Date of Award

Summer 1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Program/Concentration

Biomedical Sciences

Committee Director

Gary L. Pittenger

Committee Member

Stephen E. Buescher

Committee Member

Francis J. Liuzzi

Committee Member

Aaron I. Vinik

Committee Member

Roy L. Williams

Abstract

Diabetic neuropathy is an extremely common medical problem because of the high frequency of diabetes and its complications. Diabetic neuropathy consists of not one, but many patterns of nerve injury, each potentially with its own discrete pathogenic mechanisms. Evidence is accumulating that indicates autoimmunity plays a role in diabetic peripheral neuropathy. However, the significance of immunopathogenesis of diabetic neuropathy is as yet unclear.

Using the N1E-115 mouse neuroblastoma cell line (NB) as a model of the adrenergic autonomic neuron, we found that sera of IDDM patients with neuropathy inhibit growth and differentiation of adrenergic neurons in culture (Pittenger et al, 1993; 1995). Some sera were cytotoxic and caused neuronal death. Further characterization of the inhibiting, or toxic, factor in IDDM patient serum indicated that it had the properties of an immunoglobulin. The toxic factor was present in the immunoglobulin fraction, and was pre-absorbed by neuroblastoma cells and protein A beads. Immunocytochemistry revealed a specific cell-surface binding pattern of immunoglobulin IgG which suggested the presence of an antibody recognizing antigens on the neuroblastoma cell surface. Moreover, the inhibiting effect of IDDM serum could be reversed by heat inactivation, indicating the possible involvement of complement.

Further investigation revealed that the neuronal death induced by IDDM serum occurred through the programmed cell death mechanism, apoptosis, which was characterized by cell shrinkage, cytoplasm condensation and DNA fragmentation. A sustained increase of cytosolic calcium concentration was detected by Fura-2, a fluorescence indicator, at an early stage after exposure to IDDM serum. Apoptosis-related protein expression was also examined in our model. Fas, a cell-surface receptor, seemed to be expressed at the N1E-115 cell surface and recognized by IDDM serum. Whether it was the antigen involved in apoptotic cell death or whether other antigens were also involved remains to be further determined.

In conclusion, autoimmune-related humoral factors in the serum from IDDM patients with neuropathy had an ability to inhibit neuronal cell growth and differentiation, in some cases inducing cell death by apoptosis in cultured adrenergic neurons. However, because N1E-115 cell was a murine tumor cell line, the significance of the findings to diabetic neuropathy and clinical correlation needs to be further evaluated. These studies indicated that immunopathogenesis may play an important role in the development of diabetic neuropathy in IDDM patients.

Comments

Dissertation submitted to the Faculty of Eastern Virginia Medical School and Old Dominion University in Partial Fulfillment of the Requirement for the Degree of Doctor of Philosophy in Biomedical Sciences.

DOI

10.25777/sb2e-ad92

ISBN

9780591442632

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