Parallel signaling pathways of melatonin in the pancreatic β-cell
Parallel signaling pathways of melatonin in the pancreatic β-cell
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DOI：
10.1111/j.1600-079x.2005.00297.x
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发表时间：
2006-03-01
影响因子：
10.3
通讯作者：
Mühlbauer, E
中科院分区：
文献类型：
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作者：
Peschke, E;Bach, AG;Mühlbauer, E
先前的结果表明，褪黑激素可抑制大鼠胰岛素瘤 INS1 细胞（胰腺 β 细胞的模型）中 cAMP 的产生并刺激 IP3 的释放。这项研究探讨了褪黑激素对胰岛素释放的影响。测量了灌流系统中 INS1 细胞的胰岛素、cAMP 和 IP3 水平。最初，毛喉素用于刺激 cAMP 以及随后的胰岛素释放。将毛喉素 (5 μmol/L) 刺激的细胞与褪黑激素 (100 nmol/L) 一起孵育可抑制 cAMP 和胰岛素水平（胰岛素和 cAMP 释放量下降至 60%）。 G(i)alpha 蛋白抑制剂百日咳毒素 (PTX) 用于区分 G(i)alpha 依赖性 cAMP 途径和 G(i)alpha 不依赖性 IP3 途径。在我们的实验中，我们采用特定的刺激模式来证明 PTX 对 G(i)α 蛋白的适当抑制。在与 250 ng/mL PTX 一起孵育 24 小时的 INS1 细胞中，褪黑激素不再能够抑制毛喉素诱导的 cAMP 和胰岛素释放。在一项研究中，卡巴胆碱被用来刺激 IP3 以及随后的胰岛素释放。令人惊讶的是，将卡巴胆碱 (300 μmol/L) 刺激的细胞与褪黑激素 (100 nmol/L) 一起孵育会抑制胰岛素释放（降至胰岛素释放的 75%）。最后，在 PTX 孵育的 INS1 细胞中，褪黑素 (100 nmol/L) 增加了卡巴胆碱 (300 μmol/L) 诱导的胰岛素释放（高达胰岛素释放的 124%）。总之，我们发现胰腺 β 细胞上的褪黑激素 MT1 受体与平行的信号通路耦合，对胰岛素分泌产生相反的影响。 cAMP 和随后的胰岛素抑制信号通路涉及 PTX 敏感的 G(i)α 蛋白，并且在胰岛素释放方面起主导作用。
Previous results demonstrated that melatonin inhibits cAMP production and stimulates IP3 liberation in rat insulinoma INS1 cells, a model for the pancreatic beta-cell. This study addresses the impact of melatonin on insulin release. Insulin, cAMP and IP3 levels of INS1 cells in a superfusion system were measured. Initially, forskolin was used to stimulate cAMP and subsequently insulin release. Incubation of forskolin (5 mu mol/L)-stimulated cells with melatonin (100 nmol/L) inhibited cAMP and insulin levels (down to 60% of insulin and cAMP release). The G(i)alpha-protein-inhibitor pertussis toxin (PTX) was used to distinguish between the G(i)alpha-dependent cAMP pathway and the G(i)alpha-independent IP3 pathway. In our experiments we employed a specific stimulation pattern to prove proper inhibition of G(i)alpha-proteins by PTX. In INS1 cells incubated with 250 ng/mL PTX for 24 hr, melatonin was no longer able to inhibit the forskolin-induced cAMP and insulin release. In a study, carbachol was used to stimulate IP3 and subsequently insulin release. Surprisingly, incubation of carbachol (300 mu mol/L)-stimulated cells with melatonin (100 nmol/L) inhibited insulin release (down to 75% of insulin release). Finally, in PTX-incubated INS1 cells, melatonin (100 nmol/L) increased carbachol (300 mu mol/L)-induced insulin release (up to 124% of insulin release). In conclusion, we found that the melatonin MT1-receptor on pancreatic beta-cells is coupled to parallel signaling pathways, with opposite influences on insulin secretion. The cAMP- and subsequently insulin-inhibiting signaling pathway involves PTX-sensitive G(i)alpha-proteins and is predominant in terms of insulin release.