Amyloid fibril protein AA in Papua New Guinean amyloidosis.

In this study of protein composition of amyloid fibrils isolated from eight patients representative of the spectrum of amyloidosis found in Papua New Guinea has been investigated. All fibril preparations, including three from patients with amyloidosis secondary to lepromatous leprosy and one from an unusual juvenile case of primary amyloidosis, contained the non-immunogobulin amyloid protein, protein AA. However, only 44% of thirty-six amyloid patients had detectable levels of the protein AA-related serum component, protein SAA. Alkali-degraded material from each of the fibril preparations failed to react in double immunodiffusion test with antiserum to the amyloid-related light chain VgammaV, but evidence was found for this immunoglobulin light chain-specificity in the serum of one patient.     

Reduction in amyloid A amyloid formation in apolipoprotein-E-deficient mice.

Apolipoproteins have been implicated in the formation of amyloid fibrils. Recent studies have demonstrated that apolipoprotein E (apoE), alone or in combination with apolipoprotein J (apoJ), and other lipoproteins appear to enhance deposition of amyloid fibrils both in systemic and cerebral amyloids, especially Alzheimer's disease (AD). ApoE enhanced the ability of the amyloid beta-protein (1-40) fragment (A beta) to form fibrils in vitro, with apoE4 promoting the greatest fibril formation. ApoE was found associated with both human and mouse amyloid A (AA) deposits. To define the role of apoE in vivo, we utilized mice lacking the apoE gene by gene targeting. We used the AA model in mice to characterize the function of the apoE protein in amyloid fibrillogenesis. ApoE-deficient mice exhibited a decrease in deposition of AA when compared with heterozygous mutant or wild-type animals. In addition, apoE-deficient mice that were injected with an adenovirus that expressed the human apoE3 gene had restored AA deposition and the apoE was associated with the AA fibrils. These results are agreement with the in vitro studies using the beta-peptide and suggest that apoE is not essential for amyloid fibrillogenesis but can promote the development of amyloid deposition.     

Cerebral lipid deposition in aged apolipoprotein-E-deficient mice.

To assess the influence of age and diet on cerebral pathology in mice lacking apolipoprotein E (apoE), four male apoE knockout mice (epsilon -/-), and five male wild-type (epsilon +/+) littermate controls were placed on a high-fat/high-cholesterol diet for 7 weeks beginning at 17 months of age. All four aged knockout mice developed xanthomatous lesions in the brain consisting mostly of crystalline cholesterol clefts, lipid globules, and foam cells. Smaller xanthomas were confined mainly to the choroid plexus and ventral fornix in the roof of the third ventricle, occasionally extending subpially along the choroidal fissure and into the adjacent parenchyma. More advanced xanthomas disrupted adjoining neural tissue in the fornix, hippocampus, and dorsal diencephalon; in one case, over 60% of one telencephalic hemisphere, including nearly the entire neocortex, was obliterated by the lesion. No xanthomas were observed in aged wild-type controls fed the high-fat/high-cholesterol diet. Brains from 42 additional animals, fed only conventional chow, were examined; 3 of 15 aged (15- to 23-month-old) apoE knockout mice developed small choroidal xanthomas. In contrast, no lesions were observed in five young (2- to 4-month-old) apoE knockout mice or in any wild-type controls between the ages of 2 and 23 months. Our findings indicate that disorders of lipid metabolism can induce significant pathological changes in the central nervous system of aged apoE knockout mice, particularly those on a high-fat/high-cholesterol diet. It may be fruitful to seek potential interactions between genetic factors and diet in modulating the risk of Alzheimer's disease and other neurodegenerative disorders in aged humans.     

Amyloid A amyloidosis and systemic lupus erythematosus

Amyloid A (AA) amyloidosis occurs secondary to long-standing inflammation and causes nephropathy and various internal manifestations, which leads to mortality. It is very rare in some rheumatic diseases, such as systemic lupus erythematosus (SLE). Therefore, there are few articles that report AA amyloidosis in SLE. This article focuses on the previously reported cases of 24 patients with SLE that are complicated by AA amyloidosis, and on the underlying mechanisms.     

Beta-amyloid protein-containing inclusions in skeletal muscle of apolipoprotein-E-deficient mice.

The tibialis anterior muscle and soleus muscle of apolipoprotein-E-deficient mice were examined by light and electron microscopy. By light microscopy, sarcoplasmic inclusions were seen in tibialis anterior muscle and 40% of type 2 myofibers were affected in all animals over 8 months of age. These inclusions reacted for nonspecific esterase, cytochrome oxidase, and myoadenylate deaminase and were also periodic acid Schiff positive and stained basophilic with hematoxylin. Moreover, they reacted immunocytochemically with an antibody specific to fragment 17 to 24 of the published sequence of Alzheimer's cerebrovascular amyloid peptide. Immunoreactivity was lost when the antibody was adsorbed with the appropriate synthetic peptide. Ultrastructurally, the inclusions consisted of tubular arrays and were similar to those observed in human muscle in several pathological conditions. In type 1 myofibers of both tibialis anterior and soleus muscle, however, mitochondrial abnormalities including an increase in their number and size were detected, but tubular aggregates were not seen. These large mitochondria possessed an electron-dense inner chamber with an increased number of tightly packed cristae. The results obtained suggest that in these mice there is a disturbed lipid metabolism in skeletal muscle fibers that manifests itself with an accumulation of phospholipid in the form of sarcoplasmic reticulum tubules in the type 2 fibers and enlarged mitochondria with tightly packed cristae in the type 1 fibers. In addition, beta-amyloid protein was closely associated with the accumulated tubules and vesicles of sarcoplasmic reticulum and may represent dysregulation of amyloid precursor protein metabolism.     

Serum protein changes in experimentally induced amyloidosis in hamsters

After inducing amyloidosis in hamsters by hyperimmunization with Di-Te-Per vaccine, their serum proteins were separated by electrophoresis. Results showed that the level of alpha 1 globulin increased and that of albumin decreased after 6-8 weeks of the hyperimmunization. Gamma-globulins increased by the 10th week of the study, then their level markedly decreased. Electrophoretic separation of the serum proteins refrigerated for 24 h at 4 degrees C showed the presence of a steadily increasing protein fraction induced by the prolonged immunization, which migrated in the prealbumin band. The fraction was observed in all phases of the experiments. This fraction was stained using selective methods for lipids. New bands appearing during electrophoretic separation of hamster serum proteins in amyloidosis may represent monomeric or polimeric forms of amyloid protein.     

Spontaneous amyloidosis in LLC mice.

Practically all low leukocyte count (LLC) mice over 1 year of age develop renal amyloidosis. Renal amyloid is deposited in the glomeruli and in the interstitium between the convoluted as well as collecting tubules, with consequent development of cysts and necrosis. LLC mice die of chronic renal failure. Electron microscopic studies reveal amyloid fibrils in the mesangium, a thickening of the basement membranes, and fusion of the foot processes in the glomeruli. Massive amounts of amyloid fibrils are also present in the interstitium, where intracellular fibrils in the fibroblasts as well as in the tubular epithelium cells are found. Vesicles, which are probably formed from membrane disruption, and amorphous materials are seen along the basement membranes. LLC mouse amyloidosis is discussed with regard to its potential as a model for studies on amyloidosis as well as the etiology and origin of amyloid fibrils.     

Amyloid precursor protein increases cortical neuron size in transgenic mice

The amyloid precursor protein (APP) is the source of beta-amyloid, a pivotal peptide in the pathogenesis of Alzheimer's disease (AD). This study examines the possible effect of APP transgene expression on neuronal size by measuring the volumes of cortical neurons (microm(3)) in transgenic mouse models with familial AD Swedish mutation (APPswe), with or without mutated presenilin1 (PS1dE9), as well as in mice carrying wild-type APP (APPwt). Overexpression of APPswe and APPwt protein, but not of PS1dE9 alone, resulted in a greater percentage of medium-sized neurons and a proportionate decrease in the percentage of small-sized neurons. Our observations indicate that the overexpression of mutant (APPswe) or wild-type APP in transgenic mice is necessary and sufficient for hypertrophy of cortical neurons. This is highly suggestive of a neurotrophic effect and also raises the possibility that the lack of neuronal loss in transgenic mouse models of AD may be attributed to overexpression of APP.     

Amyloid of the seminal vesicles. A distinctive and common localized form of senile amyloidosis.

Amyloid deposits were found subepithelially in the seminal vesicles of 34 of 209 consecutively studied men. The incidence increased with age and was found in 21% of men over 75 years. This senile seminal vesicle amyloidosis (SSVA) is a localized disorder, and the amyloid substance has unique histochemical and immunochemical properties not shared with any other amyloid described until now.     

Amyloid deposits in bioprosthetic cardiac valves after long-term implantation in man. A new localization of amyloidosis

Congo red staining with microscopic examination under polarized light was performed in 30 porcine bioprosthetic cardiac valves and one autologous fascia lata valve explanted from 31 patients in order to detect the presence of amyloid. Microdeposits of amyloid were present in the sewing ring of the fascia lata valve and in 10 porcine bioprostheses, and this finding was confirmed by transmission electron microscopy in 3 porcine bioprostheses. All amyloid-laden porcine valves had been implanted for at least 33 months before removal, and all except two showed dysfunction and/or severe degeneration of cuspal tissue. Statistical analyses failed to establish any correlation between the presence of amyloid and patient-related factors. In a majority of porcine bioprostheses amyloid was permanganate-sensitive and tryptophan-positive. The pathogenesis of this new form of heart valve amyloidosis might consist in penetration of human macrophages in deteriorated bioprosthetic cusps and their interaction with blood-borne amyloid precursors.     

Amyloid A amyloidosis in non-infected and avian leukosis virus-C persistently infected inbred ducks

The breeding history of the first inbred strain of Khaki Campbell ducks is presented. The genetic homogeneity of this strain was tested on the basis of serum amyloid A (SAA) polymorphism and it was established that it harbours only the SAA allele A, which is expressed in liver, lung and bursa of Fabricius tissues. Pathogenic changes in control and avian leukosis virus-C (ALV-C) persistently infected ducks were evaluated during the period spanning 1 to 10 months after hatching. In both groups, AA amyloidosis was revealed and characterized. In spite of the inbred nature of animals, the incidence of amyloid A deposition varied among experiments, suggesting that additional non-genetic factors are involved. Similar variation was found in ALV-C persistently infected ducks, where only in one out of three experiments was the incidence ofAA amyloidosis significantly higher than in controls.     

Induction in mice of human light-chain-associated amyloidosis.

Primary (idiopathic) or multiple myeloma-associated amyloidosis is characterized by the deposition in tissue of monoclonal light chains or light-chain fragments (AL amyloidosis). In contrast to other types of amyloidosis, information regarding the pathogenesis of light-chain-related amyloid has heretofore been limited due to the lack of a suitable in vivo model. The authors report the successful experimental induction of human AL amyloid deposits. The repeated injection into mice of Bence Jones proteins obtained from two patients with AL amyloidosis produced the histopathologic lesions characteristic of this disease. Partial dehydration of animals before protein injection resulted in the acceleration of amyloid formation. The human proteins were deposited as amyloid within the mouse renal blood vessel walls and parenchymal tissue, as well as in other organs. The deposits were Congo red-positive, exhibited green birefringence, and had a fibrillar ultrastructure. As evidenced immunohistochemically, the experimentally induced amyloid deposits consisted of the injected human light chains, and in addition, contained mouse amyloid P component (AP); mouse immunoglobulin (Ig) or inflammatory-associated amyloid A protein was not detected. Extraction and characterization of the amyloid deposits found within the mouse kidney revealed the presence of a predominantly intact human light polypeptide chain. Mice injected in identical manner with a non-amyloid-associated Bence Jones protein had no or only rare amyloid deposits. The experimental mouse model provides a means to ascertain the amyloidogenic potential of human monoclonal light chains and to study further the pathogenesis of AL amyloidosis.