neuropeptide-y-(13-36) and Pheochromocytoma

In PC12 rat pheochromocytoma cells differentiated with nerve growth factor (NGF), neuropeptide Y inhibited depolarization-stimulated catecholamine synthesis as determined by in situ measurement of 3,4-dihydroxyphenylalanine (DOPA) production in the presence of the decarboxylase inhibitor m-hydroxybenzylhydrazine (NSD-1015). The inhibition by neuropeptide Y was concentration-dependent and was prevented by pretreatment with pertussis toxin, suggesting the involvement of a GTP-binding protein of the Gi or Go subtype. The neuropeptide Y analog [Leu31,Pro34]neuropeptide Y also caused inhibition of DOPA production, but was less potent than neuropeptide Y itself, while peptide YY and neuropeptide Y-(13-36) had no significant effect. This pattern is most consistent with the involvement of the neuropeptide Y Y3 receptor subtype. In PC12 cells differentiated with dexamethasone, neuropeptide Y also caused a concentration-dependent inhibition of DOPA production, while peptide YY was again without effect. Neuropeptide Y had no effect on DOPA production in undifferentiated PC12 cells. These results indicate that neuropeptide Y can modulate catecholamine synthesis in addition to its modulatory effects on catecholamine release.

Topics: Adrenal Gland Neoplasms; Analysis of Variance; Animals; Anti-Inflammatory Agents, Non-Steroidal; Aromatic Amino Acid Decarboxylase Inhibitors; Cell Differentiation; Dexamethasone; Dihydroxyphenylalanine; Dose-Response Relationship, Drug; Gastrointestinal Hormones; GTP-Binding Proteins; Hydrazines; Nerve Growth Factors; Neuropeptide Y; PC12 Cells; Peptide Fragments; Peptide YY; Peptides; Pertussis Toxin; Pheochromocytoma; Rats; Structure-Activity Relationship; Virulence Factors, Bordetella

Undifferentiated rat pheochromocytoma PC12 cells resemble immature adrenal chromaffin cells, express neuropeptide-Y (NPY) receptors of the Y1 subtype, and synthesize catecholamines as well as NPY. In the present study, we examined how phenotypic alteration of PC12 cells by nerve growth factor (NGF) or glucocorticoid affected cellular responsiveness to NPY and related agonists, especially with regard to modulation of catecholamine overflow. Unlike undifferentiated PC12 cells, cells differentiated to a sympathetic neuronal phenotype with NGF were responsive to the Y2 receptor-selective agonist, NPY 13-36. NPY 13-36 1) inhibited binding of [125I]NPY 1-36, 2) inhibited accumulation of evoked cAMP, and 3) inhibited evoked catecholamine overflow. NGF-differentiated cells were also responsive to the Y1 receptor-selective agonist [Leu31,Pro34]NPY (LP-NPY). Like NPY-(13-36), LP-NPY inhibited binding of [125I]NPY-(1-36); however, LP-NPY and NPY-(13-36) exerted their effects through heterogeneous receptors, as LP-NPY enhanced while NPY 13-36 inhibited evoked catecholamine overflow in NGF-differentiated cells, despite the fact that both agonists inhibited the evoked cAMP. In contrast to NGF-differentiated cells, cells differentiated to a mature chromaffin phenotype with dexamethasone were unresponsive to NPY-(13-36), nor did the Y2 agonist inhibit binding of [125I]NPY-(1-36). Dexamethasone-differentiated PC12 cells were, however, responsive to LP-NPY, as this agonist enhanced evoked catecholamine overflow and inhibited binding of [125I]NPY-(1-36). Peptide-YY also enhanced catecholamine overflow, but only significantly at 100 nM. The data suggest differential expression of NPY receptor subtypes on neuronal and endocrine cells where catecholamine overflow is a key feature. These studies further demonstrate inhibitory or excitatory modulation of catecholamine transmission by NPY via distinct receptor subtypes in homogeneous sympathoadrenomedullary models resembling sympathetic neurons and chromaffin cells.

Topics: Adrenal Gland Neoplasms; Animals; Binding, Competitive; Cell Differentiation; Cell Division; Colforsin; Cyclic AMP; Dose-Response Relationship, Drug; Kinetics; Nerve Growth Factors; Neurons; Neuropeptide Y; Nicotine; PC12 Cells; Peptide Fragments; Pheochromocytoma; Potassium Chloride; Rats; Receptors, Neuropeptide Y