Brown M C, Taffet S M
Department of Microbiology and Immunology, State University of New York Health Science Center at Syracuse 13210, USA.
Infect Immun. 1995 May;63(5):1960-8. doi: 10.1128/iai.63.5.1960-1968.1995.
The inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) is rapidly induced in macrophages after exposure to Mycobacterium tuberculosis. Recently it was shown that lipoarabinomannan (LAM) derived from an attenuated (H37Ra) strain of M. tuberculosis (AraLAM) was capable of macrophage activation and induction of TNF-alpha production, whereas LAM derived from the virulent Erdman strain (ManLAM) was considerably reduced in this activity. A critical component in the regulation of many genes central to immune function is the transcription factor NF-kappa B. Lipopolysaccharide (LPS)-mediated induction of TNF-alpha expression in murine macrophages has been demonstrated to be regulated in part by NF-kappa B. In this study, we demonstrate that AraLAM is capable of rapid activation of NF-kappa B- and KBF1-binding activities in C3H/HeN bone marrow-derived macrophages and the J774.A and RAW264.7 murine macrophagelike cell lines, whereas ManLAM is considerably less potent at stimulating NF-kappa B. Treatment of RAW264.7 cells with AraLAM or LPS results in the stimulation of DNA binding of both forms within 7.5 min, which peaks within 30 min and 1 h, respectively. Interestingly, treatment of RAW264.7 macrophage-like cells with AraLAM, LPS, or ManLAM for greater than 2 h resulted in significant accumulation of KBF1. Inhibition of protein synthesis blocked the transient nature of NF-kappa B activation as well as the accumulation of KBF1. Using Western immunodetection of the NF kappa B1 p50 subunit, we also show that AraLAM and LPS stimulate the loss of the NF kappa B1 p105 precursor. These results demonstrate that NF-kappa B and KBF1 are rapidly induced in response to AraLAM and may play a role in avirulent M. tuberculosis activation of TNF-alpha expression in macrophages. The differential temporal regulation of kappa B element DNA-binding activities and the transient stimulation of NF kappa B followed by the sustained accumulation of KBF1 may serve as a feedback switch ensuring transient induction of TNF-alpha transcription.
炎性细胞因子肿瘤坏死因子α（TNF-α）在巨噬细胞暴露于结核分枝杆菌后会迅速被诱导产生。最近研究表明，源自结核分枝杆菌减毒株（H37Ra）的脂阿拉伯甘露聚糖（LAM，AraLAM）能够激活巨噬细胞并诱导TNF-α的产生，而源自强毒株埃尔德曼株（ManLAM）的LAM在该活性方面则显著降低。免疫功能核心的许多基因调控中的一个关键成分是转录因子NF-κB。脂多糖（LPS）介导的小鼠巨噬细胞中TNF-α表达的诱导已被证明部分受NF-κB调控。在本研究中，我们证明AraLAM能够在C3H/HeN骨髓来源的巨噬细胞以及J774.A和RAW264.7小鼠巨噬样细胞系中快速激活NF-κB和KBF1结合活性，而ManLAM在刺激NF-κB方面的效力则低得多。用AraLAM或LPS处理RAW264.7细胞会在7.5分钟内刺激两种形式的DNA结合，分别在30分钟和1小时内达到峰值。有趣的是，用AraLAM、LPS或ManLAM处理RAW264.7巨噬样细胞超过2小时会导致KBF1的显著积累。蛋白质合成的抑制阻断了NF-κB激活的短暂特性以及KBF1的积累。使用NF-κB1 p50亚基的Western免疫检测，我们还表明AraLAM和LPS刺激NF-κB1 p105前体的丢失。这些结果表明，NF-κB和KBF1在对AraLAM的反应中被快速诱导，并且可能在无毒力结核分枝杆菌激活巨噬细胞中TNF-α表达中发挥作用。κB元件DNA结合活性的差异时间调控以及NF-κB的短暂刺激随后是KBF1的持续积累可能作为一种反馈开关，确保TNF-α转录的短暂诱导。
