No abstract

Lewy bodies are made from insoluble, phosphorylated α-synuclein, but the earliest changes that precipitate such pathology still remain conjecture. In this study, we quantify and identify relationships between the levels of the main pathologic form of phosphorylated α-synuclein over the course of Parkinson's disease in regions affected early through to end-stage disease. Brain tissue samples from 33 cases at different disease stages and 13 controls were collected through the Australian Network of Brain Banks. 500 mg of frozen putamen (affected preclinically) and frontal cortex (affected late) was homogenized, fractionated and α-synuclein levels evaluated using specific antibodies (syn-1, BD Transduction Laboratories; S129P phospho-α-synuclein, Elan Pharmaceuticals) and quantitative western blotting. Statistical analyses assessed the relationship between the different forms of α-synuclein, compared levels between groups, and determined any changes over the disease course. Soluble S129P was detected in controls with higher levels in putamen compared with frontal cortex. In contrast, insoluble α-synuclein occurred in Parkinson's disease with a significant increase in soluble and lipid-associated S129P, and a decrease in soluble frontal α-synuclein over the disease course. Increasing soluble S129P in the putamen correlated with increasing S129P in other fractions and regions. These data show that soluble non-phosphorylated α-synuclein decreases over the course of Parkinson's disease, becoming increasingly phosphorylated and insoluble. The finding that S129P α-synuclein normally occurs in vulnerable brain regions, and in Parkinson's disease has the strongest relationships to the pathogenic forms of α-synuclein in other brain regions, suggests a propagating role for putamenal phospho-α-synuclein in disease pathogenesis.

Iron and cholesterol are both essential metabolites in mammalian systems, and too much or too little of either can have serious clinical consequences. In addition, both have been associated with steatosis and its progression, contributing, inter alia, to an increase in hepatic oxidative stress. The interaction between iron and cholesterol is unclear, with no consistent evidence emerging with respect to changes in plasma cholesterol on the basis of iron status. We sought to clarify the role of iron in lipid metabolism by studying the effects of iron status on hepatic cholesterol synthesis in mice with differing iron status. Transcripts of seven enzymes in the cholesterol biosynthesis pathway were significantly upregulated with increasing hepatic iron (R 2 between 0.602 and 0.164), including those of the rate-limiting enzyme, 3-hydroxy-3-methylglutarate-coenzyme A reductase (Hmgcr; R 2 5 0.362, P < 0.002). Hepatic cholesterol content correlated positively with hepatic iron (R 2 5 0.255, P < 0.007). There was no significant relationship between plasma cholesterol and either hepatic cholesterol or iron (R 2 5 0.101 and 0.014, respectively). Hepatic iron did not correlate with a number of known regulators of cholesterol synthesis, including sterol-regulatory element binding factor 2 (Srebf2; R 2 5 0.015), suggesting that the increases seen in the cholesterol biosynthesis pathway are independent of Srebf2. Transcripts of genes involved in bile acid synthesis, transport, or regulation did not increase with increasing hepatic iron. Conclusion: This study suggests that hepatic iron loading increases liver cholesterol synthesis and provides a new and potentially important additional mechanism by which iron could contribute to the development of fatty liver disease or lipotoxicity. (HEPATOLOGY 2010;52:462-471) Abbreviations: Abc, adenosine triphosphate-binding cassette; Apo, apolipoprotein; Bhmt2, betaine-homocysteine methyltransferase 2; C/EBPa, CCAAT/enhancer binding protein a; Cyp51, lanosterol-14a demethylase; Cyp27b1, 25-hydroxyvitamin D3-1a-hydroxylase; Cyp7a1, cholesterol 7a-monooxygenase; Ebp, cholestenol-D-isomerase; Ggcx, gamma-glutamyl carboxylase; Ggps1, geranylgeranyl diphosphate synthase 1; GSEA, gene set enrichment analysis; Hmgcr, 3-hydroxy-3-methylglutarate-coenzymeA reductase; Hnf4a, hepatocyte nuclear factor 4a; Hsd17b7, 3-keto-steroid reductase; Hsd3b7, hydroxy-D5-steroid dehydrogenase; Idi1, isopentenyl-diphosphate-D-isomerase; mRNA, messenger RNA; Mvk, mevalonate kinase; NAFLD, nonalcoholic fatty liver disease; NASH, nonalcoholic steatohepatitis; Nqo1, NAD(P)H dehydrogenase (quinone) 1; Nr1h3, nuclear receptor 1H3; Nsdhl, sterol-4a-carboxylate 3-dehydrogenase; Pmvk, phosphomevalonate kinase; Psap, prosaponin; RT-PCR, real-time polymerase chain reaction; Sc5d, lathosterol oxidase; Srebf2, sterol-regulatory element binding factor 2; Tm7sf2, D14-sterol reductase; Tmem97, transmembrane protein 97; Vkorc1, vitamin K epoxide reductase complex (subunit 1); VLDL, very low density lipoprotein; Vrk3, vaccini...

Preoligodendrocytes have been described in cultures and tissue prints of adult human white matter (Armstrong et al., 1992). To characterize further these precursors of human oligodendrocytes, we have investigated whether they express genes playing a critical role in oligodendrocyte development. In the intact human brain, platelet-derived growth factor receptor alpha (PDGF alpha R) and myelin transcription factor 1 (MyTI) transcripts are expressed in 1-2% of cells of the oligodendrocyte lineage (OL), and clusters of such cells can be found in the periventricular region. Myelin basic protein transcripts containing exon 2 information (exon 2+ MBP), which are characteristic of the premyelinating stage, are detected in 15-20% of OL cells in vivo. When OL cells are separated from human white matter and allowed to regenerate in vitro, a much larger proportion of these cells express developmentally regulated genes, while exon 2- MBP and proteolipid protein (PLP) transcripts characteristic of mature OL cells appear transiently downregulated. Basic fibroblast growth factor (bFGF), even in the presence of PDGF, does not promote DNA synthesis in these cultured OL cells. Yet bFGF induces human oligodendrocytes to regenerate their processes rapidly in vitro and to express O4 antigens as well as exon 2+ MBP, MyTI, and PLP transcripts. While bFGF accelerates early regenerative processes, it also maintains high expression of exon 2+ MBP transcripts in OL cells for up to 2 weeks in vitro. In contrast, high levels of insulin in the absence of bFGF allow accumulation of exon 2- MBP and PLP transcripts in most OL cells at 2-3 weeks in vitro. We propose that the myelinated human brain harbors a small pool of precursors of oligodendrocytes and that growth factor-regulated phenotypic plasticity rather than mitogenic potential accounts for the regeneration of oligodendrocytes in the initial stages of demyelinating diseases such as multiple sclerosis.