Polymorphisms in glia maturation factor ß gene are markers of cellulose ether effectiveness in prion-infected mice.

Anti-prion effects of cellulose ether (CE) are reported in rodents, but the molecular mechanism is fully unknown. Here, we investigated the genetic background of CE effectiveness by proteomic and genetic analysis in mice. Proteomic analysis in the two mouse lines showing a dramatic difference in CE effectiveness revealed a distinct polymorphism in the glia maturation factor ß gene. This polymorphism was significantly associated with the CE effectiveness in various prion-infected mouse lines. Sequencing of this gene and its vicinity genes also revealed several other polymorphisms that were significantly related to the CE effectiveness. These polymorphisms are useful as genetic markers for finding more suitable mouse lines and exploring the genetic factors of CE effectiveness.

Melanin or a Melanin-Like Substance Interacts with the N-Terminal Portion of Prion Protein and Inhibits Abnormal Prion Protein Formation in Prion-Infected Cells.

Prion diseases are progressive fatal neurodegenerative illnesses caused by the accumulation of transmissible abnormal prion protein (PrP). To find treatments for prion diseases, we searched for substances from natural resources that inhibit abnormal PrP formation in prion-infected cells. We found that high-molecular-weight components from insect cuticle extracts reduced abnormal PrP levels. The chemical nature of these components was consistent with that of melanin. In fact, synthetic melanin produced from tyrosine or 3-hydroxy-l-tyrosine inhibited abnormal PrP formation. Melanin did not modify cellular or cell surface PrP levels, nor did it modify lipid raft or cellular cholesterol levels. Neither did it enhance autophagy or lysosomal function. Melanin was capable of interacting with PrP at two N-terminal domains. Specifically, it strongly interacted with the PrP region of amino acids 23 to 50 including a positively charged amino acid cluster and weakly interacted with the PrP octarepeat peptide region of residues 51 to 90. However, the in vitro and in vivo data were inconsistent with those of prion-infected cells. Abnormal PrP formation in protein misfolding cyclic amplification was not inhibited by melanin. Survival after prion infection was not significantly altered in albino mice or exogenously melanin-injected mice compared with that of control mice. These data suggest that melanin, a main determinant of skin color, is not likely to modify prion disease pathogenesis, even though racial differences in the incidence of human prion diseases have been reported. Thus, the findings identify an interaction between melanin and the N terminus of PrP, but the pathophysiological roles of the PrP-melanin interaction remain unclear.IMPORTANCE The N-terminal region of PrP is reportedly important for neuroprotection, neurotoxicity, and abnormal PrP formation, as this region is bound by many factors, such as metal ions, lipids, nucleic acids, antiprion compounds, and several proteins, including abnormal PrP in prion disease and the Aß oligomer in Alzheimer's disease. In the present study, melanin, a main determinant of skin color, was newly found to interact with this N-terminal region and inhibits abnormal PrP formation in prion-infected cells. However, the data for prion infection in mice lacking melanin production suggest that melanin is not associated with the prion disease mechanism, although the incidence of prion disease is reportedly much higher in white people than in black people. Thus, the roles of the PrP-melanin interaction remain to be further elucidated, but melanin might be a useful competitive tool for evaluating the functions of other ligands at the N-terminal region.

A Single Subcutaneous Injection of Cellulose Ethers Administered Long before Infection Confers Sustained Protection against Prion Diseases in Rodents.

Prion diseases are fatal, progressive, neurodegenerative diseases caused by prion accumulation in the brain and lymphoreticular system. Here we report that a single subcutaneous injection of cellulose ethers (CEs), which are commonly used as inactive ingredients in foods and pharmaceuticals, markedly prolonged the lives of mice and hamsters intracerebrally or intraperitoneally infected with the 263K hamster prion. CEs provided sustained protection even when a single injection was given as long as one year before infection. These effects were linked with persistent residues of CEs in various tissues. More effective CEs had less macrophage uptake ratios and hydrophobic modification of CEs abolished the effectiveness. CEs were significantly effective in other prion disease animal models; however, the effects were less remarkable than those observed in the 263K prion-infected animals. The genetic background of the animal model was suggested to influence the effects of CEs. CEs did not modify prion protein expression but inhibited abnormal prion protein formation in vitro and in prion-infected cells. Although the mechanism of CEs in vivo remains to be solved, these findings suggest that they aid in elucidating disease susceptibility and preventing prion diseases.

Heparinase I-specific disaccharide unit of heparin is a key structure but insufficient for exerting anti-prion activity in prion-infected cells.

Glycosaminoglycans reportedly play important roles in prion formation, but because of their structural complexity, the chemical structures affecting prion formation have not been fully evaluated. Here, we compared two types of low molecular weight heparins and found that heparinase I-sensitive structures influenced anti-prion activity in prion-infected cells. Surface plasmon resonance analyses showed significant binding of a representative heparinase I substrate disaccharide unit, GlcNS6S-IdoA2S, to recombinant prion protein (PrP) fragments, such as full-length PrP23-231 and N-terminal domain PrP23-89, but not to PrP89-230. This binding was competitively inhibited by heparin or pentosan polysulfate, but not by Cu(2+). These PrP binding profiles of the disaccharide unit are consistent with those previously reported for heparin. However, synthetic compounds comprising disaccharide unit alone or its multimers exhibited no anti-prion activity in prion-infected cells. Consequently, the findings suggest that the heparin disaccharide unit that binds to the N-terminal region of PrP is a key structure, but it is insufficient for exerting anti-prion activity.

Efficacy and mechanism of a glycoside compound inhibiting abnormal prion protein formation in prion-infected cells: implications of interferon and phosphodiesterase 4D-interacting protein.

UNLABELLED: A new type of antiprion compound, Gly-9, was found to inhibit abnormal prion protein formation in prion-infected neuroblastoma cells, in a prion strain-independent manner, when the cells were treated for more than 1 day. It reduced the intracellular prion protein level and significantly modified mRNA expression levels of genes of two types: interferon-stimulated genes were downregulated after more than 2 days of treatment, and the phosphodiesterase 4D-interacting protein gene, a gene involved in microtubule growth, was upregulated after more than 1 day of treatment. A supplement of interferon given to the cells partly restored the abnormal prion protein level but did not alter the normal prion protein level. This interferon action was independent of the Janus activated kinase-signal transducer and activator of transcription signaling pathway. Therefore, the changes in interferon-stimulated genes might be a secondary effect of Gly-9 treatment. However, gene knockdown of phosphodiesterase 4D-interacting protein restored or increased both the abnormal prion protein level and the normal prion protein level, without transcriptional alteration of the prion protein gene. It also altered the localization of abnormal prion protein accumulation in the cells, indicating that phosphodiesterase 4D-interacting protein might affect prion protein levels by altering the trafficking of prion protein-containing structures. Interferon and phosphodiesterase 4D-interacting protein had no direct mutual link, demonstrating that they regulate abnormal prion protein levels independently. Although the in vivo efficacy of Gly-9 was limited, the findings for Gly-9 provide insights into the regulation of abnormal prion protein in cells and suggest new targets for antiprion compounds. IMPORTANCE: This report describes our study of the efficacy and potential mechanism underlying the antiprion action of a new antiprion compound with a glycoside structure in prion-infected cells, as well as the efficacy of the compound in prion-infected animals. The study revealed involvements of two factors in the compound's mechanism of action: interferon and a microtubule nucleation activator, phosphodiesterase 4D-interacting protein. In particular, phosphodiesterase 4D-interacting protein was suggested to be important in regulating the trafficking or fusion of prion protein-containing vesicles or structures in cells. The findings of the study are expected to be useful not only for the elucidation of cellular regulatory mechanisms of prion protein but also for the implication of new targets for therapeutic development.

Anti-prion activity of protein-bound polysaccharide K in prion-infected cells and animals.

Protein-bound polysaccharide K (PSK) is a clinical immunotherapeutic agent that exhibits various biological activities, including anti-tumor and anti-microbial effects. In the present study, we report on the anti-prion activity of PSK. It inhibited the formation of protease-resistant abnormal prion protein in prion-infected cells without any apparent alterations in either the normal prion protein turnover or the autophagic function in the cells. Its anti-prion activity was predominantly composed of the high molecular weight component(s) of the protein portion of PSK. A single subcutaneous dose of PSK slightly but significantly prolonged the survival time of peritoneally prion-infected mice, but PSK-treated mice produced neutralizing antibodies against the anti-prion activity of PSK. These findings suggest that PSK is a new anti-prion substance that may be useful in elucidating the mechanism of prion replication, although the structure of the anti-prion component(s) of PSK requires further evaluation.

Intermolecular crosslinking of abnormal prion protein is efficiently induced by a primuline-sensitized photoreaction.

In prion diseases, infectious pathogenic particles that are composed of abnormal prion proteins (PrPSc) accumulate in the brain. PrPSc is biochemically characterized by its protease-resistance core (PrPres), but its structural features have not been fully elucidated. Here, we report that primuline, a fluorescent dye with photosensitization activity, dramatically enhances UV-irradiation-induced SDS-resistant PrPSc/res oligomer formation that can be detected by immunoblot analysis of prion-infected materials. This oligomer formation occurs specifically with PrPSc/res but not with normal prion protein, and it was demonstrated using purified PrPSc/res as well as unpurified materials. The oligomer formation proceeded in both primuline-dose- and UV irradiation time-dependent manners. Treatment with urea or formic acid did not break oligomers into monomers. Neither did the presence of aromatic amino acids modify oligomer formation. Analysis with a panel of anti-prion protein antibodies showed that the antibodies against the N-terminal region of PrPres were less reactive in the dimer than the monomer. These findings suggest that the primuline-sensitized photoreaction enhances intermolecular crosslinking of PrPSc/res molecules at a hydrophobic area of the N-terminal region of PrPres. In the screening of other compounds, photoreactive compounds such as luciferin exhibited a similar but lower activity with respect to oligomer formation than primuline. The enhanced photoreaction with these compounds will be useful for evaluating the structural features of PrPSc/res, especially the interactions between PrPSc/res molecules.

Preparation and Characterization of Cellulose Ether Liposomes for the Inhibition of Prion Formation in Prion-Infected Cells.

Prion accumulation in the brain and lymphoreticular system causes fatal neurodegenerative diseases. Our previous study revealed that cellulose ethers (CE) have anti-prion activities in vivo and in prion-infected cells when administered at high doses. This study aims to improve the bioavailability of a representative CE using a liposomal formulation and characterized CE-loaded liposomes in cultured cells. The liposomal formulation reduced the EC50 dose of CE by <1/200-fold in prion-infected cells. Compared to empty liposomes, CE-loaded liposomes were taken up much more highly by prion-infected cells and less by macrophage-like cells. Phosphatidylserine modification reduced the uptake of CE-loaded liposomes in prion-infected cells and did not change the anti-prion activity, whereas increased the uptake in macrophage-like cells. Polyethylene glycol modification reduced the uptake of CE-loaded liposomes in both types of cells and reduced the anti-prion activity in prion-infected cells. These results suggest that a liposomal formulation of CE is more practical than unformulated CE and showed that the CE-loaded liposome uptake levels in prion-infected cells were not associated with anti-prion activity. Although further improvement of the stealth function against phagocytic cells is needed, the liposomal formulation is useful to improve CE efficacy and elucidate the mechanism of CE action.

Orally administered amyloidophilic compound is effective in prolonging the incubation periods of animals cerebrally infected with prion diseases in a prion strain-dependent manner.

The establishment of effective therapeutic interventions for prion diseases is necessary. We report on a newly developed amyloidophilic compound that displays therapeutic efficacy when administered orally. This compound inhibited abnormal prion protein formation in prion-infected neuroblastoma cells in a prion strain-dependent manner: effectively for RML prion and marginally for 22L prion and Fukuoka-1 prion. When the highest dose (0.2% [wt/wt] in feed) was given orally to cerebrally RML prion-inoculated mice from inoculation until the terminal stage of disease, it extended the incubation periods by 2.3 times compared to the control. The compound exerted therapeutic efficacy in a prion strain-dependent manner such as that observed in the cell culture study: most effective for RML prion, less effective for 22L prion or Fukuoka-1 prion, and marginally effective for 263K prion. Its effectiveness depended on an earlier start of administration. The glycoform pattern of the abnormal prion protein in the treated mice was modified and showed predominance of the diglycosylated form, which resembled that of 263K prion, suggesting that diglycosylated forms of abnormal prion protein might be least sensitive or resistant to the compound. The mechanism of the prion strain-dependent effectiveness needs to be elucidated and managed. Nevertheless, the identification of an orally available amyloidophilic chemical encourages the pursuit of chemotherapy for prion diseases.

[Recent advances in the diagnosis and therapeutics for human prion diseases].

Prion diseases, or transmissible spongiform encephalopathies, are fatal, neurodegenerative disorders associated with the accumulation of a misfolded infectious prion protein which is made by a posttranslational conformational change of the host-encoded cellular prion protein. A large number of studies to reveal the pathogenesis of prion diseases have been done using such experimental models as animals, cell cultures and cell-free systems over the past 30 years. The prion pathogenesis is still enigmatic, but current explosion of the knowledge about prion biology has led to the discovery of either more reliable diagnostic measurements or more beneficial therapeutic candidates. Here, the recent advances are reviewed in the diagnostics and the therapeutics for prion diseases.

Three-repeat Tau 69 is a major tau isoform in laser-microdissected Pick bodies.

By utilizing a novel combinatorial method of a Laser Microdissection System and Western blot analysis, we demonstrate that a distinct isoform of abnormally phosphorylated tau (69 kDa, Tau 69) predominantly aggregated in laser-microdissected Pick bodies (PBs) in sporadic Pick's disease. By contrast, tau migrated as two major bands of 60 and 64 kDa (Tau 60 and 64) in total brain homogenates as previously reported. Comparative immunohistochemical analysis with anti-4-repeat antibody revealed that a major component of the abnormally phosphorylated tau in these PBs was 3-repeat tau (3R-tau). Whether 29 amino acid repeat encoded by exons 2 and 3 in the Tau 69 might accelerate the formation of PBs remains to be further investigated. Such a combination of morphological and biochemical techniques significantly complements the existing histopathological methods.

Mitochondrial localization of cellular prion protein (PrPC) invokes neuronal apoptosis in aged transgenic mice overexpressing PrPC.

Recent studies suggest that the disease isoform of prion protein (PrPSc) is non-neurotoxic in the absence of cellular isoform of prion protein (PrPC), indicating that PrPC may participate directly in the neurodegenerative damage by itself. Meanwhile, transgenic mice harboring a high-copy-number of wild-type mouse (Mo) PrPC develop a spontaneous neurological dysfunction in an age-dependent manner, even without inoculation of PrPSc and thus, investigations of these aged transgenic mice may lead to the understanding how PrPC participate in the neurotoxic property of PrP. Here we demonstrate mitochondria-mediated neuronal apoptosis in aged transgenic mice overexpressing wild-type MoPrPC (Tg(MoPrP)4053/FVB). The aged mice exhibited an aberrant mitochondrial localization of PrPC concomitant with decreased proteasomal activity, while younger littermates did not. Such aberrant mitochondrial localization was accompanied by decreased mitochondrial manganese superoxide dismutase (Mn-SOD) activity, cytochrome c release into the cytosol, caspase-3 activation, and DNA fragmentation, most predominantly in hippocampal neuronal cells. Following cell culture studies confirmed that decrease in the proteasomal activity is fundamental for the PrPC-related, mitochondria-mediated apoptosis. Hence, the neurotoxic property of PrPC could be explained by the mitochondria-mediated neuronal apoptosis, at least in part.

Association study of the chemokine, CXC motif, ligand 1 (CXCL1) gene with sporadic Alzheimer's disease in a Japanese population.

Inflammation is profoundly involved in the development of Alzheimer's disease (AD) and other neurodegenerative diseases. Chemokine, CXC motif, ligand 1 (CXCL1; or GRO1) is an inflammatory cytokine and appears to be implicated in the pathogenesis of AD. It is of interest and importance to see if the CXCL1 gene, mapped on chromosome 4q12-q13, has potential for conferring the predisposition to AD. Here we report on an association study of the CXCL1 gene with sporadic AD patients in a Japanese population; three single nucleotide polymorphisms (SNPs) in the CXCL1 locus were investigated in 103 AD patients and 130 healthy individuals. The results indicate that neither genotype frequencies nor allele frequencies of the examined SNPs attained statistical significance even after being stratified by the presence or absence of the Apolipoprotein E epsilon4 allele. Therefore, the data presented here suggests that the CXCL1 gene could not be associated with the susceptibility to AD in a Japanese population.

Structure-activity analysis and antiprion mechanism of isoprenoid compounds.

The prion strain-specific mechanism by which normal prion protein is converted to abnormal prion protein remains largely unknown. This study found that insect juvenile hormone III reduced abnormal prion protein levels only in cells infected with the RML prion. We conducted a structure-activity analysis using juvenile hormone III biosynthetic intermediates in the isoprenoid pathway. Both farnesol and geranylgeraniol, the most potent inhibitors of abnormal prion protein formation, behaved in an RML prion-dependent fashion. Neither of them modified cellular and cell surface prion protein levels. Events downstream of this pathway include cholesterol biosynthesis and protein prenylation. However, neither of these isoprenoid compounds modified lipid raft microdomains and cellular cholesterol levels and neither affected the representative prenylated protein expression levels of prenylation pathways. Therefore, these isoprenoid compounds are a new class of prion strain-dependent antiprion compounds. They are useful for exploring strain-specific prion biology.

Anti-prion activity found in beetle grub hemolymph of Trypoxylus dichotomus septentrionalis.

No remedies for prion disease have been established, and the conversion of normal to abnormal prion protein, a key event in prion disease, is still unclear. Here we found that substances in beetle grub hemolymph, after they were browned by aging for a month or heating for hours, reduced abnormal prion protein (PrP) levels in RML prion-infected cells. Active anti-prion components in the hemolymph were resistant to protease treatment and had molecular weights larger than 100 kDa. Aminoguanidine treatment of the hemolymph abolished its anti-prion activity, suggesting that Maillard reaction products are enrolled in the activity against the RML prion. However, levels of abnormal PrP in RML prion-infected cells were not decreased by incubation with the Maillard reaction products formed by amino acids or bovine serum albumin. The anti-prion components in the hemolymph modified neither cellular or cell-surface PrP levels nor lipid raft or autophagosome levels. The anti-prion activity was not observed in cells infected with 22 L prion or Fukuoka-1 prion, suggesting the anti-prion action is prion strain-dependent. Although the active components of the hemolymph need to be further evaluated, the present findings imply that certain specific chemical structures in the hemolymph, but not chemical structures common to all Maillard reaction products, are involved in RML prion formation or turnover, without modifying normal PrP expression. The anti-prion components in the hemolymph are a new tool for elucidating strain-dependent prion biology.

Secretin receptor involvement in prion-infected cells and animals.

The cellular mechanisms behind prion biosynthesis and metabolism remain unclear. Here we show that secretin signaling via the secretin receptor regulates abnormal prion protein formation in prion-infected cells. Animal studies demonstrate that secretin receptor deficiency slightly, but significantly, prolongs incubation time in female but not male mice. This gender-specificity is consistent with our finding that prion-infected cells are derived from females. Therefore, our results provide initial insights into the reasons why age of disease onset in certain prion diseases is reported to occur slightly earlier in females than males.

Non-glycosylphosphatidylinositol (GPI)-anchored recombinant prion protein with dominant-negative mutation inhibits PrPSc replication in vitro.

Dominant-negative mouse prion protein (PrP) with a lysine mutation at codon 218 (Q218K) is known to inhibit prion replication. In order to gain further mechanistic insight into such dominant negative inhibition, non-glycosylphosphatidylinositol (GPI)-anchored recombinant PrP with Q218K (rPrP-Q218K) was investigated. When applied into scrapie-infected mouse neuroblastoma (ScN2a) cells, rPrP-Q218K but not wild-type rPrP (rPrP-WT) exclusively inhibited abnormal protease-resistant pathogenic isoform (PrPSc) replication without reducing the viability of the cells. It was even more efficient than quinacrine, which has already been prescribed for sporadic Creutzfeldt-Jakob disease (CJD) patients; 50% effective concentration (EC50) = 0.20 microM, 99% effective concentration (EC99) = 0.86 microM vs. EC50 = 0.45 microM, EC99 = 1.5 microM. Besides, no apparent cell damage was observed at the concentration of up to 4.3 microM (100 micrograms/ml). In combination treatment with 0.43 microM (10 micrograms/ml) of rPrP-Q218K, EC99 of quinacrine was decreased from 1.5 microM to 0.5 microM, and the cell viability was recovered from 50% to over 90% as inversely proportional to the concentration of quinacrine. Such combination could alleviate the side effects of quinacrine by reducing its effective concentration without changing or even acceleration the inhibition efficacy. Since homogeneous, high-quality rPrPs could be easily prepared from Escherichia coli in large quantities, rPrP-Q218K is a good candidate for a prion replication antagonist.

Lack of association between TrkA single nucleotide polymorphisms and sporadic Alzheimer's disease in a Japanese population.

Nerve growth factor and its receptor with tyrosine kinase activity (TrkA) have been implicated in the development of Alzheimer's disease (AD). Entire coding regions of TrkA gene harboring exons 1 through 17 were sequenced in 114 patients with sporadic AD and 112 control subjects in a Japanese population, and six known and two novel single nucleotide polymorphisms were identified, but no mutation associated with sporadic AD was identified. Concurrently, case-control analysis of TrkA gene A1674G polymorphism in 534 patients with sporadic AD and 454 control subjects has revealed no significant differences in TrkA genotype or allele frequencies even after stratification for Apolipoprotein E epsilon4 carrier statuses. Thus, the TrkA genotype does not appear to influence the risk of developing sporadic AD in a Japanese population.

[Unfolding chaperone as a prion protein relating molecule].

Prion protein exists in two different isoforms, a normal cellular isoform (PrPc) and an abnormal infectious isoform (PrPSc), the latter is a causative agent of prion disease such as mad cow disease and Creutzfeldt-Jakob disease. Amino acid sequences of PrPc and PrPSc are identical, but their conformations are rather different; PrPc rich in non beta-sheet vs. PrPSc rich in beta-sheet isoform. Since the two isoforms have quite different conformation, this host factor might be a molecular chaperone, which enables to override an energy barrier between PrPc and PrPSc. To examine the protein unfolding activities against collectively folded structure exist or not, we constructed an assay system and purified a novel molecular chaperone. Unfolding, from S. cerevisiae. Unfolding consists of oligomeric ring-like structure with the central cavity and has an ATP-dependent protein Unfoldingg activity with broad specificity in vitro, of which targets included PrP in beta-sheet form, alpha-synuclein, and A beta protein. We have also found that mouse neuroblastoma N2a cells contained the activity. Treatment of this factor with an ATP-hydrolyzing enzyme, apyrase, caused the decrease in its protein Unfoldingg activity. It was suggested that the purified protein probably formed homo-oligomer consisting of 4-5 subunits and its activity was ATP-dependent.