Regional Multiple Pathology Scores Are Associated with Cognitive Decline in Lewy Body Dementias

Dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD) are characterized by the presence of α‐synuclein‐containing Lewy bodies and Lewy neurites. However, both dementias also show variable degrees of Alzheimer's disease (AD) pathology (senile plaques and neurofibrillary tangles), particularly in areas of the cortex associated with higher cognitive functions. This study investigates the contribution of the individual and combined pathologies in determining the rate of cognitive decline. Cortical α‐synuclein, phosphorylated tau (phosphotau) and Aβ plaque pathology in 34 PDD and 55 DLB patients was assessed semi‐quantitatively in four regions of the neocortex. The decline in cognition, assessed by Mini Mental State Examination, correlated positively with the cortical α‐synuclein load. Patients also had varying degrees of senile Aβ plaque and phosphotau pathology. Regression analyses pointed to a combined pathology (Aβ plaque plus phosphotau plus α‐synuclein‐positive features), particularly in the prefrontal cortex (BA9) and temporal lobe neocortex with the superior and middle temporal gyrus (BA21, 22), being a major determining factor in the development of dementia. Thus, cognitive decline in Lewy body dementias is not a consequence of α‐synuclein‐induced neurodegeneration alone but senile plaque and phosphorylated tau pathology also contribute to the overall deficits.     

Lysosomal cathepsin D is upregulated in Alzheimer's disease neocortex and may be a marker for neurofibrillary degeneration

Alzheimer's disease (AD) is characterized by accumulation of β‐amyloid plaques (AP) and neurofibrillary tangles (NFT) in the cortex, together with synaptic loss and amyloid angiopathy. Perturbations in the brain lysosomal system, including the cathepsin family of proteases, have been implicated in AD where they may be involved in proteolytic clearance of misfolded and abnormally aggregated peptides. However, the status of cathepsin D (catD) is unclear in Lewy body dementia, the second most common form of neurodegenerative dementia after AD, and characterized by Lewy bodies (LB) containing aggregated α‐synuclein. Furthermore, earlier reports of catD changes in AD have not been entirely consistent. We measured CatD immunoreactivities in the temporal (Brodmann area BA21) and parietal (BA40) cortices of well characterized AD brains as well as two clinical subtypes of Lewy body dementia, namely Parkinson disease dementia (PDD) and dementia with Lewy bodies (DLB), known to show varying degrees of concomitant AD pathology. Increased catD immunoreactivities in AD were found for both neocortical regions measured, where they also correlated with neuropathological NFT scores and phosphorylated pSer396 tau burden, and appeared to co‐localize at least partly to NFT‐containing neurons. In contrast, catD was increased only in BA40 in DLB and not at all in PDD, did not correlate with LB scores, and did not appreciably co‐localize with α‐synuclein inclusions. Our study suggests that catD upregulation may be an adaptive response to AD‐related processes leading to neurofibrillary degeneration, but may not be directly associated with formation of α‐synuclein inclusions in Lewy body dementia.     

Small vessel disease pathological changes in neurodegenerative and vascular dementias concomitant with autonomic dysfunction

We performed a clinicopathological study to assess the burden of small vessel disease (SVD) type of pathological changes in elderly demented subjects, who had clinical evidence of autonomic dysfunction, either carotid sinus hypersensitivity or orthostatic hypotension or both or had exhibited unexpected repeated falls. Clinical and neuropathological diagnoses in 112 demented subjects comprised dementia with Lewy bodies (DLB), Parkinson's disease with dementia (PDD), Alzheimer's disease (AD), Mixed dementia (mostly AD‐DLB) and vascular dementia (VaD). Of these, 12 DLB subjects had no recorded unexpected falls in life and therefore no evidence of concomitant autonomic dysfunction. A further 17 subjects were assessed as aging controls without significant pathology or signs of autonomic dysfunction. We quantified brain vascular pathological changes and determined severities of neurodegenerative lesions including α‐synuclein pathology. We found moderate‐severe vascular changes and high‐vascular pathology scores (P < 0.01) in all neurodegenerative dementias and as expected in VaD compared to similar age controls. Arteriolosclerosis, perivascular spacing and microinfarcts were frequent in the basal ganglia and frontal white matter (WM) across all dementias, whereas small infarcts (<5 mm) were restricted to VaD. In a sub‐set of demented subjects, we found that vascular pathology scores were correlated with WM hyperintensity volumes determined by MRI in life (P < 0.02). Sclerotic index values were increased by ~50% in both the WM and neocortex in all dementias compared to similar age controls. We found no evidence for increased α‐synuclein deposition in subjects with autonomic dysfunction. Our findings suggest greater SVD pathological changes occur in the elderly diagnosed with neurodegenerative dementias including DLB and who develop autonomic dysfunction. SVD changes may not necessarily manifest in clinically overt symptoms but they likely confound motor or cognitive dysfunction. We propose dysautonomia promotes chronic cerebral hypoperfusion to impact upon aging‐related neurodegenerative disorders and characterize their end‐stage clinical syndromes.     

Glutamatergic receptor expression changes in the Alzheimer's disease hippocampus and entorhinal cortex

Alzheimer''s Disease (AD) is the leading form of dementia worldwide. Currently, the pathological mechanisms underlying AD are not well understood. Although the glutamatergic system is extensively implicated in its pathophysiology, there is a gap in knowledge regarding the expression of glutamate receptors in the AD brain. This study aimed to characterize the expression of specific glutamate receptor subunits in post‐mortem human brain tissue using immunohistochemistry and confocal microscopy. Free‐floating immunohistochemistry and confocal laser scanning microscopy were used to quantify the density of glutamate receptor subunits GluA2, GluN1, and GluN2A in specific cell layers of the hippocampal sub‐regions, subiculum, entorhinal cortex, and superior temporal gyrus. Quantification of GluA2 expression in human post‐mortem hippocampus revealed a significant increase in the stratum (str.) moleculare of the dentate gyrus (DG) in AD compared with control. Increased GluN1 receptor expression was found in the str. moleculare and hilus of the DG, str. oriens of the CA2 and CA3, str. pyramidale of the CA2, and str. radiatum of the CA1, CA2, and CA3 subregions and the entorhinal cortex. GluN2A expression was significantly increased in AD compared with control in the str. oriens, str. pyramidale, and str. radiatum of the CA1 subregion. These findings indicate that the expression of glutamatergic receptor subunits shows brain region‐specific changes in AD, suggesting possible pathological receptor functioning. These results provide evidence of specific glutamatergic receptor subunit changes in the AD hippocampus and entorhinal cortex, indicating the requirement for further research to elucidate the pathophysiological mechanisms it entails, and further highlight the potential of glutamatergic receptor subunits as therapeutic targets.     

Synapsin III is a key component of α‐synuclein fibrils in Lewy bodies of PD brains

Lewy bodies (LB) and Lewy neurites (LN), which are primarily composed of α‐synuclein (α‐syn), are neuropathological hallmarks of Parkinson''s disease (PD) and dementia with Lewy bodies (DLB). We recently found that the neuronal phosphoprotein synapsin III (syn III) controls dopamine release via cooperation with α‐syn and modulates α‐syn aggregation. Here, we observed that LB and LN, in the substantia nigra of PD patients and hippocampus of one subject with DLB, displayed a marked immunopositivity for syn III. The in situ proximity ligation assay revealed the accumulation of numerous proteinase K‐resistant neuropathological inclusions that contained both α‐syn and syn III in tight association in the brain of affected subjects. Most strikingly, syn III was identified as a component of α‐syn‐positive fibrils in LB‐enriched protein extracts from PD brains. Finally, a positive correlation between syn III and α‐syn levels was detected in the caudate putamen of PD subjects. Collectively, these findings indicate that syn III is a crucial α‐syn interactant and a key component of LB fibrils in the brain of patients affected by PD.     

Novel genetic variants in MAPT and alterations in tau phosphorylation in amyotrophic lateral sclerosis post‐mortem motor cortex and cerebrospinal fluid

Although the molecular mechanisms underlying amyotrophic lateral sclerosis (ALS) are not yet fully understood, several studies report alterations in tau phosphorylation in both sporadic and familial ALS. Recently, we have demonstrated that phosphorylated tau at S396 (pTau‐S396) is mislocalized to synapses in ALS motor cortex (mCTX) and contributes to mitochondrial dysfunction. Here, we demonstrate that while there was no overall increase in total tau, pTau‐S396, and pTau‐S404 in ALS post‐mortem mCTX, total tau and pTau‐S396 were increased in C9ORF72‐ALS. Additionally, there was a significant decrease in pTau‐T181 in ALS mCTX compared controls. Furthermore, we leveraged the ALS Knowledge Portal and Project MinE data sets and identified ALS‐specific genetic variants across MAPT, the gene encoding tau. Lastly, assessment of cerebrospinal fluid (CSF) samples revealed a significant increase in total tau levels in bulbar‐onset ALS together with a decrease in CSF pTau‐T181:tau ratio in all ALS samples, as reported previously. While increases in CSF tau levels correlated with a faster disease progression as measured by the revised ALS functional rating scale (ALSFRS‐R), decreases in CSF pTau‐T181:tau ratio correlated with a slower disease progression, suggesting that CSF total tau and pTau‐T181 ratio may serve as biomarkers of disease in ALS. Our findings highlight the potential role of pTau‐T181 in ALS, as decreases in CSF pTau‐T181:tau ratio may reflect the significant decrease in pTau‐T181 in post‐mortem mCTX. Taken together, these results indicate that tau phosphorylation is altered in ALS post‐mortem mCTX as well as in CSF and, importantly, the newly described pathogenic or likely pathogenic variants identified in MAPT in this study are adjacent to T181 and S396 phosphorylation sites further highlighting the potential role of these tau functional domains in ALS.     

Assessment of ZnT3 and PSD95 protein levels in Lewy body dementias and Alzheimer's disease: association with cognitive impairment

The loss of zinc transporter 3 (ZnT3) has been implicated in age-related cognitive decline in mice, and the protein has been associated with plaques. We investigated the levels of ZnT3 and postsynaptic density protein 95 (PSD95), a marker of the postsynaptic terminal, in people with Parkinson's disease dementia (PDD, n = 31), dementia with Lewy bodies (DLB, n = 44), Alzheimer's disease (AD, n = 16), and controls (n = 24), using semiquantitative western blotting and immunohistochemistry in 3 cortical regions. Standardized cognitive assessments during life and semiquantitative scoring of amyloid β (Aβ), tau, and α-synuclein at postmortem were used to investigate the relationship between ZnT3 and PSD95, cognition and pathology. Associations were observed between ZnT3 and PSD95 levels in prefrontal cortex and cognitive impairment (p = 0.001 and p = 0.002, respectively) and between ZnT3 levels in the parietal cortex and cognitive impairment (p = 0.036). Associations were also seen between ZnT3 levels in cingulate cortex and severity of Aβ (p = 0.003) and tau (p = 0.011) pathologies. DLB and PDD were characterized by significant reductions of PSD95 (p < 0.05) and ZnT3 (p < 0.001) in prefrontal cortex compared with controls and AD. PSD95 levels in the parietal cortex were found to be decreased in AD cases compared with controls (p = 0.02) and PDD (p = 0.005). This study has identified Zn²⁺ modulation as a possible novel target for the treatment of cognitive impairment in DLB and PDD and the potential for synaptic proteins to be used as a biomarker for the differentiation of DLB and PDD from AD.     

Loss of capillary pericytes and the blood–brain barrier in white matter in poststroke and vascular dementias and Alzheimer’s disease

White matter (WM) disease is associated with disruption of the gliovascular unit, which involves breach of the blood–brain barrier (BBB). We quantified pericytes as components of the gliovascular unit and assessed their status in vascular and other common dementias. Immunohistochemical and immunofluorescent methods were developed to assess the distribution and quantification of pericytes connected to the frontal lobe WM capillaries. Pericytes with a nucleus were identified by collagen 4 (COL4) and platelet‐derived growth factor receptor‐β (PDGFR‐β) antibodies with further verification using PDGFR‐β‐specific ELISA. We evaluated a total of 124 post‐mortem brains from subjects with post‐stroke dementia (PSD), vascular dementia (VaD), Alzheimer’s disease (AD), AD‐VaD (Mixed) and post‐stroke non‐demented (PSND) stroke survivors as well as normal aging controls. COL4 and PDGFR‐β reactive pericytes adopted the characteristic “crescent” or nodule‐like shapes around capillary walls. We estimated densities of pericyte somata to be 225 ±38 and 200 ±13 (SEM) per COL4 mm² area or 2.0 ± 0.1 and 1.7 ± 0.1 per mm capillary length in young and older aging controls. Remarkably, WM pericytes were reduced by ~35%–45% in the frontal lobe of PSD, VaD, Mixed and AD subjects compared to PSND and controls subjects (P < 0.001). We also found pericyte numbers were correlated with PDGFR‐β reactivity in the WM. Our results first demonstrate a reliable method to quantify COL4‐positive pericytes and then, indicate that deep WM pericytes are decreased across different dementias including PSD, VaD, Mixed and AD. Our findings suggest that downregulation of pericytes is associated with the disruption of the BBB in the deep WM in several aging‐related dementias.     

Interleukin-1 mediates Alzheimer and Lewy body pathologies

Background  

Clinical and neuropathological overlap between Alzheimer's (AD) and Parkinson's disease (PD) is now well recognized. Such cases of concurrent AD and Lewy body disease (AD/LBD) show neuropathological changes that include Lewy bodies (α-synuclein aggregates), neuritic amyloid plaques, and neurofibrillary tangles (hyperphosphorylated tau aggregates). The co-occurrence of these clinical and neuropathological changes suggests shared pathogenic mechanisms in these diseases, previously assumed to be distinct. Glial activation, with overexpression of interleukin-1 (IL-1) and other proinflammatory cytokines, has been increasingly implicated in the pathogenesis of both AD and PD.     

Severe histomorphological alterations in post‐mortem olfactory glomeruli in Alzheimer’s disease

Alzheimer''s disease (AD) is the most prevalent form of dementia. Key AD symptoms include memory and cognitive decline; however, comorbid symptoms such as depression and sensory‐perceptual dysfunction are often reported. Among these, a deterioration of olfactory sensation is observed in approximately 90% of AD patients. However, the precise pathophysiological basis underlying olfactory deficits because of AD remains elusive. The olfactory glomeruli in the olfactory bulb (OB) receive sensory information in the olfactory processing pathway. Maintaining the structural and functional integrity of the olfactory glomerulus is critical to olfactory signalling. Herein, we conducted an in‐depth histopathological assessment to reveal detailed structural alterations in the olfactory glomeruli in AD patients. Fresh frozen post‐mortem OB specimens obtained from six AD patients and seven healthy age‐matched individuals were examined. We used combined immunohistochemistry and stereology to assess the gross morphology and histological alterations, such as those in the expression of Aβ protein, microglia, and neurotransmitters in the OB. Electron microscopy was employed to study the ultrastructural features in the glomeruli. Significant accumulation of Aβ, morphologic damage, altered neurotransmitter levels, and microgliosis in the olfactory glomeruli of AD patients suggests that glomerular damage could affect olfactory function. Moreover, greater neurodegeneration was observed in the ventral olfactory glomeruli of AD patients. The synaptic ultrastructure revealed distorted postsynaptic densities and a decline in presynaptic vesicles in AD specimens. These findings show that the primary olfactory pathway is affected by the pathogenesis of AD, and may provide clues to identifying the mechanism involved in olfactory dysfunction in AD.     

Early-onset dementia with Lewy bodies

The clinical and neuropathological characteristics of an atypical form of dementia with Lewy bodies (DLB) are described. The proband experienced difficulties in her school performance at 13 years of age. Neurological examination revealed cognitive dysfunction, dysarthria, parkinsonism and myoclonus. By age 14 years, the symptoms had worsened markedly and the proband died at age 15 years. On neuropathological examination, the brain was severely atrophic. Numerous intracytoplasmic and intraneuritic Lewy bodies, as well as Lewy neurites, were present throughout the cerebral cortex and subcortical nuclel; vacuolar changes were seen in the upper layers of the neocortex and severe neuronal loss and gliosis were evident in the cerebral cortex and substantia nigra. Lewy bodies and Lewy neurites were strongly immunoreactive for alpha-synuclein and ubiquitin. Lewy bodies were composed of filamentous and granular material and isolated filaments were decorated by alpha-synuclein antibodies. Immunohistochemistry for tau or beta-amyloid yielded negative results. The etiology of this atypical form of DLB is unknown, since there was no family history and since sequencing of the exonic regions of alpha-Synuclein, beta-Synuclein, Synphilin-1, Parkin, Ubiquitin C-terminal hydrolase L1 and Neurofilament-M failed to reveal a pathogenic mutation. This study provides further evidence of the clinical and pathological heterogeneity of DLB.     

RAB39B is redistributed in dementia with Lewy bodies and is sequestered within aβ plaques and Lewy bodies

Loss of function mutations within the vesicular trafficking protein Ras analogy in brain 39B (RAB39B) are associated with rare X‐linked Parkinson’s disease (PD). Physiologically, RAB39B is localized to Golgi vesicles and recycling endosomes and is required for glutamatergic receptor maturation but also for alpha‐Synuclein (aSyn) homeostasis and the inhibition of its aggregation. Despite evidence linking RAB39B to neurodegeneration, the involvement of the protein in idiopathic neurodegenerative diseases remains undetermined. Here, analysis of the spatial distribution and expression of RAB39B was conducted in post‐mortem human brain tissue from cases of dementia with Lewy bodies (DLB, n = 10), Alzheimer’s disease (AD, n = 12) and controls (n = 12). Assessment of cortical RAB39B immunoreactivity using tissue microarrays revealed an overall reduction in the area of RAB39B positive gray matter in DLB cases when compared to controls and AD cases. Strikingly, RAB39B co‐localized with beta‐amyloid (Aβ) plaques in all cases examined and was additionally present in a subpopulation of Lewy bodies (LBs) in DLB. Biochemical measures of total RAB39B levels within the temporal cortex were unchanged between DLB, AD and controls. However, upon subcellular fractionation, a reduction of RAB39B in the cytoplasmic pool was found in DLB cases, alongside an increase of phosphorylated aSyn and Aβ in whole tissue lysates. The reduction of cytoplasmic RAB39B is consistent with an impaired reserve capacity for RAB39B‐associated functions, which in turn may facilitate LB aggregation and synaptic impairment. Collectively, our data support the involvement of RAB39B in the pathogenesis of DLB and the co‐aggregation of RAB39B with Aβ in plaques suggests that age‐associated cerebral Aβ pathology may be contributory to the loss of RAB39B. Thus RAB39B, its associated functional pathways and its entrapment in aggregates may be considered as future targets for therapeutic interventions to impede the overall pathological burden and cellular dysfunction in Lewy body diseases.     

MAPT H1 haplotype is associated with enhanced α-synuclein deposition in dementia with Lewy bodies

The microtubule-associated protein tau (MAPT) H1 haplotype has been identified as a genetic risk factor for synucleinopathies. However, whether it modulates tau or α-synuclein pathology remains unknown. Our aim was to investigate the relationship between MAPT haplotypes and pathologic aggregates of tau and α-synuclein in pathologically confirmed cases of dementia with Lewy bodies (DLB). Twenty-two cases fulfilling clinical and neuropathological criteria for DLB were included. Clinical and neuropathological data were collected, and APOE and MAPT genotypes were determined. Tau and α-synuclein pathology was assessed semiquantitatively in 17 brain areas and total scores were calculated. DLB H1/H1 (n = 12) and H2 carriers (n = 10) did not differ in demographics, clinical variables, concomitant Alzheimer's pathology, or APOE genotype. Total α-synuclein scores were significantly increased in the H1/H1 group (p = 0.011), largely due to an increase in brainstem regions. This difference was driven by an increase in Lewy bodies and diffuse and punctuate cytoplasmatic α-synuclein aggregates (p = 0.007 and p = 0.025 respectively). These findings provide a mechanistic link for the genetic association between MAPT haplotypes and synucleinopathies.     

Higher Soluble Amyloid β Concentration in Frontal Cortex of Young Adults than in Normal Elderly or Alzheimer's Disease

Little is known about the relationship between soluble amyloid β (Aβ) and age. We have measured soluble and insoluble Aβ by enzyme‐linked immunosorbent assay (ELISA) in post‐mortem frontal cortex in normal brains (16–95 years) and AD. Insoluble Aβ increased with age, and was significantly higher in Alzheimer''s disease (AD) than age‐matched controls. However, levels of soluble Aβ declined with age and were significantly greater in younger adults than older adults with or without AD. In AD, insoluble : soluble Aβ ratio was much higher than in age‐matched controls. The high levels of soluble Aβ in young adults included oligomeric species of Aβ_1‐42. These observations do not preclude Aβ oligomers as neurotoxic mediators of AD but suggest that if they are, the toxicity may be restricted to certain species (eg, β‐pleated protofibrillar species not detected by our assay) or takes decades to manifest. The dramatically increased insoluble : soluble Aβ in AD points to an altered dynamic equilibrium of Aβ in AD, reflecting both enhanced aggregation and continued overproduction or impaired removal of the soluble peptide in older age, when the concentration of this peptide should be declining.     

Clinicopathologic and genetic features of multiple system atrophy with Lewy body disease

Background: Abnormal aggregates of α‐synuclein are pathologic hallmarks of multiple system atrophy (MSA) and Lewy body disease (LBD). LBD sometimes coexists with MSA, but the impact of co‐pathology, particularly diffuse LBD, on presentation of MSA has not been studied. We aimed to determine the frequency and clinicopathologic features of MSA with LBD (MSA+LBD). Methods: Using hematoxylin & eosin and α‐synuclein‐immunostained slides, we assessed the distribution and severity of LBD in 230 autopsy‐confirmed MSA patients collected from 1998 to 2018. Alzheimer‐type pathology was assessed to assign the likelihood of clinical presentations of dementia with Lewy body (DLB) using the consensus criteria for DLB. We reviewed medical records to characterize clinicopathologic features of MSA+LBD. Genetic risk factors for LBD, including APOE ε4 allele and mutations in GBA, SNCA, LRRK2, and VPS35, were analyzed. Results: LBD was observed in 11 MSA patients (5%); seven were brainstem type, three were transitional type, and one was diffuse type. The latter four had an intermediate or high likelihood of DLB. Three of the four had an antemortem diagnosis of Parkinson’s disease with dementia (PDD) or clinically probable DLB. Two patients had neuronal loss in the substantia nigra, but not in striatal or olivocerebellar systems with widespread glial cytoplasmic inclusions, consistent with minimal change MSA. In these cases, LBD was considered the primary pathology, and MSA was considered coincidental. APOE ε4 allele frequency was not different between MSA+LBD and MSA without LBD. Two of nine MSA+LBD patients had a risk variant of GBA (p.T408M and p.E365K). Conclusions: Although rare, MSA with transitional or diffuse LBD can develop clinical features of PDD or DLB. Minimal change MSA can be interpreted as a coincidental, but distinct, α‐synucleinopathy in a subset of patients with diffuse LBD.     

Brain Neurons Express Ornithine Decarboxylase‐Activating Antizyme Inhibitor 2 with Accumulation in Alzheimer's Disease

Polyamines are small cationic molecules that in adult brain are connected to neuronal signaling by regulating inward‐rectifier K⁺‐channels and different glutamate receptors. Antizyme inhibitors (AZINs) regulate the cellular uptake of polyamines and activate ornithine decarboxylase (ODC), the rate‐limiting enzyme of polyamine synthesis. Elevated levels of ODC activity and polyamines are detected in various brain disorders including stroke and Alzheimer''s disease (AD).We originally reported a novel brain‐ and testis‐specific AZIN, called AZIN2, the distribution of which we have now studied in normal and diseased human brain by in situ hybridization and immunohistochemistry. We found the highest accumulation of AZIN2 in a pearl‐on‐the‐string‐like distribution along the axons in both the white and gray matter. AZIN2 was also detected in a vesicle‐like distribution in the somas of selected cortical pyramidal neurons. Double‐immunofluorescence staining revealed co‐localization of AZIN2 and N‐methyl D‐aspartate‐type glutamate receptors (NMDARs) in pyramidal neurons of the cortex. Moreover, we found accumulation of AZIN2 in brains affected by AD, but not by other neurodegenerative disorders (CADASIL or Lewy body disease). ODC activity is mostly linked to cell proliferation, whereas its regulation by AZIN2 in post‐mitotically differentiated neurons of the brain apparently serves different purposes. The subcellular distribution of AZIN2 suggests a role in vesicular trafficking.     

TDP‐43 pathology in Alzheimer's disease,dementia with Lewy bodies and ageing

Intracellular inclusions consisting of TAR DNA binding protein‐43 (TDP‐43 pathology) are present in up to 57% of Alzheimer's disease (AD) cases and follow a distinct topographical pattern of progression described in the TDP‐43 in AD staging scheme. This scheme has not been applied to the assessment of TDP‐43 pathology in dementia with Lewy bodies (DLB) and aged controls. We investigated TDP‐43 pathology prevalence and severity in AD, DLB, mixed AD/DLB (Mx AD/DLB) and aged controls. One hundred and nineteen human post‐mortem brains were included, neuropathologically diagnosed as AD: 46, DLB: 15, Mx AD/DLB: 19 and aged controls: 39. Paraffin sections inclusive of the amygdala, hippocampus, striatum and neocortex were immunohistochemically stained with antibodies against phosphorylated TDP‐43 and staged according to the TDP‐43 in AD staging scheme. TDP‐43 pathology was present in all groups: AD: 73.9%, DLB: 33.3%, Mx AD/DLB: 52.6% and controls: 17.9%. Prevalence of TDP‐43 pathology was significantly higher in AD and Mx AD/DLB compared to controls. In controls, higher age at death was associated with prevalence of TDP‐43 pathology and higher TDP‐43 in AD stage, suggesting that this type of TDP‐43 pathology may partly be an age‐associated phenomenon. Significantly higher prevalence of TDP‐43 pathology in the AD group indicates that AD pathology possibly triggers and aggravates TDP‐43 pathology. The validity of the TDP‐43 in AD staging scheme is not limited to AD and should be applied to assess TDP‐43 pathology in post mortem brains of aged individuals to further elucidate the role of TDP‐43 pathology in age associated neurodegeneration.     

Clinical correlates of pathology in the claustrum in Parkinson's disease and dementia with Lewy bodies

Dementia and visual hallucinations are common complications of Parkinson's disease (PD), yet their patho-anatomical bases are poorly defined. We studied α-synuclein (αSyn), tau and amyloid-β (Aβ) pathology in the claustrum of 20 PD cases without dementia, 12 PD cases with dementia (PDD) and 7 cases with dementia with Lewy bodies (DLB). αSyn positivity was observed in 75% of PD cases without dementia and in 100% of PDD and DLB cases. Aβ was observed in the claustrum in 25% of PD, 58% of PDD and 100% of DLB cases. Tau was negligible in all cases restricting further analysis. Compared to PD cases without dementia, PDD cases demonstrated a significantly greater αSyn burden in the claustrum (p = 0.0003). In addition, DLB cases showed a significantly increased αSyn deposition when compared to PDD (p = 0.02) and PD without dementia (p = 0.0002). A similar hierarchy, PD < PDD < DLB was seen in terms of Aβ burden in the claustrum. Comparison of αSyn and Aβ burden in those cases with and without visual hallucinations did not reveal any significant associations (p = 0.13 and 0.1, respectively). We demonstrate that pathology in the claustrum, a region of largely obscure physiological function, strongly relates to the presence of dementia in Parkinson's disease and DLB.     

Distinct changes in all major components of the neurovascular unit across different neuropathological stages of Alzheimer's disease

In the brain capillaries, endothelial cells, pericytes, astrocytes and microglia form a structural and functional complex called neurovascular unit (NVU) which is critically involved in maintaining neuronal homeostasis. In the present study, we applied a comprehensive immunohistochemical approach to investigate the structural alterations in the NVU across different Alzheimer''s disease (AD) neuropathological stages. Post‐mortem human cortical and hippocampal samples derived from AD patients and non‐demented elderly control individuals were immunostained using a panel of markers representing specific components of the NVU including Collagen IV (basement membrane), PDGFR‐β (pericytes), GFAP (astrocytes), Iba1 (microglia), MRC1 (perivascular macrophages) and lectin as an endothelial cell label. Astrocytes (GFAP) and microglia (Iba1) were quantified both in the whole visual‐field and specifically within the NVU, and the sample set was additionally analyzed using anti‐tau (AT8) and three different anti‐Aβ (clones G2‐10, G2‐11, 4G8) antibodies. Analyses of lectin labeled sections showed an altered vascular distribution in AD patients as revealed by a reduced nearest distance between capillaries. Within the NVU, a Braak‐stage dependent reduction in pericyte coverage was identified as the earliest structural alteration during AD progression. In comparison to non‐demented elderly controls, AD patients showed a significantly higher astrocyte coverage within the NVU, which was paralleled by a reduced microglial coverage around capillaries. Assessment of perivascular macrophages moreover demonstrated a relocation of these cells from leptomeningeal arteries to penetrating parenchymal vessels in AD patients. Collectively, the results of our study represent a comprehensive first in‐depth analysis of AD‐related structural changes in the NVU and suggest distinct alterations in all components of the NVU during AD progression.     

DLB and PDD: a role for mutations in dementia and Parkinson disease genes?

Based on the substantial overlap in clinical and pathological characteristics of dementia with Lewy bodies (DLB) and Parkinson disease with dementia (PDD) with Alzheimer disease (AD) and Parkinson disease (PD) we hypothesized that these disorders might share underlying genetic factors. The contribution of both sequence and copy number variants (CNVs) in known AD and PD genes to the genetic etiology of DLB and PDD however is currently unclear. Therefore, we performed a gene-based mutation analysis of all major AD and PD genes in 99 DLB and 75 PDD patients, including familial and sporadic forms, from Flanders, Belgium. Also, copy number variants in APP, SNCA, and PARK2 were determined. In the AD genes we detected proven pathogenic missense mutations in PSEN1 and PSEN2, and 2 novel missense variants in PSEN2 and MAPT. In the PD genes we identified 1 SNCA duplication, the LRRK2 R1441C founder mutation and 4 novel heterozygous missense variants with unknown pathogenicity. Our results suggest a contribution of established AD and PD genes to the genetic etiology of DLB and PDD though to a limited extent. They do support the hypothesis of a genetic overlap between members of the Lewy body disease spectrum, but additional genes still have to exist.