Apolipoprotein E ε4 disrupts oligodendrocyte differentiation by interfering with astrocyte-derived lipid transport.

Carriers of the APOE4 (apolipoprotein E ε4) variant of the APOE gene are subject to several age-related health risks, including Alzheimer's disease (AD). The deficient lipid and cholesterol transport capabilities of the APOE4 protein are one reason for the altered risk profile. In particular, APOE4 carriers are at elevated risk for sporadic AD. While deposits o misfolded proteins are present in the AD brain, white matter (WM) myelin is also disturbed. As myelin is a lipid- and cholesterol-rich structure, the connection to APOE makes considerable biological sense. To explore the APOE-WM connection, we have analyzed the impact of human APOE4 on oligodendrocytes (OLs) of the mouse both in vivo and in vitro. We find that APOE proteins is enriched in astrocytes but sparse in OL. In human APOE4 (hAPOE4) knock-in mice, myelin lipid content is increased but the density of major myelin proteins (MBP, MAG, and PLP) is largely unchanged. We also find an unexpected but significant reduction of cell density of the OL lineage (Olig2+ ) and an abnormal accumulation of OL precursors (Nkx 2.2+ ), suggesting a disruption of OL differentiation. Gene ontology analysis of an existing RNA-seq dataset confirms a robust transcriptional response to the altered chemistry of the hAPOE4 mouse brain. In culture, the uptake of astrocyte-derived APOE during Lovastatin-mediated depletion of cholesterol synthesis is sufficient to sustain OL differentiation. While endogenous hAPOE protein isoforms have no effects on OL development, exogenous hAPOE4 abolishes the ability of very low-density lipoprotein to restore myelination in Apoe-deficient, cholesterol-depleted OL. Our data suggest that APOE4 impairs myelination in the aging brain by interrupting the delivery of astrocyte-derived lipids to the oligodendrocytes. We propose that high myelin turnover and OL exhaustion found in APOE4 carriers is a likely explanation for the APOE-dependent myelin phenotypes of the AD brain.

Chemical exchange saturation transfer MRI detects myelin changes in cuprizone mouse model at 3T.

Chemical exchange saturation transfer (CEST) sensitively detects molecular alterations in the brain, such as relayed nuclear Overhauser effect (rNOE) CEST contrast at -3.5 ppm representing aliphatic protons in both lipids and proteins, and CEST contrast at 3.5 ppm correlating with amide proton in proteins. Myelin is rich in lipids and proteins, and therefore CEST can be explored as a biomarker for myelin pathology, which could contribute to the diagnosis and prognosis of multiple sclerosis (MS). In the current study, we investigate the specificity of aliphatic rNOE and the amide pool in myelin detection using the cuprizone (CPZ) mouse model, which recapitulates the demyelination and remyelination of MS. In this study, preclinical 3T MRI was performed in 19 male C57BL/6 mice. Mice in the normal control (NC) group (n = 9) were fed a normal diet for the whole course, while mice in the CPZ group (n = 10) were fed with CPZ for 10 weeks, followed by 4 weeks with a normal diet. The CEST contrast of rNOE (-3.5 ppm) and amide (3.5 ppm) in brain regions of the corpus callosum (CC) and the caudate putamen were compared. Statistical differences between the groups were calculated using two-way ANOVA. We observed significantly decreased rNOE (NC: 4.85% ± 0.09%/s vs. CPZ: 3.88% ± 0.18%/s, p = 0.007) and amide pool (NC: 3.20% ± 0.10%/s vs. CPZ: 2.46% ± 0.16%/s, p = 0.02) in the CC after 8 weeks on CPZ diet (p < 0.05). Moreover, the rNOE in the CPZ group recovered to a level comparable with the NC group at week 14 (p = 0.39), while amide remained at a level as low as that for the NC group (p = 0.051). Significant rNOE and amide changes, validated by immunohistochemistry results for demyelination and remyelination, demonstrate the huge potential of CEST for revealing myelin pathology, which has implications for MS identification at the clinical field strength of 3T.

Deep neural network based CEST and AREX processing: Application in imaging a model of Alzheimer's disease at 3 T.

PURPOSE: To optimize and apply deep neural network based CEST (deepCEST) and apparent exchange dependent-relaxation (deepAREX) for imaging the mouse brain with Alzheimer's disease (AD) at 3T MRI. METHODS: CEST and T1 data of central and anterior brain slices of 10 AD mice and 10 age-matched wild type (WT) mice were acquired at a 3T animal MRI scanner. The networks of deepCEST/deepAREX were optimized and trained on the WT data. The CEST/AREX contrasts of AD and WT mice predicted by the networks were analyzed and further validated by immunohistochemistry. RESULTS: After optimization and training on CEST data of WT mice, deepCEST/deepAREX could rapidly (~1 s) generate precise CEST and AREX results for unseen CEST data of AD mice, indicating the accuracy and generalization of the networks. Significant lower amide weighted (3.5 ppm) signal related to amyloid ß-peptide (Aß) plaque depositions, which was validated by immunohistochemistry results, was detected in both central and anterior brain slices of AD mice compared to WT mice. Decreased magnetization transfer (MT) signal was also found in AD mice especially in the anterior slice. CONCLUSION: DeepCEST/deepAREX could rapidly generate accurate CEST/AREX contrasts in animal study. The well-optimized deepCEST/deepAREX have potential for AD differentiation at 3T MRI.

ATM and ATR play complementary roles in the behavior of excitatory and inhibitory vesicle populations.

ATM (ataxia-telangiectasia mutated) and ATR (ATM and Rad3-related) are large PI3 kinases whose human mutations result in complex syndromes that include a compromised DNA damage response (DDR) and prominent nervous system phenotypes. Both proteins are nuclear-localized in keeping with their DDR functions, yet both are also found in cytoplasm, including on neuronal synaptic vesicles. In ATM- or ATR-deficient neurons, spontaneous vesicle release is reduced, but a drop in ATM or ATR level also slows FM4-64 dye uptake. In keeping with this, both proteins bind to AP-2 complex components as well as to clathrin, suggesting roles in endocytosis and vesicle recycling. The two proteins play complementary roles in the DDR; ATM is engaged in the repair of double-strand breaks, while ATR deals mainly with single-strand damage. Unexpectedly, this complementarity extends to these proteins' synaptic function as well. Superresolution microscopy and coimmunoprecipitation reveal that ATM associates exclusively with excitatory (VGLUT1+) vesicles, while ATR associates only with inhibitory (VGAT+) vesicles. The levels of ATM and ATR respond to each other; when ATM is deficient, ATR levels rise, and vice versa. Finally, blocking NMDA, but not GABA, receptors causes ATM levels to rise while ATR levels respond to GABA, but not NMDA, receptor blockade. Taken together, our data suggest that ATM and ATR are part of the cellular "infrastructure" that maintains the excitatory/inhibitory balance of the nervous system. This idea has important implications for the human diseases resulting from their genetic deficiency.

DNA damage-associated oligodendrocyte degeneration precedes amyloid pathology and contributes to Alzheimer's disease and dementia.

INTRODUCTION: In looking for novel non-amyloid-based etiologies for Alzheimer's disease, we explore the hypothesis that age-related myelin loss is an attractive explanation for age-associated cognitive decline and dementia. METHODS: We performed a meta-analysis of data in the National Alzheimer's Coordinating Center database accompanied by quantitative histopathology of myelin and oligodendrocytes (OLs) in frontal cortices of 24 clinically characterized individuals. Pathological findings were further validated in an Alzheimer's disease mouse model and in culture. RESULTS: Myelin lesions increased with cognitive impairment in an amyloid-independent fashion with signs of degeneration appearing before neuronal loss. Myelinating OLs in the gray matter showed greater vulnerability than those in white matter, and the degenerative changes correlated with evidence of DNA damage. Similar results were found in myelinating OL cultures where DNA damage caused aberrant OL cell cycle re-entry and death. DISCUSSION: We present the first comprehensive analysis of the cell biology of early myelin loss in sporadic Alzheimer's disease.

Re-imagining Alzheimer's disease - the diminishing importance of amyloid and a glimpse of what lies ahead.

Many have criticized the amyloid cascade hypothesis of Alzheimer's disease for its inconsistencies and failures to either accurately predict disease symptoms or guide the development of productive therapies. In addition to criticisms, however, we believe that the field would benefit from having alternative narratives and disease models that can either replace or function alongside of an amyloid-centric view of Alzheimer's. This review is an attempt to meet that need. We offer three experimentally verified amyloid-independent mechanisms, each of which plausibly contributes substantially to the aetiology of Alzheimer's disease: loss of DNA integrity, faulty cell cycle regulation, regression of myelination. We outline the ways in which the failure of each can contribute to AD initiation and progression, and review how, acting alone or in combination with each other, they are sufficient for explaining the full range of AD pathologies. Yet, these three alternatives represent only a few of the many non-amyloid mechanisms that can explain AD pathogenesis. Therefore instead of proposing a single 'alternative hypothesis' to the amyloid cascade theory, sporadic AD is pictured as the result of independent yet intersecting age-related pathologies that afflict the ageing human brain. This article is part of the series "Beyond Amyloid". Cover Image for this issue: doi. 10.1111/jnc.13823.

Intrinsic mechanisms underlying the neurotrophic activity of adipose derived stem cells.

Adipose derived stem cells (ADSC) can be differentiated into Schwann cell-like cells which enhance nerve function and regeneration. However, the signalling mechanisms underlying the neurotrophic potential of ADSC remain largely unknown. In this study, we hypothesised that ADSC, upon stimulation with a combination of growth factors, could rapidly produce brain derived neurotrophic factor (BDNF) with a similar molecular mechanism to that functioning in the nervous system. Within 48 h of stimulation, ADSC demonstrated potent neurotrophic effects on dorsal root ganglion neurons, at a magnitude equivalent to that of the longer term differentiated Schwann cell-like cells. Stimulated ADSC showed rapid up-regulation of the neuronal activity dependent promoter BDNF exon IV along with an augmented expression of full length protein encoding BDNF exon IX. BDNF protein was secreted at a concentration similar to that produced by differentiated Schwann cell-like cells. Stimulation also activated the BDNF expression gating transcription factor, cAMP responsive element binding (CREB) protein. However, blocking phosphorylation of CREB with the protein kinase A small molecule inhibitor H89 did not suppress secretion of BDNF protein. These results suggest rapid BDNF production in ADSC is mediated through multiple compensatory pathways independent of, or in addition to, the CREB neuronal activation cascade.

White matter hyperintensity genetic risk factor TRIM47 regulates autophagy in brain endothelial cells.

White matter hyperintensity (WMH) is strongly correlated with age-related dementia and hypertension, but its pathogenesis remains obscure. GWAS identified TRIM47 at 17q25 locus as a top genetic risk factor for WMH formation. TRIM family is a class of E3 ubiquitin ligase with pivotal functions in autophagy, which is critical for brain endothelial cell (ECs) remodeling during hypertension. We hypothesize that TRIM47 regulates autophagy and its loss-of-function disturbs cerebrovasculature. Based on transcriptomics and immunohistochemistry, TRIM47 is found selectively expressed by brain ECs in human and mouse, and its transcription is upregulated by artificially-induced autophagy while downregulated in hypertension-like conditions. Using in silico simulation, immunocytochemistry and super-resolution microscopy, we identified the highly conserved binding site between TRIM47 and the LIR (LC3-interacting region) motif of LC3B. Importantly, pharmacological autophagy induction increased Trim47 expression on mouse ECs (b.End3) culture, while silencing Trim47 significantly increased autophagy with ULK1 phosphorylation induction, transcription and vacuole formation. Together, we confirm that TRIM47 is an endogenous inhibitor of autophagy in brain ECs, and such TRIM47-mediated regulation connects genetic and physiological risk factors for WMH formation but warrants further investigation. SUMMARY STATEMENT: TRIM47, top genetic risk factor for white matter hyperintensity formation, is a negative regulator of autophagy in brain endothelial cells and implicates a novel cellular mechanism for age-related cerebrovascular changes.

Multiple CEST contrast imaging of nose-to-brain drug delivery using iohexol liposomes at 3T MRI.

Image guided nose-to-brain drug delivery provides a non-invasive way to monitor drug delivered to the brain, and the intranasal administration could increase effective dose via bypassing Blood Brain Barrier (BBB). Here, we investigated the imaging of liposome-based drug delivery to the brain via intranasal administration, in which the liposome could penetrate mucus and could be detected by chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) at 3T field strength. Liposomes were loaded with a computed tomography (CT) contrast agent, iohexol (Ioh-Lipo), which has specific amide protons exchanging at 4.3 ppm of Z-spectrum (or CEST spectrum). Ioh-Lipo generated CEST contrasts of 35.4% at 4.3 ppm, 1.8% at -3.4 ppm and 20.6% at 1.2 ppm in vitro. After intranasal administration, these specific CEST contrasts were observed in both olfactory bulb (OB) and frontal lobe (FL) in the case of 10% polyethylene glycol (PEG) Ioh-Lipo. We observed obvious increases in CEST contrast in OB half an hour after the injection of 10% PEG Ioh-Lipo, with a percentage increase of 62.0% at 4.3 ppm, 10.9% at -3.4 ppm and 25.7% at 1.2 ppm. Interestingly, the CEST map at 4.3 ppm was distinctive from that at -3.4 pm and 1.2 ppm. The highest contrast of 4.3 ppm was at the external plexiform layer (EPL) and the region between left and right OB (LROB), while the CEST contrast at -3.4 ppm had no significant difference among all investigated regions with slightly higher signal in olfactory limbus (OL, between OB and FL) and FL, as validated with histology. While no substantial increase of CEST contrast at 4.3 ppm, -3.4 ppm or 1.2 ppm was observed in OB and FL when 1% PEG Ioh-Lipo was administered. We demonstrated for the first time the feasibility of non-invasively detecting the nose-to-brain delivery of liposomes using CEST MRI. This multiple-contrast approach is necessary to image the specific distribution of iohexol and liposome simultaneously and independently, especially when designing drug carriers for nose-to-brain drug delivery.

Cuprizone drives divergent neuropathological changes in different mouse models of Alzheimer's disease.

Myelin degradation is a normal feature of brain aging that accelerates in Alzheimer's disease (AD). To date, however, the underlying biological basis of this correlation remains elusive. The amyloid cascade hypothesis predicts that demyelination is caused by increased levels of the ß-amyloid (Aß) peptide. Here we report on work supporting the alternative hypothesis that early demyelination is upstream of amyloid. We challenged two different mouse models of AD (R1.40 and APP/PS1) using cuprizone-induced demyelination and tracked the responses with both neuroimaging and neuropathology. In oppose to amyloid cascade hypothesis, R1.40 mice, carrying only a single human mutant APP (Swedish; APP SWE ) transgene, showed a more abnormal changes of magnetization transfer ratio and diffusivity than in APP/PS1 mice, which carry both APP SWE and a second PSEN1 transgene (delta exon 9; PSEN1 dE9 ). Although cuprizone targets oligodendrocytes (OL), magnetic resonance spectroscopy and targeted RNA-seq data in R1.40 mice suggested a possible metabolic alternation in axons. In support of alternative hypotheses, cuprizone induced significant intraneuronal amyloid deposition in young APP/PS1, but not in R1.40 mice, and it suggested the presence of PSEN deficiencies, may accelerate Aß deposition upon demyelination. In APP/PS1, mature OL is highly vulnerable to cuprizone with significant DNA double strand breaks (53BP1 + ) formation. Despite these major changes in myelin, OLs, and Aß immunoreactivity, no cognitive impairment or hippocampal pathology was detected in APP/PS1 mice after cuprizone treatment. Together, our data supports the hypothesis that myelin loss can be the cause, but not the consequence, of AD pathology. SIGNIFICANCE STATEMENT: The causal relationship between early myelin loss and the progression of Alzheimer's disease remains unclear. Using two different AD mouse models, R1.40 and APP/PS1, our study supports the hypothesis that myelin abnormalities are upstream of amyloid production and deposition. We find that acute demyelination initiates intraneuronal amyloid deposition in the frontal cortex. Further, the loss of oligodendrocytes, coupled with the accelerated intraneuronal amyloid deposition, interferes with myelin tract diffusivity at a stage before any hippocampus pathology or cognitive impairments occur. We propose that myelin loss could be the cause, not the consequence, of amyloid pathology during the early stages of Alzheimer's disease.

Apolipoprotein E ε4 Mediates Myelin Breakdown by Targeting Oligodendrocytes in Sporadic Alzheimer Disease.

White matter degradation in the frontal lobe is one of the earliest detectable changes in aging and Alzheimer disease. The ε4 allele of apolipoprotein E (APOE4) is strongly associated with such myelin pathology but the underlying cellular mechanisms remain obscure. We hypothesized that, as a lipid transporter, APOE4 directly triggers pathology in the cholesterol-rich myelin sheath independent of AD pathology. To test this, we performed immunohistochemistry on brain tissues from healthy controls, sporadic, and familial Alzheimer disease subjects. While myelin basic protein expression was largely unchanged, in frontal cortex the number of oligodendrocytes (OLs) was significantly reduced in APOE4 brains independent of their Braak stage or NIA-RI criteria. This high vulnerability of OLs was confirmed in humanized APOE3 or APOE4 transgenic mice. A gradual decline of OL numbers was found in the aging brain without associated neuronal loss. Importantly, the application of lipidated human APOE4, but not APOE3, proteins significantly reduced the formation of myelinating OL in primary cell culture derived from Apoe-knockout mice, especially in cholesterol-depleted conditions. Our findings suggest that the disruption of myelination in APOE4 carriers may represent a direct OL pathology, rather than an indirect consequence of amyloid plaque formation or neuronal loss.

Expanding the horizon of research into the pathogenesis of the white matter diseases: Proceedings of the 2021 Annual Workshop of the Albert Research Institute for White Matter and Cognition.

White matter pathologies are critically involved in the etiology of vascular cognitive impairment-dementia (VCID), Alzheimer's disease (AD), and Alzheimer's disease and related diseases (ADRD), and therefore need to be considered a treatable target ( Roseborough A, Hachinski V, Whitehead S. White matter degeneration - a treatable target? Roseborough et al. JAMA Neurol [Internet]. 2020 Apr 27;77(7):793-4, [1] . To help address this often-missed area of research, several workshops have been sponsored by the Leo and Anne Albert Charitable Trust since 2015, resulting in the incorporation of "The Albert Research Institute for White Matter and Cognition" in 2020. The first annual "Institute" meeting was held virtually on March 3-4, 2021. The Institute provides a forum and workspace for communication and support of the advancement of white matter science and research to better understand the evolution and prevention of dementia. It serves as a platform for young investigator development, to introduce new data and debate biology mechanisms and new ideas, and to encourage and support new research collaborations and directions to clarify how white matter changes, with other genetic and health risk factors, contribute to cognitive impairment. Similar to previous Albert Trust-sponsored workshops (Barone et al. in J Transl Med 14:1-14, [2]; Sorond et al. in GeroScience 42:81-96, [3]), established expert investigators were identified and invited to present. Opportunities to attend and present were also extended by invitation to talented research fellows and younger scientists. Also, updates on institute-funded research collaborations were provided and discussed. The summary that follows is a synopsis of topics and discussion covered in the workshop.

ATM loss disrupts the autophagy-lysosomal pathway.

ATM (ataxia telangiectasia mutated) protein is found associated with multiple organelles including synaptic vesicles, endosomes and lysosomes, often in cooperation with ATR (ataxia telangiectasia and Rad3 related). Mutation of the ATM gene results in ataxia-telangiectasia (A-T), an autosomal recessive disorder with defects in multiple organs including the nervous system. Precisely how ATM deficiency leads to the complex phenotypes of A-T, however, remains elusive. Here, we reported that part of the connection may lie in autophagy and lysosomal abnormalities. We found that ATM was degraded through the autophagy pathway, while ATR was processed by the proteasome. Autophagy and lysosomal trafficking were both abnormal in atm-/- neurons and the deficits impacted cellular functions such as synapse maintenance, neuronal survival and glucose uptake. Upregulated autophagic flux was observed in atm-/- lysosomes, associated with a more acidic pH. Significantly, we found that the ATP6V1A (ATPase, H+ transporting, lysosomal V1 subunit A) proton pump was an ATM kinase target. In atm-/- neurons, lysosomes showed enhanced retrograde transport and accumulated in the perinuclear regions. We attributed this change to an unexpected physical interaction between ATM and the retrograde transport motor protein, dynein. As a consequence, SLC2A4/GLUT4 (solute carrier family 4 [facilitated glucose transporter], member 4) translocation to the plasma membrane was inhibited and trafficking to the lysosomes was increased, leading to impaired glucose uptake capacity. Together, these data underscored the involvement of ATM in a variety of neuronal vesicular trafficking processes, offering new and therapeutically useful insights into the pathogenesis of A-T.Abbreviations: 3-MA: 3-methyladenine; A-T: ataxia-telangiectasia; ALG2: asparagine-linked glycosylation 2 (alpha-1,3-mannosyltransferase); AMPK: adenosine 5'-monophosphate (AMP)-activated protein kinase; ATG5: autophagy related 5; ATM: ataxia telangiectasia mutated; ATP6V1A: ATPase, H+ transporting, lysosomal V1 subunit A; ATR: ataxia-telangiectasia and Rad3 related; BFA1: bafilomycin A1; CC3: cleaved-CASP3; CGN: cerebellar granule neuron; CLQ: chloroquine; CN: neocortical neuron; CTSB: cathepsin B; CTSD: cathepsin D; DYNLL1: the light chain1 of dynein; EIF4EBP1/4E-BP1: eukaryotic translation initiation factor 4E binding protein 1; Etop: etoposide; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HBS: HEPES-buffered saline; HEPES: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; HOMER1: homer protein homolog 1; KU: KU-60019; LAMP1: lysosomal-associated membrane protein 1; LC3B-II: LC3-phosphatidylethanolamine conjugate; Lyso: lysosome; LysopH-GFP: lysopHluorin-GFP; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAP2: microtubule associated protein 2; MAPK14: mitogen-activated protein kinase 14; MAPK8/JNK1: mitogen-activated protein kinase 8; MCOLN1/TRPML1: mucolipin 1; OSBPL1A: oxysterol binding protein like 1A; PIKK: phosphatidylinositol 3 kinase related kinase; Rapa: rapamycin; RILP: rab interacting lysosomal protein; ROS: reactive oxygen species; SEM: standard error of mean; SLC2A4/GLUT4: solute carrier family 2 (facilitated glucose transporter), member 4; TSC2/tuberin: TSC complex subunit 2; ULK1: unc-51 like kinase 1; UPS: ubiquitin-proteasome system; VE: VE-822; WCL: whole-cell lysate; WT: wild type.

Transcriptome Profiling of Mouse Corpus Callosum After Cerebral Hypoperfusion.

White matter damage caused by cerebral hypoperfusion is a major hallmark of subcortical ischemic vascular dementia (SIVD), which is the most common subtype of vascular cognitive impairment and dementia (VCID) syndrome. In an aging society, the number of SIVD patients is expected to increase; however, effective therapies have yet to be developed. To understand the pathological mechanisms, we analyzed the profiles of the cells of the corpus callosum after cerebral hypoperfusion in a preclinical SIVD model. We prepared cerebral hypoperfused mice by subjecting 2-month old male C57BL/6J mice to bilateral carotid artery stenosis (BCAS) operation. BCAS-hypoperfusion mice exhibited cognitive deficits at 4 weeks after cerebral hypoperfusion, assessed by novel object recognition test. RNA samples from the corpus callosum region of sham- or BCAS-operated mice were then processed using RNA sequencing. A gene set enrichment analysis using differentially expressed genes between sham and BCAS-operated mice showed activation of oligodendrogenesis pathways along with angiogenic responses. This database of transcriptomic profiles of BCAS-hypoperfusion mice will be useful for future studies to find a therapeutic target for SIVD.

Altered d-glucose in brain parenchyma and cerebrospinal fluid of early Alzheimer's disease detected by dynamic glucose-enhanced MRI.

Altered cerebral glucose uptake is one of the hallmarks of Alzheimer's disease (AD). A dynamic glucose-enhanced (DGE) magnetic resonance imaging (MRI) approach was developed to simultaneously monitor d-glucose uptake and clearance in both brain parenchyma and cerebrospinal fluid (CSF). We observed substantially higher uptake in parenchyma of young (6 months) transgenic AD mice compared to age-matched wild-type (WT) mice. Notably lower uptakes were observed in parenchyma and CSF of old (16 months) AD mice. Both young and old AD mice had an obviously slower CSF clearance than age-matched WT mice. This resembles recent reports of the hampered CSF clearance that leads to protein accumulation in the brain. These findings suggest that DGE MRI can identify altered glucose uptake and clearance in young AD mice upon the emergence of amyloid plaques. DGE MRI of brain parenchyma and CSF has potential for early AD stratification, especially at 3T clinical field strength MRI.

Proceedings from the Albert Charitable Trust Inaugural Workshop on white matter and cognition in aging.

This third in a series of vascular cognitive impairment (VCI) workshops, supported by "The Leo and Anne Albert Charitable Trust," was held from February 8 to 12 at the Omni Resort in Carlsbad, CA. This workshop followed the information gathered from the earlier two workshops suggesting that we focus more specifically on brain white matter in age-related cognitive impairment. The Scientific Program Committee (Frank Barone, Shawn Whitehead, Eric Smith, and Rod Corriveau) assembled translational, clinical, and basic scientists with unique expertise in acute and chronic white matter injury at the intersection of cerebrovascular and neurodegenerative etiologies. As in previous Albert Trust workshops, invited participants addressed key topics related to mechanisms of white matter injury, biomarkers of white matter injury, and interventions to prevent white matter injury and age-related cognitive decline. This report provides a synopsis of the presentations and discussions by the participants, including the existing knowledge gaps and the delineation of the next steps towards advancing our understanding of white matter injury and age-related cognitive decline. Workshop discussions and consensus resulted in action by The Albert Trust to (1) increase support from biannual to annual "White Matter and Cognition" workshops; (2) provide funding for two collaborative, novel research grants annually submitted by meeting participants; and (3) coordinate the formation of the "Albert Research Institute for White Matter and Cognition." This institute will fill a gap in white matter science, providing white matter and cognition communications, including annual updates from workshops and the literature and interconnecting with other Albert Trust scientific endeavors in cognition and dementia, and providing support for newly established collaborations between seasoned investigators and to the development of talented young investigators in the VCI-dementia (VCID) and white matter cognition arena.

DNA damage in the oligodendrocyte lineage and its role in brain aging.

Myelination is a recent evolutionary addition that significantly enhances the speed of transmission in the neural network. Even slight defects in myelin integrity impair performance and enhance the risk of neurological disorders. Indeed, myelin degeneration is an early and well-recognized neuropathology that is age associated, but appears before cognitive decline. Myelin is only formed by fully differentiated oligodendrocytes, but the entire oligodendrocyte lineage are clear targets of the altered chemistry of the aging brain. As in neurons, unrepaired DNA damage accumulates in the postmitotic oligodendrocyte genome during normal aging, and indeed may be one of the upstream causes of cellular aging - a fact well illustrated by myelin co-morbidity in premature aging syndromes arising from deficits in DNA repair enzymes. The clinical and experimental evidence from Alzheimer's disease, progeroid syndromes, ataxia-telangiectasia and other conditions strongly suggest that oligodendrocytes may in fact be uniquely vulnerable to oxidative DNA damage. If this damage remains unrepaired, as is increasingly true in the aging brain, myelin gene transcription and oligodendrocyte differentiation is impaired. Delineating the relationships between early myelin loss and DNA damage in brain aging will offer an additional dimension outside the neurocentric view of neurodegenerative disease.

PGE2 released by primary sensory neurons modulates Toll-like receptor 4 activities through an EP4 receptor-dependent process.

Exogenous prostaglandin E2 (PGE2) displays mixed regulatory properties with regard to inflammatory gene expression in dorsal root ganglion (DRG) cells. We show here that endogenously-produced nanomolar concentrations of PGE2, such as that generated in response to Toll-like receptor 4 (TLR4) stimulation, inhibits both cyclooxygenase-2 (COX-2) and tumour necrosis factor alpha (TNFα) mRNA expression in DRG cells in an EP4 receptor-dependent manner. DRG neurons appear to be the major source of PGE2 in the DRG and likely serve as both an autocrine and paracrine system for limiting over-activation of both DRG neurons and glial cells in response to TLR4 stimulation.

Adipose tissue and bone marrow-derived stem cells react similarly in an ischaemia-like microenvironment.

Mesenchymal stem cells (MSCs) from adipose tissue and bone marrow are promising cell sources for autologous cell therapy of nerve injuries, as demonstrated by their intrinsic neurotrophic potential. However, extensive death of transplanted cells limits their full benefits. This study investigated the effects of ischaemia (metabolically induced by sodium azide and 2-deoxyglucose) and serum-derived mitogens on the viability and functional profile of MSCs in vitro. MSCs were more susceptible to combined, rather than individual, blockade of glycolysis and oxidative phosphorylation. Apoptosis and autophagy were involved in ischaemia-induced cell death. Chemical ischaemia alone and serum withdrawal alone induced a similar amount of cell death, with significantly different intracellular ATP maintenance. Combined ischaemia and serum deprivation had additive effects on cell death. Expression of the extracellular matrix (ECM) molecules laminin and fibronectin was attenuated under ischaemia and independent of serum level; however, BDNF and NGF levels remained relatively constant. Strong upregulation of VEGF and to a lesser extent angiopoietin-1 was observed under ischaemia but not in serum withdrawal conditions. Importantly, this study demonstrated similar reactions of MSCs derived from adipose and bone marrow tissue, in ischaemia-like and mitogen-deprived microenvironments in terms of viability, cellular energetics, cell death mechanisms and expression levels of various growth-promoting molecules. Also, the results suggest that ischaemia has a larger impact on the ability of MSCs to survive transplantation than withdrawal of mitogens.