Department of Biochemistry and Immunology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil.
J Biol Chem. 2011 Apr 1;286(13):10960-9. doi: 10.1074/jbc.M110.205047. Epub 2011 Jan 26.
Dendritic cells (DCs) are powerful initiators of innate and adaptive immune responses. Ticks are blood-sucking ectoparasite arthropods that suppress host immunity by secreting immunomodulatory molecules in their saliva. Here, compounds present in Rhipicephalus sanguineus tick saliva with immunomodulatory effects on DC differentiation, cytokine production, and costimulatory molecule expression were identified. R. sanguineus tick saliva inhibited IL-12p40 and TNF-α while potentiating IL-10 cytokine production by bone marrow-derived DCs stimulated by Toll-like receptor-2, -4, and -9 agonists. To identify the molecules responsible for these effects, we fractionated the saliva through microcon filtration and reversed-phase HPLC and tested each fraction for DC maturation. Fractions with proven effects were analyzed by micro-HPLC tandem mass spectrometry or competition ELISA. Thus, we identified for the first time in tick saliva the purine nucleoside adenosine (concentration of ∼110 pmol/μl) as a potent anti-inflammatory salivary inhibitor of DC cytokine production. We also found prostaglandin E(2) (PGE(2) ∼100 nM) with comparable effects in modulating cytokine production by DCs. Both Ado and PGE(2) inhibited cytokine production by inducing cAMP-PKA signaling in DCs. Additionally, both Ado and PGE(2) were able to inhibit expression of CD40 in mature DCs. Finally, flow cytometry analysis revealed that PGE(2), but not Ado, is the differentiation inhibitor of bone marrow-derived DCs. The presence of non-protein molecules adenosine and PGE(2) in tick saliva indicates an important evolutionary mechanism used by ticks to subvert host immune cells and allow them to successfully complete their blood meal and life cycle.
树突状细胞 (DCs) 是先天和适应性免疫反应的强大启动者。蜱是吸血的外寄生虫节肢动物，通过在唾液中分泌免疫调节分子来抑制宿主免疫。在这里，鉴定了在 Rhipicephalus sanguineus 蜱唾液中存在的具有免疫调节作用的化合物，这些化合物可影响 DC 分化、细胞因子产生和共刺激分子表达。R. sanguineus 蜱唾液抑制了 IL-12p40 和 TNF-α，同时增强了 TLR-2、-4 和 -9 激动剂刺激的骨髓来源的 DC 产生的 IL-10 细胞因子。为了鉴定这些作用的分子，我们通过微过滤和反相 HPLC 对蜱唾液进行了分级，并测试了每个分级对 DC 成熟的影响。已证明具有作用的分级通过微 HPLC 串联质谱或竞争 ELISA 进行分析。因此，我们首次在蜱唾液中鉴定出嘌呤核苷腺苷 (浓度约为 110 pmol/μl) 作为一种有效的抗炎性蜱唾液细胞因子产生抑制剂。我们还发现前列腺素 E2 (PGE2 ∼100 nM) 具有类似的调节 DC 细胞因子产生的作用。Ado 和 PGE2 通过诱导 DC 中的 cAMP-PKA 信号抑制细胞因子的产生。此外，Ado 和 PGE2 都能够抑制成熟 DC 中 CD40 的表达。最后，流式细胞术分析表明 PGE2（而不是 Ado）是骨髓来源的 DC 分化抑制剂。蜱唾液中存在非蛋白分子腺苷和 PGE2 表明，蜱使用了一种重要的进化机制来颠覆宿主免疫细胞，使它们能够成功完成吸血和生命周期。
