Metabolic activation of arylamines, nitroaromatics, and related mutagens

我的研究重点是分子毒理学。我们的长期目标是了解从细胞暴露于某种化学物质到这种暴露的最终毒性后果的生化机制——例如，诱导突变，进化变化的原材料。大多数环境诱变剂被代谢成dna反应性亲电试剂。因此，我通过生物化学来研究毒理学，特别是描述催化诱变原生物转化的酶。关于芳香胺、偶氮染料和硝基芳香化合物（其中许多是致癌物）的代谢和毒理学的基本问题仍然没有答案，但现代分析和分子生物学技术正在使答案触手可及。***关于偶氮染料的毒理学，它们的合成前体，以及它们的推定还原产物芳香胺存在很大的知识空白。我们最近研究了氰基硝基苯胺（CNAs），推测是由偶氮分散染料还原形成的。在艾姆斯试验中，CNAs被证明是非常有效的化合物，这是一种广泛使用的细菌诱变化学物质试验。这一发现——本文提出的研究的起点——揭示了一种完全出乎意料的效应：苯环上三个不同的官能团（氰基、氨基、硝基）相互作用，赋予了强大的生物活性。将这些基团中的任何两个组合（例如，4-硝基苯胺）产生大多数弱诱变化合物；但将这三种方法结合起来，就能产生非常有效的诱变剂。这对我们对构效关系的理解是一个根本性的挑战。为了理解这种效应，我们需要阐明CNA生物激活的途径，而我的实验室已经做好了这样做的准备。我们已经研究了许多催化n -芳基化合物生物转化的酶，包括硝基还原酶（NRs，将硝基芳烃还原为芳基羟胺和芳香胺）；偶氮还原酶（ARs，将偶氮化合物还原为相应的芳香胺）；芳胺n -乙酰基转移酶（NATs，将乙酰辅酶a中的乙酰基转移到芳香胺和羟胺中）。我们将探索CNAs和相关化合物之间的构效关系。我们将研究代谢CNAs的酶，包括纯化的重组NRs、ar和NATs。使用LC-MS分析，我们将尝试鉴定反应性代谢物和cna衍生的DNA加合物。阐明加合物结构将有助于深入了解活化机制。***这些研究将为研究生提供良好的培训机会，他们将很好地在监管毒理学、分析和环境化学以及制药行业等领域就业。

The focus of my research program is Molecular Toxicology. Our long-term goal is to understand the biochemical mechanisms that lead from exposure of a cell to a chemical to the ultimate toxic consequences of that exposure - e.g., induction of mutations, the raw material for evolutionary change. Most environmental mutagens are metabolized to DNA-reactive electrophiles. Consequently, I approach toxicology through biochemistry - especially, characterizing the enzymes that catalyze mutagen biotransformation. Fundamental questions about the metabolism and toxicology of aromatic amines, azo dyes, and nitroaromatic compounds (many of which are carcinogens) remain unanswered, but modern analytical and molecular-biological technologies are bringing the answers within reach.***Large knowledge gaps exist concerning the toxicology of azo dyes, their synthetic precursors, and the aromatic amines that are their putative reduction products. We recently examined cyanonitroanilines (CNAs), presumed to be formed by the reduction of azo Disperse Dyes. CNAs proved to be remarkably potent compounds in the Ames test, a widely used bacterial assay for mutagenic chemicals. This discovery - the starting point for the research proposed here - reveals an entirely unexpected effect: three distinct functional groups (cyano, amino, nitro) on a benzene ring interact to confer potent biological activity. Combining any two of these groups (e.g., 4-nitroaniline) yields at most weakly mutagenic compounds; but combining all three yields exceptionally potent mutagens. This is a fundamental challenge to our understanding of structure-activity relationships. To make sense of this effect, we need to elucidate the pathways of CNA bioactivation, and my lab is well positioned to do so. We have studied many of the enzymes that catalyze the biotransformation of N-aryl compounds, including nitroreductases (NRs, which reduce nitroaromatics to arylhydroxylamines and aromatic amines); azoreductases (ARs, which reduce azo compounds to the corresponding aromatic amines); and arylamine N-acetyltransferases (NATs, which transfer acetyl groups from acetyl CoA to aromatic amines and hydroxylamines). We will explore structure-activity relationships among CNAs and related compounds. We will study the enzymes that metabolize CNAs, including purified recombinant NRs, ARs, and NATs. Using LC-MS analysis, we will attempt to identify reactive metabolites and CNA-derived DNA adducts. Elucidating adduct structures will provide insight into mechanisms of activation.***These investigations will provide excellent training opportunities for graduate students, who will be well placed to obtain employment in areas such as regulatory toxicology, analytical and environmental chemistry, and the pharmaceutical industry.