Dialysis Amyloidosis is a significant cause of carpal tunnel syndrome, osteoarthropathy, cystic radiolucencies of bone, spondyloarthropathy, and systemic amyloid that affects the majority of patients on long- term chronic hemodialysis (HD); it is also a significant morbidity for persons receiving chronic ambulatory peritoneal dialysis. Amyloid deposits in dialysis amyloidosis contain fibrils, P-component (AP), and glycosaminoglycans (GAGS); amyloid fibrils are comprised of polymerized beta2m which appears in several studies to be the full- length molecule. Since circulating beta2m in this disorder is monomeric, it is likely that polymerization occurs a the site of deposition. The overall aims of this proposal are to define the structural basis of fibrillogenesis in this disorder, and to develop an animal model to clarify pathogenesis, and in which to test novel approaches to diagnosis and therapy. To these ends, we will study the intrinsic tendency of beta2m to undergo aggregation and fibrillogenesis in vitro, as well as the relative fibrillogenic potential of proteolytically-modified or partially-denatured forms of beta2m, isolated from blood or joint fluid of patients affected by dialysis amyloidosis, recombinant/ mutagenized constructs, and synthetic peptides corresponding to parts of its primary amino acid sequence. Aggregation will be studied by changes in circular dichroism spectra, size fractionation, x-ray diffraction, and by electron microscopy for the formation of typical amyloid fibrils that bind congo red and are birefringent. An effect for potentially important cofactors such as AP, GAGs, or aluminum salts in augmenting fibrillogenesis, or in stabilizing the fibril, will be examined. Tissue amyloid obtained at surgery or postmortem will be analyzed as to the presence of modified forms of beta2m in dimeric or polymeric fractions. We will also characterize GAGs copurifying with fibrils, and search for HLA Class I heavy chain proteins, or novel amyloidogenic cofactors, both by direct extraction and by immunohistology. The synthesis and expression of beta2m on the cell surface and or shed by peripheral blood mononuclear cells of patients affected by dialysis amyloidosis will be defined, with a special view to looking for electrophoretic variants of beta2m that may be upregulated by interferon gamma and other stimuli. we will also look for spontaneous fibrillogenesis in culture supernatants, as recently described. Lastly, we will explore the feasibility of developing a rodent model for beta2m amyloidosis, by inducing chronic renal failure in transgenic lines overexpressing human beta2m and further loaded with beta2m by intraperitoneal or intra-articular injection. Additional variables that will be analyzed in animal studies are the effects of dehydration, in vivo administration of interferon, induction of sterile peritonitis, the effect of aluminum intoxication, and an accelerating effect of Amyloid Enhancing Factor. Long-term goals are to analyze the pathogenesis of dialysis amyloidosis in the context of related studies of fibrillogenesis in other forms of amyloid, crystallize novel forms of beta2m to more precisely define alterations in conformation that are likely to influence immunogenicity and interaction with specific ligands, assess biological activity of modified forms of beta2m relative to the native molecule, and to further exploit a rodent model by testing in vivo radiommunodetection and novel potential therapeutic modalities.
