The cap 'n' collar basic leucine zipper transcription factor Nrf2 (NF-E2 p45-related factor 2) controls both constitutive and inducible expression ofintestinal detoxification and glutathione biosynthetic enzymes

Northern blotting has shown that mouse small intestine contains relatively large amounts of the nuclear factor-E2 p45-related factor (Nrf) 2 transcrip tion factor but relatively little Nrf1, Regulation of intestinal antioxidan t and detoxication enzymes by Nrf2 has been assessed using a mouse line bea ring a targeted disruption of the gene encoding this factor, Both Nrf2(-/-) and Nrf2(+/+) mice were fed a control diet or one supplemented with either synthetic cancer chemopreventive agents [butylated hydroxyanisole (BHA), e thoxyquin (EQ), or oltipraz] or phytochemicals [indole-3-carbinol, cafestol and kahweol palmitate, sulfora-phane, coumarin (CMRN), or alpha -angelical actone]. The constitutive level of NAD(P)H:quinone oxidoreductase (NQO) and glutathione S-transferase (GST) enzyme activities in cytosols from small i ntestine was typically found to be between 30% and 70% lower in samples pre pared from Nrf2 mutant mice fed a control diet than in equivalent samples f rom Nrf2(+/+) mice. Most of the chemopreventive agents included in this stu dy induced NQO and GST enzyme activities in the small intestine of Nrf2(+/) mice, Increases of between 2.7- and 6.2-fold were observed in wild-type a nimals fed diets supplemented with BHA or EQ; increases of about 2-fold wer e observed with a mixture of cafestol and kahweol palmitate, CMRN, or alpha -angelicalactone; and increases of 1.5-fold were measured dth sulfora-phan e. Immunoblotting confirmed that in the small intestine, the constitutive l evel of NQO1 is lower in the Nrf2(-/-) mouse, and it also showed that induc tion of the oxidoreductase was substantially diminished in the mutant mouse . Immunoblotting class-alpha and class-mu GST showed that constitutive expr ession of most transferase subunits is also reduced in the small intestine of Nrf2 mutant mice. Significantly, induction of class-alpha and class-mu G ST by EQ, BHA, or CMRN is apparent in the gene knockout animal. No consiste nt change in the constitutive levels of the catalytic heavy submit of gamma -glutamylcysteinyl synthetase (GCS(h)) was observed in the small intestine of Nrf2(-/-) mice. However, although the expression of GCS(h) was found to be increased dramatically in the small intestine of Nrf2(+/+) mice by diet ary BHA or EQ, this induction was essentially abolished in the knockout mic e. It is apparent that Nm influences both constitutive and inducible expres sion of intestinal antioxidant and detoxication proteins in a gene-specific fashion. Immunohistochemistry revealed that induction of NQO1, class-alpha GST, and GCS(h) occurs primarily in epithelial cells of the small intestin e. This suggests that the variation in inducibility of NQO1, Gsta1/2, and G CS(h) in the mutant mouse is not attributable to the expression of the enzy mes in distinct cell types but rather to differences in the dependency of t hese genes on Nrf2 for induction.