Effect of gossypol on some oxidative respiratory enzymes

Heterogeneity of Metabolic Vulnerability in Imatinib -Resistant Gastrointestinal Stromal Tumor

Metabolic reprogramming is a hallmark of cancer cells in response to targeted therapy. Decreased glycolytic activity with enhanced mitochondrial respiration secondary to imatinib has been shown in imatinib-sensitive gastrointestional stromal tumors (GIST). However, the role of energy metabolism in imatinib-resistant GIST remains poorly characterized. Here, we investigated the effect of imatinib treatment on glycolysis and oxidative phosphorylation (OXPHOS), as well as the effect of inhibition of these energy metabolisms on cell viability in imatinib-resistant and -sensitive GIST cell lines. We observed that imatinib treatment increased OXPHOS in imatinib-sensitive, but not imatinib-resistant, GIST cells. Imatinib also reduced the expression of mitochondrial biogenesis activators (peroxisome proliferator-activated receptor coactivator-1 alpha (PGC1α), nuclear respiratory factor 2 (NRF2), and mitochondrial transcription factor A (TFAM)) and mitochondrial mass in imatinib-sensitive GIST cells. Lower TFAM levels were also observed in imatinib-sensitive GISTs than in tumors from untreated patients. Using the Seahorse system, we observed bioenergetics diversity among the GIST cell lines. One of the acquired resistant cell lines (GIST 882R) displayed a highly metabolically active phenotype with higher glycolysis and OXPHOS levels compared with the parental GIST 882, while the other resistant cell line (GIST T1R) had a similar basal glycolytic activity but lower mitochondrial respiration than the parental GIST T1. Further functional assays demonstrated that GIST 882R was more vulnerable to glycolysis inhibition than GIST 882, while GIST T1R was more resistant to OXPHOS inhibition than GIST T1. These findings highlight the diverse energy metabolic adaptations in GIST cells that allow them to survive upon imatinib treatment and reveal the potential of targeting the metabolism for GIST therapy.

Valproic acid synergistically enhances the cytotoxicity of gossypol in DU145 prostate cancer cells: an iTRTAQ-based quantitative proteomic analysis

Gossypol (GOS), a BH3 mimetic, has been investigated as a sensitizing co-therapy to radiation and chemotherapy in treatment of metastatic prostate cancer. In this study, we found that valproic acid (VPA), a histone deacetylase inhibitor (HDACI), counteracted the suppressive effect of GOS on histone H3 acetylation and enhanced the cytotoxicity of GOS to DU145 prostate cancer cells. Significant synergistic effects were observed in combined GOS and VPA treatment, culminating in more DNA damage and cell death. The iTRAQ-based quantitative proteomic analysis revealed differential proteomic profiles in cells treated with VPA, GOS or their combination. In GOS-treated cells, oxidative phosphorylation-related proteins were depressed and endoplasmic reticulum stress markers were upregulated. In the presence of VPA, the GOS-induced mitochondrial stress was further enhanced since glycolysis- and hypoxia-associated proteins were upregulated, suggesting a disruption of energy metabolism in these cells. Furthermore, the DNA damage repair ability of cells co-treated with GOS and VPA was also decreased, as evidenced by the downregulation of DNA damage repair proteins and the enhancement of DNA fragmentation and cell death. These findings suggest that GOS in combination with an HDACI has the potential to increase its clinical efficacy in the treatment of prostate cancer.

Effects of gossypol on the hepatic drug metabolizing system in rats

Gossypol, a polyphenolic pigment found in cotton plants, has been implicated as an antifertility agent. This pigment has been shown to alter myriad metabolic pathways. The objective of this study was to determine the effect of gossypol acetic acid on the hepatic microsomal drug metabolizing enzyme system in adult female Fisher 344 rats. Subcutaneous administration in both low (15 mg/kg) and high (30 mg/kg) doses of gossypol acetic acid for five consecutive days significantly (P less than 0.00001) reduced hepatic aniline hydroxylase activity, as well as cytochrome P-450 and b5 levels. Thus, compared to the controls, the low doses of gossypol decreased the hepatic aniline hydroxylase activity and cytochrome P-450 and b5 content by 73, 54, and 43 percent, respectively. The high doses of gossypol decreased the aniline hydroxylase, cytochrome P-450, and b5 levels by 60, 51, and 46 percent, respectively, as compared to controls. These data indicate that alteration of the hepatic metabolizing system may, in part, be responsible for the secondary toxemic effects seen when gossypol is used to provide antifertility action.

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.

Effects of diets containing gossypol on spermatogenic tissues of young bulls

Eighteen yearling beef bulls were used in a study to determine the effects of diets containing gossypol on spermatogenic tissues, Sertoli cells and Leydig cells. Bulls were randomly assigned to one of three (n = 6) isonitrogenous diet groups formulated from alfalfa hay and corn (gossypol-free control), control plus whole cottonseed and cottonseed hulls, or control plus cottonseed meal and cottonseed hulls as sources of gossypol. Testicular tissues collected were examined histologically, and tissues from bulls fed gossypol-free diets were compared with those fed diets containing cottonseed products. Following a 2-mo period (P(1)) when bulls were fed diets containing gossypol, one-half of the bulls were placed on a gossypol-free diet for an additional 2 mo (P(2)) to determine if gossypol effects were reversible. At the end of P(1), bulls fed whole cottonseed and cottonseed meal had larger (P<0.01) lumens in their seminiferous tubules, decreased (P<0.001) wall thickness in their seminiferous tubules, and a reduced (P<0.0001) number of cell layers in their seminiferous tubles, when compared with bulls fed a gossypol-free diet. These histological changes indicate detrimental effects to the spermatogenic tissues and associated cells. Following the initial two months (P(1)) of receiving feed containing gossypol, herd mates that were fed a gossypol-free diet for 2 mo (P(2)) showed improvement in histological characteristics, indicating that gossypol-induced effects were partially reversible.

Gossypol: a potent inhibitor of PAF-acether- and leukotriene-induced contractions of guinea-pig lung parenchyma strips

Gossypol, a substance extracted from cotton plants, markedly inhibited the contractile responses of guinea-pig lung parenchyma strips stimulated with leukotriene B4 (LTB4), leukotriene D4 (LTD4) and PAF-acether but not the responses to histamine (except at high concentration). It was slightly less potent than nordihydroguaiaretic acid (NDGA) and a PAF-antagonist (BN 52021). From previously reported effects of gossypol on the cyclooxygenase and lipoxygenases, and on the similarity of the inhibition produced by NDGA and gossypol on the lung parenchyma, it is suggested that the inhibition of the myotropic activity of the lung parenchyma by gossypol is due to interactions with the formation of cyclooxygenase products within the guinea-pig lung.

Monkey lactate dehydrogenase-C4 as a model for the interaction of enzymes with gossypol

Lactate dehydrogenase-C4 (LDH-C4) plays a central role in the metabolism of spermatogenic and mature sperm cells as well as being an enzyme which is inhibited by gossypol, a male contraceptive. Racemic and (+)-gossypol have equivalent potency as inhibitors of LDH-C4 purified from ejaculated sperm of cynomolgus monkeys. Analogues of gossypol (gossypol-glycine ester Schiff's base, 6,6-dimethoxygossypol and ethyl gossypol) have quantitatively similar inhibitory effects of LDH-C4 activity; apogossypol hexaacetate, however, has no inhibitory effect. Other effective inhibitors of LDH-C4 are antimycin, naphthoquinones and lithocholic acid. LDH-C4 may serve as a model for understanding gossypol binding domains and contraceptive action.

Specific inhibition of the testicular mitochondrial respiratory chain in vitro by gossypol

Optically inactive gossypol is an effective male antifertility agent in several mammalian species, while optically active (+)-gossypol has no antifertility effect in the rat and hamster. Recently, it was suggested that the mitochondria of spermatogenic cells may be a subcellular target of gossypol. We are reporting the effects of optically inactive gossypol and (+)-gossypol on the respiratory chain of mitochondria isolated from the testes and liver of rats and hamsters. The mitochondria were incubated with the test compounds and difference spectra were recorded. Complete inhibition of the testicular mitochondrial respiratory chain was observed at a concentration of approximately 75 microM. In contrast, no inhibition of the liver mitochondrial respiratory chain was observed with the test compounds at concentrations as high as 300 microM. These results demonstrate selective inhibition of the testicular mitochondrial respiratory chain by gossypol isomers.

Inhibition of hepatic microsomal enzymes by gossypol in the rat

The effect of the male contraceptive, gossypol, on rat liver microsomal enzymes has been studied in vitro and in vivo. In vitro, gossypol inhibited aminopyrine N-demethylase activity, the concentration causing 50% inhibition being approximately 0.03 mM; the inhibition was non-competitive. Also the metabolism of ethinylestradiol (a drug with a number of metabolic pathways) was inhibited with the main effect being reduced 2- and 16-hydroxylation. In vivo, gossypol, after 4 weeks of daily administration (30 mg/kg/day) caused a significant reduction in microsomal protein, cytochrome P450 and aminopyrine N-demethylase activity. However, despite reduced enzyme activity, the metabolism of tolbutamide (a drug with a single pathway of metabolism and hence a model substrate) was not impaired by either acute or chronic gossypol administration.

Effect of the antifertility agent, gossypol acetic acid, on the metabolism and testosterone secretion of isolated rat interstitial cells in vitro

Gossypol acetic acid is a polyphenolic compound present in the seed of cotton plants. Its antifertility activity by inhibition of spermatogenesis was proven in a large group of animals, including man. In the present study, the direct effect of gossypol acetic acid on collagenase isolated rat I-cells (interstitial cells) was investigated. It was shown that gossypol acetic acid depressed significantly the metabolic rate of the cells. Glucose utilization was abolished by a starting dose of 100 micrograms/ml. Oxygen consumption of I-cells was reduced even at a smaller dose of gossypol (50 micrograms/ml). At these doses, the vitality of the cells remained (proven by trypan blue exclusion test). 3 beta-Hydroxysteroid dehydrogenase (3 beta-HSD) histochemical stain was slightly decreased. Increasing doses of gossypol caused a marked decrease in the vitality of I-cells and a dramatic drop in histochemical stain for 3 beta-HSD. The pH of the medium was not changed at any dose of treatment. In cultures of I-cells not stimulated by hCG, gossypol did not affect the tonic slow release of testosterone. Thus, gossypol acetic acid has a direct inhibitory effect on isolated rat I-cells, depressing cell metabolism. The failure of some of the other groups to show such an effect, especially in vivo, can be attributed to differences in the dose of treatment and strain of animals.

The effect of gossypol and Lonidamine on electron transport in Ehrlich ascites tumor mitochondria

The effect of the association of gossypol and Lonidamine on the electron transport in Ehrlich ascites tumor mitochondria has been investigated by addition of drugs to isolated mitochondria. The results may be summarized as follows. (1) Low concentrations of gossypol increase the rate of oxygen consumption at the level of three energy-conserving sites of the respiratory chain. Higher concentrations result in an inhibition of oxygen consumption at (or near) both energy-conserving sites 1 and 2, while energy-conserving site 3 is unaffected. (2) Gossypol, at concentrations at which it exerts its uncoupling effect, stimulates ATPase activity. Higher concentrations inhibit the enzyme activity. (3) The addition of gossypol to mitochondria respiring on pyruvate plus malate or succinate induces a more oxidized state of NAD+ and cytochrome b, respectively. (4) Gossypol enhances the effect of Lonidamine on oxygen consumption. Lonidamine does not affect state 4 respiration, but in the presence of gossypol, it determines a marked decrease in the rate of oxygen consumption. The inhibition of oxidation of NAD-linked substrates is greater than that of FAD-linked substrates. (5) It may be concluded that gossypol is very effective in potentiating the effect of Lonidamine. Moreover, it may be suggested that the antitumor activity of Lonidamine is enhanced if it is used in combination with other drugs and/or treatments, such as hyperthermia, which modify the energy status of mitochondria.

Serum potassium and aldosterone levels in gossypol-treated rats

Male rats fed with 30 mg/kg gossypol for 2 or 4 weeks exhibited a decrease in growth but showed no change from control in serum potassium levels. Serum aldosterone levels remained unchanged, but serum testosterone levels were significantly reduced after 4 weeks of treatment. Serum T3 was significantly increased after 2 or 4 weeks of treatment, while serum T4 was not different from control. It is concluded that gossypol at a dose that is sufficient to produce sterility in rats did not change serum potassium and aldosterone levels.

The effect of the association of Gossypol and Lonidamine on the energy metabolism of Ehrlich ascites tumor cells

The effect of the association of Gossypol and Lonidamine on the energy metabolism of Ehrlich ascites tumor cells has been investigated. The action of the drug on tumor cells was studied by addition of the drugs to cells harvested from Swiss male mice. The results may be summarized as follows: (1) Low concentrations of Gossypol increase the rate of oxygen consumption by uncoupling oxidative phosphorylation. High concentrations result in an inhibition of oxygen consumption with a mechanism that must be regarded as not directly related to the uncoupling activity. (2) Gossypol, at concentrations at which it exerts an uncoupling activity, stimulates mitochondrial ATPase which in turn increases the aerobic and anaerobic rates of lactate production. The decrease of glycolysis at high concentrations of Gossypol does not depend on the inhibition of enzymes of the glycolytic pathway, but must be ascribed to cell death. (3) The association of a low concentration of Gossypol with Lonidamine brings about a further inhibition of oxygen consumption. Moreover, Lonidamine abolishes the stimulation of glycolysis induced by Gossypol and lowers lactate production to values that are quite similar to those found with Lonidamine alone. (4) It may be concluded that the association of Gossypol and Lonidamine results in a very effective decrease of the energy requirements of cancer cells.

Effect of gossypol on boar spermatozoal adenosine triphosphate metabolism

The effect of gossypol on boar spermatozoal adenosine triphosphate (ATP) metabolism was investigated. Gossypol has little effect on the activities of the total spermatozoal ATPase, the spermatozoal flagellar ATPase, and the mitochondrial fragment ATPase. The membrane ATPase, being exceedingly low, has not been considered for its susceptibility toward gossypol. Gossypol uncouples spermatozoal oxidative phosphorylation. A biphasic response (stimulation at low concentration and inhibition at high concentration) has been noticed in anaerobic lactate production and hypotonically treated spermatozoal mitochondrial ATPase activity. The ATP content, either under aerobic or anaerobic condition was reduced by gossypol with the reduction threshold of ATP more sensitive in the latter. The reduction of ATP follows two different reaction kinetics in which it is stabilized at moderate gossypol concentrations but progresses along with time at high concentrations. Since the drop in motility is more sensitive than the drop in ATP content and since the flagellar ATPase is not significantly inhibited by gossypol, a motility controlling component that is more sensitive to gossypol antimotility inhibition is proposed.

Inhibition of catechol-O-methyltransferase by gossypol: the effect of plasma proteins

Catechol-O-methyltransferase (COMT) is a key enzyme in the metabolism of catecholamines. As gossypol, a recent male contraceptive, has been reported to inhibit some respiratory enzymes in vitro, we have studied its effect on rat liver COMT activity. Varying concentrations of gossypol acetic acid were incubated with 3H-methyl-S-adenosyl-methionine, COMT, a different concentrations of norepinephrine. It was found that addition of gossypol into the incubation medium greatly depressed COMT activity, with an I50 of 0.01 mM. A series of inhibitory curves constructed from using different concentrations of the substrate suggested that the inhibition was non-competitive. Addition of blood serum or BSA significantly reduced the inhibitory effect of gossypol. We concluded that gossypol may markedly decrease COMT activity through non-competitive inhibition. Since various organs of the rat have been shown to accumulate gossypol, ingestion of gossypol for the purpose of fertility control may have important effect on the metabolism of catecholamine.

Cottonseed oil as a vaginal contraceptive

The effect of gossypol acetic acid an cottonseed oil emulsion on human spermatozoal motility was tested. Contrary to a recent report [Waller et al. (1980): Contraception 22:183-187] that gossypol acetic acid is harmless to human spermatozoal motility in vitro, 10-3 M gossypol acetic acid completely abolished spermatozoal motility. This discrepancy might have stemmed from an oversight in the gossypol solubility. Cottonseed oil emulsion also exhibited spermatozoal motility inhibition. The applicability of this natural low toxicity cottonseed oil as vaginal contraceptive was explored

Variations of gossypol sensitivity in boar spermatozoal electron transport chain segments

The concentration effect of gossypol on hypotonically-treated boar spermatozoa with either succinate or pyruvate and malate as substrate was examined. It was found that the pathways involved in the metabolism of succinate was more gossypol-sensitive. The gossypol sensitivity of various electron transport chain (ETC) segments in boar spermatozoa was also investigated with proper choice of electron donors and acceptors. The succinate to cytochrome c segment was the most sensitive one. However this inhibition threshold (1.8 X 10(-5) M gossypol), being higher than either the uncoupling threshold or the concentration threshold at which spermatozoal motility is reduced, suggests that the main target of gossypol antimotility effect does not seem to be the succinate to cytochrome c segment in the ETC.

Effect of gossypol on boar spermatozoa in vitro

Gossypol, the active component in cottonseed oil, inhibits spermatogenesis in many mammals. Gossypol enhanced respiration and abolished forward motility of boar spermatozoa. The effective concentration was 10(-5) M, similar to that reported in its uncoupling of oxidative phosphorylation in rat liver mitochondria. Its antifertility effect may be a combination of the effect on the developing spermatids as well as that on spermatozoal motility.

Some factors affecting the Hill reaction activity in cotton chloroplasts

A method of plant culture was developed for growing large leaves of glandless cotton on single stems. Chloroplasts isolated from these leaves actively reduced ferricyanide when assayed for the Hill reaction. Hill reaction activity increased 133% when the 0.5 m sucrose isolation medium was replaced with 10% (w/v) polyethylene glycol, both buffered at pH 7.6. The presence of 2 or 5% (w/v) bovine serum albumin in the sucrose buffer did not increase Hill activity. Ferricyanide reduction in the dark occurred in all assays, and the possibility of gossypol as the reductant is discussed. Half-life of the chloroplasts stored in 10% glycerol at -23 C was 23 days. The ammonium ion at 0.01 m enhanced Hill reaction activity up to 171%. Leaves containing chloroplasts with the highest Hill reaction activity were found near the 8th node below the apex. Leaf water potentials less than -28 bars reduced the activity about 50%. Daylight conditions during the winter months in the greenhouse reduced the activity about 30%.

UPTAKE OF NITRATE AND NITRITE BY DITYLUM BRIGHTWELLII-KINETICS AND MECHANISMS(1) (2)

Ditylum brightwellii grown on NO2 - as a nitrogen source took up and assimilated NO2 - only in the light, apparently via a photosynthetic nitrite reductase. Assimilation was inhibited by dichlorophenyldimethylurea (DCMU), KCN, partially by 2,4 dinitrophenol, and by NO3 -. Kinetics of inhibition of NO2 - assimilation by NO3 - appeared to be "competitive." D. brightwellii cells grown on NO2 - took up NO3 - in both light and dark and in both cases the uptake was inhibited by p-chloromercuribenzoate, but not by DCMU, KCN, or by NO2 -. Most of the NO3 - taken up in the dark was recovered unchanged from the cells. However only 40% of NO3 - taken up in light was recovered from the cells and no NO2 - was found. This suggests that a photosynthetic nitrate reduction mechanism was active in these cells. DCMU inhibited the light-induced NO3 - reduction. This mechanism of NO3 - reduction is distinct from that involving NADH nitrate reductase in D. brightwellii since the concentration of the latter enzyme is very low in cells grown on NO2 -. Saturation kinetics were observed for NO2 - and NO3 - uptake. Half-saturation concentrations (Ks values) were 4 and 2 μM, respectively. These values are compared with those obtained for NO2 - and NO3 - assimilation by other unicellular algae. The comparisons show lower Ks values in oceanic species compared with tide-pool or freshwater algae and they support the idea that Ks values for NO3 - assimilation may provide a key to understanding species succession when this is due to declining: nitrate concentrations in the sea.

Uncoupling of energy-linked functions of corn mitochondria by linoleic Acid and monomethyldecenylsuccinic Acid

Linoleic acid and monomethyldecenylsuccinic acid were tested as uncoupling agents for energy linked functions of corn mitochondria. 2,4-dinitrophenol was used as a standard for comparison. Both compounds uncoupled oxidative phosphorylation, released oligomycin-blocked respiration, and accelerated adenosine triphosphatase. Linoleic acid uncoupled calcium-activated phosphate accumulation and the increase in light scattering that accompanies the accumulation. Unlike dinitrophenol, linoleic acid at 0.1 mm had a destructive effect on membrane semipermeability. Kinetic studies indicated that dinitrophenol and linoleic acid compete with phosphate for active sites in oxidative phosphorylation.Some linoleic acid is taken up by respiring mitochondria and a major share of the uptake is incorporated into phospholipids. Calcium ion and oligomycin promote the uptake, but coenzyme A does not. It is deduced that fatty acid probably attacks the non-phosphorylated intermediate, I approximately X, producing X approximately acyl. Uncoupling results from breakdown of X approximately acyl, but sufficient X approximately acyl is maintained to serve as a source of activated fatty acid.