Insulin-like growth factor binding protein-3 is a novel mediator of apoptosis in insulin-secreting cells.
Insulin-like growth factor binding protein-3 (IGFBP-3) is emerging as a critical regulator of cell survival. There has been no study which directly examined the potential role for this major growth factor in the programmed cell death (apoptosis) of insulin-secreting cells. To determine whether IGFBP-3 mediates apoptosis in insulin-secreting cells, we performed a rigorous series of experiments with the rat insulinoma (RIN) cell line m5F and the hamster insulin-secreting tumor (HIT) T-15. Within 24 h exogenous IGFBP-3 induced significant DNA fragmentation in RIN and HIT cells, at doses ranging from 4.4 to 2000 ng/ml (P<0.05) without a classic dose-response relationship. DNA fragmentation induced by rhIGFBP-3 occurred in the presence of immunoglobulin to block the type 1 IGF receptor. As detected by flow cytometry for Annexin V exposure to the cell surface, rhIGFBP-3 treatment doubled the proportion of apoptotic HIT cells from 1.7 +/- 0.4% (serum-free control) to 3.4 +/- 0.2% (P<0.02), an effect completely reversed by co-treatment with 1000 ng/ml rhIGF-I. Immunofluorescent microscopy disclosed that pro-inflammatory Th1 cytokines increased intranuclear aggregation of endogenous IGFBP-3. Cytokine-induced DNA fragmentation was completely blocked by relatively brief pre-treatment with antisense IGFBP-3 phosphorothioate oligodeoxynucleotides. In conclusion, we have presented the first evidence that IGFBP-3 contributes to cytokine-mediated apoptosis in insulin-secreting cells.
Shim
Melanie L
ML
Department of Pediatrics, Division of Endocrinology, Mattel Children's Hospital, David Geffen School of Medicine, The University of California, Los Angeles, CA 90095-1752, USA.
Levitt Katz
Lorraine E
LE
Davis
Jason
J
Dotzler
Whittney C
WC
Cohen
Pinchas
P
Ferry
Robert J
RJ
D000818:Animals; D000906:Antibodies / Q000276:immunology; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D006224:Cricetinae; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D007340:Insulinoma; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000276:immunology; D014407:Tumor Cells, Cultured
D000906:Antibodies; D016207:Cytokines; D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D020319:Oligodeoxyribonucleotides, Antisense; D017526:Receptor, IGF Type 1; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases