Department of Pathophysiology, Second Military Medical University, Shanghai, 200433, China.
Department of Hepatobiliary Pancreatic Surgery, Changhai Hospital, Second Military Medical University, Shanghai, 200433, China.
Sci Rep. 2018 Oct 22;8(1):15579. doi: 10.1038/s41598-018-34011-8.
Toll-like receptor (TLR) signaling plays major roles in innate immune response in macrophages. Melatonin regulates TLR3- and TLR4-mediated innate immune responses in macrophages. However, it remains unknown whether melatonin regulates TLR9-mediated innate immune responses in macrophages. Here we demonstrated that melatonin suppressed TLR9 ligand-induced proinflammatory cytokines mRNA and protein production in peritoneal macrophages without interrupting the viability of peritoneal macrophages. Using a melatonin membrane receptors MT1/MT2 antagonist luzindole, we found that MT1 and MT2 were dispensable for melatonin's inhibitory effects on TLR9-mediated proinflammatory cytokines production, even though melatonin upregulated mRNA expression of MT1 and MT2 in macrophages. Furthermore, melatonin did not affect mRNA expressions of TLR9 and MyD88 but attenuated TLR9 ligand-induced ERK1/2 and AKT phosphorylation without affecting p38 and NF-κB p65 phosphorylation. Also, melatonin inhibited TLR9-mediated proinflammatory cytokines production in vivo. Taken together, our results demonstrate that melatonin suppresses TLR9-triggered proinflammatory cytokines production in macrophages via melatonin membrane receptor-independent manners and probably through inhibiting ERK1/2 and AKT activation, which further elucidates the roles of melatonin in regulating TLR-mediated innate immune responses in macrophages.
Toll 样受体（TLR）信号通路在巨噬细胞固有免疫反应中发挥重要作用。褪黑素调节 TLR3 和 TLR4 介导的巨噬细胞固有免疫反应。然而，褪黑素是否调节 TLR9 介导的巨噬细胞固有免疫反应尚不清楚。本研究表明，褪黑素抑制腹腔巨噬细胞 TLR9 配体诱导的促炎细胞因子 mRNA 和蛋白的产生，而不影响腹腔巨噬细胞的活力。使用褪黑素膜受体 MT1/MT2 拮抗剂 luzindole，我们发现 MT1 和 MT2 对于褪黑素抑制 TLR9 介导的促炎细胞因子产生的作用是可有可无的，尽管褪黑素在巨噬细胞中上调了 MT1 和 MT2 的 mRNA 表达。此外，褪黑素不影响 TLR9 和 MyD88 的 mRNA 表达，但抑制 TLR9 配体诱导的 ERK1/2 和 AKT 磷酸化，而不影响 p38 和 NF-κB p65 磷酸化。此外，褪黑素抑制 TLR9 介导的体内促炎细胞因子的产生。综上所述，我们的研究结果表明，褪黑素通过非褪黑素膜受体途径抑制 TLR9 触发的巨噬细胞促炎细胞因子的产生，可能是通过抑制 ERK1/2 和 AKT 的激活，进一步阐明了褪黑素在调节 TLR 介导的巨噬细胞固有免疫反应中的作用。
