Chloroquine: Physiological Basis of Drug Resistance in
            <i>Plasmodium berghei</i>

Macomber, Peter B.; O’Brien, Richard L.; Hahn, Fred E.

doi:10.1126/science.152.3727.1374

Cited by 107 publications

(28 citation statements)

References 6 publications

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“…Erythrocytes infected with CR parasites are less responsive to added substrate; but of the substrates studied, glucose is the best. Parasite counts are sufficiently close to permit quantitative comparisons between the CS and CR models only for two of the four substrates, glucose and glycerol; in agreement with earlier work (1,2), erythrocytes infected with CS parasites accumulate more chloroquine than erythrocytes infected with CR parasites. When the difference due to responsiveness to substrate is minimized, as it is at low glucose and glycerol concentrations, the difference between CS and CR parasites with regard to chloroquine accumulation is also minimized.…”

Section: Resultssupporting

confidence: 87%

“…By contrast, the parent strain is susceptible to treatment of infected mice with as little as 1.25 mg of chloroquine/kg of body weight daily for 4 days (12). The course and characteristics of infections with this new strain of CR P. berghei are indistinguishable from those of the CR strain developed by Macomber, O'Brien, and Hahn (1) and used previously in studies of chloroquine accumulation (1,2). The new strain of CR P. berghei had been maintained by regular passage through chloroquine-treated mice at 2-wk intervals for 2 yr before the present work.…”

Section: Methodsmentioning

confidence: 80%

“…Erythrocytes infected with malaria parasites exhibit a remarkable capacity for accumulating chloroquine (1)(2)(3)(4)(5), Received for publication 1 November 1973 and in revised form 7 January 1974. amodiaquin (6), quinine (7), dihydroquinine (4), quinacrine (8) and probably other structurally related drugs. With glucose and a pharmacologically reasonable concentration of chloroquine in the bathing medium, 10 nM for example, there may be 6,000 or more nmol of chloroquine/kg mouse erythrocytes infected with chloroquinesusceptible (CS)' Plasmodium berghei when steady-state conditions are reached (2).…”

Section: Introductionmentioning

confidence: 99%

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High-Affinity Accumulation of Chloroquine by Mouse Erythrocytes Infected with Plasmodium berghei

Fitch¹,

Yunis²,

Chevli³

et al. 1974

J. Clin. Invest.

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A B S T R A C T Washed erythrocytes infected with chloroquine-susceptible (CS) or with chloroquine-resistant (CR) P. berghei were used in model systems in vitro to study the accumulation of chloroquine with high affinity. The CS model could achieve distribution ratios (chloroquine in cells: chloroquine in medium) of 100 in the absence of substrate, 200-300 in the presence of 10 mM pyruvate or lactate, and over 600 in the presence of 1 mM glucose or glycerol. In comparable studies of the CR model, the distribution ratios were 100 in the absence of substrate and 300 or less in the presence of glucose or glycerol. The presence of lactate stimulated chloroquine accumulation in the CR model, whereas the presence of pyruvate did not. Lactate production from glucose and glycerol was undiminished in the CR model, and ATP concentrations were higher than in the CS model. Cold, iodoacetate, 2,4-dinitrophenol, or decreasing pH inhibited chloroquine accumulation in both models. These findings demonstrate substrate involvement in the accumulation of chloroquine with high affinity.In studies of the CS model, certain compounds competitively inhibited chloroquine accumulation, while others did not. This finding is attributable to a specific receptor that imposes structural constraints on the process of accumulation. For chloroquine analogues, the position and length of the side chain, the terminal nitrogen atom of the side chain, and the nitrogen atom in the quinoline ring are important determinants of binding to this receptor.

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Section: Resultssupporting

confidence: 87%

Section: Methodsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

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High-Affinity Accumulation of Chloroquine by Mouse Erythrocytes Infected with Plasmodium berghei

Fitch¹,

Yunis²,

Chevli³

et al. 1974

J. Clin. Invest.

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“…The mode of action of the drug has not been elucidated hitherto, let alone the mechanisms responsible for drug resistance. A major factor in the antimalarial action of the drug has been attributed to the ability of CQ-sensitive parasites to accumulate relatively high levels of the drug (Macomber et al, 1966). It has been proposed that this accumulation results from binding to a putative intraparasitic receptor, ferriprotoporphyrin IX (FP) with the consequent formation of a membrane lytic complex (Fitch, 1983).…”

mentioning

confidence: 99%

Identification of the acidic compartment of Plasmodium falciparum-infected human erythrocytes as the target of the antimalarial drug chloroquine.

Yayon¹,

Cabantchik²,

Ginsburg³

1984

The EMBO Journal

290

192

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Chloroquine (CQ), the most widely used antimalarial drug, is an acidotropic agent (De Duve, 1983) which accumulates to high levels in malaria-infected erythrocytes. A possible site of accumulation of the drug, the parasite's food vacuole, has been implicated in the mode of action of CQ. We have defined the various compartments of Plasmodium falciparumparasitized human erythrocytes in tenns of their pH and capacity to accumulate bases. The host cell and the parasite cytosols were differentially labeled in situ with pH-sensitive fluorescein, and the parasite food vacuole was revealed by tareting fluoresceinated dextran via endocytosis. The pH of the various compartments obtained from fluorescence excitation spectra were 6.9 for the cytosol of normal and infected erythrocytes and 5.2 for the parasite food vacuole. Determination of CQ and methylamine accumulation in infected erythrocytes, in conjunction with morphometric determination of the relative sizes of the various cellular compartments, provided an independent assessment of the vacuolar pH, yielding a value of 5.0-5.2. Perturbation of the proton gradient, either by lowering extracellular pH or by alkaliniation of the food vacuole with NH4CI or monensin, resulted in a concomitant and reversible decrease in accumulation of the probe. We conclude that drug accumulation in malariainfected erythrocytes can be fully accounted for by the steady-state proton gradients across the barriers delineating the various cellular compartments and the acidotropic properties of the drug.Key words: malaria/Plasmodium falciparum/intracellular pH/food vacuole/chloroquine/fluorescence Introducdton Chloroquine (CQ) is a widely used antimalarial drug. The development of resistance to this compound is one of the major reasons for the world wide resurgence of the disease during recent years (Peters, 1982). The mode of action of the drug has not been elucidated hitherto, let alone the mechanisms responsible for drug resistance. A major factor in the antimalarial action of the drug has been attributed to the ability of CQ-sensitive parasites to accumulate relatively high levels of the drug (Macomber et al., 1966). It has been proposed that this accumulation results from binding to a putative intraparasitic receptor, ferriprotoporphyrin IX (FP) with the consequent formation of a membrane lytic complex (Fitch, 1983). However, free FP has never been detected in malaria-infected red blood cells. Alternatively, by analogy with the lysosomotropic effects of weak bases on animal cells (Poole and Okhuma, 1981), it has been postulated that CQ accumulates to high levels in the food vacuoles of malaria parasites, causing their concomitant alkalinization (Homewood et al., 1972).In this study we defined the role of transmembrane proton gradients as the determining factor in CQ accumulation by Plasmodiumfalciparum-infected human erythrocytes (RBC). We have done this with the aid of fluorescent probes and labeling procedures which allowed us to gain access to various intracellular compartments of the in...

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“…Under conditions that prevail in vivo, however, resistant parasites receive less exposure because the infected erythrocytes fail to accumulate chloroquine avidly (3,5,9,12,14). Consequently, chloroquine resistance in this model may be attributed to reduced exposure of the parasites rather than to ineffectiveness of the drug after it reaches the parasites: This mechanism of resistance provides a basis for explaining how drugs in the same chemotherapeutic class with chloroquine could be effective in the treatment of chloroquine-resistant malaria.…”

mentioning

confidence: 93%

Chloroquine Resistance in Malaria: Accessibility of Drug Receptors to Mefloquine

Fitch

Chan

Chevli

1979

Antimicrob Agents Chemother

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The process of mefloquine accumulation was studied in mouse erythrocytes infected with either Plasmodium berghei CS (chloroquine susceptible) or P. berghei CR (chloroquine resistant). In both cases, mefloquine was accumulated by a saturable process with an apparent dissociation constant of 2.5 x 106 M and an apparent maximal capacity of 700 ,umol per kg of erythrocyte pellet; uninfected mouse erythrocytes accumulated more than half as much mefloquine as infected erythrocytes. The process of accumulation was not stimulated by providing glucose as a substrate, and it was not inhibited in infected erythrocytes by azide, iodoacetate, or incubation at 2°C. Although mefloquine was accumulated more effectively than chloroquine by uninfected erythrocytes and by erythrocytes infected with P. berghei CR, competition between chloroquine and mefloquine was observed, raising the possibility that the same process of accumulation serves both drugs. Chloroquine competitively inhibits mefloquine accumulation, with an apparent inhibitor constant of 1.7 x 10-3 M, and mefloquine competitively inhibits chloroquine accumulation, with an apparent inhibitor constant of 2 x 10' M.The same process of accumulation and the same group of receptors could serve both drugs if mefloquine has greater access than chloroquine to the receptors.Regardless of whether the same process serves both drugs, undiminished accumulation by erythrocytes infected with P. berghei CR provides an explanation for the superiority of mefloquine in treating chloroquine-resistant malaria.

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Chloroquine: Physiological Basis of Drug Resistance in Plasmodium berghei

Cited by 107 publications

References 6 publications

High-Affinity Accumulation of Chloroquine by Mouse Erythrocytes Infected with Plasmodium berghei

High-Affinity Accumulation of Chloroquine by Mouse Erythrocytes Infected with Plasmodium berghei

Identification of the acidic compartment of Plasmodium falciparum-infected human erythrocytes as the target of the antimalarial drug chloroquine.

Chloroquine Resistance in Malaria: Accessibility of Drug Receptors to Mefloquine

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