Remodeling senescent blood vessels
The retina is a thin layer of nervous tissue at the back of the eye that transforms light into neuronal signals. The retina is essential for vision and is supported ...by networks of blood vessels. In diabetic retinopathy, a common cause of vision loss, these microvessels degenerate and regrow in an aberrant manner. Such degeneration and regrowth can compromise the functioning of retinal nerve cells. Binet
et al.
observed that, after rapid proliferation, vascular endothelial cells in diseased blood vessels engaged molecular pathways linked to cellular senescence (see the Perspective by Podrez and Byzova). Senescent vascular units summoned an inflammatory response in which neutrophils extruded neutrophil extracellular traps onto diseased vessels to remodel them. This endogenous repair mechanism promoted the elimination of senescent blood vessels and could lead to beneficial vascular remodeling.
Science
, this issue p.
eaay5356
; see also p.
919
Remodeling of senescent vascular endothelial cells in the retina is mediated through neutrophil extracellular traps.
INTRODUCTION
Vision provides a critical survival advantage but requires a tight coupling between neuronal energy demands and their vascular supply. The degeneration and consequent aberrant regrowth of retinal vasculature is the hallmark of diseases such as diabetic retinopathy, retinopathy of prematurity, and age-related macular degeneration, which collectively are the most common causes of loss of sight in industrialized countries. Although considerable effort has been devoted to understanding how diseased blood vessels form, relatively little is known of the processes at play during late stages of pathological angiogenesis when blood vessels remodel and subsets of diseased vasculature regress.
RATIONALE
The retina is part of the central nervous system and thus has limited regenerative capacity. A relative exception to this rule are retinal blood vessels, which have a greater propensity to remodel depending on metabolic demand. We investigated the cellular mechanisms activated during the remodeling and regression of pathological blood vessels in retinopathy. We focused on a mouse model of oxygen-induced retinopathy, which has distinct and timed phases of vascular degeneration, neovascularization, and vascular regression. Our findings were verified in human patients with proliferative diabetic retinopathy. Understanding how diseased blood vessels remodel and yield functional networks has the potential to lead to strategies that enhance vascular normalization and helps to explain why retinas in certain patients have the propensity to repair themselves more readily than others.
RESULTS
We found that vascular remodeling in retinopathy is associated with bouts of sterile inflammation and tardy recruitment of neutrophils, an immune population typically associated with a first wave of invading leukocytes. We observed that, after rapid proliferation, vascular endothelial cells in diseased blood vessels engaged molecular pathways shared with aging and cellular damage that lead to cellular senescence. Senescent vascular units then released a secretome of cytokines and factors that attracted neutrophils and triggered the production of neutrophil extracellular traps (NETs). Through extrusion of NETs, neutrophils eliminated diseased senescent vasculature by promoting its apoptosis. By crippling the ability of neutrophils to produce NETs by genetically removing the peptidyl arginine deiminase type IV (PAD4) enzyme, clearance of senescent cells was impaired and regression of pathological angiogenesis compromised. Similar effects were observed with the neutrophil-depleting antibody anti-Ly6G or by pharmacological inhibition of the neutrophil receptor CXCR2.
CONCLUSION
We conclude that neutrophils, through the release of NETs, targeted pathological senescent vasculature for clearance and thus prepare the ischemic retina for reparative vascular regeneration. These findings imply that elimination of senescent blood vessels leads to beneficial vascular remodeling. Although cellular senescence is not necessarily synonymous with aging, our study may provide insight into a general mechanism in which senescent endothelial cells trigger NETosis and predispose to thrombotic events such as myocardial infarction, atherosclerosis, and stroke, which are typically seen in older populations.
Senescent blood vessels trigger neutrophil extracellular traps in retinopathy.
(
A
) Human samples and a mouse model were used to elucidate mechanisms of vascular remodeling in retinopathy. (
B
) Upon rapid proliferation, vascular cells in pathological tufts triggered pathways of cellular senescence, leading to cytokine secretion and the recruitment of neutrophils. (
C
) Factors secreted by senescent cells triggered NETosis. (
D
) NETs promoted the removal of senescent endothelial cells, ultimately leading to regression of pathological angiogenesis and promoting the regeneration of functional vessels.
In developed countries, the leading causes of blindness such as diabetic retinopathy are characterized by disorganized vasculature that can become fibrotic. Although many such pathological vessels often naturally regress and spare sight-threatening complications, the underlying mechanisms remain unknown. Here, we used orthogonal approaches in human patients with proliferative diabetic retinopathy and a mouse model of ischemic retinopathies to identify an unconventional role for neutrophils in vascular remodeling during late-stage sterile inflammation. Senescent vasculature released a secretome that attracted neutrophils and triggered the production of neutrophil extracellular traps (NETs). NETs ultimately cleared diseased endothelial cells and remodeled unhealthy vessels. Genetic or pharmacological inhibition of NETosis prevented the regression of senescent vessels and prolonged disease. Thus, clearance of senescent retinal blood vessels leads to reparative vascular remodeling.
Pathological neovascularization in age-related macular degeneration (nvAMD) drives the principal cause of blindness in the elderly. While there is a robust genetic association between genes of innate ...immunity and AMD, genome-to-phenome relationships are low, suggesting a critical contribution of environmental triggers of disease. Possible insight comes from the observation that a past history of infection with pathogens such as Chlamydia pneumoniae, or other systemic inflammation, can predispose to nvAMD in later life. Using a mouse model of nvAMD with prior C. pneumoniae infection, endotoxin exposure, and genetic ablation of distinct immune cell populations, we demonstrated that peripheral infections elicited epigenetic reprogramming that led to a persistent memory state in retinal CX3CR1+ mononuclear phagocytes (MNPs). The immune imprinting persisted long after the initial inflammation had subsided and ultimately exacerbated choroidal neovascularization in a model of nvAMD. Single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) identified activating transcription factor 3 (ATF3) as a central mediator of retina-resident MNP reprogramming following peripheral inflammation. ATF3 polarized MNPs toward a reparative phenotype biased toward production of proangiogenic factors in response to subsequent injury. Therefore, a past history of bacterial endotoxin-induced inflammation can lead to immunological reprograming within CNS-resident MNPs and aggravate pathological angiogenesis in the aging retina.
Abstract
The beneficial effects of brown adipose tissue (BAT) on obesity and associated metabolic diseases are mediated through its capacity to dissipate energy as heat. While immune cells, such as ...tissue-resident macrophages, are known to influence adipose tissue homeostasis, relatively little is known about their contribution to BAT function. Here we report that neuropilin-1 (NRP1), a multiligand single-pass transmembrane receptor, is highly expressed in BAT-resident macrophages. During diet-induced obesity (DIO), myeloid-resident NRP1 influences interscapular BAT mass, and consequently vascular morphology, innervation density and ultimately core body temperature during cold exposure. Thus, NRP1-expressing myeloid cells contribute to the BAT homeostasis and potentially its thermogenic function in DIO.
Cellular adaptation to low oxygen tension triggers primitive pathways that ensure proper cell function. Conditions of hypoxia and low glucose are characteristic of injured tissues and hence ...successive waves of inflammatory cells must be suited to function under low oxygen tension and metabolic stress. While Hypoxia-Inducible Factor (HIF)-1α has been shown to be essential for the inflammatory response of myeloid cells by regulating the metabolic switch to glycolysis, less is known about how HIF1α is triggered in inflammation. Here, we demonstrate that cells of the innate immune system require activity of the inositol-requiring enzyme 1α (IRE1α/XBP1) axis in order to initiate HIF1α-dependent production of cytokines such as IL1β, IL6 and VEGF-A. Knockout of either HIF1α or IRE1α in myeloid cells ameliorates vascular phenotypes in a model of retinal pathological angiogenesis driven by sterile inflammation. Thus, pathways associated with ER stress, in partnership with HIF1α, may co-regulate immune adaptation to low oxygen.
Age-related macular degeneration is a prevalent neuroinflammatory condition and a major cause of blindness driven by genetic and environmental factors such as obesity. In diseases of aging, ...modifiable factors can be compounded over the life span. We report that diet-induced obesity earlier in life triggers persistent reprogramming of the innate immune system, lasting long after normalization of metabolic abnormalities. Stearic acid, acting through Toll-like receptor 4 (TLR4), is sufficient to remodel chromatin landscapes and selectively enhance accessibility at binding sites for activator protein-1 (AP-1). Myeloid cells show less oxidative phosphorylation and shift to glycolysis, ultimately leading to proinflammatory cytokine transcription, aggravation of pathological retinal angiogenesis, and neuronal degeneration associated with loss of visual function. Thus, a past history of obesity reprograms mononuclear phagocytes and predisposes to neuroinflammation.
Obesity is a major risk factor for cancer. Conventional thought suggests that elevated adiposity predisposes to heightened inflammatory stress and potentiates tumor growth, yet underlying mechanisms ...remain ill-defined. Here, we show that tumors from patients with a body mass index >35 carry a high burden of senescent cells. In mouse syngeneic tumor models, we correlated a pronounced accretion of senescent cancer cells with poorly immunogenic tumors when mice were subjected to diet-induced obesity (DIO). Highly immunogenic tumors showed lesser senescence burden suggesting immune-mediated elimination of senescent cancer cells, likely targeted as a consequence of their senescence-associated secretory phenotype. Treatment with the senolytic BH3 mimetic small molecule inhibitor ABT-263 selectively stalled tumor growth in mice with DIO to rates comparable to regular diet-fed mice. Thus, consideration of body adiposity in the selection of cancer therapy may be a critical determinant for disease outcome in poorly immunogenic malignancies.
Cellular adaptation to low oxygen tension triggers primitive pathways that ensure proper cell function. Conditions of hypoxia and low glucose are characteristic of injured tissues and hence ...successive waves of inflammatory cells must be suited to function under low oxygen tension and metabolic stress. While Hypoxia-Inducible Factor (HIF)-1alpha has been shown to be essential for the inflammatory response of myeloid cells by regulating the metabolic switch to glycolysis, less is known about how HIF1alpha is triggered in inflammation. Here, we demonstrate that cells of the innate immune system require activity of the inositol-requiring enzyme 1alpha (IRE1alpha/XBP1) axis in order to initiate HIF1alpha-dependent production of cytokines such as IL1beta, IL6 and VEGF-A. Knockout of either HIF1alpha or IRE1alpha in myeloid cells ameliorates vascular phenotypes in a model of retinal pathological angiogenesis driven by sterile inflammation. Thus, pathways associated with ER stress, in partnership with HIF1alpha, may co-regulate immune adaptation to low oxygen. Keywords: HIF1alpha, Retina, Angiogenesis, Inflammation, IRE1alpha, Myeloid, Mononuclear phagocytes, Microglia, Hypoxia, ER stress
Compromised vascular endothelial barrier function is a salient feature of diabetic complications such as sight-threatening diabetic macular edema (DME). Current standards of care for DME manage ...aspects of the disease, but require frequent intravitreal administration and are poorly effective in large subsets of patients. Here we provide evidence that an elevated burden of senescent cells in the retina triggers cardinal features of DME pathology and conduct an initial test of senolytic therapy in patients with DME. In cell culture models, sustained hyperglycemia provoked cellular senescence in subsets of vascular endothelial cells displaying perturbed transendothelial junctions associated with poor barrier function and leading to micro-inflammation. Pharmacological elimination of senescent cells in a mouse model of DME reduces diabetes-induced retinal vascular leakage and preserves retinal function. We then conducted a phase 1 single ascending dose safety study of UBX1325 (foselutoclax), a senolytic small-molecule inhibitor of BCL-xL, in patients with advanced DME for whom anti-vascular endothelial growth factor therapy was no longer considered beneficial. The primary objective of assessment of safety and tolerability of UBX1325 was achieved. Collectively, our data suggest that therapeutic targeting of senescent cells in the diabetic retina with a BCL-xL inhibitor may provide a long-lasting, disease-modifying intervention for DME. This hypothesis will need to be verified in larger clinical trials. ClinicalTrials.gov identifier: NCT04537884 .
The investigation took place in an area of 2 km² toward the interior of a dry plain of quarzitic sands on the Floristic Managed Reservation San Ubaldo-Sabanalamar; to carry out the study they were ...located six parallel, lineal transepts of 100 m of long for 1 of wide. Was carried out a general list of the flora; in accordance with the habit, the species were determined as nurses and is estimated their covering according with the transept line method, besides calculating the distance in the land that separate each one them, are identified the species that are under the canopy of nurses and also those that occupy the empty spaces among them, counting the number of individuals for species to calculate the frequency and abundance of them, which are the plants that better recruit other species (best nurses), as well as a group of interesting associations for future studies. A floristic inventory was obtained ,was visible that the specific richness of species under the nurses was significantly superior to the empty spaces; through other analyses, was demonstrated that the species that cohabit there were not related phylogenetically, those results prove that relationships of facilitation exist between plants as well as the importance of the nurse effect in typical interactions in extreme environments, information that could be vital for restoring those degraded ecosystems with proven difficulties for the conservation ex situ of their species.
La investigación se llevó a cabo en un área de 2 km2 hacia el interior de las llanuras secas sobre arenas de cuarzo de la Reserva Florística Manejada Sabanalamar-San Ubaldo; para realizar el estudio se trazaron seis transeptos lineales paralelos de 100 m de largo por uno de ancho. Se realiza un levantamiento general de la flora; de acuerdo con el hábito, se determinaron las especies que pueden desempeñarse como nodrizas y se estimó su cobertura siguiendo el método de la línea transepta, además se calculó la distancia, en el terreno, a la que se separan cada una de ellas, se identificaron tanto las especies que están bajo las nodrizas como las que ocupaban los espacios vacíos entre ellas, contabilizando el número de individuos por especie para calcular la frecuencia y abundancia de ellas, cuales son las plantas que más reclutan otras especies o sea las mejores nodrizas así como un grupo de asociaciones interesantes para futuros estudios. Se obtuvo un inventario florístico actualizado, así mismo fue visible que la media de la riqueza específica de especies bajo las nodrizas, era significativamente superior a la de los espacios vacíos; a través de otros análisis, se demostró que las especies que conviven no están filogenéticamente emparentadas, estos resultados evidencian que existen relaciones de facilitación entre plantas así como la importancia del efecto nodriza en interacciones típicas de ambientes extremos, información que puede ser vital a la hora de restaurar estos ecosistemas degradados con dificultades probadas para la conservación ex situ de sus especies.
The investigation took place in an area of 2 km² toward the interior of a dry plain of quarzitic sands on the Floristic Managed Reservation San Ubaldo-Sabanalamar; to carry out the study they were ...located six parallel, lineal transepts of 100 m of long for 1 of wide. Was carried out a general list of the flora; in accordance with the habit, the species were determined as nurses and is estimated their covering according with the transept line method, besides calculating the distance in the land that separate each one them, are identified the species that are under the canopy of nurses and also those that occupy the empty spaces among them, counting the number of individuals for species to calculate the frequency and abundance of them, which are the plants that better recruit other species (best nurses), as well as a group of interesting associations for future studies. A floristic inventory was obtained ,was visible that the specific richness of species under the nurses was significantly superior to the empty spaces; through other analyses, was demonstrated that the species that cohabit there were not related phylogenetically, those results prove that relationships of facilitation exist between plants as well as the importance of the nurse effect in typical interactions in extreme environments, information that could be vital for restoring those degraded ecosystems with proven difficulties for the conservation ex situ of their species.
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