CO inhibits ER-stress–induced hepcidin expression and controls iron homeostasis in ER-stressed mice. C57BL/6 and C3H mice were preinjected with CORM-3 (10 mg/kg/d) and then injected 3 hours later with either recombinant mIL-6 (25 μg/kg) or TM (1.5 mg/kg). Mice were killed at the 48-hour time point. (A) Hepatic hepcidin gene expression was analyzed by RT-PCR in IL-6–injected C57BL/6 mice. (B) Hepcidin protein levels were detected from the serum of IL-6– or TM-injected C57BL/6 mice by mouse hepcidin ELISA. (C) Hepatic hepcidin gene expression was analyzed by RT-PCR in TM-injected C57BL/6 mice. (D) Serum iron levels of C57BL/6 mice were determined using an iron assay kit. (E) Iron accumulation in splenic macrophages of C3H mice were assessed by staining with Perl Prussian blue. (F) Nonheme iron content was assessed in the spleen tissue of C3H mice. Ten mice were used in each group. Values are means ± SEM from 3 independent experiments. *P < .05; **P < .01; ***P < .001. U indicates unspliced; and S, spliced.