antioxidantsystem

Antioxidant system, or antioxidant defense system, refers to the integrated network of enzymes, small molecules, and signaling pathways that limit oxidative damage by reactive oxygen and nitrogen species. The system maintains redox homeostasis by scavenging free radicals, repairing oxidatively damaged molecules, and modulating redox signaling. Reactive species are produced during normal cellular metabolism, particularly in mitochondria, and at controlled levels they participate in signaling; excessive production leads to oxidative stress associated with aging and various diseases.

The enzymatic arm includes superoxide dismutases, which convert superoxide radicals to hydrogen peroxide, and catalase or glutathione peroxidase, which reduce hydrogen peroxide to water. Additional enzymes such as peroxiredoxins and thioredoxin reductases contribute to peroxide detoxification and redox regulation. The regeneration of reduced antioxidants relies on systems like glutathione, NADPH, and glutathione reductase.

Non-enzymatic antioxidants include ascorbate (vitamin C), tocopherols (vitamin E), carotenoids, glutathione, uric acid, and various flavonoids. Glutathione serves as a major intracellular reductant and as a substrate for glutathione peroxidase. The antioxidant network also participates in redox signaling, influencing pathways such as Nrf2, which upregulates antioxidant genes in response to oxidative stress.

Regulation and health relevance: Dietary factors, physical activity, smoking, and metabolic status affect antioxidant capacity. Impaired or imbalanced defenses have been associated with neurodegenerative conditions, cardiovascular disease, and cancer. While antioxidant supplements can increase plasma or tissue antioxidant levels, clinical trials have yielded mixed results, and high-dose supplementation may disrupt normal redox signaling or have adverse effects. Research continues to clarify how best to support the endogenous antioxidant system through lifestyle and therapeutics.