The relation among NGF, EGF and insulin is important for triggering pancreatic β cell apoptosis

Background Nerve growth factor (NGF) is a well-known mediator for maintaining the survival of neurons, while recent studies report that its absence induces apoptosis in cultured beta cells of humans and rats. However, its relationship with other growth factors that have important roles in the survival and function of beta cells such as epidermal growth factor (EGF) has not yet been elucidated. The aim of this study was to investigate the effects of NGF withdrawal on the synthesis and secretion of EGF, insulin with respect to beta cell apoptosis in hyperglycemic rats. Method beta cells were isolated from euglycemic and streptozotocin-induced hyperglycemic rats and treated with NGF neutralizing antibody for withdrawal of NGF in culture medium. NGF, EGF and insulin levels in cell lysates and secretion samples were measured by enzyme-linked immunosorbent assay, and their gene expressions were determined by real-time reverse transcription polymerase chain reaction assay. Apoptosis was quantitatively determined by cytoplasmic histone-associated DNA fragments. Results Nerve growth factor neutralization triggered beta cell apoptosis. In addition decreased insulin, increased NGF and EGF were observed at gene expression and protein levels by NGF neutralization. Moreover, NGF withdrawal decreased secretion of these peptides from beta cells. Although the alterations seemed to be similar under euglycemic and hyperglycemic conditions, NGF withdrawal more strongly affected beta cells of hyperglycemic rats. Conclusions These important findings indicate that NGF is an important regulator for the synthesis and secretion of EGF and insulin from the beta cells. Moreover, results suggested that NGF withdrawal causes apoptosis by decreasing EGF, NGF and insulin secretion from beta cells of hyperglycemic rats. Copyright (C) 2012 John Wiley & Sons, Ltd.