Dysfunctions in the cardiovascular system (seen for example in diabetes mellitus, hypertension and inflammatory arthritis) are among the leading risk factors/diseases that account for global deaths and disability-adjusted life years. The interactions of immune cells, vascular cells and platelets play important roles in the development and progression of these risk factors and diseases. A tight balance between generation and detoxification of reactive oxygen/nitrogen species (ROS/RNS) has been shown to modulate cell physiology and development through redox signaling and oxidative stress. Research indicates that NADPH oxidase 2 (NOX2) is a major ROS producer in the vascular system . Recent studies reveal an important role of the antioxidant protein paraoxonase-2 (PON2) as well. Our group showed that dysregulated redox regulation in PON2-ko mice causes endothelial dysfunction, vascular inflammation and tissue factor-dependent hypercoagulability. Our ongoing experiments show that hematopoietic stem cells, endothelial cells and platelets of PON2-ko mice display marked differences in development/activation compared to wild type (WT) cells. ROS/RNS play a major role in chronic vascular and inflammatory diseases but the understanding of their cellular effects and regulation by inhibitors/inhibitory pathways in immune cells, vascular cells and platelets is limited. In order to better understand the underlying mechanisms this project aims to systematically analyze the role of cell-specific PON2 signaling pathways in hypertension, diabetes mellitus, inflammatory arthritis and ischemic heart/cerebrovascular disease. ROS/RNS signaling in the circulatory/vascular system takes place in all cell types (e.g. platelets, immune cells and vascular cells) important for cardiovascular health and disease. However, the exact contribution of each cell population to the role of PON2-dependent signaling for the development and progression of cardiovascular diseases is not known. Therefore, the redox-regulatory role of PON2 on mitochondrialand NOX2-dependent ROS formation will be investigated by using cell-specific PON2 knockout mice in combination with specific inhibitors of mitochondrial- and NOX2-dependent ROS formation.
Cell-specific PON2 knockout mice can be obtained by the Cre-lox system. PON2fl/fl mice are commercially available (INFRAFRONTIER). After establishment of a PON2fl/fl mice breeding colony in Mainz we will create cell type specific PON2 ko-mice by crossing them with mice with cell type specific expression of the Cre recombinase (Gp1ba-Cre – megakaryocytes/thrombocytes; LysM-Cre – myeloid cells; CD4-Cre – T cells; Sm22-Cre - arterial smooth muscle cells; Cadh5-Cre – endothelial cells/hematopoietic cells) already available in Mainz. In further studies (see proposed SFB project) using these mice we will perform mechanistic studies (endothelial function, immune cell activity, platelet function etc.) in animal models of hypertension and diabetes and chronic inflammatory diseases (e.g. inflammatory arthritis) which can later be extended to ischemic heart/cerebrovascular diseases. Translational aspects are based on the pharmacological targeting of the PON2-mitochondria/NOX2-ROS axis (e.g. PON2 expressional or enzyme activators, inhibitors of mitochondria/NOX-2-dependent ROS formation). In addition, we aim to setup new detection assays for oxidative stress and redox regulatory pathways. Multiple collaborations within the CTH arise from the mechanistic studies on the interactions between platelets, immune cells and vascular cells.
Prof. Dr. Andreas Daiber, Zentrum für Kardiologie, Kardiologie I
Prof. Dr. Hartmut Kleinert, Institut für Pharmakologie