Non-classical monocytes scavenge the growth factor CSF1 from endothelial cells in the peripheral vascular tree to ensure survival and homeostasis.

Unlike sessile macrophages that occupy specialized tissue niches, non-classical monocytes (NCMs)-circulating phagocytes that patrol and cleanse the luminal surface of the vascular tree-are characterized by constant movement. Here, we examined the nature of the NCM's nurturing niche. Expression of the growth factor CSF1 on endothelial cells was required for survival of NCMs in the bloodstream. Lack of endothelial-derived CSF1 did not affect blood CSF1 concentration, suggesting that NCMs rely on scavenging CSF1 present on endothelial cells. Deletion of the transmembrane chemokine and adhesion factor CX3CL1 on endothelial cells impaired NCM survival. Mechanistically, endothelial-derived CX3CL1 and integrin subunit alpha L (ITGAL) facilitated the uptake of CSF1 by NCMs. CSF1 was produced by all tissular endothelial cells, and deletion of Csf1 in all endothelial cells except bone marrow sinusoids impaired NCM survival, arguing for a model where the full vascular tree acts as a niche for NCMs and where survival and patrolling function are connected.

Spatially targeted chemokine exocytosis guides transmigration at lymphatic endothelial multicellular junctions.

Migrating cells preferentially breach and integrate epithelial and endothelial monolayers at multicellular vertices. These sites are amenable to forces produced by the migrating cell and subsequent opening of the junctions. However, the cues that guide migrating cells to these entry portals, and eventually drive the transmigration process, are poorly understood. Here, we show that lymphatic endothelium multicellular junctions are the preferred sites of dendritic cell transmigration in both primary cell co-cultures and in mouse dermal explants. Dendritic cell guidance to multicellular junctions was dependent on the dendritic cell receptor CCR7, whose ligand, lymphatic endothelial chemokine CCL21, was exocytosed at multicellular junctions. Characterization of lymphatic endothelial secretory routes indicated Golgi-derived RAB6+ vesicles and RAB3+/27+ dense core secretory granules as intracellular CCL21 storage vesicles. Of these, RAB6+ vesicles trafficked CCL21 to the multicellular junctions, which were enriched with RAB6 docking factor ELKS (ERC1). Importantly, inhibition of RAB6 vesicle exocytosis attenuated dendritic cell transmigration. These data exemplify how spatially-restricted exocytosis of guidance cues helps to determine where dendritic cells transmigrate.

Transcellular Barriers to Glucose Delivery in the Body.

Glucose is the universal fuel of most mammalian cells, and it is largely replenished through dietary intake. Glucose availability to tissues is paramount for the maintenance of homeostatic energetics and, hence, supply should match demand by the consuming organs. In its journey through the body, glucose encounters cellular barriers for transit at the levels of the absorbing intestinal epithelial wall, the renal epithelium mediating glucose reabsorption, and the tight capillary endothelia (especially in the brain). Glucose transiting through these cellular barriers must escape degradation to ensure optimal glucose delivery to the bloodstream or tissues. The liver, which stores glycogen and generates glucose de novo, must similarly be able to release it intact to the circulation. We present the most up-to-date knowledge on glucose handling by the gut, liver, brain endothelium, and kidney, and discuss underlying molecular mechanisms and open questions. Diseases associated with defects in glucose delivery and homeostasis are also briefly addressed. We propose that the universal problem of sparing glucose from catabolism in favor of translocation across the barriers posed by epithelia and endothelia is resolved through common mechanisms involving glucose transfer to the endoplasmic reticulum, from where glucose exits the cells via unconventional cellular mechanisms.

A Razor's Edge: Vascular Responses to Acute Inflammatory Lung Injury/Acute Respiratory Distress Syndrome.

Historically considered a metabolically inert cellular layer separating the blood from the underlying tissue, the endothelium is now recognized as a highly dynamic, metabolically active tissue that is critical to organ homeostasis. Under homeostatic conditions, lung endothelial cells (ECs) in healthy subjects are quiescent, promoting vasodilation, platelet disaggregation, and anti-inflammatory mechanisms. In contrast, lung ECs are essential contributors to the pathobiology of acute respiratory distress syndrome (ARDS), as the quiescent endothelium is rapidly and radically altered upon exposure to environmental stressors, infectious pathogens, or endogenous danger signals into an effective and formidable regulator of innate and adaptive immunity. These dramatic perturbations, produced in a tsunami of inflammatory cascade activation, result in paracellular gap formation between lung ECs, sustained lung edema, and multi-organ dysfunction that drives ARDS mortality. The astonishing plasticity of the lung endothelium in negotiating this inflammatory environment and efforts to therapeutically target the aberrant ARDS endothelium are examined in further detail in this review.

A ß-catenin chromobody-based probe highlights endothelial maturation during vascular morphogenesis in vivo.

Visualization of protein dynamics is a crucial step in understanding cellular processes. Chromobodies, fluorescently labelled single-domain antibodies, have emerged as versatile probes for live cell imaging of endogenous proteins. However, how these chromobodies behave in vivo and how accurately they monitor tissue changes remain poorly explored. Here, we generated an endothelial-specific ß-catenin chromobody-derived probe and analyzed its expression pattern during cardiovascular development in zebrafish. Using high-resolution confocal imaging, we show that the chromobody signal correlates with the localization of ß-catenin in the nucleus and at cell-cell junctions, and thereby can be used to assess endothelial maturation. Loss of Cadherin 5 strongly affects the localization of the chromobody at the cell membrane, confirming the cadherin-based adherens junction role of ß-catenin. Furthermore, using a genetic model to block blood flow, we observed that cell junctions are compromised in most endothelial cells but not in the endocardium, highlighting the heterogeneous response of the endothelium to the lack of blood flow. Overall, our data further expand the use of chromobodies for in vivo applications and illustrate their potential to monitor tissue morphogenesis at high resolution.

Blood endothelium transition and phenotypic plasticity: A key regulator of integrity/permeability in response to ischemia.

In the human body, the 1013 blood endothelial cells (ECs) which cover a surface of 500-700 m2 (Mai et al., 2013) are key players of tissue homeostasis, remodeling and regeneration. Blood vessel ECs play a major role in the regulation of metabolic and gaz exchanges, cell trafficking, blood coagulation, vascular tone, blood flow and fluid extravasation (also referred to as blood vascular permeability). ECs are heterogeneous in various capillary beds and have the exquisite capacity to cope with environmental changes by regulating their gene expression. Ischemia has major detrimental effects on the endothelium and ischemia-induced regulation of vascular integrity is of paramount importance for human health, as small amounts of fluid accumulation in the interstitium may be responsible for major effects on organ functions and patients outcome. In this review, we will here focus on the stimuli and the molecular mechanisms that control blood endothelium maintenance and phenotypic plasticity/transition involved in controlling blood capillary leakage that might open new avenues for therapeutic applications.

DLC1 promotes mechanotransductive feedback for YAP via RhoGAP-mediated focal adhesion turnover.

Angiogenesis is a tightly controlled dynamic process demanding a delicate equilibrium between pro-angiogenic signals and factors that promote vascular stability. The spatiotemporal activation of the transcriptional co-factors YAP (herein referring to YAP1) and TAZ (also known WWTR1), collectively denoted YAP/TAZ, is crucial to allow for efficient collective endothelial migration in angiogenesis. The focal adhesion protein deleted-in-liver-cancer-1 (DLC1) was recently described as a transcriptional downstream target of YAP/TAZ in endothelial cells. In this study, we uncover a negative feedback loop between DLC1 expression and YAP activity during collective migration and sprouting angiogenesis. In particular, our study demonstrates that signaling via the RhoGAP domain of DLC1 reduces nuclear localization of YAP and its transcriptional activity. Moreover, the RhoGAP activity of DLC1 is essential for YAP-mediated cellular processes, including the regulation of focal adhesion turnover, traction forces, and sprouting angiogenesis. We show that DLC1 restricts intracellular cytoskeletal tension by inhibiting Rho signaling at the basal adhesion plane, consequently reducing nuclear YAP localization. Collectively, these findings underscore the significance of DLC1 expression levels and its function in mitigating intracellular tension as a pivotal mechanotransductive feedback mechanism that finely tunes YAP activity throughout the process of sprouting angiogenesis.

Intramyocardial Sprouting Tip Cells Specify Coronary Arterialization.

BACKGROUND: The elaborate patterning of coronary arteries critically supports the high metabolic activity of the beating heart. How coronary endothelial cells coordinate hierarchical vascular remodeling and achieve arteriovenous specification remains largely unknown. Understanding the molecular and cellular cues that pattern coronary arteries is crucial to develop innovative therapeutic strategies that restore functional perfusion within the ischemic heart. METHODS: Single-cell transcriptomics and histological validation were used to delineate heterogeneous transcriptional states of the developing and mature coronary endothelium with a focus on sprouting endothelium and arterial cell specification. Genetic lineage tracing and high-resolution 3-dimensional imaging were used to characterize the origin and mechanisms of coronary angiogenic sprouting, as well as to fate-map selective endothelial lineages. Integration of single-cell transcriptomic data from ischemic adult mouse hearts and human embryonic data served to assess the conservation of transcriptional states across development, disease, and species. RESULTS: We discover that coronary arteries originate from cells that have previously transitioned through a specific tip cell phenotype. We identify nonoverlapping intramyocardial and subepicardial tip cell populations with differential gene expression profiles and regulatory pathways. Esm1-lineage tracing confirmed that intramyocardial tip cells selectively contribute to coronary arteries and endocardial tunnels, but not veins. Notably, prearterial cells are detected from development stages to adulthood, increasingly in response to ischemic injury, and in human embryos, suggesting that tip cell-to-artery specification is a conserved mechanism. CONCLUSIONS: A tip cell-to-artery specification mechanism drives arterialization of the intramyocardial plexus and endocardial tunnels throughout life and is reactivated upon ischemic injury. Differential sprouting programs govern the formation and specification of the venous and arterial coronary plexus.

Hypertension: Causes and Consequences of Circadian Rhythms in Blood Pressure.

Hypertension is extremely common, affecting approximately 1 in every 2 adults globally. Chronic hypertension is the leading modifiable risk factor for cardiovascular disease and premature mortality worldwide. Despite considerable efforts to define mechanisms that underlie hypertension, a potentially major component of the disease, the role of circadian biology has been relatively overlooked in both preclinical models and humans. Although the presence of daily and circadian patterns has been observed from the level of the genome to the whole organism, the functional and structural impact of biological rhythms, including mechanisms such as circadian misalignment, remains relatively poorly defined. Here, we review the impact of daily rhythms and circadian systems in regulating blood pressure and the onset, progression, and consequences of hypertension. There is an emphasis on the impact of circadian biology in relation to vascular disease and end-organ effects that, individually or in combination, contribute to complex phenotypes such as cognitive decline and the loss of cardiac and brain health. Despite effective treatment options for some individuals, control of blood pressure remains inadequate in a substantial portion of the hypertensive population. Greater insight into circadian biology may form a foundation for novel and more widely effective molecular therapies or interventions to help in the prevention, treatment, and management of hypertension and its related pathophysiology.

Prostacyclin Synthase Deficiency Leads to Exacerbation or Occurrence of Endothelium-Dependent Contraction and Causes Cardiovascular Disorders Mainly via the Non-TxA2 Prostanoids/TP Axis.

BACKGROUND: Prostaglandin I2 synthesized by endothelial COX (cyclooxygenase) evokes potent vasodilation in some blood vessels but is paradoxically responsible for endothelium-dependent constriction (EDC) in others. Prostaglandin I2 production and EDC may be enhanced in diseases such as hypertension. However, how PGIS (prostaglandin I2 synthase) deficiency affects EDC and how this is implicated in the consequent cardiovascular pathologies remain largely unknown. METHODS: Experiments were performed with wild-type, Pgis knockout (Pgis-/-) and Pgis/thromboxane-prostanoid receptor gene (Tp) double knockout (Pgis-/-Tp-/-) mice and Pgis-/- mice transplanted with unfractionated wild-type or Cox-1-/- bone marrow cells, as well as human umbilical arteries. COX-derived prostanoids were measured by high-performance liquid chromatography-mass spectrometry. Vasomotor responses of distinct types of arteries were assessed by isometric force measurement. Parameters of hypertension, vascular remodeling, and cardiac hypertrophy in mice at different ages were monitored. RESULTS: PGF2α, PGE2, and a trace amount of PGD2, but not thromboxane A2 (TxA2), were produced in response to acetylcholine in Pgis-/- or PGIS-inhibited arteries. PGIS deficiency resulted in exacerbation or occurrence of EDC ex vivo and in vivo. Endothelium-dependent hyperpolarization was unchanged, but phosphorylation levels of eNOS (endothelial nitric oxide synthase) at Ser1177 and Thr495 were altered and NO production and the NO-dependent relaxation evoked by acetylcholine were remarkably reduced in Pgis-/- aortas. Pgis-/- mice developed high blood pressure and vascular remodeling at 16 to 17 weeks and subsequently cardiac hypertrophy at 24 to 26 weeks. Meanwhile, blood pressure and cardiac parameters remained normal at 8 to 10 weeks. Additional ablation of TP (TxA2 receptor) not only restrained EDC and the downregulation of NO signaling in Pgis-/- mice but also ameliorated the cardiovascular abnormalities. Stimulation of Pgis-/- vessels with acetylcholine in the presence of platelets led to increased TxA2 generation. COX-1 disruption in bone marrow-derived cells failed to affect the development of high blood pressure and vascular remodeling in Pgis-/- mice though it largely suppressed the increase of plasma TxB2 (TxA2 metabolite) level. CONCLUSIONS: Our study demonstrates that the non-TxA2 prostanoids/TP axis plays an essential role in mediating the augmentation of EDC and cardiovascular disorders when PGIS is deficient, suggesting TP as a promising therapeutic target in diseases associated with PGIS insufficiency.

Early Injury Landscape in Vein Harvest by Single-Cell and Spatial Transcriptomics.

BACKGROUND: Vein graft failure following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. Although previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on vein graft failure. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury. METHODS: Employing a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing and spatial transcriptomics analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-carotid vein bypass implantation in a canine model (n=4). RESULTS: Spatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P<0.05) involved in the activation of endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells, namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and ECM (extracellular matrix) remodeling throughout the vein wall. Subsequent single-nuclei RNA-sequencing analysis supported these findings and further unveiled distinct EC and fibroblast subpopulations with significant upregulation (P<0.05) of markers related to endothelial injury response and cellular activation of ECs, fibroblasts, and vascular smooth muscle cells. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN, FBN1, and VEGFC, in addition to novel genes of interest, such as GLIS3 and EPHA3. These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the spatial transcriptomics and single-nuclei RNA-sequencing data sets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and fibroblasts were notably enriched in the intima and media of distended veins. Finally, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal-transitioning ECs, protomyofibroblasts, and vascular smooth muscle cells in upregulating signaling pathways associated with cellular proliferation (MDK [midkine], PDGF [platelet-derived growth factor], VEGF [vascular endothelial growth factor]), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension. CONCLUSIONS: Vein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

Senescent endothelial cells promote pathogenic neutrophil trafficking in inflamed tissues.

Cellular senescence is a hallmark of advanced age and a major instigator of numerous inflammatory pathologies. While endothelial cell (EC) senescence is aligned with defective vascular functionality, its impact on fundamental inflammatory responses in vivo at single-cell level remain unclear. To directly investigate the role of EC senescence on dynamics of neutrophil-venular wall interactions, we applied high resolution confocal intravital microscopy to inflamed tissues of an EC-specific progeroid mouse model, characterized by profound indicators of EC senescence. Progerin-expressing ECs supported prolonged neutrophil adhesion and crawling in a cell autonomous manner that additionally mediated neutrophil-dependent microvascular leakage. Transcriptomic and immunofluorescence analysis of inflamed tissues identified elevated levels of EC CXCL1 on progerin-expressing ECs and functional blockade of CXCL1 suppressed the dysregulated neutrophil responses elicited by senescent ECs. Similarly, cultured progerin-expressing human ECs exhibited a senescent phenotype, were pro-inflammatory and prompted increased neutrophil attachment and activation. Collectively, our findings support the concept that senescent ECs drive excessive inflammation and provide new insights into the mode, dynamics, and mechanisms of this response at single-cell level.

Endothelium as a Source of Cardiovascular Toxicity From Antitumor Kinase Inhibitors.

Kinase inhibitors (KIs) targeting oncogenic molecular pathways have revolutionized cancer therapy. By directly targeting specific tumor-driving kinases, targeted therapies have fewer side effects compared with chemotherapy. Despite the enhanced specificity, cardiovascular side effects have emerged with many targeted cancer therapies that limit long-term outcomes in patients with cancer. Endothelial cells lining all blood vessels are critical to cardiovascular health and are also exposed to circulating levels of systemic anticancer therapies. Both on- and off-target perturbation of signaling pathways from KIs can cause endothelial dysfunction, resulting in cardiovascular toxicity. As such, the endothelium is a potential source, and also a therapeutic target for prevention, of cardiovascular toxicity. In this review, we examine the evidence for KI-induced endothelial cell dysfunction as a mechanism for the cardiovascular toxicities of vascular endothelial growth factor inhibitors, BCR-Abl KIs, Bruton tyrosine inhibitors, and emerging information regarding endothelial toxicity of newer classes of KIs.

Single-cell transcriptomics identifies aberrant glomerular angiogenic signalling in the early stages of WT1 kidney disease.

WT1 encodes a podocyte transcription factor whose variants can cause an untreatable glomerular disease in early childhood. Although WT1 regulates many podocyte genes, it is poorly understood which of them are initiators in disease and how they subsequently influence other cell-types in the glomerulus. We hypothesised that this could be resolved using single-cell RNA sequencing (scRNA-seq) and ligand-receptor analysis to profile glomerular cell-cell communication during the early stages of disease in mice harbouring an orthologous human mutation in WT1 (Wt1R394W/+). Podocytes were the most dysregulated cell-type in the early stages of Wt1R394W/+ disease, with disrupted angiogenic signalling between podocytes and the endothelium, including the significant downregulation of transcripts for the vascular factors Vegfa and Nrp1. These signalling changes preceded glomerular endothelial cell loss in advancing disease, a feature also observed in biopsy samples from human WT1 glomerulopathies. Addition of conditioned medium from murine Wt1R394W/+ primary podocytes to wild-type glomerular endothelial cells resulted in impaired endothelial looping and reduced vascular complexity. Despite the loss of key angiogenic molecules in Wt1R394W/+ podocytes, the pro-vascular molecule adrenomedullin was upregulated in Wt1R394W/+ podocytes and plasma and its further administration was able to rescue the impaired looping observed when glomerular endothelium was exposed to Wt1R394W/+ podocyte medium. In comparative analyses, adrenomedullin upregulation was part of a common injury signature across multiple murine and human glomerular disease datasets, whilst other gene changes were unique to WT1 disease. Collectively, our study describes a novel role for altered angiogenic signalling in the initiation of WT1 glomerulopathy. We also identify adrenomedullin as a proangiogenic factor, which despite being upregulated in early injury, offers an insufficient protective response due to the wider milieu of dampened vascular signalling that results in endothelial cell loss in later disease. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

High-dose systemic adeno-associated virus vector administration causes liver and sinusoidal endothelial cell injury.

We analyzed retrospective data from toxicology studies involving administration of high doses of adeno-associated virus expressing different therapeutic transgenes to 21 cynomolgus and 15 rhesus macaques. We also conducted prospective studies to investigate acute toxicity following high-dose systemic administration of enhanced green fluorescent protein-expressing adeno-associated virus to 10 rhesus macaques. Toxicity was characterized by transaminitis, thrombocytopenia, and alternative complement pathway activation that peaked on post-administration day 3. Although most animals recovered, some developed ascites, generalized edema, hyperbilirubinemia, and/or coagulopathy that prompted unscheduled euthanasia. Study endpoint livers from animals that recovered and from unscheduled necropsies of those that succumbed to toxicity were analyzed via hypothesis-driven histopathology and unbiased single-nucleus RNA sequencing. All liver cell types expressed high transgene transcript levels at early unscheduled timepoints that subsequently decreased. Thrombocytopenia coincided with sinusoidal platelet microthrombi and sinusoidal endothelial injury identified via immunohistology and single-nucleus RNA sequencing. Acute toxicity, sinusoidal injury, and liver platelet sequestration were similarly observed with therapeutic transgenes and enhanced green fluorescent protein at doses ≥1 × 1014 GC/kg, suggesting it was the consequence of high-dose systemic adeno-associated virus administration, not green fluorescent protein toxicity. These findings highlight a potential toxic effect of high-dose intravenous adeno-associated virus on nonhuman primate liver microvasculature.

Vascular ATGL-dependent lipolysis and the activation of cPLA2-PGI2 pathway protect against postprandial endothelial dysfunction.

Adipose triglyceride lipase (ATGL) is involved in lipolysis and displays a detrimental pathophysiological role in cardio-metabolic diseases. However, the organo-protective effects of ATGL-induced lipolysis were also suggested. The aim of this work was to characterize the function of lipid droplets (LDs) and ATGL-induced lipolysis in the regulation of endothelial function. ATGL-dependent LDs hydrolysis and cytosolic phospholipase A2 (cPLA2)-derived eicosanoids production were studied in the aorta, endothelial and smooth muscle cells exposed to exogenous oleic acid (OA) or arachidonic acid (AA). Functional effects of ATGL-dependent lipolysis and subsequent activation of cPLA2/PGI2 pathway were also studied in vivo in relation to postprandial endothelial dysfunction.The formation of LDs was invariably associated with elevated production of endogenous AA-derived prostacyclin (PGI2). In the presence of the inhibitor of ATGL or the inhibitor of cytosolic phospholipase A2, the production of eicosanoids was reduced, with a concomitant increase in the number of LDs. OA administration impaired endothelial barrier integrity in vitro that was further impaired if OA was given together with ATGL inhibitor. Importantly, in vivo, olive oil induced postprandial endothelial dysfunction that was significantly deteriorated by ATGL inhibition, cPLA2 inhibition or by prostacyclin (IP) receptor blockade.In summary, vascular LDs formation induced by exogenous AA or OA was associated with ATGL- and cPLA2-dependent PGI2 production from endogenous AA. The inhibition of ATGL resulted in an impairment of endothelial barrier function in vitro. The inhibition of ATGL-cPLA2-PGI2 dependent pathway resulted in the deterioration of endothelial function upon exposure to olive oil in vivo. In conclusion, vascular ATGL-cPLA2-PGI2 dependent pathway activated by lipid overload and linked to LDs formation in endothelium and smooth muscle cells has a vasoprotective role by counterbalancing detrimental effects of lipid overload on endothelial function.

Development and dysfunction of structural cells in eosinophilic esophagitis.

Eosinophilic esophagitis (EoE) is a disorder characterized by dysfunction and chronic local inflammation of the esophagus. The incidence and prevalence of EoE are increasing worldwide. The mechanisms responsible are poorly understood, and effective treatment options are limited. From the lumen outward, the esophagus comprises stratified squamous epithelium, lamina propria, and muscle. The tissue-specific nature of EoE strongly suggests that structural cells in the esophagus are involved in the EoE diathesis. Epithelial basal cell hyperplasia and dilated intercellular spaces are cardinal features of EoE. Some patients with EoE develop lamina propria fibrosis, strictures, or esophageal muscle dysmotility. Clinical symptoms of EoE are only weakly correlated with peak eosinophil count, implying that other cell types contribute to EoE pathogenesis. Epithelial, endothelial, muscle, and fibroblast cells can each initiate inflammation and repair, regulate tissue resident immune cells, recruit peripheral leukocytes, and tailor adaptive immune cell responses. A better understanding of how structural cells maintain tissue homeostasis, respond to cell-intrinsic and cell-extrinsic stressors, and exacerbate and/or resolve inflammatory responses in the esophagus is needed. This knowledge will facilitate the development of more efficacious treatment strategies for EoE that can restore homeostasis of both hematopoietic and structural elements in the esophagus.

IL-4-STAT6 axis amplifies histamine-induced vascular endothelial dysfunction and hypovolemic shock.

BACKGROUND: Mast cell-derived mediators induce vasodilatation and fluid extravasation, leading to cardiovascular failure in severe anaphylaxis. We previously revealed a synergistic interaction between the cytokine IL-4 and the mast cell-derived mediator histamine in modulating vascular endothelial (VE) dysfunction and severe anaphylaxis. The mechanism by which IL-4 exacerbates histamine-induced VE dysfunction and severe anaphylaxis is unknown. OBJECTIVE: We sought to identify the IL-4-induced molecular processes regulating the amplification of histamine-induced VE barrier dysfunction and the severity of IgE-mediated anaphylactic reactions. METHODS: RNA sequencing, Western blot, Ca2+ imaging, and barrier functional analyses were performed on the VE cell line (EA.hy926). Pharmacologic degraders (selective proteolysis-targeting chimera) and genetic (lentiviral short hairpin RNA) inhibitors were used to determine the roles of signal transducer and activator of transcription 3 (STAT3) and STAT6 in conjunction with in vivo model systems of histamine-induced hypovolemic shock. RESULTS: IL-4 enhancement of histamine-induced VE barrier dysfunction was associated with increased VE-cadherin degradation, intracellular calcium flux, and phosphorylated Src levels and required transcription and de novo protein synthesis. RNA sequencing analyses of IL-4-stimulated VE cells identified dysregulation of genes involved in cell proliferation, cell development, and cell growth, and transcription factor motif analyses revealed a significant enrichment of differential expressed genes with putative STAT3 and STAT6 motif. IL-4 stimulation in EA.hy926 cells induced both serine residue 727 and tyrosine residue 705 phosphorylation of STAT3. Genetic and pharmacologic ablation of VE STAT3 activity revealed a role for STAT3 in basal VE barrier function; however, IL-4 enhancement and histamine-induced VE barrier dysfunction was predominantly STAT3 independent. In contrast, IL-4 enhancement and histamine-induced VE barrier dysfunction was STAT6 dependent. Consistent with this finding, pharmacologic knockdown of STAT6 abrogated IL-4-mediated amplification of histamine-induced hypovolemia. CONCLUSIONS: These studies unveil a novel role of the IL-4/STAT6 signaling axis in the priming of VE cells predisposing to exacerbation of histamine-induced anaphylaxis.

Lung-Specific mRNA Delivery Enabled by Sulfonium Lipid Nanoparticles.

Among various mRNA carrier systems, lipid nanoparticles (LNPs) stand out as the most clinically advanced. While current clinical trials of mRNA/LNP therapeutics mainly address liver diseases, the potential of mRNA therapy extends far beyond─yet to be unraveled. To fully unlock the promises of mRNA therapy, there is an urgent need to develop safe and effective LNP systems that can target extrahepatic organs. Here, we report on the development of sulfonium lipid nanoparticles (sLNPs) for systemic mRNA delivery to the lungs. sLNP effectively and specifically delivered mRNA to the lungs following intravenous administration in mice. No evidence of lung and systemic inflammation or toxicity in major organs was induced by sLNP. Our findings demonstrated that the newly developed lung-specific sLNP platform is both safe and efficacious. It holds great promise for advancing the development of new mRNA-based therapies for the treatment of lung-associated diseases and conditions.

Is the peripheral microcirculation a window into the human coronary microvasculature?

An increasing body of evidence suggests a pivotal role for the microvasculature in the development of cardiovascular disease. A dysfunctional coronary microvascular network, specifically within endothelial cells-the inner most cell layer of vessels-is considered a strong, independent risk factor for future major adverse cardiac events. However, challenges exist with evaluating this critical vascular bed, as many of the currently available techniques are highly invasive and cost prohibitive. The more easily accessible peripheral microcirculation has surfaced as a potential surrogate in which to study mechanisms of coronary microvascular dysfunction and likewise may be used to predict poor cardiovascular outcomes. In this review, we critically evaluate a variety of prognostic, physiological, and mechanistic studies in humans to answer whether the peripheral microcirculation can add insight into coronary microvascular health. A conceptual framework is proposed that the health of the endothelium specifically may link the coronary and peripheral microvascular beds. This is supported by evidence showing a correlation between human coronary and peripheral endothelial function in vivo. Although not a replacement for investigating and understanding coronary microvascular function, the microvascular endothelium from the periphery responds similarly to (patho)physiological stress and may be leveraged to explore potential therapeutic pathways to mitigate stress-induced damage.