Inhibition of System Xc- Transporter Attenuates Autoimmune Inflammatory Demyelination

T cell infiltration into the CNS is a significant underlying pathogenesis in autoimmune inflammatory demyelinating diseases. Several lines of evidence suggest that glutamate dysregulation in the CNS is an important consequence of immune cell infiltration in neuro-inflammatory demyelinating diseases; yet, the causal link between inflammation and glutamate dysregulation is not well understood. A major source of glutamate release during oxidative stress is the system X-c (-) transporter; however, this mechanism has not been tested in animal models of autoimmune inflammatory demyelination. We find that pharmacological and genetic inhibition of system X-c (-) attenuates chronic and relapsing-remitting experimental autoimmune encephalomyelitis (EAE). Remarkably, pharmacological blockade of system X-c (-) 7 d after induction of EAE attenuated T cell infiltration into the CNS, but not T cell activation in the periphery. Mice harboring a Slc7a11 (xCT) mutation that inactivated system X-c (-) were resistant to EAE, corroborating a central role for system X-c (-) in mediating immune cell infiltration. We next examined the role of the system X-c (-) transporter in the CNS after immune cell infiltration. Pharmacological inhibitors of the system X-c (-) transporter administered during the first relapse in a SJL animal model of relapsing-remitting EAE abrogated clinical disease, inflammation, and myelin loss. Primary coculture studies demonstrate that myelin-specific CD4(+) Th1 cells provoke microglia to release glutamate via the system X-c (-) transporter, causing excitotoxic death to mature myelin-producing oligodendrocytes. Taken together, these studies support a novel role for the system X-c (-) transporter in mediating T cell infiltration into the CNS as well as promoting myelin destruction after immune cell infiltration in EAE.