Contraceptive Development Research Articles

Emergency contraception

This review summarises the development of emergency contraception (EC) methods, and provides an overview on the currently available options of EC which are effective and safe back-up methods in case of non-use or failure of the regular contraception. The copper intrauterine contraceptive device is currently the most effective method. In most countries, a single dose of levonorgestrel 1.5 mg is the first-line hormonal EC given within 72 h of unprotected intercourse. The oral anti-progestogens such as mifepristone and ulipristal acetate are promising alternatives with better efficacies and a wider treatment window of up to 120 h post coitus, probably resulting from more diverse ancillary mechanisms of actions. Education on EC should be part of any contraceptive counselling. Improving access to EC by providing it over the counter or in advance would not promote its abuse nor encourage risky sexual behaviours, but may further facilitate the timely use so as to achieve the best efficacy.

Inhibition of Retinoic Acid Biosynthesis by the Bisdichloroacetyldiamine WIN 18,446 Markedly Suppresses Spermatogenesis and Alters Retinoid Metabolism in Mice

Knowledge of the regulation of testicular retinoic acid synthesis is crucial for understanding its role in spermatogenesis. Bisdichloroacetyldiamines strongly inhibit spermatogenesis. We reported previously that one of these compounds, WIN 18,446, potently inhibited spermatogenesis in rabbits by inhibiting retinoic acid synthesis. To understand how WIN 18,446 inhibits retinoic acid synthesis, we characterized its effects on human retinal dehydrogenase ALDH1A2 in vitro as well as its effects on retinoid metabolism in vivo using mice. WIN 18,446 strongly and irreversibly inhibited ALDH1A2 in vitro. In vivo, WIN 18,446 treatment completely abolished spermatogenesis after 4 weeks of treatment and modestly reduced adiposity in mice fed a chow diet. Effects of WIN 18,446 on retinoid concentrations were tissue-dependent. Although lung and liver retinyl ester concentrations were lower in WIN 18,446-treated animals, adipose retinyl ester levels were increased following the treatment. Interestingly, animals treated with WIN 18,446 had significantly higher circulating retinol concentrations compared with control mice. The effect on spermatogenesis by WIN 18,446 was not prevented by simultaneous treatment with retinoic acid, whereas effects on other tissues were partially or completely reversed. Cessation of WIN 18,446 treatment for 4 weeks reversed most retinoid-related phenotypes except for inhibition of spermatogenesis. Our data suggest that WIN 18,446 may be a useful model of systemic acquired retinoic acid deficiency. Given the effects observed in our study, inhibition of retinoic acid biosynthesis may have relevance for the treatment of obesity and in the development of novel male contraceptives.

A prostaglandin E2 receptor antagonist prevents pregnancies during a preclinical contraceptive trial with female macaques.

Can administration of a prostaglandin (PG) E2 receptor 2 (PTGER2) antagonist prevent pregnancy in adult female monkeys by blocking periovulatory events in the follicle without altering menstrual cyclicity or general health? This is the first study to demonstrate that a PTGER2 antagonist can serve as an effective non-hormonal contraceptive in primates. The requirement for PGE2 in ovulation and the release of an oocyte surrounded by expanded cumulus cells (cumulus-oocyte expansion; C-OE) was established through the generation of PTGS2 and PTGER2 null-mutant mice. A critical role for PGE2 in primate ovulation is supported by evidence that intrafollicular injection of indomethacin in rhesus monkeys suppressed follicle rupture, whereas co-injection of PGE2 with indomethacin resulted in ovulation. First, controlled ovulation protocols were performed in adult, female rhesus monkeys to analyze the mRNA levels for genes encoding PGE2 synthesis and signaling components in the naturally selected pre-ovulatory follicle at different times after the ovulatory hCG stimulus (0, 12, 24, 36 h pre-ovulation; 36 h post-ovulation, n = 3-4/time point). Second, controlled ovarian stimulation cycles were utilized to obtain multiple cumulus-oocyte complexes (COCs) from rhesus monkeys to evaluate the role of PGE2 in C-OE in vitro (n = 3-4 animals/treatment; ≥3 COCs/animal/treatment). Third, adult cycling female cynomolgus macaques were randomly assigned (n = 10/group) to vehicle (control) or PTGER2 antagonist (BAY06) groups to perform a contraceptive trial. After the first treatment cycle, a male of proven fertility was introduced into each group and they remained housed together for the duration of the 5-month contraceptive trial that was followed by a post-treatment reversibility trial. Quantitative real-time PCR, COC culture and expansion, immunofluorescence/confocal microscopy, enzyme immunoassay, contraceptive trial, ultrasonography, complete blood counts, serum biochemistry tests and blood lipid profiles. Several mRNAs encoding proteins involved in PGE2 synthesis, metabolism and signaling increase (P < 0.05) in the periovulatory follicle after administration of an ovulatory hCG bolus. PGE2 signaling through PTGER2 induces cumulus cell expansion and production of hyaluronic acid, which are critical events for fertilization. Moreover, chronic administration of a selective PTGER2 antagonist resulted in a significant (P < 0.05 versus vehicle-treated controls) contraceptive effect without altering steroid hormone patterns or menstrual cyclicity during a 5-months contraceptive trial. Fertility recovered as early as 1 month after ending treatment. This is a proof-of-concept study in a non-human primate model. Further investigations are warranted to elucidate the mechanism(s) of PTGER2 antagonist action in the primate ovary. Although PTGER2 antagonist treatment did not produce any obvious undesirable effects, improvements in the mode of administration, as well as the efficacy of these compounds, are necessary to consider such a contraceptive for women. Monitoring as well as improving the efficacy and safety of female contraceptives is an important public health activity. Even though hormonal contraceptives are effective for women, concerns remain regarding their side-effects and long-term use because of the widespread actions of such steroidal products in many tissues. Moreover, some women cannot take hormones for medical reasons. Thus, development of non-hormonal contraceptives for women is warranted. Supported by Bayer HealthCare Pharmaceuticals, The Eunice Kennedy Shriver NICHD Contraceptive Development and Research Center (U54 HD055744), NIH Office of the Director (Oregon National Primate Research Center P51 OD011092), and a Lalor Foundation Postdoctoral Basic Research Fellowship (MCP). The use of the Leica confocal was supported by grant number S10RR024585. Some of the authors (N.B., A.R., K.-H.F., U.F., B.B. and B.L.) are employees of Bayer Healthcare Pharma.

Reproductive biology: Sperm protein finds its mate.

Knowledge of the sperm-specific protein that is required for the attachment of sperm to eggs during fertilization in mammals has led to the identification of the protein's receptor on the egg's plasma membrane. See Article p.483 Little is known about how sperm and egg specifically recognize each other. A sperm cell surface protein that is required for male fertility (called Izumo) was identified in 2005, but the identity of its partner on the egg has remained elusive. Gavin Wright and colleagues have now identified the egg receptor for Izumo, which they name Juno. Female mice lacking Juno are infertile and Juno-deficient eggs do not fuse with normal sperm. The authors show that the interaction is conserved within mammals, so these findings may open possible opportunities for the development of new fertility treatments and contraceptives.

Juno is the egg Izumo receptor and is essential for mammalian fertilization.

Fertilisation occurs when sperm and egg recognise each other and fuse to form a new, genetically distinct organism. The molecular basis of sperm-egg recognition is unknown, but is likely to require interactions between receptor proteins displayed on their surface. Izumo1 is an essential sperm cell surface protein, but its egg receptor has remained a mystery. Here, we identify Juno as the receptor for Izumo1 on mouse eggs, and show this interaction is conserved within mammals. Female mice lacking Juno are infertile and Juno-deficient eggs do not fuse with normal sperm. Rapid shedding of Juno from the oolemma after fertilisation suggests a mechanism for the membrane block to polyspermy, ensuring eggs normally fuse with just a single sperm. Our discovery of an essential receptor pair at the nexus of conception provides opportunities for the rational development of new fertility treatments and contraceptives.

A Question for Women's Health: Chemicals in Feminine Hygiene Products and Personal Lubricants

Vaginal research got a desperately needed boost at the National Institutes of Health (NIH) in 1992. That’s when Penny Hitchcock took over the Sexually Transmitted Diseases Branch at the National Institute of Allergy and Infectious Diseases and Nancy Alexander became chief of the Contraceptive Development Branch in the NIH Center for Population Research—posts previously held by men. “Those two got together and discovered NIH had no programs for vaginal research,” says Richard Cone, a Johns Hopkins biophysics professor. Cone had begun developing vaginal contraceptives that would protect against sexually transmitted infections (STIs) in 1980, and until then, struggled to get funding. Mucous membranes in the vagina and vulva rapidly absorb chemicals without metabolizing them. But until recently scant research existed on how chemicals in feminine hygiene products and personal lubricants may affect women’s health. Hitchcock and Alexander soon initiated research programs on vaginal physiology, immunology, and microbicides, eventually funding Cone’s work. These new programs led to groundbreaking discoveries in animals and humans that certain chemicals—including glycerin (glycerol), a common base for personal lubricants—can damage or irritate vaginal1 and rectal2 epithelial cells, potentially increasing the transmission of STIs such as herpes and human immunodeficiency virus. When it comes to reproductive health, research on contraceptives and STIs continues to garner interest worldwide. But a related area—chemical exposures from feminine hygiene products and personal lubricants—has received much less attention. In the United States alone, women spend well over $2 billion per year on feminine hygiene products,3 including tampons, pads, feminine washes, sprays, powders, and personal wipes. But until recently, scant research existed on how chemicals in these products may affect women’s health. As scattered findings emerge, several scientists and interest groups are calling for more research to fill in the gaps.4,5 A recent report by the nonprofit Women’s Voices for the Earth (WVE) points out that feminine hygiene products may use ingredients that are known or suspected endocrine-disrupting chemicals (EDCs), carcinogens, or allergens. And while nearly all women use tampons and sanitary pads, black and Latina women use douches, wipes, powders, and deodorizers more often than women of other races, putting them at greater risk of potential chemical exposures.4 “It’s a little bit edgy. People have been shocked, saying things like ‘I’ve never really thought about [the vagina] being an important internal link to your body,’” says Alexandra Scranton, director of science and research for WVE. “Although it is well known that the vaginal ecosystem is more sensitive and more absorbent than typical skin, there is surprisingly little research out there on feminine care products.” Surveys conducted in the 1990s–2000s gave a sense not only of how commonly some products are used but also how widely use can vary across racial/ethnic groups.

New and emerging contraceptives: a state-of-the-art review.

BackgroundThe first hormonal contraceptive was introduced onto the market in several countries 50 years ago; however, the portfolio of contraceptive methods remains restricted with regards to their steroid composition, their cost, and their ability to satisfy the requirements of millions of women/couples in accordance with their different reproductive intentions, behaviors, cultures, and settings.MethodsA literature review was conducted using Medline, Embase, and Current Contents databases, up to September 1, 2013 to identify publications reporting new contraceptives in development using combinations of the search terms: contraception, contraceptives, oral contraceptives, patch, vaginal ring, implants, intrauterine contraceptives, and emergency contraception (EC). Also, several experts in the field were also consulted to document ongoing projects on contraception development. Additionally, the Clinicaltrial.gov website was searched for ongoing studies on existing contraceptive methods and new and emerging female contraceptives developed over the past 5 years. Information was also obtained from the pharmaceutical industry.ResultsEarly sexual debut and late menopause means that women may require contraception for up to 30 years. Although oral, injectable, vaginal, transdermal, subdermal, and intrauterine contraceptives are already available, new contraceptives have been developed in an attempt to reduce side effects and avoid early discontinuation, and to fulfill women’s different requirements. Research efforts are focused on replacing ethinyl-estradiol with natural estradiol to reduce thrombotic events. In addition, new, less androgenic progestins are being introduced and selective progesterone receptor modulators and new delivery systems are being used. In addition, research is being conducted into methods that offer dual protection (contraception and protection against human immunodeficiency virus transmission), and contraceptives for use “on demand.” Studies are also investigating non-hormonal contraceptive methods that have additional, non-contraceptive benefits.ConclusionThe most pressing need worldwide is, first, that the highly effective contraceptive methods already available should be affordable to most of the population and also that these methods should fulfill the needs of women of different ages and with different reproductive requirements. The development of new contraceptive methods should also take advantage of the knowledge obtained over the past 30 years on gamete physiology and gamete interaction to avoid the use of steroid compounds.

RNA Interference-Mediated Downregulation of sAC Gene Inhibits Sperm Hyperactivation in Male Rats (Rattus norvegicus)

Hyperactivation is one of the most critical parts for fertilization. cAMP generated by soluble adenylyl cyclase (sAC) is necessary to activate sperm and is a prerequisite for sperm hyperactivation. The aim of this study is to investigate the function of sAC in hyperactivation in male rats. Four siRNAs of sAC gene were designed and separately transformed into rat sperm using electrotransformation method. Cultured for 12 and 24 h, physiological and biochemical indexes of these sperm were analyzed, and the expressions of some hyperactivation-related genes were detected using real-time PCR. We demonstrated 26.3–30.8% and 49.1–50.5% reduction in sAC at the protein by Western blot and mRNA levels by real-time PCR, respectively. The results showed that two siRNAs, Actb-717 and Actb-4205, were the best RNAi sites for silencing sAC. The VCL (curvilinear velocity) and ALH (amplitude of lateral head displacement) of RNA interference (RNAi)-transfected sperm were reduced. cAMP and protein phosphorylation in RNAi transfected sperm were also decreased. The hyperactivation-related genes, such as CatSper2, LDHC and PKA, were downregulated in the sperm, which sAC was knockdown. These findings demonstrated that sAC might play a critical role in cAMP signaling in the rat sperm hyperactivation, and downregulated sAC gene might prevent the expression of these hyperactivation-ralated genes resulting in sperm dysfunction. These findings suggest that these hyperactivation-ralated genes and sAC are functionally related in sperm hyperactivation and sAC falls into an expanding group of sperm proteins that appear to be promising targets for the development of male contraceptives.

Unraveling the intricacies of mammalian fertilization.

It is imperative to understand the molecular basis of various steps involved during fertilization. In the manuscript by Bianchi et al.1 a novel protein, Juno on egg membrane (oolemma) has been characterized that binds to sperm specific protein, Izumo-1. Monoclonal antibodies against Juno inhibited in vitro fertilization. Juno knock-out female mice failed to deliver litters on mating. It is rapidly shed from oolemma after fertilization, suggesting its role in preventing polyspermy. Taken together these studies will help in our understanding of sperm-egg recognition mechanisms and also facilitate development of new fertility treatment regimens and novel contraceptives.

Contracepção em mulheres com condições clínicas especiais. Critérios médicos e elegibilidade

Pregnancy planning is important for the physical, mental, and social health of women and families. For women with underlying medical disorders, pregnancy planning assumes even greater importance, because ensuring a healthy woman and healthy child becomes more challenging. Unfortunately, some medical conditions also complicate the ability to use reliable contraception safely. Although numerous studies have addressed the safety and effectiveness of hormonal contraceptive use in healthy women, data are far less complete for women with underlying medical problems or other special circumstances. Using the best available scientific evidence and based on the American College of Obstetrics and Gynecology Practice Bulletin, this review provides information to help clinicians and women with coexisting medical conditions to make decisions regarding the selection and appropriateness of various hormonal contraceptives. The review includes recent advances in the development of oral contraception, emergency contraception, injectable contraception, vaginal rings, subdermal implants, transdermal contraception and intrauterine devices.

The preparation and application of N-terminal 57 amino acid protein of the follicle-stimulating hormone receptor as a candidate male contraceptive vaccine.

Follicle-stimulating hormone receptor (FSHR), which is expressed only on Sertoli cells and plays a key role in spermatogenesis, has been paid attention for its potential in male contraception vaccine research and development. This study introduces a method for the preparation and purification of human FSHR 57-amino acid protein (FSHR-57aa) as well as determination of its immunogenicity and antifertility effect. A recombinant pET-28a(+)-FSHR-57aa plasmid was constructed and expressed in Escherichia coli strain BL21 Star™ (DE3) and the FSHR-57aa protein was separated and collected by cutting the gel and recovering activity by efficient refolding dialysis. The protein was identified by Western blot and high-performance liquid chromatography analysis with a band of nearly 7 kDa and a purity of 97.4%. Male monkeys were immunized with rhFSHR-57aa protein and a gradual rising of specific serum IgG antibody was found which reached a plateau on day 112 (16 weeks) after the first immunization. After mating of one male with three female monkeys, the pregnancy rate of those mated with males immunized against FSHR-57aa was significantly decreased while the serum hormone levels of testosterone and estradiol were not disturbed in the control or the FSHR-57aa groups. By evaluating pathological changes in testicular histology, we found that the blood-testis barrier remained intact, in spite of some small damage to Sertoli cells. In conclusion, our study demonstrates that the rhFSHR-57aa protein might be a feasible male contraceptive which could affect sperm production without disturbing hormone levels.

Cloning and characterization of lactate dehydrogenase C4 from Ochotona curzoniae

Lactate dehydrogenase C4 (LDH-C4) is considered to be a good target protein for the development of contraceptive drugs. To develop contraceptive rodenticide against pika (Ochotona curzoniae) LDH-C4, the pika LDH-C gene was cloned and expressed in Escherichia coli. The recombinant protein was purified and characterized. The cDNA of pika LDH-C gene was cloned by RACE method. The cDNA was 1498 bp in length containing an ORF of 996 bp which encoded a polypeptide of 332 amino acids. The ORF of pika LDH-C was introduced in E. coli and expressed with no fusion tags added. The recombinant LDH-C4 protein was purified by heating, affinity chromatography and ion-exchange chromatography. The recombinant pika LDH-C4 was a tetramer with a molecular weight of approximately 140 kDa, and it had temperature-dependent catalytic activity, as it was thermally stable up to 60 degrees C. The optimal pH values in the forward and backward reactions were around 7.48 and 10.28, respectively. The apparent Michaelis constants for pyruvate and lactate were 51.2 +/- 3.8 and 8568.8 +/- 409 microM respectively. The inhibition constant for oxalic acid was 11.8 +/- 3.5 mM. This study laid a solid foundation for contraceptive rodenticide development against pika LDH-C4.

Inhibiting Human Lactate Dehydrogenase-C for Male Fertility Control; Initial Hits

Lactate dehydrogenase-C (LDH-C) is an oxido-reductive enzyme of LDH (EC 1.1.1.27) family which is present abundantly in testes, spermatocytes, spermatids and sperms. It plays an important role in maintaining glycolysis and ATP production in the flagellum during sperm capacitation, therefore essential for male fertility. Profuse expression exclusively in these tissues makes LDH-C a potential target for male contraceptive development. However, creating a specific inhibitor for LDH-C is challenging due to its extensive sequence similarity (84-89%) with somatic isozymes LDH-A and B.

Small Molecule Proprotein Convertase Inhibitors for Inhibition of Embryo Implantation

Uterine proprotein convertase (PC) 6 plays a critical role in embryo implantation and is pivotal for pregnancy establishment. Inhibition of PC6 may provide a novel approach for the development of non-hormonal and female-controlled contraceptives. We investigated a class of five synthetic non-peptidic small molecule compounds that were previously reported as potent inhibitors of furin, another PC member. We examined (i) the potency of these compounds in inhibiting PC6 activity in vitro; (ii) their binding modes in the PC6 active site in silico; (iii) their efficacy in inhibiting PC6-dependent cellular processes essential for embryo implantation using human cell-based models. All five compounds showed potent inhibition of PC6 activity in vitro, and in silico docking demonstrated that these inhibitors could adopt a similar binding mode in the PC6 active site. However, when these compounds were tested for their inhibition of decidualization of primary human endometrial stromal cells, a PC6-dependent cellular process critical for embryo implantation, only one (compound 1o) showed potent inhibition. The lack of activity in the cell-based assay may reflect the inability of the compounds to penetrate the cell membrane. Because compound's lipophilicity is linked to cell penetration, a measurement of lipophilicity (logP) was calculated for each compound. Compound 1o is unique as it appears the most lipophilic among the five compounds. Compound 1o also inhibited another crucial PC6-dependent process, the attachment of human trophoblast spheroids to endometrial epithelial cells (a model for human embryo attachment). We thus identified compound 1o as a potent small molecule PC6 inhibitor with pharmaceutical potential to inhibit embryo implantation. Our findings also highlight that human cell-based functional models are vital to complement the biochemical and in silico analyses in the selection of promising drug candidates. Further investigations for compound 1o are warranted in animal models to test its utility as an implantation-inhibiting contraceptive drug.

MANAGING WILDLIFE WITH CONTRACEPTION: WHY IS IT TAKING SO LONG?

Biologists have been testing wildlife contraceptives in the field for nearly a half century. Although effective new contraceptive agents have been identified, new delivery technologies developed, and some success with population management demonstrated, progress in this area should be further along. Why is it taking so long? First, the task is complex. Most drugs and vaccines fail in development. The technical leaps from in vitro to in vivo, from controlled studies to field studies, from effectiveness in individuals to management of populations, are all formidable and frequent failures are inevitable. Testing the long-acting contraceptives required for successful population management demands experiments that take 3-5 yr to complete. Development of wildlife contraceptives has been further hampered by the lack of large-scale investment and the complex and shifting regulatory landscape that often greets novel enterprises. But there has also been focused resistance to the implementation of wildlife contraceptive studies and to the dissemination of results such studies have produced. This phenomenon, which sociologists label "socially constructed ignorance," has taken a variety of forms including denial of research permits, omission from research reports and management documents, and repetition of misleading or false information in public forums and the media. The persistence and effectiveness of this social resistance suggest that the ethical foundation of wildlife contraception is incomplete. As the institutional affiliations of participants of the 7th International Conference on Fertility Control for Wildlife confirmed, wildlife contraception has its ethical roots in the animal welfare and integrated pest-management communities. Absent from the discussion are the conservation community and the values they represent. To secure societal acceptance of wildlife contraception as a management technique, researchers and advocates for wildlife contraception must address conservation issues and build an ethical foundation that balances concern for individual animals and human needs with concern for the health of biologic communities.

DOSE AND DURATIONAL EFFECTS OF THE GONADOTROPIN-RELEASING HORMONE AGONIST, DESLORELIN: THE MALE RAT (RATTUS NORVEGICUS) AS A MODEL

Gonadotropin-releasing hormone (GnRH) agonists are routinely used to suppress the reproductive axis of many mammals, especially in zoos. Current treatments are reversible. There is a need to develop nonreversible agents, and this study investigates the effects of high-dose and long-duration exposure to the GnRH agonist, deslorelin, in the rat model. Studies indicate that the follicle-stimulating hormone (FSH) gonadotropin is predominantly affected, and following high-dose exposure to deslorelin for a long duration, the ability of gonadotropes to synthesize FSH may be compromised, perhaps permanently. Understanding the mechanisms by which such persistent suppression of FSH occurs may facilitate the development of novel next-generation contraceptives. It is hypothesized that direct testicular effects of GnRH agonists may play a critical role in the efficacy of GnRH agonists in male contraception.

Mapping of the N-Linked Glycoproteome of Human Spermatozoa

N-Linked glycosylation, a type of post-translational modification, plays important roles in cell-cell recognition, adhesion, and interactions. Although N-linked glycosylated proteins in sperm are known to be important for gamete binding, little is known about the composition of these proteins, particularly glycosylation sites, in humans. In the present study, the use of glyco-FASP, coupled with the tandem mass spectrometry (MS/MS) method, led to the identification of 554 N-glycosylation sites and 297 N-glycosylated proteins in human sperm. Bioinformatics analysis revealed enrichment of proteins with functions in cell recognition and fertilization. Overall, about 91% of the human sperm N-glycosylated proteins were classified into "membrane", "extracellular region", and "lysosome" groups, based on subcellular localization annotation. Furthermore, glutathione peroxidase 4 (GPX4), a membrane glycoprotein identified in our glycoproteome, was shown to play a significant role in gamete interactions using the in vitro fertilization assay. Accordingly, we propose that characterization of the human sperm glycoproteome should effectively aid in clarifying the mechanisms of fertilization and provide a valuable resource for the future development of male contraceptives and diagnosis of male infertility.

Identification of adenine nucleotide translocase 4 inhibitors by molecular docking

The protein adenine nucleotide translocase (ANT) is localized in the mitochondrial inner membrane and plays an essential role in transporting ADP into the mitochondrial matrix and ATP out from the matrix for cell utilization. In mammals there are four paralogous ANT genes, of which ANT4 is exclusively expressed in meiotic germ cells. Since ANT4 has been shown essential for spermatogenesis and male fertility in mice, inhibition of ANT4 appears to be a reasonable target for male contraceptive development. Further, in contrast to ANT1, ANT2 and ANT3 that are highly homologous to each other, ANT4 has a distinguishable amino acid sequence, which serves as a basis to develop a selective ANT4 inhibitor. In this study, we aimed to identify candidate compounds that can selectively inhibit ANT4 activity over the other ANTs. We used a structure-based method in which ANT4 was modeled then utilized as the basis for selection of compounds that interact with sites unique to ANT4. A large chemical library (>100,000 small molecules) was screened by molecular docking and effects of these compounds on ADP/ATP exchange through ANT4 were examined using yeast mitochondria expressing human ANT4. Through this, we identified one particular candidate compound, [2,2′-methanediylbis(4-nitrophenol)], which inhibits ANT4 activity with a lower IC50 than the other ANTs (5.8μM, 4.1μM, 5.1μM and 1.4μM for ANT1, 2, 3 and 4, respectively). This newly identified active lead compound and its chemical structure are expected to provide new opportunities to optimize selective ANT4 inhibitors for contraceptive purposes.

Review on Research of Suppression Male Fertility and Male Contraceptive Drug Development by Natural Products

Male contraceptive development in the present scenario is most viable aspect of research due to uncontrolled population growth in the world. In this respect investigators are busy to find out a safe male contraceptive drug. Researchers have started their finding for a suitable drug from natural sources because these are safe and easily acceptable for common man, most of natural sources are plants and their products. In this review 137 plants and their effects on reproduction and reproductive physiology are summarized. Some of them have intense effect on male reproductive system and do not produce any side effects. Reproductive toxicological studies are also important aspects of these kinds of researches, so it is important that drugs are safe and widely acceptable. An ideal male contraceptive can influence semen, testes, hormone level, accessory reproductive organs and general physiology of animals and produced some alterations. Many plants in this review are showing antifertility as well as antispermatogenic effects, so these may be used for further study for contraceptives development but it is important to find out the mechanism of reaction and further laboratory and clinical research on some plants are needed for final male contraceptive drug development. In conclusion this review will help for finding suitable plant products for male contraceptive clinical and laboratory studies.

The cytoplasmic droplet may be indicative of sperm motility and normal spermiogenesis

Although the cytoplasm of spermatids is removed at the end of spermiogenesis, a tiny portion is usually retained in the sperm flagellum, which is termed the cytoplasmic droplet (CD) in mammals. CDs are believed to play a role in sperm volume adaptation. However, we have noticed that epididymal spermatozoa that display initial (flagellation in situ) and progressive motility mostly possess CDs, whereas spermatozoa without CDs are rarely motile, suggesting that CDs have a role in motility development during sperm epididymal maturation. In the present study, we analyzed the relationship between the presence or absence of CDs, motility development and positional changes of CDs during sperm epididymal maturation in mice and monkeys. We also examined CDs on spermatozoa of three knockout mouse lines with late spermiogenic defects. Our data suggest that the CD is a normal organelle transiently present exclusively on epididymal spermatozoa, and normal CD morphology and location are associated with normal motility development during epididymal maturation of spermatozoa. Abnormal CD formation, e.g., a complete lack of CDs or ectopic CDs, is indicative of defective spermiogenesis. If CDs are essential for sperm motility development, then CDs may represent an ideal drug target for the development of non-hormonal male contraceptives.