Exogenous CO or heme-induced HO-1 can inhibit LPS-induced TNF-α production through the upregulation of the immune response gene 1 (IRG1)/tumor necrosis factor and alpha-inducible protein 3 (TNFAIP3 or A20) pathway to suppress endotoxemia inflammation in mice [169]. This evidence concerns the gene TNFAIP3 and serum lipopolysaccharide activity.