antimycin and Diabetes-Mellitus--Type-1

Microvascular damage caused by diabetes is a leading cause of visual loss. Identifying events early in the course of diabetic retinopathy may help in understanding and, perhaps, preventing this disorder. The hypothesis that cell-to-cell communication within the retinal microvasculature may be affected soon after the onset of diabetes was tested.. Streptozotocin was used to induce diabetes in rats. To assess cell-to-cell coupling the gap junction-permeant tracer, Neurobiotin, was delivered via patch pipettes into pericytes located on microvessels freshly isolated from the retinas of diabetic and control animals. Subsequently, immunohistochemical methods revealed the extent of the intercellular spread of the tracer. Electrophysiological methods were also used to detect intercellular communication.. In retinal microvessels of control rats, Neurobiotin spread hundreds of micrometers from the tracer-loaded pericytes. However, within days after the onset of diabetes, this cell-to-cell coupling was dramatically reduced. In contrast, microvessels of insulin-treated diabetic rats showed no significant loss of intercellular communication. Consistent with protein kinase C (PKC) playing a role in the diabetes-induced inhibition of gap junction pathways, exposure of microvessels to a PKC activator (phorbol myristate acetate) markedly reduced tracer coupling.. Within retinal microvessels there is extensive cell-to-cell coupling, which is markedly reduced soon after the onset of streptozotocin-induced diabetes. The closure of gap junction pathways disrupts the multicellular organization of retinal microvessels and may contribute to vascular dysfunction.

Topics: Animals; Antimycin A; Biotin; Capillaries; Cell Communication; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Electrophysiology; Gap Junctions; Iodoacetates; Patch-Clamp Techniques; Protein Kinase C; Rats; Rats, Long-Evans; Retinal Vessels; Tetradecanoylphorbol Acetate

It has been hypothesised that mitochondrial dysfunction in pancreatic beta cells could produce hyper-expression of glutamic acid decarboxylase (GAD), a major autoantigen in insulin-dependent diabetes mellitus (IDDM) (Degli Esposti, M. and Mackay, I.R. Diabetologia 40: 352-356, 1997). Here we report that specific inhibition of mitochondrial respiration enhances the expression of GAD in both foetal mouse pancreatic tissue and hamster HIT-T15 cells. Inhibitors of NADH-ubiquinone oxidoreductase (complex I) seem to be particularly effective in increasing the expression of GAD in both foetal mouse pancreas and HIT-T15 hamster beta cells, especially in the presence of nutrients such as arginine and glucose. These results represent the first evidence that GAD expression is enhanced under conditions that are toxic to pancreatic beta cells, and establish a link between mitochondrial dysfunction and expression of IDDM autoantigens.

Topics: Animals; Antimycin A; Arginine; Carboxin; Cells, Cultured; Cricetinae; Cytotoxins; Diabetes Mellitus, Type 1; Dopamine Antagonists; Furans; Gene Expression Regulation, Enzymologic; Glutamate Decarboxylase; Haloperidol; Image Processing, Computer-Assisted; Immunohistochemistry; Insulin; Islets of Langerhans; Mice; Mitochondria; Oxidative Phosphorylation; Phenylurea Compounds; Radioimmunoassay; Rodenticides; Rotenone; Uncoupling Agents