Increased frequencies of micronucleated reticulocytes and T-cell receptor mutation in Aldh2 knockout mice exposed to acetaldehyde

Aldehyde dehydrogenase-2 (ALDH2) metabolizes acetaldehyde produced from ethanol into acetate and plays a major role in the oxidation of acetaldehyde in vivo. About half of all Japanese people have inactive ALDH2. We generated homozygous Aldh2 null (Aldh2-/-) mice by gene targeting knockout as a model of ALDH2-deficient humans. To investigate the mutagenicity of acetaldehyde, a micronucleus assay and a T-cell receptor (TCR) gene mutation assay were performed in Aldh2-/- mice and wild-type (Aldh2+/+) mice exposed to acetaldehyde. The mice were continuously exposed to 125 and 500 ppm of acetaldehyde vapor for 2 weeks. Another group was orally administered 100 mg/k once a day for 2 weeks continuously. The mice were killed after 2 weeks of exposure to acetaldehyde, and the frequency of micronucleated reticulocytes was measured by flow cytometry. We also observed the incidence of TCR gene mutations in T-lymphocytes by measuring the variant CD3(-)CD4(+) expression by flow cytometry. The frequency of micronucleated reticulocytes induced by acetaldehyde was significantly increased in Aldh2-/- mice, but not in Aldh2+/+ mice. TCR mutant frequency was also associated with acetaldehyde exposure in Aldh2-/- mice, especially after oral administration however, it was not associated with acetaldehyde exposure in Aldh2+/+ mice. In conclusion, Aldh2-/- mice showed high sensitivity in the micronuclei and TCR mutation assays compared with Aldh2+/+ mice after exposure to acetaldehyde.