K. Pattanapanyasat et al., FLOW CYTOMETRIC ASSESSMENT OF HYDROXYPYRIDINONE IRON CHELATORS ON IN-VITRO GROWTH OF DRUG-RESISTANT MALARIA, Cytometry, 27(1), 1997, pp. 84-91
The resurgence of drug-resistant malaria makes urgent the evaluation o
f new antimalarial agents. This study describes a flow cytometric meth
od (FCM) for testing in vitro drug susceptibility of Plasmodium falcip
arum malaria to several orally active hydroxypyridinone (CP) iron chel
ators and to the parenteral iron chelator desferrioxamine (DF). After
exposure of parasites to various concentrations of iron chelating agen
ts, aliquots of cultures were fixed with glutaraldehyde. The fixed sam
ples were washed and stained for parasite DNA with propidium iodide an
d analyzed by how cytometry, The remaining cells were pulsed with H-3-
hypoxanthine, using the microdilution radioisotope method. Both CP and
DF showed dose-dependent inhibition of parasite growth. Of the compou
nds studied, DF exerted a stronger inhibitory effect. Fifty percent of
inhibitory concentrations (IC50) of CP and DF determined by DNA fluor
escence profiles in the now cytometer were consistent with those obtai
ned from the radioisotope method and by microscopic examination, Moreo
ver, the minimum inhibitory concentrations (MIC) of drug required to i
nhibit parasite growth, as detected by the decreasing DNA fluorescence
intensity of the schizont, correlated with observed abnormal microsco
pic morphology, The validity of the MIG, as indicated by deceased fluo
rescence intensity, was confirmed by subsequent parasite culture. Our
FCM study demonstrated the sensitivity of both chloroquine- and pyrime
thamine-resistant malaria parasites to iron chelators, Addition of equ
imolar concentrations of ferric ion completely abolished the inhibitor
y effect of fron chelators, indicating the importance of iron for para
site growth and the primary effect of the compounds as iron (III) chel
ating agents. These data demonstrate that FCM provides a simple and re
liable means for antimalarial drug susceptibility testing, and suggest
that iron chelators have potential for the treatment of drug-resistan
t malaria. (C) 1997 Wiley-Liss, Inc.