Fig. 2.

Reactive oxygen species (ROS) contribute to fibrosis via various feed-forward and feedback loops. Insults resulting from infectious diseases, trauma, toxins, drugs and radiation (UV, ionizing) induce ROS generation. Subsequently, ROS contribute to the fibrotic process either directly or indirectly via enhanced inflammation. Fibrosis and the inflammation itself might feedback into the pathway and further increase ROS formation or stimulate the production of cytokines and growth factors. The last two mentioned substances can also contribute to ROS formation. In a non-fibrotic process, inflammation and ROS formation end in tissue regeneration