BackgroundClearance at the blood-brain barrier (BBB) plays an important role in removal of Alzheimer’s amyloid-β (Aβ) toxin from brain both in humans and animal models. Apolipoprotein E (apoE), the major genetic risk factor for AD, disrupts Aβ clearance at the BBB. The cellular and molecular mechanisms, however, still remain unclear, particularly whether the BBB-associated brain capillary pericytes can contribute to removal of aggregated Aβ from brain capillaries, and whether removal of Aβ aggregates by pericytes requires apoE, and if so, is Aβ clearance on pericytes apoE isoform-specific.MethodsWe performed immunostaining for Aβ and pericyte biomarkers on brain capillaries (< 6 μm in diameter) on tissue sections derived from AD patients and age-matched controls, and APPSwe/0 mice and littermate controls. Human Cy3-Aβ42 uptake by pericytes was studied on freshly isolated brain slices from control mice, pericyte LRP1-deficient mice (Lrplox/lox;Cspg4-Cre) and littermate controls. Clearance of aggregated Aβ42 by mouse pericytes was studied on multi-spot glass slides under different experimental conditions including pharmacologic and/or genetic inhibition of the low density lipoprotein receptor related protein 1 (LRP1), an apoE receptor, and/or silencing mouse endogenous Apoe in the presence and absence of human astrocyte-derived lipidated apoE3 or apoE4. Student’s t-test and one-way ANOVA followed by Bonferroni's post-hoc test were used for statistical analysis.ResultsFirst, we found that 35% and 60% of brain capillary pericytes accumulate Aβ in AD patients and 8.5-month-old APPSw/0 mice, respectively, compared to negligible uptake in controls. Cy3-Aβ42 species were abundantly taken up by pericytes on cultured mouse brain slices via LRP1, as shown by both pharmacologic and genetic inhibition of LRP1 in pericytes. Mouse pericytes vigorously cleared aggregated Cy3-Aβ42 from multi-spot glass slides via LRP1, which was inhibited by pharmacologic and/or genetic knockdown of mouse endogenous apoE. Human astrocyte-derived lipidated apoE3, but not apoE4, normalized Aβ42 clearance by mouse pericytes with silenced mouse apoE.ConclusionsOur data suggest that BBB-associated pericytes clear Aβ aggregates via an LRP1/apoE isoform-specific mechanism. These data support the role of LRP1/apoE interactions on pericytes as a potential therapeutic target for controlling Aβ clearance in AD.Electronic supplementary materialThe online version of this article (10.1186/s13024-018-0286-0) contains supplementary material, which is available to authorized users.
OBJECTIVEAlthough enhanced recovery after surgery (ERAS) programs have gained acceptance in various surgical specialties, no established neurosurgical ERAS protocol for patients undergoing elective craniotomy has been reported in the literature. Here, the authors describe the design, implementation, safety, and efficacy of a novel neurosurgical ERAS protocol for elective craniotomy in a tertiary care medical center located in China.METHODSA multidisciplinary neurosurgical ERAS protocol for elective craniotomy was developed based on the best available evidence. A total of 140 patients undergoing elective craniotomy between October 2016 and May 2017 were enrolled in a randomized clinical trial comparing this novel protocol to conventional neurosurgical perioperative management. The primary endpoint of this study was the postoperative hospital length of stay (LOS). Postoperative morbidity, perioperative complications, postoperative pain scores, postoperative nausea and vomiting, duration of urinary catheterization, time to first solid meal, and patient satisfaction were secondary endpoints.RESULTSThe median postoperative hospital LOS (4 days) was significantly shorter with the incorporation of the ERAS protocol than that with conventional perioperative management (7 days, p < 0.0001). No 30-day readmission or reoperation occurred in either group. More patients in the ERAS group reported mild pain (visual analog scale score 1–3) on postoperative day 1 than those in the control group (79% vs. 33%, OR 7.49, 95% CI 3.51–15.99, p < 0.0001). Similarly, more patients in the ERAS group had a shortened duration of pain (1–2 days; 53% vs. 17%, OR 0.64, 95% CI 0.29–1.37, p = 0.0001). The urinary catheter was removed within 6 hours after surgery in 74% patients in the ERAS group (OR 400.1, 95% CI 23.56–6796, p < 0.0001). The time to first oral liquid intake was a median of 8 hours in the ERAS group compared to 11 hours in the control group (p < 0.0001), and solid food intake occurred at a median of 24 hours in the ERAS group compared to 72 hours in the control group (p < 0.0001).CONCLUSIONSThis multidisciplinary, evidence-based, neurosurgical ERAS protocol for elective craniotomy appears to have significant benefits over conventional perioperative management. Implementation of ERAS is associated with a significant reduction in the postoperative hospital stay and an acceleration in recovery, without increasing complication rates related to elective craniotomy. Further evaluation of this protocol in large multicenter studies is warranted.Clinical trial registration no.: ChiCTR-INR-16009662 (chictr.org.cn)
Background Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Microglial/macrophage activation and neuroinflammation are key cellular events following TBI, but the regulatory and functional mechanisms are still not well understood. Myeloid-epithelial-reproductive tyrosine kinase (Mer), a member of the Tyro-Axl-Mer (TAM) family of receptor tyrosine kinases, regulates multiple features of microglial/macrophage physiology. However, its function in regulating the innate immune response and microglial/macrophage M1/M2 polarization in TBI has not been addressed. The present study aimed to evaluate the role of Mer in regulating microglial/macrophage M1/M2 polarization and neuroinflammation following TBI. Methods The controlled cortical impact (CCI) mouse model was employed. Mer siRNA was intracerebroventricularly administered, and recombinant protein S (PS) was intravenously applied for intervention. The neurobehavioral assessments, RT-PCR, Western blot, magnetic-activated cell sorting, immunohistochemistry and confocal microscopy analysis, Nissl and Fluoro-Jade B staining, brain water content measurement, and contusion volume assessment were performed. Results Mer is upregulated and regulates microglial/macrophage M1/M2 polarization and neuroinflammation in the acute stage of TBI. Mechanistically, Mer activates the signal transducer and activator of transcription 1 (STAT1)/suppressor of cytokine signaling 1/3 (SOCS1/3) pathway. Inhibition of Mer markedly decreases microglial/macrophage M2-like polarization while increases M1-like polarization, which exacerbates the secondary brain damage and sensorimotor deficits after TBI. Recombinant PS exerts beneficial effects in TBI mice through Mer activation. Conclusions Mer is an important regulator of microglial/macrophage M1/M2 polarization and neuroinflammation, and may be considered as a potential target for therapeutic intervention in TBI.
Mild traumatic brain injury (mTBI) represents more than 80% of total TBI cases and is a robust environmental risk factor for neurodegenerative diseases including Alzheimer's disease (AD). Besides direct neuronal injury and neuroinflammation, bloodbrain barrier (BBB) dysfunction is also a hallmark event of the pathological cascades after mTBI. However, the vascular link between BBB impairment caused by mTBI and subsequent neurodegeneration remains undefined. In this review, we focus on the preclinical evidence from murine models of BBB dysfunction in mTBI and provide potential mechanistic links between BBB disruption and the development of neurodegenerative diseases.
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