A role for vessel-associated extracellular matrix proteins in multiple sclerosis pathology

Multiple sclerosis (MS) is unsurpassed for its clinical and pathological hetherogeneity, but the biological determinants of this variability are unknown. HLA-DRB1*15, the main genetic risk factor for MS, influences the severity and distribution of MS pathology. This study set out to unravel the molecular determinants of the heterogeneity of MS pathology in relation to HLA-DRB1*15 status. Shotgun proteomics from a discovery cohort of MS spinal cord samples segregated by HLA-DRB*15 status revealed overexpression of the extracellular matrix (ECM) proteins, biglycan, decorin, and prolargin in HLA-DRB*15-positive cases, adding to established literature on a role of ECM proteins in MS pathology that has heretofore lacked systematic pathological validation. These findings informed a neuropathological characterisation of these proteins in a large autopsy cohort of 41 MS cases (18 HLA-DRB1*15-positive and 23 HLA-DRB1*15-negative), and seven non-neurological controls on motor cortical, cervical and lumbar spinal cord tissue. Biglycan and decorin demonstrate a striking perivascular expression pattern in controls that is reduced in MS (-36.5%, p = 0.036 and - 24.7%, p = 0.039; respectively) in lesional and non-lesional areas. A concomitant increase in diffuse parenchymal accumulation of biglycan and decorin is seen in MS (p = 0.015 and p = 0.001, respectively), particularly in HLA-DRB1*15-positive cases (p = 0.007 and p = 0.046, respectively). Prolargin shows a faint parenchymal pattern in controls that is markedly increased in MS cases where a perivascular deposition pattern is observed (motor cortex +97.5%, p = 0.001; cervical cord +49.1%, p = 0.016). Our findings point to ECM proteins and the vascular interface playing a central role in MS pathology within and outside the plaque area. As ECM proteins are known potent pro-inflammatory molecules, their parenchymal accumulation may contribute to disease severity. This study brings to light novel factors that may contribute to the heterogeneity of the topographical variation of MS pathology.

ATP1A3 related disease manifesting as rapid onset dystonia-parkinsonism with prominent myoclonus and exaggerated startle

We report ATP1A3-associated rapid-onset dystonia-parkinsonism with an atypical presentation including myoclonus and exaggerated startle in four patients. Their prominence over parkinsonism prompted consideration of a syndromic diagnosis of myoclonus dystonia. ATP1α3 dysfunction in GABAergic neurons could explain these examination findings. The spectrum of ATP1A3-associated movement disorders includes myoclonus-dystonia.

Regional contribution of vascular dysfunction in white matter dementia: clinical and neuropathological insights

The maintenance of adequate blood supply and vascular integrity is fundamental to ensure cerebral function. A wide range of studies report vascular dysfunction in white matter dementias, a group of cerebral disorders characterized by substantial white matter damage in the brain leading to cognitive impairment. Despite recent advances in imaging, the contribution of vascular-specific regional alterations in white matter dementia has been not extensively reviewed. First, we present an overview of the main components of the vascular system involved in the maintenance of brain function, modulation of cerebral blood flow and integrity of the blood-brain barrier in the healthy brain and during aging. Second, we review the regional contribution of cerebral blood flow and blood-brain barrier disturbances in the pathogenesis of three distinct conditions: the archetypal white matter predominant neurocognitive dementia that is vascular dementia, a neuroinflammatory predominant disease (multiple sclerosis) and a neurodegenerative predominant disease (Alzheimer's). Finally, we then examine the shared landscape of vascular dysfunction in white matter dementia. By emphasizing the involvement of vascular dysfunction in the white matter, we put forward a hypothetical map of vascular dysfunction during disease-specific progression to guide future research aimed to improve diagnostics and facilitate the development of tailored therapies.

Brain biopsy in neurological disease of unknown etiology: A single-center 12-year retrospective analysis

There are no international guidelines for brain biopsy in neurological disease of unknown etiology, yet most practicing neurologists will encounter difficult cases in which biopsy is considered. This patient cohort is heterogenous, and it is unclear in which circumstances biopsy is most useful. We performed an audit of brain biopsies reviewed in our neuropathology department from 2010 to 2021. Of 9,488 biopsies, 331 biopsies undertaken for an undiagnosed neurological disease were identified. Where documented, the commonest symptoms were hemorrhage, encephalopathy, and dementia. 29% of biopsies were non-diagnostic. The most common clinically relevant findings on biopsy were infection, cerebral amyloid angiopathy with or without angiitis, and demyelination. Rarer conditions included CNS vasculitis, non-infectious encephalitis, and Creutzfeldt Jakob Disease. We highlight the value of brain biopsy in the workup of cryptogenic neurological disease despite recent advances in less invasive diagnostics.

BK polyomavirus associated progressive multifocal leukoencephalopathy in a person living with HIV

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease of the white matter central nervous system occurring in immunocompromised patients particularly those with T cell deficiency such as in HIV, haematological and solid organ malignancies and those taking immunomodulatory medications. PML is caused by JC virus however in rare cases BK virus has been isolated in the cerebral spinal fluid of patients presenting with PML.

In this case we describe a 49 year old man who presented to the emergency department with a 2 week history of progressive right sided weakness and dysarthria. His background history included HIV diagnosed in 2005, he had not engaged with care in the past 2 years and had not been taking anti-retroviral therapy (ART). Other past medical history included untreated hepatitis C. His CD4 count was 90 (11%) cells/mm³ on admission and his HIV viral load VL) was 141,000 copies/ml. Magnetic resonance imaging(MRI) showed a hypointense lesion on T1, hyperintense on T2 and FLAIR without diffusion restriction and without mass effect. A lumbar puncture was performed which confirmed JC virus was positive (PCR <50 copies/ml) and also revealed BK virus was positive (PCR 46,511 copies/ml). The patient was commenced on tenofovir alafenamide fumarate/emtricitabine/darunavir/cobicistat in combination with dolutegravir 50mg twice daily. On day 40 post commencement of ART the patient was readmitted with worsening of his right arm weakness and dysarthria. A repeat MRI was performed which showed the hyperdense lesion on T2 and FLAIR appeared slightly larger with some slight enhancement with gadolinium contrast but no other features suggesting PML immune reconstitution inflammatory syndrome (IRIS). The CD4 count had increased to 141(17%) and HIV VL had decreased to 85 copies/ml. A clinical diagnosis of PML IRIS was made and the patient was commenced on prednisolone 30mg BD which lead to an initial improvement in symptoms.

Interestingly in this case, both JC virus and BK virus were detected in the CSF of this patient with the level of JC virus being too low to quantify. BK virus was not detectable on peripheral serum sampling suggesting that BK virus is replicating in the CNS independent of other body sites. There have been 5 case reports in the literature of BK virus as the cause of PML.

Testing for BK virus should be considered in patients presenting with signs and symptoms of PML and encephalitis particularly when no other cause is found.

Paraneoplastic neurologic syndromes with multiple neural autoantibodies: A report of two cases

We present two patients who presented with classical paraneoplastic syndromes with multiple central nervous system (CNS) autoantibodies in each case. The presence of multiple antibodies made the detection of a malignancy more likely and both patients were subsequently diagnosed with small cell lung carcinoma (SCLC). We highlight that the presence of multiple CNS autoantibodies increases the likelihood of detecting a malignancy but that the clinical presentation and response to treatment can vary despite similar antibody profiles. Clinicians should be alert to the need to search for occult malignancy in patients with multiple CNS autoantibodies.

Rash developing after cessation of Daclizumab for relapsing remitting MS; a case series

Daclizumab, a monoclonal antibody directed against CD25, a subunit of the high-affinity IL-2 receptor, was licensed as a disease modifying therapy (DMT) for relapsing remitting multiple sclerosis in 2017. Interference with IL-2 signalling is hypothesised to modulate T cell function. For example it results in a preferential shift of innate lymphoid cell (ILC) into CD56^bright natural killer cells and a decrease in regulatory T Cells. We present three patients who developed urticarial papulovesicular rashes at a median of 3 months after discontinuation of Daclizumab. We propose an unexpected T cell mediated immune reaction as the cause.

New versus old: Implications of evolving diagnostic criteria for relapsing–remitting multiple sclerosis

The International Panel on Diagnosis of Multiple Sclerosis (MS) recently revised the 2010 McDonald criteria and made recommendations for revision, allowing for the earliest possible, accurate diagnosis of MS. For relapsing–remitting MS, positive, unmatched cerebrospinal fluid oligoclonal bands may substitute for dissemination in time. Symptomatic lesions, including brainstem and spinal cord, may demonstrate dissemination in space or in time if enhancing (with the exception of the optic nerve). Cortical and juxtacortical lesions are equivalent. In this retrospective analysis, we applied revised criteria to 250 patients previously diagnosed with relapsing–remitting MS according to 2010 criteria and assessed for change in diagnostic times. There was a significant improvement in time to diagnosis between 2010 and 2017 groups ( p < 0.01). Median time to diagnosis according to McDonald 2010 was 7.4 months, compared with 2.3 months for McDonald 2017. Use of cerebrospinal fluid results most frequently resulted in a reduction in time to diagnosis. Symptomatic gadolinium-enhancing lesions led to earliest diagnostic times.

Investigation of the Brain Biodistribution of the Lipoprotein-Associated Phospholipase A2 (Lp-PLA2) Inhibitor [18F]GSK2647544 in Healthy Male Subjects

Purpose

GSK2647544 is a potent and specific inhibitor of lipoprotein-associated phospholipase A₂ (Lp-PLA₂), which was in development as a potential treatment for Alzheimer’s disease (AD). In order to refine therapeutic dose predictions and confirm brain penetration, a radiolabelled form of the inhibitor, [¹⁸F]GSK2647544, was manufactured for use in a positron emission tomography (PET) biodistribution study.

Procedures

[¹⁸F]GSK2647544 was produced using a novel, copper iodide (Cu(I)) mediated, [¹⁸F]trifluoromethylation methodology. Healthy male subjects (n = 4, age range 34–42) received an oral dose of unlabelled GSK2647544 (100 mg) and after 2 h an intravenous (iv) injection of [¹⁸F]GSK2647544 (average injected activity and mass were 106 ± 47 MBq and 179 ± 55 μg, respectively) followed by dynamic PET scans for 120 min. Defined regions of interest (ROI) throughout the brain were used to obtain regional time-activity curves (TACs) and compartmental modelling analysis used to estimate the primary outcome measure, whole brain volume of distribution (V_T). Secondary PK and safety endpoints were also recorded.

Results

PET dynamic data were successfully obtained from all four subjects and there were no clinically significant variations of the safety endpoints. Inspection of the TACs indicated a relatively homogenous uptake of [¹⁸F]GSK2647544 across all the ROIs examined. The mean whole brain V_T was 0.56 (95 % CI, 0.41–0.72). Secondary PK parameters, C_max (geometric mean) and T_max (median), were 354 ng/ml and 1.4 h, respectively. Metabolism of GSK2647544 was relatively consistent across subjects, with 20–40 % of the parent compound [¹⁸F]GSK2647544 present after 120 min.

Conclusions

The study provides evidence that GSK2647544 is able to cross the blood brain barrier in healthy male subjects leading to a measurable brain exposure. The administered doses of GSK2647544 were well tolerated. Exploratory modelling suggested that a twice-daily dose of 102 mg, at steady state, would provide ~80 % trough inhibition of brain Lp-PLA₂ activity.

Trial Registration

Clintrials.gov: NCT01924858.

Electronic supplementary material

The online version of this article (doi:10.1007/s11307-016-0982-5) contains supplementary material, which is available to authorized users.

A 24-week study to evaluate the effect of rilapladib on cognition and cerebrospinal fluid biomarkers of Alzheimer's disease

Background

The lipoprotein-associated phospholipase A₂ inhibitor (Lp-PLA₂), rilapladib (SB659032), is being evaluated as a potential treatment to slow the progression of Alzheimer's disease (AD).

Methods

One hundred twenty-four subjects with possible mild AD and with neuroimaging evidence of cerebrovascular disease were randomized to placebo or 250-mg rilapladib once daily, for 24 weeks, in addition to stable background acetylcholinesterase inhibitor and/or memantine. The study assessed the safety and tolerability of rilapladib and its effects on cognition, mechanistic, and disease-related biomarkers. Although the overall intent behind the study was to take a broad exploratory view of the data, two primary end points of interest (cerebrospinal fluid [CSF] amyloid beta peptide 1–42 [Aβ_1–42] and CogState executive function/working memory [EF/WM] composite score at week 24) were prespecified in the analysis plan for inferential statistical analysis.

Results

Rilapladib was well tolerated with no significant safety concerns. A significant difference from placebo was observed for rilapladib on change from baseline in EF/WM (effect size, 0.45; P = .026). There was no significant difference between groups on the change from baseline in CSF Aβ_1–42 (P = .133). Preliminary evidence of effects was detected on other mechanistic (albumin quotient) and disease-related biomarkers (tau/P-tau and neurofilament light chain).

Conclusion

These data provide initial evidence supporting Lp-PLA₂ inhibition as a novel treatment for dementia.

Clinical Trial Registration

Clinicaltrials.gov identifier: NCT01428453.

Cholestenoic acids regulate motor neuron survival via liver X receptors

Cholestenoic acids are formed as intermediates in metabolism of cholesterol to bile acids, and the biosynthetic enzymes that generate cholestenoic acids are expressed in the mammalian CNS. Here, we evaluated the cholestenoic acid profile of mammalian cerebrospinal fluid (CSF) and determined that specific cholestenoic acids activate the liver X receptors (LXRs), enhance islet-1 expression in zebrafish, and increase the number of oculomotor neurons in the developing mouse in vitro and in vivo. While 3β,7α-dihydroxycholest-5-en-26-oic acid (3β,7α-diHCA) promoted motor neuron survival in an LXR-dependent manner, 3β-hydroxy-7-oxocholest-5-en-26-oic acid (3βH,7O-CA) promoted maturation of precursors into islet-1+ cells. Unlike 3β,7α-diHCA and 3βH,7O-CA, 3β-hydroxycholest-5-en-26-oic acid (3β-HCA) caused motor neuron cell loss in mice. Mutations in CYP7B1 or CYP27A1, which encode enzymes involved in cholestenoic acid metabolism, result in different neurological diseases, hereditary spastic paresis type 5 (SPG5) and cerebrotendinous xanthomatosis (CTX), respectively. SPG5 is characterized by spastic paresis, and similar symptoms may occur in CTX. Analysis of CSF and plasma from patients with SPG5 revealed an excess of the toxic LXR ligand, 3β-HCA, while patients with CTX and SPG5 exhibited low levels of the survival-promoting LXR ligand 3β,7α-diHCA. Moreover, 3β,7α-diHCA prevented the loss of motor neurons induced by 3β-HCA in the developing mouse midbrain in vivo.Our results indicate that specific cholestenoic acids selectively work on motor neurons, via LXR, to regulate the balance between survival and death.

Imaging as a biomarker in drug discovery for Alzheimer's disease: is MRI a suitable technology?

This review provides perspectives on the utility of magnetic resonance imaging (MRI) as a neuroimaging approach in the development of novel treatments for Alzheimer’s disease. These considerations were generated in a roundtable at a recent Wellcome Trust meeting that included experts from academia and industry. It was agreed that MRI, either structural or functional, could be used as a diagnostic, for assessing worsening of disease status, for monitoring vascular pathology, and for stratifying clinical trial populations. It was agreed also that MRI implementation is in its infancy, requiring more evidence of association with the disease states, test-retest data, better standardization across multiple clinical sites, and application in multimodal approaches which include other imaging technologies, such as positron emission tomography, electroencephalography, and magnetoencephalography.

Reference measurement procedures for Alzheimer's disease cerebrospinal fluid biomarkers: definitions and approaches with focus on amyloid β42

Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in clinical settings, research and drug trials. However, their broad-scale use on different technology platforms is hampered by the lack of standardization at the level of sample handling, determination of concentrations of analytes and the absence of well-defined performance criteria for in vitro diagnostic or companion diagnostic assays, which influences the apparent concentration of the analytes measured and the subsequent interpretation of the data. There is a need for harmonization of CSF AD biomarker assays that can reliably, across centers, quantitate CSF biomarkers with high analytical precision, selectivity and stability over long time periods. In this position paper, we discuss reference procedures for the measurement of CSF AD biomarkers, especially amyloid β42 and tau. We describe possible technical approaches, focusing on a selected reaction monitoring mass spectrometry assay as a candidate reference method for quantification of CSF amyloid β42.

Plasma lipoprotein-associated phospholipase A2 activity in Alzheimer's disease, amnestic mild cognitive impairment, and cognitively healthy elderly subjects: a cross-sectional study

Introduction

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a circulating enzyme with pro-inflammatory and oxidative activities associated with cardiovascular disease and ischemic stroke. While high plasma Lp-PLA₂ activity was reported as a risk factor for dementia in the Rotterdam study, no association between Lp-PLA₂ mass and dementia or Alzheimer's disease (AD) was detected in the Framingham study. The objectives of the current study were to explore the relationship of plasma Lp-PLA₂ activity with cognitive diagnoses (AD, amnestic mild cognitive impairment (aMCI), and cognitively healthy subjects), cardiovascular markers, cerebrospinal fluid (CSF) markers of AD, and apolipoprotein E (APOE) genotype.

Methods

Subjects with mild AD (n = 78) and aMCI (n = 59) were recruited from the Memory Clinic, University Hospital, Basel, Switzerland; cognitively healthy subjects (n = 66) were recruited from the community. Subjects underwent standardised medical, neurological, neuropsychological, imaging, genetic, blood and CSF evaluation. Differences in Lp-PLA₂ activity between the cognitive diagnosis groups were tested with ANOVA and in multiple linear regression models with adjustment for covariates. Associations between Lp-PLA₂ and markers of cardiovascular disease and AD were explored with Spearman's correlation coefficients.

Results

There was no significant difference in plasma Lp-PLA₂ activity between AD (197.1 (standard deviation, SD 38.4) nmol/min/ml) and controls (195.4 (SD 41.9)). Gender, statin use and low-density lipoprotein cholesterol (LDL) were independently associated with Lp-PLA₂ activity in multiple regression models. Lp-PLA₂ activity was correlated with LDL and inversely correlated with high-density lipoprotein (HDL). AD subjects with APOE-ε4 had higher Lp-PLA₂ activity (207.9 (SD 41.2)) than AD subjects lacking APOE-ε4 (181.6 (SD 26.0), P = 0.003) although this was attenuated by adjustment for LDL (P = 0.09). No strong correlations were detected for Lp-PLA₂ activity and CSF markers of AD.

Conclusion

Plasma Lp-PLA₂ was not associated with a diagnosis of AD or aMCI in this cross-sectional study. The main clinical correlates of Lp-PLA₂ activity in AD, aMCI and cognitively healthy subjects were variables associated with lipid metabolism.

Cerebrospinal fluid steroidomics: are bioactive bile acids present in brain?

In this study we have profiled the free sterol content of cerebrospinal fluid by a combination of charge tagging and liquid chromatography-tandem mass spectrometry. Surprisingly, the most abundant cholesterol metabolites were found to be C(27) and C(24) intermediates of the bile acid biosynthetic pathways with structures corresponding to 7alpha-hydroxy-3-oxocholest-4-en-26-oic acid (7.170 +/- 2.826 ng/ml, mean +/- S.D., six subjects), 3beta-hydroxycholest-5-en-26-oic acid (0.416 +/- 0.193 ng/ml), 7alpha,x-dihydroxy-3-oxocholest-4-en-26-oic acid (1.330 +/- 0.543 ng/ml), and 7alpha-hydroxy-3-oxochol-4-en-24-oic acid (0.172 +/- 0.085 ng/ml), and the C(26) sterol 7alpha-hydroxy-26-norcholest-4-ene-3,x-dione (0.204 +/- 0.083 ng/ml), where x is an oxygen atom either on the CD rings or more likely on the C-17 side chain. The ability of intermediates of the bile acid biosynthetic pathways to activate the liver X receptors (LXRs) and the farnesoid X receptor was also evaluated. The acidic cholesterol metabolites 3beta-hydroxycholest-5-en-26-oic acid and 3beta,7alpha-dihydroxycholest-5-en-26-oic acid were found to activate LXR in a luciferase assay, but the major metabolite identified in this study, i.e. 7alpha-hydroxy-3-oxocholest-4-en-26-oic acid, was not an LXR ligand. 7Alpha-hydroxy-3-oxocholest-4-en-26-oic acid is formed from 3beta,7alpha-dihydroxycholest-5-en-26-oic acid in a reaction catalyzed by 3beta-hydroxy-Delta(5)-C(27)-steroid dehydrogenase (HSD3B7), which may thus represent a deactivation pathway of LXR ligands in brain. Significantly, LXR activation has been found to reduce the symptoms of Alzheimer disease (Fan, J., Donkin, J., and Wellington C. (2009) Biofactors 35, 239-248); thus, cholesterol metabolites may play an important role in the etiology of Alzheimer disease.

Interaction of the amyloid imaging tracer FDDNP with hallmark Alzheimer's disease pathologies

The distinctive cortical uptake of the tracer (18)F-FDDNP (2-(1-{6-[(2-fluoroethyl(methyl)amino]-2-naphthyl}ethylidene)malononitrile) in Alzheimer's disease (AD) is believed to be because of its binding to both neurofibrillary tangles (NFTs) and highly fibrillar senile plaques. We therefore investigated the binding of a tracer concentration of (3)H-FDDNP to brain sections containing AD hallmark pathologies. Semi-adjacent sections were labelled with (3)H-PIB (Pittsburgh compound-B, 2-[4'-(methylamino)phenyl]-6-hydroxybenzothiazole) and (14)C-SB13 (4-N-methylamino-4'-hydroxystilbene) for comparison. Neocortical sections containing widespread senile plaques and cerebrovascular amyloid angiopathy, produced a sparse and weak labelling following incubation with (3)H-FDDNP. Furthermore, in sections containing NFTs, there was no overt labelling of the pathology by (3)H-FDDNP. In contrast, sections labelled with (3)H-PIB displayed extensive labelling of diffuse plaques, classical plaques, cerebrovascular amyloid angiopathy and NFTs. (14)C-SB13 produced a broadly similar binding pattern to PIB. Radioligand binding assays employing in vitro generated amyloid-beta peptide fibrils demonstrated a approximately 10-fold reduced affinity for (3)H-FDDNP (85.0 +/- 2.0 nM) compared with (3)H-PIB (8.5 +/- 1.3 nM). These data provide an alternative mechanistic explanation for the observed low cortical uptake of (18)F-FDDNP in AD; in that the ligand is only weakly retained by the hallmark neuropathology because of its low affinity for amyloid structures.

Discovering oxysterols in plasma: a window on the metabolome

While the proteome defines the expressed gene products, the metabolome results from reactions controlled by such gene products. Plasma represents an accessible "window" to the metabolome both in regard of availability and content. The wide range of the plasma metabolome, in terms of molecular diversity and abundance, makes its comprehensive analysis challenging. Here we demonstrate an analytical method designed to target one region of the metabolome, that is, oxysterols. Since the discovery of their biological activity as ligands to nuclear receptors there has been a reawakening of interest in oxysterols and their analysis. In addition, the oxysterols, 24S- and 27-hydroxycholesterol, are currently under investigation as potential biomarkers associated with neurodegenerative disorders such as Alzheimer's disease and multiple sclerosis; widespread analysis of these lipids in clinical studies will require the development of robust, sensitive and rapid analytical techniques. In this communication we present results of an investigation of the oxysterols content of human plasma using a newly developed high-performance liquid chromatography-mass spectrometry (HPLC-MS) method incorporating charge-tagging and high-resolution MS. The method has allowed the identification in plasma of monohydroxylated cholesterol molecules, 7alpha-, 24S-, and 27-hydroxycholesterol; the cholestenetriol 7alpha,27-dihydroxycholesterol; and 3beta-hydroxycholest-5-en-27-oic acid and its metabolite 3beta,7alpha-dihydroxycholest-5-en-27-oic acid. The methodology described is also applicable for the analysis of other sterols in plasma, that is, cholesterol, 7-dehydrocholesterol, and desmosterol, as well as cholesterol 5,6- seco-sterols and steroid hormones. Although involving derivatization, sample preparation is straightforward and chromatographic analysis rapid (17 min), while the MS method offers high sensitivity (ng/mL of sterol in plasma, or pg on-column) and specificity. The methodology is suitable for targeted metabolomic analysis of sterols, oxysterols, and steroid hormones opening a "window" to view this region of the metabolome.

In vitro high affinity alpha-synuclein binding sites for the amyloid imaging agent PIB are not matched by binding to Lewy bodies in postmortem human brain

Amyloid containing deposits are a defining neuropathological feature of a wide range of dementias and movement disorders. The positron emission tomography tracer PIB (Pittsburgh Compound-B, 2-[4′-(methylamino)phenyl]-6-hydroxybenzothiazole) was developed to target senile plaques, an amyloid containing pathological hallmark of Alzheimer's disease, formed from the amyloid-β peptide. Despite the fact that PIB was developed from the pan-amyloid staining dye thioflavin T, no detailed characterisation of its interaction with other amyloid structures has been reported. In this study, we demonstrate the presence of a high affinity binding site (K_d∼4 nM) for benzothiazole derivatives, including [3H]-PIB, on α-synuclein (AS) filaments generated in vitro, and further characterise this binding site through the use of radioligand displacement assays employing 4-N-methylamino-4′-hydroxystilbene (SB13) (K_i = 87 nM) and 2-(1-{6-[(2-fluoroethyl(methyl)amino]-2-naphthyl}ethylidene)malononitrile (FDDNP) (K_i = 210 nM). Despite the presence of a high-affinity binding site on AS filaments, no discernible interaction of [3H]-PIB was detected with amygdala sections from Parkinson's disease cases containing frequent AS-immunoreactive Lewy bodies and related neurities. These findings suggest that the density and/or accessibility of AS binding sites in vivo are significantly less than those associated with amyloid-β peptide lesions. Lewy bodies pathology is therefore unlikely to contribute significantly to the retention of PIB in positron emission tomography imaging studies.

J. Neurochem. (2008) 105, 1428–1437.

PIB is a non-specific imaging marker of amyloid-beta (Abeta) peptide-related cerebral amyloidosis

The in vivo imaging probe [11C]-PIB (Pittsburgh Compound B, N-methyl[11C]2-(4'-methylaminophenyl-6-hydroxybenzathiazole) is under evaluation as a key imaging tool in Alzheimer's disease (AD) and to date has been assumed to bind with high affinity and specificity to the amyloid structures associated with classical plaques (CPs), one of the pathological hallmarks of the disease. However, no studies have systematically investigated PIB binding to human neuropathological brain specimens at the tracer concentrations achieved during in vivo imaging scans. Using a combination of autoradiography and histochemical techniques, we demonstrate that PIB, in addition to binding CPs clearly delineates diffuse plaques and cerebrovascular amyloid angiopathy (CAA). The interaction of PIB with CAA was not fully displaceable and this may be linked to the apolipoprotein E-epsilon4 allele. PIB was also found to label neurofibrillary tangles, although the overall intensity of this binding was markedly lower than that associated with the amyloid-beta (Abeta) pathology. The data provide a molecular explanation for PIB's limited specificity in diagnosing and monitoring disease progression in AD and instead indicate that the ligand is primarily a non-specific marker of Abeta-peptide related cerebral amyloidosis.

Imaging Alzheimer's disease pathology: one target, many ligands

Over the past five years there has been a surge of interest in using positron emission tomography (PET) to determine the in vivo density of the senile plaque, a key pathological feature of Alzheimer's disease. The development of the tracers [(11)C]-PIB, [(11)C]-SB13 and [(18)F]-FDDNP has coincided with drug strategies aimed at altering the brain metabolism of amyloid-beta peptides. The evolution of these novel ligands serves not only as an excellent example of how rapidly imaging technologies can progress but also as a reminder that the fundamental biological knowledge, which is necessary to fully interpret the PET data, can be left trailing behind.

Characterisation of the binding of amyloid imaging tracers to rodent Abeta fibrils and rodent-human Abeta co-polymers

Despite the application of amyloid imaging agents such as PIB, SB13, and FDDNP in Alzheimer's disease (AD) patients, the successful use of these agents in transgenic mice models of AD has not been reported to date. As a first step in understanding the behaviour of these ligands in transgenic models of AD, we have investigated in a series of in vitro ligand binding assays the interaction of selected agents, including PIB, FDDNP, SB13, and BSB, with amyloid fibrils produced from rodent Abeta(1-40) (roAbeta) peptide. The data indicate that the ligand binding affinities together with the pattern and number of binding sites on the roAbeta fibrils are broadly conserved with that reported previously for human Abeta(1-40) (huAbeta) fibrils. However, characterisation of huAbeta fibrils formed in the presence of increasing amounts of roAbeta (1, 5, 10% w/w) demonstrated a dose-dependent reduction in the number of high affinity [(3)H]Me-BTA-1 binding sites such that at the highest amount of roAbeta the specific signal was reduced by approximately 95%. These studies suggest that (i) the presence of small amounts of roAbeta in huAbeta fibrils has the potential to cause subtle ultrastructural alterations in the polymers and (ii) the weak binding signal observed in vivo in the transgenic mouse models of AD may in part be due to the decreased number of high affinity binding sites on the Abeta fibrils.

Fluorinase mediated C–18F bond formation, an enzymatic tool for PET labelling

The fluorinase enzyme from S. cattleya is applied as a catalyst for the efficient incorporation of [18F]-fluoride into [18F]-5'-fluoro-5'-deoxyadenosine, [18F]-5'-fluoro-5'-deoxyinosine and [18F]-5-fluoro-5-deoxyribose for positron emission tomography (PET) applications.

Delineation of positron emission tomography imaging agent binding sites on beta-amyloid peptide fibrils

A range of imaging agents for use in the positron emission tomography of Alzheimer's disease is currently under development. Each of the main compound classes, derived from thioflavin T (PIB), Congo Red (BSB), and aminonaphthalene (FDDNP) are believed to bind to mutually exclusive sites on the beta-amyloid (Abeta) peptide fibrils. We recently reported the presence of three classes of binding sites (BS1, BS2, BS3) on the Abeta fibrils for thioflavin T derivatives and now extend these findings to demonstrate that these sites are also able to accommodate ligands from the other chemotype classes. The results from competition assays using [3H]Me-BTA-1 (BS3 probe) indicated that both PIB and FDDNP were able to displace the radioligand with Ki values of 25 and 42 nM, respectively. BSB was unable to displace the radioligand tracer from the Abeta fibrils. In contrast, each of the compounds examined were able to displace thioflavin T (BS1 probe) from the Abeta fibrils when evaluated in a fluorescence competition assay with Ki values for PIB, FDDNP, and BSB of 1865, 335, and 600 nM, respectively. Finally, the Kd values for FDDNP and BSB binding to Abeta fibrils were directly determined by monitoring the increases in the ligand intrinsic fluorescence, which were 290 and 104 nM, respectively. The results from these assays indicate that (i) the three classes of thioflavin T binding sites are able to accommodate a wide range of chemotype structures, (ii) BSB binds to two sites on the Abeta fibrils, one of which is BS2, and the other is distinct from the thioflavin T derivative binding sites, and (iii) there is no independent binding site on the fibrils for FDDNP, and the ligand binds to both the BS1 and BS3 sites with significantly lower affinities than previously reported.

Evidence for the presence of three distinct binding sites for the thioflavin T class of Alzheimer's disease PET imaging agents on beta-amyloid peptide fibrils

Imaging the progression of Alzheimer's disease would greatly facilitate the discovery of therapeutics, and a wide range of ligands are currently under development for the detection of beta-amyloid peptide (Abeta)-containing plaques by using positron emission tomography. Here we report an in-depth characterization of the binding of seven previously described ligands to in vitro generated Abeta-(1-40) polymers. All of the compounds were derived from the benzothiazole compound thioflavin T and include 2-[4'-(methylamino)phenyl]benzothiazole and 2-(4'-dimethylamino-)phenyl-imidazo[1,2-a]-pyridine derivatives, 2-[4'-(dimethylamino)phenyl]-6-iodobenzothiazole and 2-[4'-(4''-methylpiperazin-1-yl)phenyl]-6-iodobenzothiazole, and a benzofuran compound (5-bromo-2-(4-dimethylaminophenyl)benzofuran). By using a range of fluorescent and radioligand binding assays, we find that these compounds display a more complex binding pattern than described previously and are consistent with three classes of binding sites on the Abeta fibrils. All of the compounds bound with very high affinity (low nm K(d)) to a low capacity site (BS3) (1 ligand-binding site per approximately 300 Abeta-(1-40) monomers) consistent with the previously recognized binding site for these compounds on the fibrils. However, the compounds also bound with high affinity (K(d) approximately 100 nm) to either one of two additional binding sites on the Abeta-(1-40) polymer. The properties of these sites, BS1 and BS2, suggest they are adjacent or partially overlapping and have a higher capacity than BS3, occurring every approximately 35 or every approximately 4 monomers of Abeta-(1-40)-peptide, respectively. Compounds appear to display selectivity for BS2 based on the presence of a halogen substitution (2-[4'-(dimethylamino)phenyl]-6-iodobenzothiazole, 2-[4'-(4''-methylpiperazin-1-yl)phenyl]-6-iodobenzothiazole, and 5-bromo-2-(4-dimethylaminophenyl)benzofuran) on their aromatic ring system. The presence of additional ligand-binding sites presents potential new targets for ligand development and may allow a more complete modeling of the current positron emission tomography data.

Kinesin heads fused to hinge-free myosin tails drive efficient motility

The rat kinesin motor domain was fused at residues 433, 411, 376 or 367, respectively, to the C-terminal 1185, 1187, 1197 or 1185 residues of the brush border myosin tail. In motility assays, K433myt and K411myt, which preserve the head-proximal kinesin hinge, and K367myt, which deletes it, drove rapid microtubule sliding ( approximately 0.6 microms(-1)) that was optimal when the head-pairs were spaced apart by adding 1:1 headless myosin tails. K376myt, which partially deletes the head-proximal hinge, showed poor motility in sliding assays but wild type processivity, velocity and stall force in single molecule optical trapping. Accordingly, the head-proximal kinesin hinge is functionally dispensable.

PPARgamma activation enhances cell surface ENaCalpha via up-regulation of SGK1 in human collecting duct cells

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent transcription factor that belongs to the nuclear receptor family that plays a critical role in adipocyte differentiation and lipid metabolism. Here we report for the first time that PPARgamma is expressed in human renal cortical collecting ducts (CCD), segments of the nephor involved in regulation of sodium and water homeostasis via action of the epithelial sodium channel (ENaC). ENaC activity is regulated by the hormones aldosterone and insulin, primarily through co-ordinate actions on serum and glucocorticoid regulated kinase 1 (SGK1). We show that SGK1 activity is stimulated by treatment of a human CCD cell line with PPARgamma agonists, paralleled by an increase in SGK1 mRNA that is abolished by pretreatment with a specific PPARgamma antagonist, and that this leads to increased levels of cell surface ENaCalpha. Electrophoretic mobility shift assays suggest that these effects are caused by binding of PPARgamma to a specific response element in the SGK1 promoter. Our results identify SGK1 as a target for PPARgamma and suggest a novel role for PPARgamma in regulation of sodium re-absorption in the CCD via stimulation of ENaC activity. This pathway may play a role in sodium retention caused by activation of PPARgamma in man.

The peripheral benzodiazepine receptor ligand PK11195 binds with high affinity to the acute phase reactant alpha1-acid glycoprotein: implications for the use of the ligand as a CNS inflammatory marker

The peripheral benzodiazepine receptor ligand PK11195 has been used as an in vivo marker of neuroinflammation in positron emission tomography studies in man. One of the methodological issues surrounding the use of the ligand in these studies is the highly variable kinetic behavior of [(11)C]PK11195 in plasma. We therefore undertook a study to measure the binding of [(3)H]PK11195 to whole human blood and found a low level of binding to blood cells but extensive binding to plasma proteins. Binding assays using [(3)H]PK11195 and purified human plasma proteins demonstrated a strong binding to alpha1-acid glycoprotein (AGP) and a much weaker interaction with albumin. Immunodepletion of AGP from plasma resulted in the loss of plasma [(3)H]PK11195 binding demonstrating: (i) the specificity of the interaction and (ii) that AGP is the major plasma protein to which PK11195 binds with high affinity. PK11195 was able to displace fluorescein-dexamethasone from AGP with IC(50) of <1.2 microM, consistent with a high affinity interaction. These findings are important for understanding the behavior of the ligand in positron emission tomography studies for three reasons. Firstly, AGP is an acute phase protein and its levels will vary during infection and pathological inflammatory diseases such as multiple sclerosis. This could significantly alter the free plasma concentrations of the ligand and contribute to its variable kinetic behavior. Secondly, AGP and AGP-bound ligand may contribute to the access of [(11)C]PK11195 to the brain parenchyma in diseases with blood brain barrier breakdown. Finally, local synthesis of AGP at the site of brain injury may contribute the pattern of [(11)C]PK11195 binding observed in neuroinflammatory diseases.

The mandibular canal of the edentulous jaw

The morphology of the mandibular canal after loss of teeth has received little detailed attention. Improved documentation of this topic would allow better interpretation of dental radiographs and would enable those engaged in tooth implantation to better understand the nature of the tissue into which the prostheses are placed. In this study on mandibles from seven dissecting room cadavers panoramic radiographs usually showed the mandibular canal clearly, an incisive canal less so. The wall of the mandibular canal was similar in dentate and edentulous mandibles, and was highly perforated, as suggested by Cryer (Anderson et al., 1991). In edentulous specimens, it was composed mainly of cancellous bone with only occasional single osteons. The inferior alveolar nerve near the mandibular foramen was a large trunk, consisting of three to four nerve bundles with connective tissue sheaths. It became more loosely arranged toward the mental foramen. Medial to the mental foramen, the nerves were frequently in the form of small bundles in the marrow. Any incisive canal was ill-defined and neurovascular bundles, when present, ran through a labyrinth of intertrabecular spaces.

Physiological aspects of pig-to-primate renal xenotransplantation

BACKGROUND

Few data exist on the physiological aspects of pig-to-primate renal xenotransplantation.

METHODS

Use of organs transgenic for human decay accelerating factor has allowed assessment of the metabolic and hormonal functions of these xenografts.

RESULTS

Porcine renal xenografts largely maintain plasma electrolyte homeostasis. An increase in proteinuria was detected that may result from graft injury. In contrast to allotransplantation a severe anaemia developed requiring recipient treatment with exogenous human erythropoietin.

CONCLUSIONS

Our experience provides qualified encouragement for the likely physiological compatibility of pig and primate species, but identifies areas where a xenograft may not match the performance of an allograft.

[Epidemiological study of genetic and environmental factors in asthma, bronchial hyperresponsiveness and atopy. Protocol and potential selection bias]

BACKGROUND

The EGEA study combines a case-control study and a family study to assess genetic and environmental risk factors and their interactions for asthma, bronchial hyperresponsiveness and atopy. Information is scanty regarding potential selection biases, in particular regarding familial ressemblance in epidemiological surveys of this kind.

METHODS

Asthmatic probands (adult and paediatric) were recruited in chest clinics of six clinical centres. Controls were mostly population-based (electoral rolls) for adults and recruited in surgery departments for children.

RESULTS

The population examined includes 348 nuclear families ascertained by one asthmatic and 416 controls, totalling 1847 subjects (EGEA I) and an additional sample of 40 families ascertained by two asthmatic siblings (EGEA II). Potential biases for the various types of analyses have been studied. Quantification of the consequences of the greater participation of probands with a parental history of asthma shows it does not introduce a major bias in the estimates of familial resemblance. Cases and controls showed a good comparability regarding sex, age, area of residence and familial geographical origin, allowing proper associations studies for environmental and candidate genetic factors.

CONCLUSIONS

The case-control component of the study will allow to perform studies on environmental factors and association studies for various genetic polymorphisms. Using the family base collected, segregation and genetic linkage/association analyses with DNA markers may be performed.

Designing meaningful industry metrics for clinical productivity for anesthesiology departments

IMPLICATIONS

Clinical productivity measurements that account for differences in clinical settings and concurrencies provided more precise comparisons between two anesthesiology groups. The data show that different concurrencies confound the current industry standard, "per full-time equivalent" measurements, whereas "per operating room site" and "per case" measurements allowed for more meaningful comparisons.

Genome screen for asthma and related phenotypes in the French EGEA study

A genome-wide search was conducted in 107 nuclear families with at least two siblings with asthma, as part of the French EGEA study. A two-stage analysis strategy was applied to the 107 families divided into two independent subsets of 46 and 61 families, where all regions detected in the first set of families were tested for replication in the second set. In addition, all regions reported by published genome scans in different populations were examined in the total sample. A total of 254 markers were typed in the first set of families and 70% of them in the second set. Linkage was investigated by model-free methods for asthma and four asthma-related phenotypes: bronchial responsiveness (BR), skin test response, total immunoglobulin E (IgE) levels, and eosinophil count. The two-stage analysis led to the detection of three regions: 11p13 for IgE, 12q24 for eosinophils, and 17q12-21 for asthma and skin tests. Among the regions reported by published genome screens, seven were found in the 107 French EGEA families: three being already detected by the two-stage analysis, 11p13 (p = 0.005), 12q24 (p = 0.0008), and 17q12-21 (p = 0.001), and four additional ones, 1p31 (p = 0.005) for asthma, 11q13 (p = 0.006) for IgE, 13q31 (p = 0.001) for eosinophils, and 19q13 (p = 0.02) for BR.

Association of PEEP with two different inflation volumes in ARDS patients: effects on passive lung deflation and alveolar recruitment

OBJECTIVE

To assess the effects of the association of positive end-expiratory pressure (PEEP) with different inflation volumes (V(T)'s) on passive lung deflation and alveolar recruitment in ARDS patients.

DESIGN

Clinical study using PEEP with two different V(T)'s and analyzing whether passive lung deflation and alveolar recruitment (Vrec) depend on end-inspired (EILV) or end-expired (EELV) lung volume in mechanically ventilated ARDS patients.

SETTING

Medical intensive care unit in a university hospital.

PATIENTS AND PARTICIPANTS

Six mechanically ventilated consecutive supine patients with ARDS.

INTERVENTIONS

Time-course of thoracic volume decay during passive expiration and Vrec were investigated in six ARDS patients ventilated on PEEP with baseline V(T) (V(T),b) and 0.5V(T) (0.5V(T),b), and on zero PEEP (ZEEP) with V(T),b. Time constants of the fast (tau1) and slow (tau2) emptying compartments, as well as resistances and elastances were also determined.

MEASUREMENTS AND RESULTS

(a) the biexponential model best fitted the volume decay in all instances. The fast compartment was responsible for 84+/-7 (0.5V(T),b) and 86+/-5% (V(T),b) on PEEP vs 81+/-6% (V(T),b) on ZEEP (P:ns) of the exhaled V(T), with tau1 of 0.50+/-0.13 and 0.58+/-0.17 s vs 0.35+/-0.11 s, respectively; (b) only tau1 for V(T),b on PEEP differed significantly (P < 0.02) from the one on ZEEP, suggesting a slower initial emptying; (c) for the same PEEP, Vrec was higher with a higher volume (V(T)b) than at a lesser one (0.5V(T),b), reflecting the higher V(T).

CONCLUSIONS

In mechanically ventilated ARDS patients: (a) the behavior of airway resistance seems to depend on the degree of the prevailing lung distension; (b) alveolar recruitment appears to be more important when higher tidal volumes are used during mechanical ventilation on PEEP; (c) PEEP changes the mechanical properties of the respiratory system fast-emptying compartment.