Dependence of Plasmodium falciparum in vitro growth on the cation permeability of the human host erythrocyte.
Intraerythrocyte growth of the malaria parasite Plasmodium falciparum induces a Ca2+-permeable unselective cation conductance in the host cell membrane which is inhibited by ethylisopropylamiloride (EIPA) and is paralleled by an exchange of K+ by Na+ in the host cytosol. The present study has been performed to elucidate the functional significance of the electrolyte exchange. Whole-cell patch-clamp experiments confirmed the Ca2+ permeability and EIPA sensitivity of the Plasmodium falciparum induced cation channel. In further experiments, ring stage-synchronized parasites were grown in vitro for 48 h in different test media. Percentage of Plasmodium-infected and phosphatidylserine-exposing erythrocytes was measured with FACS analysis by staining with the DNA-dye Syto16 and annexin V, respectively. The increase of infected cells was not significantly affected by an 8 h replacement of NaCl in the culture medium with Na-gluconate but was significantly blunted by replacement of NaCl with KCl, NMDG-Cl or raffinose. Half maximal growth was observed at about 25 mM Na+. The increase of infected cells was further inhibited by EIPA (IC50< 10 microM) and at low extracellular free Ca2+. Infected cells displayed significantly stronger annexin binding, an effect mimicked by exposure of noninfected erythrocytes to oxidative stress (1 mM T-butylhydroperoxide for 15 min) or to Ca2+ ionophore ionomycin (1 microM for 60 min). The observations indicate that parasite growth requires the entry of both, Na+ and Ca2+ cations into the host erythrocyte probably through the EIPA sensitive cation channel. Ca2+ entry further induces break-down of the phospholipid asymmetry in the host membrane.
Brand
Verena B
VB
Department of Physiology, University of Tuebingen, Germany.
Sandu
Ciprian D
CD
Duranton
Christophe
C
Tanneur
Valerie
V
Lang
Karl S
KS
Huber
Stephan M
SM
Lang
Florian
F
D000584:Amiloride / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002412:Cations / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002463:Cell Membrane Permeability; D002712:Chlorides / Q000494:pharmacology; D004553:Electric Conductivity; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism* / Q000469:parasitology*; D006801:Humans; D007502:Iron Chelating Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010718:Phosphatidylserines / Q000378:metabolism; D010963:Plasmodium falciparum / Q000187:drug effects / Q000254:growth & development*; D012964:Sodium / Q000494:pharmacology
D002412:Cations; D002712:Chlorides; D007502:Iron Chelating Agents; D010718:Phosphatidylserines; D000584:Amiloride; D012964:Sodium; D002118:Calcium; C039614:ethylisopropylamiloride