title: Immunolocalization of caspase-3 in pancreatic islets of NOD mice during cyclophosphamide-accelerated diabetes.
abstract: Apoptosis may be a major mechanism of beta cell loss during insulin-dependent diabetes mellitus. Caspase-3 is a key enzyme involved in the terminal steps of this death process. Here, the intra-islet expression of caspase-3 in the NOD mouse was examined immunohistochemically following acceleration of the disease with cyclophosphamide. Female NOD mice were treated at day 95 with cyclophosphamide, and caspase-3 expression in pancreatic sections was studied at days 0, 4, 7, 11, and 14 and compared with age-matched control tissue. In the treated group at day 0, caspase-3 labeling was seen in several peri-islet macrophages and only extremely rarely in beta cells. At day 4, only a few beta cells weakly expressed the enzyme. From day 7, caspase-3 expression began to increase in intra-islet macrophages and reached a peak at days 11 and 14, when a small number of CD4 and CD8 T cells also showed positive labeling. Beta cell expression of caspase-3 at days 11 and 14 was rare. At this stage, several intra-islet immune cells with positive labeling for the enzyme coexpressed either Fas or interleukin-1beta. Only a small proportion of intra-islet caspase-3 cells showed apoptotic nuclei judged by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). We conclude that, during cyclophosphamide-accelerated diabetes, the predominant caspase-3 immunolabeling in intra- and extra-islet macrophages suggests that apoptosis of macrophages may be an important mechanism for their elimination. The virtual absence of caspase-3 immunolabeling in most beta cells even during the height of beta cell loss supports the need for developing other markers of early beta cell apoptosis in the NOD mouse.
authors.affiliation: School of Biological Sciences, Department of Pediatrics, University of Auckland, Auckland, New Zealand. s.reddy@auckland.ac.nz
authors.forename: Shiva
authors.initials: S
authors.lastname: Reddy
authors.forename: Joshua
authors.initials: J
authors.lastname: Bradley
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Ross
mesh_terms: D000818:Animals; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D003520:Cyclophosphamide / Q000494:pharmacology*; D003922:Diabetes Mellitus, Type 1 / Q000139:chemically induced / Q000201:enzymology*; D005260:Female; D007150:Immunohistochemistry; D007515:Islets of Langerhans / Q000201:enzymology*; D051379:Mice; D016688:Mice, Inbred NOD
chemical_list: D003520:Cyclophosphamide; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases