Abstract
All aerobic organisms from bacteria to mammals use oxgen to generate energy but at the same time produce various reactive oxygen species (ROS). The ROS causes cell injury by interacting with nucleic acid, proteins, lipids and carbohydrates, occasionally leading to cell death (necrosis and apoptosis). Therefore, these organisms are endowed with extensive antioxidant defensive mechanisms against the damaging effects caused by ROS. The protective enzymes include superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT), whereas the non-enzymatic protective substances include a-tocopherol, /3-carotene and flavonoids. The oxidative stress due to imbalance of the redox governed by levels of the oxidative and antioxidative molecules undergoes changes in the intracellular signal transduction. Hydrogen peroxide (H2O2) is often employed as a model molecule of ROS, since it can easily permeate the plasma membrane and the oxidative state can be modulated. This article will focus on the H2O2-mediated lipid signaling with special reference to phospholipase D (PLD) and also will discuss some other topics in lipid signaling.
