Free radicals, particularly reactive oxygen species (ROS) and reactive nitrogen species (RNS), play a significant role in the inflammatory process.
These molecules are highly reactive due to their unpaired electrons and can influence inflammation in several ways:
1. Activation of Inflammatory Cells:
Free radicals are produced as a natural part of the metabolic processes in various cells, including immune cells like macrophages and neutrophils.
When these cells are activated in response to infection or injury, they produce an increased amount of ROS and RNS as part of the body’s defense mechanism.
This burst of free radicals helps to destroy pathogens but can also lead to tissue damage if not regulated properly.
2. Signal Transduction and Gene Expression:
Free radicals can modify proteins and lipids, influencing signal transduction pathways that control the expression of inflammatory genes.
For instance, ROS can activate nuclear factor kappa B (NF-κB), a key transcription factor that regulates the expression of many inflammatory cytokines, chemokines, and adhesion molecules.
This results in an amplified inflammatory response.
3. Tissue Damage and Inflammatory Response:
Excessive production of free radicals can directly damage cellular structures, including lipids, proteins, and DNA.
This damage can lead to cell death and the release of additional signals (such as damage-associated molecular patterns, DAMPs) that further attract and activate immune cells, perpetuating the inflammatory cycle.
4. Resolution of Inflammation:
While free radicals are often viewed negatively due to their potential for causing damage, they also play a role in resolving inflammation.
Certain ROS are involved in signaling pathways that help to terminate the inflammatory response and begin the healing process.
5. Chronic Inflammation and Disease:
Persistent oxidative stress due to an imbalance between free radicals and antioxidants can lead to chronic inflammation.
This chronic state is a contributing factor in many diseases, such as atherosclerosis, rheumatoid arthritis, and chronic obstructive pulmonary disease (COPD), where prolonged inflammation driven by free radicals continues to damage tissues over time.
Antioxidant Defense:
The body’s antioxidant defense systems, including enzymes like superoxide dismutase (SOD), catalase, and glutathione peroxidase, along with non-enzymatic antioxidants like vitamin C, vitamin E, and glutathione, work to neutralize excess free radicals and limit their damaging effects on inflammation.