Macrophages are versatile cells of the innate immune system that perform diverse functions by responding to dynamic changes in their microenvironment. While the effects of soluble cues, including cytokines and chemokines, have been widely studied, the effects of physical cues, including mechanical stimuli, in regulating macrophage form and function are less well understood. In this study, we examined the effects of static and cyclic uniaxial stretch on macrophage inflammatory and healing activation. We found that cyclic stretch altered macrophage morphology and responses to IFNγ/LPS and IL4/IL13. Interestingly, we found that both static and cyclic stretch suppressed IFNγ/LPS induced inflammation. In contrast, IL4/IL13 mediated healing responses were suppressed with cyclic but enhanced with static stretch conditions. Mechanistically, both static and cyclic stretch increased expression of the integrin CD11b (α_M integrin), decreased expression of the mechanosensitive ion channel Piezo1, and knock down of either CD11b or Piezo1 through siRNA abrogated stretch-mediated changes in inflammatory responses. Moreover, we found that knock down of CD11b enhanced the expression of Piezo1, and conversely knock down of Piezo1 enhanced CD11b expression, suggesting the potential for crosstalk between integrins and ion channels. Finally, stretch-mediated differences in macrophage activation were also dependent on actin, since pharmacological inhibition of actin polymerization abrogated the changes in activation with stretch. Together, this study demonstrates that the physical environment synergizes with biochemical cues to regulate macrophage morphology and function, and suggests a role for CD11b and Piezo1 crosstalk in mechanotransduction in macrophages.

巨噬细胞是先天免疫系统的多功能细胞，通过响应微环境的动态变化来执行多种功能。虽然可溶性信号（包括细胞因子和趋化因子）的作用已被广泛研究，但物理信号（包括机械刺激）在调节巨噬细胞形式和功能方面的作用尚不清楚。在这项研究中，我们研究了静态和循环单轴拉伸对巨噬细胞炎症和愈合激活的影响。我们发现循环拉伸改变了巨噬细胞的形态以及对 IFNγ/LPS 和 IL4/IL13 的反应。有趣的是，我们发现静态和循环拉伸均可抑制 IFNγ/LPS 诱导的炎症。相比之下，IL4/IL13 介导的愈合反应在循环条件下受到抑制，但在静态拉伸条件下得到增强。从机制上讲，静态和循环拉伸都会增加整合素 CD11b（α _M整合素）的表达，降低机械敏感离子通道 Piezo1 的表达，并通过 siRNA 消除拉伸介导的炎症反应变化来敲低 CD11b 或 Piezo1。此外，我们发现敲低 CD11b 会增强 Piezo1 的表达，相反敲低 Piezo1 会增强 CD11b 的表达，这表明整合素和离子通道之间存在潜在的串扰。最后，拉伸介导的巨噬细胞活化差异也依赖于肌动蛋白，因为肌动蛋白聚合的药理学抑制消除了拉伸引起的活化变化。总之，这项研究表明物理环境与生化信号协同作用来调节巨噬细胞的形态和功能，并表明 CD11b 和 Piezo1 串扰在巨噬细胞的机械转导中的作用。