Department of Cardiology, Lund University, 22185, Lund, Sweden.
Purinergic Signal. 2013 Mar;9(1):67-79. doi: 10.1007/s11302-012-9331-6. Epub 2012 Sep 1.
While high levels of glucose and saturated fatty acids are known to have detrimental effects on beta cell function and survival, the signalling pathways mediating these effects are not entirely known. In a previous study, we found that ADP regulates beta cell insulin secretion and beta cell apoptosis. Using MIN6c4 cells as a model system, we investigated if autocrine/paracrine mechanisms of ADP and purinergic receptors are involved in this process. High glucose (16.7 mmol/l) and palmitate (100 μmol/l) rapidly and potently elevated the extracellular ATP levels, while mannitol was without effect. Both tolbutamide and diazoxide were without effect, while the calcium channel blocker nifedipine, the volume-regulated anion channels (VRAC) inhibitor NPPB, and the pannexin inhibitor carbenoxolone could inhibit both effects. Similarly, silencing the MDR1 gene also blocked nutrient-generated ATP release. These results indicate that calcium channels and VRAC might be involved in the ATP release mechanism. Furthermore, high glucose and palmitate inhibited cAMP production, reduced cell proliferation in MIN6c4 and increased activated Caspase-3 cells in mouse islets and in MIN6c4 cells. The P2Y(13)-specific antagonist MRS2211 antagonized all these effects. Further studies showed that blocking the P2Y(13) receptor resulted in enhanced CREB, Bad and IRS-1 phosphorylation, which are known to be involved in beta cell survival and insulin secretion. These findings provide further support for the concept that P2Y(13) plays an important role in beta cell apoptosis and suggest that autocrine/paracrine mechanisms, related to ADP and P2Y(13) receptors, contribute to glucolipotoxicity.
虽然高浓度的葡萄糖和饱和脂肪酸已知对β细胞功能和存活有不利影响,但介导这些影响的信号通路尚不完全清楚。在之前的一项研究中,我们发现 ADP 调节β细胞胰岛素分泌和β细胞凋亡。我们使用 MIN6c4 细胞作为模型系统,研究了 ADP 和嘌呤能受体的自分泌/旁分泌机制是否参与了这一过程。高葡萄糖(16.7mmol/l)和棕榈酸(100μmol/l)可迅速且强烈地升高细胞外 ATP 水平,而甘露醇则没有作用。甲苯磺丁脲和二氮嗪均没有作用,而钙通道阻滞剂硝苯地平、体积调节阴离子通道(VRAC)抑制剂 NPPB 和泛素通道抑制剂 carbenoxolone 均可抑制这两种作用。同样,沉默 MDR1 基因也可阻断营养物质产生的 ATP 释放。这些结果表明钙通道和 VRAC 可能参与了 ATP 释放机制。此外,高葡萄糖和棕榈酸抑制 cAMP 生成,减少 MIN6c4 细胞的增殖,并增加小鼠胰岛和 MIN6c4 细胞中激活的 Caspase-3 细胞。P2Y(13)特异性拮抗剂 MRS2211 拮抗了所有这些作用。进一步的研究表明,阻断 P2Y(13)受体可增强 CREB、Bad 和 IRS-1 的磷酸化,这些已知与β细胞存活和胰岛素分泌有关。这些发现为 P2Y(13)在β细胞凋亡中发挥重要作用提供了进一步的支持,并表明与 ADP 和 P2Y(13)受体相关的自分泌/旁分泌机制有助于糖脂毒性。