Inositol 1,4,5-Trisphosphate Induced Ca2+Release from Chloroquine-Sensitive and -Insensitive Intracellular Stores in the Intraerythrocytic Stage of the Malaria ParasiteP. chabaudi

Antimalarial drugs disrupt ion homeostasis in malarial parasites

“…A: dose-response effect of bafilomycin (Baf) on cytosolic calcium fluorescence (mean data of fluorescence ratio remaining from ten cells in three different trials); B: addition of bafilomycin (increase of 1.3 ± 0.1; n = 6) and nigericin (Nig) (20 µM); C: addition of nigericin (1.42 ± 0.1; n = 6) and bafilomycin (4 µM); D: addition of bafilomycin (1.5 ± 0.2; n = 6) and thapsigargin (Thg) (10 µM); E: addition of nigericin (1.65 ± 0.3; n = 6) and thapsigargin (10 µM). We have previously shown that the acidic pool also functions as a Ca 2+ store in permeabilized malaria parasites and that chloroquine causes Ca 2+ release from this store (Passos & Garcia 1998). In the present study, intact parasites were labeled with the calcium indicator, Fluo-3 AM to measure parasite cytosolic Ca 2+ mobilization, and we also investigated the acidic pools in intact parasites within the RBC, using confocal microscopy.…”

“…The acidic vacuole in malaria parasite is the site of hemoglobin digestion and it is believed of drug action. In the rodent malaria parasite P. chabaudi the second messenger IP 3 is known to induced-Ca 2+ mobilization from this compartment (Passos & Garcia 1998). These findings are of major significance, because they raise the possibility that chloroquine and artemisinin action in malaria parasites may involve alterations in ion homeostasis.…”

“…Other mechanisms for pH regulation described in malaria parasites may involve the V-H + -ATPase and the V-H + -PPase in acidocalcisomes (Marchesini et al 2000, McIntosh & Vaidya 2002, Saliba et al 2003, Biagini et al 2003. We have reported the existence of Ca 2+ pools in the acidic compartment of rodent as well as human malaria parasites as a possible mechanism for the regulation of calcium concentration in these parasites , Passos & Garcia 1998. Calcium homeostasis in malaria parasites has been extensively studied by several authors (Tanabe et al 1982, Krungkrai & Yuthavong 1983, Scheibel et al 1987, Wasserman et al 1990, Adovelande et al 1993, Garcia et al 1997, Gazarini et al 2003, Gazarini & Garcia 2004, Beraldo et al, 2005, Budu et al 2007).…”

“…Infected RBC (10 7 ml -1 ) was lysed in PBS with 60 µg.ml -1 saponin. RBC membranes were removed by centrifugation (9000 g for 10 min at 4 o C), the parasites were washed twice in MOPS buffer (116 mM NaCl, 5.4 mM KCl, 0.8 mM MgSO 4 , 5.5 mM D-glucose, 50 mM MOPS, and 2 mM CaCl 2 , pH 7.2) and dispensed in the same buffer at room temperature (Passos & Garcia 1998).…”

“…Calcium homeostasis in malaria parasites has been extensively studied by several authors (Tanabe et al 1982, Krungkrai & Yuthavong 1983, Scheibel et al 1987, Wasserman et al 1990, Adovelande et al 1993, Garcia et al 1997, Gazarini et al 2003, Gazarini & Garcia 2004, Beraldo et al, 2005, Budu et al 2007). Interestingly, in P. chabaudi, the second messenger IP 3 , mobilizes Ca 2+ not only from the classical ER-like pool but also from an acidic compartment, implying that these parasites utilize a calcium-mediated cell signaling mechanism similar to higher organisms (Passos & Garcia 1998). Nevertheless, we still have no clear picture of signaling events and the role of the acidic compartment in malaria parasite signaling, or its significance in the therapeutic actions of antimalarial drugs such as chloroquine (Yayon et al 1984, Dzekunov et al 2000.…”