RESUMEN
The aim of this study was to evaluate the effect of piperidine nitroxides and their amine precursors on deoxyribose oxidation in the Fenton system. Protecting activity of nitroxides was found to be concentration-dependent and strongly influenced by ring substituents, while secondary amines did not provide any protection. The reported results suggest a mechanism of nitroxide action through iron oxidation rather than through direct scavenging of hydroxyl radicals. Moreover, presented data point to the danger of interference of nitroxides during the TBARS assay procedure.
Asunto(s)
Desoxirribosa/química , Óxidos de Nitrógeno/metabolismo , Sustancias Protectoras/metabolismo , Aminas/química , Aminas/metabolismo , Antioxidantes/química , Antioxidantes/metabolismo , Óxidos N-Cíclicos/química , Óxidos N-Cíclicos/metabolismo , Desoxirribosa/metabolismo , Radicales Libres/química , Radicales Libres/metabolismo , Peróxido de Hidrógeno , Hierro , Espectroscopía de Resonancia Magnética , Estructura Molecular , Óxidos de Nitrógeno/química , Oxidación-Reducción , Sustancias Protectoras/química , Marcadores de Spin , Relación Estructura-Actividad , Superóxido Dismutasa/metabolismo , Sustancias Reactivas al Ácido Tiobarbitúrico/metabolismoRESUMEN
The novel nitroxyl, Tempicol-3 (nitroxide-N-oxide) was synthesized and its capacity to act as a scavenger of hydroxyl radicals was tested. The concentration-dependent reducibility of this novel compound was also examined and compared with those of previously characterized nitroxides, Tempo and Tempace. The cytotoxicity of Tempicol-3 in vitro was measured by the modified tetrazolium assay (MTT), using, model cells for neoplastic phenotype (mouse NIH 3T3 fibroblast line). The ability of Tempicol-3 to act as an antitumor agent in vivo was also investigated in a pharmacological test, using rats bearing 3-day old Yoshida Sarcoma (promotion phase of the disease). Our results clearly indicated that Tempicol-3 acts as an effective and promising hydroxyl radical scavenger-antioxidant. Structure- and concentration-dependent bioreduction of Tempicol-3 by ascorbic acid may account for some of its biological effects, causing modulation of the antioxidant status of cells. The presence of one nitrone moiety per molecule of Tempicol-3 caused a significant decrease in nitroxide cytotoxicity as compared with Tempo, in vitro. The results clearly confirmed that the toxic effect could result either from the presence or structure of substituent(s) at position 4 of the free radical piperidine moiety. It can be stated that Tempicol-3 is a lowtoxicity nitroxide, which could be effective in providing antioxidative activity. We have also observed that lowtoxic Tempicol-3, at m.e.d. (minimal effective dose) suppressed tumorigenesis, acting as a cell proliferation modifier and apoptosis inducer in vivo. This work provides the base for further investigations on nitroxide-N-oxide derivatives since the serious question remains to be solved as to what is the molecular mechanism of action of the nitroxide-N-oxides.
Asunto(s)
Antineoplásicos/farmacología , Antioxidantes/farmacología , Apoptosis/efectos de los fármacos , División Celular/efectos de los fármacos , Sarcoma de Yoshida/tratamiento farmacológico , Células 3T3/efectos de los fármacos , Animales , Antineoplásicos/química , Antioxidantes/química , Ascitis/tratamiento farmacológico , Ascitis/patología , Óxidos N-Cíclicos/química , Óxidos N-Cíclicos/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Ratones , Piperidinas/farmacología , Ratas , Ratas Endogámicas BUF , Sarcoma de Yoshida/patología , Relación Estructura-ActividadRESUMEN
As a part of our studies on the chemical, biochemical and pharmacological characteristics of the newly synthesized antioxidants, nitroxide derivatives, we designed a novel nitroxide, named Tempicol-2. Its capacity to act as antioxidant of potential pharmacological application was tested in three model systems: xanthine/xanthine oxidase, iron- and ascorbate Fenton reaction(s) and gamma-radiolysis. The antioxidant properties of Tempicol-2 as a function of concentration were compared with those previously characterized nitroxide derivatives Tempace and Rutoxyl which we had synthesized. The possibility of one-electron reduction of the novel substance by ascorbic acid was also examined and compared. The ability of Tempicol-2 to act as anticancer agent in vivo was also investigated in pharmacologic tests. The administration of Tempicol-2 to rats bearing 3 day-old Yoshida Sarcoma (promotion phase) led to both growth inhibition and the induction of apoptotic cells(s) death, comparable to the effects of Tempace and Rutoxyl under the same experimental conditions. Our results confirmed the suggested involvement of free radicals in the pathogenesis of model. Yoshida Sarcoma, thus indicating that anticancer activity of the investigated nitroxides may indirectly involve an antioxidant mechanism. The results reported here are encouraging as we find a limited correlation between the molecular redox properties, structure of nitroxides and their antitumor action. Tempicol-2, similarly to Tempace and Rutoxyl, is a promising antioxidant which can induce apoptosis, thus providing the basis for further investigations of the concentration and phase-dependent effects and the exact mechanisms of nitroxide(s) apoptotic action using cell line(s) model.