INDUCTION OF HEME OXYGENASE-1 (HO-1) IN THE CONTUSED SPINAL-CORD OF THE RAT

The induction of heme oxygenase-1 (HO-1) was studied in intact spinal cords and injured spinal cords after a moderate, thoracic contusion in jury. HO-1 was immunolocalized in the normal cord and along the axis o f the cord at 1, 2, 3 and 4 days after contusion. Induction of this en zyme in astrocytes and microglia/macrophages was evaluated using immun ofluorescent double labeling with monoclonal antibodies to HO-1 and ei ther glial fibrillary acidic protein or the complement C3bi receptor. HO-1 was expressed in neurons in the normal spinal cord. After contusi on, HO-1 was induced in both gray and white matter at the impact site. In segments of cord that were 1 cm proximal or distal to the injury, HO-1 was primarily induced in the dorsal columns and occasionally in t he lateral white matter. This pattern of induction was noted at all ti me points. The HO-1 was induced primarily in microglia/macrophages. Th e distribution of the HO-1 positive cells closely correlated with the pattern of intraparenchymal hemorrhage. These findings demonstrate acu te induction of HO-1 in non-neuronal cells in the injured spinal cord. Induction of HO-1 in glia may be a consequence of multiple factors in cluding exposure to heme proteins, hypoxia and oxidative stress. (C) 1 998 Elsevier Science B.V. All rights reserved.