[Show abstract][Hide abstract] ABSTRACT: Problem statement: Cellular drug resistance to anticancer agents is major obstacle in cancer chemotherapy and the mechanisms by which these MDR cells possess for protecting themselves to survive prolonged exposure to cytotoxic agents still debating. The study aimed to clarify the role of P-glycoprotein (Pgp) and enhanced drug sequestration in lysosomes to confer the multidrug resistance K562 cells with varied degree of Pgp expression. Approach: Erythromyelogenous leukemic K562 and its corresponding Pgp-over expression K562/adr (RF = 26.5) and K562/10000 (RF = 39.6) cells were used. The transport of intrinsic fluorescence molecules including acridine orange and pirarubicin across plasma membrane of living cells was performed by using spectrofluorometric and flow cytometric analysis. Results: Pirarubicin passively diffused through the plasma membrane of K562, K562/adr and K562/10000 cells with the same values of k<SUB>+</SUB> = 3.4�0.3 pL. s<SUP>-1</SUP>.cell<SUP>-1</SUP>. Similar results were found for acridine orange, which passively diffused through plasma membrane of these cell lines about 30-fold faster than pirarubicin. The mean rate of Pgp-mediated efflux coefficient (k<SUB>a</SUB>) of pirarubicin was equal to 2.6 � 0.9 pL.s<SUP>-1</SUP>.cell<SUP>-1</SUP> for K562/adr and 4.7 � 1.0 pL.s<SUP>-1</SUP>.cell<SUP>-1</SUP> for K562/10000 cells. The Pgp-mediated efflux of acridine orange could not be determined for K562/adr cells while an enhancement of exocytosis in K562/10000 cells was characterized. The acridine orange exhibited antiproliferative activity and IC<SUB>50</SUB> for K562, K562/adr and K562/10000 cells was 447�40, 715�19 and 1,719�258 nM, respectively. Cytotoxicity of acridine orange was increased by 2-fold in the presence of and 25 nM monensin. Conclusion: The results clearly demonstrated for the first time that by using the same methods and cell lines. The predominant cellular defense mechanism determined in multidrug resistant cells depends upon the nature of molecular probes used. As molecular probe, pirarubicin clearly showed that the Pgp-mediated efflux of drug play as predominant mechanism while AO clearly demonstrated the role of drug sequestration in lysosomes following an enhance exocytosis in both MDR sublines.
Preview · Article · Sep 2009 · American Journal of Applied Sciences
[Show abstract][Hide abstract] ABSTRACT: Multidrug resistance was an obstacle in cancer chemotherapy because the cells decreased their intracellular drug accumulation by energy-dependent compounds efflux pumps such as P-glycoprotein (P-gp). This study observed some iodinated radiographic contrast media, diatrizoate, iopromide and iotrolan affected the cellular energetic state and the kinetics of P-gp in drug-sensitive K562 and drug resistant K562/adr cell lines using spectrophotometer and spectrofluorometer. By colorimetric MTT assay, it was found that contrast media (0-3500 M) had no effect on both K562 and K562/adr cell viabilities, but in co-treatment with daunorubicin (DNR), diatrizoate decreased cell viability in K562/adr cells by decreasing ICso of DNR from 610.7 74.5 nM to 360108.9 nM. The change in cellular energetic state was studied using rhodamine B as a probe to estimate mitochondrial membrane potential (m). The results showed that 3500 M diatrizoate decreased m from 162.20.3 mV to 86.99.9 mV in K562/adr cells. The kinetics of P-gp-mediated efflux of DNR could be reduced by diatrizoate from 0 (no inhibition) to 0.650.11. This inhibition could be partially prevented in co-incubation with 20 nM concanamycin A or 10 M cytochalasin B. Among the three molecules, diatrizoate showed the best efficiency. It could be proposed for further studies that diatrizoate could be used as MDR identification or MDR imaging and also acted as MDR sensitizing agent in cancer treatments.
Preview · Article · Mar 2009 · American Journal of Applied Sciences
[Show abstract][Hide abstract] ABSTRACT: Problem statement: Plant derived fungicides are now being subjects of many research groups. These secondary metabolites have enormous potential to inspire and influence modern agrochemical research. The study aimed to investigate the antifungal activity and their potential use as fungicides in the agriculture of crude extracts and purified compounds derived from plants used in traditional medicines. Approach: Four medicinal plants including A. galanga, C. longa, B. pandurata and C. odorata were selected and percolated with hexane, ethyl acetate, acetone or methanol. The extracts were purified and elucidated their chemical structures. Disc mycelial growth inhibition was applied in order to determine their anti P. capsici activity and the field study was performed to determine their potential use in controlling fungal infection in chili plants compared with commercial fungicides such as captan and bio-control Trichoderma virens. Results: All crude extract inhibited mycelial growth of the fungus performed with similar efficacy. ED90 was equal to 300 ppm. Among plants studied B. pandurata was the most potent against P. capsici. The proposed active ingredients were pinostrobin and pinocembrin. In the field study, pinocembrin mediated the same anti P. capsici activity as captan. B. pandurata can protect chili from infection, thus increasing crop yield of chili comparable to Trichoderma virens. Conclusion: The results clearly showed that the extracts of the four plants studied could be considered as potential sources of novel fungicides. Particularly, B. pandurata has a very high potential as raw material for developing the antifungal molecule of non-petrochemical, naturally eco-friendly, easily obtainable and not toxic to human beings and environment, at least for use in chili growing.
Preview · Article · Jan 2009 · American Journal of Agricultural and Biological Science