Flow-Induced Shear Stress Primes NLRP3 Inflammasome Activation in Macrophages via Piezo1.

The NLRP3 inflammasome is a crucial component of the innate immune system, playing a pivotal role in initiating and regulating the body's inflammatory response to various pathogens and cellular damage. Environmental stimuli, such as temperature, pH level, and nutrient availability, can influence the behavior and functions of innate immune cells, including immune cell activity, proliferation, and cytokine production. However, there is limited understanding regarding how mechanical forces, like shear stress, govern the intrinsic inflammatory reaction, particularly the activation of the NLRP3 inflammasome, and how shear stress impacts NLRP3 inflammasome activation through its capacity to induce alterations in gene expression and cytokine secretion. Here, we investigated how shear stress can act as a priming signal in NLRP3 inflammasome activation by exposing immortalized bone marrow-derived macrophages (iBMDMs) to numerous physiologically relevant magnitudes of shear stress before chemically inducing inflammasome activation. We demonstrated that shear stress of large magnitudes was able to prime iBMDMs more effectively for inflammasome activation compared to lower shear stress magnitudes, as quantified by the percentage of cells where ASC-CFP specks formed and IL-1β secretion, the hallmarks of inflammasome activation. Testing this in NLRP3 and caspase-1 knockout iBMDMs showed that the NLRP3 inflammasome was primarily primed for activation due to shear stress exposure. Quantitative polymerase chain reaction (qPCR) and a small-molecule inhibitor study mechanistically determined that shear stress regulates the NLRP3 inflammasome by upregulating Piezo1, IKKβ, and NLRP3. These findings offer insights into the mechanistic relationship among physiological shear stresses, inflammasome activation, and their impact on the progression of inflammatory diseases and their interconnected pathogenesis.