| In a recent appeal by a panel of international experts from various disciplines it was recommended that, in order to better understand the role of oxidative stress in physiology and pathology, the chemistry of reactive oxygen species (ROS) in cells needs to be made more explicit. The challenge for chemistry is to make this possible by developing novel molecular tools for imaging and manipulating specific reactive oxygen species in their (sub-)cellular environment. Here we will address some of these challenges. Reactive oxygen species (ROS) play a crucial, albeit paradoxical role in biology and medicine. On the one hand they are recognized as playing an important role in biological processes such signaling and the immune response; on the other hand they are linked to oxidative stress and oxidative damage, which in turn is commonly related to aging and pathologies such as cancer. Whereas there is considerable knowledge in chemistry about the reactivity of ROS, the chemistry of ROS in cells, including its relation to pathology is generally poorly understood. Biological phenomena are sometimes ascribed to ROS or oxidative damage without understanding or appreciating what is chemically feasible and/or based on technically inadequate experiments. For example, ?reactive oxygen species? are often presented as a single entity, whereas in reality this term encompasses a large variety of species with very different stabilities and reactivities. Here we aim at the development and application of a new generation of molecular tools, involving a novel design approach, for the study of reactive oxygen species and oxidative stress in healthy and cancer cells. This proposal comprises two projects that are independent, yet mutually beneficial. In project 1, new molecular tools for the intracellular detection of O2●- and H2O2, in an organelle specific fashion, will be developed and applied to probing and imaging of primary ROS levels in healthy and cancer cells. In project 2, N4Py based systems capable of inducing oxidative stress in specific compartments will be exploited in the context of ovarian cancer to a) determine differences in cellular responses to mitochondrial versus nuclear oxidative stress; b) provide more insights in epigenetic mechanisms underlying these cellular response pathways; while the project ultimately aims to c) identify epigenetic responses to differential oxidative stress inducers underlying malignancy by comparing normal versus malignant cells. These two projects have in common that they rely on a common design principle for the molecular systems: they are based on a transition metal catalyst that can convert H2O2 and O2●- into highly reactive oxidizing species (hROS), which may include diffusible radicals such as ●OH, or metal based species such as FeIIIOOH or FeIVO, that are amenable to detection and capable of generating controlled oxidative stress inside the (sub-)cellular environment. The bio-inspired oxidation catalyst based on the N4Py ligand are ideally suited for this purpose. This study will serve as the starting point for further combined chemical/biomedical investigations of the role of ROS in epigenetics (including histone modifications), with possibly important implications for major societal problems such as aging and many pathologies. A better understanding of oxidative stress and how to manipulate it on the subcellular level also offers opportunities for the development of novel selective chemotherapeutics that can take advantage of locally elevated ROS levels found in cancer cells. |
