Effect of artemisinins and amino alcohol partner antimalarials on mammalian sarcoendoplasmic reticulum calcium adenosine triphosphatase activity

The aim of this study was to assess the ability of currently deployed antimalarials to inhibit mammalian sarcoendoplasmic reticulum calcium adenosine triphosphatase (SERCA). Artemisinins exert their antiplasmodial action by inhibiting parasite PfATP6, a SERCA enzyme, and possess neurotoxic potential; mefloquine is neurotoxic and inhibits mammalian SERCA, an orthologue of PfATP6. SERCA in rabbit muscle was tested in vitro for inhibition by artemisinin and amino alcohol antimalarials. Significant inhibition of mammalian SERCA, as mean difference from uninhibited, control values was seen with both enantiomers of mefloquine: (+)-mefloquine (10 mu M: -35.83, 95% CI -59.63 to -12.03; 50 mu M: -54.06, 95% CI -77.86 to -30.26); (-)-mefloquine (10 mu M: -24.35, 95% CI -41.56 to -7.15; 50 mu M: -58.42, 95% CI -75.62 to -41.22); lumefantrine (1 mu M: -25.46, 95% CI -45.82 to -5.10; 5 mu M -34.83, 95% CI -60.08 to -9.58; 10 mu M: -25.80, 95% CI -51.05 to -0.55); desbutyl-lumefantrine (5 mu M: -50.16, 95% CI -84.24 to -16.08); dihydroartemisinin (1 mu M: -39.25, 95% CI -63.74 to -14.76; 5 mu M: -39.30, 95% CI -64.88 to -13.72). Dihydroartemisinin in higher concentrations (10 mu M) stimulated SERCA activity: (+40.90, 95% CI 11.37 to 70.44). No statistically significant inhibition was seen with artemether at 1, 5 and 10 mu M. Equimolar combinations of artemether and lumefantrine or of dihydroartemisinin and lumefantrine, when studied at concentrations that inhibit SERCA individually, failed to show any inhibition. Dihydroartemisinin, mefloquine, lumefantrine and desbutyl lumefantrine inhibit mammalian SERCA at periphysiological concentrations, although the neurotoxicity of mefloquine is not wholly attributable to this property. Candidate antimalarials should be screened pre-clinically for SERCA inhibition.