Hydrogen peroxide as a central redox signaling molecule in physiological oxidative stress: Oxidative eustress()

Hydrogen peroxide emerged as major redox metabolite operative in redox sensing, signaling and redox regulation. Generation, transport and capture of H(2)O(2) in biological settings as well as their biological consequences can now be addressed. The present overview focuses on recent progress on metabolic sources and sinks of H(2)O(2) and on the role of H(2)O(2) in redox signaling under physiological conditions (1–10 nM), denoted as oxidative eustress. Higher concentrations lead to adaptive stress responses via master switches such as Nrf2/Keap1 or NF-κB. Supraphysiological concentrations of H(2)O(2) (>100 nM) lead to damage of biomolecules, denoted as oxidative distress. Three questions are addressed: How can H(2)O(2) be assayed in the biological setting? What are the metabolic sources and sinks of H(2)O(2)? What is the role of H(2)O(2) in redox signaling and oxidative stress?