PTGS2 and rheumatoid arthritis: While NFIL-3 is reported to enhance Per2 expression in isolated and cultured synovial cells when stimulated by TNFα, during progression rheumatoid arthritis (Yoshida et al., 2013), it has also been shown to act as a transcriptional repressor reducing inflammation in dexamethasone induced-ID-13 fibroblast-like synoviocytes by transcriptionally repressing inflammatory genes inducible nitric oxide synthase (Gustavsson et al., 1995) (inducible nitric oxide synthase), COX-2 (Cyclo-oxygenase-2), and cPLA2 (cytoplasmic phospholipase A2) (Wallace et al., 1997) (Figure 2-bottom orange panel).