Ehrlich II –2nd World Conference on Magic Bullets

Drug-Drug and Drug-Biomolecule Photoinduced Reactions in Preparations for Topical Use ALBINI A^1, FASANI E^1, DONDI D^2, SERPONE N,^1 FAGNONI M^1 ^1Dep. Org. Chem., Univ. PAVIA; ^2Dep. Gen. Chem., Univ. PAVIA, Pavia, Italy. Background: There is a growing concern for the adverse effects caused by exposure to indoor/outdoor light after assumption of drugs. The first concern is obviously for topical preparations. The rather sparse literature on phototoxicity rarely examines the chemical reactions underlying to the biological effect. In general, there is a feeling that oxygen activation is the main mechanism, but the example below show that this is not always the case. Methods: In vitro studies were carried out by irradiating aqueous solution of the drugs under indoor/outdoor light at a measured flux. The photoproducts were isolated and the structure determined. The exploration was repeated in the presence of heterocycles mimicking the behaviour of nucleotides. Time-resolved studies for the detection of chemical intermediates were also performed. These studies and the structure of the products allowed to propose viable mechanisms, here concerning some UV filters used in sunscreens as well as some bactericides with eye-toxicity. Results: Dibenzoylmethanes (DBM, in the tautomeric form under the applicative conditions) are a virtually constant component of commercial sunscreens in view of the high absorption in the UV-A. These products are quite photostable but are often associated with cynnamates in the preparations, because the latters absorb the UV-B. However, if the combination of the two filters is exposed to light, both are rapidly consumed via a photocycloaddition reaction. Furthermore, irradiated DMBs photo-add to a variety of molecules present in the skin, e.g. to fats. As for antibacterials we refer here to fluoroquinolones used in eye drops, such as lomefloxacin (LOM), and to oxazolidinones such as linezolid, known to cause damage to the eye. In both cases a fast photoinduced decomposition takes place, with liberation of fluoride and formation of an aggressive intermediate (an aryl cation) that adds to a various compounds, including electron-rich heterocycles considered as a model of nucleotides, but not to water. This negative effect support that exposure to light should be minimized (e.g. LOM has been found to be genotoxic), but also suggest that fluorinated heterocycles may be considered for a novel type of photodynamic therapy based on the selective addition to biomolecules by photoproduced aryl cations, veritable magic bullets.

Protective Effect of Dimebon on the TNF-alpha–Induced Lipid Disorders in Mice Brain ALESSENKO AV^1, KARATASSO YO^1., SHEVTSOVA EF^2, *SHINGAROVA LN^1, BACHURIN SO^2 ^1Institute of Biochemical Physics of the Russian Academy of Sciences, Moscow, Russia, ^2Institute of Physiologically Active Substances, Russian Academy of Sciences, Chernogolovka, Russia. Background: Dimebon (Dimebolin) is an antihistamine drug which has been used clinically in Russia since 1983. Recently Dimebolin has attracted renewed interest after being shown to have positive effects on persons suffering from Alzheimer’s disease. Animal studies have shown that dimebon operates through multiple mechanisms of action, both blocking the action of neurotoxic beta-amyloid proteins and inhibiting L-type calcium channels, modulating the action of AMPA and NMDA glutamate receptors, and may exert a neuroprotective effect by blocking cytotoxic signals induced by proinflammatory citokines such as TNF-alphawhich are believed to play a central role in Alzheimer's disease. Inflammatory response induced by TNF-alpha suggests that this cytokine affects the phospholipid metabolism and subsequent production of eicosanoids, ceramide, and ROS that may potentiate brain injury. Methods: This study included 65 male mice (weight: 20  2 g, aerage  SD). TNF-alpha (10mkg per mouse), dimebon (0,2 mg/kg ) and their combination were injected to mice interperitonealy. Changes in level of phospholipids molecular species (phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, sphingomyelin) and galactosylceramide in hippocampus, cerebellum and cerebral cortex within 30 min, 2, 4 and 24 hours after injection were detected by chromato-mass-spectrometry. Results: Maximal changes in phospholipids and galactosylceramides contents of different molecular species after single TNF-alpha administration were found in the hippocampus, and were less expressed in the cerebral cortex and cerebellum after 24 hours. Dimebon itself did not induce changes in lipids spectrum in brain sections, but protected lipids against disorders induced by TNF-alpha in mice brain. Conclusions: Modern strategies in the search of new therapeutic approaches are based on the multitarget properties of new drugs. According to our results TNF-alpha may serve as a new target for dimebon. Dimebon preventing lipids disorders in brain induced by TNF-alpha might have a positive anti-inflammatory effects, preventing the negative response of nerve cells to the pathological process.

The Role of cell membrane lipid environment in antigenic peptide structure-function ALFSEN, A. ^1, 2, YU, H.F. ^1, 2 and BOMSEL, M. ^1, 2 ^1Entrée muqueuse du VIH et Immunité muqueuse; Département de Biologie Cellulaire, Institut Cochin, Université Paris Descartes, CNRS (UMR 8104), Paris, France;^2Inserm, U567, Paris. Background : The cell membranes control the extra- and intracellular exchange. The lipid structure, their organization in the membrane and around membrane proteins but also their dynamics in the two dimensions of the membrane are all essential characteristics of each cell type, for their selective role in the cell traffic. The aim of our study was to address the role of the lipids on an HIV-1 vaccine epitope structure and on the interaction with target cell membranes : either CD4+ T cells or epithelial cells. Methods: Biophysical, biochemical and biological methods have been used. Peptides derived from HIV-1 glycoprotein envelope gp41 were chemically synthesized or produced as recombinant peptides. To study lipid dynamics and domain organization due to protein interaction, liposomes of different lipid composition, mimicking either the viral membrane or target cell membranes were chemically obtained and fluorescence resonance energy transfer (FRET) has been used. Nuclear Magnetic Resonance (NMR) allowed defining peptide solution structure in presence of micelles. Binding of known HIV-1 antibodies to the epitopes inserted into liposomes were measured by enzyme linked immunoassays (ELISA). Results: Different peptides from conserved regions of the HIV-1 envelope glycoprotein gp41 have been studied, including: 1) P1, the minimal Membrane Proximal Region (MPR) that permits interaction with mucosal galactosyl ceramide HIV-receptor and contains epitopes recognized by gp41-specific, broadly neutralizing IgGs, 2F5 and 4E10, and 2) P5, P1 extended at its N-terminal by a calcium binding site. The alpha-helical structure of the peptides on DPC micelles appeared pH-dependent. P1 was derivatized with phosphatidylethanolamine (PE) at its C-terminal and inserted into liposomes of varied lipid composition, thereby enabling P1 to move laterally within liposome bilayer. The Kds of both 2F5 and 4E10 IgGs measured on viral liposome and infectious virus are similar in the nM range and much lower than for the binding of the free P1 peptide. For P5, the role of cell calcium on its structure and its antiviral properties when in interaction with lipids was shown essential. Conclusions/Significance: Thus, the defined lipid environment of MPER-derived peptides and environmental conditions (pH, calcium, ...) appear as essential for their structure and therefore for the design of an immunogen inducing broadly neutralizing antibodies to HIV-1, and also microbicides.

Protective effects of Nigella sativa extract and its components against chromium VI-induced toxicity in Nile tilapia (Oreochromis niloticus) and zebrafish (Danio rerio) KHALIL WKB^1**, ALI Fagr K^2, BELATTAR N^3, SENATOR A^2, ABDEL-WAHHAB MA^4** ^1Cell Biology Department, ^2Water Pollution Department, ^4Food Toxicology & Contaminants Department, National Research Centre, 12622 Dokki, Cairo, Egypt ^2Laboratory of Applied Biochemistry, Biology Department, Faculty of Sciences, Ferhat Abbes University, 19000 Sétif, Algeria. Background: Chromium is an increasing health concern for aquatic environments, however, the mechanism of chromium toxicity in aquatic species is yet unknown. Hexavalent chromium VI (CrVI) is the dominant toxicant at some Superfund sites within Egypt. Methods: The aim of the current study was to evaluate the genotoxicty potential of chromium VI (CrVI) in Nile tilapia (Oreochromis niloticus) and zebrafish (Danio rerio) using semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR), and possible protective effects of N. sativa. The test fish within the two species were divided into eight groups and treated with Cr(VI) alone or in combination with the crude extract of N. sativa, N. sativa oil, or its derivative thymoquinone for 30 days. Results: The semi-quantitative RT-PCR results indicated that treatment with Cr(VI) at 4.37 and 1.75 mg/l for tilapia and zebrafish, respectively resulted in a significant increase in hepatic and brain mRNA level of cytochrome 450 gene family including CYP1A2, CYP3A and CYP2E1 in both fish species compared to control group. Moreover, Cr(VI) was found to induce severe histological changes in liver, brain and gills of the tested fish. On the other hand, the combined treatment showed that mRNA level of CYP1A2, CYP3A and CYP2E1 decreased significantly in the groups treated with Cr(VI) plus N. sativa oil or thymoquinone compared to the groups treated with the crude extract or Cr(VI) alone accompanied with a significant improvement in the histological picture of the liver, brain and gills. However, N. sativa was found to be more effective. Conclusion: It could be concluded that N. sativa is a promise candidate against DNA damage resulted from the exposure to different environmental pollutants. ** Corresponding author: Fax: [phone], E-mail: [e-mail] ** Corresponding author: Fax: [phone], E-mail: [e-mail]