Mechanical signaling regulates NLRP3 activation in macrophages

Abstract Macrophage controls infection and inflammation via releasing pro-inflammatory cytokine IL-1β. NLRP3 inflammasomes assembly triggers a signaling cascade to process pro-IL-1β in the active form via activating caspase-1. In the lungs, dysregulated NLRP3 activation escalates inflammatory diseases such as acute lung injury (ALI), ventilator-induced lung injury (VILI), and idiopathic pulmonary fibrosis (IPF). These inflammatory disorders are associated with changing tissue compliance/stiffness due to accumulated extracellular matrix (ECM). Tissue-resident macrophages interaction with ECM via integrins transduce “mechanotransduction” signaling. However, the molecular mechanism of how mechanotransduction cross-talks with NLRP3 pathways and inflammatory response is not clear yet. We are examining NLRP3 activation in lung resident alveolar macrophages (AMs) during mechanical stress. For that, we culture macrophages on collagen-coated surfaces with altered stiffness (elastic modulus of 0.2 to 64 Kilo Pascals (kPa)). We observed that the NLRP3 inflammasome pathway is responsive to surface stiffness and IL-1β processing suppressed by a stiffer surface (64 kPa) when compared to a softer surface (0.2 kPa). Similarly, culture surface stiffness also regulates monocyte-to-macrophage differentiation. AMs show altered transcriptome signatures with changing the stiffness and favored activated macrophage phenotype at 0.2 kPa. Further, activation of the integrin-induced signaling also reduced the NLRP3-induced IL-1β release. Future examination of adhesion-based integrin-induced mechanical signaling and NLRP3 pathway will reveal the therapeutic potential in associated inflammatory diseases such as ALI/fibrosis. National Institutes of Health grants R01- AI104732, R21EB030171, R01 AI118719, HL148033, R01AI139540, and R56 AI104732, National Science Foundation grants CBET-1900277 and CMMI1548571, American Lung Association grant ETRA 736343, Washington University in Saint Louis Children’s Discovery Institute grants CDI-CORE-2019-813 and CDI-CORE-2015-505, Foundation for Barnes-JewishHospital grants 3770 and 4642, American Association of Immunologists AAICareers in immunology fellowship.