Gossypol blood levels and inhibition of spermatogenesis in men taking gossypol as a contraceptive. A multicenter, international, dose-finding study

Optimizing drug discovery for snakebite envenoming via a high-throughput phospholipase A2 screening platform

Snakebite envenoming is a neglected tropical disease that causes as many as 1.8 million envenomings and 140,000 deaths annually. To address treatment limitations that exist with current antivenoms, the search for small molecule drug-based inhibitors that can be administered as early interventions has recently gained traction. Snake venoms are complex mixtures of proteins, peptides and small molecules and their composition varies substantially between and within snake species. The phospholipases A2 (PLA2) are one of the main pathogenic toxin classes found in medically important viper and elapid snake venoms, yet varespladib, a drug originally developed for the treatment of acute coronary syndrome, remains the only PLA2 inhibitor shown to effectively neutralise venom toxicity in vitro and in vivo, resulting in an extremely limited drug portfolio. Here, we describe a high-throughput drug screen to identify novel PLA2 inhibitors for repurposing as snakebite treatments. We present method optimisation of a 384-well plate, colorimetric, high-throughput screening assay that allowed for a throughput of ∼2,800 drugs per day, and report on the screening of a ∼3,500 post-phase I repurposed drug library against the venom of the Russell's viper, Daboia russelii. We further explore the broad-spectrum inhibitory potential and efficacy of the resulting top hits against a range of medically important snake venoms and demonstrate the utility of our method in determining drug EC50s. Collectively, our findings support the future application of this method to fully explore the chemical space to discover novel PLA2-inhibiting drugs of value for preventing severe pathology caused by snakebite envenoming.

Effect of cottonseed milk on growth performance, hematological and semen characteristics in male Wistar albino rats

Various plant based milk extract is appropriate for human nutrition among which cottonseed is one of the potential crops with the advantages of stable milk emulsion, improved nutrient profile with affordable waste utilization. Although cottonseed milk is a popular indigenous beverage, it has not been exploited worldwide for regular consumption owing to the presence of gossypol. The gossypol toxicity and associated gossypol-iron complex formation in the intestine lead to changes in hematological characteristics and alternation of sperm motility in monogastric animals. Male Wistar albino rats weighing 60 to 70 g were divided into four groups of five animals each. The group fed the standard diet (STD) served as control, and the experimental groups included the group (i) rats fed cottonseed diet (CSD) supplemented at 10% of cottonseed level (ii) rats fed conventional aqueous extracted cottonseed milk (CCM) diet (CAD) and (iii) rats fed enzymatic assisted aqueous extracted cottonseed milk (ECM) diet (EAD). The CAD and EAD feed was administrated @ 1 ml/100 g of animal body weight /day for the study period of 45 days among the experimental groups and control group. A significant difference in weight gain of the experimental rats was noticed between the CCM and ECM cottonseed milk extracts fed experimental groups compared with the standard and cottonseed fed groups. The rats fed with CSD, CCM and ECM diet exhibited higher white blood cell counts, also reducing the red blood cells count, hemoglobin hematocrit and platelet in the group compared with STD. No significant difference in semen motility characteristics was noticed among the CSD, CCM and ECM fed groups. In conclusion, the intake of less than the permissible level of gossypol from selected cottonseed and its aqueous extracted milk samples has influenced the hematological parameters and whereas an improved effect was shown in semen characteristics.

Graphical Abstract

Rising trends towards the development of oral herbal male contraceptive: an insight review

Background

Acknowledging population control to be an essential step for global health promotes wide research study in the area of male contraception. Although there are a great number of synthetic contraceptives available in the market, they have plenty of adverse effects. Different potential strategies for male contraception were investigated over a long period time consisting of hormonal, chemical, and immunological interventions, although these methods showed good antifertility results with low failure rates relative to condoms.

Main text

This review is based upon the concept of herbal contraceptives which are an effective method for controlling the fertility of animals and humans. This review has highlighted herbal medicinal plants and plant extracts which have been reported to possess significant antifertility action in males. The review considers those plants which are used traditionally for their spermicidal and antispermatogenic activities and imbalance essential hormones for fertility purposes and plants with reported animal studies as well as some with human studies for antifertility effect along with their doses, chemical constituents, and mechanism of action of the antifertility effect of the plants. This review also explains the phases of sperm formation, hormone production, and the mechanism of male contraceptives.

Conclusion

As far as the relevance of the current review is discussed, it might be quite useful in generating monographs on plants and recommendations on their use. A lot of the plant species listed here might appear promising as effective alternative oral fertility-regulating agents in males. Therefore, significant research into the chemical and biological properties of such less-explored plants is still needed to determine their contraceptive efficacy and also to possibly define their toxic effects so that these ingredients can be utilized with confidence to regulate male fertility. The new inventions in this field are necessary to concentrate on modern, more potent drugs with less harmful content and that are self-administrable, less costly, and entirely reversible.

The effects of feeding graded levels of whole cottonseed on semen characteristics and testicular profiles of Red Sokoto Bucks

The present work evaluated the effects of feeding graded levels of whole cottonseed on reproductive parameters of Red Sokoto bucks. Twenty Red Sokoto bucks were used for the experiment. After a 14-day pre-treatment period, bucks were assigned for 90 days to one of four isonitrogeneous treatments: control (diet A); 0 mg kg-1 of total gossypol, (diet B); 15% mg kg-1 of total gossypol, (diet C); 30% mg kg-1 of total gossypol and (diet D); 45% mg kg-1 of total gossypol. The mean percentage sperm gross motility was significantly (p < 0.05) lower in group D (45% WCS) compared to groups C (30% WCS) and A (control) at days 60, 75 and 90. The mean semen pH and reaction time were not significantly (p > 0.05) different among treatment groups. Semen colour of the bucks in the control group was majorly creamy, in group C (30% WCS) and B (15% WCS) creamy to milky and group D (45% WCS) colourless. The mean semen volume was significantly (p < 0.05) higher in groups C and A compared to group D (45% WCS) at days 60, 75 and 90. The mean semen concentration was significantly (p < 0.05) lower in group D (45% WCS) when compared to group A (control) at days 30, 45, 60, 75 and 90. Group A (control) bucks had significantly (p < 0.05) higher percentage live sperm compared to those in group D (45% WCS) at days 45, 60, 75 and 90. Mean Sperm morphological abnormalities including detached head, free tail curved tail and midpiece droplets were significantly (p < 0.05) higher in group D (45%) than in group A (Control) at day 15 (for free tails) and day 90 (for all). Testicular and epididymal sperm reserves were higher in animals supplemented with up to 30% whole cottonseed. In conclusion, feeding bucks above 30% WCS resulted in more deleterious effects on the semen characteristics and testicular profile.

A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

Development of an RP-UHPLC-PDA method for quantification of free gossypol in cottonseed cake and fungal-treated cottonseed cake

Cottonseed cake biomass, which is a residue of oil extraction, is potentially appropriate for use as animal feed, given the high mineral, fibre and protein content. The presence of free gossypol, however, a toxic pigment in the glands of the cotton plant, limits use of this biomass for monogastric livestock. A promising method to detoxify cottonseed cake relies on fermentation by fungi, which can eliminate up to 100% of gossypol. In order to quantify trace levels of free gossypol in different cotton materials, including cottonseed cake treated with macrofungi, a simple and rapid chromatographic detection method was developed and validated. Under optimized conditions, extraction was performed using 70% acetone. The extract was then analysed by Ultra High-Performance Liquid Chromatography (UHPLC), with gradient elution on a C18 reverse phase column KINETEX^® (100 x 2.10 mm, 2.6 μm). Methanol-0.1% TFA aqueous solution was employed as mobile phase and PDA detection conducted at 254 nm. The optimized method was validated by analysis of specificity, linearity and range, limit of detection, limit of quantification, precision and accuracy. Detection and quantification limits were observed at 0.2 and 0.5 μg/mL, respectively. With good reproducibility, with precision (RSD)<10% and recovery greater than 94%, the developed assay was appropriate for quantification of low quantities of free gossypol. The validated method was successfully applied to determine trace levels of free gossypol cottonseed treated with a macrofungus.

The future of male contraception: a fertile ground

The continued and rapid expansion of the Earth’s population mandates the need for safe and effective measures of contraception. While a plethora of options exist for women, methods of contraception for the male partner are limited to condoms and vasectomy. The sequela of this discrepancy has led to the family planning burden falling disproportionately on the female partner. For the past several decades, extensive research has been undertaken exploring the feasibility of hormonal male contraception. This proposed method of contraception has focused on suppressing spermatogenesis by exploiting the hypothalamic-pituitary-gonadal (HPG) axis. Beginning with proof of concept studies in the early nineties, administration of testosterone in healthy male subjects has been shown to be an efficacious method of inducing sterility. Owing to ethnic differences in spermatogenesis suppression and the comparatively low rate of azoospermia in Caucasian men with androgen-only regimens, investigators have explored the addition of progestins to further enhance the efficacy of hormonal contraception. Though studies have revealed promise with androgen-progestin regimens, the lack of long-term studies has precluded the development of a marketable product. Recently, more research has been directed towards identifying non-hormonal alternatives to male contraception. These non-hormonal options have ranged from the development of devices facilitating reversible occlusion of the vas deferens lumen to medications disrupting various pathways in the process of spermatogenesis. Underlying the development of hormonal and non-hormonal strategies is the shared enthusiasm men and women have towards these male directed methods. The willingness of couples to pursue these alternatives combined with the global need to reduce the psychological and socioeconomic implications of unintended pregnancy ensures that research will continue to bring this goal to fruition.

Antimetabolic Effects of Polyphenols in Breast Cancer Cells: Focus on Glucose Uptake and Metabolism

In the last years, metabolic reprogramming became a new key hallmark of tumor cells. One of its components is a deviant energetic metabolism, known as Warburg effect—an aerobic lactatogenesis—characterized by elevated rates of glucose uptake and consumption with high-lactate production even in the presence of oxygen. Because many cancer cells display a greater sensitivity to glucose deprivation-induced cytotoxicity than normal cells, inhibitors of glucose cellular uptake (facilitative glucose transporter 1 inhibitors) and oxidative metabolism (glycolysis inhibitors) are potential therapeutic targets in cancer treatment. Polyphenols, abundantly contained in fruits and vegetables, are dietary components with an established protective role against cancer. Several molecular mechanisms are involved in the anticancer effect of polyphenols, including effects on apoptosis, cell cycle regulation, plasma membrane receptors, signaling pathways, and epigenetic mechanisms. Additionally, inhibition of glucose cellular uptake and metabolism in cancer cell lines has been described for several polyphenols, and this effect was shown to be associated with their anticarcinogenic effect. This work will review data showing an antimetabolic effect of polyphenols and its involvement in the chemopreventive/chemotherapeutic potential of these dietary compounds, in relation to breast cancer.

Gossypol ameliorates liver fibrosis in diabetic rats induced by high-fat diet and streptozocin

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) inhibitors have been shown to treat type 2 diabetes (T2D). Since gossypol is an 11β-HSD1 inhibitor, the objective of the present study was to treat T2D and T2D-related liver fibrosis in rat model using low-dose gossypol. T2D was induced by feeding with high fat diet plus injection of streptozocin (30mg/kg). Diabetic rats were treated with either vehicle control or racemic gossypol with a dose of 15mg/kg/day for 4weeks followed by 15mg/kg/week for additional 8weeks. Blood glucose, cholesterol, LDL, and triglycerides were measured. Messenger mRNA levels of glucocorticoid receptor (Nr3c1), phosphoenolpyruvate carboxykinase (Pck1), glucose-6-phosphatase (G6pc), collagen I (Col1a1), collagen III (Col3a1), fibronectin (Fn1), tissue inhibitor of metalloproteinase 1 (Timp1), and 2 (Timp2) were measured. T2D rats had higher serum glucose, cholesterol, LDL, and triglyceride levels compared to control. Liver Nr3c1, Col1a1, Col3a1, Fn1, Timp1, and Timp2 were increased in T2D rats. T2D liver showed significant fibrosis with the increases of α-smooth muscle actin and fibronectin. After gossypol treatment, serum glucose level was lowered by 64%. Liver fibrosis was significantly ameliorated. Nr3c1, Col1a1, Col3a1, Fn1, Timp1, Timp2, Pck1 as well as G6pc levels were significantly reduced. In conclusion, low dose gossypol is effective for the treatment of T2D and T2D-related fibrosis.

La contraception masculine « verte »: mythe ou réalité ?

Le refus des solutions « chimiques », souvent jugées suspectes, mène un nombre croissant de contemporains à rechercher une alternative naturelle chaque fois qu’elle existe. Le domaine médical — et en particulier celui qui concerne la reproduction — échappe d’autant moins à cette aspiration qu’il s’y trouve des bases historiques multimillénaires. Il a également des justifications économiques dans tous les pays où l’accès aux médicaments est problématique, sinon illusoire. La contraception masculine n’est pas oubliée dans ce contexte; en particulier dans les pays émergents où la natalité élevée pose un problème de société. Des principes actifs extraits de plantes ont fait — et font encore-l’objet de recherches très circonstanciées. Il existe de bonnes raisons de penser que des solutions existent dans ce registre. Des tests menés in vivo chez l’animal (surtout), mais aussi in vitro sur des spermatozoïdes isolés concluent à l’existence d’effets centraux, périphériques ou spermicides significatifs. Les vertus thérapeutiques souvent multiples des plantes concernées mènent toutefois à rester vigilants pour ne pas associer, en cas d’utilisation systémique, un effet secondaire indésirable à l’effet contraceptif recherché.

A validated HPLC assay for the determination of R-(-)-gossypol in human plasma and its application in clinical pharmacokinetic studies

R-(-)-gossypol acetic acid (AT-101), a natural BH3 mimetic, is investigated in a Phase I/II clinical trial for the treatment of advanced solid tumor malignancies. Gossypol undergoes rapid degradation in solution phase, which causes major technical difficulty for its quantitation in plasma. We developed and validated a sensitive HPLC assay for pharmacokinetic evaluation of gossypol. Acetonitrile deproteinization method was chosen for sample preparation and Schiff's base derivative, R-(-)-gossypol-diamino-propanol (GDP), was used as internal standard. Chromatographic separation of gossypol in plasma was performed using a Zorbax Eclipse XDB column C(18) at 30 °C. The mobile phase consists of 10 mmol/L KH(2)PO(4) (pH 3.0) and acetonitrile (20:80) at 1.0 mL/min flow rate. Linearity ranged over 56-3585 ng/mL (R(2)=0.9997±0.0003, n=4), and the limit of detection was 28 ng/mL. The intra- and inter-assay precision was less than 13.7% and the bias ranged from -7.4 to 7.0%. The method was successfully applied to characterize the pharmacokinetics of AT-101 in a Phase I clinical trial. The validated assay is accurate, and sensitive with minimum loss and rapid analysis time and suitable for quantification of gossypol for pharmacokinetics evaluation.

Inhibitors of the anti-apoptotic Bcl-2 proteins: a patent review

INTRODUCTION

The B-cell lymphoma-2 (Bcl-2) family of proteins is central to the regulation of apoptosis, which is vital for proper tissue development and cellular homeostasis. Anti-apoptotic proteins, members of the Bcl-2 family, are an important survival factor for many cancers and their overexpression has been associated with tumor initiation, progression, and resistance to current anticancer therapies. Therefore, strategies seeking to antagonize the function of Bcl-2 anti-apoptotic proteins have been extensively studied for developing a novel cancer therapy.

AREAS COVERED

This review covers research and patent literature of the last 15 years dealing with the discovery and development of inhibitors of the Bcl-2 protein family.

EXPERT OPINION

The feasibility of disrupting protein-protein interactions between anti-apoptotic and pro-apoptotic proteins, members of the Bcl-2 family, using peptidomimetics and small-molecule inhibitors has been successfully established. Three small-molecule inhibitors have entered human clinical trials, which will allow the evaluation of this potential therapeutic approach in cancer patients. It will be important to gain a better understanding of pan and selective Bcl-2 inhibitors in order to facilitate future drug design efforts.

Small-molecule inhibitors reveal a new function for Bcl-2 as a proangiogenic signaling molecule

Cancer has a complex etiology and displays a wide range of cellular escape pathways that allow it to circumvent treatment. Signaling molecules functionally downstream of the circumvented pathways, and particularly at checkpoints where several of these pathways intersect, provide valuable targets for the development of novel anti-cancer drugs. Bcl-2, a pro-survival signaling molecule, is one such protein. This review examines the efficacy, potency, and function of several small molecule inhibitor drugs targeted to the Bcl-2 family of proteins. The review focuses on the compounds with most available data within the literature and discusses both the anti-cancer and the recently unveiled anti-angiogenic potential of this new class of drugs.

Effects of combined administration of low-dose gossypol with steroid hormones on the mitotic phase of spermatogenesis of rat

Our previous studies suggested that combined low-dose gossypol with steroid hormones possesses a reversible antifertility role on adult male rat. Spermatocyte apoptosis during the meiosis of spermatogenesis is the main reason for the antifertility. This study evaluates the effects of the regimen on the mitosis of spermatogenesis. Thirty-two adult male rats were divided into four groups randomly, Group GH: rats were fed orally with gossypol acetic acid (GA, 12.5 mg/kg d) and desogestrel (DSG, 0.125 mg/kg d)/ethinylestradiol (EE, 0.025 mg/kg d)/testosterone undecanoate (TU, 100 mg/kg d); Group G: a single dose of GA (12.5 mg/kg d); Group H: the same dosage of DSG/EE/TU as in Group GH; Group C: rats were treated with vehicle (1% methyl cellulose) as control. Testes were removed at the 8th week after treatment to assess the weight, volumes, diameter, and degenerated rate of seminiferous tubule, spermatogonia is quantitated by stereological assay. TUNEL assay and proliferating cell nuclear antigen immunohistochemistry were used to determine the germ cell apoptosis and proliferation. The changes of gene expression of glial cell line-derived neurotrophic factor (GDNF) and Ets variant gene 5 (Etv5) were analyzed. The results manifested that the spermatogenesis was suppressed, the type A and intermediate spermatogonia reduced, and spermatocyte and spermatid apoptosis increased both in Group GH and Group H. The expressions of GDNF protein in these two groups were downregulated, but no change was observed in Etv5 expression. However, the numbers of spermatogonia, germ cell apoptosis and proliferation, and the expressions of GDNF and Etv5 were unchanged in Group G compared with Group C. Above all, we concluded that the mitotic phase of spermatogenesis is suppressed by the combination regimen, it might be the steroid hormones in the regimen that caused the reduction of spermatogonia through the downregulation of GDNF.

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 (+)- and (-)-gossypols potently inhibit both 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase 3 in human and rat testes

Androgen deprivation is commonly used in the treatment of metastatic prostate cancer. The (-)-gossypol enantiomer has been demonstrated as an effective inhibitor of Bcl-2 in the treatment of prostate cancer. However, the mechanism of gossypol as an inhibitor of androgen biosynthesis is not clear. The present study compared (+)- and (-)-gossypols in the inhibition of 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-HSD isoform 3 (17beta-HSD3) in human and rat testes. Gossypol enantiomers were more potent inhibitors of rat 3beta-HSD with IC(50)s of approximately 0.2microM compared to 3-5microM in human testes. However, human 17beta-HSD3 was more sensitive to inhibition by gossypol enantiomers, with IC(50)s of 0.36+/-0.09 and 1.13+/-0.12 for (-)- and (+)-gossypols, respectively, compared to 3.43+/-0.46 and 10.93+/-2.27 in rat testes. There were species- and enantiomer-specific differences in the sensitivity of the inhibition of 17beta-HSD3. Gossypol enantiomers competitively inhibited both 3beta-HSD and 17beta-HSD3 by competing for the cofactor binding sites of these enzymes. Gossypol enantiomers, fed orally to rats (20mg/kg), inhibited 3beta-HSD but not 17beta-HSD3. This finding was consistent with the in vitro data, in which rat 3beta-HSD was more sensitive to gossypol inhibition than rat 17beta-HSD3. As the reverse was true for the human enzymes, gossypol might be useful for treating metastatic prostate cancer.

The (+)- and (-)-gossypols potently inhibit human and rat 11beta-hydroxysteroid dehydrogenase type 2

Gossypol has been proven to be a very effective male contraceptive. However, clinical trials showed that the major side effect of gossypol was hypokalemia. Gossypol occurs naturally as enantiomeric mixtures of (+)-gossypol and (-)-gossypol. The (-)-gossypol is found to be the active component of antifertility. 11beta-Hydroxysteroid dehydrogenase 2 (11betaHSD2) has been demonstrated to be a mineralocorticoid receptor (MR) protector by inactivating active glucocorticoids including corticosterone (CORT) in rats, and therefore mutation or suppression of 11betaHSD2 causes hypokalemia and hypertension. In the present study, the potency of gossypol enantiomers was tested for the inhibition of 11betaHSD1 and 2 in rat and human. Both (+) and (-)-gossypols showed a potent inhibition of 11betaHSD2 with the half maximal inhibitory concentration (IC(50)) of 0.61 and 1.33 microM for (+) and (-)-gossypols, respectively in rats and 1.05 and 1.90 microM for (+) and (-)-gossypols, respectively in human. The potency of gossypol to inhibit 11betaHSD1 was far less; the IC(50) was > or =100 microM for racemic gossypol. The gossypol-induced hypokalemia is likely associated with its potent inhibition of kidney 11betaHSD2.

Expanding circle of inhibition: small-molecule inhibitors of Bcl-2 as anticancer cell and antiangiogenic agents

The specific targeting of diseases, particularly cancer, is a primary aim in drug development, as specificity reduces unwelcome effects on healthy tissue and increases drug efficacy at the target site. Drug specificity can be increased by improving the delivery system or by selecting drugs with affinity for a molecular ligand specific to the disease state. The role of the prosurvival Bcl-2 protein in maintaining the normal balance between apoptosis and cellular survival has been recognized for more than a decade. Bcl-2 is vital during development, much less so in adults. It has also been noted that some cancers evade apoptosis and obtain a survival advantage through aberrant expression of Bcl-2. The new and remarkably diverse class of drugs, small-molecule inhibitors of Bcl-2 (molecular weight approximately 400 to 800 Daltons), is examined herein. We present the activities of these compounds along with clinical observations, where available. The effects of Bcl-2 inhibition on attenuation of tumor cell growth are discussed, as are studies revealing the potential for Bcl-2 inhibitors as antiangiogenic agents. Despite an enormous body of work published for the Bcl-2 family of proteins, we are still learning exactly how this group of molecules interacts and indeed what they do. The small-molecule inhibitors of Bcl-2, in addition to their therapeutic potential, are proving to be an important investigative tool for understanding the function of Bcl-2.

CP/MAS spectroscopy in the determination of the tautomeric forms of gossypol, its Schiff bases and hydrazones in the solid state

New Schiff bases and new hydrazones were synthesized and studied by (13)C and (15)N CP/MAS spectroscopy and by (1)H--(1)H COSY, (1)H--(13)C HMBC, (1)H--(13)C HSQC, (1)H--(15)N HMQC and (1)H--(15)N HSQC correlations. The CP/MAS investigation of gossypol has demonstrated that in the solid state it exists exclusively in the aldehyde-aldehyde tautomeric form. In contrast, CP/MAS studies of hydrazones and Schiff bases reveal that these compounds occur in the solid state in the N-imine-N-imine and enamine-enamine tautomeric forms, respectively. It is shown that the (13)C resonances of C-6, C-7 and C-11 carbon atoms are suitable for distinguishing between the tautomeric forms of aza-derivatives of gossypol in the solid state. Furthermore, we have proved that the (15)N CP/MAS spectra can be used to identify these tautomeric forms.

Effect of Ruta graveolens and Cannabis sativa alcoholic extract on spermatogenesis in the adult wistar male rats

Objective:

The present study was undertaken to evaluate the effects of alcohol extracts of Ruta graveolens and Cannabis sativa that were used traditionally in medieval Persian medicine as male contraceptive drugs, on spermatogenesis in the adult male rats.

Materials and Methods:

Ethanol extracts of these plants were obtained by the maceration method. The male rats were injected intraperitionaly with C. sativa and R. graveolens 5% ethanol extracts at dose of 20 mg/day for 20 consecutive days, respectively. Twenty-four hours after the last treatment, testicular function was assessed by epididymal sperm count.

Result:

The statistical results showed that the ethanol extracts of these plants reduced the number of sperms significantly (P=0.00) in the treatment groups in comparison to the control group. The results also showed that the group, treated by extract of R. graveolens reduced spermatogenesis more than the group treated by extracts of C. sativa.

Conclusion:

The present study demonstrated the spermatogenesis reducing properties of the ethanol extracts of R. graveolens and C. sativa in the adult male wistar rats but more studies are necessary to reveal the mechanism of action that is involved in spermatogenesis.

Contraceptions masculines non déférentielles : revue de la littérature

OBJECTIVES

To review the state of progress of the various male contraceptive methods (with the exception of deferential methods).

MATERIAL AND METHODS

A review of the literature was performed by using the key words: male/contraception, limiting the search to original articles in English and French. Articles on vasectomy and the other deferential methods of contraception are not considered in the present review.

RESULTS

Three methods of male contraception are widely used at the present time: withdrawal, male condom and vasectomy, although other types of male contraception have been shown to be effective, including hormonal contraception, which appears to be the most promising technique and the subject of the majority of research. Other contraceptive methods (immunological, thermal...) could constitute possible alternatives.

CONCLUSION

Male contraception remains under-used, as only male condoms are commonly used (apart from withdrawal and vasectomy). Consequently, new research protocols in the field of male contraception must be strongly encouraged.

Gossypol inhibits calcineurin phosphatase activity at multiple sites

Calcineurin, the Ca2+/calmodulin-dependant serine/threonine phosphatase is the target for the immunosuppressant drugs FK506 and cyclosporine-A. These established calcineurin inhibitors each require an immunophilin protein cofactor. Gossypol, a polyphenol produced by the cotton plant, inhibits calcineurin (IC50=15 microM), in a noncompetitive, reversible manner, and is independent of any cofactor. We found that gossypol acts by at least two mechanisms to inhibit calcineurin phosphatase activity. A calmodulin-independent form of calcineurin was less sensitive to inhibition by gossypol than native calcineurin (IC50=41 and 18 microM, respectively) indicating that gossypol may interfere with calmodulin binding. A fluorescence polarization based assay demonstrated that 100 microM gossypol reduced the affinity of calmodulin for calcineurin (from K(d)=2.4 to 250 nM). Inhibition of calcineurin phosphatase activity by gossypol could not be overcome by adding excess calmodulin or by testing the inhibition toward a calmodulin-independent calcineurin indicating that gossypol acts at a site different from the calmodulin-binding site. Gossypol decreased the affinity of calcineurin for immunosuppressant/immunophilin complexes only in the presence of calmodulin, indicating that gossypol blocks the effects of calmodulin binding to calcineurin. In addition, gossypol had a stimulatory effect on native calcineurin in the absence of calmodulin, possibly indicating a calmodulin mimetic effect. Gossypol exists in two enantiomeric forms which are reported to have different potency for cell toxicity. (+) and (-) gossypol had equivalent potency for inhibition of native and calmodulin-independent calcineurin phosphatase activity, and for inhibition of calmodulin binding. The inhibition of calcineurin by gossypol via multiple binding sites without stereo-specificity indicates that gossypol is not a specific calcineurin inhibitor.

Epididymis-Specific Pathologic Disorders in Rats Exposed to Gossypol from Weaning Through Puberty

Previous work in our laboratory revealed that the pubertal period of reproductive development in the male rat was particularly vulnerable to gossypol exposure, with a higher frequency of round structures in the lumen of the cauda epididymidis in the treated rats. Herein, we utilized hemicastration and electron microscopy to confirm that the epididymis is a definitive target of gossypol. Although exposure to gossypol from weaning through puberty caused a significant decrease in daily sperm production, as well as in the concentration of sperm in the epididymis, serum testosterone levels and reproductive organ weights were not altered. In gossypol treated rats, sperm morphology was compromised severely, but the epithelium in testis and epididymis appeared morphologically normal. Ultrastructural examination revealed that round structures, present only in gossypol exposed males, represented: (1) principal cells exfoliated from the epididymal epithelium; (2) epididymal epithelial cell cytoplasm containing degenerating sperm; and (3) degenerating epithelial cells, consisting of vesicles and particles of different sizes, forms and densities. Taken together, the data confirm that gossypol targets the epididymis, disturbing both the structure and function of this organ, and presumably disrupts sperm maturation.

Nonhormonal drugs for contraception in men: a systematic review

Nonhormonal drugs for contraception in men may have advantages over hormonal methods. The nonhormonal methods can have more rapid onset and less interference with androgen-dependent functions. This systematic review summarizes the clinical studies evaluating nonhormonal drugs administered to men for contraception. Relevant clinical results were found for gossypol, which is derived from the cotton plant, and for extracts of Tripterygium, a plant used in Chinese traditional medicine. Randomized, controlled trials were available on the efficacy of gossypol and on the effect of gossypol on potassium levels. Gossypol had problems with low efficacy and toxicity. For Tripterygium, 2 observational studies described men who were treated for rheumatoid arthritis. Although sperm density was lower among those taking Tripterygium, later reports indicated some toxicity. Nonclinical research continues on isolates of Tripterygium. No clinical studies for contraception in men were found for nonhormonal vaccines or neem, which is also a plant used for medicinal purposes. Clinical trials studied injecting styrene maleic anhydride into the vas deferens, but no comparative data were provided. At this time, no safe and effective nonhormonal drug is available for contraception in men.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to state that the number of studies concerning the use of nonhormonal drugs for male contraception are very limited, point out that the two nonhormonal drugs used to a small degree have varying results and serious side effects, and recall that there are limited clinical studies on use of vas deferens injections and vaccines in humans.

Combined administration of low-dose gossypol acetic acid with desogestrel/mini-dose ethinylestradiol/testosterone undecanoate as an oral contraceptive for men

To evaluate the efficacy and feasibility of a new regimen of low-dose gossypol acetic acid (GA) combined with desogestrel/ethinylestradiol and testosterone undecanoate (DSG/E/TU) as a male contraceptive, adult male rats were fed orally with GA (12.5 mg/kg/day) and DSG (0.125 mg/kg)/E (0.025 mg/kg)/TU (100 mg/kg) daily for 8 weeks as loading dose until infertility, and a similar low dose of GA alone for infertility maintenance. Control animals were administered a single low dose of GA (12.5 mg/kg/day) or DSG (0.125 mg/kg)/E (0.025 mg/kg)/TU (100 mg/kg), and vehicle, respectively. Results demonstrated that the combined dosage regimen could damage epididymal sperm motility and density, and induce infertility within 8 weeks in rats; the infertility could be consistently sustained by giving single GA (12.5 mg/kg/day), and was reversible in about 8 weeks following withdrawal of gossypol. The regimen rendered treated male rats with spermiation failure within a period of 6-20 weeks of treatment. Also, the serum luteinizing hormone, follicle-stimulating hormone and testicular interstitial fluid testosterone levels showed a transient decrease at the end of 6 or 8 weeks, which returned to control levels after 8 weeks of recovery phase. No hypokalemia or other adverse effects in viscera were observed. These results provide a promising approach to using the new regimen for the development of an effective and reversible oral male contraceptive.

Male contraception-a topic with many facets

In addition to the scientific issues associated with male contraception, there are a variety of other concerns that must be addressed before new male contraceptives reach the market. Cultural attitudes toward contraception will play a role both in the acceptability of any contraceptive and in compliance and usage. Delivery methods must also be considered; different methods are favored depending on the social context. Prevention of sexually transmitted diseases by a combined contraceptive/microbicidal treatment is a laudable goal, and may enhance public acceptance of a male contraceptive. This review is the result of a workshop that was convened to address these topics.

Schiff base of gossypol with 3,6,9-trioxa-decylamine complexes with monovalent cations studied by mass spectrometry,1H-NMR, FTIR, and PM5 semiempirical methods

A new Schiff base of gossypol with 3,6,9-trioxo-decylamine (GSTB) forms stable complexes with monovalent cations. This process of complex formation was studied by electrospray ionization mass spectrometry, (1)H-NMR and FTIR spectroscopy, and the PM5 (parametric method 5) semiempirical method. It is found that GSTB forms 1 : 1 and 1 : 2 complexes with Li(+) and Na(+) and 1 : 1 complexes with K(+), Rb(+), or Cs(+) cations and exists in all these complexes in the enamine-enamine tautomeric form. Moreover, within these complexes only Li(+) cations can fluctuate between the oxygen atoms of trioxo-alkyl chains. All other cations are strongly localized. In the complex of GSTB with two protons localized on the N atoms of the Schiff base, the imine-imine tautomeric form is realized. The complexes of the Schiff base with K(+), Rb(+), or Cs(+) cations are the 1 : 1 type with the oxygen atoms of the trioxo-alkyl chains, as well as the O(1)H or O(1')H group coordinating the cation. The structures of the complexes are calculated by the PM5 semiempirical method and discussed.

Tadalafil has no detrimental effect on human spermatogenesis or reproductive hormones

PURPOSE

We assessed the effects on spermatogenesis of placebo vs 10 or 20 mg tadalafil administered daily for 6 months to healthy men and men with mild erectile dysfunction.

MATERIALS AND METHODS

In 2 studies 421 healthy men or men with mild erectile dysfunction who were 45 years or older and met semen criteria derived from WHO reference values were randomized to 6 months of treatment with placebo (101) or 10 mg tadalafil (103), or to placebo (106) or 20 mg tadalafil (111). Semen samples and serum for reproductive hormones (testosterone, luteinizing hormone and follicle-stimulating hormone) were collected at baseline, after 3 months and at the end of treatment.

RESULTS

Tadalafil had no adverse effects on spermatogenesis, as assessed by sperm concentration, sperm count per ejaculate, percent sperm motility, normal morphology or serum reproductive hormones. Tadalafil was well tolerated. Common adverse events were headache, dyspepsia and back pain.

CONCLUSIONS

Chronic daily administration of tadalafil at doses of 10 and 20 mg for 6 months had no adverse effects on spermatogenesis or on reproductive hormones in men older than 45 years.

Some aspects relating to the evaluation of the effects of chemicals on male fertility

Reviews and studies on individual compounds were analyzed as to the suitability of different study designs and endpoints for detecting adverse effects of chemicals on male reproduction in animal species. Of the endpoints investigated, the most sensitive proved to be histopathology of the testes. Using refined histopathology, effects could be detected with a high degree of sensitivity as early as 4 weeks after treatment. Other sensitive endpoints were the weights of reproductive organs, including accessory glands, i.e., testis, epididymis, prostate, and of the seminal vesicle, as well as sperm parameters such as sperm count, sperm morphology, and sperm motility. Sperm motility was found to be in some cases more sensitive than histopathology. The above parameters showed a higher sensitivity than fertility parameters. In fact, in most cases, not only one but several endpoints were affected. Continuous breeding studies and 90-day studies with additional measurements of sperm parameters were similarly effective in detecting compounds which affect male fertility. Interspecies extrapolation factors (IEFs) have been derived for the most sensitive endpoints in laboratory animals. If the calculation is based on caloric demand and a sensitive endpoint of reproductive toxicity, many IEFs tend to be about 1, indicating that humans are generally not more susceptible to reproductive toxicants than laboratory animals. With respect to hazard identification, it is possible to detect adverse effects on male reproduction in a standard subacute study with concentrations that produce significant general toxicity. If effects are found, for the risk assessment the NOAEL has to be determined by testing specific sensitive parameters as specified above.

Male contraception

The provision of safe, effective contraception has been revolutionized in the past 40 yr following the development of synthetic steroids and the demonstration that administration of combinations of sex steroids can be used to suppress ovulation and, subsequently, other reproductive functions. This review addresses the current standing of male contraception, long the poor relation in family planning but currently enjoying a resurgence in both scientific and political interest as it is recognized that men have a larger role to play in the regulation of fertility, whether seen in geopolitical or individual terms. Condoms and vasectomy continue to be popular at particular phases of the reproductive lifespan and in certain cultures. Although not perfect contraceptives, condoms have the additional advantage of offering protection from sexually transmitted infection. The hormonal approach may have acquired the critical mass needed to make the transition from academic research to pharmaceutical development. Greatly increased understanding of male reproductive function, partly stimulated by interest in ageing and the potential benefits of androgen replacement, is opening up other avenues for investigation taking advantage of nonhormonal regulatory pathways specific to spermatogenesis and the reproductive tract.

Different pathways of cell killing by gossypol enantiomers

Gossypol, a polyphenolic, aldehyde-containing constituent of cottonseed, produced partial responses (>50% reduction in tumor size) in some patients with advanced cancer and suppressed sperm as an antifertility agent for men. This action in vivo and its novel side effect profile suggest a specific mechanism of the action of gossypol. Using the random homozygous knockout approach of Li and Cohen (1), we developed a cell line resistant to killing by gossypol, but sensitive to methotrexate and doxorubicin. It showed stereospecific resistance to killing by (-) gossypol (ED(50) 4.9 microM) compared with wild type (ED(50) 2.0 microM). The resistant and wild-type cells were equally sensitive to (+) gossypol (ED(50) 8.8 and 8.4 microM, respectively), methotrexate, and doxyrubicin. We conclude that gossypol affects cells by a stereospecific pathway for (-) gossypol, possibly related to its selective effects, and a nonstereospecific pathway for (+) gossypol and higher concentrations of (-) gossypol. Further knowledge about the stereospecific pathway may lead to new therapeutic drugs.

Spectroscopic studies and PM3 semiempirical calculations of Schiff bases of gossypol with L-amino acid methyl esters

Three Schiff bases of racemic gossypol with L-amino acid methyl esters are synthesized and studied by FTIR and (1)H-NMR spectroscopy, and their structures are calculated by the PM3 semiempirical method. The Schiff bases in the study exist in the solid state and in solutions as enamine forms. The existence of diastereoisomers is very visible in the (1)H-NMR spectra. The amount of the diastereoisomers depends on the amount of time the solutions are rested in diffused light. The epimerization from D,L-isomer to L,L-isomer is very slow. The structures of the Schiff bases and the hydrogen bonds within these structures are discussed.

Gossypol: a contraceptive for men

Gossypol is a polyphenol isolated from the seed, roots, and stem of the cotton plant (Gossypium sp.). The substance, a yellow pigment similar to flavonoids, is present in cottonseed oil. In the plant, it acts as a natural defensive agent against predators, provoking infertility in insects. In most animals, gossypol provokes infertility, and in man it causes spermatogenesis arrest at relatively low doses. Studies carried out in China, Africa, and Brazil have shown that the substance is well tolerated, causing no side effects that lead to discontinuation. The reported hypokalemia of early studies has not been confirmed in the latest trials. The only concern at present appears to be lack of reversibility in over 20% of subjects. Gossypol should be prescribed preferably to men who have completed their families or for those who would accept permanent infertility after a few years of use.

Inhibition of hamster sperm acrosomal enzyme by gossypol is closely associated with the decrease in fertilization capacity

To elucidate the mechanism of sterility induced by gossypol, we studied the relationship between the activities of acrosomal enzymes and their fertilizing capacity in the hamster. The results showed that the ability of spermatozoa to penetrate into bovine cervical mucus, hyperactivated motility (HAM) and fertility in vivo were significantly inhibited when spermatozoa were exposed to gossypol (2.5 microg - 60 microg/mL) for 15 min in vitro. Also, following administration of gossypol (12.5 mg/kg/day) for 6 weeks, sperm motility, HAM and rate of fertilization in vitro by the hamster cauda epididymal spermatozoa were significantly decreased and the extracts of testis delayed dispersion of the cumulus oophorus cells, suggesting that hyaluronidase and other acrosomal enzymes might be inhibited by gossypol. In addition, acrosin and arylsulfatase activities were also markedly inhibited. These data show that the inhibition of acrosin and arylsulfatase activities is the main cause of gossypol-induced infertility. The inhibition was dependent upon gossypol dose and the duration of administration. Thus, the assay of acrosin and arylsulfatase activities may provide a useful tool for monitoring sterility induced by gossypol.