Figure 8. Infection with high dose of K. pneumoniae recruits corepressor complex to the IL-10 URR and amelioration of pathogenicity by short-chain fatty acid.

(a–c) C57BL/6J mice were infected i.t. with either low dose (100 c.f.u.) or high dose (1,000 c.f.u.) of K. pneumoniae (n=3–4 mice per group at the conclusion of experiment). Four days post-infection, lung MDSCs were purified. (a) Coimmunoprecipitation and (b) ChIP experiments were performed using NCOR-, HDAC3- or p300-specific antibodies. Data shown are representative of two independent experiments. qPCR quantitation represents analysis of two independent ChIP experiments (lower panel). (c) IL-10 protein level in the lung on day 6 was measured by magnetic bead-based cytokine assay. Data shown are mean±s.d. and representative of two independent experiments. (d–i) C57BL/6J mice were infected with 1,000 c.f.u. of K. pneumonia. Day 1 post-infection, mice were randomly divided into two groups. One group was treated i.p. with NaB (200 mg kg⁻¹ body weight) for five consecutive days while the other group received only vehicle (PBS). Day 6 post-treatment, the following parameters of inflammation were studied: (d) Change in body weight. (e) Percentage of survival represented by Kaplan–Meier survival curves of PBS-treated mice or mice infected with Kleb±NaB treatment. Data shown are mean±s.d. from three pooled experiments with n=12 mice in PBS group, 15 in bacteria only group and 20 in bacteria+NaB group. The P value was calculated using log-rank (Mantel-Cox) test. (f) Lung pathology by H&E staining of lung tissue sections. (g) MPO activity in BAL fluid, (h) BAL albumin level by ELISA, and (i) secreted cytokines assayed in lung homogenates using magnetic bead-based assay. Experiments in c,d and f–i were initiated with n=8 and 6 mice in Klebsiella and Klebsiella+NaB groups, respectively. At the conclusion of the experiment, 3 mice in bacteria only group and 4 mice in bacteria+NaB group were available for analysis. Statistical significance was calculated using Student's unpaired two-tailed t test for comparisons involving two groups or one-way ANOVA with Bonferroni's post hoc test for multiple pairwise comparisons. Data shown are mean±s.d. and are representative of two independent experiments. *P≤0.05, **P≤0.01, ***P≤0.001.