4‐Hydroxynonenal, a Lipid Peroxidation Product, Rapidly Accumulates Following Traumatic Spinal Cord Injury and Inhibits Glutamate Uptake

Abstract

Traumatic injury to the spinal cord initiates a host of pathophysiological events that are secondary to the initial insult. One such event is the accumulation of free radicals that damage lipids, proteins, and nucleic acids. A major reactive product formed following lipid peroxidation is the aldehyde, 4‐hydroxynonenal (HNE), which cross‐links to side chain amino acids and inhibits the function of several key metabolic enzymes. In the present study, we used immunocytochemical and immunoblotting techniques to examine the accumulation of protein‐bound HNE, and synaptosomal preparations to study the effects of spinal cord injury and HNE formation on glutamate uptake. Protein‐bound HNE increased in content in the damaged spinal cord at early times following injury (1–24 h) and was found to accumulate in myelinated fibers distant to the site of injury. Immunoblots revealed that protein‐bound HNE levels increased dramatically over the same postinjury interval. Glutamate uptake in synaptosomal preparations from injured spinal cords was decreased by 65% at 24 h following injury. Treatment of control spinal cord synaptosomes with HNE was found to decrease significantly, in a dose‐dependent fashion, glutamate uptake, an effect that was mimicked by inducers of lipid peroxidation. Taken together, these findings demonstrate that the lipid peroxidation product HNE rapidly accumulates in the spinal cord following injury and that a major consequence of HNE accumulation is a decrease in glutamate uptake, which may potentiate neuronal cell dysfunction and death through excitotoxic mechanisms.

Antioxidant Therapies for Acute Spinal Cord Injury

“…However, subsequent studies using one of the more contemporary rat contusion SCI paradigms and more sensitive immunoblotting of the immunohistochemical assay methods have more completely and specifically defined the time course of LP (4-HNE, acrolein) and protein oxidation (protein carbonyl), and nitration (3-NT) following SCI. The first of these showed a peak increase in 4-HNE immunostaining at 24 h [21] or 48 h [20] after SCI. A more recent and more extended immunoblotting/immunohistochemical time course study in the rat contusion model has confirmed that the increase in 4-HNE occurs as early as 1 h, peaks at 24 h, and remains significantly elevated for at least 7 days [23].…”

“…Second, free radical mechanisms have been demonstrated to potentiate glutamate release, an effect that is antagonized by free radical scavenging agents [53]. Third, the accumulation of LP products such as 4-HNE in synaptosomal membranes harvested from injured spinal cord tissue is associated with an impairment of synaptosomal glutamate uptake [21]. Additionally, it has been demonstrated in other in vitro studies that induction of LP in synaptosomes [54] or spinal neuronal cultures [55] impairs amino acid uptake mechanisms.…”

“…An increase in LP that appears in the injured cord within the first hour has also been evidenced in terms of a depletion of endogenous antioxidants, including ascorbic acid [16], alpha-tocopherol (also known as vitamin E) [17], glutathione [18], and ubiquinol-9 and ubiqunol-10 [19]. More contemporary immunohistochemical and immunoblotting methods have been recently used, which reveals an impressive increase in the levels of the LP-derived aldehydic breakdown products 4-HNE [20][21][22][23] and acrolein [24,25].…”

The increase of reactive oxygen species and their inhibition in an isolated guinea pig spinal cord compression model

“…6 ± 8 It is well established that ROS increase signi®cantly following CNS mechanical trauma in live animals. 6,9,10 The inhibition of ROS can provide behavioral and functional recovery following various types of injuries. 1,6,11 Therefore, reducing oxidative stress of the tissue is considered to be a potential target for e ective pharmacological intervention to reduce the secondary neuron damage and enhance overall functional recovery following trauma.…”

Modifications of proteins by 4-hydroxy-2-nonenal in the ventilatory muscles of rats

“…Increased HNE formation has been detected in the brain of patients with Alzheimer disease (25), in the spinal cord following traumatic injury (33), in the plasma of children with autoimmune diseases (14), and in the lungs following ozone exposure (42). HNE exerts broad biological toxicity effects including inhibition of DNA and protein synthesis, modification of low-density lipoprotein, and modulation of gene expression (11).…”