Joshi Hemant, Anaya Edgar, Addanki Anvitha, Almgren-Bell Alison, Todd Elizabeth M, Morley Sharon Celeste
Division of Infectious Diseases, Department of Pediatrics, Washington School of Medicine in St. Louis, St. Louis, MO, United States.
Division of Immunobiology, Department of Pathology and Immunology, Washington School of Medicine in St. Louis, St. Louis, MO, United States.
Front Immunol. 2025 Mar 6;16:1420325. doi: 10.3389/fimmu.2025.1420325. eCollection 2025.
Macrophages sustain tissue homeostasis through host defense and wound repair. To promote host defense, macrophages upregulate surface markers associated with antigen processing and secrete pro-inflammatory mediators such as IL-6 and IL-1β. After pathogen clearance, macrophages shift phenotype to promote wound repair. Shifts in phenotypes are termed "polarization" and have historically been modeled by exposure to soluble mediators such as LPS+IFNγ (host defense) or IL-4+IL-13 (tissue repair). Greater emphasis is now being placed on understanding how the mechanical environment of macrophages, such as tissue compliance, regulates macrophages responses. Here, we compare incubation of primary macrophages on collagen-coated silica gels of varying stiffness to treatment with the small molecule integrin activator, leukadherin-1 (LA1), to examine how substrate stiffness alters macrophage polarization in response to multiple stimuli. LA1 was developed as an immunomodulator to treat inflammatory diseases by impairing trafficking of inflammatory cells. A recent clinical trial examining LA1 as an immunomodulator in solid tumors was terminated early because no benefit was observed. We hypothesized that LA1 treatment may exert additional, unexpected effects on macrophage polarization by replicating mechanotransduction. Specifically, we hypothesized that LA1 would mimic effects of incubation on stiffer substrates, as both conditions would be predicted to activate integrins. Our results show that soft substrate (0.2 kPa) trends towards upregulation of host defense molecules, in contrast to prior reports using different experimental systems. We further show that soft substrates enhance NLRP3-mediated IL-1β production, compared to stiff, in both primary mouse and human macrophages. LA1 mimicked incubation on stiff substrates in inhibiting NLRP3 activation and in regulating expression of several surface markers but differed by reducing IL-6 production. Our results show that macrophage inflammatory responses are regulated by adhesion-based, integrin-mediated mechanical signaling. Modulation of NLRP3-mediated IL-1β production by LA1 supports the possibility of repurposing LA1 to treat NLRP3-dependent inflammatory diseases.
巨噬细胞通过宿主防御和伤口修复维持组织稳态。为促进宿主防御，巨噬细胞上调与抗原加工相关的表面标志物，并分泌促炎介质，如白细胞介素-6（IL-6）和白细胞介素-1β（IL-1β）。病原体清除后，巨噬细胞转变表型以促进伤口修复。表型的转变被称为“极化”，历史上一直通过暴露于可溶性介质如脂多糖（LPS）+干扰素γ（IFNγ）（宿主防御）或白细胞介素-4（IL-4）+白细胞介素-13（IL-13）（组织修复）来模拟。现在人们更加重视了解巨噬细胞的机械环境，如组织顺应性，如何调节巨噬细胞反应。在这里，我们比较了原代巨噬细胞在不同硬度的胶原包被硅胶上孵育与用小分子整合素激活剂白细胞黏附素-1（LA1）处理的情况，以研究底物硬度如何响应多种刺激改变巨噬细胞极化。LA1被开发为一种免疫调节剂，通过损害炎症细胞的运输来治疗炎症性疾病。最近一项将LA1作为实体瘤免疫调节剂的临床试验提前终止，因为未观察到益处。我们假设LA1治疗可能通过复制机械转导对巨噬细胞极化产生额外的、意想不到的影响。具体而言，我们假设LA1会模拟在更硬底物上孵育的效果，因为预计这两种情况都会激活整合素。我们的结果表明，与使用不同实验系统的先前报告相比，软底物（0.2千帕）有上调宿主防御分子的趋势。我们进一步表明，在原代小鼠和人类巨噬细胞中，与硬底物相比，软底物增强了NLRP3介导的IL-1β产生。LA1在抑制NLRP3激活和调节几种表面标志物的表达方面模拟了在硬底物上的孵育，但在降低IL-6产生方面有所不同。我们的结果表明，巨噬细胞炎症反应受基于黏附的、整合素介导的机械信号调节。LA1对NLRP3介导的IL-1β产生的调节支持了重新利用LA1治疗NLRP3依赖性炎症性疾病可能性。
