Zamri, Noor Hafizah Mohd
(2018)
The feeding process of Plasmodium falciparum in resealed erythrocytes containing endocytic markers and its role in artemisinin action.
Masters thesis, Universiti Sains Malaysia.
Abstract
Haemoglobin metabolism during the intraerythrocytic stage of the
malaria parasite, Plasmodium falciparum is a preferable target for artemisinin, which
is widely used for treatment and control of malaria. It has previously been reported
that the parasite ingests haemoglobin via mouth-like structures named cytostomes.
Haemoglobin-containing vesicles that bud off from cytostomes are transported to the
digestive vacuole (DV) where the haemoglobin is degraded. However, the details of
endocytic process as well as how artemisinin affects this process are still debatable.
Hence, in this study we re-examined the endocytic process of the parasite and
observed the effect of artemisinin on this process by using an endocytic marker,
tetramethylrhodamine-dextran (TMR-dextran) and a pH indicator, Lysosensor Blue
(LB) and SNARF-1-dextran. Resealed erythrocytes containing TMR-dextran were
prepared at an optimised ratio of 1:3 of erythrocytes to haemolysis buffer volume.
The resealed erythrocytes permitted retention of 33.56 ± 7.84% of the original
haemoglobin contents and showed comparable parasite‟s invasion efficiency to
normal erythrocytes. An early endocytic event of the parasites was initiated at mid
ring stage with appearance of typical small endocytic compartments and a large
spherical structure termed as a “big gulp”. An acidic DV concentrated with TMRdextran
and labelled with LB, appeared at the later stages of trophozoite and
schizont. Artemisinin treatments on this process showed no modification on thehaemoglobin intake by the parasite and no alterations of the LB label and SNARF-1-
dextran of the DV indicating no major pH changes of the vacuole. In conclusion,
haemoglobin is ingested by the parasite at early intraerythrocytic stage and
accumulated in the acidic DV where the vacuole showed no significant pH
alterations upon the artemisinin treatments.
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