Department of Anesthesiology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong 524000, China.
Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, China.
J Immunol. 2020 Aug 1;205(3):767-775. doi: 10.4049/jimmunol.1900860. Epub 2020 Jun 24.
Receptor for advanced glycation end-products (RAGE) and TLR4 play an important role in the inflammatory response against High-mobility group box 1 protein (HMGB1), a late proinflammatory cytokine and a damage-associated molecular pattern. As cell surface receptors, both RAGE and TLR4 are constantly trafficking between the cytoplasm and plasma membrane. However, whether TLR4 is related to the intracellular transport of RAGE in HMGB1-induced inflammation remains unknown. In this study, we demonstrated that HMGB1 not only increased RAGE expression in both the cytoplasm and plasma membrane but also upregulated the expression of TLR4 in the plasma membrane. Knocking out of RAGE led to decreased MAPK activation, TLR4 cellular membrane expression, and corresponding inflammatory cytokine generation. Meanwhile, inhibiting MAPK activation also decreased TLR4 surface expression. These results indicated that HMGB1 may bind to cell surface RAGE receptors on the cell surface, leading to MAPK activation, thus promoting TLR4 translocation on the cell surface, but does not regulate its transcription and translation. In contrast, TLR4 can increase the transcription and translation of RAGE, which translocates to the cell surface and is able to bind to more HMGB1. The cell surface receptors TLR4 and RAGE bind to HMGB1, leading to the transcription and secretion of inflammatory cytokines. Finally, we also observed these results in the mice pseudofracture model, which is closely related to HMGB1-induced inflammatory response. All these results demonstrated that the interplay between RAGE and TLR4 are critical for HMGB1-induced inflammatory response.
晚期糖基化终产物受体（RAGE）和 Toll 样受体 4（TLR4）在对高迁移率族蛋白 B1（HMGB1）的炎症反应中发挥重要作用，HMGB1 是一种晚期促炎细胞因子和损伤相关分子模式。作为细胞表面受体，RAGE 和 TLR4 都在细胞质和质膜之间不断运输。然而，TLR4 是否与 HMGB1 诱导炎症中 RAGE 的细胞内运输有关尚不清楚。在本研究中，我们证实 HMGB1 不仅增加了细胞质和质膜中 RAGE 的表达，而且还上调了质膜中 TLR4 的表达。敲除 RAGE 导致 MAPK 激活、TLR4 细胞膜表达和相应的炎症细胞因子生成减少。同时，抑制 MAPK 激活也降低了 TLR4 表面表达。这些结果表明，HMGB1 可能与细胞表面的 RAGE 受体结合，导致 MAPK 激活，从而促进 TLR4 在细胞表面的易位，但不调节其转录和翻译。相反，TLR4 可以增加 RAGE 的转录和翻译，使其易位到细胞表面，并能够与更多的 HMGB1 结合。细胞表面受体 TLR4 和 RAGE 与 HMGB1 结合，导致炎症细胞因子的转录和分泌。最后，我们在与 HMGB1 诱导的炎症反应密切相关的小鼠假性骨折模型中也观察到了这些结果。所有这些结果表明，RAGE 和 TLR4 之间的相互作用对于 HMGB1 诱导的炎症反应至关重要。
