title: Biological importance of reactive oxygen species in relation to difficulties of treating pathologies involving oxidative stress by exogenous antioxidants.
abstract: Findings about involvement of reactive oxygen species (ROS) not only in defense processes, but also in a number of pathologies, stimulated discussion about their role in etiopathogenesis of various diseases. Yet questions regarding the role of ROS in tissue injury, whether ROS may serve as a common cause of different disorders or whether their uncontrolled production is just a manifestation of the processes involved, remain unexplained. Dogmatically, increased ROS formation is considered to be responsible for development of the so-called free-radical diseases. The present review discusses importance of ROS in various biological processes, including origin of life, evolution, genome plasticity, maintaining homeostasis and organism protection. This may be a reason why no significant benefit was found when exogenous antioxidants were used to treat free-radical diseases, even though their causality was primarily attributed to ROS. Here, we postulate that ROS unlikely play a causal role in tissue damage, but may readily be involved in signaling processes and as such in mediating tissue healing rather than injuring. This concept is thus in a contradiction to traditional understanding of ROS as deleterious agents. Nonetheless, under conditions of failing autoregulation, ROS may attack integral cellular components, cause cell death and deteriorate the evolving injury.
authors.affiliation: Institute of Experimental Pharmacology & Toxicology, Slovak Academy of Sciences, Bratislava, Slovakia. Electronic address: ivo.juranek@savba.sk.
authors.forename: Ivo
authors.initials: I
authors.lastname: Juránek
authors.forename: Dragana
authors.initials: D
authors.lastname: Nikitovic
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kouretas
authors.forename: A Wallace
authors.initials: AW
authors.lastname: Hayes
authors.forename: Aristidis M
authors.initials: AM
authors.lastname: Tsatsakis
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use*; D044822:Biodiversity; D005075:Biological Evolution; D002986:Clinical Trials as Topic; D003600:Cytosol / Q000378:metabolism; D005609:Free Radicals; D016678:Genome; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D017382:Reactive Oxygen Species; D010100:Oxygen
keywords: Biological importance of reactive oxygen species; Deleterious action; Exogenous antioxidants; Signaling role; Tissue injury