Citations

Triggering receptor expressed on myeloid cells 2 (TREM2) is an innate immune receptor expressed in microglia in the brain. A soluble form of TREM2 (sTREM2) derived from proteolytic cleavage of the cell surface receptor is increased in the preclinical stages of AD and positively correlates with the amounts of total and phosphorylated tau in the cerebrospinal fluid. However, the physiological and pathological functions of sTREM2 remain unknown. Here, we show that sTREM2 promotes microglial survival in a PI3K/Akt-dependent manner and stimulates the production of inflammatory cytokines depending on NF-κB. Variants of sTREM2 carrying AD risk-associated mutations were less potent in both suppressing apoptosis and triggering inflammatory responses. Importantly, sTREM2 delivered to the hippocampi of both wild-type and Trem2-knockout mice elevated the expression of inflammatory cytokines and induced morphological changes of microglia. Collectively, these data indicate that sTREM2 triggers microglial activation inducing inflammatory responses and promoting survival. This study has implications for the pathogenesis of AD and provides insights into targeting sTREM2 pathway for AD therapy.

Findings from genetic, animal model, and human studies support the observation that accumulation of the β-amyloid (Aβ) peptide in the brain plays a central role in the pathogenic cascade of Alzheimer’s disease (AD). Human studies suggest that one key factor leading to accumulation is a defect in brain Aβ clearance. We have developed a novel microimmunoelectrode (MIE) to study the kinetics of Aβ clearance using an electrochemical approach. This is the first study using MIEs in vivo to measure rapid changes in Aβ levels in the brains of living mice. Extracellular, interstitial fluid (ISF) Aβ levels were measured in the hippocampus of APP/PS1 mice. Baseline levels of Aβ40 in the ISF are relatively stable and begin to decline within minutes of blocking Aβ production with a γ-secretase inhibitor. Pretreatment with a P-glycoprotein inhibitor, which blocks blood–brain barrier transport of Aβ, resulted in significant prolongation of Aβ40 half-life, but only in the latter phase of Aβ clearance from the ISF.

Deleting neuronal heparan sulfates in a mouse model of Alzheimer’s disease results in faster Aβ clearance, reduced Aβ aggregation, and less amyloid pathology.

ObjectiveApolipoprotein E (apoE), a major cholesterol carrier in the brain, is associated with a strong risk for Alzheimer disease. Compared to the risky APOE4 gene allele, the effects of the protective APOE2 gene allele are vastly understudied, and thus need to be further clarified.MethodsWe reviewed National Alzheimer's Coordinating Center clinical records and performed preclinical experiments using human apoE‐targeted replacement (apoE‐TR) mice, which do not show amyloid pathology.ResultsClinically, the APOE2 allele was associated with less cognitive decline during aging. This effect was also seen in subjects with little amyloid pathology, or after adjusting for Alzheimer disease‐related pathologies. In animal studies, aged apoE2‐TR mice also exhibited preserved memory function in water maze tests. Regardless, apoE2‐TR mice showed similar or greater age‐related changes in synaptic loss, neuroinflammation, and oxidative stress compared to apoE3‐TR or apoE4‐TR mice. Interestingly, apoE concentrations in the cortex, hippocampus, plasma, and cerebrospinal fluid (CSF) were positively correlated with memory performance across apoE isoforms, where apoE2‐TR mice had higher apoE levels. Moreover, apoE2‐TR mice exhibited the lowest levels of cholesterol in the cortex, despite higher levels in CSF and plasma. These cholesterol levels were associated with apoE levels and memory performance across apoE isoforms.InterpretationAPOE2 is associated with less cognitive decline during aging. This can occur independently of age‐related synaptic/neuroinflammatory changes and amyloid accumulation. Higher levels of apoE and associated cholesterol metabolism in APOE2 carriers might contribute to this protective effect. Ann Neurol 2016;79:758–774

Background and Purpose— Age-related changes in the cerebrovasculature, including blood–brain barrier (BBB) disruption, are emerging as potential risks for diverse neurological conditions. Because the accumulation of senescent cells in tissues is increasingly recognized as a critical step leading to age-related organ dysfunction, we evaluated whether senescent vascular cells are associated with compromised BBB integrity. Methods— Effects of vascular cell senescence on tight junction and barrier integrity were studied using an in vitro BBB model, composed of endothelial cells, pericytes, and astrocytes. In addition, tight junction coverage in microvessels and BBB integrity in BubR1 hypomorphic (BubR1 H/H ) mice, which display senescence cell-dependent phenotypes, were examined. Results— When an in vitro BBB model was constructed with senescent endothelial cells and pericytes, tight junction structure and barrier integrity (evaluated by transendothelial electric resistance and tracer efflux assay using sodium fluorescein and Evans blue-albumin were significantly impaired. Endothelial cells and pericytes from BubR1 H/H mice had increased senescent-associated β-galactosidase activity and p16 INK4a expression, demonstrating an exacerbation of senescence. The coverage by tight junction proteins in the cortical microvessels were reduced in BubR1 H/H mice, consistent with a compromised BBB integrity from permeability assays. Importantly, the coverage of microvessels by end-feet of aquaporin 4–immunoreactive astrocytes was not altered in the cortex of the BubR1 H/H mice. Conclusions— Our results indicate that accumulation of senescent vascular cells is associated with compromised BBB integrity, providing insights into the mechanism of BBB disruption related to biological aging.

Background and purposeLow density lipoprotein receptor related proteins (LRPs) 1 and 6 have been implicated in cerebral ischaemia. In addition, genetic variation in LRP1 and LRP6 has been linked with various factors that are related to risk of ischaemic stroke. The aim of this study was to examine the association of LRP1 and LRP6 gene variants with risk of ischaemic stroke as part of the Ischemic Stroke Genetics Study (ISGS).MethodsA Caucasian series (434 stroke patients, 319 controls) and an African American series (161 stroke patients, 116 controls) were included. Fourteen LRP6 variants and three LRP1 variants were genotyped and assessed for association with ischaemic stroke.ResultsIn the Caucasian series, significant associations with ischaemic stroke were observed for LRP6 rs2075241 [odds ratio (OR) 0.42, P = 0.023], rs2302685 (OR 0.44, P = 0.049), rs7975614 (OR 0.07, P = 0.017), rs10492120 (OR 0.62, P = 0.036) and rs10743980 (OR 0.66, P = 0.037). Risk of ischaemic stroke was significantly lower for carriers of any of these five protective LRP6 variants (24.0% of subjects) compared to non‐carriers (OR 0.57, P = 0.003). The protective association for LRP6 rs2075241 was observed at a similar magnitude across ischaemic stroke subtypes, whilst the effects of rs23022685, rs10492120 and rs10743980 were most apparent for cardioembolic and large vessel stroke. In the African American series, LRP1 rs11172113 was associated with an increased risk of stroke (OR 1.89, P = 0.006).ConclusionsThe results of our preliminary study provide evidence that LRP6 and LRP1 variants may be associated with risk of ischaemic stroke. Validation in larger studies is warranted.

Significance Endocytic sorting of amyloid precursor protein (APP) governed by the vacuolar protein sorting (Vps10) family of receptors plays a decisive role in controlling the outcome of APP proteolytic processing and the generation of amyloid β (Aβ) peptides, the key pathogenic factor of Alzheimer's disease (AD). This study provides the first evidence to our knowledge that a G protein-coupled receptor, namely, the α 2A adrenergic receptor, modulates APP endocytic sorting and promotes Aβ generation through disrupting APP interaction with a Vps10 family protein, sorting-related receptor with A repeat. Significantly, blockade of α 2A AR by a clinical antagonist reduces AD-related pathology and ameliorates cognitive deficits in an AD transgenic model, suggesting repurposing clinical α 2 AR antagonists as a new direction for AD treatment.

BACKGROUNDDespite targeted antiemetics, data support an unmet need related to the management of delayed nausea and vomiting (NV). Promising pilot data informed this phase III trial evaluating gabapentin for delayed NV from highly emetogenic chemotherapy (HEC).METHODSParticipants were randomized to receive prophylactic treatment with 20 mg of dexamethasone and a 5HT3 receptor antagonist (RA) on the day of chemotherapy, followed by gabapentin 300 mg twice a day and dexamethasone (dex) or placebo and dex after HEC. Gabapentin/placebo was started the day of chemotherapy and continued through day 5 for the first chemotherapy cycle, whereas dex was titrated down on days 2‐4. The primary end point was complete response (CR), defined as no emesis and no use of rescue medications on days 2‐6, using an NV diary. The percentages of those in each group with a CR were compared by Fisher's exact test.RESULTSFour hundred thirty patients were enrolled in this study. Forty‐seven percent of patients in the gabapentin arm and 41% in the placebo arm had a CR (P = .23). Mean number of emesis episodes was <0.5 daily, and mean nausea severity was < 2 (mild). In both arms, patient satisfaction with NV control was greater than 8 (with 10 being perfectly satisfied). There were no significant differences in unwanted side effects.CONCLUSIONSIn this study, gabapentin did not significantly improve delayed NV. Patients were satisfied with the control of their nausea and vomiting irrespective of arm. The use of a 5HT3 RA and dexamethasone provided good control of nausea and vomiting for most patients. Cancer 2014;120:3575–3583. © 2014 American Cancer Society.

Purpose Painful oral mucositis (OM) is a significant toxicity during radiotherapy for head and neck cancers. The aim of this randomized, double-blind, placebo-controlled trial was to test the efficacy of doxepin hydrochloride in the reduction of radiotherapy-induced OM pain. Patients and Methods In all, 155 patients were randomly allocated to a doxepin oral rinse or a placebo for the treatment of radiotherapy-related OM pain. Patients received a single dose of doxepin or placebo on day 1 and then crossed over to receive the opposite agent on a subsequent day. Pain questionnaires were administered at baseline and at 5, 15, 30, 60, 120, and 240 minutes. Patients were then given the option to continue doxepin. The primary end point was pain reduction as measured by the area under the curve (AUC) of the pain scale using data from day 1. Results Primary end point analysis revealed that the AUC for mouth and throat pain reduction was greater for doxepin (−9.1) than for placebo (−4.7; P < .001). Crossover analysis of patients completing both phases confirmed that patients experienced greater mouth and throat pain reduction with doxepin (intrapatient changes of 4.1 for doxepin-placebo arm and −2.8 for placebo-doxepin arm; P < .001). Doxepin was associated with more stinging or burning, unpleasant taste, and greater drowsiness than the placebo rinse. More patients receiving doxepin expressed a desire to continue treatment than did patients with placebo after completion of each of the randomized phases of the study. Conclusion A doxepin rinse diminishes OM pain. Further studies are warranted to determine its role in the management of OM.