SOD2 and rheumatoid arthritis: Finally, SOD2 was involved in response to superoxide, hypoxia, release of cytochrome c, glutathione, and superoxide metabolic process, apoptotic signaling, and negative regulation of fibroblast proliferation, which are key features in RA (Fig 8a–d) (Additional File; S7, S8, S9, S10 in S1 File).