Download STUDIES OF EFFLUX ACTIVITIES IN MICROORGANISMS AND

STUDIES OF EFFLUX ACTIVITIES IN MICROORGANISMS AND CANCER CELL
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Rimantas Daugelavičius
Department of Biochemistry, Vytautas Magnus University, Kaunas, LITHUANIA
Efflux pumps are systems devoted to the extrusion of noxious compounds from prokaryotic and
eukaryotic cells. The expression of these pumps can raise cell resistance by several orders of
magnitude, rendering some antibiotics and cytostatic compounds clinically useless. Efflux systems
play a particularly important role in multidrug resistance (MDR) and is a challenging direction of
research in the fields of antimicrobials and chemotherapy.
In addition to low outer membrane permeability and high activity of periplasmic lactamases, efflux is one of the major causes for antibiotic resistance in opportunistic pathogens
such as Salmonella enterica, Escherichia coli or Pseudomonas aeruginosa. In Gram-negative
bacteria, clinically the most important efflux pumps depend to Resistance-nodulation-division
(RND) family. Prevention of the efflux of administered antibiotics using the pump inhibitors could
increase efficiency of the treatment. Phenylalanyl-arginyl--naphthylamide (PAN) or 1-(1naphthylmethyl)-piperazine (NMP) are universal inhibitors of the RND family pumps. Activity of
the pumps, efficiency of the inhibitors and permeability of the bacterial outer membrane can be
monitored in real time using potentiometry and selective electrodes. Monitoring of
tetraphenylphosphonium (TPP+) or ethidium accumulation in bacterial cells in the absence and in
the presence of the pump inhibitors allows to evaluate the total activity of efflux. Studies using
PAN and NMP-selective electrodes revealed that gram-negative bacteria bind high amount of
PAN because of 1) the affinity of this inhibitor to lipopolysaccharides (LPS) and 2) the membrane
voltage-dependent accumulation this compound in bacterial cytosol. Our results suggest that the
high affinity of PAN to bacterial LPS is an important factor strengthening the action of this
inhibitor.
A special intriguing feature of the efflux pumps is a lack of specificity. In experiments with
the cancer cell lines we discovered that cultivation of cells in the presence of TPP+ leads to the
activation of doxorubicin efflux. Due to demethylation of the promotor region and amplification
of the genes, in media with TPP+ expression of ABCB1 efflux pump dramatically increases.
Cultivation of Gram-negative bacteria in the presence of TPP+ and ethidium leads also to the
increased efficiency of biofilm formation. Results of our experiments indicate a possible influence
of household products on the spread of MDR in bacteria and the development of resistance to
chemotherapy in cancer cells.