1,721,022 research outputs found
Dysfunctional lysosomal autophagy leads to peroxisomal oxidative burnout and damage during endotoxin-induced stress
No full textMammalian peroxisomes are ubiquitous organelles that possess a comprehensive ensemble of more than 50 enzymes. Cells regulate the number of organelles through dynamic interplay between biogenesis and degradation. Under basal conditions, approximately 30% of the peroxisomal pool is turned over daily. Recycling of peroxisomes is necessary for preservation of their functional competence, and correctly functioning autophagic/lysosomal pathways play a central role. In this study, we investigated (1) how lipopolysaccharide (LPS) influences peroxisomal dynamics and functions; and (2) how a superimposed lysosomal dysfunction affects pexophagy and modifies peroxisomal responses to LPS. We demonstrated that a transiently increased autophagic degradation of peroxisomes, pexophagy, followed by increased proliferation of peroxisomes is a default response to endotoxic stress. Impairment of autophagy due to lysosomal dysfunction, however, abolishes the above peroxisomal dynamics and results in accumulation of functionally compromised peroxisomes. These exhibit an imbalance between preserved hydrogen peroxide (H2O2)-generating acyl-CoA oxidase (ACOX) and dysfunctional/inactivated catalase (CAT), which leads to intra-peroxisomal redox disequilibrium. This metabolic-oxidative mismatch causes further worsening of peroxisomal functions, peroxisomal burnout, with the consequence of enhanced oxidative stress and aggravated organ injury.NIDDK NIH HHS [R01 DK045462, R01 DK084394
Auotphagy: The missing link between non-enzymatically glycated proteins inducing apoptosis and premature senescence of endothelial cells
No full textIn a series of studies into the fate of endothelial cells exposed to non-enzymatically glycated collagen I, a model of cytotoxic of cytotoxic molecules relevant to diabetic vasculopathy, we demonstrate that cells either undergo apoptosis or become prematurely senescent despite relatively spared telomeres and telomerase activity. Our most recent work shows that long-lived advanced glycation end product(AGE)-modified proteins induce (1) lysosomal permeabilization leading to the inefficiency of autophagy due to the reduced digestion (early) and non-fusion (later) of lysosomes with phagosomes-a frustrated autophagy; and (2) accumulation of lipid mediators, such as ceramide and sphingosine-1-phosphate, known to be involved in autophagic cell death. Under the experimental conditions described here, the seesaw relations between premature senescence and apoptosis are integrated by autophagy, which plays a novel function of a cellular switch between states of premature senescence and apoptosis
Sirtuin 1 ablation in endothelial cells is associated with impaired angiogenesis and diastolic dysfunction
No full textDiscordant myocardial growth and angiogenesis can explain left ventricular (LV) hypertrophy progressing toward heart failure with aging. Sirtuin 1 expression declines with age; therefore we explored the role played by angiogenesis and Sirtuin 1 in the development of cardiomyopathy. We compared the cardiac function of 10-to 15-wk-old (wo), 30-40 wo, and 61-70 wo endothelial Sirtuin 1-deleted (Sirt1(endo-/-)) mice and their corresponding knockout controls (Sirt1(Flox)/(Flox)). After 30-40 wk, Sirt1(endo-/)-animals exhibited diastolic dysfunction (DD), decreased mRNA expression of Serca2a in the LV, and decreased capillary density compared with control animals despite a similar VEGFa mRNA expression. However, LV fibrosis and hypoxia-inducible factor (HIF)1 alpha expression were not different. The creation of a transverse aortic constriction (TAC) provoked more severe DD and LV fibrosis in Sirt1(endo-/)-compared with control TAC animals. Although the VEGFa mRNA expression was not different and the protein expression of HIF1 alpha was higher in the Sirt1(endo-/)-TAC animals, capillary density remained reduced. In cultured endothelial cells administration of Sirtuin 1 inhibitor decreased mRNA expression of VEGF receptors FLT 1 and FLK 1. Ex vivo capillary sprouting from aortic explants showed impaired angiogenic response to VEGF in the Sirt1(endo-/-) mice. In conclusion, the data demonstrate 1) a defect in angiogenesis preceding development of DD; 2) dispensability of endothelial Sirtuin 1 under unstressed conditions and during normal aging; and 3) impaired angiogenic adaptation and aggravated DD in Sirt1(endo-/-) mice challenged with LV overload
Weibel–Palade bodies—sentinels of acute stress
No full textWeibel-Palade bodies are uniquely present in endothelial cells and harbor a range of bioactive substances that participate in hemostasis, vasomotion, inflammation and fibrinolysis, in addition to modulating vascular permeability, angiogenic sprouting, and stem cell mobilization. this perspectives article examines the latest insights into the biogenesis of these organelles and the cellular and molecular mechanisms of their exocytosis. in addition, we advance two hypotheses on the pathogenic role of these organelles: first, in the development of endothelial dysfunction associated with the reduction of nitric oxide bioavailability and accumulation of peroxynitrite and second, as a first-line response to acute stress that determines the balance between regenerative and proinflammatory signals.NIDDK NIH HHS [DK54602, R01 DK084394, DK45462, DK052783
Curtailing Endothelial TGF-beta Signaling Is Sufficient to Reduce Endothelial-Mesenchymal Transition and Fibrosis in CKD
No full textExcessive TGF-beta signaling in epithelial cells, pericytes, or fibroblasts has been implicated in CKD. This list has recently been joined by endothelial cells (ECs) undergoing mesenchymal transition. Although several studies focused on the effects of ablating epithelial or fibroblast TGF-beta signaling on development of fibrosis, there is a lack of information on ablating TGF-beta signaling in the endothelium because this ablation causes embryonic lethality. We generated endothelium-specific heterozygous TGF-beta receptor knockout (T beta R parallel to(endo+/-)) mice to explore whether curtailed TGF-beta signaling significantly modifies nephrosclerosis. These mice developed normally, but showed enhanced angiogenic potential compared with T beta R parallel to(endo+/+) mice under basal conditions. After induction of folic acid nephropathy or unilateral ureteral obstruction, T beta R parallel to(endo+/-) mice exhibited less tubulointerstitial fibrosis, enhanced preservation of renal microvasculature, improvement in renal blood flow, and less tissue hypoxia than T beta R parallel to(endo+/+) counterparts. In addition, partial deletion of T beta R parallel to in the endothelium reduced endothelial-to-mesenchymal transition (EndoMT). TGF-beta-induced canonical Smad2 signaling was reduced in T beta R parallel to(endo+/-) ECs; however, activin receptor-like kinase 1 (ALK1)-mediated Smad1/5 phosphorylation in T beta R parallel to(+/-) ECs remained unaffected. Furthermore, the S-endoglin/L-endoglin mRNA expression ratio was significantly lower in T beta R parallel to(+/-) ECs compared with T beta R parallel to(endo+/+) ECs. These observations support the hypothesis that EndoMT contributes to renal fibrosis and curtailing endothelial TGF-beta signals favors Snnad1/5 proangiogenic programs and dictates increased angiogenic responses. Our data implicate endothelial TGF-beta signaling and EndoMT in regulating angiogenic and fibrotic responses to injury
Endothelial Glycocalyx--The Battleground for Complications of Sepsis and Kidney Injury
No full textAfter briefly discussing endothelial glycocalyx and its role in vascular physiology and renal disease, this overview focuses on its degradation very early in the course of microbial sepsis. We describe our recently proposed mechanism for glycocalyx degradation induced by exocytosis of lysosome-related organelles and release of their cargo. Notably, an intermediate in nitric oxide synthesis, NG-hydroxy-l-arginine, shows efficacy in curtailing exocytosis of these organelles and improvement in animal survival. These data not only depict a novel mechanism responsible for very early glycocalyx degradation, but may also outline a potential preventive therapy. The second issue discussed in this article is related to the therapeutic acceleration of restoration of already degraded endothelial glycocalyx. Here, using as an example our recent findings obtained with sulodexide, we illustrate the importance of the expedited repair of degraded endothelial glycocalyx for the survival of animals with severe sepsis. These two focal points of the review on glycocalyx may not only have broader disease applicability, but they may also provide additional evidence to buttress the idea of the importance of endothelial glycocalyx and its maintenance and repair in the prevention and treatment of an array of renal and nonrenal diseases
Table_1_Fibrogenic Secretome of Sirtuin 1-Deficient Endothelial Cells: Wnt, Notch and Glycocalyx Rheostat.docx
Full text linkSirtuins (SIRT) are ubiquitous histone and protein deacetylases and a member of this family, SIRT1, is the best-studied one. Its functions in endothelial cells encompass branching angiogenesis, activation of endothelial nitric oxide synthase, regulation of proapoptotic and proinflammatory pathways, among others. Defective SIRT1 activity has been described in various cardiovascular, renal diseases and in aging-associated conditions. Therefore, understanding of SIRT1-deficient, endothelial dysfunctional phenotype has much to offer clinically. Here, we summarize recent studies by several investigative teams of the characteristics of models of global endothelial SIRT1 deficiency, the causes of facilitative development of fibrosis in these conditions, dissect the protein composition of the aberrant secretome of SIRT1-deficient endothelial cells and present several components of this aberrant secretome that are involved in fibrogenesis via activation of fibroblasts to myofibroblasts. These include ligands of Wnt and Notch pathways, as well as proteolytic fragments of glycocalyx core protein, syndecan-4. The latter finding is crucial for understanding the degradation of glycocalyx that accompanies SIRT1 deficiency. This spectrum of abnormalities associated with SIRT1 deficiency in endothelial cells is essential for understanding the origins and features of endothelial dysfunction in a host of cardiovascular and renal diseases.</p
Endothelial Peroxisomal Dysfunction and Impaired Pexophagy Promotes Oxidative Damage in Lipopolysaccharide-Induced Acute Kidney Injury
No full textAims: We examined that (a) how the endotoxic stress affects peroxisomal function and autophagic degradation of peroxisomes-pexophagy, (b) how a superimposed dysfunction of lysosomes and pexophagy modifies responses to lipopolysaccharide (LPS), and (c) the mechanisms of peroxisomal contribution to renal injury. To accomplish this, we used lysosome-defective Lyst-mice in vivo and primary endothelial cells in vitro, and compared the responses with wild-type (WT) littermates. Results: LPS induced pexophagic degradation, followed by proliferation of peroxisomes in WT mice, which was abolished in Lyst-mice. Lyst-mice exhibited impaired activation of catalase, which together with preserved hydrogen peroxide-generating beta-oxidation resulted in redox disequilibrium. LPS treatment induced a heightened inflammatory response, increased oxidative damage, and aggravated renal injury in Lyst-mice. Similarly, as in vivo, LPS-activated lysosomal (LYS) pexophagy and transiently repressed peroxisomes in vitro, supported by reduced peroxisomal density in the vicinity of lysosomes. Peroxisomal dynamics was also abolished in lysosome-defective cells, which accumulated peroxisomes with compromised functions and intraorganellar redox imbalance. Innovation: We demonstrated that pexophagy is a default response to endotoxic injury. However, when LYS dysfunction (a frequent companion of chronic diseases) is superimposed, recycling and functioning of peroxisomes are impaired, and an imbalance between hydrogen peroxide-generating beta-oxidation and hydrogen peroxide-detoxifying catalase ensues, which ultimately results in peroxisomal burnout. Conclusion: Our data strongly suggest that pexophagy, a cellular mechanism per se, is essential in functional maintenance of peroxisomes during LPS exposure. Inhibition of pexophagy results in accumulation of impaired peroxisomes, redox disequilibrium, and aggravated renal damage
Endothelial Dysfunction is a Superinducer of Syndecan-4: Fibrogenic Role of its Ectodomain
No full textSyndecan-4 (Synd4) is a member of the membrane-spanning, glycocalyx-forming proteoglycan family. It has been suggested that Synd4 participates in renal fibrosis. We compared wild-type and fibrosis-prone endothelial sirtuin 1-deficient (Sirt1(endo-/-)) mice, the latter being a model of global endothelial dysfunction. We performed mass spectrometry analysis, which revealed that Synd4 was highly enriched in the secretome of renal microvascular endothelial cells obtained from Sirt1(endo-/-) mice upon stimulation with transforming growth factor-beta1; notably, all detectable peptides were confined to the ectodomain of Synd4. Elevated Synd4 was due to enhanced NF-kappaB signaling in Sirt1(endo-/-) mice, while its shedding occurred as a result of oxidative stress in Sirt1 deficiency. Synd4 expression was significantly enhanced after unilateral ureteral obstruction compared with contralateral kidneys. Furthermore, hyperplasia of renal myofibroblasts accompanied by microvascular rarefaction and overexpression of Synd4 were detected in Sirt1(endo-/-) mice. The ectodomain of Synd4 acted as a chemoattractant for monocytes with higher levels of macrophages and higher expression levels of Synd4 in the extracellular matrix of Sirt1(endo-/-) mice. In vitro, ectodomain application resulted in generation of myofibroblasts from cultured renal fibroblasts, while in vivo, subcapsular injection of ectodomain increased interstitial fibrosis. Moreover, the endothelial glycocalyx was reduced in Sirt1(endo-/-) mice, highlighting the induction of Synd4 occurring in parallel with the depletion of its intact form and accumulation of its ectodomain in Sirt1(endo-/-) mice. On the basis of our experimental results, we propose that it is the Synd4 ectodomain per se that is partially responsible for fibrosis in unilateral ureteral obstruction, especially when it is combined with endothelial dysfunction. NEW & NOTEWORTHY Our findings suggest that endothelial dysfunction induces the expression of syndecan-4 via activation of the NF-kappaB pathway. Furthermore, we show that syndecan-4 is shed to a greater amount because of increased oxidative stress in dysfunctional endothelial cells and that the release of the syndecan-4 ectodomain leads to tubulointerstitial fibrosis
Endothelial Sirtuin 1 Deficiency Perpetrates Nephrosclerosis through Downregulation of Matrix Metalloproteinase-14: Relevance to Fibrosis of Vascular Senescence
No full textSirtuin 1 (SIRT1) depletion in vascular endothelial cells mediates endothelial dysfunction and premature senescence in diverse cardiovascular and renal diseases. However, the molecular mechanisms underlying these pathologic effects remain unclear. Here, we examined the phenotype of a mouse model of vascular senescence created by genetically ablating exon 4 of Sirt1 in endothelial cells (Sirt1(endo-/-)). Under basal conditions, Sirt1(endo-/-) mice showed impaired endothelium-dependent vasorelaxation and angiogenesis, and fibrosis occurred spontaneously at low levels at an early age. In contrast, induction of nephrotoxic stress (acute and chronic folic acid-induced nephropathy) in Sirt1(endo-/-) mice resulted in robust acute renal functional deterioration followed by an exaggerated fibrotic response compared with control animals. Additional studies identified matrix metalloproteinase-14 (MMP-14) as a target of SIRT1. In the kidneys of Sirt1(endo-/-) mice, impaired angiogenesis, reduced matrilytic activity, and retention of the profibrotic cleavage substrates tissue transglutaminase and endoglin accompanied MMP-14 suppression. Furthermore, restoration of MMP-14 expression in SIRT1-depeleted mice improved angiogenic and matrilytic functions of the endothelium, prevented renal dysfunction, and attenuated nephrosclerosis. Our findings establish a novel mechanistic molecular link between endothelial SIRT1 depletion, downregulation of MMP-14, and the development of nephrosclerosis
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