Elsevier

Brain Research

Volume 795, Issues 1–2, 8 June 1998, Pages 17-24
Brain Research

Research report
Induction of heme oxygenase-1 (HO-1) in the contused spinal cord of the rat

https://doi.org/10.1016/S0006-8993(98)00230-3Get rights and content

Abstract

The induction of heme oxygenase-1 (HO-1) was studied in intact spinal cords and injured spinal cords after a moderate, thoracic contusion injury. HO-1 was immunolocalized in the normal cord and along the axis of the cord at 1, 2, 3 and 4 days after contusion. Induction of this enzyme in astrocytes and microglia/macrophages was evaluated using immunofluorescent double labeling with monoclonal antibodies to HO-1 and either glial fibrillary acidic protein or the complement C3bi receptor. HO-1 was expressed in neurons in the normal spinal cord. After contusion, 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 the lateral white matter. This pattern of induction was noted at all time points. The HO-1 was induced primarily in microglia/macrophages. The distribution of the HO-1 positive cells closely correlated with the pattern of intraparenchymal hemorrhage. These findings demonstrate acute 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 including exposure to heme proteins, hypoxia and oxidative stress.

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.

Section snippets

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.

References (35)

  • H. Pelham

    Speculations on the functions of the major heat shock and glucose-related proteins

    Cell

    (1986)
  • A. Takeda et al.

    Regional difference in induction of heme oxygenase-1 protein following rat transient forebrain ischemia

    Neurosci. Lett.

    (1996)
  • A. Takeda et al.

    Increased expression of heme oxygenase mRNA in rat brain following transient forebrain ischemia

    Brain Res.

    (1994)
  • G. Trakshel et al.

    Purification and characterization of the major constitutive form of the testicular heme oxygenase

    J. Biol. Chem.

    (1986)
  • J. Anathan et al.

    Abnormal proteins serve as eukaryotic stress signals and trigger the activation of heat shock genes

    Science

    (1986)
  • L. Applegate et al.

    Induction of heme oxygenase: a general response to oxidant stress in cultured mammalian cells

    Cancer Res.

    (1991)
  • J. Braugler et al.

    Central nervous system trauma and stroke: 1. Biochemical consideration for oxygen radical formation and lipid peroxidation

    Free Rad. Biol. Med.

    (1989)
  • Cited by (0)

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