Maruyama Kentaro, Sakisaka Yukihiko, Suto Mizuki, Tada Hiroyuki, Nakamura Takashi, Yamada Satoru, Nemoto Eiji
Department of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Department of Oral Immunology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Front Physiol. 2018 Jun 28;9:802. doi: 10.3389/fphys.2018.00802. eCollection 2018.
Macrophages are immune cells of hematopoietic origin that play diverse roles in host defenses and tissue homeostasis. In mechanical microenvironments, macrophages receive mechanical signals that regulate various cellular functions. However, the mechanisms by which mechanical signals influence the phenotype and function of macrophages in the process of inflammation have not yet been elucidated in detail. We herein examined the effects of cyclic stretch (CS) on NLR family, pyrin domain-containing 3 (NLRP3) inflammasome activation in J774.1, a murine macrophage cell line, and mouse primary bone marrow-derived macrophages. We showed that cyclic stretch inhibited adenosine triphosphate (ATP)-stimulated interleukin (IL)-1β secretion in lipopolysaccharide (LPS)-primed macrophages using ELISA and Western blot analyses. Cyclic stretch did not affect the degradation of the Inhibitor of κB or the nuclear translocation/transcriptional activity of nuclear factor (NF)-κB, suggesting that cyclic stretch-mediated inhibition was independent of the NF-κB signaling pathway. Consistent with these results, cyclic stretch did not affect the LPS-induced expression of inflammasome components, such as pro-IL-1β and NLRP3, which is known to require the activation of NF-κB signaling. We showed that the cyclic stretch-mediated inhibition of IL-1β secretion was caused by the suppression of caspase-1 activity. The addition of compound C, a specific inhibitor of adenosine monophosphate-activated protein kinase (AMPK), to LPS-primed macrophages inhibited IL-1β secretion as well as caspase-1 activation, suggesting that AMPK signaling is involved in ATP-triggered IL-1β secretion. Furthermore, the phosphorylation of AMPK induced by ATP in LPS-primed macrophages was significantly suppressed by cyclic stretch, indicating that cyclic stretch negatively regulates IL-1β secretion through the inhibition of caspase-1 activity by attenuating the AMPK pathway. Our results suggest that mechanical stress functions to maintain homeostasis through the prevention of excessive inflammasome activation in macrophages in mechanical microenvironments.
巨噬细胞是造血来源的免疫细胞，在宿主防御和组织稳态中发挥多种作用。在机械微环境中，巨噬细胞接收调节各种细胞功能的机械信号。然而，在炎症过程中机械信号影响巨噬细胞表型和功能的机制尚未完全阐明。我们在此研究了周期性拉伸（CS）对小鼠巨噬细胞系J774.1和小鼠原代骨髓来源巨噬细胞中NLR家族含pyrin结构域3（NLRP3）炎性小体激活的影响。我们通过酶联免疫吸附测定（ELISA）和蛋白质免疫印迹分析表明，周期性拉伸抑制了脂多糖（LPS）预处理的巨噬细胞中三磷酸腺苷（ATP）刺激的白细胞介素（IL）-1β分泌。周期性拉伸不影响κB抑制蛋白的降解或核因子（NF）-κB的核转位/转录活性，这表明周期性拉伸介导的抑制作用独立于NF-κB信号通路。与这些结果一致，周期性拉伸不影响LPS诱导的炎性小体成分如前体IL-1β和NLRP3的表达，已知这需要NF-κB信号通路的激活。我们表明，周期性拉伸介导的IL-1β分泌抑制是由半胱天冬酶-1活性的抑制引起的。向LPS预处理的巨噬细胞中添加化合物C（一种单磷酸腺苷激活蛋白激酶（AMPK）的特异性抑制剂）可抑制IL-1β分泌以及半胱天冬酶-1激活，这表明AMPK信号通路参与了ATP触发的IL-1β分泌。此外，LPS预处理的巨噬细胞中ATP诱导的AMPK磷酸化被周期性拉伸显著抑制，这表明周期性拉伸通过减弱AMPK途径抑制半胱天冬酶-1活性来负向调节IL-1β分泌。我们的结果表明，机械应力通过防止机械微环境中巨噬细胞过度的炎性小体激活来维持稳态。
