Ethanol Induced Apoptosis in Zebrafish Embryos and Prevention Through Sulforaphane Exposure

Abstract

Fetal Alcohol Spectrum Disorders (FASDs) are severe developmental disorders that are present in 2 out of every 100 children born in the US. FASDs are caused by exposure to ethanol in the womb, which triggers the formation of Reactive Oxygen Species (ROS) that interfere with N-methyl-D-aspartate (NMDA) receptors and glutamate metabolism. Both are essential for the regulation of synaptogenesis during development. Nuclear factor erythroid 2–related factor 2 (Nrf2) is a transcription factor that regulates the expression of genes that prevent ROS damage. Nrf2 expression can be increased with exposure to sulforaphane, a small molecule drug, and has been shown to prevent damage from oxidative stress when organisms are exposed to environmental toxins. Oxidative stress, which causes FASDs, through damage to mRNA, tRNA and glutamate metabolism, leading to apoptosis. Increased expression of Nrf2 has also been demonstrated to protect against tRNA associated damage. Both oxidative stress and damage to RNA contribute to apoptosis in the neural crest. Apoptosis leads to many of the defects in FASDs. Because Nrf2 protects against damage from oxidative stress, sulforaphane exposure, which upregulates Nrf2, will likely protect against apoptotic neurodegeneration. To examine this, a group of zebrafish embryos will be exposed to ethanol (1.25%), an additional group will be exposed to ethanol and sulforaphane (40μM), and a control group will be exposed to neither. If Nrf2 protects embryos from apoptotic neurodegeneration, then zebrafish embryos exposed to sulforaphane and ethanol will exhibit reduced apoptosis compared to zebrafish embryos exposed to only ethanol.