Project description:Atherosclerotic plaque hypoxia is detrimental for macrophage function. Prolyl hydroxylases (PHDs) initiate cellular responses to hypoxia and may therefore govern macrophage function in plaque hypoxia. PHD inhibitors are clinically investigated to treat anemia in patients with chronic kidney disease, but the consequences for cardiovascular disease are not clear. Hence, we studied the influence of myeloid specific PHD deficiency on atherosclerotic plaque development and stability.
Project description:Atherosclerotic plaque hypoxia is detrimental for macrophage function. Prolyl hydroxylases (PHDs) initiate cellular responses to hypoxia and may therefore govern macrophage function in plaque hypoxia. PHD inhibitors are clinically investigated to treat anemia in patients with chronic kidney disease, but the consequences for cardiovascular disease are not clear. Hence, we studied the influence of myeloid specific PHD deficiency on atherosclerotic plaque development and stability.
Project description:BACKGROUND: The deSUMOylase SENP2 exerts athero-protective effects by inhibiting endothelial cell (EC) activation through attenuating ERK5 and p53 SUMOylation. Publicly available datasets show that SENP2 S344 is phosphorylated by Checkpoint Kinase 1 (CHK1), but the functional role remains unknown. METHODS: Mouse SENP2 S343A (human S344A) phosphodeficient knock in (KI) mutant was generated by CRISPR/Cas9, and vascular-specific function was assessed via bone marrow transplantation (BMT). ECs from KI and wild type (WT) mice were exposed to smooth (laminar flow; l-flow) or grooved (disturbed flow; d-flow) cone-and-plate devices and characterized by RNA sequencing (RNA-seq). RESULTS: L-flow increased CHK1 S280 and SENP2 S344 phosphorylation, which inhibited ERK5 and p53 SUMOylation and atherogenesis in vivo. BMT-generated vascular specific SENP2 S344A KI showed more atherogenesis but thinner fibrous cap formation specifically in the aortic arch area (d-flow) compared to that of WT mice. Ionizing radiation (IR) decreased CHK1 expression and SENP2 S344 phosphorylation, which might account for differences between systemic and BMT-generated vascular specific SENP2 S344A KI models. RNA-seq data analysis showed that SENP2 S344 phosphorylation in ECs in response to l-flow inhibited EC activation and fibrotic changes without interfering EC lineage phenotype. Lastly, l-flow-induced expression of genes was regulated by SENP2 S344 phosphorylation through ERK5 activation and inhibited EC apoptosis. CONCLUSIONS: We uncovered a novel mechanism by which l-flow inhibits EC activation, including proliferation, migration, inflammation, and fibrotic changes, via upregulating CHK1-mediated SENP2 S344 phosphorylation to attenuate atherogenesis. We also uncovered a unique expression pattern of fibrotic changes without affecting EC lineage, which is distinct from endothelial-to-mesenchymal transition and therefore should be considered a unique type of EC activation for its potential role in vulnerable plaque formation.
Project description:Idiopathic pulmonary fibrosis (IPF) is the prototypic progressive fibrotic lung disease with a median survival of 2-4 years. Injury to and/or dysfunction of alveolar epithelium are strongly implicated in IPF disease initiation, but what factors determine why fibrosis progresses rather than normal tissue repair occurs remain poorly understood. We previously demonstrated that ZEB1-mediated epithelial-mesenchymal transition (EMT) in human alveolar epithelial type II (ATII) cells augments TGF-β-induced profibrogenic responses in underlying lung fibroblasts by paracrine signalling. Here we investigated bi-directional epithelial-mesenchymal crosstalk and its potential to drive fibrosis progression. RNA sequencing (RNA-seq) of lung fibroblasts exposed to conditioned media from ATII cells undergoing RAS-induced EMT identified many differentially expressed genes including those involved in cell migration and extracellular matrix (ECM) regulation. We confirmed that paracrine signalling between AS-activated ATII cells and fibroblasts augmented fibroblast recruitment and demonstrated that this involved a ZEB1-tissue plasminogen activator (tPA) axis. In a reciprocal fashion, paracrine signalling from TGF-β-activated lung fibroblasts or IPF fibroblasts induced RAS activation in ATII cells, at least partially via the secreted protein, SPARC. Together these data identify that aberrant bi-directional epithelial-mesenchymal crosstalk in IPF drives a chronic feedback loop that maintains a wound-healing phenotype and provides self-sustaining pro-fibrotic signals.