Serum lactate as a novel potential biomarker in multiple sclerosis.

Multiple sclerosis (MS) is a primary inflammatory demyelinating disease associated with a probably secondary progressive neurodegenerative component. Impaired mitochondrial functioning has been hypothesized to drive neurodegeneration and to cause increased anaerobic metabolism in MS. The aim of our multicentre study was to determine whether MS patients had values of circulating lactate different from those of controls. Patients (n=613) were recruited, assessed for disability and clinically classified (relapsing-remitting, secondary progressive, primary progressive) at the Catholic University of Rome, Italy (n=281), at the MS Centre Amsterdam, The Netherlands (n=158) and at the S. Camillo Forlanini Hospital, Rome, Italy (n=174). Serum lactate levels were quantified spectrophotometrically with the analyst being blinded to all clinical information. In patients with MS serum lactate was three times higher (3.04±1.26mmol/l) than that of healthy controls (1.09±0.25mmol/l, p<0.0001) and increased across clinical groups, with higher levels in cases with a progressive than with a relapsing-remitting disease course. In addition, there was a linear correlation between serum lactate levels and the expanded disability scale (EDSS) (R(2)=0.419; p<0.001). These data support the hypothesis that mitochondrial dysfunction is an important feature in MS and of particular relevance to the neurodegenerative phase of the disease. Measurement of serum lactate in MS might be a relative inexpensive test for longitudinal monitoring of "virtual hypoxia" in MS and also a secondary outcome for treatment trials aimed to improve mitochondrial function in patients with MS.

Neuroglobin expression and oxidant/antioxidant balance after graded traumatic brain injury in the rat.

Neuroglobin is a neuron-specific hexacoordinated globin capable of binding various ligands, including O2, NO, and CO, the biological function of which is still uncertain. Various studies seem to indicate that neuroglobin is a neuroprotective agent when overexpressed, acting as a potent inhibitor of oxidative and nitrosative stress. In this study, we evaluated the pathophysiological response of the neuroglobin gene and protein expression in the cerebral tissue of rats sustaining traumatic brain injury of differing severity, while simultaneously measuring the oxidant/antioxidant balance. Two levels of trauma (mild and severe) were induced in anesthetized animals using the weight-drop model of diffuse axonal injury. Rats were then sacrificed at 6, 12, 24, 48, and 120 h after traumatic brain injury, and the gene and protein expression of neuroglobin and the concentrations of malondialdehyde (as a parameter representative of reactive oxygen species-mediated damage), nitrite + nitrate (indicative of NO metabolism), ascorbate, and glutathione (GSH) were determined in the brain tissue. Results indicated that mild traumatic brain injury, although causing a reversible increase in oxidative/nitrosative stress (increase in malondialdehyde and nitrite + nitrate) and an imbalance in antioxidants (decrease in ascorbate and GSH), did not induce any change in neuroglobin. Conversely, severe traumatic brain injury caused an over nine- and a fivefold increase in neuroglobin gene and protein expression, respectively, as well as a remarkable increase in oxidative/nitrosative stress and depletion of antioxidants. The results of this study, showing a lack of effect in mild traumatic brain injury as well as asynchronous time course changes in neuroglobin expression, oxidative/nitrosative stress, and antioxidants in severe traumatic brain injury, do not seem to support the role of neuroglobin as an endogenous neuroprotective antioxidant agent, at least under pathophysiological conditions.

The molecular mechanisms affecting N-acetylaspartate homeostasis following experimental graded traumatic brain injury.

To characterize the molecular mechanisms of N-acetylaspartate (NAA) metabolism following traumatic brain injury (TBI), we measured the NAA, adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentrations and calculated the ATP/ADP ratio at different times from impact, concomitantly evaluating the gene and protein expressions controlling NAA homeostasis (the NAA synthesizing and degrading enzymes N-acetyltransferase 8-like and aspartoacylase, respectively) in rats receiving either mild or severe TBI. The reversible changes in NAA induced by mild TBI were due to a combination of transient mitochondrial malfunctioning with energy crisis (decrease in ATP and in the ATP/ADP ratio) and modulation in the gene and protein levels of N-acetyltransferase 8-like and increase of aspartoacylase levels. The irreversible decrease in NAA following severe TBI, was instead characterized by profound mitochondrial malfunctioning (constant 65% decrease of the ATP/ADP indicating permanent impairment of the mitochondrial phosphorylating capacity), dramatic repression of the N-acetyltransferase 8-like gene and concomitant remarkable increase in the aspartoacylase gene and protein levels. The mechanisms underlying changes in NAA homeostasis following graded TBI might be of note for possible new therapeutic approaches and will help in understanding the effects of repeat concussions occurring during particular periods of the complex NAA recovery process, coincident with the so called window of brain vulnerability.

Decrease in N-acetylaspartate following concussion may be coupled to decrease in creatine.

OBJECTIVES: To assess the time course changes in N-acetylaspartate (NAA) and creatine (Cr) levels in the brain of athletes who suffered a sport-related concussion. PARTICIPANTS: Eleven nonconsecutive athletes with concussive head injury and 11 sex- and age-matched control volunteers MAIN OUTCOME MEASURES: : At 3, 15, 30, and 45 days postinjury, athletes were examined by proton magnetic resonance spectroscopy for the determination of NAA, Cr, and choline (Cho) levels. Proton magnetic resonance spectroscopic data recorded for the control group were used for comparison. RESULTS: Compared with controls (2.18 ± 0.19), athletes showed an increase in the NAA/Cr ratio at 3 (2.71 ± 0.16; P < .01) and 15 (2.54 ± 0.21; P < .01) days postconcussion, followed by a decrease and subsequent normalization at 30 (1.95 ± 0.16, P < .05) and 45 (2.17 ± 0.20; P < .05) days postconcussion. The NAA/Cho ratio decreased at 3, 15, and 30 days postinjury (P < .01 compared with controls), with no differences observed in controls at 45 days postconcussion. Compared with controls, significant increase in the Cho/Cr ratio after 3 (+33%, P < .01) and 15 (+31.5%, P < .01) days postinjury was observed whereas no differences were recorded at 30 and 45 days postinjury. CONCLUSIONS: This cohort of athletes indicates that concussion may cause concomitant decrease in cerebral NAA and Cr levels. This provokes longer time for normalization of metabolism, as well as longer time for resolution of concussion-associated clinical symptoms.

Potentially neuroprotective gene modulation in an in vitro model of mild traumatic brain injury.

In this study, we investigated the hypothesis that mild traumatic brain injury (mTBI) triggers a controlled gene program as an adaptive response finalized to neuroprotection, similar to that found in hibernators and in ischemic preconditioning. A stretch injury device was used to produce an equi-biaxial strain field in rat organotypic hippocampal slice cultures at a specified Lagrangian strain of 10 % and a constant strain rate of 20 s(-1). After 24 h from injury, propidium iodide staining, HPLC analysis of metabolites and microarray analysis of cDNA were performed to evaluate cell viability, cell energy state and gene expression, respectively. Compared to control cultures, 10 % stretch injured cultures showed no change in viability, but demonstrated a hypometabolic state (decreased ATP, ATP/ADP, and nicotinic coenzymes) and a peculiar pattern of gene modulation. The latter was characterized by downregulation of genes encoding for proteins of complexes I, III, and IV of the mitochondrial electron transport chain and of ATP synthase; downregulation of transcriptional and translational genes; downregulation and upregulation of genes controlling the synthesis of glutamate and GABA receptors, upregulation of calmodulin and calmodulin-binding proteins; proper modulation of genes encoding for proapoptotic and antiapoptotic proteins. These results support the hypothesis that, following mTBI, a hibernation-type response is activated in non-hibernating species. Unlike in hibernators and ischemic preconditioning, this adaptive gene programme, aimed at achieving maximal neuroprotection, is not triggered by decrease in oxygen availability. It seems rather activated to avoid increase in oxidative/nitrosative stress and apoptosis during a transient period of mitochondrial malfunctioning.

The pathophysiology of concussion.

Concussion is defined as a biomechanically induced brain injury characterized by the absence of gross anatomic lesions. Early and late clinical symptoms, including impairments of memory and attention, headache, and alteration of mental status, are the result of neuronal dysfunction mostly caused by functional rather than structural abnormalities. The mechanical insult initiates a complex cascade of metabolic events leading to perturbation of delicate neuronal homeostatic balances. Starting from neurotoxicity, energetic metabolism disturbance caused by the initial mitochondrial dysfunction seems to be the main biochemical explanation for most postconcussive signs and symptoms. Furthermore, concussed cells enter a peculiar state of vulnerability, and if a second concussion is sustained while they are in this state, they may be irreversibly damaged by the occurrence of swelling. This condition of concussion-induced brain vulnerability is the basic pathophysiology of the second impact syndrome. N-acetylaspartate, a brain-specific compound representative of neuronal metabolic wellness, is proving a valid surrogate marker of the post-traumatic biochemical damage, and its utility in monitoring the recovery of the aforementioned "functional" disturbance as a concussion marker is emerging, because it is easily detectable through proton magnetic resonance spectroscopy.

Biochemical and neurochemical sequelae following mild traumatic brain injury: summary of experimental data and clinical implications.

Although numerous studies have been carried out to investigate the pathophysiology of mild traumatic brain injury (mTBI), there are still no standard criteria for the diagnosis and treatment of this peculiar condition. The dominant theory that diffuse axonal injury is the main neuropathological process behind mTBI is being revealed as weak at best or inconclusive, given the current literature and the fact that neuronal injury inherent to mTBI improves, with few lasting clinical sequelae in the vast majority of patients. Clinical and experimental evidence suggests that such a course, rather than being due to cell death, is based on temporal neuronal dysfunction, the inevitable consequence of complex biochemical and neurochemical cascade mechanisms directly and immediately triggered by the traumatic insult. This report is an attempt to summarize data from a long series of experiments conducted in the authors' laboratories and published during the past 12 years, together with an extensive analysis of the available literature, focused on understanding the biochemical damage produced by an mTBI. The overall clinical implications, as well as the metabolic nature of the post-mTBI brain vulnerability, are discussed. Finally, the application of proton MR spectroscopy as a possible tool to monitor the full recovery of brain metabolic functions is emphasized.

Assessment of metabolic brain damage and recovery following mild traumatic brain injury: a multicentre, proton magnetic resonance spectroscopic study in concussed patients.

Concussive head injury opens a temporary window of brain vulnerability due to the impairment of cellular energetic metabolism. As experimentally demonstrated, a second mild injury occurring during this period can lead to severe brain damage, a condition clinically described as the second impact syndrome. To corroborate the validity of proton magnetic resonance spectroscopy in monitoring cerebral metabolic changes following mild traumatic brain injury, apart from the magnetic field strength (1.5 or 3.0 T) and mode of acquisition, we undertook a multicentre prospective study in which a cohort of 40 athletes suffering from concussion and a group of 30 control healthy subjects were admitted. Athletes (aged 16-35 years) were recruited and examined at three different institutions between September 2007 and June 2009. They underwent assessment of brain metabolism at 3, 15, 22 and 30 days post-injury through proton magnetic resonance spectroscopy for the determination of N-acetylaspartate, creatine and choline-containing compounds. Values of these representative brain metabolites were compared with those observed in the group of non-injured controls. Comparison of spectroscopic data, obtained in controls using different field strength and/or mode of acquisition, did not show any difference in the brain metabolite ratios. Athletes with concussion exhibited the most significant alteration of metabolite ratios at Day 3 post-injury (N-acetylaspartate/creatine: -17.6%, N-acetylaspartate/choline: -21.4%; P < 0.001 with respect to controls). On average, metabolic disturbance gradually recovered, initially in a slow fashion and, following Day 15, more rapidly. At 30 days post-injury, all athletes showed complete recovery, having metabolite ratios returned to values detected in controls. Athletes self-declared symptom clearance between 3 and 15 days after concussion. Results indicate that N-acetylaspartate determination by proton magnetic resonance spectroscopy represents a non-invasive tool to accurately measure changes in cerebral energy metabolism occurring in mild traumatic brain injury. In particular, this metabolic evaluation may significantly improve, along with other clinical assessments, the management of athletes suffering from concussion. Further studies to verify the effects of a second concussive event occurring at different time points of the recovery curve of brain metabolism are needed.

Concussion occurrence and knowledge in italian football (soccer).

The purpose of the study was to investigate concussion history, knowledge, injury identification, and management strategies among athletes, coaches, and medical staff in Italian club level football (soccer) clubs. Surveys (N=727) were distributed among Italian football clubs. Athletes' surveys were designed to evaluate athlete knowledge of concussive signs and symptoms and injury reporting. Coaches' surveys explored the understanding of concussive signs and symptoms and management practices. Medical staff surveys explored the standard of care regarding concussions. A total of 342 surveys were returned, for a 47% response rate. Descriptive analyses indicated 10% of athletes sustaining a concussion in the past year and 62% of these injuries were not reported, primarily due to the athletes not thinking the injury was serious enough. Coaches consistently identified non-concussion related symptoms (98.7%), but were unable to identify symptoms associated with concussion (38.9%). Most understood that loss of consciousness is not the sole indicator of injury (82.6%). Medical staff reported a heavy reliance on the clinical exam (92%) and athlete symptom reports (92%) to make the concussion diagnosis and return to play decision, with little use of neurocognitive (16.7%) or balance (0.0%) testing. Italian football athletes appear to report concussions at a rate similar to American football players, with a slightly higher rate of unreported injuries. Most of these athletes were aware they were concussed, but did not feel the injury was serious enough to report. Although coaches served as the primary person to whom concussions were reported, the majority of coaches were unable to accurately identify concussion related symptoms. With little use for neurocognitive and postural control assessments, the medical personnel may be missing injuries or returning athletes to play too soon. Collectively, these findings suggest that athletes, coaches, and medical personnel would benefit from concussion based educational materials on the signs, symptoms, and evaluative techniques of concussion. Key pointsItalian football (soccer) athletes report less than 40% of concussions.Injuries are most commonly reported to coaches, who may not be fully aware of concussive signs and symptoms.International educational measures on concussion awareness and management may be of use.

Transcriptomics of traumatic brain injury: gene expression and molecular pathways of different grades of insult in a rat organotypic hippocampal culture model.

Traumatic brain injury (TBI) is the one of the most common forms of head trauma, and it remains a leading cause of death and disability. It is known that the initial mechanical axonal injury triggers a complex cascade of neuroinflammatory and metabolic events, the understanding of which is essential for clinical, translational, and pharmacological research. These can occur even in mild TBI, and are associated with several post-concussion manifestations, including transiently heightened vulnerability to a second insult. Recent studies have challenged the tenet that ischemia is the ultimate modality of tissue damage following TBI, as metabolic dysfunction can develop in the presence of normal perfusion and before intracranial hypertension. In order to elucidate the cellular and molecular changes occurring in TBI as a direct result of neuronal injury and in the absence of ischemic damage, we performed a microarray analysis of expressed genes and molecular interaction pathways for different levels of severity of trauma using an in-vitro model. A stretch injury, equivalent to human diffuse axonal injury, was delivered to rat organotypic hippocampal slice cultures, and mRNA levels following a 10% (mild) and 50% (severe) stretch were compared with controls at 24 h. More genes were differentially expressed following 10% stretch than 50% stretch, indicating the early activation of complex cellular mechanisms. The data revealed remarkable differential gene expression following mTBI, even in the absence of cell damage. Pathway analysis revealed that molecular interactions in both levels of injury were similar, with IL-1beta playing a central role. Additional pathways of neurodegeneration involving RhoA (ras homolog gene family, member A) were found in 50% stretch.

Transient alterations of creatine, creatine phosphate, N-acetylaspartate and high-energy phosphates after mild traumatic brain injury in the rat.

In this study, the concentrations of creatine (Cr), creatine phosphate (CrP), N-acetylaspartate (NAA), ATP, ADP and phosphatidylcholine (PC) were measured at different time intervals after mild traumatic brain injury (mTBI) in whole brain homogenates of rats. Anaesthetized animals underwent to the closed-head impact acceleration "weight-drop" model (450 g delivered from 1 m height = mild traumatic brain injury) and were killed at 2, 6, 24, 48 and 120 h after the insult (n = 6 for each time point). Sham-operated rats (n = 6) were used as controls. Compounds of interest were synchronously measured by HPLC in organic solvent deproteinized whole brain homogenates. A reversible decrease of all metabolites but PC was observed, with minimal values recorded at 24 h post-injury (minimum of CrP = 48 h after impact). In particular, Cr and NAA showed a decrease of 44.5 and 29.5%, respectively, at this time point. When measuring NAA in relation to other metabolites, as it is commonly carried out in "in vivo" (1)H-magnetic resonance spectroscopy ((1)H-MRS), an increase in the NAA/Cr ratio and a decrease in the NAA/PC ratio was observed. Besides confirming a transient alteration of NAA homeostasis and ATP imbalance, our results clearly show significant changes in the cerebral concentration of Cr and CrP after mTBI. This suggests a careful use of the NAA/Cr ratio to measure NAA by (1)H-MRS in conditions of altered cerebral energy metabolism. Viceversa, the NAA/PC ratio appears to be a better indicator of actual NAA levels during energy metabolism impairment. Furthermore, our data suggest that, under pathological conditions affecting the brain energetic, the Cr-CrP system is not a suitable tool to buffer possible ATP depletion in the brain, thus supporting the growing indications for alternative roles of cerebral Cr.

Increase of uric acid and purine compounds in biological fluids of multiple sclerosis patients.

OBJECTIVES: In this study, the concentrations of uric acid, purine profile and creatinine in samples of cerebrospinal fluid and serum of multiple sclerosis (MS) patients were measured by HPLC and compared with corresponding values recorded in patients without MS (cerebrospinal fluid) and healthy subjects (serum). DESIGN AND METHODS: All samples were deproteinized with ultrafiltration (which ensures minimal sample manipulation and efficient protein removal) and then assayed for the synchronous HPLC separation of uric acid, hypoxanthine, xanthine, inosine, adenosine, guanosine and creatinine. RESULTS: The values of all compounds assayed were significantly higher in both biological fluids of MS patients with respect to values measured in controls. In particular, serum hypoxanthine, xanthine, uric acid and sum of oxypurines were, respectively, 3.17, 3.11, 1.23 and 1.27-fold higher in these patients than corresponding values recorded in controls (p<0.001). CONCLUSIONS: Differently from what previously reported, we here demonstrate that all purine compounds, including uric acid, are elevated in biological fluids of MS patients. Reinforced by the trend observed for creatinine, this corroborates the notion of sustained purine catabolism, possibly due to imbalance in ATP homeostasis, under these pathological conditions. These results cast doubt on the hypothesis that uric acid is depleted in MS because of increased oxidative stress, rather suggesting that this disease causes a generalized increase in purine catabolism. As observed in other pathological states, uric acid, purine compounds and creatinine, can be considered markers of metabolic energy imbalance rather than of reactive oxygen species, even in MS.

Temporal window of metabolic brain vulnerability to concussion: a pilot 1H-magnetic resonance spectroscopic study in concussed athletes--part III.

OBJECTIVE: In the present study, the occurrence of the temporal window of brain vulnerability was evaluated in concussed athletes by measuring N-acetylaspartate (NAA) using proton magnetic resonance (H-MR) spectroscopy. METHODS: Thirteen nonprofessional athletes who had a sport-related concussive head injury were examined for NAA determination by means of H-MR spectroscopy at 3, 15, and 30 days postinjury. All athletes but three suspended their physical activity. Those who continued their training had a second concussive event and underwent further examination at 45 days from the initial injury. The single case of one professional boxer, who was studied before the match and 4, 7, 15, and 30 days after a knockout, is also presented. Before each magnetic resonance examination, patients were asked for symptoms of mild traumatic brain injury, including physical, cognitive, emotional, and sleep disturbances. Data for H-MR spectroscopy recorded in five normal, age-matched, control volunteers, who were previously screened to exclude previous head injuries, were used for comparison. Semiquantitative analysis of NAA relative to creatine (Cr)- and choline (Cho)-containing compounds was performed from proton spectra obtained with a 3-T magnetic resonance system. RESULTS: Regarding the values of the NAA-to-Cr ratio (2.21 +/- 0.11) recorded in control patients, singly concussed athletes, at 3 days after the concussion, showed a decrease of 18.5% (1.80 +/- 0.04; P < 0.001). Only a modest 3% recovery was observed at 15 days (1.88 +/- 0.1; P < 0.001); at 30 days postinjury, the NAA-to-Cr ratio was 2.15 +/- 0.1, revealing full metabolic recovery with values not significantly different from those of control patients. These patients declared complete resolution of symptoms at the time of the 3-day study. The three patients who had a second concussive injury before the 15-day study showed an identical decrease of the NAA-to-Cr ratio at 3 days (1.78 +/- 0.08); however, at 15 days after the second injury, a further diminution of the NAA-to-Cr ratio occurred (1.72 +/- 0.07; P < 0.05 with respect to singly concussed athletes). At 30 days, the NAA-to-Cr ratio was 1.82 +/- 0.1, and at 45 days postinjury, the NAA-to-Cr ratio showed complete recovery (2.07 +/- 0.1; not significant with respect to control patients). This group of patients declared a complete resolution of symptoms at the time of the 30-day study. CONCLUSION: Results of this pilot study carried out in a cohort of singly and doubly concussed athletes, examined by H-MR spectroscopy for their NAA cerebral content at different time points after concussive events, demonstrate that also in humans, concussion opens a temporal window of brain metabolic imbalance, the closure of which does not coincide with resolution of clinical symptoms. The recovery of brain metabolism is not linearly related to time. A second concussive event prolonged the time of NAA normalization by 15 days. Although needing confirmation in a larger group of patients, these results show that NAA measurement by H-MR spectroscopy is a valid tool in assessing the full cerebral metabolic recovery after concussion, thereby suggesting its use in helping to decide when to allow athletes to return to play after a mild traumatic brain injury.

Temporal window of metabolic brain vulnerability to concussions: mitochondrial-related impairment--part I.

OBJECTIVE: In the present study, we investigate the existence of a temporal window of brain vulnerability in rats undergoing repeat mild traumatic brain injury (mTBI) delivered at increasing time intervals. METHODS: Rats were subjected to two diffuse mTBIs (450 g/1 m height) with the second mTBI delivered after 1 (n = 6), 2 (n = 6), 3 (n = 6), 4 (n = 6), and 5 days (n = 6) and sacrificed 48 hours after the last impact. Sham-operated animals were used as controls (n = 6). Two further groups of six rats each received a second mTBI after 3 days and were sacrificed at 120 and 168 hours postinjury. Concentrations of adenine nucleotides, N-acetylated amino acids, oxypurines, nucleosides, free coenzyme A, acetyl CoA, and oxidized and reduced nicotinamide adenine dinucleotides, oxidized nicotinamide adenine dinucleotide phosphate, and reduced nicotinamide adenine dinucleotide, reduced nicotinamide adenine dinucleotide phosphate nicotinic coenzymes were measured in deproteinized cerebral tissue extracts (three right and three left hemispheres), whereas the gene expression of N-acetylaspartate acylase, the enzyme responsible for N-acetylaspartate (NAA) degradation, was evaluated in extracts of three left and three right hemispheres. RESULTS: A decrease of adenosine triphosphate, adenosine triphosphate/adenosine diphosphate ratio, NAA, N-acetylaspartylglutamate, oxidized and reduced nicotinamide adenine dinucleotide, reduced nicotinamide adenine dinucleotide, and acetyl CoA and increase of N-acetylaspartate acylase expression were related to the interval between impacts with maximal changes recorded when mTBIs were spaced by 3 days. In these animals, protracting the time of sacrifice after the second mTBI up to 1 week failed to show cerebral metabolic recovery, indicating that this type of damage is difficult to reverse. A metabolic pattern similar to controls was observed only in animals receiving mTBIs 5 days apart. CONCLUSION: This study shows the existence of a temporal window of brain vulnerability after mTBI. A second concussive event falling within this time range had profound consequences on mitochondrial-related metabolism. Furthermore, because NAA recovery coincided with normalization of all other metabolites, it is conceivable to hypothesize that NAA measurement by 1H-NMR spectroscopy might be a valid tool in assessing full cerebral metabolic recovery in the clinical setting and with particular reference to sports medicine in establishing when to return mTBI-affected athletes to play. This study also shows, for the first time, the influence of TBI on acetyl-CoA, N-acetylaspartate acylase gene expression, and N-acetylaspartylglutamate, thus providing novel data on cerebral biochemical changes occurring in head injury.

Temporal window of metabolic brain vulnerability to concussions: oxidative and nitrosative stresses--part II.

OBJECTIVE: In the present study, we investigated the occurrence of oxidative and nitrosative stresses in rats undergoing repeat mild traumatic brain injury (mTBI) delivered with increasing time intervals. METHODS: Rats were subjected to two diffuse mTBIs (450 g/1 m height), with the second mTBI delivered after 1 (n = 6), 2 (n = 6), 3 (n = 6), 4 (n = 6), or 5 days (n = 6). The rats were sacrificed 48 hours after the last mTBI. Sham-operated animals were used as controls (n = 6). Concentrations of biochemical indices of oxidative stress (malondialdehyde, ascorbic acid, reduced and oxidized glutathione) and nitrosative stress (nitrite, nitrate) were synchronously measured by high-performance liquid chromatography in deproteinized tissue extracts (three right + three left hemispheres for each group of animals). RESULTS: Increase of malondialdehyde, reduced/oxidized glutathione ratio, nitrite, nitrate, and decrease of ascorbic acid and glutathione were dependent on the interval between impacts with maximal changes recorded when mTBIs were spaced by 3 days. Biochemical markers of oxidative and nitrosative stresses were near control levels only in animals receiving mTBIs 5 days apart. CONCLUSION: This study shows the remarkable negative contribution of reactive oxygen species overproduction and activation of inducible nitric oxide synthase in repeat mTBI. Because these effects were maximal when mTBIs were spaced by 3 days, it can be inferred that occurrence of a second mTBI within the temporal window of brain vulnerability not only causes profound derangement of mitochondrial functions, but also induces sustained oxidative and nitrosative stresses. Both phenomena certainly play a major role in the overall brain tissue damage occurring under these pathological conditions.

Extracellular N-acetylaspartate depletion in traumatic brain injury.

N-Acetylaspartate (NAA) is almost exclusively localized in neurons in the adult brain and is present in high concentration in the CNS. It can be measured by proton magnetic resonance spectroscopy and is seen as a marker of neuronal damage and death. NMR spectroscopy and animal models have shown NAA depletion to occur in various types of chronic and acute brain injury. We investigated 19 patients with traumatic brain injury (TBI). Microdialysis was utilized to recover NAA, lactate, pyruvate, glycerol and glutamate, at 12-h intervals. These markers were correlated with survival and a 6-month Glasgow Outcome Score. Eleven patients died and eight survived. A linear mixed model analysis showed a significant effect of outcome and of the interaction between time of injury and outcome on NAA levels (p = 0.009 and p = 0.004, respectively). Overall, extracellular NAA was 34% lower in non-survivors. A significant non-recoverable fall was observed in this group from day 4 onwards, with a concomitant rise in lactate-pyruvate ratio and glycerol. These results suggest that mitochondrial dysfunction is a significant contributor to poor outcome following TBI and propose extracellular NAA as a potential marker for monitoring interventions aimed at preserving mitochondrial function.

Hypothesis of the postconcussive vulnerable brain: experimental evidence of its metabolic occurrence.

OBJECTIVE: We evaluated the effects of two consecutive concussive injuries on brain energy metabolism and N-acetylaspartate (NAA) to investigate how the temporal interval between traumatic events influences overall injury severity. METHODS: Rats were injured to induce diffuse traumatic brain injury (TBI) (mild, 450 g/1 m; severe, 450 g/2 m). In two groups, two mild TBIs were delivered in 3- or 5-day intervals. Three additional animal groups were used: single mild TBI, single severe TBI, and sham. All animals were killed 48 hours postinjury. Adenosine 5'-triphosphate (ATP), adenosine diphosphate, and NAA concentrations were analyzed with high-performance liquid chromatography on deproteinized whole brain extracts. RESULTS: In control animals, the NAA concentration was 9.17 +/- 0.38 micromol/g wet weight, the ATP concentration was 2.25 +/- 0.21 micromol/g wet weight, and the ATP-to-adenosine diphosphate ratio was 9.38 +/- 1.23. These concentrations decreased to 6.68 +/- 1.12 micromol/g wet weight, 1.68 +/- 0.24 micromol/g wet weight, and 6.10 +/- 1.21 micromol/g wet weight, respectively, in rats that received two mild TBIs at a 5-day interval (P < 0.01; not different from results in rats with single mild TBI). When a second TBI was delivered after 3 days, the NAA concentration was 3.86 +/- 0.53 micromol/g wet weight, the ATP concentration was 1.11 +/- 0.18 micromol/g wet weight, and the ATP-to-adenosine diphosphate ratio was 2.64 +/- 0.43 (P < 0.001 versus both controls and 3-day interval; not different from rats receiving a single severe TBI). CONCLUSION: The biochemical modification severity in double TBI is dependent on the interval between traumatic events, which demonstrates the metabolic state of the vulnerable brain after mild TBI. These data support the hypothesis of the application of proton magnetic resonance spectroscopy to measure NAA as a possible tool to monitor the full recovery of brain metabolic functions in the clinical setting, particularly in sports medicine.

Cerebral oxidative stress and depression of energy metabolism correlate with severity of diffuse brain injury in rats.

OBJECTIVE: The combined effect of traumatic brain injury (TBI) and secondary insult on biochemical changes of cerebral tissue is not well known. For this purpose, we studied the time-course changes of parameters reflecting ROS-mediated oxidative stress and modifications of cell energy metabolism determined in rats subjected to cerebral insult of increasing severity. METHODS: Rats were divided into four groups: 1) sham-operated, 2) subjected to 10 minutes of hypoxia and hypotension (HH), 3) subjected to severe diffuse TBI, and 4) subjected to severe diffuse TBI + HH. Rats were killed at different times after injury, and analyses of malondialdehyde, ascorbate, high-energy phosphates, nicotinic coenzymes, oxypurines, nucleosides, and N-acetylaspartate (NAA) were made by high-performance liquid chromatography on whole-brain tissue extracts. RESULTS: Data indicated a close relationship between degree of oxidative stress and severity of brain insult, as evidenced by the highest malondialdehyde values and lowest ascorbate levels in rats subjected to TBI + HH. Similarly, modifications of parameters related to cell energy metabolism were modulated by increasing severity of brain injury, as demonstrated by the lowest values of energy charge potential, nicotinic coenzymes, and NAA and the highest levels of oxypurines and nucleosides recorded in TBI + HH rats. Both the intensity of oxidative stress-mediated cerebral damage and perturbation of energy metabolism were minimally affected in rats subjected to HH only. CONCLUSION: These results showed that the severity of brain insult can be graded by measuring biochemical modifications, specifically, reactive oxygen species-mediated damage, energy metabolism depression, and NAA, thereby validating the rodent model of closed-head diffuse TBI coupled with HH and proposing NAA as a marker with diagnostic relevance to monitor the metabolic state of postinjured brain.

Biochemical analysis of the cerebrospinal fluid: evidence for catastrophic energy failure and oxidative damage preceding brain death in severe head injury: a case report.

OBJECTIVES: To compare biochemical and clinical parameters in a case of fatal severe traumatic brain injury (TBI) with secondary insult. DESIGN AND METHODS: A TBI patient was catheterized for intracranial pressure (ICP) monitoring and cerebrospinal fluid (CSF) analysis of ascorbate, malondialdehyde, oxypurines, and nucleosides. RESULTS: Oxidative brain damage preceded ATP catabolite increment in the CSF even with ICP below 20 mm Hg. Sustained oxidative stress caused irreversible energy state derangement followed by a refractory ICP rise. Massive oxypurine and nucleoside release was recorded 36 h before brain death. CONCLUSIONS: Molecular events, detected by biochemical CSF analysis and preceding modification of clinical parameters in severe TBI with secondary insult, are discussed.