BDADs for Male Contraception

描述(申请人提供)：大约50年前，口服双二氯乙酰二胺(BDADs)，如Win 18,446，被证明安全、完全和可逆地抑制男性的精子发生。然而，这些化合物并没有作为男性避孕药推向市场，因为它们会引起“双硫胺反应”，特征是与酒精一起摄入时会出现脸红、恶心和呕吐。由于缺乏对BDAD造成这些影响的机制的了解，这一领域的进一步研究停滞不前。现在已知二硫兰反应是由肝酶乙醛脱氢酶(ALDH2)抑制引起的，该酶通常参与酒精的新陈代谢。当BDAD和酒精混合时引发二硫胺反应表明BDAD也抑制ALDH2。BDADs似乎也通过抑制乙醛脱氢酶来调节其对精子发生的影响。在睾丸的生精小管内，一种名为ALDH1a2的睾丸特有的乙醛脱氢酶生物合成维甲酸，维甲酸是一种已知对精子发生至关重要的维生素A衍生物。因此，我们假设BDADs如Win 18,446通过抑制ALDH1a2在睾丸生精小管内合成维甲酸来抑制精子发生。在本提案的具体目标#1中，我们将努力证明BDAD(如Win 18,446)抑制精子发生的机制涉及抑制睾丸内维甲酸的形成。这将在体外使用新生精原细胞的原代培养完成，也将在体内使用维生素A缺乏的小鼠模型和正常兔完成。在特定的目标#2中，我们将努力证明Win 18,446使用稳定转导编码ALDH1a2酶的细胞系来特异性抑制ALDH1a2。接下来，在特定的目标#3中，我们将合成新型的Win 18,446衍生物，它能特异性地抑制ALDH1a2，同时将对ALDH2介导的酒精代谢的抑制降至最低。然后，我们将检验这些新化合物在体外和体内抑制精子发生的能力。这项工作将提供对精子发生的生理学的洞察，并导致在开发安全有效的口服、非激素、可逆男性避孕药方面取得实质性进展。 公共相关性：尽管目前有避孕措施可用，但世界人口超过65亿，而且还在以每年8000万的速度增长。这种人口增长在很大程度上是意外的，是由于避孕措施不足造成的。目前，男性导向的避孕选择特别有限。这项提案中描述的研究可能最终允许开发一种安全有效的男性避孕口服方法，这将有助于大大降低意外怀孕和人口增长的风险。

DESCRIPTION (provided by applicant): Almost fifty years ago, oral administration of Bis-dichloroacetyl-diamines (BDADs) such as WIN 18,446 was shown to safely, completely and reversibly inhibit spermatogenesis in men. These compounds were not brought to market as male contraceptives, however, because they caused a "disulfiram reaction" characterized by flushing, nausea and vomiting when co-ingested with alcohol. Further research in this area was stalled by lack of knowledge regarding the mechanism by which BDADs caused these effects. The disulfiram reaction is now known to be caused by the inhibition of the liver enzyme aldehyde dehydrogenase (ALDH2), normally involved in the metabolism of alcohol. The triggering of a disulfiram reaction when BDADs and alcohol are mixed suggests that BDADs also inhibit ALDH2. It seems plausible that BDADs also mediate their effects on spermatogenesis via inhibition of an aldehyde dehydrogenase. Within the seminiferous tubules of the testes, a testes-specific aldehyde dehydrogenase called ALDH1a2 biosynthesizes retinoic acid, a vitamin-A derivative known to be essential for spermatogenesis. Therefore, we hypothesize that BDADs such as WIN 18,446 suppress spermatogenesis by inhibiting the biosynthesis of retinoic acid by ALDH1a2 within the seminiferous tubules of the testes. In specific aim #1 of this proposal, we will endeavor to demonstrate that the mechanism by which BDADs such as WIN 18,446 suppress spermatogenesis involves inhibition of the formation of intratesticular retinoic acid. This will be accomplished in vitro using primary cell cultures of neonatal spermatogonia, as well as in vivo using the vitamin-A deficient mouse model and normal rabbits. In specific aim #2, we will endeavor to demonstrate that WIN 18,446 specifically inhibits ALDH1a2 using cell lines stably transduced with a cDNA encoding this enzyme. Next, in specific aim #3, we will synthesize novel derivatives of WIN 18,446 that specifically inhibit ALDH1a2 while minimizing inhibition of ALDH2-mediated alcohol metabolism. We will then examine the ability of these novel compounds to inhibit spermatogenesis both in vitro and in vivo. This work will provide insight into the physiology of spermatogenesis and result in substantial progress towards the development of a safe and effective oral, non-hormonal, reversible contraceptive for men. PUBLIC RELEVANCE: Despite currently available contraceptives, the world's population exceeds six and a half billion and is increasing by 80 million yearly. Much of this population growth is unintended and is due to inadequate contraception. Currently, male-directed contraceptive options are particularly limited. The research described in this proposal may eventually allow for the development of a safe and effective oral approach to male contraception, which will serve to greatly decrease the risk of unintended pregnancy and population growth.