Glyceollin Effects on MRP2 and BCRP in Caco-2 Cells, and Implications for Metabolic and Transport Interactions.

Glyceollins are phytoalexins produced in soybeans under stressful growth conditions. On the basis of prior evaluations, they show potential to treat multiple diseases, including certain cancers, Type 2 diabetes, and cardiovascular conditions. The aim of the present study was to expand on recent studies designed to initially characterize the intestinal disposition of glyceollins. Specifically, studies were undertaken in Caco-2 cells to evaluate glyceollins' effects on apical efflux transporters, namely, MRP2 and BCRP, which are the locus of several intestinal drug-drug and drug-food interactions. 5- (and 6)-carboxy-2',7'-dichloroflourescein (CDF) was used to provide a readout on MRP2 activity, whereas BODIPY-prazosin provided an indication of BCRP alteration. Glyceollins were shown to reverse MRP2-mediated CDF transport asymmetry in a concentration-dependent manner, with activity similar to the MRP2 inhibitor, MK-571. Likewise, they demonstrated concentration-dependent inhibition of BCRP-mediated efflux of BODIPY-prazosin with a potency similar to that of Ko143. Glyceollin did not appreciably alter MRP2 or BCRP expression following 24 h of continuous exposure. The possibility that glyceollin mediated inhibition of genistein metabolite efflux by either transporter was evaluated. However, results demonstrated an interaction at the level of glyceollin inhibition of genistein metabolism rather than inhibition of metabolite transport.

Glyceollin transport, metabolism, and effects on p-glycoprotein function in Caco-2 cells.

Glyceollins are phytoalexins produced in soybeans from their isoflavone precursor daidzein. Their impressive anticancer and glucose normalization effects in rodents have generated interest in their therapeutic potential. The aim of the present studies was to begin to understand glyceollin intestinal transport and metabolism, and their potential effects on P-glycoprotein (Pgp) in Caco-2 cells. At 10 and 25 µM, glyceollin permeability was 2.4±0.16×10(-4) cm/sec and 2.1±0.15×10(-4) cm/sec, respectively, in the absorptive direction. Basolateral to apical permeability at 25 µM was 1.6±0.10×10(-4) cm/sec. Results suggest high absorption potential of glyceollin by a passive-diffusion-dominated mechanism. A sulfate conjugate at the phenolic hydroxyl position was observed following exposure to Caco-2 cells. In contrast to verapamil inhibition of the net secretory permeability of rhodamine 123 (R123) and its enhancement of calcein AM uptake into Caco-2 cells, neither glyceollin nor genistein inhibited Pgp (MDR1; ABCB1) up to 300 µM. There was no significant change in MDR1 mRNA expression, Pgp protein expression, or R123 transport in cells exposed to glyceollin or genistein for 24 h up to 100 µM. Collectively, these results suggest that glyceollin has the potential to be well absorbed, but that, similar to the isoflavone genistein, its absorption may be reduced substantially by intestinal metabolism; further, they indicate that glyceollin does not appear to alter Pgp function in Caco-2 cells.