Selective protection by stably transfected human ALDH3A1 (but not human ALDH1A1) against toxicity of aliphatic aldehydes in V79 cells

Toxic medium chain length alkanals, alkenals, and 4-hydroxyalkenals that ar e generated during lipid peroxidation are potential substrates for aldehyde dehydrogenase (ALDH) isoforms. We have developed transgenic cell lines to examine the potential for either human ALDH1A1 or ALDH3A1 to protect agains t damage mediated by these toxic aldehydes. Using crude cytosols from stabl y transfected cell lines, these aldehydes were confirmed to be excellent su bstrates for ALDH3A1, but were poorly oxidized by ALDH1A1. Expression of AL DH3A1 by stable transfection in V79 cells conferred a high level of protect ion against growth inhibition by the medium-chain length aldehyde substrate s with highest substrate activity, including hexanal, trans-2-hexenal, tran s-2-octenal, trans-2-nonenal, and 4-hydroxy-2-nonenal (HNE). This was refle cted in a parallel ability of ALDH3A1 to prevent depletion of glutathione b y these aldehydes. Expression of hALDH3 completely blocked the potent induc tion of apoptosis by HNE in both V79 cells and in a RAW 264.7 murine macrop hage cell line, consistent with the observed total prevention of HNE-protei n adduct formation. Structure-activity studies indicated that the rank orde r of potency for the contributions of HNE functional groups to toxicity was aldehyde greater than or equal to C2 = C3 double bond > > C4-hydroxyl grou p. Oxidation of the aldehyde moiety of HNE to a carboxyl by ALDH3A1 express ed in stably transfected cell lines drastically reduced its potency for gro wth inhibition and apoptosis induction. In contrast, ALDH1A1 expression pro vided only moderate protection against trans-2-nonenal (t2NE), and none aga inst the other six-nine carbon aldehydes. Neither ALDH1A1 nor ALDH3A1 confe rred any protection against acrolein, acetaldehyde, or chloroacetaldehyde. A small degree of protection against malonelialdehyde was afforded by ALDH1 A1, but not ALDH3A1. Paradoxically, cells expressing ALDH3A1 were 1.5-fold more sensitive to benzaldehyde toxicity than control V79 cells. These studi es demonstrate that expression of class 3 ALDH, but not class 1 ALDH, call be an important determinant of cellular resistance to toxicity mediated by aldehydes of intermediate chain length that are produced during lipid perox idation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.