Metabolism and tissue distribution of sulforaphane in Nrf2 knockout and wild-type mice

Abstract

Purpose: To determine the metabolism and tissue distribution of the dietary chemoprotective agent sulforaphane following oral administration to wild-type and Nrf2 knockout (Nrf2(-/-)) mice.

Methods: Male and female wild-type and Nrf2(-/-) mice were given sulforaphane (5 or 20 μmoles) by oral gavage; plasma, liver, kidney, small intestine, colon, lung, brain and prostate were collected at 2, 6 and 24 h (h). The five major metabolites of sulforaphane were measured in tissues by high performance liquid chromatography coupled with tandem mass spectrometry.

Results: Sulforaphane metabolites were detected in all tissues at 2 and 6 h post gavage, with the highest concentrations in the small intestine, prostate, kidney and lung. A dose-dependent increase in sulforaphane concentrations was observed in all tissues except prostate. At 5 μmole, Nrf2(-/-) genotype had no effect on sulforaphane metabolism. Only Nrf2(-/-) females given 20 μmoles sulforaphane for 6 h exhibited a marked increase in tissue sulforaphane metabolite concentrations. The relative abundance of each metabolite was not strikingly different between genders and genotypes.

Conclusions: Sulforaphane is metabolized and reaches target tissues in wild-type and Nrf2(-/-) mice. These data provide further evidence that sulforaphane is bioavailable and may be an effective dietary chemoprevention agent for several tissue sites.

Figure 1. Dose dependent increase and rapid clearance of total SFN metabolites in most wild-type mouse tissues

(A) Male and female wild-type mice received gavage of either 5 (open bars) or 20 (solid bars) µmoles of SFN and tissues were collected at 2, 6, and 24 h. Data in graphs represent the mean ± SEM of the sum of all SFN metabolites normalized to tissue weight (n=12 for all tissues except prostate; prostate n=6). (B) Two-way ANOVA analysis of the data.

Figure 2. Nrf2 status has no effect on SFN metabolite concentrations in male mice

(A) Data shown in graph are male wild-type (open bars) and male Nrf2^−/− (solid bars) mice treated with either 5 or 20 µmoles of SFN for 6 h. Data in graphs represent the mean ± SEM of the sum of all SFN metabolites normalized to tissue weight (n=6). (B) Two-way ANOVA analysis of the data.

Figure 3. Female Nrf2^−/− mice had dramatically higher SFN metabolite concentrations compared to female wild-type mice

(A) Data shown in graph are female wild-type (open bars) and female Nrf2^−/− (solid bars) mice treated with either 5 or 20 µmoles of SFN for 6 h. Data in graphs represent the mean ± SEM of the sum of all SFN metabolites normalized to tissue weight (n=6). (B) Two-way ANOVA analysis of the data.

Figure 4. The relative abundance of each SFN metabolite is similar across genotype and gender but variable between tissues

Percent each SFN metabolite represents within the SFN metabolites in different tissues in male (M) or female (F) and wild-type (Wt) or Nrf2^−/− (K/O) mice at 2 (A) and 6 (B) h after 20 µmole dose of SFN. Data in graphs represent mean ± SEM (n=6).