Cyclic strain-induced monocyte chemotactic protein-1 gene expression in endothelial cells involves reactive oxygen species activation of activator protein 1

Platelet and endothelial cell responses under concurrent shear stress and tensile strain

Thrombosis can lead to significant mortality and morbidity. Both platelets and vascular endothelial cells play significant roles in thrombosis. Platelets' response to blood flow-induced shear stress can vary greatly depending on shear stress magnitude, pattern and shear exposure time. Endothelial cells are also sensitive to the biomechanical environment. Endothelial cell activation and dysfunction can occur under low oscillatory shear stress and low tensile strain. Platelet and endothelial cell interaction can also be affected by mechanical conditions. The goal of this study was to investigate how blood flow-induced shear stress, vascular wall tensile strain, platelet-endothelial cell stress history, and platelet-endothelial cell interaction affect platelet thrombogenicity. Platelets and human coronary artery endothelial cells were pretreated with physiological and pathological shear stress and/or tensile strain separately. The pretreated cells were then put together and exposed to pulsatile shear stress and cyclic tensile strain simultaneously in a shearing-stretching device. Following treatment, platelet thrombin generation rate, platelet and endothelial cell activation, and platelet adhesion to endothelial cells was measured. The results demonstrated that shear stress pretreatment of endothelial cells and platelets caused a significant increase in platelet thrombin generation rate, cell surface phosphatidylserine expression, and adhesion to endothelial cells. Shear stress pretreatment of platelets and endothelial cells attenuated endothelial cell ICAM-1 expression under stenosis conditions, as well as vWF expression under recirculation conditions. These results indicate that platelets are sensitized by prior shearing, while in comparison, the interaction with shear stress-pretreated platelets may reduce endothelial cell sensitivity to pathological shear stress and tensile strain.

Sox13 is a novel flow-sensitive transcription factor that prevents inflammation by repressing chemokine expression in endothelial cells

Atherosclerosis is a chronic inflammatory disease and occurs preferentially in arterial regions exposed to disturbed blood flow (d-flow) while the stable flow (s-flow) regions are spared. D-flow induces endothelial inflammation and atherosclerosis by regulating endothelial gene expression partly through the flow-sensitive transcription factors (FSTFs). Most FSTFs, including the well-known Kruppel-like factors KLF2 and KLF4, have been identified from in vitro studies using cultured endothelial cells (ECs). Since many flow-sensitive genes and pathways are lost or dysregulated in ECs during culture, we hypothesized that many important FSTFs in ECs in vivo have not been identified. We tested the hypothesis by analyzing our recent gene array and single-cell RNA sequencing (scRNAseq) and chromatin accessibility sequencing (scATACseq) datasets generated using the mouse partial carotid ligation model. From the analyses, we identified 30 FSTFs, including the expected KLF2/4 and novel FSTFs. They were further validated in mouse arteries in vivo and cultured human aortic ECs (HAECs). These results revealed 8 FSTFs, SOX4, SOX13, SIX2, ZBTB46, CEBPβ, NFIL3, KLF2, and KLF4, that are conserved in mice and humans in vivo and in vitro. We selected SOX13 for further studies because of its robust flow-sensitive regulation, preferential expression in ECs, and unknown flow-dependent function. We found that siRNA-mediated knockdown of SOX13 increased endothelial inflammatory responses even under the unidirectional laminar shear stress (ULS, mimicking s-flow) condition. To understand the underlying mechanisms, we conducted an RNAseq study in HAECs treated with SOX13 siRNA under shear conditions (ULS vs. oscillatory shear mimicking d-flow). We found 94 downregulated and 40 upregulated genes that changed in a shear- and SOX13-dependent manner. Several cytokines, including CXCL10 and CCL5, were the most strongly upregulated genes in HAECs treated with SOX13 siRNA. The robust induction of CXCL10 and CCL5 was further validated by qPCR and ELISA in HAECs. Moreover, the treatment of HAECs with Met-CCL5, a specific CCL5 receptor antagonist, prevented the endothelial inflammation responses induced by siSOX13. In addition, SOX13 overexpression prevented the endothelial inflammation responses. In summary, SOX13 is a novel conserved FSTF, which represses the expression of pro-inflammatory chemokines in ECs under s-flow. Reduction of endothelial SOX13 triggers chemokine expression and inflammatory responses, a major proatherogenic pathway.

Mitochondria Lead the Way: Mitochondrial Dynamics and Function in Cellular Movements in Development and Disease

The dynamics, distribution and activity of subcellular organelles are integral to regulating cell shape changes during various physiological processes such as epithelial cell formation, cell migration and morphogenesis. Mitochondria are famously known as the powerhouse of the cell and play an important role in buffering calcium, releasing reactive oxygen species and key metabolites for various activities in a eukaryotic cell. Mitochondrial dynamics and morphology changes regulate these functions and their regulation is, in turn, crucial for various morphogenetic processes. In this review, we evaluate recent literature which highlights the role of mitochondrial morphology and activity during cell shape changes in epithelial cell formation, cell division, cell migration and tissue morphogenesis during organism development and in disease. In general, we find that mitochondrial shape is regulated for their distribution or translocation to the sites of active cell shape dynamics or morphogenesis. Often, key metabolites released locally and molecules buffered by mitochondria play crucial roles in regulating signaling pathways that motivate changes in cell shape, mitochondrial shape and mitochondrial activity. We conclude that mechanistic analysis of interactions between mitochondrial morphology, activity, signaling pathways and cell shape changes across the various cell and animal-based model systems holds the key to deciphering the common principles for this interaction.

Knockdown of hypoxia-inducible factor 1-alpha (HIF1α) interferes with angiopoietin-like protein 2 (ANGPTL2) to attenuate high glucose-triggered hypoxia/reoxygenation injury in cardiomyocytes

To investigate the role of hypoxia-inducible factor 1-alpha (HIF1A) in hypoxia/reoxygenation (H/R) injury of cardiomyocytes induced by high glucose (HG). The in vitro model of coronary heart disease with diabetes was that H9c2 cells were stimulated by H/R and HG. Quantitative reverse transcription PCR (RT-qPCR) and Western blot analysis were used to detect the expression of HIF1A and angiopoietin-like protein 2 (ANGPTL2) in H9c2 cells. Cell viability and apoptosis were, respectively, estimated by Cell Counting Kit 8 (CCK-8) and TUNEL assays. Lactate dehydrogenase (LDH) activity, inflammation and oxidative stress were in turn detected by their commercial assay kits. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were used to confirm the association between HIF1A and ANGPTL2 promoter. The expression of nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway-related proteins and apoptosis-related proteins were also detected by Western blot analysis. As a result, ANGPTL2 expression was upregulated in H9c2 cells induced by HG or/and H/R. ANGPTL2 positively modulated HIF1A expression in H9c2 cells. HG or/and H/R suppressed the cell viability and promoted apoptosis, inflammatory response and oxidative stress levels in H9c2 cells. However, the knockdown of ANGPTL2 could reverse the above phenomena in H/R-stimulated-H9c2 cells through activation of Nrf2/HO-1 pathway. HIF1A transcriptionally activated ANGPTL2 expression. The effect of knockdown of ANGPTL2 on H/R triggered-H9c2 cells was weakened by HIF1A overexpression. In conclusion, knockdown of HIF1A downregulated ANGPTL2 to alleviate H/R injury in HG-induced H9c2 cells by activating the Nrf2/HO-1 pathway.

Acute hypotension attenuates brachial flow-mediated dilation in young healthy men

PURPOSE

This study aimed to test our hypothesis that acute hypotension attenuates brachial flow-mediated dilation (FMD) as an index of endothelial function in healthy humans.

METHODS

Twelve healthy men (21.8 ± 1.6 years, body mass index; 22.2 ± 1.6 kg/m²) participated in this study. Brachial FMD was measured in three trials: standardized FMD protocol (control trial), abrupt decrease in blood pressure (BP) via thigh cuff inflation-deflation (hypotension trial) and decrease in shear rate (SR) via a shortened forearm occlusion time (SR reduction trial). Brachial diameter and blood velocity were measured using Duplex ultrasound.

RESULTS

Mean arterial pressure during reactive hyperaemia showed a marked decrease in the hypotension trial (- 23.7 ± 6.0 mmHg), but not in the control and SR reduction trials. SR area under the curve was attenuated in the SR reduction trial (P < 0.001), but not in the control and hypotension trials (P = 0.316). Consequently, FMD was attenuated in the hypotension and SR reduction trials compared with that in the control trial (P = 0.003 and P = 0.043, respectively), and was attenuated to a greater extent in the hypotension trial compared with the SR reduction trial (P = 0.006; control, 6.9 ± 3.5%; hypotension, 3.5 ± 1.7%; SR reduction, 5.0 ± 2.2%). After adjusting FMD using SR, FMD remained attenuated in the hypotension trial (P = 0.014), but not in the SR reduction trial.

CONCLUSION

Our findings indicate that arterial pressure as well as sympathetic nervous system activation could be an important determinant of FMD. Blunted FMD of peripheral arteries may be a rational response to restore BP and/or prevent further reduction of BP following acute hypotension in healthy humans.

Cafestol and Kahweol: A Review on Their Bioactivities and Pharmacological Properties

Cafestol and kahweol are natural diterpenes extracted from coffee beans. In addition to the effect of raising serum lipid, in vitro and in vivo experimental results have revealed that the two diterpenes demonstrate multiple potential pharmacological actions such as anti-inflammation, hepatoprotective, anti-cancer, anti-diabetic, and anti-osteoclastogenesis activities. The most relevant mechanisms involved are down-regulating inflammation mediators, increasing glutathione (GSH), inducing apoptosis of tumor cells and anti-angiogenesis. Cafestol and kahweol show similar biological activities but not exactly the same, which might due to the presence of one conjugated double bond on the furan ring of the latter. This review aims to summarize the pharmacological properties and the underlying mechanisms of cafestol-type diterpenoids, which show their potential as functional food and multi-target alternative medicine.

Endothelial Cell Biomechanical Responses are Dependent on Both Fluid Shear Stress and Tensile Strain

Introduction

The goal of this study was to investigate how concurrent shear stress and tensile strain affect endothelial cell biomechanical responses.

Methods

Human coronary artery endothelial cells were exposed to concurrent pulsatile shear stress and cyclic tensile strain in a programmable shearing and stretching device. Three shear stress-tensile strain conditions were used: (1) pulsatile shear stress at 1 Pa and cyclic tensile strain at 7%, simulating normal stress/strain conditions in a healthy coronary artery; (2) shear stress at 3.7 Pa and tensile strain at 3%, simulating pathological stress/strain conditions near a stenosis; (3) shear stress at 0.7 Pa and tensile strain at 5%, simulating pathological stress/strain conditions in a recirculation zone. Cell morphology was quantified using immunofluorescence microscopy. Cell surface PECAM-1 phosphorylation, ICAM-1 expression, ERK1/2 and NF-κB activation were measured using ELISA or Western blot.

Results

Simultaneous stimulation from pulsatile shear stress and cyclic tensile strain induced a significant increase in cell area, compared to that induced by shear stress or tensile strain alone. The combined stimulation caused significant increases in PECAM-1 phosphorylation. The combined stimulation also significantly enhanced EC surface ICAM-1 expression (compared to that under shear stress alone) and transcriptional factor NF-κB activation (compared to that under control conditions).

Conclusion

Pulsatile shear stress and cyclic tensile strain could induce increased but not synergistic effect on endothelial cell morphology or activation. The combined mechanical stimulation can be relayed from cell membrane to nucleus. Therefore, to better understand how mechanical conditions affect endothelial cell mechanotransduction and cardiovascular disease development, both shear stress and tensile strain need to be considered.

Mechanosensing and Mechanoregulation of Endothelial Cell Functions

Vascular endothelial cells (ECs) form a semiselective barrier for macromolecules and cell elements regulated by dynamic interactions between cytoskeletal elements and cell adhesion complexes. ECs also participate in many other vital processes including innate immune reactions, vascular repair, secretion, and metabolism of bioactive molecules. Moreover, vascular ECs represent a unique cell type exposed to continuous, time-dependent mechanical forces: different patterns of shear stress imposed by blood flow in macrovasculature and by rolling blood cells in the microvasculature; circumferential cyclic stretch experienced by the arterial vascular bed caused by heart propulsions; mechanical stretch of lung microvascular endothelium at different magnitudes due to spontaneous respiration or mechanical ventilation in critically ill patients. Accumulating evidence suggests that vascular ECs contain mechanosensory complexes, which rapidly react to changes in mechanical loading, process the signal, and develop context-specific adaptive responses to rebalance the cell homeostatic state. The significance of the interactions between specific mechanical forces in the EC microenvironment together with circulating bioactive molecules in the progression and resolution of vascular pathologies including vascular injury, atherosclerosis, pulmonary edema, and acute respiratory distress syndrome has been only recently recognized. This review will summarize the current understanding of EC mechanosensory mechanisms, modulation of EC responses to humoral factors by surrounding mechanical forces (particularly the cyclic stretch), and discuss recent findings of magnitude-specific regulation of EC functions by transcriptional, posttranscriptional and epigenetic mechanisms using -omics approaches. We also discuss ongoing challenges and future opportunities in developing new therapies targeting dysregulated mechanosensing mechanisms to treat vascular diseases. © 2019 American Physiological Society. Compr Physiol 9:873-904, 2019.

Aerobic training status does not attenuate prolonged sitting-induced lower limb vascular dysfunction

This study examined if the degree of aerobic training protects against the lower limb vascular dysfunction associated with a prolonged sitting bout. Ten young, aerobically trained (AT) and 10 young, untrained (UT) individuals completed a prolonged (3 h) sitting bout. Leg vascular function was measured prior to and at 1.5 and 3 h into the prolonged sitting bout using the passive leg movement (PLM) technique. PLM-induced hyperemia was significantly reduced from baseline at 1.5 and 3 h into the prolonged sitting bout in both groups when evaluated as peak change in leg blood flow from baseline (Δ LBF) (UT: 956 ± 140, 586 ± 80, and 599 ± 96 mL·min^-1 at baseline, 1.5 h, and 3 h, respectively; AT: 955 ± 183, 789 ± 193, and 712 ± 131 mL·min^-1 at baseline, 1.5 h, and 3 h, respectively) and LBF area under the curve (UT: 283 ± 73, 134 ± 31, and 164 ± 42 mL·min^-1 at baseline, 1.5 h, and 3 h, respectively; AT: 336 ± 86, 242 ± 86, and 245 ± 73 mL·min^-1 at baseline, 1.5 h, and 3 h, respectively), but no significant differences between groups were revealed. No significant correlations were observed when examining the relationship between maximal oxygen uptake (relative and absolute) and reductions in leg vascular function at 1.5 and 3 h into the prolonged sitting bout. This study revealed that aerobic training did not provide a protective effect against prolonged sitting-induced lower limb vascular dysfunction and further highlights the importance of reducing excessive sitting in all populations.

The role of senescence, telomere dysfunction and shelterin in vascular aging

In the United States and other westernized nations, CVDs are the leading cause of death in adults over 65 years of age. Large artery stiffness and endothelial dysfunction are increased with age and age-associated arterial dysfunction is an important antecedent of CVDs. One age-associated change that may contribute to vascular dysfunction and CVD risk is an increase in the number of resident senescent cells in the vasculature. Senescent cells display a pro-oxidant, pro-inflammatory phenotype known as the SASP. However, the mechanisms that drive the SASP and the vascular aging phenotype remain elusive. A putative mechanism is the involvement of oxidative stress and inflammation in telomere function. Telomeres are the end caps of chromosomes which are maintained by a six-protein complex known as shelterin. Disruption of shelterin can uncap telomeres and induce cellular senescence. Accordingly, in this review, we propose that oxidative stress and inflammation disrupt shelterin in vascular cells, driving telomere dysfunction and that this mechanism may be responsible for the induction of SASP. The proposed mechanisms may represent some of the initial changes that lead to vascular dysfunction in advanced age.

Cafestol Inhibits Cyclic-Strain-Induced Interleukin-8, Intercellular Adhesion Molecule-1, and Monocyte Chemoattractant Protein-1 Production in Vascular Endothelial Cells

Moderate coffee consumption is inversely associated with cardiovascular disease mortality; however, mechanisms underlying this causal effect remain unclear. Cafestol, a diterpene found in coffee, has various properties, including an anti-inflammatory property. This study investigated the effect of cafestol on cyclic-strain-induced inflammatory molecule secretion in vascular endothelial cells. Cells were cultured under static or cyclic strain conditions, and the secretion of inflammatory molecules was determined using enzyme-linked immunosorbent assay. The effects of cafestol on mitogen-activated protein kinases (MAPK), heme oxygenase-1 (HO-1), and sirtuin 1 (Sirt1) signaling pathways were examined using Western blotting and specific inhibitors. Cafestol attenuated cyclic-strain-stimulated intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein- (MCP-) 1, and interleukin- (IL-) 8 secretion. Cafestol inhibited the cyclic-strain-induced phosphorylation of extracellular signal-regulated kinase and p38 MAPK. By contrast, cafestol upregulated cyclic-strain-induced HO-1 and Sirt1 expression. The addition of zinc protoporphyrin IX, sirtinol, or Sirt1 silencing (transfected with Sirt1 siRNA) significantly attenuated cafestol-mediated modulatory effects on cyclic-strain-stimulated ICAM-1, MCP-1, and IL-8 secretion. This is the first study to report that cafestol inhibited cyclic-strain-induced inflammatory molecule secretion, possibly through the activation of HO-1 and Sirt1 in endothelial cells. The results provide valuable insights into molecular pathways that may contribute to the effects of cafestol.

Macrophage-dependent impairment of α2-adrenergic autoreceptor inhibition of Ca2+ channels in sympathetic neurons from DOCA-salt but not high-fat diet-induced hypertensive rats

DOCA-salt and obesity-related hypertension are associated with inflammation and sympathetic nervous system hyperactivity. Prejunctional α₂-adrenergic receptors (α₂ARs) provide negative feedback to norepinephrine release from sympathetic nerves through inhibition of N-type Ca²⁺ channels. Increased neuronal norepinephrine release in DOCA-salt and obesity-related hypertension occurs through impaired α₂AR signaling; however, the mechanisms involved are unclear. Mesenteric arteries are resistance arteries that receive sympathetic innervation from the superior mesenteric and celiac ganglia (SMCG). We tested the hypothesis that macrophages impair α₂AR-mediated inhibition of Ca²⁺ channels in SMCG neurons from DOCA-salt and high-fat diet (HFD)-induced hypertensive rats. Whole cell patch-clamp methods were used to record Ca²⁺ currents from SMCG neurons maintained in primary culture. We found that DOCA-salt, but not HFD-induced, hypertension caused macrophage accumulation in mesenteric arteries, increased SMCG mRNA levels of monocyte chemoattractant protein-1 and tumor necrosis factor-α, and impaired α₂AR-mediated inhibition of Ca²⁺ currents in SMCG neurons. α₂AR dysfunction did not involve changes in α₂AR expression, desensitization, or downstream signaling factors. Oxidative stress impaired α₂AR-mediated inhibition of Ca²⁺ currents in SMCG neurons and resulted in receptor internalization in human embryonic kidney-293T cells. Systemic clodronate-induced macrophage depletion preserved α₂AR function and lowered blood pressure in DOCA-salt rats. HFD caused hypertension without obesity in Sprague-Dawley rats and hypertension with obesity in Dahl salt-sensitive rats. HFD-induced hypertension was not associated with inflammation in SMCG and mesenteric arteries or α₂AR dysfunction in SMCG neurons. These results suggest that macrophage-mediated α₂AR dysfunction in the mesenteric circulation may only be relevant to mineralocorticoid-salt excess. NEW & NOTEWORTHY Here, we identify a contribution of macrophages to hypertension development through impaired α₂-adrenergic receptor (α₂AR)-mediated inhibition of sympathetic nerve terminal Ca²⁺ channels in DOCA-salt hypertensive rats. Impaired α₂AR function may involve oxidative stress-induced receptor internalization. α₂AR dysfunction may be unique to mineralocorticoid-salt excess, as it does not occur in obesity-related hypertension.

NADPH oxidase 4 mediates ROS production in radiation-induced senescent cells and promotes migration of inflammatory cells

Excessive DNA damage induced by ionising radiation (IR) to normal tissue cells is known to trigger cellular senescence, a process termed stress-induced premature senescence (SIPS). SIPS is often accompanied by the production of reactive oxygen species (ROS), and this is reported to be important for the initiation and maintenance of SIPS. However, the source of ROS during SIPS after IR and their significance in radiation-induced normal tissue damage remain elusive. In the present study, we tested the hypothesis that the NADPH oxidase (NOX) family of proteins mediates ROS production in SIPS-induced cells after IR and plays a role in SIPS-associated biological events. X-irradiation of primary mouse embryonic fibroblasts (MEFs) resulted in cellular senescence and the concomitant increase of intracellular ROS. Among all six murine NOX isoforms (NOX1-4 and DUOX1/2), only NOX4 was detectable under basal conditions and was upregulated following IR. In addition, radiation-induced ROS production was diminished by genetic or pharmacological inhibition of NOX4. Meanwhile, NOX4 deficiency did not affect the induction of cellular senescence after IR. Furthermore, the migration of human monocytic U937 cells to the culture medium collected from irradiated MEFs was significantly reduced by NOX4 inhibition, suggesting that NOX4 promotes the recruitment of inflammatory cells. Collectively, our findings imply that NOX4 mediates ROS production in radiation-induced senescent cells and contributes to normal tissue damage after IR via the recruitment of inflammatory cells and the exacerbation of tissue inflammation.

NADPH Oxidase-4 Driven Cardiac Macrophage Polarization Protects Against Myocardial Infarction-Induced Remodeling

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The reactive oxygen species–generating enzyme NADPH oxidase 4 (Nox4) is up-regulated in the heart after myocardial infarction.

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Mice with cardiomyocyte-targeted overexpression of Nox4 display an increase in macrophages in the heart, with skewing of polarization toward an M2 phenotype.

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After myocardial infarction, Nox4-induced skewing of macrophage polarization toward an M2 phenotype is accompanied by a higher survival, decreased cardiac remodeling, and improved contractile function.

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The protective effects of cardiomyocyte Nox4 may, in part, involve the attenuation of cardiac matrix metalloproteinase–2 activity.

The reactive oxygen species–generating enzyme NADPH oxidase 4 (Nox4) is up-regulated in the heart after myocardial infarction (MI). Mice with cardiomyocyte-targeted Nox4 overexpression (TG) displayed increased macrophages in the heart at baseline, with skewing toward an M2 phenotype compared with wild-type controls (WT). After MI, TG mice had a higher proportion of M2 macrophages along with higher survival, decreased cardiac remodeling, and better contractile function than wild-type mice. The post-MI increase in cardiac matrix metalloproteinase–2 activity was substantially blunted in TG mice. These results indicate that cardiomyocyte Nox4 modulates macrophage polarization toward an M2 phenotype, resulting in improved post-MI survival and remodeling, likely through the attenuation of cardiac matrix metalloproteinase–2 activity.

Stretchable impedance sensor for mammalian cell proliferation measurements

This paper presents the fabrication and testing of a novel stretchable electric cell-substrate impedance sensing (ECIS) lab on a chip device. This is the first time that ECIS electrodes were fabricated on a stretchable polydimethylsiloxane (PDMS) substrate and ECIS measurements were performed on mammalian cells exposed to cyclic strain. The stretchable ECIS biosensors simulate in vitro the dynamic environment of organisms, such as pulsation, bending and stretching, which enables investigations on cell behavior that undergoes mechanical stimuli in biological tissue. Usually cell-based assays used in cell mechanobiology rely on endpoint cell tests, which provide a limited view on dynamic cellular mechanisms. The ECIS technique is a label-free, real-time and noninvasive method to monitor the cellular response to mechanical stimuli. Bovine aortic endothelial cells (BAECs) have been used in this research because the BAECs are exposed in vivo to cyclic physiologic elongation produced by blood circulation in the arteries. These innovative stretchable ECIS biosensors were used to analyze the proliferation of BAECs under different cyclic mechanical stimulations. The results of fluorescence based cell proliferation assays confirmed that the stretchable ECIS sensors were able to analyze in real-time the BAEC proliferation. The novel stretchable ECIS sensor has the ability to analyse cell proliferation, determine the cell number and density, and apply mechanical stimulation at the same time.

Endovascular biopsy: Strategy for analyzing gene expression profiles of individual endothelial cells obtained from human vessels✩

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The combination of guide wire sampling, FACS and high throughput microfluidic single-cell quantitative RT-PCR, is an effective strategy for analyzing molecular changes of ECs in vascular lesions.

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Although heterogeneous, the ECs in normal iliac artery fall into two classes.

Purpose

To develop a strategy of achieving targeted collection of endothelial cells (ECs) by endovascular methods and analyzing the gene expression profiles of collected single ECs.

Methods and results

134 ECs and 37 leukocytes were collected from four patients' intra-iliac artery endovascular guide wires by fluorescence activated cell sorting (FACS) and analyzed by single-cell quantitative RT-PCR for expression profile of 48 genes. Compared to CD45⁺ leukocytes, the ECs expressed higher levels (p < 0.05) of EC surface markers used on FACS and other EC related genes. The gene expression profile showed that these isolated ECs fell into two clusters, A and B, that differentially expressed 19 genes related to angiogenesis, inflammation and extracellular matrix remodeling, with cluster B ECs have demonstrating similarities to senescent or aging ECs.

Conclusion

Combination of endovascular device sampling, FACS and single-cell quantitative RT-PCR is a feasible method for analyzing EC gene expression profile in vascular lesions.

Carbon monoxide induces heme oxygenase-1 to modulate STAT3 activation in endothelial cells via S-glutathionylation

IL-6/STAT3 pathway is involved in a variety of biological responses, including cell proliferation, differentiation, apoptosis, and inflammation. In our present study, we found that CO releasing molecules (CORMs) suppress IL-6-induced STAT3 phosphorylation, nuclear translocation and transactivity in endothelial cells (ECs). CO is a byproduct of heme degradation mediated by heme oxygenase (HO-1). However, CORMs can induce HO-1 expression and then inhibit STAT3 phosphorylation. CO has been found to increase a low level ROS and which may induce protein glutathionylation. We hypothesized that CORMs increases protein glutathionylation and inhibits STAT3 activation. We found that CORMs increase the intracellular GSSG level and induce the glutathionylation of multiple proteins including STAT3. GSSG can inhibit STAT3 phosphorylation and increase STAT3 glutathionylation whereas the antioxidant enzyme catalase can suppress the glutathionylation. Furthermore, catalase blocks the inhibition of STAT3 phosphorylation by CORMs treatment. The inhibition of glutathione synthesis by BSO was also found to attenuate STAT3 glutathionylation and its inhibition of STAT3 phosphorylation. We further found that HO-1 increases STAT3 glutathionylation and that HO-1 siRNA attenuates CORM-induced STAT3 glutathionylation. Hence, the inhibition of STAT3 activation is likely to occur via a CO-mediated increase in the GSSG level, which augments protein glutathionylation, and CO-induced HO-1 expression, which may enhance and maintain its effects in IL-6-treated ECs.

NADPH oxidases in vascular pathology

SIGNIFICANCE

Reactive oxygen species (ROS) play a critical role in vascular disease. While there are many possible sources of ROS, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases play a central role. They are a source of "kindling radicals," which affect other enzymes, such as nitric oxide synthase endothelial nitric oxide synthase or xanthine oxidase. This is important, as risk factors for atherosclerosis (hypertension, diabetes, hypercholesterolemia, and smoking) regulate the expression and activity of NADPH oxidases in the vessel wall.

RECENT ADVANCES

There are seven isoforms in mammals: Nox1, Nox2, Nox3, Nox4, Nox5, Duox1 and Duox2. Nox1, Nox2, Nox4, and Nox5 are expressed in endothelium, vascular smooth muscle cells, fibroblasts, or perivascular adipocytes. Other homologues have not been found or are expressed at very low levels; their roles have not been established. Nox1/Nox2 promote the development of endothelial dysfunction, hypertension, and inflammation. Nox4 may have a role in protecting the vasculature during stress; however, when its activity is increased, it may be detrimental. Calcium-dependent Nox5 has been implicated in oxidative damage in human atherosclerosis.

CRITICAL ISSUES

NADPH oxidase-derived ROS play a role in vascular pathology as well as in the maintenance of normal physiological vascular function. We also discuss recently elucidated mechanisms such as the role of NADPH oxidases in vascular protection, vascular inflammation, pulmonary hypertension, tumor angiogenesis, and central nervous system regulation of vascular function and hypertension.

FUTURE DIRECTIONS

Understanding the role of individual oxidases and interactions between homologues in vascular disease is critical for efficient pharmacological regulation of vascular NADPH oxidases in both the laboratory and clinical practice.

Arterial wall stress controls NFAT5 activity in vascular smooth muscle cells

Background

Nuclear factor of activated T‐cells 5 (NFAT5) has recently been described to control the phenotype of vascular smooth muscle cells (VSMCs). Although an increase in wall stress or stretch (eg, elicited by hypertension) is a prototypic determinant of VSMC activation, the impact of this biomechanical force on the activity of NFAT5 is unknown. This study intended to reveal the function of NFAT5 and to explore potential signal transduction pathways leading to its activation in stretch‐stimulated VSMCs.

Methods and Results

Human arterial VSMCs were exposed to biomechanical stretch and subjected to immunofluorescence and protein‐biochemical analyses. Stretch promoted the translocation of NFAT5 to the nucleus within 24 hours. While the protein abundance of NFAT5 was regulated through activation of c‐Jun N‐terminal kinase under these conditions, its translocation required prior activation of palmitoyltransferases. DNA microarray and ChiP analyses identified the matrix molecule tenascin‐C as a prominent transcriptional target of NFAT5 under these conditions that stimulates migration of VSMCs. Analyses of isolated mouse femoral arteries exposed to hypertensive perfusion conditions verified that NFAT5 translocation to the nucleus is followed by an increase in tenascin‐C abundance in the vessel wall.

Conclusions

Collectively, our data suggest that biomechanical stretch is sufficient to activate NFAT5 both in native and cultured VSMCs where it regulates the expression of tenascin‐C. This may contribute to an improved migratory activity of VSMCs and thus promote maladaptive vascular remodeling processes such as hypertension‐induced arterial stiffening.

ROS, Notch, and Wnt signaling pathways: crosstalk between three major regulators of cardiovascular biology

Reactive oxygen species (ROS), traditionally viewed as toxic by-products that cause damage to biomolecules, now are clearly recognized as key modulators in a variety of biological processes and pathological states. The development and regulation of the cardiovascular system require orchestrated activities; Notch and Wnt/β-catenin signaling pathways are implicated in many aspects of them, including cardiomyocytes and smooth muscle cells survival, angiogenesis, progenitor cells recruitment and differentiation, arteriovenous specification, vascular cell migration, and cardiac remodelling. Several novel findings regarding the role of ROS in Notch and Wnt/β-catenin modulation prompted us to review their emerging function in the cardiovascular system during embryogenesis and postnatally.

Shear-induced endothelial mechanotransduction: the interplay between reactive oxygen species (ROS) and nitric oxide (NO) and the pathophysiological implications

Hemodynamic shear stress, the blood flow-generated frictional force acting on the vascular endothelial cells, is essential for endothelial homeostasis under normal physiological conditions. Mechanosensors on endothelial cells detect shear stress and transduce it into biochemical signals to trigger vascular adaptive responses. Among the various shear-induced signaling molecules, reactive oxygen species (ROS) and nitric oxide (NO) have been implicated in vascular homeostasis and diseases. In this review, we explore the molecular, cellular, and vascular processes arising from shear-induced signaling (mechanotransduction) with emphasis on the roles of ROS and NO, and also discuss the mechanisms that may lead to excessive vascular remodeling and thus drive pathobiologic processes responsible for atherosclerosis. Current evidence suggests that NADPH oxidase is one of main cellular sources of ROS generation in endothelial cells under flow condition. Flow patterns and magnitude of shear determine the amount of ROS produced by endothelial cells, usually an irregular flow pattern (disturbed or oscillatory) producing higher levels of ROS than a regular flow pattern (steady or pulsatile). ROS production is closely linked to NO generation and elevated levels of ROS lead to low NO bioavailability, as is often observed in endothelial cells exposed to irregular flow. The low NO bioavailability is partly caused by the reaction of ROS with NO to form peroxynitrite, a key molecule which may initiate many pro-atherogenic events. This differential production of ROS and RNS (reactive nitrogen species) under various flow patterns and conditions modulates endothelial gene expression and thus results in differential vascular responses. Moreover, ROS/RNS are able to promote specific post-translational modifications in regulatory proteins (including S-glutathionylation, S-nitrosylation and tyrosine nitration), which constitute chemical signals that are relevant in cardiovascular pathophysiology. Overall, the dynamic interplay between local hemodynamic milieu and the resulting oxidative and S-nitrosative modification of regulatory proteins is important for ensuing vascular homeostasis. Based on available evidence, it is proposed that a regular flow pattern produces lower levels of ROS and higher NO bioavailability, creating an anti-atherogenic environment. On the other hand, an irregular flow pattern results in higher levels of ROS and yet lower NO bioavailability, thus triggering pro-atherogenic effects.

Differential effects of aliskiren/amlodipine combination and high-dose amlodipine monotherapy on endothelial function in elderly hypertensive patients

BACKGROUND

The aim of this study was to compare the effects of direct renin inhibitor, aliskiren, and amlodipine combination therapy with those of high-dose amlodipine monotherapy on endothelial function in elderly hypertensive patients.

METHODS

Participants included 105 patients (mean age 77 years) who had receive 5mg amlodipine for 4 weeks. Patients were allocated to the aliskiren/amlodipine group (AL/AM) or the high-dose amlodipine (AM) group. The AL/AM group received 150mg aliskiren in addition to 5mg amlodipine for 8 weeks; then the dose of aliskiren was doubled to 300mg for another 8 weeks. The AM group received 10mg amlodipine for 16 weeks. Of the 105 patients, 87 who underwent measurements of brachial flow-mediated vasodilation (FMD) and nitroglycerin-mediated vasodilation (NMD) before and after the study were included in the analysis.

RESULTS

Blood pressure-lowering effects were similar in the 2 groups. Plasma renin activity significantly decreased in the AL/AM group (P < 0.001) but increased in the AM group (P < 0.001). Improvement of FMD was found in the AL/AM group (2.6% to 3.7%, P = 0.001) but not in the AM group, while NMD did not change in either group. The changes in 24-hour systolic blood pressure (r = -0.60, P < 0.001) and diastolic blood pressure (r = -0.46, P = 0.004) were significantly correlated with improvement of FMD in the AL/AM group but not in the AM group.

CONCLUSION

Addition of aliskiren improved endothelial function in elderly hypertensive patients treated with amlodipine.

CLINICAL TRIAL REGISTRY NUMBER

UMIN000010163.

The protective effect of Bcl-xl overexpression against oxidative stress-induced vascular endothelial cell injury and the role of the Akt/eNOS pathway

Restenosis after intraluminal or open vascular reconstruction remains an important clinical problem. Vascular endothelial cell (EC) injury induced by oxidative stress plays an important role in the development of intimal hyperplasia. In this study, we sought to evaluate the protective effects of Bcl-xl overexpression in vitro on oxidative stress-induced EC injury and the role of the Akt/endothelial nitric oxide synthase (eNOS) pathway. Human umbilical vein endothelial cells (HUVECs) exposed to hydrogen peroxide (H₂O₂, 0.5 mM) were used as the experimental oxidative stress model. The Bcl-xl gene was transferred into HUVECs through recombinant adenovirus vector pAdxsi-GFP-Bcl-xl before oxidative treatment. Cell apoptosis was evaluated by Annexin V/propidium iodide and Hoechst staining, caspase-7 and PARP cleavage. Cell viability was assessed using the cell counting kit-8 assay, proliferating cell nuclear antigen (PCNA) immunocytochemical detection and the scratching assay. Expressions of Akt, phospho-Akt and eNOS were detected by Western blotting. Our results showed that H₂O₂ induced apoptosis and decreased the cell viability of HUVECs. Bcl-xl overexpression significantly protected cells from H₂O₂-induced cell damage and apoptosis and maintained the cell function. Furthermore, the level of phospho-Akt and eNOS protein expression was significantly elevated when pretreated with Bcl-xl gene transferring. These findings suggest that Bcl-xl overexpression exerts an anti-apoptotic and protective effect on EC function. The Akt/eNOS signaling pathway is probably involved in these processes.

Vein graft failure

After the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, which are commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, although somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored.

Whole brain radiation-induced cognitive impairment: pathophysiological mechanisms and therapeutic targets

Radiation therapy, the most commonly used for the treatment of brain tumors, has been shown to be of major significance in tu-mor control and survival rate of brain tumor patients. About 200,000 patients with brain tumor are treated with either partial large field or whole brain radiation every year in the United States. The use of radiation therapy for treatment of brain tumors, however, may lead to devastating functional deficits in brain several months to years after treatment. In particular, whole brain radiation therapy results in a significant reduction in learning and memory in brain tumor patients as long-term consequences of treatment. Although a number of in vitro and in vivo studies have demonstrated the pathogenesis of radiation-mediated brain injury, the cel-lular and molecular mechanisms by which radiation induces damage to normal tissue in brain remain largely unknown. Therefore, this review focuses on the pathophysiological mechanisms of whole brain radiation-induced cognitive impairment and the iden-tification of novel therapeutic targets. Specifically, we review the current knowledge about the effects of whole brain radiation on pro-oxidative and pro-inflammatory pathways, matrix metalloproteinases (MMPs)/tissue inhibitors of metalloproteinases (TIMPs) system and extracellular matrix (ECM), and physiological angiogenesis in brain. These studies may provide a foundation for defin-ing a new cellular and molecular basis related to the etiology of cognitive impairment that occurs among patients in response to whole brain radiation therapy. It may also lead to new opportunities for therapeutic interventions for brain tumor patients who are undergoing whole brain radiation therapy.

Hypertension impairs myocardin function: a novel mechanism facilitating arterial remodelling

AIMS

Hypertension evokes detrimental changes in the arterial vessel wall that facilitate stiffening and thus lead to a further rise in mean blood pressure, eventually causing heart failure. The underlying pathophysiological remodelling process is elicited by an increase in wall stress (WS) and is strictly dependent on the activation of vascular smooth muscle cells (SMC). However, it remains unclear as to why these cells fail to maintain their contractile and quiescent phenotype in a hypertensive environment.

METHODS AND RESULTS

In this context, we reveal that the knockdown of myocardin--a pivotal transcriptional determinant of the contractile SMC phenotype--is sufficient to induce SMC proliferation. In line with this observation, immunofluorescence analysis of the media of remodelling arteries from hypertensive mice demonstrated a significant decrease in the abundance of myocardin and an increase in SMC proliferation. Subsequent analyses of isolated perfused mouse arteries and human cultured SMCs exposed to cyclic stretch (i.e. mimicking one component of WS) suggested that this biomechanical force facilitates serine phosphorylation of myocardin. Furthermore, this biomechanical stimulus promotes rapid translocation of myocardin from the nucleus to the cytoplasm, inhibits its mRNA expression, and causes proteasomal degradation of the cytoplasmic protein.

CONCLUSIONS

Collectively, these findings suggest that hypertension negates the activity of myocardin in SMCs on multiple levels, hence eliminating a crucial determinant of SMC quiescence. This mechanism may control the initial switch from the contractile towards the synthetic SMC phenotype during hypertension and may offer an interesting novel approach to prevent cardiovascular disease.

Cell signaling through protein kinase C oxidation and activation

Due to the growing importance of cellular signaling mediated by reactive oxygen species (ROS), proteins that are reversibly modulated by these reactant molecules are of high interest. In this context, protein kinases and phosphatases, which act coordinately in the regulation of signal transduction through the phosphorylation and dephosphorylation of target proteins, have been described to be key elements in ROS-mediated signaling events. The major mechanism by which these proteins may be modified by oxidation involves the presence of key redox-sensitive cysteine residues. Protein kinase C (PKC) is involved in a variety of cellular signaling pathways. These proteins have been shown to contain a unique structural feature that is susceptible to oxidative modification. A large number of scientific studies have highlighted the importance of ROS as a second messenger in numerous cellular processes, including cell proliferation, gene expression, adhesion, differentiation, senescence, and apoptosis. In this context, the goal of this review is to discuss the mechanisms by which PKCs are modulated by ROS and how these processes are involved in the cellular response.

HIV-1, reactive oxygen species, and vascular complications

Over 1 million people in the United States and 33 million individuals worldwide suffer from HIV/AIDS. Since its discovery, HIV/AIDS has been associated with an increased susceptibility to opportunistic infection due to immune dysfunction. Highly active antiretroviral therapies restore immune function and, as a result, people infected with HIV-1 are living longer. This improved survival of HIV-1 patients has revealed a previously unrecognized risk of developing vascular complications, such as atherosclerosis and pulmonary hypertension. The mechanisms underlying these HIV-associated vascular disorders are poorly understood. However, HIV-induced elevations in reactive oxygen species (ROS), including superoxide and hydrogen peroxide, may contribute to vascular disease development and progression by altering cell function and redox-sensitive signaling pathways. In this review, we summarize the clinical and experimental evidence demonstrating HIV- and HIV antiretroviral therapy-induced alterations in reactive oxygen species and how these effects are likely to contribute to vascular dysfunction and disease.

Solid-phase immunoglobulins IgG and IgM activate macrophages with solid-phase IgM acting via a novel scavenger receptor a pathway

IgG may accelerate atherosclerosis via ligation of proinflammatory Fcγ receptors; however, IgM is unable to ligate FcγR and is often considered vasculoprotective. IgM aggravates ischemia-reperfusion injury, and solid-phase deposits of pure IgM, as seen with IgM-secreting neoplasms, are well known clinically to provoke vascular inflammation. We therefore examined the molecular mechanisms by which immunoglobulins can aggravate vascular inflammation, such as in atherosclerosis. We compared the ability of fluid- and solid-phase immunoglobulins to activate macrophages. Solid-phase immunoglobulins initiated prothrombotic and proinflammatory functions in human macrophages, including NF-κB p65 activation, H(2)O(2) secretion, macrophage-induced apoptosis, and tissue factor expression. Responses to solid-phase IgG (but not to IgM) were blocked by neutralizing antibodies to CD16 (FcγRIII), consistent with its known role. Macrophages from mice deficient in macrophage scavenger receptor A (SR-A; CD204) had absent IgM binding and no activation by solid-phase IgM. RNA interference-mediated knockdown of SR-A in human macrophages suppressed activation by solid-phase IgM. IgM binding to SR-A was demonstrated by both co-immunoprecipitation studies and the binding of fluorescently labeled IgM to SR-A-transfected cells. Immunoglobulins on solid-phase particles around macrophages were found in human plaques, increased in ruptured plaques compared with stable ones. These observations indicate that solid-phase IgM and IgG can activate macrophages and destabilize vulnerable plaques. Solid-phase IgM activates macrophages via a novel SR-A pathway.

The glutathionylation of p65 modulates NF-κB activity in 15-deoxy-Δ¹²,¹⁴-prostaglandin J₂-treated endothelial cells

Protein glutathionylation is a posttranslational modification of cysteine residues with glutathione in response to mild oxidative stress. Because 15-deoxy-Δ12,14-prostaglandin J(2) (15d-PGJ(2)) is an electrophilic prostaglandin that can increase glutathione (GSH) levels and augment reactive oxygen species (ROS) production, we hypothesized that it induces NF-κB-p65 glutathionylation and would exert anti-inflammatory effects. Herein, we show that 15d-PGJ(2) suppresses the expression of ICAM-1 and NF-κB-p65 nuclear translocation. 15d-PGJ(2) upregulates the Nrf2-related glutathione synthase gene and thereby increases the GSH levels. Consistent with this, Nrf2 siRNA molecules abolish the inhibition of p65 nuclear translocation in 15d-PGJ(2)-induced endothelial cells (ECs). ECs treated with GSSG show increased thiol modifications of p65 and also a block in TNFα-induced p65 nuclear translocation and ICAM-1 expression, but not in IκBα degradation. However, the overexpression of glutaredoxin 1 was found to be accompanied by a modest increase in NF-κB activity. Furthermore, we found that multiple cysteine residues in p65 are responsible for glutathionylation. 15d-PGJ(2) was observed to induce p65 glutathionylation and is suppressed by a GSH synthesis inhibitor, buthionine sulfoximine, by catalase, and by Nrf2 siRNA molecules. Our results thus indicate that the GSH/ROS-dependent glutathionylation of p65 is likely to be responsible for 15d-PGJ(2)-mediated NF-κB inactivation and for the enhanced inhibitory effects of 15d-PGJ(2) on TNFα-treated ECs.

Nicorandil attenuates cyclic strain-induced endothelin-1 expression via the induction of activating transcription factor 3 in human umbilical vein endothelial cells

Nicorandil is an adenosine triphosphate-sensitive potassium channel opener that combines an organic nitrate and a nicotinamide group which respectively confer to nicorandil the additional properties of being a nitric oxide (NO) donor and antioxidant; it also induces vasodilation, decreases the blood pressure, and protects the heart. However, the intracellular mechanism of nicorandil remains to be delineated. The aims of this study were to test the hypothesis that nicorandil alters strain-induced endothelin-1 secretion and NO production, and to identify the putative underlying signaling pathways in human umbilical vein endothelial cells (HUVECs). Cultured HUVECs were exposed to cyclic strain in the presence of nicorandil; endothelin-1 expression was examined by reverse-transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. Activation of extracellular signal-regulated protein kinase (ERK), endothelial NO synthase (eNOS), and activating transcription factor (ATF)-3 was assessed by Western blot analysis. We show that nicorandil inhibited strain-induced endothelin-1 expression. Nicorandil also inhibited strain-increased reactive oxygen species formation and ERK phosphorylation. On the contrary, NO production, eNOS phosphorylation, and ATF3 expression were enhanced by nicorandil; however, L-NAME (an inhibitor of eNOS) and LY294002 (an inhibitor of phosphatidylinositol 3-kinase) inhibited nicorandil-increased ATF3 expression. Moreover, treatment of HUVECs with either an NO donor (NOC18; 3,3-bis[aminoethyl]-1-hydroxy-2-oxo-1-triazene) or an ATF3 activator (MG-132; carbobenzoxy-L-leucyl-L-leucyl-L-leucinal) resulted in repression of strain-induced endothelin-1 expression. Furthermore, L-NAME, and small interfering RNA transfection of eNOS also partially attenuated the inhibitory effect of nicorandil on strain-induced endothelin-1 expression. We demonstrate for the first time that nicorandil inhibits strain-induced endothelin-1 secretion via an increase in NO and upregulation of ATF3 in HUVECs. This study provides important new insights into the molecular pathways that may contribute to the beneficial effects of nicorandil in the cardiovascular system.

Regulation of endothelial function by mitochondrial reactive oxygen species

Mitochondria are well known for their central roles in ATP production, calcium homeostasis, and heme and steroid biosynthesis. However, mitochondrial reactive oxygen species (ROS), including superoxide and hydrogen peroxide, once thought to be toxic byproducts of mitochondrial physiologic activities, have recently been recognized as important cell-signaling molecules in the vascular endothelium, where their production, conversion, and destruction are highly regulated. Mitochondrial reactive oxygen species appear to regulate important vascular homeostatic functions under basal conditions in a variety of vascular beds, where, in particular, they contribute to endothelium-dependent vasodilation. On exposure to cardiovascular risk factors, endothelial mitochondria produce excessive ROS in concert with other cellular ROS sources. Mitochondrial ROS, in this setting, act as important signaling molecules activating prothrombotic and proinflammatory pathways in the vascular endothelium, a process that initially manifests itself as endothelial dysfunction and, if persistent, may lead to the development of atherosclerotic plaques. This review concentrates on emerging appreciation of the importance of mitochondrial ROS as cell-signaling molecules in the vascular endothelium under both physiologic and pathophysiologic conditions. Future potential avenues of research in this field also are discussed.

Effects of shear stress and stretch on endothelial function

Vascular endothelial cells (ECs) play a central role in the control of blood vessel function and circulatory system homeostasis. It is well known that that EC functions are regulated by chemical mediators, including hormones, cytokines, and neurotransmitters, but it has recently become apparent that EC functions are also controlled by hemodynamic forces such as shear stress and stretch (cyclic strain). ECs recognize shear stress and cyclic strain as mechanical stimuli, and transmit the signal into the interior of the cells, thereby triggering a variety of cellular responses that involve alterations in cell morphology, cell function, and gene expression. Impaired EC responses to shear stress and cyclic strain lead to vascular diseases, including hypertension, thrombosis, and atherosclerosis. A great deal of research has already been conducted on the mechanotransduction of shear stress and cyclic strain, and its molecular mechanisms are gradually coming to be understood. However, much remains unclear, and further studies of mechanotransduction should increase our understanding of the molecular basis of the hemodynamic-force-mediated control of vascular functions.

Tyrosine nitration limits stretch-induced CD40 expression and disconnects CD40 signaling in human endothelial cells

Hemodynamic forces are important effectors of endothelial cell phenotype and function. Because CD40-CD154 interactions between endothelial cells and mononuclear leukocytes or activated platelets play an important role in vascular dysfunction, we investigated the effects of cyclic stretch on CD40 expression in human cultured endothelial cells. Short-term stretch transiently up-regulated CD40 expression while long-term stretch resulted in a distinct decline in CD40 protein which was prevented by inhibition of the 20S proteasome or scavenging of peroxynitrite. Tyrosine nitration of CD40 also occurred under static conditions on addition of authentic peroxynitrite, and according to mass spectrometry analysis Tyr-82 but not Tyr-31 was its target in the native protein. Immunofluorescence analysis of endothelial cells transduced with a control or Tyr-82 to Ala mutated AAV9-CD40-eGFP expression construct confirmed a peroxynitrite-dependent redistribution of the protein from the cell membrane to the cytoplasm, which was prevented by methyl-β-cyclodextrin. Moreover, CD154-stimulated IL-12p40 and E-selectin expression markedly decreased after exposure to authentic peroxynitrite or cyclic stretch, respectively. Coimmunoprecipitation demonstrated a decreased binding of TRAF2 and TRAF6 to the CD40 protein after tyrosine nitration. Through this posttranslational oxidative modification of an important costimulatory molecule, endothelial cells are able to quickly adapt to unfavorable hemodynamics and maintain their anti-inflammatory phenotype.

Role of shear stress and stretch in vascular mechanobiology

Blood vessels are under constant mechanical loading from blood pressure and flow which cause internal stresses (endothelial shear stress and circumferential wall stress, respectively). The mechanical forces not only cause morphological changes of endothelium and blood vessel wall, but also trigger biochemical and biological events. There is considerable evidence that physiologic stresses and strains (stretch) exert vasoprotective roles via nitric oxide and provide a homeostatic oxidative balance. A perturbation of tissue stresses and strains can disturb biochemical homeostasis and lead to vascular remodelling and possible dysfunction (e.g. altered vasorelaxation, tone, stiffness, etc.). These distinct biological endpoints are caused by some common biochemical pathways. The focus of this brief review is to point out some possible commonalities in the molecular pathways in response to endothelial shear stress and circumferential wall stretch.

Vascular effects of exercise: endothelial adaptations beyond active muscle beds

Endothelial adaptations to exercise training are not exclusively conferred within the active muscle beds. Herein, we summarize key studies that have evaluated the impact of chronic exercise on the endothelium of vasculatures perfusing nonworking skeletal muscle, brain, viscera, and skin, concluding with discussion of potential mechanisms driving these endothelial adaptations.

Effects of exercise on endothelium and endothelium/smooth muscle cross talk: role of exercise-induced hemodynamics

Physical activity, exercise training, and fitness are associated with decreased cardiovascular risk. In the context that a risk factor "gap" exists in the explanation for the beneficial effects of exercise on cardiovascular disease, it has recently been proposed that exercise generates hemodynamic stimuli which exert direct effects on the vasculature that are antiatherogenic. In this review we briefly introduce some of the in vitro and in vivo evidence relating exercise hemodynamic modulation and vascular adaptation. In vitro data clearly demonstrate the importance of shear stress as a potential mechanism underlying vascular adaptations associated with exercise. Supporting this is in vivo human data demonstrating that exercise-mediated shear stress induces localized impacts on arterial function and diameter. Emerging evidence suggests that exercise-related changes in hemodynamic stimuli other than shear stress may also be associated with arterial remodeling. Taken together, in vitro and in vivo data strongly imply that hemodynamic influences combine to orchestrate a response to exercise and training that regulates wall stress and peripheral vascular resistance and contributes to the antiatherogenic impacts of physical activity, fitness, and training.

L-carnitine reduces doxorubicin-induced apoptosis through a prostacyclin-mediated pathway in neonatal rat cardiomyocytes

BACKGROUND

Clinical use of doxorubicin is greatly limited by its severe cardiotoxic side effects. L-carnitine is a vitamin-like substance which has been successfully used in many cardiomyopathies, however, the intracellular mechanism(s) remain unclear. The objective of this study was set to evaluate the protective effect of L-carnitine on doxorubicin-induced cardiomyocyte apoptosis, and to explore its intracellular mechanism(s).

METHODS

Primary cultured neonatal rat cardiomyocytes were treated with doxorubicin (1 µM) with or without pretreatment with L-carnitine (1-30 mM). Lactate dehydrogenase assay, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling staining, and flow cytometry measurement were used to assess cytotoxicity and apoptosis. Fluorescent probes 2',7'-dichlorofluorescein diacetate and chemiluminescence assay of superoxide production were used to detect the production of reactive oxygen species. Western blotting was used to evaluate the quantity of cleaved caspase-3, cytosol cytochrome c, and Bcl-x(L) expression.

RESULTS

L-carnitine inhibited doxorubicin-induced reactive oxygen species generation and NADPH oxidase activation, reduced the quantity of cleaved caspase-3 and cytosol cytochrome c, and increased Bcl-x(L) expression, resulting in protecting cardiomyocytes from doxorubicin-induced apoptosis. In addition, L-carnitine was found to increase the prostacyclin (PGI(2)) generation in cardiomyocytes. The siRNA transfection for PGI(2) synthase significantly reduced L-carnitine-induced PGI(2) and L-carnitine's protective effect. Furthermore, blockade the potential PGI(2) receptors, including PGI(2) receptors (IP receptors), and peroxisome proliferator-activated receptors alpha and delta (PPARα and PPARδ), revealed that the siRNA-mediated blockage of PPARα considerably reduced the anti-apoptotic effect of L-carnitine.

CONCLUSIONS

These findings suggest that L-carnitine protects cardiomyocytes from doxorubicin-induced apoptosis in part through PGI(2) and PPARα-signaling pathways, which may potentially protect the heart from the severe toxicity of doxorubicin.

Upregulation of NF-E2-related factor-2-dependent glutathione by carnosol provokes a cytoprotective response and enhances cell survival

AIM

To explore whether glutathione (GSH) increased through Nrf-2 activation is involved in the cytoprotective effects of carnosol in HepG2 cells.

METHODS

Human hepatoma cell line HepG2 were exposed to rosemarry essential oil or carnosol. Cell viability was measured using an Alamar blue assay. The production of intracellular GSH was determined using monochlorobimane. The level of protein or mRNA was examined by Western blotting or RT-PCR, respectively.

RESULTS

Rosemarry essential oil (0.005%-0.02%) and carnosol (5 and 10 mol/L) increased the intracellular GSH levels and GSH synthesis enzyme subunit GCLC/GCLM expression. Rosemary essential oil and carnosol increased nuclear accumulation of Nrf2 and enhanced Nrf2-antioxidant responsive element (ARE)-reporter activity. Transfection of the treated cells with an Nrf2 siRNA construct blocks GCLC/GCLM induction. Furthermore, pretreatment of the HepG2 cells with essential oil and carnosol exerted significant cytoprotective effects against H(2)O(2) or alcohol. In TNFα-treated cells, the nuclear translocation and transcriptional activity of NF-κB was abolished for 12 h following carnosol pretreatment. Cotreatment with GSH also suppressed NF-κB nuclear translocation, whereas cotreatment with BSO, a GSH synthesis blocker, blocked the inhibitory effects of carnosol.

CONCLUSION

This study demonstrated that Nrf2 is involved in the cytoprotective effects by carnasol, which were at least partially mediated through increased GSH biosynthesis.

Current perspectives of oxidative stress and its measurement in chronic obstructive pulmonary disease

Cigarette smoking, the principal aetiology of chronic obstructive pulmonary disease (COPD) in the developed countries, delivers and generates oxidative stress within the lungs. This imbalance of oxidant burden and antioxidant capacity has been implicated as an important contributing factor in the pathogenesis of COPD. Oxidative processes and free radical generation orchestrate the inflammation, mucous gland hyperplasia, and apoptosis of the airway lining epithelium which characterises COPD. Pivotal oxidative stress/pro-inflammatory molecules include reactive oxygen species such as the superoxides and hydroxyl radicals, pro-inflammatory cytokines including leukotrienes, interleukins, tumour necrosis factor alpha, and activated transcriptional factors such as nuclear factor kappa-B and activator protein 1. The lung has a large reserve of antioxidant agents such as glutathione and superoxide dismutase to counter oxidants. However, smoking also causes the depletion of antioxidants, which further contributes to oxidative tissue damage. The downregulation of antioxidant pathways has also been associated with acute exacerbations of COPD. The delivery of redox-protective antioxidants may have preventative and therapeutic potential of COPD. Although these observations have yet to translate into common clinical practice, preliminary clinical trials and studies of animal models have shown that interventions to counter this oxidative imbalance may have potential to better manage COPD. There is, thus, a need for the ability to monitor such interventions and exhaled breath condensate is rapidly emerging as a novel and noninvasive approach in the sampling of airway epithelial lining fluid which could be used for repeated analysis of oxidative stress and inflammation in the lungs.

Calcium- and phosphatidylinositol 3-kinase/Akt-dependent activation of endothelial nitric oxide synthase by apigenin

AIMS

The generation of NO by endothelial nitric oxide synthase (eNOS) plays a major role in maintaining cardiovascular homeostasis. The objective of our present study was to investigate the effects of the flavone compound, apigenin, on eNOS activity and elucidate the molecular mechanisms underlying these effects in endothelial cells (ECs).

MAIN METHODS

Bovine artery endothelial cells (BAECs) were exposed in a serum-free medium to apigenin. Cell viability was measured using an Alamar blue assay. The production of intracellular NO was determined using DAF-2/DA. The level of protein was examined by Western blotting. The intracellular Ca(2+) was measured using a fluorescent dye, Fura 2-AM.

KEY FINDINGS

Apigenin significantly induced NO production after 6h of treatment. This production was inhibited by pretreatment with the eNOS inhibitor, N(ω)-nitro l-arginine methyl ester (L-NAME). However, treatment with apigenin did not alter the eNOS protein levels but induced a sustained activation of eNOS Ser(1179) phosphorylation. Apigenin was further found to activate ERK1/2, JNK and Akt over various time courses in ECs. Treatment with specific PI3-kinase inhibitors significantly inhibited the increases in NO production and phosphorylation. In contrast, the inhibition of (ERK)1/2, JNK and p38 had no influence on NO production. In addition, apigenin stimulates an increase in the cytosolic Ca(2+) concentration. Apigenin-induced eNOS Ser(1179) phosphorylation and NO production are calcium-dependent, as pretreatment with extracellular or intracellular Ca(2+) chelators inhibits these processes.

SIGNIFICANCE

Apigenin-induced calcium-dependent activation of eNOS is primarily mediated via phosphatidylinositol 3-kinase- and Akt pathways, and occurs independently of the eNOS protein content.

Oxidative stress in COPD and its measurement through exhaled breath condensate

Oxidative stress and airway inflammation together form a vicious cycle, which is responsible for the disease progression in chronic pulmonary obstructive disease (COPD). The damaging effects of oxidative stress accumulate over the years, causing increased bronchial hyperresponsiveness and inflammation and destruction of airway epithelial cells and impairing the functions of antiproteases and surfactant. Although the lung expresses a number of antioxidants, cigarette smoking and recurrent infections associated with this disease overwhelm this protective mechanism. Studies of antioxidants in COPD have yielded conflicting results, probably due to the compartmentalization of these mediators, and because of the fact that the lung is a difficult organ to sample. Chronic exposure to oxidants upregulates the production of antioxidants, which become depleted during acute exacerbations. Future studies of the pathogenesis of COPD require a noninvasive yet accurate sampling procedure, of which exhaled breath condensate (EBC) is a good candidate. EBC samples the epithelial lining fluid, which contains the local oxidative stress markers in the lung. Oxidative stress markers such as hydrogen ions, hydrogen peroxide, 8-isoprostanes, thiobarbituric acid reactive products, nitrosothiols, and nitrite/nitrate have been identified in EBC of COPD patients, whereas many other markers of the oxidative-antioxidative balance have yet to be investigated.

Role of NADPH oxidase in interleukin-4-induced monocyte chemoattractant protein-1 expression in vascular endothelium

OBJECTIVE AND DESIGN

The pro-oxidative and pro-inflammatory pathways in vascular endothelium have been implicated in the development of atherosclerosis. In the present study, we investigated effect of interleukin-4 (IL-4) on monocyte chemoattractant protein-1 (MCP-1) expression in vascular endothelium and examined the role of distinct sources of reactive oxygen species (ROS) in this process.

METHODS AND RESULTS

Real-time reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay showed that IL-4 significantly up-regulated mRNA and protein expression of MCP-1 in human aortic endothelial cells (HAEC) and C57BL/6 mice. A significant and dose-dependent inhibition of IL-4-induced MCP-1 expression was observed in HAEC pre-treated with antioxidants, such as pyrrolidine dithiocarbamate and epigallocatechin gallate, indicating that IL-4-induced MCP-1 expression is mediated via a ROS-dependent mechanism. Additionally, pharmacological inhibitors of NADPH oxidase (NOX) significantly attenuated IL-4-induced MCP-1 expression in HAEC. Furthermore, the disruption of the NOX gene dramatically reduced IL-4-induced MCP-1 expression in NOX knockout mice (B6.129S6-Cybb(tm1Din)/J). In contrast, overexpression of MCP-1 in IL-4-stimulated HAEC was not affected by inhibiting other ROS generating pathways, such as xanthine oxidase and the mitochondrial electron transport chain.

CONCLUSIONS

These results demonstrate that IL-4 up-regulates MCP-1 expression in vascular endothelium through NOX-mediated ROS generation.

Interleukin-4, Oxidative Stress, Vascular Inflammation and Atherosclerosis

The pro-oxidative and pro-inflammatory pathways in vascular endothelium have been implicated in the initiation and progression of atherosclerosis. In fact, inflammatory responses in vascular endothelium are primarily regulated through oxidative stress-mediated signaling pathways leading to overexpression of pro-inflammatory mediators. Enhanced expression of cytokines, chemokines and adhesion molecules in endothelial cells and their close interactions facilitate recruiting and adhering blood leukocytes to vessel wall, and subsequently stimulate transendothelial migration, which are thought to be critical early pathologic events in atherogenesis. Although interleukin-4 (IL-4) was traditionally considered as an anti-inflammatory cytokine, recent in vitro and in vivo studies have provided robust evidence that IL-4 exerts pro-inflammatory effects on vascular endothelium and may play a critical role in the development of atherosclerosis. The cellular and molecular mechanisms responsible for IL-4-induced atherosclerosis, however, remain largely unknown. The present review focuses on the distinct sources of IL-4-mediated reactive oxygen species (ROS) generation as well as the pivotal role of ROS in IL-4-induced vascular inflammation. These studies will provide novel insights into a clear delineation of the oxidative mechanisms of IL-4-mediated stimulation of vascular inflammation and subsequent development of atherosclerosis. It will also contribute to novel therapeutic approaches for atherosclerosis specifically targeted against pro-oxidative and pro-inflammatory pathways in vascular endothelium.

The glutaredoxin/glutathione system modulates NF-kappaB activity by glutathionylation of p65 in cinnamaldehyde-treated endothelial cells

Reversible protein glutathionylation is an important posttranslational modification that provides protection against oxidation. In endothelial cells (ECs), cinnamaldehyde is an electrophilic compound that can increase the intracellular glutathione (GSH) levels or reactive oxygen species (ROS) production depending on the treatment duration. ECs treated with GSH and H(2)O(2) show increased sulfhydryl modifications of the p65 subunit of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB), which are responsible for NF-kappaB inactivation, and also a block in TNF-alpha-induced p65 nuclear translocation and inter-cellular adhesion molecule-1 (ICAM-1) expression. In our current study, we find that cinnamaldehyde induces p65 glutathionylation and inhibits TNF-alpha-induced p65 nuclear translocation and ICAM-1 expression within 12 h of treatment. Our analyses also reveal that p65 glutathionylation is suppressed by a GSH synthesis inhibitor, buthionine sulfoximine (BSO), and we further observed that the inhibitory effects of p65 nuclear translocation and ICAM-1 expression are also suppressed by BSO. NF-E2-related factor-2 small interfering RNA (siRNA) molecules not only inhibit glutamate-cysteine ligase catalytic subunit (GCLC) and glutamate-cysteine ligase modifier subunit (GCLM) induction and increases in GSH but also abolish cinnamaldehyde-induced p65 glutathionylation and its inhibitory effects. The gene expression and activity of glutaredoxin-1 (Grx-1), which catalyzes the formation of protein-glutathione mixed disulfides (protein-SSG), were also found to be increased after cinnamaldehyde treatment. A knock down of endogenous Grx-1 by siRNA or pretreatment with an inhibitor of Grx-1 activity, CdCl(2), abolishes p65-SSG formation. In addition, Grx-1 siRNA blocks the inhibition of p65 nuclear translocation and ICAM-1 expression, suggesting that this enzyme is involved in the cinnamaldehyde-mediated NF-kappaB inhibition. Our current results thus indicate that the GSH/Grx-1-dependent glutathionylation of p65 is likely to be responsible for cinnamaldehyde-mediated NF-kappaB inactivation and for the enhanced inhibitory effects of cinnamaldehyde upon TNF-alpha-treated ECs.