Effect Of Acetaminophen Exposure On Expression Levels Of Antioxidant Genes In Drosophila Melanogaster Larvae

Acetaminophen (APAP) is the most common analgesic drug and is the second leading cause of toxic drug overdose in the U.S. It is commonly prescribed to treat pain and inflammation, but because of its high availability patients are prone to overdose. Research on the effects of APAP overdose in adults have been thoroughly performed but not so for expecting mothers and children. We have been studying the effects of APAP on antioxidant gene expression levels in the developing larvae of Drosophila melanogaster. APAP is metabolized in the liver in humans, but when concentrations become high it is converted to n-acetyl-p-benzoquinone imine (NAPQI). NAPQI is toxic to the cells and induces apoptosis and reactive oxygen species (ROS). In eukaryotic organisms, ROS is typically kept low with the expression of antioxidant genes in the cell. Previous research suggests that superoxide dismutase (SOD) and catalase (CAT) are not responsible for lowering the effects of NAPQI in Drosophila. In their absence, the survival of larvae exposed to APAP increases and we theorize that the removal of SOD and CAT from the cell causes upregulation of other antioxidant genes. In our current studies, we are measuring the expression levels of genes involved in GSH synthesis and recycling in larvae exposed to APAP and comparing them to controls. In Drosophila, GSH is synthesized by glutamate-cysteine ligase (GCL), which is composed of two subunits, GCLc and GCLm. GSH recycling in Drosophila is performed by thioredoxin (TRX). Drosophila has two TRX genes, TRXr-1 and TRXr-2. RNA was isolated from 2 nd to 3 rd instar Oregon R larvae raised on either control food or food containing 30mM APAP. The RNA was then used for cDNA synthesis and real-time PCR (RT- PCR) to determine relative levels of expression of the GCLc, GCLm, Trxr-1, and Trxr-2 genes. We expect the treated larvae to have significantly higher expression levels of the GCL and TRX genes with TRX having the largest increase. In addition, a colleague is also comparing the expression levels of these genes in SOD and CAT null mutants compared to control flies to verify the upregulation of GSH and TRX as the contributing factors in the higher survival rate of SOD and CAT null mutants on APAP food