Dihydroxyacetone and methylglyoxal as permeants of the Plasmodium aquaglyceroporin inhibit parasite proliferation

AbstractThe aquaglyceroporin of Plasmodium falciparum (PfAQP) is a bi-functional channel with permeability for water and solutes. Its functions supposedly are in osmotic protection of parasites and in facilitation of glycerol permeation for glycerolipid biosynthesis. Here, we show PfAQP permeability for the glycolysis-related metabolites methylglyoxal, a cytotoxic byproduct, and dihydroxyacetone, a ketotriose. AQP3, the red cell aquaglyceroporin, also passed dihydroxacetone but excluded methylglyoxal. Proliferation of malaria parasites was inhibited by methylglyoxal with an IC50 around 200 μM. Surprisingly, also dihydroxyacetone, which is an energy source in human cells, was antiproliferative in chloroquine-sensitive and resistant strains with an IC50 around 3 mM. We expressed P. falciparum glyceraldehyde 3-phosphate dehydrogenase (PfGAPDH) to examine whether it is inhibited by either carbonyl compound. Methylglyoxal did not affect PfGAPDH on incubation with 2.5 mM for 20 h. Treatment with 2.5 mM dihydroxyacetone, however, abolished PfGAPDH activity within 6 h. Aquaglyceroporin permeability for glycolytic metabolites may thus be of physiological significance

Analysis of the CCR5 gene coding region diversity in five South American populations reveals two new non-synonymous alleles in Amerindians and high CCR5*D32 frequency in Euro-Brazilians

The CC chemokine receptor 5 (CCR5) molecule is an important co-receptor for HIV. The effect of the CCR5*D32 allele in susceptibility to HIV infection and AIDS disease is well known. Other alleles than CCR5*D32 have not been analysed before, neither in Amerindians nor in the majority of the populations all over the world. We investigated the distribution of the CCR5 coding region alleles in South Brazil and noticed a high CCR5*D32 frequency in the Euro-Brazilian population of the Paraná State (9.3%), which is the highest thus far reported for Latin America. The D32 frequency is even higher among the Euro-Brazilian Mennonites (14.2%). This allele is uncommon in Afro-Brazilians (2.0%), rare in the Guarani Amerindians (0.4%) and absent in the Kaingang Amerindians and the Oriental-Brazilians. R223Q is common in the Oriental-Brazilians (7.7%) and R60S in the Afro-Brazilians (5.0%). A29S and L55Q present an impaired response to β-chemokines and occurred in Afro- and Euro-Brazilians with cumulative frequencies of 4.4% and 2.7%, respectively. Two new non-synonymous alleles were found in Amerindians: C323F (g.3729G > T) in Guarani (1.4%) and Y68C (g.2964A > G) in Kaingang (10.3%). The functional characteristics of these alleles should be defined and considered in epidemiological investigations about HIV-1 infection and AIDS incidence in Amerindian populations

Molecular characterization of regulatory polymorphisms in the promoter region of the STAT6 gene in a Gabonese population

Parasites remain competent invaders of host immunity. Their invasion strategies have proven to impact immunorelevant genes leading to diversity among gene families. We focussed on signal transducer and activator of transcription (STAT6) factor that plays a fundamental role in signal transduction and activation of transcription. Recent studies have highlighted the role of STAT6 variants in control of infection levels. We identified and investigated regulatory single nucleotide polymorphisms (SNPs) in the promoter regions of the STAT6 gene in a group of Gabonese individuals exposed to a variety of parasitic infections. Three promoter variants were identified in 40 individual subjects. We further validated these promoter variants for their allelic gene expression using transient transfection assays. One promoter variant, rs3024944 (G/C), revealed an altered expression of the marker gene. The identification of function-altering SNPs in the promoter may facilitate studying parasite susceptibility in association studies

The blood transcriptome of childhood malariaResearch in context

Background: Transcriptomic research of blood cell lineages supports the understanding of distinct features of the immunopathology in human malaria. Methods: We used microarray hybridization, validated by real-time RT-PCR to analyze whole blood gene expression in healthy Gabonese children and children with various conditions of Plasmodium falciparum infection, including i) asymptomatic infection, ii) uncomplicated malaria, iii) malaria associated with severe anemia and iv) cerebral malaria. Findings: Our data indicate that the expression profile of 22 genes significantly differed among the investigated groups. Immunoglobulin production, complement regulation and IFN beta signaling, in particular IRF7 and ISRE binding signatures in the corresponding genes, were most conspicuous. Down-regulation in cerebral malaria seems to rely on AhRF, GABP and HIF1 hypoxia transcription factors. ARG1, BPI, CD163, IFI27, HP and TNFAIP6 transcript levels correlated positively with lactatemia, and negatively with hemoglobin concentrations. Interpretation: Differences in gene expression profile reflect distinct immunopathological mechanisms of P. falciparum infection. They emerge as potential prognostic markers for early therapeutic measures and need to be validated further. Fund: This work was supported by a grant of the NGFN (Nationales Genomforschungsnetz 01GS0114) and by a CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil) PhD scholarship for A. B. W. Boldt. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Keywords: Uncomplicated malaria, Severe malaria, Cerebral malaria, Transcriptome, Plasmodium falciparum, Microarray, Gabo