Cell volume tunes macrophage innate inflammatory responses through promoting type I interferon signalling.

Macrophages are key effectors in co-ordinating inflammatory and immune responses to threats to the host. How macrophages decipher diverse danger signals to tailor inflammatory responses remains an unanswered question. Cell volume control is critical for normal cellular function. Disturbances in extracellular and intracellular homeostasis induce changes in cell volume, but the impact of disruptions in cell volume in controlling macrophage inflammatory responses is poorly understood. Here, we discover that macrophages use cell volume control as a bona fide danger sensing mechanism to promote and augment inflammatory responses. Using macrophages deficient in the volume regulated anion channel (VRAC), which lack cell volume control under hypo-osmotic conditions, we show that disruptions in cell volume are sensed by macrophages to drive a large transcriptomic response and induction of inflammation. Cell volume disruption, particularly loss of cell volume control, induces type I interferon signalling through a DNA- and STING-dependent mechanism, but independent of cGAS and 23cGAMP transport. Further, we found that cell volume changes synergise with diverse pathogen-mediated signalling to augment type I interferon responses and exacerbate the cytokine storm in a mouse model of hyperinflammation. Our findings highlight cell volume as an important regulator in shaping inflammatory responses, adding to our understanding of how macrophages sense complex danger signals and threats.