Nutritional antioxidants and the modulation of inflammation: theory and practice

Abstract

Highly potent substances are produced by the immune system. These substances include cytokines and oxidant molecules, such as hydrogen peroxide, free radicals, and hypochlorous acid. The purpose of immune cell products is to destroy invading organisms and damaged tissue, bringing about recovery. However, oxidants and cytokines can damage healthy tissue. Excessive or inappropriate production of these substances is associated with mortality and morbidity after infection and trauma, and in inflammatory diseases. Oxidants enhance interleukin-1, interleukin-8, and tumor necrosis factor production in response to inflammatory stimuli by activating the nuclear transcription factor, NF kappa B. Sophisticated antioxidant defenses directly and indirectly protect the host against the damaging influence of cytokines and oxidants. Indirect protection is afforded by antioxidants, which reduce activation of NF kappa B, thereby preventing up-regulation of cytokine production by oxidants. Cytokines increase both oxidant production and antioxidant defenses, thus minimizing damage to the host. While antioxidant defenses interact when a component is compromised, the nature and extent of the defenses are influenced by dietary intake of sulfur amino acids, for glutathione synthesis, and vitamins E and C. In animal studies, in vivo and in vitro responses to inflammatory stimuli are influenced by dietary intake of copper, zinc, selenium, N-acetylcysteine, cysteine, methionine, taurine, and vitamin E. Information from animal studies has yet to be fully translated into a clinical context. However, N-acetylcysteine, vitamin E, and a cocktail of antioxidant nutrients have reduced inflammatory symptoms in inflammatory joint disease, acute and chronic pancreatitis, and adult respiratory distress syndrome. Impaired antioxidant defenses may contribute to disease progression after infection with human immunodeficiency virus. Powerful arguments have been advanced for treatment with antioxidants to slow progression of acquired immunodeficiency syndrome.