Reduction of Leukocyte Microvascular Adherence and Preservation of Blood-Brain Barrier Function by Superoxide-Lowering Therapies in a Piglet Model of Neonatal Asphyxia.

Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical ( O 2 ⋅ _ ) promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removing O 2 ⋅ _ by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical. Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously. Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition of O 2 ⋅ _ production by oxypurinol, or elimination of O 2 ⋅ _ by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels. Conclusion: Using three different strategies to either prevent formation or enhance elimination of O 2 ⋅ _ during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lower O 2 ⋅ _ in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia.

Longitudinal Cerebrospinal Fluid Biomarker Changes in Preclinical Alzheimer Disease During Middle Age.

IMPORTANCE: Individuals in the presymptomatic stage of Alzheimer disease (AD) are increasingly being targeted for AD secondary prevention trials. How early during the normal life span underlying AD pathologies begin to develop, their patterns of change over time, and their relationship with future cognitive decline remain to be determined. OBJECTIVE: To characterize the within-person trajectories of cerebrospinal fluid (CSF) biomarkers of AD over time and their association with changes in brain amyloid deposition and cognitive decline in cognitively normal middle-aged individuals. DESIGN, SETTING, AND PARTICIPANTS: As part of a cohort study, cognitively normal (Clinical Dementia Rating [CDR] of 0) middle-aged research volunteers (n = 169) enrolled in the Adult Children Study at Washington University, St Louis, Missouri, had undergone serial CSF collection and longitudinal clinical assessment (mean, 6 years; range, 0.91-11.3 years) at 3-year intervals at the time of analysis, between January 2003 and November 2013. A subset (n = 74) had also undergone longitudinal amyloid positron emission tomographic imaging with Pittsburgh compound B (PiB) in the same period. Serial CSF samples were analyzed for ß-amyloid 40 (Aß40), Aß42, total tau, tau phosphorylated at threonine 181 (P-tau181), visinin-like protein 1 (VILIP-1), and chitinase-3-like protein 1 (YKL-40). Within-person measures were plotted according to age and AD risk defined by APOE genotype (ε4 carriers vs noncarriers). Linear mixed models were used to compare estimated biomarker slopes among middle-age bins at baseline (early, 45-54 years; mid, 55-64 years; late, 65-74 years) and between risk groups. Within-person changes in CSF biomarkers were also compared with changes in cortical PiB binding and progression to a CDR higher than 0 at follow-up. MAIN OUTCOMES AND MEASURES: Changes in Aß40, Aß42, total tau, P-tau181, VILIP-1, and YKL-40 and, in a subset of participants, changes in cortical PiB binding. RESULTS: While there were no consistent longitudinal patterns in Aß40 (P = .001-.97), longitudinal reductions in Aß42 were observed in some individuals as early as early middle age (P ≤ .05) and low Aß42 levels were associated with the development of cortical PiB-positive amyloid plaques (area under receiver operating characteristic curve = 0.9352; 95% CI, 0.8895-0.9808), especially in mid middle age (P < .001). Markers of neuronal injury (total tau, P-tau181, and VILIP-1) dramatically increased in some individuals in mid and late middle age (P ≤ .02), whereas the neuroinflammation marker YKL-40 increased consistently throughout middle age (P ≤ .003). These patterns were more apparent in at-risk ε4 carriers (Aß42 in an allele dose-dependent manner) and appeared to be associated with future cognitive deficits as determined by CDR. CONCLUSIONS AND RELEVANCE: Longitudinal CSF biomarker patterns consistent with AD are first detectable during early middle age and are associated with later amyloid positivity and cognitive decline. Such measures may be useful for targeting middle-aged, asymptomatic individuals for therapeutic trials designed to prevent cognitive decline.

Brain Imaging and Blood Biomarker Abnormalities in Children With Autosomal Dominant Alzheimer Disease: A Cross-Sectional Study.

IMPORTANCE: Brain imaging and fluid biomarkers are characterized in children at risk for autosomal dominant Alzheimer disease (ADAD). OBJECTIVE: To characterize and compare structural magnetic resonance imaging (MRI), resting-state and task-dependent functional MRI, and plasma amyloid-ß (Aß) measurements in presenilin 1 (PSEN1) E280A mutation-carrying and noncarrying children with ADAD. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional measures of structural and functional MRI and plasma Aß assays were assessed in 18 PSEN1 E280A carriers and 19 noncarriers aged 9 to 17 years from a Colombian kindred with ADAD. Recruitment and data collection for this study were conducted at the University of Antioquia and the Hospital Pablo Tobon Uribe in Medellín, Colombia, between August 2011 and June 2012. MAIN OUTCOMES AND MEASURES: All participants had blood sampling, structural MRI, and functional MRI during associative memory encoding and resting-state and cognitive assessments. Outcome measures included plasma Aß1-42 concentrations and Aß1-42:Aß1-40 ratios, memory encoding-dependent activation changes, resting-state connectivity, and regional gray matter volumes. Structural and functional MRI data were compared using automated brain mapping algorithms and search regions related to AD. RESULTS: Similar to findings in adult mutation carriers, in the later preclinical and clinical stages of ADAD, mutation-carrying children were distinguished from control individuals by significantly higher plasma Aß1-42 levels (mean [SD]: carriers, 18.8 [5.1] pg/mL and noncarriers, 13.1 [3.2] pg/mL; P < .001) and Aß1-42:Aß1-40 ratios (mean [SD]: carriers, 0.32 [0.06] and noncarriers, 0.21 [0.03]; P < .001), as well as less memory encoding task-related deactivation in parietal regions (eg, mean [SD] parameter estimates for the right precuneus were -0.590 [0.50] for noncarriers and -0.087 [0.38] for carriers; P < .005 uncorrected). Unlike carriers in the later stages, mutation-carrying children demonstrated increased functional connectivity of the posterior cingulate cortex with medial temporal lobe regions (mean [SD] parameter estimates were 0.038 [0.070] for noncarriers and 0.190 [0.057] for carriers), as well as greater gray matter volumes in temporal regions (eg, left parahippocampus; P < . 049, corrected for multiple comparisons). CONCLUSIONS AND RELEVANCE: Children at genetic risk for ADAD have functional and structural brain changes and abnormal levels of plasma Aß1-42. The extent to which the underlying brain changes are either neurodegenerative or developmental remains to be determined. This study provides additional information about the earliest known biomarker changes associated with ADAD.

Brain imaging and fluid biomarker analysis in young adults at genetic risk for autosomal dominant Alzheimer's disease in the presenilin 1 E280A kindred: a case-control study.

BACKGROUND: We have previously characterised functional brain abnormalities in young adults at genetic risk for late-onset Alzheimer's disease. To gain further knowledge on the preclinical phase of Alzheimer's disease, we sought to characterise structural and functional MRI, CSF, and plasma biomarkers in a cohort of young adults carrying a high-penetrance autosomal dominant mutation that causes early-onset Alzheimer's disease. METHODS: Between January and August, 2010, 18-26-year-old presenilin 1 (PSEN1) E280A mutation carriers and non-carriers from the Colombian Alzheimer's Prevention Initiative Registry in Medellín Antioquia, Colombia, had structural MRI, functional MRI during associative memory encoding and novel viewing and control tasks, and cognitive assessments. Consenting participants also had lumbar punctures and venepunctures. Outcome measures were task-dependent hippocampal or parahippocampal activations and precuneus or posterior cingulate deactivations, regional grey matter reductions, CSF Aß(1-42), total tau and phospho-tau(181) concentrations, and plasma Aß(1-42) concentrations and Aß(1-42):Aß(1-40) ratios. Structural and functional MRI data were compared using automated brain mapping algorithms and search regions related to Alzheimer's disease. Cognitive and fluid biomarkers were compared using Mann-Whitney tests. FINDINGS: 44 participants were included: 20 PSEN1 E280A mutation carriers and 24 non-carriers. The carrier and non-carrier groups did not differ significantly in their dementia ratings, neuropsychological test scores, or proportion of apolipoprotein E (APOE) ɛ4 carriers. Compared with non-carriers, carriers had greater right hippocampal and parahippocampal activation (p=0·001 and p<0·014, respectively, after correction for multiple comparisons), less precuneus and posterior cingulate deactivation (all p<0·010 after correction), and less grey matter in several parietal regions (all p<0·002 uncorrected and corrected p=0·009 in the right parietal search region). In the 20 participants (ten PSEN1 E280A mutation carriers and ten non-carriers) who had lumbar punctures and venepunctures, mutation carriers had higher CSF Aß(1-42) concentrations (p=0·008) and plasma Aß(1-42) concentrations (p=0·01) than non-carriers. INTERPRETATION: Young adults at genetic risk for autosomal dominant Alzheimer's disease have functional and structural MRI findings and CSF and plasma biomarker findings consistent with Aß(1-42) overproduction. Although the extent to which the underlying brain changes are either neurodegenerative or developmental remain to be determined, this study shows the earliest known biomarker changes in cognitively normal people at genetic risk for autosomal dominant Alzheimer's disease. FUNDING: Banner Alzheimer's Foundation, Nomis Foundation, Anonymous Foundation, Forget Me Not Initiative, Boston University Department of Psychology, Colciencias, National Institute on Aging, National Institute of Neurological Disorders and Stroke, and the State of Arizona.

Cerebrospinal fluid proteins predict longitudinal hippocampal degeneration in early-stage dementia of the Alzheimer type.

OBJECTIVE: Biomarkers are needed to improve the sensitivity and accuracy of diagnosis, and also prognosis, in individuals with early Alzheimer disease (AD). Measures of brain structure and disease-related proteins in the cerebrospinal fluid (CSF) have been proposed as biomarkers, yet relatively little is known about the relationships between such measures. The present study was conducted to assess the relationship between CSF Aß and tau protein levels and longitudinal measures of hippocampal structure in individuals with and without very mild dementia of the Alzheimer type. DESIGN: A single CSF sample and longitudinal magnetic resonance scans were collected. The CSF samples were assayed for tau, phosphorylated tau181 (p-tau181), Aß1-42, and Aß1-40 using an enzyme-linked immunosorbent assay. Large-deformation diffeomorphic metric mapping was used to generate hippocampal surfaces, and a composite hippocampal surface (previously constructed from 86 healthy participants) was used as a structural reference. PATIENTS OR OTHER PARTICIPANTS: Thirteen participants with very mild AD (Clinical Dementia Rating, CDR 0.5) and 11 cognitively normal participants (CDR 0). INTERVENTION: None. MAIN OUTCOME MEASURES: Initial and rate-of-change measures of total hippocampal volume and displacement of the hippocampal surface within zones overlying the CA1, subiculum, and CA2-4+DG cellular subfields, and their correlations with initial CSF measures. RESULTS: Lower CSF Αß1-42 levels and higher tau/Αß1-42 and p-tau181/Αß1-42 ratios were strongly correlated with decreases in hippocampal volume and measures of progressive inward deformations of the CA1 subfield in participants with early AD, but not in cognitively normal participants. CONCLUSIONS: Despite the small sample size, we found that Αß1-42 related and tau-related CSF measures were associated with hippocampal degeneration in individuals with clinically diagnosed early AD and may reflect an association with a common underlying disease mechanism.

Identification and validation of novel cerebrospinal fluid biomarkers for staging early Alzheimer's disease.

BACKGROUND: Ideally, disease modifying therapies for Alzheimer disease (AD) will be applied during the 'preclinical' stage (pathology present with cognition intact) before severe neuronal damage occurs, or upon recognizing very mild cognitive impairment. Developing and judiciously administering such therapies will require biomarker panels to identify early AD pathology, classify disease stage, monitor pathological progression, and predict cognitive decline. To discover such biomarkers, we measured AD-associated changes in the cerebrospinal fluid (CSF) proteome. METHODS AND FINDINGS: CSF samples from individuals with mild AD (Clinical Dementia Rating [CDR] 1) (n = 24) and cognitively normal controls (CDR 0) (n = 24) were subjected to two-dimensional difference-in-gel electrophoresis. Within 119 differentially-abundant gel features, mass spectrometry (LC-MS/MS) identified 47 proteins. For validation, eleven proteins were re-evaluated by enzyme-linked immunosorbent assays (ELISA). Six of these assays (NrCAM, YKL-40, chromogranin A, carnosinase I, transthyretin, cystatin C) distinguished CDR 1 and CDR 0 groups and were subsequently applied (with tau, p-tau181 and Aß42 ELISAs) to a larger independent cohort (n = 292) that included individuals with very mild dementia (CDR 0.5). Receiver-operating characteristic curve analyses using stepwise logistic regression yielded optimal biomarker combinations to distinguish CDR 0 from CDR>0 (tau, YKL-40, NrCAM) and CDR 1 from CDR<1 (tau, chromogranin A, carnosinase I) with areas under the curve of 0.90 (0.85-0.94 95% confidence interval [CI]) and 0.88 (0.81-0.94 CI), respectively. CONCLUSIONS: Four novel CSF biomarkers for AD (NrCAM, YKL-40, chromogranin A, carnosinase I) can improve the diagnostic accuracy of Aß42 and tau. Together, these six markers describe six clinicopathological stages from cognitive normalcy to mild dementia, including stages defined by increased risk of cognitive decline. Such a panel might improve clinical trial efficiency by guiding subject enrollment and monitoring disease progression. Further studies will be required to validate this panel and evaluate its potential for distinguishing AD from other dementing conditions.

SNPs associated with cerebrospinal fluid phospho-tau levels influence rate of decline in Alzheimer's disease.

Alzheimer's Disease (AD) is a complex and multifactorial disease. While large genome-wide association studies have had some success in identifying novel genetic risk factors for AD, case-control studies are less likely to uncover genetic factors that influence progression of disease. An alternative approach to identifying genetic risk for AD is the use of quantitative traits or endophenotypes. The use of endophenotypes has proven to be an effective strategy, implicating genetic risk factors in several diseases, including anemia, osteoporosis and heart disease. In this study we identify a genetic factor associated with the rate of decline in AD patients and present a methodology for identification of other such factors. We have used an established biomarker for AD, cerebrospinal fluid (CSF) tau phosphorylated at threonine 181 (ptau(181)) levels as an endophenotype for AD, identifying a SNP, rs1868402, in the gene encoding the regulatory sub-unit of protein phosphatase B, associated with CSF ptau(181) levels in two independent CSF series (P(combined) = 1.17 x 10(-05)). We show no association of rs1868402 with risk for AD or age at onset, but detected a very significant association with rate of progression of disease that is consistent in two independent series (P(combined) = 1.17 x 10(-05)). Our analyses suggest that genetic variants associated with CSF ptau(181) levels may have a greater impact on rate of progression, while genetic variants such as APOE4, that are associated with CSF Aß(42) levels influence risk and onset but not the rate of progression. Our results also suggest that drugs that inhibit or decrease tau phosphorylation may slow cognitive decline in individuals with very mild dementia or delay the appearance of memory problems in elderly individuals with low CSF Aß(42) levels. Finally, we believe genome-wide association studies of CSF tau/ptau(181) levels should identify novel genetic variants which will likely influence rate of progression of AD.

Absence of Pittsburgh compound B detection of cerebral amyloid beta in a patient with clinical, cognitive, and cerebrospinal fluid markers of Alzheimer disease: a case report.

BACKGROUND: To date, there have been no reports of individuals who have been characterized longitudinally using clinical and cognitive measures and who transitioned from cognitive normality to early symptomatic Alzheimer disease (AD) during a period when both cerebrospinal fluid (CSF) markers and Pittsburgh Compound B (PiB) amyloid imaging were obtained. OBJECTIVE: To determine the temporal relationships of clinical, cognitive, CSF, and PiB amyloid imaging markers of AD. DESIGN: Case report. SETTING: Alzheimer disease research center. PARTICIPANT: Longitudinally assessed 85-year-old man in a memory and aging study who was cognitively normal at his initial and next 3 annual assessments. MAIN OUTCOME MEASURES: Serial clinical and psychometric assessments over 6 years in addition to PiB imaging with positron emission tomography (PET) and CSF biomarker assays before autopsy. RESULTS: Decline in measures of episodic memory and, to a lesser degree, working memory began at about age 88 years. PiB PET amyloid imaging was negative at age 88(1/2) years, but at age 89(1/2) years there was reduced amyloid beta 42 and elevated levels of tau in the CSF. Beginning at age 89 years, very mild cognitive and functional decline reported by his collateral source resulted in a diagnosis of very mild dementia of the Alzheimer type. After death at age 91 years, the autopsy revealed foci of frequent neocortical diffuse amyloid beta plaques sufficient to fulfill Khachaturian neuropathologic criteria for definite AD, but other neuropathologic criteria for AD were not met because only sparse neuritic plaques and neurofibrillary tangles were present. Postmortem biochemical analysis of the cerebral tissue confirmed that PiB PET binding was below the level needed for in vivo detection. CONCLUSION: Clinical, cognitive, and CSF markers consistent with AD may precede detection of cerebral amyloid beta using amyloid imaging agents such as PiB that primarily label fibrillar amyloid beta plaques.

Cerebrospinal fluid biomarkers and rate of cognitive decline in very mild dementia of the Alzheimer type.

BACKGROUND: Cerebrospinal fluid (CSF) levels of Abeta peptide 1-42 (Abeta 42), tau, and phosphorylated tau (ptau) are potential biomarkers of Alzheimer disease. OBJECTIVE: To determine whether Abeta 42, tau, and ptau predict the rate of cognitive change in individuals with very mild dementia of the Alzheimer type (DAT). DESIGN: Retrospective analysis of CSF biomarkers and clinical data. SETTING: An academic Alzheimer disease research center. PARTICIPANTS: Research volunteers in a longitudinal study of aging and cognition. Participants (n = 49) had a clinical diagnosis of very mild DAT with a Clinical Dementia Rating (CDR) of 0.5 at the time of lumbar puncture. All the participants had at least 1 follow-up assessment (mean [SD] follow-up, 3.5 [1.8] years). MAIN OUTCOME MEASURES: Baseline CSF levels of Abeta 42, Abeta 40, tau, and ptau at threonine 181 (ptau181) and the rate of dementia progression as measured using the CDR sum of boxes (CDR-SB) score and psychometric performance. RESULTS: The rate of dementia progression was significantly more rapid in individuals with lower baseline CSF Abeta 42 levels, higher tau or ptau181 levels, or high tau: Abeta 42 ratios. For example, the annual change in the CDR-SB score was 1.1 for the lowest 2 tertiles of Abeta 42 values and 0.3 for the highest tertile of Abeta 42 values. CONCLUSIONS: In individuals with very mild DAT, lower CSF Abeta 42 levels, high tau or ptau181 levels, or high tau:Abeta 42 ratios quantitatively predict more rapid progression of cognitive deficits and dementia. Biomarkers of CSF may be useful prognostically and to identify individuals who are more likely to progress for participation in therapeutic clinical trials.

Neutrophil elastase and neurovascular injury following focal stroke and reperfusion.

Neutrophil elastase (NE) degrades basal lamina and extracellular matrix molecules, and recruits leukocytes during inflammation; however, a basic understanding of the role of NE in stroke pathology is lacking. We measured an increased number of extravascular NE-positive cells, as well as increased levels of tissue elastase protein and activity, following transient middle cerebral artery occlusion (tMCAo). Both pharmacologic inhibition of NE with ZN200355 (ZN), and genetic deletion of NE, significantly reduced infarct volume, blood-brain barrier disruption, vasogenic edema, and leukocyte-endothelial adherence 24 h after tMCAo. ZN also reduced infarct volume in MMP9-null mice following tMCAo. There were, however, no reductions in infarct volume or vasogenic edema in NE-null mice in two models of permanent middle cerebral artery occlusion. Our findings confirm the involvement of NE in neurovascular stroke pathology, when reperfusion allows neutrophils access to vulnerable brain, with pharmacologic or genetic inhibition of NE being both neuro- and vasculo-protective in this setting.

Decreased cerebrospinal fluid Abeta(42) correlates with brain atrophy in cognitively normal elderly.

OBJECTIVE: For therapies for Alzheimer's disease (AD) to have the greatest impact, it will likely be necessary to treat individuals in the "preclinical" (presymptomatic) stage. Fluid and neuroimaging measures are being explored as possible biomarkers of AD pathology that could aid in identifying individuals in this stage to target them for clinical trials and to direct and monitor therapy. The objective of this study was to determine whether cerebrospinal fluid (CSF) biomarkers for AD suggest the presence of brain damage in the preclinical stage of AD. METHODS: We investigated the relation between structural neuroimaging measures (whole-brain volume) and levels of CSF amyloid-beta (Abeta)(40), Abeta(42), tau, and phosphorylated tau(181) (ptau(181)), and plasma Abeta(40) and Abeta(42) in well-characterized research subjects with very mild and mild dementia of the Alzheimer type (n = 29) and age-matched, cognitively normal control subjects (n = 69). RESULTS: Levels of CSF tau and ptau(181), but not Abeta(42), correlated inversely with whole-brain volume in very mild and mild dementia of the Alzheimer type, whereas levels of CSF Abeta(42), but not tau or ptau(181), were positively correlated with whole-brain volume in nondemented control subjects. INTERPRETATION: Reduction in CSF Abeta(42), likely reflecting Abeta aggregation in the brain, is associated with brain atrophy in the preclinical phase of AD. This suggests that there is toxicity associated with Abeta aggregation before the onset of clinically detectable disease. Increases in CSF tau (and ptau(181)) are later events that correlate with further structural damage and occur with clinical onset and progression.

Cerebrospinal fluid tau and ptau(181) increase with cortical amyloid deposition in cognitively normal individuals: implications for future clinical trials of Alzheimer's disease.

Alzheimer's disease (AD) pathology is estimated to develop many years before detectable cognitive decline. Fluid and imaging biomarkers may identify people in early symptomatic and even preclinical stages, possibly when potential treatments can best preserve cognitive function. We previously reported that cerebrospinal fluid (CSF) levels of amyloid-beta(42) (Abeta(42)) serve as an excellent marker for brain amyloid as detected by the amyloid tracer, Pittsburgh compound B (PIB). Using data from 189 cognitively normal participants, we now report a positive linear relationship between CSF tau/ptau(181) (primary constituents of neurofibrillary tangles) with the amount of cortical amyloid. We observe a strong inverse relationship of cortical PIB binding with CSF Abeta(42) but not for plasma Abeta species. Some individuals have low CSF Abeta(42) but no cortical PIB binding. Together, these data suggest that changes in brain Abeta(42) metabolism and amyloid formation are early pathogenic events in AD, and that significant disruptions in CSF tau metabolism likely occur after Abeta(42) initially aggregates and increases as amyloid accumulates. These findings have important implications for preclinical AD diagnosis and treatment.

Apolipoprotein E levels in cerebrospinal fluid and the effects of ABCA1 polymorphisms.

BACKGROUND: Animal studies suggest that brain apolipoprotein E (apoE) levels influence amyloid-beta (Abeta) deposition and thus risk for Alzheimer's disease (AD). We have previously demonstrated that deletion of the ATP-binding cassette A1 transporter (ABCA1) in mice causes dramatic reductions in brain and cerebrospinal fluid (CSF) apoE levels and lipidation. To examine whether polymorphisms in ABCA1 affect CSF apoE levels in humans, we measured apoE in CSF taken from 168 subjects who were 43 to 91 years old and were either cognitively normal or who had mild AD. We then genotyped the subjects for ten previously identified ABCA1 single nucleotide polymorphisms (SNPs). RESULTS: In all subjects, the mean CSF apoE level was 9.09 microg/ml with a standard deviation of 2.70 microg/ml. Levels of apoE in CSF samples taken from the same individual two weeks apart were strongly correlated (r2 = 0.93, p < 0.01). In contrast, CSF apoE levels in different individuals varied widely (coefficient of variation = 46%). CSF apoE levels did not vary according to AD status, APOE genotype, gender or race. Average apoE levels increased with age by approximately 0.5 microg/ml per 10 years (r2 = 0.05, p = 0.003). We found no significant associations between CSF apoE levels and the ten ABCA1 SNPs we genotyped. Moreover, in a separate sample of 1225 AD cases and 1431 controls, we found no association between the ABCA1 SNP rs2230806 and AD as has been previously reported. CONCLUSION: We found that CSF apoE levels vary widely between individuals, but are stable within individuals over a two-week interval. AD status, APOE genotype, gender and race do not affect CSF apoE levels, but average CSF apoE levels increase with age. Given the lack of association between CSF apoE levels and genotypes for the ABCA1 SNPs we examined, either these SNPs do not affect ABCA1 function or if they do, they do not have strong effects in the CNS. Finally, we find no evidence for an association between the ABCA1 SNP rs2230806 and AD in a large sample set.

Inverse relation between in vivo amyloid imaging load and cerebrospinal fluid Abeta42 in humans.

OBJECTIVES: Amyloid-beta(42) (Abeta(42)) appears central to Alzheimer's disease (AD) pathogenesis and is a major component of amyloid plaques. Mean cerebrospinal fluid (CSF) Abeta(42) is decreased in dementia of the Alzheimer's type. This decrease may reflect plaques acting as an Abeta(42) "sink," hindering transport of soluble Abeta(42) between brain and CSF. We investigated this hypothesis. METHODS: We compared the in vivo brain amyloid load (via positron emission tomography imaging of the amyloid-binding agent, Pittsburgh Compound-B [PIB]) with CSF Abeta(42) and other measures (via enzyme-linked immunosorbent assay) in clinically characterized research subjects. RESULTS: Subjects fell into two nonoverlapping groups: those with positive PIB binding had the lowest CSF Abeta(42) level, and those with negative PIB binding had the highest CSF Abeta(42) level. No relation was observed between PIB binding and CSF Abeta(40), tau, phospho-tau(181), plasma Abeta(40), or plasma Abeta(42). Importantly, PIB binding and CSF Abeta(42) did not consistently correspond with clinical diagnosis; three cognitively normal subjects were PIB-positive with low CSF Abeta(42), suggesting the presence of amyloid in the absence of cognitive impairment (ie, preclinical AD). INTERPRETATION: These observations suggest that brain amyloid deposition results in low CSF Abeta(42), and that amyloid imaging and CSF Abeta(42) may potentially serve as antecedent biomarkers of (preclinical) AD.

Role of matrix metalloproteinases in apoptosis after transient focal cerebral ischemia in rats and mice.

The involvement of matrix metalloproteinases (MMPs) in cerebral ischemia-induced apoptosis was investigated in a model of transient focal cerebral ischemia in rats treated intracerebroventricularly (i.c.v.) with 4-((3-(4-phenoxylphenoxy)propylsulfonyl)methyl)-tetrahydropyran-4-carboxylic acid N-hydroxy amide, a broad spectrum non-peptidic hydroxamic acid MMP inhibitor, and in MMP-9-deficient mice. Our results showed that MMP inhibition reduced DNA fragmentation by 51% (P < 0.001) and cerebral infarct by 60% (P < 0.05) after ischemia. This protection was concomitant with a 29% reduction of cytochrome c release into the cytosol (P < 0.005) and a 54% reduction of calpain-related alpha-spectrin degradation (P < 0.05), as well as with an 84% increase in the immunoreactive signal of the native form of poly(ADP) ribose polymerase (P < 0.01). By contrast, specific targeting of the mmp9 gene in mice did reduce cerebral damage by 34% (P < 0.05) but did not modify the apoptotic response after cerebral ischemia. However, i.c.v. injection of MMP-9-deficient mice with the same broad-spectrum inhibitor used in rats significantly reduced DNA degradation by 32% (P < 0.05) and contributed even further to the protection of the ischemic brain. Together, our pharmacological and genetic results indicate that MMPs other than MMP-9 are actively involved in cerebral ischemia-induced apoptosis.

Multi-germ layer lineage central nervous system repair: nerve and vascular cell generation by embryonic stem cells transplanted in the injured brain.

OBJECT: To restore proper function to a damaged central nervous system (CNS) through transplantation, it is necessary to replace both neural and nonneural elements that arise from different germ layers in the embryo. Mounting evidence indicates the importance of signals related to vasculogenesis in governing neural proliferation and differentiation in early CNS development. Here, the authors examined whether embryonic stem cell (ESC)-derived progenitors can selectively generate both neural and endothelial cells after transplantation in the damaged CNS. METHODS: Injections of 20 nmol N-methyl-D-aspartate created a unilateral striatal injury in 7-day-old rats. One week postinjury, murine ESCs, neural-induced with retinoic acid, were transplanted into the injured striatum. Histological staining, laser confocal microscopy, and transmission electron microscopy of grafted ESCs were performed 1 week posttransplantation. CONCLUSIONS: Transplanted ESCs differentiated into neural cells, which segregated into multiple pools and formed neurons that conformed to host cytoarchitecture. The ESCs also generated endothelial cells, which integrated with host cells to form chimeric vasculature. The combination of ESC pluripotentiality and multiple germ layer differentiation provides a new conceptual framework for CNS repair.

Leukocyte-derived matrix metalloproteinase-9 mediates blood-brain barrier breakdown and is proinflammatory after transient focal cerebral ischemia.

Results of recent studies reveal vascular and neuroprotective effects of matrix metalloproteinase-9 (MMP-9) inhibition and MMP-9 gene deletion in experimental stroke. However, the cellular source of MMP-9 produced in the ischemic brain and the mechanistic basis of MMP-9-mediated brain injury require elucidation. In the present study, we used MMP-9-/- mice and chimeric knockouts lacking either MMP-9 in leukocytes or in resident brain cells to test the hypothesis that MMP-9 released from leukocytes recruited to the brain during postischemic reperfusion contributes to this injury phenotype. We also tested the hypothesis that MMP-9 promotes leukocyte recruitment to the ischemic brain and thus is proinflammatory. The extent of blood-brain barrier (BBB) breakdown, the neurological deficit, and the volume of infarction resulting from transient focal stroke were abrogated to a similar extent in MMP-9-/- mice and in chimeras lacking leukocytic MMP-9 but not in chimeras with MMP-9-containing leukocytes. Zymography and Western blot analysis from these chimeras confirmed that the elevated MMP-9 expression in the brain at 24 h of reperfusion is derived largely from leukocytes. MMP-9-/- mice exhibited a reduction in leukocyte-endothelial adherence and a reduction in the number of neutrophils plugging capillaries and infiltrating the ischemic brain during reperfusion; microvessel immunopositivity for collagen IV was also preserved in these animals. These latter results document proinflammatory actions of MMP-9 in the ischemic brain. Overall, our findings implicate leukocytes, most likely neutrophils, as a key cellular source of MMP-9, which, in turn, promotes leukocyte recruitment, causes BBB breakdown secondary to microvascular basal lamina proteolysis, and ultimately contributes to neuronal injury after transient focal stroke.

Ischemia-reperfusion injury of retinal endothelium by cyclooxygenase- and xanthine oxidase-derived superoxide.

The formation of reactive oxygen species (ROS) may be important in the pathogenesis of microvascular dysfunction and injury in ischemic retinopathies. The authors hypothesized that retinal endothelial cells can generate injurious levels of superoxide radical in response to ischemia/reperfusion, that endothelial xanthine oxidase and cyclooxygenase are important enzymatic sources of superoxide radical under these conditions, and that superoxide scavengers and inhibitors of these enzymes can protect endothelium from ischemic injury. The authors used confluent cultures of mouse retinal endothelial cells (MREC) subjected to exogenously generated superoxide or simulated ischemia-reperfusion to test these hypotheses. Cell injury was assessed biochemically by lactate dehydrogenase release into the culture medium. MREC were injured in a duration-dependent fashion by exposure to the superoxide-generating mix of hypoxanthine and xanthine oxidase. Increasing periods of oxygen and glucose deprivation (OGD) for 5-9 hr followed by replenishment of substrates for 2 hr led to progressive increases in endothelial cell injury; a significant proportion of the injury occurred during the period of substrate replenishment. Significant MREC protection was achieved by the superoxide scavengers SOD (1000 U ml(-1)) and a carboxylic acid derivative of carboxyfullerene (10 microM), the xanthine oxidase inhibitors oxypurinol (100 microM) and diphenyleneiodonium (DPI) (100 n M), and the cyclooxygenase inhibitors indomethacin (300 microM) and ibuprofen (300 microM). It is concluded that MREC are vulnerable to auto-oxidative injury by superoxide radical generated following a period of OGD. Both xanthine oxidase- and cyclooxygenase-dependent pathways are important enzymatic sources of superoxide formation in this setting. These enzymes and the ROS produced from their activity may be viable therapeutic targets to reduce microvascular dysfunction and injury in ischemic retinopathies.