Functional ultrastructure of the vascular endothelium: changes in various pathologies

Exploring Zika Virus Impact on Endothelial Permeability: Insights into Transcytosis Mechanisms and Vascular Leakage

Treating brain disease is challenging, and the Zika virus (ZIKV) presents a unique obstacle due to its neuroinvasive nature. In this review, we discuss the immunopathogenesis of ZIKV and explore how the virus interacts with the body's immune responses and the role of the protein Mfsd2a in maintaining the integrity of the blood-brain barrier (BBB) during ZIKV neuroinvasion. ZIKV has emerged as a significant public health concern due to its association with severe neurological problems, including microcephaly and Gillain-Barré Syndrome (GBS). Understanding its journey through the brain-particularly its interaction with the placenta and BBB-is crucial. The placenta, which is designed to protect the fetus, becomes a pathway for ZIKV when infected. The BBB is composed of brain endothelial cells, acts as a second barrier, and protects the fetal brain. However, ZIKV finds ways to disrupt these barriers, leading to potential damage. This study explores the mechanisms by which ZIKV enters the CNS and highlights the role of transcytosis, which allows the virus to move through the cells without significantly disrupting the BBB. Although the exact mechanisms of transcytosis are unclear, research suggests that ZIKV may utilize this pathway.

miR-133a-3p/TRPM4 axis improves palmitic acid induced vascular endothelial injury

Background: Vascular endothelial injury is a contributing factor to the development of atherosclerosis and the resulting cardiovascular diseases. One particular factor involved in endothelial cell apoptosis and atherosclerosis is palmitic acid (PA), which is a long-chain saturated fatty acid. In addition, transient receptor potential melastatin 4 (TRPM4), a non-selective cation channel, plays a significant role in endothelial dysfunction caused by various factors related to cardiovascular diseases. Despite this, the specific role and mechanisms of TRPM4 in atherosclerosis have not been fully understood. Methods: The protein and mRNA expressions of TRPM4, apoptosis - and inflammation-related factors were measured after PA treatment. The effect of TRPM4 knockout on the protein and mRNA expression of apoptosis and inflammation-related factors was detected. The changes of intracellular Ca2+, mitochondrial membrane potential, and reactive oxygen species were detected by Fluo-4 AM, JC-1, and DCFH-DA probes, respectively. To confirm the binding of miR-133a-3p to TRPM4, a dual luciferase reporter gene assay was conducted. Finally, the effects of miR-133a-3p and TRPM4 on intracellular Ca2+, mitochondrial membrane potential, and reactive oxygen species were examined. Results: Following PA treatment, the expression of TRPM4 increases, leading to calcium overload in endothelial cells. This calcium influx causes the assemblage of Bcl-2, resulting in the opening of mitochondrial calcium channels and mitochondrial damage, ultimately triggering apoptosis. Throughout this process, the mRNA and protein levels of IL-1β, ICAM-1, and VCAM1 significantly increase. Database screenings and luciferase assays have shown that miR-133a-3p preferentially binds to the 3'UTR region of TRPM4 mRNA, suppressing TRPM4 expression. During PA-induced endothelial injury, miR-133a-3p is significantly decreased, but overexpression of miR-133a-3p can attenuate the progression of endothelial injury. On the other hand, overexpression of TRPM4 counteracts the aforementioned changes. Conclusion: TRPM4 participates in vascular endothelial injury caused by PA. Therefore, targeting TRPM4 or miR-133a-3p may offer a novel pharmacological approach to preventing endothelial injury.

Long term outcomes of ultrathin versus standard thickness second-generation drug eluting stents: Meta-analysis of randomized trials

OBJECTIVE

Identify the effect of ultrathin drug eluting stents on long term outcomes in coronary artery disease.

BACKGROUND

Although second-generation drug eluting stents (DES) are superior to first-generation DES, persistence of adverse outcomes has led to continued refinement in design. Ultrathin second-generation DES have been shown to improve outcomes at 1-year follow-up. Beyond 1-year their effect remains unknown.

METHODS

PubMed, Embase and Cochrane Database were searched for randomized controlled trials that compared ultrathin (defined as <70 um) to standard thickness second-generation DES. Studies were chosen according to the PROSPERO protocol (CRD42020185374). Data from randomized controlled trials were pooled using random-effects model (Mantel-Haenszel). The primary outcome was target lesion failure (TLF) at 2 years, a composite of cardiac death, target vessel myocardial infarction, and ischemia-driven target vessel revascularization. Secondary outcomes included TLF at 3 and 5 years, the components of TLF and definite or probable stent thrombosis. Differences in outcomes between groups were presented in Forest plots as risk ratios (RR) with corresponding 95% confidence intervals (CIs) for each trial.

RESULTS

We identified 18 publications from 10 trials with14,649 patients. At 2-years there was a significant 12% reduction in TLF (RR, 0.88; 95% CI 0.78-0.99; p < 0.05) associated with the use of ultrathin DES. At 3-years, there was a significant 19% reduction in TLF with ultrathin DES (RR, 0.79; 95% CI 0.64-0.98; p < 0.05).

CONCLUSION

In patients undergoing percutaneous coronary intervention, ultrathin DES improve long term clinical outcomes.

Azilsartan ameliorates ox-LDL-induced endothelial dysfunction via promoting the expression of KLF2

Background: Oxidized LDL(Ox-LDL) mediated endothelial dysfunction is involved in the pathogenesis of various cardiovascular diseases, including atherosclerosis. Azilsartan is a potent agent for the treatment of hypertension as the antagonist of the angiotensin II receptor. This study will investigate whether Azilsartan possesses a beneficial effect against endothelial cell dysfunction induced by ox-LDL and explore the underlying preliminary mechanism.

Methods: Ox-LDL was applied to construct an in vitro endothelial dysfunction model in human umbilical vascular endothelial cells (HUVECs). The expression of lectin-type oxidized LDL receptor 1 (LOX-1), endothelial nitric oxide synthase (eNOS), tight junction protein occludin, and transcriptional factor Krüppel-like factor 2 (KLF2) was detected using qRT-PCR and Western blot. ELISA and qRT-PCR were utilized to evaluate the production of chemokine monocyte chemotactic protein 1 (MCP-1) and chemokine (C-X-C motif) Ligand 1 Protein (CXCL1) in treated HUVECs. The generation of nitro oxide (NO) was determined using DAF-FM DA staining assay. KLF2 was silenced by transfecting the cells with specific Small interfering RNA (siRNA). FITC-dextran permeation assay was used to check the endothelial monolayer permeability of treated HUVECs.

Results: Firstly, the elevated expressions of LOX-1, MCP-1, and CXCL-1 induced by stimulation with ox-LDL were significantly suppressed by Azilsartan. The downregulated eNOS and reduced production of NO induced by ox-LDL were reversed by the introduction of Azilsartan. Secondly, enlarged endothelial monolayer permeability and decreased expression of occludin stimulated with ox-LDL were greatly reversed by treatment with Azilsartan but were abolished by silencing the expression of KLF2. Lastly, the inhibited expression of KLF2 induced by ox-LDL was significantly elevated by the introduction of Azilsartan.

Conclusion: Azilsartan might ameliorate ox-LDL-induced endothelial damage via elevating the expression of KLF2.

Endothelial Dysfunction, Inflammation and Coronary Artery Disease: Potential Biomarkers and Promising Therapeutical Approaches

Coronary artery disease (CAD) and its complications are the leading cause of death worldwide. Inflammatory activation and dysfunction of the endothelium are key events in the development and pathophysiology of atherosclerosis and are associated with an elevated risk of cardiovascular events. There is great interest to further understand the pathophysiologic mechanisms underlying endothelial dysfunction and atherosclerosis progression, and to identify novel biomarkers and therapeutic strategies to prevent endothelial dysfunction, atherosclerosis and to reduce the risk of developing CAD and its complications. The use of liquid biopsies and new molecular biology techniques have allowed the identification of a growing list of molecular and cellular markers of endothelial dysfunction, which have provided insight on the molecular basis of atherosclerosis and are potential biomarkers and therapeutic targets for the prevention and or treatment of atherosclerosis and CAD. This review describes recent information on normal vascular endothelium function, as well as traditional and novel potential biomarkers of endothelial dysfunction and inflammation, and pharmacological and non-pharmacological therapeutic strategies aimed to protect the endothelium or reverse endothelial damage, as a preventive treatment for CAD and related complications.

Novel Supreme Drug-Eluting Stents With Early Synchronized Antiproliferative Drug Delivery to Inhibit Smooth Muscle Cell Proliferation After Drug-Eluting Stents Implantation in Coronary Artery Disease: Results of the PIONEER III Randomized Clinical Trial

BACKGROUND

Accelerated endothelial healing after targeted antiproliferative drug delivery may limit the long-term inflammatory response of drug-eluting stents (DESs). The novel Supreme DES is designed to synchronize early drug delivery within 4 to 6 weeks of implantation, leaving behind a prohealing permanent base layer. Whether the Supreme DES is safe and effective in the short term and can improve long-term clinical outcomes is not known.

METHODS

In an international, 2:1 randomized, single-blind trial, we compared treatment with Supreme DES to durable polymer everolimus-eluting stents (DP-EES) in patients with acute and chronic coronary syndromes. The primary end point was target lesion failure-a composite of cardiac death, target vessel myocardial infarction, or clinically driven target lesion revascularization. The trial was designed to demonstrate noninferiority (margin of 3.58%) of the Supreme DES at 12 months compared with DP-EES (URL: https://www.clinicaltrials.gov; Unique identifier: NCT03168776).

RESULTS

From October 2017 to July 2019, a total of 1629 patients were randomly assigned (2:1) to the Supreme DES (N=1086) or DP-EES (N=543). At 12 months, target lesion failure occurred in 57 of 1057 patients (5.4%) in the Supreme DES group and in 27 of 532 patients (5.1%) in the DP-EES group (absolute risk difference, 0.32% [95% CI, -1.87 to 2.5]; P_{noninferiority}=0.002]. There were no significant differences in rates of device success, clinically driven target lesion revascularization, or stent thrombosis at 12 months, and the safety composite of cardiovascular death and target vessel myocardial infarction was 3.5% versus 4.6% (hazard ratio, 0.76 [95% CI, 0.46-1.25]) with Supreme DES compared with DP-EES, although rates of combined clinically and non-clinically driven target lesion revascularization at 12 months were higher with Supreme DES.

CONCLUSIONS

Among patients with acute and chronic coronary syndromes undergoing percutaneous coronary intervention, the Supreme DES proved to be noninferior to the standard DP-EES. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03168776.

Microvasculature in hepatocellular carcinoma: An ultrastructural study

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most vascularized tumor types, and is characterized by development of heterogeneous immature vessels with increased permeability. Here, we analyzed morphology and vascular permeability-related structures in endothelial cells of HCC microvessels.

METHODS

Small (Type I) and large (Type II) peritumoral blood microvessels were assessed in HCC-bearing mice. By transmission electron microscopy, endothelial cell cytoplasm area, free transport vesicles, vesiculo-vacuolar organelles and clathrin-coated vesicles were measured.

RESULTS

The phenotypic changes in the HCC microvessels included presence of sinusoidal capillarization, numerous luminal microprocesses and abnormal luminal channels, irregular dilatations of interendothelial junctions, local detachment of basement membranes and widened extracellular space. Endothelial cells Type I microvessels showed increased vesicular trafficking-related structures.

CONCLUSION

Ultrastructural characteristics of microvessels Type I can associate with HCC new-formed microvessels. The morphological changes observed in HCC microvessels might explain the increased transcellular and paracellular permeability in HCC endothelial cells.

Heteromeric TRPV4/TRPC1 channels mediate calcium-sensing receptor-induced relaxations and nitric oxide production in mesenteric arteries: comparative study using wild-type and TRPC1-/- mice

We have previously provided pharmacological evidence that stimulation of calcium-sensing receptors (CaSR) induces endothelium-dependent relaxations of rabbit mesenteric arteries through activation of heteromeric TRPV4/TRPC1 channels and nitric oxide (NO) production. The present study further investigates the role of heteromeric TRPV4/TRPC1 channels in these CaSR-induced vascular responses by comparing responses in mesenteric arteries from wild-type (WT) and TRPC1^-/- mice. In WT mice, stimulation of CaSR induced endothelium-dependent relaxations of pre-contracted tone and NO generation in endothelial cells (ECs), which were inhibited by the TRPV4 channel blocker RN1734 and the TRPC1 blocking antibody T1E3. In addition, TRPV4 and TRPC1 proteins were colocalised at, or close to, the plasma membrane of endothelial cells (ECs) from WT mice. In contrast, in TRPC1^-/- mice, CaSR-mediated vasorelaxations and NO generation were greatly reduced, unaffected by T1E3, but blocked by RN1734. In addition, the TRPV4 agonist GSK1016790A (GSK) induced endothelium-dependent vasorelaxations which were blocked by RN1734 and T1E3 in WT mice, but only by RN1734 in TRPC1^-/- mice. Moreover, GSK activated cation channel activity with a 6pS conductance in WT ECs but with a 52 pS conductance in TRPC1^-/- ECs. These results indicate that stimulation of CaSR activates heteromeric TRPV4/TRPC1 channels and NO production in ECs, which are responsible for endothelium-dependent vasorelaxations. This study also suggests that heteromeric TRPV4-TRPC1 channels may form the predominant TRPV4-containing channels in mouse mesenteric artery ECs. Together, our data further implicates CaSR-induced pathways and heteromeric TRPV4/TRPC1 channels in the regulation of vascular tone.

Endothelial permeability, LDL deposition, and cardiovascular risk factors-a review

Early atherosclerosis features functional and structural changes in the endothelial barrier function that affect the traffic of molecules and solutes between the vessel lumen and the vascular wall. Such changes are mechanistically related to the development of atherosclerosis. Proatherogenic stimuli and cardiovascular risk factors, such as dyslipidaemias, diabetes, obesity, and smoking, all increase endothelial permeability sharing a common signalling denominator: an imbalance in the production/disposal of reactive oxygen species (ROS), broadly termed oxidative stress. Mostly as a consequence of the activation of enzymatic systems leading to ROS overproduction, proatherogenic factors lead to a pro-inflammatory status that translates in changes in gene expression and functional rearrangements, including changes in the transendothelial transport of molecules, leading to the deposition of low-density lipoproteins (LDL) and the subsequent infiltration of circulating leucocytes in the intima. In this review, we focus on such early changes in atherogenesis and on the concept that proatherogenic stimuli and risk factors for cardiovascular disease, by altering the endothelial barrier properties, co-ordinately trigger the accumulation of LDL in the intima and ultimately plaque formation.

ATRA improves endothelial dysfunction in atherosclerotic rabbits by decreasing CAV‑1 expression and enhancing eNOS activity

The aim of the present study was to explore the protective effects and possible mechanisms of all‑trans‑retinoic acid (ATRA) against atherosclerosis (AS). Rabbits were randomly allocated for standard or high‑fat diet with or without ATRA. After 12 weeks, the aortic rings of the rabbits were removed. Endothelium‑dependent relaxation (EDR) induced by acetylcholine and non‑endothelium‑dependent relaxation induced by sodium nitroprusside in the thoracic aorta were evaluated. NO level and eNOS activity were measured according to the protocol of NO and eNOS ELISA kits. The permeability and morphology of the arterial walls were identified by immunofluorescence and H&E staining respectively. The expression of caveolin‑1 (CAV‑1) and occludin was analyzed using western blotting and immunohistochemistry. The EDR function was significantly reduced in the AS rabbits compared with the normal group, however it was elevated following treatment with ATRA. The eNOS activity and NO level were reduced in the AS group, however were notably increased following oral administration of ATRA. There was an enhancement of endothelial permeability in the AS group compared with the normal group, which decreased following ATRA treatment. Western blot analysis and immunohistochemical analysis identified an increase in occludin expression after treatment with ATRA, in contrast to CAV‑1 expression under the same conditions. ATRA is able to ameliorate high‑fat‑induced AS in rabbits, which is mediated through the activation of eNOS and downregulating CAV‑1 expression.

Transcytosis Involvement in Transport System and Endothelial Permeability of Vascular Leakage during Dengue Virus Infection

The major role of endothelial cells is to maintain homeostasis of vascular permeability and to preserve the integrity of vascular vessels to prevent fluid leakage. Properly functioning endothelial cells promote physiological balance and stability for blood circulation and fluid components. A monolayer of endothelial cells has the ability to regulate paracellular and transcellular pathways for transport proteins, solutes, and fluid. In addition to the paracellular pathway, the transcellular pathway is another route of endothelial permeability that mediates vascular permeability under physiologic conditions. The transcellular pathway was found to be associated with an assortment of disease pathogeneses. The clinical manifestation of severe dengue infection in humans is vascular leakage and hemorrhagic diatheses. This review explores and describes the transcellular pathway, which is an alternate route of vascular permeability during dengue infection that corresponds with the pathologic finding of intact tight junction. This pathway may be the route of albumin transport that causes endothelial dysfunction during dengue virus infection.

Investigation of highly expressed PCSK9 in atherosclerotic plaques and ox-LDL-induced endothelial cell apoptosis

The present study aimed to explore the direct toxicity of proprotein convertase subtilisin/kexin type 9 (PCSK9) to atherosclerosis (AS) and its association with apoptotic endothelial cells. Apolipoprotein E−/− mice were randomly divided into two groups, control and experimental. The control group was administered a normal diet and the experimental group was administered a high-fat diet. After 20 weeks, the aorta was isolated and dissected. Hematoxylin and eosin staining, and immunohistochemical analysis were performed. Human umbilical vein endothelial cells were incubated with varied concentrations of oxidized low-density lipoprotein (ox-LDL) for different times. The apoptotic rate was detected by flow cytometry. Western blotting and reverse transcription-quantitative polymerase chain reaction analysis were conducted to detect the expression of PCSK9, B-cell lymphoma 2 (Bcl-2), bcl-2-like protein 4 (Bax) and caspase-3. Short hairpin (sh) RNA-PCSK9 was transfected into endothelial cells using lentiviral transfection. The expression levels of PCSK9, Bax, Bcl-2, caspase-3 and the mitogen-activated protein kinase (MAPK) pathway proteins were detected. The high-fat group was successfully established as an AS model and PCSK9 was highly expressed in the AS plaque. Treatment with ox-LDL induced apoptosis and increased mRNA and protein levels of PCSK9. PCSK9 mRNA and proteins levels were downregulated by shRNA-PCSK9. The deficiency of PCSK9 markedly inhibited the expression of pro-apoptotic proteins and promoted anti-apoptotic proteins. In addition, phosphorylation of p38 and c-Jun N-terminal kinases was altered by shRNA-PCSK9. Targeting of PCSK9 by shRNA-PCSK9 may repress endothelial cell apoptosis through MAPK signaling in AS, providing a novel direction for understanding the mechanism and treatment of AS.

Caveolae-mediated albumin transcytosis is enhanced in dengue-infected human endothelial cells: A model of vascular leakage in dengue hemorrhagic fever

Vascular leakage is a life-threatening complication of dengue virus (DENV) infection. Previously, association between “paracellular” endothelial hyperpermeability and plasma leakage had been extensively investigated. However, whether “transcellular” endothelial leakage is involved in dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) remained unknown. We thus investigated effects of DENV (serotype 2) infection on transcellular transport of albumin, the main oncotic plasma protein, through human endothelial cell monolayer by Western blotting, immunofluorescence staining, fluorescence imaging, and fluorometry. The data showed that Alexa488-conjugated bovine serum albumin (Alexa488-BSA) was detectable inside DENV2-infected cells and its level was progressively increased during 48-h post-infection. While paracellular transport could be excluded using FITC-conjugated dextran, Alexa488-BSA was progressively increased and decreased in lower and upper chambers of Transwell, respectively. Pretreatment with nystatin, an inhibitor of caveolae-dependent endocytic pathway, significantly decreased albumin internalization into the DENV2-infected cells, whereas inhibitors of other endocytic pathways showed no significant effects. Co-localization of the internalized Alexa488-BSA and caveolin-1 was also observed. Our findings indicate that DENV infection enhances caveolae-mediated albumin transcytosis through human endothelial cells that may ultimately induce plasma leakage from intravascular compartment. Further elucidation of this model in vivo may lead to effective prevention and better therapeutic outcome of DHF/DSS.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.

Alteration of actin dependent signaling pathways associated with membrane microdomains in hyperlipidemia

Background

Membrane microdomains represent dynamic membrane nano-assemblies enriched in signaling molecules suggesting their active involvement in not only physiological but also pathological molecular processes. The hyperlipidemic stress is a major risk factor of atherosclerosis, but its exact mechanisms of action at the membrane microdomains level remain elusive. The aim of the present study was to determine whether membrane-cytoskeleton proteome in the pulmonary tissue could be modulated by the hyperlipidemic stress, a major risk factor of atherosclerosis.

Results

High resolution mass spectrometry based proteomics analysis was performed for detergent resistant membrane microdomains isolated from lung homogenates of control, ApoE deficient and statin treated ApoE deficient mice. The findings of the study allowed the identification with high confidence of 1925 proteins, 291 of which were found significantly altered by the modified genetic background, by the statin treatment or both conditions. Principal component analysis revealed a proximal partitioning of the biological replicates, but also a distinct spatial scattering of the sample groups, highlighting different quantitative profiles. The statistical significant over-representation of Regulation of actin cytoskeleton, Focal adhesion and Adherens junction Kyoto Encyclopedia of Genes and Genomes signaling pathways was demonstrated through bioinformatics analysis. The three inter-relation maps comprised 29 of regulated proteins, proving membrane-cytoskeleton coupling targeting and alteration by hyperlipidemia and/or statin treatment.

Conclusions

The findings of the study allowed the identification with high confidence of the main proteins modulated by the hyperlipidemic stress involved in the actin-dependent pathways. Our study provides the basis for future work probing how the protein activities at the membrane-cytoskeleton interface are dependent upon genetic induced hyperlipidemia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-015-0087-0) contains supplementary material, which is available to authorized users.

Oxidized LDL and NO synthesis--Biomarkers of endothelial dysfunction and ageing

Oxidized LDL (oxLDL) and nitric oxide (NO) exert contradictory actions within the vascular endothelium microenvironment influencing key events in atherogenesis. OxLDL and NO are so far regarded as representative parameters of oxidative stress and endothelial dysfunction, new targets in prevention, diagnosis and therapy of cardiovascular diseases, and also as candidate biomarkers in evaluating the human biological age. The aim of this review is to explore recent literature on molecular mechanisms and pathophysiological relationships between LDL oxidation, NO synthesis and vascular endothelium function/dysfunction in ageing, focusing on the following aspects: (1) the impact of metabolic status on both LDL oxidation and NO synthesis in relation with oxidative stress, (2) the use of oxidized LDL and NO activity as biomarkers in human studies reporting on cardiovascular outcomes, and (3) evidences supporting the importance of oxidized LDL and NO activity as relevant biomarkers in vascular ageing and age-related diseases.

An activator of mTOR inhibits oxLDL-induced autophagy and apoptosis in vascular endothelial cells and restricts atherosclerosis in apolipoprotein E⁻/⁻ mice

Oxidized low-density lipoprotein (oxLDL) inhibits mammalian target of rapamycin (mTOR) and induces autophagy and apoptosis in vascular endothelial cells (VECs) that play very critical roles for the cardiovascular homostasis. We recently defined 3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran-2(3H)-one (3BDO) as a new activator of mTOR. Therefore, we hypothesized that 3BDO had a protective role in VECs and thus stabilized atherosclerotic lesions in apolipoprotein E^-/- (apoE^-/-) mice. Our results showed that oxLDL inhibited the activity of mTOR and increased the protein level of autophagy-related 13 (ATG13) and its dephosphorylation, thus inducing autophagy in human umbilical vein endothelial cells (HUVECs). All of these effects were strongly inhibited by 3BDO. In vivo experiments confirmed that 3BDO activated mTOR and decreased the protein level of ATG13 in the plaque endothelium of apoE^-/- mice. Importantly, 3BDO did not affect the activity of mTOR and autophagy in macrophage cell line RAW246.7 and vascular smooth muscle cells of apoE^-/- mice, but suppressed plaque endothelial cell death and restricted atherosclerosis development in the mice. 3BDO protected VECs by activating mTOR and thus stabilized atherosclerotic lesions in apoE^-/- mice.

Impact of exercise and metabolic disorders on heat shock proteins and vascular inflammation

Heat shock proteins (Hsp) play critical roles in the body's self-defense under a variety of stresses, including heat shock, oxidative stress, radiation, and wounds, through the regulation of folding and functions of relevant cellular proteins. Exercise increases the levels of Hsp through elevated temperature, hormones, calcium fluxes, reactive oxygen species (ROS), or mechanical deformation of tissues. Isotonic contractions and endurance- type activities tend to increase Hsp60 and Hsp70. Eccentric muscle contractions lead to phosphorylation and translocation of Hsp25/27. Exercise-induced transient increases of Hsp inhibit the generation of inflammatory mediators and vascular inflammation. Metabolic disorders (hyperglycemia and dyslipidemia) are associated with type 1 diabetes (an autoimmune disease), type 2 diabetes (the common type of diabetes usually associated with obesity), and atherosclerotic cardiovascular disease. Metabolic disorders activate HSF/Hsp pathway, which was associated with oxidative stress, increased generation of inflammatory mediators, vascular inflammation, and cell injury. Knock down of heat shock factor-1 (HSF1) reduced the activation of key inflammatory mediators in vascular cells. Accumulating lines of evidence suggest that the activation of HSF/Hsp induced by exercise or metabolic disorders may play a dual role in inflammation. The benefits of exercise on inflammation and metabolism depend on the type, intensity, and duration of physical activity.

The importance of the endothelium in atherothrombosis and coronary stenting

Deployment of drug-eluting stents instead of bare-metal stents has dramatically reduced restenosis rates, but rates of very late stent thrombosis (>1 year postimplantation) have increased. Vascular endothelial cells normally provide an efficient barrier against thrombosis, lipid uptake, and inflammation. However, endothelium that has regenerated after percutaneous coronary intervention is incompetent in terms of its integrity and function, with poorly formed cell junctions, reduced expression of antithrombotic molecules, and decreased nitric oxide production. Delayed arterial healing, characterized by poor endothelialization, is the primary cause of late (1 month-1 year postimplantation) and very late stent thrombosis following implantation of drug-eluting stents. Impairment of vasorelaxation in nonstented proximal and distal segments of stented coronary arteries is more severe with drug-eluting stents than bare-metal stents, and stent-induced flow disturbances resulting in complex spatiotemporal shear stress can also contribute to increased thrombogenicity and inflammation. The incompetent endothelium leads to late stent thrombosis and the development of in-stent neoatherosclerosis. The process of neoatherosclerosis occurs more rapidly, and more frequently, following deployment of drug-eluting stents than bare-metal stents. Improved understanding of vascular biology is crucial for all cardiologists, and particularly interventional cardiologists, as maintenance of a competently functioning endothelium is critical for long-term vascular health.

A new, rapid and reproducible method to obtain high quality endothelium in vitro

Human umbilical vein endothelial cells (HUVECs) cultured in vitro are a commonly used experimental system. When properly differentiated they acquire the so-called cobblestone phenotype; thereby mimicking an endothelium in vivo that can be used to shed light on multiple endothelial-related processes. In the present paper we report a simple, flexible, fast and reproducible method for an efficient isolation of viable HUVECs. The isolation is performed by sequential short trypsinization steps at room temperature. As umbilical cords are often damaged during labor, it is noteworthy that this new method can be applied even to short pieces of cord with success. In addition, we describe how to culture HUVECs as valid cobblestone cells in vitro on different types of extracellular matrix (basement membrane matrix, fibronectin and gelatin). We also show how to recognize mature cobblestone HUVECs by ordinary phase contrast microscopy. Our HUVEC model is validated as a system that retains important features inherent to the human umbilical vein endothelium in vivo. Phase contrast microscopy, immuno-fluorescence and electron microscopy reveal a tight cobblestone monolayer. Therein cells show Weibel-Palade bodies, caveolae and junctional complexes (comparable to the in vivo situation, as also shown in this study) and can internalize human low density lipoprotein. Isolation and culture of HUVECs as reported in this paper will result in an endothelium-mimicking experimental model convenient for multiple research goals.

Modified low density lipoproteins decrease the activity and expression of lysosomal acid lipase in human endothelial and smooth muscle cells

Lysosomal acid lipase (LAL), the only lysosomal enzyme involved in the hydrolysis of LDL-cholesteryl esters, is a key regulator of cellular cholesterol and fatty acid homeostasis and its deficiency contributes to the pathophysiology of various diseases. In this study, we questioned whether oxidized or glycated LDL, a common occurrence in atherosclerosis and diabetes, affect the activity and expression of LAL in vascular endothelial cells (EC) and smooth muscle cells (SMC). LAL activity and expression were assayed in cultured human EC and SMC exposed to oxidized LDL (oxLDL), (±)9-hydroxyoctadecadienoic acid-cholesteryl ester (HODE), glycated LDL (gLDL), or native LDL (nLDL) as control, in the presence or absence of LXR or PPAR-gamma agonists. We found that LAL activity and expression were significantly down regulated by oxLDL and HODE in EC, and by gLDL in SMC. The LXR agonist T0901317 reversed the decreased LAL expression in modified LDL- or HODE-exposed EC (P < 0.001) and in gLDL-exposed SMC, whereas PPAR-gamma agonist rosiglitazone induced a low effect only in EC. In conclusion, modified LDL down regulates LAL expression in human EC and SMC by a process involving the LXR signaling pathway. This is the first demonstration that modified LDL modulate LAL expression, in a cell specific manner.

The vascular contribution to Alzheimer's disease

AD (Alzheimer's disease) is a progressive neurodegenerative disease of unknown origin. Despite questions as to the underlying cause(s) of this disease, shared risk factors for both AD and atherosclerotic cardiovascular disease indicate that vascular mechanisms may critically contribute to the development and progression of both AD and atherosclerosis. An increased risk of developing AD is linked to the presence of the apoE4 (apolipoprotein E4) allele, which is also strongly associated with increased risk of developing atherosclerotic cardiovascular disease. Recent studies also indicate that cardiovascular risk factors, including elevated blood cholesterol and triacylglycerol (triglyceride), increase the likelihood of AD and vascular dementia. Lipids and lipoproteins in the circulation interact intimately with the cerebrovasculature, and may have important effects on its constituent brain microvascular endothelial cells and the adjoining astrocytes, which are components of the neurovascular unit. The present review will examine the potential mechanisms for understanding the contributions of vascular factors, including lipids, lipoproteins and cerebrovascular Abeta (amyloid beta), to AD, and suggest therapeutic strategies for the attenuation of this devastating disease process. Specifically, we will focus on the actions of apoE, TGRLs (triacylglycerol-rich lipoproteins) and TGRL lipolysis products on injury of the neurovascular unit and increases in blood-brain barrier permeability.

Characterization of endothelial basement membrane nanotopography in rhesus macaque as a guide for vessel tissue engineering

Basement membranes have many features that greatly influence vascular endothelial cell function, including a complex three-dimensional topography. As a first step in the design and development of vascular prosthetics, we undertook a thorough characterization of the topographic features of endothelial vascular basement membranes utilizing transmission electron microscopy and scanning electron microscopy. Specifically, we quantitatively analyzed the topographic features present in the aorta, carotid, saphenous, and inferior vena cava vessels in the rhesus macaque. Our results indicate that vascular basement membranes are composed of a complex meshwork consisting of pores and fibers in the submicron (100-1000 nm) and nanoscale (1-100 nm) range, consistent with what has previously been reported in basement membranes of other tissues. We found significant differences (p<0.05) in basement membrane thickness and pore and fiber diameter depending on the location and physical properties of the vessel. These results have relevance to our fundamental understanding of vascular endothelial cell-matrix interactions in health and disease, evolving strategies in cell and tissue engineering and the design of cardiovascular prosthetic devices.

Administration of sesamol improved blood-brain barrier function in streptozotocin-induced diabetic rats

Uncontrolled or poorly controlled blood glucose during diabetes is an important factor in worsened vascular function. While evidence suggests that hyperglycemia-induced oxidative stress plays a prominent role in development of microangiopathy of the retina, kidney, and nerves, the role oxidative stress plays on blood-brain barrier (BBB) function and structure has lagged behind. In this study, a natural antioxidant, sesamol, was administered to streptozotocin (STZ)-induced diabetic rats to examine the role that oxidative stress plays on BBB structure and function. Experiments were conducted at 56 days after STZ injection. Male Sprague-Dawley rats randomly were divided into four treatment groups CON--control; STZ--STZ-induced diabetes; CON + S--control + sesamol; STZ + S--STZ-induced diabetes + sesamol. Functional and structural changes to the BBB were measured by in situ brain perfusion and western blot analysis of changes in tight junction protein expression. Oxidative stress markers were visualized by fluorescent confocal microscopy and assayed by spectrophotometric analysis. Results demonstrated that the increased BBB permeability observed in STZ-induced diabetic rats was attenuated in STZ + S rats to levels observed in CON. Sesamol treatment reduced the negative impact of STZ-induced diabetes on tight junction protein expression in isolated cerebral microvessels. Oxidative stress markers were elevated in STZ as compared to CON. STZ + S displayed an improved antioxidant capacity which led to a reduced expression of superoxide and peroxynitrite and reduced lipid peroxidation. In conclusion, this study showed that sesamol treatment enhanced antioxidant capacity of the diabetic brain and led to decreased perturbation of hyperglycemia-induced changes in BBB structure and function.

Membrane rafts and caveolae in cardiovascular signaling

PURPOSE OF REVIEW

Substantial evidence documents the key role of lipid (membrane) rafts and caveolae as microdomains that concentrate a wide variety of receptors and postreceptor components regulated by hormones, neurotransmitters and growth factors.

RECENT FINDINGS

Recent data document that these microdomains are important in regulating vascular endothelial and smooth muscle cells and renal epithelial cells, and particularly in signal transduction across the plasma membrane.

SUMMARY

Raft/caveolae domains are cellular regions, including in cardiovascular and renal epithelial cells, which organize a large number of signal transduction components, thereby providing spatially and temporally efficient regulation of cell function.

Vascular endothelium in atherosclerosis

Their strategic location between blood and tissue and their constitutive properties allow endothelial cells (EC) to monitor the transport of plasma molecules, by employing bidirectional receptor-mediated and receptor-independent transcytosis and endocytosis, and to regulate vascular tone, cellular cholesterol and lipid homeostasis. These cells are also involved in signal transduction, immunity, inflammation and haemostasis. Cardiovascular risk factors, such as hyperlipaemia/dyslipidaemia trigger the molecular machinery of EC to respond to insults by modulation of their constitutive functions followed by dysfunction and ultimately by injury and apoptosis. The gradual activation of EC consists initially in the modulation of two constitutive functions: (1) permeability, i.e. increased transcytosis of lipoproteins, and (2) biosynthetic activity, i.e. enhanced synthesis of the basement membrane and extracellular matrix. The increased transcytosis and the reduced efflux of beta-lipoproteins (betaLp) lead to their retention within the endothelial hyperplasic basal lamina as modified lipoproteins (MLp) and to their subsequent alteration (oxidation, glycation, enzymatic modifications). MLp generate chemoattractant and inflammatory molecules, triggering EC dysfunction (appearance of new adhesion molecules, secretion of chemokines, cytokines), characterised by monocyte recruitment, adhesion, diapedesis and residence within the subendothelium. In time, EC in the athero-prone areas alter their net negative surface charge, losing their non-thrombogenic ability, become loaded with lipid droplets and turn into foam cells. Prolonged and/or repeated exposure to cardiovascular risk factors can ultimately exhaust the protective effect of the endogenous anti-inflammatory system within EC. As a consequence, EC may progress to senescence, lose their integrity and detach into the circulation.

Magnetic and fluorescent nanoparticles for multimodality imaging

The development of nanoparticulate contrast agents is providing an increasing contribution to the field of diagnostic and molecular imaging. Such agents provide several advantages over traditional compounds. First, they may contain a high payload of the contrast-generating material, which greatly improves their detectability. Second, multiple properties may be easily integrated within one nanoparticle to allow its detection with several imaging techniques or to include therapeutic qualities. Finally, the surface of such nanoparticles may be modified to improve circulation half-lives or to attach targeting groups. Magnetic resonance imaging and optical techniques are highly complementary imaging methods. Combining these techniques would therefore have significant advantages and may be realized through the use of nanoparticulate contrast agents. This review gives a survey of the different types of fluorescent and magnetic nanoparticles that have been employed for both magnetic resonance and optical imaging studies.

Endothelial cells and macrophages, partners in atherosclerotic plaque progression

Heart disease and stroke, the main cardiovascular diseases (CVD), have become global epidemics in our days. High levels of cholesterol and other abnormal lipids are among the main risk factors of atherosclerosis, the number one killer in the world. However, recent advances in CVD treatment together with improvements in surgical techniques have increased the quality of life and reduced premature death rates and disabilities. Nevertheless, they still add a heavy burden to the rising global costs of health care. The medical priorities highlight not only the need for early recognition of the warning signs of a heart attack, but also the need for early biomarkers for prevention. Two active partners in the development and progression of atherosclerotic plaques are the macrophages and endothelial cells that influence each other and modify the microenvironment composition of the plaque leading to either rapid progression or regression of individual lesions in patients. In this review we address two specific aspects related to atherosclerosis: i) the way in which folic acid and folic acid conjugates may be helpful to identify activated macrophages and ii) the high potential of proteomic analysis to evidence and identify the multiple changes induced in activated vascular cells.