Severity of experimental traumatic brain injury modulates changes in concentrations of cerebral free amino acids

Potential neuroprotective and autophagy-enhancing effects of alogliptin on lithium/pilocarpine-induced seizures in rats: Targeting the AMPK/SIRT1/Nrf2 axis

BACKGROUND

Status epilepticus (SE) as a severe neurodegenerative disease, greatly negatively affects people's health, and there is an urgent need for innovative treatments. The valuable neuroprotective effects of glucagon-like peptide-1 (GLP-1) in several neurodegenerative diseases have raised motivation to investigate the dipeptidyl peptidase-4 (DPP-4) inhibitor; alogliptin (ALO), an oral antidiabetic drug as a potential treatment for SE. ALO has shown promising neuroprotective effects in Alzheimer's and Parkinson's diseases, but its impact on SE has not yet been studied.

AIM

The present study aimed to explore the repurposing potential for ALO in a lithium/pilocarpine (Li/Pil)-induced SE model in rats.

MAIN METHODS

ALO (30 mg/kg/day) was administered via gavage for 14 days, and SE was subsequently induced in the rats using a single dose of Li/Pil (127/60 mg/kg), while levetiracetam was used as a standard antiepileptic drug.

KEY FINDINGS

The results showed that ALO reduced seizure severity and associated hippocampal neurodegeneration. ALO also increased γ-aminobutyric acid (GABA) levels, diminished glutamate spikes, and corrected glial fibrillary acidic protein (GFAP) changes. At the molecular level, ALO increased GLP-1 levels and activated its downstream signaling pathway, AMP-activated protein kinase (AMPK)/sirtuin-1 (SIRT1). ALO also dampened the brain's pro-oxidant response, curbed neuroinflammation, and counteracted hippocampal apoptosis affording neuroprotection. In addition, it activated autophagy as indicated by Beclin1 elevation.

SIGNIFICANCE

This study suggested that the neuroprotective properties and autophagy-enhancing effects of ALO make it a promising treatment for SE and can potentially be used as a management approach for this condition.

Mapping small metabolite changes after traumatic brain injury using AP-MALDI MSI

Traumatic brain injury (TBI) is an alteration of brain function caused by a sudden transmission of an external force to the head. The biomechanical impact induces acute and chronic metabolic changes that highly contribute to injury evolution and outcome. TBI heterogeneity calls for approaches allowing the mapping of regional molecular and metabolic changes underpinning disease progression, with mass spectrometry imaging (MSI) as an efficient tool to study the spatial distribution of small metabolites. In this study, we applied an innovative targeted atmospheric pressure-MALDI mass spectrometry imaging (AP-MALDI MSI) approach, starting from an extensive list of metabolites, representative of different metabolic pathways, individually validated on the tissue under analysis with original standards using 2,5-dihydroxybenzoic acid (DHB), to characterize the impact of TBI on regional changes to small metabolites in the brain. Brains from sham and TBI mice obtained 21 days post-injury were analyzed to examine the spatial metabolic profile of small metabolites belonging to different metabolic pathways. By a whole brain analysis, we identified four metabolites (alanine, lysine, histidine, and inosine) with higher abundance in TBI than sham mice. Within the TBI group, lysine, histidine, and inosine were higher in the hemisphere ipsilateral to the biomechanical impact vs. the contralateral one. Images showed a major involvement of the ipsilateral thalamus characterized by the increase of arginine, lysine, histidine, and inosine and a significant reduction of glutamic acid, and N-acetylaspartic acid compared to the contralateral thalamus. These findings indicate high-resolution imaging mass spectrometry as a powerful tool to identify region-specific changes after a TBI to understand the metabolic changes underlying brain injury evolution.

Uninterrupted in vivo cerebral microdialysis measures of the acute neurochemical response to a single or repeated concussion in a rat model combining force and rotation

Altered extracellular amino acid concentrations following concussion or mild traumatic brain injury can result in delayed neuronal damage through overactivation of NMDA glutamatergic receptors. However, the consequences of repeated concussions prior to complete recovery are not well understood. In this study, we utilized in vivo cerebral microdialysis and a weight-drop model to investigate the acute neurochemical response to single and repeated concussions in adult rats that were fully conscious. A microdialysis probe was inserted into the hippocampus and remained in place during impact. Primary outcomes included concentrations of glutamate, GABA, taurine, glycine, glutamine, and serine, while secondary outcomes were righting times and excitotoxic indices. Compared to sham injury, the first concussion resulted in significant increases in glutamate, GABA, taurine, and glycine levels, longer righting times, and higher excitotoxic indices. Following the second concussion, righting times were significantly longer, suggesting cumulative effects of repeated concussion while only partial increases were observed in glutamate and taurine levels. GABA and glycine levels, and excitotoxic indices were comparable to sham injury. These findings suggest that single and repeated concussions may induce acute increases in several amino acids, while repeated concussions could exacerbate neurological symptoms despite less pronounced neurochemical changes.

Annexin-A1 tripeptide enhances functional recovery and mitigates brain damage in traumatic brain injury by inhibiting neuroinflammation and preventing ANXA1 nuclear translocation in mice

This study explores the role and mechanism of Annexin-A1 Tripeptide (ANXA1sp) in mitigating neuronal damage and promoting functional recovery in a mouse model of traumatic brain injury (TBI). Our goal is to identify ANXA1sp as a potential therapeutic drug candidate for TBI treatment. Adult male C57BL/6J mice were subjected to controlled cortical impact (CCI) to simulate TBI, supplemented by an in vitro model of glutamate-induced TBI in HT22 cells.  We assessed neurological deficits using the Modified Neurological Severity Score (mNSS), tested sensorimotor functions with beam balance and rotarod tests, and evaluated cognitive performance via the Morris water maze. Neuronal damage was quantified using Nissl and TUNEL staining, while microglial activation and inflammatory responses were measured through immunostaining, quantitative PCR (qPCR), Western blotting, and ELISA. Additionally, we evaluated cell viability in response to glutamate toxicity using the Cell Counting Kit-8 (CCK-8) assay and lactate dehydrogenase (LDH) release. Intraperitoneal administration of ANXA1sp significantly enhanced neurological outcomes, markedly reducing sensorimotor and cognitive impairments caused by TBI. This treatment resulted in a significant reduction in lesion volume and decreased neuronal cell death in the ipsilateral cortex. Moreover, ANXA1sp effectively diminished microglial activation around the brain lesion and decreased the levels of pro-inflammatory markers such as IL-6, IL-1β, TNF-α, and TGF-β in the cortex, indicating a significant reduction in neuroinflammation post-TBI. ANXA1sp also offered protection against neuronal cell death induced by glutamate toxicity, primarily by inhibiting the nuclear translocation of ANXA1, highlighting its potential as a neuroprotective strategy in TBI management. Administration of ANXA1sp significantly reduced neuroinflammation and neuronal cell death, primarily by blocking the nuclear translocation of ANXA1. This treatment substantially reduced brain damage and improved neurological functional recovery after TBI. Consequently, ANXA1sp stands out as a promising neuroprotective agent for TBI therapy.

Exploring cerebral structural and functional abnormalities in a mouse model of post-traumatic headache induced by mild traumatic brain injury

Mild traumatic brain injury (mTBI)-induced post-traumatic headache (PTH) is a pressing public health concern and leading cause of disability worldwide. Although PTH is often accompanied by neurological disorders, the exact underlying mechanism remains largely unknown. Identifying potential biomarkers may prompt the diagnosis and development of effective treatments for mTBI-induced PTH. In this study, a mouse model of mTBI-induced PTH was established to investigate its effects on cerebral structure and function during short-term recovery. Results indicated that mice with mTBI-induced PTH exhibited balance deficits during the early post-injury stage. Metabolic kinetics revealed that variations in neurotransmitters were most prominent in the cerebellum, temporal lobe/cortex, and hippocampal regions during the early stages of PTH. Additionally, variations in brain functional activities and connectivity were further detected in the early stage of PTH, particularly in the cerebellum and temporal cortex, suggesting that these regions play central roles in the mechanism underlying PTH. Moreover, our results suggested that GABA and glutamate may serve as potential diagnostic or prognostic biomarkers for PTH. Future studies should explore the specific neural circuits involved in the regulation of PTH by the cerebellum and temporal cortex, with these two regions potentially utilized as targets for non-invasive stimulation in future clinical treatment.

Mechanistic and therapeutic relationships of traumatic brain injury and γ-amino-butyric acid (GABA)

Traumatic brain injury (TBI) is a highly prevalent medical condition for which no medications specific for the prophylaxis or treatment of the condition as a whole exist. The spectrum of symptoms includes coma, headache, seizures, cognitive impairment, depression, and anxiety. Although it has been known for years that the inhibitory neurotransmitter γ-amino-butyric acid (GABA) is involved in TBI, no novel therapeutics based upon this mechanism have been introduced into clinical practice. We review the neuroanatomical, neurophysiological, neurochemical, and neuropharmacological relationships of GABA neurotransmission to TBI with a view toward new potential GABA-based medicines. The long-standing idea that excitatory and inhibitory (GABA and others) balances are disrupted by TBI is supported by the experimental data but has failed to invent novel methods of restoring this balance. The slow progress in advancing new treatments is due to the complexity of the disorder that encompasses multiple dynamically interacting biological processes including hemodynamic and metabolic systems, neurodegeneration and neurogenesis, major disruptions in neural networks and axons, frank brain lesions, and a multitude of symptoms that have differential neuronal and neurohormonal regulatory mechanisms. Although the current and ongoing clinical studies include GABAergic drugs, no novel GABA compounds are being explored. It is suggested that filling the gap in understanding the roles played by specific GABAA receptor configurations within specific neuronal circuits could help define new therapeutic approaches. Further research into the temporal and spatial delivery of GABA modulators should also be useful. Along with GABA modulation, research into the sequencing of GABA and non-GABA treatments will be needed.

Perinatal exposure to bisphenol A impairs cognitive function via the gamma-aminobutyric acid signaling pathway in male rat offspring

Bisphenol A (BPA) is a common synthetic endocrine disruptor that can be utilized in the fabrication of materials such as polycarbonates and epoxy resins. Numerous studies have linked BPA to learning and memory problems, although the precise mechanism remains unknown. Gamma-aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in the vertebrate central nervous system, and it is intimately related to learning and memory. This study aims to evaluate whether altered cognitive behavior involves the GABA signaling pathway in male offspring of rats exposed to BPA during the prenatal and early postnatal periods. Pregnant rats were orally given BPA (0, 0.04, 0.4, and 4 mg/kg body weight (BW)/day) from the first day of pregnancy to the 21st day of breastfeeding. Three-week-old male rat offspring were selected for an open-field experiment and a new object recognition experiment to evaluate the effect of BPA exposure on cognitive behavior. Furthermore, the role of GABA signaling markers in the cognition affected by BPA was investigated at the molecular level using western blotting and real-time polymerase chain reaction (RT-PCR). The research demonstrated that BPA exposure impacted the behavior and memory of male rat offspring and elevated the expression of glutamic acid decarboxylase 67 (GAD67), GABA type A receptors subunit (GABAARα1), and GABA vesicle transporter (VGAT) in the hippocampus while decreasing the expression levels of GABA transaminase (GABA-T) and GABA transporter 1 (GAT-1). These findings indicate that the alteration in the expression of GABA signaling molecules may be one of the molecular mechanisms by which perinatal exposure to BPA leads to decreased learning and memory in male rat offspring.

Quantifying acute changes in neurometabolism following blast-induced traumatic brain injury

Brain health is largely dependent on the metabolic regulation of amino acids. Brain injuries, diseases, and disorders can be detected through alterations in free amino acid (FAA) concentrations; and thus, mapping the changes has high diagnostic potential. Common methods focus on optimizing neurotransmitter quantification; however, recent focus has expanded to investigate the roles of molecular precursors in brain metabolism. An isocratic method using high performance liquid chromatography with electrochemical cell detection was developed to quantify a wide range of molecular precursors and neurotransmitters: alanine, arginine, aspartate, serine, taurine, threonine, tyrosine, glycine, glutamate, glutamine, and γ-Aminobutyric acid (GABA) following traumatic brain injury. First, baseline concentrations were determined in the serum, cerebrospinal fluid, hippocampus, cortex, and cerebellum of naïve male Sprague Dawley rats. A subsequent study was performed investigating acute changes in FAA concentrations following blast-induced traumatic brain injury (bTBI). Molecular precursor associated FAAs decreased in concentration at 4 h after injury in both the cortex and hippocampus while those serving as neurotransmitters remained unchanged. In particular, the influence of oxidative stress on the observed changes within alanine and arginine pathways following bTBI should be further investigated to elucidate the full therapeutic potential of these molecular precursors at acute time points.

Using metabolomics to predict severe traumatic brain injury outcome (GOSE) at 3 and 12 months

BACKGROUND

Prognostication is very important to clinicians and families during the early management of severe traumatic brain injury (sTBI), however, there are no gold standard biomarkers to determine prognosis in sTBI. As has been demonstrated in several diseases, early measurement of serum metabolomic profiles can be used as sensitive and specific biomarkers to predict outcomes.

METHODS

We prospectively enrolled 59 adults with sTBI (Glasgow coma scale, GCS ≤ 8) in a multicenter Canadian TBI (CanTBI) study. Serum samples were drawn for metabolomic profiling on the 1st and 4th days following injury. The Glasgow outcome scale extended (GOSE) was collected at 3- and 12-months post-injury. Targeted direct infusion liquid chromatography-tandem mass spectrometry (DI/LC-MS/MS) and untargeted proton nuclear magnetic resonance spectroscopy (¹H-NMR) were used to profile serum metabolites. Multivariate analysis was used to determine the association between serum metabolomics and GOSE, dichotomized into favorable (GOSE 5-8) and unfavorable (GOSE 1-4), outcomes.

RESULTS

Serum metabolic profiles on days 1 and 4 post-injury were highly predictive (Q² > 0.4-0.5) and highly accurate (AUC > 0.99) to predict GOSE outcome at 3- and 12-months post-injury and mortality at 3 months. The metabolic profiles on day 4 were more predictive (Q² > 0.55) than those measured on day 1 post-injury. Unfavorable outcomes were associated with considerable metabolite changes from day 1 to day 4 compared to favorable outcomes. Increased lysophosphatidylcholines, acylcarnitines, energy-related metabolites (glucose, lactate), aromatic amino acids, and glutamate were associated with poor outcomes and mortality.

DISCUSSION

Metabolomic profiles were strongly associated with the prognosis of GOSE outcome at 3 and 12 months and mortality following sTBI in adults. The metabolic phenotypes on day 4 post-injury were more predictive and significant for predicting the sTBI outcome compared to the day 1 sample. This may reflect the larger contribution of secondary brain injury (day 4) to sTBI outcome. Patients with unfavorable outcomes demonstrated more metabolite changes from day 1 to day 4 post-injury. These findings highlighted increased concentration of neurobiomarkers such as N-acetylaspartate (NAA) and tyrosine, decreased concentrations of ketone bodies, and decreased urea cycle metabolites on day 4 presenting potential metabolites to predict the outcome. The current findings strongly support the use of serum metabolomics, that are shown to be better than clinical data, in determining prognosis in adults with sTBI in the early days post-injury. Our findings, however, require validation in a larger cohort of adults with sTBI to be used for clinical practice.

Biomarkers of hypoxic-ischemic encephalopathy: a systematic review

BACKGROUND

Current diagnostic criteria for hypoxic-ischemic encephalopathy in the early hours lack objective measurement tools. Therefore, this systematic review aims to identify putative molecules that can be used in diagnosis in daily clinical practice (PROSPERO ID: CRD42021272610).

DATA SOURCES

Searches were performed in PubMed, Web of Science, and Science Direct databases until November 2020. English original papers analyzing samples from newborns > 36 weeks that met at least two American College of Obstetricians and Gynecologists diagnostic criteria and/or imaging evidence of cerebral damage were included. Bias was assessed by the Newcastle-Ottawa Scale. The search and data extraction were verified by two authors separately.

RESULTS

From 373 papers, 30 met the inclusion criteria. Data from samples collected in the first 72 hours were extracted, and increased serum levels of neuron-specific enolase and S100-calcium-binding protein-B were associated with a worse prognosis in newborns that suffered an episode of perinatal asphyxia. In addition, the levels of glial fibrillary acidic protein, ubiquitin carboxyl terminal hydrolase isozyme-L1, glutamic pyruvic transaminase-2, lactate, and glucose were elevated in newborns diagnosed with hypoxic-ischemic encephalopathy. Moreover, pathway analysis revealed insulin-like growth factor signaling and alanine, aspartate and glutamate metabolism to be involved in the early molecular response to insult.

CONCLUSIONS

Neuron-specific enolase and S100-calcium-binding protein-B are potential biomarkers, since they are correlated with an unfavorable outcome of hypoxic-ischemic encephalopathy newborns. However, more studies are required to determine the sensitivity and specificity of this approach to be validated for clinical practice.

Hindering NAT8L expression in hepatocellular carcinoma increases cytosolic aspartate delivery that fosters pentose phosphate pathway and purine biosynthesis promoting cell proliferation

N-acetylaspartate (NAA) is synthesized by the mitochondrial enzyme NAT8L, which uses acetyl-CoA and aspartate as substrates. These metabolites are fundamental for bioenergetics and anabolic requirements of highly proliferating cells, thus, NAT8L modulation may impinge on the metabolic reprogramming of cancer cells. Specifically, aspartate represents a limiting amino acid for nucleotide synthesis in cancer. Here, the expression of the NAT8L enzyme was modulated to verify how it impacts the metabolic adaptations and proliferative capacity of hepatocellular carcinoma. We demonstrated that NAT8L downregulation is associated with increased proliferation of hepatocellular carcinoma cells and immortalized hepatocytes. The overexpression of NAT8L instead decreased cell growth. The pro-tumoral effect of NAT8L silencing depended on glutamine oxidation and the rewiring of glucose metabolism. Mechanistically, NAT8L downregulation triggers aspartate outflow from mitochondria via the exporter SLC25A13 to promote glucose flux into the pentose phosphate pathway, boosting purine biosynthesis. These results were corroborated by the analyses of human and mouse hepatocellular carcinoma samples revealing a decrease in NAT8L expression compared to adjacent non-tumoral tissues. Overall, this work demonstrates that NAT8L expression in liver cells limits the cytosolic availability of aspartate necessary for enhancing the pentose phosphate pathway and purine biosynthesis, counteracting cell proliferation.

Macromolecular-Suppressed GABA-Edited MR Spectroscopy in the Posterior Cingulate Cortex of Patients With Acute Mild Traumatic Brain Injury

BACKGROUND

Mild traumatic brain injury (mTBI) causes a number of molecular and cellular alterations. There is evidence of an imbalance between the main excitatory (glutamate, Glu) and the main inhibitory (gamma-aminobutyric acid [GABA]) neurotransmitters following mTBI. In vivo human GABA-Glu balance studies following mTBI are sparse.

PURPOSE

To investigate the effect of acute mTBI on the GABA concentration measured in the posterior cingulate cortex (PCC) of pediatric patients by using the macromolecular (MM)-suppressed GABA J-editing technique.

STUDY TYPE

Prospective patient and phantom.

PARTICIPANTS

A total of 14 pediatric patients (mean age 16.0 ± 1.7) with acute mTBI (<3 days after trauma; Glasgow Coma Scale 15) and 16 healthy volunteers (mean age 16.9 ± 2.8). Phantom: 524 cm³ sphere containing 10 mM glycine, 10 mM GABA.

FIELD STRENGTH/SEQUENCE

A 3 T, MEGA-PRESS pulse sequence.

ASSESSMENT

GABA spectra were processed in Gannet software. MM-suppressed GABA editing efficiency was derived from the phantom study. Absolute GABA and glutamate + glutamine (Glx) concentrations were quantified using different types of correction and compared between groups. N-acetyl aspartate (NAA) and choline (Cho) levels relative to tCr were also compared.

STATISTICAL TESTS

Shapiro-Wilk test, Mann-Whitney U test, Student t-test, Pearson or Spearman correlations. P < 0.01 was considered statistically significant.

RESULTS

The MM-suppressed GABA editing efficiency was 0.63. GABA signal fit error was <16% for all participants. The GABA concentration in the PCC of the mTBI group was significantly different from that in healthy controls: GABA/tCr was higher by 27%, absolute GABA concentration with different types of correction was higher by ≈17%. No significant differences were observed in Glx concentrations (P ≥ 0.32) or in Glx/tCr (P ≥ 0.1), NAA/tCr (P = 0.55), and Cho/tCr levels (P = 0.85).

DATA CONCLUSION

We report an increase in the GABA concentration in the PCC region in acute mTBI pediatric patients. This may suggest activation of GABA synthesis and impairment of the GABAergic system after acute mTBI.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 1.

Branched-Chain Amino Acids Are Neuroprotective Against Traumatic Brain Injury and Enhance Rate of Recovery: Prophylactic Role for Contact Sports and Emergent Use

Branched-chain amino acids (BCAAs) are known to be neurorestorative after traumatic brain injury (TBI). Despite clinically significant improvements in severe TBI patients given BCAAs after TBI, the approach is largely an unrecognized option. Further, TBI continues to be the most common cause of morbidity and mortality in adolescents and adults. To date, no study has evaluated whether BCAAs can be preventive or neuroprotective if taken before a TBI. We hypothesized that if BCAAs were elevated in the circulation before TBI, the brain would readily access the BCAAs and the severity of injury would be reduced. Before TBI induction with a standard weight-drop method, 50 adult mice were randomized into groups that were shams, untreated, and pre-treated, post-treated, or pre- + post-treated with BCAAs. Pre-treated mice received BCAAs through supplemented water and were dosed by oral gavage 45 min before TBI induction. All mice underwent beam walking to assess motor recovery, and the Morris water maze assessed cognitive function post-injury. On post-injury day 14, brains were harvested to assess levels of astrocytes and microglia with glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (IBA-1) immunohistochemistry, respectively. Pre-treated and pre- +post-treated mice exhibited significantly better motor recovery and cognitive function than the other groups. The pre- + post-treated group had the best overall memory performance, whereas the pre-treated and post-treated groups only had limited improvements in memory compared to untreated animals. Pre- + post-treated brains had levels of GFAP that were similar to the sham group, whereas the pre-only and post-only groups showed increases. Although trends existed, no meaningful changes in IBA-1 were detected. This is the first study, animal or human, to demonstrate that BCAA are neuroprotective and substantiates their neurorestorative benefits after TBI, most likely through the important roles of BCAAs to glutamate homeostasis.

ILB®, a Low Molecular Weight Dextran Sulphate, Restores Glutamate Homeostasis, Amino Acid Metabolism and Neurocognitive Functions in a Rat Model of Severe Traumatic Brain Injury

In a previous study, we found that administration of ILB®, a new low molecular weight dextran sulphate, significantly improved mitochondrial functions and energy metabolism, as well as decreased oxidative/nitrosative stress, of brain tissue of rats exposed to severe traumatic brain injury (sTBI), induced by the closed-head weight-drop model of diffused TBI. Using aliquots of deproteinized brain tissue of the same animals of this former study, we here determined the concentrations of 24 amino acids of control rats, untreated sTBI rats (sacrificed at 2 and 7 days post-injury) and sTBI rats receiving a subcutaneous ILB® administration (at the dose levels of 1, 5 and 15 mg/kg b.w.) 30 min post-impact (sacrificed at 2 and 7 days post-injury). Additionally, in a different set of experiments, new groups of control rats, untreated sTBI rats and ILB®-treated rats (administered 30 min after sTBI at the dose levels of 1 or 5 mg/kg b.w.) were studied for their neurocognitive functions (anxiety, locomotor capacities, short- and long-term memory) at 7 days after the induction of sTBI. Compared to untreated sTBI animals, ILB® significantly decreased whole brain glutamate (normalizing the glutamate/glutamine ratio), glycine, serine and g-aminobutyric acid. Furthermore, ILB® administration restored arginine metabolism (preventing nitrosative stress), levels of amino acids involved in methylation reactions (methionine, L-cystathionine, S-adenosylhomocysteine), and N-acetylaspartate homeostasis. The macroscopic evidences of the beneficial effects on brain metabolism induced by ILB® were the relevant improvement in neurocognitive functions of the group of animals treated with ILB® 5 mg/kg b.w., compared to the marked cognitive decline measured in untreated sTBI animals. These results demonstrate that ILB® administration 30 min after sTBI prevents glutamate excitotoxicity and normalizes levels of amino acids involved in crucial brain metabolic functions. The ameliorations of amino acid metabolism, mitochondrial functions and energy metabolism in ILB®-treated rats exposed to sTBI produced significant improvement in neurocognitive functions, reinforcing the concept that ILB® is a new effective therapeutic tool for the treatment of sTBI, worth being tested in the clinical setting.

The role of L-arginine metabolism in neurocritical care patients

Nitric oxide is an important mediator of vascular autoregulation and is involved in pathophysiological changes after acute neurological disorders. Nitric oxide is generated by nitric oxide synthases from the amino acid L-arginine. L-arginine can also serve as a substrate for arginases or lead to the generation of dimethylarginines, asymmetric dimethylarginine, and symmetric dimethylarginine, by methylation. Asymmetric dimethylarginine is an endogenous inhibitor of nitric oxide synthase and can lead to endothelial dysfunction. This review discusses the role of L-arginine metabolism in patients suffering from acute and critical neurological disorders often requiring neuro-intensive care treatment. Conditions addressed in this review include intracerebral hemorrhage, aneurysmal subarachnoid hemorrhage, and traumatic brain injury. Recent therapeutic advances in the field are described including current randomized controlled trials for traumatic brain injuries and hemorrhagic stroke.

Biochemical Discrimination of the Down Syndrome-Related Metabolic and Oxidative/Nitrosative Stress Alterations from the Physiologic Age-Related Changes through the Targeted Metabolomic Analysis of Serum

Down Syndrome (DS) is a neurodevelopmental disorder that is characterized by an accelerated aging process, frequently associated with the development of Alzheimer’s disease (AD). Previous studies evidenced that DS patients have various metabolic anomalies, easily measurable in their serum samples, although values that were found in DS patients were compared with those of age-matched non-DS patients, thus hampering to discriminate the physiologic age-related changes of serum metabolites from those that are truly caused by the pathologic processes associated with DS. In the present study we performed a targeted metabolomic evaluation of serum samples from DS patients without dementia of two age classes (Younger DS Patients, YDSP, aging 20–40 years; Aged DS Patients, ADSP, aging 41–60 years), comparing the results with those that were obtained in two age classes of non-DS patients (Younger non-DS Patients, YnonDSP, aging 30–60 years; Aged-nonDS Patients, AnonDSP, aging 75–90 years). Of the 36 compounds assayed, 30 had significantly different concentrations in Pooled non-DS Patients (PnonDSP), compared to Pooled DS Patients (PDSP). Age categorization revealed that 11/30 compounds were significantly different in AnonDSP, compared to YnonDSP, indicating physiologic, age-related changes of their circulating concentrations. A comparison between YDSP and ADSP showed that 19/30 metabolites had significantly different values from those found in the corresponding classes of non-DS patients, strongly suggesting pathologic, DS-associated alterations of their serum levels. Twelve compounds selectively and specifically discriminated PnonDSP from PDSP, whilst only three discriminated YDSP from ADSP. The results allowed to determine, for the first time and to the best of our knowledge, the true, age-independent alterations of metabolism that are measurable in serum and attributable only to DS. These findings may be of high relevance for better strategies (pharmacological, nutritional) aiming to specifically target the dysmetabolism and decreased antioxidant defenses that are associated with DS.

Effects of Traumatic Brain Injury on the Gut Microbiota Composition and Serum Amino Acid Profile in Rats

Traumatic brain injury (TBI) heavily impacts the body: it damages the brain tissue and the peripheral nervous system and shifts homeostasis in many types of tissue. An acute brain injury compromises the “brain–gut-microbiome axis”, a well-balanced network formed by the brain, gastrointestinal tract, and gut microbiome, which has a complex effect: damage to the brain alters the composition of the microbiome; the altered microbiome affects TBI severity, neuroplasticity, and metabolic pathways through various bacterial metabolites. We modeled TBI in rats. Using a bioinformatics approach, we sought to identify correlations between the gut microbiome composition, TBI severity, the rate of neurological function recovery, and blood metabolome. We found that the TBI caused changes in the abundance of 26 bacterial genera. The most dramatic change was observed in the abundance of Agathobacter species. The TBI also altered concentrations of several metabolites, specifically citrulline and tryptophan. We found no significant correlations between TBI severity and the pre-existing gut microbiota composition or blood metabolites. However, we discovered some differences between the two groups of subjects that showed high and low rates of neurological function recovery, respectively. The present study highlights the role of the brain–gut-microbiome axis in TBI.

Extracellular tau oligomers affect extracellular glutamate handling by astrocytes through downregulation of GLT-1 expression and impairment of NKA1A2 function

AIMS

Several studies reported that astrocytes support neuronal communication by the release of gliotransmitters, including ATP and glutamate. Astrocytes also play a fundamental role in buffering extracellular glutamate in the synaptic cleft, thus limiting the risk of excitotoxicity in neurons. We previously demonstrated that extracellular tau oligomers (ex-oTau), by specifically targeting astrocytes, affect glutamate-dependent synaptic transmission via a reduction in gliotransmitter release. The aim of this work was to determine if ex-oTau also impair the ability of astrocytes to uptake extracellular glutamate, thus further contributing to ex-oTau-dependent neuronal dysfunction.

METHODS

Primary cultures of astrocytes and organotypic brain slices were exposed to ex-oTau (200 nM) for 1 hour. Extracellular glutamate buffering by astrocytes was studied by: Na⁺ imaging; electrophysiological recordings; high-performance liquid chromatography; Western blot and immunofluorescence. Experimental paradigms avoiding ex-oTau internalization (i.e., heparin pre-treatment and amyloid precursor protein knockout astrocytes) were used to dissect intracellular vs. extracellular effects of oTau.

RESULTS

Ex-oTau uploading in astrocytes significantly affected glutamate-transporter-1 expression and function, thus impinging on glutamate buffering activity. Ex-oTau also reduced Na-K-ATPase activity because of pump mislocalization on the plasma membrane, with no significant changes in expression. This effect was independent of oTau internalization and it caused Na⁺ overload and membrane depolarization in ex-oTau-targeted astrocytes.

CONCLUSIONS

Ex-oTau exerted a complex action on astrocytes, at both intracellular and extracellular levels. The net effect was dysregulated glutamate signalling in terms of both release and uptake that relied on reduced expression of glutamate-transporter-1, altered function and localization of NKA1A1, and NKA1A2. Consequently, Na⁺ gradients and all Na⁺ -dependent transports were affected.

Neuroprotective Role of Nutritional Supplementation in Athletes

BACKGROUND

Neurodegenerative disorders belong to different classes of progressive/chronic conditions that affect the peripheral/central nervous system. It has been shown through studies that athletes who play sports involving repeated head trauma and sub-concussive impacts are more likely to experience neurological impairments and neurodegenerative disorders in the long run.

AIMS

The aim of the current narrative review article is to provide a summary of various nutraceuticals that offer promise in the prevention or management of sports-related injuries, especially concussions and mild traumatic brain injuries.

METHODS

This article reviews the various potential nutraceutical agents and their possible mechanisms in providing a beneficial effect in the injury recovery process. A thorough survey of the literature was carried out in the relevant databases to identify studies published in recent years. In the present article, we have also highlighted the major neurological disorders along with the associated nutraceutical(s) therapy in the management of disorders.

RESULTS

The exact pathological mechanism behind neurodegenerative conditions is complex as well as idiopathic. However, mitochondrial dysfunction, oxidative stress as well as intracellular calcium overload are some common reasons responsible for the progression of these neurodegenerative disorders. Owing to the multifaceted effects of nutraceuticals (complementary medicine), these supplements have gained importance as neuroprotective. These diet-based approaches inhibit different pathways in a physiological manner without eliciting adverse effects. Food habits and lifestyle of an individual also affect neurodegeneration.

CONCLUSION

Studies have shown nutraceuticals (such as resveratrol, omega-3-fatty acids) to be efficacious in terms of their neuroprotection against several neurodegenerative disorders and to be used as supplements in the management of traumatic brain injuries. Protection prior to injuries is needed since concussions or sub-concussive impacts may trigger several pathophysiological responses or cascades that can lead to long-term complications associated with CNS. Thus, the use of nutraceuticals as prophylactic treatment for neurological interventions has been proposed.

Traumatic Brain Injury: Mechanisms of Glial Response

Traumatic brain injury (TBI) is a heterogeneous disorder that involves brain damage due to external forces. TBI is the main factor of death and morbidity in young males with a high incidence worldwide. TBI causes central nervous system (CNS) damage under a variety of mechanisms, including synaptic dysfunction, protein aggregation, mitochondrial dysfunction, oxidative stress, and neuroinflammation. Glial cells comprise most cells in CNS, which are mediators in the brain’s response to TBI. In the CNS are present astrocytes, microglia, oligodendrocytes, and polydendrocytes (NG2 cells). Astrocytes play critical roles in brain’s ion and water homeostasis, energy metabolism, blood-brain barrier, and immune response. In response to TBI, astrocytes change their morphology and protein expression. Microglia are the primary immune cells in the CNS with phagocytic activity. After TBI, microglia also change their morphology and release both pro and anti-inflammatory mediators. Oligodendrocytes are the myelin producers of the CNS, promoting axonal support. TBI causes oligodendrocyte apoptosis, demyelination, and axonal transport disruption. There are also various interactions between these glial cells and neurons in response to TBI that contribute to the pathophysiology of TBI. In this review, we summarize several glial hallmarks relevant for understanding the brain injury and neuronal damage under TBI conditions.

Efficacy of prophylactic versus therapeutic administration of the NMDA receptor antagonist MK-801 on the acute neurochemical response to a concussion in a rat model combining force and rotation

OBJECTIVE

Alterations in amino acid concentrations are a major contributor to the persistent neurological and behavioral effects induced by concussions and mild traumatic brain injuries (TBIs). Glutamate, the most abundant excitatory amino acid in the CNS, has a major role in the pathophysiological process of concussion. The indiscriminate liberation of glutamate immediately after a concussion triggers an excitotoxic response that leads to cell death, neuronal damage, and the dysfunction of surviving neurons, largely by overactivation of N-methyl-d-aspartate (NMDA) glutamatergic receptors. The aim of the present study was to investigate the efficacy of prophylactic versus therapeutic administration of MK-801, a promising NMDA receptor antagonist, on the acute changes in amino acid extracellular concentrations involved in excitotoxicity resulting from a concussive trauma.

METHODS

The immediate neurochemical response to a concussion cannot be characterized in humans. Therefore, the authors used their previously validated combination of a weight-drop concussion rat model and in vivo cerebral microdialysis. The microdialysis probe was inserted inside the hippocampus and left inserted at impact to allow uninterrupted sampling of amino acids of interest immediately after concussion. The primary outcome included amino acid concentrations and the secondary outcome included righting time. Samples were taken in 10-minute increments for 60 minutes before, during, and 60 minutes after impact, and analyzed for glutamate, gamma-aminobutyric acid, taurine, glycine, glutamine, and serine using high-performance liquid chromatography. Righting time was acquired as a neurological restoration indicator. Physiological saline or 10 mg/kg MK-801 was administrated intraperitoneally 60 minutes before or immediately following induction of sham injury or concussion.

RESULTS

Following induction of concussion, glutamate, taurine, and glycine levels as well as righting times in cases from the MK-801 treatment group were comparable to those of vehicle-treated animals. In contrast, righting times and amino acid concentrations observed within the first 10 minutes after induction of concussion in cases assigned to the MK-801 prophylaxis group were comparable to those of sham-injured animals.

CONCLUSIONS

These results suggest that presynaptic actions and peak availability of MK-801 following prophylactic administration significantly inhibit the immediate and indiscriminate release of glutamate, taurine, and glycine in extracellular fluid after a concussion.

JUMPt: Comprehensive Protein Turnover Modeling of In Vivo Pulse SILAC Data by Ordinary Differential Equations

Recent advances in mass spectrometry (MS)-based proteomics allow the measurement of turnover rates of thousands of proteins using dynamic labeling methods, such as pulse stable isotope labeling by amino acids in cell culture (pSILAC). However, when applying the pSILAC strategy to multicellular animals (e.g., mice), the labeling process is significantly delayed by native amino acids recycled from protein degradation in vivo, raising a challenge of defining accurate protein turnover rates. Here, we report JUMPt, a software package using a novel ordinary differential equation (ODE)-based mathematical model to determine reliable rates of protein degradation. The uniqueness of JUMPt is to consider amino acid recycling and fit the kinetics of the labeling amino acid (e.g., Lys) and whole proteome simultaneously to derive half-lives of individual proteins. Multiple settings in the software are designed to enable simple to comprehensive data inputs for precise analysis of half-lives with flexibility. We examined the software by studying the turnover of thousands of proteins in the pSILAC brain and liver tissues. The results were largely consistent with the proteome turnover measurements from previous studies. The long-lived proteins are enriched in the integral membrane, myelin sheath, and mitochondrion in the brain. In summary, the ODE-based JUMPt software is an effective proteomics tool for analyzing large-scale protein turnover, and the software is publicly available on GitHub (https://github.com/JUMPSuite/JUMPt) to the research community.

Glutamate, Glutamine, GABA and Oxidative Products in the Pons Following Cortical Injury and Their Role in Motor Functional Recovery

Brain injury leads to an excitatory phase followed by an inhibitory phase in the brain. The clinical sequelae caused by cerebral injury seem to be a response to remote functional inhibition of cerebral nuclei located far from the motor cortex but anatomically related to the injury site. It appears that such functional inhibition is mediated by an increase in lipid peroxidation (LP). To test this hypothesis, we report data from 80 rats that were allocated to the following groups: the sham group (n = 40), in which rats received an intracortical infusion of artificial cerebrospinal fluid (CSF); the injury group (n = 20), in which rats received CSF containing ferrous chloride (FeCl₂, 50 mM); and the recovery group (n = 20), in which rats were injured and allowed to recover. Beam-walking, sensorimotor and spontaneous motor activity tests were performed to evaluate motor performance after injury. Lipid fluorescent products (LFPs) were measured in the pons. The total pontine contents of glutamate (GLU), glutamine (GLN) and gamma-aminobutyric acid (GABA) were also measured. In injured rats, the motor deficits, LFPs and total GABA and GLN contents in the pons were increased, while the GLU level was decreased. In contrast, in recovering rats, none of the studied variables were significantly different from those in sham rats. Thus, motor impairment after cortical injury seems to be mediated by an inhibitory pontine response, and functional recovery may result from a pontine restoration of the GLN-GLU-GABA cycle, while LP may be a primary mechanism leading to remote pontine inhibition after cortical injury.

Combination of Polygoni Multiflori Radix Praeparata and Acori Tatarinowii Rhizoma Alleviates Learning and Memory Impairment in Scopolamine-Treated Mice by Regulating Synaptic-Related Proteins

Polygoni Multiflori Radix Praeparata (ZhiHeShouWu, PMRP) and Acori Tatarinowii Rhizoma (ShiChangPu, ATR) and their traditional combination (PA) are frequently used in traditional Chinese medicine to prevent and treat Alzheimer disease (AD) based on the theory that PMRP tonifies the kidney and ATR dissipates phlegm. However, the components of PA and their mechanisms of action are not known. The present study analyzed the active components of PA, and investigated the protective effect of PA against cognitive impairment induced by scopolamine in mice along with the underlying mechanism.The aqueous extract of PA was analyzed by high-performance liquid chromatography–mass spectrometry (HPLC-MS) and gas chromatography (GC)-MS in order to identify the major components. To evaluate the protective effect of PA against cognitive dysfunction, mice were orally administered PA, PMRP, or ATR for 30 days before treatment with scopolamine. Learning and memory were assessed in mice with the Morris water maze test; neurotransmitter levels in the hippocampus were analyzed by HPLC-MS; and the expression of synapse-related proteins in the hippocampus was detected by western blotting and immunohistochemistry. Eight active compounds in PA and rat plasma were identified by HPLC-MS and GC-MS. Plasma concentrations of 2,3,5,4′-tetrahydroxystilbene-2-O-β-d-glucoside, emodin, α-asarone, and asarylaldehyde were increased following PA administration; meanwhile, gallic acid, emodin-8-O-β-d-glucopyranoside, β-asarone, and cis-methyl isoeugenol concentrations were similar in rats treated with PA, PMRP, and ATR. In scopolamine-treated mice, PA increased the concentrations of neurotransmitters in the hippocampus, activated the brain-derived neurotrophic factor (BDNF)/extracellular signal-regulated kinase (ERK)/cAMP response element binding protein (CREB) signaling pathway, and increased the expression of p90 ribosomal S6 kinase (p90RSK) and postsynaptic density (PSD)95 proteins. Thus, PA alleviates cognitive deficits by enhancing synaptic-related proteins, suggesting that it has therapeutic potential for the treatment of aging-related diseases such as AD.

Nitric Oxide-Dependent Pathways as Critical Factors in the Consequences and Recovery after Brain Ischemic Hypoxia

Brain ischemia is one of the leading causes of disability and mortality worldwide. Nitric oxide (NO^•), a molecule that is involved in the regulation of proper blood flow, vasodilation, neuronal and glial activity constitutes the crucial factor that contributes to the development of pathological changes after stroke. One of the early consequences of a sudden interruption in the cerebral blood flow is the massive production of reactive oxygen and nitrogen species (ROS/RNS) in neurons due to NO^• synthase uncoupling, which leads to neurotoxicity. Progression of apoptotic or necrotic neuronal damage activates reactive astrocytes and attracts microglia or lymphocytes to migrate to place of inflammation. Those inflammatory cells start to produce large amounts of inflammatory proteins, including pathological, inducible form of NOS (iNOS), which generates nitrosative stress that further contributes to brain tissue damage, forming vicious circle of detrimental processes in the late stage of ischemia. S-nitrosylation, hypoxia-inducible factor 1α (HIF-1α) and HIF-1α-dependent genes activated in reactive astrocytes play essential roles in this process. The review summarizes the roles of NO^•-dependent pathways in the early and late aftermath of stroke and treatments based on the stimulation or inhibition of particular NO^• synthases and the stabilization of HIF-1α activity.

Therapies to Restore Consciousness in Patients with Severe Brain Injuries: A Gap Analysis and Future Directions

Background/Objective

For patients with disorders of consciousness (DoC) and their families, the search for new therapies has been a source of hope and frustration. Almost all clinical trials in patients with DoC have been limited by small sample sizes, lack of placebo groups, and use of heterogeneous outcome measures. As a result, few therapies have strong evidence to support their use; amantadine is the only therapy recommended by current clinical guidelines, specifically for patients with DoC caused by severe traumatic brain injury. To foster and advance development of consciousness-promoting therapies for patients with DoC, the Curing Coma Campaign convened a Coma Science Work Group to perform a gap analysis.

Methods

We consider five classes of therapies: (1) pharmacologic; (2) electromagnetic; (3) mechanical; (4) sensory; and (5) regenerative. For each class of therapy, we summarize the state of the science, identify gaps in knowledge, and suggest future directions for therapy development.

Results

Knowledge gaps in all five therapeutic classes can be attributed to the lack of: (1) a unifying conceptual framework for evaluating therapeutic mechanisms of action; (2) large-scale randomized controlled trials; and (3) pharmacodynamic biomarkers that measure subclinical therapeutic effects in early-phase trials. To address these gaps, we propose a precision medicine approach in which clinical trials selectively enroll patients based upon their physiological receptivity to targeted therapies, and therapeutic effects are measured by complementary behavioral, neuroimaging, and electrophysiologic endpoints.

Conclusions

This personalized approach can be realized through rigorous clinical trial design and international collaboration, both of which will be essential for advancing the development of new therapies and ultimately improving the lives of patients with DoC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12028-021-01227-y.

Evidence to Support the Use of S-Adenosylmethionine for Treatment of Post-Concussive Sequelae in the Military

INTRODUCTION

Since the year 2000, over 413,000 service members have sustained traumatic brain injury (TBI) and may present with post-concussive sequelae including headaches, fatigue, irritability, cognitive problems, depression, insomnia, and chronic pain. Although the focus of the article is on military TBI, the usefulness of S-adenosylmethionine (SAMe) would extend to both civilian and military populations. This narrative review examines the preclinical and clinical literature of SAMe's metabolism and alterations seen in disease states such as depressive disorders, pain disorders, fatigue, cognition, dementia, use in pregnancy and peripartum, children, adolescents, and adults, to the elderly with and without dementia, stroke, and neurodegeneration, in order to highlight its potential benefit in post-concussive sequelae after TBI.

MATERIALS AND METHODS

A MEDLINE/PubMed and Cochrane Database search was conducted between May 3, 2018 and July 30, 2019 by combining search terms for SAMe with terms for relevant disease states including depression, brain injury, dementia, Alzheimer's disease, Parkinson's disease, cognition, fatigue, and pain. This search retrieved a total of 676 references. 439 were excluded for being over a 10-year publication date, except where clinically relevant. After additional removal of repeated articles, the number of articles were totaled 197. An additional 59 articles were excluded: 10 not in English, 4 duplicates, 4 not original investigations, and 41 outside the scope of this article. The remaining 138 articles were used in this review and included 25 clinical studies, 46 preclinical studies, 63 reviews, and 4 case reports.

RESULTS

This narrative review examined the preclinical and clinical literature of SAMe's metabolism and alterations seen in MDD, pain disorders, fatigue, cognition and memory, dementia, and other disorders to highlight the potential benefit of SAMe in post-concussive sequelae in mTBI. The literature showed potential for improvement, safety, and tolerability in these symptom clusters commonly seen in military mild TBI (mTBI).

CONCLUSION

There is evidence of a potential benefit of SAMe as an intervention to help with symptoms across the range of post-concussive sequelae and syndromes commonly seen in military mTBI. Since the discovery of SAMe in 1952, this pleiotropic molecule has shown the significance of its involvement in several metabolic cascades in such disparate systems as epigenetics, bioenergetics, DNA methylation, neurotransmitter systems, and potential usefulness in military TBI. Significant limitations include disparate presentations seen in patients with mild TBI, those with post-concussive syndrome, as well as those with comorbid depression and posttraumatic stress disorder. Also, over-the-counter medications are not regulated and SAMe products may vary widely in price and quality. Given the potential for mania in patients with bipolar disorder, evaluation and recommendations should be made by a physician able to evaluate the underlying bipolar diathesis. Furthermore, this narrative review serves as the rationale for future open-label and double-blind placebo-controlled trials in military mTBI and SAMe.

Severe Spinal Cord Injury in Rats Induces Chronic Changes in the Spinal Cord and Cerebral Cortex Metabolism, Adjusted by Thiamine That Improves Locomotor Performance

Our study aims at developing knowledge-based strategies minimizing chronic changes in the brain after severe spinal cord injury (SCI). The SCI-induced long-term metabolic alterations and their reactivity to treatments shortly after the injury are characterized in rats. Eight weeks after severe SCI, significant mitochondrial lesions outside the injured area are demonstrated in the spinal cord and cerebral cortex. Among the six tested enzymes essential for the TCA cycle and amino acid metabolism, mitochondrial 2-oxoglutarate dehydrogenase complex (OGDHC) is the most affected one. SCI downregulates this complex by 90% in the spinal cord and 30% in the cerebral cortex. This is associated with the tissue-specific changes in other enzymes of the OGDHC network. Single administrations of a pro-activator (thiamine, or vitamin B1, 1.2 mmol/kg) or a synthetic pro-inhibitor (triethyl glutaryl phosphonate, TEGP, 0.02 mmol/kg) of OGDHC within 15–20 h after SCI are tested as protective strategies. The biochemical and physiological assessments 8 weeks after SCI reveal that thiamine, but not TEGP, alleviates the SCI-induced perturbations in the rat brain metabolism, accompanied by the decreased expression of (acetyl)p53, increased expression of sirtuin 5 and an 18% improvement in the locomotor recovery. Treatment of the non-operated rats with the OGDHC pro-inhibitor TEGP increases the p53 acetylation in the brain, approaching the brain metabolic profiles to those after SCI. Our data testify to an important contribution of the OGDHC regulation to the chronic consequences of SCI and their control by p53 and sirtuin 5.

Integrated metabolomics and network pharmacology to reveal the mechanisms of hydroxysafflor yellow A against acute traumatic brain injury

Traumatic brain injury (TBI) has become a leading cause of mortality, morbidity and disability worldwide. Hydroxysafflor yellow A (HSYA) is effective in treating TBI, but the potential mechanisms require further exploration. We aimed to reveal the mechanisms of HSYA against acute TBI by an integrated strategy combining metabolomics with network pharmacology. A controlled cortical impact (CCI) rat model was established, and neurological functions were evaluated. Metabolomics of brain tissues was used to identify differential metabolites, and the metabolic pathways were enriched by MetaboAnalyst. Then, network pharmacology was applied to dig out the potential targets against TBI induced by HSYA. The integrated network of metabolomics and network pharmacology was constructed based on Cytoscape. Finally, the obtained key targets were verified by molecular docking. HSYA alleviated the neurological deficits of TBI. Fifteen potentially significant metabolites were found to be involved in the therapeutic effects of HSYA against acute TBI. Most of these metabolites were regulated to recover after HSYA treatment. We found 10 hub genes according to network pharmacology, which was partly consistent with the metabolomics findings. Further integrated analysis focused on 4 key targets, including NOS1, ACHE, PTGS2 and XDH, as well as their related core metabolites and pathways. Molecular docking showed high affinities between key targets and HSYA. Region-specific metabolic alterations in the cortex and hippocampus were illuminated. This study reveals the complicated mechanisms of HSYA against acute TBI. Our work provides a novel paradigm to identify the potential mechanisms of pharmacological effects derived from a natural compound.

Whole-brain irradiation differentially modifies neurotransmitters levels and receptors in the hypothalamus and the prefrontal cortex

BACKGROUND

Whole-brain radiotherapy is a primary treatment for brain tumors and brain metastasis, but it also induces long-term undesired effects. Since cognitive impairment can occur, research on the etiology of secondary effects has focused on the hippocampus. Often overlooked, the hypothalamus controls critical homeostatic functions, some of which are also susceptible after whole-brain radiotherapy. Therefore, using whole-brain irradiation (WBI) in a rat model, we measured neurotransmitters and receptors in the hypothalamus. The prefrontal cortex and brainstem were also analyzed since they are highly connected to the hypothalamus and its regulatory processes.

METHODS

Male Wistar rats were exposed to WBI with 11 Gy (Biologically Effective Dose = 72 Gy). After 1 month, we evaluated changes in gamma-aminobutyric acid (GABA), glycine, taurine, aspartate, glutamate, and glutamine in the hypothalamus, prefrontal cortex, and brainstem according to an HPLC method. Ratios of Glutamate/GABA and Glutamine/Glutamate were calculated. Through Western Blott analysis, we measured the expression of GABAa and GABAb receptors, and NR1 and NR2A subunits of NMDA receptors. Changes were analyzed comparing results with sham controls using the non-parametric Mann-Whitney U test (p < 0.05).

RESULTS

WBI with 11 Gy induced significantly lower levels of GABA, glycine, taurine, aspartate, and GABAa receptor in the hypothalamus. Also, in the hypothalamus, a higher Glutamate/GABA ratio was found after irradiation. In the prefrontal cortex, WBI induced significant increases of glutamine and glutamate, Glutamine/Glutamate ratio, and increased expression of both GABAa receptor and NMDA receptor NR1 subunit. The brainstem showed no statistically significant changes after irradiation.

CONCLUSION

Our findings confirm that WBI can affect rat brain regions differently and opens new avenues for study. After 1 month, WBI decreases inhibitory neurotransmitters and receptors in the hypothalamus and, conversely, increases excitatory neurotransmitters and receptors in the prefrontal cortex. Increments in Glutamate/GABA in the hypothalamus and Glutamine/Glutamate in the frontal cortex indicate a neurochemical imbalance. Found changes could be related to several reported radiotherapy secondary effects, suggesting new prospects for therapeutic targets.

Are there any differential responses to concussive injury in civilian versus athletic populations: a neuroimaging study

Accurate identification and classification of patients suffering from mild traumatic brain injury (mTBI) is a significant challenge faced by clinicians and researchers. To examine if there are different pathophysiological responses to concussive injury in different populations, evaluated here comparing collegiate athletes versus age-matched non-athletes. Resting-state fMRI data were acquired in the acute phase of concussion from 30 collegiate athletes and from 30 injury and age matched non-athletes. Resting-state functional connectivity measures revealed group differences with reduced connectivity in the anterior cingulate cortex (p < .05) and posterior cingulate cortex (p < 0.05) hubs of the Default Mode Network in the athletes. Given the known positive effects of exercise on brain functional reserves and neural efficiency concept, we expected less pronounced effect of concussion in athletic population. In contrast, there were significant decreases in functional connectivity in athletes that could be a result of previous repetitive subconcussive impacts and history of concussion.

Metabolomics Deciphers Potential Targets of Xuefu Zhuyu Decoction Against Traumatic Brain Injury in Rat

Xuefu Zhuyu decoction (XFZYD) performs multiple functions for traumatic brain injury (TBI) treatment. However, its clinical application is limited by the incomplete exploration of targets and inadequate discussion of mechanisms. We aimed to investigate the metabolic alterations of XFZYD in acute and chronic stages of TBI. Sprague-Dawley rats were randomly divided into the sham, controlled cortical impact (CCI) and XFZYD group. Behavioral and histopathological tests were used to evaluate the neuroprotective effects. Coagulation assays were performed to assess safety. Moreover, we analyzed the metabolomic profiling of hippocampal samples with different time intervals after CCI by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Differential metabolites were screened by multivariate data analysis. To further uncover the association between candidate metabolites and biological interaction networks, we applied bioinformatics analysis using MetaboAnalyst 4.0, STITCH 5.0 and TCMSP. The potential mechanism was verified by ELISA and Western blot. XFZYD ameliorated neurological deficiencies post-CCI without impairing blood coagulation in the rat’s model. Seventeen and fourteen metabolites were filtered on d 3 and 21, respectively. Eleven of potential metabolites were common at these time points, involving two significant pathways (arginine and proline metabolism, phenylalanine, tyrosine and tryptophan biosynthesis). Gamma-aminobutyric acid (GABA) and the related pathways were specifically affected by XFZYD at the acute phase of TBI, while biosynthesis of amino acids was the major pathway influenced at the chronic phase. This study provides broad insights into the therapeutic effects of XFZYD in treating TBI through the whole phases.

The Role of NLRP3 Inflammasome in the Pathogenesis of Traumatic Brain Injury

Traumatic brain injury (TBI) represents an important problem of global health. The damage related to TBI is first due to the direct injury and then to a secondary phase in which neuroinflammation plays a key role. NLRP3 inflammasome is a component of the innate immune response and different diseases, such as neurodegenerative diseases, are characterized by NLRP3 activation. This review aims to describe NLRP3 inflammasome and the consequences related to its activation following TBI. NLRP3, caspase-1, IL-1β, and IL-18 are significantly upregulated after TBI, therefore, the use of nonspecific, but mostly specific NLRP3 inhibitors is useful to ameliorate the damage post-TBI characterized by neuroinflammation. Moreover, NLRP3 and the molecules associated with its activation may be considered as biomarkers and predictive factors for other neurodegenerative diseases consequent to TBI. Complications such as continuous stimuli or viral infections, such as the SARS-CoV-2 infection, may worsen the prognosis of TBI, altering the immune response and increasing the neuroinflammatory processes related to NLRP3, whose activation occurs both in TBI and in SARS-CoV-2 infection. This review points out the role of NLRP3 in TBI and highlights the hypothesis that NLRP3 may be considered as a potential therapeutic target for the management of neuroinflammation in TBI.

Ca2+ -dependent release of ATP from astrocytes affects herpes simplex virus type 1 infection of neurons

Astrocytes provide metabolic support for neurons and modulate their functions by releasing a plethora of neuroactive molecules diffusing to neighboring cells. Here we report that astrocytes also play a role in cortical neurons' vulnerability to Herpes simplex virus type-1 (HSV-1) infection through the release of extracellular ATP. We found that the interaction of HSV-1 with heparan sulfate proteoglycans expressed on the plasma membrane of astrocytes triggered phospholipase C-mediated IP₃ -dependent intracellular Ca²⁺ transients causing extracellular release of ATP. ATP binds membrane purinergic P2 receptors (P2Rs) of both neurons and astrocytes causing an increase in intracellular Ca²⁺ concentration that activates the Glycogen Synthase Kinase (GSK)-3β, whose action is necessary for HSV-1 entry/replication in these cells. Indeed, in co-cultures of neurons and astrocytes HSV-1-infected neurons were only found in proximity of infected astrocytes releasing ATP, whereas in the presence of fluorocitrate, an inhibitor of astrocyte metabolism, switching-off the HSV-1-induced ATP release, very few neurons were infected. The addition of exogenous ATP, mimicking that released by astrocytes after HSV-1 challenge, restored the ability of HSV-1 to infect neurons co-cultured with metabolically-inhibited astrocytes. The ATP-activated, P2R-mediated, and GSK-3-dependent molecular pathway underlying HSV-1 infection is likely shared by neurons and astrocytes, given that the blockade of either P2Rs or GSK-3 activation inhibited infection of both cell types. These results add a new layer of information to our understanding of the critical role played by astrocytes in regulating neuronal functions and their response to noxious stimuli including microbial agents via Ca²⁺ -dependent release of neuroactive molecules.

Proteomic analysis identifies plasma correlates of remote ischemic conditioning in the context of experimental traumatic brain injury

Remote ischemic conditioning (RIC), transient restriction and recirculation of blood flow to a limb after traumatic brain injury (TBI), can modify levels of pathology-associated circulating protein. This study sought to identify TBI-induced molecular alterations in plasma and whether RIC would modulate protein and metabolite levels at 24 h after diffuse TBI. Adult male C57BL/6 mice received diffuse TBI by midline fluid percussion or were sham-injured. Mice were assigned to treatment groups 1 h after recovery of righting reflex: sham, TBI, sham RIC, TBI RIC. Nine plasma metabolites were significantly lower post-TBI (six amino acids, two acylcarnitines, one carnosine). RIC intervention returned metabolites to sham levels. Using proteomics analysis, twenty-four putative protein markers for TBI and RIC were identified. After application of Benjamini–Hochberg correction, actin, alpha 1, skeletal muscle (ACTA1) was found to be significantly increased in TBI compared to both sham groups and TBI RIC. Thus, identified metabolites and proteins provide potential biomarkers for TBI and therapeutic RIC in order to monitor disease progression and therapeutic efficacy.

Going the Extra (Synaptic) Mile: Excitotoxicity as the Road Toward Neurodegenerative Diseases

Excitotoxicity is a phenomenon that describes the toxic actions of excitatory neurotransmitters, primarily glutamate, where the exacerbated or prolonged activation of glutamate receptors starts a cascade of neurotoxicity that ultimately leads to the loss of neuronal function and cell death. In this process, the shift between normal physiological function and excitotoxicity is largely controlled by astrocytes since they can control the levels of glutamate on the synaptic cleft. This control is achieved through glutamate clearance from the synaptic cleft and its underlying recycling through the glutamate-glutamine cycle. The molecular mechanism that triggers excitotoxicity involves alterations in glutamate and calcium metabolism, dysfunction of glutamate transporters, and malfunction of glutamate receptors, particularly N-methyl-D-aspartic acid receptors (NMDAR). On the other hand, excitotoxicity can be regarded as a consequence of other cellular phenomena, such as mitochondrial dysfunction, physical neuronal damage, and oxidative stress. Regardless, it is known that the excessive activation of NMDAR results in the sustained influx of calcium into neurons and leads to several deleterious consequences, including mitochondrial dysfunction, reactive oxygen species (ROS) overproduction, impairment of calcium buffering, the release of pro-apoptotic factors, among others, that inevitably contribute to neuronal loss. A large body of evidence implicates NMDAR-mediated excitotoxicity as a central mechanism in the pathogenesis of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and epilepsy. In this review article, we explore different causes and consequences of excitotoxicity, discuss the involvement of NMDAR-mediated excitotoxicity and its downstream effects on several neurodegenerative disorders, and identify possible strategies to study new aspects of these diseases that may lead to the discovery of new therapeutic approaches. With the understanding that excitotoxicity is a common denominator in neurodegenerative diseases and other disorders, a new perspective on therapy can be considered, where the targets are not specific symptoms, but the underlying cellular phenomena of the disease.

Dual roles of astrocytes in plasticity and reconstruction after traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of fatality and disability worldwide. Despite its high prevalence, effective treatment strategies for TBI are limited. Traumatic brain injury induces structural and functional alterations of astrocytes, the most abundant cell type in the brain. As a way of coping with the trauma, astrocytes respond in diverse mechanisms that result in reactive astrogliosis. Astrocytes are involved in the physiopathologic mechanisms of TBI in an extensive and sophisticated manner. Notably, astrocytes have dual roles in TBI, and some astrocyte-derived factors have double and opposite properties. Thus, the suppression or promotion of reactive astrogliosis does not have a substantial curative effect. In contrast, selective stimulation of the beneficial astrocyte-derived molecules and simultaneous attenuation of the deleterious factors based on the spatiotemporal-environment can provide a promising astrocyte-targeting therapeutic strategy. In the current review, we describe for the first time the specific dual roles of astrocytes in neuronal plasticity and reconstruction, including neurogenesis, synaptogenesis, angiogenesis, repair of the blood-brain barrier, and glial scar formation after TBI. We have also classified astrocyte-derived factors depending on their neuroprotective and neurotoxic roles to design more appropriate targeted therapies.

Inhibiting α5 Subunit-Containing γ-Aminobutyric Acid Type A Receptors Attenuates Cognitive Deficits After Traumatic Brain Injury

OBJECTIVES

Cognitive deficits after traumatic brain injury are a leading cause of disability worldwide, yet no effective pharmacologic treatments exist to improve cognition. Traumatic brain injury increases proinflammatory cytokines, which trigger excess function of α5 subunit-containing γ-aminobutyric acid type A receptors. In several models of brain injury, drugs that inhibit α5 subunit-containing γ-aminobutyric acid type A receptor function improve cognitive performance. Thus, we postulated that inhibiting α5 subunit-containing γ-aminobutyric acid type A receptors would improve cognitive performance after traumatic brain injury. In addition, because traumatic brain injury reduces long-term potentiation in the hippocampus, a cellular correlate of memory, we studied whether inhibition of α5 subunit-containing γ-aminobutyric acid type A receptors attenuated deficits in long-term potentiation after traumatic brain injury.

DESIGN

Experimental animal study.

SETTING

Research laboratory.

SUBJECTS

Adult male mice and hippocampal brain slices.

INTERVENTIONS

Anesthetized mice were subjected to traumatic brain injury with a closed-head, free-weight drop method. One week later, the mice were treated with L-655,708 (0.5 mg/kg), an inhibitor that is selective for α5 subunit-containing γ-aminobutyric acid type A receptors, 30 minutes before undergoing behavioral testing. Problem-solving abilities were assessed using the puzzle box assay, and memory performance was studied with novel object recognition and object place recognition assays. In addition, hippocampal slices were prepared 1 week after traumatic brain injury, and long-term potentiation was studied using field recordings in the cornu Ammonis 1 region of slices that were perfused with L-655,708 (100 nM).

MEASUREMENTS AND MAIN RESULTS

Traumatic brain injury increased the time required to solve difficult but not simple tasks in the puzzle box assay and impaired memory in the novel object recognition and object place recognition assays. L-655,708 improved both problem solving and memory in the traumatic brain injury mice. Traumatic brain injury reduced long-term potentiation in the hippocampal slices, and L-655,708 attenuated this reduction.

CONCLUSIONS

Pharmacologic inhibition of α5 subunit-containing γ-aminobutyric acid type A receptors attenuated cognitive deficits after traumatic brain injury and enhanced synaptic plasticity in hippocampal slices. Collectively, these results suggest that α5 subunit-containing γ-aminobutyric acid type A receptors are novel targets for pharmacologic treatment of traumatic brain injury-induced persistent cognitive deficits.

Antioxidant Therapies in Traumatic Brain Injury

Due to a multiplicity of causes provoking traumatic brain injury (TBI), TBI is a highly heterogeneous pathology, characterized by high mortality and disability rates. TBI is an acute neurodegenerative event, potentially and unpredictably evolving into sub-chronic and chronic neurodegenerative events, with transient or permanent neurologic, cognitive, and motor deficits, for which no valid standardized therapies are available. A vast body of literature demonstrates that TBI-induced oxidative/nitrosative stress is involved in the development of both acute and chronic neurodegenerative disorders. Cellular defenses against this phenomenon are largely dependent on low molecular weight antioxidants, most of which are consumed with diet or as nutraceutical supplements. A large number of studies have evaluated the efficacy of antioxidant administration to decrease TBI-associated damage in various animal TBI models and in a limited number of clinical trials. Points of weakness of preclinical studies are represented by the large variability in the TBI model adopted, in the antioxidant tested, in the timing, dosages, and routes of administration used, and in the variety of molecular and/or neurocognitive parameters evaluated. The analysis of the very few clinical studies does not allow strong conclusions to be drawn on the real effectiveness of antioxidant administration to TBI patients. Standardizing TBI models and different experimental conditions, as well as testing the efficacy of administration of a cocktail of antioxidants rather than only one, should be mandatory. According to some promising clinical results, it appears that sports-related concussion is probably the best type of TBI to test the benefits of antioxidant administration.

VISSA-PLS-DA-Based Metabolomics Reveals a Multitargeted Mechanism of Traditional Chinese Medicine for Traumatic Brain Injury

Metabolomics is an emerging tool to uncover the complex pathogenesis of disease, as well as the multitargets of traditional Chinese medicines, with chemometric analysis being a key step. However, conventional algorithms are not suitable for directly analyzing data at all times. The variable iterative space shrinkage approach-partial least squares-discriminant analysis, a novel algorithm for data mining, was first explored to screen metabolic varieties to reveal the multitargets of Xuefu Zhuyu decoction (XFZY) against traumatic brain injury (TBI) by the 7th day. Rat plasma from Sham, Vehicle, and XFZY groups was used for gas chromatography/mass spectrometry-based metabolomics. This method showed an improved discrimination ability (area under the curve = 93.64%). Threonine, trans-4-hydroxyproline, and creatinine were identified as the direct metabolic targets of XFZY against TBI. Five metabolic pathways affected by XFZY in TBI rats, were enriched using Metabolic Pathway Analysis web tool (i.e., phenylalanine, tyrosine, and tryptophan biosynthesis; phenylalanine metabolism; galactose metabolism; alanine, aspartate, and glutamate metabolism; and tryptophan metabolism). In conclusion, metabolomics coupled with variable iterative space shrinkage approach-partial least squares-discriminant analysis model may be a valuable tool for identifying the holistic molecular mechanisms involved in the effects of traditional Chinese medicine, such as XFZY.

Using Serum Amino Acids to Predict Traumatic Brain Injury: A Systematic Approach to Utilize Multiple Biomarkers

Traumatic brain injury (TBI) can cause biochemical and metabolomic alterations in the brain tissue and serum. These alterations can be used for diagnosis and prognosis of TBI. Here, the serum concentrations of seventeen amino acids (AA) were studied for their potential utility as biomarkers of TBI. Twenty-five female, 4-week-old piglets received diffuse (n = 13) or focal (n = 12) TBI. Blood samples were obtained both pre-injury and at either 24-h or 4-days post-TBI. To find a robust panel of biomarkers, the results of focal and diffuse TBIs were combined and multivariate logistic regression analysis, coupled with the best subset selection technique and repeated k-fold cross-validation method, was used to perform a thorough search of all possible subsets of AAs. The combination of serum glycine, taurine, and ornithine was optimal for TBI diagnosis, with 80% sensitivity and 86% overall prediction rate, and showed excellent TBI diagnostic performance, with 100% sensitivity and 78% overall prediction rate, on a separate validation dataset including four uninjured and five injured animals. We found that combinations of biomarkers outperformed any single biomarker. We propose this 3-AA serum biomarker panel to diagnose mild-to-moderate focal/diffuse TBI. The systematic approaches implemented herein can be used for combining parameters from various TBI assessments to develop/evaluate optimal multi-factorial diagnostic/prognostic TBI metrics.

Aconitase 2 inhibits the proliferation of MCF-7 cells promoting mitochondrial oxidative metabolism and ROS/FoxO1-mediated autophagic response

Background

Deregulation of the tricarboxylic acid cycle (TCA) due to mutations in specific enzymes or defective aerobic metabolism is associated with tumour growth. Aconitase 2 (ACO2) participates in the TCA cycle by converting citrate to isocitrate, but no evident demonstrations of its involvement in cancer metabolism have been provided so far.

Methods

Biochemical assays coupled with molecular biology, in silico, and cellular tools were applied to circumstantiate the impact of ACO2 in the breast cancer cell line MCF-7 metabolism. Fluorescence lifetime imaging microscopy (FLIM) of NADH was used to corroborate the changes in bioenergetics.

Results

We showed that ACO2 levels are decreased in breast cancer cell lines and human tumour biopsies. We generated ACO2- overexpressing MCF-7 cells and employed comparative analyses to identify metabolic adaptations. We found that increased ACO2 expression impairs cell proliferation and commits cells to redirect pyruvate to mitochondria, which weakens Warburg-like bioenergetic features. We also demonstrated that the enhancement of oxidative metabolism was supported by mitochondrial biogenesis and FoxO1-mediated autophagy/mitophagy that sustains the increased ROS burst.

Conclusions

This work identifies ACO2 as a relevant gene in cancer metabolic rewiring of MCF-7 cells, promoting a different utilisation of pyruvate and revealing the potential metabolic vulnerability of ACO2-associated malignancies.

UPLC-ESI-IT-TOF-MS metabolomic study of the therapeutic effect of Xuefu Zhuyu decoction on rats with traumatic brain injury

It has been widely reported that Xuefu Zhuyu decoction (XFZYD), a traditional Chinese medicine, is effective in the treatment of traumatic brain injury (TBI). However, the mechanism of the therapeutic process is still not fully understood. Metabolomic technique can be used to explore the mechanisms underlying the treatment of TBI with XFZYD. The purpose of this work was to investigate the metabolic characteristics of blood samples from rats with and without XFZYD treatment and the dynamic changes in metabolite profiles on days 1, 3, 7, 14 and 21 after injury (within the severe phase of TBI) based on untargeted UPLC-ESI-IT-TOF-MS analysis. Pattern recognition, clustering analysis and metabolic pathway analysis were used to analyse the metabolomic data of three groups (a sham-operated group, a TBI model, and an XFZYD-treated TBI model). The results showed that XFZYD reversed the abnormalities in the levels of small-molecule metabolites (such as L-acetylcarnitine, L-tryptophan, indoleacrylic acid, γ-aminobutyric acid, hypotaurine, LysoPC(18:1)(11Z), creatine, L-phenylalanine and L-leucine) in TBI rats through six metabolic pathways (including phenylalanine, tyrosine and tryptophan biosynthesis; phenylalanine metabolism; valine, leucine and isoleucine biosynthesis; taurine and hypotaurine metabolism; tryptophan metabolism; and alanine, aspartate and glutamate metabolism) involved in the therapy process. XFZYD regulated the metabolic disorders of endogenous markers by the possible mechanisms of neuroprotection, energy metabolism, inflammatory response and oxidative stress. This study revealed the holistic and dynamic metabolic changes caused by XFZYD in rats with TBI and provided important research methods and approaches for exploring the multiple metabolites and metabolic pathways involved in the therapeutic effect of XFZYD on TBI.

Pyruvate Dehydrogenase and Tricarboxylic Acid Cycle Enzymes Are Sensitive Targets of Traumatic Brain Injury Induced Metabolic Derangement

Using a closed-head impact acceleration model of mild or severe traumatic brain injury (mTBI or sTBI, respectively) in rats, we evaluated the effects of graded head impacts on the gene and protein expressions of pyruvate dehydrogenase (PDH), as well as major enzymes of mitochondrial tricarboxylic acid cycle (TCA). TBI was induced in anaesthetized rats by dropping 450 g from 1 (mTBI) or 2 m height (sTBI). After 6 h, 12 h, 24 h, 48 h, and 120 h gene expressions of enzymes and subunits of PDH. PDH kinases and phosphatases (PDK1-4 and PDP1-2, respectively), citrate synthase (CS), isocitrate dehydrogenase (IDH), oxoglutarate dehydrogenase (OGDH), succinate dehydrogenase (SDH), succinyl-CoA synthase (SUCLG), and malate dehydrogenase (MDH) were determined in whole brain extracts (n = 6 rats at each time for both TBI levels). In the same samples, the high performance liquid chromatographic (HPLC) determination of acetyl-coenzyme A (acetyl-CoA) and free coenzyme A (CoA-SH) was performed. Sham-operated animals (n = 6) were used as controls. After mTBI, the results indicated a general transient decrease, followed by significant increases, in PDH and TCA gene expressions. Conversely, permanent PDH and TCA downregulation occurred following sTBI. The inhibitory conditions of PDH (caused by PDP1-2 downregulations and PDK1-4 overexpression) and SDH appeared to operate only after sTBI. This produced almost no change in acetyl-CoA and free CoA-SH following mTBI and a remarkable depletion of both compounds after sTBI. These results again demonstrated temporary or steady mitochondrial malfunctioning, causing minimal or profound modifications to energy-related metabolites, following mTBI or sTBI, respectively. Additionally, PDH and SDH appeared to be highly sensitive to traumatic insults and are deeply involved in mitochondrial-related energy metabolism imbalance.

GABAergic imbalance is normalized by dopamine D1 receptor activation in the striatum contralateral to the cortical injury in motor deficit-recovered rats

RATIONALE

The sensorimotor cortex and the striatum are interconnected by the corticostriatal pathway, suggesting that cortical injury alters the striatal function, which may be modulated by dopamine.

OBJECTIVES

We studied whether the activation of dopamine D₁ receptors (D₁Rs) modulates the γ-aminobutyric acid (GABA) and glutamate levels in the striatum of recovered rats at 192 h after cortical injury.

METHODS

The D₁R agonist SKF-38393 (0, 2, 3, or 4 mg/kg) was administered at 24, 48, 96, and 192 h post-injury, and then rats were decapitated to determine GABA and glutamate levels and the levels of D₁R mRNA on both sides of the striatum.

RESULTS

GABAergic imbalance in the striatum contralateral to the injury site was normalized by the administration of the D₁R agonist, but this treatment did not produce a significant effect on glutamate levels, suggesting that glutamate was metabolized into GABA. The administration of SKF-38393 (2 mg/kg) decreased the levels of D₁R mRNA in the striatum contralateral to the injury, and this effect was blocked by the coadministration of the D₁R antagonist SCH-23390 (2 mg/kg). In the striatum ipsilateral to the injury, the D₁R agonist increased the D₁R mRNA levels, an effect that was blocked by SCH-23390.

CONCLUSION

The reversal of the GABAergic imbalance in the striatum contralateral to the cortical injury can be modulated by extrastriatal D₁R activation, and the D₁R agonist-induced increases in the D₁R mRNA levels in the striatum ipsilateral to the injury suggest that the striatum may be necessary to achieve functional recovery.

Longitudinal Changes in Magnetic Resonance Spectroscopy in Pediatric Concussion: A Pilot Study

Background: Nearly 20% of US adolescents report at least one lifetime concussion. Pathophysiologic models suggest that traumatic biomechanical forces caused by rotational deceleration lead to shear stress, which triggers a neurometabolic cascade beginning with excitotoxicity and leading to significant energy demands and a period of metabolic crisis for the injured brain. Proton magnetic resonance spectroscopy (¹H MRS) offers a means for non-invasive measurement of neurometabolic changes after concussion.

Objective: Describe longitudinal changes in metabolites measured in vivo in the brains of adolescent patients with concussion.

Methods: We prospectively recruited 9 patients ages 11 to 20 who presented to a pediatric Emergency Department within 24 h of concussion. Patients underwent MRI scanning within 72 h (acute, n = 8), 2 weeks (subacute, n = 7), and at approximately 1 year (chronic, n = 7). Healthy, age and sex-matched controls were recruited and scanned once (n = 9). ¹H MRS was used to measure N-acetyl-aspartate, choline, creatine, glutamate + glutamine, and myo-inositol concentrations in six regions of interest: left and right frontal white matter, posterior white matter and thalamus.

Results: There was a significant increase in total thalamus glutamate+glutamine/choline at the subacute (p = 0.010) and chronic (p = 0.010) time points, and a significant decrease in total white matter myo-inositol/choline (p = 0.030) at the chronic time point as compared to controls.

Conclusion: There are no differences in ¹H MRS measurements in the acute concussive period; however, changes in glutamate+glutamine and myo-inositol concentrations detectable by ¹H MRS may develop beyond the acute period.

Neuroimaging and Neuropsychological Studies in Sports-Related Concussions in Adolescents: Current State and Future Directions

Sports-related concussion, is a serious neurological concern that many adolescent athletes will face during their athletic careers. In some instances, the effects of sports-related head injury are long-lasting. Due to their still-developing brains, adolescents appear to be more vulnerable to long-term repercussions of these injuries. As all sports-related concussions are mild traumatic brain injuries (mTBI), this review we will examine the pathophysiology of mTBI, its acute effects and long-term risks from sustaining injury, and current and needed advancements in the areas of neuropsychological testing, accelerometer telemetry, and neuroimaging. Current methods do not adequately measure the extent of an injury that an athlete may sustain, potentially putting these athletes at a much greater risk for long-term effects. To better understand mTBI, neuropsychological testing best practices need to be developed, standardized, and implemented based on sound scientific evidence in order to be propagated as clinical guidelines. Wearable accelerometers can be used to assess thresholds for mTBI and cumulative effects of concussive and subconcussive injuries. Novel neuroimaging methods that can detect anatomical abnormalities and functional deficits with more specificity and sensitivity should be developed. Young athletes are particularly a vulnerable population warranting immediate and significant research aimed at protecting them against sports related injury and mitigating their long-term deficits.