Macrophage extracellular traps promote peritoneal fibrosis through the ROS/TGF-β/Smad pathway under high-glucose dialysis conditions.

BACKGROUND: Long-term exposure to peritoneal dialysis fluid (PDF) can lead to peritoneal fibrosis (PF), ultimately compromising dialysis efficacy and patient outcomes. Although macrophage extracellular traps (METs) have been implicated in sterile inflammation and fibrotic diseases, their role in PF remains poorly characterized.

METHODS: A murine model of PF was established via daily intraperitoneal injections of high-glucose PDF (HG-PDF) containing 40 mM methylglyoxal. A co-culture system of RAW264.7 macrophages and HMrSV5 mesothelial cells was employed to evaluate the effects of METs on mesothelial inflammatory responses and mesothelial-to-mesenchymal transition (MMT). MET formation, oxidative stress, and the expression of inflammatory, angiogenesis and fibrotic markers were assessed using immunohistochemistry, immunofluorescence, Western blotting, and ELISA. DNase I and N-acetylcysteine were used to inhibit METs and reactive oxygen species (ROS), respectively.

RESULTS: MET formation was significantly elevated in the peritoneum of PF mice, accompanied by upregulation of IL-1β, TNF-α, VEGF, and collagen I, together with increased vascular density and peritoneal thickening. Administration of DNase I effectively diminished MET accumulation and mitigated these pathological alterations. In vitro, HG-PDF induced MET release from RAW264.7 macrophages through a partially ROS-dependent mechanism. Co-culture experiments revealed that METs activated the ROS/TGF-β/Smad2/3 pathway in mesothelial cells, promoting inflammation and MMT, whereas DNase I significantly attenuated these effects.

CONCLUSION: This study suggests that METs contribute to HG-PDF-induced peritoneal fibrosis. Excessive MET release was associated with enhanced inflammation, angiogenesis, and MMT via activation of the ROS/TGF-β/Smad pathway, offering mechanistic insights into PD-associated PF.