Lymphotoxin β receptor (LtβR):: Dual roles in demyelination and remyelination and successful therapeutic intervention using LtβR-Ig protein

Inflammation mediated by macrophages is increasingly found to play a central role in diseases and disorders that affect a myriad of organs, prominent among these are diseases of the CNS. The neurotoxicant-induced, cuprizone model of demyelination is ideally suited for the analysis of inflammatory events. Demyelination on exposure to cuprizone is accompanied by predictable microglial activation and astrogliosis, and, after cuprizone withdrawal, this activation reproducibly diminishes during remyelination. This study demonstrates enhanced expression of lymphotoxin beta receptor (Lt beta R) during the demyelination phase of this model, and Lt beta R is found in areas enriched with microglial and astroglial cells. Deletion of the Lt beta R gene (Lt beta R-/-) resulted in a significant delay in demyelination but also a slight delay in remyelination. Inhibition of Lt beta R signaling by an Lt beta R-Ig fusion decoy protein successfully delayed demyelination in wild-type mice. Unexpectedly, this Lt beta R-Ig decoy protein dramatically accelerated the rate of remyelination, even after the maximal pathological disease state had been reached. This strongly indicates the beneficial role of Lt beta R-Ig in the delay of demyelination and the acceleration of remyelination. The discrepancy between remyelination rates in these systems could be attributed to developmental abnormalities in the immune systems of Lt beta R-/- mice. These findings bode well for the use of an inhibitory Lt beta R-Ig as a candidate biological therapy in demyelinating disorders, because it is beneficial during both demyelination and remyelination.