Posttranslational modifications in Marfan’s disease mediated by myeloperoxidase
We plan to elucidate the role of MPO in vascular remodeling in MFS. In Aim 1, we will characterize PMN activation and the MPO-dependent vascular phenotype of the aorta in murine models of MFS. Thereby, we will study the mechanisms underlying PMN activation and MPO degranulation in this disease and characterize the inding capacity of MPO to the aorta. Aim 2 will focus on the functional role of MPO in the vessel wall and dissect out the effects of MPO on endothelial inflammation and function, as well as NO bioavailability. Aim 3 will analyze the role of MPO in posttranslational ECM modifications, for example by direct modifications of ECM proteins or indirectly by MMP activation, and will reveal SMC apoptosis triggered by MPO in the vessel. Finally, in Aim 4 we will test the effects of pharmacological inhibition of MPO on the aortic phenotype and endothelial function on MFS.
Necroptosis in aortic aneurysm disease - significance of inflammation in MLKL dependent
In Aim 1, we will focus on the role of necroptotic cell death pathways on vascular phenotypic changes in AAA formation. We will analyze aneurysm progression in mice lacking the specific necroptosis executing protein MLKL (Mlkl-/-) in vivo. Aim 2 will clarify how necroptosis drives the innate immune response in AAA and will determine the underlying mechanisms and extent of neutrophil recruitment and activation, since necroptosis not only enhances but is also induced by inflammation. Aim 3 will assess whether and how neutrophil-derived oxidants induce necroptosis in AAA.
In summary, this project will elucidate the role of necroptosis, the effect of necroptosis on recruitment and activation of leukocytes, and the role of vascular inflammatory mediators on necroptosis as critical drivers of AAA formation. This may ultimately help to identify necroptosis and its mediator MLKL as a potential pharmacologic target for this disease.
Role of PI 3- kinase isoform p110α for vascular integrity and aortic aneurysm formation
The pathobiology of vascular diseases like aortic aneurysms involves distinct cell types of the aortic wall and is characterized by vascular inflammation, extracellular matrix degeneration, and, in particular, by loss and dedifferentiation of vascular smooth muscle cells (SMCs). In mature blood vessels, the integrity of the vessel wall is maintained by a balanced homeostasis between low-grade mitogenic and anti-apoptotic/necroptotic signals, which are mainly mediated by receptor tyrosine kinase (RTK)-dependent activation of phosphatidylinositol 3’-kinase (PI3K). RTKs activate class IA PI3K isoforms, which are characterized by one of three catalytic p110 subunits. In SMCs, the p110α subunit mediates RTK-dependent proliferation, chemotaxis, and survival. Moreover, SMCs from smooth muscle specific p110α-deficient mice (SM-p110α-/-) have largely lost their plasticity. SM-p110α-/- mice display reduced medial wall thickness, substantially reduced neointima formation and media hypertrophy after balloon injury of the carotid artery, and protection from experimentalpulmonary hypertension. Detailed analysis of the aortic wall in SM-p110α-/- mice uncovers a disturbed structure of the media and increased vascular inflammation. Furthermore, preliminary data indicate that p110α deficiency in SMCs promotes abdominal aortic aneurysm (AAA) formation in mice. These data suggest a significant role of p110α for vascular integrity and thus for the pathobiology of aortic aneurysms.
We hypothesize that loss of p110α signaling impairs vascular integrity and promotes development and progression of aortic aneurysms.
We plan to elucidate how p110α signaling can affect aortic aneurysm formation, SMC phenotypic modulation, extracellular matrix homoeostasis, and vascular inflammation. In Aim 1, we will address the specific role of p110α signaling in the development and progression of abdominal and thoracic aortic aneurysms in mice and humans. Aim 2 focuses on the effects of p110α deficiency on SMC phenotypic modulation (synthetic versus contractile), whereas Aim 3 concentrates on the impact of p110α on expression and structure of extracellular matrix (ECM) components and elastic fibers. Finally, Aim 4 addresses the impact of p110α deficiency in SMCs on vascular inflammation, EC function, and cell death. Since recently developed selective p110α inhibitors are currently being tested in clinical trials for the treatment of various malignant diseases, characterization of the importance of p110α for the pathobiology of AAAs is of the utmost relevance, in order to avoid exposition of individuals with a predisposition to AAAs to p110α inhibition, but also to identify a targetable mediator as a novel strategy for the treatment and prevention of AAA formation.
Dysregulated extracellular signaling pathways in aortic aneurysm formation in Marfan syndrome
In this proposal, we aim to investigate how structural changes induced by fibrillin-1 mutation impact fibrillin microfibril architecture, which then translates into an altered activation state of the targeted growth factors. In Aim 1, we will investigate how structural alterations in FMF ultrastructure trigger dysregulated growth-factor signaling causative for initiation and progression of aortic disease. For this purpose we will utilize different Fbn1 mouse models with defined structural alterations in FMF, either triggering or protection from severe aneurysm formation (Fbn1-/-: severe aneurysm formation; GT8: C-terminal truncation of fibrillin-1: severe aneurysm formation; H1Δ: deletion of TGF-β anchoring site: no aneurysm formation; WMΔ: deletion of ADAMTSL binding site: no aneurysm formation). In Aim 2, we will test whether interference with BMP signaling represents a new therapeutic strategy in aortic aneurysm formation in MFS. Thereby treating GT8 mice with inhibitors of BMP signaling in combination with genetic approaches (cross-breeding to BMP ligand null, or SOST null mice) will let us explore new therapeutic avenues for MFS. In Aim 3, we will investigate whether genetic ablation of MMPs will delay the onset of aneurysm formation in MFS. Specifically, we will aim to test whether genetic ablation or pharmacological inhibition of MMP-13 will delay the onset of aortic aneurysm in GT8 mice. In Aim 4, we will explore Raman microspectroscopy as a diagnostic tool for the initiation and progression of aneurysm by comparing Raman parameters from skin and aortic samples isolated from fibrillin mutant mouse models with defined structural changes in FMF and well-characterized patient cohorts.