Figure 6. Complement C5a mediates diet-induced inflammation and intestinal neoplasia.

B6.Apc^+/+ and B6.Apc^Min/+ mice were fed the LFD or HFD with coconut (purple), corn (green), or olive oil (blue) as a source of fat for 30 days. Circulating levels of the complement activation fragment C5a were measured in the plasma at Day 30 of treatment (A). (B–F) B6.Apc^Min/+ (+/+; Min/+) and the complement-deficient C5aR^+/−; Apc^Min/+ (C5aR+/−; Min/+), and C5aR^−/−; Apc^Min/+ (C5aR−/−; Min/+) strains were fed HFD_Coco or LFD_Coco for 30 days. The total number of polyps (B) and polyp mass (C) were measured in the intestine of each mouse at Day 30 of treatment. (n=5–20/group). Intestinal inflammation was measured in mice genetically deficient in C5aR (D–F). Protein levels of VEGF (D), TNFα (E), and IL-23 (F) were measured in the intestine (n=3–5/group) B6.Apc^+/+ and B6.Apc^Min/+ mice were fed HFD_Coco for 30 days, and concomitantly treated with the C5aR antagonist peptide (PMX53) or a scrambled inactive peptide (control) (2 mg/kg s.c.) every other day (B, C). (D, E) Intestinal inflammation was measured in males treated with PMX53 or control inhibitor (n=3–5). Total polyp number (B) and polyp mass (C) were measured. Protein levels of VEGF (G), TNF-α (H), and IL-23 (I) and expression of IL-1β (J) and Myc (K) were measured in the intestine of males treated with PMX53 or the control inhibitor (n=3–6/group). (L) The percentage of viable CD11b⁺/GR-1⁺ neutrophils was measured with flow cytometry in the intestinal lamina propria of B6.Apc^+/+ and B6.Apc^Min/+ males treated with PMX53 or the control peptide (n=4/group). Levels of phosphorylated AKT (pS473), IKK (pS176) and NFκB (pS536) were assessed with Western blotting (M) in polyp tissue of B6.Apc^Min/+ males or normal intestinal tissue of B6.Apc^+/+ males treated with PMX53 or the control peptide. Levels of AKT and NFκB were measured as a control for the protein amount loaded. Results are representative of 3 independent experiments. *P<0.05, **P<0.01, ***P<0.001 compared to same strain fed corresponding LFD. #P<0.05, ##P<0.01, ###P<0.001 compared to B6.Apc^+/+ or B6.Apc^Min/+ fed the same diet. $P<0.05, $$P<0.01, $$$P<0.001 compared to same strain treated with the control inhibitor.