Antifertility mechanisms of gossypol acetic acid in female rats

Gossypol and Semisynthetic Derivatives: Chemistry, Bioactivities, and Mechanism of Actions

Gossypol, a polyphenolic compound predominantly derived from cotton plants, has garnered significant attention as a notable plant-derived bioactive compound with significant relevance in medicinal chemistry due to its diverse biological activities and potential therapeutic applications. Despite its inherent toxicity, gossypol exhibits insecticidal, antimicrobial, antiviral, antifertility, antiparasitic, anti-inflammatory, antioxidant, and anticancer properties. Furthermore, gossypol serves as a core molecule for synthesizing various derivatives, such as gossypol Schiff bases, gossypolone, and apogossypol, which are less toxic yet retain similar therapeutic benefits. The aim of this review is to provide a comprehensive overview of gossypol's diverse biological activities, with a particular focus on its anticancer potential, mechanisms of action, and recent advancements in its therapeutic applications. It highlights gossypol's wide-ranging biological activities, including its potent anticancer, antimicrobial, and antioxidant effects. Recent studies have shown promise in reducing gossypol's toxicity through the synthesis of derivatives, while advanced drug delivery methods, including nanocarriers, have been explored to enhance its therapeutic efficacy. Furthermore, gossypol has demonstrated significant synergistic potential when used in combination with conventional anticancer drugs, offering new avenues for cancer therapy.

Gossypol promotes degeneration of ovarian follicles in rats

The present study aimed to determine if gossypol interferes with ovarian follicles in rats. Twenty-four female Wistar rats were assigned to two equal groups: one control group and the other dosed with gossypol (25 mg/kg/day, subcutaneously) for 15 days. Ovarian follicles were histologically classified according to the stage of development and as normal or atretic. Gossypol treatment reduced the length of estrous with an increase in the duration of the diestrus phase. This compound was responsible for reduced serum levels of T4 and progesterone. Treatment with gossypol was responsible for a significant reduction in the number of normal ovarian follicles and a significant increase in the number of atretic follicles, both in all stages of development. Thus, treatment of rats with gossypol was responsible for reduction in the number of viable follicles and changes in hormone levels that resulted in interference of the estrous cycle.

Effects of diets containing free gossypol on follicular development, embryo recovery and corpus luteum function in Brangus heifers treated with bFSH

Thirty 2 yr old Brangus heifers were randomly assigned to 1 of 3 dietary treatments: Control, 0 g of free gossypol (FG) per head per day (FGHD) from corn and soybean meal (SBM); 5 g of FGHD from cottonseed meal (CSM); and 15 g of FGHD from whole cottonseed (WCS). Blood samples were collected weekly for serum progesterone (P(4)) and later quantified by RIA. Whole blood was collected on Days 1, 28, 42, 56 and 70 for erythrocyte fragility (EF) analysis. Following 65 d on dietary treatments and estrus detection, the heifers received bovine-FSH (bFSH) once daily on Days 10, 11 and 12 postestrus, and PGF(2alpha) on Day 12 postestrus. Fifteen of the thirty heifers were randomly selected, and 12 h following PGF(2alpha), the ovaries were removed and follicular diameters, ovarian weight and stromal weights were recorded. Follicular fluid was analyzed for steroid content by RIA. The remaining fifteen heifers were artificially inseminated. Embryos were recovered non-surgically on Day 7 postestrus and graded, and the recovery efficiencies were calculated. Following embryo collection, both ovaries were removed, the number of CLs was recorded, and CL P(4) content was determined by RIA. By Day 42 of treatment, heifers receiving CSM had elevated (P < 0.04) EF compared with the Controls, and remained elevated above that of Controls throughout the study. At Day 70, the CSM heifers tended to have higher (P < 0.07) EF than the WCS group, which in turn tended to be higher (P < 0.06) than the Controls. The Control and CSM heifers gained weight during the 70 d treatment period, while heifers consuming WCS lost weight (P < 0.05). Ovarian and stromal weights did not differ (P > 0.10) among treatment groups. Heifers receiving CSM had fewer (P < 0.05) follicles > 5 mm than WCS or Control heifers. Follicular fluid weights and steroid content did not differ (P > 0.10) among treatments. Both CL weight and the number of CLs per heifer were similar (P > 0.10) among treatments. Heifers receiving CSM or WCS had a higher (P < 0.003) CL P(4) content per gram of CL tissue than the Controls. Progesterone content per CL was greater in WCS heifers (P < 0.003) than in CSM heifers, while both the CSM and WCS heifers had a higher CL P(4) content than the Control heifers. Weekly and Day 7 postestrus serum concentrations of P(4) were similar (P > 0.10) among treatments. The number of embryos recovered, number of degenerated embryos, embryo grades and recovery efficiencies were not affected (P > 0.10) by dietary treatments. To standardize heifers relative to the number of degenerated embryos, the percentage of degenerated embryos recovered was calculated and tended to be greater (P < 0.06) in heifers consuming CSM than in either the Control or WCS groups. While most ovarian, follicular and embryo characteristics were not affected by dietary free gossypol, these results suggest that differences in the availability of free gossypol and/or dietary components between CSM and WCS may influence weight gain, CL P(4) content and embryo viability.

Genotoxic effects of gossypol acetate on the ovary of Rhinopoma kinneari wroughton (Microchiroptera: Mammalia)

Female Rhinopoma kinneari, a microchiropteran bat (body weight Ca 15.0 gm to 20.0 gm), was used as a model to evaluate the effect of a single oral dose of 10 mg of gossypol acetate on the ovarian histology at day 2, 4, 6 and 8, respectively. Maximal damage to these organs was seen on day 2. The test drug induced widespread disturbance in the ovarian histoarchitecture as evidenced by an extensive degeneration of follicle types. Degenerative changes were marked by pycnosis, chromatolysis of nuclei, desquamation of granulosa cells and their subsequent dissolution. Intensity of protein staining was increased with time, indicating marked damage to ovarian constituents. It is suggested that gossypol may cause antifolliculogenic activity.

Inhibition of in vitro fertilization and early embryonic development in hamsters by gossypol

We have previously reported an inhibitory effect of gossypol and its metabolite on bovine and mouse early embryonic development. In the present study, eggs were collected from oviducts of superovulated hamsters. Epididymal sperm were used for in vitro fertilization (IVF). Gossypol at 5, 10, and 30 micrograms/ml significantly inhibited the formation of 2 pronuclei by 45, 65 and 95%, respectively. On the first day of pregnancy, hamsters were given an intrauterine treatment of 200 micrograms of gossypol in 100 microliters of corn oil per uterine horn. On day 3, embryos from controls were in morula (65%) and early morula (17%) stages, while less than 2% of embryos from the gossypol-treated hamsters were in the morula stage. The numbers of embryo implantation sites on day 8 and pups in controls (14 +/- 2.0 and 12 +/- 1.5, respectively) were significantly higher than those in the gossypol-treated hamsters (8.5 +/- 2.0 and 4.0 +/- 1.5, respectively). Our results suggest that gossypol is able to affect fertilization, embryonic development, embryo implantation, and the number of pups in hamsters through a not-yet-defined mechanism.

Binding of 3H-gossypol in organelles of cultured bovine luteal cells

Gossypol is an antifertility agent which inhibits steroidogenesis in both sexes. The present study investigated the binding of gossypol in organelles of cultured bovine luteal cell to elucidate its inhibitory site of action in steroid biosynthesis. Cultured bovine luteal cells were incubated with 3H-gossypol (4.3 or 2.15 microM) for 3 hours. At the end of treatment, cultured bovine luteal cells were harvested, homogenized and centrifuged for organelle preparation. The radioactivity of gossypol was measured in each subcellular fraction. The cell membrane fraction has the highest binding capacity for gossypol, and the majority of gossypol was located in the particulate fractions. Results of the present study provide information in understanding the regulatory mechanism of gossypol on antisteroidogenic and/or toxic effects in cultured bovine luteal cells.

Zone-specific hepatotoxicity of gossypol in perfused rat liver

Gossypol selectively damages the periportal region of lobules in perfused rat liver, while retrograde perfusion caused pericentral liver damage. Moreover, the addition of 0.4% bovine serum albumin(BSA) to the perfusate completely prevented the toxic effect of gossypol on hepatocytes, decreasing the absorption of gossypol by the liver. This study indicates that the damage caused by gossypol depends upon the direction of exposure and can be protected against by its binding to BSA.

Inhibitory effect of gossypol on steroidogenic pathways in cultured bovine luteal cells

Gossypol inhibits the reproductive system and steroidogenesis in both sexes. The present study investigated some possible sites subsequent to cAMP formation at which gossypol may inhibit progesterone biosynthesis. Bovine luteal cells were cultured with dibutyryl cAMP (dbcAMP), 25-OH cholesterol, or pregnenolone in the presence or absence of gossypol. Gossypol, at 17-34 microM, inhibited dbcAMP-induced progesterone secretion. Gossypol significantly inhibited the conversions of exogenous 25-OH cholesterol and pregnenolone to progesterone. However, the conversion of 25-OH cholesterol to pregnenolone was not significantly inhibited by gossypol at low doses (less than or equal to 34 microM). These results suggest that gossypol inhibits progesterone synthesis in bovine luteal cells by suppressing steroidogenic enzyme activity.

Premature farrowings caused by feeding cottonseed meal

Increasing the level of cottonseed meal (CSM) in sow diets from less than 5% to 10% increased the incidence of premature farrowings (gestation length less than 111 days) from 1.1% to 2.7% (p less than 0.001) and reduced the mean gestation length from 114.07 +/- 1.53 to 113.70 +/- 1.59 days (p less than 0.0001). Survival of piglets born prematurely was poor. After removal of CSM from the diet there was a residual effect lasting several weeks before the gestation length returned to normal. Experimental feeding of diets containing 20% and 40% CSM to small groups of sows caused significant shortening of gestation length and 3 of 26 sows fed 40% CSM farrowed prematurely. The mechanism by which CSM causes this effect has yet to be determined.

Inhibitory effect of gossypol on human chorionic gonadotropin (hCG)-induced progesterone secretion in cultured bovine luteal cells

Inhibitory effects of gossypol on the female reproductive system have been recently reported. This study investigated a possible site of gossypol action on progesterone synthesis. Bovine luteal cells were cultured with hCG and forskolin in the presence or absence of gossypol. At 10 micrograms/ml, gossypol significantly inhibited hCG- and forskolin-stimulated progesterone secretion and intracellular cAMP formation; at 20 micrograms/ml, gossypol completely abolished the stimulative effect of hCG and forskolin. The results suggest that adenylate cyclase may be a site of gossypol action on steroidogenesis of bovine luteal cells.

An ultrastructural study of the effects of gossypol on the endometrium of the female rat

Abnormal desmosomes were found in the endometrial epithelial cells of rats treated orally with gossypol acetic acid at a dose of 60 mg/kg/day for 30 days. Desmosomes in the endometrium of rats treated at 40 mg/kg/day were similar to those of controls. Abnormalities included an increase in desmosome number with prominent filamentous interconnections, asymmetry, disorganization of tonofilaments, missing tonofilaments, missing desmosomal plaques that did not appear to line up with those of the adjacent cell. It is thought that the antifertility actions of gossypol may be due to a disturbance of desmosome formation. This would cause a disruption of endometrial cell adhesion as well as an alteration in the microenvironment within cytoplasmic domains. These changes could lead to an endometrial environment unfavorable to fetal development.