Curcumin induces the mitochondrial permeability transition pore mediated by membrane protein thiol oxidation.

Curcumin is a natural compound showing antiproliferative properties. Recent studies suggest that these properties might be due to its ability to induce apoptosis in tumor cells. As mitochondria play a pivotal role in the induction of the apoptotic process, we analyzed the effect of curcumin on mitochondrial function. Curcumin induced an increase in rat liver mitochondrial membrane permeability, resulting in swelling, loss of membrane potential and inhibition of ATP synthesis. These effects were mediated by the opening of the permeability transition pore. Curcumin pore induction involved the oxidation of membrane thiol functions and required the presence of low Ca(2+) concentrations. These data suggest that mitochondria might be a target by which curcumin induces apoptosis of tumor cells.

NO-Mediated aromatic nitration during decomposition of phenolic S-nitrosothiols in non-aqueous aerobic medium.

Five novel S-nitrosothiol compounds (6-10) derived from L-cysteine were generated in solution and their decomposition rate was followed by UV spectroscopy. In acetonitrile, compounds 9 and 10 were the most stable of this series with a half-life of 24 h. The final organic decomposition products of the five S-nitrosothiols were also analysed. Derivatives 8, 9, and 10, possessing a phenolic hydroxyl group, afforded an unexpected decomposition pathway, with nitration of aromatic ring occurring in non-aqueous media. A mechanism involving a phenoxy radical seems to be implicated.

[(3)H]-trimetazidine mitochondrial binding sites: regulation by cations, effect of trimetazidine derivatives and other agents and interaction with an endogenous substance.

Trimetazidine, an antiischaemic drug, has been shown to restore impaired mitochondrial functions. Specific binding sites for [(3)H]-trimetazidine have been previously detected in liver mitochondria. In the present study we confirm this observation and provide additional evidence for the involvement of these sites in the pharmacological effects of the drug. Inhibition experiments using a series of trimetazidine derivatives revealed the presence of three classes of binding sites. An N-benzyl substituted analogue of trimetazidine exhibited a very high affinity (K(i)=7 nM) for one of these classes of sites. Compounds from different pharmacological classes were evaluated for their ability to inhibit [(3)H]-trimetazidine binding. Among the drugs tested pentazocine, ifenprodil, opipramol, perphenazine, haloperidol, and to a lower extent prenylamine, carbetapentane and dextromethorphan competed with high affinity, suggesting a similarity of high affinity [(3)H]-trimetazidine sites with sigma receptors. [(3)H]-Trimetazidine binding was modulated by pH. Neutral trimetazidine had about 10 fold higher affinity than protonated trimetazidine for its mitochondrial binding sites. Various cations also affected [(3)H]-trimetazidine binding. Ca(2+) was the most potent inhibitor and totally suppressed the binding of [(3)H]-trimetazidine to the sites of medium affinity. An endogenous cytosolic ligand was able to displace [(3)H]-trimetazidine from its binding sites. Its activity was not affected by boiling for 15 min, suggesting a non-protein compound. These data suggest that mitochondrial [(3)H]-trimetazidine binding sites could have a physiological relevance and be involved in the antiischaemic effects of the drug.

Novel donors of nitric oxide derived of S-nitrosocysteine possessing antioxidant activities.

Novel S-nitrosothiols possessing a phenolic function were investigated as nitric oxide (NO) donors. A study of NO release from these derivatives was carried out by electron spin resonance (ESR). All compounds gave rise to a characteristic three-line ESR signal in the presence of the complex [Fe(II)(MGD)2], revealing the formation of the complex [Fe(II)(MGD)2(NO)]. Furthermore, tests based on cytochrome c reduction were performed in order to study the ability of each phenolic disulfide, the final organic decomposition product of S-nitrosothiols, to trap superoxide radical anion (O2-). This study revealed a high reactivity of 1b and 3b towards O2-. For these two compounds, the respective inhibitory concentration (IC) 50 values were 92 microM and 43 microM.

Structure-property relationships of trimetazidine derivatives and model compounds as potential antioxidants.

Twenty-five compounds (trimetazidine derivatives and other compounds, mostly having a free phenolic group) were examined for their radical scavenging and antioxidant properties. Their reaction with DPPH (2,2-diphenyl-1-picrylhydrazyl) as a measure of radical scavenging capacity was assessed by two parameters, namely EC50 (the concentration of antioxidant decreasing DPPH by 50%), and log Z, a kinetic parameter proposed here and derived from initial second-order rate constants and antioxidant/DPPH ratios. Antioxidant activities were determined by the inhibition of lipid peroxidation and albumin oxidation. The most active compounds were derivatives having a trolox or hydroquinone moiety. Physicochemical and structural properties were determined by molecular modeling as lipophilicity (virtual log P calculations) and H-Surf (solvent-accessible surface of hydroxyl hydrogen) and by quantum mechanical calculations (deltaH(ox) = oxidation enthalpy; deltaH(abs) = enthalpy of hydrogen abstraction). QSAR models were derived to identify molecular mechanisms responsible for the reactivity toward the DPPH radical and for the inhibition of lipid peroxidation. A useful prediction of antioxidant capacity could be achieved from calculated molecular properties and the kinetic parameter developed here.

Curcumin and curcumin derivatives inhibit Tat-mediated transactivation of type 1 human immunodeficiency virus long terminal repeat.

The transcription of HIV1 provirus is regulated by both cellular and viral factors. Various evidence suggests that Tat protein secreted by HIV1-infected cells may have additional action in the pathogenesis of AIDS because of its ability to also be taken up by non-infected cells. Curcumin [diferuloylmethane or 1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] is the yellow pigment in turmeric Curcuma longa (Linn). It exhibits a variety of pharmacological effects including antiinflammatory and antiretroviral activities. Here, we demonstrated that curcumin used at 10 to 100 nM inhibited Tat transactivation of HIV1-LTR lacZ by 70 to 80% in HeLa cells. In order to develop more efficient curcumin derivatives, we synthesized and tested in the same experimental system the inhibitory activity of reduced curcumin (C1), which lacks the spatial structure of curcumin; allyl-curcumin (C2), which possesses a condensed allyl derivative on curcumin that plays the role of metal chelator; and tocopheryl-curcumin (C3), which enhances the antioxidant activity of the molecule. Results obtained with C1, C2 and C3 curcumin derivatives showed a significant inhibition (70 to 85%) of Tat transactivation. Despite the fact that tocopheryl-curcumin (C3) failed to scavenge O2.-, this curcumin derivative exhibited the most activity; 70% inhibition was obtained at 1 nM, while only 35% inhibition was obtained with the curcumin.

Protective effects of the lipophilic redox conjugate tocopheryl succinyl-ethyl ferulate on HIV replication.

Previously, we demonstrated that ferulate ethyl and tocopherol reduced HIV replication. In this study, we investigate whether the conjugation of both compounds (O-tocopheryl succinyl O-ethyl ferulate) can increase HIV inhibition. We show here for the first time that O-tocopheryl succinyl O-ethyl ferulate inhibits 80% of HIV replication (HIV-1 acute infection and HIV transmission), inhibits cell lipoperoxidation and prevents cellular glutathione consumption. Compared to ferulate ethyl and tocopheryl succinyl, O-tocopheryl succinyl O-ethyl ferulate inhibits more HIV replication. This may be due in part to the great increase in the lipophilicity of this compound.

[Thionitrites as potent donors of nitric oxide: example of S-nitroso- and S,S'-dinitroso-dihydrolipoic acids]. / Les thionitries comme agents donneurs potentiels de monoxyde d'azote: exemple des acides S-nitroso- et S,S'-dinitroso-dihydrolipoïque.

Until recently, nitric oxide (NO.) was considered as a toxic radical, but it appears now as an essential messenger implicated in a wide range of biological processes, including immune system, cardiovascular system, and nervous system. An aspect of NO. metabolism in vivo is the formation of a variety of high and low molecular weight nitrosothiols. S-nitrosocysteine and S-nitrosoglutathione are among the biologically derived S-nitrosothiols that are postulated to be carriers of NO.. Although most of the S-nitrosothiols are unstable and spontaneously break down to produce NO. and a disulfide, some of them, including protein thiols, can show significant stability. These molecules are able to convey nitric oxide, that is, to keep, to carry, and then to generate NO. in physiological media, and might display pharmacological effects as potential vasodilators or neuroprotectors. Here, we present the development of new thionitrites R-S-NO having intrinsic antioxidant properties. We report the preparation, the characterization, and the stability studies in aqueous solutions of S-nitroso derivatives of dihydro-alpha-lipoic acid, known for its antioxidant properties.

[Effect of the liposolubility of free radical scavengers on the production of antigen P24 from a HIV infected monocytic cell line]. / Influence de la liposolubilité des molécules antiradicalaires sur la production d'antigène P24 par des cellules monocytaires infectées par le VIH.

A large body of evidence indicates that AIDS may be the consequence of a virus-induced antioxidant deficiency and implicates reactive oxygen species (ROS) in the pathogenesis of HIV infection. The high level of antigenic acid and cytokines activities in AIDS results in the production of superoxides (O2-), hydrogen peroxide (H202) and hydroxyl radicals (OH). HIV-infected T cells display low levels of SOD, catalase, thioredoxin and glutatione peroxidase rendering them susceptible to undergo apoptosis. Induction of NF kappa B and HIV replication are at least in part dependent on reactive oxygen intermediates. We examined the protective effects of two antioxidants. Ferulic Acid (FA) and Ethyl Ferulate (EF) at 1, 5, 10, 10 microM on the TNF induced HIV activation in the chronically infected promonocytic U1 cell line. FA and EF at 5 microM elicit a marked decrease of HIV p24 release. HIV inhibition was greater after pretreatment with EF than with FA. At these concentrations, no cytotoxicity was observed. When SOD (100 UI) was combined with EF and FA no more inhibition was observed. But when SOD was added alone, it induced a marked inhibition (30%). This class of drugs may present potential interest as antiviral agents or as adjuvant therapy in AIDS.

[Substituted methoxyphenol with antioxidative activity: correlation between physicochemical and biological results]. / Méthoxyphénols substitués à activité antioxydante: corrélation entre les résultats physico-chimiques et biologiques.

Guaiacol moiety has been found in antiinflammatory compounds present in traditional african or chinese medicine. As the activity of these products could be due to reactions with the reactive oxygen species (ROS) or enzymes involved in the inflammatory reaction, a comparative study has been done between biological and physico-chemical investigations. Antioxidant properties of six guaiacol derivatives were measured in vitro by the inhibition of cyclooxygenase activities in human platelets and of the release of ROS by human polymorphonuclear leucocytes (PMNs). PMNs were stimulated by the bacterial peptide N-fMetLeuPhe (FMLP) and the protein kinase C activator phorbol myristate acetate (PMA) using luminol as chemiluminescent probe. Electron Spin Resonance (ESR) and the technique of spin-trapping with 5,5-dimethyl-pyrroline-N-oxide (DMPO) have been used to quantify hydroxyl and superoxide scavenging activities. Hydroxyl radicals were generated by the Fenton's reaction (Fe2+/H2O2) and the superoxide anion by the acetaldehyde/xanthine oxydase system (AC/XOD). The PMNs tests revealed that curcumin and methyl ferulate appeared as the most active compounds. Platelet cycloxygenase activity was inhibited by curcumin and cyclovalone. ESR studies showed a better ROS scavenging activity for vanillin, methyl ferulate and curcumin. Whatever test we used, curcumin and methylferulate appeared as the most interesting antioxidative compounds.

Synthesis and nematocidal activity of arylmercaptovinyltetrahydropyrimidines.

A set of mercaptovinyl tetrahydropyrimidines was synthesized in good yields by lithiation of 1,2-dimethyltetrahydropyrimidine with n-butyl lithium in tetrahydrofurane, followed by condensation with aromatic thioesters. Against three nematode genera, anthelminthic screening shows little activity; 2b and 2d were the most potent against Molinema dessetae.