Reactive oxygen species (ROS) and lipid peroxidation (LPO) have been associated with numerous diseases that few other pathological factors can match, including aging, neoplasia, trauma, and ischemia-reperfusion injury (Halliwell and Gutteridge 1999). The mechanism of involvement of LPO has been an area of intense research aiming to prevent, slow down, and even reverse the development of various diseases. In the case of spinal cord injury, it is well established that LPO plays an important role in neuronal degeneration, cell death, and overall functional deficits (Hall 1989(Hall , 1991Hall and Braughler 1993). This is believed due in part to that fact that neuronal cells contain a relatively large proportion of polyunsaturated fatty acids and are rich in mitochondria, both of which are a potential target and source of free radicals. Because of these unique features, the CNS is particularly vulnerable to oxidative injury. In spite of strong evidence suggesting that post-trauma oxidative stress plays a critical role in the pathogenesis of spinal cord injury, conventional strategies aiming to scavenge free radicals have largely failed to produce any effective treatment that can curtail oxidative injury. Hence, further understanding of the mechanisms of oxidative stress and identification of a novel and more effective target is highly warranted and desirable.In addition to the much studied ROS, highly reactive a,b-unsaturated aldehydes, including malondialdehyde, 4-hydroxynonenal (HNE), and acrolein, are produced as a byproduct of LPO (Witz 1989;Esterbauer et al. 1991;Uchida 1999;O'Brien et al. 2005). Among them, acrolein has been shown to be by far the most reactive with various biomolecules including proteins, DNA, and glutathione, and reacts 110-150 times faster with glutathione than HNE or Abbreviations used: AD, Alzheimer's disease; CAP, compound action potential conduction; DTNB, 5,5¢-Dithiobis (2-nitrobenzoic acid); HE, dihydroethidium; HNE, 4-hydroxynonenal; LDH, lactate dehydrogenase; LPO, lipid peroxidation; PB, phosphate buffer; PBS, phosphatebuffered saline; ROS, reactive oxygen species; SOD, superoxide dismutase; TMR, tetramethyl rhodamine dextran. AbstractWe have previously shown that acrolein, a lipid peroxidation byproduct, is significantly increased following spinal cord injury in vivo, and that exposure to neuronal cells results in oxidative stress, mitochondrial dysfunction, increased membrane permeability, impaired axonal conductivity, and eventually cell death. Acrolein thus may be a key player in the pathogenesis of spinal cord injury, where lipid peroxidation is known to be involved. The current study demonstrates that the acrolein scavenger hydralazine protects against not only acrolein-mediated injury, but also compression in guinea pig spinal cord ex vivo. Specifically, hydralazine (500 lmol/L to 1 mmol/L) can significantly alleviate acrolein (100-500 lmol/ L)-induced superoxide production, glutathione depletion, mitochondrial dysfunction, loss of membrane integrity, and reduced compound act...

Acrolein, an α,β-unsaturated aldehyde and a reactive product of lipid peroxidation, has been suggested as a key factor in neural post-traumatic secondary injury in SCI, mainly based on in vitro and ex vivo evidence. Here we demonstrate an increase of acrolein up to 300%; the elevation lasted at least two weeks in a rat SCI model. More importantly, hydralazine, a known acrolein scavenger can provide neuroprotection when applied systemically. Besides effectively reducing acrolein, hydralazine treatment also resulted in significant amelioration of tissue damage, motor deficits, and neuropathic pain. This effect was further supported by demonstrating the ability of hydralazine to reach spinal cord tissue at a therapeutic level following intraperitoneal application. This suggests that hydralazine is an effective neuroprotective agent not only in vitro, but in a live animal model of SCI as well. Finally, the role of acrolein in SCI was further validated by the fact that acrolein injection into the spinal cord caused significant SCI-like tissue damage and motor deficits. Taken together, available evidence strongly suggests a critical causal role of acrolein in the pathogenesis of spinal cord trauma. Since acrolein has been linked to a variety of illness and conditions, we believe that acrolein-scavenging measures have the potential to be expanded significantly ensuring a broad impact on human health.

No abstract

Immediately following amputation of the limb in salamanders, a strong, steady, and polarized flow of ionic current is produced by the injury. Current flows in a proximodistal direction within the limb stump and is associated with a fall in electrical potential of about 50 mV/mm near the stump's end. This current is electrogenically driven by the Na(+)-dependent, internally positive transcutaneous voltage of the intact skin of the limb stump. Reduction of this EMF, the skin's battery, by topical application of Na+ blocking agents leads to inhibition or disruption of normal limb regeneration. This suggests electrical factors are a critical control of limb regeneration. Here we test another means to reduce the injury current and its associated electrical field within the forelimb stump of red spotted newts. A fine (40 gauge), insulated, multistrand wire was inserted beneath the skin of the animal's back, with the uninsulated portion terminating either at the shoulder region or at the base of the tail. When this cathodal (negative) electrode is connected to a regulated current source, sufficient current was pulled into the stump end from an external anode (placed in the water the animal was immersed in) to markedly reduce or null the endogenous current for the first 8 days following amputation. The extent of limb regeneration in sham-treated and experimentally treated animals was determined 1 month following amputation at the elbow. Sham-treated animals regenerated normally, with most producing digits within this time. Limb regeneration was completely arrested, or caused to be strikingly hypomorphic, in half of the experimentally treated animals. This effect was independent of where the subcutaneous electrode was placed and suggests that electrical (physiological) factors are indeed a critical control of limb regeneration in urodeles.

We have tested the effectiveness of polyethylene glycol (PEG) to restore the integrity of neuronal membranes after mechanical damage secondary to severe traumatic brain injury (TBI) produced by a standardized head injury model in rats. We provide additional detail on the standardization of this model, particularly the use and storage of foam bedding that serves to both support the animal during the impact procedure-and as a dampener to the acceleration of the brass weight. Further, we employed a dye exclusion technique using ethidium bromide (EB; quantitative evaluation) and horseradish peroxidase (HRP; qualitative evaluation). Both have been successfully used previously to evaluate neural injury in the spinal cord since they enter cells when their plasma membranes are damaged. We quantified EB labeling (90 microM in 110 microL of sterile saline) after injection into the left lateral ventricle of the rat brain 2 h after injury. At six h after injection and 8 h after injury, the animals were sacrificed and the brains were analyzed. In the injured rat brain, EB entered cells lining and medial to the ventricles, particularly the axons of the corpus callosum. There was minimal EB labeling in uninjured control brains, limited to cells lining the luminal surfaces of the ventricles. Intravenous injections of PEG (1 cc of saline, 30% by volume, 2000 MW) immediately after severe TBI resulted in significantly decreased EB uptake compared with injured control animals. A similar result was achieved using the larger marker, HRP. PEG-treated brains closely resembled those of uninjured animals.