Effects of Brassica vegetable juice on the induction of apoptosis and aberrant crypt foci in rat colonic mucosal crypts in vivo

Glucosinolates are sulfur-containing glycosides found in the Brassica vegetables. Their breakdown products include isothiocyanates, which are produced following exposure to the endogenous plant enzyme myrosinase. Isothiocyanates are pungent, biologically active compounds that suppress carcinogenesis in vivo, and induce apoptosis in vitro. We have shown previously that oral administration of the isolated glucosinolate sinigrin induces apoptosis, and suppresses aberrant crypt foci in the colonic mucosa of rats treated previously with 1,2-dimethylhydrazine (DMH). In this study we explored the effects of both raw and thermally processed Brussels sprout tissue on the modulation of crypt cell apoptosis and mitosis, and the frequency of aberrant crypt foci in the colon. Freeze-dried raw and microwave-cooked Brussels sprouts contained high levels of intact glucosinolates, but they were absent from freshly prepared sprout juice. Oral administration of uncooked Brussels sprouts, whether as a juice, or as a freeze-dried powder, was associated with significantly enhanced levels of apoptosis and reduced mitosis in the colonic crypts. However, this effect was confined to rats previously injected (48 h) with DMH, in which levels of apoptosis and mitosis following DNA damage were already high. There was no effect of treatment in control animals. There was also little evidence of these effects when intact glucosinolates were administered in blanched sprout tissue, which lacked active myrosinase. We conclude that glucosinolate breakdown products derived from Brassica vegetables can exert a profound effect on the balance of colorectal cell proliferation and death in an animal model of colorectal neoplasia.