Biology subjects

Mueller, O. J.

Publications and source records attributed to Mueller, O. J..

7 recordsLinked to original sources

bioRxiv2026

Sphingolipid-Driven Lipotoxicity Promotes Calcific Aortic Valve Disease Through ER-Stress-NF-κB-EndMT Signaling and Is Therapeutically Targetable Through Serine Palmitoyltransferase Inhibition

Background: Calcific aortic valve disease (CAVD) lacks disease-modifying therapy. LDL-cholesterol lowering does not attenuate valvular calcification, suggesting cholesterol-independent drivers. Thus, we tested whether ceramide accumulation drives CAVD and whether inhibiting sphingolipid de novo synthesis is therapeutic. Methods: We integrated lipidomics and proteomics of calcified and non-calcified human aortic valves with matched plasma. Mechanistic effects of ceramides were tested in primary human valvular interstitial cells (VICs). Therapeutic efficacy of serine palmitoyltransferase (SPT) inhibition with Myriocin was evaluated in ApoE-/- mice with PCSK9DY-AAV-driven hyperlipidemia on Western diet using preventive treatment and therapeutic initiation after echocardiographically verified gradient elevation. Myriocin was additionally tested in a normolipidemic wild-type aortic valve wire-injury model. Hemodynamics, valve structure, lipid composition, and cell-state transitions were assessed by echocardiography, histology, lipidomics, and single-cell RNA sequencing. Results: Calcified human valves showed enrichment of long-chain ceramides linked to NF-{kappa}B, endothelial-to-mesenchymal transition (EndMT), and ER-stress/unfolded protein response (UPR) programs, whereas matched plasma sphingolipids were not elevated. In hVICs, long-chain C18 ceramide induced GRP78/BiP, CHOP, and ATF4, activated NF-{kappa}B, and promoted dose-dependent calcification. In vivo, SPT inhibition with Myriocin lowered valvular ceramides, reduced leaflet inflammation and mineralization, and improved cusp separation and transvalvular hemodynamics without lowering plasma LDL-cholesterol. In a therapeutic protocol initiated after gradient elevation, Myriocin halted further hemodynamic progression, providing the first evidence that de novo sphingolipid synthesis can be targeted after established CAVD onset in vivo. Myriocin also attenuated injury-induced stenosis in normolipidemic mice. Single-cell RNA sequencing showed reduced NF-{kappa}B/EndMT and ER-stress signatures and shifted VIC states away from osteogenic phenotypes. Conclusions: Human valve lipidomics and human VIC experiments identify ceramide-driven lipotoxicity as a driver of an ER-stress-NF-{kappa}B-EndMT axis in CAVD. In vivo, de novo sphingolipid synthesis is an actionable, LDL-independent target capable of modifying established hemodynamic disease progression, supporting SPT inhibition as a tractable strategy for medical CAVD therapy.

molecular biology↗

bioRxiv2026

Platelet C5aR1 mediates sex-specific ischemia-driven revascularization through estradiol-dependent CXCL4 release

BackgroundSex-specific differences in cardiovascular diseases remain incompletely understood at the molecular level. ObjectivesHere, we investigated the role of the platelet complement receptor C5aR1 as a sex-specific critical mediator of revascularization following hindlimb ischemia. MethodsIschemia-driven revascularization was analyzed in the hind limb ischemia (HLI) model using wild type (WT) and complement receptor-deficient male and female mice, and involved mechanisms were analyzed in platelets and megakaryocyte-shed platelets ex vivo. ResultsIn WT mice, ischemic tissue exhibited robust complement activation with C3b and C5a accumulation that correlated strongly with deposition of the anti-angiogenic factor CXCL4 (PF4). Mechanistically, C5a stimulation of platelets triggered CXCL4 secretion, and female animals with a platelet-specific deletion of C5aR1 (using PF4-Cre-C5aR1fl/fl mice) showed a significantly delayed revascularization. Female mice exhibited substantially lower platelet C5aR1 expression, and C5a-induced CXCL4 secretion was virtually abolished compared to male animals. The sex-specific difference in tissue CXCL4 deposition was not present any more in the absence of C5aR1 from platelets. We observed that megakaryocytes, which give rise to platelets, express estradiol receptors. Importantly, estradiol stimulation of megakaryocytes suppressed C5aR1 expression during pro-platelet formation, uncovering a hormone-dependent regulatory mechanism. ConclusionsThe here described estradiol-C5aR1-CXCL4 axis provides a molecular explanation for sex-specific differences in ischemic revascularization known from patient studies. Our findings establish a novel and unexpected mechanistic link between sex hormones, a complement-platelet crosstalk and the angiogenic response to ischemia with potential clinical implications for sex-specific personalized therapeutic strategies.

immunology↗

bioRxiv2026

FYCO1 improves postischemic cardiac remodeling via enhanced autophagic flux and attenuation of proinflammatory signaling

Acute myocardial infarction (MI) is associated with severe metabolic and oxidative stress that triggers cardiomyocyte death, pro-inflammatory signaling and progressive structural remodeling frequently culminating in heart failure. Although significant advances in reperfusion therapy improved acute survival in patients, therapeutic strategies that directly target intracellular processes in response to injury remain limited. One key response mechanism, autophagy, is rapidly activated to ameliorate ischemic stress. Yet, defective autophagic flux may exacerbate cardiomyocyte injury and maladaptive tissue remodeling. Here we identify FYCO1 as a cardiomyocyte-enriched key regulator of autophagy that enhances autophagic flux and promotes myocardial resilience following ischemic injury. Using cardiomyocyte-specific FYCO1 transgenic mice subjected to permanent coronary ligation, we demonstrate that FYCO1 overexpression limits infarct expansion, reduces cardiomyocyte injury, and preserves cardiac function during remodeling. In vivo RFP-EGFP-LC3 autophagy reporter analyses reveal that FYCO1 promotes a sustained increase of autophagic flux by coordinating autophagosome formation and efficient autolysosomal clearance. Transcriptomic profiling identifies a cardioprotective gene program in FYCO1-Tg animals subjected to MI, with suppression of proinflammatory, proapoptotic and stress-response pathways. Systemic serum cytokine and chemokine profiling as well as transcriptomic analyses of myocardium confirm reduced inflammatory signaling and subsequent reduction in macrophage recruitment into the infarct border zone. Together these findings position FYCO1 as a key regulator of cardiomyocyte autophagy and reveal a previously unrecognized link between autophagy and inflammation in shaping cardiac remodeling following myocardial infarction. FYCO1-mediated autophagy promotes myocardial preservation and functional recovery, highlighting autophagic flux as a promising target for cardioprotective interventions.

molecular biology↗

bioRxiv2025

Endothelial expression of ZBTB16 protects against cardiac aging

Background and aimAging significantly increases the risk of cardiovascular diseases, characterized by progressive cardiac dysfunction. The vascular niche is crucial for maintaining cardiac homeostasis, yet endothelial cell (EC) impairment during aging remains poorly understood. This study investigates epigenetically regulated mechanisms mediating EC-dependent cardiac aging and identifies a critical role of Zinc finger and BTB domain-containing protein 16 (ZBTB16). MethodsChromatin accessibility (snATAC-seq) and transcriptomic (snRNA-seq) analyses were performed on aged hearts to identify age-related regulatory changes. Functional studies using genetic models, assessed cardiac aging phenotypes. In vitro assays examined EC senescence and secretory profiles, while co-culture experiments analyzed the impact of ZBTB16-deficient EC supernatants on fibroblasts, cardiomyocytes, and neurons. Overexpression experiments in vitro and in vivo tested the potential for ZBTB16 to mitigate aging-associated dysfunction. ResultsAged hearts exhibited decreased chromatin accessibility and expression of the transcription factor ZBTB16 in both human and mice. Loss of ZBTB16 in young mice, including Zbtb16 haploinsufficient and endothelial-specific knockout mice, led to premature aging, diastolic dysfunction, and increased secretion of pro-fibrotic and inflammatory factors. Supernatants from ZBTB16-deficient ECs activated fibroblasts, induced cardiomyocyte hypertrophy, and impaired neuronal sprouting. Overexpression of ZBTB16 reversed these effects in senescent ECs and aged mice and reduced diastolic dysfunction. Mechanistic studies identified key downstream targets of ZBTB16, including nuclear receptor-interacting protein 1 (NRIP1). ZBTB16 suppressed NRIP1 expression, limiting fibroblast activation and pro-fibrotic signaling. ConclusionsZBTB16 is a key regulator of endothelial function, maintaining vascular niche homeostasis and mitigating aging-associated cardiac dysfunction. Its loss promotes EC senescence and pro-fibrotic signaling, contributing to diastolic dysfunction. Overexpression of ZBTB16 presents a potential therapeutic strategy for preserving cardiac function during aging. These findings establish a novel role for ZBTB16 in endothelial aging and cardiovascular disease prevention. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/681100v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1a56e2org.highwire.dtl.DTLVardef@13e23fforg.highwire.dtl.DTLVardef@ad681eorg.highwire.dtl.DTLVardef@8eca8b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2025

Immunomodulatory endothelial cells contribute to T cell recruitment and activation through antigen presentation on MHC class II

AimsA subset of endothelial cells referred to as immunomodulatory endothelial cells (IMEC) has been proposed to regulate T cell responses in atherosclerosis, but their phenotype and function remain poorly understood. Here, we characterized the inflammation-induced emergence of IMEC and their crosstalk with T cells. Methods and ResultsAn in vitro model to study IMEC was established and characterized using flow cytometry and proteomics. Single-cell transcriptome data from human atherosclerotic arteries as well as single cell transcriptome and endothelial cell-specific translatome data from a murine atherogenesis model were used to determine pathophysiological relevance. Immunopeptidomics was performed to detect antigen presentation. T cell chemotaxis, adhesion and activation were assessed through flow cytometry and microscopy. IMEC were induced by treating human endothelial cells with interleukin-1{beta}, interferon-{gamma}, and transforming growth factor-{beta}2. These cells expressed lower levels of classical endothelial cell markers but expressed major histocompatibility complex (MHC) class II, proteins involved in antigen processing and presentation (CD83, CD80 and CD86) and pro-inflammatory cytokines as well as chemokines, including CXCL9. An endothelial cell subpopulation with similar immunomodulatory features was identified in a mouse model of accelerated atherogenesis as well as in human atheromas. Conditioned medium from IMEC enhanced the migration of peripheral blood mononuclear cells and induced T cell chemotaxis, the latter being partially inhibited by antagonizing CXCL9. Proteins related to glycosaminoglycan degradation were significantly downregulated in IMEC which was relevant inasmuch as the glycocalyx plays a key role in the establishment of chemokine gradients. Indeed, the accumulation of heparan sulfates in IMEC contributed to the adhesion of T cells. Notably, IMEC that had been exposed to monocyte lysates presented 627 peptide antigens on MHC class II and induced T cell activation. ConclusionOur data demonstrate the role of IMEC as non-professional antigen-presenting cells that potentially contribute to T cell-mediated immune responses in cardiovascular disease. Translational PerspectiveThis study characterizes immunomodulatory endothelial cells (IMEC) as critical mediators of vascular inflammation through their capacity to process and present exogenous antigens and activate T cells. Induced by pro-atherogenic cytokines (IFN-{gamma}, IL-1{beta}, TGF-{beta}2), IMEC upregulate MHC class II and costimulatory molecules, promote leukocyte chemotaxis, and enhance T cell adhesion through surface heparan sulfate. The identification of IMEC-like populations in both murine models and human atherosclerotic plaques indicates a conserved immunological function in atherogenesis. These findings position IMEC as novel, non-professional antigen-presenting cells and potential therapeutic targets to modulate vascular immune responses in atherosclerotic cardiovascular disease.

immunology↗

bioRxiv2025

Titin cleavage impairs cardiac mechanical connectivity to drive diastolic failure and fibrosis

Titin, the largest human protein, serves as the elastic backbone of sarcomeres in muscle cells and imparts passive stiffness to cardiomyocytes. While proteolytic cleavage of elastic titin has been linked to cardiovascular disease, the isolated effects of titin stiffness loss in the living heart remain poorly understood. Here, we developed a knock-in mouse model allowing for the selective cleavage of cardiac titin springs in vivo. Using a time-resolved approach combining MRI, echocardiography, immunofluorescence, and molecular profiling, we demonstrate that titin cleavage does not dilate the heart but induces concentric remodeling, impaired diastolic function, and low-output heart failure. Mechanistically, compromised titin-based restoring forces trigger internal mechanical imbalance and dysconnectivity, which activate fibroblasts and promote extracellular matrix remodeling, revealing titins essential role in maintaining cardiac mechanical homeostasis.

physiology↗

bioRxiv2022

A novel role for cystathionine gamma lyase in the control of p53: impact on endothelial senescence and metabolic reprograming

AimsAdvanced age is unequivocally linked to the development of cardiovascular disease, however, the mechanisms leading to loss of endothelial cell regenerative capacity during aging remain poorly understood. Here we aimed to investigate novel mechanisms involved in endothelial cell senescence, that impact on endothelial cell transcription and the vascular repair response upon injury Methods and resultsRNA sequencing of a unique collection of native endothelial cells from young and aged individuals, showed that aging (20 vs. 80 years) is characterized by p53- mediated reprogramming to promote the expression of senescence-associate genes. Molecular analysis revelead that p53 accumulated and acetylated in the nucleus of aged human endothelial cells to suppress glycolysis. Metabolic flux analysis identified an associated reduction in glucose uptake and ATP availability that inhibited the assembly of the telomerase complex, which was essential for proliferation. Nuclear translocation of p53 in aged endothelial cells was attributed to the loss of the vasoprotective enzyme, cystathionine {gamma}-lyase (CSE), which physically anchored p53 in the cytosol. In mice, loss of endothelial cell CSE activated p53 and arrested vascular repair upon injury, while the AAV9 mediated re-expression of an active CSE mutant retained p53 in the cytosol, maintained endothelial glucose metabolism and proliferation, and prevented endothelial cell senescence. Adenoviral overexpression of CSE in human native aged endothelial cells maintained low p53 activity and re-activated telomerase to revert endothelial cell senescence. ConclusionOur data identified the interaction between CSE and p53 as a promising target to preserve vascular regeneration during aging. Key QuestionTo identify the mechanisms that regulate endothelial cell senescence under native conditions and their impact on vascular repair in aging. Key FindingLack of a physical interaction between CSE and p53 metabolically reprogrammes endothelial cells to reduce telomerase activity and halt endothelial cell regeneration. Take home messageInterventions to increase CSE expression represent a novel therapy against p53-induced endothelial cell cycle arrest and senescense Translational perspectiveEndothelial rejuvenation strategies could serve as promising therapies against age-related cardiovascular diseases. By investigating human native endothelial cells from young and aged individuals, we identified that the age-related nuclear accumulation of p53 reprograms endothelial cell metabolism, regulates telomerase activity and inhibits endothelial cell regeneration. Nuclear localization of p53 resulted from a loss of its interaction with the cysteine catabolizing enzyme cystathionine {gamma}-lyase in the cytoplasm. Enhancing the physical interaction of p53 with CSE by gene therapy could revert endothelial cell senescence and activate endothelial reparative responses.

cell biology↗