Ohnishi Masatoshi, Monda Ayaka, Takemoto Ryoko, Fujimoto Yukina, Sugitani Mitsumasa, Iwamura Takahiro, Hiroyasu Takashi, Inoue Atsuko
Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
Neurochem Int. 2014 Sep;75:32-8. doi: 10.1016/j.neuint.2014.05.007. Epub 2014 Jun 2.
To clarify the mechanism of high-mobility group box (HMGB) 1-induced brain edema formation, this study focused on the effect of HMGB1 on aquaporin (AQP) 4, a water channel, in rat brain. Treatments for 6h with 100-1000ng/ml HMGB1, not showing self-toxicity, of primary-cultured rat astrocytes didnot increase AQP4 mRNA, unexpectedly. In contrast, intracerebroventricular (i.c.v.) injection of 300ng of HMGB1 significantly increased AQP4 protein after 8h and formed edema after 24h in vivo. Thus, we investigated the roles of microglia as well as astrocytes. HMGB1 (1000ng/ml) drastically increased interleukin (IL)-1β in the primary-cultured rat microglia after 2h. The exposure of microglia to conditioned medium with HMGB1 and 3mM adenosine 5'-triphosphate for 6h significantly increased AQP4 mRNA in astrocytes after 6h. Although 1000ng/ml HMGB1 didnot induce transfer of nuclear factor (NF)-κB into the nucleus in astrocytes after 1h, the conditioned medium containing IL-1β led to its nuclear import. As factors likely to be involved in the nuclear import of NF-κB besides IL-1β, nitric oxide and tumor necrosis factor-α didnot contribute under these conditions. Finally, i.c.v. injection of 30nmol parthenolide, an NF-κB inhibitor, reversed 300ng of HMGB1 injection-induced AQP4 protein increase after 8h in vivo. The effect of parthenolide and the outcomes obtained so far suggest that HMGB1 indirectly up-regulates AQP4 expression through diffusible factor(s) such as IL-1β from microglia since HMGB1 by itself didnot affect NF-κB intracellular localization in astrocytes.
为阐明高迁移率族蛋白盒1（HMGB1）诱导脑水肿形成的机制，本研究聚焦于HMGB1对大鼠脑内水通道蛋白4（AQP4）的影响。用100 - 1000ng/ml的HMGB1处理原代培养的大鼠星形胶质细胞6小时，该浓度未显示出自身毒性，但出乎意料的是，并未增加AQP4 mRNA水平。相反，脑室内（i.c.v.）注射300ng HMGB1在体内8小时后显著增加了AQP4蛋白水平，并在24小时后形成了水肿。因此，我们研究了小胶质细胞以及星形胶质细胞的作用。HMGB1（1000ng/ml）在2小时后显著增加了原代培养的大鼠小胶质细胞中的白细胞介素（IL）-1β水平。小胶质细胞在含有HMGB1和3mM腺苷5'-三磷酸的条件培养基中暴露6小时后，6小时后星形胶质细胞中的AQP4 mRNA显著增加。虽然1000ng/ml HMGB1在1小时后未诱导星形胶质细胞中核因子（NF）-κB转移至细胞核，但含有IL-1β的条件培养基导致其核内导入。作为除IL-1β外可能参与NF-κB核内导入的因素，一氧化氮和肿瘤坏死因子-α在这些条件下并无作用。最后，脑室内注射30nmol的NF-κB抑制剂小白菊内酯，可逆转体内8小时后300ng HMGB1注射诱导的AQP4蛋白增加。小白菊内酯的作用以及目前所获得的结果表明，由于HMGB1本身并不影响星形胶质细胞中NF-κB的细胞内定位，因此HMGB1通过来自小胶质细胞的诸如IL-1β等可扩散因子间接上调AQP4表达。
