Magnetic resonance imaging of white matter response to diesel exhaust particles.

Air pollution is associated with risks of dementia and accelerated cognitive decline. Rodent air pollution models have shown white matter vulnerability. This study uses diffusion tensor imaging (DTI) to quantify changes to white matter microstructure and tractography in multiple myelinated regions after exposure to diesel exhaust particulate (DEP). Adult C57BL/6 male mice were exposed to re-aerosolized DEP (NIST SRM 2975) at a concentration of 100 ug/m3 for 200 hours. Ex-vivo MRI analysis and fractional anisotropy (FA)-aided white matter tractography were conducted to study the effect of DEP exposure on the brain white matter tracts. Immunohistochemistry was used to assess myelin and axonal structure. DEP exposure for 8 weeks altered myelin composition in multiple regions. Diffusion tensor imaging (DTI) showed decreased FA in the corpus callosum (30%), external capsule (15%), internal capsule (15%), and cingulum (31 %). Separate immunohistochemistry analyses confirmed prior findings. Myelin basic protein (MBP) was decreased (corpus callosum: 28%, external capsule: 29%), and degraded MPB increased (corpus callosum: 32%, external capsule: 53%) in the DEP group. White matter is highly susceptible to chronic DEP exposure. This study demonstrates the utility of DTI as a neuroanatomical tool in the context of air pollution and white matter myelin vulnerability.

Air pollution nanoparticle and alpha-synuclein fibrils synergistically decrease glutamate receptor A1, depending upon nPM batch activity.

Background: Epidemiological studies have variably linked air pollution to increased risk of Parkinson's disease (PD). However, there is little experimental evidence for this association. Alpha-synuclein (α-syn) propagation plays central roles in PD and glutamate receptor A1 (GluA1) is involved in memory and olfaction function. Methods: Each mouse was exposed to one of three different batches of nano-particulate matter (nPM) (300 µg/m3, 5 h/d, 3 d/week), collected at different dates, 2017-2019, in the same urban site. After these experiments, these nPM batches were found to vary in activity. C57BL/6 female mice (3 mo) were injected with pre-formed murine α-synuclein fibrils (PFFs) (0.4 µg), which act as seeds for α-syn aggregation. Two exposure paradigms were used: in Paradigm 1, PFFs were injected into olfactory bulb (OB) prior to 4-week nPM (Batch 5b) exposure and in Paradigm 2, PFFs were injected at 4th week during 10-week nPM exposure (Batches 7 and 9). α-syn pSer129, microglia Iba1, inflammatory cytokines, and Gria1 expression were measured by immunohistochemistry or qPCR assays. Results: As expected, α-syn pSer129 was detected in ipsilateral OB, anterior olfactory nucleus, amygdala and piriform cortex. One of the three batches of nPM caused a trend for elevated α-syn pSer129 in Paradigm 1, but two other batches showed no effect in Paradigm 2. However, the combination of nPM and PFF significantly decreased Gria1 mRNA in both the ipsi- and contra-lateral OB and frontal cortex for the most active two nPM batches. Neither nPM nor PFFs alone induced responses of microglia Iba1 and expression of Gria1 in the OB and cortex. Conclusion: Exposures to ambient nPM had weak effect on α-syn propagation in the brain in current experimental paradigms; however, nPM and α-syn synergistically downregulated the expression of Gria1 in both OB and cortex.

Neurotoxicity of Diesel Exhaust Particles.

BACKGROUND: Air pollution particulate matter (PM) is strongly associated with risks of accelerated cognitive decline, dementia and Alzheimer's disease. Ambient PM batches have variable neurotoxicity by collection site and season, which limits replicability of findings within and between research groups for analysis of mechanisms and interventions. Diesel exhaust particles (DEP) offer a replicable model that we define in further detail. OBJECTIVE: Define dose- and time course neurotoxic responses of mice to DEP from the National Institute of Science and Technology (NIST) for neurotoxic responses shared by DEP and ambient PM. METHODS: For dose-response, adult C57BL/6 male mice were exposed to 0, 25, 50, and 100µg/m3 of re-aerosolized DEP (NIST SRM 2975) for 5 h. Then, mice were exposed to 100µg/m3 DEP for 5, 100, and 200 h and assayed for amyloid-ß peptides, inflammation, oxidative damage, and microglial activity and morphology. RESULTS: DEP exposure at 100µg/m3 for 5 h, but not lower doses, caused oxidative damage, complement and microglia activation in cerebral cortex and corpus callosum. Longer DEP exposure for 8 weeks/200 h caused further oxidative damage, increased soluble Aß, white matter injury, and microglial soma enlargement that differed by cortical layer. CONCLUSION: Exposure to 100µg/m3 DEP NIST SRM 2975 caused robust neurotoxic responses that are shared with prior studies using DEP or ambient PM0.2. DEP provides a replicable model to study neurotoxic mechanisms of ambient PM and interventions relevant to cognitive decline and dementia.

Urban Air Pollution Nanoparticles from Los Angeles: Recently Decreased Neurotoxicity.

BACKGROUND: Air pollution is widely associated with accelerated cognitive decline at later ages and risk of Alzheimer's disease (AD). Correspondingly, rodent models demonstrate the neurotoxicity of ambient air pollution and its components. Our studies with nano-sized particulate matter (nPM) from urban Los Angeles collected since 2009 have shown pro-amyloidogenic and pro-inflammatory responses. However, recent batches of nPM have diminished induction of the glutamate receptor GluA1 subunit, Iba1, TNFα, Aß42 peptide, and white matter damage. The same methods, materials, and mouse genotypes were used throughout. OBJECTIVE: Expand the nPM batch comparisons and evaluate archived brain samples to identify the earliest change in nPM potency. METHODS: Batches of nPM were analyzed by in vitro cell assays for NF-κB and Nrf2 induction for comparison with in vivo responses of mouse brain regions from mice exposed to these batches, analyzed by PCR and western blot. RESULTS: Five older nPM batches (2009-2017) and four recent nPM batches (2018, 2019) for NF-κB and Nrf2 induction showed declines in nPM potency after 2017 that paralleled declines of in vivo activity from independent exposures in different years. CONCLUSION: Transcription-based in vitro assays of nPM corresponded to the loss of in vivo potency for inflammatory and oxidative responses. These recent decreases of nPM neurotoxicity give a rationale for evaluating possible benefits to the risk of dementia and stroke in Los Angeles populations.

Mouse brain transcriptome responses to inhaled nanoparticulate matter differed by sex and APOE in Nrf2-Nfkb interactions.

The neurotoxicity of air pollution is undefined for sex and APOE alleles. These major risk factors of Alzheimer's disease (AD) were examined in mice given chronic exposure to nPM, a nano-sized subfraction of urban air pollution. In the cerebral cortex, female mice had two-fold more genes responding to nPM than males. Transcriptomic responses to nPM had sex-APOE interactions in AD-relevant pathways. Only APOE3 mice responded to nPM in genes related to Abeta deposition and clearance (Vav2, Vav3, S1009a). Other responding genes included axonal guidance, inflammation (AMPK, NFKB, APK/JNK signaling), and antioxidant signaling (NRF2, HIF1A). Genes downstream of NFKB and NRF2 responded in opposite directions to nPM. Nrf2 knockdown in microglia augmented NFKB responses to nPM, suggesting a critical role of NRF2 in air pollution neurotoxicity. These findings give a rationale for epidemiologic studies of air pollution to consider sex interactions with APOE alleles and other AD-risk genes.

Cell-based assays that predict in vivo neurotoxicity of urban ambient nano-sized particulate matter.

Exposure to urban ambient particulate matter (PM) is associated with risk of Alzheimer's disease and accelerated cognitive decline in normal aging. Assessment of the neurotoxic effects caused by urban PM is complicated by variations of composition from source, location, and season. We compared several in vitro cell-based assays in relation to their in vivo neurotoxicity for NF-κB transcriptional activation, nitric oxide induction, and lipid peroxidation. These studies compared batches of nPM, a nanosized subfraction of PM2.5, extracted as an aqueous suspension, used in prior studies. In vitro activities were compared with in vivo responses of mice chronically exposed to the same batch of nPM. The potency of nPM varied widely between batches for NF-κB activation, analyzed with an NF-κB reporter in human monocytes. Three independently collected batches of nPM had corresponding differences to responses of mouse cerebral cortex to chronic nPM inhalation, for levels of induction of pro-inflammatory cytokines, microglial activation (Iba1), and soluble Aß40 & -42 peptides. The in vitro responses of BV2 microglia for NO-production and lipid peroxidation also differed by nPM batch, but did not correlate with in vivo responses. These data confirm that batches of nPM can differ widely in toxicity. The in vitro NF-κB reporter assay offers a simple, high throughput screening method to predict the in vivo neurotoxic effects of nPM exposure.

Nuclear F-actin and myosins drive relocalization of heterochromatic breaks.

Heterochromatin mainly comprises repeated DNA sequences that are prone to ectopic recombination. In Drosophila cells, 'safe' repair of heterochromatic double-strand breaks by homologous recombination relies on the relocalization of repair sites to the nuclear periphery before strand invasion. The mechanisms responsible for this movement were unknown. Here we show that relocalization occurs by directed motion along nuclear actin filaments assembled at repair sites by the Arp2/3 complex. Relocalization requires nuclear myosins associated with the heterochromatin repair complex Smc5/6 and the myosin activator Unc45, which is recruited to repair sites by Smc5/6. ARP2/3, actin nucleation and myosins also relocalize heterochromatic double-strand breaks in mouse cells. Defects in this pathway result in impaired heterochromatin repair and chromosome rearrangements. These findings identify de novo nuclear actin filaments and myosins as effectors of chromatin dynamics for heterochromatin repair and stability in multicellular eukaryotes.

Activation of the Unfolded Protein Response in Sporadic Inclusion-Body Myositis but Not in Hereditary GNE Inclusion-Body Myopathy.

Muscle fibers in patients with sporadic inclusion-body myositis (s-IBM),the most common age-associated myopathy, are characterized by autophagic vacuoles and accumulation of ubiquitinated and congophilic multiprotein aggregates that contain amyloid-ß and phosphorylated tau. Muscle fibers of autosomal-recessive hereditary inclusion-body myopathy caused by the GNE mutation (GNE-h-IBM) display similar pathologic features, except with less pronounced congophilia. Accumulation of unfolded/misfolded proteins inside the endoplasmic reticulum (ER) lumen leads to ER stress, which elicits the unfolded protein response (UPR) as a protective mechanism. Here we demonstrate for the first time that UPR is activated in s-IBM muscle biopsies, since there was 1) increased activating transcription factor 4 (ATF4) protein and increased mRNA of its target C/EBP homologous protein; 2) cleavage of the ATF6 and increased mRNA of its target glucose-regulated protein 78; and 3) an increase of the spliced form of X-box binding protein 1 and increased mRNA of ER degradation-enhancing α-mannosidase-like protein, target of heterodimer of cleaved ATF6 and spliced X-box binding protein 1. In contrast, we did not find similar evidence of the UPR induction in GNE-h-IBM patient muscle, suggesting that different intracellular mechanisms might lead to similar pathologic phenotypes. Interestingly, cultured GNE-h-IBM muscle fibers had a robust UPR response to experimental ER stress stimuli, suggesting that the GNE mutation per se is not responsible for the lack of UPR in GNE-h-IBM biopsied muscle.

Sodium phenylbutyrate reverses lysosomal dysfunction and decreases amyloid-ß42 in an in vitro-model of inclusion-body myositis.

Sporadic inclusion-body myositis (s-IBM) is a severe, progressive muscle disease for which there is no enduring treatment. Pathologically characteristic are vacuolated muscle fibers having: accumulations of multi-protein aggregates, including amyloid-ß(Aß) 42 and its toxic oligomers; increased γ-secretase activity; and impaired autophagy. Cultured human muscle fibers with experimentally-impaired autophagy recapitulate some of the s-IBM muscle abnormalities, including vacuolization and decreased activity of lysosomal enzymes, accompanied by increased Aß42, Aß42 oligomers, and increased γ-secretase activity. Sodium phenylbutyrate (NaPB) is an orally bioavailable small molecule approved by the FDA for treatment of urea-cycle disorders. Here we describe that NaPB treatment reverses lysosomal dysfunction in an in vitro model of inclusion-body myositis, involving cultured human muscle fibers. NaPB treatment improved lysosomal activity, decreased Aß42 and its oligomers, decreased γ-secretase activity, and virtually prevented muscle-fiber vacuolization. Accordingly, NaPB might be considered a potential treatment of s-IBM patients.

Activation of the γ-secretase complex and presence of γ-secretase-activating protein may contribute to Aß42 production in sporadic inclusion-body myositis muscle fibers.

The muscle-fiber phenotype of sporadic inclusion-body myositis (s-IBM), the most common muscle disease associated with aging, shares several pathological abnormalities with Alzheimer disease (AD) brain, including accumulation of amyloid-ß 42 (Aß42) and its cytotoxic oligomers. The exact mechanisms leading to Aß42 production within s-IBM muscle fibers are not known. Aß42 and Aß40 are generated after the amyloid-precursor protein (AßPP) is cleaved by ß-secretase and the γ-secretase complex. Aß42 is considered more cytotoxic than Aß40, and it has a higher propensity to oligomerize, form amyloid fibrils, and aggregate. Recently, we have demonstrated in cultured human muscle fibers that experimental inhibition of lysosomal enzyme activities leads to Aß42 oligomerization. In s-IBM muscle, we here demonstrate prominent abnormalities of the γ-secretase complex, as evidenced by: a) increase of γ-secretase components, namely active presenilin 1, presenilin enhancer 2, nicastrin, and presence of its mature, glycosylated form; b) increase of mRNAs of these γ-secretase components; c) increase of γ-secretase activity; d) presence of an active form of a newly-discovered γ-secretase activating protein (GSAP); and e) increase of GSAP mRNA. Furthermore, we demonstrate that experimental inhibition of lysosomal autophagic enzymes in cultured human muscle fibers a) activates γ-secretase, and b) leads to posttranslational modifications of AßPP and increase of Aß42. Since autophagy is impaired in biopsied s-IBM muscle, the same mechanism might be responsible for its having increased γ-secretase activity and Aß42 production. Accordingly, improving lysosomal function might be a therapeutic strategy for s-IBM patients.

Abnormalities of NBR1, a novel autophagy-associated protein, in muscle fibers of sporadic inclusion-body myositis.

Intra-muscle fiber accumulation of ubiquitinated protein aggregates containing several conformationally modified proteins, including amyloid-ß and phosphorylated tau, is characteristic of the pathologic phenotype of sporadic inclusion-body myositis (s-IBM), the most common progressive degenerative myopathy of older persons. Abnormalities of protein-degradation, involving both the 26S proteasome and autophagic-lysosomal pathways, were previously demonstrated in s-IBM muscle. NBR1 is a ubiquitin-binding scaffold protein importantly participating in autophagic degradation of ubiquitinated proteins. Whereas abnormalities of p62, a ubiquitin-binding protein, were previously described in s-IBM, abnormalities of NBR1 have not been reported in s-IBM. We have now identified in s-IBM muscle biopsies that NBR1, by: (a) immunohistochemistry, was strongly accumulated within s-IBM muscle-fiber aggregates, where it closely co-localized with p62, ubiquitin, and phosphorylated tau; (b) immunoblots, was increased threefold (p < 0.001); and (c) immunoprecipitation, was associated with p62 and LC3. By real-time PCR, NBR1 mRNA was increased twofold (p < 0.01). None of the various disease- and normal-control muscle biopsies had any NBR1 abnormality. In cultured human muscle fibers, NBR1 also physically associated with both p62 and LC3, and experimental inhibition of either the 26S proteasome or the lysosomal activity resulted in NBR1 increase. Our demonstration of NBR1 abnormalities in s-IBM provides further evidence that altered protein degradation pathways may be critically involved in the s-IBM pathogenesis. Accordingly, attempts to unblock defective protein degradation might be a therapeutic strategy for s-IBM patients.

Novel demonstration of conformationally modified tau in sporadic inclusion-body myositis muscle fibers.

s-IBM is the most common muscle disease of older persons. Its muscle fiber molecular phenotype has close similarities to Alzheimer disease (AD) brain, including intra-muscle-fiber accumulations of (a) Aß42 and its oligomers, and (b) large, squiggly or linear, clusters of paired-helical filaments (PHFs) that are immunoreactive with various antibodies directed against several epitopes of phosphorylated tau (p-tau), and thereby strongly resembling neurofibrillary tangles of AD brain. In AD brain, conformational changes of tau, including its modifications detectable with specific antibodies TG3 (recognizing phosphorylated-Thr231), and Alz50 and MC1 (both recognizing amino acids 5-15 and 312-322) are considered early and important modifications leading to tau's abnormal folding and assembly into PHFs. We have now identified conformationally modified tau in 14 s-IBM muscle biopsies by (a) light-and electron-microscopic immunohistochemistry, (b) immunoblots, and (c) dot-immunoblots, using TG3, Alz50 and MC1 antibodies. Our double-immunolabeling on the light- and electron-microscopic levels, which combined an antibody against p62 that recognizes s-IBM clusters of PHFs, revealed that TG3 immunodecorated, abundantly and exclusively, all p62 immunopositive clusters, while Alz50 labeling was less abundant, and MC1 was mainly diffusely immunoreactive. Interestingly, in the very atrophic degenerating fibers, TG3 co-localized with PHF-1 antibody that recognizes tau phosphorylated at Ser396/404, which is considered a later change in the formation of PHFs; however, most of TG3-positive inclusions in non-atrophic fibers were immunonegative with PHF-1. None of the 12 normal- and disease-control muscle biopsies contained conformational or PHF-1 immunoreactive tau. This first demonstration of conformational tau in s-IBM, because of its abundance in non-atrophic muscle fibers, suggests that it might play an early role in s-IBM PHFs formation and thus be pathogenically important.

Novel demonstration of amyloid-ß oligomers in sporadic inclusion-body myositis muscle fibers.

Accumulation of amyloid-ß (Aß) within muscle fibers has been considered an upstream step in the development of the s-IBM pathologic phenotype. Aß42, which is considered more cytotoxic than Aß40 and has a higher propensity to oligomerize, is preferentially increased in s-IBM muscle fibers. In Alzheimer disease (AD), low-molecular weight Aß oligomers and toxic oligomers, also referred to as "Aß-Derived Diffusible Ligands" (ADDLs), are considered strongly cytotoxic and proposed to play an important pathogenic role. ADDLs have been shown to be increased in AD brain. We now report for the first time that in s-IBM muscle biopsies Aß-dimer, -trimer, and -tetramer are identifiable by immunoblots. While all the s-IBM samples we studied had Aß-oligomers, their molecular weights and intensity varied between the patient samples. None of the control muscle biopsies had Aß oligomers. Dot-immunoblots using highly specific anti-ADDL monoclonal antibodies also showed highly increased ADDLs in all s-IBM biopsies studied, while controls were negative. By immunofluorescence, in some of the abnormal s-IBM muscle fibers ADDLs were accumulated in the form of plaque-like inclusions, and were often increased diffusely in very small fibers. Normal and disease-controls were negative. By gold-immuno-electron microscopy, ADDL-immunoreactivities were in close proximity to 6-10 nm amyloid-like fibrils, and also were immunodecorating amorphous and floccular material. In cultured human muscle fibers, we found that inhibition of autophagy led to the accumulation of Aß oligomers. This novel demonstration of Aß42 oligomers in s-IBM muscle biopsy provides additional evidence that intra-muscle fiber accumulation of Aß42 oligomers in s-IBM may contribute importantly to s-IBM pathogenic cascade.

Impaired autophagy in sporadic inclusion-body myositis and in endoplasmic reticulum stress-provoked cultured human muscle fibers.

The hallmark pathologies of sporadic inclusion-body myositis (s-IBM) muscle fibers are autophagic vacuoles and accumulation of ubiquitin-positive multiprotein aggregates that contain amyloid-beta or phosphorylated tau in a beta-pleated sheet amyloid configuration. Endoplasmic reticulum stress (ERS) and 26S proteasome inhibition, also associated with s-IBM, putatively aggrandize the accumulation of misfolded proteins. However, autophagosomal-lysosomal pathway formation and function, indicated by autophagosome maturation, have not been previously analyzed in this system. Here we studied the autophagosomal-lysosomal pathway using 14 s-IBM and 30 disease control and normal control muscle biopsy samples and our cultured human muscle fibers in a microenvironment modified to resemble aspects of s-IBM pathology. We report for the first time that in s-IBM, lysosomal enzyme activities of cathepsin D and B were decreased 60% (P < 0.01) and 40% (P < 0.05), respectively. We also detected two indicators of increased autophagosome maturation, the presence of LC3-II and decreased mammalian target of rapamycin-mediated phosphorylation of p70S6 kinase. Moreover, in cultured human muscle fibers, ERS induction significantly decreased activities of cathepsins D and B, increased levels of LC3-II, decreased phosphorylation of p70S6 kinase, and decreased expression of VMA21, a chaperone for assembly of lysosomal V-ATPase. We conclude that in s-IBM muscle, decreased lysosomal proteolytic activity might enhance accumulation of misfolded proteins, despite increased maturation of autophagosomes, and that ERS is a possible cause of s-IBM-impaired lysosomal function. Thus, unblocking protein degradation in s-IBM muscle fibers may be a desirable therapeutic strategy.

Decreased SIRT1 deacetylase activity in sporadic inclusion-body myositis muscle fibers.

SIRT1 belongs to the sirtuin family of NAD(+)-dependent histone/protein deacetylases. Experimentally, increased activity of SIRT1 facilitates calorie-restricted longevity, and decreases NF-kappaB activation and the amount of the amyloid-beta (Abeta). We studied SIRT1 in an aging-associated muscle disease, sporadic inclusion-body myositis (s-IBM), whose muscle fibers contain increased NF-kappaB activation and abnormal accumulation of Abeta. We show that, as compared to the age-matched controls, in s-IBM muscle fibers: (1) SIRT1 activity and deacetylation of SIRT1 targets, H4, NF-kappaB and p53 were decreased; (2) SIRT1 mRNA and protein were significantly increased; (3) in the cytoplasm, SIRT1 protein was accumulated in the form of cytoplasmic aggregates; (4) in the nuclei, SIRT1 protein was decreased. To our knowledge, this is the first demonstration of SIRT1 abnormalities, including decreased SIRT1 deacetylase activity, in human disease associated with aging. We propose that in s-IBM muscle fibers, inadequate activity of SIRT1 may be detrimental by increasing NF-kappaB activation and contributing to abnormal Abeta accumulation. Improving SIRT1 action by treatment with known SIRT1 activators might benefit s-IBM patients.

p62/SQSTM1 is overexpressed and prominently accumulated in inclusions of sporadic inclusion-body myositis muscle fibers, and can help differentiating it from polymyositis and dermatomyositis.

p62, also known as sequestosome1, is a shuttle protein transporting polyubiquitinated proteins for both the proteasomal and lysosomal degradation. p62 is an integral component of inclusions in brains of various neurodegenerative disorders, including Alzheimer disease (AD) neurofibrillary tangles (NFTs) and Lewy bodies in Parkinson disease. In AD brain, the p62 localized in NFTs is associated with phosphorylated tau (p-tau). Sporadic inclusion-body myositis (s-IBM) is the most common progressive muscle disease associated with aging, and its muscle tissue has several phenotypic similarities to AD brain. Abnormal accumulation of intracellular multiprotein inclusions, containing p-tau in the form of paired helical filaments, amyloid-beta, and several other "Alzheimer-characteristic proteins", is a characteristic feature of the s-IBM muscle fiber phenotype. Diminished proteasomal and lysosomal protein degradation appear to play an important role in the formation of intra-muscle-fiber inclusions. We now report that: (1) in s-IBM muscle fibers, p62 protein is increased on both the protein and the mRNA levels, and it is strongly accumulated within, and as a dense peripheral shell surrounding, p-tau containing inclusions, by both the light- and electron-microscopy. Accordingly, our studies provide a new, reliable, and simple molecular marker of p-tau inclusions in s-IBM muscle fibers. The prominent p62 immunohistochemical positivity and pattern diagnostically distinguish s-IBM from polymyositis and dermatomyositis. (2) In normal cultured human muscle fibers, experimental inhibition of either proteasomal or lysosomal protein degradation caused substantial increase of p62, suggesting that similar in vivo mechanisms might contribute to the p62 increase in s-IBM muscle fibers.

Amyloid-beta42 is preferentially accumulated in muscle fibers of patients with sporadic inclusion-body myositis.

Sporadic inclusion-body myositis (s-IBM) is the only muscle disease in which accumulation of amyloid-beta (Abeta) in abnormal muscle fibers appears to play a key pathogenic role. Increased amyloid-beta precursor protein (AbetaPP) and Abeta accumulation have been reported to be upstream steps in the development of the s-IBM pathologic phenotype, based on cellular and animal models. Abeta is released from AbetaPP as a 40 or 42 aminoacid peptide. Abeta42 is considered more cytotoxic than Abeta40, and it has a higher propensity to aggregate and form amyloid fibrils. Using highly specific antibodies, we evaluated in s-IBM muscle biopsies intra-muscle fiber accumulation of Abeta40 and Abeta42-immunoreactive aggregates by light- and electron-microscopic immunocytochemistry, and quantified their amounts by ELISA. In s-IBM, 80-90% of the vacuolated muscle fibers and 5-20% of the non-vacuolated muscle fibers contained plaque-like Abeta42-immunoreactive inclusions, while only 69% of those fibers also contained Abeta40 deposits. By immuno-electronmicroscopy, Abeta42 was associated with 6-10 nm amyloid-like fibrils, small electron-dense floccular clumps and larger masses of amorphous material. Abeta40 was present only on small patches of floccular clumps and amorphous material; it was not associated with 6-10 nm amyloid fibrils. By ELISA, in s-IBM muscle biopsies Abeta42 was present in values 8.53-44.7 pg/ml, while Abeta40 was not detectable; normal age-matched control biopsies did not have any detectable Abeta42 or Abeta40. Thus, in s-IBM muscle fibers, Abeta42 is accumulated more than Abeta40. We suggest that Abeta42 oligomers and their cytotoxicity may play an important role in the s-IBM pathogenesis.

Neuropathology of Parkinson's disease associated with the LRRK2 Ile1371Val mutation.

Leucine-Rich Repeat Kinase 2 (LRRK2) gene mutations are the most common known cause of Parkinson's disease (PD), but neuropathological studies are available on very few patients with LRRK2 mutation. The reported findings range from Lewy body-positive pathology to different pathologies, including nigral degeneration without distinctive features, neuronal loss with only ubiquitin-positive inclusions, and tau-positive-only pathology. Here we report the first neuropathological study in an Italian PD case carrying a different LRRK2 mutation, Ile1371Val, and showing typical ubiquitin- and alpha-synuclein-positive Lewy body pathology. These findings support the concept that the neurodegeneration associated with LRRK2 mutations might be clinically and pathologically indistinguishable from typical PD.

Anaplasia is rare and does not influence prognosis in adult medulloblastoma.

Histopathologic grading based on increasing anaplasia predicts clinical behavior of pediatric medulloblastomas. The present study was aimed at grading 86 medulloblastomas of adult patients (aged 18 and older) by anaplasia and analyzing the predictive power. Nodularity, desmoplasia, nuclear size, nuclear pleomorphism, necrosis, and endothelial proliferations have been evaluated. Morphometric analysis of nuclear size was performed using the Eclipse Net program. Patients treated with standard postoperative radiotherapy (35 Gy to craniospinal axis and 50 Gy to posterior fossa) were considered for correlation with survival. Pathologic data and total survival were compared by Kaplan-Meier and logrank analysis. No correlation was found between total survival duration and individual pathologic features. Cooccurrence of nuclear pleomorphism, large nuclear diameter, microvascular proliferations, and necroses did not predict outcome. Severe nuclear pleomorphism was found in 4 of 86 cases; the only large-cell medulloblastoma was from an 18-year-old patient. Histopathologic factors have no clinical use for stratification of patients in risk groups. The histologic spectrum of medulloblastoma in adults is different from that in children.