Erythrocytic plasma membrane calcium ATPase (PMCA4b) variations mediate redox imbalance to determine artemisinin sensitivity in malaria

Artemisinin resistance in Plasmodium falciparum remains a major public health challenge for the ongoing malaria elimination programs. Till now, artemisinin resistance is linked with the variations in the genome of P. falciparum which are mainly clustered in the Pfkelch13 gene. Several studies reported artemisinin resistance in the malaria endemic areas without finding any evidence of genetic variation in parasite for this occurrence. This study interrogated whether host genetic variations have any association with artemisinin sensitivity of malaria parasite. We investigated the relationship of 1) genetic variations in the human ATP2B4 gene and 2) the resultant surface expression of plasma membrane calcium ATPase (PMCA4b) with the intraerythrocytic levels of calcium, reactive oxygen species (ROS) and the resistance towards artemisinin in the intraerythrocytic parasite. This study found negative correlation of PMCA4b expression level with intraerythrocytic calcium and ROS levels. Further in-vitro growth assays revealed that artemisinin sensitivity is reduced in the parasites growing within the RBCs having low PMCA4b and high oxidative stress. Overall, this study highlights the strong association of host PMCA4b in cellular calcium mediated redox imbalance, which significantly contributes to artemisinin resistance in malaria parasite. Hence, this is the first study to document the effect of host variations on artemisinin sensitivity of the parasite. We further emphasize that many redox modulating RBC polymorphisms that are prevalent in malaria endemic areas could influence artemisinin resistance and can serve as potential biomarkers for predicting therapeutic response. Thus, detailed population specific research may provide new insights for personalized malaria treatment and may inform future drug development strategies. SignificanceThe human host and malaria parasite share a closely interconnected relationship hence host variations could influence parasite drug resistance. This study demonstrates that reduced PMCA4b expression, the primary calcium efflux pump in RBCs, significantly increases the erythrocytic calcium and reactive oxygen species (ROS) levels, thereby decreasing the P. falciparum growth as well as artemisinin sensitivity. Many ROS inducing RBC polymorphisms, such as sickle cell, thalassemia, G6PD deficiency, PMCA4b variations etc. have emerged as strong malaria protective traits in several studies in malaria endemic areas. But these traits could also influence artemisinin resistance and can serve as potential biomarkers for predicting therapeutic response and highlights the importance of host erythrocytes oxidative microenvironment surveillance in monitoring antimalarial drug resistance.