B4GALT6 regulates astrocyte activation during CNS inflammation (INM8P.360)

Abstract

Abstract Astrocytes play complex roles in neuroinflammation. Thus, it is important to characterize the mechanisms regulating astrocyte function, as well as potential targets for the therapeutic modulation of astrocyte activity. Here we report that during the chronic-progressive phase of EAE, astrocytes promote disease pathogenesis by a lipid-dependent signaling pathway. In line with previous studies, depletion of reactive astrocytes during the acute phase of chronic-progressive EAE exacerbated disease. However, depletion of astrocytes in the chronic phase ameliorated the disease. Hence, to understand this dichotomy we compared gene expression profiles of astrocytes from mice in acute and chronic stages of EAE. One gene associated with the chronic stage was B4GALT6, which codes for the β-1,4-galactosyltransferase 6 that catalyzes the synthesis of lactosylceramide (LacCer). We observed that LacCer levels are upregulated in the CNS during chronic EAE, and that LacCer synthesized by the astrocytes acts in an autocrine manner to trigger transcriptional programs that promote the recruitment and activation of infiltrating monocytes and microglia, and neurodegeneration. We also detected increased B4GALT6 expression and LacCer levels in MS lesions. Finally, the inhibition of LacCer synthesis suppressed CNS innate immunity and neurodegeneration, and interfered with the activation of human astrocytes. Thus, B4GALT6 is a potential therapeutic target for MS and neuroinflammatory disorders.