Pathological accumulation of aged neutrophils contributes to intestinal inflammation in inflammatory bowel disease

Neutrophils play a dual role in inflammatory bowel diseases (IBD), contributing to both host defense and tissue damage. Among them, CXCR4+CD62Llo aged neutrophils have been implicated in chronic inflammation, though their precise involvement in the pathogenesis of IBD remains unclear. This study aimed to explore the functional characteristics and therapeutic potential of aged neutrophils in IBD. Samples of peripheral blood and colonic biopsies from 61 patients with IBD (47 with active disease, 14 with inactive disease) and 36 healthy controls were analyzed to quantify aged neutrophils. Flow cytometry, immunofluorescence, and neutrophil-peripheral blood mononuclear cell co-culture assays were used to assess their function. The therapeutic effects of the CXCR4 antagonist AMD3100 were tested in a dextran sulfate sodium-induced acute colitis model. Our results demonstrated a marked accumulation of aged neutrophils in both peripheral blood and inflamed intestinal tissues of patients with active IBD, and their abundance was positively correlated with disease severity. Functionally, these cells displayed elevated β-galactosidase activity, heightened reactive oxygen species generation, enhanced formation of neutrophil extracellular traps, and increased secretion of pro-inflammatory cytokines, including IL-6, IL-17A, and TNF-α. Additionally, aged neutrophils were associated with enhanced T- and B-cell activation. CXCR4 inhibition reduced aged neutrophil accumulation, alleviated inflammation, and restored intestinal barrier integrity by upregulating tight junction proteins (ZO-1, occludin). Collectively, these findings indicate that aged neutrophils may contribute to the pathogenesis of IBD by linking innate and adaptive immunity, amplifying inflammatory cascades, and promoting mucosal injury. Targeting these cells represents a promising therapeutic strategy for IBD.