Nomura Y, Uehara T, Nishiya T
Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Nihon Yakurigaku Zasshi. 1999 Oct;114 Suppl 1:92P-95P. doi: 10.1254/fpj.114.supplement_92.
To elucidate the intracellular mechanism of NF-kappa B activation, we performed the involvement of I kappa B alpha of NF-kappa B in the expression of inducible NO synthase (iNOS) and chemokine (CINC) following pretreatment with bacterial endotoxin (LPS) or IL-1 beta, respectively, using rat C6 glioma cells. We found that herbimycin A, a tyrosine protein kinase inhibitor, blocked: 1) LPS/IFN gamma-induced iNOS expression, 2) LPS-induced intranuclear translocation of activated NF-kappa B (p50. p65) and 3) IFN gamma-induced autophosphorylation and activation of Jak 2 and Stat 1 as well as intranuclear translocation of phosphorylated Stat 1. Furthermore, transfection of a dominant negative form of I kappa B alpha (SS-->AA) suppressed LPS/IFN gamma-induced iNOS expression, suggesting that NF-kappa B, in particular, I kappa B alpha molecules could play important roles in the iNOS expression. We also found in IL-1 beta-induced CINC expression using cultured C6 glioma cells, the transient translocation of NF-kappa B in response to IL-1 beta is partly dependent on transient proteasome activation. Thus we suggest that the formation of heterodimer p50.p65 from inactive trimer p50.p65.I kappa B alpha, particularly, proteolytic degradation and dissociation of I kappa B alpha from p50.p65 are a critical phase in NF-kappa B activation during LPS-induced iNOS and IL-1 beta-induced CINC expression in astroglial cells.
为了阐明核因子-κB（NF-κB）激活的细胞内机制，我们利用大鼠C6胶质瘤细胞，分别研究了在细菌内毒素（LPS）或白细胞介素-1β（IL-1β）预处理后，NF-κB的抑制蛋白α（IκBα）在诱导型一氧化氮合酶（iNOS）和趋化因子（CINC）表达中的作用。我们发现，酪氨酸蛋白激酶抑制剂赫曲霉素A可阻断：1）LPS/γ干扰素诱导的iNOS表达；2）LPS诱导的活化NF-κB（p50、p65）的核内转位；3）γ干扰素诱导的Jak 2和信号转导子和转录激活子1（Stat 1）的自磷酸化及激活，以及磷酸化Stat 1的核内转位。此外，转染显性负性形式的IκBα（SS→AA）可抑制LPS/γ干扰素诱导的iNOS表达，这表明NF-κB，尤其是IκBα分子可能在iNOS表达中发挥重要作用。我们还发现，在使用培养的C6胶质瘤细胞进行的IL-1β诱导的CINC表达中，NF-κB对IL-1β的瞬时转位部分依赖于瞬时蛋白酶体激活。因此我们认为，由无活性三聚体p50.p65.IκBα形成异二聚体p50.p65，特别是IκBα从p50.p65的蛋白水解降解和解离，是星形胶质细胞中LPS诱导iNOS和IL-1β诱导CINC表达过程中NF-κB激活的关键阶段。
