DOI

https://doi.org/10.25772/KN6P-W405

Author ORCID Identifier

0000-0002-0283-2420

Defense Date

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Pharmaceutical Sciences

First Advisor

Joseph L. McClay, Ph.D.

Second Advisor

Patricia W. Slattum, Pharm.D, Ph.D.

Third Advisor

MaryPeace McRae, Pharm.D, Ph.D.

Fourth Advisor

Elvin T. Price, Pharm.D, Ph.D.

Fifth Advisor

Matthew S. Halquist, Ph.D.

Sixth Advisor

Mikhail Dozmorov, Ph.D.

Abstract

Geriatric populations are at a higher risk for adverse drug reactions (ADRs). This may be partly due to changes in drug metabolism in old age, but the underlying mechanisms are poorly understood. Prior research in humans and mice has shown age-associated changes to the expression of several genes involved in drug metabolism. Furthermore, studies of human blood showed that epigenetic regulation of genes encoding drug metabolizing enzymes change with age. However, it is unknown if genes in the liver are similarly affected. Therefore, we hypothesize that genes encoding drug metabolizing enzymes may show differential epigenetic regulation in the liver with age, and that this will affect rates of drug metabolism.

We selected genes encoding phase I and II drug metabolizing enzymes showing the strongest evidence of age-related epigenetic changes in prior genome-wide studies of human blood DNA. We mapped the homologues of these genes in mice and analyzed DNA methylation and histone acetylation levels in liver samples from aged mice (4, 18, 24 and 32 months) coupled with functional investigations at those genes. We successfully demonstrated a strong relationship between DNA methylation and histone acetylation (H3K9ac) levels at cytochrome P450 2E1 (Cyp2e1) and sulfotransferase family 1A member 1 (Sult1a1) and their expression levels in liver. Moreover, intrinsic clearance of the CYP2E1 probe drug chlorzoxazone was strongly associated with DNA methylation and histone acetylation at two regulatory regions of Cyp2e1. Next, we investigated DNA methylation levels at these genes in peripheral blood and organs like the liver and the brain. We show that DNA methylation levels of Cyp2e1 and Sult1a1 are substantially different between blood, liver, and the brain and are correlated to various extents and directions of effects. Finally, we report an optimized method for genome-wide investigation, Reduced Representation Bisulfite Sequencing (RRBS), of methylation levels using the innovative Adaptase technology for utilization in larger aging studies of epigenetics and drug metabolism by our group in the future. Our successful demonstration of epigenetic control of drug metabolism in an aged mouse model could pave the way for future clinical studies to develop epigenetic biomarkers of pharmacokinetic pathways in geriatric patients.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-5-2020

Available for download on Wednesday, May 05, 2021

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