Functional, Structural, and Neurotoxicity Biomarkers in Integrative Assessment of Concussions.

Concussion is a complex, heterogeneous process affecting the brain. Accurate assessment and diagnosis and appropriate management of concussion are essential to ensure that athletes do not prematurely return to play or others to work or active military duty, risking re-injury. To date, clinical diagnosis relies primarily on evaluating subjects for functional impairment using instruments that include neurocognitive testing, subjective symptom report, and neurobehavioral assessments, such as balance and vestibular-ocular reflex testing. Structural biomarkers, defined as advanced neuroimaging techniques and biomarkers assessing neurotoxicity and immunoexcitotoxicity, may complement the use of functional biomarkers. We hypothesize that neurotoxicity AMPA, NMDA, and kainite receptor biomarkers might be utilized as a part of comprehensive approach to concussion evaluations, with the goal of increasing diagnostic accuracy and facilitating treatment planning and prognostic assessment.

AMPAR peptide values in blood of nonathletes and club sport athletes with concussions.

OBJECTIVES: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) peptide, a product of the proteolytic degradation of AMPA receptors in healthy nonathletes and athletes with concussions, is assessed. The detection of AMPAR peptide in conjunction with neuropsychological testing and neuroimaging is undertaken. SUBJECTS: Persons (n = 124, 19-23 years) are enrolled in the pilot-blinded study according to approved Institutional Review Board protocols at Kennesaw State University and DeKalb Medical. METHODS: AMPAR peptide plasma assay was performed using magnetic particles-enzyme-linked immunosorbent assay. All participants had neurocognitive tests (ImPACT); selected subjects with concussions were followed-up with magnetic resonance imaging and neurologic consultations. RESULTS: Athletes (n = 33) with clinically defined single or multiple concussions were compared to 91 age and gender matched controls without a history of concussion. AMPAR peptide values of 0.05-0.40 ng/mL for controls and 1.0-8.5 ng/mL for concussions are found. The biomarker sensitivity of 91% and a specificity of 92% (0.4 ng/mL cut off) to assess concussions are calculated. Poorer ImPACT scores correlated with abnormal levels of the biomarker. In athletes with multiple concussions, increased AMPAR peptide values (2.0-12.0 ng/mL) were associated with minor findings on magnetic resonance imaging. CONCLUSION: AMPAR peptide assay combined with ImPACT and neuroimaging is a promising tool for assessment of concussions. Additional clinical validation studies are required.

Correction: Diagnostic Potential of the NMDA Receptor Peptide Assay for Acute Ischemic Stroke.

[This corrects the article DOI: 10.1371/journal.pone.0042362.].

Diagnostic potential of the NMDA receptor peptide assay for acute ischemic stroke.

BACKGROUND: The acute assessment of patients with suspected ischemic stroke remains challenging. The use of brain biomarker assays may improve the early diagnosis of ischemic stroke. The main goal of the study was to evaluate whether the NR2 peptide, a product of the proteolytic degradation of N-methyl-D-aspartate (NMDA) receptors, can differentiate acute ischemic stroke (IS) from stroke mimics and persons with vascular risk factors/healthy controls. A possible correlation between biomarker values and lesion sizes was investigated as the secondary objective. METHODS AND FINDINGS: A total of 192 patients with suspected stroke who presented within 72 h of symptom onset were prospectively enrolled. The final diagnosis was determined based on clinical observations and radiological findings. Additionally gender- and age-matched healthy controls (n = 52) and persons with controlled vascular risk factors (n = 48) were recruited to compare NR2 peptide levels. Blinded plasma was assayed by rapid magnetic particles (MP) ELISA for NR2 peptide within 30 min and results for different groups compared using univariate and multivariate statistical analyses. There was a clinical diagnosis of IS in 101 of 192 (53%) and non-stroke in 91 (47%) subjects. The non-stroke group included presented with acute stroke symptoms who had no stroke (n = 71) and stroke mimics (n = 20). The highest NR2 peptide elevations where found in patients with IS that peaked at 12 h following symptom onset. When the biomarker cut off was set at 1.0 ug/L, this resulted in a sensitivity of 92% and a specificity of 96% to detect IS. A moderate correlation (r(s) = 0.73) between NR2 peptide values and acute ischemic cortical lesions (<200 mL) was found. CONCLUSIONS: This study suggests that the NR2 peptide may be a brain specific biomarker to diagnose acute IS and may allow the differentiation of IS from stroke mimics and controls. Additional larger scale clinical validation studies are required.

NR2 antibodies: risk assessment of transient ischemic attack (TIA)/stroke in patients with history of isolated and multiple cerebrovascular events.

BACKGROUND AND PURPOSE: Predicting stroke using biomarkers would enable clinicians to help prevent stroke or mitigate damage. Several stroke biomarkers have been investigated but none has shown near term predictive value. METHODS: We studied patients presenting with a history of stroke or transient ischemic attack (TIA) to determine whether serum levels of autoantibodies to the NMDA receptor NR2 peptide (NR2Ab) reflected the presence of recent stroke compared with controls. Antibody levels were also correlated with clinical risk factors for stroke, including diabetes, hypertension, hyperlipidemia, and history of recent TIA or stroke. RESULTS: Of the 245 patients that presented with acute stroke or TIA, 130 consented to participate and results are available for the 120. Volunteers from the community were recruited as controls. Males and females with multiple recent strokes and females with acute strokes had elevated NR2Ab levels compared to non-stroke patients or controls. Using a multiple regression model, the predictive value for NR2Ab was compared to clinical risk factors. In men, the presence of stroke correlated with hypertension (p<0.001) and NR2Ab levels (p<0.01) and in women the presence of stroke correlated with hypertension (p<0.001), diabetes (p<0.05), atrial fibrillation (p<0.05) and NR2Ab (p<0.01). CONCLUSION: These results suggest that NR2Ab levels reflect a history of multiple strokes and may serve as a predictive factor for stroke.

NMDA receptor antibodies predict adverse neurological outcome after cardiac surgery in high-risk patients.

BACKGROUND AND PURPOSE: The goal of this study was to compare the predictive ability of S100B, N-methyl-D-aspartate (NMDA) receptor antibodies (NR2Ab) and C-reactive protein (CRP) for neurological deficits after cardiac surgery with cardiopulmonary bypass (CPB). METHODS: We investigated 557 high-risk adult patients who underwent coronary artery or valve replacement surgery using CPB as a substudy of a prospective, blinded, multicenter clinical trial. Serum concentrations of S100B (n=513 patients), NR2Ab (n=398) and CRP (n=510) were measured preoperatively, 24 and 48 hours after CPB. Neurological adverse events were assessed at baseline and postoperative days 1 and 2; neurocognitive function (mini-mental status examination) was assessed at baseline and on postoperative days 1, 7 and 28. RESULTS: Fifty-five (9.9%) patients had moderate or severe neurological adverse events (confusion/delirium, transient ischemic attack, or stroke) within 48 hours of CPB. Women had significantly more neurological complications than men (15.5% versus 7.8%; P=0.007). Ninety-six percent (24/25) of patients with NR2Ab concentrations > or =2.0 ng/mL preoperatively had neurological complications within 48 hours post-CPB, versus only 5.4% (20/373) of patients with NR2Ab concentrations <2.0 ng/mL, resulting in a 17.9-fold increase (95% CI, 11.6 to 27.6) in postoperative neurological complications for patients with high levels of NR2A antibodies. Preoperative serum S100B and CRP did not predict neurological complications from CPB. Decreased mini-mental status examination scores for orientation, attention and recall were associated with neurological adverse events early after CPB. CONCLUSIONS: Preoperative serum concentrations of NR2Ab, but not S100B or CRP, are predictive of severe neurological adverse events after CPB. Patients with a positive NR2Ab test (> or =2.0 ng/mL) preoperatively were nearly 18 times more likely to experience a postoperative neurological event than patients with a negative test (<2.0 ng/mL).

Blood test detecting autoantibodies to N-methyl-D-aspartate neuroreceptors for evaluation of patients with transient ischemic attack and stroke.

BACKGROUND: Stroke is a multisystemic disorder that includes mechanisms of thrombosis and neurotoxic coupling. Key metabolites of the molecular cascade following biochemical events appear simultaneously in brain tissue, the blood-brain barrier, and brain vessels, activating the immune system and generating autoantibodies (aAbs) to brain-specific antigens. We developed an ELISA blood test to measure aAbs to a subtype of N-methyl-D-aspartate (NMDA) receptors, which are the key markers of neurotoxicity underlying cerebral ischemia. We investigated the diagnostic accuracy of serum aAbs to NR2A/2B, a subtype of NMDA receptors, in assessing transient ischemic attack (TIA) and ischemic stroke (IS) and its ability to distinguish cerebral ischemia from intracerebral hemorrhage (ICH). METHODS: Autoantibodies to NR2A/2B were measured in 360 serum samples: 105 from TIA/stroke patients and 255 from controls, including patients with controlled hypertension/atherosclerosis and gender- and age-matched healthy individuals. RESULTS: Patients with TIA (n = 56) and acute IS (n = 31) had significantly higher NR2A/2B aAb concentrations than controls (P <0.0001). The test sensitivities for TIA and IS were 95% and 97%, respectively, and predictive values were 86% and 91% at a cutoff point of 2.0 micro g/L. The area under the ROC curve was 0.99. Monitoring NR2A/2B aAbs within 72 h differentiated IS and ICH (P <0.001) and was confirmed by magnetic resonance imaging and computed tomography. CONCLUSIONS: NR2A/2B aAbs are independent and sensitive serologic markers capable of detecting TIA with a high posttest probability and, in conjunction with neurologic observation and neuroimaging, ruling out ICH. The test may help assess risk of TIA in routine general practice and may potentially be useful in assisting diagnosis of acute IS in the emergency setting.

Recombinant mu-delta receptor as a marker of opiate abuse.

The brain is particularly vulnerable to drugs of abuse changing the neuroreceptor functions. Opiates interact and overstimulate heterogeneous opioid receptors leading to their desensitization, internalization, and activation of recombinant opioid receptor. The molecular properties of rat and human brain recombinant mu-delta receptor were compared with those of purified mu- and delta-receptors. cDNA coding the unique fragment of recombinant mu-delta receptor was isolated and sequenced. We hypothesized that recombinant mu-delta receptor may be a hallmark of opiate abuse. Peptide fragments of the mu- (MOR), delta- (DOR), and recombinant mu-delta- (MDOR) receptors were used as antigens to assess the presence of autoantibodies in the blood of rats that self-administered heroin and cocaine, as well as drug abusers. Significant steady elevation of MDOR autoantibodies were measured in sera of rats that self-administered heroin compared to that for cocaine and vehicle animals. The appearance and increased level of MDOR autoantibodies in opiate abusers correlated with severity of the disorder and duration of drug exposure.