In contrast to Smad1/5/8 activation by iron, activation by inflammatory stimuli does not lead to the expected induction in hepcidin and has no impact on the expression of its hepatocyte targets, Id1 and Smad7. (A) Fresh protein extracts were prepared from livers of wild-type (WT) and Bmp6^−/− mice. Phospho-Smad5 and total Smad5 were detected by immunoblot techniques on a Chemidoc MP Imaging System (Bio-Rad). (B) Serum hepcidin levels were measured by competitive ELISA in wild-type and Bmp6-deficient mice at baseline and 4 hours after LPS challenge. Values shown are geometric means ± 95% confidence intervals (CIs). Comparisons of log-transformed serum hepcidin levels were made by 2-way analysis of variance followed by Sidak’s multiple comparison tests of planned contrasts. Results of comparisons with baseline levels in mice of the same genotype are shown above the bars. Results of comparison between wild-type and Bmp6^−/− mice are indicated by connecting lines. **P < .01; ***P < .001; ****P < .0001. (C-F) Evolution over time of Id1 (C-D) and Smad7 (E-F) mRNA expression was examined in wild-type and Inhbb^−/− mice challenged with LPS or infected with E coli. Point estimates of the fold change (FC) in gene expression relative to baseline (2^−ΔΔCt) are shown on the graphs, together with their 95% CIs. When the upper limit of the fold-change CI is below 1, gene expression is significantly repressed relative to baseline.