Effects of the sulforaphane analog compound 30, indole-3-carbinol, D-limonene or relafen on glutathione S-transferases and glutathione peroxidase of the rat digestive tract.

Several dietary compounds have been demonstrated to reduce gastrointestinal cancer rates in both humans and animals. We showed that high human gastrointestinal tissue levels of glutathione S-transferase (GST), a family of detoxification enzymes consisting of class Alpha, Mu, Pi and Theta isoforms, were inversely correlated with cancer risk. We now investigated whether the sulforaphane analog compound 30, indole-3-carbinol, D-limonene or relafen, supplemented in the diet for two weeks at 1450, 250, 10,000, and 200 ppm, respectively, influenced (i) GST activity, (ii) GST isoenzyme levels, (iii) GSH levels, or (iv) glutathione peroxidase (GPx) activity in the gastrointestinal tract of male Wistar rats. Sulforaphane analog compound 30 enhanced GST activity in all organs studied (1.2-2.4 x). It induced GST Alpha levels in small intestine and liver, GST Mu levels in stomach and small intestine, GST Pi levels in stomach and small and large intestine, and GSH levels in stomach and proximal and middle small intestine. Indole-3-carbinol induced gastric GST Mu and hepatic GST Alpha levels. D-limonene induced hepatic GST Alpha, colonic GST Pi levels and proximal small intestinal GST enzyme activity and GST Pi levels. Relafen induced hepatic GST Alpha levels, distal small intestinal and gastric GST Pi levels, and oesophageal and proximal small intestinal GSH levels. GPx activity was enhanced by relafen in oesophagus, and in distal small intestine by sulforaphane analog compound 30. Enhancement of GSTs and to a lesser extent GPx and GSH, resulting in a more efficient detoxification, may explain at least in part the anticarcinogenic properties of sulforaphane analog compound 30, and to a much lesser extent of indole-3-carbinol and D-limonene.

Differential use of transcription activation function 2 domain of the vitamin D receptor by 1,25-dihydroxyvitamin D3 and its A ring-modified analogs.

Analogs of 1,25-dihydroxyvitamin D3 (1,25D3) can be used to elucidate details of vitamin D receptor (VDR) activation. The A ring-modified analog, (TN-2) has 15-fold less affinity for VDR, but its transcriptional activity is diminished 1000-fold. Likewise, the ability of TN-2 to induce a protease-resistant conformation in VDR is 1/1000 that of 1,25D3. The stability of the VDR-TN-2 complexes is also significantly lower than VDR-1,25D3 complexes. Mapping the VDR-binding site of TN-2 showed that it had a significantly greater requirement for transcription activation function 2 (AF-2) residues than 1,25D3 did. These results suggest that the increased requirement for AF-2 residues that was induced by the A ring modifications is associated with diminished receptor activation. To determine whether restoring the potency of TN-2 by additional structural modifications would change the requirements for AF-2 residues, we synthesized hybrid analogs with 1beta-hydroxymethyl-3-epi groups and with dimethyl groups at positions 26 and 27 of the side chain, without or with a double bond between CD ring positions 16 and 17. We found that the side chain modification enhanced transcriptional activity 150-fold, increased the ability of the receptor to form a protease-resistant conformation 100-fold, and stabilized the VDR-analog complexes. The addition of the 16-ene group further reduced the analog's dissociation rate and increased its potency in the protease assays. These functional changes in the hybrid analogs were associated with a significant reduction in interaction with AF-2 residues. We conclude that there is an inverse relationship between analogs' potencies and their interaction with AF-2 residues of VDR.

DDT levels in milk of rural indigent blacks.

Human milk samples from low-income blacks residing in rural Mississippi and Arkansas and middle-class whites residing in metropolitan Nashville, Tenn, were analyzed for concentrations of DDT and its metabolites. The mean total DDT concentration (DDE [derivative of DDT]+DDT) of 38 samples from the blacks was 447 parts per billion (ppb); the range was 59 to 1,900 ppb. The mean of the 14 samples from Nashville residents was 75 ppb (range, 15 to 133 ppb). The difference in the DDT concentrations in the two populations indicates that rural low-income blacks are still highly contaminated with pesticides, even though the general use of DDT has been banned. Due to the limited amount of information from the donors, no correlation could be made between the DDT concentration and diet, age of child, home pesticide use, or distance of residence from farming fields.