NATURAL HEMOZOIN AND Plasmodium INFECTION INDUCE LOWER PLATELET COUNT AND DYSMEGAKARYOPOIESIS IN EXPERIMENTAL MALARIA

When Plasmodium ssp. is inside the erythrocytes, it uses the globin portion of hemoglobin for its nutrition and converts the heme portion into hemozoin crystals as a detoxification method. Hemozoin (HZ) is released in the circulation during erythrocyte lysiscontributing to inflammation, tissue damage and cell activation. Our group has shown that HZ induces platelet death through ER-stress-induced apoptosis and ferroptosis as well as induces platelet activation in vitro. This current work aims to address the impact of HZ crystals in platelets and megakaryocytes (MKS) in vivo. For this, CD57B/6 mice received by intraocular route 750 ug of natural HZ for 6 hours before euthanasia. The results were compared to the control (PBS 1x injection) and Plasmodium berghei NK65 (PbN) infected mice (at day 6 post-infection). We observed, through flow cytometry, that in the peripheral circulation, both HZ injection and infection induce a drop in the platelet count and platelet activation. In both models, there are more platelets in the spleen and thymus, whereas the infection induces a reduction in platelets in the liver and lungs. We observed that in both models there was increase median platelet volume and size parameters of platelets, suggesting alterations in the production of these cells. We found that during the infection, there are more MKS in the bone marrow (BM) and both models induce a reduction in the MKS ploidy and present more activated platelets in the BM environment. Our results further suggest that the alterations in platelet count in the circulation and BM may not be driven by changes in trombopoitin (TPO) expression. Finally, we observed higher expression of IL-1β, TNF-α and IFN-Ɣ in the BM environment, which can contribute to aberrant thrombopoiesis. Together, the results suggest that Hz, as well as PbN infection, is able to induce platelet activation and desmegakaryopiesis in vivo, which contributes for the thrombocytopenia seen during malaria infection