title: Systemic inflammation disrupts oligodendrocyte gap junctions and induces ER stress in a model of CNS manifestations of X-linked Charcot-Marie-Tooth disease.
abstract: X-linked Charcot-Marie-Tooth disease (CMT1X) is a common form of inherited neuropathy resulting from different mutations affecting the gap junction (GJ) protein connexin32 (Cx32). A subset of CMT1X patients may additionally present with acute fulminant CNS dysfunction, typically triggered by conditions of systemic inflammation and metabolic stress. To clarify the underlying mechanisms of CNS phenotypes in CMT1X we studied a mouse model of systemic inflammation induced by lipopolysaccharide (LPS) injection to compare wild type (WT), connexin32 (Cx32) knockout (KO), and KO T55I mice expressing the T55I Cx32 mutation associated with CNS phenotypes. Following a single intraperitoneal LPS or saline (controls) injection at the age of 40-60 days systemic inflammatory response was documented by elevated TNF-α and IL-6 levels in peripheral blood and mice were evaluated 1 week after injection. Behavioral analysis showed graded impairment of motor performance in LPS treated mice, worse in KO T55I than in Cx32 KO and in Cx32 KO worse than WT. Iba1 immunostaining revealed widespread inflammation in LPS treated mice with diffusely activated microglia throughout the CNS. Immunostaining for the remaining major oligodendrocyte connexin Cx47 and for its astrocytic partner Cx43 revealed widely reduced expression of Cx43 and loss of Cx47 GJs in oligodendrocytes. Real-time PCR and immunoblot analysis indicated primarily a down regulation of Cx43 expression with secondary loss of Cx47 membrane localization. Inflammatory changes and connexin alterations were most severe in the KO T55I group. To examine why the presence of the T55I mutant exacerbates pathology even more than in Cx32 KO mice, we analyzed the expression of ER-stress markers BiP, Fas and CHOP by immunostaining, immunoblot and Real-time PCR. All markers were increased in LPS treated KO T55I mice more than in other genotypes. In conclusion, LPS induced neuroinflammation causes disruption of the main astrocyte-oligodendrocyte GJs, which may contribute to the increased sensitivity of Cx32 KO mice to LPS and of patients with CMT1X to various stressors. Moreover the presence of an intracellularly retained, misfolded CMT1X mutant such as T55I induces ER stress under inflammatory conditions, further exacerbating oligodendrocyte dysfunction and pathological changes in the CNS.
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
authors: Margarita
authors: M
authors: Olympiou
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
authors: Irene
authors: I
authors: Sargiannidou
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
authors: Kyriaki
authors: K
authors: Markoullis
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
authors: Christos
authors: C
authors: Karaiskos
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
authors: Alexia
authors: A
authors: Kagiava
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus.
authors: Styliana
authors: S
authors: Kyriakoudi
authors: Department of Neurology and Rehabilitation, University of Illinois at Chicago, Chicago, USA.
authors: Charles K
authors: CK
authors: Abrams
authors: Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, Nicosia, Cyprus. kleopa@cing.ac.cy.|Neurology Clinics, The Cyprus Institute of Neurology and Genetics and Cyprus School of Molecular Medicine, 6 International Airport Avenue, P.O. Box 23462, , 1683, Nicosia, Cyprus. kleopa@cing.ac.cy.
authors: Kleopas A
authors: KA
authors: Kleopa
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000276:immunology / Q000473:pathology; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002607:Charcot-Marie-Tooth Disease / Q000276:immunology* / Q000473:pathology; D018031:Connexin 43 / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000276:immunology* / Q000473:pathology; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D004926:Escherichia coli; D017629:Gap Junctions / Q000276:immunology* / Q000473:pathology; D007249:Inflammation / Q000276:immunology* / Q000473:pathology; D015850:Interleukin-6 / Q000097:blood; D008070:Lipopolysaccharides; D008297:Male; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000378:metabolism; D015213:Neuroimmunomodulation / Q000502:physiology; D009836:Oligodendroglia / Q000276:immunology* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000097:blood; D000097002:Gap Junction beta-1 Protein
chemical_list: D002135:Calcium-Binding Proteins; D018031:Connexin 43; D017630:Connexins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D008840:Microfilament Proteins; D014409:Tumor Necrosis Factor-alpha; D000097002:Gap Junction beta-1 Protein; C491049:Aif1 protein, mouse; C543076:GJA1 protein, mouse; C427305:connexin 47; C577686:interleukin-6, mouse
keywords: CMT1X; Cx43; Cx47; Gap junctions; LPS model; Oligodendrocytes