HepG2 cells, a human
hepatoma cell line, stably expressing
NADPH-cytochrome P450 reductase (OR) and/or
cytochrome P450 2D6 wild-type (CYP2D6-WT) or its variants (Pro34Ser, Gly42Arg, Arg296Cys and Ser486Thr) were established in the present study. The cultivation of HepG2 cells expressing CYP2D6-WT in the culture medium containing
dimethyl sulfoxide (
DMSO, 0.1% of final concentration) markedly increased the
bufuralol (BF) 1''-hydroxylase activity compared with that of control cells when cultivated without
DMSO. A similar effect was also observed in HepG2 cells stably expressing
CYP2D6 and OR. The addition of
hemin in place of
DMSO to the culture medium resulted in no increase in the
enzyme activity. Western blot analysis revealed that the levels of
CYP2D6 protein were similar between
DMSO-treated and non-treated HepG2 cells regardless of OR expression. Spectrophotometric analysis of reduced
carbon monoxide-difference spectra of HepG2 cells expressing CYP2D6-WT and/or OR demonstrated that the addition of
DMSO increased the peak height of functional
CYP2D6 at 450 nm. These results suggest that the increase in
CYP2D6 activity is attributable to the radical-scavenging effect of
DMSO. The HepG2 cell lines stably expressing OR and
CYP2D6 or its variants in combination with
DMSO treatment may be useful for screening the cytotoxicity of chemical compounds which undergo oxidation by
CYP2D6.