The pathologic role for COX-2 in apoptotic oligodendrocytes in virus induced demyelinating disease: Implications for multiple sclerosis

The objective of this study was examine whether the inducible isoform of the enzyme cyclooxygenase (COX-2) was expressed in dying oligodendrocytes in the Theiler's murine encephalomyelitis virus (TMEV) induced demyelinating disease (TMEV-IDD), an experimental animal model for multiple sclerosis (MS). COX-2 is an enzyme that is tightly coupled to neuronal excitotoxic death. Since neuronal expression of COX-2 contributes to the susceptibility of neurons to excitotoxic death, we asked whether COX-2 was expressed in oligodendrocytes in MS plaques and in lesions during TMEV-IDD. COX-2 was expressed in oligodendrocytes in chronic active lesions from two MS patients. Similar pathology was present in TMEV-IDD spinal cord lesions. COX-2 was expressed in oligodendrocytes four weeks after infection with TMEV coincident with the onset of demyelination. A marker for apoptotic death, activated caspase 3, was present in a subset of oligodendrocytes that expressed COX-2. Oligodendrocyte expression of COX-2 in TMEV-IDD and MS lesions is consistent with a pathological role for this enzyme in demyelination. The presence of the cell death marker (activated caspase 3) with COX-2 in oligodendrocytes is direct evidence linking COX-2 with cell death of oligodendrocytes in these demyelinating diseases.