Figure 3.

The AIEC LF82 strain counteracts the anti-inflammatory effect of propionate in vitro.

(a) Secreted TNF-α amounts, quantified by ELISA, in supernatants of murine macrophage RAW264.7 cells incubated or not with propionate (30 mM) for 30 min before a short period of infection with AIEC LF82 (MOI 10). (b) The AIEC LF82 strain, the LF82ΔprpC mutant and trans-complemented LF82ΔprpC:prpC were preincubated with propionate for 24 h. The RAW264.7 cells were incubated with this incubation medium before infection with the LF82 strain. Secreted TNF-α levels in supernatants of murine RAW264.7 macrophages were measured. (c) Secreted TNF-α amounts in supernatants of murine macrophage RAW264.7 cells incubated with LF82, LF82ΔprpC or LF82ΔprpC:prpC (MOI 10) pretreated with propionate (propionate +) before incubation with cells and then infected or not with AIEC LF82 (n = 3). The results are the mean ± SEM of three experiments. Statistical analysis was carried out by normality testing using the Kolmogorov-Smirnov test and subsequent two-tailed Student’s t-test (A) or a one-way ANOVA with the Bonferroni post hoc test (c) (*p < .05, **p < .01, ****p < .0001).