Characterization of a rat NADPH-dependent aldo-keto reductase (AKR1B13) induced by oxidative stress

A rat aldo-keto reductase (AKR1B13) was identified as a hepatoma-derived protein, exhibiting high sequence identity with mouse fibroblast growth factor (FGF)-induced reductase, AKR1B8. In this study, AKR1B13 was characterized in terms of its enzymatic properties, tissue distribution and regulation. Recombinant AKR1B13 exhibited NADPH-linked reductase activity towards various aldehydes and α-dicarbonyl compounds, which include reactive compounds such as methylglyoxal, glyoxal, acrolein, 4-hydroxynonenal and 3-deoxyglucosone. The enzyme exhibited low NADP+-linked dehydrogenase activity towards aliphatic and aromatic alcohols, and was inhibited by aldose reductase inhibitors, flavonoids, benzbromarone and hexestrol. Immunochemical and reverse transcription-PCR analyses revealed that the enzyme is expressed in many rat tissues, endothelial cells and fibroblasts. Gene expression in YPEN-1 and NRK cells was up-regulated by treatments with submicromolar concentrations of hydrogen peroxide and 1,4-naphthoquinone, but not with FGF-1, FGF-2, 5α-dihydrotestosterone and 17β-estradiol. These results indicate that AKR1B13 differs from AKR1B8 in tissue distribution and gene regulation, and suggest that it functions as a defense system against oxidative stress in rat tissues.