Xia Luo

Accumulation of neutrophil extracellular traps (NETs) in ulcerative colitis (UC) is associated with impaired intestinal epithelial barrier integrity. However, little is known about how NETs affect intestinal epithelial repair. This study sheds light on the molecular mechanisms through which excess NETs cause intestinal epithelial damage in UC mice. We found that UC mice had elevated levels of circulating cell‐free DNA (cfDNA), mainly from NET byproducts (e.g., NET‐DNA). NET‐DNA in the intestine worsened UC symptoms, while DNase I treatment to eliminate it alleviated these symptoms. RNA‐seq analysis revealed significant changes in IL‐22 mRNA between wild‐type and peptidylarginine deiminase 4 knockout (PAD4 ^−/− ) mice. Flow cytometry results indicated that NET‐DNA mainly affected IL‐22 secretion by group 3 innate lymphoid cells (ILC3s), while other forms of DNA had little influence on IL‐22 expression. The IL‐22 ⁺ ILC3s ratio was restored in both DNase I‐treated and PAD4 ^−/− mice; moreover, levels of mucin, tight junction proteins, and Ki67 were significantly increased. Co‐incubating ILC3s or the mouse lymphocyte cell line MNK3 with NET‐DNA decreased IL‐22 levels. ILC3s expressed the NET‐DNA receptor coiled‐coil domain containing protein 25 (CCDC25); however, NET‐DNA did not affect IL‐22 secretion in shCCDC25‐MNK3 cells. Additionally, inhibiting ILK‐HIF‐1α proteins, downstream of CCDC25, increased IL‐22 production in MNK3 cells. Finally, we established an in vitro culture system using MNK3 and Caco‐2 cells. The supernatant from NET‐DNA‐treated MNK3 cells increased FITC‐dextran permeability and reduced ZO‐1 expression in Caco‐2 cells. Thus, CCDC25 in ILC3s responds to NET‐DNA by reducing IL‐22 levels in UC mice, negatively impacting mucosal healing.

In this study, we assessed the therapeutic effects of Bifidobacterium animalis subsp. lactis GOLDGUT-BB69 (BB69) on diarrhea in mice by monitoring diarrhea scores, intestinal histopathology, detecting cytokine and protein expression, and intestinal microbial composition and metabolism. The results showed that BB69 significantly reduced the disease symptoms of diarrhea in mice, attenuated the pathological features of the intestine, decrease the protein expression in the TLR4/NF-κB signaling pathway, reduced intestinal inflammation, lowered intestinal permeability, and significantly increased the expression of mucin and tight junction proteins (ZO-1, occludin), which repaired intestinal mucosal injuries and enhanced the intestinal barrier function. In addition, BB69 significantly reduced the gut dysbiosis of mice with diarrhea by increasing the abundance and diversity of intestinal microorganisms and the content of short-chain fatty acids (SCFAs). Our findings suggest that BB69 can act as a functional probiotic, alleviating diarrhea-related symptoms by inhibiting the inflammatory response and promoting the restoration of the intestinal mucosal barrier and intestinal flora.