Ahasan Mohammad M, Hardy Rowan, Jones Christopher, Kaur Kirren, Nanus Dominika, Juarez Maria, Morgan Stuart A, Hassan-Smith Zaki, Bénézech Cécile, Caamaño Jorge H, Hewison Martin, Lavery Gareth, Rabbitt Elizabeth H, Clark Andrew R, Filer Andrew, Buckley Christopher D, Raza Karim, Stewart Paul M, Cooper Mark S
Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham and Queen Elizabeth Hospital, Edgbaston, Birmingham, UK.
Arthritis Rheum. 2012 Jul;64(7):2404-13. doi: 10.1002/art.34414.
Tissue glucocorticoid (GC) levels are regulated by the GC-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). This enzyme is expressed in cells and tissues arising from mesenchymal stromal cells. Proinflammatory cytokines dramatically increase expression of 11β-HSD1 in stromal cells, an effect that has been implicated in inflammatory arthritis, osteoporosis, obesity, and myopathy. Additionally, GCs act synergistically with proinflammatory cytokines to further increase enzyme expression. The present study was undertaken to investigate the mechanisms underlying this regulation.
Gene reporter analysis, rapid amplification of complementary DNA ends (RACE), chemical inhibition experiments, and genetic disruption of intracellular signaling pathways in mouse embryonic fibroblasts (MEFs) were used to define the molecular mechanisms underlying the regulation of 11β-HSD1 expression.
Gene reporter, RACE, and chemical inhibitor studies demonstrated that the increase in 11β-HSD1 expression with tumor necrosis factor α (TNFα)/interleukin-1β (IL-1β) occurred via the proximal HSD11B1 gene promoter and depended on NF-κB signaling. These findings were confirmed using MEFs with targeted disruption of NF-κB signaling, in which RelA (p65) deletion prevented TNFα/IL-1β induction of 11β-HSD1. GC treatment did not prevent TNFα-induced NF-κB nuclear translocation. The synergistic enhancement of TNFα-induced 11β-HSD1 expression with GCs was reproduced by specific inhibitors of p38 MAPK. Inhibitor and gene deletion studies indicated that the effects of GCs on p38 MAPK activity occurred primarily through induction of dual-specificity phosphatase 1 expression.
The mechanism by which stromal cell expression of 11β-HSD1 is regulated is novel and distinct from that in other tissues. These findings open new opportunities for development of therapeutic interventions aimed at inhibiting or stimulating local GC levels in cells of mesenchymal stromal lineage during inflammation.
组织糖皮质激素（GC）水平受GC激活酶11β-羟基类固醇脱氢酶1型（11β-HSD1）调节。该酶在间充质基质细胞来源的细胞和组织中表达。促炎细胞因子可显著增加基质细胞中11β-HSD1的表达，这一作用与炎性关节炎、骨质疏松症、肥胖症和肌病有关。此外，GC与促炎细胞因子协同作用可进一步增加该酶的表达。本研究旨在探究这种调节作用的潜在机制。
采用基因报告分析、互补DNA末端快速扩增（RACE）、化学抑制实验以及对小鼠胚胎成纤维细胞（MEF）细胞内信号通路进行基因敲除，以确定11β-HSD1表达调控的分子机制。
基因报告、RACE和化学抑制剂研究表明，肿瘤坏死因子α（TNFα）/白细胞介素-1β（IL-1β）导致的11β-HSD1表达增加是通过近端HSD11B1基因启动子实现的，且依赖于核因子κB（NF-κB）信号传导。使用NF-κB信号传导靶向敲除的MEF证实了这些发现，其中RelA（p65）缺失可阻止TNFα/IL-1β诱导11β-HSD1。GC处理并不能阻止TNFα诱导的NF-κB核转位。p38丝裂原活化蛋白激酶（MAPK）的特异性抑制剂重现了GC与TNFα协同增强TNFα诱导的11β-HSD1表达的作用。抑制剂和基因敲除研究表明，GC对p38 MAPK活性的影响主要通过诱导双特异性磷酸酶1表达来实现。
基质细胞中11β-HSD1表达的调节机制是新颖的，且与其他组织不同。这些发现为开发旨在在炎症期间抑制或刺激间充质基质谱系细胞中局部GC水平的治疗干预措施提供了新的机会。
