Prion diseases: current understanding of epidemiology and pathogenesis, and therapeutic advances.

The bovine spongiform encephalopathy (BSE) epidemic, along with the related threat to human health posed by the transmission of the BSE agent to humans, has highlighted the importance of prion diseases. These fatal neurodegenerative diseases are characterised by spongiform changes in the CNS, and comprise a wide spectrum of clinicopathological entities in humans and animals, such as Creutzfeldt-Jakob disease (CJD) and its emerging new variant (vCJD) in humans, and BSE and scrapie in animals. This article reviews the geographical distribution and the temporal trends of CJD and vCJD; the major events in the pathogenesis of prion diseases; the risk factors for sporadic CJD and vCJD; and the possible strategies for treating them.

Gerstmann-Sträussler-Scheinker disease amyloid protein polymerizes according to the "dock-and-lock" model.

Prion protein (PrP) amyloid formation is a central feature of genetic and acquired prion diseases such as Gerstmann-Sträussler-Scheinker disease (GSS) and variant Creutzfeldt-Jakob disease. The major component of GSS amyloid is a PrP fragment spanning residues approximately 82-146, which when synthesized as a peptide, readily forms fibrils featuring GSS amyloid. The present study employed surface plasmon resonance (SPR) to characterize the binding events underlying PrP82-146 oligomerization at the first stages of fibrillization, according to evidence suggesting a pathogenic role of prefibrillar oligomers rather than mature amyloid fibrils.

PEN-2 gene mutation in a familial Alzheimer's disease case.

Genetic evidence indicates a central role of cerebral accumulation of beta-amyloid (Abeta) in the pathogenesis of Alzheimer's disease (AD). Beside presenilin 1 and 2, three other recently discovered proteins (Aph 1, PEN 2 and nicastrin) are associated with gamma-secretase activity, the enzymatic complex generating Abeta. Alterations in genes encoding these proteins were candidates for a role in AD.

Genotype-dependent activity of tryptophan hydroxylase-2 determines the response to citalopram in a mouse model of depression.

Polymorphism of tryptophan hydroxylase, the rate-limiting enzyme in the synthesis of brain serotonin (5-HT), is associated with less synthesis of brain 5-HT in DBA/2J and BALB/c than in C57BL/6J and 129/Sv mice. We selected the forced swimming test, a mouse model used to assess the antidepressant potential of drugs, and neurochemical techniques to study strain differences in the response to citalopram, a selective 5-HT reuptake inhibitor. Citalopram reduced immobility time in C57BL/6J and 129/Sv mice but had no such effect in DBA/2J and BALB/c mice.

Role of plasminogen in propagation of scrapie.

To investigate whether plasminogen may feature in scrapie infection, we inoculated plasminogen-deficient (Plg(-/-)), heterozygous plasminogen-deficient (Plg(+/-)), and wild-type (Plg(+/+)) mice by the intracerebral or intraperitoneal (i.p.) route with the RML scrapie strain and monitored the onset of neurological signs of disease, survival time, brain, and accumulation of scrapie disease-associated forms of the prion protein (PrP(Sc)).

The T-786C NOS3 polymorphism in Alzheimer's disease: association and influence on gene expression.

A common single nucleotide polymorphism (SNP), consisting in a T-->C transition (T-786C) in endothelial nitric oxide synthase (NOS3), has been reported to be associated with vascular pathologies, but no information are available on a possible association with AD. T-786C genotype was determined by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) assay in an Italian population of 432 AD patients compared with 360 healthy controls, matched for ethnic background, age and gender. Peripheral blood mononuclear cells (PBMC) from 22 subjects (11 AD and 11 controls) carrying different genotypes were isolated.

Rat nicastrin gene: cDNA isolation, mRNA variants and expression pattern analysis.

Nicastrin is a type 1 transmembrane glycoprotein that interacts with presenilin, Aph-1, and Pen-2 proteins to form a high molecular complex with gamma secretase activity. Then, nicastrin has a central role in presenilin-mediated processing of beta-amyloid precursor protein and in some aspects of Notch/glp-1 signaling in vivo. Here, we isolated a rat nicastrin cDNA and investigated gene expression in embryonic and adult rat tissues.

Influence of the Glu298Asp polymorphism of NOS3 on age at onset and homocysteine levels in AD patients.

The distribution of the Glu298Asp polymorphism in NOS3 gene was determined in 405 Italian patients with "probable" Alzheimer's disease (AD) compared with 253 age-matched controls. Total plasma homocysteine (tHcy) levels were evaluated in 97 patients and 23 controls, and were correlated with the Glu298Asp genotype. A significantly increased frequency of the Glu/Glu genotype in late onset AD (LOAD) patients was found.

Cytosolic prion protein (PrP) is not toxic in N2a cells and primary neurons expressing pathogenic PrP mutations.

Inherited prion diseases are linked to mutations in the prion protein (PrP) gene, which favor conversion of PrP into a conformationally altered, pathogenic isoform. The cellular mechanism by which this process causes neurological dysfunction is unknown. It has been proposed that neuronal death can be triggered by accumulation of PrP in the cytosol because of impairment of proteasomal degradation of misfolded PrP molecules retrotranslocated from the endoplasmic reticulum (Ma, J.

The neurotoxicity of prion protein (PrP) peptide 106-126 is independent of the expression level of PrP and is not mediated by abnormal PrP species.

A synthetic peptide homologous to region 106-126 of the prion protein (PrP) is toxic to cells expressing PrP, but not to PrP knockout neurons, arguing for a specific role of PrP in mediating the peptide's activity. Whether this is related to a gain of toxicity or a loss of function of PrP is not clear. We explored the possibility that PrP106-126 triggered formation of PrP(Sc) or other neurotoxic PrP species.

CCR2-64I polymorphism and CCR5Delta32 deletion in patients with Alzheimer's disease.

Monocyte chemoattractant protein-1 (MCP-1) and RANTES, as well as their related receptors, have been shown to be involved in Alzheimer's disease (AD) pathogenesis. Genes for their related receptors, CCR2 and CCR5, respectively, are characterized by the presence of two polymorphisms: a conservative change of a valine with an isoleucine at codon 64 of CCR2 (CCR2-64I) and a 32-bp deletion in the coding region of CCR5 (CCR5Delta32), which leads to the expression of a nonfunctional receptor. The distribution of the CCR2-64I and CCR5Delta32 polymorphisms was determined in 290 AD patients and in 222 controls.

Protective effect of TAT-delivered alpha-synuclein: relevance of the C-terminal domain and involvement of HSP70.

Alpha-synuclein (alpha-syn) is a 140-amino acid presinaptic protein whose mutations A30P and A53T have been linked to familiar Parkinson's disease (PD). Many data suggest that alpha-syn aggregation is the key event that triggers alpha-syn-mediated neurotoxicity. Nevertheless, other lines of evidence proposed a protective role of alpha-syn against oxidative stress (a major feature of PD), even if the exact mechanism of this protective action and the role of the pathogenetic mutations to this respect have not been elucidated yet.

MCP-1 in Alzheimer's disease patients: A-2518G polymorphism and serum levels.

MCP-1 levels are increased in CSF of patients with Alzheimer's disease (AD) compared with controls, suggesting a role in the development of dementia. Recently, a biallelic A/G polymorphism in the MCP-1 promoter at position -2518 has been found, influencing the level of MCP-1 expression in response to an inflammatory stimulus. The distribution of the A-2518G SNP was determined in 269 AD patients and in 203 healthy age matched controls, showing no differences between the two groups.

Homocysteine, folate, and vitamin B-12 in mild cognitive impairment, Alzheimer disease, and vascular dementia.

Background: Evidence supports an independent association between plasma total homocysteine concentrations and the risk of vascular disease. Recent epidemiologic studies reappraised the possibility that vascular risk factors might play a role in the pathogenesis not only of vascular dementia (VaD) but also of Alzheimer disease (AD).

Objective: The objective was to investigate the relations of mild cognitive impairment, AD, and VaD with blood homocysteine, folate, and vitamin B-12.

Proteasome inhibition and aggregation in Parkinson's disease: a comparative study in untransfected and transfected cells.

Dysfunction of the ubiquitin-proteasome system (UPS) has been implicated in Parkinson's disease (PD) and other neurodegenerative disorders. We have investigated the effect of UPS inhibition on the metabolism of alpha-synuclein (SYN) and parkin, two proteins genetically and histopathologically associated to PD. Pharmacological inhibition of proteasome induced accumulation of both parkin and SYN in transfected PC12 cells.

Quinacrine blocks PrP (106-126)-formed channels.

We investigated the action of the acridine derivative, quinacrine (QC), which has been shown to act as a noncompetitive channel inhibitor. The main effects of QC are voltage- and concentration-dependent changes in the kinetics of the prion protein fragment (PrP[106-126])-formed cation channels. The current-voltage relationships show that the maximal current (I) was not affected whereas the physiologically important mean current (I') was reduced as a result of changes in channel kinetics.

Nicastrin gene in familial and sporadic Alzheimer's disease.

Nicastrin is a protein recently discovered associated to presenilins and involved in the production of amyloid beta peptide that accumulates in Alzheimer's disease (AD) brain. In this study the nicastrin gene was examined for unknown mutations and polymorphisms in 104 patients with familial AD (52 early-onset and 52 late-onset), 174 sporadic AD and 191 healthy neurological controls of Italian origin. The scanning of the nicastrin gene identified a missense mutation (N417Y) in two patients with sporadic AD, in an early-onset familial AD and in a young control subject.

Structural properties of Gerstmann-Straussler-Scheinker disease amyloid protein.

Prion protein (PrP) amyloid formation is a central feature of genetic and acquired forms of prion disease such as Gerstmann-Sträussler-Scheinker disease (GSS) and variant Creutzfeldt-Jakob disease. The major component of GSS amyloid is a PrP fragment spanning residues approximately 82-146. To investigate the determinants of the physicochemical properties of this fragment, we synthesized PrP-(82-146) and variants thereof, including entirely and partially scrambled peptides.

Evaluation of quinacrine treatment for prion diseases.

Based on in vitro observations in scrapie-infected neuroblastoma cells, quinacrine has recently been proposed as a treatment for Creutzfeldt-Jakob disease (CJD), including a new variant CJD which is linked to contamination of food by the bovine spongiform encephalopathy (BSE) agent. The present study investigated possible mechanisms of action of quinacrine on prions. The ability of quinacrine to interact with and to reduce the protease resistance of PrP peptide aggregates and PrPres of human and animal origin were analyzed, together with its ability to inhibit the in vitro conversion of the normal prion protein (PrPc) to the abnormal form (PrPres).

Channels formed with a mutant prion protein PrP(82-146) homologous to a 7-kDa fragment in diseased brain of GSS patients.

A major prion protein (PrP) mutant that forms amyloid fibrils in the diseased brain of patients with Gerstmann-Sträussler-Scheinker syndrome (GSS) is a fragment of 7 kDa spanning from residues 81-82 to 144-153 of PrP. Analysis of ionic membrane currents, recorded with a lipid bilayer technique, revealed that the wild-type fragment PrP(82-146) WT and the partially scrambled PrP(82-146) (127-146) SC are capable of forming heterogeneous ion channels that are similar to those channels formed with PrP(106-126). In contrast, PrP(82-146) peptides in which the region from residue 106 to 126 had been scrambled (SC) showed a reduction in interaction with lipid membranes and did not form channels.

Tumor necrosis factor alpha polymorphism C-850T is not associated with Alzheimer's disease and vascular dementia in an Italian population.

A pathogenic role of inflammatory factors has been proposed both in Alzheimer's disease (AD) and vascular dementia (VD). A previous report indicated the presence of polymorphism C-850T of tumor necrosis factor (TNF) alpha as a genetic risk factor for VD and, associated with apolipoprotein E epsilon 4, for AD. We have assessed the association between TNF-alpha polymorphism and dementias in Italian populations of AD, VD and elderly controls.

Therapeutic approaches to prion diseases.

Prion diseases are unique in that they comprise sporadic, genetic, and iatrogenically or environmentally acquired forms. When disease is acquired by peripheral route, neuroinvasion occurs via at least two different neural pathways (vague and splanchnic nerves) and is usually preceded by prion propagation in secondary lymphoid organs. Conversely, in the other etiologic forms, PrPSc formation occurs within, and is apparently limited to, the CNS.

Effect of beta-amyloid on endothelial cells: lack of direct toxicity, enhancement of MTT-induced cell death and intracellular accumulation.

Several cerebrovascular alterations have been described in Alzheimer's disease (AD) including an accumulation of beta-amyloid (betaA) on the vascular walls in the brain. To investigate the potential toxic activity of betaA on endothelial cells (EC), two endothelial murine cell lines derived from heart and brain were exposed to betaA1-42 and the biologically active fragment betaA25-35 in the range from 5nM to 50 microM. In a low concentration range (50 nM to 2.

Molecular analysis of iatrogenic scrapie in Italy.

An accidental intra- and interspecies transmission of scrapie occurred in Italy in 1997 and 1998 following exposure to a vaccine against Mycoplasma agalactiae. PrP(Sc) in affected sheep and goats, collected from a single flock exposed to vaccination 2 years earlier, was molecularly typed. In five animals with iatrogenic scrapie, a PrP(Sc) type with a 20 kDa core fragment was found in all areas of the brain investigated.