments, and verify their effectiveness across cancer types. The ongoing clinical trials continue to support its potential, suggesting a future where gossypol could play a significant role in cancer treatment protocols.

Molecular mechanisms of gossypol action on sperm motility

1. Gossypol acetic acid inhibits collective motility of ejaculated ram spermatozoa. 2. Oxygen consumption was stimulated at low gossypol concentrations and inhibited as the concentrations are increased. 3. Gossypol inhibits respiration of permeabilized spermatozoa supported by durohydroquinome, which indicates a direct inhibition of mitochondrial electron transport chain. 4. The rapid reduction of mitochondrial dependent motility, high uncoupling effect and almost complete inhibition of mitochondrial calcium accumulation, indicate that gossypol inhibits motility in a mechanism by which mitochondrial uncoupling is involved.

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.

Electrolyte composition of rete testis fluid and cauda epididymal plasma and spermatozoa from rats following gossypol treatment

This investigation was undertaken to study the potassium and sodium concentrations in rete testis fluid and cauda epididymal plasma and spermatozoa following gossypol treatment. Rats were treated orally with gossypol acetic acid at a dose of 15 mg/kg/day for 3 and 6 weeks respectively. There were not abnormal findings in the ionic concentrations of cauda epididymal plasma following 3 or 6-week-treatment. After 6 but not 3 weeks the spermatozoa in the cauda epididymidis were rendered almost completely immotile and malformed with a significant reduction in their potassium concentration and rise in their sodium concentration. No abnormal findings in the morphological picture of the germinal epithelium were observed under such circumstances and fluid and sperm from the rete testis were normal. Therefore, a direct action of gossypol may be exerted locally on the spermatozoa in the epididymis.

Gossypol-hypokalaemia interrelationships

Around 1% of 8806 volunteers taking gossypol as a male contraceptive had hypokalaemic paralysis and more had simple hypokalaemia, the direct cause being renal potassium loss. In gossypol takers not showing hypokalaemia, serum potassium levels were within the normal range but were significantly lower than levels in controls. In the majority of patients suffering from gossypol-induced hypokalaemia, recovery was prompt and complete following potassium repletion, but in some men there were recurrent attacks of hypokalaemia during a period of several months to years after cessation of gossypol treatment. The incidence of hypokalaemic paralysis in gossypol takers showed distinct regional differences, being much higher in Nanjing, where the dietary potassium level of the inhabitants was low, than in Taian, where the dietary potassium level was high. In rats fed a low-K fodder, gossypol reduced the intracellular Mg and K concentrations of the skeletal muscle, while in regularly fed rats, this effect of gossypol was not observed. A potassium deficient diet could thus be considered a contributing factor in the development of gossypol-induced hypokalaemia. Potassium deficiency has also been shown to enhance the anti-spermatogenic effect of gossypol. Suggested mechanisms for the development of gossypol-induced hypokalaemia include inhibition of Na-K-ATPase activity, stimulation of prostaglandin biosynthesis, damage to the renal tubule, and modification of membrane transport.

Antitumor effects of gossypol on murine tumors

Since the male antifertility drug, gossypol, was shown to be a specific inhibitor of DNA synthesis at moderately low doses in cultured cells, its antitumor potential has been evaluated in three murine tumor models. The effects of gossypol on tumor growth and the survival of 10- to 12-week-old BDF1 mice bearing mouse mammary adenocarcinoma 755 (Ca 755) or P388 or L1210 leukemias, all injected IP, were measured. At an optimum dose of 0.5 mg/mouse given as a single injection at 2 days (48 h) after the inoculation of 10(5) Ca 755 tumor cells, gossypol rendered 66% of the mice free of tumor cells, whereas the remaining 34% died of drug toxicity. The survival rate decreased sharply at doses on either side of the optimum. At suboptimal doses a major proportion of the tumor-bearing mice died of tumor, whereas at higher doses all the animals died of drug toxicity. In other words, the effective dose range of gossypol was rather narrow. The rapidly proliferating mouse leukemias, P388 and L1210, failed to respond to gossypol. Histopathological studies of various organs in the gossypol-treated mice revealed no consistent lesions that could give an indication of organ-specific toxicity of gossypol. The reduction in the myeloid series in the bone marrow of gossypol-treated mice may have been due to depletion rather than direct toxic effect. Further studies are essential to evaluate this compound with regard to its antitumor activity in other murine models.

Gossypol inhibits Ehrlich ascites tumor cell proliferation

Neutral gossypol solution injected peritoneally into NMRI mice preimplanted with Ehrlich ascites tumour cell, at a dose of 25-100 micrograms/mouse per day, lengthened the number of survival days of the hosts. This gossypol effect on tumour cell proliferation is concentration dependent. The optimum dose is 100 micrograms. However, at too high a dose, the gossypol caused a body weight loss and the death of the tumour-bearing mice.