Modification of β2m with advanced glycation end products as observed in dialysis-related amyloidosis by 3-DG accumulating in uremic serum

Abstract

β2-microglobulin (β2m) isolated from the amyloid deposits in patients with dialysis-related amyloidosis (DRA) has been demonstrated to be modified with advanced glycation end products (AGEs). We demonstrated that AGE was localized to amyloid deposits in patients with DRA by immunohistochemistry using a monoclonal anti-AGE antibody. To clarify the mechanism of AGE modification of β2m-amyloid, we studied the effects of 3-deoxyglucosone (3-DG), a potent protein crosslinking intermediate of the Maillard reaction, on the AGE modification of β2m, and quantified the serum levels of 3-DG in patients undergoing hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD), and undialyzed patients. The serum levels of 3-DG were markedly increased in the dialyzed and undialyzed uremic patients. Although the serum level of 3-DG decreased after HD with a mean reduction rate of 67%, it was still significantly higher than in normal serum. Incubation of β2m with 3-DG at 37°C emitted fluorescence characteristic for AGE, and caused AGE modification and dimer formation of β2m as demonstrated by Western blotting using the same monoclonal anti-AGE antibody used for immunohistochemical demonstration of AGE in DRA. The AGE-modified dimer of p,m could be extracted from the amyloid tissue of a patient with DRA. 3-DG showed more intense and faster reactivity with β2m to form AGE and dimer as compared with glucose, and aminoguanidine suppressed the AGE and dimer formation of β2m by 3-DG. In conclusion, 3-DG accumulating in uremic serum may be involved in the AGE modification of β2m-amyloid.