The histopathological hallmark of Parkinson's disease (PD) is the presence of fibrillar aggregates referred to as Lewy bodies (LBs), in which α-synuclein is a major constituent. Pale bodies, the precursors of LBs, may serve the material for that LBs continue to expand. LBs consist of a heterogeneous mixture of more than 90 molecules, including PD-linked gene products (α-synuclein, DJ-1, LRRK2, parkin, and PINK-1), mitochondria-related proteins, and molecules implicated in the ubiquitin-proteasome system, autophagy, and aggresome formation. LB formation has been considered to be a marker for neuronal degeneration because neuronal loss is found in the predilection sites for LBs. However, recent studies have indicated that nonfibrillar α-synuclein is cytotoxic and that fibrillar aggregates of α-synuclein (LBs and pale bodies) may represent a cytoprotective mechanism in PD.

We reviewed the methods of nonheme-iron histochemistry with special focus on the underlying chemical principles. The term nonheme-iron includes heterogeneous species of iron complexes where iron is more loosely bound to low-molecular weight organic bases and proteins than that of heme (iron-protoporphyrin complex). Nonheme-iron is liberated in dilute acid solutions and available for conventional histochemistry by the Perls and Turnbull and other methods using iron chelators, which depend on the production of insoluble iron compounds. Treatment with strong oxidative agents is required for the liberation of heme-iron, which therefore is not stained by conventional histochemistry. The Perls method most commonly used in laboratory investigations largely stains ferric iron, but stains some ferrous iron as well, while the Turnbull method is specific for the latter. Although the Turnbull method performed on sections fails in staining ferrous iron or stains only such parts of the tissue where iron is heavily accumulated, an in vivo perfusion-Turnbull method demonstrated the ubiquitous distribution of ferrous iron, particularly in lysosomes. The Perls or Turnbull reaction is enhanced by DAB/silver/gold methods for electron microscopy. The iron sulfide method and the staining of redox-active iron with H(2)O(2) and DAB are also applicable for electron microscopy. Although the above histochemical methods have advantages for visualizing iron by conventional light and electron microscopy, the quantitative estimation of iron is not easy. Recent methods depending on the quenching of fluorescent divalent metal indicators by Fe(2+) and dequenching by divalent metal chelators have enabled the quantitative estimation of chelatable Fe(2+) in isolated viable cells.

Ubiquilin-1 (UBQLN1), a member of the ubiquitin-like protein family (UBQLN1-4), is associated with neurofibrillary tangles in Alzheimer's disease (AD) and with Lewy bodies (LBs) in Parkinson's disease (PD) [7]. Mutations in UBQLN2 cause dominant X-linked amyotrophic lateral sclerosis (ALS) [4]. UBQLN2-immunoreactive neuronal cytoplasmic inclusions (NCIs) are found in the hippocampus and spinal cord in ALS with or without UBQLN2 mutation. Moreover, a distinct pattern of UBQLN2 pathology is seen in cases of ALS and frontotemporal lobar degeneration with TDP-43-positive inclusions (FTLD-TDP) showing C9ORF72-hexanucleotide repeat expansion [2], which is the most common genetic abnormality in ALS/ FTLD [3,12]. Here we report that UBQLN2 immunoreactivity is present in cytoplasmic and nuclear inclusions in various neurodegenerative diseases.Post-mortem cases of sporadic ALS (n = 5), FTLD-TDP type B (n = 4), PD (n = 5), neocortical-type DLB (n = 5), multiple system atrophy (MSA; n = 5), AD (n = 5), Pick's disease (n = 4), progressive supranuclear palsy (n = 4), corticobasal degeneration (n = 4), argyrophilic grain disease (n = 4), Huntington's disease (HD; n = 3), dentatorubral-pallidoluysian atrophy (DRPLA; n = 5), spinal and bulbar muscular atrophy (SBMA; n = 3), spinocerebellar ataxia type 1 (SCA1; n = 3), SCA2 (n = 1), SCA3 (n = 5), intranuclear inclusion body disease (INIBD; n = 5) and controls (n = 5) were utilized. Immunohistochemistry was performed as described previously [10] with the following antibodies: UBQLN2, UBQLN1, phosphorylated a-synuclein, phosphorylated tau, ubiquitin, polyglutamine and TDP-43 (Online Resource). The total number of inclusions immunostained with each antibody was counted in contiguous sections.In controls, neuronal nuclei were weakly immunolabeled with anti-UBQLN2 (Fig. 1a). UBQLN2-immunoreactive NCIs were found in the temporal cortex in FTLD-TDP (25 % relative to TDP-43-positive inclusions) as well as in the spinal cord in ALS (14 %) (Fig. 1b). In PD/DLB, both brainstem type and cortical LBs were intensely stained (Fig. 1c, d). Contiguous sections stained with anti-UB-QLN2 and anti-a-synuclein revealed that 21 % of brainstem-type LBs and 48 % of cortical LBs were positive for UBQLN2. In MSA, 82 % of glial cytoplasmic inclusions (GCIs) were positive for UBQLN2 (Fig. 1e). In HD, DRPLA, SBMA, SCA1-3 and INIBD, more than 95 % of neuronal nuclear inclusions (NNIs) were strongly immunolabeled ( Fig. 1f-l). In addition, Marinesco bodies (MBs)

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Oxidative stress has been proposed as a potential mechanism for neurodegenerative diseases, such as Alzheimer disease (AD), Parkinson disease (PD), and amyotrophic lateral sclerosis (ALS). In response to oxidative stress, the levels of numerous cytoprotective products are increased via alteration of the Kelch-like ECH-associated protein 1 (Keap1) and NF-E2-related factor 2 (Nrf2) system. One of the Nrf2 targets, p62, has been known to be incorporated into a wide spectrum of cytoplasmic inclusions in neurodegenerative diseases and interact with Keap1. However, it remains unclear whether Keap1 is associated with the pathogenesis of neurodegenerative diseases. In this study, we investigated the relationship between p62 and Keap1 in the brains of patients with AD, PD, dementia with Lewy bodies (DLB), and ALS. Biochemical analyses showed that p62 and Keap1 interacted with each other in AD and DLB brains and were extracted into similar detergent-soluble and -insoluble fractions. Pathologic examination demonstrated that anti-Keap1 antibodies immunostained Lewy bodies in PD and DLB, neurofibrillary tangles in AD, and skeinlike inclusions in ALS. Further analysis showed that the levels of common Nrf2 target genes were increased in AD compared with those in controls. However, there were no statistical significances in the levels of Nrf2 target genes in DLB relative to controls. Our pathologic and biochemical results suggest a molecular basis for stress response to be involved in the formation of cytoplasmic inclusions observed in several neurodegenerative diseases.