On the other hand, ROS could be generated by rheumatoid synovial cells via the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system (Nox), during exposure to two major rheumatoid arthritis (RA) cytokines, interleukin-1β (IL-1β) and TNF-α [104, 105]. Here, TNF is linked to rheumatoid arthritis.