Lipid membranes accelerate amyloid formation in the mouse model of AA amyloidosis.

INTRODUCTION: AA amyloidosis develops as a result of prolonged inflammation and is characterized by deposits of N-terminal proteolytic fragments of the acute phase reactant serum amyloid A (SAA). Macrophages are usually found adjacent to amyloid, suggesting their involvement in the formation and/or degradation of the amyloid fibrils. Furthermore, accumulating evidence suggests that lipid membranes accelerate the fibrillation of different amyloid proteins. METHODS: Using an experimental mouse model of AA amyloidosis, we compared the amyloidogenic effect of liposomes and/or amyloid-enhancing factor (AEF). Inflammation was induced by subcutaneous injection of silver nitrate followed by intravenous injection of liposomes and/or AEF to accelerate amyloid formation. RESULTS: We showed that liposomes accelerate amyloid formation in inflamed mice, but the amyloidogenic effect of liposomes was weaker compared with AEF. Regardless of the induction method, amyloid deposits were mainly found in the marginal zones of the spleen and coincided with the depletion of marginal zone macrophages, while red pulp macrophages and metallophilic marginal zone macrophages proved insensitive to amyloid deposition. CONCLUSIONS: We conclude that increased intracellular lipid content facilitates AA amyloid fibril formation and show that the mouse model of AA amyloidosis is a suitable system for further mechanistic studies.

Noncerebral Amyloidoses: Aspects on Seeding, Cross-Seeding, and Transmission.

More than 30 proteins form amyloid in humans, most of them outside of the brain. Deposition of amyloid in extracerebral tissues is very common and seems inevitable for an aging person. Most deposits are localized, small, and probably without consequence, but in some instances, they are associated with diseases such as type 2 diabetes. Other extracerebral amyloidoses are systemic, with life-threatening effects on the heart, kidneys, and other organs. Here, we review how amyloid may spread through seeding and whether transmission of amyloid diseases may occur between humans. We also discuss whether cross-seeding is important in the development of amyloidosis, focusing specifically on the amyloid proteins AA, transthyretin, and islet amyloid polypeptide (IAPP).

Evaluation of tubulin ß-3 as a novel senescence-associated gene in melanocytic malignant transformation.

Malignant melanoma might develop from melanocytic nevi in which the growth-arrested state has been broken. We analyzed the gene expression of young and senescent human melanocytes in culture and compared the gene expression data with a dataset from nevi and melanomas. A concordant altered gene expression was identified in 84 genes when comparing the growth-arrested samples with proliferating samples. TUBB3, which encodes the microtubule protein tubulin ß-3, showed a decreased expression in senescent melanocytes and nevi and was selected for further studies. Depletion of tubulin ß-3 caused accumulation of cells in the G2/M phase and decreased proliferation and migration. Immunohistochemical assessment of tubulin ß-3 in benign lesions revealed strong staining in the superficial part of the intradermal components, which faded with depth. In contrast, primary melanomas exhibited staining without gradient in a disordered pattern and strong staining of the invasive front. Our results describe an approach to find clinically useful diagnostic biomarkers to more precisely identify cutaneous malignant melanoma and present tubulin ß-3 as a candidate marker.

Depletion of spleen macrophages delays AA amyloid development: a study performed in the rapid mouse model of AA amyloidosis.

AA amyloidosis is a systemic disease that develops secondary to chronic inflammatory diseases Macrophages are often found in the vicinity of amyloid deposits and considered to play a role in both formation and degradation of amyloid fibrils. In spleen reside at least three types of macrophages, red pulp macrophages (RPM), marginal zone macrophages (MZM), metallophilic marginal zone macrophages (MMZM). MMZM and MZM are located in the marginal zone and express a unique collection of scavenger receptors that are involved in the uptake of blood-born particles. The murine AA amyloid model that resembles the human form of the disease has been used to study amyloid effects on different macrophage populations. Amyloid was induced by intravenous injection of amyloid enhancing factor and subcutaneous injections of silver nitrate and macrophages were identified with specific antibodies. We show that MZMs are highly sensitive to amyloid and decrease in number progressively with increasing amyloid load. Total area of MMZMs is unaffected by amyloid but cells are activated and migrate into the white pulp. In a group of mice spleen macrophages were depleted by an intravenous injection of clodronate filled liposomes. Subsequent injections of AEF and silver nitrate showed a sustained amyloid development. RPMs that constitute the majority of macrophages in spleen, appear insensitive to amyloid and do not participate in amyloid formation.

A child with a long-standing, intensely itching subcutaneous nodule on a thigh: an uncommon (?) reaction to commonly used vaccines.

A 2-year-old girl presented with an intensely itching subcutaneous nodule on the front of a thigh. The nodule persisted for 10 months until it was excised. Subsequent investigation for malignancy and systemic disease showed no pathological findings. The diagnosis, persistent itching vaccination granuloma, was revealed by hazard almost 2 years after the onset of symptoms. Persistent itching subcutaneous nodules at the injection site for aluminium containing vaccines (mostly diphtheria-tetanus-pertussis combination vaccines for primary immunisation of infants) may appear with a long delay after the vaccination (months), cause prolonged itching (years) and are often associated with contact allergy to aluminium. The condition is poorly recognised in Health Care which may lead to prolonged symptoms and unnecessary investigations.

Fibrils from designed non-amyloid-related synthetic peptides induce AA-amyloidosis during inflammation in an animal model.

BACKGROUND: Mouse AA-amyloidosis is a transmissible disease by a prion-like mechanism where amyloid fibrils act by seeding. Synthetic peptides with no amyloid relationship can assemble into amyloid-like fibrils and these may have seeding capacity for amyloid proteins. PRINCIPAL FINDINGS: Several synthetic peptides, designed for nanotechnology, have been examined for their ability to produce fibrils with Congo red affinity and concomitant green birefringence, affinity for thioflavin S and to accelerate AA-amyloidosis in mice. It is shown that some amphiphilic fibril-forming peptides not only produced Congo red birefringence and showed affinity for thioflavin S, but they also shortened the lag phase for systemic AA-amyloidosis in mice when they were given intravenously at the time of inflammatory induction with silver nitride. Peptides, not forming amyloid-like fibrils, did not have such properties. CONCLUSIONS: These observations should caution researchers and those who work with synthetic peptides and their derivatives to be aware of the potential health concerns.

Protein fibrils in nature can enhance amyloid protein A amyloidosis in mice: Cross-seeding as a disease mechanism.

Secondary, or amyloid protein A (AA), amyloidosis is a complication of chronic inflammatory diseases, both infectious and noninfectious. AA constitutes the insoluble fibrils, which are deposited in different organs, and is a major N-terminal part of the acute phase protein serum AA. It is not known why only some patients with chronic inflammation develop AA amyloidosis. Nucleation is a widely accepted mechanism in amyloidogenesis. Preformed amyloid-like fibrils act as nuclei in amyloid fibril formation in vitro, and AA amyloid fibrils and synthetic amyloid-like fibrils also may serve as seed for fibril formation in vivo. In addition to amyloid fibrils, there is a variety of similar nonmammalian protein fibrils with beta-pleated structure in nature. We studied three such naturally occurring protein fibrils: silk from Bombyx mori, Sup35 from Saccharomyces cerevisiae, and curli from Escherichia coli. Our results show that these protein fibrils exert amyloid-accelerating properties in the murine experimental AA amyloidosis, suggesting that such environment factors may be important risk factors in amyloidogenesis.

Transmissibility of systemic amyloidosis by a prion-like mechanism.

The generation of amyloid fibrils from an amyloidogenic polypeptide occurs by a nucleation-dependent process initiated in vitro by seeding the protein solution with preformed fibrils. This phenomenon is evidenced in vivo by the fact that amyloid protein A (AA) amyloidosis in mice is markedly accelerated when the animals are given, in addition to an inflammatory stimulus, an i.v. injection of protein extracted from AA amyloid-laden mouse tissue. Heretofore, the chemical nature of this "amyloid enhancing factor" (AEF) has not been definitively identified. Here we report that the active principle of AEF extracted from the spleen of mice with silver nitrate-induced AA amyloidosis was identified unequivocally as the AA fibril itself. Further, we demonstrated that this material was extremely potent, being active in doses <1 ng, and that it retained its biologic activity over a considerable length of time. Notably, the AEF was also effective when administered orally. Our studies have provided evidence that AA and perhaps other forms of amyloidosis are transmissible diseases, akin to the prion-associated disorders.