Cytoprotective role of mitochondrial amyloid beta peptide-binding alcohol dehydrogenase against a cytotoxic aldehyde

Abstract

Recent reports on amyloid beta peptide (A beta) binding-alcohol dehydrogenase (ABAD) have revealed the link of A beta with oxidative stress derived from mitochondria in the pathogenesis of Alzheimer's disease (AD). As a novel function of ABAD, we speculate that ABAD may detoxify aldehydes, such as 4-hydroxy-2-nonenal (4-HNE). To verify this speculation, we transfected cDNA encoding ABAD into cultured cells (HeLa and SH-SY5Y), where ABAD was localized to mitochondria. ABAD-transfectants decreased the levels of externally added 4-HNE in cultured medium as detected by TLC and became resistant against external 4-HNE. Moreover, ABAD suppressed the cytotoxic effects caused by cellular 4-HNE, which were produced through excess reactive oxygen species (ROS) by treatment with an inhibitor of mitochondrial respiration, antimycin A or by adding H(2)O(2). Catabolism of 4-HNE by ABAD was inhibited by A beta, resulting in the abolishment of the cytoprotective function by ABAD against ROS. These results propose an additional role of ABAD in neural cell death in AD: ABAD detoxifies aldehydes, such as 4-HNE derived from lipid peroxides in healthy brains, and inhibited by A beta in the development of AD.