Elucidation of the molecular pathogenesis of dialysis-related amyloidosis.

β2-微球蛋白（β2-m）相关性淀粉样变性（dialysis-related amyloidosis，β2-m）是长期透析患者常见的严重并发症，β2-m是β2-m淀粉样纤维（fAβ 2 M）的主要结构成分。本研究的目的是：（1）建立β2-m单体形成fAβ 2 M的分子模型;（2）阐明各种生物分子或化合物对纤维形成和降解的影响，以及对纤维化发病机制的影响;（3）在研究分子相互作用的基础上提出治疗纤维化的策略。结果：在fAβ 2 M形成过程中，β2-m的部分解折叠是其组装成纤维的先决条件。(1)在中性pH条件下，三氟乙醇（5-20%）可诱导β2-m去淀粉样折叠并稳定纤维，导致fAβ 2 M的延伸。此外，一些糖胺聚糖可能通过与纤维结合并稳定纤维而促进纤维的延伸。(2)在临界胶束浓度附近，磷脂类似物十二烷基硫酸钠（sodium dodecyl sulfate，SDS）在中性条件下也能诱导fA β 2 M的伸展，其作用机制是诱导β2-m在中性条件下发生淀粉样变性去折叠。这些是第一组可能参与患者纤维形成的生理因素。(4)本研究成功地制备了人β2-m转基因小鼠，并证实其血清中β2-m水平比长期透析患者高出数倍，在阐明fAβ 2 M体外形成的分子机制和制备转基因小鼠作为体内模型系统方面取得了显著进展。

β2-Microglobulin (β2-m)-related amyloidosis (dialysis-related amyloidosis, DRA) is a frequent and serious complication in patients on long-term dialysis, and β2-m is a major structural component of β2-m amyloid fibril (fAβ2M). The aims of this study are (1) establishment of molecular model of fAβ2M formation from β2-m monomer, (2) elucidation of the effect of various biological molecules or chemical compounds on the fibril formation and degradation, and on the pathogenesis of DRA, (3) proposition of a strategy for the treatment of DRA on the basis of molecular interaction investigated. For these purpose, we improved the previous in vitro amyloid fibril formation system and also developed a transgenic mouse for the model of DRA.Results : In fAβ2M formation, partial unfolding of β2-m is believed to be prerequisite to its assembly into fibrils. (1) Trifluoroethanol (5-20%) was found to induce the amyloidogenic unfolding of β2-m and to stabilize the fibrils, resulted in the extension of fAβ2M at a neutral pH. In addition, some glycosamonoglycans enhanced the fibril extension probably by binding to the fibrils and stabilizing them. (2) At around the critical micelle concentration, sodium dodecyl sulfate, an analogue of phospholipids, was also found to induce the extension of fAβ2M by inducing the amyloidogenic unfolding of β2-m at a neutral pH. (3) Some anionic lysophospholipids were found to extend fAβ2M at a neutral pH in vitro. These are the first group of physiological agents, which may participate in the fibrillogenesis in the patients. (4) The human β2-m transgenic mice were successfully produced and confirmed that the levels of β2-m in the serum were elevated to several times higher than those of the patients on long-term dialysis.As the conclusion of this study, the remarkable advance on the clarification of the molecular mechanism of fAβ2M formation in vitro, and on the production of transgenic mouse as a in vivo model system were obtained.