Myrsén-Axcrona U, Karlsson S, Sundler F, Ahrén B
Department of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, Lund University, 221 85 Lund, Sweden.
J Biol Chem. 1997 Apr 18;272(16):10790-6. doi: 10.1074/jbc.272.16.10790.
Neuropeptide Y (NPY) occurs in adrenergic as well as in non-adrenergic nerves innervating the islets of Langerhans and inhibits glucose-stimulated insulin secretion. Recently we demonstrated that NPY is expressed within islet beta cells of the rat pancreas following treatment with dexamethasone in vivo. In this study we examined the cellular expression of NPY following dexamethasone treatment of the insulin-producing cell line RINm5F, which under control conditions does not express or release NPY. The cells were cultured with or without dexamethasone (100 nM) for 5 days. Over the 5-day culture period, dexamethasone time dependently induced an increased release of NPY with a concomitant decrease in the release of insulin. Northern blot and in situ hybridization revealed a corresponding time-dependent increase in the amount of NPY transcripts and in the number of cells labeled for NPY mRNA, whereas immunocytochemistry for NPY revealed only a few immunoreactive cells, indicating a rapid release of the formed peptide. Following 5 days of culture with dexamethasone, acute stimulation with D-glyceraldehyde (10 mM) or KCl (20 mM) Ca2+ dependently stimulated the release of insulin. In contrast neither stimulation with D-glyceraldehyde or KCl nor removal of extracellular Ca2+ affected the release of NPY. Furthermore the D-glyceraldehyde- and KCl-induced increase in cytosolic Ca2+, evident in control RINm5F cells, was impaired after dexamethasone treatment. We conclude that RINm5F cells show steroid-sensitive plasticity and express NPY after dexamethasone treatment concomitantly with a decreased insulin secretion and impaired increase in cytosolic Ca2+ upon depolarization with KCl or stimulation with D-glyceraldehyde. We also conclude that NPY and insulin secretion are regulated differently and suggest that the inability of the removal of extracellular Ca2+ to inhibit NPY secretion and the failure of D-glyceraldehyde and KCl to stimulate NPY secretion reflect a constitutive release of this peptide from the cells in contrast to the regulated release of insulin.
神经肽Y（NPY）存在于支配胰岛的肾上腺素能神经和非肾上腺素能神经中，并抑制葡萄糖刺激的胰岛素分泌。最近我们证明，在体内用 dexamethasone 治疗后，大鼠胰腺胰岛β细胞内表达 NPY。在本研究中，我们检测了用 dexamethasone 处理胰岛素分泌细胞系 RINm5F 后 NPY 的细胞表达，该细胞系在对照条件下不表达或释放 NPY。将细胞在有或无 dexamethasone（100 nM）的情况下培养5天。在5天的培养期内，dexamethasone 随时间依赖性地诱导 NPY 释放增加，同时胰岛素释放减少。Northern 印迹和原位杂交显示 NPY 转录本数量和标记为 NPY mRNA 的细胞数量随时间相应增加，而 NPY 的免疫细胞化学仅显示少数免疫反应性细胞，表明形成的肽快速释放。在用 dexamethasone 培养5天后，用 D -甘油醛（10 mM）或 KCl（20 mM）急性刺激可 Ca2 +依赖性地刺激胰岛素释放。相反，用 D -甘油醛或 KCl 刺激或去除细胞外 Ca2 +均不影响 NPY 的释放。此外，在 dexamethasone 处理后，对照 RINm5F 细胞中明显的 D -甘油醛和 KCl 诱导的胞质 Ca2 +增加受损。我们得出结论，RINm5F 细胞表现出类固醇敏感性可塑性，在用 dexamethasone 处理后表达 NPY，同时胰岛素分泌减少，并且在用 KCl 去极化或用 D -甘油醛刺激时胞质 Ca2 +增加受损。我们还得出结论，NPY 和胰岛素分泌受到不同调节，并表明去除细胞外 Ca2 +不能抑制 NPY 分泌以及 D -甘油醛和 KCl 不能刺激 NPY 分泌反映了该肽从细胞中的组成性释放，与胰岛素的调节性释放形成对比。
