These potentially include NO production via rhythms in Nos2 expression and rhythmic MMP3 production, both previously linked to arthritis-associated joint damage and regulation of inflammation [18,33,34], as well as other inflammation-associated disease effectors (Cxcl5, Ccl20, Mmp13, Rankl/Tnfsf11). This evidence concerns the gene MMP13 and arthritic joint disease.