Transcription-blocking DNA damage in aging: a mechanism for hormesis.

Recent evidence from studies on DNA repair systems that are implicated in accelerated aging syndromes, have revealed a mechanism through which low levels of persistent damage might exert beneficial effects for both cancer prevention and longevity assurance. Beneficial effects of adaptive responses to low doses of insults that in higher concentrations show adverse effects are generally referred to as hormesis. There are numerous examples of hormetic effects ranging from mild stresses of irradiation to heat stress, hypergravity, pro-oxidants, or food restriction. Although the notion of hormesis is supported by many observations in various organisms, at least two major caveats have thus far prevented the application of hormesis for disease prevention in humans. First, the very nature of hormesis using toxins as a treatment regimen harbors the inherent danger of detrimental consequences. Second, the molecular mechanisms through which insults might exert beneficial effects have thus far remained elusive. Here, I discuss a mechanistic basis for hormesis and its implications for cancer prevention and healthy aging.