Tang Chih-Hsin, Lu Da-Yuu, Yang Rong-Sen, Tsai Huei-Yann, Kao Ming-Ching, Fu Wen-Mei, Chen Yuh-Fung
Department of Pharmacology, China Medical University, Taichung, Taiwan.
J Immunol. 2007 Jul 15;179(2):1292-302. doi: 10.4049/jimmunol.179.2.1292.
Leptin, the adipocyte-secreted hormone that centrally regulates weight control, is known to function as an immunomodulatory regulator. We investigated the signaling pathway involved in IL-6 production caused by leptin in microglia. Microglia expressed the long (OBRl) and short (OBRs) isoforms of the leptin receptor. Leptin caused concentration- and time-dependent increases in IL-6 production. Leptin-mediated IL-6 production was attenuated by OBRl receptor antisense oligonucleotide, PI3K inhibitor (Ly294002 and wortmannin), Akt inhibitor (1L-6-hydroxymethyl-chiro-inositol-2-((R)-2-O-methyl-3-O-octadecylcarbonate)), NF-kappaB inhibitor (pyrrolidine dithiocarbamate), IkappaB protease inhibitor (L-1-tosylamido-2-phenylenylethyl chloromethyl ketone), IkappaBalpha phosphorylation inhibitor (Bay 117082), or NF-kappaB inhibitor peptide. Transfection with insulin receptor substrate (IRS)-1 small-interference RNA or the dominant-negative mutant of p85 and Akt also inhibited the potentiating action of leptin. Stimulation of microglia with leptin activated IkappaB kinase alpha/IkappaB kinase beta, IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation at Ser(276), p65 and p50 translocation from the cytosol to the nucleus, and kappaB-luciferase activity. Leptin-mediated an increase of IkappaB kinase alpha/IkappaB kinase beta activity, kappaB-luciferase activity, and p65 and p50 binding to the NF-kappaB element was inhibited by wortmannin, Akt inhibitor, and IRS-1 small-interference RNA. The binding of p65 and p50 to the NF-kappaB elements, as well as the recruitment of p300 and the enhancement of histone H3 and H4 acetylation on the IL-6 promoter was enhanced by leptin. Our results suggest that leptin increased IL-6 production in microglia via the leptin receptor/IRS-1/PI3K/Akt/NF-kappaB and p300 signaling pathway.
瘦素是一种由脂肪细胞分泌的激素，可在中枢调节体重控制，已知其具有免疫调节功能。我们研究了小胶质细胞中瘦素引起白细胞介素-6（IL-6）产生所涉及的信号通路。小胶质细胞表达瘦素受体的长（OBRl）和短（OBRs）两种亚型。瘦素引起IL-6产生呈浓度和时间依赖性增加。OBRl受体反义寡核苷酸、磷脂酰肌醇-3激酶（PI3K）抑制剂（Ly294002和渥曼青霉素）、蛋白激酶B（Akt）抑制剂（1L-6-羟甲基-手性-肌醇-二-（（R）-2-O-甲基-3-O-十八烷基碳酸酯））、核因子κB（NF-κB）抑制剂（吡咯烷二硫代氨基甲酸盐）、IκB蛋白酶抑制剂（L-1-甲苯磺酰氨基-2-苯乙基氯甲基酮）、IκBα磷酸化抑制剂（Bay 117082）或NF-κB抑制剂肽可减弱瘦素介导的IL-6产生。用胰岛素受体底物（IRS）-1小干扰RNA或p85和Akt的显性负突变体转染也可抑制瘦素的增强作用。用瘦素刺激小胶质细胞可激活IκB激酶α/IκB激酶β、IκBα磷酸化、IκBα降解、Ser（276）处的p65磷酸化、p65和p50从胞质溶胶转位至细胞核以及κB-荧光素酶活性。渥曼青霉素、Akt抑制剂和IRS-1小干扰RNA可抑制瘦素介导的IκB激酶α/IκB激酶β活性、κB-荧光素酶活性以及p65和p50与NF-κB元件的结合增加。瘦素增强了p65和p50与NF-κB元件的结合，以及p300的募集和IL-6启动子上组蛋白H3和H4乙酰化作用增强。我们的结果表明，瘦素通过瘦素受体/IRS-1/PI3K/Akt/NF-κB和p300信号通路增加小胶质细胞中IL-6的产生。
