FIGURE 1.

Generation and signaling pathways of ROS. ROS emanates from diverse sources, notably oxidative phosphorylation transpiring in the electron transport chain on the inner mitochondrial membrane. Concurrently, metabolic reactions within peroxisomes contribute to ROS production. Another subset of ROS is engendered by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX), which catalyze the conversion of oxygen into superoxide. Additionally, ROS can stem from cyclooxygenases, lipoxygenases, and thymidine phosphorylase. Significantly, transition metals, particularly iron, can initiate ROS formation independently of enzymatic processes through a Fenton reaction. Noteworthy is the involvement of ROS in cell metabolism signaling pathways, influencing the survival, death, and proliferation of cells. TNF, tumor necrosis factor; JNK, c‐jun N‐terminal kinase; HIFs, hypoxia‐inducible transcription factors; VEGF, vascular endothelial growth factor; ERK/MAPK, the extracellular‐signal‐regulated kinase/mitogen‐activated protein kinase pathway.