Figure 1.

The role of ROS in cell homeostasis and fate determination. The level of ROS determines its function and cell fate. High quantities of ROS irreversibly changes organelles and intracellular substances and make large-scale damange and lower level of ROS, as a redox sensitive second message, maintain cellular homeostasis. A growing amount of evidence in recent years argues for ROS functioning as a signaling intermediate to facilitate cellular adaptation in response to pathophysiological stress, such as regulation of autophagy. Therefore, ROS is not absolutely harmful, and treatment must consider the important role of ROS in physiologic and adaptive response.