Identification of pentosidine as a native structure for advanced glycation end products in β₂-microglobulin-containing amyloid fibrils in patients with dialysis-related amyloidosis

β₂-Microglobulin (β₂m) is a major constituent of amyloid fibrils in patients with dialysis-related amyloidosis (DRA). Recently, we found that the pigmented and fluorescent adducts formed nonenzymatically between sugar and protein, known as advanced glycation end products (AGEs), were present in β₂m-containing amyloid fibrils, suggesting the possible involvement of AGE- modified β₂m in bone and joint destruction in DRA. As an extension of our search for the native structure of AGEs in β₂m of patients with DRA, the present study focused on pentosidine, a fluorescent cross-linked glycoxidation product. Determination by both HPLC assay and competitive ELISA demonstrated a significant amount of pentosidine in amyloid-fibril β₂m from long-term hemodialysis patients with DRA, and the acidic isoform of β₂m in the serum and urine of hemodialysis patients. A further immunohistochemical study revealed the positive immunostaining for pentosidine and immunoreactive AGEs and β₂m in macrophage-infiltrated amyloid deposits of long-term hemodialysis patients with DRA. These findings implicate a potential link of glycoxidation products in long-lived β₂m-containing amyloid fibrils to the pathogenesis of DRA.