Marvin Haag (Heidelberg / DE), Jessica Kehrer (Heidelberg / DE), Cecilia Sanchez (Heidelberg / DE), Prof. Dr. Marcel Deponte (Kaiserslautern / DE; Heidelberg / DE), Prof. Dr. Michael Lanzer (Heidelberg / DE)
Abstract text
1. Introduction
The redox state of the host-parasite unit has been hypothesized to play a central role for the fitness of the intraerythrocytic blood stages of the human malaria parasite Plasmodium falciparum. In particular, hemoglobinopathies have been suggested to cause a more oxidizing environment, thereby protecting from severe malaria.
2. Objectives
We wanted to determine the redox state of the host-parasite unit during P. falciparum blood-stage development in wild-type (hemoglobin AA) or sickle trait (hemoglobin AS) erythrocytes.
3. Materials & Methods
We used parasite-encoded targeted variants of the redox-sensitive green-fluorescent protein 2 (roGFP2) for stage-dependent confocal microscopy redox measurements in wild-type or sickle trait erythrocytes.
4. Results
Our roGFP2 single-cell measurements revealed a reducing steady-state redox potential of −304 ± 11 mV for the erythrocyte cytosol during ring-stage development and a rather sudden oxidation to −278 ± 12 mV during trophozoite-stage development around 28 h post invasion. There was no significant difference between wild-type or sickle trait erythrocytes regarding the stage dependence and the detected increase of the redox potential during the intraerythrocytic life cycle. The steady-state redox potential of the parasite cytosol, between −304 and −313 mV, was highly reducing throughout the life cycle. The redox potential in the parasitophorous vacuole at the interface between the secretory pathway and the erythrocyte was −284 ± 10 mV and remained stable during trophozoite-stage development with implications for the export of disulfide-containing proteins.
5. Conclusion
Non-invasive roGFP2 measurements revealed a much more reducing steady-state redox potential of the erythrocyte and parasite cytosol than deduced from invasive glutathione measurements. Parasite-dependent modifications of its host cell result in a physiological +30 mV jump in erythrocyte redox potential during trophozoite-stage development that can be explained by a drastic efflux of reduced glutathione. Most important, there was no difference between the stage-dependent steady-state redox potentials of infected wild-type or sickle trait erythrocytes in contrast to the often iterated hypothesis that so-called oxidative stress protects from malaria [1].
[1] Haag M et al. 2022 Redox Biol 58: 102536.