title: The intrinsic microglial clock system regulates interleukin-6 expression.
abstract: Similar to neurons, microglia have an intrinsic molecular clock. The master clock oscillator Bmal1 modulates interleukin-6 upregulation in microglial cells exposed to lipopolysaccharide. Bmal1 can play a role in microglial inflammatory responses. We previously demonstrated that gliotransmitter ATP induces transient expression of the clock gene Period1 via P2X7 purinergic receptors in cultured microglia. In this study, we further investigated mechanisms underlying the regulation of pro-inflammatory cytokine production by clock molecules in microglial cells. Several clock gene transcripts exhibited oscillatory diurnal rhythmicity in microglial BV-2 cells. Real-time luciferase monitoring also showed diurnal oscillatory luciferase activity in cultured microglia from Per1::Luciferase transgenic mice. Lipopolysaccharide (LPS) strongly induced the expression of pro-inflammatory cytokines in BV-2 cells, whereas an siRNA targeting Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), a core positive component of the microglial molecular clock, selectively inhibited LPS-induced interleukin-6 (IL-6) expression. In addition, LPS-induced IL-6 expression was attenuated in microglia from Bmal1-deficient mice. This phenotype was recapitulated by pharmacological disruption of oscillatory diurnal rhythmicity using the synthetic Rev-Erb agonist SR9011. Promoter analysis of the Il6 gene revealed that Bmal1 is required for LPS-induced IL-6 expression in microglia. Mice conditionally Bmal1 deficient in cells expressing CD11b, including microglia, exhibited less potent upregulation of Il6 expression following middle cerebral artery occlusion compared with that in control mice, with a significant attenuation of neuronal damage. These results suggest that the intrinsic microglial clock modulates the inflammatory response, including the positive regulation of IL-6 expression in a particular pathological situation in the brain, GLIA 2016. GLIA 2017;65:198-208.
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.|Division of Molecular Cell Signaling, Cancer Research Institute, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Nakazato
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Hotta
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.|Department of Pharmacology, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yamada
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Kou
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Saki
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan.|Department of Molecular and Cellular Biochemistry, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, 565-0871, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Takahata
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Tei
authors.affiliation: Department of Environmental and Life Sciences, and Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, Toyohashi, Aichi, 441-8580, Japan.
authors.forename: Rika
authors.initials: R
authors.lastname: Numano
authors.affiliation: Department of Psychophysiology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Kodaira, Tokyo, 187-8553, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Hida
authors.affiliation: Department of Health Science, College of Pharmacy, Nihon University, Chiba, 274-8555, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shimba
authors.affiliation: Department of Molecular Neuroscience and Integrative Physiology, Faculty of Medicine, Kanazawa University, Kanazawa, Ishikawa, 920-8640, Japan.
authors.forename: Michihiro
authors.initials: M
authors.lastname: Mieda
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Hinoi
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Yoneda
authors.affiliation: Division of Pharmaceutical Sciences, Laboratory of Molecular Pharmacology, Kanazawa University Graduate School, Kanazawa, Ishikawa, 920-1192, Japan.|Department of Regenerative Science, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, 700-8558, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Takarada
mesh_terms: D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D018345:Mice, Knockout; D008822:Mice, Transgenic; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D013997:Time Factors; D015533:Transcriptional Activation / Q000187:drug effects*; D015854:Up-Regulation
chemical_list: D015850:Interleukin-6; D008070:Lipopolysaccharides; C577686:interleukin-6, mouse
keywords: Bmal1; IL-6; clock genes; microglia