Astrocytic tight junctions control inflammatory CNS lesion pathogenesis
Sam Horng, … , Candice Chapouly, Gareth R. John
Sam Horng, … , Candice Chapouly, Gareth R. John
Published August 1, 2017; First published July 24, 2017
Citation Information: J Clin Invest. 2017;127(8):3136-3151. https://doi.org/10.1172/JCI91301.
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Research Article Immunology Neuroscience

Astrocytic tight junctions control inflammatory CNS lesion pathogenesis

Abstract

Lesions and neurologic disability in inflammatory CNS diseases such as multiple sclerosis (MS) result from the translocation of leukocytes and humoral factors from the vasculature, first across the endothelial blood-brain barrier (BBB) and then across the astrocytic glia limitans (GL). Factors secreted by reactive astrocytes open the BBB by disrupting endothelial tight junctions (TJs), but the mechanisms that control access across the GL are unknown. Here, we report that in inflammatory lesions, a second barrier composed of reactive astrocyte TJs of claudin 1 (CLDN1), CLDN4, and junctional adhesion molecule A (JAM-A) subunits is induced at the GL. In a human coculture model, CLDN4-deficient astrocytes were unable to control lymphocyte segregation. In models of CNS inflammation and MS, mice with astrocyte-specific Cldn4 deletion displayed exacerbated leukocyte and humoral infiltration, neuropathology, motor disability, and mortality. These findings identify a second inducible barrier to CNS entry at the GL. This barrier may be therapeutically targetable in inflammatory CNS disease.

Authors

Sam Horng, Anthony Therattil, Sarah Moyon, Alexandra Gordon, Karla Kim, Azeb Tadesse Argaw, Yuko Hara, John N. Mariani, Setsu Sawai, Per Flodby, Edward D. Crandall, Zea Borok, Michael V. Sofroniew, Candice Chapouly, Gareth R. John

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Figure 1

Reactive astrocytes upregulate CLDN1, CLDN4, and JAM-A in vitro and in vivo.

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Reactive astrocytes upregulate CLDN1, CLDN4, and JAM-A in vitro and in v...
(A and B) Western immunoblots (2 replicates depicted) (A) and mean values of densitometric quantification of immunoblot band intensities (from 3 biological replicates) (B) from cultured human astrocytes treated with 10 ng/ml IL-1β, IFN-γ, or TGF-β1 for 24 hours. CLDN1, CLDN4, and JAM-A are all induced by IL-1β, and CLDN1 and CLDN4 are also induced by TGF-β1. The TJ-associated protein tricellulin is induced by TGF-β1 alone. CLDN5 is not expressed by astrocytes. See also Supplemental Figure 1, A and B. (C) Following treatment with 10 ng/ml IL-1β, CLDN4 induction begins at 6 hours, is maintained at 24 and 48 hours, and decreases at 72 hours. (D) Immunostaining of human astrocyte cultures demonstrates that IL-1β induces expression of CLDN1, CLDN4, and JAM-A (red), which localize to the cell membranes of cells positive for the astrocyte marker GFAP. Scale bars: 20 μm. (E) In control C57BL/6 mice, cortical microinjection in vivo of adenovirus expressing IL-1 (AdIL-1), but not a control sequence, AdDL70 (AdCtrl), induces reactive astrocyte morphology and upregulation of CLDN1, CLDN4, and JAM-A at 7 days postinjection (7 dpi). Images are 3-dimensionally rendered projections. Scale bars: 40 μm. Data are representative of findings from 3 (A–C, and E) or more than 3 (D) biological replicates. *P < 0.05, **P < 0.01, ***P < 0.001.