Fig 2: Antioxidant and anti-inflammatory activities of hydrogels in vitro. (A) Determination of DPPH clearance by different hydrogels. (B) Represents ROS fluorescence intensity. (C) Intracellular ROS detection under different hydrogels (Green fluorescence indicates ROS). The secretion of (D) TNF-α and (E) IL-6 (F) IL-10 by RAW264.7 cells on different samples were quantitatively analyzed. (*P < 0.05, **P < 0.01, ***P < 0.001)

Fig 3: Chronic SF exacerbated the inflammatory response and promoted the formation of NETs in MI/RI mice. (A to C) Plasma concentrations of IL-1β, IL-6, and IL-18 in mice were measured by ELISA (n = 8 per group). (D to F) qRT-PCR assays were performed to determine mRNA levels of IL-1β, IL-6, and IL-18 in the hearts of MI/RI mice with SF (n = 6 per group). (G) Representative images of immunofluorescence staining of NETs in myocardial tissues from Sham, SF + Sham, MI/RI, and SF + MI/RI groups (green: MPO, red: citH3, blue: DAPI) (n = 6 per group). (H) Cell-free DNA (cfDNA) of each group (n = 6 per group). (I) The MPO–DNA complex relative levels were assessed in mice (n = 6 per group). Data are presented as mean ± SD. ###P < 0.001 versus Sham group; ***P < 0.001 versus SF + Sham group; $$P < 0.01 versus MI/RI group; $$$P < 0.001 versus MI/RI group. (J and K) Western blotting was used to analyze the expression of CXCR2 in NEs after treatment with EPI for 6 h (n = 6 per group). Data are presented as mean ± SD. ###P < 0.001 versus Control group. C + EPI, Control + EPI. (L) Schematic diagram of coculture of EPI-induced NEs and CMECs exposed to H/R. CMECs were treated with hypoxia for 12 h and reoxygenation for 24 h and then cocultured with NEs for 6 h. (M) Statistical analysis of the number of migrated NEs after coculture with H/R-induced CMECs (n = 6 independent experiments). (N and O) The cfDNA and MPO–DNA complex levels were assessed (n = 5 independent experiments). (P) After coculture, the ultrastructure of NEs was observed via the electron microscope. Data are presented as mean ± SD. ###P < 0.001 versus Control + NEs group; ***P < 0.001 versus H/R + NEs group. Scale bars, 50 μm (G) and 2.5 μm (P). NEs, neutrophils; EPI, epinephrine.

Fig 4: Therapeutic efficacy of M2-EVs@DNase I in septic mice. (A) Flow cytometry analysis of M1-phenotype macrophages (CD11b+F4/80+CD86+) and M2-phenotype macrophages (CD11b+F4/80+CD206+) in the peritoneal cavity. (B) Ratios of M2/M1 macrophages. (C, D) Flow cytometry and quantitative analysis of TLR9+ macrophages (CD11b+F4/80+TLR9+). (E) The levels of cfDNA in the peritoneal fluid. (F—I) The concentrations of TNF-α, IL-1β, IL-6, and IL-10 in the peritoneal fluid. (J) Plasma cfDNA levels. (K-Q) Serum levels of PCT, CRP, SAA, TNF-α, IL-1β, IL-6, and IL-10 in each group. n = 3. Data are mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Fig 5: Schematic illustration of F. nucleatum-induced macrophage inflammatory activation and colitis exacerbation through the succinic acid–SUCNR1–NF-κB axis. F. nucleatum colonization increases succinic acid levels in the intestine and circulation. Succinic acid engages its cognate receptor, SUCNR1, on intestinal macrophages and activates downstream NF-κB signaling, thereby promoting pro-inflammatory macrophage activation characterized by increased expression of CD86 and iNOS and enhanced production of inflammatory cytokines, including IL-6, TNF-a, and IL-1ß. These macrophage-associated inflammatory responses are accompanied by epithelial barrier disruption, reduced goblet cell abundance and mucus barrier integrity, increased epithelial apoptosis, and aggravated mucosal and systemic inflammation. By contrast, the fumarate reductase-deficient (frdA-KO) F. nucleatum strain, which exhibits impaired succinic acid production, shows a reduced capacity to induce macrophage inflammatory activation or aggravate colitis. Exogenous succinic acid restores these effects, whereas SUCNR1 knockdown or NF-κB inhibition attenuates succinic acid-induced macrophage inflammatory activation. Together, these findings support a model in which F. nucleatum aggravates colitis through a macrophage-centered succinic acid–SUCNR1–NF-κB signaling axis.