Figure 5. The additional deletion of Arg2 or Nos2 in Tie2-Cre Arg1^fl/fl mice further ameliorates colitis.

(A) The concentration of l-arginine was determined by high-performance liquid chromatography (HPLC) in the feces of DSS-treated Tie2-Cre Arg1^fl/fl mice and WT control litters. (B–E) The expression of NOS2 (B–D) and Arg2 (E) were assessed by qPCR (B), Western blotting (C and D), and RNA-Seq (E) in colonic tissues (B and E) and mLNs (C and D) of 4 to 24 DSS-treated Tie2-Cre Arg1^fl/fl and 3–28 Arg1-expressing littermates (Arg1^fl/fl). The ratio of the mRNA copies of the indicated genes relative to the Hprt copies was calculated (B), and the relative increase in the respective gene copy numbers is displayed. Western blot signals from 3 experiments containing 2 to 3 mice per group in each cohort were quantitated using ImageJ software (D). (F and G) Severity of colitis in the indicated mouse strains was monitored by endoscopy (n = 3–8). Depending on the number of groups and the distribution of data, data were analyzed using 1-way ANOVA followed by Bonferroni’s post hoc test for pairwise comparisons if the former was significant, or for multiple comparisons, the Mann-Whitney U test or the Kruskal-Wallis test followed by Dunn’s post hoc test was used if the former was significant. *P ≤ 0.05; **P < 0.01; ***P < 0.001. Error bars indicate SD of the mean.