Beneficial effect of aurothiomalate on murine malaria

<p>Abstract</p> <p>Background</p> <p>Premature death of <it>Plasmodium</it>-infected erythrocytes is considered to favourably influence the clinical course of malaria. Aurothiomalate has previously been shown to trigger erythrocyte death or eryptosis, which is characterized by cell membrane scrambling leading to phosphatidylserine exposure at the cell surface. Phosphatidylserine-exposing cells are rapidly cleared from circulating blood. The present study thus tested whether sodium aurothiomalate influences the intraerythrocytic parasite development <it>in vitro </it>and the clinical course of murine malaria <it>in vivo</it>.</p> <p>Methods</p> <p>Human erythrocytes were infected with <it>Plasmodium falciparum </it>BinH <it>in vitro </it>and mice were infected (intraperitoneal injection of 1 × 10⁶parasitized murine erythrocytes) with <it>Plasmodium berghei </it>ANKA <it>in vivo</it>.</p> <p>Results</p> <p>Exposure to aurothiomalate significantly decreased the <it>in vitro </it>parasitemia of <it>P. falciparum</it>-infected human erythrocytes without influencing the intraerythrocytic DNA/RNA content. Administration of sodium aurothiomalate <it>in vivo </it>(daily 10 mg/kg b.w. s.c. from the 8^thday of infection) enhanced the percentage of phosphatidylserine-exposing infected and noninfected erythrocytes in blood. All nontreated mice died within 30 days of infection. Aurothiomalate-treatment delayed the lethal course of malaria leading to survival of more than 50% of the mice 30 days after infection.</p> <p>Conclusions</p> <p>Sodium aurothiomalate influences the survival of <it>Plasmodium berghei</it>-infected mice, an effect only partially explained by stimulation of eryptosis.</p

Azathioprine favourably influences the course of malaria

<p>Abstract</p> <p>Background</p> <p>Azathioprine triggers suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and exposure of phosphatidylserine at the erythrocyte surface. Eryptosis may accelerate the clearance of <it>Plasmodium</it>-infected erythrocytes. The present study thus explored whether azathioprine influences eryptosis of <it>Plasmodium</it>-infected erythrocytes, development of parasitaemia and thus the course of malaria.</p> <p>Methods</p> <p>Human erythrocytes were infected <it>in vitro </it>with <it>Plasmodium falciparum (P. falciparum) </it>(strain BinH) in the absence and presence of azathioprine (0.001 – 10 μM), parasitaemia determined utilizing Syto16, phosphatidylserine exposure estimated from annexin V-binding and cell volume from forward scatter in FACS analysis. Mice were infected with <it>Plasmodium berghei (P. berghei) </it>ANKA by injecting parasitized murine erythrocytes (1 × 10⁶) intraperitoneally. Where indicated azathioprine (5 mg/kg b.w.) was administered subcutaneously from the eighth day of infection.</p> <p>Results</p> <p><it>In vitro </it>infection of human erythrocytes with <it>P. falciparum </it>increased annexin V-binding and initially decreased forward scatter, effects significantly augmented by azathioprine. At higher concentrations azathioprine significantly decreased intraerythrocytic DNA/RNA content (≥ 1 μM) and <it>in vitro </it>parasitaemia (≥ 1 μM). Administration of azathioprine significantly decreased the parasitaemia of circulating erythrocytes and increased the survival of <it>P. berghei</it>-infected mice (from 0% to 77% 22 days after infection).</p> <p>Conclusion</p> <p>Azathioprine inhibits intraerythrocytic growth of <it>P. falciparum</it>, enhances suicidal death of infected erythrocytes, decreases parasitaemia and fosters host survival during malaria.</p

Anti-malarial effect of gum arabic

<p>Abstract</p> <p>Background</p> <p>Gum Arabic (GA), a nonabsorbable nutrient from the exudate of <it>Acacia senegal</it>, exerts a powerful immunomodulatory effect on dendritic cells, antigen-presenting cells involved in the initiation of both innate and adaptive immunity. On the other hand GA degradation delivers short chain fatty acids, which in turn have been shown to foster the expression of foetal haemoglobin in erythrocytes. Increased levels of erythrocyte foetal haemoglobin are known to impede the intraerythrocytic growth of <it>Plasmodium </it>and thus confer some protection against malaria. The present study tested whether gum arabic may influence the clinical course of malaria.</p> <p>Methods</p> <p>Human erythrocytes were <it>in vitro </it>infected with <it>Plasmodium falciparum </it>in the absence and presence of butyrate and mice were <it>in vivo </it>infected with <it>Plasmodium berghei </it>ANKA by injecting parasitized murine erythrocytes (1 × 10⁶) intraperitoneally. Half of the mice received gum arabic (10% in drinking water starting 10 days before the day of infection).</p> <p>Results</p> <p>According to the <it>in vitro </it>experiments butyrate significantly blunted parasitaemia only at concentrations much higher (3 mM) than those encountered <it>in vivo </it>following GA ingestion (<1 μM). According to the <it>in vivo </it>experiments the administration of gum arabic slightly but significantly decreased the parasitaemia and significantly extended the life span of infected mice.</p> <p>Discussion</p> <p>GA moderately influences the parasitaemia and survival of <it>Plasmodium-</it>infected mice. The underlying mechanism remained, however, elusive.</p> <p>Conclusions</p> <p>Gum arabic favourably influences the course of murine malaria.</p

60kDa Lysophospholipase, a New Sgk1 Molecular Partner Involved in the Regulation of ENaC

The serum- and glucocorticoid-regulated kinase (Sgk1) is essential for hormonal regulation of ENaC-mediated sodium transport and is involved in the transduction of growth-factor-dependent cell survival and proliferation. The identification of molecular partners for Sgk1 is crucial for the understanding of its mechanisms of action. We performed a yeast two-hybrid screening based on a human kidney cDNA library to identify molecular partners of Sgk1. As a result the screening revealed a specific interaction between Sgk1 and a 60 kDa Lysophospholipase (LysoLP). LysoLP is a poorly characterized enzyme that, based on sequence analysis, might possess lysophospholipase and asparaginase activities. We demonstrate that LysoLP has indeed a lysophospholipase activity and affects metabolic functions related to cell proliferation and regulation of membrane channels. Moreover we demonstrate in the Xenopus oocyte expression system that LysoLP downregulates basal and Sgk1-dependent ENaC activity. In conclusion LysoLP may represent a new player in the regulation of ENaC and Sgk1-dependent signaling

Features of Muon Arrival Time Distributions of High Energy EAS at Large Distances From the Shower Axis

In view of the current efforts to extend the KASCADE experiment (KASCADE-Grande) for observations of Extensive Air Showers (EAS) of primary energies up to 1 EeV, the features of muon arrival time distributions and their correlations with other observable EAS quantities have been scrutinised on basis of high-energy EAS, simulated with the Monte Carlo code CORSIKA and using in general the QGSJET model as generator. Methodically various correlations of adequately defined arrival time parameters with other EAS parameters have been investigated by invoking non-parametric methods for the analysis of multivariate distributions, studying the classification and misclassification probabilities of various observable sets. It turns out that adding the arrival time information and the multiplicity of muons spanning the observed time distributions has distinct effects improving the mass discrimination. A further outcome of the studies is the feature that for the considered ranges of primary energies and of distances from the shower axis the discrimination power of global arrival time distributions referring to the arrival time of the shower core is only marginally enhanced as compared to local distributions referring to the arrival of the locally first muon.Comment: 24 pages, Journal Physics G accepte

Plasmodium falciparum-Infected Erythrocytes Induce Granzyme B by NK Cells through Expression of Host-Hsp70

In the early immune response to Plasmodium falciparum-infected erythrocytes (iRBC), Natural Killer (NK) cells are activated, which suggests an important role in innate anti-parasitic immunity. However, it is not well understood whether NK cells directly recognize iRBC or whether stimulation of NK cells depends mainly on activating signals from accessory cells through cell-to-cell contact or soluble factors. In the present study, we investigated the influence of membrane-bound host Heat shock protein (Hsp) 70 in triggering cytotoxicity of NK cells from malaria-naïve donors or the cell line NK92 against iRBC. Hsp70 and HLA-E membrane expression on iRBC and potential activatory NK cell receptors (NKG2C, CD94) were assessed by flow cytometry and immunoblot. Upon contact with iRBC, Granzyme B (GzmB) production and release was initiated by unstimulated and Hsp70-peptide (TKD) pre-stimulated NK cells, as determined by Western blot, RT-PCR and ELISPOT analysis. Eryptosis of iRBC was determined by Annexin V-staining. Our results suggest that presence of Hsp70 and absence of HLA-E on the membrane of iRBC prompt the infected host cells to become targets for NK cell-mediated cytotoxicity, as evidenced by impaired parasite development. Contact of iRBC with NK cells induced release of GzmB. We propose that following GzmB uptake, iRBC undergo eryptosis via a perforin-independent, GzmB-mediated mechanism. Since NK activity toward iRBC could be specifically enhanced by TKD peptide and abrogated to baseline levels by blocking Hsp70 exposure, we propose TKD as an innovative immunostimulatory agent to be tested as an adjunct to anti-parasitic treatments in vivo

Novel insights into the mechanisms mediating the local antihypertrophic effects of cardiac atrial natriuretic peptide: role of cGMP-dependent protein kinase and RGS2

Cardiac atrial natriuretic peptide (ANP) locally counteracts cardiac hypertrophy via the guanylyl cyclase-A (GC-A) receptor and cGMP production, but the downstream signalling pathways are unknown. Here, we examined the influence of ANP on β-adrenergic versus Angiotensin II (Ang II)-dependent (Gs vs. Gαq mediated) modulation of Ca2+i-handling in cardiomyocytes and of hypertrophy in intact hearts. L-type Ca2+ currents and Ca2+i transients in adult isolated murine ventricular myocytes were studied by voltage-clamp recordings and fluorescence microscopy. ANP suppressed Ang II-stimulated Ca2+ currents and transients, but had no effect on isoproterenol stimulation. Ang II suppression by ANP was abolished in cardiomyocytes of mice deficient in GC-A, in cyclic GMP-dependent protein kinase I (PKG I) or in the regulator of G protein signalling (RGS) 2, a target of PKG I. Cardiac hypertrophy in response to exogenous Ang II was significantly exacerbated in mice with conditional, cardiomyocyte-restricted GC-A deletion (CM GC-A KO). This was concomitant to increased activation of the Ca2+/calmodulin-dependent prohypertrophic signal transducer CaMKII. In contrast, β-adrenoreceptor-induced hypertrophy was not enhanced in CM GC-A KO mice. Lastly, while the stimulatory effects of Ang II on Ca2+-handling were absent in myocytes of mice deficient in TRPC3/TRPC6, the effects of isoproterenol were unchanged. Our data demonstrate a direct myocardial role for ANP/GC-A/cGMP to antagonize the Ca2+i-dependent hypertrophic growth response to Ang II, but not to β-adrenergic stimulation. The selectivity of this interaction is determined by PKG I and RGS2-dependent modulation of Ang II/AT1 signalling. Furthermore, they strengthen published observations in neonatal cardiomyocytes showing that TRPC3/TRPC6 channels are essential for Ang II, but not for β-adrenergic Ca2+i-stimulation in adult myocytes