Taura L. Barr

Blood–Brain Barrier Disruption in Humans Is Independently Associated With Increased Matrix Metalloproteinase-9

Background and Purpose— Matrix metalloproteinases (MMP) may play a role in blood–brain barrier (BBB) disruption after ischemic stroke. We hypothesized that plasma concentrations of MMP-9 are associated with a marker of BBB disruption in patients evaluated for acute stroke. Methods— Patients underwent MRI on presentation and ≈24 hours later. The MRI marker, termed hyperintense acute reperfusion injury marker (HARM), is gadolinium enhancement of cerebrospinal fluid on fluid-attenuated inversion recovery MRI. Plasma MMP-9 and tissue inhibitor of matrix metalloproteinase-1 were measured by enzyme-linked immunosorbent assay. Logistic regression models tested for predictors of HARM on 24-hour follow-up scans separately for MMP-9 and the ratio of MMP-9 to TIMP-1. Results— For the 41 patients enrolled, diagnoses were: acute ischemic cerebrovascular syndrome, 33 (80.6%); intracerebral hemorrhage, 6 (14.6%); stroke mimic, 1 (2.4%); and no stroke, 1 (2.4%). HARM was present in 17 (41.5%) patients. In model 1, HARM was associated with baseline plasma MMP-9 concentration (odds ratio [OR], 1.01; 95% confidence interval [CI], 1.001–1.019; P=0.033). In model 2, HARM was associated with the ratio of MMP-9 to tissue inhibitor of matrix metalloproteinase-1 (OR, 4.94; 95% CI, 1.27–19.14; P=0.021). Conclusions— Baseline MMP-9 was a significant predictor of HARM at 24-hour follow-up, supporting the hypothesis that MMP-9 is associated with BBB disruption. If the association between MMP-9 and BBB disruption is confirmed in future studies, HARM may be a useful imaging marker to evaluate MMP-9 inhibition in ischemic stroke and other populations with BBB disruption.

Genomic biomarkers and cellular pathways of ischemic stroke by RNA gene expression profiling

Objective: The objective of this study was to provide insight into the molecular mechanisms of acute ischemic cerebrovascular syndrome (AICS) through gene expression profiling and pathway analysis. Methods: Peripheral whole blood samples were collected from 39 MRI-diagnosed patients with AICS and 25 nonstroke control subjects ≥18 years of age. Total RNA was extracted from whole blood stabilized in Paxgene RNA tubes, amplified, and hybridized to Illumina HumanRef-8v2 bead chips. Gene expression was compared in a univariate manner between stroke patients and control subjects using t test in GeneSpring. The significant genes were tested in a logistic regression model controlling for age, hypertension, and dyslipidemia. Inflation of type 1 error was corrected by Bonferroni and Ingenuity Systems Pathway analysis was performed. Validation was performed by QRT-PCR using Taqman gene expression assays. Results: A 9-gene profile was identified in the whole blood of ischemic stroke patients using gene expression profiling. Five of these 9 genes were identified in a previously published expression profiling study of stroke and are therefore likely biomarkers of stroke. Pathway analysis revealed toll-like receptor signaling as a highly significant canonical pathway present in the peripheral whole blood of patients with AICS. Conclusions: Our study highlights the relevance of the innate immune system through toll-like receptor signaling as a mediator of response to ischemic stroke and supports the claim that gene expression profiling can be used to identify biomarkers of ischemic stroke. Further studies are needed to validate and refine these biomarkers for their diagnostic potential.

Sleep Disorders in US Military Personnel: A High Rate of Comorbid Insomnia and Obstructive Sleep Apnea

BACKGROUND Sleep disturbances are among the most common symptoms of military personnel who return from deployment. The objective of our study was to determine the presence of sleep disorders in US military personnel referred for evaluation of sleep disturbances after deployment and examine associations between sleep disorders and service-related diagnoses of depression, mild traumatic brain injury, pain, and posttraumatic stress disorder (PTSD). METHODS This was a cross-sectional study of military personnel with sleep disturbances who returned from combat within 18 months of deployment. Sleep disorders were assessed by clinical evaluation and polysomnogram with validated instruments to diagnose service-related illnesses. RESULTS Of 110 military personnel included in our analysis, 97.3% were men (mean age, 33.6 ± 8.0 years; mean BMI, 30.0 ± 4.3 kg/m2), and 70.9% returned from combat within 12 months. Nearly one-half (47.3%) met diagnostic criteria for two or more service-related diagnoses. Sleep disorders were diagnosed in 88.2% of subjects; 11.8% had a normal sleep evaluation and served as control subjects. Overall, 62.7% met diagnostic criteria for obstructive sleep apnea (OSA) and 63.6% for insomnia. The exclusive diagnoses of insomnia and OSA were present in 25.5% and 24.5% of subjects, respectively; 38.2% had comorbid insomnia and OSA. Military personnel with comorbid insomnia and OSA were significantly more likely to meet criteria for depression (P < .01) and PTSD (P < .01) compared with control subjects and those with OSA only. CONCLUSIONS Comorbid insomnia and OSA is a frequent diagnosis in military personnel referred for evaluation of sleep disturbances after deployment. This diagnosis, which is difficult to treat, may explain the refractory nature of many service-related diagnoses.

Traumatic Brain Injury in Intimate Partner Violence: A Critical Review of Outcomes and Mechanisms

The prevalence of intimate partner violence (IPV) is striking, as are its consequences to the lives of women. The IPV often includes physical assault, which can include injuries to the head and attempted strangulation injuries. Both types of injuries can result in traumatic brain injury (TBI). The TBI sustained during IPV often occurs over time, which can increase the risk for health declines and postconcussive syndrome (PCS). Current studies have identified sequelae of cognitive dysfunction, posttraumatic stress disorder, and depression in women experiencing IPV, yet, most fail to determine the role of TBI in the onset and propagation of these disorders. Although imaging studies indicate functional differences in neuronal activation in IPV, they also have not considered the possibility of TBI contributing to these outcomes. This review highlights the significant gaps in current findings related to neuropsychological complications and medical and psychosocial symptoms that likely result in greater morbidity, as well as the societal costs of failing to acknowledge the association of IPV and TBI in women.

Targeting the neurovascular unit for treatment of neurological disorders

Drug discovery for CNS disorders has been restricted by the inability for therapeutic agents to cross the blood-brain barrier (BBB). Moreover, current drugs aim to correct neuron cell signaling, thereby neglecting pathophysiological changes affecting other cell types of the neurovascular unit (NVU). Components of the NVU (pericytes, microglia, astrocytes, and neurons, and basal lamina) act as an intricate network to maintain the neuronal homeostatic microenvironment. Consequently, disruptions to this intricate cell network lead to neuron malfunction and symptoms characteristic of CNS diseases. A lack of understanding in NVU signaling cascades may explain why current treatments for CNS diseases are not curative. Current therapies treat symptoms by maintaining neuron function. Refocusing drug discovery to sustain NVU function may provide a better method of treatment by promoting neuron survival. In this review, we will examine current therapeutics for common CNS diseases, describe the importance of the NVU in cerebral homeostasis and discuss new possible drug targets and technologies that aim to improve treatment and drug delivery to the diseased brain.

Cytokines: their role in stroke and potential use as biomarkers and therapeutic targets.

Inflammatory mechanisms both in the periphery and in the CNS are important in the pathophysiologic processes occurring after the onset of ischemic stroke (IS). Cytokines are key players in the inflammatory mechanism and contribute to the progression of ischemic damage. This literature review focuses on the effects of inflammation on ischemic stroke, and the role pro-inflammatory and anti-inflammatory cytokines play on deleterious or beneficial stroke outcome. The discovery of biomarkers and novel therapeutics for stroke has been the focus of extensive research recently; thus, understanding the roles of pro-inflammatory and anti-inflammatory cytokines that are up-regulated during stroke will help us further understand how inflammation contributes to the progression of ischemic damage and provide potential targets for novel therapeutics and biomarkers for diagnosis and prognosis of stroke.

Rapid mitochondrial dysfunction mediates TNF-alpha-induced neurotoxicity

Tumor necrosis factor alpha (TNF‐α) is known to exacerbate ischemic brain injury; however, the mechanism is unknown. Previous studies have evaluated the effects of TNF‐α on neurons with long exposures to high doses of TNF‐α, which is not pathophysiologically relevant. We characterized the rapid effects of TNF‐α on basal respiration, ATP production, and maximal respiration using pathophysiologically relevant, post‐stroke concentrations of TNF‐α. We observed a reduction in mitochondrial function as early as 1.5 h after exposure to low doses of TNF‐α, followed by a decrease in cell viability in HT‐22 cells and primary neurons. Subsequently, we used the HT‐22 cell line to determine the mechanism by which TNF‐α causes a rapid and profound reduction in mitochondrial function. Pre‐treating with TNF‐R1 antibody, but not TNF‐R2 antibody, ameliorated the neurotoxic effects of TNF‐α, indicating that TNF‐α exerts its neurotoxic effects through TNF‐R1. We observed an increase in caspase 8 activity and a decrease in mitochondrial membrane potential after exposure to TNF‐α which resulted in a release of cytochrome c from the mitochondria into the cytosol. These novel findings indicate for the first time that an acute exposure to pathophysiologically relevant concentrations of TNF‐α has neurotoxic effects mediated by a rapid impairment of mitochondrial function.

Admission neutrophil–lymphocyte ratio predicts 90 day outcome after endovascular stroke therapy

Objective Immune dysregulation influences outcome following acute ischemic stroke (AIS). Admission white blood cell (WBC) counts are routinely obtained, making the neutrophil–lymphocyte ratio (NLR) a readily available biomarker of the immune response to stroke. This study sought to identify the relationship between NLR and 90 day AIS outcome. Methods A retrospective analysis was performed on patients who underwent endovascular therapy for AIS at West Virginia University Hospitals, Morgantown, West Virginia. Admission WBC differentials were analyzed as the NLR. Stroke severity was measured by the National Institutes of Health Stroke Scale (NIHSS) score and outcome by the modified Rankin Scale (mRS) score at 90 days. Univariate relationships between NLR, age, NIHSS, and mRS were established by correlation coefficients; the t test was used to compare NLR with recanalization and stroke location (anterior vs posterior). Logistic regression models were developed to identify the ability of NLR to predict mRS when controlling for age, recanalization, and treatment with IV tissue plasminogen activator (tPA). Results 116 patients were reviewed from 2008 to 2011. Mean age of the sample was 67 years, and 54% were women. Mean baseline NIHSS score was 17 and 90 day mRS score was 4. There was a significant relationship between NLR and mRS (p=0.02) that remained when controlling for age, treatment with IV tPA, and recanalization. NLR ≥5.9 predicted poor outcome and death at 90 days. Conclusions This study shows that the NLR, a readily available biomarker, may be a clinically useful tool for risk stratification when evaluating AIS patients as candidates for endovascular therapies.

Influence of PARP-1 Polymorphisms in Patients after Traumatic Brain Injury

Poly(ADP-ribose) polymerase-1 (PARP-1) plays an important role in the cellular response to stress and DNA damage. However, excessive activity of PARP-1 exacerbates brain injury via NAD+ depletion and energy failure. The purpose of this study was to determine if tagging single nucleotide polymorphisms (tSNPs) covering multiple regions of the PARP-1 gene are related to outcome after traumatic brain injury (TBI) in humans. DNA from 191 adult patients with severe TBI was assayed for four tSNPs corresponding to haplotype blocks spanning the PARP-1 gene. Categorization as favorable or poor outcome was based on Glasgow Outcome Scale (GOS) score assigned at 6 months. PARP-1 enzyme activity was indirectly evaluated by quantifying poly-ADP-ribose (PAR)-modified proteins in cerebrospinal fluid (CSF) using an enzyme-linked immunosorbent assay. In multiple logistic regression analysis controlling for age, initial Glasgow Coma Scale score, and gender, the AA genotype of SNP rs3219119 was an independent predictor of favorable neurologic outcome. This SNP tags a haplotype block spanning the automodification and catalytic domains of the PARP-1 gene. SNP rs2271347 correlated with CSF PAR-modified protein level. This SNP, which did not correlate with outcome, tags a haplotype block spanning the promoter region of the PARP-1 gene. We conclude that after severe TBI in humans, a PARP-1 polymorphism within the automodification-catalytic domain is associated with neurological outcome, while a polymorphism within the promoter region was associated with CSF PAR-modified protein level. These findings must be replicated in a prospective study before the relevance of PARP-1 polymorphisms after TBI can be established.

The transcriptome of cerebral ischemia

The molecular causality and response to stroke is complex. Yet, much of the literature examining the molecular response to stroke has focused on targeted pathways that have been well-characterized. Consequently, our understanding of stroke pathophysiology has made little progress by way of clinical therapeutics since tissue plasminogen activator was approved for treatment nearly a decade ago. The lack of clinical translation is in part due to neuron-focused studies, preclinical models of cerebral ischemia and the paradoxical nature of neuro-inflammation. With the evolution of the Stroke Therapy Academic Industry Roundtable criteria streamlining research efforts and broad availability of genomic technologies, the ability to decipher the molecular fingerprint of ischemic stroke is on the horizon. This review highlights preclinical microarray findings of the ischemic brain, discusses the transcriptome of cerebral preconditioning and emphasizes the importance of further characterizing the role of the neurovascular unit and peripheral white blood cells in mediating stroke damage and repair within the penumbra.