Biology subjects

Geissen, S.

Publications and source records attributed to Geissen, S..

5 recordsLinked to original sources

bioRxiv2023

Remodelling of the endothelial cell transcriptional program via paracrine and DNA-binding activities of MPO

Myeloperoxidase (MPO) is an enzyme that functions in host defence by catalysing the formation of reactive oxygen intermediates. Synthesized majorly by myeloid progenitor cell types and neutrophils, MPO is released into the vascular lumen during inflammation, where it may adhere and subsequently enter endothelial cells coating vascular walls. Here, we show that MPO actually enters the nucleus of these endothelial cells and binds chromatin independently of its enzymatic activity to cause changes in chromatin structure. At its binding sites, MPO drives chromatin decondensation, while enhancing condensation at flanking regions. We further show that MPO binds loci relevant for the activation of the endothelial-to- mesenchymal transition (EndMT) and the migratory potential of ECs. Finally, MPO interacts with the RNA- binding factor ILF3 affecting its relative abundance between cytoplasm and nucleus. This leads to ILF3:MPO- driven transcriptional and post-transcriptional regulation. Accordingly, MPO-knockout mice show reduced EC numbers at scars formed after myocardial infarction, indicating reduced neovascularization. In summary, we describe a non-enzymatic role for MPO in coordinating EndMT and controlling the fate of endothelial cells through direct chromatin binding and association with such co-factors as ILF3.

genomics↗

bioRxiv2022

Vascular ultrasound for in vivo assessment of arterial pathologies in a murine model of atherosclerosis and aortic aneurysm

BackgroundVascular diseases like atherosclerosis or aortic aneurysms are common pathologies in the western world, promoting various, potentially fatal conditions. Hence, a plethora of animal models have been developed to investigate underlying mechanisms and potential therapeutics. Here we evaluate high resolution (HR) ultrasound in mouse models of atherosclerosis and abdominal aortic aneurysm (AAA) for noninvasive monitoring of morphological and functional vascular changes in vivo. MethodsEight-week-old ApoE-/- mice were used for disease models. For induction of atherosclerosis, mice were fed a western diet over 12 weeks. To trigger AAA development, osmotic minipumps were implanted, permanently releasing Angiotensin II continuously for 28 days. All animals were on C57Bl6/J background. HR vascular ultrasound of the carotid artery or the abdominal aorta was performed, respectively. Images obtained were analyzed by a speckle tracking algorithm (VevoVasc software) and were correlated with histological analyses by Picro Sirius Red staining and automated collagen quantification. ResultsArterial wall distensibility and global radial strain (GRS) as measures of arterial wall elasticity were reduced in the carotids of atherosclerotic mice as well as in the aortas of AAA mice. Pulse wave velocity (PWV) was elevated in both disease models. Intima-media thickness (IMT) was significantly increased in the atherosclerosis model. Matching those findings, area of the tunica media was enlarged in ApoE-/- mice fed a western diet, and in Angiotensin II treated mice as measured by automated image analysis, depicting higher collagen depositions in diseased arteries. Simple regression analysis revealed a strong correlation of media collagen content and area in AAA with IMT and GRS, respectively. In atherosclerosis, media collagen content significantly correlated with PWV and GRS, whereas wall distensibility was associated with the size of media area. ConclusionVascular imaging using latest generation HR ultrasound devices is suitable to trace changes of arterial wall properties in murine models of atherosclerosis and AAA. Obtained results not only correlate with histological findings but deliver information on functional parameters which may be used as early disease and risk markers in a longitudinal experimental approach.

physiology↗

bioRxiv2022

Targeting of MMP-13 prevents aortic aneurysm formation in Marfan mice

Fibrillin-1 assembles into microfibrils that not only define the structural integrity and biomechanics of the aorta but also target and sequester growth factors within the extracellular microenvironment of aortic resident cells. To better understand how dominant negative effects on fibrillin microfibril stability manifest in growth factor driven aortic disease, we analyzed early events of aortic aneurysm formation within the first two weeks of postnatal life in the dominant negative Fbn1 GT8 Marfan mouse model. Echocardiography analysis of homozygous GT8 Fbn1 mice showed significant aortic root enlargement within the second week of postnatal life which correlated with the onset of fibrillin-1 fiber degradation, aberrantly increased BMP activity and upregulated transcript levels of the collagenase MMP-13. We also found the aortic collagen network structurally disturbed where the mutant GT8-fibrillin-1 was detected. Genetic ablation or pharmacological inhibition of MMP-13 in Fbn1 GT8 Marfan mice prevents aortic root dilatation implicating the relevance of this mechanism in aortic aneurysm formation in Marfan syndrome.

biochemistry↗

bioRxiv2022

Inhibition of myeloperoxidase prevents thoracic aortic aneurysm formation in Marfan mice

Marfan syndrome (MFS) is the most prevalent inherited connective tissue disorder, still remains uncurable, and is characterized by high mortality at early age driven by dissection and rupture of thoracic aortic aneurysms. MFS is caused by mutations in the fibrillin-1 gene and aberrant TGF{beta} signaling. Here we addressed whether myeloperoxidase (MPO), a leukocyte derived enzyme with potent matrix modulating properties also influences the aortic phenotype in MFS. MFS patients displayed increased circulating MPO levels compared to controls as well as marked aortic MPO deposition. In an MFS mouse model, MPO induced inflammatory endothelial activation and endothelial to mesenchymal transition which triggered aortic leukocyte recruitment. Moreover, MPO directly contributed to adverse extracellular matrix remodeling by promoting oxidative stress and nitration of proteins within the vascular wall. Genetic MPO deficiency and pharmacological MPO inhibition attenuated MFS-related aneurysm formation. We herein identify MPO as a critical mediator of MFS-related thoracic aortic aneurysm formation and - in the absence of any pharmacological treatment so far in this disease - a first anti-inflammatory target to modulate disease progression.

immunology↗

bioRxiv2022

Inhibition of MLKL impairs abdominal aortic aneurysm development by attenuating smooth muscle cell necroptosis

BackgroundReceptor-interacting serine/threonine-protein kinase 1 and 3 (RIPK1 and RIPK3) dependent cell death has been identified as a crucial mediator of abdominal aortic aneurysm (AAA) development. RIPK3 mediates phosphorylation of Mixed lineage kinase domain like pseudokinase (MLKL) thereby inducing its oligomerization and translocation to the cell membrane. Given the dual role of RIPKs being involved in necroptosis as well as in apoptosis induction, the specific role of MLKL-induced necroptotic cell death in AAA remains unclear. MethodsWe monitored elastase-perfusion (PPE) induced progression of AAA in C57BL/6N (WT), RIPK1 kinase-inactive (Ripk1D138N/D138N), MLKL knockout (Mlkl-/-) and MLKL phospho-deficient (MlklAA) mice by ultrasound measurements, histological analyses and bulk mRNA sequencing to assess structural and molecular aortic changes. Bone marrow transplantations in WT and MlklAA mice were utilized to dissect the role of MLKL in smooth muscle cells (SMCs) and myeloid cells in AAA development. MLKL expressing human SMCs were generated to investigate necroptosis-induced proinflammatory cytokine secretion and subsequent polymorphonuclear neutrophil (PMN) migration and activation in vitro. ResultsUltrasound analysis showed that ~70% of the WT animals developed PPE induced-AAA with significant aortic structural alterations and enhanced myeloid cell infiltration. In contrast, Ripk1D138N/D138N, MlklAA, and Mlkl-/- mice were protected from AAA. This protection was associated with reduced adverse extracellular matrix (ECM) remodeling and leukocyte infiltration. MLKL deficiency was associated with a significant downregulation of genes involved in fibrinolysis, anti-inflammatory response, immune response and complement activation in aortic tissue in AAA. Bone marrow transplantation studies showed the lack of MLKL in SMCs to be the main driver of AAA protection. Proinflammatory cytokine secretion was elevated in necroptosis induced SMCs and resulted in a significant accumulation and activation of PMN. ConclusionsOverall, these findings indicate that MLKL-induced necroptotic SMC death and subsequent proinflammatory leukocyte activation play a causative role in AAA development and suggest that pharmacological inhibition of MLKL may represent a promising treatment strategy for AAA disease.

cell biology↗