Contributions
Abstract: 107
Type: Oral
Abstract Category: Pathology and pathogenesis of MS - 18 Neurobiology
Neuromyelitis optica (NMO) is a rare autoimmune demyelinating disease mediated by a specific autoantibody (NMO-IgG) directed against the astrocytic protein aquaporin-4 (AQP4). NMO-IgG identification was a quantum leap in understanding NMO physiopathology. However, there are still major open questions, especially the link between the astrocytopathy and demyelination. Connexins (Cx) are transmembrane proteins that form either hemichannel (HC) or gap junction channel (GJC). Those two different functions allow a paracellular dialogue as well as a quick cell-to-cell exchange of ions and small molecules (e.g. calcium, glutamate, ATP, D-glucose) in the neuroglial cell network. HC and GJC have been shown to be oppositely regulated during inflammation. Moreover, Cx have been shown to be essential for myelination as they participate in the maintenance of a neuroglial syncytium.
We hypothesized that, in NMO, connexins are the support of a pathogenic dialogue between astrocytes, oligodendrocytes and neurons triggered by NMO-IgG, leading to demyelination.NMO-IgG were purified from 6 NMO patients' sera, and control-IgG (Ctrl-IgG) from a healthy donor. We first studied effects of NMO-IgG on myelin integrity in a myelinated culture made from embryonic rat spinal cord. We found that NMO-IgG induce demyelination shown not only with a reduced myelin segment size (-34,9%; p< 0,001) but also a decrease of the density of myelinated axons (-47,9%; p< 0,001) compared to Ctrl-IgG. The implication of Cx is under investigation by using of peptide inhibitors of Cx HC and GJC functions. We then studied Cx43 membrane expression by cell fractioning assay and western blot analysis and found a early loss of Cx43 at the membrane after 1h contact with NMO-IgG and a reexpression after 24h. We further studied Cx43 Gap Junction plaque size by electron microscopy which was increased by NMO-IgG after 24h contact (+54% p< 0,001 compared to Ctrl-IgG). We then studied GJC activity with scrap loading dye transfer technic and found that dye diffusion was dramatically reduced by NMO-IgG (-67%; p< 0,001; compared to Ctrl-IgG). The HC function is under investigation.
Thus, we demonstrate that NMO-IgG profoundly alter Cx expression and function in astrocyte leading to a modification of the microenvironment, known to participate in myelin formation and integrity. This is a first step in understanding how astrocytopathy and notably Cx alteration could lead to demyelination in NMO.
Disclosure: Nothing to disclose
Abstract: 107
Type: Oral
Abstract Category: Pathology and pathogenesis of MS - 18 Neurobiology
Neuromyelitis optica (NMO) is a rare autoimmune demyelinating disease mediated by a specific autoantibody (NMO-IgG) directed against the astrocytic protein aquaporin-4 (AQP4). NMO-IgG identification was a quantum leap in understanding NMO physiopathology. However, there are still major open questions, especially the link between the astrocytopathy and demyelination. Connexins (Cx) are transmembrane proteins that form either hemichannel (HC) or gap junction channel (GJC). Those two different functions allow a paracellular dialogue as well as a quick cell-to-cell exchange of ions and small molecules (e.g. calcium, glutamate, ATP, D-glucose) in the neuroglial cell network. HC and GJC have been shown to be oppositely regulated during inflammation. Moreover, Cx have been shown to be essential for myelination as they participate in the maintenance of a neuroglial syncytium.
We hypothesized that, in NMO, connexins are the support of a pathogenic dialogue between astrocytes, oligodendrocytes and neurons triggered by NMO-IgG, leading to demyelination.NMO-IgG were purified from 6 NMO patients' sera, and control-IgG (Ctrl-IgG) from a healthy donor. We first studied effects of NMO-IgG on myelin integrity in a myelinated culture made from embryonic rat spinal cord. We found that NMO-IgG induce demyelination shown not only with a reduced myelin segment size (-34,9%; p< 0,001) but also a decrease of the density of myelinated axons (-47,9%; p< 0,001) compared to Ctrl-IgG. The implication of Cx is under investigation by using of peptide inhibitors of Cx HC and GJC functions. We then studied Cx43 membrane expression by cell fractioning assay and western blot analysis and found a early loss of Cx43 at the membrane after 1h contact with NMO-IgG and a reexpression after 24h. We further studied Cx43 Gap Junction plaque size by electron microscopy which was increased by NMO-IgG after 24h contact (+54% p< 0,001 compared to Ctrl-IgG). We then studied GJC activity with scrap loading dye transfer technic and found that dye diffusion was dramatically reduced by NMO-IgG (-67%; p< 0,001; compared to Ctrl-IgG). The HC function is under investigation.
Thus, we demonstrate that NMO-IgG profoundly alter Cx expression and function in astrocyte leading to a modification of the microenvironment, known to participate in myelin formation and integrity. This is a first step in understanding how astrocytopathy and notably Cx alteration could lead to demyelination in NMO.
Disclosure: Nothing to disclose