An immunohistochemical study of nitrotyrosine expression in pancreatic islets of cases with increasing duration of type 1 diabetes and without diabetes
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Peroxynitrite-induced nitration of cellular proteins has been shown to associate with various human pathologies. The expression of pancreatic nitrotyrosine and its cellular source relative to insulitis were analysed in cases with increasing duration of type 1 diabetes and compared with non-diabetic autoantibody-negative and -positive cases. Pancreatic tail sections from non-diabetic autoantibody-negative cases (Group 1; n = 7), non-diabetic autoantibody-positive cases (Group 2; n = 6), recently diagnosed cases (Group 3; n = 6), 0.25–5 years of diabetes (Group 4; n = 8) and 7–12 years of diabetes (Group 5; n = 6) were immunostained sequentially for nitrotyrosine, insulin and leucocytes. Nitrotyrosine expression was observed in selective beta cells only. In group 1, the percentage of insulin-positive islets with nitrotyrosine ranged from 7.6 to 58.8%. In group 2, it was minimally expressed in 2 cases and was present in 4.7–19.3% of insulin-positive islets in 3 cases and in all islets in 1 case. In group 3, it was absent in 1 case and in the remaining 5 cases, the values were 17.4–85.7%. In group 4, nitrotyrosine was absent in 6 cases and positive in 1.8 and 22.2% of insulin-positive islets in 2 cases. In group 5, the values were 60% (1 case) and 100% (2 cases), being absent in 3 cases, consistent with insulin-negativity. This case analysis shows that nitrotyrosine immunostaining is independent of the presence and severity of insulitis. Variable nitrotyrosine expression is present in some non‐diabetic cases. Its increased expression in beta cells of recent-onset and long-standing disease requires further studies to determine whether beta cell nitration plays a pathogenic role during T1D.
KeywordsBeta cells Human type 1 diabetes Nitrosative stress Nitrotyrosine Islets
Binding immunoglobulin protein
C/EBP homologous protein
Diabetes Virus Detection
Network for Pancreatic Organ Donors with Diabetes
We thank Drs Peter Butler and Tatyana Gurlos from the University of California Medical Centre, Los Angeles, USA, for advice on developing a protocol for nitrotyrosine immunohistochemistry, Dr Sarah Richardson, Exeter Medical School, United Kingdom for recommending antibodies and protocols and Dr. Peter Browett, University of Auckland for ongoing encouragement. This study was supported by a partial grant from the New Zealand Society for the Study of Diabetes. Pancreatic tail sections from newly diagnosed living donors with T1D were from the DiViD Study, funded by South-Eastern Norway Regional Health Authority (Grant to KDJ), The Novo Nordisk Foundation (Grant to KDJ) and through the PEVNET Study Group funded by the European Union’s Seventh Framework Programme (FP7/2007-2013) under Agreement No. 26441 PEVNET. Pancreatic sections from cadaveric pancreas were kindly supplied by nPOD.
Author contribution statement
Satya Amirapu and Fiona Wu provided histological and editing support, respectively. Shiva Reddy led the study and wrote the manuscript.
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Conflict of interest
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