title: High-mobility group box 1 up-regulates aquaporin 4 expression via microglia-astrocyte interaction.
abstract: 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.
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan. Electronic address: ohnishi@fupharm.fukuyama-u.ac.jp.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ohnishi
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Monda
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Ryoko
authors.initials: R
authors.lastname: Takemoto
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Yukina
authors.initials: Y
authors.lastname: Fujimoto
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Sugitani
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Iwamura
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hiroyasu
authors.affiliation: Department of Pharmacotherapeutics, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, 985-1 Sanzo, Higashimura-cho, Fukuyama, Hiroshima 729-0292, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Inoue
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000235:genetics / Q000502:physiology*; D001253:Astrocytes / Q000166:cytology* / Q000378:metabolism; D001483:Base Sequence; D017931:DNA Primers; D024002:HMGB Proteins / Q000502:physiology*; D053583:Interleukin-1beta / Q000096:biosynthesis; D017628:Microglia / Q000166:cytology* / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D051401:Aquaporin 4; D017931:DNA Primers; D024002:HMGB Proteins; D053583:Interleukin-1beta; D016328:NF-kappa B; D012333:RNA, Messenger
keywords: Aquaporin 4; Astrocyte; High-mobility group box 1; Interleukin-1β; Microglia; Nuclear factor-κB