Functions and dysfunctions of nitric oxide in brain

Nitric oxide (NO) works as a retrograde neurotransmitter in synapses, allows the brain blood flow and also has important roles in intracellular signaling in neurons from the regulation of the neuronal metabolic status to the dendritic spine growth. Moreover NO is able to perform post-translational modifications in proteins by the S-nitrosylation of the thiol amino acids, which is a physiological mechanism to regulate protein function. On the other hand, during aging and pathological processes the behavior of NO can turn harmful when reacts with superoxide anion to form peroxynitrite. This gaseous compound can diffuse easily throughout the neuronal membranes damaging lipid, proteins and nucleic acids. In the case of proteins, peroxynitrite reacts mostly with the phenolic ring of the tyrosines forming nitro-tyrosines that affects dramatically to the physiological functions of the proteins. Protein nitrotyrosination is an irreversible process that also yields to the accumulation of the modified proteins contributing to the onset and progression of neurodegenerative processes such as Alzheimer's disease or Parkinson's disease.     

A branched-chain organic acid linked to multiple sclerosis: first identification by NMR spectroscopy of CSF

(1)H NMR spectroscopy of cerebrospinal fluid (CSF) is currently being used to study metabolic profiles characteristic of distinct multiple sclerosis (MS) manifestations. For select MS patient groups, we have previously detected significantly increased concentrations of several identified metabolites and one unidentified compound. We now present, for the first time, the identification of the latter molecule, beta-hydroxyisobutyrate (BHIB). A combination of dedicated 1D and 2D (1)H NMR experiments was employed for signal assignment. To our knowledge, BHIB has not previously been identified in (1)H NMR spectra of biofluids or biological tissues. Our assignment suggests new biochemical pathways involved in specific MS pathologies.     

Neuropeptide changes and neuroactive amino acids in CSF from humans and sheep with neuronal ceroid lipofuscinoses (NCLs, Batten disease)

Anomalies in neuropeptides and neuroactive amino acids have been postulated to play a role in neurodegeneration in a variety of diseases including the inherited neuronal ceroid lipofuscinoses (NCLs, Batten disease). These are often indicated by concentration changes in cerebrospinal fluid (CSF). Here we compare CSF neuropeptide concentrations in patients with the classical juvenile CLN3 form of NCL and the classical late infantile CLN2 form with neuropeptide and neuroactive amino acid concentrations in CSF from sheep with the late infantile variant CLN6 form.A marked disease related increase in CSF concentrations of neuron specific enolase and tau protein was noted in the juvenile CLN3 patients but this was not observed in an advanced CLN2 patient nor CLN6 affected sheep. No changes were noted in S-100b, GFAP or MBP in patients or of S-100b, GFAP or IGF-1 in affected sheep. There were no disease related changes in CSF concentrations of the neuroactive amino acids, aspartate, glutamate, serine, glutamine, glycine, taurine and GABA in these sheep.The changes observed in the CLN3 patients may be progressive markers of neurodegeneration, or of underlying metabolic changes perhaps associated with CLN3 specific changes in neuroactive amino acids, as have been postulated. The lack of changes in the CLN2 and CLN6 subjects indicate that these changes are not shared by the CLN2 or CLN6 forms and changes in CSF concentrations of these compounds are unreliable as biomarkers of neurodegeneration in the NCLs in general.     

Uptake and Metabolism of Choline by Rat Brain After Acute Choline Administration

The present study is concerned with the uptake and metabolism of choline by the rat brain. Intraperitoneal administration of choline chloride (4-60 mg/kg) caused a dose-dependent elevation of the plasma choline concentration from 11.8 to up to 165.2 microM within 10 min and the reversal of the negative arteriovenous difference (AVD) of choline across the brain to positive values at plasma choline levels of greater than 23 microM. Net choline release and uptake were linearly dependent on the plasma choline level in the physiological range of 10-50 microM, whereas the CSF choline level was significantly increased only at plasma choline levels of greater than 50 microM. The bolus injection of 60 mg/kg of [3H]choline chloride caused the net uptake of greater than 500 nmol/g of choline by the brain as calculated from the AVD, which was reflected in a minor increase of free choline level and a long-lasting increase of brain phosphorylcholine content, which paralleled the uptake curve. Loss of label from phosphorylcholine 30 min to 24 h after choline administration was accompanied by an increase of label in phosphatidylcholine, an indication of a delayed transfer of newly taken-up choline into membrane choline pools. In conclusion, homeostasis of brain choline is maintained by a complex system that interrelates choline net movements into and out of the brain and choline incorporation into and release from phospholipids.     

The Significance of Homovanillic Acid and 3,4-Dihydroxyphenylacetic Acid Concentrations in Human Lumbar Cerebrospinal Fluid

The concentrations of the acidic dopamine (DA) catabolites homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) measured in human CSF are supposed to reflect the "turnover" of DA in the brain. The notion of "turnover" is, however, not synonymous with impulse nerve activity in the dopaminergic systems. Significant amounts of DOPAC and HVA could, indeed, be demonstrated in brain structures wherein dopaminergic innervation has not been documented. It must also be noted that DA is not only a neurotransmitter itself, but also a precursor of norepinephrine and epinephrine. Furthermore, in lumbar CSF, levels of biogenic amine catabolites partially reflect metabolism in the spinal cord and may have limited relevance to neurotransmission in the brain. To elucidate these points further, we determined the concentrations of DOPAC and HVA in 22 areas of six human brains and eight levels of six human spinal cords. The data were correlated with the concentration of DA. Quantitative determinations were done using HPLC with electrochemical detection, after solvent and ion-pair extraction. In this study, significant amounts of both DOPAC and HVA were demonstrated in brain structures not previously associated with dopaminergic innervation. The relatively lower DA concentration in these structures suggests that in these regions, the DOPAC and HVA concentrations are unrelated to dopaminergic neurotransmission. The possible role of capillary walls and glial cells in the catabolism of DA must be further evaluated. The demonstration of DOPAC and HVA in the spinal cord is another argument against the hypothesis that CSF levels of HVA and DOPAC reflect closely the activity of the dopaminergic systems in the brain.     

Erp1/Emi2 is essential for the meiosis I to meiosis II transition in Xenopus oocytes

Erp1 (also called Emi2), an inhibitor of the APC/C ubiquitin ligase, is a key component of cytostatic factor (CSF) responsible for Meta-II arrest in vertebrate eggs. Reportedly, however, Erp1 is expressed even during meiosis I in Xenopus oocytes. If so, it is a puzzle why normally maturing oocytes cannot arrest at Meta-I. Here, we show that actually Erp1 synthesis begins only around the end of meiosis I in Xenopus oocytes, and that specific inhibition of Erp1 synthesis by morpholino oligos prevents entry into meiosis II. Furthermore, we demonstrate that premature, ectopic expression of Erp1 at physiological Meta-II levels can arrest maturing oocytes at Meta-I. Thus, our results show the essential role for Erp1 in the meiosis I/meiosis II transition in Xenopus oocytes and can explain why normally maturing oocytes cannot arrest at Meta-I.     

Comparative peptidome analyses of the profiles of the peptides ranging from 1­–10 KD in CSF samples pooled from probable sporadic CJD and non-CJD patients

The shotgun strategy applying tandem mass spectrometry has been widely used to identify the proteins that are differentially distributed among diseases for its high reliability and efficiency. To find out the potential difference of protein profiles in cerebrospinal fluids (CSF) between Creutzfeldt-Jakob disease (CJD) and non-CJD patients, especially in the fraction ranging from 1–10 KD, the CSF samples of 40 probable sporadic CJD (sCJD) patients, 32 non-CJD cases with dementia and 17 non-CJD cases without dementia were separately pooled and enriched by the magnetic beads based weak cation exchange chromatography (MB-WCX). After trypsin digestion, each enriched CSF was separated and identified by RP-HPLC-ESI-QTOF MS/MS. In total, 42, 53 and 47 signals of proteins were identified in the pooled CSF fraction less than 10 KD of probable sCJD, non-CJD with dementia and non-CJD without dementia, respectively. Compared with that of probable sCJD, the similarity of CSF protein profiles of non-CJD with dementia (76.2%) were higher than that of non-CJD without dementia (57.1%). Nine CSF proteins were found to be specially observed in probable sCJD group. Those data may help to select the potential biomarkers for diagnosis of CJD. Additionally, further studies of the small segments of cellular proteins in CSF of CJD patients may also provide scientific clues for understanding the neuropathogenesis of TSEs.