Heat treatment of Brussels sprouts retains their ability to induce detoxification enzyme expression in vitro and in vivo.

UNLABELLED: The bioactive metabolites of glucosinolates, such as isothiocyanates, contained in cruciferous vegetables have been shown to reduce the risk of cancers through the induction of detoxification enzymes. However, cruciferous vegetables are commonly processed before consumption, significantly altering the phytochemical composition of these vegetables. Compared to freeze-dried Brussels sprouts, oven-dried Brussels sprouts contain low concentrations of glucosinolates (22.14 and 0.85 µmol/g, respectively) and isothiocyanates (3.68 and 0.15 µmol/g, respectively). The effect of oven-dried Brussels sprouts on the expression of detoxification enzymes was evaluated in vitro and in vivo. Treatment of immortalized human hepatoma cells with the aqueous extract from oven-dried Brussels sprouts significantly increased quinone activity (0.5 and 1.5 mg/mL) and the activity of the antioxidant response element (EC50=2.39 mg/mL) and xenobiotic response element (EC50 2.92 mg/mL). C3H/HeJ mice fed a diet containing 20% oven-dried Brussels sprout diets for 2 wk demonstrated significantly higher expression than animals fed a nutrient-matched control diet of CYP1A1, CYP1A2, and epoxide hydrolase in the liver and CYP1A1, CYP1A2, CYP1B1, epoxide hydrolase, UGT1A1, thioredoxin reductase, and heme oxygenase in the lungs. The low concentrations of glucosinolates and isothiocyanates in oven-dried Brussels sprouts suggest that other compounds, such as the Maillard reaction products that are produced during heating, are responsible for the induction of detoxification enzymes in vitro and in vivo. PRACTICAL APPLICATION: The manner in which cruciferous vegetables are processed prior to consumption has significant effects on what compounds people are exposed to. The presence of glucosinolates or isothiocyanates can be a good indicator of the ability of cruciferous vegetables to induce detoxification enzymes. However, the data presented here demonstrate that while heat processing of Brussels sprouts greatly reduced the concentrations of glucosinolates and isothiocyanates, their ability to induce detoxification enzymes in vitro and in vivo was retained.

Raphasatin is a more potent inducer of the detoxification enzymes than its degradation products.

UNLABELLED: The biological activity of cruciferous vegetables is hypothesized to be due to the metabolites of a class of phytochemicals called glucosinolates. The chemical properties of these metabolites, including isothiocyanates, determine the biological activity of these compounds and thus their effects on human health. The 2 primary radish (Raphanus sativus L.) glucosinolates, glucoraphasatin, and glucoraphenin, were isolated using solid phase extraction followed by preparative HPLC purification. In an aqueous environment, 77.6% of the maximum amount of sulforaphene produced by the metabolism of glucoraphenin was present after 24 h. Under the same conditions raphasatin, the isothiocyanate metabolite of glucoraphasatin and the oxidized counterpart of sulforaphene, was highly unstable with a half-life of less than 30 min and no raphasatin was detectable after 24 h. In HepG2 cells, raphasatin-induced quinone reductase activity and the RNA expression of several phase 1 and 2 detoxification enzymes by a significantly greater amount than the degradation products of raphasatin. Raphasatin, but not its degradation products, activated the antioxidant response element (ARE) in a stably-transfected reporter cell line. Mice fed a diet consisting of 20% freeze dried radishes for 2 wk had significantly higher liver expression of cytochrome P450 (CYP) 1A1, 1A2, quinone reductase, microsomal epoxide hydrolase, and glutathione S-transferase α2 than mice fed a nutritionally-matched control diet. PRACTICAL APPLICATION: Glucoraphasatin, the primary glucosinolate in radishes, is metabolized into an isothiocyanate (raphasatin) that has biological activity but is also unstable in an aqueous environment. Despite the instability of raphasatin, dietary exposure to radishes produced significant induction of detoxification enzymes. Understanding the chemical properties of raphasatin, both in terms of biological activity and instability, could help develop processing methods to retain the most activity from radishes, glucoraphasatin, and raphasatin.

Induction of detoxification enzymes by feeding unblanched Brussels sprouts containing active myrosinase to mice for 2 wk.

In cruciferous vegetables, myrosinase metabolizes the relatively inactive glucosinolates into isothiocyanates and other products that have the ability to increase detoxification enzyme expression. Thus, maintaining myrosinase activity during food preparation may be critical to receiving the maximum benefit of consumption of Brussels sprouts or other cruciferous vegetables. To test the importance of maintaining myrosinase activity for maximizing bioactivity, experimental diets containing 20% unblanched (active myrosinase) or 20% blanched (inactivated myrosinase) freeze-dried Brussels sprouts and a nutrient-matched control diet were evaluated in vitro and in vivo for their ability to induce detoxification enzymes. Treatment of immortalized HepG2 human hepatoma cells with the unblanched Brussels sprout diet caused a greater increase quinone activity compared to the blanched Brussels sprout diet. C3H/HeJ mice fed the unblanched Brussels sprout diets for 2 wk had significantly higher plasma sulforaphane concentrations. Liver expression of CYP1A1 and epoxide hydrolase, measured using real-time PCR, was correlated with the plasma concentration of sulforaphane. In the lung, expression of epoxide hydrolase, thioredoxin reductase, UDP glucuronosyltransferase, quinone reductase, heme oxygenase, CYP1A1, CYP1A2, and CYP1B1 were also correlated with the plasma concentration of sulforaphane. Together these data demonstrate that, as predicted by the in vitro experiment, in vivo exposure to Brussels sprouts with active myrosinase resulted in greater induction of both phase I and phase II detoxification enzymes in the liver and the lungs that correlated with plasma sulforaphane concentrations.

Pulsatile gonadotropin-releasing hormone release from hypothalamic explants of male marmoset monkeys compared with male rats.

The present study was conducted to quantify in vitro gonadotropin-releasing hormone (GnRH) release parameters in the male marmoset. We established primary cultures of marmoset hypothalamic tissues for approximately 2 days (marmosets) to assess GnRH release profiles in vitro in hypothalamic explants from testis-intact and gonadectomized males. Pulsatile GnRH release profiles were readily demonstrated from in vitro hypothalamic explants isolated from adult male marmoset monkeys. Gonadectomy of male marmosets resulted in elevated mean GnRH and pulse amplitude from hypothalamic explants on the 1st day of culture (day 0). GnRH pulse amplitude increased by day 2 in approximately 67% of hypothalamic explants from testis-intact marmosets, suggesting release from an endogenous regulator of GnRH. We also measured GnRH release profiles in vitro in hypothalamic explants from testis-intact and gonadectomized rats. Male rats showed no changes in any concentration or frequency release parameters for GnRH following gonadectomy or during successive days in culture. The present study represents a unique examination of GnRH release from male marmoset monkey hypothalamic tissue and compares release dynamics directly with those obtained from male rat, suggesting a species difference in feedback regulation of GnRH release.

Influence of pocket gopher mounds on a Texas coastal prairie.

Effects of pocket gopher (Geomys attwateri) mound-building activity on plant community composition and soil nutrient concentrations were investigated in south Texas on both burned and unburned coastal prairie sites. Pocket gophers deposited large amounts of soil which were lower in nutrient content than randomly-collected samples. Above-ground plant biomass was greater around mounds than in random samples mainly because of increased dicots around mounds on the burned area when compared with random samples on the same area. Pocket gophers may have concentrated their activities (and therefore, mounds) in areas with higher dicot biomass on the burned area since they prefer perennial dicots as food, or the presence of mounds may have ameliorated the apparent negative effect of fire on dicots.