White Matter Inflammation Research Articles

Interleukin-1 blockade attenuates white matter inflammation and oligodendrocyte loss after progressive systemic lipopolysaccharide exposure in near-term fetal sheep

BackgroundIncreased systemic and tissue levels of interleukin (IL)-1β are associated with greater risk of impaired neurodevelopment after birth. In this study, we tested the hypothesis that systemic IL-1 receptor antagonist (Ra) administration would attenuate brain inflammation and injury in near-term fetal sheep exposed to lipopolysaccharide (LPS).MethodsChronically instrumented near-term fetal sheep at 0.85 of gestation were randomly assigned to saline infusion (control, n = 9), repeated LPS infusions (0 h = 300 ng, 24 h = 600 ng, 48 h = 1200 ng, n = 8) or repeated LPS plus IL-1Ra infusions (13 mg/kg infused over 4 h) started 1 h after each LPS infusion (n = 9). Sheep were euthanized 4 days after starting infusions for histology.ResultsLPS infusions increased circulating cytokines and were associated with electroencephalogram (EEG) suppression with transiently reduced mean arterial blood pressure, and increased carotid artery perfusion and fetal heart rate (P < 0.05 vs. control for all). In the periventricular and intragyral white matter, LPS-exposure increased IL-1β immunoreactivity, numbers of caspase 3+ cells and microglia, reduced astrocyte and olig-2+ oligodendrocyte survival but did not change numbers of mature CC1+ oligodendrocytes, myelin expression or numbers of neurons in the cortex and subcortical regions. IL-1Ra infusions reduced circulating cytokines and improved recovery of EEG activity and carotid artery perfusion. Histologically, IL-1Ra reduced microgliosis, IL-1β expression and caspase-3+ cells, and improved olig-2+ oligodendrocyte survival.ConclusionIL-1Ra improved EEG activity and markedly attenuated systemic inflammation, microgliosis and oligodendrocyte loss following LPS exposure in near-term fetal sheep. Further studies examining the long-term effects on brain maturation are now needed.

Spotlight on the August 10 Issue

#### Notable in Neurology This Week This issue features an article that evaluates the association of serum neurofilament light levels and chronic white matter inflammation in patients with multiple sclerosis; another investigates whether the use of screening continuous EEG (cEEG) in neonates with encephalopathy is associated with greater odds of successful seizure treatment compared with use of confirmatory cEEG. A featured Contemporary Issues in Practice, Education & Research article examines health care disparities among people with headache disorders. ### Association of Epilepsy Surgery With Changes in Imaging-Defined Brain Age This …

Deep learning to automate the labelling of head MRI datasets for computer vision applications

ObjectivesThe purpose of this study was to build a deep learning model to derive labels from neuroradiology reports and assign these to the corresponding examinations, overcoming a bottleneck to computer vision model development.MethodsReference-standard labels were generated by a team of neuroradiologists for model training and evaluation. Three thousand examinations were labelled for the presence or absence of any abnormality by manually scrutinising the corresponding radiology reports (‘reference-standard report labels’); a subset of these examinations (n = 250) were assigned ‘reference-standard image labels’ by interrogating the actual images. Separately, 2000 reports were labelled for the presence or absence of 7 specialised categories of abnormality (acute stroke, mass, atrophy, vascular abnormality, small vessel disease, white matter inflammation, encephalomalacia), with a subset of these examinations (n = 700) also assigned reference-standard image labels. A deep learning model was trained using labelled reports and validated in two ways: comparing predicted labels to (i) reference-standard report labels and (ii) reference-standard image labels. The area under the receiver operating characteristic curve (AUC-ROC) was used to quantify model performance. Accuracy, sensitivity, specificity, and F1 score were also calculated.ResultsAccurate classification (AUC-ROC > 0.95) was achieved for all categories when tested against reference-standard report labels. A drop in performance (ΔAUC-ROC > 0.02) was seen for three categories (atrophy, encephalomalacia, vascular) when tested against reference-standard image labels, highlighting discrepancies in the original reports. Once trained, the model assigned labels to 121,556 examinations in under 30 min.ConclusionsOur model accurately classifies head MRI examinations, enabling automated dataset labelling for downstream computer vision applications.Key Points• Deep learning is poised to revolutionise image recognition tasks in radiology; however, a barrier to clinical adoption is the difficulty of obtaining large labelled datasets for model training.• We demonstrate a deep learning model which can derive labels from neuroradiology reports and assign these to the corresponding examinations at scale, facilitating the development of downstream computer vision models.• We rigorously tested our model by comparing labels predicted on the basis of neuroradiology reports with two sets of reference-standard labels: (1) labels derived by manually scrutinising each radiology report and (2) labels derived by interrogating the actual images.

RP11-362K2.2:RP11-767I20.1 Genetic Variation Is Associated with Post-Reperfusion Therapy Parenchymal Hematoma. A GWAS Meta-Analysis.

Stroke is one of the most common causes of death and disability. Reperfusion therapies are the only treatment available during the acute phase of stroke. Due to recent clinical trials, these therapies may increase their frequency of use by extending the time-window administration, which may lead to an increase in complications such as hemorrhagic transformation, with parenchymal hematoma (PH) being the more severe subtype, associated with higher mortality and disability rates. Our aim was to find genetic risk factors associated with PH, as that could provide molecular targets/pathways for their prevention/treatment and study its genetic correlations to find traits sharing genetic background. We performed a GWAS and meta-analysis, following standard quality controls and association analysis (fastGWAS), adjusting age, NIHSS, and principal components. FUMA was used to annotate, prioritize, visualize, and interpret the meta-analysis results. The total number of patients in the meta-analysis was 2034 (216 cases and 1818 controls). We found rs79770152 having a genome-wide significant association (beta 0.09, p-value 3.90 × 10−8) located in the RP11-362K2.2:RP11-767I20.1 gene and a suggestive variant (rs13297983: beta 0.07, p-value 6.10 × 10−8) located in PCSK5 associated with PH occurrence. The genetic correlation showed a shared genetic background of PH with Alzheimer’s disease and white matter hyperintensities. In addition, genes containing the ten most significant associations have been related to aggregated amyloid-β, tau protein, white matter microstructure, inflammation, and matrix metalloproteinases.

Precocious White Matter Inflammation and Behavioural Inflexibility Precede Learning and Memory Impairment in the TgAPP21 Rat Model of Alzheimer Disease.

Neuroinflammation and behavioural inflexibility are both common in late adulthood but far more profound in Alzheimer disease (AD). To investigate the relationship between ageing, AD, neuroinflammation, and behavioural flexibility, male wild-type Fischer 344 (Wt) and the transgenic APP21 (TgAPP21) rats were aged to 4, 8, 13, and 22months and evaluated for neuroinflammation and cognitive impairment. TgAPP21 rats overexpress a pathogenic variant of the human amyloid precursor protein (hAPP; Swedish and Indiana mutations) but do not spontaneously develop overt pathology related to AD. In both genotypes, learning and memory were similarly impaired in older rats. However, at 8months of age, TgAPP21 rats demonstrated behavioural inflexibility in set shifting, reversal, and the Morris water maze, while Wt rats showed inflexibility at 13 and 22months of age. This early inflexibility in TgAPP21 rats was accompanied by a precocious increase in microglia activation within the corpus callosum; 8- and 13-month-old TgAPP21 rats had similar levels of microglia activation as 13- and 22-month-old Wt rats, respectively. However, while neuroinflammation within the white matter continued to progress with age, behavioural inflexibility peaked in 8-month-old TgAPP21 rats; in older TgAPP21 rats, memory and learning impairments masked inflexibility. These findings suggest that the behavioural inflexibility and white matter inflammation seen in normal ageing are accelerated in AD and may precede impairments of learning and memory.

Chronic White Matter Inflammation and Serum Neurofilament Levels in Multiple Sclerosis.

ObjectiveTo assess whether chronic white matter inflammation in patients with multiple sclerosis (MS) as detected in vivo by paramagnetic rim MRI lesions (PRLs) is associated with higher serum neurofilament light chain (sNfL) levels, a marker of neuroaxonal damage.MethodsIn 118 patients with MS with no gadolinium-enhancing lesions or recent relapses, we analyzed 3D-submillimeter phase MRI and sNfL levels. Histopathologic evaluation was performed in 25 MS lesions from 20 additional autopsy MS cases.ResultsIn univariable analyses, participants with ≥2 PRLs (n = 43) compared to those with ≤1 PRL (n = 75) had higher age-adjusted sNfL percentiles (median, 91 and 68; p < 0.001) and higher Multiple Sclerosis Severity Scale scores (MSSS median, 4.3 and 2.4; p = 0.003). In multivariable analyses, sNfL percentile levels were higher in PRLs ≥2 cases (βadd, 16.3; 95% confidence interval [CI], 4.6–28.0; p < 0.01), whereas disease-modifying treatment (DMT), Expanded Disability Status Scale (EDSS) score, and T2 lesion load did not affect sNfL. In a similar model, sNfL percentile levels were highest in cases with ≥4 PRLs (n = 30; βadd, 30.4; 95% CI, 15.6–45.2; p < 0.01). Subsequent multivariable analysis revealed that PRLs ≥2 cases also had higher MSSS (βadd, 1.1; 95% CI, 0.3–1.9; p < 0.01), whereas MSSS was not affected by DMT or T2 lesion load. On histopathology, both chronic active and smoldering lesions exhibited more severe acute axonal damage at the lesion edge than in the lesion center (edge vs center: p = 0.004 and p = 0.0002, respectively).ConclusionChronic white matter inflammation was associated with increased levels of sNfL and disease severity in nonacute MS, suggesting that PRL contribute to clinically relevant, inflammation-driven neurodegeneration.

‘Starry sky’ appearance on brain CT in neurocysticercal encephalitis

A 12-year-old boy, living in a tropical area, with no medical history, presented to the emergency department for generalized seizures evolving over a period of 6 months. Intermittent moderate headaches and decreased visual acuity for 3 months were also reported. A cerebral computed tomography (CT) scan showed the presence of multiple millimetric hyperdense spots spread over the whole brain parenchyma (white matter, grey matter, basal ganglia), giving the appearance of a ‘starry sky’ (Figure 1A). Some of these hyperdensities were contained in a vesicle corresponding to a scolex (Figure 1B). There was focal white matter inflammation (Figure 1C). All of these findings allowed the diagnosis of cysticercosis encephalitis. Antiepileptic treatment associated with intravenous methylprednisolone was started for 1 week, with a decrease in the headaches and seizures. The patient was discharged with oral prednisolone, and antiepileptic and antiparasitic drugs. Cysticercosis is a parasitic infection by the larval phase of Taenia solium with possible central nervous system or other involvement. It is more frequent in tropical environments with poor hygiene conditions and pork consumption (Tale et al., 2017Tale S. Chhabria B.A. Gawalkar A.A. Banavath H.N. Bhalla A. ‘Sleeping under the starry sky’—cysticercal encephalitis.QJM Int J Med. 2017; 110: 833-834Crossref PubMed Scopus (2) Google Scholar). Cysticercosis encephalitis is a form of neurological presentation in patients with multiple cysts where there is reactive brain inflammation after the cyst dies either spontaneously or after treatment (Tale et al., 2017Tale S. Chhabria B.A. Gawalkar A.A. Banavath H.N. Bhalla A. ‘Sleeping under the starry sky’—cysticercal encephalitis.QJM Int J Med. 2017; 110: 833-834Crossref PubMed Scopus (2) Google Scholar). Neurocysticercosis can be parenchymal, intraventricular, subarachnoid, or spinal. The parenchymal localization is mainly manifested by seizures, whereas the intraventricular localization is responsible for intracranial hypertension (Garcia et al., 2014bGarcia H.H. Nash T.E. Del Brutto O.H. Clinical symptoms, diagnosis, and treatment of neurocysticercosis.Lancet Neurol. 2014; 13: 1202-1215https://doi.org/10.1016/S1474-4422(14)70094-8Abstract Full Text Full Text PDF PubMed Scopus (256) Google Scholar). The starry sky appearance on brain imaging is found in the case of numerous calcified neurocysticercosis lesions and testifies to a high parasite load. Treatment should initially include corticosteroid therapy and avoid antiparasitic treatment, which may exacerbate the inflammatory response and increase symptoms (Garcia et al., 2014aGarcia H.H. Gonzales I. Lescano A.G. Bustos J.A. Pretell E.J. Saavedra H. et al.Enhanced steroid dosing reduces seizures during antiparasitic treatment for cysticercosis and early after.Epilepsia. 2014; 55: 1452-1459https://doi.org/10.1111/epi.12739Crossref PubMed Scopus (40) Google Scholar).

The Distribution of GPR17-Expressing Cells Correlates with White Matter Inflammation Status in Brain Tissues of Multiple Sclerosis Patients

In multiple sclerosis (MS), oligodendrocyte precursor cells (OPCs) are recruited to the site of injury to remyelinate damaged axons; however, in patients this process is often ineffective due to defects in OPC maturation. The membrane receptor GPR17 timely regulates the early stages of OPC differentiation; however, after reaching its highest levels in immature oligodendrocytes, it has to be downregulated to allow terminal maturation. Since, in several animal models of disease GPR17 is upregulated, the aim of this work was to characterize GPR17 alterations in MS patients. We developed immunohistochemistry and immunofluorescence procedures for the detection of GPR17 in human tissues and stained post-mortem MS brain lesions from patients with secondary progressive MS and control subjects. The inflammatory activity in each lesion was evaluated by immunohistochemistry for the myelin protein MOG and the HLA antigen to classify them as active, chronic inactive or chronic active. Hence, we assessed the distribution of GPR17-positive cells in these lesions compared to normal appearing white matter (NAWM) and white matter (WM) of control subjects. Our data have shown a marked increase of GPR17-expressing oligodendroglial cells accumulating at NAWM, in which moderate inflammation was also found. Furthermore, we identified two distinct subpopulations of GPR17-expressing oligodendroglial cells, characterized by either ramified or rounded morphology, that differently populate the WM of healthy controls and MS patients. We concluded that the coordinated presence of GPR17 in OPCs at the lesion sites and inflamed NAWM areas suggests that GPR17 could be exploited to support endogenous remyelination through advanced pharmacological approaches.

Connection between JAK/STAT and PPARγ Signaling During the Progression of Multiple Sclerosis: Insights into the Modulation of T-Cells and Immune Responses in the Brain.

Multiple Sclerosis (MS) is a severe brain and spinal cord condition with a diverse autoimmune response and a wide variety of demyelination symptoms that primarily affect young adults. The primary reason for this disease is inflammation of white and grey matter caused by increased production of proinflammatory cytokines, which further damages the progenitor oligodendrocytes and appears to induce hypertrophy of the astrocytes and gliosis. Overexpression of the JAK/STAT signaling pathway contributes directly to physiological and pathological results in motor neuron diseases. Cytokines such as IL-17, IL-6, IL-12, TNF-α, and INF-ϒ use JAK/STAT signaling to trigger self-reactive CD4+ T-cells and differentiate them into Th1 phenotypes that overactivate immune reactions in the brain. Similarly, PPARγ plays a critical role in regulating the immune response by providing an anti-inflammatory effect by inhibiting macrophage and cytokine production activation. PPARγ also mediates the intrinsic molecular process of the T-cell, which selectively regulates the differentiation of Th17. Various studies indicate the neuroprotective function of PPARγ agonists by attenuating the JAK/STAT mediated activation of glial cells, inhibiting interleukin, and the differentiation of Th1 cells. Therefore, to maintain the brain's immune system, both PPARγ and JAK/STAT oppositely regulate each other. Dysregulation in JAK/STAT and PPARγ signaling contributes to several physiological changes leading to neurological disorders, including MS. Based on the above view, we have summarized the combined role of JAK/STAT-PPARγ signaling in MS and explored potential therapeutic strategies for disease improvement by the use of pathway modulators.

Mitochondria, Oxidative Stress, cAMP Signalling and Apoptosis: A Crossroads in Lymphocytes of Multiple Sclerosis, a Possible Role of Nutraceutics.

Multiple sclerosis (MS) is a complex inflammatory and neurodegenerative chronic disease that involves the immune and central nervous systems (CNS). The pathogenesis involves the loss of blood–brain barrier integrity, resulting in the invasion of lymphocytes into the CNS with consequent tissue damage. The MS etiology is probably a combination of immunological, genetic, and environmental factors. It has been proposed that T lymphocytes have a main role in the onset and propagation of MS, leading to the inflammation of white matter and myelin sheath destruction. Cyclic AMP (cAMP), mitochondrial dysfunction, and oxidative stress exert a role in the alteration of T lymphocytes homeostasis and are involved in the apoptosis resistance of immune cells with the consequent development of autoimmune diseases. The defective apoptosis of autoreactive lymphocytes in patients with MS, allows these cells to perpetuate, within the CNS, a continuous cycle of inflammation. In this review, we discuss the involvement in MS of cAMP pathway, mitochondria, reactive oxygen species (ROS), apoptosis, and their interaction in the alteration of T lymphocytes homeostasis. In addition, we discuss a series of nutraceutical compounds that could influence these aspects.

Activation of inflammatory/coagulation system following electrical cardioversion of patient with recent onset atrial fibrillation: an explorative study of the relation to white matter hyperintensities

Abstract Background White matter hyperintensities (WMH), assessed using Fazekas scale, are more prevalent in patients with atrial fibrillation (AF), although its pathophysiologic mechanism(s) is unclear. Purpose The study objective was to explore the association between cardiac, inflammatory and coagulation biomarkers and white matter hyperintensities in anticoagulant-naïve patients following electrical cardioversion (CV) of recent onset AF. Methods Patients with AF duration &amp;lt;48 hours were prospectively included. Brain magnetic resonance imaging (MRI), C-reactive protein (CRP), high-sensitivity troponin T (hs-TNT), NT-proBNP, Interleukin 6, P-selectin, D-dimer, prothrombin fragment 1+2, von Willebrand factor Ag, coagulation factor VIII C and fibrinogen, were obtained sequentially prior, after (2–4 hours) and 7–10 days following CV. Repeated measure analysis of variance was performed. Results Forty-three patients (84% males), aged 55±9.6 years, (mean±SD) with median CHA2DS2-VASc score 1 (interquartile range 0–1) were included. Sequential MRI showed no new brain lesions after CV, while WMH were present at baseline in 21/43 (49%) patients. Repeated measure analysis of variance revealed a statistically significant overall change for hs-TNT: F(2,84)=6.056, p=0.03, NT-proBNP: F(2,84)=106.02, p&amp;lt;0.001, P-selectin: F(2,84)=8.69, p&amp;lt;0.001 and vWF:Ag: F(2,84)=4.078, p=0.02. CRP, IL-6, coagulation factor VIII-C and fibrinogen showed the same pattern, however none reached statistical significance. Patients with WMH had persistent higher values for CRP, hs-TNT, D-dimer, prothrombin fragment 1+2 and fibrinogen prior and after CV, as values at 7–10 days coincided; however, statistical interaction was not significant. Conclusion Transient activation of inflammatory and coagulation systems during atrial fibrillation subsides within 7–10 days after electric cardioversion of recent onset atrial fibrillation. A tendency of higher degree of activation during atrial fibrillation was observed in patients with white matter hyperintensities. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Swedish Heart-Lung Foundation, Swedish Research Council, Correvio International Sárl (Geneva Switzerland), Selanders Stiftelse

Large-Scale Evidence for an Association Between Peripheral Inflammation and White Matter Free Water in Schizophrenia and Healthy Individuals.

Clarifying the role of neuroinflammation in schizophrenia is subject to its detection in the living brain. Free-water (FW) imaging is an in vivo diffusion-weighted magnetic resonance imaging (dMRI) technique that measures water molecules freely diffusing in the brain and is hypothesized to detect inflammatory processes. Here, we aimed to establish a link between peripheral markers of inflammation and FW in brain white matter. All data were obtained from the Australian Schizophrenia Research Bank (ASRB) across 5 Australian states and territories. We first tested for the presence of peripheral cytokine deregulation in schizophrenia, using a large sample (N = 1143) comprising the ASRB. We next determined the extent to which individual variation in 8 circulating pro-/anti-inflammatory cytokines related to FW in brain white matter, imaged in a subset (n = 308) of patients and controls. Patients with schizophrenia showed reduced interleukin-2 (IL-2) (t = -3.56, P = .0004) and IL-12(p70) (t = -2.84, P = .005) and increased IL-6 (t = 3.56, P = .0004), IL-8 (t = 3.8, P = .0002), and TNFα (t = 4.30, P < .0001). Higher proinflammatory signaling of IL-6 (t = 3.4, P = .0007) and TNFα (t = 2.7, P = .0007) was associated with higher FW levels in white matter. The reciprocal increases in serum cytokines and FW were spatially widespread in patients encompassing most major fibers; conversely, in controls, the relationship was confined to the anterior corpus callosum and thalamic radiations. No relationships were observed with alternative dMRI measures, including the fractional anisotropy and tissue-related FA. We report widespread deregulation of cytokines in schizophrenia and identify inflammation as a putative mechanism underlying increases in brain FW levels.

TSPO PET detects acute neuroinflammation but not diffuse chronically activated MHCII microglia in the rat

BackgroundAccurate and sensitive imaging biomarkers are required to study the progression of white matter (WM) inflammation in neurodegenerative diseases. Radioligands targeting the translocator protein (TSPO) are considered sensitive indicators of neuroinflammation, but it is not clear how well the expression of TSPO coincides with major histocompatibility complex class II (MHCII) molecules in WM. This study aimed to test the ability of TSPO to detect activated WM microglia that are immunohistochemically positive for MHCII in rat models of prodromal Alzheimer’s disease and acute subcortical stroke.MethodsFischer 344 wild-type (n = 12) and TgAPP21 (n = 11) rats were imaged with [18F]FEPPA PET and MRI to investigate TSPO tracer uptake in the corpus callosum, a WM region known to have high levels of MHCII activated microglia in TgAPP21 rats. Wild-type rats subsequently received an endothelin-1 (ET1) subcortical stroke and were imaged at days 7 and 28 post-stroke before immunohistochemistry of TSPO, GFAP, iNOS, and the MHCII rat antigen, OX6.Results[18F]FEPPA PET was not significantly affected by genotype in WM and only detected increases near the ET1 infarct (P = 0.033, infarct/cerebellum uptake ratio: baseline = 0.94 ± 0.16; day 7 = 2.10 ± 0.78; day 28 = 1.77 ± 0.35). Immunohistochemistry confirmed that only the infarct (TSPO cells/mm2: day 7 = 555 ± 181; day 28 = 307 ± 153) and WM that is proximal to the infarct had TSPO expression (TSPO cells/mm2: day 7 = 113 ± 93; day 28 = 5 ± 7). TSPO and iNOS were not able to detect the chronic WM microglial activation that was detected with MHCII in the contralateral corpus callosum (day 28 OX6% area: saline = 0.62 ± 0.38; stroke = 4.30 ± 2.83; P = .029).ConclusionTSPO was only expressed in the stroke-induced insult and proximal tissue and therefore was unable to detect remote and non-insult-related chronically activated microglia overexpressing MHCII in WM. This suggests that research in neuroinflammation, particularly in the WM, would benefit from MHCII-sensitive radiotracers.

Bioinformatics Analysis of Gut Microbiota and CNS Transcriptome in Virus-Induced Acute Myelitis and Chronic Inflammatory Demyelination; Potential Association of Distinct Bacteria With CNS IgA Upregulation.

Virus infections have been associated with acute and chronic inflammatory central nervous system (CNS) diseases, e.g., acute flaccid myelitis (AFM) and multiple sclerosis (MS), where animal models support the pathogenic roles of viruses. In the spinal cord, Theiler's murine encephalomyelitis virus (TMEV) induces an AFM-like disease with gray matter inflammation during the acute phase, 1 week post infection (p.i.), and an MS-like disease with white matter inflammation during the chronic phase, 1 month p.i. Although gut microbiota has been proposed to affect immune responses contributing to pathological conditions in remote organs, including the brain pathophysiology, its precise role in neuroinflammatory diseases is unclear. We infected SJL/J mice with TMEV; harvested feces and spinal cords on days 4 (before onset), 7 (acute phase), and 35 (chronic phase) p.i.; and examined fecal microbiota by 16S rRNA sequencing and CNS transcriptome by RNA sequencing. Although TMEV infection neither decreased microbial diversity nor changed overall microbiome patterns, it increased abundance of individual bacterial genera Marvinbryantia on days 7 and 35 p.i. and Coprococcus on day 35 p.i., whose pattern-matching with CNS transcriptome showed strong correlations: Marvinbryantia with eight T-cell receptor (TCR) genes on day 7 and with seven immunoglobulin (Ig) genes on day 35 p.i.; and Coprococcus with gene expressions of not only TCRs and IgG/IgA, but also major histocompatibility complex (MHC) and complements. The high gene expression of IgA, a component of mucosal immunity, in the CNS was unexpected. However, we observed substantial IgA positive cells and deposition in the CNS, as well as a strong correlation between CNS IgA gene expression and serum anti-TMEV IgA titers. Here, changes in a small number of distinct gut bacteria, but not overall gut microbiota, could affect acute and chronic immune responses, causing AFM- and MS-like lesions in the CNS. Alternatively, activated immune responses would alter the composition of gut microbiota.

Sex-specific differences in rim appearance of multiple sclerosis lesions on quantitative susceptibility mapping

BackgroundSusceptibility MRI techniques, such as phase and quantitative susceptibility mapping (QSM) reveal lesion heterogeneity in MS, including the presence of lesions with outer rims suggestive of iron accumulation in macrophages and microglia, indicative of chronic-active inflammatory white matter lesions (WMLs). ObjectiveTo evaluate the in vivo relationship between chronic-active WMLs (as visualized by rimmed lesions on QSM) and several clinical metrics. Methods39 patients (15 men, 24 women) with MS underwent 7 Tesla brain MRIs and clinical evaluation. Contrast patterns of lesions identified on FLAIR and quantitative susceptibility maps were reviewed and compared to demographic characteristics and disability scores. Results1279 lesions were identified on FLAIR MRI; 846 (66.2%) of these were visible on QSM, 119 (14.1%) of which had visible rims. Lesions visible on QSM were more likely to have rims in men (16.1%, vs 4.9% in women, p=0.009). In a logistic regression model accounting for several factors, male sex conferred a >10-fold risk of having ≥1 rimmed lesion(s) (p=0.026). ConclusionOur findings provide in vivo support for the body of histopathologic literature indicating sex-specific differences in MS WML formation and suggest that QSM can be used to study these sex differences in the future.

Targeting white matter microgliosis using minocycline in a co‐morbid preclinical rat model of Alzheimer’s disease and stroke

Current literature indicates a potential synergistic interaction between stroke and Alzheimer’s disease (AD). White matter (WM) inflammation, which is commonly triggered by cerebrovascular disease and AD, disrupts the normal function of white matter; and can trigger and exacerbate dementia‐type symptoms such as memory loss and executive dysfunction. Recent work in our lab demonstrated, for the first time, a link between stroke, AD‐related pathology, and WM inflammation. A unilateral lacunar stroke induction in a comorbid rat model of AD and stroke resulted in microglial activation within the WM tracts and subsequent impairment in behavioural flexibility, an important component of executive function. As such, the aim of the current study was to evaluate the effect of microglia targeting on WM pathology, executive function, learning, and memory in the co‐morbid rat model of AD (TgAPP21) and stroke. Minocycline, a tetracycline‐class antibiotic and an anti‐inflammatory drug, has been shown to decrease apoptosis, inflammation, and microglial activation following cerebrovascular injury. To study the behavioural outcomes of minocycline treatment, TgAPP21 rats received an endothelin‐1‐induced subcortical stroke at the age of 8 months. Following stroke, animals received intraperitoneal injections of minocycline or saline twice daily for four days to supress microglial activation. Cognitive behavioural flexibility post‐stroke was analyzed using set‐shifting operant conditioning test, while spatial learning and memory were assessed using Morris water maze. Immunohistochemistry was performed to evaluate the extent of microglial activation by detection of OX‐6 positive microglia in corpus callosum, internal capsule, and hippocampus. Minocycline treatment significantly decreased the number of errors committed by TgAPP21 rats on the visual cue component of the set‐shifting test, suggesting improved learning of the original visual cue task. However, minocycline also impaired animals’ ability to undergo an extra‐dimensional strategy shift from the original visual cue to a new spatial cue task, suggesting impaired behavioural flexibility. Further, minocycline treatment showed no significant effect on learning and memory of the Morris water maze task in TgAPP21 rats. Collectively, the data indicate that minocycline has distinct effects on the learning component of set‐shifting and Morris water maze tests, though further histological evaluation of OX‐6 positive microglia within WM tracts and hippocampus will contextualize current findings.Support or Funding InformationNatural Sciences and Engineering Research Council (NSERC), Canadian Institutes of Health Research (CIHR), Canadian Foundation for Innovation (CFI), Canadian Consortium for Neurodegeneration and Aging (CCNA)

Long Term Cognitive Impairment and Increased Inflammation following Mild Traumatic Brain Injury using the CHIMERA Model

IntroductionTraumatic brain injury (TBI) affects a vast number of people worldwide. Mild TBI (mTBI), including concussions, accounts for most of the TBI cases. mTBI patients experience enduring symptoms, including headaches, mild cognitive dysfunction, emotional instability, psychiatric symptoms, and increased risk of neurodegenerative disease. Repetitive closed head impact model of engineered rotational acceleration (rCHIMERA) is a recently developed nonsurgical animal model of TBI that primarily produces diffuse axonal injury characterized by white matter inflammation and axonal damage, which mimic the mTBI in humans. However, the majority of studies on rCHIMERA were conducted in mice, which are not suitable for assessment of complex behavior.MethodsThis study was designed to validate our rCHIMERA‐induced rat mTBI model using advanced and cutting‐edge behavioral tests and immunofluorescence staining of key biomarkers of TBI. Adult male Sprague‐Dawley rats (~350 g) were divided into sham and injured groups. All rats were anesthetized with dexmedetomidine (IV, 0.2 mg/kg/hr). Following anesthesia, the rats designated for injury received 6 closed‐head impacts of 2 Joules (J) energy over 3 days with 1‐day interval (3 impacts on days 1 &amp; 3, with 30‐seconds between impacts, and rested on day 2). The sham rats were handled the same way as the injured without the impacts. The rats were subsequently subjected to a battery of behavioral tests at specified time points post‐injury: neurological severity score (NSS), automated home‐cage (CleverSys), behavioral spectrometer (Biobserve), rotarod test, and fear conditioning. Histological assessment of the injury was performed in targeted rat brain areas from sham and injured rats. Immunohistochemistry staining for amyloid precursor protein (APP), ionized calcium‐binding adapter molecule 1 (Iba‐1) and glial fibrillary acidic protein (GFAP) were used to determine axonal damage, inflammatory response and astrocytic activation, respectively, in sham and injured rats. The weights of the rats were also monitored for the duration of the studies.Results3 months after mTBI, there was no significant difference in body weight and NSS between sham and injured rats. Injury did not affect motor activity and motor learning with the rotarod test, but did impair associative fear learning and memory in fear conditioning tests 4 weeks and 3 months after mTBI (n=9 shams and 9 mTBI). APP immunohistochemistry in the injured brains revealed induced diffusive axonal injury in the the cortex. The number of GFAP positive cells was increased in the prefrontal cortex and hippocampus after injury and the astrocytes showed distinct hypertrophic morphology. The number of Iba‐1 positive cells was also increased after injury, indicating enhanced inflammation.ConclusionThe results suggest that our mTBI model in rats induces short‐term changes in affect and activity, long‐term cognitive impairments, and histological changes. These observations validate the CHIMERA, using the rat, as a model that replicates clinical mTBI.Support or Funding InformationThis work is supported by the Advancing a Healthier Wisconsin Endowment (#5520444) to AC.

Benefits of physical exercise on cognition and glial white matter pathology in a mouse model of vascular cognitive impairment and dementia.

White matter (WM) pathology is a clinically predictive feature of vascular cognitive impairment and dementia (VCID). Mice overexpressing transforming growth factor-β1 (TGF) with an underlying cerebrovascular pathology when fed a high cholesterol diet (HCD) develop cognitive deficits (VCID mice) that we recently found could be prevented by physical exercise (EX). Here, we further investigated cognitive and WM pathology in VCID mice and examined the cellular substrates of the protective effects of moderate aerobic EX focusing on WM alterations. Six groups were studied: Wild-type (WT) and TGF mice (n = 20-24/group) fed standard lab chow or a 2% HCD, with two HCD-fed groups given concurrent access to running wheels. HCD had a significant negative effect in TGF mice that was prevented by EX on working and object recognition memory, the latter also altered in WT HCD mice. Whisker-evoked increases in cerebral blood flow (CBF) were reduced in HCD-fed mice, deficits that were countered by EX, and baseline WM CBF was similarly affected. VCID mice displayed WM functional deficits characterized by lower compound action potential amplitude not found in EX groups. Moreover, there was an increased number of collapsing capillaries, galectin-3-expressing microglial cells, as well as a reduced number of oligodendrocytes in the WM of VCID mice; all of which were prevented by EX. Our findings indicate that a compromised cerebral circulation precedes reduced WM vascularization, enhanced WM inflammation and impaired oligodendrogenesis that all likely account for the increased susceptibility to memory impairments in VCID mice, which can be prevented by EX. MAIN POINTS: A compromised cerebral circulation increases susceptibility to anatomical and functional white matter changes that develop alongside cognitive deficits when challenged with a high cholesterol diet; preventable by a translational regimen of exercise.

Prospectively Collected Cardiovascular Biomarkers and White Matter Hyperintensity Volume in Ischemic Stroke Patients

Background: Few prospective cohort studies collect detailed information on stroke characteristics among individuals who experience ischemic stroke, including white matter hyperintensity volume, and thus cannot explore how prospectively collected biomarkers prior to the stroke influence white matter hyperintensity volume. We explored the association between a large panel of prospectively collected lipid and inflammatory biomarkers and white matter hyperintensity volume among participants in the Women's Health Study with incident ischemic stroke. Methods: Among Women's Health Study participants with first ischemic stroke who had baseline serum biomarkers and available magnetic resonance imaging, we measured white matter hyperintensity volume using a validated semi-automated method. Linear regression was used to explore the associations between biomarkers and log-transformed white matter hyperintensity volume. Results: After multivariate adjustment, a 1% increment in HbA1c% was associated with an increase in white matter hyperintensity volume (P value = .05). Evidence of a nonlinear association between high density lipoprotein cholesterol levels and ApoA1 levels with white matter hyperintensity volume was noted (P values for nonlinearity = .01 and .001, respectively). No other biomarkers were significantly associated with white matter hyperintensity volume. Conclusions: Chronic hyperglycemia as evidenced by HbA1c levels measured years prior to stroke is associated with white matter hyperintensity volume at the time of stroke. Additional research is needed to explain why low levels of high density lipoprotein cholesterol levels and ApoA1 may be associated with similar white matter hyperintensity volume as high levels.

Neonatal hydrocephalus leads to white matter neuroinflammation and injury in the corpus callosum of Ccdc39 hydrocephalic mice.

The authors sought to determine if hydrocephalus caused a proinflammatory state within white matter as is seen in many other forms of neonatal brain injury. Common causes of hydrocephalus (such as trauma, infection, and hemorrhage) are inflammatory insults themselves and therefore confound understanding of how hydrocephalus itself affects neuroinflammation. Recently, a novel animal model of hydrocephalus due to a genetic mutation in the Ccdc39 gene has been developed in mice. In this model, ciliary dysfunction leads to early-onset ventriculomegaly, astrogliosis, and reduced myelination. Because this model of hydrocephalus is not caused by an antecedent proinflammatory insult, it was utilized to study the effect of hydrocephalus on inflammation within the white matter of the corpus callosum. A Meso Scale Discovery assay was used to measure levels of proinflammatory cytokines in whole brain from animals with and without hydrocephalus. Immunohistochemistry was used to measure macrophage activation and NG2 expression within the white matter of the corpus callosum in animals with and without hydrocephalus. In this model of hydrocephalus, levels of cytokines throughout the brain revealed a more robust increase in classic proinflammatory cytokines (interleukin [IL]-1β, CXCL1) than in immunomodulatory cytokines (IL-10). Increased numbers of macrophages were found within the corpus callosum. These macrophages were polarized toward a proinflammatory phenotype as assessed by higher levels of CD86, a marker of proinflammatory macrophages, compared to CD206, a marker for antiinflammatory macrophages. There was extensive structural damage to the corpus callosum of animals with hydrocephalus, and an increase in NG2-positive cells. Hydrocephalus without an antecedent proinflammatory insult induces inflammation and tissue injury in white matter. Future studies with this model will be useful to better understand the effects of hydrocephalus on neuroinflammation and progenitor cell development. Antiinflammatory therapy for diseases that cause hydrocephalus may be a powerful strategy to reduce tissue damage.