Accumulation of protein carbonyls within cerebellar astrocytes in murine experimental autoimmune encephalomyelitis

Recent work from our laboratory has implicated protein carbonylation in the pathophysiology of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). The present study was designed to determine the changes in protein carbonylation during disease progression and to identify the target cells and modified proteins in the cerebellum of EAE animals, prepared by active immunization of C57/BL6 mice with MOG(35-55) peptide. In this model, protein carbonylation was maximal at the peak of the disease (acute phase), to decrease thereafter (chronic phase). Double-immunofluorescence microscopy of affected cerebella showed that carbonyls accumulate in white matter astrocytes and to a lesser extent in microglia/macrophages, in both the acute and the chronic phase. Surprisingly, T cells, oligodendrocytes, and neurons were barely stained. By 2D oxyblot and mass spectrometry, β-actin, β-tubulin, GFAP, and HSC-71 were identified as the major targets of carbonylation throughout the disease. Using a pull-down/Western blot method, we found a significant increase in the proportion of carbonylated β-actin, β-tubulin, and GFAP in the chronic phase but not in the acute phase. These results suggest that as disease progresses from the inflammatory to the neurodegenerative phase there may be an inappropriate removal of oxidized cytoskeletal proteins. Additionally, the extensive accumulation of carbonylated GFAP in the chronic phase of EAE may be responsible for the abnormal shape of astrocytes observed at this stage.