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PubMed1985

Hamster female protein, a sex-limited pentraxin, is a constituent of Syrian hamster amyloid.

Female protein (FP) is a pentraxin of Syrian hamster which is a homologue of two human pentraxins, C-reaction protein (CRP) and amyloid P component (AP). Functionally, FP has been shown to be similar to CRP, although FP has more homology at the amino terminus with AP. The present work investigated amyloid in the Syrian hamster to determine whether FP was involved in a manner analogous to AP. FP was found to be a constituent of Syrian hamster amyloid. This conclusion was based on the following results: (a) FP was consistently detected in amyloid deposits by fluorescent microscopy with specific antisera; (b) The amount of FP extractable from hamster livers directly correlated with the presence of amyloid; and (c) 125I-FP injected intravenously into amyloidotic hamsters rapidly left the intravascular compartment and was found subsequently in amyloid deposits. This unusual alteration of plasma metabolism and amyloid localization of 125I-FP was a characteristic finding in amyloidotic hamsters and was specific for 125I-FP. Therefore, as an amyloid component, FP appears to be functionally similar to human AP. However, FP synthesis is under sex steroid control and the unique sex-limited expression of this pentraxin was associated with an equally novel propensity for deposition of amyloid in female hamsters under normal or experimental conditions. Thus, a high serum level of FP, as found in normal females or diethylstilbestrol-treated males, was associated with enhanced amyloidosis. Although speculative at present, a primary role for serum FP in hamster amyloid deposition may be experimentally approachable by hormonal manipulation of FP synthesis.

Age Factors↗

PubMed1991

A temporal and ultrastructural relationship between heparan sulfate proteoglycans and AA amyloid in experimental amyloidosis.

Previous histochemical studies have suggested a close temporal relationship between the deposition of highly sulfated glycosaminoglycans (GAGs) and amyloid during experimental AA amyloidosis. In the present investigation, we extended these initial observations by using specific immunocytochemical probes to analyze the temporal and ultrastructural relationship between heparan sulfate proteoglycan (HSPG) accumulation and amyloid deposition in a mouse model of AA amyloidosis. Antibodies against the basement membrane-derived HSPG (either protein core or GAG chains) demonstrated a virtually concurrent deposition of HSPGs and amyloid in specific tissue sites regardless of the organ involved (spleen or liver) or the induction protocol used (amyloid enhancing factor + silver nitrate, or daily azocasein injections). Polyclonal antibodies to AA amyloid protein and amyloid P component also demonstrated co-localization to sites of HSPG deposition in amyloid sites, whereas no positive immunostaining was observed in these locales with a polyclonal antibody to the protein core of a dermatan sulfate proteoglycan (known as "decorin"). Immunogold labeling of HSPGs (either protein core or GAG chains) in amyloidotic mouse spleen or liver revealed specific localization of HSPGs to amyloid fibrils. In the liver, heparan sulfate GAGs were also immunolocalized to the lysosomal compartment of hepatocytes and/or Kupffer cells adjacent to sites of amyloid deposition, suggesting that these cells are involved in HSPG production and/or degradation. The close temporal and ultrastructural relationship between HSPGs and AA amyloid further implies an important role for HSPGs during the initial stages of AA amyloidosis.

Amyloidosis↗

PubMed1994

Islet amyloid polypeptide in human insulinomas. Evidence for intracellular amyloidogenesis.

Amyloid deposits that characteristically form in the pancreatic islets of patients with non-insulin-dependent diabetes mellitus (NIDDM) and in insulinomas are both derived from islet amyloid polypeptide (IAPP). Evidence from previous studies has suggested that deposition of IAPP-derived amyloid is related to inherent amyloidogenic sequences present within normal human IAPP, together with an increased production and local concentration of IAPP. However, whether the aggregation of IAPP to form amyloid fibrils is primarily an intra- or extracellular event is not clear. To address this question, we studied 20 human insulinomas by light and electron microscopy. By light microscopy, amyloid deposits were demonstrated in 13 of 20 (65%) human insulinomas. Furthermore, evaluation of Congo red-stained tumor sections showed small, globular or irregular, congophilic amyloid deposits within the cytoplasm of many tumor cells in 10 of 13 (77%) amyloid-containing insulinomas. Dense, punctate areas of IAPP immunoreactivity within tumor cells corresponded with the congophilic intracellular deposits. Ubiquitin immunoreactivity also was observed as punctate intracellular labeling and within large extracellular amyloid deposits. Among the 10 insulinomas available for electron microscopic evaluation, pathological IAPP-immunoreactive (immunogold) deposits were found in 3 of 5 insulinomas in which amyloid was demonstrated by light microscopy and in none of 5 tumors found negative for amyloid by light microscopy. Morphology of IAPP-immunoreactive deposits varied from those with the classical distinct 7- to 10-nm diameter nonbranching fibrils to those with distinct but faint fibrillarity to those without discernable fibrils.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

beta-cell glucokinase deficiency and hyperglycemia are associated with reduced islet amyloid deposition in a mouse model of type 2 diabetes.

Type 2 diabetes is characterized by impaired beta-cell function, hyperglycemia, and islet amyloid deposition. The primary constituent of islet amyloid is the 37-amino acid beta-cell product called islet amyloid polypeptide (IAPP) or amylin. To study mechanisms of islet amyloid formation, we developed a transgenic mouse model that produces and secretes the amyloidogenic human IAPP (hIAPP) molecule and have shown that 81% of male transgenic mice develop islet amyloid after 14 months on a high-fat diet. To test whether impaired beta-cell function and hyperglycemia could enhance islet amyloid formation, we cross-bred our hIAPP transgenic mice with beta-cell glucokinase-knockout mice (GKKO) that have impaired glucose-mediated insulin secretion and fasting hyperglycemia. The resulting new (hIAPPxGKKO) line of mice had higher basal plasma glucose concentrations than the hIAPP transgenic mice at 3, 6, and 12 months of age (P < 0.05), as did GKKO mice compared with hIAPP transgenic mice at 6 and 12 months of age (P < 0.05). Basal plasma immunoreactive insulin (IRI) levels were lower in hIAPP x GKKO mice than in hIAPP transgenic mice at 6 months of age (P < 0.05). The area under the glucose curve in response to an intraperitoneal glucose challenge (1 g/kg body weight) was larger in hIAPPxGKKO mice than in hIAPP transgenic mice at 3, 6, and 12 months of age (P < 0.005) and in GKKO mice compared with hIAPP transgenic mice at 6 and 12 months of age (P < 0.005). The area under the IRI curve was lower in hIAPPxGKKO mice at 6 and 12 months of age (P < 0.05) than in hIAPP transgenic mice and in GKKO mice compared with hIAPP transgenic mice at 12 months of age (P < 0.05). Despite the presence of hyperglycemia, hIAPPxGKKO mice had a lower incidence (4 of 17 vs. 12 of 19, P < 0.05) and amount (0.40 +/- 0.24 vs. 1.2 +/- 0.3 arbitrary units, P < 0.05) of islet amyloid than hIAPP transgenic mice had. As expected, no islet amyloid was observed in GKKO mice lacking the hIAPP transgene (0 of 13). There was no difference in pancreatic content of IRI and hIAPP among the three groups of mice. Thus, despite the presence of impaired islet function and hyperglycemia, hIAPPxGKKO mice had a decreased incidence and quantity of islet amyloid. Therefore, our data suggest that impaired beta-cell glucose metabolism or hyperglycemia are not likely to contribute to islet amyloid formation in diabetes. Furthermore, this finding may explain the lack of progression of glycemia in patients with maturity-onset diabetes of the young.

Aging↗

PubMed1985

Histochemical and immunohistochemical characterization of amyloid associated with chronic hemodialysis as beta 2-microglobulin.

The carpal tunnel syndrome has been associated with amyloid deposits and is now regarded as a major complication in patients undergoing chronic hemodialysis. The hemodialysis-associated amyloidosis appears to have systemic rather than local involvement, although its full extent is yet to be determined. In an attempt to examine the chemical and immunologic nature of the amyloid, the authors carried out a series of histochemical and immunohistochemical studies with the following results. The amyloid was "sensitive" to the "permanganate treatment," suggesting it was the AA (secondary) type. On immunohistochemistry, however, anti-human AA did not give positive reaction with the amyloid deposits, suggesting that this would be a new form of amyloid. As reported elsewhere, the authors' preliminary results on the amino acid sequence analysis in one specimen have revealed homology of its amino terminal sequence to beta 2-microglobulin. In the present study, anti-beta 2-microglobulin did indeed react positively (with appropriate controls) with the amyloid deposits in the tissues collected from five different patients, confirming the beta 2-microglobulin-related nature of the amyloid. The present observations are significant in two points: (a) they confirm that hemodialysis-associated amyloid is of beta 2-microglobulin origin since it shares same antigenic determinant(s) with it and since the amino acid sequence is homologous; and (b) it adds what many have suspected, i.e., "permanganate-sensitive" amyloid is not specific for the AA type but includes AA and beta 2-microglobulin amyloid deposits at the minimum.

Amyloid↗

PubMed1996

A high resolution ultrastructural study of experimental murine AA amyloid.

An essential and distinguishing feature of all amyloids is the presence of fibrillar structures of approximately 10-nm width. The precise nature of the fibril is not yet clearly understood, particularly in situ, and the ultrastructure of isolated fibrils differs significantly from that of fibrils observed in situ. The fibrils are generally believed to be composed of a protein specific to each type of amyloid, but increasing evidence suggests additional associations with other components such as heparan sulfate proteoglycan (HSPG) and amyloid P component (AP). Experimental AA amyloidosis was induced in mice by amyloid enhancing factor and an inflammatory stimulus (subcutaneous AgNO3); fibrils were thereafter examined in detail. Particular attention was paid to ultrastructural characteristics known to represent particular molecular components of basement membranes such as HSPG and AP. Additionally, rabbit anti-mouse AA antisera was used with 5-nm and 1-nm gold particles to establish the location of the AA protein in-situ. Amyloid fibrils could be identified in their mature form as well as at apparent intermediate stages of formation. The fibril contained an apparent core which is composed of an assembly of 3.5-nm wide pentosomal particles having the characteristics of AP. Wound around the AP assembly in a helical fashion is a "double tracked" ribbon-like entity, 3 nm wide, having the morphologic characteristics of chondroitin sulfate proteoglycan (CSPG). Covering the surface of this structure is a second ribbon-like double track structure, but this one is wider (4.6 nm vs 3.0 nm) than the CSPG. These have the ultrastructural characteristics of HSPG. Routine fixation and tissue preparation techniques that usually remove HSPG from microfibrils did not do so with amyloid fibrils, suggesting an alteration in affinity between these components. The AA protein could be identified as a 1 - to 2-nm filament network on the most exterior surface of the fibril. The ultrastructure of AA amyloid fibrils in situ resembles that of connective tissue microfibrils, and, in addition to AA protein, is likely composed of HSPG, CSPG, and AP. Amyloid fibrils can be distinguished from microfibrils by the apparently stronger binding of HSPG to the surface of the amyloid fibril and the presence of the AA filaments. A model of the in situ organization of AA amyloid fibrils is proposed.

Amyloidosis↗

PubMedDate not supplied

The amyloid peptide and its precursor in Alzheimer's disease.

Alzheimer's disease, the most frequent cause of dementia, is characterized by the formation in the brain of neurofibrillary tangles and senile plaques. Neurofibrillary tangles are composed of bundles of paired helical filaments containing the microtubule-associated protein tau. In autopsy-derived brain samples from patients with Alzheimer's disease, tau is hyperphosphorylated and constitutes a promising disease marker. Senile plaques contain a small amyloid peptide derived from the amyloid precursor protein. Mutations of the amyloid precursor protein gene have been identified in rare cases of familial Alzheimer's disease, suggesting a causal role for amyloid peptide deposition in the disease. However, Alzheimer's disease has been demonstrated to be characterized by an important genetic heterogeneity. The identification of pathogenic DNA mutations, different from those of the amyloid precursor protein gene, will reveal whether the corresponding genes are involved in either an increased production of the amyloid peptide or a decrease of its removal, or in the fibrillogenic properties of the peptide, which seem to be related to its toxicity. Several mammalian cells are able to produce the amyloid peptide from its precursor. Understanding the cellular mechanisms that determine how cleavages occur in cells could help to identify new strategies for modulating amyloid peptide production. In attempts to produce animal models of Alzheimer's disease, investigators have used transgenic strategies. To date, these efforts have not been very successful. However, the expression in transgenic mice of both mutated amyloid peptide precursor and amyloid associated proteins should prove useful for examining the importance of putative etiological factors, and for testing novel therapies including anti-amyloidogenic strategies.

Aged↗

PubMed1997

Serum amyloid P component enhances induction of murine amyloidosis.

Serum amyloid P component (SAP), a common component of all known types of amyloid fibrils, protects amyloid fibrils from proteolysis in vitro. It is therefore speculated to contribute to the deposition of amyloid fibrils in various types of amyloidoses. However, a role for SAP in amyloid deposition is not yet known. To investigate the relationship between SAP and amyloid deposition, we used gene targeting techniques to generate a unique strain of mice carrying a null mutation at the sap locus. The resultant SAP-deficient mice displayed no obvious phenotypic abnormalities. We asked whether experimental amyloid A (AA) amyloidosis could be induced in the SAP-deficient mice. The wild-type and SAP-deficient mice did not differ in their synthesis of serum amyloid A, the precursor protein of AA amyloid fibril, in response to acute inflammation. The induction of AA amyloidosis, however, was significantly retarded in the SAP-deficient mice relative to wild-type mice. Our experiments present, for the first time, compelling evidence that, although not essential in the deposition of AA amyloid, SAP significantly accelerates this reaction. Thus, SAP enhances the induction of murine amyloidosis and may play an important role in the pathogenesis of human amyloidoses, including Alzheimer's disease.

Acute-Phase Reaction↗

PubMed1999

Entorhinal cortex beta-amyloid load in individuals with mild cognitive impairment.

The deposition of beta-amyloid within the entorhinal cortex (EC) may play a key role in the development of mild cognitive impairment (MCI) in the elderly. To examine the relationship of beta-amyloid deposition to MCI, EC tissue immunostained for this protein was quantitated from a cohort of aged Catholic religious clergy with a clinical diagnosis of MCI and compared to those with no cognitive impairment (NCI) and Alzheimer's disease (AD). beta-amyloid staining was seen in 12 of the 20 NCI, in 10 of 12 MCI, and in all 12 AD cases within the EC. beta-amyloid immunoreactivity displayed two patterns within the EC: (1) a crescent-shaped band within layers 3-4 or (2) bilaminar staining mainly within layers 2-3 and 5-6. Ten cases failed to display any detectable beta-amyloid imunoreactivity. Despite the heterogeneity of beta-amyloid loads within the clinical groups, decomposing an analysis of variance revealed a significant difference across groups in mean beta-amyloid load within the EC based upon a linear trend analysis. Multiple comparisons testing revealed that NCI individuals had a significantly lower mean beta-amyloid load (1.32) than AD individuals (4.55). The MCI individuals had a mean intermediate (2.60) load between NCI and AD, but not statistically distinguishable from the mean for either NCI or AD. Spearman rank correlation showed a trend for decreasing MMSE with increasing amyloid load that failed to reach statistical significance. Since many NCI cases displayed beta-amyloid loads equal to or greater than that seen in some MCI and some AD cases, it is mostly likely that deposition of this protein is not the sole pathogenic event underlying cognitive impairment in the elderly.

Aged↗

PubMed1994

Relationship of microglia and scrapie amyloid-immunoreactive plaques in kuru, Creutzfeldt-Jakob disease and Gerstmann-Sträussler syndrome.

Kuru, Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler syndrome (GSS) are transmissible dementias affecting humans characterized neuropathologically by intraneuronal vacuolation, spongiform change, astrocytic hypertrophy and hyperplasia and the variable presence of amyloid plaques. It has been suggested that microglia are amyloid-forming cells, which play an essential role in amyloid plaque formation. To study the relationship between microglia and amyloid plaques in kuru, CJD and GSS, cerebellar tissues were examined by the double-immunostaining technique using anti-ferritin antibodies as the microglial marker and anti-scrapie amyloid antibody as plaque marker. Ferritin-immunoreactive microglia were observed interdigitating with and among unicentric, multicentric and diffuse types of scrapie amyloid-immunoreactive plaques and were found to a lesser extent in the neuropil. In kuru and CJD, scrapie amyloid-immunoreactive plaques were predominantly unicentric and were observed in the granular layer. In kuru, 53% of the amyloid plaques were associated with microglia, whereas only 30% of plaques in CJD were. In contrast, scrapie-amyloid-immunoreactive plaques in GSS were of the multicentric type, predominantly observed in the molecular layer, and 90% of these plaques were associated with microglia. Our data indicate that microglia are frequently associated with scrapie amyloid-immunoreactive plaques in GSS, less commonly in kuru and to a much lesser extent in CJD, suggesting that microglia may play a variable but important role in the formation of plaques in the transmissible spongiform encephalopathies.

Adolescent↗

PubMed1990

Amyloid in the brains of aged squirrel monkeys.

In this immunocytochemical study, the brains of nine squirrel monkeys (Saimiri sciureus), ranging from 8 to 27 years of age, were examined for the presence and distribution of beta/A4 amyloid, a 4-kilodalton peptide. In aged squirrel monkeys, amyloid is associated primarily with intracerebral and meningeal capillaries and arterioles and occurs to a lesser degree as small and/or diffuse deposits in the neural parenchyma and in the dense cores of senile plaques. Cerebrovascular amyloid is found primarily in neocortex, amygdala, and septum verum and is rare or nonexistent in other subcortical gray structures, white matter, cerebellum, and spinal cord; this pattern of localization is comparable to that in humans with cerebral amyloid angiopathy. There is a significant correlation between cerebrovascular and parenchymal deposits of amyloid. However, cerebrovascular amyloid is always the most abundant form in squirrel monkeys, even in cases of severe cerebral amyloidosis. In contrast to squirrel monkeys, aged rhesus monkeys (Macaca mulatta) develop mostly parenchymal deposits of amyloid and have relatively less vascular amyloid. This species difference in the histological distribution of amyloid suggests that separate mechanisms may influence the accumulation of amyloid in cerebral blood vessels and in the neural parenchyma. These data also indicate that the squirrel monkey can serve as a model for investigations of cerebrovascular amyloidosis.

Aging↗

PubMed1985

A new method to classify amyloid fibril proteins.

The permanganate method, the immunoperoxidase method, and a newly developed autoclave method were used to distinguish different types of amyloid fibril proteins in formalin-fixed, paraffin-embedded tissue sections. All tissues from permanganate-sensitive cases (AA type) lost the affinity of Congo red and green birefringence under polarized light after incubation with special autoclave treatment. AL type systemic amyloidosis and amyloid plaques of CJD and GSS were permanganate-resistant, but decreased markedly the affinity of Congo red after prolonged autoclaving. On the other hand, prealbumin type systemic amyloidosis and senile plaques of SDAT were resistant to both permanganate oxidation and prolonged autoclaving. Thus, amyloid plaques of CJD and GSS are identical to AL type in systemic amyloidosis, and senile plaques are similar to the prealbumin type. However, anti-prealbumin antiserum did not stain senile plaque amyloid. The anti-human P component stained positively systemic amyloids and cerebral amyloid plaques of SSE, but failed to stain senile plaques of SDAT. Therefore, the amyloid fibril protein of senile plaques is apparently different from other types of amyloid depositions. Amyloid plaques of SSE are different from senile plaques not only with regard to fibril proteins, but also to globular protein in the amyloid.

Adolescent↗

PubMed1983

Manifestation and ultrastructural typing of amyloid deposits in the heart.

Using light and electron microscopy, 65 cases of amyloid deposits in the heart were examined. Five different groups were distinguished: I. isolated atrial amyloidosis, II. senile cardiac amyloidosis, III. cardiac amyloid accompanying chronic infections and tumors, IV. cardiac amyloid accompanying plasma cell dyscrasia, V. idiopathic cardiac amyloidosis. Seen structurally, no principal differences in the precise localization of the amyloid deposits were found in any of the groups investigated. Amyloid is always deposited in the vicinity of cells with myocytic cell differentiation (i.e. the heart muscle cells, non-striated muscle cells of the vessels), whereby the relevant basement membranes serve as conductors. A systematic relationship between amyloid and the collagenous fibers of the interstitium or the tunica adventitia of the vessels could not be demonstrated, which shows the concept "pericollagen" to be inadequate for the morphological characterization of amyloid deposits in the heart. Whereas for group I a localized mechanism for the production of amyloid must be considered, in the case of groups II-V a vascular principle expression of a generalized amyloidosis seems to be the major factor. The question of the differing concentration of amyloid deposits in the heart suggests that localized factors (e.g. changes in the myocytic basement membranes) and quantitative changes of the amyloid-building proteins may also be important.

Adolescent↗

PubMed1991

Conservation of the sequence of the Alzheimer's disease amyloid peptide in dog, polar bear and five other mammals by cross-species polymerase chain reaction analysis.

Neuritic plaque and cerebrovascular amyloid deposits have been detected in the aged monkey, dog, and polar bear and have rarely been found in aged rodents (Biochem. Biophy. Res. Commun., 12 (1984) 885-890; Proc. Natl. Acad. Sci. U.S.A., 82 (1985) 4245-4249). To determine if the primary structure of the 42-43 residue amyloid peptide is conserved in species that accumulate plaques, the region of the amyloid precursor protein (APP) cDNA that encodes the peptide region was amplified by the polymerase chain reaction and sequenced. The deduced amino acid sequence was compared to those species where amyloid accumulation has not been detected. The DNA sequences of dog, polar bear, rabbit, cow, sheep, pig and guinea pig were compared and a phylogenetic tree was generated. We conclude that the amino acid sequence of dog and polar bear and other mammals which may form amyloid plaques is conserved and the species where amyloid has not been detected (mouse, rat) may be evolutionarily a distinct group. In addition, the predicted secondary structure of mouse and rat amyloid that differs from that of amyloid bearing species is its lack of propensity to form a beta sheeted structure. Thus, a cross-species examination of the amyloid peptide may suggest what is essential for amyloid deposition.

Alzheimer Disease↗

PubMed1990

Amyloid deposits in basal cell carcinoma of the skin. A pathologic study of 199 cases.

Deposits of amyloid were detected in 101 of 199 basal cell carcinomas (51%). The frequency of amyloid deposits in solid, adenoid, and cystic histologic subtypes was slightly higher than overall, whereas in partial sclerosing and morphea-like tumors the frequency was much lower. The amyloid of basal cell carcinoma showed histochemical characteristics that were different from those of locally deposited amyloid in endocrine tumors such as medullary carcinoma thyroid and from those of "secondary" amyloid. No major differences in the histochemical characteristics, however, were observed between amyloid associated with basal cell carcinoma and myeloma-associated or "primary" amyloid. Nevertheless, immunohistochemical staining with rabbit antihuman keratin antibodies by the peroxidase antiperoxidase technique demonstrated positivity only in amyloid deposits associated with basal cell carcinoma and not in those of myeloma-associated amyloid. This evidence supports the concept that amyloid of basal cell carcinoma is produced in the stroma from degenerated epithelial cells through filamentous degeneration or apoptosis.

Amyloid↗

PubMed2004

Methionine 35 oxidation reduces toxic effects of the amyloid beta-protein fragment (31-35) on human red blood cell.

Amyloid beta-peptide, the central constituent of senile plaques in Alzheimer's disease brain, has been shown to be a source of free radical oxidative stress that may lead to neurodegeneration. In particular, it is well known that oxidation of methionine 35, is strongly related to the pathogenesis of Alzheimer's disease, since it represents the residue in the beta-amyloid peptide most susceptible to oxidation "in vivo". In this study, the fragment 31-35 of the beta-amyloid peptide, which has a single methionine at residue 35, was used to investigate the influence of the oxidation state of methionine-35 on the beta-amyloid peptide (31-35) mediated cytotoxic effects. Because no extensive studies have yet addressed whether amyloid beta peptides-mediated toxic effects can occur in the absence of mitochondria, human red blood cells were used as cell model. Exposure of intact red blood cells to beta-amyloid peptide (31-35) induced a marked stimulation (approximately 45%) of the pentose phosphate pathway and a significant inhibition of the red cell enzyme catalase, compared with the results observed in control red blood cells. In contrast, exposure of red blood cells to the beta-amyloid peptide (31-35)-Met35OX i.e. in which the sulfur of methionine is oxidised to sulfoxide, induced a slight activation of PPP (approximately 19%), and an inhibition of catalase activity lower with respect to the results observed in beta-amyloid peptide (31-35)-treated red blood cells. Since the activities of red cell phosphofructokinase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, glutathione reductase and the functionality of hemoglobin were not modified within the red cell following to beta-amyloid peptides exposure, it is likely that beta-amyloid (31-35)-catalase interaction may represent a selective toxic event. Together, these results support the hypothesis that Abeta peptide and the oxidative state of Met-35 may be involved in the mechanisms responsible of neurodegeneration in Alzheimer's disease.

Alzheimer Disease↗

PubMed2004

In vitro conversion of full-length mammalian prion protein produces amyloid form with physical properties of PrP(Sc).

The "protein only" hypothesis postulates that the infectious agent of prion diseases, PrP(Sc), is composed of the prion protein (PrP) converted into an amyloid-specific conformation. However, cell-free conversion of the full-length PrP into the amyloid conformation has not been achieved. In an effort to understand the mechanism of PrP(Sc) formation, we developed a cell-free conversion system using recombinant mouse full-length PrP with an intact disulfide bond (rPrP). We demonstrate that rPrP will convert into the beta-sheet-rich oligomeric form at highly acidic pH (<5.5) and at high concentrations, while at slightly acidic or neutral pH (>5.5) it assembles into the amyloid form. As judged from electron microscopy, the amyloid form had a ribbon-like assembly composed of two non-twisted filaments. In contrast to the formation of the beta-oligomer, the conversion to the amyloid occurred at concentrations close to physiological and displayed key features of an autocatalytic process. Moreover, using a shortened rPrP consisting of 106 residues (rPrP 106, deletions: Delta23-88 and Delta141-176), we showed that the in vitro conversion mimicked a transmission barrier observed in vivo. Furthermore, the amyloid form displayed a remarkable resistance to proteinase K (PK) and produced a PK-resistant core identical with that of PrP(Sc). Fourier transform infrared spectroscopy analyses showed that the beta-sheet-rich core of the amyloid form remained intact upon PK-digestion and accounted for the extremely high thermal stability. Electron and real-time fluorescent microscopy revealed that proteolytic digestion induces either aggregation of the amyloid ribbons into large clumps or further assembly into fibrils composed of several ribbons. Fibrils composed of ribbons were very fragile and had a tendency to fragment into short pieces. Remarkably, the amyloid form treated with PK preserved high seeding activity. Our work supports the protein only hypothesis of prion propagation and demonstrates that formation of the amyloid form that recapitulates key physical properties of PrP(Sc) can be achieved in vitro in the absence of cellular factors or a PrP(Sc) template.

Amyloid↗

PubMed2000

4'-Iodo-4'-deoxydoxorubicin disrupts the fibrillar structure of transthyretin amyloid.

Transthyretin (TTR) is a tetrameric protein synthesized mainly by the liver and the choroid plexus, from where it is secreted into the plasma and the cerebrospinal fluid, respectively. Some forms of polyneuropathy, vitreopathy, and cardiomyopathy are caused by the deposition of normal and/or mutant TTR molecules in the form of amyloid fibrils. Familial amyloidotic polyneuropathy is the most common form of TTR amyloidosis related to the V30M variant. It is still unclear the process by which soluble proteins deposit as amyloid. The treatment of amyloid-related disorders might attempt the stabilization of the soluble protein precursor to retard or inhibit its deposition as amyloid; or aim at the resorption of the deposited amyloid. The anthracycline 4'-iodo-4'-deoxydoxorubicin (I-DOX) has been shown to reduce the amyloid load in immunoglobulin light-chain amyloidosis. We investigated 1) whether I-DOX has affinity for TTR amyloid in tissues, 2) determined the I-DOX binding constants to TTR synthetic fibrils, and 3) determined the nature of the effect of I-DOX on TTR fibrils. We report that 1) I-DOX co-localizes with amyloid deposits in tissue sections of patients with familial amyloidotic polyneuropathy; 2) I-DOX strongly interacts with TTR amyloid fibrils and presents two binding sites with k(d) of 1.5 x 10(-11) mol/L and 5.6 x 10(-10) mol/L, respectively; and 3) I-DOX disrupts the fibrillar structure of TTR amyloid into amorphous material, as assessed by electron microscopy but does not solubilize the fibrils as confirmed by filter assays. These data support the hypothesis that I-DOX and less toxic derivatives can prove efficient in the treatment of TTR-related amyloidosis.

Amyloid↗