Projects of CRC 1365 Renoprotection
The 17 consortium projects are grouped into the three categories "Targets" (projects area A), "General Pathways" (project area B), and "Specific Models" (projects area C), reflecting the process of translational research. However, several projects include aspects of two or even all three project areas. For instance, targets can involve the application of different models and general pathways.
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Project A01 (Müller/Wilck/Forslund): Gut microbiome in renoprotection
This project investigates key mechanisms of gut microbiome involvement in hypertensive CKD for identifying new targets in renoprotection. A deeper understanding of microbiota-host interaction in hypertensive CKD is needed, especially with regards to inflammation. Proof-of-concept experiments will be performed in a trans-species approach using microbiome sequencing, metabolomics and immunophenotyping alongside quantification of renal damage, allowing for an integrative network analysis. The effects of commonly used drugs known to interfere with the microbiota as well as the effects of microbiota from CKD patients will be investigated in established rodent models.
Project A02 (Patzak/Persson): Dilating renal medullary microvessels by the NO-sGC-cGMP pathway for renoprotection
We set out to elucidate the protective role of sGC-activation in acute kidney injury and in developing chronic kidney disease by assessing the functional capacity of sGC under hypoxia/re-oxygenation in vitro and after ischemia/re-perfusion ex vivo. Functional investigations on microvessels that supply the area-at-risk for kidney damage performed here are unique. Combining measurements of renal perfusion and autoregulation as well as MR based imaging of renal oxygenation represents a distinctive approach for characterizing substance based, vessel-targeted, renal protection. Inclusion of human medullary microvessels allows translating pharmacological effects into the human setting.
A03 (Dragun/Scheerer): Renoprotection by understanding functional and structural G-protein-coupled receptor activation
Autoantibodies (immunoglobulins - IgGs) induce several renal pathologies by targeting the G-protein-coupled receptors (GPCRs), Angiotensin II type 1 and Endothelin-1 type A. We aim to identify and characterize determinants and signaling pathways that are specific for pathogenic IgG binding and receptor-activation as compared to endogenous peptide receptor-agonists. By a combination of G-protein signaling assays in yeast or mammalian cells with biophysical in vitro assays, protein X-ray crystallography and cryo-electron microscopy, we will elucidate molecular insights into autoimmune GPCR activation, which finally will support a rational design of new specific renoprotective drugs.
A04 (Scholl): Renoprotection in primary aldosteronism – development and testing of mutant KCNJ5 inhibitors in genetically engineered pigs
The goal of this project is the development of novel strategies for renoprotection in primary aldosteronism. As the most common cause of secondary hypertension, primary aldosteronism can be caused by benign adrenal tumors. Because 40% of these tumors show mutations in the potassium channel gene KCNJ5, we aim to investigate the diagnostic and therapeutic potential of macrolide compounds that specifically inhibit mutant KCNJ5 channels. We will use CRIPSR/Cas9 to generate a pig model with a pathogenic KCNJ5 mutation and study the effects of macrolides on aldosterone production, blood pressure, adrenal morphology and renal injury.
A05 (Schleifenbaum/Gollasch): Targeting renoprotection downstream of the angiotensin II type 1 receptor
By modulating TRPC-mediated Ca2+ signaling in pre-glomerular cells, we aim to achieve renoprotection that is more specific than blockade of GPCRs such as AT1R. Using high-resolution particle analysis, we will characterize the general intracellular Ca2+ signals in the pre-glomerular region of a kidney slice model (Cx40 GCaMP mouse with a genetically encoded Ca2+ sensor in Cx40-expressing cells). Specific TRPC5/C6-mediated Ca2+ signals will be studied using knock-out mice and novel specific inhibitors. Based on an altered expression profile of TRPC channels in mouse models of metabolic syndrome (NZO) and subacute chronic renal failure (UUO), we plan a detailed characterization of the (modified) Ca2+ signals in these mouse models.
B01 (Fähling/Rosenberger): A renal function of 2,3-bisphosphoglycerate mutase (BPGM)
BPGM generates 2,3-bisphosphoglycerate (2,3-BPG) to reduce oxygen binding to hemoglobin, and improve tissue oxygenation. We show that in the nephron BPGM is constitutively expressed, and up-regulated under conditions such as acute kidney injury, clear cell renal carcinoma, or knock-out of the tumor suppressor von Hippel Lindau protein. Moreover, hypoxia or osmotic stress up-regulate BPGM in kidney cells in vitro. In renal cells BPGM modulates glucose utilization, promotes scavenging of reactive oxygen species, as well as cell survival under stress. We postulate that BPGM is renoprotective.
B02 (Jentsch): Role of volume-regulated anion channels (VRACs) in kidney integrity
The volume-regulated anion channel VRAC, recently identified by us to be formed by LRRC8 heteromers, has important roles in cell volume regulation, apoptosis, and probably transepithelial transport. An important role of VRAC in the maintenance of kidney integrity is inferred by renal tubular degeneration upon VRAC disruption. Extrapolating from VRAC’s likely role in brain and cardiac ischemia, we assume that it importantly modulates ischemia-reperfusion injury (IRI) in the kidney. Through analysis in different mouse models, we will localize all 5 LRRC8 subunits in the kidney, investigate their physiological roles in tubular processes, and will clarify their role in IRI. VRAC may turn out to be a novel target for treating kidney injury.
B03 (Klussmann/Bähring): Targeting PDE3A for protecting from hypertension-induced chronic kidney disease
The negative influence of hypertension on CKD progression is substantial. We identified mutations in the phosphodiesterase 3A (PDE3A) gene that cause a Mendelian form of hypertension (HTNB), but hardly affects kidney function. Our preliminary data indicate that mutant PDE3A is aberrantly located in cells and changes cAMP signaling in microdomains. We have now generated rat strains, PDE3A-activating, PDE3A-deleted, and litter-mate wild-type (WT), and a transgenic Cre-PDE3A-activatable mouse strain that will allow us to search for the protective changes and thus new renoprotective targets. The protective mechanisms form the basis for designing novel pharmacological strategies to favorably influence the course of CKD.
B04 (Niendorf/Seeliger): Promoting renoprotection by unravelling the roles of renal oxygenation, energy metabolism and inflammation by physiometabolic magnetic resonance
Current treatments targeting acute kidney injury (AKI) and chronic kidney disease (CKD) are sparse due to the complexity of AKI pathophysiology and its progression to CKD. Renal tissue hypoperfusion, hypoxia, altered high energy metabolism and inflammation are tightly entangled. In this project, we will study the contributions and cause-effect relationships of hypoperfusion, hypoxia, energy metabolism and inflammation in AKI of various origins. These processes will be examined with an integrated multi-modality approach (MR-PHYSIOL-NIRS): magnetic resonance (1H, 19F, 31P MR), physiological readouts (PHYSIOL) and near infrared spectroscopy (NIRS). Our approach bridges physiometabolic MR in rodents with translational research leading to clinical studies.
B05 (Kirschner/Scholz): The polyamine system in gender-related renoprotection
We will investigate how changes in the polyamine system contribute to the gender-dependent susceptibility to AKI. To recognize the influence of sex-related polyamine levels on the outcome of AKI, we will expose male mice with and without gonadectomy and female mice with and without testosterone treatment to renal IRI. Polyamine production and breakdown in these animals will be blocked to explore whether gender-dependent differences in the outcome of AKI can be attenuated by pharmacologic inhibition of the polyamine system. Furthermore, murine embryonic kidney explants and zebrafish larvae will be used as screening tools to investigate how testosterone interferes with prospective drugs targeting the homeostasis of polyamines for renoprotection.
B06 (Alenina/Bader): Renoprotective role of Angiotensin-(1–7)
The ACE2/Angiotensin (Ang)-(1-7)/Mas axis of the renin-angiotensin system may play an important role in renal diseases. Therefore, we will study the expression of components of this axis and the signaling pathways of Ang-(1-7) and Mas in different renal cell types. Moreover, we will generate transgenic animal models with targeted dysregulation of this axis in defined renal cell types. We will expose these animals to renal disease models and will analyse renal function and damage using state-of-the-art physiological, histological and imaging technologies. As a first step into translation of these results, we will use newly developed orally available Mas agonists for the preclinical evaluation of therapies for renal diseases based on the ACE2/Ang-(1-7)/Mas axis.
C01 (Kettritz/Schreiber): Renoprotection in crescentic glomerulonephritis by ANCA
We will test the hypothesis that regulated cell death pathways, namely necroptosis and ferroptosis, mediate kidney injury in autoimmune ANCA-associated vasculitides (AV) and that inhibiting key elements of these pathways provides renoprotection. Specifically, we will characterize (I) mechanisms involved in the regulation of the generation of neutrophil extracellular traps (NETs) and monocyte extracellular traps (METs) in AV, (II) necroptotic and ferroptotic cell deaths in the different kidney compartments, and (III) therapeutic targets of regulated cell death pathways that cause AV-induced kidney damage. Our studies will elucidate AV disease mechanisms and identify renoprotective treatment strategies that will then be tested in clinical trials.
C02 (Aigner/Ashraf): Renoprotective role of Lipocalin-2 in allograft rejection following kidney transplantation
Using a mouse model of kidney transplantation, we recently demonstrated a renoprotective role of exogenously administered recombinant Lcn2:Siderophore:Fe complex (rLcn2) during the early phase of allograft rejection. In this project, we aim at (I) understanding the route and mechanisms of immunoregulation and/or cytoprotection, mediated by the exogenousrLcn2; and (II) characterizing the source and nature of endogenous Lipocalin-2 i.e. whether it is complexed with mammalian iron binding catechols and may contribute to allograft survival in the long run. Our ultimate goal is to pave the way for transplant renoprotection via recombinant Lipocalin-2.
C03 (Panáková/Kreutz): Renoprotective prostaglandin reductase 2 (PTGR2)
Prostaglandin reductase-2 (PTGR2) catalyzes the reduction of the 15-keto form of prostaglandin E2 (PGE2) into 13,14-dihydro-15-keto-PGE2, thereby initiating the terminal inactivation of PGE2. Our exhaustive genomic analysis in the genetic Munich Wistar Frömter rat (MWF) CKD model identified PTGR2 as a high impact candidate gene for albuminuria development; while our genetic substitution studies underscore its tentative renoprotective properties. By combination of complementary in vitro studies, in vivo experiments in zebrafish and rat models, and by explorative analysis of biopsies from selected patients, we will test the renoprotective role of PTGR2, and the potential to target PGE2/15-keto-PGE2/PTGR2 pathway for renoprotection.
C04 (Bachmann/Mutig): Managing calcineurin inhibitor-induced nephrotoxicity for renoprotection
Calcineurin inhibitors such as cyclosporin A and tacrolimus are first-line immunosuppressive drugs widely used to prevent rejection of transplanted organs. Despite their success, nephrotoxic side effects such as damage of the glomeruli, vasculature, and tubulointerstitium are common. Here, drugs may affect proteostasis by causing cell stress and maladaption of the pathways of protein quality control. A disequilibrium between cytoprotective and proapoptotic responses may result. This project aims at understanding the functions of cellular proteostasis under calcineurin inhibition, and at discovering renoprotective strategies such as the application of small molecular chaperones.
C05 (Knauf/Eckardt): Targeting interleukin-1α for renoprotection in crystal-induced kidney disease
Oxalate is a compound found in the diet we ingest, and it is also produced as a waste product by the human body. When oxalate levels increase in blood and urine, oxalate crystals can deposit. Interleukin-1α (IL-1α) expression is increased in kidneys of mice with crystal damage. Il1a-/- mice are completely protected from progressive kidney failure. We now plan to define the role of IL-1α in renoprotection. We will investigate the mechanism(s) of IL-1α release in vitro and in vivo, we will test whether pharmacological inhibition of IL-1α is renoprotective, and examine whether increased IL-1α concentrations predict chronic kidney disease progression in humans.
C06 (Schmidt-Ott): Targeting collecting duct barrier function for renoprotection
The renal collecting duct is composed of a tight epithelium that maintains steep concentration gradients between the renal medullary interstitium and the urinary space and, at the same time, facilitates highly regulated transport mechanisms for water and ions. In this project, we will analyze the physiological, cellular and molecular mechanisms and consequences of collecting duct injury during and after acute kidney injury, and its role in limiting the progression to chronic kidney disease. We will utilize cellular and murine models of acute kidney injury and combine them with genetic and pharmacologic approaches to modulate collecting duct epithelial barrier function.
S01 (Bachmann): Imaging techniques – Advanced histopathology – superresolution microscopy – live imaging – electron microscopy
This service project will provide a wide range of state-of-the-art imaging techniques ranging from standard histopathology to the structural biology of macromolecular complexes. Based on an established core facility for electron microscopy and an affiliated light microscopy facility, histological and advanced cell biological methodology will be provided. The project will include a section for the development and application of new ultrastructural techniques such as field emission scanning electron microscopy or high-end Cryo electron tomography. Both techniques will serve to reconstruct tissue and cell volumes ranging from micrometer to angstrom resolutions. Correlated protein identification strategies will reach the point of 'visual proteomics' of structures within their physiological environment.
S02 (Niendorf): Advanced magnetic resonance imaging for in vivo phenotyping of renal pathophysiology and renoprotection
Magnetic Resonance Imaging (MRI) is a non-invasive, clinically applicable imaging modality that can be customized to probe different stages of renal disease in vivo. This project supports studies investigating the pathophysiology of renal disease or therapeutic strategies for renoprotection. It does so by providing in vivo phenotyping via advanced imaging MR techniques established by our group to probe morphology, function, haemodynamics, oxygenation and inflammation. To advance the capabilities of renal MRI, the scientific work packages of this project will focus on the development of novel techniques and imaging protocols to probe renal microstructure (e.g. susceptibility mapping for fibrosis) and function (e.g. 23Na MR for electrolyte mapping).
Z (Persson): Central Tasks of the Collaborative Research Centre
Here we will manage global funds provided for equal opportunities, clinical rotation positions, visiting scientists, symposia, publication costs and travel. Notably, we apply for a Mercator Fellow. A central issue of CRC 1365 is perturbed renal hemodynamics in kidney injury. Fortunately, we could secure Prof. Enyin Lai for investigating the particular mouse vasa recta, which has never been performed before and would be important for the CRC, as several models are in the mouse.