scholarly journals Chloroquine Potentiates Primaquine Activity against Active and Latent Hepatic Plasmodia Ex Vivo: Potentials and Pitfalls

2020 ◽  
Vol 65 (1) ◽  
pp. e01416-20
Author(s):  
Laurent Dembélé ◽  
Jean-François Franetich ◽  
Valérie Soulard ◽  
Nadia Amanzougaghene ◽  
Shahin Tajeri ◽  
...  
Keyword(s):  
Cell Line ◽  
Ex Vivo ◽  
Plasmodium Yoelii ◽  
Human Hepatocytes ◽  
Dependent Manner ◽  
Primary Hepatocytes ◽  
Content Type ◽  
Primary Human Hepatocytes ◽  
Hepatocarcinoma Cell ◽  
Hepatocarcinoma Cell Line

ABSTRACTFor a long while, 8-aminoquinoline compounds have been the only therapeutic agents against latent hepatic malaria parasites. These have poor activity against the blood-stage plasmodia causing acute malaria and must be used in conjunction with partner blood schizontocidal agents. We examined the impacts of one such agent, chloroquine, upon the activity of primaquine, an 8-aminoquinoline, against hepatic stages of Plasmodium cynomolgi, Plasmodium yoelii, Plasmodium berghei, and Plasmodium falciparum within several ex vivo systems—primary hepatocytes of Macaca fascicularis, primary human hepatocytes, and stably transformed human hepatocarcinoma cell line HepG2. Primaquine exposures to formed hepatic schizonts and hypnozoites of P. cynomolgi in primary simian hepatocytes exhibited similar 50% inhibitory concentration (IC50) values near 0.4 μM, whereas chloroquine in the same system exhibited no inhibitory activities. Combining chloroquine and primaquine in this system decreased the observed primaquine IC50 for all parasite forms in a chloroquine dose-dependent manner by an average of 18-fold. Chloroquine also decreased the primaquine IC50 against hepatic P. falciparum in primary human hepatocytes, P. berghei in simian primary hepatocytes, and P. yoelii in primary human hepatocytes. Chloroquine had no impact on primaquine IC50 against P. yoelii in HepG2 cells and, likewise, had no impact on the IC50 of atovaquone (hepatic schizontocide) against P. falciparum in human hepatocytes. We describe important sources of variability in the potentiation of primaquine activity by chloroquine in these systems. Chloroquine potentiated primaquine activity against hepatic forms of several plasmodia. We conclude that chloroquine specifically potentiated 8-aminoquinoline activities against active and dormant hepatic-stage plasmodia in normal primary hepatocytes but not in a hepatocarcinoma cell line.

scholarly journals Immunization with the MAEBL M2 Domain Protects against Lethal Plasmodium yoelii Infection

2015 ◽  
Vol 83 (10) ◽  
pp. 3781-3792 ◽  
Author(s):  
Juliana A. Leite ◽  
Daniel Y. Bargieri ◽  
Bruna O. Carvalho ◽  
Letusa Albrecht ◽  
Stefanie C. P. Lopes ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Plasmodium Yoelii ◽  
Parasite Development ◽  
Effective Vaccine ◽  
Dependent Manner ◽  
Content Type ◽  
Apical Membrane Antigen 1 ◽  
Erythrocyte Invasion ◽  
Erythrocyte Binding ◽  
Native Antigen

Malaria remains a world-threatening disease largely because of the lack of a long-lasting and fully effective vaccine. MAEBL is a type 1 transmembrane molecule with a chimeric cysteine-rich ectodomain homologous to regions of the Duffy binding-like erythrocyte binding protein and apical membrane antigen 1 (AMA1) antigens. Although MAEBL does not appear to be essential for the survival of blood-stage forms, ectodomains M1 and M2, homologous to AMA1, seem to be involved in parasite attachment to erythrocytes, especially M2. MAEBL is necessary for sporozoite infection of mosquito salivary glands and is expressed in liver stages. Here, thePlasmodium yoeliiMAEBL-M2 domain was expressed in a prokaryotic vector. C57BL/6J mice were immunized with doses ofP. yoeliirecombinant protein rPyM2-MAEBL. High levels of antibodies, with balanced IgG1 and IgG2c subclasses, were achieved. rPyM2-MAEBL antisera were capable of recognizing the native antigen. Anti-MAEBL antibodies recognized different MAEBL fragments expressed in CHO cells, showing stronger IgM and IgG responses to the M2 domain and repeat region, respectively. After a challenge withP. yoeliiYM (lethal strain)-infected erythrocytes (IE), up to 90% of the immunized animals survived and a reduction of parasitemia was observed. Moreover, splenocytes harvested from immunized animals proliferated in a dose-dependent manner in the presence of rPyM2-MAEBL. Protection was highly dependent on CD4+, but not CD8+, T cells toward Th1. rPyM2-MAEBL antisera were also able to significantly inhibit parasite development, as observed inex vivoP. yoeliierythrocyte invasion assays. Collectively, these findings support the use of MAEBL as a vaccine candidate and open perspectives to understand the mechanisms involved in protection.

scholarly journals In VitroAnalysis of the Interaction between Atovaquone and Proguanil against Liver Stage Malaria Parasites

2016 ◽  
Vol 60 (7) ◽  
pp. 4333-4335 ◽  
Author(s):  
Lídia Barata ◽  
Pascal Houzé ◽  
Khadija Boutbibe ◽  
Gigliola Zanghi ◽  
Jean-François Franetich ◽  
...  
Keyword(s):  
Plasmodium Yoelii ◽  
Human Hepatocytes ◽  
High Efficacy ◽  
Liver Stage ◽  
Content Type ◽  
Cytochrome P450 Activity ◽  
Main Target ◽  
P450 Activity ◽  
Pharmacological Basis

ABSTRACTThe interaction between atovaquone and proguanil has never been studied against liver stage malaria, which is the main target of this drug combination when used for chemoprevention. Using human hepatocytes lacking cytochrome P450 activity, and thus avoiding proguanil metabolizing into potent cycloguanil, we showin vitrothat the atovaquone-proguanil combination synergistically inhibits the growth of rodentPlasmodium yoeliiparasites. These results provide a pharmacological basis for the high efficacy of atovaquone-proguanil used as malaria chemoprevention.

scholarly journals Klebsiella pneumoniae Expressing VIM-1 Metallo-β-Lactamase Is Resensitized to Cefotaxime via Thiol-Mediated Zinc Chelation

2019 ◽  
Vol 88 (1) ◽  
Author(s):  
Harpa Karadottir ◽  
Maarten Coorens ◽  
Zhihai Liu ◽  
Yang Wang ◽  
Birgitta Agerberth ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Ex Vivo ◽  
Reductase Activity ◽  
Urine Samples ◽  
Dependent Manner ◽  
Content Type ◽  
Endogenous Factors ◽  
Reducing Ability ◽  
Zinc Chelation ◽  
Ht 29

ABSTRACT Antibiotic-resistant Klebsiella pneumoniae isolates constitute a great clinical challenge. One important resistance mechanism in K. pneumoniae is the metallo-β-lactamases (MBLs), which require zinc for their function. Thus, zinc chelation could be a strategy to resensitize K. pneumoniae to β-lactams. However, the potential role for endogenous zinc chelators for this purpose remains to be explored. The aim was to search for endogenous factors that could resensitize MBL-expressing K. pneumoniae to cefotaxime (CTX). Clinical K. pneumoniae isolates expressing different MBLs were screened for sensitivity to CTX in supernatants from human HT-29 colonic epithelial cells. Factors influencing CTX susceptibility were isolated and identified with chromatographic and biochemical methods. Free zinc was measured with a Zinquin assay, the thiol content was assessed with a fluorometric thiol assay, and the reducing ability of the supernatant was measured with a fluorescent l-cystine probe. Urine samples from healthy volunteers were used to validate findings ex vivo. VIM-1-expressing K. pneumoniae regained susceptibility to CTX when grown in supernatants from HT-29 cells. This effect was mediated via free thiols in the supernatant, including l-cysteine, and could be prevented by inhibiting thioredoxin reductase activity in the supernatant. Free thiols in urine samples appeared to have a similar function in restoring CTX activity against VIM-1-expressing K. pneumoniae in a zinc-dependent manner. We have identified l-cysteine as an endogenous zinc chelator resulting in the resensitization of VIM-1-expressing K. pneumoniae to CTX. These results suggest that natural zinc chelators in combination with conventional antibiotics could be used to treat infections caused by VIM-1-expressing pathogens.

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