Lipopolysaccharide (LPS) is a major component of the outer membrane of Gram-negative bacteria and a potent inflammatory stimulus for the innate immune response via toll-like receptor (TLR) 4 activation. Type 2 diabetes is associated with changes in gut microbiota and impaired intestinal barrier functions, leading to translocation of microbiota-derived LPS into the circulatory system, a condition referred to as metabolic endotoxemia. We investigated the effects of metabolic endotoxemia after experimental stroke with transient middle cerebral artery occlusion (MCAO) in a murine model of type 2 diabetes (db/db) and phenotypically normal littermates (db/+). Compared to db/+ mice, db/db mice exhibited an altered gut microbial composition, increased intestinal permeability, and higher plasma LPS levels. In addition, db/db mice presented increased infarct volumes and higher expression levels of LPS, TLR4, and inflammatory cytokines in the ischemic brain, as well as more severe neurological impairments and reduced survival rates after MCAO. Oral administration of a non-absorbable antibiotic modulated the gut microbiota and improved metabolic endotoxemia and stroke outcomes in db/db mice; these effects were associated with reduction of LPS levels and neuroinflammation in the ischemic brain. These data suggest that targeting metabolic endotoxemia may be a novel potential therapeutic strategy to improve stroke outcomes.

Background and Purpose—: Exosomes play a pivotal role in neurogenesis. In the peri-infarct area after stroke, axons begin to regenerate but are inhibited by astrocyte scar formation. The direct effect and underlying molecular mechanisms of astrocyte-derived exosomes on axonal outgrowth after ischemia are not known. Methods—: Using a semaphorin 3A (Sema3A) inhibitor, we explored neuronal signaling during axonal outgrowth after ischemia in rats subjected to middle cerebral artery occlusion and in cultured cortical neurons challenged with oxygen-glucose deprivation. Furthermore, we assessed whether this inhibitor suppressed astrocyte activation and regulated astrocyte-derived exosomes to enhance axonal outgrowth after ischemia. Results—: In rats subjected to middle cerebral artery occlusion, we administered a Sema3A inhibitor into the peri-infarct area from 7 to 21 days after occlusion. We found that phosphorylated high-molecular weight neurofilament-immunoreactive axons were increased, glial fibrillary acidic protein–immunoreactive astrocytes were decreased, and functional recovery was promoted at 28 days after middle cerebral artery occlusion. In cultured neurons, the Sema3A inhibitor decreased Rho family GTPase 1, increased R-Ras, which phosphorylates Akt and glycogen synthase kinase 3β (GSK-3β), selectively increased phosphorylated GSK-3β in axons, and thereby enhanced phosphorylated high-molecular weight neurofilament-immunoreactive axons after oxygen-glucose deprivation. In cultured astrocytes, the Sema3A inhibitor suppressed activation of astrocytes induced by oxygen-glucose deprivation. Exosomes secreted from ischemic astrocytes treated with the Sema3A inhibitor further promoted axonal elongation and increased prostaglandin D ₂ synthase expression on microarray analysis. GSK-3β ⁺ and prostaglandin D ₂ synthase ⁺ neurons were robustly increased after treatment with the Sema3A inhibitor in the peri-infarct area. Conclusions—: Neuronal Rho family GTPase 1/R-Ras/Akt/GSK-3β signaling, axonal GSK-3β expression, and astrocyte-derived exosomes with prostaglandin D ₂ synthase expression contribute to axonal outgrowth and functional recovery after stroke.

Background: Anti-inflammatory therapies reduce recurrent vascular events in coronary disease. Existing studies have reported highly conflicting findings for the association of blood inflammatory markers with vascular recurrence after stroke leading to uncertainty about the potential of anti-inflammatory therapies after stroke and no consensus about the utility of measurement of inflammatory markers in current guidelines. Methods: We investigated the association between hsCRP (high-sensitivity C-reactive protein), IL-6 (interluekin-6), and recurrent major adverse cardiovascular events (MACE), and stroke from individual participant data from 8420 patients with ischemic stroke/transient ischemic attack from 10 prospective studies. We did within-study multivariable regression analyses and then combined adjusted risk ratio (RR) by random-effects meta-analysis. Results: During 18 920 person-years of follow-up, 1407 (16.7% [95% CI, 15.9–17.5]) patients had MACE and 1191 (14.1% [95% CI, 13.4–14.9]) patients had recurrent stroke. On bivariate analysis, baseline IL-6 was associated with MACE (RR, 1.26 [95% CI, 1.10–1.43]) and recurrent stroke (RR, 1.18 [95% CI, 1.05–1.32]), per unit increase log _e IL-6. Similar associations were observed for hsCRP (MACE RR, 1.19 [95% CI, 1.09–1.29]; recurrent stroke RR, 1.12 [95% CI, 1.04–1.21], per unit increase log _e hsCRP). After adjustment for vascular risk factors and treatment, independent associations remained with MACE (IL-6, RR, 1.12 [95% CI, 1.04–1.21]; hsCRP, RR, 1.09 [95% CI, 1.04–1.15]) and recurrent stroke (IL-6, RR, 1.09 [95% CI, 1.00–1.19]; hsCRP, RR, 1.05 [95% CI, 1.00–1.11]). Comparing the top with the bottom quarters (Q4 versus Q1), IL-6 (RR, 1.35 [95% CI, 1.09–1.67]) and hsCRP (RR, 1.31 [95% CI, 1.07–1.61]) were associated with MACE after adjustment. Similar results were observed for recurrent stroke for IL-6 (RR, 1.33 [95% CI, 1.08–1.65]) but not hsCRP (RR, 1.16 [95% CI, 0.93–1.43]). Conclusions: Blood markers of inflammation were independently associated with vascular recurrence after stroke, strengthening the rationale for randomized trials of anti-inflammatory therapies for secondary prevention after ischemic stroke/TIA.

Chronic cerebral hypoperfusion causes white-matter lesions (WMLs) with oxidative stress and cognitive impairment. However, the biologic mechanisms that regulate axonal plasticity under chronic cerebral hypoperfusion have not been fully investigated. Here, we investigated whether L-carnitine, an antioxidant agent, enhances axonal plasticity and oligodendrocyte expression, and explored the signaling pathways that mediate axonal plasticity in a rat chronic hypoperfusion model. Adult male Wistar rats subjected to ligation of the bilateral common carotid arteries (LBCCA) were treated with or without L-carnitine. L-carnitine-treated rats exhibited significantly reduced escape latency in the Morris water maze task at 28 days after chronic hypoperfusion. Western blot analysis indicated that L-carnitine increased levels of phosphorylated high-molecular weight neurofilament (pNFH), concurrent with a reduction in phosphorylated phosphatase tensin homolog deleted on chromosome 10 (PTEN), and increased phosphorylated Akt and mammalian target of rapamycin (mTOR) at 28 days after chronic hypoperfusion. L-carnitine reduced lipid peroxidation and oxidative DNA damage, and enhanced oligodendrocyte marker expression and myelin sheath thickness after chronic hypoperfusion. L-carnitine regulates the PTEN/Akt/mTOR signaling pathway, and enhances axonal plasticity while concurrently ameliorating oxidative stress and increasing oligodendrocyte myelination of axons, thereby improving WMLs and cognitive impairment in a rat chronic hypoperfusion model.

Myelin-oligodendrocyte glycoprotein antibody (MOG antibodies) was found in various demyelinated diseases. This is the first report of a patient with longitudinally extensive transverse myelitis with an extremely high titer of MOG antibodies after an influenza infection. This case supports the view that MOG antibodies are linked to longitudinally extensive transverse myelitis and that influenza infection might trigger the MOG antibodies. A 32-year-old healthy male developed high fever, dysesthesia and paraesthesia below the C2 area, muscle weakness of the bilateral lower extremities, and urinary retention ten days after an influenza type A infection. Magnetic resonance imaging revealed a longitudinal lesion in the spinal cord extending from C2 to the spinal conus. There were no lesions in the brain or optic nerves. Established cell-based immunoassays revealed that he was positive for MOG antibodies (titer = 65,536) and negative for anti-aquaporin 4 antibodies (AQP4 antibodies). He fully recovered after steroid pulse therapy followed by 60 mg prednisolone. This is the first report of influenza A-associated longitudinally extensive transverse myelitis with a high titer anti-MOG antibodies. Our case report supports a relationship between anti-MOG antibodies and longitudinally extensive transverse myelitis, which was triggered by influenza infection. Further studies are needed to establish the clinical significance of anti-MOG antibodies for diagnosis, treatment, and prognosis.

Anti-inflammatory therapies reduce major adverse cardiovascular events (MACE) in coronary artery disease but remain unproven after stroke. Establishing the subtype-specific association between inflammatory markers and recurrence risk is essential for optimal selection of patients in randomized trials (RCTs) of anti-inflammatory therapies for secondary stroke prevention. Using individual participant data (IPD) identified from a systematic review, we analyzed the association between high-sensitivity C-reactive protein, interleukin-6 (IL-6), and vascular recurrence after ischemic stroke or transient ischemic attack. The prespecified coprimary end points were (1) any recurrent MACE (first major coronary event, recurrent stroke, or vascular death) and (2) any recurrent stroke (ischemic, hemorrhagic, or unspecified) after sample measurement. Analyses were performed stratified by stroke mechanism, per quarter and per biomarker unit increase after log_e transformation. We then did study-level meta-analysis with comparable published studies not providing IPD. Preferred Reporting Items for Systematic Review and Meta-Analyses IPD guidelines were followed. IPD was obtained from 10 studies (8,420 patients). After adjustment for vascular risk factors and statins/antithrombotic therapy, IL-6 was associated with recurrent MACE in stroke caused by large artery atherosclerosis (LAA) (risk ratio [RR] 2.30, 95% CI 1.21-4.36, p = 0.01), stroke of undetermined cause (UND) (RR 1.78, 1.19-2.66, p = 0.005), and small vessel occlusion (SVO) (RR 1.71, 0.99-2.96, p = 0.053) (quarter 4 [Q4] vs quarter 1 [Q1]). No association was observed for stroke due to cardioembolism or other determined cause. Similar results were seen for recurrent stroke and when analyzed per log_e unit increase for MACE (LAA, RR 1.26 [1.06-1.50], p = 0.009; SVO, RR 1.22 [1.01-1.47], p = 0.04; UND, RR 1.18 [1.04-1.34], p = 0.01). High-sensitivity CRP was associated with recurrent MACE in UND stroke only (Q4 vs Q1 RR 1.45 [1.04-2.03], p = 0.03). Findings were consistent on study-level meta-analysis of the IPD results with 2 other comparable studies (20,136 patients). Our data provide new evidence for the selection of patients in future RCTs of anti-inflammatory therapy in stroke due to large artery atherosclerosis, small vessel occlusion, and undetermined etiology according to inflammatory marker profile.