Reduced Monocyte and Neutrophil Infiltration and Activation by P-Selectin/CD62P Inhibition Enhances Thrombus Resolution in Mice

BACKGROUND

Venous thromboembolism is a major health problem. After thrombus formation, its resolution is essential to re-establish blood flow, which is crucially mediated by infiltrating neutrophils and monocytes in concert with activated platelets and endothelial cells. Thus, we aimed to modulate leukocyte function during thrombus resolution post-thrombus formation by blocking P-selectin/CD62P-mediated cell interactions.

METHODS

Thrombosis was induced by inferior vena cava stenosis through ligation in mice. After 1 day, a P-selectin-blocking antibody or isotype control was administered and thrombus composition and resolution were analyzed.

RESULTS

Localizing neutrophils and macrophages in thrombotic lesions of wild-type mice revealed that these cells enter the thrombus and vessel wall from the caudal end. Neutrophils were predominantly present 1 day and monocytes/macrophages 3 days after vessel ligation. Blocking P-selectin reduced circulating platelet-neutrophil and platelet-Ly6Chigh monocyte aggregates near the thrombus, and diminished neutrophils and Ly6Chigh macrophages in the cranial thrombus part compared with isotype-treated controls. Depletion of neutrophils 1 day after thrombus initiation did not phenocopy P-selectin inhibition but led to larger thrombi compared with untreated controls. In vitro, P-selectin enhanced human leukocyte function as P-selectin-coated beads increased reactive oxygen species production by neutrophils and tissue factor expression of classical monocytes. Accordingly, P-selectin inhibition reduced oxidative burst in the thrombus and tissue factor expression in the adjacent vessel wall. Moreover, blocking P-selectin reduced thrombus density determined by scanning electron microscopy and increased urokinase-type plasminogen activator levels in the thrombus, which accelerated caudal fibrin degradation from day 3 to day 14. This accelerated thrombus resolution as thrombus volume declined more rapidly after blocking P-selectin.

CONCLUSIONS

Inhibition of P-selectin-dependent activation of monocytes and neutrophils accelerates venous thrombosis resolution due to reduced infiltration and activation of innate immune cells at the site of thrombus formation, which prevents early thrombus stabilization and facilitates fibrinolysis.

Interleukin-4 receptor alpha signaling regulates monocyte homeostasis

Interleukin‐4 (IL‐4) and its receptors (IL‐4R) promote the proliferation and polarization of macrophages. However, it is unknown if IL‐4R also influences monocyte homeostasis and if steady state IL‐4 levels are sufficient to affect monocytes. Employing full IL‐4 receptor alpha knockout mice (IL‐4Rα^−/−) and mice with a myeloid‐specific deletion of IL‐4Rα (IL‐4Rα^f/f LysM^cre), we show that IL‐4 acts as a homeostatic factor regulating circulating monocyte numbers. In the absence of IL‐4Rα, murine monocytes in blood were reduced by 50% without altering monocytopoiesis in the bone marrow. This reduction was accompanied by a decrease in monocyte‐derived inflammatory cytokines in the plasma. RNA sequencing analysis and immunohistochemical staining of splenic monocytes revealed changes in mRNA and protein levels of anti‐apoptotic factors including BIRC6 in IL‐4Rα^−/− knockout animals. Furthermore, assessment of monocyte lifespan in vivo measuring BrdU⁺ cells revealed that the lifespan of circulating monocytes was reduced by 55% in IL‐4Rα^−/− mice, whereas subcutaneously applied IL‐4 prolonged it by 75%. Treatment of human monocytes with IL‐4 reduced the amount of dying monocytes in vitro. Furthermore, IL‐4 stimulation reduced the phosphorylation of proteins involved in the apoptosis pathway, including the phosphorylation of the NFκBp65 protein. In a cohort of human patients, serum IL‐4 levels were significantly associated with monocyte counts. In a sterile peritonitis model, reduced monocyte counts resulted in an attenuated recruitment of monocytes upon inflammatory stimulation in IL‐4Rα^f/f LysM^cre mice without changes in overall migratory function. Thus, we identified a homeostatic role of IL‐4Rα in regulating the lifespan of monocytes in vivo.

The plasminogen receptor Plg-RKT regulates adipose function and metabolic homeostasis

BACKGROUND

Plg-RKT , a unique transmembrane plasminogen receptor, enhances the activation of plasminogen to plasmin, and localizes the proteolytic activity of plasmin on the cell surface.

OBJECTIVES

We investigated the role of Plg-RKT in adipose function, metabolic homeostasis, and obesity.

METHODS

We used adipose tissue (AT) sections from bariatric surgery patients and from high fat diet (HFD)-induced obese mice together with immunofluorescence and real-time polymerase chain reaction to study adipose expression of Plg-RKT . Mice genetically deficient in Plg-RKT and littermate controls fed a HFD or control low fat diet (LFD) were used to determine the role of Plg-RKT in insulin resistance, glucose tolerance, type 2 diabetes, and associated mechanisms including adipose inflammation, fibrosis, and ectopic lipid storage. The role of Plg-RKT in adipogenesis was determined using 3T3-L1 preadipocytes and primary cultures established from Plg-RKT -deficient and littermate control mice.

RESULTS

Plg-RKT was highly expressed in both human and mouse AT, and its levels dramatically increased during adipogenesis. Plg-RKT -deficient mice, when fed a HFD, gained more weight, developed more hepatic steatosis, and were more insulin resistant/glucose intolerant than HFD-fed wild-type littermates. Mechanistically, these metabolic defects were linked with increased AT inflammation, AT macrophage and T-cell accumulation, adipose and hepatic fibrosis, and decreased insulin signaling in the AT and liver. Moreover, Plg-RKT regulated the expression of PPARγ and other adipogenic molecules, suggesting a novel role for Plg-RKT in the adipogenic program.

CONCLUSIONS

Plg-RKT coordinately regulates multiple aspects of adipose function that are important to maintain efficient metabolic homeostasis.

Innate Immune Training with Bacterial Extracts Enhances Lung Macrophage Recruitment to Protect from Betacoronavirus Infection

Training of the innate immune system with orally ingested bacterial extracts was demonstrated to have beneficial effects on infection clearance and disease outcome. The aim of our study was to identify cellular and molecular processes responsible for these immunological benefits. We used a murine coronavirus (MCoV) A59 mouse model treated with the immune activating bacterial extract Broncho-Vaxom (BV) OM-85. Tissue samples were analysed with qPCR, RNA sequencing, histology, and flow cytometry. After BV OM-85 treatment, interstitial macrophages accumulated in lung tissue leading to a faster response of type I interferon (IFN) signalling after MCoV infection resulting in overall lung tissue protection. Moreover, RNA sequencing showed that lung tissue from mice receiving BV OM-85 resembled an intermediate stage between healthy and viral infected lung tissue at day 4, indicating a faster return to normal tissue homoeostasis. The pharmacologic effect was mimicked by adoptively transferring naive lung macrophages into lungs from recipient mice before virus infection. The beneficial effect of BV OM-85 was abolished when inhibiting initial type I IFN signalling. Overall, our data suggest that BV OM-85 enhances lung macrophages allowing for a faster IFN response towards a viral challenge as part of the oral-induced innate immune system training.

S-nitroso human serum albumin as a nitric oxide donor in drug-eluting vascular grafts: Biofunctionality and preclinical evaluation

Currently available synthetic small diameter vascular grafts reveal low patency rates due to thrombosis and intimal hyperplasia. Biofunctionalized grafts releasing nitric oxide (NO) in situ may overcome these limitations. In this study, a drug-eluting vascular graft was designed by blending polycaprolactone (PCL) with S-nitroso-human-serum-albumin (S-NO-HSA), a nitric oxide donor with prolonged half-life. PCL-S-NO-HSA grafts and patches were fabricated via electrospinning. The fabrication process was optimized. Patches were characterized in vitro for their morphology, drug release, biomechanics, inflammatory effects, cell proliferation, and expression of adhesion molecules. The selected optimized formulation (8%PCL-S-NO-HSA) had superior mechanical/morphological properties with high protein content revealing extended NO release (for 28 days). 8%PCL-S-NO-HSA patches significantly promoted endothelial cell proliferation while limiting smooth muscle cell proliferation. Expression of adhesion molecules (ICAM-1, VCAM-1) and pro-inflammatory macrophage/cytokine markers (CD80, IL-1α, TNF-α) was significantly reduced. 8%PCL-S-NO-HSA patches had superior immunomodulatory properties by up-regulating anti-inflammatory cytokines (IL-10) and M2 macrophage marker (CD163) at final time points. Grafts were further evaluated in a small rodent model as aortic implants up to 12 weeks. Grafts were assessed by magnetic resonance imaging angiography (MRI) in vivo and after retrieval by histology. All grafts remained 100 % patent with no signs of thrombosis or calcification. 8%PCL-S-NO-HSA vascular grafts supported rapid endothelialization, whereas smooth muscle cell proliferation was hampered in earlier phases. This study indicates that 8%PCL-S-NO-HSA grafts effectively support long-term in situ release of bioactive NO. The beneficial effects observed can be promising features for long-term success of small diameter vascular grafts. STATEMENT OF SIGNIFICANCE: Despite extensive research in the field of small diameter vascular graft replacement, there is still no appropriate substitute to autografts yet. Various limitations are associated with currently available synthetic vascular grafts such as thrombogenicity and intimal hyperplasia. Therefore, developing new generations of such conduits has become a major focus of research. One of the most significant signaling molecules that are involved in homeostasis of the vascular system is nitric oxide. The new designed nitric-oxide eluting vascular grafts described in this study induce rapid surface endothelialization and late migration of SMCs into the graft wall. These beneficial effects have potential to improve current limitations of small diameter vascular grafts.

Pharmacological inhibition of fatty acid oxidation reduces atherosclerosis progression by suppression of macrophage NLRP3 inflammasome activation

BACKGROUND

Inflammation is a key process during atherosclerotic lesion development and propagation. Recent evidence showed clearly that especially the inhibition of interleukin (IL)-1β reduced atherosclerotic adverse events in human patients. Fatty acid oxidation (FAO) was previously demonstrated to interact with the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) pathway which is required for mature IL-1β secretion. To understand possible anti-inflammatory properties of FAO inhibition, we tested the effect of pharmacological FAO inhibition using the inhibitor for long-chain 3-ketoacyl coenzyme A thiolase trimetazidine on atherosclerotic plaque development and inflammation.

EXPERIMENTAL APPROACH

The effect of FAO inhibition was determined in LDL-R^-/- male mice on a C57/BL6 background. In vitro effects of trimetazidine treatment were analyzed in human umbilical vein endothelial cells and human monocyte derived macrophages.

KEY RESULTS

We were able to demonstrate that inhibition of FAO reduced atherosclerotic plaque growth. We did not find direct anti-inflammatory properties of trimetazidine in endothelial cells or macrophages in vitro. However, we found that the activation of the NLRP3 system and the secretion of IL-1β were significantly reduced in macrophages after FAO inhibition. These results were confirmed in atherosclerotic lesions of mice treated with trimetazidine as they showed a significant reduction of IL-1β and cleaved caspase-1 in the atherosclerotic lesion as well as of IL-1β and IL-18 in the circulation.

CONCLUSION

Overall, we therefore suggest that the main mechanism of reducing inflammation of trimetazidine and FAO inhibition is the reduction of the NLRP-3 activation leading to reduced levels of the proinflammatory cytokine IL-1β.

Alternative activation of human macrophages enhances tissue factor expression and production of extracellular vesicles

Macrophages are versatile cells that can be polarized by the tissue environment to fulfill required needs. Proinflammatory polarization is associated with increased tissue degradation and propagation of inflammation whereas alternative polarization within a Th2 cytokine environment is associated with wound healing and angiogenesis. To understand whether polarization of macrophages can lead to a procoagulant macrophage subset we polarized human monocyte-derived macrophages to proinflammatory and alternative activation states. Alternative polarization with interleukin-4 and interleukin-13 led to a macrophage phenotype characterized by increased tissue factor (TF) production and release and by an increase in extracellular vesicle production. In addition, TF activity was enhanced in extracellular vesicles of alternatively polarized macrophages. This TF induction was dependent on signal transducer and activator of transcription- 6 signaling and poly ADP ribose polymerase activity. In contrast to monocytes, human macrophages did not show increased TF expression upon stimulation with lipopolysaccharide and interferon-γ. Previous polarization to either a proinflammatory or an alternative activation subset did not change the subsequent stimulation of TF. The inability of proinflammatory activated macrophages to respond to lipopolysaccharide and interferon- γ with an increase in TF production seemed to be due to an increase in TF promoter methylation and was reversible when these macrophages were treated with a demethylating agent. In conclusion, we provide evidence that proinflammatory polarization of macrophages does not lead to enhanced procoagulatory function, whereas alternative polarization of macrophages leads to an increased expression of TF and increased production of TF-bearing extracellular vesicles by these cells suggesting a procoagulatory phenotype of alternatively polarized macrophages.

Effects of Nicorandil on Inflammation, Apoptosis and Atherosclerotic Plaque Progression

Nicorandil, a balanced vasodilator, is used in the second-line therapy of angina pectoris. In this study, we aimed to illuminate the effects of nicorandil on inflammation, apoptosis, and atherosclerotic plaque progression. Twenty-five LDL-R -/- mice were fed a high-fat diet for 14 weeks. After 6 weeks mice were randomly allocated to treatment with nicorandil (10 mg/kg/day) or tap water. Nicorandil treatment led to a more stable plaque phenotype, displaying an increased thickness of the fibrous cap (p = 0.014), a significant reduction in cholesterol clefts (p = 0.045), and enhanced smooth muscle cell content (p = 0.009). In endothelial cells nicorandil did not reduce the induction of adhesion molecules or proinflammatory cytokines. In H₂O₂ challenged endothelial cells, pretreatment with nicorandil significantly reduced the percentage of late apoptotic/necrotic cells (p = 0.016) and the ratio of apoptotic to living cells (p = 0.036). Atherosclerotic lesions of animals treated with nicorandil exhibited a significantly decreased content of cleaved caspase-3 (p = 0.034), lower numbers of apoptotic nuclei (p = 0.040), and reduced 8-oxogunanine staining (p = 0.039), demonstrating a stabilizing effect of nicorandil in established atherosclerotic lesions. We suggest that nicorandil has a positive effect on atherosclerotic plaque stabilization by reducing apoptosis.

Assessment of a long-term in vitro model to characterize the mechanical behavior and macrophage-mediated degradation of a novel, degradable, electrospun poly-urethane vascular graft

An assessment tool to evaluate the degradation of biodegradable materials in a more physiological environment is still needed. Macrophages are critical players in host response, remodeling and degradation. In this study, a cell culture model using monocyte-derived primary macrophages was established to study the degradation, macro-/micro-mechanical behavior and inflammatory behavior of a new designed, biodegradable thermoplastic polyurethane (TPU) scaffold, over an extended period of time in vitro. For in vivo study, the scaffolds were implanted subcutaneously in a rat model for up to 36 weeks. TPU scaffolds were fabricated via the electrospinning method. This technique provided a fibrous scaffold with an average fiber diameter of 1.39 ± 0.76 μm and an average pore size of 7.5 ± 1.1 μm. The results showed that TPU scaffolds supported the attachment and migration of macrophages throughout the three-dimensional matrix. Scaffold degradation could be detected in localized areas, emphasizing the role of adherent macrophages in scaffold degradation. Weight loss, molecular weight and biomechanical strength reduction were evident in the presence of the primary macrophage cells. TPU favored the switch from initial pro-inflammatory response of macrophages to an anti-inflammatory response over time both in vitro and in vivo. Expression of MMP-2 and MMP-9 (the key enzymes in tissue remodeling based on ECM modifications) was also evident in vitro and in vivo. This study showed that the primary monocyte-derived cell culture model represents a promising tool to characterize the degradation, mechanical behavior as well as biocompatibility of the scaffolds during an extended period of observation.

Neutrophil Extracellular Trap Degradation by Differently Polarized Macrophage Subsets

Supplemental Digital Content is available in the text.

Macrophages are immune cells, capable to remodel the extracellular matrix, which can harbor extracellular DNA incorporated into neutrophil extracellular traps (NETs). To study the breakdown of NETs we studied the capability of macrophage subsets to degrade these structures in vitro and in vivo in a murine thrombosis model. Furthermore, we analyzed human abdominal aortic aneurysm samples in support of our in vitro and in vivo results.

Tenascin-C aggravates ventricular dilatation and angiotensin-converting enzyme activity after myocardial infarction in mice

AIMS

Tenascin-C (TN-C) is suggested to be detrimental in cardiac remodelling after myocardial infarction (MI). The aim of this study is to reveal the effects of TN-C on extracellular matrix organization and its haemodynamic influence in an experimental mouse model of MI and in myocardial cell culture during hypoxic conditions.

METHODS AND RESULTS

Myocardial infarction was induced in TN-C knockout (TN-C KO) and wild-type mice. Six weeks later, cardiac function was studied by magnetic resonance imaging and under isolated working heart conditions. Myocardial mRNA levels and immunoreactivity of TN-C, TIMP-1, TIMP-3, and matrix metalloproteinase (MMP)-9, as well as serum and tissue activities of angiotensin-converting enzyme (ACE), were determined at 1 and 6 weeks after infarction. Cardiac output and external heart work were higher, while left ventricular wall stress and collagen expression were decreased (P < 0.05) in TN-C KO mice as compared with age-matched controls at 6 weeks after infarction. TIMP-1 expression was down-regulated at 1 and 6 weeks, and TIMP-3 expression was up-regulated at 1 week (P < 0.01) after infarction in knockout mice. MMP-9 level was lower in TN-C KO at 6 weeks after infarction (P < 0.05). TIMP-3/MMP-9 ratio was higher in knockout mice at 1 and 6 weeks after infarction (P < 0.01). ACE activity in the myocardial border zone (i.e. between scar and free wall) was significantly lower in knockout than in wild-type mice 1 week after MI (P < 0.05).

CONCLUSIONS

Tenascin-C expression is induced by hypoxia in association with ACE activity and MMP-2 and MMP-9 elevations, thereby promoting left ventricular dilatation after MI.

Genetic associations and regulation of expression indicate an independent role for 14q32 snoRNAs in human cardiovascular disease

AIMS

We have shown that 14q32 microRNAs are highly involved in vascular remodelling and cardiovascular disease. However, the 14q32 locus also encodes 41 'orphan' small nucleolar RNAs (snoRNAs). We aimed to gather evidence for an independent role for 14q32 snoRNAs in human cardiovascular disease.

METHODS AND RESULTS

We performed a lookup of the 14q32 region within the dataset of a genome wide association scan in 5244 participants of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER). Single nucleotide polymorphisms (SNPs) in the snoRNA-cluster were significantly associated with heart failure. These snoRNA-cluster SNPs were not linked to SNPs in the microRNA-cluster or in MEG3, indicating that snoRNAs modify the risk of cardiovascular disease independently. We looked at expression of 14q32 snoRNAs throughout the human cardio-vasculature. Expression profiles of the 14q32 snoRNAs appeared highly vessel specific. When we compared expression levels of 14q32 snoRNAs in human vena saphena magna (VSM) with those in failed VSM-coronary bypasses, we found that 14q32 snoRNAs were up-regulated. SNORD113.2, which showed a 17-fold up-regulation in failed bypasses, was also up-regulated two-fold in plasma samples drawn from patients with ST-elevation myocardial infarction directly after hospitalization compared with 30 days after start of treatment. However, fitting with the genomic associations, 14q32 snoRNA expression was highest in failing human hearts. In vitro studies show that the 14q32 snoRNAs bind predominantly to methyl-transferase Fibrillarin, indicating that they act through canonical mechanisms, but on non-canonical RNA targets. The canonical C/D-box snoRNA seed sequences were highly conserved between humans and mice.

CONCLUSION

14q32 snoRNAs appear to play an independent role in cardiovascular pathology. 14q32 snoRNAs are specifically regulated throughout the human vasculature and their expression is up-regulated during cardiovascular disease. Our data demonstrate that snoRNAs merit increased effort and attention in future basic and clinical cardiovascular research.

The adipokine vaspin is associated with decreased coronary in-stent restenosis in vivo and inhibits migration of human coronary smooth muscle cells in vitro

BACKGROUND

Percutaneous coronary intervention represents the most important treatment modality of coronary artery stenosis. In-stent restenosis (ISR) is still a limitation for the long-term outcome despite the introduction of drug eluting stents. It has been shown that adipokines directly influence vessel wall homeostasis by influencing the function of endothelial cells and arterial smooth muscle cells. Visceral adipose tissue-derived serpin vaspin was recently identified as a member of serine protease inhibitor family and serveral studies could demonstrate a relation to metabolic diseases. The aim of this study was to investigate a role of vaspin in the development of in-stent restenosis in vivo and on migration of smooth muscle cells and endothelial cells in vitro.

METHODS

We studied 85 patients with stable coronary artery disease who underwent elective and successful PCI with implatation of drug eluting stents. Blood samples were taken directly before PCI. Vaspin plasma levels were measured by specific ELISA. ISR was evaluated eight months later by coronary angiography. Human coronary artery smooth muscle cells (HCASMC) and human umbilical vein endothelial cells (HUVEC) migration was analyzed by an in-vitro migration assay with different concentrations (0.004ng/mL up to 40ng/mL) of vaspin as well as by an scratch assay. For proliferation an impedance measurement with specialiced E-Plates was performed.

RESULTS

During the follow up period, 14 patients developed ISR. Patients with ISR had significantly lower vaspin plasma levels compared to patients without ISR (0.213 ng/ml vs 0.382 ng/ml; p = 0.001). In patients with plasma vaspin levels above 1.35 ng/ml we could not observe any restenosis. There was also a significant correlation of plasma vaspin levels and late lumen loss in the stented coronary segments. Further we could demonstrate that vaspin nearly abolishes serum induced migration of HCASMC (100% vs. 9%; p<0.001) in a biphasic manner but not migration of HUVEC. Proliferation of HCASMC and HUVEC was not modulated by vaspin treatment.

CONCLUSION

We were able to show that the adipokine vaspin selectively inhibits human coronary SMC migration in vitro and has no effect on HUVEC migration. Vaspin had no effect on proliferation of HUVEC which is an important process of the healing of the stented vessel. In addition, the occurrence of ISR after PCI with implantation of drug eluting stents was significantly associated with low vaspin plasma levels before intervention. Determination of vaspin plasma levels before PCI might be helpful in the identification of patients with high risk for development of ISR after stent implantation. In addition, the selective effects of vaspin on smooth muscle cell migration could potentially be used to reduce ISR without inhibition of re-endothelialization of the stented segment.

The pro-inflammatory marker soluble suppression of tumorigenicity-2 (ST2) is reduced especially in diabetic morbidly obese patients undergoing bariatric surgery

Background

High soluble suppression of tumorigenicity-2 (sST2) is a marker of poor prognosis in chronic inflammatory conditions. ST2 and its ligand interleukin (IL)-33 are elevated in adipose tissue of obese individuals. We aimed to evaluate circulating sST2 and IL-33 as possible markers of metabolic benefit in morbidly overweight patients after Roux-en-Y gastric bypass (RYGB) bariatric surgery.

Methods

sST2, IL-33, high sensitive IL-6, high sensitive C-reactive protein (hsCRP), leptin, cholesterol metabolism and liver parameters were measured in 80 morbidly obese individuals before and 1 year after bariatric surgery.

Results

sST2 was higher (P = 0.03) in diabetics as compared to individuals without diabetes. Baseline sST2 was also higher in males than in females (P= 0.0002). One year after bariatric surgery, sST2 levels were decreased (median 120, IQR 59–176 pg/mL) as compared to sST2 before surgery (median 141, IQR 111–181, P = 0.0024), and the diabetic group showed most pronounced reduction in sST2 (P = 0.0016). An association was found between sST2 and liver function parameters before and after bariatric surgery, and between baseline sST2 and total cholesterol, triglyceride, total low density lipoprotein (LDL), small dense LDL, Apolipoprotein B as well as with small dense high density lipoproteins (HDL). In the subgroup of diabetic patients positive correlation between IL-33 and sST2 (r = 0.44, P = 0.05) was noticed.

Conclusions

Circulating sST2 is associated with markers of liver functions and lipid metabolism in severely obese patients and a reduction of sST2 was shown after successful bariatric surgery, most prominently in diabetic patients.

Long Term Evaluation of Nanofibrous, Bioabsorbable Polycarbonate Urethane Grafts for Small Diameter Vessel Replacement in Rodents

OBJECTIVE

Biodegradable materials for in situ vascular tissue engineering could meet the increasing clinical demand for sufficient synthetic small diameter vascular substitutes in aortocoronary bypass and peripheral vascular surgery. The aim of this study was to design a new degradable thermoplastic polycarbonate urethane (dPCU) with improved biocompatibility and optimal biomechanical properties. Electrospun conduits made from dPCU were evaluated in short and long term follow up and compared with expanded polytetrafluoroethylene (ePTFE) controls.

METHODS

Both conduits were investigated prior to implantation to assess their biocompatibility and inflammatory potential via real time polymerase chain reaction using a macrophage culture. dPCU grafts (n = 28) and ePTFE controls (n = 28) were then implanted into the infrarenal abdominal aorta of Sprague-Dawley rats. After seven days, one, six, and 12 months, grafts were analysed by histology and immunohistochemistry (IHC) and assessed biomechanically.

RESULTS

Anti-inflammatory signalling was upregulated in dPCU conduits and increased significantly over time in vitro. dPCU and ePTFE grafts offered excellent long and short term patency rates (92.9% in both groups at 12 months) in the rat model without dilatation or aneurysm formation. In comparison to ePTFE, dPCU grafts showed transmural ingrowth of vascular specific cells resulting in a structured neovessel formation around the graft. The graft material was slowly reduced, while the compliance of the neovessel increased over time.

CONCLUSION

The newly designed dPCU grafts have the potential to be safely applied for in situ vascular tissue engineering applications. The degradable substitutes showed good in vivo performance and revealed desirable characteristics such as biomechanical stability, non-thrombogenicity, and minimal inflammatory response after long term implantation.

Roux-en-Y-Bariatric Surgery Reduces Markers of Metabolic Syndrome in Morbidly Obese Patients

Background

Obesity is closely linked to increased markers of metabolic syndrome and development of diabetes. Roux-en-Y bariatric surgery reduces hyperinsulinemia and improves insulin sensitivity and hence benefits morbidly obese patients.

Aim

To determine changes in markers of metabolic syndrome, pancreatic function, and hepatic insulin sensitivity in patients before and 1 year after undergoing Roux-en-Y gastric bypass surgery.

Methods

We enrolled 43 consecutive patients in a single center. Markers for metabolic syndrome included proinsulin, insulin, C-peptide, liver enzymes, and serum levels of selected microRNAs hsa-miR-122, hsa-miR-130, hsa-miR-132, and hsa-miR-375.

Results

After surgery, all patients showed a significant 37% drop of body mass index (p < 0.001). Furthermore, proinsulin (59% reduction, p < 0.001), insulin (76% reduction, p < 0.001), and C-peptide (56% reduction, p < 0.001) were all reduced 1 year after surgery. Using the hepatic insulin clearance score, we determined a significant increase in hepatic insulin clearance after surgery (76% increase, p < 0.001). Especially diabetic patients showed a marked 2.1-fold increase after surgery. Hepatic enzymes ALT (35% reduction, p = 0.002) and γGT (48% reduction, p < 0.001) were significantly reduced in all patients with similar improvement in diabetic and non-diabetic patients. miRNAs hsa-miR-122, hsa-miR-130, and hsa-miR-132 were all significantly reduced whereas hsa-miR-375 was increased after gastric bypass surgery (p < 0.001 for all miRNAs).

Conclusion

Both liver and pancreatic stress parameters were reduced significantly 1 year after Roux-en-Y gastric bypass surgery suggesting an overall amelioration of the metabolic syndrome in all patients regardless of previous health status.

Reduction of Premature Aging Markers After Gastric Bypass Surgery in Morbidly Obese Patients

Background

Obesity is considered to be a major comorbidity. Obese patients suffer from an increased proinflammatory state associated with a premature aging phenotype including increased secretion of senescence-associated secretory proteins (SASP) and reduced telomere length. Micro-ribonucleic acids (miRNAs) are non-coding RNA molecules that could modify the post-transcriptional process. Several studies have reported associations between miRNAs and metabolic unhealthy conditions.

Aim

To determine if bariatric surgery and the resulting weight loss could reverse the premature aging phenotype.

Methods

We enrolled 58 morbidly obese patients undergoing bariatric surgery. Markers of premature aging including the SASP IL-6, CRP and PAI-1, 7 miRNAs, as well as telomere length and telomere oxidation in mononuclear cells were evaluated.

Results

Patients showed a significant drop of body mass index (BMI; 43.98 ± 3.5 versus 28.02 ± 4.1, p < 0.001). We observed a significant reduction in SASP including a reduction of 55% of plasma IL-6 levels (p = 0 < 0.001), 83% of CRP levels (p = 0.001) and 15% of plasma PAI-1 levels (p < 0.001). Telomere length doubled in the patient cohort (p < 0.001) and was accompanied by a reduction in the telomere oxidation index by 70% (p < 0.001). Telomere length was inversely correlated with telomere oxidation. The aging-associated miRNA miR10a_5p was upregulated significantly (p = 0.039), while the other tested miRNAs showed no difference.

Conclusion

Our data indicate a significant reduction of the proinflammatory SASP after bariatric surgery. We observed an increase in telomere length and reduced oxidative stress at telomeres. miR10a_5p which is downregulated during aging was upregulated after surgery. Overall, bariatric surgery ameliorated the premature aging phenotype.

Mitochondria Are a Subset of Extracellular Vesicles Released by Activated Monocytes and Induce Type I IFN and TNF Responses in Endothelial Cells

RATIONALE

Extracellular vesicles, including microvesicles, are increasingly recognized as important mediators in cardiovascular disease. The cargo and surface proteins they carry are considered to define their biological activity, including their inflammatory properties. Monocyte to endothelial cell signaling is a prerequisite for the propagation of inflammatory responses. However, the contribution of microvesicles in this process is poorly understood.

OBJECTIVE

To elucidate the mechanisms by which microvesicles derived from activated monocytic cells exert inflammatory effects on endothelial cells.

METHODS AND RESULTS

LPS (lipopolysaccharide)-stimulated monocytic cells release free mitochondria and microvesicles with mitochondrial content as demonstrated by flow cytometry, quantitative polymerase chain reaction, Western Blot, and transmission electron microscopy. Using RNAseq analysis and quantitative reverse transcription-polymerase chain reaction, we demonstrated that both mitochondria directly isolated from and microvesicles released by LPS-activated monocytic cells, as well as circulating microvesicles isolated from volunteers receiving low-dose LPS-injections, induce type I IFN (interferon), and TNF (tumor necrosis factor) responses in endothelial cells. Depletion of free mitochondria significantly reduced the ability of these microvesicles to induce type I IFN and TNF-dependent genes. We identified mitochondria-associated TNFα and RNA from stressed mitochondria as major inducers of these responses. Finally, we demonstrated that the proinflammatory potential of microvesicles and directly isolated mitochondria were drastically reduced when they were derived from monocytic cells with nonrespiring mitochondria or monocytic cells cultured in the presence of pyruvate or the mitochondrial reactive oxygen species scavenger MitoTEMPO.

CONCLUSIONS

Mitochondria and mitochondria embedded in microvesicles constitute a major subset of extracellular vesicles released by activated monocytes, and their proinflammatory activity on endothelial cells is determined by the activation status of their parental cells. Thus, mitochondria may represent critical intercellular mediators in cardiovascular disease and other inflammatory settings associated with type I IFN and TNF signaling.

Bariatric surgery in morbidly obese individuals affects plasma levels of protein C and thrombomodulin

Obesity is associated with a prothrombotic milieu and an increased risk for thrombotic events. Bariatric surgery is the most effective treatment for obesity resulting in dramatic weight loss and reduced inflammation and extrinsic coagulation pathway activation. Blood samples were drawn from 60 patients undergoing Roux-en-Y gastric bypass surgery before and 1 year after the intervention. Protein C (PC), activated PC (APC), soluble thrombomodulin (TM), soluble E-selectin (E-Sel), prothrombin time (PT) and activated partial thromboplastin time (aPTT) were evaluated. Both PC (187.4 ± 64.5% before surgery to 118.1 ± 48% 1 year after surgery, p < 0.001) and APC (138.7 ± 64.4% before surgery to 69.1 ± 65.7% after surgery, p < 0.001) were reduced following surgical intervention. TM showed a similar behavior with a reduction of soluble TM after the procedure from 5.7 ± 2.6 to 3.2 ± 1.4 ng/ml (p < 0.001). Similarly, soluble E-Sel was reduced after surgery from 26.6 ± 12.7 to 5.5 ± 4.1 ng/ml (p < 0.001). In contrast, aPTT was not shortened but slightly increased from 29.1 ± 4.8 s. before surgery to 31 ± 4.4 s. (p = 0.001) after surgery and levels of PT were reduced after surgery to 89.6 ± 15.5% from an initial 97.5 ± 13.5% (p < 0.001). In conclusion, we demonstrate a reduction of PC and APC 1 year after bariatric surgery accompanied by a reduction in soluble TM and soluble E-Sel. The reduction of PC and APC is not paralleled by a reduction but in contrast by a prolongation of aPTT suggesting a compensatory upregulation of PC during obesity. The reduction of TM and E-Sel might hint towards an improved endothelial function in this cohort of patients.

The impact of age on cardiac function and extracellular matrix component expression in adverse post-infarction remodeling in mice

The aim of this study was to describe the potential associations of the expression of matricellular components in adverse post-infarction remodeling of the geriatric heart. In male geriatric (OM, age: 18 months) and young (YM, age: 11 weeks) OF1 mice myocardial infarction (MI) was induced by permanent ligation of the left anterior descending coronary artery. Cardiac function was evaluated by MRI. Plasma and myocardial tissue samples were collected 3d, 7d, and 32d post-MI. Age and MI were associated with impaired cardiac function accompanied by left-ventricular (LV) dilatation. mRNA expression of MMP-2 (7d: p < 0.05), TIMP-1 (7d: p < 0.05), TIMP-2 (7d: p < 0.05), Collagen-1 (3d and 7d: p < 0.05) and Collagen-3 (7d: p < 0.05) in LV non-infarcted myocardium was significantly higher in YM than in OM after MI. MMP-9 activity in plasma was increased in OM after MI (3d: p < 0.01). Tenascin-C protein levels assessed by ELISA were decreased in OM as compared to YM after MI in plasma (3d: p < 0.001, 7d: p < 0.05) and LV non-infarcted myocardium (7d: p < 0.01). Dysregulation in ECM components in non-infarcted LV might be associated and contribute to adverse LV remodeling and impaired cardiac function. Thus, targeting ECM might be a potential therapeutic approach to enhance cardiac function in geriatric patients following MI.

Cardioprotective cytokine interleukin-33 is up-regulated by statins in human cardiac tissue

Interleukin (IL)‐33 is a member of the IL‐1 family and is able to act cardioprotective. The aim of this study was to investigate the regulation of IL‐33 by 3‐hydroxy‐3‐methylglutaryl‐coenzyme‐A (HMG‐CoA) reductase inhibitors (statins) and bisphosphonates (BPs) in human cardiac tissue. The lipophilic fluvastatin, simvastatin, atorvastatin, and lovastatin as well as the nitrogenous BPs alendronate and ibandronate, but not hydrophilic pravastatin increased IL‐33 mRNA and intracellular IL‐33 protein levels in both human adult cardiac myocytes (HACM) and fibroblasts (HACF). Additionally, fluvastatin reduced soluble ST2 secretion from HACM. IL‐33 was also up‐regulated by the general inhibitor of prenylation perillic acid, a RhoA kinase inhibitor Y‐27632, and by latrunculin B, but statin‐induced IL‐33 expression was inhibited by mevalonate, geranylgeranyl pyrophosphate (GGPP) and RhoA activator U‐46619. The IL‐33 promoter was 2.3‐fold more accessible in statin‐treated HACM compared to untreated cells (P = 0.037). In explanted hearts of statin‐treated patients IL‐33 protein was up‐regulated as compared with the hearts of non‐statin‐treated patients (P = 0.048). As IL‐33 was previously shown to exert cardioprotective effects, one could speculate that such up‐regulation of IL‐33 expression in human cardiac cells, which might happen mainly through protein geranylgeranylation, could be a novel mechanism contributing to known cardioprotective effects of statins and BPs.

Thrombin Augments Vascular Cell-dependent Migration of Human Mast Cells: Role of MGF

Recent data suggest that auricular thrombosis is associated with accumulation of mast cells (MC) in the upper endocardium (where usually no MC reside) and local expression of MGF (mast cell growth factor) (25). In this study, the role of vascular cells, thrombin-activation and MGF, in MC-migration was analyzed. For this purpose, cultured human auricular endocardial cells (HAUEC), umbilical vein endothelial cells (HUVEC) and uterine-(HUTMEC) and skin-derived (HSMEC) microvascular endothelial cells were exposed to thrombin or control medium, and the migration of primary tissue MC (lung, n = 6) and HMC-1 cells (human MC-line) against vascular cells (supernatants) measured. Supernatants (24 h) of unstimulated vascular cells (monolayers of endocardium or endothelium) as well as recombinant (rh) MGF induced a significant migratory response in HMC-1 (control: 3025 ± 344 cells [100 ± 11.4%] vs. MGF, 100 ng/ml: 8806 ± 1019 [291 ± 34%] vs. HAUEC: 9703 ± 1506 [320.8 ± 49.8%] vs. HUTMEC: 8950 ± 1857 [295.9 ± 61.4%] vs. HSMEC: 9965 ± 2018 [329.4 ± 66.7%] vs. HUVEC: 9487 ± 1402 [313.6 ± 46.4%], p <0.05) as well as in primary lung MC. Thrombin-activation (5 U/ml, 12 h) of vascular cells led to an augmentation of the directed migration of MC as well as to a hirudin-sensitive increase in MGF synthesis and release. Moreover, a blocking anti-MGF antibody was found to inhibit MC-migration induced by unstimulated or thrombin-activated vascular cells. Together, these data show that endocardial and other vascular cells can induce migration of human MC. This MC-chemotactic signal of the vasculature is associated with expression and release of MGF, augmentable by thrombin, and may play a role in the pathophysiology of (auricular) thrombosis.

Acellular vascular matrix grafts from human placenta chorion: Impact of ECM preservation on graft characteristics, protein composition and in vivo performance

Small diameter vascular grafts from human placenta, decellularized with either Triton X-100 (Triton) or SDS and crosslinked with heparin were constructed and characterized. Graft biochemical properties, residual DNA, and protein composition were evaluated to compare the effect of the two detergents on graft matrix composition and structural alterations. Biocompatibility was tested in vitro by culturing the grafts with primary human macrophages and in vivo by subcutaneous implantation of graft conduits (n = 7 per group) into the flanks of nude rats. Subsequently, graft performance was evaluated using an aortic implantation model in Sprague Dawley rats (one month, n = 14). In situ graft imaging was performed using MRI angiography. Retrieved specimens were analyzed by electromyography, scanning electron microscopy, histology and immunohistochemistry to evaluate cell migration and the degree of functional tissue remodeling. Both decellularization methods resulted in grafts of excellent biocompatibility in vitro and in vivo, with low immunogenic potential. Proteomic data revealed removal of cytoplasmic proteins with relative enrichment of ECM proteins in decelluarized specimens of both groups. Noteworthy, LC-Mass Spectrometry analysis revealed that 16 proteins were exclusively preserved in Triton decellularized specimens in comparison to SDS-treated specimens. Aortic grafts showed high patency rates, no signs of thrombus formation, aneurysms or rupture. Conduits of both groups revealed tissue-specific cell migration indicative of functional remodeling. This study strongly suggests that decellularized allogenic grafts from the human placenta have the potential to be used as vascular replacement materials. Both detergents produced grafts with low residual immunogenicity and appropriate mechanical properties. Observed differences in graft characteristics due to preservation method had no impact on successful in vivo performance in the rodent model.

Matrix Metalloproteinase-2 Impairs Homing of Intracoronary Delivered Mesenchymal Stem Cells in a Porcine Reperfused Myocardial Infarction: Comparison With Intramyocardial Cell Delivery

Background

Intracoronary (IC) injection of mesenchymal stem cells (MSCs) results in a prompt decrease of absolute myocardial blood flow (AMF) with late and incomplete recovery of myocardial tissue perfusion. Here, we investigated the effect of decreased AMF on oxidative stress marker matrix metalloproteinase-2 (MMP-2) and its influence on the fate and homing and paracrine character of MSCs after IC or intramyocardial cell delivery in a closed-chest reperfused myocardial infarction (MI) model in pigs.

Methods

Porcine MSCs were transiently transfected with Ad-Luc and Ad-green fluorescent protein (GFP). One week after MI, the GFP-Luc-MSCs were injected either IC (group IC, 11.00 ± 1.07 × 10⁶) or intramyocardially (group IM, 9.88 ± 1.44 × 10⁶). AMF was measured before, immediately after, and 24 h post GFP-Luc-MSC delivery. In vitro bioluminescence signal was used to identify tissue samples containing GFP-Luc-MSCs. Myocardial tissue MMP-2 and CXCR4 receptor expression (index of homing signal) were measured in bioluminescence positive and negative infarcted and border, and non-ischemic myocardial areas 1-day post cell transfer. At 7-day follow-up, myocardial homing (cadherin, CXCR4, and stromal derived factor-1alpha) and angiogenic [fibroblast growth factor 2 (FGF2) and VEGF] were quantified by ELISA of homogenized myocardial tissues from the bioluminescence positive and negative infarcted and border, and non-ischemic myocardium. Biodistribution of the implanted cells was quantified by using Luciferase assay and confirmed by fluorescence immunochemistry. Global left ventricular ejection fraction (LVEF) was measured at baseline and 1-month post cell therapy using magnet resonance image.

Results

AMF decreased immediately after IC cell delivery, while no change in tissue perfusion was found in the IM group (42.6 ± 11.7 vs. 56.9 ± 16.7 ml/min, p = 0.018). IC delivery led to a significant increase in myocardial MMP-2 64 kD expression (448 ± 88 vs. 315 ± 54 intensity × mm², p = 0.021), and decreased expression of CXCR4 (592 ± 50 vs. 714 ± 54 pg/tissue/ml, p = 0.006), with significant exponential decay between MMP-2 and CXCR4 (r = 0.679, p < 0.001). FGF2 and VEGF of the bioluminescence infarcted and border zone of homogenized tissues were significantly elevated in the IM goups as compared to IC group. LVEF increase was significantly higher in IM group (0.8 ± 8.4 vs 5.3 ± 5.2%, p = 0.046) at the 1-month follow up.

Conclusion

Intracoronary stem cell delivery decreased AMF, with consequent increase in myocardial expression of MMP-2 and reduced CXCR4 expression with lower level of myocardial homing and angiogenic factor release as compared to IM cell delivery.

The estrogen metabolite 17β-dihydroequilenin counteracts interleukin-1α induced expression of inflammatory mediators in human endothelial cells in vitro via NF-κB pathway

In most studies showing cardio- and vasculoprotective effects of estrogens, 17β-estradiol was used and little information on possible effects of different estrogen metabolites is yet available. We investigated whether particular estrogen metabolites are effective in counteracting inflammatory activation of human endothelium. Human endothelial cells were incubated with 17α-dihydroequilenin, 17β-dihydroequilenin, δ-8,9-dehydroestrone, estrone and 17β-estradiol and stimulated with interleukin (IL)-1α.The expression of IL-6, IL-8 and monocyte chemoattractant protein-1 (MCP-1) was determined. 17β-dihydroequilenin and 17β-estradiol at a concentration of 1µM reduced IL-1α-induced up regulation of IL-6, IL-8 and MCP-1 close to control levels. When both compounds were used in combination an additive effect was observed. 17α-dihydroequilenin and δ-8,9-dehydroestrone showed a similar anti-inflammatory effect only when used at 10µM whereas estrone had no effect. The effect of 17β-dihydroequilenin on IL-1α-induced production of IL-6, IL-8 and MCP-1 was reversed by the estrogen receptor antagonist ICI 182,780. 17β-dihydroequilenin also inhibited IL-1α-induced translocation of p50 and p65 to the nucleus of the cells. We have identified the estrogen metabolite 17β-dihydroequilenin, as an inhibitor of inflammatory activation of human endothelial cells. Characterization of specific estrogens – as shown in our study – could provide the basis for tailored therapies, which might be able to achieve vasoprotection without adverse side effects.

Anti-thrombotic and pro-fibrinolytic effects of levosimendan in human endothelial cells in vitro

AIMS

Levosimendan is an inodilator for the treatment of acute decompensated heart failure (HF). Data from clinical studies suggest that levosimendan is particularly effective in HF due to myocardial infarction. After acute revascularization, no reflow-phenomenon is a common complication that may lead to pump failure and cardiogenic shock. Our aim was to examine whether levosimendan interferes with the pro-thrombotic phenotype of activated endothelial cells in vitro.

METHODS

Human heart microvascular endothelial cells (HHMEC) and human umbilical vein endothelial cells (HUVEC) were treated with interleukin-1β (IL-1β) (200U/mL) or thrombin (5U/mL) and co-treated with or without levosimendan (0.1-10μM) for 2-24h. In addition, flow experiments were performed. Effects on plasminogen activator inhibitor-1 (PAI-1) and tissue factor (TF) expression and activity were measured by rt-PCR, specific ELISA and flow cytometry.

RESULTS

Treatment with IL-1β or thrombin significantly increased the expression of PAI-1 and TF in endothelial cells. Co-treatment with levosimendan strongly attenuated the effects of IL-1β and thrombin on PAI-1 and TF mRNA by up to 50% and 45%, in a dose- and time-dependent manner. Similar results were obtained under flow conditions. Furthermore, co-treatment with levosimendan dampened the antigen production of PAI-1 and the surface expression of TF by 35% and 45%, respectively. Additionally, levosimendan diminished both TF and PAI-1 activity.

CONCLUSION

Levosimendan down-regulates the expression of the pro-thrombotic and anti-fibrinolytic biomolecules TF and PAI-1 in activated human endothelial cells. Our findings may, at least in part, explain some of the beneficial effects of levosimendan after myocardial reperfusion.

Inhibition of CD34+ cell migration by matrix metalloproteinase-2 during acute myocardial ischemia, counteracted by ischemic preconditioning

Background. Mobilization of bone marrow-origin CD34+ cells was investigated 3 days (3d) after acute myocardial infarction (AMI) with/without ischemic preconditioning (IP) in relation to stromal-derived factor-1 (SDF-1α)/ chemokine receptor type 4 (CXCR4) axis, to search for possible mechanisms behind insufficient cardiac repair in the first days post-AMI.  Methods. Closed-chest reperfused AMI was performed by percutaneous balloon occlusion of the mid-left anterior descending (LAD) coronary artery for 90min, followed by reperfusion in pigs. Animals were randomized to receive either IP initiated by 3x5min cycles of re-occlusion/re-flow prior to AMI (n=6) or control AMI (n=12). Blood samples were collected at baseline, 3d post-AMI, and at 1-month follow-up to analyse chemokines and mobilized CD34+ cells. To investigate the effect of acute hypoxia, SDF-1α and matrix metalloproteinase (MMP)-2 in vitro were assessed, and a migration assay of CD34+ cells toward cardiomyocytes was performed.  Results. Reperfused AMI induced significant mobilisation of CD34+ cells (baseline: 260±75 vs. 3d: 668±180; P<0.001) and secretion of MMP-2 (baseline: 291.83±53.40 vs. 3d: 369.64±72.89; P=0.011) into plasma, without affecting the SDF-1α concentration. IP led to the inhibition of MMP-2 (IP: 165.67±47.99 vs. AMI: 369.64±72.89; P=0.004) 3d post-AMI, accompanied by increased release of SDF-1α (baseline: 23.80±12.36 vs. 3d: 45.29±11.31; P=0.05) and CXCR4 (baseline: 0.59±0.16 vs. 3d: 2.06±1.42; P=0.034), with a parallel higher level of mobilisation of CD34+ cells (IP: 881±126 vs. AMI: 668±180; P=0.026), compared to non-conditioned AMI. In vitro, CD34+ cell migration toward cardiomyocytes was enhanced by SDF-1α, which was completely abolished by 90min hypoxia and co-incubation with MMP-2.  Conclusions. Non-conditioned AMI induces MMP-2 release, hampering the ischemia-induced increase in SDF-1α and CXCR4 by cleaving the SDF-1α/CXCR4 axis, with diminished mobilization of the angiogenic CD34+ cells. IP might influence CD34+ cell mobilization via inhibition of MMP-2.

Reduced Ang2 expression in aging endothelial cells

Aging endothelial cells are characterized by increased cell size, reduced telomere length and increased expression of proinflammatory cytokines. In addition, we describe here that aging reduces the migratory distance of endothelial cells. Furthermore, we observe an increase of the quiescence protein Ang1 and a decrease of the endothelial activation protein Ang2 upon aging. Supplementing Ang2 to aged endothelial cells restored their migratory capacity. We conclude that aging shifts the balance of the Ang1/Ang2 network favouring a quiescent state. Activation of endothelial cells in aging might be necessary to enhance wound healing capacities.

Intermittent Hypoxia Causes Inflammation and Injury to Human Adult Cardiac Myocytes

BACKGROUND

Intermittent hypoxia may occur in a number of clinical scenarios, including interruption of myocardial blood flow or breathing disorders such as obstructive sleep apnea. Although intermittent hypoxia has been linked to cardiovascular and cerebrovascular disease, the effect of intermittent hypoxia on the human heart is not fully understood. Therefore, in the present study, we compared the cellular responses of cultured human adult cardiac myocytes (HACMs) exposed to intermittent hypoxia and different conditions of continuous hypoxia and normoxia.

METHODS

HACMs were exposed to intermittent hypoxia (0%-21% O2), constant mild hypoxia (10% O2), constant severe hypoxia (0% O2), or constant normoxia (21% O2), using a novel cell culture bioreactor with gas-permeable membranes. Cell proliferation, lactate dehydrogenase release, vascular endothelial growth factor release, and cytokine (interleukin [IL] and macrophage migration inhibitory factor) release were assessed at baseline and after 8, 24, and 72 hours of exposure. A signal transduction pathway finder array was performed to determine the changes in gene expression.

RESULTS

In comparison with constant normoxia and constant mild hypoxia, intermittent hypoxia induced earlier and greater inflammatory response and extent of cell injury as evidenced by lower cell numbers and higher lactate dehydrogenase, vascular endothelial growth factor, and proinflammatory cytokine (IL-1β, IL-6, IL-8, and macrophage migration inhibitory factor) release. Constant severe hypoxia showed more detrimental effects on HACMs at later time points. Pathway analysis demonstrated that intermittent hypoxia primarily altered gene expression in oxidative stress, Wnt, Notch, and hypoxia pathways.

CONCLUSIONS

Intermittent and constant severe hypoxia, but not constant mild hypoxia or normoxia, induced inflammation and cell injury in HACMs. Cell injury occurred earliest and was greatest after intermittent hypoxia exposure. Our in vitro findings suggest that intermittent hypoxia exposure may produce rapid and substantial damage to the human heart.

Interleukin-33 stimulates GM-CSF and M-CSF production by human endothelial cells

Interleukin (IL)-33, a member of the IL-1 family of cytokines, is involved in various inflammatory conditions targeting amongst other cells the endothelium. Besides regulating the maturation and functions of myeloid cells, granulocyte macrophage-colony stimulating factor (GM-CSF) and macrophage-CSF (M-CSF) have been shown to play a role in such pathologies too. It was the aim of our study to investigate a possible influence of IL-33 on GM-CSF and M-CSF production by human endothelial cells. IL-33, but not IL-18 or IL-37, stimulated GM-CSF and M-CSF mRNA expression and protein production by human umbilical vein endothelial cells (HUVECs) and human coronary artery ECs (HCAECs) through the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway in an IL-1-independent way. This effect was inhibited by the soluble form of ST2 (sST2), which is known to act as a decoy receptor for IL-33. The 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor fluvastatin could also be shown to moderately reduce the IL-33-mediated effect on M-CSF, but not on GM-CSF expression. In addition, IL-33, IL-1β, GM-CSF and M-CSF were detected in endothelial cells of human carotid atherosclerotic plaques using immunofluorescence. Upregulation of GM-CSF and M-CSF production by human endothelial cells, an effect that appears to be mediated by NF-κB and to be independent of IL-1, may be an additional mechanism through which IL-33 contributes to inflammatory activation of the vessel wall.

Tissue factor is induced by interleukin-33 in human endothelial cells: a new link between coagulation and inflammation

Tissue factor (TF) is the primary trigger of coagulation. Elevated levels of TF are found in atherosclerotic plaques, and TF leads to thrombus formation when released upon plaque rupture. Interleukin (IL)-33 was previously shown to induce angiogenesis and inflammatory activation of endothelial cells (ECs). Here, we investigated the impact of IL-33 on TF in human ECs, as a possible new link between inflammation and coagulation. IL-33 induced TF mRNA and protein in human umbilical vein ECs and coronary artery ECs. IL-33-induced TF expression was ST2- and NF-κB-dependent, but IL-1-independent. IL-33 also increased cell surface TF activity in ECs and TF activity in ECs-derived microparticles. IL-33-treated ECs reduced coagulation time of whole blood and plasma but not of factor VII-deficient plasma. In human carotid atherosclerotic plaques (n = 57), TF mRNA positively correlated with IL-33 mRNA expression (r = 0.691, p < 0.001). In this tissue, IL-33 and TF protein was detected in ECs and smooth muscle cells by immunofluorescence. Furthermore, IL-33 and TF protein co-localized at the site of clot formation within microvessels in plaques of patients with symptomatic carotid stenosis. Through induction of TF in ECs, IL-33 could enhance their thrombotic capacity and thereby might impact on thrombus formation in the setting of atherosclerosis.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) is Associated with Symptomatic Carotid Atherosclerosis and Drives Pro-inflammatory State In Vitro

OBJECTIVE

Neutrophil gelatinase-associated lipocalin (NGAL), a protein found in activated neutrophils, is expressed in kidney tubule cells in response to noxious stimuli, and is thus recognized as a marker of acute kidney injury. Recent studies have suggested that NGAL could also have pathophysiological importance in cardiovascular diseases. The aim of the present study was to examine NGAL expression in human carotid endarterectomy tissues ex vivo as well as the effects of NGAL in the main cell types involved in atherogenesis, namely in human macrophages, endothelial cells, and smooth muscle cells in vitro.

METHODS

NGAL protein was analyzed in human endarterectomy samples from patients with asymptomatic and symptomatic carotid stenosis by immunofluorescence, and NGAL mRNA expression was detected using RealTime-PCR. Human monocyte derived macrophages (MDM), human coronary artery smooth muscle cells (HCASMC), and human umbilical vein endothelial cells (HUVEC) were treated with recombinant human (rh) NGAL at different concentrations. Interleukin (IL)-6, IL-8, and monocyte chemo-attractant protein-1 (MCP-1) were determined by specific enzyme linked immunosorbent assays (ELISAs) in culture supernatants of such treated cells.

RESULTS

Expression of NGAL protein was demonstrated by macrophages, smooth muscle cells, and endothelial cells in human carotid atherosclerotic tissue. NGAL mRNA expression was detected at a higher rate in atherosclerotic tissue of patients with symptomatic carotid stenosis (in 70%; n = 19) compared with asymptomatic patients (in 37%; n = 20, p < .001). Treatment of MDM, HCASMC, and HUVEC with rhNGAL led to a significant (p < 0.05) and concentration dependent increase of pro-inflammatory cytokines IL-6, IL-8, and MCP-1 in all cell types analyzed.

CONCLUSION

By induction of pro-inflammatory mediators in human macrophages, smooth muscle cells and endothelial cells, NGAL, which is predominantly expressed in atherosclerotic plaques of symptomatic patients, could be involved in creating the local and systemic pro-inflammatory environment characteristic for atherosclerosis.

Age intrinsic loss of telomere protection via TRF1 reduction in endothelial cells

Aging is a major factor predisposing for multiple diseases. Telomeres at the ends of chromosomes protect the integrity of chromosomal DNA. A specialized six-protein complex termed shelterin protects the telomere from unwanted interaction with DNA damage pathways. The aim of our study was to evaluate the integrity of telomeres and the stability of telomere protection during aging in endothelial cells (EC). We describe that aging EC can be characterized by an increased cell size (40%, p=0.02) and increased expression of PAI 1 (4 fold, p=0.02), MCP1 (10 fold, p=0.001) and GMCSF (15 fold, p=0.004). Telomeric state in aging cells is defined by an increased telomere oxidation (27%, p=0.01), reduced telomere length (62%, p=0.02), and increased DNA damage foci formation (5% in young EC versus 16% in aged EC, p=0.003). This telomeric dysfunction is accompanied by a reduction in the shelterin component TRF1 (33% mRNA, p=0.001; 24% protein, p=0.007). Overexpression of TRF1 in aging EC reduced telomere-associated DNA damage foci to 5% (p=0.02) and reduced expression levels of MCP1 (18% reduction, p=0.008). Aged EC have increased telomere damage and an intrinsic loss of telomere protection. Reestablishing telomere integrity could therefore be a target for rejuvenating endothelial cell function.

Cyclic and constant hyperoxia cause inflammation, apoptosis and cell death in human umbilical vein endothelial cells

BACKGROUND

Perioperative high-dose oxygen (O2 ) exposure can cause hyperoxia. While the effect of constant hyperoxia on the vascular endothelium has been investigated to some extent, the impact of cyclic hyperoxia largely remains unknown. We hypothesized that cyclic hyperoxia would induce more injury than constant hyperoxia to human umbilical vein endothelial cells (HUVECs).

METHODS

HUVECs were exposed to cyclic hyperoxia (5-95% O2 ) or constant hyperoxia (95% O2 ), normoxia (21% O2 ), and hypoxia (5% O2 ). Cell growth, viability (Annexin V/propidium iodide and 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT) lactate dehydrogenase (LDH), release, cytokine (interleukin, IL and macrophage migration inhibitory factor, MIF) release, total antioxidant capacity (TAC), and superoxide dismutase activity (SOD) of cell lysate were assessed at baseline and 8, 24, and 72 h. A signal transduction pathway finder array for gene expression analysis was performed after 8 h.

RESULTS

Constant and cyclic hyperoxia-induced gradually detrimental effects on HUVECs. After 72 h, constant or cyclic hyperoxia exposure induced change in cytotoxic (LDH +12%, P = 0.026; apoptosis +121/61%, P < 0.01; alive cells -15%, P < 0.01; MTT -16/15%, P < 0.01), inflammatory (IL-6 +142/190%, P < 0.01; IL-8 +72/43%, P < 0.01; MIF +147/93%, P < 0.01), or redox-sensitive (SOD +278%, TAC-25% P < 0.01) markers. Gene expression analysis revealed that constant and cyclic hyperoxia exposure differently activates oxidative stress, nuclear factor kappa B, Notch, and peroxisome proliferator-activated receptor pathways.

CONCLUSIONS

Extreme hyperoxia exposure induces inflammation, apoptosis and cell death in HUVECs. Although our findings cannot be transferred to clinical settings, results suggest that hyperoxia exposure may cause vascular injury that could play a role in determining perioperative outcome.

Levosimendan exerts anti-inflammatory effects on cardiac myocytes and endothelial cells in vitro

Levosimendan is a positive inotropic drug for the treatment of acute decompensated heart failure (HF). Clinical trials showed that levosimendan was particularly effective in HF due to myocardial infarction. Myocardial necrosis induces a strong inflammatory response, involving chemoattractants guiding polymorphonuclear neutrophils (PMN) into the infarcted myocardial tissue. Our aim was to examine whether levosimendan exhibits anti-inflammatory effects on human adult cardiac myocytes (HACM) and human heart microvascular endothelial cells (HHMEC). Cardiac myocytes and endothelial cells were stimulated with interleukin-1β (IL)-1β (200 U/ml) and treated with levosimendan (0.1-10 µM) for 2-48 hours. IL-1β strongly induced expression of IL-6 and IL-8 in HACM and E-selectin and intercellular adhesion molecule-1 (ICAM-1) in HHMEC and human umbilical vein endothelial cells (HUVEC). Treatment with levosimendan strongly attenuated IL-1β-induced expression of IL-6 and IL-8 in HACM as well as E-selectin and ICAM-1 in ECs. Levosimendan treatment further reduced adhesion of PMN to activated endothelial cells under both static and flow conditions by approximately 50 %. Incubation with 5-hydroxydecanoic acid, a selective blocker of mitochondrial ATP-dependent potassium channels, partly abolished the above seen anti-inflammatory effects. Additionally, levosimendan strongly diminished IL-1β-induced reactive oxygen species and nuclear factor-κB (NF-κB) activity through inhibition of S536 phosphorylation. In conclusion, levosimendan exhibits anti-inflammatory effects on cardiac myocytes and endothelial cells in vitro. These findings could explain, at least in part, the beneficial effects of levosimendan after myocardial infarction.

Interleukin-33 induces urokinase in human endothelial cells--possible impact on angiogenesis

BACKGROUND

Urokinase-type plasminogen activator (u-PA) plays a pivotal role in extracellular proteolysis and is thought to be critically involved in the modulation of angiogenesis. Interleukin (IL)-33 is a member of the IL-1 cytokine family, which is thought to act as danger signal that is released from cells after injury. IL-33 is involved in the pathogenesis of various inflammatory diseases and previously was shown to induce angiogenesis and inflammatory activation of endothelial cells.

OBJECTIVE

We investigated the impact of IL-33 on u-PA in endothelial cells as a new possible function for IL-33.

METHODS AND RESULTS

We could demonstrate that IL-33 upregulated u-PA mRNA expression and protein production in human coronary artery and human umbilical vein endothelial cells in a time- and concentration-dependent manner via interaction with its receptor ST2 and activation of the nuclear factor-κB pathway but independent of autocrine IL-1-induced effects. The hydroxymethylglutaryl-coenzyme A reductase inhibitor simvastatin abrogated the IL-33-induced increase in u-PA, thus providing further evidence for pleiotropic effects of statins. IL-33 induced u-PA-dependent capillary-like tube formation and vessel sprouting. In human carotid atherosclerotic plaques (n = 16), u-PA mRNA positively correlated with IL-33 mRNA expression (r = 0.780, P < 0.001). Furthermore, IL-33 and u-PA protein were detected in endothelial cells in these samples using fluorescence immunohistochemistry.

CONCLUSIONS

We hypothesize that IL-33, representing a danger signal that is released after tissue damage, in addition to its role in the inflammatory activation of endothelial cells, is involved in u-PA-driven angiogenesis, a process that has been shown before to be linked to inflammation in various pathologies.

Glycoprotein 130 polymorphism predicts soluble glycoprotein 130 levels

OBJECTIVE

Interleukin-6 (IL-6) is a key cytokine in inflammatory diseases. It exerts its biological function via binding to a homodimer of its signal transducer glycoprotein 130 (gp130). Soluble gp130 (sgp130) is the natural inhibitor of IL-6 trans-signalling. The aim of this study was to test a possible influence of the gp130 genotype on sgp130 serum levels.

MATERIAL AND METHODS

In two separate populations, subjects were genotyped for the gp130 polymorphism G148C. Sgp130, IL-6 and soluble interleukin-6 receptor (sIL-6R) levels were measured. The OSLO population consisted of 546 male subjects at high risk for CAD. The VIENNA population consisted of 299 male subjects with angiographically proven CAD.

RESULTS

In the OSLO population, 124 (22.7%) subjects were hetero- or homozygote for the rare C allele. Individuals carrying the polymorphism had significantly higher levels of sgp130. In a multivariate linear regression model this association remained significant (adjusted p=0.001). In the VIENNA population, 48 (16.1%) subjects were hetero- or homozygote for the rare C allele. Consistent with the former study, sgp130 levels were significantly higher in carriers of the polymorphism compared to wildtype carriers (adjusted p=0.038). In the VIENNA population, sgp130 levels were significantly higher in diabetic patients. In the OSLO population, sgp130 was higher in patients with increased body mass index and in smokers (p<0.05).

CONCLUSIONS

Sgp130 serum levels are significantly higher in subjects carrying the gp130 polymorphism G148C compared to wildtype carriers. This finding proposes a possible genetical influence on sgp130 levels which may alter individual coping mechanisms in inflammatory diseases.

More than a simple storage organ: adipose tissue as a source of adipokines involved in cardiovascular disease

Overweight and obesity in many countries have developed into a serious health problem by themselves and by their impact on other pathologies such as insulin resistance, type 2 diabetes, hypertension, heart disease and cancer. The modulation of these diseases by adipose tissue-derived biomolecules, so-called adipokines, could be the key to differentiate between metabolically healthy and unhealthy obesity. This review will discuss the pathophysiological role of selected adipokines, primarily focusing on cardiovascular diseases. Furthermore, we will highlight possible therapeutic approaches, which target these biomolecules.

Components of the interleukin-33/ST2 system are differentially expressed and regulated in human cardiac cells and in cells of the cardiac vasculature

Interleukin-33 (IL-33) is a recently described member of the IL-1 family of cytokines, which was identified as a ligand for the ST2 receptor. Components of the IL-33/ST2 system were shown to be expressed in normal and pressure overloaded human myocardium, and soluble ST2 (sST2) has emerged as a prognostic biomarker in myocardial infarction and heart failure. However, expression and regulation of IL-33 in human adult cardiac myocytes and fibroblasts was not tested before. In this study we found that primary human adult cardiac fibroblasts (HACF) and human adult cardiac myocytes (HACM) constitutively express nuclear IL-33 that is released during cell necrosis. Tumor necrosis factor (TNF)-α, interferon (IFN)-γ and IL-1β significantly increased both IL-33 protein and IL-33 mRNA expression in HACF and HACM as well as in human coronary artery smooth muscle cells (HCASMC). The nuclear factor-κB (NF-κB) inhibitor dimethylfumarate inhibited TNF-α- and IL-1β-induced IL-33 production as well as nuclear translocation of p50 and p65 NF-κB subunits in these cells. Mitogen-activated protein/extracellular signal-regulated kinase inhibitor U0126 abrogated TNF-α-, IFN-γ-, and IL-1β-induced and Janus-activated kinase inhibitor I reduced IFN-γ-induced IL-33 production. We detected IL-33 mRNA in human myocardial tissue from patients undergoing heart transplantation (n=27) where IL-33 mRNA levels statistically significant correlated with IFN-γ (r=0.591, p=0.001) and TNF-α (r=0.408, p=0.035) mRNA expression. Endothelial cells in human heart expressed IL-33 as well as ST2 protein. We also reveal that human cardiac and vascular cells have different distribution patterns of ST2 isoforms (sST2 and transmembrane ST2L) mRNA expression and produce different amounts of sST2 protein. Both human macrovascular (aortic and coronary artery) and heart microvascular endothelial cells express specific mRNA for both ST2 isoforms (ST2L and sST2) and are a source for sST2 protein, whereas cardiac myocytes, cardiac fibroblasts and vascular SMC express only minor amounts of ST2 mRNA and do not secrete detectable amounts of sST2 antigen. In accordance with the cellular distribution of ST2 receptor, human cardiac fibroblasts and myocytes as well as HCASMC did not respond to treatment with IL-33, as recombinant human IL-33 did not induce NF-κB p50 and p65 subunits nuclear translocation or increase IL-6, IL-8, and monocyte chemoattractant protein (MCP-1) level in HACF, HACM and HCASMC. In summary, we found that endothelial cells seem to be the source of sST2 and the target for IL-33 in the cardiovascular system. IL-33 is expressed in the nucleus of human adult cardiac fibroblasts and myocytes and released during necrosis. Proinflammatory cytokines TNF-α, IFN-γ and IL-1β increase IL-33 in these cells in vitro, and IL-33 mRNA levels correlated with TNF-α and IFN-γ mRNA expression in human myocardial tissue.

Transtemporal ultrasound application potentially elevates brain temperature: results of an anthropomorphic skull model

PURPOSE

Transtemporal sonothrombolysis is a tool for a more effective treatment in acute stroke patients. However, some reports revealed side effects, which might be potentially connected to temperature elevation. To gain better insight into cerebral temperature changes during transtemporal sonication, diagnostic and therapeutic ultrasound (US) applications were evaluated using an anthropomorphic skull model.

MATERIALS AND METHODS

The impact of diagnostic (PW-Doppler, 1.8-MHz, 0.11 W/cm², TIC 1.2) and therapeutic (1-MHz and 3-MHz, 0.07 - 0.71 W/cm², continuous and pulsed mode) US application on temperature changes was evaluated at the level of muscle/temporal bone (TB), TB/brain, brain and at the middle cerebral artery (MCA) using 4 miniature thermocouples along the US beam. Sonication lasted 120 minutes.

RESULTS

Diagnostic ultrasound revealed a maximum temperature increase of 1.45°/0.60°/0.39°/0.41°C (muscle/TB, TB/brain, brain, MCA) after 120 minutes. Therapeutic-1-MHz ultrasound raised temperature by 4.33°/2.02°/1.05 °C/0.81°C (pulsed 1:20) and by 10.38°/4.95°/2.43°/2.08°C (pulsed 1:5) over 120 minutes. Therapeutic-3-MHz US raised temperature by 4.89°/2.56°/1.24/1.25°C (pulsed 1:20) and by 14.77°/6.59°/3.56°/2.86°C (pulsed 1:5) over 120 minutes, respectively. Continuous application of therapeutic US (1-MHz and 3-MHz) led to a temperature increase of 13.86°/3.63°/1.66°/1.48°C and 17.09°/4.28°/1.38/0.99°C within 3 minutes.

CONCLUSION

Diagnostic PW-Doppler showed only a moderate temperature increase and can be considered as safe. Therapeutic sonication is very powerful in delivering energy so that even pulsed application modes resulted in significant and potentially harmful temperature increases.

A novel mRNA binding protein complex promotes localized plasminogen activator inhibitor-1 accumulation at the myoendothelial junction

OBJECTIVE

Plasminogen activator inhibitor-1 (PAI-1) has previously been shown to be key to the formation of myoendothelial junctions (MEJs) in normal and pathological states (eg, obesity). We therefore sought to identify the mechanism whereby PAI-1 could be selectively accumulated at the MEJ.

METHODS AND RESULTS

We identified PAI-1 protein enrichment at the MEJ in obese mice and in response to tumor necrosis factor (TNF-α) with a vascular cell coculture. However, PAI-1 mRNA was also found at the MEJ and transfection with a PAI-1-GFP with TNF-α did not demonstrate trafficking of the protein to the MEJ. We therefore hypothesized the PAI-1 mRNA was being locally translated and identified serpine binding protein-1, which stabilizes PAI-1 mRNA, as being enriched in obese mice and after treatment with TNF-α, whereas Staufen, which degrades PAI-1 mRNA, was absent in obese mice and after TNF-α application. We identified nicotinamide phosphoribosyl transferase as a serpine binding protein-1 binding partner with a functional τ-like microtubule binding domain. Application of peptides against the microtubule binding domain significantly decreased the number of MEJs and the amount of PAI-1 at the MEJ.

CONCLUSIONS

We conclude that PAI-1 can be locally translated at the MEJ as a result of a unique mRNA binding protein complex.