Antimicrobial peptides enhance the candidacidal activity of antifungal drugs by promoting the efflux of ATP from Candida cells.
OBJECTIVE
To establish a novel strategy of fungal infection control.


METHODS
We examined the influences of antimicrobial peptides including a synthesized short lactoferrin peptide (FKCRRWQWRM, Peptide 2; Pep2) on the synthesis of Candida cell wall polysaccharides, ergosterol synthesis, membrane permeability and the efflux of ATP.


RESULTS
Colony formation of Candida albicans was synergistically suppressed by a combination of low concentrations of each drug and peptide. All peptides and amphotericin B, but not itraconazole, revealed weak inhibitory activities against ergosterol synthesis and the peptides weakly suppressed the synthesis of Candida cell wall components, glucan, mannan and chitin. Cell membrane permeability was not only increased by these peptides but also clearly increased by both amphotericin B and itraconazole. ATP efflux was however up-regulated by low concentrations of the peptides, especially by Pep2 and Hst5, although both antifungal drugs did not exert any influence on ATP efflux. The expression of the Candida drug resistance genes 1 and 2 (CDR1 and CDR2) was increased by both drugs, but this increase was suppressed by each peptide. In addition, larger amounts of amphotericin B and itraconazole remained in Candida cells in the presence of Pep2 or Hst5 due to the lower excretion. The effects of both peptides on ATP efflux and increase of intercellular amphotericin B and itraconazole were blocked by anion channel inhibitors 4,4'-diisothiocyanatestilbene-2, 2'-disulphonic acid and 5-nitro-2-(3-phenylpropylamino) benzoic acid.


CONCLUSIONS
The examined peptides, especially Pep2 and Hst5, enhance the candidacidal activity of antifungal drugs by promoting anion channel-associated ATP efflux from Candida cells and decreasing efflux of the drugs, which could be useful clinical applications.
Tanida
Toyohiro
T
Department of Oral Oncology, Kochi Medical School, Kochi University, Kohasu, Oko-cho, Nankoku-city, Kochi 783-8505, Japan.
Okamoto
Tetsuro
T
Ueta
Eisaku
E
Yamamoto
Tetsuya
T
Osaki
Tokio
T
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000935:Antifungal Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D025141:Drug Resistance, Fungal / Q000187:drug effects / Q000235:genetics; D004357:Drug Synergism; D004875:Ergosterol / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D007781:Lactoferrin / Q000737:chemistry / Q000494:pharmacology*; D026901:Membrane Transport Proteins / Q000235:genetics; D008826:Microbial Sensitivity Tests; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D011135:Polysaccharides, Bacterial / Q000378:metabolism
D018528:ATP-Binding Cassette Transporters; D000935:Antifungal Agents; C094693:CDR1 protein, Candida albicans; D005656:Fungal Proteins; D026901:Membrane Transport Proteins; D010446:Peptide Fragments; D011135:Polysaccharides, Bacterial; D000255:Adenosine Triphosphate; D007781:Lactoferrin; D004875:Ergosterol