Reactive Sulfur Species: Challenging the Reactive Oxygen Species Paradigm

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The proposed research will use biochemical and cellular techniques to examine metabolism and biochemical pathways of reactive sulfur species (RSS) in cells under physiologically relevant oxygen levels. Derivatives of oxygen form reactive oxygen species (ROS), the most biologically relevant oxidant and the target of most antioxidants, which are thought to improve human health. Natural and synthetic antioxidants, however, have either had limited therapeutic value or their activity appears independent of ROS. This research proposes that many of the assumed actions of reactive oxygen species are better explained by reactive sulfur species. This hypothesis builds upon recent work by the principal researcher, and is based on the following observations: sulfur and oxygen are chemically and biologically similar, cellular antioxidant pathways efficiently metabolize RSS, ‘antioxidant’ health foods affect RSS, many ROS assays cannot distinguish between ROS and RSS and thereby overestimate ROS, and most experiments are performed in room air where oxygen levels are many times greater than the levels within cells, which artificially increases ROS and depletes RSS. In this research project, RSS metabolism by canonical antioxidant pathways will be examined in greater detail and the effects of antioxidant health food ‘nutraceuticals’ on cellular RSS will be examined in detail. The results will have broad implications for basic biology as well as for human health and nutrition. This research will help train one graduate student, one postdoctoral fellow, and several undergraduate students. A solid postdoctoral mentoring program guided by senior faculty will ensure future success in any professional setting.Oxidants, antioxidants, and oxidative stress from reactive oxygen species (ROS) are implicated in endogenous signaling systems and associated with pathophysiological conditions in virtually all organ systems. Work, mainly from the principal investigator’s laboratory, has shown that many of the effects attributed to ROS can be mediated by reactive sulfur species (RSS) due to their chemical similarity, interchangeability in cysteine-mediated signaling systems (hydrogen peroxide ~ hydrogen disulfide), inability to analytically distinguish between the two, and the preponderance of experiments performed under supra-physiological oxygen tensions (room air). The proposed research will show that canonical ROS antioxidant pathways affect RSS metabolism independent of ROS and identify these catalytic mechanisms, will examine RSS metabolism by nutraceutical and synthetic antioxidants, and will show that cellular RSS metabolism is greatly enhanced and diversified when experiments are conducted in ‘physioxic’ environments. Combinations of antioxidants, antioxidant pathway inhibitors, hydrogen sulfide scavengers, and genetically altered cells will be used to manipulate and understand RSS metabolism, measured in buffer and in cells under physiological oxygen concentrations, using specific fluorophores, amperometric electrodes, and mass spectrometry. The proposed research will provide the biochemical and physiological basis for the role of RSS in cell signaling and homeostasis under physiologically relevant conditions. These results will broaden our understanding of RSS in health and disease and open novel areas in biological and biomedical research. It will also provide training for one postdoctoral fellow, one graduate student, and numerous undergraduate students, preparing them for professional careers in the biomedical sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.