Erk Inhibition as a Promising Therapeutic Strategy for High IL-8-Secreting and Low SPTAN1-Expressing Colorectal Cancer.

Tumor recurrence and drug resistance are responsible for poor prognosis in colorectal cancer (CRC). DNA mismatch repair (MMR) deficiency or elevated interleukin-8 (IL-8) levels are characteristics of CRCs, which have been independently correlated with treatment resistance to common therapies. We recently demonstrated significantly impaired therapeutical response and increased IL-8 release of CRC cell lines with reduced expression of MMR protein MLH1 as well as cytoskeletal non-erythrocytic spectrin alpha II (SPTAN1). In the present study, decreased intratumoral MLH1 and SPTAN1 expression in CRCs could be significantly correlated with enhanced serum IL-8. Furthermore, using stably reduced SPTAN1-expressing SW480, SW620 or HT-29 cell lines, the RAS-mediated RAF/MEK/ERK pathway was analyzed. Here, a close connection between low SPTAN1 expression, increased IL-8 secretion, enhanced extracellular-signal-regulated kinase (ERK) phosphorylation and a mesenchymal phenotype were detected. The inhibition of ERK by U0126 led to a significant reduction in IL-8 secretion, and the combination therapy of U0126 with FOLFOX optimizes the response of corresponding cancer cell lines. Therefore, we hypothesize that the combination therapy of FOLFOX and U0126 may have great potential to improve drug efficacy on this subgroup of CRCs, showing decreased MLH1 and SPTAN1 accompanied with high serum IL-8 in affected patients.

Effect of Thrombin on the Metabolism and Function of Murine Macrophages.

Macrophages are plastic and heterogeneous immune cells that adapt pro- or anti-inflammatory phenotypes upon exposure to different stimuli. Even though there has been evidence supporting a crosstalk between coagulation and innate immunity, the way in which protein components of the hemostasis pathway influence macrophages remains unclear. We investigated the effect of thrombin on macrophage polarization. On the basis of gene expression and cytokine secretion, our results suggest that polarization with thrombin induces an anti-inflammatory, M2-like phenotype. In functional studies, thrombin polarization promoted oxLDL phagocytosis by macrophages, and conditioned medium from the same cells increased endothelial cell proliferation. There were, however, clear differences between the classical M2a polarization and the effects of thrombin on gene expression. Finally, the deletion and inactivation of secreted modular Ca2+-binding protein 1 (SMOC1) attenuated phagocytosis by thrombin-stimulated macrophages, a phenomenon revered by the addition of recombinant SMOC1. Manipulation of SMOC1 levels also had a pronounced impact on the expression of TGF-ß-signaling-related genes. Taken together, our results show that thrombin induces an anti-inflammatory macrophage phenotype with similarities as well as differences to the classical alternatively activated M2 polarization states, highlighting the importance of tissue levels of SMOC1 in modifying thrombin-induced macrophage polarization.

NFAT5/TonEBP Limits Pulmonary Vascular Resistance in the Hypoxic Lung by Controlling Mitochondrial Reactive Oxygen Species Generation in Arterial Smooth Muscle Cells.

Chronic hypoxia increases the resistance of pulmonary arteries by stimulating their contraction and augmenting their coverage by smooth muscle cells (SMCs). While these responses require adjustment of the vascular SMC transcriptome, regulatory elements are not well defined in this context. Here, we explored the functional role of the transcription factor nuclear factor of activated T-cells 5 (NFAT5/TonEBP) in the hypoxic lung. Regulatory functions of NFAT5 were investigated in cultured artery SMCs and lungs from control (Nfat5fl/fl) and SMC-specific Nfat5-deficient (Nfat5(SMC)-/-) mice. Exposure to hypoxia promoted the expression of genes associated with metabolism and mitochondrial oxidative phosphorylation (OXPHOS) in Nfat5(SMC)-/- versus Nfat5fl/fl lungs. In vitro, hypoxia-exposed Nfat5-deficient pulmonary artery SMCs elevated the level of OXPHOS-related transcripts, mitochondrial respiration, and production of reactive oxygen species (ROS). Right ventricular functions were impaired while pulmonary right ventricular systolic pressure (RVSP) was amplified in hypoxia-exposed Nfat5(SMC)-/- versus Nfat5fl/fl mice. Scavenging of mitochondrial ROS normalized the raise in RVSP. Our findings suggest a critical role for NFAT5 as a suppressor of OXPHOS-associated gene expression, mitochondrial respiration, and ROS production in pulmonary artery SMCs that is vital to limit ROS-dependent arterial resistance in a hypoxic environment.

Cyp2c44 epoxygenase-derived epoxyeicosatrienoic acids in vascular smooth muscle cells elicit vasoconstriction of the murine ophthalmic artery.

Cytochrome P450 (CYP) signalling pathway has been shown to play a vital role in the vasoreactivity of wild type mouse ophthalmic artery. In this study, we determined the expression, vascular responses and potential mechanisms of the CYP-derived arachidonic acid metabolites. The expression of murine CYP (Cyp2c44) and soluble epoxide hydrolase (sEH) in the wild type ophthalmic artery was determined with immunofluorescence, which showed predominant expression of Cyp2c44 in the vascular smooth muscle cells (VSMC), while sEH was found mainly in the endothelium of the wild type ophthalmic artery. Artery of Cyp2c44-/- and sEH-/- mice were used as negative controls. Targeted mass spectrometry-based lipidomics analysis of endogenous epoxide and diols of the wild type artery detected only 14, 15-EET. Vasorelaxant responses of isolated vessels in response to selective pharmacological blockers and agonist were analysed ex vivo. Direct antagonism of epoxyeicosatrienoic acids (EETs) with a selective inhibitor caused partial vasodilation, suggesting that EETs may behave as vasoconstrictors. Exogenous administration of synthetic EET regioisomers significantly constricted the vessels in a concentration-dependent manner, with the strongest responses elicited by 11, 12- and 14, 15-EETs. Our results provide the first experimental evidence that Cyp2c44-derived EETs in the VSMC mediate vasoconstriction of the ophthalmic artery.

Secreted modular calcium-binding protein 1 binds and activates thrombin to account for platelet hyperreactivity in diabetes.

Secreted modular calcium-binding protein 1 (SMOC1) is an osteonectin/SPARC-related matricellular protein, whose expression is regulated by microRNA-223 (miR-223). Given that platelets are rich in miR-223, this study investigated the expression of SMOC1 and its contribution to platelet function. Human and murine platelets expressed SMOC1, whereas platelets from SMOC1+/- mice did not present detectable mature SMOC1 protein. Platelets from SMOC1+/- mice demonstrated attenuated responsiveness to thrombin (platelet neutrophil aggregate formation, aggregation, clot formation, Ca2+ increase, and ß3 integrin phosphorylation), whereas responses to other platelet agonists were unaffected. SMOC1 has been implicated in transforming growth factor-ß signaling, but no link to this pathway was detected in platelets. Rather, the SMOC1 Kazal domain directly bound thrombin to potentiate its activity in vitro, as well as its actions on isolated platelets. The latter effects were prevented by monoclonal antibodies against SMOC1. Platelets from miR-223-deficient mice expressed high levels of SMOC1 and exhibited hyperreactivity to thrombin that was also reversed by preincubation with monoclonal antibodies against SMOC1. Similarly, SMOC1 levels were markedly upregulated in platelets from individuals with type 2 diabetes, and the SMOC1 antibody abrogated platelet hyperresponsiveness to thrombin. Taken together, we have identified SMOC1 as a novel thrombin-activating protein that makes a significant contribution to the pathophysiological changes in platelet function associated with type 2 diabetes. Thus, strategies that target SMOC1 or its interaction with thrombin may be attractive therapeutic approaches to normalize platelet function in diabetes.

Mapping the Endothelial Cell S-Sulfhydrome Highlights the Crucial Role of Integrin Sulfhydration in Vascular Function.

BACKGROUND: In vascular endothelial cells, cysteine metabolism by the cystathionine γ lyase (CSE), generates hydrogen sulfide-related sulfane sulfur compounds (H2Sn), that exert their biological actions via cysteine S-sulfhydration of target proteins. This study set out to map the "S-sulfhydrome" (ie, the spectrum of proteins targeted by H2Sn) in human endothelial cells. METHODS: Liquid chromatography with tandem mass spectrometry was used to identify S-sulfhydrated cysteines in endothelial cell proteins and ß3 integrin intraprotein disulfide bond rearrangement. Functional studies included endothelial cell adhesion, shear stress-induced cell alignment, blood pressure measurements, and flow-induced vasodilatation in endothelial cell-specific CSE knockout mice and in a small collective of patients with endothelial dysfunction. RESULTS: Three paired sample sets were compared: (1) native human endothelial cells isolated from plaque-free mesenteric arteries (CSE activity high) and plaque-containing carotid arteries (CSE activity low); (2) cultured human endothelial cells kept under static conditions or exposed to fluid shear stress to decrease CSE expression; and (3) cultured endothelial cells exposed to shear stress to decrease CSE expression and treated with solvent or the slow-releasing H2Sn donor, SG1002. The endothelial cell "S-sulfhydrome" consisted of 3446 individual cysteine residues in 1591 proteins. The most altered family of proteins were the integrins and focusing on ß3 integrin in detail we found that S-sulfhydration affected intraprotein disulfide bond formation and was required for the maintenance of an extended-open conformation of the ß leg. ß3 integrin S-sulfhydration was required for endothelial cell mechanotransduction in vitro as well as flow-induced dilatation in murine mesenteric arteries. In cultured cells, the loss of S-sulfhydration impaired interactions between ß3 integrin and Gα13 (guanine nucleotide-binding protein subunit α 13), resulting in the constitutive activation of RhoA (ras homolog family member A) and impaired flow-induced endothelial cell realignment. In humans with atherosclerosis, endothelial function correlated with low H2Sn generation, impaired flow-induced dilatation, and failure to detect ß3 integrin S-sulfhydration, all of which were rescued after the administration of an H2Sn supplement. CONCLUSIONS: Vascular disease is associated with marked changes in the S-sulfhydration of endothelial cell proteins involved in mediating responses to flow. Short-term H2Sn supplementation improved vascular reactivity in humans highlighting the potential of interfering with this pathway to treat vascular disease.

Shear stress regulates cystathionine γ lyase expression to preserve endothelial redox balance and reduce membrane lipid peroxidation.

Cystathionine γ lyase (CSE) is the major source of hydrogen sulfide-derived species (H2Sn) in endothelial cells and plays an important role in protecting against atherosclerosis. Here we investigated the molecular mechanisms underlying the regulation of CSE expression in endothelial cells by fluid shear stress/flow. Fluid shear stress decreased CSE expression in human and murine endothelial cells and was negatively correlated with the transcription factor Krüppel-like factor (KLF) 2. CSE was identified as a direct target of the KLF2-regulated microRNA, miR-27b and high expression of CSE in native human plaque-derived endothelial cells, was also inversely correlated with KLF2 and miR-27b levels. One consequence of decreased CSE expression was the loss of Prx6 sulfhydration (on Cys47), which resulted in Prx6 hyperoxidation, decamerization and inhibition, as well as a concomitant increase in endothelial cell reactive oxygen species and lipid membrane peroxidation. H2Sn supplementation in vitro was able to reverse the redox state of Prx6. Statin therapy, which is known to activate KLF2, also decreased CSE expression but increased CSE activity by preventing its phosphorylation on Ser377. As a result, the sulfhydration of Prx6 was partially restored in samples from plaque containing arteries from statin-treated donors. Taken together, the regulation of CSE expression by shear stress/disturbed flow is dependent on KLF2 and miR-27b. Moreover, in murine and human arteries CSE acts to maintain endothelial redox balance at least partly by targeting Prx6 to prevent its decamerization and inhibition of its peroxidase activity.

Nitric oxide maintains endothelial redox homeostasis through PKM2 inhibition.

Decreased nitric oxide (NO) bioavailability and oxidative stress are hallmarks of endothelial dysfunction and cardiovascular diseases. Although numerous proteins are S-nitrosated, whether and how changes in protein S-nitrosation influence endothelial function under pathophysiological conditions remains unknown. We report that active endothelial NO synthase (eNOS) interacts with and S-nitrosates pyruvate kinase M2 (PKM2), which reduces PKM2 activity. PKM2 inhibition increases substrate flux through the pentose phosphate pathway to generate reducing equivalents (NADPH and GSH) and protect against oxidative stress. In mice, the Tyr656 to Phe mutation renders eNOS insensitive to inactivation by oxidative stress and prevents the decrease in PKM2 S-nitrosation and reducing equivalents, thereby delaying cardiovascular disease development. These findings highlight a novel mechanism linking NO bioavailability to antioxidant responses in endothelial cells through S-nitrosation and inhibition of PKM2.

Myeloid-Specific Deletion of the AMPKα2 Subunit Alters Monocyte Protein Expression and Atherogenesis.

The AMP-activated protein kinase (AMPK) is an energy sensing kinase that is activated by a drop in cellular ATP levels. Although several studies have addressed the role of the AMPKα1 subunit in monocytes and macrophages, little is known about the α2 subunit. The aim of this study was to assess the consequences of AMPKα2 deletion on protein expression in monocytes/macrophages, as well as on atherogenesis. A proteomics approach was applied to bone marrow derived monocytes from wild-type mice versus mice specifically lacking AMPKα2 in myeloid cells (AMPKα2∆MC mice). This revealed differentially expressed proteins, including methyltransferases. Indeed, AMPKα2 deletion in macrophages increased the ratio of S-adenosyl methionine to S-adenosyl homocysteine and increased global DNA cytosine methylation. Also, methylation of the vascular endothelial growth factor and matrix metalloproteinase-9 (MMP9) genes was increased in macrophages from AMPKα2∆MC mice, and correlated with their decreased expression. To link these findings with an in vivo phenotype, AMPKα2∆MC mice were crossed onto the ApoE-/- background and fed a western diet. ApoExAMPKα2∆MC mice developed smaller atherosclerotic plaques than their ApoExα2fl/fl littermates, that contained fewer macrophages and less MMP9 than plaques from ApoExα2fl/fl littermates. These results indicate that the AMPKα2 subunit in myeloid cells influences DNA methylation and thus protein expression and contributes to the development of atherosclerotic plaques.

Tolerizing CTL by Sustained Hepatic PD-L1 Expression Provides a New Therapy Approach in Mouse Sepsis.

Cytotoxic T lymphocyte (CTL) activation contributes to liver damage during sepsis, but the mechanisms involved are largely unknown. Understanding the underlying principle will permit interference with CTL activation and thus, provide a new therapeutic option. Methods: To elucidate the mechanism leading to CTL activation we used the Hepa1-6 cell line in vitro and the mouse model of in vivo polymicrobial sepsis, following cecal-ligation and -puncture (CLP) in wildtype, myeloid specific NOX-2, global NOX2 and NOX4 knockout mice, and their survival as a final readout. In this in vivo setting, we also determined hepatic mRNA and protein expression as well as clinical parameters of liver damage - aspartate- and alanine amino-transaminases. Hepatocyte specific overexpression of PD-L1 was achieved in vivo by adenoviral infection and transposon-based gene transfer using hydrodynamic injection. Results: We observed downregulation of PD-L1 on hepatocytes in the murine sepsis model. Adenoviral and transposon-based gene transfer to restore PD-L1 expression, significantly improved survival and reduced the release of liver damage, as PD-L1 is a co-receptor that negatively regulates T cell function. Similar protection was observed during pharmacological intervention using recombinant PD-L1-Fc. N-acetylcysteine blocked the downregulation of PD-L1 suggesting the involvement of reactive oxygen species. This was confirmed in vivo, as we observed significant upregulation of PD-L1 expression in NOX4 knockout mice, following sham operation, whereas its expression in global as well as myeloid lineage NOX2 knockout mice was comparable to that in the wild type animals. PD-L1 expression remained high following CLP only in total NOX2 knockouts, resulting in significantly reduced release of liver damage markers. Conclusion: These results suggest that, contrary to common assumption, maintaining PD-L1 expression on hepatocytes improves liver damage and survival of mice during sepsis. We conclude that administering recombinant PD-L1 or inhibiting NOX2 activity might offer a new therapeutic option in sepsis.

Endothelial AMP-Activated Kinase α1 Phosphorylates eNOS on Thr495 and Decreases Endothelial NO Formation.

AMP-activated protein kinase (AMPK) is frequently reported to phosphorylate Ser1177 of the endothelial nitric-oxide synthase (eNOS), and therefore, is linked with a relaxing effect. However, previous studies failed to consistently demonstrate a major role for AMPK on eNOS-dependent relaxation. As AMPK also phosphorylates eNOS on the inhibitory Thr495 site, this study aimed to determine the role of AMPKα1 and α2 subunits in the regulation of NO-mediated vascular relaxation. Vascular reactivity to phenylephrine and acetylcholine was assessed in aortic and carotid artery segments from mice with global (AMPKα-/-) or endothelial-specific deletion (AMPKαΔEC) of the AMPKα subunits. In control and AMPKα1-depleted human umbilical vein endothelial cells, eNOS phosphorylation on Ser1177 and Thr495 was assessed after AMPK activation with thiopental or ionomycin. Global deletion of the AMPKα1 or α2 subunit in mice did not affect vascular reactivity. The endothelial-specific deletion of the AMPKα1 subunit attenuated phenylephrine-mediated contraction in an eNOS- and endothelium-dependent manner. In in vitro studies, activation of AMPK did not alter the phosphorylation of eNOS on Ser1177, but increased its phosphorylation on Thr495. Depletion of AMPKα1 in cultured human endothelial cells decreased Thr495 phosphorylation without affecting Ser1177 phosphorylation. The results of this study indicate that AMPKα1 targets the inhibitory phosphorylation Thr495 site in the calmodulin-binding domain of eNOS to attenuate basal NO production and phenylephrine-induced vasoconstriction.

Tyrosine phosphorylation of eNOS regulates myocardial survival after an ischaemic insult: role of PYK2.

AIMS: Endothelial nitric oxide (NO) synthase (eNOS) is known to play a cardioprotective protective. However, the molecular mechanisms regulating eNOS activity during ischaemia/reperfusion (I/R) injury are incompletely understood. eNOS is a substrate for several kinases that positively or negatively affect its enzymatic activity. Herein, we sought to correlate eNOS phosphorylation status with cardiomyocyte survival and we investigated the contribution of the proline-rich tyrosine kinase 2 (PYK2)/eNOS axis to the regulation of myocardial infarct size in vivo. METHODS AND RESULTS: Exposure of H9c2 cardiomyocytes to H2O2 lead to PYK2 phosphorylation on its activator site (Y402) and eNOS phosphorylation on the inhibitor site Y656 and the activator site S1176. Both H2O2-induced eNOS phosphorylation events were abolished by PYK2 pharmacological inhibition or gene knockdown. Activity assays demonstrated that phosphorylation of the tyrosine inhibitory site exerts a dominant effect over S1176. In cardiomyocytes subjected to oxidative stress or oxygen-glucose deprivation, inhibition of PYK2 limited cell injury; this effect was prevented by inhibition of NO production. In vivo, ischaemia-reperfusion induced an early activation of PYK2, leading to eNOS phosphorylation on Y656, which, in turn, reduced NO output, as judged by the low tissue levels of its downstream effector cGMP. Moreover, pharmacological blockade of PYK2 alleviated eNOS inhibition and prevented cardiac damage following I/R injury in wild-type, but not in eNOS KO mice. CONCLUSION: The current studies demonstrate that PYK2 is a pivotal regulator of eNOS function in myocardial infarction and identify PYK2 as a novel therapeutic target for cardioprotection.

AMP-Activated Protein Kinase α2 in Neutrophils Regulates Vascular Repair via Hypoxia-Inducible Factor-1α and a Network of Proteins Affecting Metabolism and Apoptosis.

RATIONALE: The AMP-activated protein kinase (AMPK) is stimulated by hypoxia, and although the AMPKα1 catalytic subunit has been implicated in angiogenesis, little is known about the role played by the AMPKα2 subunit in vascular repair. OBJECTIVE: To determine the role of the AMPKα2 subunit in vascular repair. METHODS AND RESULTS: Recovery of blood flow after femoral artery ligation was impaired (>80%) in AMPKα2-/- versus wild-type mice, a phenotype reproduced in mice lacking AMPKα2 in myeloid cells (AMPKα2ΔMC). Three days after ligation, neutrophil infiltration into ischemic limbs of AMPKα2ΔMC mice was lower than that in wild-type mice despite being higher after 24 hours. Neutrophil survival in ischemic tissue is required to attract monocytes that contribute to the angiogenic response. Indeed, apoptosis was increased in hypoxic neutrophils from AMPKα2ΔMC mice, fewer monocytes were recruited, and gene array analysis revealed attenuated expression of proangiogenic proteins in ischemic AMPKα2ΔMC hindlimbs. Many angiogenic growth factors are regulated by hypoxia-inducible factor, and hypoxia-inducible factor-1α induction was attenuated in AMPKα2-deficient cells and accompanied by its enhanced hydroxylation. Also, fewer proteins were regulated by hypoxia in neutrophils from AMPKα2ΔMC mice. Mechanistically, isocitrate dehydrogenase expression and the production of α-ketoglutarate, which negatively regulate hypoxia-inducible factor-1α stability, were attenuated in neutrophils from wild-type mice but remained elevated in cells from AMPKα2ΔMC mice. CONCLUSIONS: AMPKα2 regulates α-ketoglutarate generation, hypoxia-inducible factor-1α stability, and neutrophil survival, which in turn determine further myeloid cell recruitment and repair potential. The activation of AMPKα2 in neutrophils is a decisive event in the initiation of vascular repair after ischemia.

ß-Catenin Is Required for Endothelial Cyp1b1 Regulation Influencing Metabolic Barrier Function.

UNLABELLED: The canonical Wnt/ß-catenin signaling pathway is crucial for blood-brain barrier (BBB) formation in brain endothelial cells. Although glucose transporter 1, claudin-3, and plasmalemma vesicular-associated protein have been identified as Wnt/ß-catenin targets in brain endothelial cells, further downstream targets relevant to BBB formation and function are incompletely explored. By Affymetrix expression analysis, we show that the cytochrome P450 enzyme Cyp1b1 was significantly decreased in ß-catenin-deficient mouse endothelial cells, whereas its close homolog Cyp1a1 was upregulated in an aryl hydrocarbon receptor-dependent manner, hence indicating that ß-catenin is indispensable for Cyp1b1 but not for Cyp1a1 expression. Functionally, Cyp1b1 could generate retinoic acid from retinol leading to cell-autonomous induction of the barrier-related ATP-binding cassette transporter P-glycoprotein. Cyp1b1 could also generate 20-hydroxyeicosatetraenoic acid from arachidonic acid, decreasing endothelial barrier function in vitro In mice in vivo pharmacological inhibition of Cyp1b1 increased BBB permeability for small molecular tracers, and Cyp1b1 was downregulated in glioma vessels in which BBB function is lost. Hence, we propose Cyp1b1 as a target of ß-catenin indirectly influencing BBB properties via its metabolic activity, and as a potential target for modulating barrier function in endothelial cells. SIGNIFICANCE STATEMENT: Wnt/ß-catenin signaling is crucial for blood-brain barrier (BBB) development and maintenance; however, its role in regulating metabolic characteristics of endothelial cells is unclear. We provide evidence that ß-catenin influences endothelial metabolism by transcriptionally regulating the cytochrome P450 enzyme Cyp1b1 Furthermore, expression of its close homolog Cyp1a1 was inhibited by ß-catenin. Functionally, Cyp1b1 generated retinoic acid as well as 20-hydroxyeicosatetraenoic acid that regulated P-glycoprotein and junction proteins, respectively, thereby modulating BBB properties. Inhibition of Cyp1b1 in vivo increased BBB permeability being in line with its downregulation in glioma endothelia, potentially implicating Cyp1b1 in other brain pathologies. In conclusion, Wnt/ß-catenin signaling regulates endothelial metabolic barrier function through Cyp1b1 transcription.

miR-223-IGF-IR signalling in hypoxia- and load-induced right-ventricular failure: a novel therapeutic approach.

AIMS: Pulmonary hypertension is a progressive disease with poor prognosis, characterized by pathological inward remodelling and loss of patency of the lung vasculature. The right ventricle is co-affected by pulmonary hypertension, which triggers events such as hypoxia and/or increased mechanical load. Initially the right ventricle responds with 'adaptive' hypertrophy, which is often rapidly followed by 'maladaptive' changes leading to right heart decompensation and failure, which is the ultimate cause of death. METHODS AND RESULTS: We report here that miR-223 is expressed in the murine lung and right ventricle at higher levels than in the left ventricle. Moreover, lung and right-ventricular miR-223 levels were markedly down-regulated by hypoxia. Correspondingly, increasing right-ventricular load by pulmonary artery banding, induced right-ventricular ischaemia, and the down-regulation of miR-223. Lung and right ventricle miR-223 down-regulation were linked with increased expression of the miR-223 target; insulin-like growth factor-I receptor (IGF-IR) and IGF-I downstream signalling. Similarly, miR-223 was decreased and IGF-IR increased in human pulmonary hypertension. Notably in young mice, miR-223 overexpression, the genetic inactivation or pharmacological inhibition of IGF-IR, all attenuated right-ventricular hypertrophy and improved right heart function under conditions of hypoxia or increased afterload. CONCLUSION: These findings highlight the early role of pulmonary and right-ventricular miR-223 and the IGF-IR in the right heart failure programme initiated by pulmonary hypoxia and increased mechanical load and may lead to the development of novel therapeutic strategies that target the development of PH and right heart failure.

Renal cell carcinoma alters endothelial receptor expression responsible for leukocyte adhesion.

Renal cell carcinoma (RCC) escapes immune recognition. To elaborate the escape strategy the influence of RCC cells on endothelial receptor expression and endothelial leukocyte adhesion was evaluated. Human umbilical vein endothelial cells (HUVEC) were co-cultured with the RCC cell line, Caki-1, with and without tumor necrosis factor (TNF)-alpha. Intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), endothelial (E)-selectin, standard and variants (V) of CD44 were then analysed in HUVEC, using flow cytometry and Western blot analysis. To determine which components are responsible for HUVEC-Caki-1 interaction causing receptor alteration, Caki-1 membrane fragments versus cell culture supernatant were applied to HUVECS. Adhesion of peripheral blood lymphocytes (PBL) and polymorphonuclear neutrophils (PMN) to endothelium was evaluated by co-culture adhesion assays. Relevance of endothelial receptor expression for adhesion to endothelium was determined by receptor blockage. Co-culture of RCC and HUVECs resulted in a significant increase in endothelial ICAM-1, VCAM-1, E-selectin, CD44 V3 and V7 expression. Previous stimulation of HUVECs with TNF-alpha and co-cultivation with Caki-1 resulted in further elevation of endothelial CD44 V3 and V7 expression, whereas ICAM-1, VCAM-1 and E-selectin expression were significantly diminished. Since Caki-1 membrane fragments also caused these alterations, but cell culture supernatant did not, cell-cell contact may be responsible for this process. Blocking ICAM-1, VCAM-1, E-selectin or CD44 with respective antibodies led to a significant decrease in PBL and PMN adhesion to endothelium. Thus, exposing HUVEC to Caki-1 results in significant alteration of endothelial receptor expression and subsequent endothelial attachment of PBL and PMN.

MicroRNA-30 mediates anti-inflammatory effects of shear stress and KLF2 via repression of angiopoietin 2.

MicroRNAs are endogenously expressed small noncoding RNAs that regulate gene expression. Laminar blood flow induces atheroprotective gene expression in endothelial cells (ECs) in part by upregulating the transcription factor KLF2. Here, we identified KLF2- and flow-responsive miRs that affect gene expression in ECs. Bioinformatic assessment of mRNA expression patterns identified the miR-30-5p seed sequence to be highly enriched in mRNAs that are downregulated by KLF2. Indeed, KLF2 overexpression and shear stress stimulation in vitro and in vivo increased the expression of miR-30-5p family members. Furthermore, we identified angiopoietin 2 (Ang2) as a target of miR-30. MiR-30 overexpression reduces Ang2 levels, whereas miR-30 inhibition by LNA-antimiRs induces Ang2 expression. Consistently, miR-30 reduced basal and TNF-α-induced expression of the inflammatory cell­cell adhesion molecules E-selectin, ICAM1 and VCAM1, which was rescued by stimulation with exogenous Ang2. In summary, KLF2 and shear stress increase the expression of the miR-30-5p family which acts in an anti-inflammatory manner in ECs by impairing the expression of Ang2 and inflammatory cell­cell adhesion molecules. The upregulation of miR-30-5p family members may contribute to the atheroprotective effects of shear stress.

Role of secreted modular calcium-binding protein 1 (SMOC1) in transforming growth factor ß signalling and angiogenesis.

AIMS: Secreted modular calcium-binding protein 1 (SMOC1) is a matricellular protein that potentially interferes with growth factor receptor signalling. The aim of this study was to determine how its expression is regulated in endothelial cells and its role in the regulation of endothelial cell function. METHODS AND RESULTS: SMOC1 was expressed by native murine endothelial cells as well as by cultured human, porcine, and murine endothelial cells. SMOC1 expression in cultured cells was increased by hypoxia via the down-regulation of miR-223, and SMOC1 expression was increased in lungs from miR-223-deficient mice. Silencing SMOC1 (small interfering RNA) attenuated endothelial cell proliferation, migration, and sprouting in in vitro angiogenesis assays. Similarly endothelial cell sprouting from aortic rings ex vivo as well as postnatal retinal angiogenesis in vivo was attenuated in SMOC1(+/-) mice. In endothelial cells, transforming growth factor (TGF)-ß signalling via activin-like kinase (ALK) 5 leads to quiescence, whereas TGF-ß signalling via ALK1 results in endothelial cell activation. SMOC1 acted as a negative regulator of ALK5/SMAD2 signalling, resulting in altered α2 integrin levels. Mechanistically, SMOC1 associated (immunohistochemistry, proximity ligation assay, and co-immunoprecipitation) with endoglin; an endothelium-specific type III auxiliary receptor for the TGF-ß super family and the effects of SMOC1 down-regulation on SMAD2 phosphorylation were abolished by the down-regulation of endoglin. CONCLUSION: These results indicate that SMOC1 is an ALK5 antagonist produced by endothelial cells that tips TGF-ß signalling towards ALK1 activation, thus promoting endothelial cell proliferation and angiogenesis.