Hydralazine inhibits compression and acrolein‐mediated injuries in ex vivo spinal cord

Abstract

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...

Protein modification by acrolein: Relevance to pathological conditions and inhibition by aldehyde sequestering agents

“…The same authors [105] also confirmed the critical role of ACR in secondary injury following ex vivo spinal cord trauma, by demonstrating that ACR-Lys adducts are capable of diffusing from compressed tissue to adjacent, otherwise uninjured tissue and that injury is significantly attenuated by HY. As HY treatment resulted in significantly less membrane damage 2 h following compression injury, but not immediately after, it was suggested that ACR, increased to pathologic concentrations following spinal cord injury, may contribute significantly to secondary injury.…”

Antioxidant Therapies for Acute Spinal Cord Injury

“…However, these 2 products have been repeatedly shown to be cytotoxic. For example, Hamann et al [25,108,109] have demonstrated that 4-HNE and acrolein are neurotoxic in SCI models, and that chemical scavenging of these toxic LP-derived aldehydes with certain hydrazinecontaining compounds that can covalently bind them is neuroprotective. The author's laboratory has also demonstrated that mitochondrial function is exquisitely sensitive to impairment by 4-HNE, and moreso to acrolein, and also that spinal cord mitochondria are 10-fold more sensitive than brain mitochondria [48].…”

Phenelzine Mitochondrial Functional Preservation and Neuroprotection after Traumatic Brain Injury Related to Scavenging of the Lipid Peroxidation-Derived Aldehyde 4-Hydroxy-2-Nonenal

“…Second, we examined the effect of the hydrazine-containing compound phenelzine (PZ) on 4-HNE-induced mitochondrial dysfunction using the Seahorse XF 24 analyzer for measuring oxygen consumption rates (OCR). The basis for this experiment was the demonstration by others that hydrazine-containing compounds including PZ can covalently scavenge 4-HNE and other LP-derived aldehydic products [11][12][13] and might be useful for inhibiting the mitochondrial toxic effect of 4-HNE after acute CNS injury. We therefore undertook experiments to determine if the hydrazine function of PZ could also neutralize 4-HNE and thus block its toxicity in isolated rat brain mitochondria.…”