Produces IAA, has been reported to attenuate inflammatory responses in rheumatoid arthritis by modulating NF‐κB and Mitogen‐Activated Protein Kinase (MAPK) phosphorylation through AHR activation.[30] Ji et al.[31] demonstrated that IAA reduces LPS‐induced inflammatory responses and free radical production in RAW264.7 macrophages by inducing Heme Oxygenase 1 (HO‐1) expression and directly neutralizing free radicals. Here, HMOX1 is linked to rheumatoid arthritis.