RESUMO
Glycation products are generated during the Maillard reaction, a non-enzymatic reaction between reducing sugars and the amino groups of proteins, which accumulate in the body with aging and cause many diseases. Herein, we have focused on dihydropyrazines (DHPs), which are glycation products formed by the dimerization of D-glucosamine or 5-aminolevulinic acid, and have reported that DHPs can produce several kinds of radicals and induce cytotoxicity via oxidative stress. To advance our understanding of DHP-mediated cytotoxicity, we selected a DHP, 3-hydro-2,2,5,6-tetramethylpyrazine (DHP-3), and two major Maillard reaction products, Nε-(carboxymethyl)-L-lysine (CML) and acrylamide, and performed comparative experiments focusing on their cytotoxicity and their ability to induce oxidative stress. The order of increasing cytotoxicity was DHP-3, acrylamide, and CML, and the LC50 value could be calculated only for DHP-3 (0.53 mM), indicating that DHP-3 is more toxic than the other Maillard reaction products. However, their toxicities were significantly lower than those of common toxic chemicals. Further, the results of their cytotoxicity assay were consistent with the results of intracellular reactive oxygen species production and activation of oxidative stress response signaling. These results indicate that the acute toxicity of Maillard reaction products is closely related to their ability to induce oxidative stress, and that DHP-3 is a particularly strong inducer of oxidative stress and thus exhibits high cytotoxicity among Maillard reaction products. In addition, we have shown that a comprehensive analysis comparing multiple Maillard reaction products is effective for elucidating their complex and diverse toxicities.
Assuntos
Estresse Oxidativo , Proteínas , Espécies Reativas de Oxigênio/metabolismo , Produtos Finais de Glicação Avançada/toxicidade , Produtos Finais de Glicação Avançada/metabolismo , Acrilamidas/farmacologiaRESUMO
Dihydropyrazines (DHPs) are one of glycation products that are non-enzymatically generated in vivo and in food. We had previously revealed that 3-hydro-2,2,5,6-tetramethylpyrazine (DHP-3), a methyl-substituted DHP, elicited redox imbalance and cytotoxicity in cultured cells. However, the molecular mechanisms underlying DHP-3-induced cytotoxicity remain unclear. To address this issue, we examined the involvement of the receptor for advanced glycation end products (RAGE) in DHP-3-induced cytotoxicity. To evaluate the role of RAGE, we prepared HeLa cells that constitutively expressed RAGE and its deletion mutant, which lacks the cytoplasmic domain (RAGEΔcyto), using an episomal vector. After transfection with the vector, cells were selected following incubation with multiple concentrations of hygromycin to remove non-transfected cells. The expression of RAGE and RAGEΔcyto in the cells was confirmed by immunoblotting. RAGE and RAGEΔcyto were apparently expressed in transfected cells; however, there were no significant differences in DHP-3-induced cytotoxicity between these cells and mock vector-transfected cells. These results suggested that DHP-3 elicits cytotoxicity in a RAGE-independent manner.
Assuntos
Produtos Finais de Glicação Avançada , Produtos Finais de Glicação Avançada/metabolismo , Produtos Finais de Glicação Avançada/toxicidade , Células HeLa , Humanos , Oxirredução , Receptor para Produtos Finais de Glicação Avançada/genética , Receptor para Produtos Finais de Glicação Avançada/metabolismoRESUMO
An oxidative methyl esterification of aldehydes was effectively achieved. The trivalent indium reagent, indium(III) triflate, was revealed to accelerate the reactions in many cases. Aromatic aldehydes with various substituents were subjected to this method, and each produced the corresponding methyl esters in good to excellent yields within a relatively short reaction time.
Assuntos
Aldeídos/química , Hidrocarbonetos Aromáticos/química , Mesilatos/química , Ácidos Sulfúricos/química , Esterificação , Metilação , OxirreduçãoRESUMO
Oligonucleotides that incorporate a reactive moiety to form an interstrand cross-link have been widely studied for their potential toward inhibiting gene expression or as basic tools for chemical biology studies. The 6-vinylpurine (2) newly designed in the current study serves well as a new purine-base moiety for increasing cross-link reactivity to target cytosine. Thus, oligonucleotides containing 6-vinylpurine exhibit a more selective and much smoother DNA cross-linking ability to cytosine than the oligonucleotide analogs derived from 2-amino-6-vinylpurine (1) previously explored.
Assuntos
Reagentes de Ligações Cruzadas/química , DNA/química , Purinas/química , Compostos de Vinila/química , Fosfatase Alcalina/química , Cromatografia Líquida de Alta Pressão , Citosina/química , DNA/síntese química , DNA/isolamento & purificação , Clivagem do DNA , Oligodesoxirribonucleotídeos/síntese química , Oligodesoxirribonucleotídeos/química , Oligodesoxirribonucleotídeos/isolamento & purificação , Diester Fosfórico Hidrolases/químicaRESUMO
The various biological activity of dihydropyrazines(DHPs)due to the radical generation potency has been described in previous papers. Detailed data about radical species generating be mentioned here. The electron spin resonance (ESR) spin-trapping technique revealed that DHPs generate free radical species such as ·OH, ·OOH, ·CHR(2) and ·CR(3). Oxygen radicals and two carbon-centered radicals were detected as adducts of the spin traps DMPO and DBNBS, respectively. All the 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)- and 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS)-adducts of compounds DHP-1-8 exhibited approximately the same signal patterns, with various levels of intensity depending on the substituent of the dihydropyrazine ring. The ESR signal intensity of DHPs also increased remarkably upon addition of Cu(2+), resulting that the effects of DHPs were enhanced.
Assuntos
DNA/metabolismo , Radicais Livres/metabolismo , Pirazinas/química , DNA/química , Quebras de DNA de Cadeia Dupla , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Pirazinas/síntese químicaRESUMO
Perchlorotriphenylmethyl triethylester radical (PTM-TE) is a hydrophobic, stable radical giving a narrow singlet ESR signal with a small satellite signal for (13)C in organic solvents. In order to use PTM-TE as a label of liposomal membranes, its manner of incorporation into liposomal membranes was studied. Two components, broad and narrow signals, were observed on the ESR spectrum of PTM-TE incorporated into liposomal membranes composed of egg yolk phosphatidylcholine (egg-PC). The broad signal was increased by the presence of cholesterol in the membranes. The spectral anisotropy of the broad signal was very small as analyzed with oriented planar multilamellar membranes. The narrow signal increased with an increase in temperature in the absence of cholesterol, whereas only a small increase in the signal was observed in the presence of cholesterol. The g-value and line width of the narrow signal were very close to those of PTM-TE in mineral oil, whose viscosity is close to the microviscosity in the hydrophobic region of egg-PC membranes. On the other hand, the g-value and line width of the broad signal were close to those of solid PTM-TE. These observations indicate that the broad signal observed in liposomes originates from PTM-TE clusters in the membranes. The clusters were dissolved in egg-PC membranes at a PTM-TE/egg-PC molar ratio of less than 0.017. However, the clusters were hardly dissolved in the presence of cholesterol.
Assuntos
Colesterol/farmacologia , Sistemas de Liberação de Medicamentos/métodos , Hidrocarbonetos Clorados/química , Lecitinas/metabolismo , Lipossomos/metabolismo , Membranas Artificiais , Radioisótopos de Carbono/química , Colesterol/química , Gema de Ovo/química , Gema de Ovo/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Ésteres/química , Radicais Livres/química , Interações Hidrofóbicas e Hidrofílicas , Percloratos/química , Compostos de Tritil/químicaRESUMO
A convergent one-step transformation of tetrahydropyranyl (THP) ethers is described. According to our earlier experiments, indium(III) triflate has proven to be an efficient catalyst for the transformation of THP ethers into their corresponding acetates. In further intensive work, we have developed a useful transforming reaction of THP ethers using various anhydride moieties. Indium(III) triflate was confirmed as a suitable catalyst, furnishing good to excellent yields. The details of this one-step transformation are described.
Assuntos
Índio/química , Mesilatos/química , Compostos Organometálicos/química , Pironas/química , Catálise , Pironas/síntese químicaRESUMO
The carboxylic acids are efficiently converted into the methyl esters in methanol using indium(III) chloride as the catalyst. This method is applicable for aromatic and aliphatic carboxyl moieties as well as amino acids in high yields.
Assuntos
Índio/química , Aminoácidos/química , Ácidos Carboxílicos/química , Catálise , Cloretos/química , Esterificação , Hidrocarbonetos Aromáticos/química , Metanol/químicaRESUMO
Retinoids are natural and synthetic analogues of all-trans retinoic acid (ATRA). Cancer and other serious hyperproliferative diseases are attractive therapeutic targets for retinoids. We report here the design and synthesis of novel cyclic urea compounds with retinoidal activity. YR105 exhibited potent differentiation-inducing ability toward human promyelocytic leukemia HL-60 cells at the concentration of 10(-9)M: its potency was almost equal to that of the native ligand, all-trans retinoic acid.
Assuntos
Retinoides/farmacologia , Ureia/química , Células HL-60 , Humanos , Modelos Moleculares , Ureia/síntese química , Ureia/farmacologiaRESUMO
A catechin analogue in which the geometry was constrained to be planar was synthesized. The planar catechin showed excellent radical-scavenging ability, comparable to that of quercetin, and efficient protection against DNA strand breakage induced by the Fenton reaction.