Melatonin as a free radical scavenger in experimental head trauma

Lipid Peroxidation and Antioxidant Consumption as Early Markers of Neurosurgery-Related Brain Injury in Children

BACKGROUND AND AIMS

Lipid peroxidation represents a marker of secondary brain injury both in traumatic and in non-traumatic conditions-as in major neurosurgical procedures-eventually leading to brain edema amplification and further brain damage. Malondialdehyde (MDA), a lipid peroxidation marker, and ascorbate, a marker of antioxidant status, can represent early indicators of this process within the cerebrospinal fluid (CSF). We hypothesized that changes in cerebral lipid peroxidation can be measured ex vivo following neurosurgery in children.

METHODS

Thirty-six children (M:F = 19/17, median age 32.9 months; IQR 17.6-74.6) undergoing neurosurgery for brain tumor removal were admitted to the pediatric intensive care unit (PICU) in the postoperative period with an indwelling intraventricular catheter for intracranial pressure monitoring and CSF drainage. Plasma and CSF samples were obtained for serial measurement of MDA, ascorbate, and cytokines.

RESULTS

An early brain-limited increase in lipid peroxidation was measured, with a significant increase from baseline of MDA in CSF (p = 0.007) but not in plasma. In parallel, ascorbate in CSF decreased (p = 0.05). Systemic inflammatory response following brain surgery was evidenced by plasma IL-6/IL-8 increase (p 0.0022 and 0.0106, respectively). No correlation was found between oxidative response and tumor site or histology (according to World Health Organization grading). Similarly, lipid peroxidation was unrelated to the length of surgery (mean 321 ± 73 min), or intraoperative blood loss (mean 20.9 ± 16.8% of preoperative volemia, 44% given hemotransfusions). Median PICU stay was 3.5 days (IQL range 2-5.5 d.), and postoperative ventilation need was 24 h (IQL range 20-61.5 h). The elevation in postoperative MDA in CSF compared with preoperative values correlated significantly with postoperative ventilation need (P = 0.05, r² 0168), while no difference in PICU stay was recorded.

CONCLUSIONS

Our results indicate that lipid peroxidation increases consistently following brain surgery, and it is accompanied by a decrease in antioxidant defences; intraventricular catheterization offers a unique chance of oxidative process monitoring. Further studies are needed to evaluate whether monitoring post-neurosurgical oxidative stress in CSF is of prognostic utility.

Melatonin's neuroprotective role in mitochondria and its potential as a biomarker in aging, cognition and psychiatric disorders

Melatonin is an ancient molecule that is evident in high concentrations in various tissues throughout the body. It can be separated into two pools; one of which is synthesized by the pineal and can be found in blood, and the second by various tissues and is present in these tissues. Pineal melatonin levels display a circadian rhythm while tissue melatonin does not. For decades now, melatonin has been implicated in promoting and maintaining sleep. More recently, evidence indicates that it also plays an important role in neuroprotection. The beginning of our review will summarize this literature. As an amphiphilic, pleiotropic indoleamine, melatonin has both direct actions and receptor-mediated effects. For example, melatonin has established effects as an antioxidant and free radical scavenger both in vitro and in animal models. This is also evident in melatonin's prominent role in mitochondria, which is reviewed in the next section. Melatonin is synthesized in, taken up by, and concentrated in mitochondria, the powerhouse of the cell. Mitochondria are also the major source of reactive oxygen species as a byproduct of mitochondrial oxidative metabolism. The final section of our review summarizes melatonin's potential role in aging and psychiatric disorders. Pineal and tissue melatonin levels both decline with age. Pineal melatonin declines in individuals suffering from psychiatric disorders. Melatonin's ability to act as a neuroprotectant opens new avenues of exploration for the molecule as it may be a potential treatment for cases with neurodegenerative disease.

Melatonin as a Therapy for Traumatic Brain Injury: A Review of Published Evidence

Melatonin (MEL) is a hormone that is produced in the brain and is known to bind to MEL-specific receptors on neuronal membranes in several brain regions. MEL’s documented neuroprotective properties, low toxicity, and ability to cross the blood-brain-barrier have led to its evaluation for patients with traumatic brain injury (TBI), a condition for which there are currently no Food and Drug Administration (FDA)-approved therapies. The purpose of this manuscript is to summarize the evidence surrounding the use of melatonin after TBI, as well as identify existing gaps and future directions. To address this aim, a search of the literature was conducted using Pubmed, Google Scholar, and the Cochrane Database. In total, 239 unique articles were screened, and the 22 preclinical studies that met the a priori inclusion/exclusion criteria were summarized, including the study aims, sample (size, groups, species, strain, sex, age/weight), TBI model, therapeutic details (preparation, dose, route, duration), key findings, and conclusions. The evidence from these 22 studies was analyzed to draw comparisons across studies, identify remaining gaps, and suggest future directions. Taken together, the published evidence suggests that MEL has neuroprotective properties via a number of mechanisms with few toxic effects reported. Notably, available evidence is largely based on data from adult male rats and, to a lesser extent, mice. Few studies collected data beyond a few days of the initial injury, necessitating additional longer-term studies. Other future directions include diversification of samples to include female animals, pediatric and geriatric animals, and transgenic strains.

Brain injury results in lower levels of melatonin receptors subtypes MT1 and MT2

BACKGROUND

Traumatic brain injury (TBI) is a devastating and costly acquired condition that affects individuals of all ages, races, and geographies via a number of mechanisms. The effects of TBI on melatonin receptors remain unknown.

PURPOSE

The purpose of this study is to explore whether endogenous changes in two melatonin receptor subtypes (MT1 and MT2) occur after experimental TBI.

SAMPLE

A total of 25 adult male Sprague Dawley rats were used with 6 or 7 rats per group.

METHODS

Rats were randomly assigned to receive either TBI modeled using controlled cortical impact or sham surgery and to be sacrificed at either 6- or 24-h post-operatively. Brains were harvested, dissected, and flash frozen until whole cell lysates were prepared, and the supernatant fluid aliquoted and used for western blotting. Primary antibodies were used to probe for melatonin receptors (MT1 and MT2), and beta actin, used for a loading control. ImageJ and Image Lab software were used to quantify the data which was analyzed using t-tests to compare means.

RESULTS

Melatonin receptor levels were reduced in a brain region- and time point- dependent manner. Both MT1 and MT2 were reduced in the frontal cortex at 24h and in the hippocampus at both 6h and 24h.

DISCUSSION

MT1 and MT2 are less abundant after injury, which may alter response to MEL therapy. Studies characterizing MT1 and MT2 after TBI are needed, including exploration of the time course and regional patterns, replication in diverse samples, and use of additional variables, especially sleep-related outcomes.

CONCLUSION

TBI in rats resulted in lower levels of MT1 and MT2; replication of these findings is necessary as is evaluation of the consequences of lower receptor levels.

The Neuroprotective Effect of Glycyrrhizic Acid on an Experimental Model of Focal Cerebral Ischemia in Rats

Cerebral ischemia is still one of the most important topics in neurosciences. Our study aimed to investigate the neuroprotective and anti-oxidant effects of glycyrrhizic acid on focal cerebral ischemia in rats. Twenty-four rats were divided equally into three groups. A middle cerebral artery occlusion model was performed in this study where sham and glycyrrhizic acid were administered intraperitoneally following middle cerebral artery occlusion. Group I was evaluated as control. Malondialdehyde (MDA), superoxide dismutase (SOD), and nuclear respiratory factor-1 (NRF1) levels were analyzed biochemically on the right cerebral hemisphere, while ischemic histopathological studies were completed to investigate the anti-oxidant status. Biochemical results showed that SOD and NRF1 levels were significantly increased in the glycyrrhizic acid group compared with the sham group while MDA levels were significantly decreased. On histopathological examination, cerebral edema, vacuolization, degeneration, and destruction of neurons were decreased in the glycyrrhizic acid group compared with the sham group. Cerebral ischemia was attenuated by glycyrrhizic acid administration. These observations indicate that glycyrrhizic acid may have potential as a therapeutic agent in cerebral ischemia by preventing oxidative stress.

Differential effects of early postinjury treatment with neuroprotective drugs in a mouse model using diffuse reflectance spectroscopy

The time required for the arrival of an ambulance crew and administration of first aid is critical to clinical outcome, particularly in the case of head injury victims requiring neuroprotective drugs following a car accident, falls, and assaults. Short response times of the medical team, together with proper treatment, can limit injury severity and even save a life before transportation to the nearest medical center. We present a comparative evaluation of five different neuroprotective drugs frequently used in intensive care and operating units in the early phase following traumatic brain injury (TBI): hypertonic saline (HTS), mannitol, morphine, melatonin, and minocycline. The effectiveness of these drugs in terms of changes in brain tissue morphology (cell organelle size, density, distribution, etc.) and biochemical tissue properties (chromophores' content) was experimentally evaluated through analysis of the spectral reduced scattering and optical absorption coefficient parameters in the near-infrared (NIR) optical range (650 to 1000 nm). Experiments were conducted on anesthetized male mice subjected to a noninvasive closed head weight-drop model of focal TBI ([Formula: see text] and [Formula: see text] control) and monitored using an NIR diffuse reflectance spectroscopy system utilizing independent source-detector separation and location. After 10 min of baseline measurement, focal TBI was induced and measurements were conducted for 20 min. Subsequently, a neuroprotective drug was administrated and measurements were recorded for another 30 min. This work's major findings are threefold: first, minocycline was found to improve hemodynamic outcome at the earliest time postinjury. Second, HTS decreased brain water content and inhibited the increase in intracranial pressure. Third, the efficacy of neuroprotective drugs can be monitored noninvasively with diffuse reflectance spectroscopy. The demonstrated ability to noninvasively detect cerebral physiological properties following early administration of neuroprotective drugs underlines the need for more extensive investigation of the combined use of clinical drugs in larger-scale preclinical experiments to find the most beneficial drug treatment for brain injury patients.

Melatonin reduced microglial activation and alleviated neuroinflammation induced neuron degeneration in experimental traumatic brain injury: Possible involvement of mTOR pathway

This study was designed to detect the modulation manner of melatonin on microglial activation and explore herein possible involvement of mammalian target of rapamycin (mTOR) pathway following traumatic brain injury (TBI). ICR mice were divided into four groups: sham group, TBI group, TBI+sal group and TBI+Melatonin group. A weight-drop model was employed to cause TBI. Neurological severity score (NSS) tests were performed to measure behavioral outcomes. Nissl staining was conducted to observe the neuronal degeneration and wet-to-dry weight ratio indicated brain water content. Immunofluorescence was designed to investigate microglial activation. Enzyme-linked immunosorbent assay (ELISA) was employed to evaluate proinflammatory cytokine levels (interleukin-beta (IL-1β), tumor necrosis factor-alpha (TNF-α)). Western blotting was engaged to analyze the protein content of mammalian target of rapamycin (mTOR), p70 ribosomal S6 kinase (p70S6K) and S6 ribosomal protein (S6RP). Melatonin administration was associated with markedly restrained microglial activation, decreased release of proinflammatory cytokines and increased the number of surviving neurons at the site of peri-contusion. Meanwhile, melatonin administration resulted in dephosphorylated mTOR pathway. In conclusion, this study presents a new insight into the mechanisms responsible for the anti-neuroinflammation of melatonin, with possible involvement of mTOR pathway.

Effect of melatonin on intracranial pressure and brain edema following traumatic brain injury: role of oxidative stresses

BACKGROUND AND AIMS

Traumatic brain injury (TBI) is one of the main causes of brain edema and increased intracranial pressure (ICP). In the clinic it is essential to limit the development of ICP after TBI. In the present study, the effects of melatonin on these parameters at different time points and alterations of oxidant factors as one of the probable involved mechanisms have been evaluated.

METHODS

Albino N-Mary rats were divided into five groups of sham, TBI, TBI + vehicle, TBI + Mel5 and TBI + Mel20. Brain injury was induced by Marmarou method. Melatonin was injected i.p. at 1, 24, 48 and 72 h after brain trauma. Brain water and Evans blue dye contents as well as oxidant/antioxidant factors were measured 72 h after TBI. ICP and neurological scores were determined at -1, 1, 24, 48 and 72 h post-TBI.

RESULTS

Brain water and Evans blue dye contents in melatonin-treated groups decreased as compared to the TBI + vehicle group (p <0.001). Veterinary coma scale (VCS) at 24, 48 and 72 h after TBI showed a significant increase in melatonin groups (TBI + Mel5: p <0.01 and TBI + Mel20: p <0.001) in comparison to the TBI + vehicle group. ICP at 24, 48 and 72 h after TBI decreased in melatonin groups as compared to the TBI + vehicle group (p <0.001). Superoxide dismutase and glutathione peroxidase activities showed a significant increase, whereas malondialdehyde level in these groups was significantly lower in melatonin groups in comparison to the TBI + vehicle group (p <0.001).

CONCLUSION

Melatonin decreases brain edema, BBB permeability and ICP, but increases VCS after TBI. These effects are probably due to inhibition of oxidative stress.

Therapeutic targets for neuroprotection and/or enhancement of functional recovery following traumatic brain injury

Traumatic brain injury (TBI) is a significant public health concern. The number of injuries that occur each year, the cost of care, and the disabilities that can lower the victim's quality of life are all driving factors for the development of therapy. However, in spite of a wealth of promising preclinical results, clinicians are still lacking a therapy. The use of preclinical models of the primary mechanical trauma have greatly advanced our knowledge of the complex biochemical sequela that follow. This cascade of molecular, cellular, and systemwide changes involves plasticity in many different neurochemical systems, which represent putative targets for remediation or attenuation of neuronal injury. The purpose of this chapter is to highlight some of the promising molecular and cellular targets that have been identified and to provide an up-to-date summary of the development of therapeutic compounds for those targets.

Posttreatment with uridine and melatonin following traumatic brain injury reduces edema in various brain regions in rats

Traumatic brain injury (TBI) is a major health problem and a significant cause of death, disability, and neurobehavioral deficits. We investigated the effect of posttreatment with uridine and melatonin, separate and in combination, on edema in various brain regions following TBI via lateral fluid percussion. Uridine (16 and 32 mg/kg, i.p.) and melatonin (200 mg/kg, i.p.), individually reduced edema in impacted striatum versus TBI. Combination treatment of uridine (32) and melatonin (200) decreased edema in impacted as well as non-impacted hippocampus (75.7 +/- 0.5% and 75.4 +/- 0.3%) and striatum (69.7 +/- 1.2% and 72.6 +/- 0.5%) respectively, as compared to the group that received vehicle following TBI. Combination of uridine (16) and melatonin (200) attenuated edema levels in impacted hippocampus (76.6 +/- 0.4%) and striatum (71.7 +/- 0.5% and 74 +/- 0.3%, respectively). Combination of uridine and melatonin may be a possible treatment strategy for the damage caused by TBI and its neuroprotective potential needs to be evaluated further.

Antioxidant therapies for traumatic brain injury

Free radical-induced oxidative damage reactions, and membrane lipid peroxidation (LP), in particular, are among the best validated secondary injury mechanisms in preclinical traumatic brain injury (TBI) models. In addition to the disruption of the membrane phospholipid architecture, LP results in the formation of cytotoxic aldehyde-containing products that bind to cellular proteins and impair their normal functions. This article reviews the progress of the past three decades in regard to the preclinical discovery and attempted clinical development of antioxidant drugs designed to inhibit free radical-induced LP and its neurotoxic consequences via different mechanisms including the O(2)(*-) scavenger superoxide dismutase and the lipid peroxidation inhibitor tirilazad. In addition, various other antioxidant agents that have been shown to have efficacy in preclinical TBI models are briefly presented, such as the LP inhibitors U83836E, resveratrol, curcumin, OPC-14177, and lipoic acid; the iron chelator deferoxamine and the nitroxide-containing antioxidants, such as alpha-phenyl-tert-butyl nitrone and tempol. A relatively new antioxidant mechanistic strategy for acute TBI is aimed at the scavenging of aldehydic LP byproducts that are highly neurotoxic with "carbonyl scavenging" compounds. Finally, it is proposed that the most effective approach to interrupt posttraumatic oxidative brain damage after TBI might involve the combined treatment with mechanistically complementary antioxidants that simultaneously scavenge LP-initiating free radicals, inhibit LP propagation, and lastly remove neurotoxic LP byproducts.

Biochemical effects of experimental epidural hematoma on brain parenchyma of rats

INTRODUCTION

The management of epidural hematoma is classified into surgical or conservative treatment according to clinical and radiologic parameters. In the recent years, the number of paper suggesting conservative management has been increasing. The experimental works that have been performed are based on especially the effects of epidural hematomas. Basic pathophysiologic factors on ischemia result of brain trauma are based on biochemical mediators. Nitric oxide (NO) and malondialdehyde (MDA) are the substances that play important roles in brain damage after trauma.

MATERIAL AND METHOD

In this study, 36 rats are divided into three groups (n = 12/group). Epidural hematoma was achieved by 0.1 ml autolog blood in rat epidural space with balloon model. Early and late phase biochemical effects on parenchyma of epidural hematoma operated in a volume which neither alters intracranial pressure (ICP) nor creates shift effect were observed. Biochemical changes of NO and MDA levels were examined in each of three experimental groups.

RESULTS

NO values increased significantly in the early group (6 hours) compared with those in the control group. Difference of NO values between the control and late groups was not significant. An increase has been found in MDA values in the control group compared with those in the early group. MDA values of the late group (30 days) were closer to that of the control group.

CONCLUSION

In this study, considering biochemical results, we have found that conservative volumes which neither increase ICP nor cause brain shift do not lead to permanent changes on brain.

Peroxynitrite-mediated oxidative damage to brain mitochondria: Protective effects of peroxynitrite scavengers

Peroxynitrite-mediated oxidative damage has been implicated in brain mitochondrial respiratory dysfunction after traumatic brain injury (TBI), which precedes the onset of neuronal loss. The aim of this study was to investigate the detrimental effects of the peroxynitrite donor SIN-1 (3-morpholinosydnonimine) on isolated brain mitochondria and to screen penicillamine, a stoichiometric (1:1) peroxynitrite-scavenging agent, and tempol, a catalytic scavenger of peroxynitrite-derived radicals, as antioxidant mitochondrial protectants. Exposure of the isolated mitochondria to SIN-1 caused a significant dose-dependent decrease in the respiratory control ratio and was accompanied by a significant increase in state II respiration, followed by significant decreases (P < 0.05) in states III and V. These functional alterations occurred together with significant increases in mitochondrial protein carbonyl (PC), lipid peroxidation-related 4-hydroxynonenal (4-HNE), and 3-nitrotyrosine (3-NT) content. Penicillamine hydrochloride (10 microM) partially but significantly (P < 0.05) protected against SIN-1-induced decreases in states III and V. However, a 2.5 microM concentration of tempol was able to significantly antagonize a 4-fold molar excess (10 microM) concentration of SIN-1 as effectively as were higher tempol concentrations, consistent with the likelihood that tempol works by a catalytic mechanism. The protection of mitochondrial respiration by penicillamine and tempol occurred in parallel with attenuation of PC, 4-HNE, and 3-NT. These results indicate that SIN-1 causes mitochondrial oxidative damage and complex I dysfunction and that antioxidant compounds that target either peroxynitrite or its radicals may be effective mitochondrial protectants in the treatment of neural injury.

The potential of melatonin in reducing morbidity-mortality after craniocerebral trauma

Craniocerebral trauma (CCT) is the most frequent cause of morbidity-mortality as a result of an accident. The probable origins and etiologies are multifactorial and include free radical formation and oxidative stress, the suppression of nonspecific resistance, lymphocytopenia (disorder in the adhesion and activation of cells), opportunistic infections, regional macro and microcirculatory alterations, disruptive sleep-wake cycles and toxicity caused by therapeutic agents. These pathogenic factors contribute to the unfavorable development of clinical symptoms as the disease progresses. Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine endogenously produced in the pineal gland and in other organs and it is protective agent against damage following CCT. Some of the actions of melatonin that support its pharmacological use after CCT include its role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes (e.g. superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase), inhibition of pro-inflammatory cytokines and activation-adhesion molecules which consequently reduces lymphocytopenia and infections by opportunistic organisms. The chronobiotic capacity of melatonin may also reset the natural circadian rhythm of sleep and wakefulness. Melatonin reduces the toxicity of the drugs used in the treatment of CCT and increases their efficacy. Finally, melatonin crosses the blood-brain barrier and reduces contusion volume and stabilizes cellular membranes preventing vasospasm and apoptosis of endothelial cells that occurs as a result of CCT.

Time course of post-traumatic mitochondrial oxidative damage and dysfunction in a mouse model of focal traumatic brain injury: implications for neuroprotective therapy

In the present study, we investigate the hypothesis that mitochondrial oxidative damage and dysfunction precede the onset of neuronal loss after controlled cortical impact traumatic brain injury (TBI) in mice. Accordingly, we evaluated the time course of post-traumatic mitochondrial dysfunction in the injured cortex and hippocampus at 30 mins, 1, 3, 6, 12, 24, 48, and 72 h after severe TBI. A significant decrease in the coupling of the electron transport system with oxidative phosphorylation was observed as early as 30 mins after injury, followed by a recovery to baseline at 1 h after injury. A statistically significant (P<0.0001) decline in the respiratory control ratio was noted at 3 h, which persisted at all subsequent time-points up to 72 h after injury in both cortical and hippocampal mitochondria. Structural damage seen in purified cortical mitochondria included severely swollen mitochondria, a disruption of the cristae and rupture of outer membranes, indicative of mitochondrial permeability transition. Consistent with this finding, cortical mitochondrial calcium-buffering capacity was severely compromised by 3 h after injury, and accompanied by significant increases in mitochondrial protein oxidation and lipid peroxidation. A possible causative role for reactive nitrogen species was suggested by the rapid increase in cortical mitochondrial 3-nitrotyrosine levels shown as early as 30 mins after injury. These findings indicate that post-traumatic oxidative lipid and protein damage, mediated in part by peroxynitrite, occurs in mitochondria with concomitant ultrastructural damage and impairment of mitochondrial bioenergetics. The data also indicate that compounds which specifically scavenge peroxynitrite (ONOO(-)) or ONOO(-)-derived radicals (e.g. ONOO(-)+H(+) --> ONOOH --> (*)NO(2)+(*)OH) may be particularly effective for the treatment of TBI, although the therapeutic window for this neuroprotective approach might only be 3 h.

Effect of pinealectomy and melatonin replacement on morphological and biochemical recovery after traumatic brain injury

Numerous studies showed that melatonin, a free radical scavenger, is neuroprotective. In this study, we investigated the effect of pinealectomy and administration of exogenous melatonin on oxidative stress and morphological changes after experimental brain injury. The animals were divided into six groups, each having 12 rats. Group 1 underwent craniotomy alone. Group 2 underwent craniotomy followed by brain trauma and received no medication. Group 3 underwent craniotomy followed by brain trauma and received melatonin. Group 4 underwent pinealectomy and craniotomy alone. Group 5 underwent pinealectomy and craniotomy followed by brain injury and received no medication. Group 6 underwent pinealectomy and craniotomy followed by brain trauma and received melatonin. Melatonin (100 mg/kg) was given intraperitoneally immediately after trauma to the rats in Groups 3 and 6. Pinealectomy caused a significant increase in the malondialdehyde (MDA), nitric oxide (NO), glutathione (GSH), and xanthine oxidase (XO) levels, and a decrease in GSH levels as compared to the control group. Trauma to pinealectomized rats causes significantly higher oxidative stress. Exogeneous melatonin administration significantly reduced MDA, XO and NO levels, increased GSH levels, and attenuated tissue lesion area. These findings suggest that reduction in endogenous melatonin after pinealectomy makes the rats more vulnerable to trauma, and exogenous melatonin administration has an important neuroprotective effect.

Determination of 8-oxoguanine and 8-hydroxy-2'-deoxyguanosine in the rat cerebral cortex using microdialysis sampling and capillary electrophoresis with electrochemical detection

A rapid and sensitive method to determine 8-oxoguanine (8oxoG) and 8-hydroxydeoxyguanosine (8OHdG), biomarkers for oxidative DNA damage, in cerebral cortex microdialysate samples using capillary electrophoresis (CE) with electrochemical detection (CEEC) was developed. Samples were concentrated on-column using pH-mediated stacking for anions. On-column anodic detection was performed with a carbon fiber working electrode and laser-etched decoupler. The method is linear over the expected extracellular concentration range for 8oxoG and 8-OHdG during induced ischemia-reperfusion, with R.S.D. values Collapse

Key Words Collapse

MESH Headings

• Animals
• Biomarkers/analysis
• Cerebral Cortex/chemistry
• Chromatography, Liquid/methods
• Deoxyadenosines/analysis
• Electrochemistry
• Electrophoresis, Capillary/methods
• Female
• Guanine/analogs & derivatives
• Guanine/analysis
• Mass Spectrometry/methods
• Microdialysis/methods
• Rats
• Rats, Sprague-Dawley

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Grants

• R01 EB000247 NIBIB NIH HHS
• R01 HL069014-02 NHLBI NIH HHS
• R01EB00247 NIBIB NIH HHS
• T32 CA009242 NCI NIH HHS
• R01 HL069014 NHLBI NIH HHS
• T32CA09242 NCI NIH HHS

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Affiliation(s)

Stacy D. Arnett Department of Chemistry, University of Kansas, Lawrence, KS 66045
Damon M. Osbourn Department of Chemistry, University of Kansas, Lawrence, KS 66045
Kimberly D. Moore Department of Chemistry, University of Kansas, Lawrence, KS 66045
Shannon S. Vandaveer Department of Chemistry, University of Kansas, Lawrence, KS 66045
Craig E. Lunte Department of Chemistry, University of Kansas, Lawrence, KS 66045

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Peroxynitrite-mediated protein nitration and lipid peroxidation in a mouse model of traumatic brain injury

The role of reactive oxygen-induced oxidative damage to lipids (i.e., lipid peroxidation, LP) and proteins has been strongly supported in previous work. Most notably, a number of free radical scavengers and lipid antioxidants have been demonstrated to be neuroprotective in traumatic brain injury (TBI) models. However, the specific sources of reactive oxygen species (ROS), the time course of oxidative damage and its relationship to post-traumatic neurodegeneration in the injured brain have been incompletely defined. The present study was directed at an investigation of the role of the ROS, peroxynitrite (PON), in the acute pathophysiology of TBI and its temporal relationship to neurodegeneration in the context of the mouse model of diffuse head injury model. Male CF-1 mice were subjected to a moderately severe head injury and assessed at 1-, 3-, 6-, 12-, 24-, 48-, 72, 96- and 120-h post-injury for neurodegeneration using quantitative image analysis of silver staining and semi-quantitative analysis of PON-mediated oxidative damage to proteins (3-nitrotyrosine, 3-NT) and lipids (4-hydroxynonenal, 4-HNE). Significant evidence of silver staining was not apparent until 24-h post-injury, with peak staining seen between 72- and 120-h. This time-course of neurodegeneration was preceded by intense immunostaining for 3-NT and 4-HNE, which occurred within the first hour post-injury. The time course and staining pattern for 3-NT and 4-HNE were similar, with the highest staining intensity noted within the first 48-h in areas surrounding trauma-induced contusions. In the case of 3-NT, neuronal perikarya and processes and microvessels displayed staining. The temporal and spatial coincidence of protein nitration and LP damage suggests that PON is involved in both. However, lipid-peroxidative (4-HNE) immunoreactivity was broader and more diffuse than 3-NT, suggesting that other reactive oxygen mechanisms, such as iron-dependent LP, may also contribute to the more widespread 4-HNE immunoreactivity. This indicates that optimal pharmacological inhibition of post-traumatic oxidative damage in TBI may need to combine two functionalities: one to scavenge PON or PON-derived radicals, and the second to inhibit LP caused by multiple ROS species.

Melatonin‐induced neuroprotection after closed head injury is associated with increased brain antioxidants and attenuated late‐phase activation of NF‐κB and AP‐1

Traumatic brain injury (TBI) is followed by massive production of reactive oxygen species (ROS), which mediate secondary cellular damage. Low molecular weight antioxidants (LMWA) constitute one of the defense mechanisms of the brain, and their levels correlate with post-TBI outcome. Melatonin, the main pineal hormone, possesses antioxidant properties. We investigated the effects of melatonin on neurobehavioral recovery, brain LMWA, and activation of the redox-sensitive transcription factors nuclear factor-kappaB (NF-kappaB) and AP-1 in mice subjected to closed head injury (CHI). Given 1 h after CHI, melatonin facilitated recovery during at least 1 wk (P<0.05) and decreased lesion size by approximately twofold (P<0.01). The dose response displayed a bell-shape, i.e., neuroprotection was achieved with 5 but not 1 or 10 mg/kg. At the neuroprotective dose, melatonin treatment was associated with sustained (4 days) elevation of brain LMWA, including ascorbic acid (P<0.05). In contrast, LMWA were unaffected by the administration of the neuroprotective endocannabinoid 2-arachidonoyl glycerol. Furthermore, melatonin did not alter early phase (24 h) CHI-induced activation of NF-kappaB and AP-1; however, it blocked the robust late-phase (8 days) activation of NF-kappaB and decreased that of AP-1 to below basal levels. Our results demonstrate that melatonin induces neuroprotection, presumably via potentiation of brain antioxidants and attenuation of NF-kappaB and AP-1 activation.

Restorative neurosurgery

Restorative neurosurgery currently is the frontier of neuroscientists for the restoration of lost neuronal function especially in neurodegenerative diseases and ischemic and traumatic central nervous system (CNS) disorders. The striking developments in molecular neurobiology and bio-technology are progressively offering new opportunities for a better quality of life to patients suffering from loss of neuronal function. Besides all new and challenging medical therapeutic interventions, great emphasis is also given to transplantation for neuronal restoration as well.

Lipid peroxidation in cerebral tumors

BACKGROUND

Serum and tissue concentrations of tumor markers or some metabolites are considered to be helpful in diagnosis and follow-up of the central nervous system (CNS) disease. However, markers currently available are not sufficiently sensitive and specific to be used as actual diagnostic tools. Differentiation between the malignant and benign lesions of the CNS is very important, both for determining the optimum therapeutic approach and to predict morbidity and mortality of the disease. Accurate diagnosis of a malignant disease is mostly performed through a surgical resection and histopathologic evaluation. Free oxygen radicals (FOR) are thought to take part in oncogenesis and cellular differentiation. We explored whether FORs can be used as diagnostic tumor markers.

METHODS

We investigated the concentration of malondialdehyde (MDA) in the serum and tumor tissue of patients with glial tumor. We have studied 30 patients with malign glial tumor (grades III and IV astrocytoma), 30 patients with low grade glial tumor, 28 healthy individuals, and 10 patients with nontumorous lesions (lobectomy for epilepsy).

RESULTS

Patients with CNS tumors showed higher serum MDA concentration compared to control groups (epilepsy patients and healthy subjects). These patients had a higher tumor tissue MDA concentration compared to lobectomy tissue from epilepsy patients. Serum and tissue MDA concentrations were also higher in the malignant glial tumor group compared to the low grade glial tumor group.

CONCLUSIONS

Although not specific, tissue and serum concentrations of FORs can be used as a marker to detect the presence and grade of CNS tumors. Further studies are needed to determine the optimum cutoff value for use of serum and tissue MDA concentrations in brain tumors.

Different responsiveness of central nervous system tissues to oxidative conditions and to the antioxidant effect of melatonin

Melatonin, a product of the pineal gland, is an effective free-radical scavenger both in vitro and in vivo. Free-radical-mediated lipid peroxidation has been increasingly considered as an important factor in post-traumatic neuronal degeneration. The aim of the present study was (i). to examine the responses of different regions of central nervous system (CNS) to free-radical generation induced in vitro and (ii). to test the efficacy of melatonin in reducing oxidative damage in different regions of the CNS. Rat brain, total spinal cord, spinal cord white matter and optic nerves were dissected with the rats under general anesthesia and immediately frozen at -20 degrees C. Thiobarbituric acid reactive substances were measured as an index of lipid peroxidation. Peroxidation was induced with ferrous iron (0.02 mm), ascorbate (1 mm), and hydrogen peroxide (H2O2) (0.5 mm). All tissue samples showed increased lipid peroxidation levels after treatment with free-radical generating agents. The highest amount of damage was observed in the presence of ferrous iron, ascorbate, and H2O2. Melatonin showed antioxidant effects in the brain, total spinal cord, optic nerve, and spinal cord white matter. The results show that melatonin has differential protective effects on CNS tissues in vitro and the most potent effect is observed in the spinal cord white matter.