Silica induces nuclear factor-κB activation through tyrosine phosphorylation of IκB-α in RAW264.7 macrophages
Silica induces nuclear factor-κB activation through tyrosine phosphorylation of IκB-α in RAW264.7 macrophages
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DOI：
10.1006/taap.2000.9039
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发表时间：
2000-11-15
影响因子：
3.8
通讯作者：
Castranova, V
中科院分区：
文献类型：
--
作者：
Kang, JL;Pack, IS;Castranova, V
先前报道，蛋白酪氨酸激酶(PTK)而不是蛋白激酶C或A在二氧化硅诱导的巨噬细胞核因子-kappaB活化中起重要作用。提出的问题是，在二氧化硅刺激的巨噬细胞中，PTK的刺激和NF-kappaB的激活是否通过I kappaB-α的酪氨酸磷酸化直接相关。结果表明，二氧化硅刺激巨噬细胞可通过酪氨酸磷酸化而不是丝氨酸磷酸化来激活核因子-kappaB。蛋白酪氨酸激酶的特定抑制剂，如金雀异黄素和酪磷蛋白AG126，阻止了二氧化硅对I kappaB-α的酪氨酸磷酸化反应。SiO_2刺激后60min，I-kappaB-α蛋白水平保持相对不变。此外，抑制蛋白酶体的蛋白分解活性并不影响二氧化硅抗氧化剂如超氧化物歧化酶(SOD)、N-乙酰半胱氨酸(NAC)和吡咯烷二硫代氨基甲酸酯(PDTC)的激活，阻断二氧化硅诱导的I kappaB-α的酪氨酸磷酸化，提示活性氧物种(ROS)可能是通过I kappaB-α的酪氨酸磷酸化而激活NF-kappaB的重要调节分子。结果表明，在二氧化硅刺激的巨噬细胞中，I kappaB-α的酪氨酸磷酸化代表了一种不依赖于蛋白酶体蛋白分解活性的激活核因子-kappaB的机制，该机制直接将核因子-kappaB与细胞酪氨酸激酶偶联。这一被提出的二氧化硅诱导核因子-kappaB活化的机制可作为抗炎和抗纤维化药物开发的靶点，(C)2000学术出版社。
It was previously reported that protein tyrosine kinase (PTK) but not protein kinase C or A plays an important role in silica-induced activation of NF-kappaB in macrophages. The question is raised whether PTK stimulation and NF-kappaB activation in silica-stimulated macrophages are directly connected through tyrosine phosphorylation of I kappaB-alpha. Results indicate that stimulation of macrophages with silica led to NF-kappaB activation through tyrosine phosphorylation without serine phosphorylation. Specific inhibitors of protein tyrosine kinase, such as genistein and tyrophostin AG126, prevented tyrosine phosphorylation of I kappaB-alpha in response to silica. I kappaB-alpha protein levels remained relatively unchanged for up to 60 min after silica stimulation. Moreover, inhibition of proteasome proteolytic activity did not affect NF-kappaB activation by silica Antioxidants, such as superoxide dismutase (SOD), N-acetylcysteine (NAC), and pyrrolidine dithiocarbamate (PDTC), blocked tyrosine phosphorylation of I kappaB-alpha: induced by silica, suggesting reactive oxygen species (ROS) may be important regulatory molecules in NF-kappaB activation through tyrosine phosphorylation of I kappaB-alpha. The results suggest that tyrosine phosphorylation of I kappaB-alpha represents a proteasome proteolytic activity-independent mechanism for NF-kappaB activation that directly couples NF-kappaB to cellular tyrosine kinase in silica-stimulated macrophages. This proposed mechanism of NF-kappaB activation induced by silica could be used as a target for development of antiinflammatory and antifibrosis drugs, (C) 2000 Academic Press.