Most chemicals, including drugs, are transformed in animals and humans to a variety of metabolites. Although many of these metabolites are physiologically inactive, some are active either therapeutically or toxicologically. Research in our laboratory is focused primarily on the elucidation of chemical and biochemical mechanisms by which highly reactive, toxic metabolites are formed, on their structural identification, and on characterization of their interactions with cellular macromolecules, such as proteins and DNA. We hope that knowledge of pathogenetic mechanisms will lead to the introduction of safer drugs and other chemicals. We are also investigating the effects of protein-protein interactions on structure/function relationships of drug metabolizing enzymes.

During the course of our investigation, we often synthesize analogs of the chemicals to probe the sites at which tissue enzymes react with the chemical to form toxic metabolites. For example, we have prepared methylated analogs of the widely used analgesic, acetaminophen, to determine which of several possible mechanisms is most responsible for the propensity of this drug to cause liver damage when it is ingested in large doses. We have prepared deuterated analogs of a natural product terpene, which has been used to induce abortions, to identify the sites of enzymic oxidation of the compound to form a liver and lung toxin. Genomic, proteomic and metabonic studies help us better define cellular pathways involved in drug toxicities and generate new testable hypotheses.

Finally, we are using the knowledge obtained from such studies to synthesize new chemicals and drugs that are less toxic or are directed to damage-selected enzyme target in order to achieve a beneficial therapeutic action. For example, we have synthesized some thiol analogs of a steroid that form reactive metabolites at a selected site to chemically inactive an enzyme that is important in the growth of some breast cancers.

In all of our studies, we utilize a combination of sophisticated, state-of-the-art analytical techniques (IR, UV, NMR, GC, HPLC, MS) to characterize our synthetic products and to both qualitatively and quantitatively assay metabolites.

Recent Publications

• C.A. Gartner, S.J. Thompson, A.E. Rettie and S.D. Nelson: Human Aromatase in High Yield and Purity by Perfusion Chromatography and Its Characterization by Difference Spectroscopy and Mass Spectrometry. Protein Expression and Purification 22:443-454 (2001).
• M.L. Adams, R.H. Pierce, M.E. Vail, R.P. Tonge, N. Fausto, S.D. Nelson and S.A. Bruschi: Enhanced Panlobular Hepatotoxicity to Acetaminophen in BCL-2 Overexpressing Transgenic Mice. Mol. Pharmacol. 60:907-915 (2001).
• P.D. Senter, Y. Al-Abed, C.N. Metz, F. Benigni, R.A. Mitchell, J. Chesney, J. Han, C.G. Gartner, S.D. Nelson, G.J. Todaro, and R. Bucala: Inhibition of macrophage migration inhibitory factor (MIF) tautomerase and biological activities by acetaminophen metabolites. Proc. Natl. Acad. Sci., USA 99:144-149 (2002).
• E.A. James, S.P. Gygi, M.L. Adams, R.H. Pierce, N. Fausto, R.H. Aebersold, S.D. Nelson and S.A. Bruschi: Mitochondrial Aconitase Modification, Functional Inhibition and Evidence for a Supramolecular Complex of the TCA Cycle by the Renal Toxicant S-(1,1,2,2-Tetrafluoroethyl)-L Cysteine. Biochemistry 41: 6789-6797 (2002).
• R.H. Pierce, C.C. Franklin, J.S. Campbell, R.P. Tonge, W. Chen, N. Fausto, S.D. Nelson and S.A. Bruschi: Cell Culture Model for Acetaminophen-Induced Hepatocyte Death In Vivo. Biochem. Pharmacol. 64:413-424 (2002).
• S.D. Nelson, J.T. Slattery, K.E. Thummel and P.B. Watkins: CAR Unlikely to Significantly Modulate Acetaminophen Hepatotoxicity in Most Humans. Hepatotology 38:254-257 (2003).
• H. Lee, E.C. Yi, B. Wen, T.P. Reilly, L. Pohl, S.D. Nelson, R. Abersold and D.R. Goodlett: Optimization of Reversed-Phase Microcapillary Liquid Chromatography for Quantitative Proteomics. J. Chromatog. B 803:101-110 (2004)
• H.K. Ho, Z-H Hu, S-P Tzung, D. M. Hockenbery, N. Fausto, S. D. Nelson and S.A. Bruschi: BCL-xL Overexpression Effectively Protects Against Tetrafluoroethylcysteine-induced Intramitochondrial Damage and Cell Death. Biochem. Pharmacol. 69:147-157 (2005)
• B. Wen, C.E. Doneanu, C.A. Gartner, A.G. Roberts, W.M. Atkins and S.D. Nelson: Fluorescent Photoaffinity Labeling of Cytochrome P450 3A4 by Lapachenole: Identification of Modification Sites by Mass Spectrometry. Biochemistry 44:1833-1845 (2005)
• C.A. Gartner, B. Wen, J. Wan, R.S. Becker, G. Jones, S.P. Gygi and S.D. Nelson: Photochromic Agents as Tools for Protein Structure Study: Lapachenole is a Photoaffinity Ligand of Cytochrome P450 3A4. Biochemistry 44:1846 - 1855 (2005)
• H.K. Ho, C.C. White, C. Fernandez, N. Fausto, T.S. Kavanaugh, S.D. Nelson and S.A. Bruschi: Nrf2 Activation Involves An Oxidative-Stress Independent Pathway in Tetrafluoroethycysteine-Induced Cytotoxicity. Toxicol. Sci. 86:354-364 (2005)
• K.D. Welch, B. Wen, D.R. Goodlett, E.C. Yi, H. Lee, T.P. Reilly, S.D. Nelson and L.R. Pohl: Proteomic Identification of Potential Susceptibility Factors in Drug-Induced Liver Disease. Chem. Res. Toxicol. 18:924-933 (2005)
• K.A. Regal, K.L. Kunze, R.M. Peter and S.D. Nelson: Oxidation of Caffeine by CYP1A2: Isotope Effects and Metabolic Switching, Drug Metab. Dispos. 33:1837-1844 (2005)
• M.D. Cameron, B. Wen, K.E. Allen, A.G. Roberts, J.T. Schuman, A.P. Campbell, K.L. Kunze and S.D. Nelson: Cooperative Binding of Midazolam with Testosterone and ±-Naphthoflavone within the CYP3A4 Active Site: A NMR T1 Paramagnetic Relaxation Study. Biochemistry 44:14143-14151 (2005)
• B. Wen, C.E. Doneanu, J.N. Lampe, A.G. Roberts, W.M. Atkins and S.D. Nelson: Probing the CYP3A4 Active Site by Cysteine Scanning Mutagenesis and Photoaffinity Labeling. Arch. Biochem. Biophys. 444:100-111 (2005)
• Q. Gao, S. Xue, C.E. Doneanu, S.A. Shaffer, D.R. Goodlett and S.D. Nelson: Pro-CrossLink - A Software Tool for Protein Crosslinking and Mass Spectrometry, Anal. Chem. 78:2145-2149 (2006)
• H.K. Ho, Y. Jia, K.J. Coe, Q. Gao, C.E. Doneanu, Z. Hu, T.K. Bammler, R.P. Beyer, N. Fausto, S.A. Bruschi and S.D. Nelson: Cytosolic Heat Shock Proteins and Heme Oxygenase-1 are Preferentially Induced in Response to Specific and Localized Intramitochondrial Damage by Tetrafluoroethylcysteine, Biochem. Pharmacol. 72:80-90 (2006).
• K.J. Coe, S.D. Nelson, R.G. Ulrich, Y. He, X. Dai, O. Cheng, M. Caguyong, C.J. Roberts and J.G. Slatter: Profiling the Hepatic Effects of Flutamide in Rats: A Microarray Comparison with Classical Aryl Hydrocarbon Receptor Ligands and Atypical CYP1A Inducers. Drug Metab. Dispos. 34:1266-1275 (2006).
• Q. Gao, C.E. Doneanu, S.A. Shaffer, E.T. Adman, D.R. Goodlett and S.D. Nelson: Identification of the Interactions Between Cytochrome P450 2E1 and Cytochrome b5 by Mass Spectrometry and Site-Directed Mutagenesis. J. Biol. Chem. 281:20404-20417 (2006).
• B. Wen, J.N. Lampe, A.G. Roberts, W.M. Atkins, A.D. Rodrigues and S.D. Nelson: Cysteine 98 in CYP3A4 Contributes to Conformational Integrity Required for P450 Interaction with CYP Reductase. Arch. Biochem. Biophys. 454:42-54 (2006).
• A. Mutlib, P. Jinag, J. Atherton, L. Obert, S. Kostrubsky, S. Madore and S.D. Nelson: Identification of Potential Genomic Biomarkers of Hepatotoxicity Caused by Reactive Metabolites of N-Methylformamide: Application of Stable Isotope Labeled Compounds in Toxicogenomic Studies. Chem. Res. Toxicol. 19:1270-1283 (2006).
• K.J. Coe, Y. Jia, H.K. Ho, P. Rademacher, T.K. Bammler, R.P. Beyer, F.M. Farin, L. Woodke, S.R. Plymate, N. Fausto and S.D. Nelson: Comparison of the Cytotoxicity of the Nitroaromatic Drug Flutamide to Its Cyano Analogue in the Hepatocyte Cell Line TAMH: Evidence for Complex I Inhibitiion and Mitochondrial Dysfunction Using Toxicogenomic Screening. Chem. Res. Toxicol. 20:1277-1290 (2007).
• M.D. Cameron, B. Wen, A.G. Roberts, W.M. Atkins, A.P. Campbell and S.D. Nelson: Cooperative Binding of Acetaminophen and Caffeine within the P450 3A4 Active Site. Chem. Res. Toxicol. 20:1434-1441 (2007).
• S.E. Kostrubsky, S.C. Strom, E. Ellis, S.D. Nelson and A.E. Mutlib: Transport, Metabolism, and Hepatotoxicity of Flutamide, Drug-Drug Interaction with Acetaminophen Involving Phase I and Phase II Metabolites. Chem. Res. Toxicol. 20:1503-1512 (2007).
• J.P. Harrelson, K.R. Henne, D.O.V. Alonso and S.D. Nelson: A Comparison of Substrate Dynamics in Human CYP2E1 and CYP2A6. Biochem. Biophys. Res. Commun. 352:843-849 (2007).
• J.P. Harrelson, W.M. Atkins and S.D. Nelson: Multiple Ligand Binding in CYP2A6: Probing Mechanisms of Cytochrome P450 Cooperativity by Assessing Substrate Dynamics. Biochemistry (in press)
• B. Wen, L. Ma, S.D. Nelson and M. Zhu: High-Throughput Screening and Characterization of Reactive Metabolites Using Polarity Switching of Hybrid Triple Quadrupole Linear Ion Trap Mass Spectrometry. Anal. Chem. (in press)

Recent Book Chapters and Review Articles:

• S.D. Nelson: Drug-Drug Interactions: Toxicological Perspectives, in "Drug-Drug Interactions: From Basic Pharmacokinetic Concepts to Marketing Issues," A.D. Rodrigues, ed., Marcel Dekker, Inc., New York, 2001, pp. 585-604..
• S.D. Nelson: Structure Toxicity Relationships - How Useful Are They in Predicting Toxicities of New Drugs?, in "Biological Reactive Intermediates VI," P.M. Dansette et al., eds., Kluwer Academic/Plenum Publishers, New York, 2001, pp. 33-43.
• S.D. Nelson: Molecular Mechanisms of Adverse Drug Reactions, Current Therapeutic Research 62:885-899 (2001).
• C.A. Gartner and S.D. Nelson: Aromatase, the Enzyme Responsible for Estrogen Biosynthesis, in “Wiley Encyclopedia of Molecular Medicine,” John Wiley and Sons, Inc., New York, 2002, pp. 253-225.
• S. D. Nelson and S. A. Bruschi: Mechanisms of Acetaminophen-Induced Liver Disease, in "Drug-Induced Liver Disease," N. Kaplowitz and L. DeLeve, eds., Marcel Dekker, Inc., New York, 2002, pp. 287-326.
• S.D. Nelson and W.F. Trager: The Use of Deuterium Isotope Effects to Probe the Active Site Properties, Mechanism of Cytochrome P450-Catalyzed Reactions, and Mechanisms of Metabolically Dependent Toxicity. Drug Metab. Dispos. 31:1481-1498 (2003).
• S.D. Nelson and S.A. Bruschi: Mechanisms of Acetaminophen-Induced Liver Disease, in “Drug-Induced Liver Disease, Second Edition” N. Kaplowitz and L. DeLeve, eds. Informa Healthcare, USA Inc., New York, 2007, pp. 353-388.
• S.D. Nelson: Drug-Drug Interactions: Toxicological Perspectives, in “Drug-Drug Interactions, Second Edition” A.D. Rodrigues, ed. Inform Healthcare, USA Inc., New York, 2008.

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