Kuroda Noriyuki, Inoue Kouji, Ikeda Tadayuki, Hara Yaiko, Wake Kenjiro, Sato Tetsuji
Department of Anatomy and Histocytology, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
Research Center of Electron Microscopy, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
PLoS One. 2014 Apr 1;9(4):e92884. doi: 10.1371/journal.pone.0092884. eCollection 2014.
HMGB1 is a nuclear component involved in nucleosome stabilization and transcription regulation, but extracellularly it is able to serve as a potential late mediator of lethality. In the present study, we explored inflammation-promoting activity of HMGB1 and blockade of extracellular release of HMGB1 by glycyrrhizin (GL) in LPS/GalN-triggered mouse liver injury. At 1 to 10 h after LPS/GalN-treatment, mice were anesthetized to collect blood from heart puncture, and serum transaminase and HMGB1 were evaluated. Administration of LPS/GalN precipitated tissue injury associated with time-dependent alteration in HMGB1 serum levels. At 8 h nuclear immunoreactive products were remarkably reduced and extracellular HMGB1 expression was found exclusively in the pericentral foci. The treatment with GL significantly down-regulated the serum levels of ALT, AST, and HMGB1 in addition to the strong inhibition of tissue injury and extracellular immunoreactivity to HMGB1 and to acetylated-lysine. Furthermore, GL brought about a significant decrease in the number of apoptotic hepatocytes labeled with TUNEL-method. On the basis of these results, three apoptosis-associated genes were identified with microarray analysis and real-time PCR. The ChIP-assay revealed the binding of HMGB1 protein to Gsto1 promoter sequence in LPS/GalN-treated mice and the remarkable decrease in combined HMGB1 protein by GL. The current findings claim that a single injection of LPS/GalN might stimulate apoptosis of hepatocytes through the binding of HMGB1 protein to Gsto1 promoter region and that GL-treatment might prevent the apoptosis and inflammatory infiltrates caused with LPS/GalN-injection by disturbing the binding of HMGB1 protein to Gsto1 promoter sequence.
高迁移率族蛋白B1（HMGB1）是一种参与核小体稳定和转录调控的核成分，但在细胞外它可作为致死性的潜在晚期介质。在本研究中，我们探讨了HMGB1的促炎活性以及甘草甜素（GL）对LPS/GalN诱导的小鼠肝损伤中HMGB1细胞外释放的阻断作用。在LPS/GalN处理后1至10小时，将小鼠麻醉，通过心脏穿刺采集血液，评估血清转氨酶和HMGB1。给予LPS/GalN会引发与HMGB1血清水平随时间变化相关的组织损伤。在8小时时，核免疫反应产物显著减少，细胞外HMGB1表达仅在中央周围病灶中发现。GL治疗除了能强烈抑制组织损伤以及对HMGB1和乙酰化赖氨酸的细胞外免疫反应外，还显著下调了ALT、AST和HMGB1的血清水平。此外，GL使TUNEL法标记的凋亡肝细胞数量显著减少。基于这些结果，通过微阵列分析和实时PCR鉴定了三个与凋亡相关的基因。染色质免疫沉淀分析显示，在LPS/GalN处理的小鼠中，HMGB1蛋白与Gsto1启动子序列结合，而GL使结合的HMGB1蛋白显著减少。目前的研究结果表明，单次注射LPS/GalN可能通过HMGB1蛋白与Gsto1启动子区域结合刺激肝细胞凋亡，而GL治疗可能通过干扰HMGB1蛋白与Gsto1启动子序列的结合来预防LPS/GalN注射引起的凋亡和炎症浸润。
