In vitro chloroquine resistance modulation study on fresh isolates of Brazilian Plasmodium falciparum: intrinsic antimalarial activity of phenothiazine drugs

Abstract

Phenothiazine drugs -fluphenazine, chlorpromazine, methotrimeprazine and trifluoperazine -were evaluated as modulating agents against Brazilian chloroquine-resistant fresh isolates ofKey words: antimalarial -chloroquine -multidrug resistance -phenothiazines -modulating agents -chemosensitizer agentsThe global situation of malaria is claiming attention more than ever. It has been estimated that about 300 million acute clinical cases are reported each year, with at least one million deaths (WHO 2000). Antimalarial drug resistance is among the principal factors responsible for this serious public health problem. Resistance has been associated with the parasite's natural biological mechanisms in response to uncontrolled and unregulated drug distribution programs, resulting in genetic mutations (Wellems & Plowe 2001).Many efforts have been made in the search for a new and effective antimalarial agent. However, little success has been achieved and, therefore, the restoration of current available drugs becomes an important alternative. Combination therapy is particularly studied concerning chloroquine (Fig. 1), although the major Plasmodium falciparum strains and the emergent P. vivax are resistant, this drug remains the most important antimalarial agent. Good pharmacokinectic features, easy use and low cost are its principal properties (Ward & Bray 2001).With the purpose of restoring chloroquine efficacy and considering the reported reversal effect of tricyclic drugs on resistant malaria (Bitonti et al. 1988, Basco & Le Bras 1990, 1991, Kyle et al. 1990, 1993, Peters et al. 1990, Basco & Le Bras 1992, Miki et al. 1992, Oduola et al. 1998 we evaluated the potential effect of the phenothiazine drugs -fluphenazine, chlorpromazine, methotrimeprazine and trifluoperazine (Fig. 1) -, on modulating the chloroquine resistance of Brazilian P. falciparum fresh isolates. MATERIALS AND METHODSThe drugs used were chloroquine diphosphate (Fundação para o Remédio Popular), chlorpromazine hydrochloride, fluphenazine dihydrochloride and methotrimeprazine maleate (Cristália Produtos Químicos e Farmacêuticos Ltda.), and trifluoperazine dihydrochloride (SmithKline Beecham).Two fresh isolates of P. falciparum were used: Isolate 1 (Sucen 198/94) and Isolate 2 (Sucen 206/94). Isolate 1 was collected from a 37-year-old woman in her third infection (6,600 asexual parasites per mm 3 ) and Isolate 2 from a 21 year-old-man in his second infection (7,500 asexual parasites per mm 3 ). The infections occurred in the North of Brazil and the individuals had not been submitted to antimalarial treatment in the previous 28 days (BruceChwatt 1986). Blood samples were collected after formal consent from the patients.Assays were performed in microplates with 96 flatbottomed wells. The culture medium was RPMI-1640, HEPES buffer, gentamicine sulphate, glucose, hypoxanthine, sodium bicarbonate and human type A serum.The statistical analysis was carried out using the software S-Plus, version 4.5, and the Microsoft Excel for Windows, version 5.0.In vitro assays ...

Chloroquine Resistance Reversal Agents as Promising Antimalarial Drugs

“…5) can enhance in vitro the potency of CQ against P. falciparum CQ-resistant strains [132][133][134][156][157][158]. Phenothiazines have also been shown to reduce or reverse antibiotic resistance in bacteria [159][160][161] and in yeast [162].…”

“…It now seems likely that phenothiazines may exert their CQ resistance reversal activity by interacting with Pgh1 [208]. Phenothiazine drugs would reverse the CQ-resistant South American parasites with a lesser degree of susceptibility, compared to the African and Southeast Asian isolates as verapamil does [97,126,157,158]. Chlorpromazine has been shown to bind to the human Pglycoprotein and to modulate the multidrug resistance in cancer cells [163].…”

Chloroquine susceptibility and reversibility in a Plasmodium falciparum genetic cross

“…CQR reversibility by VP and the 8‐aminoquinoline, primaquine (Bray et al ., 2005), like CQR itself, has been attributed to PfCRT, yet the possibility of non‐target based mechanisms suggests the interaction of multiple transporters. Reversal agents themselves are toxic to the parasites (Adovelande et al ., 1998; Menezes et al ., 2002; 2003), but it is not known if these structurally diverse reversal agents exert their toxic effect solely by PfCRT or involve additional genes, nor if their inherent anti‐plasmodial effects predict the degree of reversibility of CQR. For example, some CQ‐resistant parasites such as the South American 7G8 strain, are less responsive to the VP reversal effect (Mehlotra et al ., 2001; Sa et al ., 2009).…”

Chemosensitizers in Drug Transport Mechanisms Involved in Protozoan Resistance

“…Antipsychotic agents like phenothiazine drugs (chlorpromazine, trifluoperazine, prochlorperazine), can enhance in vitro the potency of CQ against P. falciparum CQ-resistant strains [249][250][251][273][274][275]. Phenothiazines have also been shown to reduce or reverse antibiotic resistance in bacteria [276][277][278] and in yeast [279].…”

“…It now seems increasingly likely that phenothiazines may exert their CQ resistance reversal activity by interacting with Pgh1 [200]. Phenothiazine drugs would reverse the CQ-resistant South American parasites with a lesser degree of susceptibility, compared to the African and Southeast Asian isolates as verapamil does [215,243,274,275]. Chlorpromazine has been shown to bind to the human P-glycoprotein and to modulate the multidrug resistance in cancer cells [280].…”