Endocrine Abstracts

Background and objectives: Sulforaphane is one of the best studied Nrf2-activating compounds. In preclinical studies, it is usually administered either intravenously or via gavage. While these administration methods are efficacious in activating Nrf2 in target tissues, they have certain disadvantages: (i) they are invasive and thus not optimal from the perspective of the 3Rs (Replacement-Reduction-Refinement), notably regarding Refinement; (ii) their invasive nature may potentially affect certain molecular or behavioral readouts; (iii) they are labor-intensive for the personnel working with the experimental animals and require proper training to avoid injury to the animals; (iv) they do not recapitulate the preferred mode of administration of drugs to humans (i.e., oral intake). An oral sulforaphane-producing supplement (Avmacol^®) in the form of a pill is on the market for human use. Each pill supplies broccoli seed extract that contains the sulforaphane precursor glucoraphanin as well as an active myrosinase enzyme that converts glucoraphanin into sulforaphane in the small intestine. Studies in humans have supported that this supplement can effectively activate Nrf2 in vivo. The main objective of the present study was to test whether oral administration of the supplement to mice via the drinking water is safe and efficacious in activating Nrf2 in various target tissues.

Methods: First, the supplement was dissolved in water and the capacity of the resulting solution to activate Nrf2 was tested by treating cells stably transfected with an ARE-luciferase construct. Dose-dependent Nrf2 activation was consistently observed. Maintaining the solution at room temperature for up to 7 days before treating the cells had no effect on its capacity to activate Nrf2 in vitro. Next, male and female adult mice were treated with the supplement, which was dissolved in their drinking water. The mice had continuous access to the supplement solution, which was their only source of drinking water. The solution was changed every 2-3 days, and the mice were treated for a total of 3 months. No adverse events or altered behavior were observed during this period. The mice were then sacrificed, and various tissues were harvested for molecular and histological analyses.

Results: A mild induction of Nrf2 activity was observed in the liver and other tissues, as reflected in an increase of Nqo1 mRNA expression levels. At the histological level, no signs of tissue damage were observed.

Conclusions: These data demonstrate that administration of a commercially available sulforaphane-producing supplement to mice via the drinking water over 3 months is safe and efficacious in activating Nrf2. This method is then suitable for preclinical studies in the field of Nrf2-related research.