Molecular Evaluation of Impacted Reproductive Physiology in Fathead Minnow Testes Provides Mechanistic Insights into Insensitive Munitions Toxicology
Molecular Evaluation of Impacted Reproductive Physiology in Fathead Minnow Testes Provides Mechanistic Insights into Insensitive Munitions Toxicology
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DOI：
10.1016/j.aquatox.2019.05.006
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发表时间：
2019-08-01
影响因子：
4.5
通讯作者：
Chappell, Pornsawan
中科院分区：
文献类型：
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作者：
Gust, Kurt A.;Lotufo, Guilherme R.;Chappell, Pornsawan
以前对不敏感弹药（IM）3-硝基-1，2，4-三唑-5-酮（NTO）的毒理学研究表明，对哺乳动物睾丸有组织病理学和生理学影响。这些发现对鱼类的影响尚不清楚，因此我们研究了成年雄性黑头呆鱼长期（21天）暴露于NTO和含NTO的IM制剂IMX-101（由2，4-二硝基苯甲醚（DNAN），硝基胍（NQ）和NTO组成）的影响，以评估对睾丸的影响是否保守。NTO暴露在最大暴露浓度（720 mg/L，测量值）下未导致显著死亡，但NTO引起睾丸影响，在两个最高暴露浓度（383 mg/L和720 mg/L）下导致精子发生显著异常和次级精母细胞坏死，在最高暴露浓度下导致睾丸变性。基于微阵列的转录组学分析确定了显着丰富的类固醇代谢途径和mTORC信号控制的精原细胞分化的NTO曝光，每个观察到的异步精子发生具有逻辑连接。此外，NTO损害支持精子结构和鞭毛发育的基因的转录表达，包括精子相关抗原6（Spag 6）。这些功能性转录组反应被假设为NTO暴露中影响生殖生理学的贡献者，最终导致精子减少。与NTO相比，顶X-101制剂在25.2和50.9 mg/L的两个最高暴露浓度下引起显著死亡率（DNAN标称值+ NTO测量值+ NQ测量值）。与NTO和NQ不同，顶X-101制剂的DNAN组分在21天暴露中经历了显著的转化。根据以前的调查，NTO和NQ在> 1000 mg/L时均未引起鱼类死亡，这表明本研究中的死亡率是由DNAN /DNAN转化产物引起的。12.6 mg/L IMX-101暴露对睾丸造成显著的亚致死影响，包括精子坏死、间质纤维化和支持样细胞增生。IMX-101的转录谱表明在支持精子发生、有丝分裂/减数分裂和鞭毛结构的多个信号通路上显著富集，所有这些都与观察到的精子坏死在逻辑上相关。此外，在已知的DNAN靶点的PPAR α-RXR α通路内的显著转录增加已被假设为对应于支持细胞增生，推测为在精子发生期间实现支持细胞的养育功能的补偿反应。总体而言，转录结果表明NTO和顶X-101的独特分子应答。关于化学危害，NTO影响睾丸并损害精子发生，但在高暴露浓度（>= 192 mg/L）下，而IMX-101制剂引起死亡并影响生殖生理学，这可能是由DNAN及其转化产物引起的，其浓度远低于IMX-101混合物制剂中的NTO组分浓度。
Previous toxicological investigations of the insensitive munition (IM), 3-nitro-1,2,4-triazol-5-one (NTO), demonstrated histopathological and physiological impacts in mammalian testes. The implications of these findings for fish was unknown, therefore we investigated the effects of chronic (21 day) exposures to NTO and an NTO-containing IM formulation called IMX-101 (composed of 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), and NTO) in adult male fathead minnows to assess if impacts on testes were conserved. The NTO exposure caused no significant mortality through the maximum exposure concentration (720 mg/L, measured), however NTO elicited testicular impacts causing significant asynchrony in spermatogenesis and necrosis in secondary spermatocytes at the two highest exposure concentrations (383 mg/L and 720 mg/L) and testicular degeneration at the highest exposure. Microarray-based transcriptomics analysis identified significant enrichment of steroid metabolism pathways and mTORC-signal control of spermatogonia differentiation in NTO exposures each having logical connections to observed asynchronous spermatogenesis. Additionally, NTO impaired transcriptional expression for genes supporting sperm structural and flagellar development including sperm-associated antigen 6 (Spag6). These functional transcriptomic responses are hypothesized contributors to impacted reproductive physiology in NTO exposures that ultimately lead to reductions in spermatozoa. In contrast to NTO, the IMX-101 formulation elicited significant mortality at the two highest exposure concentrations of 25.2 and 50.9 mg/L (DNAN nominal + NTO measured + NQ measured). Unlike NTO and NQ, the DNAN component of the IMX-101 formulation underwent significant transformation in the 21d exposure. From previous investigations, neither NTO nor NQ caused mortality in fish at > 1000 mg/L suggesting that mortality in the present study arose from DNAN / DNAN-attributable transformation products. The 12.6 mg/L IMX-101 exposure caused significant sublethal impacts on testes including sperm necrosis, interstitial fibrosis, and Sertoli-like cell hyperplasia. Transcriptional profiles for IMX-101 indicated significant enrichment on multiple signaling pathways supporting spermatogenesis, mitosis / meiosis, and flagellar structure, all logically connected to observed sperm necrosis. Additionally, pronounced transcriptional increases within the PPAR alpha-RXR alpha pathway, a known DNAN target, has been hypothesized to correspond to Sertoli cell hyperplasia, presumably as a compensatory response to fulfill the nurse-function of Sertoli cells during spermatogenesis. Overall, the transcriptional results indicated unique molecular responses for NTO and IMX-101. Regarding chemical hazard, NTO impacted testes and impaired spermatogenesis, but at high exposure concentrations (>= 192 mg/L), whereas the IMX-101 formulation, elicited mortality and impacts on reproductive physiology likely caused by DNAN and its transformation products present at concentrations well below the NTO-component concentration within the IMX-101 mixture formulation.