Altered bcl-2 and bax expression and intracellular Ca2+ signaling in apoptosis of pancreatic cells and the impairment of glucose-induced insulin secretion.
Apoptosis is the process of cellular self-destruction, and genes such as bcl-2 and bax are known to inhibit and promote apoptosis, respectively. In this study, we show that apoptosis can be induced in pancreatic beta-cell lines, and we investigate the apoptotic pathways through the bcl-2 and bax genes and intracellular Ca2+. Serum deprivation induces apoptosis in the MIN6 and RINm5F pancreatic beta-cell lines, and alters the bcl-2 messenger RNA (mRNA) and protein. KCl, BayK, A23187, and ionomycin elicit an elevation of cytosolic/nuclear Ca2+, which, however, is insufficient to evoke apoptosis or to alter bcl-2 or bax mRNA expression in MIN6 cells. The extracellular Ca2+ chelators, EGTA and 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, tetrapotassium salt, hydrate, evoke apoptosis and also alter the ratio of bcl-2 to bax mRNA and protein concomitantly with the depletion of cytosolic/nuclear Ca2+. This indicates that there are at least two apoptotic pathways in pancreatic beta-cells: through serum deprivation and through a decrease in cytosolic/nuclear Ca2+. MIN6 cells exhibit reduced insulin secretion induced by glucose regardless of the molecular pathway of apoptosis. Apoptosis in pancreatic beta-cells, therefore, may be closely related to the impairment of insulin secretion in certain pathological conditions such as diabetes mellitus.
Mizuno
N
N
Department of Metabolism and Clinical Nutrition, Kyoto University School of Medicine, Japan. mizuno@metab.kuhp.kyoto-u.ac.jp
Yoshitomi
H
H
Ishida
H
H
Kuromi
H
H
Kawaki
J
J
Seino
Y
Y
Seino
S
S
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D053938:DNA Fragmentation; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D019254:Genes, bcl-2; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis*; D051028:bcl-2-Associated X Protein
D007328:Insulin; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D004533:Egtazic Acid; D005947:Glucose; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D002118:Calcium