Kupffer Cell-Derived Exosomal S100A8/A9 Promotes Inflammasome-Dependent Pyroptotic Lung Injury in Acute Pancreatitis

Acute pancreatitis frequently progresses to systemic inflammation and acute lung injury, but the circulating mediators that couple pancreatic inflammation to remote organ damage remain poorly characterized. Following our finding that plasma exosomes induce acute pancreatitis-associated lung injury by triggering NOD-like receptor protein 3-dependent pyroptotic death in alveolar macrophages, this study aims to identify exosome-encapsulated S100A8/A9 derived from Kupffer cells as a critical propagator of this inflammatory cascade.

Levels of S100A8/A9 in plasma-derived exosomes from mice with acute pancreatitis were quantified and correlated with pulmonary cytokine profiles. Plasma exosomes were characterized and administered to alveolar macrophages and healthy mice, followed by evaluation of their capacity to induce pyroptosis and lung injury. The specific role of S100A8/A9 was tested using genetic knockout and/or pharmacologic inhibition. Furthermore, Kupffer cells were investigated as a putative cellular source of these exosomes by utilizing a combination of in vitro stimulation and in vivo depletion models. Finally, the role of S100A8/A9 in perturbing the lysosomal pathway was mechanistically dissected to reveal the pathway underlying NOD-like receptor protein 3 inflammasome activation and pyroptosis.

Elevated plasma S100A8/A9 levels paralleled pulmonary cytokines increases in mice with acute pancreatitis, and the circulating S100A8/A9 was predominantly carried by exosomes. Rapidly internalized by alveolar macrophages, acute pancreatitis-derived exosomes delivered S100A8/A9 to induce pyroptosis. Adoptive transfer of acute pancreatitis-derived exosomes into healthy mice reproduced lung injury, whereas exosomes lacking S100A9 or from Kupffer cell-depleted acute pancreatitis mice caused markedly less pathologic alterations. Mechanistically, exosomal S100A8/A9 activated the NOD-like receptor protein 3 inflammasome and executed pyroptosis through a pathway via suppression of heat shock protein 70-dependent acid sphingomyelinase, leading to sphingomyelin accumulation and lysosomal membrane permeabilization.

These findings uncover a pancreas-liver-lung inflammatory axis in which Kupffer cell-derived exosomal S100A8/A9 drives systemic inflammation in acute pancreatitis, representing a tractable therapeutic target to prevent extrapancreatic organ injury.