Identification of the physiological function of the NADPH oxidase Nox4 in the kidney

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The only known enzymatic function of NADPH oxidase enzymes of the Nox-family is the production of reactive oxygen species (ROS: H2O2 or O2•-). Nox enzymes differ in their regulation, site of expression and type of ROS produced. The isoform Nox4, differently to all other Nox isoforms, is constitutively active and under physiological conditions almost exclusively expressed in the kidney. Despite intense research, the renal function of Nox4 is, however, completely unknown. The aim of the present application is to uncover this function focusing on transport processes in the proximal tubule of the kidney. Preliminary untargeted metabolomics from plasma, urine and renal tissue of wild type and Nox4-/- mice suggested that the enzyme controls metabolism of sulphur amino acids and/or reabsorption of vitamins of the complex B. In this application, these aspects will be further explored, largely in vivo, using global and kidney-specific inducible Nox4 knockout mice. Metabolites will be analysed by targeted LC-MS/MS from plasma and urine of mice with low sulphur and vitamin B-deficient diet interventions. Moreover, the intracellular localization and interaction partners of the enzyme will be identified using a Nox4-FLAG knock-in mouse, generated in preparation for this application. In summary, the project will identify the physiological function of Nox4 in the kidney using in vivo models.