Arsenic inhibits NF-κB-mediated gene transcription by blocking IκB kinase activity and IκBα phosphorylation and degradation
Arsenic inhibits NF-κB-mediated gene transcription by blocking IκB kinase activity and IκBα phosphorylation and degradation
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DOI：
10.1006/abbi.2000.1770
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发表时间：
2000-05-01
影响因子：
3.9
通讯作者：
Barchowsky, A
中科院分区：
文献类型：
--
作者：
Roussel, RR;Barchowsky, A
炎性细胞因子TNF-α通过涉及蛋白酶体介导的I κ B α降解和NF-κ B活化的机制诱导IL-8基因转录。在这里，我们研究了砷是否可以抑制泛素-蛋白酶体途径，抑制TNF-α介导的IL-8表达增加。使用RT-PCR，我们表明，TNF-α加入人支气管上皮细胞（BEAS 2B）或胚胎肾细胞（HEK 293）导致IL-8 mRNA的稳态水平增加。在此之前，细胞I κ B α水平快速下降，如Western分析所示，核NF-κ B水平增加，如凝胶位移分析所示。进一步证实了NF-κ B B的活化，TNF-α诱导了NF-κ B依赖性报告基因的转录。在加入TNF-α之前，将细胞暴露于500 μ M的亚砷酸盐中，完全抑制I κ B α降解、NF-κ B易位、NF-κ B依赖性基因转录和IL-8内源性基因的转录。蛋白酶体抑制剂MG-132不影响I kappa B α的磷酸化和泛素化，而亚砷酸盐抑制I kappa B α的磷酸化。此外，亚砷酸盐直接阻断IKK的活性，IKK是负责I κ B α磷酸化的激酶。这些研究表明，高水平的砷可能通过特异性阻断IKK活性来抑制NF-κ B介导的基因转录，从而限制NF-κ B抑制剂I κ B α的磷酸化和随后的降解。(C)北京大学出版社.
The inflammatory cytokine, TNF-alpha, induces IL-8 gene transcription via a mechanism involving proteasome-mediated I kappa B alpha degradation and NF-kappa B activation. Here, we investigated whether arsenic, which has been shown to inhibit the ubiquitin-proteasome pathway, could inhibit TNF-alpha-mediated increases in IL-8 expression. Using RT-PCR, we show that the addition of TNF-alpha to human bronchial epithelial (BEAS 2B) or embryonic kidney (HEK293) cells resulted in increased steady-state levels of IL-8 mRNA. This was preceded by a rapid decrease in cellular I kappa B alpha levels, as demonstrated by Western analysis, and an increase in nuclear levels of NF-kappa B, as demonstrated by gel shift analysis. Further demonstrating the activation of NF-kappa B, TNF-alpha induced the transcription of a NF-kappa B-dependent reporter gene. Exposing the cells to 500 mu M arsenite, prior to adding TNF-alpha; completely inhibited I kappa B alpha degradation, NF-kappa B translocation, NF-kappa B-dependent gene transcription, and transcription of the endogenous gene for IL-8. In comparison with the proteasome inhibitor MG-132, which does not affect the phosphorylation and ubiquitination of I kappa B alpha; arsenite inhibited the phosphorylation of I kappa B alpha. Furthermore, arsenite directly blocked the activity of IKK, the kinase responsible for I kappa B alpha phosphorylation. These studies demonstrate that high levels of arsenic may inhibit NF-kappa B-mediated gene transcription by specifically blocking IKK activity, thereby limiting the phosphorylation and subsequent degradation of the NF-kappa B inhibitor, I kappa B alpha. (C) 2000 Academic Press.