Reactive oxygen species roles

G. Waris et al., Reactive oxygen species Role in the development of cancer and various chronic conditions. J. Carcinog. 5, 14 (2006)... 

Taking into account all of the abovementioned studies, one is compelled by the evidence to conclude that, at least under conditions of ischaemia/reperfiision, the brain certainly has the capacity to generate reactive oxygen species and that these reactive oxygen species are likely to play an important role in the pathology that results from... 

At the present time it is difficult to single out any one factor that could be held ultimately responsible for cell death after cerebral ischaemia. Recent studies, however, have provided us with sufficient evidence to conclude that free radical damage is at least one component in a chain of events that leads to cell death in ischaemia/reperfiision injury. As noted earlier in this review, much of the evidence for free radicals in the brain and the sources of free radicals come from studies in animals subjected to cerebral ischaemia. Perhaps the best evidence for a role for free radicals or reactive oxygen species in cerebral ischaemia is derived from studies that demonstrate protective effects of antioxidants. Antioxidants and inhibitors of lipid peroxidation have been shown to have profound protective effects in models of cerebral ischaemia. Details of some of these studies will be mentioned later. Several reviews have been written on the role of oxygen radicals in cerebral ischaemia (Braughler and HaU, 1989 Hall and Btaughler, 1989 Kontos, 1989 Floyd, 1990 Nelson ef /., 1992 Panetta and Clemens, 1993). 

Ranadive, N.S. and Menon, I.A. (1986). Role of reactive oxygen species and free radicals from melanins in photoin-duced cutaneous inflammation. Pathol. Immunopathol. Res. 5, 118-139. 

The role of iron in an acute model of skin inflammation induced by reactive oxygen species (ROS). Br. J. Dermatol. 126, 250-256. 

Van der Vliet, A. and Bast, A. (1992). Role of reactive oxygen species in intestinal diseases. Free Rad. Biol. Med. 12, 499-513. 

Cancer is one of the diseases in which a role has been implicated (see Table 13.1) for free radicals. Comprehensive accounts of the involvement of reactive oxygen species in human diseases may be found in Halliwell and Gutteridge (1989), Aruoma (1993) and in Cheeseman and Slater (1993). 

In addition to the QM structure of the natural terpene QMs, the reactive oxygen species (ROS) may also play a significant role in the observed biological activities. In the synthesis of taxodione and taxodone, QMs were formed from the catechol precursors through the spontaneous oxidation in the presence of silica gel.7, 8,49-51... 

Flowers, L. Ohnishi, T. Penning, T. M. DNA strand scission by polycylic hydrocarbon o-quinone role of reactive oxygen species, Cu(II)/(I) redox cycling, and o-semiquinone anion radicals. Biochemistry 1997, 36, 8640-8648. 

This situation may be about to change as we look at the role of iron and its implications in the formation of reactive oxygen species, with their potential to attack, modify, and ultimately destroy cells. The signalling function of ROS, not to mention RNS, has been underlined earlier. Yet, we tread a delicate, and poorly understood balance between low levels of ROS, required both for cell signalling and to maintain the antioxidative defences of the cell in a state of alert1"1, and levels which become toxic. This remains an extremely important area of therapeutic concern, since oxidative stress, whether proven to be due to iron or not, is... 

That the oxidative burst is directly involved in the chemical defense of these algae is clear. This reaction can be inhibited by diphenyleneiodonium, a suicide inhibitor of NADPH-oxidase which suppresses both the production of reactive oxygen species and the natural resistance to epiphytic bacteria. In addition a role in the defense against endophytes was indicated, since pre-treatment with oligomeric guluronates resulted in decreased infection of L. digitata with the pathogen Laminariocolax tomentosoides [141]. 

Xanthine oxidase is not the only source of reactive species in ischemia-reoxygenation injury. Another source of oxygen radicals is NADPH oxidase. For example, it has been shown that endothelial NADPH oxidase produced reactive oxygen species in lungs exposed to ischemia [13]. (The role of NADPH oxidase as a producer of oxygen radicals in tissue is considered below.)... 

---