ABSTRACT
Reactive oxygen species (ROS) are produced in the cells by various environmental stimuli such as infection of microbes (viruses, bacteria, etc.), ionizing and UV irradiation, and pollutants (i.e., oxidants), which are collectively called ‘‘oxidative stress.’’ These environmental challenges elicit inflammatory and immune responses (1). Interestingly, these factors are also regarded as risk factors and disease-accelerating factors for autoimmune diseases including rheumatoid arthritis (RA) (Fig. 1). In addition, inflammatory responses in mammals are often associated with ROS production from neutrophils and macrophages. Therefore, this natural
defense system for the organism contains a potentially dangerous option conforming a positive feed-back loop which is considered responsible for further augmentation and expansion of the response if the feed-back regulatory system, antioxidant system, and negative-cytokine network do not work efficiently.
