Human Microglia Respond to Malaria-Induced Extracellular Vesicles.

Smart Ikechukwu Mbagwu,Nils Lannes,Michael Walch,Pierre-Yves Mantel,Luis Filgueira

doi:10.3390/pathogens9010021

Abstract

Microglia are the chief immune cells of the brain and have been reported to be activated in severe malaria. Their activation may drive towards neuroinflammation in cerebral malaria. Malaria-infected red blood cell derived-extracellular vesicles (MiREVs) are produced during the blood stage of malaria infection. They mediate intercellular communication and immune regulation, among other functions. During cerebral malaria, the breakdown of the blood–brain barrier can promote the migration of substances such as MiREVs from the periphery into the brain, targeting cells such as microglia. Microglia and extracellular vesicle interactions in different pathological conditions have been reported to induce neuroinflammation. Unlike in astrocytes, microglia–extracellular vesicle interaction has not yet been described in malaria infection. Therefore, in this study, we aimed to investigate the uptake of MiREVs by human microglia cells and their cytokine response. Human blood monocyte-derived microglia (MoMi) were generated from buffy coats of anonymous healthy donors using Ficoll-Paque density gradient centrifugation. The MiREVs were isolated from the Plasmodium falciparum cultures. They were purified by ultracentrifugation and labeled with PKH67 green fluorescent dye. The internalization of MiREVs by MoMi was observed after 4 h of co-incubation on coverslips placed in a 24-well plate at 37 °C using confocal microscopy. Cytokine-gene expression was investigated using rt-qPCR, following the stimulation of the MoMi cells with supernatants from the parasite cultures at 2, 4, and 24 h, respectively. MiREVs were internalized by the microglia and accumulated in the perinuclear region. MiREVs-treated cells increased gene expression of the inflammatory cytokine TNFα and reduced gene expression of the immune suppressive IL-10. Overall, the results indicate that MiREVs may act on microglia, which would contribute to enhanced inflammation in cerebral malaria.

Highlights

Malaria remains a global health burden, despite constant efforts channeled to its eradication.The disease is caused by the plasmodium parasite of different species, with Plasmodium falciparum (P. falciparum) being predominant and the most virulent [1]
Malaria-infected red blood cell derived-extracellular vesicles (MiREVs) uptake by endothelial cells has been reported by Mantel et al [19] and shown to contribute to alteration in barrier properties of these cells, indicating MiREVs’ potential effect in the disruption of the blood–brain barrier (BBB), which could lead to increased vascular permeability
In order to achieve this, we treated monocyte-derived microglia (MoMi) cells generated from the peripheral blood mononuclear cells with PKH67 fluorescent green dye-labeled MiREVs derived from red blood cells infected with

Summary

Introduction

Malaria remains a global health burden, despite constant efforts channeled to its eradication. The disease is caused by the plasmodium parasite of different species, with Plasmodium falciparum (P. falciparum) being predominant and the most virulent [1]. According to the World Health Organization (WHO) [2], 216 million malaria cases have been recorded annually, with approximately 500 thousand deaths due to malaria infection. Sub-Saharan Africa bears the greatest burden of malaria infection. Preventive measures have been promoted in the management of the disease, in addition to formulation of therapeutics, there have been limitations to achieve eradication due to widespread drug resistance as a result of parasite genetic factors [3,4,5,6].

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