Dual Roles of ROS: Oxidative Stress vs. Signaling
Reactive oxygen species (ROS) are molecules generated through regular cellular processes and, at low levels, act as regulators of cellular functions. When regulated, ROS production is beneficial to the cell. Low, localized, and transient production of ROS is good and healthy for the cell. However, there is a difference between oxidative stress and signaling. And this can alter ROS redox signaling when imbalanced.
Low levels of ROS production are okay because of compartmentalization within the cell. Compartmentalization is a neat function the cell uses to keep chemical reactions within the cell, so that the reactions of different organelles do not affect one another. Cellular adaptation to ROS is helpful to the cell.
Cysteine oxidation occurs when the thiol side chains of cysteine residues are modified by ROS, leading to post-translational cellular modifications. These modifications made by the ROS change how the protein functions within the cell. Redox signaling plays an essential role in these oxidative reactions and in maintaining cellular homeostasis. Redox signaling uses these chemical reactions to make biological changes. ROS is also a transcription factor that acts as a signaling molecule for the transcription process. It modifies the structure and DNA-binding capacity.
To put it simply, ROS is beneficial to the cell when it is regulated properly. If not, and made in excess, it can cause oxidative stress, which leads to chronic damage to DNA, lipids, and proteins; chronic disease; and redox imbalance.
Damage to DNA increases oxidative stress, which causes DNA strands to break. It damages lipids through lipid peroxidation, a process in which free radicals (oxidative stress) attack unsaturated fats in cell membranes, damaging the cell itself. For proteins, it produces oxidative stress, which causes non-specific damage to the cells, structural alterations, and backbone fragmentation. It affects redox balance because it increases the amount of oxidative stress, which ultimately leads to all the damage mentioned above.
Chronic oxidative stress increases the likelihood of chronic disease because cells are damaged and cannot fix themselves. When oxidative stress is excessive, a redox imbalance occurs, increasing the risk of disease.
https://www.sciencedirect.com/science/article/pii/S0960982214003261
