Targeted nuclear degranulation of neutrophils promotes the progression of pneumonia in ulcerative colitis.

Background: Both intestinal and pulmonary systems are parts of the mucosal immune system, comprising ∼80% of all immune cells. These immune cells migrate or are transported between various mucosal tissues to maintain tissue homeostasis.

Methods: In this study, we isolated neutrophils from the peripheral blood of patients and utilized immunofluorescence, flow cytometry, and Western blotting to confirm the incidence of "nucleus-directed degranulation" . Subsequently, we conducted a precise analysis using arivis software. Furthermore, using the DSS mouse model of colitis and tissue clearing technologies, we validated the "targeted nuclear degranulation" of neutrophils and their migration to the lungs in an inflammatory intestinal environment.

Result: In this study, we found that among patients with ulcerative colitis, the migration of neutrophils with "targeted nuclear degranulation" from the intestinal mucosa to the lungs significantly exacerbates lung inflammation during pulmonary infections. Notably, patients with ulcerative colitis exhibited a higher abundance of neutrophils with targeted nuclear degranulation. Using DSS mice, we observed that neutrophils with targeted nuclear degranulation from the intestinal mucosa migrated to the lung and underwent activation during pulmonary infections. These neutrophils rapidly released a high amount of neutrophil extracellular traps to mediate the progression of lung inflammation. Alterations in the neutrophil cytoskeleton and its interaction with the nuclear membrane represent the primary mechanisms underlying targeted nuclear degranulation.

Conclusion: This study revealed that neutrophils accelerate lung inflammation progression in colitis, offering new insights and potential treatment targets for lung infections for patients with colitis.