SAP ‐Derived Exosomes Promote Intestinal Barrier Injury Through FKBP5‐Mediated Suppression of RIPK 3/ MLKL Signaling

ABSTRACT

To investigate the role of circulating exosomes in intestinal barrier dysfunction during severe acute pancreatitis (SAP) and to elucidate the underlying molecular mechanisms, with a particular focus on Fkbp5‐mediated suppression of RIPK3/MLKL necroptotic signaling. Serum exosomes were isolated from early‐stage SAP patients and healthy controls and characterized by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). A mouse model of SAP was induced by repeated intraperitoneal injections of caerulein followed by lipopolysaccharide (LPS) administration, and interventions with the exosome release inhibitor GW4869, the Fkbp5 inhibitor SAFit2, and the RIPK3 inhibitor GSK872 were performed. Histological staining, immunohistochemistry, serum biomarker assays, intestinal permeability tests, and transcriptomic sequencing were used to evaluate the effects of exosomes and Fkbp5 on intestinal injury associated with SAP. An exosome readministration experiment was performed after GW4869 treatment, and membrane‐associated p‐MLKL was assessed by dual immunofluorescence staining with E‐cadherin. Serum exosome levels were significantly elevated in SAP patients. Circulating exosomes from SAP mice promoted intestinal epithelial barrier disruption and inflammatory responses. GW4869 treatment significantly improved pancreatic and intestinal histopathological injury, reduced serum inflammatory markers and intestinal permeability, and downregulated Fkbp5 expression in intestinal tissues. Transcriptomic analysis and qRT‐PCR validation revealed that Fkbp5 was markedly upregulated in the intestines of SAP mice. Inhibition of Fkbp5 restored the phosphorylation of RIPK3 and MLKL, attenuating intestinal injury in SAP mice, while FKBP12 inhibition conferred no protective effect. In vitro, SAP‐derived exosomes suppressed necroptosis signaling in intestinal epithelial cells, whereas GW4869 reversed this suppression. Readministration of SAP‐derived, but not control‐derived, exosomes partially restored pancreatic and intestinal injury after GW4869 treatment, accompanied by increased intestinal FKBP5 expression, reduced Occludin and Claudin‐1 expression, and decreased membrane‐associated p‐MLKL. Furthermore, inhibition of RIPK3 by GSK872 aggravated pancreatic and intestinal injury in SAP mice. These findings suggest that circulating exosomes in severe acute pancreatitis may upregulate Fkbp5, thereby suppressing the necroptotic pathway and consequently disrupting intestinal homeostasis. Circulating exosomes in SAP exacerbate intestinal barrier dysfunction by upregulating Fkbp5, which suppresses the RIPK3/MLKL necroptotic signaling pathway. Targeting the exosome‐Fkbp5 axis may offer a therapeutic strategy for SAP‐related intestinal injury.