In vitro increase in chloroquine accumulation induced by dihydroethano- and ethenoanthracene derivatives in Plasmodium falciparum-parasitized erythrocytes

MalariaCount: An image analysis-based program for the accurate determination of parasitemia

Malaria is a serious global health problem and rapid, precise determination of parasitemia is necessary for malaria research and in clinical settings. Manual counting by light microscopy is the most widely used technique for parasitemia determination but it is a time-consuming and laborious process. The aim of our study was to develop an automated image analysis-based system for the rapid and accurate determination of parasitemia. We have developed, for the first time, a software, MalariaCount, that automatically generates parasitemias from images of Giemsa-stained blood smears. The potential application and robustness of MalariaCount was tested in normal and drug-treated in vitro cultures of Plasmodium falciparum. The results showed a tight correlation between MalariaCount and manual count parasitemia values. These findings suggest that MalariaCount can potentially be used as a tool to provide rapid and accurate determination of parasitemia in research laboratories where frequent, large-scale, efficient determination of parasitemia is required.

Arylsulfonyl acridinyl derivatives acting on Plasmodium falciparum

Several arylacridinyl sulfones have been synthesized and their antimalarial action was tested on Plasmodium falciparum. PABA (para-aminobenzoic acid) has no antagonistic effect with these compounds as opposed to the observed effect with dapsone and sulfonamides previously studied. A possible relationship between the ability of cleavage of the S-9C acridinic bond and activity is suggested.

Polymorphism in plasmodium falciparum drug transporter proteins and reversal of in vitro chloroquine resistance by a 9,10-dihydroethanoanthracene derivative

BG958 reverses resistance in chloroquine-resistant isolates from different countries. Five mutations in the Plasmodium falciparum crt (pfcrt) gene resulting in the amino acid changes K76T, M74I, N75E, A220S, and R371I are systematically identified in resistance-reversed Asian, African, and Brazilian parasites which possess the pfcrt (CIET) haplotype. In combination with BG958, the activity of chloroquine is increased in parasites with the N86Y mutation in pfmdr1.

Dihydroethanoanthracene derivatives as in vitro malarial chloroquine resistance reversal agents

The ability of four 9,10-dihydroethanoanthracene derivatives (BG920, BG932, BG958, and BG996), as well as verapamil and promethazine, to reverse chloroquine resistance was assessed against 24 chloroquine-resistant and 10 chloroquine-susceptible strains of Plasmodium falciparum from different countries. The 9,10-dihydroethanoanthracene derivatives clearly increase chloroquine susceptibility only in chloroquine-resistant isolates.

Cellular uptake of a catechol iron chelator and chloroquine into Plasmodium falciparum infected erythrocytes

Our study demonstrates the capacity of FR160, a catechol iron chelator, to reach and accumulate into infected Plasmodium falciparum erythrocytes and parasites (cellular accumulation ratio between 12 and 43). Steady-state FR160 accumulation is obtained after 2 hr of exposure. After 2 hr exposure, it reaches intracellular levels that are 4- to 10-fold higher in infected red blood cells than those attained in normal erythrocytes. There is quite a good correlation between the accumulation of chloroquine and FR160 in the different strains (r=0.939) and in the IC(50) values (r=0.719). In contrast, the accumulation of FR160 and its activity is poorly correlated (r=0.500), suggesting that activity of FR160 may be independent of its penetration into infected erythrocytes. The mechanism of accumulation is yet unknown but based on inhibitor studies, the uptake of FR160 seems to be not associated with the calcium pump or channel, the potassium channel or the Na(+)/H(+) exchanger. Combinations of FR160 with verapamil, diltiazem, clotrimazole, amiloride, diazoxide, 4-aminopyridine, and picrotoxin should be avoided (antagonistic effects). The potent in vitro activity of FR160 on chloroquine-resistant strains or isolates, its lower toxicity against Vero cells, its mechanisms of action, its capacity to reach rapidly and accumulate into infected erythrocytes suggest that FR160 holds much promise as a new structural lead and effective antimalarial agent or at least a promising adjuvant in treatment of malaria.