There are also many other nonenzymatic antioxidants in the body, such as selenium, carotenoids, lipoic acid, coenzyme Q, melatonin, etc, which are detailed in recent reviews. ROS involves a number of cellular signaling pathways in controlling cell survival, migration and proliferation.HO, the end degeneration, serves as a signal molecule through oxidative modification of signaling product of O proteins.Mitogenactivated protein kinases are another family of serinethreonine kinases.Among them, the extracellular signalregulated kinase pathway has most commonly been associated with the regulation of cell proliferation.Oxygen radicals elicit phosphorylation of these receptors, resulting in Naloxone hydrochloride activation of the ERK pathway in relation to mitogenic signaling. In fact, the activation of the ERK pathway is not limited to receptor levels.An array of stresses such as oxidative stress can activate ASK and initiate the differentiation process of myoblasts. As a signaling molecule, ROS has been shown to mediate the function of angiogenic factors like VEGF or angiopoietin in directing cell migration. In addition to the regulation of cellular signaling pathways as secondary messengers, ROS are also involved in cell defense against infectious agents.Under an inflammatory condition, activated neutrophils and macrophages produce large quantities of superoxide radical and other ROS via the phagocytic isoform of NAD H oxidase, where the concentration of HO may reach M to facilitate the defense requirement. As memories are thought to be encoded by modification of synaptic strength, LTP is widely considered as one of the major cellular mechanisms that underlie learning and memory.Longterm potentiation is considered one of the major cellular mechanisms for learning and memory.The activation of these receptors results in calcium influx, which then activates different kinases in the cascade to facilitate LTP formation.In contrast, LTP is negatively regulated by phosphatases, including protein phosphatase A and B. Activation of glutamate receptors result in O accumulation, possibly through the conversion of NADPH oxidase. One such molecule may be protein kinase M, an atypical isoform of PKC whose synthesis increases following LTP induction. PKM thus appears important for the persistence of memory and would be expected to be important in the maintenance of longterm memory since PKM becomes a requirement for LTP maintenance only during the late phase of LTP. ROS are considered cellular 5-hydroxytryptophan messengers in the formation of LTP.Superoxide accumulates in rodent hippocampal slices after NMDA receptor activation and plays an important role in LTP.Scavenging superoxide in hippocampal slices blocks highfrequency stimulationinduced LTP. Incubation of hippocampal slices with exogenous superoxide dismutase attenuates LTP. Oxidative stress can result from over generation of ROS in various conditions, such as injury, inflammation, aging, chronic diseases, etc.Alternatively, ROS accumulation and oxidative stress could be due to the diminished abilities in the elimination of ROS.Lipid peroxidation caused by ROS leads to membrane leakage. The oxidation of amino acid residues results in the formation of proteinprotein crosslinks, leading to dysfunction of these proteins.In addition, oxidation of kinase and phosphatase dysregulates the signal pathways as well.The principal oxidative DNA damage, hydroxyguanine, dihydroxy,dihydrothymine and, diaminohydroxyformamidopyrimidine. RNA may be more vulnerable to oxidative insults than DNA given its generally singlestranded state and accessibility to the oxidantproducing mitochondria.