Differential activity of methylene blue against erythrocytic and hepatic stages of Plasmodium

Henriette Bosson-Vanga,Olaf Müller,Olivier Silvie,Jean-François Franetich,Bocar Kane,Dominique Mazier,Valérie Soulard,Jean-Christophe Vaillant,Steffen Borrmann,Daniel Sossau,Nathalie Dereuddre-Bosquet,Maurel Tefit,Roger Le Grand

doi:10.1186/s12936-018-2300-y

Abstract

BackgroundIn the context of malaria elimination/eradication, drugs that are effective against the different developmental stages of the parasite are highly desirable. The oldest synthetic anti-malarial drug, the thiazine dye methylene blue (MB), is known for its activity against Plasmodium blood stages, including gametocytes. The aim of the present study was to investigate a possible effect of MB against malaria parasite liver stages.MethodsMB activity was investigated using both in vitro and in vivo models. In vitro assays consisted of testing MB activity on Plasmodium falciparum, Plasmodium cynomolgi and Plasmodium yoelii parasites in human, simian or murine primary hepatocytes, respectively. MB in vivo activity was evaluated using intravital imaging in BALB/c mice infected with a transgenic bioluminescent P. yoelii parasite line. The transmission-blocking activity of MB was also addressed using mosquitoes fed on MB-treated mice.ResultsMB shows no activity on Plasmodium liver stages, including hypnozoites, in vitro in primary hepatocytes. In BALB/c mice, MB has moderate effect on P. yoelii hepatic development but is highly effective against blood stage growth. MB is active against gametocytes and abrogates parasite transmission from mice to mosquitoes.ConclusionWhile confirming activity of MB against both sexual and asexual blood stages, the results indicate that MB has only little activity on the development of the hepatic stages of malaria parasites.

Highlights

In the context of malaria elimination/eradication, drugs that are effective against the different develop‐ mental stages of the parasite are highly desirable
In vitro activity against Plasmodium liver stages methylene blue (MB) was tested at concentrations ranging from 0.02 to 100 μM on primary murine, human and simian hepatocytes infected, respectively, with P. yoelii, P. falciparum and P. cynomolgi
MB and PQ (Fig. 1) cytotoxicity was evaluated by assessing cell confluence and number of DAPI-positive hepatocytes after drug treatment and antimalarial activity was evaluated by counting exo-erythrocytic forms (EEFs) (Figs. 2 and 3)

Summary

Introduction

In the context of malaria elimination/eradication, drugs that are effective against the different develop‐ mental stages of the parasite are highly desirable. The oldest synthetic anti-malarial drug, the thiazine dye methylene blue (MB), is known for its activity against Plasmodium blood stages, including gametocytes. The aim of the present study was to investigate a possible effect of MB against malaria parasite liver stages. Malaria remains a major cause of morbidity and mortality in many regions of the world [1]. In 2016 the World Health Organization estimated a total of 212 million cases of malaria, which resulted in 429,000 deaths. Human malaria is caused by five different species of Plasmodium parasites. Due to the ability to rapidly develop drug resistance, Plasmodium parasites continue to be a major challenge for effective case management [3, 4]. Malaria parasites consist of several life cycle stages that have to be individually targeted to reach malaria elimination [5]

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