Multidrug resistance is a major cause of chemotherapy failure in cancer patients. One of the resistance mechanisms is the overexpression of drug efflux pumps such as P-glycoprotein and multidrug resistance protein 1 (MRP1, (ABCC1)). In this study, curcumin mixture and three major curcuminoids purified from turmeric (curcumin I, II, and III) were tested for their ability to modulate the function of MRP1 using HEK293 cells stably transfected with MRP1-pcDNA3.1 and pcDNA3.1 vector alone. The IC(50) of curcuminoids in these cell lines ranged from 14.5-39.3 microM. Upon treating the cells with etoposide in the presence of 10 microM curcuminoids, the sensitivity of etoposide was increased by several folds only in MRP1 expressing and not in pcDNA3.1-HEK 293 cells. Western blot analysis showed that the total cellular level of MRP1 protein level was not affected by treatment with 10 microM curcuminoids for three days. The modulatory effect of curcuminoids on MRP1 function was confirmed by the inhibition of efflux of two fluorescent substrates, calcein-AM and fluo4-AM. Although all the three curcuminoids increased the accumulation of fluorescent substrates in a concentration-dependent manner, curcumin I was the most effective inhibitor. In addition, curcuminoids did not affect 8-azido[alpha-(32)P]ATP binding, however they did stimulate the basal ATPase activity and inhibited the quercetin-stimulated ATP hydrolysis of MRP1 indicating that these bioflavonoids interact most likely at the substrate-binding site(s). In summary, these results demonstrate that curcuminoids effectively inhibit MRP1-mediated transport and among curcuminoids, curcumin I, a major constituent of curcumin mixture, is the best modulator.

A life-detection system based on the expectation that any viable organism will utilize stereoisomers of a given compound asymmetrically is examined. Aqueous extracts of common soil, Mars regolith simulant JSC Mars-1, and suspensions of E. coli and S. cerevisiae were incubated with stereoisomer pairs. The enantiomeric pairs were either D- and L-glucose or a pair of chiral tetrasaccharides. Following an incubation period of 10 days, stereoisomeric selectivity is detectable with the glucose pair by mass spectrometry in extracts made from soil at 0.5 g/ml, in extracts made from JSC Mars-1 at 2.5 g/ml, and in cell suspensions down to 1.0 x 10(7) cells/ml. For the tetrasaccharide pair, stereoisomeric selectivity was detected in extracts made from 0.5 g/ml or more of common soil but not in JSC Mars-1 simulant. The effective sensitivity in extracts was 2.5 x 10(7) cells/ml or better for the glucose pair and 5.0 x 10(8) cells/ml or better for the tetrasaccharide pair. The sensitivity of the glucose pair was such that it could detect life in samples that would be found to be devoid of organic matter by the GCMS system carried by the Viking landers. The results demonstrate the utility of the approach in the search for biological activity on Mars. However, sensitivity is a function of the enantiomer pair used, and this might also be different for hypothetical martian organisms. Therefore, it will be necessary to characterize additional stereoisomeric pairs and, ultimately, to include several in a single test environment.