Part 1: the Role of Oxygen Reactive Species (ros) in Health and Disease Oxidants and Antioxidative Defense

Much confusion surrounds the concept of hormesisand what its biological meaning represents. This paperprovides a definition of hormesis that addresses itshistorical foundations, quantitative features, and under-lying evolutionaryand toxicologically-based mechanisticstrategies. Hormesis should be considered an adaptiveresponse characterized by biphasic dose responses ofgenerally similar quantitative features with respect toamplitude and range of the stimulatory response that areeither directly induced or the result of compensatorybiological processes following an initial disruption inhomeostasis. Given the limited magnitude of the stimula-tory response (i.e., usually 30-60% greater than controlsat maximum), heightened study design and replicationrequirements are often necessary to ensure reliablejudgments on causality. Even though hormesis is consid-ered an adaptive response, the issue of beneficial/harmful effects should not be part of the definition ofhormesis, but reserved to a subsequent evaluation of thebiological and ecological context of the response.