GLUCOSE-INDUCED IN SITU IMMUNE COMPLEXES IN DIABETES

We propose to investigate the hypothesis that the chronic tissue damage
associated with long-term diabetes mellitus may arise in part from in situ
immune complex formation by accumulated immunoglobulins and/or antigens
covalently bound to long-lived structural proteins which have undergone
excessive nonenzymatic glycosylation with subsequent generation of reactive
carbonyls. In the diabetic kidney, such immobilized immune complexes may
serve as a chronic stimulus for tissue destruction by macrophages. The
specific aims of the studies described in this proposal are to: I) Characterize the covalent trapping of lysine and proteins by
nonenzymatically glycosylated collagen (chemical and kinetic studies),
using soluble collagen immobilized on Agarose. The effect of time and
reactant concentrations will be evaluated, and binding will be assessed
both in vitro and in vivo; II) Quantitate in situ formation of immune complexes by antigen or antibody
bound covalently to nonenzymatically glycosylated collagen, using
radioiodinated soluble proteins; II) Investigate the effect of immune complexes bound to glycosylated
collagen on macrophage tissue-injury mechanisms. Phagocytosis will be
evaluated using antibody-sensitized sheep erythrocytes labelled with 51Cr,
and hydrolytic enzyme secretion will be investigated by measuring selected
glycohydrolases, neutral proteases, and plasminogen activator; IV) Evaluate the effect of diabetes and high in vitro glucose concentration
on macrophage response to nonenzymatically glycosylated collagen-bound
immune complexes. Results from these studies may provide a basis for future development of
new therapeutic agents useful in the treatment of diabetic complications.