Diabetes Research Group, Division of Diabetes & Nutritional Sciences, School of Medicine, 2.9N Hodgkin Building, King's College London, Guy's Campus, London, SE1 1UL, UK.
Diabetologia. 2013 Nov;56(11):2467-76. doi: 10.1007/s00125-013-3022-x. Epub 2013 Aug 27.
AIMS/HYPOTHESIS: Chemokine (C-C motif) ligand 5 (CCL5) acts at C-C chemokine receptors (CCRs) to promote immune cell recruitment to sites of inflammation, but is also an agonist at G-protein-coupled receptor 75 (GPR75), which has very limited homology with CCRs. GPR75 is coupled to Gq to elevate intracellular calcium, so we investigated whether islets express this receptor and whether its activation by CCL5 increases beta cell calcium levels and insulin secretion.
Islet CCL5 receptor mRNA expression was measured by quantitative RT-PCR and GPR75 was detected in islets by western blotting and immunohistochemistry. In some experiments GPR75 was downregulated by transient transfection with small interfering RNA. Real-time changes in intracellular calcium were determined by single-cell microfluorimetry. Dynamic insulin secretion from perifused islets was quantified by radioimmunoassay. Glucose homeostasis in lean and obese mice was determined by measuring glucose and insulin tolerance, and insulin secretion in vivo.
Mouse and human islets express GPR75 and its ligand CCL5. Exogenous CCL5 reversibly increased intracellular calcium in beta cells via GPR75, this phenomenon being dependent on phospholipase C activation and calcium influx. CCL5 also stimulated insulin secretion from mouse and human islets in vitro, and improved glucose tolerance in lean mice and in a mouse model of hyperglycaemia and insulin resistance (ob/ob). The improvement in glucose tolerance was associated with enhanced insulin secretion in vivo, without changes in insulin sensitivity.
CONCLUSIONS/INTERPRETATION: Although CCL5 is implicated in the pathogenesis of diabetes through activation of CCRs, it has beneficial effects on beta cells through GPR75 activation.
目的/假设：趋化因子（C-C 基序）配体 5（CCL5）通过 C-C 趋化因子受体（CCR）发挥作用，促进免疫细胞募集到炎症部位，但它也是 G 蛋白偶联受体 75（GPR75）的激动剂，GPR75 与 CCRs 具有非常有限的同源性。GPR75 与 Gq 偶联以升高细胞内钙，因此我们研究了胰岛是否表达这种受体，以及 CCL5 对其的激活是否增加β细胞钙水平和胰岛素分泌。
通过定量 RT-PCR 测量胰岛 CCL5 受体 mRNA 表达，通过 Western blot 和免疫组织化学检测胰岛 GPR75。在一些实验中，通过瞬时转染小干扰 RNA 下调 GPR75。通过单细胞微荧光法测定细胞内钙的实时变化。通过放射免疫测定法量化灌流胰岛的动态胰岛素分泌。通过测量葡萄糖和胰岛素耐量以及体内胰岛素分泌来确定瘦鼠和肥胖鼠的葡萄糖稳态。
小鼠和人胰岛表达 GPR75 和其配体 CCL5。外源性 CCL5 通过 GPR75 可逆地增加β细胞内的钙，这种现象依赖于磷脂酶 C 激活和钙内流。CCL5 还刺激小鼠和人胰岛的胰岛素分泌，并改善瘦鼠和高血糖和胰岛素抵抗（ob/ob）小鼠模型中的葡萄糖耐量。葡萄糖耐量的改善与体内胰岛素分泌增强有关，而胰岛素敏感性没有变化。
结论/解释：尽管 CCL5 通过激活 CCRs 与糖尿病的发病机制有关，但它通过激活 GPR75 对β细胞具有有益作用。
