Research reportInduction of heme oxygenase-1 (HO-1) in the contused spinal cord of the rat
Introduction
HO-1 is a 32 kDa member of the heat shock protein (HSP) family. Induction of heme oxygenase-1 (HO-1) has been observed in tissues that are challenged with various stimuli, including heat shock, metals, and oxidative stress 3, 7, 9, 17, 18. In recent studies we have demonstrated induction of HO-1 in the hemisected spinal cord [24]. The protein is consistently induced in degenerating pathways. The present study is an extension of this work and specifically explores the pattern of induction of HO-1 after contusion injury.
The contusion injury markedly differs from hemisection in that it generates substantial subarachnoid and intraparenchymal hemorrhage. The inducible HO-1 gene is regulated by a number of elements in the promoter including a metal/heme binding site that makes it responsive to heme 1, 25. Thus, we hypothesized that post-traumatic hemorrhage may play a key role in the induction of HO-1 after contusion injury.
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Experimental model
Adult male Sprague–Dawley rats (N=21), weighing 300–350 g, were used in this study. Animals were anesthetized with 4% chloral hydrate (0.9 ml/100 g body weight) intraperitoneally and either immediately euthanized (N=3) as a control or prepared for spinal cord injury. A two segment laminectomy was performed at the T9–10 level in the anesthetized rat. A moderate injury was produced by dropping the New York University injury device rod (10 g) from a distance of 12.5 cm onto the intact dura as
Results
In the immunocytochemical controls, there was no staining in the absence of the primary antibody or when the antibody was preabsorbed with purified antigen. In the normal animal HO-1 was localized in certain spinal cord neurons (Fig. 1).
HO-1 was induced at the impact site in the central gray matter, particularly around the central canal and in the dorsal columns at 1 day post-injury (Fig. 2). At sites more removed from the impact, HO-1 was induced in the dorsal columns and occasionally in the
Discussion
There are few studies that have examined HO-1 in the normal spinal cord. Dwyer et al. [6]found very low levels of HO-1 in normal spinal cord homogenates. Ewing et al. [11]reported HO-1 positive alpha motor neurons in normal rat spinal cord. In this study, we confirm the localization of HO-1 in ventral horn motor neurons and also localize the protein in pericentral neurons.
In the present study, animals were subjected to a moderate spinal cord injury. This level of injury results in a central
Acknowledgements
The authors wish to thank Glenda Ross for her technical assistance. This research supported by NS23324 to LN and BMBF-Grant 01KO9405/4 to AM.
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