SERUM FROM PATIENTS WITH TYPE-2 DIABETES WITH NEUROPATHY INDUCES COMPLEMENT-INDEPENDENT, CALCIUM-DEPENDENT APOPTOSIS IN CULTURED NEURONAL CELLS

We hypothesized that sera from type 2 diabetic patients with neuropath y contains an autoimmune immunoglobulin that promotes complement-indep endent, calcium-dependent apoptosis in neuronal cell lines. Neuronal c ells were cultured in the presence of complement-inactivated sera obta ined from patients with type 2 diabetes with and without neuropathy an d healthy adult control patients. Serum from diabetic patients with ne uropathy was associated with a significantly greater induction of apop tosis, compared to serum from diabetic patients without neuropathy and controls. In the presence of calcium channel antagonists, induction o f apoptosis was reduced by similar to 50%. Pretreatment of neuronal ce lls with serum from diabetic patients with neuropathy was associated w ith a significant increase in elevated K+-evoked cytosolic calcium con centration. Serum-induced enhancement in cytosolic calcium and calcium current density was blocked by treatment with trypsin and filtration of the serum using a 100,000-kd molecular weight filter. Treatment wit h an anti-human IgG antibody was associated with intense fluorescence on the surface of neuronal cells exposed to sera from patients with ty pe 2 diabetes mellitus with neuropathy. We conclude that sera from typ e 2 diabetic patients with neuropathy contains an autoimmune immunoglo bulin that induces complement-independent, calcium-dependent apoptosis in neuronal cells.