Oxygen Signaling Research Group, Maternal and Child Health Sciences, School of Medicine, Ninewells Hospital and Medical School, University of Dundee, Dundee, Scotland, UK.
Neuroscience. 2009 Dec 29;164(4):1509-20. doi: 10.1016/j.neuroscience.2009.09.056. Epub 2009 Sep 25.
The transcription factor nuclear factor kappaB (NF-kappaB) is one member of a ubiquitously expressed family of Rel-related transcription factors that serve as critical regulators of many proinflammatory genes and immunomodulators. Nevertheless, the immunomodulatory potential of thymulin and its effect on NF-kappaB in vivo, and particularly in the central nervous system (CNS), is not well characterized. In this study, the role of endotoxin (ET/LPS) in regulating NF-kappaB was deciphered in various compartments of the CNS. Stereotaxic localization reverberated specific intracerebroventricular (ICV) injection of ET into the CNS, with or without pretreatment with ICV thymulin. Treatment with ET (1 microg for 45 min; ICV) upregulated the expression and nuclear localization of NF-kappaB(1) (p50), NF-kappaB(2) (p52), RelA (p65), RelB (p68) and c-Rel (p75) in the hippocampus (HC), an effect abrogated, in a dose-dependent manner, by ICV pretreatment (30 min) with thymulin. Thymulin modulated the phosphorylation of IkappaB-alpha in the HC by upregulating the cytosolic accumulation of IkappaB-alpha and downregulating its phosphorylation (pIkappaB-alpha). Further analysis of the DNA-binding activity revealed an upregulated activity in the HC relative to saline-constitutive expression of the RelA (p65) subunit, the specificity of which was determined by a mutant oligonucleotide of RelA and a cold, non-specific competitor. ET did not induce the DNA-binding activity of NF-kappaB in the diencephalon (DE) or substantia nigra (SN) at various time points, when compared with baseline levels of expression. Intraperitoneal (IP) injections of ET (25 microg for 15 min) in vivo upregulated the expression of NF-kappaB subunits in the liver and reduced the cytosolic accumulation of IkappaB-alpha by inducing pIkappaB-alpha. Furthermore, IP pretreatment with thymulin followed by ICV injection of ET attenuated and reduced the DNA-binding activity of NF-kappaB in the HC. These results indicate that ICV injection of ET regulates the nuclear translocation and activation of NF-kappaB subunits within specific compartments in the brain, an effect particularly localized to the hippocampus. Additionally, thymulin attenuated the ET-induced response, with particular involvement of the transduction pathway implicating IkappaB-alpha, the major cytosolic inhibitor of NF-kappaB. The in vivo molecular regulation of thymulin via the NF-kappaB pathway is critical to understanding the alleviating anti-inflammatory role of this nonapeptide and paving the way to unraveling pathways associated with neuroimmune interactions mediating proinflammatory signals in the CNS.
转录因子核因子 kappaB（NF-kappaB）是一类广泛表达的 Rel 相关转录因子家族的成员之一，作为许多促炎基因和免疫调节剂的关键调节因子。然而，胸腺肽的免疫调节潜力及其在体内，特别是中枢神经系统（CNS）中的对 NF-kappaB 的影响尚未得到很好的描述。在这项研究中，阐明了内毒素（ET/LPS）在中枢神经系统不同隔室中对 NF-kappaB 的调节作用。立体定位反应证实了特定的侧脑室（ICV）注射 ET 进入中枢神经系统，同时或不预先进行 ICV 胸腺肽处理。用 ET（1μg，45min；ICV）处理可上调海马体（HC）中 NF-kappaB（1）（p50）、NF-kappaB（2）（p52）、RelA（p65）、RelB（p68）和 c-Rel（p75）的表达和核定位，这种作用以剂量依赖的方式被 ICV 预处理（30min）胸腺肽所阻断。胸腺肽通过上调 IkappaB-alpha 的细胞质积累并下调其磷酸化（pIkappaB-alpha）来调节 HC 中 IkappaB-alpha 的磷酸化。进一步分析 DNA 结合活性显示，相对于生理盐水组成型表达，HC 中 RelA（p65）亚基的活性上调，其特异性由 RelA 的突变寡核苷酸和冷非特异性竞争物决定。与基线表达相比，在不同时间点，ET 不会在间脑（DE）或黑质（SN）中诱导 NF-kappaB 的 DNA 结合活性。体内腹腔内（IP）注射 ET（25μg，15min）可上调肝脏中 NF-kappaB 亚基的表达，并通过诱导 pIkappaB-alpha 减少 IkappaB-alpha 的细胞质积累。此外，IP 预处理胸腺肽后 ICV 注射 ET 可减弱并降低 HC 中 NF-kappaB 的 DNA 结合活性。这些结果表明，ICV 注射 ET 调节脑内特定隔室中 NF-kappaB 亚基的核易位和激活，这种作用特别局限于海马体。此外，胸腺肽减弱了 ET 诱导的反应，特别是涉及 IkappaB-alpha 的转导途径，IkappaB-alpha 是 NF-kappaB 的主要细胞质抑制剂。通过 NF-kappaB 途径对胸腺肽的体内分子调节对于理解这种非肽的抗炎作用的缓解作用以及为揭示与中枢神经系统中促炎信号的神经免疫相互作用相关的途径铺平道路至关重要。
