Estudio del estrés oxidativo hepático en un modelo in vivo de deficiencia en vitamina E. Papel de NF-kappaB en la regulación de los genes de la gamma-glutamilcisteína sintetasa y genes implicados en el control del ciclo celular.

Resumen

Vitamin E is an essential antioxidant nutrient that is receiving considerable public attention. Interest in vitamin E is high because new scientific data suggest optimal intake can help delay or prevent the onset of cancer, atherosclerosis, cataracts and other major diseases. Such degenerative diseases have been linked to damage from free radicals originated in body processes of oxidative stress. The redox-sensitive transcription factor Nuclear Factor-kappaB (NF-?B) has been implicated as mediator in process of liver injury induced by oxidative stress. The purpose of this study was to determinate liver DNA-binding activity of NF-?B and the response of target redox-sensitive genes and cell-cycle modulators in an in vivo model of oxidative stress induced by chronic vitamin E deficiency. Rats were fed either control diet or vitamin E free diet until 60 or 90 days after birth. Liver from 90 days vitamin E-deficient rats and isolated liver mitochondria from 60 or 90 days vitamin E deficient rats showed an increase in malondialdehyde (MDA) levels and a decrease in glutathione (GSH) concentration when compared with values found in its respective control rats. Vitamin E deficiency enhanced liver DNA-binding activity of NF-?B (EMSA analysis) and up-regulated gamma-glutamylcysteine synthetase ( ?GCSC; ?GCSM), cyclin D1 and cyclin E. We also showed down-regulation of p21(Waf1/Cip1) transcription. Moreover, chromatin inmunoprecipitation (ChIP) assay demosntrated that NF-?B directly regulates transcription of ?GCS (both subunits) and cyclin D1 through the binding of NF-?B to the corresponding gene promotors, which was enhanced in vitamin E-deficiency. These findings show that vitamin E-deficiency induces significant molecular events related to liver cell damage with altered expression of either gene markers of oxidative stress and genes that control the cell cycle and demonstrate that liver NF-?B is envolved in this response. Our results emphasize the importance of maintaining an adequate vitamin E consumption not only to prevent liver oxidative damage but also in modulating signal transduction.