Department of Medicine, Rheumatology Unit, Karolinska Institutet, Stockholm, Sweden.
Mol Med. 2012 Mar 27;18(1):224-30. doi: 10.2119/molmed.2011.00327.
The nuclear protein high mobility group box protein 1 (HMGB1) promotes inflammation upon extracellular release. HMGB1 induces proinflammatory cytokine production in macrophages via Toll-like receptor (TLR)-4 signaling in a redox-dependent fashion. Independent of its redox state and endogenous cytokine-inducing ability, HMGB1 can form highly immunostimulatory complexes by interaction with certain proinflammatory mediators. Such complexes have the ability to enhance the induced immune response up to 100-fold, compared with induction by the ligand alone. To clarify the mechanisms for these strong synergistic effects, we studied receptor requirements. Interleukin (IL)-6 production was assessed in supernatants from cultured peritoneal macrophages from mice each deficient in one of the HMGB1 receptors (receptor for advanced glycation end products [RAGE], TLR2 or TLR4) or from wild-type controls. The cultures were stimulated with the TLR4 ligand lipopolysaccaride (LPS), the TLR2 ligand Pam₃CysSerLys₄ (Pam₃CSK₄), noninflammatory HMGB1 or each TLR ligand in complex with noninflammatory HMGB1. The activity of the HMGB1-TLR ligand complexes relied on engagement of the same receptor as for the noncomplexed TLR ligand, since HMGB1-LPS complexes used TLR4 and HMGB1-Pam₃CSK₄ complexes used TLR2. Deletion of any of the intracellular adaptor molecules used by TLR2 (myeloid differentiation factor-88 [MyD88], TIR domain-containing adaptor protein [TIRAP]) or TLR4 (MyD88, TIRAP, TIR domain-containing adaptor-inducing interferon-β [TRIF], TRIF-related adaptor molecule [TRAM]) had similar effects on HMGB1 complex activation compared with noncomplexed LPS or Pam₃CSK₄. This result implies that the enhancing effects of HMGB1-partner molecule complexes are not regulated by the induction of additional signaling cascades. Elucidating HMGB1 receptor usage in processes where HMGB1 acts alone or in complex with other molecules is essential for the understanding of basic HMGB1 biology and for designing HMGB1-targeted therapies.
核蛋白高迁移率族蛋白 B1（HMGB1）在细胞外释放时会促进炎症反应。HMGB1 通过 Toll 样受体（TLR）-4 信号以依赖氧化还原的方式诱导巨噬细胞产生促炎细胞因子。HMGB1 可以与某些促炎介质相互作用形成高度免疫刺激性复合物，而不依赖其氧化还原状态和内源性细胞因子诱导能力。与配体单独诱导相比，这些复合物具有将诱导的免疫反应增强高达 100 倍的能力。为了阐明这些强大协同作用的机制，我们研究了受体的要求。从缺乏 HMGB1 受体（晚期糖基化终产物受体 [RAGE]、TLR2 或 TLR4）之一或野生型对照的小鼠培养的腹腔巨噬细胞的上清液中评估白细胞介素（IL）-6 的产生。将培养基用 TLR4 配体脂多糖（LPS）、TLR2 配体 Pam₃CysSerLys₄（Pam₃CSK₄）、非炎症性 HMGB1 或每种 TLR 配体与非炎症性 HMGB1 复合物刺激。HMGB1-TLR 配体复合物的活性依赖于与未复合 TLR 配体相同的受体结合，因为 HMGB1-LPS 复合物使用 TLR4，而 HMGB1-Pam₃CSK₄ 复合物使用 TLR2。TLR2（髓样分化因子-88 [MyD88]、TIR 结构域包含衔接蛋白 [TIRAP]）或 TLR4（MyD88、TIRAP、TIR 结构域包含衔接子诱导干扰素-β [TRIF]、TRIF 相关衔接子分子 [TRAM]）的任何一种细胞内衔接子分子的缺失对 HMGB1 复合物的激活具有相似的影响与未复合的 LPS 或 Pam₃CSK₄ 相比。这一结果表明，HMGB1-伙伴分子复合物的增强作用不受额外信号级联诱导的调节。阐明 HMGB1 在单独或与其他分子复合物作用时的受体使用对于理解基本的 HMGB1 生物学和设计针对 HMGB1 的治疗方法至关重要。
