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Exposure to ambient air pollution particulate matter (PM) is associated with increased risk of dementia and accelerated cognitive loss. Vascular contributions to cognitive impairment are well recognized. Chronic cerebral hypoperfusion (CCH) promotes neuroinflammation and blood-brain barrier weakening, which may augment neurotoxic effects of PM. This study examined interactions of nanoscale particulate matter (nPM; fine particulate matter with aerodynamic diameter ) and CCH secondary to bilateral carotid artery stenosis (BCAS) in a murine model to produce white matter injury. Based on other air pollution interactions, we predicted synergies of nPM with BCAS. nPM was collected using a particle sampler near a Los Angeles, California, freeway. Mice were exposed to 10 wk of reaerosolized nPM or filtered air (FA) for 150 h. CCH was induced by BCAS surgery. Mice (C57BL/6J males) were randomized to four exposure paradigms: ) FA, ) nPM, ) , and ) . Behavioral outcomes, white matter injury, glial cell activation, inflammation, and oxidative stress were assessed. The joint group exhibited synergistic effects on white matter injury (2.3× the additive nPM and scores) with greater loss of corpus callosum volume on T2 magnetic resonance imaging (MRI) (30% smaller than FA group). Histochemical analyses suggested potential microglial-specific inflammatory responses with synergistic effects on corpus callosum C5 immunofluorescent density and whole brain nitrate concentrations (2.1× and 3.9× the additive nPM and effects, respectively) in the joint exposure group. Transcriptomic responses (RNA-Seq) showed greater impact of than individual additive effects, consistent with changes in proinflammatory pathways. Although nPM exposure alone did not alter working memory, the cohort demonstrated impaired working memory when compared to the group. Our data suggest that nPM and CCH contribute to white matter injury in a synergistic manner in a mouse model. Adverse neurological effects may be aggravated in a susceptible population exposed to air pollution. https://doi.org/10.1289/EHP8792.

Epidemiological studies have established an association between air pollution particulate matter exposure (PM2.5) and neurocognitive decline. Experimental data suggest that microglia play an essential role in air pollution PM-induced neuroinflammation and oxidative stress. This study examined the effect of nano-sized particulate matter (nPM) on complement C5 deposition and microglial activation in the corpus callosum of mice (C57BL/6J males). nPM was collected in an urban Los Angeles region impacted by traffic emissions. Mice were exposed to 10 weeks of re-aerosolized nPM or filtered air for a cumulative 150 hours. nPM-exposed mice exhibited reactive microglia and 2-fold increased local deposition of complement C5/ C5α proteins and complement component C5a receptor 1 (CD88) in the corpus callosum. However, serum C5 levels did not differ between nPM and filtered air cohorts. These findings demonstrate white matter C5 deposition and microglial activation secondary to nPM exposure. The C5 upregulation appears to be localized to the brain.

Exposure to ambient air pollution has been associated with white matter damage and neurocognitive decline. However, the mechanisms of this injury are not well understood and remain largely uncharacterized in experimental models. Prior studies have shown that exposure to particulate matter (PM), a sub-fraction of air pollution, results in neuroinflammation, specifically the upregulation of inflammatory microglia. This study examines white matter and axonal injury, and characterizes microglial reactivity in the corpus callosum of mice exposed to 10 weeks (150 hours) of PM. Nanoscale particulate matter (nPM, aerodynamic diameter ≤200 nm) consisting primarily of traffic-related emissions was collected from an urban area in Los Angeles. Male C57BL/6J mice were exposed to either re-aerosolized nPM or filtered air for 5 hours/day, 3 days/week, for 10 weeks (150 hours; n = 18/group). Microglia were characterized by immunohistochemical double staining of ionized calcium-binding protein-1 (Iba-1) with inducible nitric oxide synthase (iNOS) to identify pro-inflammatory cells, and Iba-1 with arginase-1 (Arg) to identify anti-inflammatory/ homeostatic cells. Myelin injury was assessed by degraded myelin basic protein (dMBP). Oligodendrocyte cell counts were evaluated by oligodendrocyte transcription factor 2 (Olig2). Axonal injury was assessed by axonal neurofilament marker SMI-312. iNOS-expressing microglia were significantly increased in the corpus callosum of mice exposed to nPM when compared to those exposed to filtered air (2.2 fold increase; p<0.05). This was accompanied by an increase in dMBP (1.4 fold increase; p<0.05) immunofluorescent density, a decrease in oligodendrocyte cell counts (1.16 fold decrease; p<0.05), and a decrease in neurofilament SMI-312 (1.13 fold decrease; p<0.05) immunofluorescent density. Exposure to nPM results in increased inflammatory microglia, white matter injury, and axonal degradation in the corpus callosum of adult male mice. iNOS-expressing microglia release cytokines and reactive oxygen/ nitrogen species which may further contribute to the white matter damage observed in this model.

Cerebrovascular pathologies are commonly associated with dementia. Because air pollution increases arterial disease in humans and rodent models, we hypothesized that air pollution would also contribute to brain vascular dysfunction. We examined the effects of exposing mice to nanoparticulate matter (nPM; aerodynamic diameter ≤200 nm) from urban traffic and interactions with cerebral hypoperfusion. C57BL/6 mice were exposed to filtered air or nPM with and without bilateral carotid artery stenosis (BCAS) and analyzed by multiparametric MRI and histochemistry. Exposure to nPM alone did not alter regional cerebral blood flow (CBF) or blood brain barrier (BBB) integrity. However, nPM worsened the white matter hypoperfusion (decreased CBF on DSC-MRI) and exacerbated the BBB permeability (extravascular IgG deposits) resulting from BCAS. White matter MRI diffusion metrics were abnormal in mice subjected to cerebral hypoperfusion and worsened by combined nPM+BCAS. Axonal density was reduced equally in the BCAS cohorts regardless of nPM status, whereas nPM exposure caused demyelination in the white matter with or without cerebral hypoperfusion. In summary, air pollution nPM exacerbates cerebrovascular pathology and demyelination in the setting of cerebral hypoperfusion, suggesting that air pollution exposure can augment underlying cerebrovascular contributions to cognitive loss and dementia in susceptible elderly populations.

Abstract Flow diversion is a safe and effective treatment for many types of brain aneurysms. Even so, there remain some aneurysms that persist despite initial treatment. In studies with the longest follow-up (5 yr), at least 5% of aneurysms persist with this treatment modality. As the cumulative experience and clinical indications for flow diversion continue to expand, the anatomic and functional characteristics that are associated with aneurysm persistence are increasingly described. Identification of these factors preoperatively can help to guide initial treatment decisions, enhance monitoring protocols in the follow-up period, and establish best practices for re-treatment when necessary. Herein, we review published clinical series and provide examples to highlight variables implicated in aneurysm persistence after treatment with flow diversion.

RationaleElevated whole-blood serotonin (5-HT) is a robust biomarker in ~ 30% of patients with autism spectrum disorders, in which repetitive behavior is a core symptom. Furthermore, elevated whole-blood 5-HT has also been described in patients with pediatric obsessive-compulsive disorder. The 5-HT1B receptor is associated with repetitive behaviors seen in both disorders. Chronic blockade of serotonin transporter (SERT) reduces 5-HT1B receptor levels in the orbitofrontal cortex (OFC) and attenuates the sensorimotor deficits and hyperactivity seen with the 5-HT1B agonist RU24969. We hypothesized that enhanced SERT function would increase 5-HT1B receptor levels in OFC and enhance sensorimotor deficits and hyperactivity induced by RU24969.ObjectivesWe examined the impact of the SERT Ala56 mutation, which leads to enhanced SERT function, on 5-HT1B receptor binding and 5-HT1B-mediated sensorimotor deficits.MethodsSpecific binding to 5-HT1B receptors was measured in OFC and striatum of naïve SERT Ala56 or wild-type mice. The impact of the 5-HT1A/1B receptor agonist RU24969 on prepulse inhibition (PPI) of startle, hyperactivity, and expression of cFos was examined.ResultsWhile enhanced SERT function increased 5-HT1B receptor levels in OFC of Ala56 mice, RU24969-induced PPI deficits and hyperlocomotion were not different between genotypes. Baseline levels of cFos expression were not different between groups. RU24969 increased cFos expression in OFC of wild-types and decreased cFos in the striatum.ConclusionsWhile reducing 5-HT1B receptors may attenuate sensorimotor gating deficits, increased 5-HT1B levels in SERT Ala56 mice do not necessarily exacerbate these deficits, potentially due to compensations during neural circuit development in this model system.

PurposeUnplanned readmission of post-operative brain tumor patients is often attributed to hospital and patient characteristics and is associated with higher mortality and cost. Previous studies demonstrate multiple patient outcome disparities in safety net hospitals (SNHs) when compared to non-SNHs. This study uses the Nationwide Readmissions Database (NRD) to determine if initial brain tumor resection at SNHs is associated with increased 30-day non-elective readmission rates.MethodsPatients with benign or malignant primary or metastatic brain tumor undergoing craniotomy for surgical resection were retrospectively identified in the NRD from 2010 to 2014. SNHs were defined as hospitals with Medicaid and uninsured patient burden in the top quartile. Descriptive and multivariate analyses employing survey-adjusted logistic regression evaluated patient and hospital level factors influencing 30-day readmissions.ResultsDuring the study period, 83,367 patients met inclusion criteria. 44.7% of patients had a benign tumor, and 55.3% had a malignant tumor. Secondary CNS neoplasm (5.99%), post-operative infection (5.96%), and septicemia (4.26%) caused most readmissions within 30 days. Patients had increased unplanned readmission rates if they underwent craniotomy for tumor resection at a SNH in a small metropolitan area (OR 1.11, 95% CI 1.02–1.21, p = 0.01), but not at a SNH in a large metropolitan area (OR 0.99, 95% CI 0.93–1.05, p = 0.73).ConclusionThis finding may reflect differences in access to care and disparities in neurosurgical resources between small and large metropolitan areas. Inequities in expertise and capacity are relevant as surgical volume was also related to readmission rates. Further studies may be warranted to address such disparities.

•Tobacco is associated with increased odds of readmission after craniotomy.•The association remains after controlling for other patient and disease factors.•The craniotomies in this study including a variety of indications. Tobacco use increases morbidity and mortality following craniotomy. Readmission is an important hospital metric of patient outcomes and has been used to inform reimbursement. This study aims to determine if tobacco use is associated with readmission within 90 days of hospital discharge among patients undergoing elective craniotomy. The Nationwide Readmissions Database (NRD), a population-based, nationally representative database, was queried from 2010-2014. Patients undergoing craniotomy for benign or malignant tumors, vascular pathologies, and epilepsy were identified. Readmissions within 90 days of index hospitalization were characterized by admitting diagnoses. Tobacco use was defined by ICD-9 coding for active or prior use. Descriptive and multivariable regression analyses evaluated patient and hospital factors associated with readmission. The study population included 77,903 patients treated with craniotomy. Of these, 17,674 (22.6%) were readmitted within 90 days. The most common reasons for readmission were post-operative infection (5.8%), septicemia (4.2%), pulmonary embolism (3.9%), and pneumonia (2.9%). Tobacco use was associated with a 7% increased likelihood of 90-day readmission (OR 1.07, 95% CI 1.03-1.11, p = 0.0008) after accounting for other patient-, disease-, and hospital-level factors in multivariate analysis. Tobacco use was associated with increased 90-day readmission in patients undergoing craniotomy. Recognizing tobacco use as a modifiable risk factor of readmission presents an opportunity to identify susceptible patients.

BackgroundStroke systems of care employ a hub-and-spoke model, with fewer centers performing mechanical thrombectomy (MT) compared with stroke-receiving centers, where a higher number offer high-level, centralized treatment to a large number of patients.ObjectiveTo characterize rates and outcomes of readmission to index and non-index hospitals for patients with ischemic stroke who underwent MT.MethodsThis study leveraged a population-based, nationally representative sample of patients with stroke undergoing MT from the Nationwide Readmissions Database between 2010 and 2014. Descriptive, logistic regression analyses, and univariate and multivariate logistic regression models were carried out to determine patient- and hospital-level factors, mortality, complications, and subsequent readmissions associated with index and non-index hospitals' 90-day readmissions.ResultsIn the study, 2111 patients with a stroke were treated with MT, of whom 534 were readmitted within 90 days. The most common reasons for readmission were: septicemia (5.9%), atrial fibrillation (4.8%), and cerebral artery occlusion with infarct (4.8%). Among readmitted patients, 387 (74%) were readmitted to index and 136 (26%) to non-index hospitals. On multivariable logistic regression analysis, non-index hospital readmission was not independently associated with major complications (p=0.09), mortality (p=0.34), neurological complications (p=0.47), or second readmission (p=0.92).ConclusionOne-quarter of patients with a stroke treated with MT were readmitted within 90 days, and one quarter of these patients were readmitted to non-index hospitals. Readmission to a non-index hospital was not associated with mortality or increased complication rates. In a hub-and-spoke model it is important that follow-up care for a specialized procedure can be performed effectively at a vast number of non-index hospitals covering a large geographic area.