Although large amounts of oxygen radicals can act as metabolic toxins causing oxidative stress, nontoxic levels of radicals may be beneficial to cellular communication and cellular defense. Many cellular functions are carried out through the use of intracellular messengers such as camp, diacylglycerols, and inositol triphosphates. Recently, there has been evidence to support the notion that cellular radicals might also function in similar roles.One cellular communication role of free radicals may be the regulation of eicosanoid production. Free radicalinduced lipid peroxidation can stimulate phospholipase A2, which causes the release of fatty acids from membranes. These fatty acids are involved in the formation of leukotrienes, thromboxanes, and prostaglandins commonly known as the eicosanoids.
In addition, free radicals can disrupt enzymatic pathways to regulate cell response. In the adrenal cortex, cytochrome P450-derived radicals reduce enzyme activity that controls corticosteroid hormone secretion. In addition, radicals generated from arachidonic acid metabolism can inactivate cyclo-
oxygenase enzyme activity and slow prostaglandin synthesis.
As a defense mechanism, superoxide radicals are produced by neutrophils in response to invading organisms. These radicals are involved in the destruction and clearance of invaders such as bacteria and viruses. During this process, not only do the radicals assist in phagocytosis, but they also stimulate the gathering of more neutrophils to continue cellular defense.
It appears that although an imbalance of pro-oxidants to antioxidants may be linked to pathological conditions, radicals are nonetheless important in cellular communication and defense. This makes them necessary in small, noncytotoxic quantities.
Tags:Antioxidant Supplementation, antioxidants, arachidonic acid metabolism, cellular communication, eicosanoid production, fatty acids, inositol, leukotrienes, lipid peroxidation, oxygen radicals, prostaglandin synthesis superoxide radicals
Leave a comment