Vitamin E deficiency induces liver nuclear factor-kappaB DNA-binding activity and changes in related genes.
The biological functions of vitamin E have been classically attributed to its property as a potent inhibitor of lipid peroxidation in cellular membranes. However, in 1991, Azzi's group first described that alpha-tocopherol inhibits smooth muscle cell proliferation in a protein kinase C (PKC)-dependent way, demonstrating a non-antioxidant cell signalling function for vitamin E. More recently, the capacity of alpha-tocopherol to modulate gene expression with the implication of different transcription factors, beyond its antioxidant properties, has also been established. This study was to determine the effect of vitamin E-deficiency on liver nuclear factor-kappa B (NF-kappaB) DNA-binding activity and the response of target antioxidant-defense genes and cell cycle modulators. Rats were fed either control diet or vitamin-E free diet until 60 or 90 days after birth. Vitamin E-deficiency enhanced liver DNA-binding activity of NF-kappaB [electrophoretic mobility-shift assay, (EMSA)] and up-regulated transcription of gamma-glutamylcysteine synthetase (gamma-GCSM; gamma-GCSC), cyclin D1 and cyclin E. We also showed down-regulation of p21(Waf1/Cip1) transcription. Western-blot analysis demonstrated that gamma-glutamylcysteine synthetase catalytic subunit (gamma-GCSC) and cyclin D1 showed a similar pattern to that found in the RT-PCR analysis. Moreover, chromatin immunoprecipitation (ChIP) assay demonstrated that NF-kappaB directly regulates transcription of gamma-GCS (both subunits) and cyclin D1 through the binding of NF-kappaB to the corresponding gene promoters, which was enhanced in vitamin E-deficiency. These findings show that vitamin E-deficiency induces significant molecular regulatory properties in liver cells with an altered expression of both antioxidant-defense genes and genes that control the cell cycle and demonstrate that liver NF-kappaB activation is involved 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.
Morante
María
M
Universitat de València, Departamentos de Bioquímica y Biología Molecular y Fisiología, València, Spain.
Sandoval
Juan
J
Gómez-Cabrera
Mari-Carmen
MC
Rodríguez
José L
JL
Pallardó
Federico V
FV
Viña
Juan R
JR
Torres
Luis
L
Barber
Teresa
T
D000818:Animals; D015153:Blotting, Western; D001835:Body Weight; D047369:Chromatin Immunoprecipitation; D016213:Cyclins / Q000235:genetics; D004247:DNA / Q000378:metabolism*; D005786:Gene Expression Regulation; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D014810:Vitamin E / Q000378:metabolism; D014811:Vitamin E Deficiency / Q000235:genetics / Q000378:metabolism*
D016213:Cyclins; D016328:NF-kappa B; D012333:RNA, Messenger; D014810:Vitamin E; D008315:Malondialdehyde; D004247:DNA; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione