beta(2)-Microglobulin modified with advanced glycation end products delays monocyte apoptosis.
BACKGROUND
A local inflammatory reaction to beta(2)-microglobulin (beta(2)m) amyloid deposits by monocytes/macrophages is a characteristic histologic feature of dialysis-related amyloidosis (DRA). Since beta(2)m modified with advanced glycation end products (AGE-beta(2)m) is a major constituent of amyloid in DRA, we tested the hypothesis that AGE-beta(2)m affects apoptosis and phenotype of human monocytes.


METHODS
Human peripheral blood monocytes were incubated with or without in vitro-derived AGE-beta(2)m, and their viability, extent of apoptosis, morphology, and function examined over the subsequent four days.


RESULTS
AGE-modified but not unmodified beta(2)m significantly delayed spontaneous apoptosis of human peripheral blood monocytes in adherent and nonadherent cultures. The effect of AGE-beta(2)m on monocytes apoptosis was time- and dose-dependent and was attenuated by a blocking antibody directed against the human AGE receptor (RAGE). There was no difference in effect between AGE-beta(2)m and that of AGE-modified human serum albumin. Culture of monocytes with AGE-beta(2)m did not alter membrane expression of Fas or Fas ligand. Monocytes cultured with AGE-beta(2)m underwent substantial changes in morphology similar to those observed when monocytes differentiate into macrophages. The cultured cells increased in size and vacuolization, and their content of beta-glucuronidase and acid phosphatase increased by 5- to 10-fold at day 4. Expression of the monocyte--macrophage membrane antigens HLA-DR, CD11b, and CD11c also increased at day 4. Although exhibiting phenotypic characteristics of macrophages, monocytes cultured with AGE-beta(2)m functioned differently than macrophages cultured with serum. Superoxide production in response to phorbol myristic acetate was maintained in monocytes cultured with AGE-beta(2)m, but declined with time in cells cultured with serum. Constitutive synthesis of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and prostaglandin E2 (PGE2) increased in monocytes cultured for four to six days with AGE-beta(2)m.


CONCLUSIONS
These findings support a novel role for AGE-modified proteins such as AGE-beta(2)m that may contribute to the development of a local inflammatory response, with predominant accumulation of monocytes/macrophages, in DRA.
Hou
F F
FF
Duke Institute of Renal Outcomes Research and Health Policy, Division of Nephrology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Miyata
T
T
Boyce
J
J
Yuan
Q
Q
Chertow
G M
GM
Kay
J
J
Schmidt
A M
AM
Owen
W F
WF
D000906:Antibodies / Q000494:pharmacology; D000954:Antigens, Surface / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D015232:Dinoprostone / Q000378:metabolism; D053222:Fas Ligand Protein; D017127:Glycation End Products, Advanced / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D007425:Intracellular Membranes / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D008264:Macrophages / Q000276:immunology; D008562:Membrane Glycoproteins / Q000378:metabolism; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors / Q000276:immunology; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D001613:beta 2-Microglobulin / Q000494:pharmacology*; D019014:fas Receptor / Q000378:metabolism
D000906:Antibodies; D000954:Antigens, Surface; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D017127:Glycation End Products, Advanced; D007375:Interleukin-1; D008562:Membrane Glycoproteins; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic; D014409:Tumor Necrosis Factor-alpha; D001613:beta 2-Microglobulin; D019014:fas Receptor; D013481:Superoxides; D015232:Dinoprostone