24 research outputs found
The point of zero charge of hydrous RuO2
No full textHydrous RuO2 has been prepared by alkaline fusion of Ru+KNO3+ KOH and successive decomposition of the ruthenate and perruthenate. The product has been analyzed by thermogravimetric analysis, differential thermal analysis, X-ray diffraction and scanning electron microscopy. Aqueous suspensions of samples of the hydrous oxide calcined at various temperatures between 300 and 500°C have been titrated potentiometrically to determine the point of zero charge. The results have been compared with commercial RuO2·xH2O. The two oxides have been found to differ in composition, structure, morphology and acid-base properties. In particular, hydrous RuO2 contains chemically bound water besides physically bound water, which is the only water present in the commercial sample. The dependence of the point of zero charge of the hydrous RuO2 on calcination temperature follows the same pattern as RuO2 obtained by thermal decomposition of RuCl3, while the behaviour of the commercial sample diverges below the temperature where the chemically bound water is lost by the hydrous RuO2. © 1989
Benzothiadiazole (BTH) activates sterol pathway and affects vitamin D3 metabolism in Solanum malacoxylon cell cultures
No full textBenzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a particularly efficient inducer of systemic acquired resistance (SAR), was developed as an immunizing agent to sensitize various crop species against pathogen infections. Recent works highlighted its activating effect on different metabolic pathways, concerning both primary and secondary metabolites. In this study, we investigated the effect of BTH treatment on sterol levels and vitamin D-3 metabolism in Solanum malacoxylon cultures. Calli of S. malacoxylon were incubated in Gamborg B5 liquid medium alone or added with 50 mu M BTH for different times (one, two or three cycles of light). Histocytochemical investigations performed on our experimental system using 3,3'-diaminobenzidine (DAB) for hydrogen peroxide (H2O2) detection and phloroglucinol for lignin staining showed that BTH causes H2O2 accumulation and lignin deposition in treated calli. Gas chromatographic analysis of principal cell membrane sterols (beta-sitosterol, campesterol, stigmasterol) showed that BTH transiently increases their cellular levels. Callus cultures were found to contain also cholesterol, 7-dehydrocholesterol, the putative precursor of vitamin D-3, and the hydroxylated metabolites 25-hydroxyvitamin D-3 [25(OH)D-3] and 1 alpha,25-dihydroxyvitamin D-3 [1 alpha,25(OH)(2)D-3]. BTH treatment enhanced 7-dehydrocholesterol while reduced cholesterol. HPLC analysis of sample extracts showed that BTH does not affect the cell content of vitamin D3, though results of ELISA tests highlighted that this elicitor moderately enhances the levels of 25(OH)D-3 and 1 alpha,25(OH)(2)D-3 metabolites. In conclusion, BTH treatment not only causes cell wall strengthening, a typical plant defence response, as just described in other experimental models, but in the same time increases the cellular level of the main sterols and 7-dehydrocholesterol
Inhibition of DC-SIGN-mediated HIV infection by a linear trimannoside mimic in a tetravalent presentation
No full textHIV infection is pandemic in humans and is responsible for millions of deaths every year. The discovery of new cellular targets that can be used to prevent the infection process represents a new opportunity for developing more effective antiviral drugs. In this context, dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN), a lectin expressed at the surface of immature dendritic cells and involved in the initial stages of HIV infection, is a promising therapeutic target. Herein we show the ability of a new tetravalent dendron containing four copies of a linear trimannoside mimic to inhibit the trans HIV infection process of CD4+ T lymphocytes at low micromolar range. This compound presents a high solubility in physiological media, a neglectable cytotoxicity, and a long-lasting effect and is based on carbohydrate-mimic units. Notably, the HIV antiviral activity is independent of viral tropism (X4 or R5). The formulation of this compound as a gel could allow its use as topical microbicide
Pseudosaccharide functionalized dendrimers as potent inhibitors of DC-SIGN dependent Ebola pseudotyped viral infection
No full textThe development of compounds with strong affinity for the receptor DC-SIGN is a topic of remarkable interest due to the role that this lectin plays in several pathogen infection processes and in the modulation of the immune response. DC-SIGN recognizes mannosylated and fucosylated oligosaccharides in a multivalent manner. Therefore, multivalent carbohydrate systems are required to interact in an efficient manner with this receptor and compete with the natural ligands. We have previously demonstrated that linear pseudodi- and pseudotrisaccharides are adequate ligands for DC-SIGN. In this work, we show that multivalent presentations of these glycomimetics based on polyester dendrons and dendrimers lead to very potent inhibitors (in the nanomolar range) of cell infection by Ebola pseudotyped viral particles by blocking DC-SIGN receptor. Furthermore, SPR model experiments confirm that the described multivalent glycomimetic compounds compete in a very efficient manner with polymannosylated ligands for binding to DC-SIGN
Glycomimetic antagonists of the C-lectin DC-SIGN
No full textDC-SIGN (Dendritic Cell-Specific Intercellular adhesion molecule 3-Grabbing Nonintegrin), a specific C-type lectin recognizing pathogen-cell surface glycoproteins, is a trans-membrane receptor on immature dendritic cells (DC) which binds a number of pathogen-associated molecular patterns. Normally, this binding event triggers internalization of the DC-SIGN-pathogen complex followed by lysosomal degradation of the pathogen and conjugation of the resulting fragments with MHC-II to initiate an adaptive immune response from T cells. Some pathogens, however, have been reported to take advantage of this mechanism, as they appear to deter DC maturation through DC-SIGN-mediated signalling and inhibit antigen presentation to T cells. In particular, van Kooyk’s group has shown that HIV-1 enters DC via DC-SIGN avoiding lytic degradation [1]. By doing so, HIV-1 not only escapes the host immune system, but also is presented directly to T cells, which enables fully disseminated HIV-1 infection.
Inhibition of pathogen interaction using DC-SIGN specific antagonists is considered as a plausible concept for the development of novel anti-infective agents. Several groups have recently demonstrated that inhibition of DC-SIGN, either by designed glycoconjugates or by antibodies, prevents pathogen attachment to DC and inhibits the infection of other immune cells at its earliest steps [2].
Our group has been active in this area and, in collaboration with the European network Carmusys [3] has developed mannose-based and fucose-based glycomimetic ligands that inhibit DC-SIGN mediated HIV infection in cellular and tissue models [4].
The presentation will deal with the design and synthesis of the glycomimetic monovalent ligands, the process of structural optimization which allowed us to build affinity and selectivity in their structure, the synthesis and optimization of polyvalent constructs that allowed us to achieve high affinity interaction with the lectin.
[1] van Kooyk, Y. ; Geijtenbeek, T.B.H. Nat Rev Immunol, 3, 2003, 697.
[2] For reviews, see: (a) Ernst, B. ; Magnani J.L. Nat Rev Drug Discov 8, 2009, 661 and references therein; (b) Anderluh, M., et al. Curr Med Chem, 2012, 19, 992 and references therein.
[4] http://www.carmusys.iiq.csic.es/
[5] (a) Berzi, A.; Reina, J. J.; Ottria, R.; Sutkeviciute, I.; Antonazzo, P.; Sanchez-Navarro, M.; Chabrol, E.; Biasin, M.; Trabattoni, D.; Cetin, I.; Rojo, J.; Fieschi, F.; Bernardi, A.; Clerici, M. Aids 2012, 26, 127-37; (b) Obermajer, N.; Sattin, S.; Colombo, C.; Bruno, M.; Svajger, U.; Anderluh, M.; Bernardi, A. Mol Divers 2011, 15, 347-360; (c) Luczkowiak, J.; Sattin, S.; Sutkeviciute, I.; Juan Reina, J.; Sanchez-Navarro, M.; Thepaut, M.; Martinez-Prats, L.; Daghetti, A.; Fieschi, F.; Delgado, R.; Bernardi, A.; Rojo, J. Bioconjugate Chem 2011, 22, 1354-1365; (d) Guzzi, C.; Angulo, J.; Doro, F.; Reina, J. J.; Thepaut, M.; Fieschi, F.; Bernardi, A.; Rojo, J.; Nieto, P. M. Org Biomol Chem 2011, 9, 7705-7712; (e) Andreini, M.; Doknic, D.; Sutkeviciute, I.; Reina, J. J.; Duan, J.; Chabrol, E.; Thepaut, M.; Moroni, E.; Doro, F.; Belvisi, L.; Weiser, J.; Rojo, J.; Fieschi, F.; Bernardi, A. Org Biomol Chem 2011, 9, 5778-5786; (f) Sattin, S.; Daghetti, A.; Thepaut, M.; Berzi, A.; Sanchez-Navarro, M.; Tabarani, G.; Rojo, J.; Fieschi, F.; Clerici, M.; Bernardi, A. Acs Chem Biol 2010, 5, 301-31
Application of the Gouy-Chapman-Stern-Grahame model of the electrical double layer to the determination of single ion activities of KF aqueous solutions
No full textPseudosaccharides Functionalized Dendrons Inhibitors of MBL Are Able to Prevent Ischemic Injury In Mice
No full textRecently, it has been demonstrated that the powerful protective effect of recombinant human complement C1-inhibitor (rhC1-INH) in cerebral ischemia is due to its ability to inhibit the activation of complement lectin pathway by binding to mannose binding lectin (MBL),1 likely through its mannose-enriched N-terminal domain. To explore the relevance of the lectin pathway in cerebral ischemia we have determined if newly synthesized mannosylated mimetic molecules, characterized and selected for their binding to MBL, are able to prevent ischemic injury in mice. Multivalent carbohydrate systems are required to interact in an efficient manner with this receptor and compete with the natural ligands. We have previously demonstrated that linear pseudodi- and pseudotrisaccharides are adequate ligands for lectins that recognize mannose, for example, DC-SIGN.2 In this work, we show that multivalent presentations of these glycomimetics based on dendrons lead to very potent inhibitors of MBL and also we indicate that the inhibition of this protein leads to neuroprotection. The affinity of mannosylated molecules to MBL was measured by surface plasmon resonance (SPR). The molecule showing the highest affinity to MBL was administered intravenously to ischemic mice and neurological deficits and infarct volume were evaluated. Polyman002, a dendron exposing four copies of the pseudo-trisaccharide bind MBL with a KD=2.3±0.7μM and induced a significant reduction of neurological deficits and ischemic volume in vivo. Our findings, together with those recently published by Cervera et al.,3 indicate that MBL inhibition may represent a novel therapeutic target for stroke.
References
1. Gesuete, R., Storini, C., Fantin, A., Stravalaci, M., Zanier, E.R., Orsini, F., Vietsch, H., Mannessem M.L., Ziere, B., Gobbi, M., De Simoni, M.G., Ann. Neurol., 2009, 66, 332-342.
2. (a) Sattin, S., Daghetti, A., Thépaut, M., Berzi, A., Sánchez-Navarro, M., Tabarani, G., Rojo, J., Fieschi, F., Clerici, M., Bernardi, A., ACS Chem. Biol., 2010, 3, 301-312. (b) Luczkowiak, J., Sattin, S., Reina, J.J., Sánchez-Navarro, M., Sutkevičiūtė, I., Thépaut, M., Martínez-Prats, L., Daghetti, A., Fieschi, F., Delgado, R., Bernardi, A., Rojo. J., unpublished results.
3. Cervera, A., Planas, A.M., Justicia, C., Urra, X., Jensenius, J.C., Torres, F., Lozano, F., Chamorro, A., PLoS One, 2010, 5, e8433
Scaffold optimization of tetravalent C-lectin antagonists
No full textIn recent years our group, in collaboration with the Rojo group (Glycosystems Laboratory, IIQ-CSIC, Sevilla), has demonstrated that tetravalent polyester dendrimers[1] functionalised with glycomimetic pseudo-dimannoside and pseudo-trimannoside ligands work as good inhibitors of the C-type lectins DC-SIGN[1] and MBL[2].
MBL is a circulating C-type lectin that has crucial role in first line of host defense. MBL recognizes polyglycosylated cell surfaces present both on pathogens and self damaged cells and has great importance in the activation of complement, promotion of opsonophagocytosis, promotion of apoptosis and also modulation of inflammation.[3] Recent studies have shown that the capability of MBL in generating an inflammatory environment may be a main cause of the reperfusion damage that occurs after a stroke event, highlighting MBL as a promising target for this pathology.[2,4]
The antagonists that we developed so far are able to bind MBL with dissociation constant in the low micromolar range (SPR binding assays). Moreover, the inhibitor 1 bearing as a ligand the pseudo-trimannoside 2 (Figure 1) was tested in vivo and showed a great capability of reducing the ischemic volume in mice with an uncommon wide therapeutic window.[2]
The main drawback of this construct consists in its limited half-life in plasma, due to the instability of the succinyl ester which also determines the chromatographic lability of the dendron. Here we present an attempt in the optimization of this scaffold. We are particularly interested in obtaining a product that is still soluble in water and no longer sensitive to hydrolysis and therefore characterised by easier purification procedures and chemical and enzymatic stability.
Our results will be shown in the poster.
References:
1. J. Luczkowiak, S. Sattin, I. Sutkecičiūtė, J. J. Reina, M. Sánchez-Navarro, M. Thépaut, L. Martínez-Prats, A. Daghetti, F. Fieschi, R. Delgado, A. Bernardi, J. Rojo Bioconjugate Chem. 2011, 22, 1354.
2. F. Orsini, P. Villa, S. Parrella, R. Zangari, E. R. Zanier, R. Gesuete, M. Stravalaci, S. Fumagalli, R. Ottria, J. J. Reina, A. Paladini, E. Micotti, R. Ribeiro-Viana, J. Rojo, V. I. Pavlov, G. L. Stahl, A. Bernardi, M. Gobbi, M.-G. De Simoni Circulation 2012, 126, 1484.
3. M. W. Turner Molecular Immunology 2003, 40, 423; b) A. Cervera, A. M. Planas, C. Justicia, X.Urra, J. C. Jensenius, F. Torres, F. Lozano, A. Chamorro PLOS ONE 2010, 5, e8433.
4. R. Gesuete, C. Storini, A. Fantin, M. Stravalaci, E. R. Zanier, F. Orsini, H. Vietsch, M. L. M. Mannesse, B. Ziere, M. Gobbi, M.-G. De Simoni Annals of Neurology 2009, 66, 332
