Brain monoamine abnormalities in the two types of Creutzfeldt-Jakob disease

Transmitter deficits in Alzheimer's disease

The pattern of neurotransmitter pathway losses in Alzheimer's disease are reviewed. Deficits of the cholinergic pathway from the nucleus basalis, the noradrenergic pathway from the locus coeruleus and the serotoninergic pathway from the raphe nuclei are established. Cortical somatostatin interneurons are affected and dopaminergic neurons may be affected although these may be late or secondary phenomena in the disease process. Other neuronal systems, particularly in the hippocampus and temporal cortex, are also damaged. However, the disease is not one of generalised neuronal atrophy since some neurons are selectively spared. The established pathway-specific losses are discussed in relation to the clinical symptomatology and the pathology of the disorder. The biochemical and histological findings are compared with similar measurements made on tissues from other dementing disorders in an attempt to trace features common to dementias. Finally, as an addendum, a hypothesis is briefly outlined which attempts to explain the common features of the affected neurons and the pathogenesis of the disorder.

Unaltered susceptibility to scrapie in serotonin transporter deficient mice

The serotonergic system has been hypothesized to play an important role in prion diseases. Specifically, hyperactivity of the serotonergic system in prion diseases is suggested by an increase in the turnover rate of the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) in human and experimental prion diseases. The 5-HT transporter (5-HTT) determines the duration of serotonergic neurotransmission by way of reuptake of 5-HT from the extracellular space. 5-HTT availability is reduced in brains of patients with the human prion disease familial fatal insomnia. To further clarify a possible role of the 5-HTT in prion diseases we investigated whether mice lacking the 5-HTT display an altered susceptibility to experimental scrapie infection. Surprisingly, 5-HTT knockout mice developed mouse scrapie in a time course similar to wildtype control mice with accumulation of the pathological prion protein, PrP(Sc) and with typical pathological hallmarks of the disease. These findings argue against a major role of the 5-HTT in the pathogenesis of prion diseases in mice.

Effects on the serotoninergic system in sub-acute transmissible spongiform encephalopathies: current data, hypotheses, suggestions for experimentation

Sub-acute transmissible spongiform encephalopathies (TSEs), or prion diseases, are affections in which little is known of their etiology. The predominant theory stipulates that an abnormal protease-resistant prion protein (PrPres) would be infectious by directly inducing its defective conformation to the normal native protein (PrPC). The function of PrPC remains unknown. The preferred localization of PrPC at the level of the synapses supposes a function in neuronal transmission. Several neurotransmitter systems (acetylcholine, GABA, dopamine, etc.) are damaged in TSEs, mainly the serotonin (5-HT) system. At a hypothetical level, PrPC would play a trophic and functional role by regulating the capture of amino acid precursors of neurotransmitters and the functions of neuroreceptors, in particular regarding tryptophan and 5-HT receptors. By comparison with the modes of action of Ras proteins and of the envelope glycoprotein of jaagsiekte sheep retrovirus, the adaptation of an oncogenic model is suggested for the mode of action of PrPres. The sequence of events could be the following: capture of PrPres and forming of an abnormal receptor, chronic disturbance of transduction pathways, more particularly of the phosphatidylinositol-3 kinase (PI-3K)/protein kinase B (Akt)/glycogen synthetase kinase 3 (GSK 3)/Wnt-beta catenin pathway, deregulation of the PrP gene and infrequent and transitory forming of abnormal RNA messengers and, finally, the forming of abnormal proteins and the deterioration of the serotoninergic system. The involvement of endogenous nucleic acids is supposed. The infectious agent of TSEs could be an ancestral form of retrovirus, such as a retrotransposon using the prion protein as an envelope glycoprotein. Pharmacological tests, by comparison with a rare disease of unknown etiology in cattle, bovine spastic paresis, are suggested with the amino acid precursors of neuromediators (tryptophan, tyrosine, glutamic acid, etc.) and with lithium, neuroprotector and regulator of the serotonergic system.

Does an ultra violet photooxidation of the manganese-loaded/copper-depleted prion protein in the retina initiate the pathogenesis of TSE?

Ecosystems supporting clusters of sporadic transmissible spongiform encephalopathy (TSE) are characterized by common properties of high-manganese/low-copper, zinc, selenium mineral status, and high-altitude/snow-covered/pre-cambrian mountain terrain where above-average intensities of ultra violet/ozone oxidants are prevalent. Cell culture trials have confirmed the hypothesis that manganese (Mn) substitutes at Prion Protein's (PrP's) vacated copper (Cu) domain, whereupon PrP loses its Cu-mediated antioxidant function, transforming into a protease-resistant misfolded isoform that aggregates into fibril 'tombstone' structures - the key hallmark distinguishing TSE central nervous system (CNS) pathology. The cellular localisation of PrP suggests PrP serves a 'front line' contributory role in neutralizing radicals generated by incoming environmental oxidants, whilst an intensive expression of PrP messenger ribonucleic acid (mRNA) in the retina, melanocytes, epidermis, etc., suggests PrP performs a key antioxidant role as a 'photooxidative shock absorber'; binding of porphyrin IX, Congo red and other photosensitisers to PrPc suggests PrPc serves as an integral associate of the porphyrin/melanin chromophore electron transfer chain; thereby serving as a quencher of singlet O2/superoxide generated by photoenergised chromophores/xeno photosensitisers. It is proposed that sporadic TSE pathogenesis is initiated in the retina of environmentally/genetically predisposed individuals via a two-stage chronic toxic process - Mn substitution at PrP's Cu domain forming a stable Mn2+-PrP complex, followed by an ultra violet in situ photo-oxidization of the Mn2+ component; whereby the latent 'Jekyll and Hyde' capacity of the Mn2+-PrP conjugate is activated into the fully fledged, 'infectious' lethal auto-oxidizing, Mn3+-PrP 'prion' agent. Thus, PrPc's Cu-mediated antioxidant function is replaced by a Mn3+-mediated autooxidant dysfunction. Could the UK's increased loading of a cocktail of environmental oxidants that penetrated the CNS of the UK bovine (ultra violet microwaves/ozone/systemic cu-chelating insecticides) account for a more virulent Mn4+ mediated acceleration of the TSE degenerative process in Mn-contaminated/genetically predisposed individuals, manifesting as the widespread emergence of new-variant bovine spongiform encephalopathy (BSE)/variant Creutzfeldt-Jacob disease (VCJD)/FSE in younger mammals?

Ecosystems supporting clusters of sporadic TSEs demonstrate excesses of the radical-generating divalent cation manganese and deficiencies of antioxidant co factors Cu, Se, Fe, Zn. Does a foreign cation substitution at prion protein's Cu domain initiate TSE?

Analyses of food chains supporting isolated clusters of sporadic TSEs (CWD in N Colorado, scrapie in Iceland, CJD in Slovakia) demonstrate a consistent 2 1/2+ fold greater concentration of the pro-oxidant divalent cation, manganese (Mn), in relation to normal levels recorded in adjoining TSE-free localities. Deficiencies of the antioxidant co factors Cu/Se/Zn/Fe and Mg, P and Na were also consistently recorded in TSE foodchains. Similarities between the clinical/pathological profile of TSEs and Mn delayed psycho-neurotoxicity in miners are cited, and a novel theory generated which suggests that sporadic TSE results from early life dependence of TSE susceptible genotypes on ecosystems characterised by this specific pattern of mineral imbalance. Low Cu/Fe induces an excessive absorption of Mn in ruminants and an increased oxidation of Mn2+ into its pro oxidant species, Mn3+, which accumulates in mitochondria of CNS astrocytes in Mn SOD deficient genotypes. Deficiencies of scavenger co factors Cu/Zn/Se/Fe in the CNS permits Mn3+ initiated chain reactions of auto-oxidant mediated neuronal degeneration to proliferate, which, in turn, up-regulates the expression of the Cu-metalloprotein, prion protein (PrP). Once the rate of PrP turnover and its demand for Cu exceeds the already depleted supply of Cu within the CNS, PrP can no longer bind sufficient Cu to maintain its conformation. Mn3+ substitutes at the vacated Cu domain on PrP, thus priming up a latent capacity for lethal auto-oxidative activity to be carried along with PrP like a 'trojan horse'; where Mn 3+ serves as the integral 'infectious' transmissible component of the misfolded PrP-cation complex. The Mn overactivation of concanavalin A binding to glycoprotein and Mn-initiated autoxidation results in a diverse pathological profile involving receptor capping, aggregation/modification of CNS membrane/cytoskeletal proteins. TSE ensues. The BSE/nv CJD strain entails a 'synthetic' induction of the same CNS mineral disturbance, where 'in utero' exposure to Cu-chelating insecticides/Mn supplements accelerates the onset of a more virulent 'strain' of adolescent TSE.

Viral antibodies in recent onset, nonorganic psychoses: correspondence with symptomatic severity

A parallel of generalized viral infection with psychiatric symptoms has been reported in nonorganic psychotic disorders. The patients concerned had been ill for long periods and some of them had been readmitted. In order to determine the presence of viral infection at the very onset of the psychosis, antibodies in blood and cerebrospinal fluid (CSF) to six viruses [cytomegalovirus (CMV), herpes simplex (HSV) Type 1, mumps, measles, varicella zoster virus (VZV), and Japanese encephalitis virus (JEV)] were assayed in 35 psychotic patients [14 schizophrenics; 13 manic patients; and 8 patients with psychosis not otherwise specified (NOS)] within 1 month of onset of illness. Ten (28.6%) patients had a diagnostic (fourfold) change in the antibody titer in the paired serum and/or CSF samples (drawn at 2-week intervals) and another 10 had high titers (above 2 SDs from the mean in 35 control subjects). The striking temporal correlation with the initial severity and resolution of psychopathology by 2 weeks on the Brief Psychiatric Rating Scale (BPRS) suggests a causally significant, currently active viral infection in these 20 cases.

Unusual findings in Creutzfeldt-Jakob disease. Case report

We present a definite case of Creutzfeldt-Jakob disease (CJD) with visual evoked response (VER) and CSF oligoclonal band abnormalities and discuss the neurobiological significance and diagnostic value of these findings.

Changes in the serotonergic, noradrenergic and dopaminergic levels in the brain of scrapie-infected rats

Levels of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylethyleneglycol (DHPG) were determined by high-performance liquid chromatography in different brain areas of scrapie-infected rats, 8.5 months after intracerebral inoculation of a rat-adapted strain from mice brain (C 506). At this time, rats developed early clinical signs of the disease. Scrapie-infected rats showed a reduction in the levels of 5-HT and 5-HIAA (frontal cortex, hippocampus, mesolimbic structure). Concentrations of DHPG decreased in the frontal and parietal cortices but remained unchanged in the hippocampus. DOPAC levels decreased in the striatum but not in the mesolimbic structure. These results confirm that the serotonergic, noradrenergic and dopaminergic systems are altered in the brain of scrapie-infected rats. They can partly account for clinical signs of scrapie and are in agreement with the scarce data provided by the postmortem analysis of Creutzfeldt-Jakob disease brains.

Monoamine abnormalities in the brain of scrapie-infected rats

The effects of the scrapie agent on the levels of monoamines and their metabolites, and on choline acetyltransferase (CAT) activity have been investigated in discrete brain areas in the rat. Two strains of scrapie (8745 from sheep brain and C506 M3 from mice brain) were inoculated. Scrapie-infected rats showed a reduction in the levels of serotonin (prefrontal cortex, hippocampus, striatum) and dopamine (striatum) and an elevation of 5-HIAA levels (cerebral cortex, striatum, thalamus). Noradrenaline levels were decreased only in the cerebral cortex and cerebellum of rats infected with the scrapie strain C506 M3. CAT activity remained unchanged. These data suggest that the scrapie agent causes a derangement of noradrenergic, serotonergic and dopaminergic systems in the rat brain.