Clinical course of myelin oligodendrocyte glycoprotein 35-55 induced experimental autoimmune encephalomyelitis is aggravated by glia maturation factor.

The role of glia maturation factor (GMF) in myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide-induced experimental autoimmune encephalomyelitis (EAE) was investigated using GMF-deficient (GMF-KO) mice. We demonstrate that GMF-KO mice were resistant to the MOG 35-55 peptide-induced EAE as compared to wild type (Wt) mice (two in eight versus 10 in 10). Next, we examined the effect of administration of recombinant human GMF (rGMF) on MOG 35-55 peptide-induced EAE in mice. Daily administration of rGMF, staring days 1-14, resulted in significant exacerbation of clinical symptoms. Following rGMF injections, both GMF-KO (six in eight) and Wt mice (eight in eight) developed severe EAE (maximal clinical score of 3.5-4.0) with high frequency. The histological examination revealed severe infiltration of inflammatory cells in the spinal cord of MOG-immunized Wt mice while the resistance to EAE in GMF-KO mice was characterized by the absence of inflammatory cells. Administration of rGMF in Wt mice and GMF-KO mice resulted in a significant increase in infiltrating cells in the spinal cord following MOG-immunizations. We also evaluated cytokines and chemokines production as parameters of severity of inflammation in the spinal cord of Wt versus GMF-KO mice with and without GMF-reconstitution following MOG-immunizations. Cytokines (TNF-α, IFN-γ, IL-1ß, IL-6) and chemokines (CCL2, CCL3, CXCL10, GM-CSF) production were significantly greater in Wt mice than in GMF-KO mice following MOG-immunization. Furthermore, the reconstitution experiment with rGMF showed that the administration of rGMF in both, Wt mice and GMF-KO mice produced significant increase in the GMF-mediated cytokine/chemokine production.

Glia maturation factor overexpression in neuroblastoma cells activates glycogen synthase kinase-3beta and caspase-3.

In the present study we report that a replication-defective adenovirus construct of GMF cDNA (GMF-V) induced overexpression of GMF protein in neuroblastoma (N18) cells caused cytotoxicity and loss of cell viability. A significant increase in activation of GSK-3beta occurred after infection with GMF-V when compared with mock and lacZ controls. Overexpression of GMF also increased caspase-3 activity, an early marker of apoptosis. Depletion of GMF gene by introducing GMF-specific siRNA (GsiRNA) completely blocked both activation of GSK-3beta and caspase-3 activation whereas a control scrambled siRNA (CsiRNA) had no effect. A cell-permeable peptide inhibitor of GSK-3beta, and lithium completely prevented GMF-dependent activation of caspase-3. These results demonstrate that GSK-3 mediates activation of the death domain caspase by GMF overexpression. We also show that the phosphorylation of GSK-3-dependent site of Tau was a consequence of GMF-overexpression in N18 cells. Taken together our results imply that GMF is involved in the signaling leading to the activation of GSK-3beta and caspase-3 in N18 cells and strongly suggest its involvement in neurodegeneration since GSK-3beta is known to hyperphosphorylate tau which is associated with the neurotoxicity of neurofibrillary tangles in Alzheimer's disease.