Luteolin, a food-derived flavonoid, suppresses adipocyte-dependent activation of macrophages by inhibiting JNK activation

Interaction between adipocytes and macrophages contributes to the development of insulin resistance in obese adipose tissues. In this study, we examined whether luteolin, food-derived flavonoid, could suppress the production of inflammatory mediators of the interaction between adipocytes and macrophages. Experiments using a coculture system of adipocytes and macrophages showed that luteolin suppressed the production of inflammatory mediators. In addition, activated macrophages were targets for the suppressive effect of luteolin. Luteolin inhibited the phosphorylation of JNK and suppressed the production of inflammatory mediators in the activated macrophages. The findings indicate that luteolin can inhibit the interaction between adipocytes and macrophages to suppress the production of inflammatory mediators, suggesting that luteolin is a valuable food-derived compound for the treatment of metabolic syndrome.     

Aurothioglucose inhibits induced NF-kB and AP-1 activity by acting as an IL-1 functional antagonist

We have designed a series of recombinant CAT genes to study IL-1 signal transduction in murine fibroblast NIH 3T3 cells. We demonstrate that the HSV thymidine kinase (tk) promoter does not respond to IL-1, but that IL-1 induction of this promoter is observed after insertion of either NF-kB or AP-1 binding sites upstream of the HSV tk cap-site. We have studied the effects of indomethacin, dexamethasone and aurothioglucose (which have been used in the treatment of patients affected by rheumatoid arthritis) in the IL-1 inducible CAT assay. We show that aurothioglucose or dexamethasone is able to inhibit IL-1 induced CAT activity whereas a non-steroidal anti-inflammatory drug (indomethacin) is inactive. Order of addition experiments indicate that aurothiglucose, which has disease-modifying activity in treated patients, ats as an IL-1 functional antagonist in this system.     

EB病毒LMP-1上调鼻咽癌细胞系AP-1的活性

为了探讨 EB病毒潜伏膜蛋白 1 ( LMP- 1 )通过信号传导途径介导的致瘤分子机制 ,由此首先构建了 AP- 1报告基因 ,用佛波酯诱导确定了其报道 AP- 1的功能 ;通过建立荧光素酶双报道系统 ,研究了 LMP- 1表达对 AP- 1和 NFκB活性的影响 .研究发现 :在 LMP- 1阴性鼻咽癌 ( NPC)细胞系 ,导入 LMP- 1表达质粒后 ,AP- 1和 NFκB的活性均升高 4～ 5倍 ;而在 LMP- 1阳性 NPC细胞系中 ,当导入 LMP- 1反义表达质粒 ,AP- 1和 NFκB的活性则受抑制 ,活性下调 3～ 4倍 .结果表明 ,LMP- 1能上调 NPC细胞系 AP- 1的活性 ,同时再次证实了 LMP- 1能活化 NFκB.     

红藻氨酸致敏癫痫大鼠海马内AP-1 DNA结合活性和成分的改变

一次皮下注射惊厥剂量（７．５ｍｇ／ｋｇ）的红藻氨酸（ｋａｉｎｉｃ ａｃｉｄ,ＫＡ）诱发Ｆｉｓｈｅｒ３４４大鼠出现急性癫痫发作,７ｄ后即可形成癫痫敏感大鼠,继用Ｇｅｌ ｓｈｉｆｔ、Ｓｕｐｅｒ－ｓｈｉｆｔ和Ｗｅｓｔｅｍ ｂｌｏｔ方法测定大鼠海马内ＡＰ－１ ＤＮＡ结合活性及其组成成分。Ｇｅｌ ｓｈｉｆｔ结合显示,癫痫敏感大鼠海马内ＡＰ－１ ＤＮＡ结合活性的基础水平较对照组为高;Ｓｕｐｅｒ－ｓｈｉｆｔ实研     

AP-1与STAT5相互作用协同调节血管紧张素原基因表达

为研究AP-1和STAT5协同调节血管紧张素原基因表达的作用机制,用凝胶电泳迁移率改变分析（EMSA）和染色质免疫沉淀分析（ChIP assay）检测血管紧张素Ⅱ（AngⅡ）诱导的AP-1和STAT5的DNA结合活性;用凝胶超迁移分析和免疫共沉淀方法观察AP-1和STAT5的相互作用. 结果显示,AngⅡ可分别促进AP-1和STAT5与血管紧张素原基因调控区顺式元件的结合以及二者之间的相互作用;核蛋白与含AP-1结合位点的寡核苷酸探针结合形成的复合物可与抗c-Jun抗体和抗STAT5抗体形成超迁移电泳区带;而用抗c-Jun抗体也可从STAT5 染色质免疫沉淀复合物洗脱液中检测到AP-1的存在. 而且,AP-1和STAT5的相互作用程度及其二者与DNA的结合活性与血管紧张素原表达活性具有一致关系,该效应可被JAK2特异抑制剂AG490所抑制. 上述结果提示,与顺式元件结合的AP-1和STAT5通过相互作用而形成四元复合物协同调节血管紧张素原基因的表达,JAK2对该过程具有诱导活化作用.     

Identification of acidic dileucine signals in LRP9 that interact with both GGAs and AP-1/AP-2

The Golgi-localized, gamma-ear-containing, ADP ribosylation factor-binding family of monomeric clathrin adaptors (GGAs) is known to bind cargo molecules through short C-terminal peptide motifs conforming to the sequence DXXLL (X = any amino acid), while the heterotetrameric adaptors AP-1 and AP-2 utilize a similar but discrete sorting motif of the sequence [D,E]XXXL[L,I]. While it has been established that a single cargo molecule may contain either or both types of these acidic cluster-dileucine (AC-LL) sorting signals, there are no examples of cargo with overlapping GGA and AP-1/AP-2-binding motifs. In this study, we report that the cytosolic tail of low-density lipoprotein receptor-related protein (LRP)9 contains a bifunctional GGA and AP-1/AP-2-binding motif at its carboxy-terminus (EDEPLL). We further demonstrate that the internal EDEVLL sequence of LRP9 also binds to GGAs in addition to AP-2. Either AC-LL motif of LRP9 is functional in endocytosis. These findings represent the first study characterizing the trafficking of LRP9 and also have implications for the identification of additional GGA cargo molecules.     

The flavonoid galangin inhibits the L1 metallo-beta-lactamase from Stenotrophomonas maltophilia

The flavonoid galangin inhibits the partially purified metallo-beta-lactamase from Stenotrophomonas maltophilia. The effect was not reversed by the addition of ZnCl(2) suggesting that the inhibitory effect is not related to metal chelation. The flavonoid quercetin also has some inhibitory effect against the enzyme. Using the crystal structure of the enzyme, a molecular modelling study predicts a possible orientation of galangin at the active site of the enzyme.     

Hyperbaric oxygen induces VEGF expression through ERK, JNK and c-Jun/AP-1 activation in human umbilical vein endothelial cells

Summary Hyperbaric oxygen (HBO) is increasingly used in a number of areas of medical practice, such as selected problem infections and wounds. The beneficial effects of HBO in treating ischemia-related wounds may be mediated by stimulating angiogenesis. We sought to investigate VEGF, the main angiogenic regulator, regulated by HBO in human umbilical vein endothelial cells (HUVECs). In this study, we found that VEGF was up regulated both at mRNA and protein levels in HUVECs treated with HBO dose- and time-dependently. Since there are several AP-1 sites in the VEGF promoter, and the c-Jun/AP-1 is activated through stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and extracellular signal regulated kinase (ERK), we further examined the c-Jun, JNK and ERK that might be involved in the VEGF induced by HBO. The VEGF mRNA induced by HBO was blocked by both PD98059 and SP600125, the ERK and JNK inhibitors respectively. HBO induced phospho-ERK and phospho-JNK expressions within 15 min. We further demonstrated that c-Jun phosphorylation was induced within 60 min of HBO treatment. HBO also induced the nuclear AP-1 binding ability within 30–60 min, but the AP-1 induction was blocked by treatment with either the ERK or JNK inhibitor. To verify that the VEGF expression induced by HBO is through the AP-1 trans-activation and VEGF promoter, both the VEGF promoter and AP-1 driving luciferase activity were found increased by the cells treated with HBO. The c-Jun mRNA, which is also driven by AP-1, was also induced by HBO, and the induction of c-Jun was blocked by ERK and JNK inhibitors. We suggest that VEGF induced by HBO is through c-Jun/AP-1 activation, and through simultaneous activation of ERK and JNK pathways.     

AP-1 activation through endogenous H(2)O(2) generation by alveolar macrophages

Reactive oxygen species released during the respiratory burst are known to participate in cell signaling. Here we demonstrate that hydrogen peroxide produced by the respiratory burst activates AP-1 binding. Stimulation of the macrophage cell line NR8383 with respiratory burst agonists ADP and C5a increased AP-1 binding activity. Importantly, this increase in binding was blocked by catalase, confirming mediation by endogenous H₂O₂. Moreover, exogenously added H₂O₂ mimicked the agonists, and also activated AP-1. Antibodies revealed that the activated AP-1 complex is composed predominantly of c-Fos/c-Jun heterodimers. Treatment of the cells with ADP, C5a and H₂O₂ (100 μM) all increased the phosphorylation of c-Jun. c-Fos protein was increased in cells treated with C5a or high dose (200 μM) H₂O₂, but not in cells treated with ADP. The MEK inhibitor, PD98059, partially blocked the C5a-mediated increase in AP-1 binding. A novel membrane-permeable peptide inhibitor of JNK, JNKi, also inhibited AP-1 activation. Together these data suggest that C5a-mediated AP-1 activation requires both the activation of the ERK and JNK pathways, whereas activation of the JNK pathway is sufficient to increase AP-1 binding with ADP. Thus, AP-1 activation joins the list of pathways for which the respiratory burst signals downstream events in the macrophage.