Biomedical subjects

Donatella Taramelli

Publications and source records attributed to Donatella Taramelli.

At least 19 recordsLinked to original sources

PubMed2006

High antiplasmodial activity of novel plasmepsins I and II inhibitors.

The aim of this study was to develop new antiplasmodial compounds acting through distinct mechanisms during both the liver and the blood stages of the parasite life cycle. Compounds were designed on the basis of the "double-drug" approach: primaquine, which has been linked to statine-based inhibitors of plasmepsins (PLMs), the plasmodial aspartic proteases involved in degradation of hemeoglobin. The compounds were tested in vitro for anti-PLM I/PLM II activities and against chloroquine-sensitive (D10) and chloroquine-resistant (W2) strains of P. falciparum. An antiplasmodial activity (IC(50)) as low as 0.1 microM was obtained, an excellent improvement in comparison with inhibitors previously reported (IC(50) = 2-20 microM). The killing activity was equally directed against both P. falciparum strains and was correlated to lipophilicity (calculated as ALogP), for all compounds but one (9). All compounds inhibited PLM I and PLM II in the nanomolar range (K(i) = 1-700 nM). The most promising compounds (2, 6, 10) were not cytotoxic against human fibroblasts at 100 microM and were highly selective for PLMs vs human cathepsin D.

Aminoquinolines↗

PubMed2006

Endoperoxide derivatives from marine organisms: 1,2-dioxanes of the plakortin family as novel antimalarial agents.

Plakortin (1) is a remarkably simple 1,2-dioxane derivative, extracted from the marine sponge Plakortis simplex, showing a submicromolar activity against chloroquine-resistant strains of Plasmodium falciparum. Using plakortin as a novel antimalarial hit, we have prepared a series of semisynthetic derivatives in order to gain insights into the structural requirements of simple 1,2-dioxanes for exhibiting antimalarial activity. Their synthesis, spectroscopic and computational analysis, and in vitro antimalarial activity are herein reported. Results obtained, besides confirming the crucial role of the cycloperoxide functionality, revealed other structural features critical for antimalarial activity, namely the "Western" alkyl side chain, the dioxane ring conformation, and the absolute configuration of the stereogenic carbons on the 1,2-dioxane ring, when affecting the bioactive ring conformation.

Animals↗

PubMed2006

Synthesis of N1-arylidene-N2-quinolyl- and N2-acrydinylhydrazones as potent antimalarial agents active against CQ-resistant P. falciparum strains.

A series of N1-arylidene-N2-quinolyl- and N2-acrydinylhydrazones were synthesized and tested for their antimalarial properties. These compounds showed remarkable anti-plasmodial activity in vitro especially against chloroquine-resistant strains. Their potent biological activity makes them promising lead structures for the development of new antimalarial drugs.

Animals↗

PubMed2006

[Molecular epidemiology of imported malaria in Italy: the use of genetic markers and in vitro sensitivity test in a study of chloroquine resistance in Plasmodium falciparum].

The emergence of Plasmodium falciparum drug-resistance, especially chloroquine resistance, represents one of the main obstacles to the control of malaria. Several studies have shown that in P. falciparum the mechanism of chloroquine resistance is linked to specific point mutations in the pfcrt gene of the parasite. In the present study we have analyzed 120 Italian imported malaria cases to evaluate the prevalence of 76T and 220S mutantions in the pfcrt gene. Moreover, the correlation between the presence of pfcrt point mutations and in vitro chloroquine resistance has been evaluated on 25 plasmodial isolates. The results showed a high prevalence of the pfcrt point mutations in isolates analyzed and a significant association between point mutations and in vitro chloroquine resistance. Molecular screening on imported malaria cases can be a useful tool to be employed in surveillance activity and also in monitoring the development and spread of drug resistance in endemic areas.

Adolescent↗

PubMed2005

Damicoside from Axinella damicornis: the influence of a glycosylated galactose 4-OH group on the immunostimulatory activity of alpha-galactoglycosphingolipids.

Alpha-galactoglycosphingolipids (alpha-GalGSLs) are unique immunostimulatory glycosphingolipids from marine sponges. Analysis of the glycosphingolipid composition of the marine sponge Axinella damicornis revealed the presence of a new alpha-GalGSL, damicoside (3a), which is the first alpha-GalGSL with a glycosylated galactose 4-OH group. Structure elucidation of damicoside was performed using spectroscopic and chemical methods. When tested in a spleen cell proliferation assay, 3a exhibited a stimulatory activity comparable to that of agelasphin (2), showing that a free galactose 4-OH group is not essential for the immunostimulatory activity of alpha-GalGSLs and providing a further step toward the complete understanding of their structure-activity relationship.

Adjuvants, Immunologic↗

PubMed2005

High-density lipoproteins attenuate interleukin-6 production in endothelial cells exposed to pro-inflammatory stimuli.

The purpose of the present study was to investigate the ability of high-density lipoproteins (HDL) to attenuate endothelial dysfunction, by assessing down-regulation of cytokine-induced interleukin-6 (IL-6) production in cultured endothelial cells, and measuring plasma IL-6 levels in three groups of healthy individuals with low, average, or high plasma HDL-cholesterol. Human plasma HDL caused a concentration-dependent inhibition of TNFalpha-induced IL-6 production in human endothelial cells (by 58.5+/-1.5% at 2 mg of HDL-protein/ml). Reconstituted HDL made with apolipoprotein A-I (apoA-I) and phosphatidylcholine were as effective as plasma HDL, while lipid-free apoA-I or phosphatidylcholine liposomes had no effect. HDL attenuated IL-6 mRNA levels, an effect which occurs through inhibition of p38 MAP kinase. The median plasma IL-6 concentration was significantly higher in subjects with low HDL-cholesterol (2.54 pg/ml) compared with those with average or high HDL-cholesterol (1.31 pg/ml and 1.47 pg/ml, respectively). When all subjects were considered together, a lower HDL-cholesterol was the strongest independent predictor of higher IL-6 (F=25.38, P<0.001). By inhibiting IL-6 production and lowering plasma IL-6 concentration, HDL may limit the pro-atherogenic effects of both acute and chronic inflammatory states, of which IL-6 is a key orchestrator.

Cells, Cultured↗

PubMed2005

4-Aminoquinoline quinolizidinyl- and quinolizidinylalkyl-derivatives with antimalarial activity.

A set of quinolizidinyl and quinolizidinylalkyl derivatives of 4-amino-7-chloroquinoline and of 9-amino-6-chloro-2-methoxyacridine were prepared and tested in vitro against CQ-sensitive (D-10) and CQ-resistant (W-2) strains of Plasmodium falciparum. All compounds but one exerted significant antimalarial activity. Some of the quinolizidine derivatives were from 5 to 10 times more active than chloroquine on the CQ-resistant strain. No toxicity against mammalian cells was observed.

Aminoquinolines↗

PubMed2005

Regulation of human erythrocyte glyceraldehyde-3-phosphate dehydrogenase by ferriprotoporphyrin IX.

Erythrocyte glyceraldehyde-3-phosphate dehydrogenase (G3PD) is a glycolytic enzyme containing critical thiol groups and whose activity is reversibly inhibited by binding to the cell membrane. Here, we demonstrate that the insertion of ferriprotoporphyrin IX (FP) into the red cell membranes exerts two opposite effects on membrane bound G3PD. First, the enzyme is partially inactivated through oxidation of critical thiols. Dithiothreitol restores part of the activity, but some critical thiols are irreversibly oxidized or crosslinked to products of FP-induced lipid peroxidation. Second, G3PD binding to the membrane is modified and the enzyme is activated through displacement into the cytosol and/or release from its binding site.

Cell Membrane↗

PubMed2005

Prevalence of pfcrt point mutations and level of chloroquine resistance in Plasmodium falciparum isolates from Africa.

The development in Plasmodium falciparum of the resistance to chloroquine (CQ) constitutes a public health priority, due to its direct influence in childhood mortality. The molecular basis for CQ resistance (CQR) is still unclear but, recently, a new relevant gene, named pfcrt, with several point mutations was identified in P. falciparum. Two mutations, K76T and A220S, have been considered crucial for CQR in further studies, making the pfcrt a good candidate as determinant for CQR in P. falciparum. To contribute to this topic, we have undertaken a molecular screening on 164 P. falciparum isolates from Africa: 120 isolates were Italian imported malaria cases, 27 and 17 isolates were from a school-children survey from Congo and Tanzania, respectively. In vitro tests (pLDH and WHO-Mark III tests) for CQ sensitivity have been also carried out on 28 plasmodial isolates and results compared to those obtained by molecular analysis in the same isolates. The SVIET pfcrt haplotype has been identified in the samples from Congo, and this is the first time that this haplotype is detected in Africa. Our results give further evidence to the reliability of the 76T (and the linked 74I-75E) pfcrt point mutation as molecular marker for CQR.

Adolescent↗

PubMed2005

Synthesis and antimalarial activities of some furoxan sulfones and related furazans.

Furoxan derivatives bearing a sulfone moiety at position 3 or 4 were synthesized and tested for their antimalarial action on the chloroquine-sensitive D10 and the chloroquine-resistant W2 strains of Plasmodium falciparum. The furazan analogues were considered for comparison. The most active compounds were the products in which the -SO2R groups are at the 3-position of the furoxan system. These latter substances displayed an antimalarial activity in the microM range, possibly related in part to their ability to release NO.

Animals↗

PubMed2005

Synthesis of some cryptolepine analogues, assessment of their antimalarial and cytotoxic activities, and consideration of their antimalarial mode of action.

A series of analogues of cryptolepine (1) have been synthesized and evaluated for their in vitro antiplasmodial and cytotoxic properties. The IC(50) values of several compounds (11a, 11k-m, 11o, 13) against Plasmodium falciparum (strain K1) were <0.1 muM, 5-10-fold lower than that of 1 but their cytotoxicities were only 2-4 times greater than that of 1. Compounds with a halogen in the quinoline ring and a halogen or a nitro group in the indole ring have enhanced antiplasmodial activity. In mice infected with P. berghei, the 7-bromo-2-chloro (11k) and 2-bromo-7-nitro (13) derivatives of 1 suppressed parasitemia by >90% at doses of 25 mg kg(-1) day(-1) with no apparent toxicity to the mice. 2,7-Dibromocryptolepine (15) was evaluated at several dose levels, and a dose-dependent suppression of parasitemia was seen (ED(90) = 21.6 mg kg(-1) day(-1)). The antimalarial mode of action of 1 appears to be similar to that of chloroquine and involves the inhibition of hemozoin formation. A number of analogues were assessed for their effects on the inhibition of beta-hematin (hemozoin) formation, and the results were compared with their antiplasmodial activities having taken account of their predicted accumulation into the acidic parasite food vacuole. No correlation was seen (r(2) = 0.0781) suggesting that the potent antimalarial activity of compounds such as 15 involves other mechanisms in addition to the inhibition of hemozoin formation.

Algorithms↗

PubMed2005

Destabilisation and subsequent lysis of human erythrocytes induced by Plasmodium falciparum haem products.

In falciparum malaria, both infected and uninfected red cells have structural and functional alterations. To investigate the mechanisms of these modifications, we studied the effects of two Plasmodium falciparum haem products (haematin and malaria pigment in the synthetic form beta-haematin) on isolated human red blood cells (RBCs) and purified RBC ghosts. A dose- and time-dependent incorporation of haematin into RBC ghosts and intact cells was observed, which was in proportion to the extent of haematin- induced haemolysis. RBCs pre-incubated with haematin were more sensitive to haemolysis induced by hypotonic shock, low pH, H2O2 or haematin itself. Haemolysis was not related to membrane lipid peroxidation and only partially to oxidation of protein sulphydryl groups and it could not be prevented by scavengers of lipid peroxidation or hydroperoxide groups. N-acetylcysteine partly protected the oxidation of SH groups and significantly reduced haemolysis. In contrast, beta-haematin was neither haemolytic nor oxidative towards protein sulphydryl groups. Beta-haematin did destabilise the RBC membrane, but to a lesser extent than haematin, inducing increased susceptibility to lysis caused by hypotonic medium, H2O2 or haematin. This study suggests that the destabilising effect of haematin and, to a much less extent, beta-haematin on the RBC membrane does not result from oxidative damage of membrane lipids but from direct binding or incorporation which may affect the reciprocal interactions between the membrane and cytoskeleton proteins. These changes could contribute to the reduced red cell deformability associated with severe malaria.

Animals↗

PubMed2004

Evidence that haem iron in the malaria parasite is not needed for the antimalarial effects of artemisinin.

The role of haem iron (II) and oxidative stress in the activation and antimalarial activity of artemisinin is unclear. Thus, we submitted malaria parasite to modified culture conditions: artemisinin activity increased by 20-30% under an oxygen-rich atmosphere (20% O2 instead of "standard" 1% O2), and by 40-50% in the presence of carboxy-haemoglobin, and 2% carbon monoxide, conditions which inhibit haem iron (II) reactivity. In all cases, parasite growth and chloroquine activity were unaffected. We conclude that in the malaria parasite artemisinin is not activated by haem iron and that free radicals are not needed for its toxicity.

Animals↗

PubMed2004

Plasmepsin II inhibition and antiplasmodial activity of Primaquine-Statine 'double-drugs'.

Statine-based inhibitors of Plasmepsin II (PLMII) coupled with Primaquine have been designed using the 'double-drug' approach. The IC50 values for PLMII inhibition ranged from 0.59 to 400 nM and the best IC50 value for inhibition of Plasmodium falciparum growth in vitro was 0.4 microM, which represent a remarkable improvement compared to other statine-based PLMII inhibitors.

Amino Acids↗

PubMed2004

4-Alkyl- and 4-phenylcoumarins from Mesua ferrea as promising multidrug resistant antibacterials.

Supercritical CO2 selectively extracted a series of 4-alkyl and 4-phenyl 5,7-dihydroxycoumarins from Mesua ferrea blossoms. Chemical modifications of the isolated compounds allowed us to confirm the structures elucidated by spectroscopic means and to prepare new derivatives amenable to SAR studies and potential pharmaceutical development. Biological investigations towards the screening on a number of bacteria strains and Plasmodium falciparum, identified compounds 1-9 as weak antiprotozoal agents and potent antibacterials on resistant Gram-positive strains.

Animals↗

PubMed2003

Accelerated senescence of human erythrocytes cultured with Plasmodium falciparum.

Red blood cells infected withPlasmodium falciparum(IRBCs) undergo changes primarily in their membrane composition that contribute to malaria pathogenesis. However, all manifestations (eg, anemia) cannot be accounted for by IRBCs alone. Uninfected erythrocytes (URBCs) may play a role, but they have been under-researched. We wanted to document changes in the erythrocyte membrane that could contribute to URBC reduced life span and malaria-associated anemia. Human erythrocytes were cultured withP falciparumand washed at the trophozoite stage. IRBCs and URBCs were separated on Percoll density gradient, thus obtaining erythrocyte fractions of different densities/ages. IRBC- and URBC-purified membranes were analyzed and compared with control normal erythrocytes (NRBCs) of the same age, from the same donor, kept in the same conditions.P falciparumaccelerated aging of both IRBCs and URBCs, causing a significant shift in the cell population toward the denser (old) fraction. Protein, phospholipid, and cholesterol content were reduced in IRBCs and young URBCs. Young and medium uninfected fractions had higher levels of lipid peroxidation and phospholipid saturation (because of the loss of polyunsaturated fatty acids, PUFAs) and lower phosphatidylserine. In IRBCs, thiobarbituric reactive substances (TBARSs) were higher, and PUFAs and phosphatidylserine lower than in NRBCs and URBCs. In comparison, trophozoite membranes had lower phospholipid (particularly sphingomyelin and phosphatidylserine) and cholesterol content and a higher degree of saturation. Parasite-induced peroxidative damage might account for these modifications. In summary, we demonstrated that membrane damage leading to accelerated senescence of both infected and uninfected erythrocytes will likely contribute to malaria anemia.

Animals↗

PubMed2003

1-40 Beta-amyloid protein fragment modulates the expression of CD44 and CD71 on the astrocytoma cell line in the presence of IL1beta and TNFalpha.

The modulation of CD44, VCAM-1 and CD71 expression was analysed by flow cytometry in the 1321N1 astrocytoma cell line in the presence of interleukin-1beta (IL1beta), tumour necrosis factor-alpha (TNFalpha) and 1-40 or 25-35 beta-amyloid (Abeta) fragments. The percentage of 1321N1 astrocytoma cell line expressing these markers increased significantly after treatment with TNFalpha or IL1beta. The presence of Abeta 1-40 fragment, alone or in combination with IL1beta, induced an increase in the percentage of cells expressing CD44, but not VCAM-1. However, the concomitant presence of Abeta 1-40 fragment and of IL1beta or TNFalpha caused an increase in the percentage of CD71 positive cells. In contrast, the shorter Abeta 25-35 fragment was always inactive. These results indicates that Abeta 1-40 fragment, in association with cytokines, can activate this astrocyte-derived cell line and add further elements in favour of the hypothesis that beta-amyloid can act as immunological mediator.

Amyloid beta-Peptides↗

PubMed2003

In vitro studies on the mechanism of action of two compounds with antiplasmodial activity: ellagic acid and 3,4,5-trimethoxyphenyl(6'-O-aalloyl)-beta-D-glucopyranoside.

To investigate the mechanism of action of two antiplasmodial compounds, ellagic acid and 3,4,5-trimethoxyphenyl (6'-O-galloyl)-beta-D-glucopyranoside (TMPGG), we studied in vitro two metabolic reactions of intraerythrocytic parasites: the activity of recombinant plasmepsin II, one of the haemoglobin proteases, and the detoxification of haematin into beta-haematin. Both compounds inhibited plasmepsin II activity, but at concentrations ten-fold higher than those needed for inhibiting parasite growth. Moreover, ellagic acid inhibited the formation of beta-haematin, with an IC50 only 3-fold higher than that of chloroquine. These data suggest that the antiplasmodial activity of ellagic acid could be related to the inhibition of beta-haematin formation, whereas plasmepsin II does not represent the main target of the two compounds.

Animals↗