The mechanisms leading to degeneration of dopaminergic neurons (DNs) in the substantia nigra of patients with Parkinson's disease (PD) are not completely understood. Here, we show, in the postmortem human tissue, that these neurons aberrantly express mitosis-associated proteins, including the E2F-1 transcription factor, and appear to duplicate their nuclear DNA. We further demonstrate that the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injected into mice and application of its active metabolite 1-methyl-4-phenylpyridinium to mesencephalic cultures activate the retinoblastoma-E2F pathway in postmitotic DNs. We also find that cell death rather than mitotic division followed the toxin-induced replication of DNA, as determined by BrdU incorporation in DNs. In addition, blocking E2F-1 transcription protected cultured DNs against 1-methyl-4-phenylpyridinium toxicity. Finally, E2F-1-deficient mice were significantly more resistant to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced dopaminergic cell death than their wild-type littermates. Altogether, BrdU incorporation in mature neurons and lack of evidence for newborn neurons argue against neuronal turnover in normal conditions or during pathological states in the substantia nigra. Instead, our results demonstrate that mitosis-like signals are activated in mature DNs in patients with PD and mediate neuronal death in experimental models of the disease. Inhibition of mitosis-like signals may therefore provide strategies for neuroprotection in PD.adult neurogenesis ͉ neurodegeneration ͉ retinoblastoma ͉ apoptosis ͉ dopamine

When stimulated by inflammation, peripheral blood cells signal directly to neurons in the brain via the transfer of functional RNA enclosed in extracellular vesicles.

No abstract

Quantitative imaging analysis of endogenous an exogenous elements throughout entire organisms is required for studies of bioavailability, transport processes, distribution, contamination and to monitor environmental risks using indicator organisms. An imaging mass spectrometric technique using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was developed to analyze selenium and metal distributions in longitudinal sections (thickness, 100 microm) of entire slugs (genus arion). Slugs were fed with either a placebo or solutions containing 1000 microg mL(-1) Se. Samples (raster area, 25 mmx45 mm) were scanned together with synthetic matrix-matched standards with a focused beam of a Nd:YAG laser (wavelength, 266 nm; diameter of laser crater, 50 microm; laser power density, 3x10(9) W cm(-2)) in a large laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a double focusing sector field ICPMS. Ion intensities of selenium (78Se+, 82Se+) were measured together with 13C+, 63Cu+, and 64Zn+ within the entire tissue section. The regression coefficient of the calibration curve was 0.998. Inhomogeneous distributions for Se but also for C, Cu, and Zn were found. Selenium was enriched in the kidney (150 microg g(-1) in Se-treated animals versus 15 microg g(-1) in the placebo-treated animal, respectively) and in the digestive gland (200 microg g(-1) versus 25 microg g(-1)). Highest Se concentrations were detected in the gut of Se-treated slugs (250 microg g(-1)), and additional Se occurred in the skin of these animals. Cu was enriched in the heart and the mucous ventral skin. Interestingly, in addition to the localization in the digestive gland, Zn was detected only in the dorsal skin but not the ventral skin. The developed analytical technique allows the quantitative imaging of selenium together with selected metals in thin sections of biological tissue with limits of detection at the submicrogram per gram range.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been established as a powerful technique for the determination of metal and nonmetal distributions within biological systems with high sensitivity. An imaging LA-ICP-MS technique for Fe, Cu, Zn, and Mn was developed to produce large series of quantitative element maps in native brain sections of mice subchronically intoxicated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridin (MPTP) as a model of Parkinson's disease. Images were calibrated using matrix-matched laboratory standards. A software solution allowing a precise delineation of anatomical structures was implemented. Coronal brain sections were analyzed crossing the striatum and the substantia nigra, respectively. Animals sacrificed 2 h, 7 d, or 28 d after the last MPTP injection and controls were investigated. We observed significant decreases of Cu concentrations in the periventricular zone and the fascia dentata at 2 h and 7d and a recovery or overcompensation at 28 d, most pronounced in the rostral periventricular zone (+40%). In the cortex Cu decreased slightly to -10%. Fe increased in the interpeduncular nucleus (+40%) but not in the substantia nigra. This pattern is in line with a differential regulation of periventricular and parenchymal Cu, and with the histochemical localization of Fe, and congruent to regions of preferential MPTP binding described in the rodent brain. The LA-ICP-MS technique yielded valid and statistically robust results in the present study on 39 slices from 19 animals. Our findings underline the value of routine micro-local analytical techniques in the life sciences and affirm a role of Cu availability in Parkinson's disease.

SUMMARY1. We investigate here for the first time in primate brain the combinatorial expression of the three major functionally relevant proteins for catecholaminergic neurotrans-mission tyrosine hydroxylase (TH), aromatic acid acid decarboxylase (AADC), and the brain-specific isoform of the vesicular monoamine transporter, VMAT2, using highly specific antibodies and immunofluorescence with confocal microscopy to visualize combinatorial expression of these proteins.2. In addition to classical TH, AADC, and VMAT2-copositive catecholaminergic neurons, two unique kinds of TH-positive neurons were identified based on co-expression of AADC and VMAT2.3. TH and AADC co-positive, but VMAT2-negative neurons, are termed "nonexocytotic catecholaminergic TH neurons." These were found in striatum, olfactory bulb, cerebral cortex, area postrema, nucleus tractus solitarius, and in the dorsal motor nucleus of the vagus.4. TH-positive neurons expressing neither AADC nor VMAT2 are termed "dopaergic TH neurons." We identified these neurons in supraoptic, paraventricular and periventricular hypothalamic nuclei, thalamic paraventicular nucleus, habenula, parabrachial nucleus, cerebral cortex and spinal cord. We were unable to identify any dopaergic (TH-positive, AADC-negative) neurons that expressed VMAT2, suggesting that regulatory mechanisms exist for shutting off VMAT2 expression in neurons that fail to biosynthesize its substrates.5. In several cases, the corresponding TH phenotypes were identified in the adult rat, suggesting that this rodent is an appropriate experimental model for further investigation of these TH-positive

Mechanisms behind how the immune system signals to the brain in response to systemic inflammation are not fully understood. Transgenic mice expressing Cre recombinase specifically in the hematopoietic lineage in a Cre reporter background display recombination and marker gene expression in Purkinje neurons. Here we show that reportergene expression in neurons is caused by intercellular transfer of functional Cre recombinase messenger RNA from immune cells into neurons in the absence of cell fusion. In vitro purified secreted extracellular vesicles (EVs) from blood cells contain Cre mRNA, which induces recombination in neurons when injected into the brain. Although Cre-mediated recombination events in the brain occur very rarely in healthy animals, their number increases considerably in different injury models, particularly under inflammatory conditions, and extend beyond Purkinje neurons to other neuronal populations in cortex, hippocampus, and substantia nigra. Recombined Purkinje neurons differ in their miRNA profile from their nonrecombined counterparts, indicating physiological significance. These observations reveal the existence of a previously unrecognized mechanism to communicate RNA-based signals between the hematopoietic system and various organs, including the brain, in response to inflammation.

Naturally occurring antibodies directed against beta-amyloid (Abeta) were detected in intravenous immunoglobulin preparations. After intravenous immunoglobulin treatment in patients with different neurological diseases, total Abeta and Abeta(1-42) in the cerebrospinal fluid was reduced significantly compared with baseline values. In the serum, total Abeta levels increased after intravenous immunoglobulin treatment, whereas no significant change was observed in Abeta(1-42) levels. Antibodies against Abeta were found to be increased in the serum and cerebrospinal fluid after intravenous immunoglobulin treatment. This study provides evidence that intravenous immunoglobulin or purified Abeta antibodies may modify Abeta and Abeta(1-42) levels, suggesting potential utility as a therapy for Alzheimer disease.