Low and high levels of alpha-tocopherol exert opposite effects on IL-2 possibly through the modulation of PPAR-gamma, IkappaBalpha, and apoptotic pathway in activated splenocytes.
OBJECTIVE
We previously demonstrated that a high dose of alpha-tocopheryl succinate inhibits interleukin-2 (IL-2) mRNA and production in autoimmune-prone MRL/lpr mice. In the present study, we investigated the regulation of alpha-tocopherol (alphaTOC) on IL-2 gene expression by examining the mRNA of IL-2, inhibitor kappaBalpha (IkappaBalpha), and peroxisome proliferator-activated receptor-gamma (PPARgamma).


METHODS
Messenger RNA expression in active splenocytes of BALB/c mice was investigated with reverse transcriptase polymerase chain reaction.


RESULTS
Levels of IL-2 mRNA in phorbol 12-myristate 13-acetate/ionomycin activated splenocytes and cytokine in T-helper-1 cells were increased by 50 microM of alphaTOC but decreased by 1 mM of alphaTOC. In addition, the IkappaBalpha gene expression significantly increased by the high dose (>or=500 microM) of alphaTOC, suggesting an inhibition on nuclear factor-kappaB pathway for activation of IL-2 expression. PPARgamma mRNA level in activated splenocytes was upregulated by 1 mM of alphaTOC. PPARgamma mRNA level in unstimulated splenocytes was upregulated by alphaTOC in a dose-dependent manner, suggesting that alphaTOC might enhance the PPARgamma signaling pathway. High-dose alphaTOC induced apoptosis of splenocytes and inhibited phytohemagglutinin-stimulated T-cell proliferation. Conversely, the proliferative response of splenocytes was enhanced by 5 microM of alphaTOC. Low-dose (50 microM) alphaTOC increased IL-2 expression, which may have been due to the absence of downregulation of PPARgamma and IkappaBalpha on the IL-2 gene.


CONCLUSIONS
The results indicated that low and high doses of alphaTOC exert opposite effects on IL-2, possibly through modulation of PPARgamma, IkappaBalpha, and apoptosis pathways. The present findings support our previous observation of opposite effects of low- and high-dose vitamin E on survival of MRL/lpr mice.
Department of Biochemical Science and Technology, Institute of Microbiology and Biochemistry, College of Life Science, National Taiwan University, Taipei, Taiwan, Republic of China.
Chia-Chien
CC
Hsieh
Ching-Jang
CJ
Huang
Bi-Fong
BF
Lin
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D020672:I-kappa B Proteins / Q000187:drug effects / Q000378:metabolism*; D007376:Interleukin-2 / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D000072000:NF-KappaB Inhibitor alpha; D047495:PPAR gamma / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology; D024502:alpha-Tocopherol / Q000494:pharmacology*
D000975:Antioxidants; D020672:I-kappa B Proteins; D007376:Interleukin-2; C000606205:Nfkbia protein, mouse; D047495:PPAR gamma; D012333:RNA, Messenger; D000072000:NF-KappaB Inhibitor alpha; D024502:alpha-Tocopherol