Immunolocalization of caspase-3 in pancreatic islets of NOD mice during cyclophosphamide-accelerated diabetes.
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.
Reddy
Shiva
S
School of Biological Sciences, Department of Pediatrics, University of Auckland, Auckland, New Zealand. s.reddy@auckland.ac.nz
Bradley
Joshua
J
Ross
Jacqueline M
JM
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
D003520:Cyclophosphamide; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases