The conserved lymphokine element 0 is a powerful activator and target for corticosteroid inhibition in human interleukin-5 transcription

The role of eosinophilia in allergic disorders indicates hIL-5 as a potential target for therapy. The conservation of hIL-5 gene proximal elements suggests they are important in controlling expression. Corticosteroids are important in the treatment of allergy, and are powerful inhibitors of IL-5 expression. This study aimed at understanding the role of hIL-5 conserved proximal elements, and elucidating the target of corticosteroid activity, in hIL-5 gene expression. Methods used include transient transfection of PBMC and PER117 cells with hIL-5 deletion constructs, EMSA, Western Blotting, and RT-PCR.

The conserved proximal CLE0/TATA elements driving a reporter gene gave similar or higher expression than a 500 bp promoter in primary human T cells and a T-cell line. Two and three copies of IL-5 CLE0 upstream of the silent IL-4 minimal promoter gave 30–45 fold increases in expression in forward orientation, but little activity in reverse orientation. Consequently, CLE0 is a powerful activator but not a classical enhancer. Deletion analysis identified CLE0 as the key element in the inhibition of IL-5 reporter constructs by dexamethasone, and RT-PCR analysis indicated that GILZ expression correlated with dexamethasone-induced inhibition of IL-5. Ectopic expression of GILZ, confirmed by western blotting, gave a 90% inhibition of promoter constructs in absence of dexamethasone. CLE0 is a powerful activator sufficient for the inducible expression of IL-5, and functions when moved upstream in a heterologous promoter. CLE0 is also the main target for IL-5 inhibition by dexamethasone, and we present evidence consistent with a role of GILZ in this.     

Search for a functional glucocorticoid receptor in the mammalian lens

Prolonged glucocorticoid treatment of medical conditions such as rheumatoid arthritis or asthma can lead to the formation of a posterior subcapsular cataract as a negative side effect. Currently, the only treatment for this cataract is surgery because very little is known about the mechanism of glucocorticoid action in the mammalian lens. Understanding of a lens glucocorticoid response is essential for the treatment and prevention of a steroid induced cataract. It has been suggested that glucocorticoids exert their effects on the lens indirectly, non-specifically, or through non-classical mechanisms. While these modes of action may contribute to the formation of glucocorticoid induced posterior subcapsular cataract, the finding of a classical, specific, functional lens glucocorticoid receptor suggests that glucocorticoids target lens epithelial cells directly, specifically, and similar to what has been observed in other cells types. This review explores the discovery of the glucocorticoid receptor in humans lens epithelial cells and the lens specific glucocorticoid response. The distinct changes in lens epithelial cell signaling pathways (MAPK and PI3K-AKT) suggest that glucocorticoids modulate several cellular functions and may explain why a lens glucocorticoid response has been difficult to elucidate.     

淫羊藿苷抑制亮氨酸拉链蛋白表达调节糖皮质激素诱导的MC3T3-E1成骨基因的表达失衡

目的考察成骨细胞MC3T3-E中亮氨酸拉链蛋白（GILZ）的表达与淫羊藿苷（icraiin,ICR）和糖皮质激素地塞米松（dexamethasone,DEX）之间的关系以及对部分成骨相关基因的表达影响。方法将诱导成熟分化的MC3T3-E1细胞分为3组,分别为DEX组、ICR组以及ICR＋DEx组,通过Real—TimeRT—PCR来检测不同组中GILZ、骨保护素（OPG）、破骨细胞分化因子（RANKL）、骨钙素（Oc）和碱性磷酸酶（ALP）mRNA表达。结果DEX能够提升GILZ、RANKL和ALP的表达,降低OPG、OC的表达,提高RANKL／OPG表达比率。ICR能够抑制G[LZ、RANKL和ALP的表达,提升OPG、OC的表达,降低RANKL／OPG表达比率。并且ICR能够抑制DEX诱导的GILZ、RANKL和ALP表达升高,逆转DEX诱导的OPG、OC的表达抑制。同时显著降低了RANKL／OPG表达比率。结论ICR通过抑制GILZ的mRNA表达,降低RANKL／OPG的表达比率,抑制破骨细胞成熟激活。ICR通过抑制ALP表达和提高OC表达提高成骨细胞的增殖能力。     

GILZ in sepsis: “Poor is the pupil who does not surpass his master”

With the legendary saying of Leonardo da Vinci in the title, we suggest that Glucocorticoid Induced Leucine Zipper (GILZ) may have more promising effects against polymicrobial sepsis, than glucocorticoids (GC). Indeed, the use of GCs in sepsis remains a matter of debate. The rationale for their use in sepsis is to modulate the exaggerated inflammatory response while maintaining innate immunity. However, GC resistance and side-effects limit their therapeutic value in sepsis. Hence, there is a growing interest in understanding the mechanisms by which GCs modulate immune responses upon infection. In this issue of the European Journal of Immunology, Ellouze et al. provide data demonstrating that deregulated expression of GILZ, a GC-induced protein, in monocytes/macrophages (M/M) recovered from septic shock patients may contribute to the pathogenesis. Furthermore, the authors demonstrate that GILZ overexpression in M/M improves outcome in septic animals by limiting systemic inflammation while increasing bacterial clearance. Overall, these data provide evidence that GCs may modulate immune responses via GILZ and that GILZ is a valuable alternative for GC therapy in sepsis.     

糖皮质激素诱导的亮氨酸拉链蛋白(GILZ)在人气道上皮细胞中的表达及对MAPK信号通路的影响

目的:探讨糖皮质激素诱导的亮氨酸拉链蛋白(GILZ)在人气道上皮细胞9HTE0中的表达以及对MAPK信号通路因子Raf-1、Mek1/2、Erk1/2的影响。方法:采用RT-PCR及Western blot法检测地塞米松(Dex)作用后GILZ mRNA及蛋白的表达,同时细胞免疫荧光法检测GILZ蛋白的定位;合成三条GILZ-SiRNA分别转染人气道上皮细胞9HTE0,用Q-PCR及Western blot法筛选出沉默效果最佳的一条;Western blot法检测MAPK信号通路因子Raf-1、Mek1/2、Erk1/2磷酸化蛋白及其总蛋白的表达。结果:Dex能够明显刺激人气道上皮细胞9HTE0GILZ mRNA及蛋白的表达,GILZ蛋白主要定位在细胞浆中,Dex抑制了Raf-1、Mek1/2、Erk1/2磷酸化蛋白的表达,而GILZ-SiRNA转染后,Raf-1.Mek1/2、Erk1/2磷酸化水平有所回升。结论:糖皮质激素作为支气管哮喘一线用药,虽然能够诱导GILZ表达并发挥一定的抗炎作用,但同时GILZ却抑制了在气道上皮修复中起重要作用的MAPK信号通路的激活,这为临床上研究哮喘防治新措施提供了理论依据。