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Dennis R. Koop, Ph.D.
- Scientist, CROET
- Professor, Department of Physiology and Pharmacology, School of Medicine, OHSU
Dr. Koop received his doctoral degree in Biochemistry from Northwestern University
Medical School, Chicago, Illinois. He completed a post-doctoral program in Biological
Chemistry in the Medical School of the University of Michigan. He was a Lecturer
and Assistant Professor in the Department of Biological Chemistry at the Medical
School of the University of Michigan. He was Assistant Professor, then Associate
Professor in the Department of Environmental Health Sciences, Case Western Reserve
University, School of Medicine. He has special expertise in biochemical isolation,
purification and characterization of proteins.
Research Interests
The cytochrome P450 system is essential in most organisms for the biosynthesis
of endogenous compounds such as steroids, fatty acids, prostaglandins and pheromones.
However, the largest number of P450 substrates are foreign chemicals that include
drugs, plant metabolites, environmental pollutants and food additives. In general,
the role of P450 is to detoxify chemicals and increase elimination from the body.
However, in some cases the oxidized products can initiate cell toxicity, including
chemical carcinogenesis, mutagenesis and teratogenesis. These detrimental properties
of this enzyme family underscores the importance of understanding the regulation of
the individual members of the gene family.
Research in my laboratory is focused on characterizing the regulation and catalytic
activity of P450 2E1 (CYP2E1), and examining the effect of antioxidants on stress
signaling pathways and P450-dependent metabolism. The level of CYP2E1 is increased
by alcohol consumption, and it is hypothesized that many ethanol-associated toxicities
are due to the induction of this enzyme in hepatic and extrahepatic tissues. For
example, an increased hepatotoxicity of acetaminophen is thought to be due to
metabolism of this commonly used over-the-counter pain medication to a reactive
metabolite by higher levels of CYP2E1. The induction of CYP2E1 also is associated
with an increased generation of active oxygen species that can initiate cellular
damage. Since the degree of damage is related to the level of the enzyme, it is
important to find those factors that control its intracellular concentration and
to identify compounds that can alter its metabolic activity and expression. The
research in my laboratory utilizes cell lines expressing the normal CYP2E1 and
selectively modified forms of the enzyme to identify those regions important in
its degradation. In addition, the expression is monitored in genetic models of
iron overload where induction of CYP2E1 could exacerbate drug-induced toxicity.
The effect of constituents of natural products such as those found in herbal tinctures
and alcoholic beverages on P450 dependent expression and metabolism are also being
investigated. |
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