JCAD promotes arterial thrombosis through PI3K/Akt modulation: a translational study.

AIMS: Variants of the junctional cadherin 5 associated (JCAD) locus associate with acute coronary syndromes. JCAD promotes experimental atherosclerosis through the large tumor suppressor kinase 2 (LATS2)/Hippo pathway. This study investigates the role of JCAD in arterial thrombosis. METHODS AND RESULTS: JCAD knockout (Jcad-/-) mice underwent photochemically induced endothelial injury to trigger arterial thrombosis. Primary human aortic endothelial cells (HAECs) treated with JCAD small interfering RNA (siJCAD), LATS2 small interfering RNA (siLATS2) or control siRNA (siSCR) were employed for in vitro assays. Plasma JCAD was measured in patients with chronic coronary syndrome or ST-elevation myocardial infarction (STEMI). Jcad-/- mice displayed reduced thrombogenicity as reflected by delayed time to carotid occlusion. Mechanisms include reduced activation of the coagulation cascade [reduced tissue factor (TF) expression and activity] and increased fibrinolysis [higher thrombus embolization episodes and D-dimer levels, reduced vascular plasminogen activator inhibitor (PAI)-1 expression]. In vitro, JCAD silencing inhibited TF and PAI-1 expression in HAECs. JCAD-silenced HAECs (siJCAD) displayed increased levels of LATS2 kinase. Yet, double JCAD and LATS2 silencing did not restore the control phenotype. si-JCAD HAECs showed increased levels of phosphoinositide 3-kinases (PI3K)/ proteinkinase B (Akt) activation, known to downregulate procoagulant expression. The PI3K/Akt pathway inhibitor-wortmannin-prevented the effect of JCAD silencing on TF and PAI-1, indicating a causative role. Also, co-immunoprecipitation unveiled a direct interaction between JCAD and Akt. Confirming in vitro findings, PI3K/Akt and P-yes-associated protein levels were higher in Jcad-/- animals. Lastly, as compared with chronic coronary syndrome, STEMI patients showed higher plasma JCAD, which notably correlated positively with both TF and PAI-1 levels. CONCLUSIONS: JCAD promotes arterial thrombosis by modulating coagulation and fibrinolysis. Herein, reported translational data suggest JCAD as a potential therapeutic target for atherothrombosis.

Endothelial SIRT6 deficiency promotes arterial thrombosis in mice.

OBJECTIVE: Arterial thrombosis may be initiated by endothelial inflammation or denudation, activation of blood-borne elements or the coagulation system. Tissue factor (TF), a central trigger of the coagulation cascade, is regulated by the pro-inflammatory NF-κB-dependent pathways. Sirtuin 6 (SIRT6) is a nuclear member of the sirtuin family of NAD+-dependent deacetylases and is known to inhibit NF-κB signaling. Its constitutive deletion in mice shows early lethality with hypoglycemia and accelerated aging. Of note, the role of SIRT6 in arterial thrombosis remains unknown. Thus, we hypothesized that endothelial SIRT6 protects from arterial thrombosis by modulating inhibition of NF-κB-associated pathways. APPROACH AND RESULTS: Using a laser-induced carotid thrombosis model, in vivo arterial occlusion occurred 45% faster in 12-week-old male endothelial-specific Sirt6-/- mice as compared to Sirt6fl/fl controls (n ≥ 9 per group; p = 0.0012). Levels of procoagulant TF were increased in animals lacking endothelial SIRT6 as compared to control littermates. Similarly, in cultured human aortic endothelial cells, SIRT6 knockdown increased TF mRNA, protein and activity. Moreover, SIRT6 knockdown increased mRNA levels of NF-κB-associated genes tumor necrosis factor alpha (TNF-α), poly [ADP-ribose] polymerase 1 (PARP-1), vascular cell adhesion molecule 1 (VCAM-1), and cyclooxygenase-2 (COX-2); at the protein level, COX-2, VCAM-1, TNF-α, and cleaved PARP-1 remained increased after Sirt6 knockdown. CONCLUSIONS: Endothelium-specific Sirt6 deletion promotes arterial thrombosis in mice. In cultured human aortic endothelial cells, SIRT6 silencing enhances TF expression and activates pro-inflammatory pathways including TNF-α, cleaved PARP-1, VCAM-1 and COX-2. Hence, endogenous endothelial SIRT6 exerts a protective role in experimental arterial thrombosis.

Biventricular Arrhythmogenic Cardiomyopathy Associated with a Novel Heterozygous Plakophilin-2 Early Truncating Variant.

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is a hereditary condition that can cause sudden cardiac death in young, frequently athletic individuals under the age of 35 due to malignant arrhythmias. Competitive and endurance exercise may hasten the onset and progression of ARVC, leading to right ventricular dysfunction and potentially fatal ventricular arrhythmias earlier in life. In this article, we present a novel, pathogenic, early truncating heterozygous variant in the PKP2 gene that causes biventricular arrhythmogenic cardiomyopathy and affects a family, of which the only member with the positive phenotype is a competitive endurance athlete.

TNFα induces endothelial dysfunction in rheumatoid arthritis via LOX-1 and arginase 2: reversal by monoclonal TNFα antibodies.

AIMS: Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting joints and blood vessels. Despite low levels of low-density lipoprotein cholesterol (LDL-C), RA patients exhibit endothelial dysfunction and are at increased risk of death from cardiovascular complications, but the molecular mechanism of action is unknown. We aimed in the present study to identify the molecular mechanism of endothelial dysfunction in a mouse model of RA and in patients with RA. METHODS AND RESULTS: Endothelium-dependent relaxations to acetylcholine were reduced in aortae of two tumour necrosis factor alpha (TNFα) transgenic mouse lines with either mild (Tg3647) or severe (Tg197) forms of RA in a time- and severity-dependent fashion as assessed by organ chamber myograph. In Tg197, TNFα plasma levels were associated with severe endothelial dysfunction. LOX-1 receptor was markedly up-regulated leading to increased vascular oxLDL uptake and NFκB-mediated enhanced Arg2 expression via direct binding to its promoter resulting in reduced NO bioavailability and vascular cGMP levels as shown by ELISA and chromatin immunoprecipitation. Anti-TNFα treatment with infliximab normalized endothelial function together with LOX-1 and Arg2 serum levels in mice. In RA patients, soluble LOX-1 serum levels were also markedly increased and closely related to serum levels of C-reactive protein. Similarly, ARG2 serum levels were increased. Similarly, anti-TNFα treatment restored LOX-1 and ARG2 serum levels in RA patients. CONCLUSIONS: Increased TNFα levels not only contribute to RA, but also to endothelial dysfunction by increasing vascular oxLDL content and activation of the LOX-1/NFκB/Arg2 pathway leading to reduced NO bioavailability and decreased cGMP levels. Anti-TNFα treatment improved both articular symptoms and endothelial function by reducing LOX-1, vascular oxLDL, and Arg2 levels.

TNF-α antagonism rescues the effect of ageing on stroke: Perspectives for targeting inflamm-ageing.

AIMS: Epidemiologic evidence links ischemic stroke to age, yet the mechanisms that underlie the specific and independent effects of age on stroke remain elusive, impeding the development of targeted treatments. This study tested the hypothesis that age directly aggravates stroke outcomes and proposes inflamm-aging as a mediator and potential therapeutic target. METHODS: 3 months- (young) and 18-20 months-old (old) mice underwent transient middle cerebral artery occlusion (tMCAO) for 30 minutes followed by 48 hours of reperfusion. Old animals received weekly treatment with the TNF-α neutralizing antibody adalimumab over 4 weeks before tMCAO in a separate set of experiments. Plasma levels of TNF- α were assessed in patients with ischemic stroke and correlated with age and outcome. RESULTS: Old mice displayed larger stroke size than young ones with increased neuromotor deficit. Immunohistochemical analysis revealed impairment of the blood-brain barrier in old mice, i.e. increased post-stroke degradation of endothelial tight junctions and expression of tight junctions-digesting and neurotoxic matrix metalloproteinases. At baseline, old animals showed a broad modulation of several circulating inflammatory mediators. TNF-α displayed the highest increase in old animals and its inhibition restored the volume of stroke, neuromotor performance, and survival rates of old mice to the levels observed in young ones. Patients with ischemic stroke showed increased TNF-α plasma levels which correlated with worsened short-term neurological outcome as well as with age. CONCLUSIONS: This study identifies TNF-α as a causative contributor to the deleterious effect of aging on stroke and points to inflamm-aging as a mechanism of age-related worsening of stroke outcomes and potential therapeutic target in this context. Thus, this work provides a basis for tailoring novel stroke therapies for the particularly vulnerable elderly population.

Apold1 deficiency associates with increased arterial thrombosis in vivo.

BACKGROUND: Endothelial cells regulate the formation of blood clots; thus, genes selectively expressed in these cells could primarily determine thrombus formation. Apold1 (apolipoprotein L domain containing 1) is a gene expressed by endothelial cells; whether Apold1 directly contributes to arterial thrombosis has not yet been investigated. Here, we assessed the effect of Apold1 deletion on arterial thrombus formation using an in vivo model of carotid thrombosis induced by photochemical injury. MATERIAL AND METHODS: Apold1 knockout (Apold1-/- ) mice and wild-type (WT) littermates underwent carotid thrombosis induced by photochemical injury, and time to occlusion was recorded. Tissue factor (TF) activity and activation of mitogen-activated protein kinases (MAPKs) and phosphatidyl-inositol-3 kinase (PI3K)/Akt pathways were analysed by colorimetric assay and Western blotting in both Apold1-/- and WT mice. Finally, platelet reactivity was assessed using light transmission aggregometry. RESULTS: After photochemical injury, Apold1-/- mice exhibited shorter time to occlusion as compared to WT mice. Moreover, TF activity was increased in carotid arteries of Apold1-/- when compared to WT mice. Underlying mechanistic markers such as TF mRNA and MAPKs activation were unaffected in Apold1-/- mice. In contrast, phosphorylation of Akt was reduced in Apold1-/- as compared to WT mice. Additionally, Apold1-/- mice displayed increased platelet reactivity to stimulation with collagen compared with WT animals. CONCLUSIONS: Deficiency of Apold1 results in a prothrombotic phenotype, accompanied by increased vascular TF activity, decreased PI3K/Akt activation and increased platelet reactivity. These findings suggest Apold1 as an interesting new therapeutic target in the context of arterial thrombosis.

AP-1 (Activated Protein-1) Transcription Factor JunD Regulates Ischemia/Reperfusion Brain Damage via IL-1ß (Interleukin-1ß).

Background and Purpose- Inflammation is a major pathogenic component of ischemia/reperfusion brain injury, and as such, interventions aimed at inhibiting inflammatory mediators promise to be effective strategies in stroke therapy. JunD-a member of the AP-1 (activated protein-1) family of transcription factors-was recently shown to regulate inflammation by targeting IL (interleukin)-1ß synthesis and macrophage activation. The purpose of the present study was to assess the role of JunD in ischemia/reperfusion-induced brain injury. Methods- WT (wild type) mice randomly treated with either JunD or scramble (control) siRNA were subjected to 45 minutes of transient middle cerebral artery occlusion followed by 24 hours of reperfusion. Stroke size, neurological deficit, plasma/brain cytokines, and oxidative stress determined by 4-hydroxynonenal immunofluorescence staining were evaluated 24 hours after reperfusion. Additionally, the role of IL-1ß was investigated by treating JunD siRNA mice with an anti-IL-1ß monoclonal antibody on reperfusion. Finally, JunD expression was assessed in peripheral blood monocytes isolated from patients with acute ischemic stroke. Results- In vivo JunD knockdown resulted in increased stroke size, reduced neurological function, and increased systemic inflammation, as confirmed by higher neutrophil count and lymphopenia. Brain tissue IL-1ß levels were augmented in JunD siRNA mice as compared with scramble siRNA, whereas no difference was detected in IL-6, TNF-α (tumor necrosis factor-α), and 4-hydroxynonenal levels. The deleterious effects of silencing of JunD were rescued by treating mice with an anti-IL-1ß antibody. In addition, JunD expression was decreased in peripheral blood monocytes of patients with acute ischemic stroke at 6 and 24 hours after onset of stroke symptoms compared with sex- and age-matched healthy controls. Conclusions- JunD blunts ischemia/reperfusion-induced brain injury via suppression of IL-1ß.

Post-ischaemic administration of the murine Canakinumab-surrogate antibody improves outcome in experimental stroke.

Aims: The CANTOS trial underscored the efficacy of selective antibody-based interleukin (IL)-1ß inhibition with Canakinumab in secondary prevention of cardiovascular events. Despite the success of the trial, incidence of stroke was not reduced likely due to the low number of events and the relatively young age of patients enrolled. Given the established role of IL-1ß in stroke, we tested the efficacy of the murine Canakinumab-equivalent antibody in a mouse model of ischaemic stroke. To mimic the clinical scenario of modern stroke management, IL-1ß inhibition was performed post-ischaemically upon reperfusion as it would be the case in patients presenting to the emergency room and eligible for thrombolytic therapy. Methods and results: Transient middle cerebral artery occlusion (tMCAO) was performed in wild type mice; upon reperfusion, mice were randomly allocated to anti-IL-1ß antibody or vehicle treatment. Following tMCAO, cerebral IL-1ß levels, unlike tumour necrosis factor-α, were increased underscoring a role for this cytokine. Post-ischaemic treatment with IL-1ß antibody reduced infarct size, cerebral oedema and improved neurological performance as assessed by 2,3,5-triphenyltetrazolium chloride staining, Bederson and RotaRod tests. Antibody-treated animals also exhibited a reduced neutrophil and matrix metalloproteinase (MMP)-2 but not MMP-9, activity in ipsilateral hemispheres as compared to vehicle-treated mice. Noteworthy, tMCAO associated vascular endothelial-cadherin reduction was blunted in IL-1ß antibody-treated mice compared to vehicle-treated, likely providing the mechanistic explanation for the improved outcome. Conclusion: Our data for the first time demonstrate the efficacy of selective post-ischaemic IL-1ß blockade in improving outcome following experimental ischaemia/reperfusion brain injury in the mouse and encourage further focused clinical studies assessing the potential of the approved IL-1ß antibody Canakinumab, as an adjuvant therapy to thrombolysis in acute ischaemic stroke patients.

Ticagrelor, but not clopidogrel active metabolite, displays antithrombotic properties in the left atrial endocardium.

AIMS: Oral anticoagulation is considered standard therapy for stroke prevention in atrial fibrillation (AF). Endocardial activation triggers expression of pro-thrombotic mediators including tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1), and contributes to thrombus formation in the left atrial appendage (LAA) of AF patients. Recently, pleiotropic effects of specific P2Y12 receptor antagonists were demonstrated; however, whether these drugs possess antithrombotic effects on LAA endocardial cells currently remains unknown. METHODS AND RESULTS: LAA were obtained from 14 patients with known AF undergoing elective cardiac surgery including LAA removal at the University Hospital Zurich. LAA endocardial cells were isolated and pre-incubated with ticagrelor (10-7, 10-6, 10-5M) or clopidogrel active metabolite (CAM) (1.5 × 10-8, 1.5 × 10-7, 1.5 × 10-6 M) before stimulation with tumour necrosis factor-alpha (TNF-α) (10 ng/mL). Finally, TF and PAI-1 expression and activity were analysed. Ticagrelor, unlike CAM, concentration dependently decreased TNF-α-induced TF expression and TF activity in LAA endocardial cells. Further, ticagrelor, but not CAM reduced PAI-1 expression and enzyme activity in TNF-α-stimulated LAA endocardial cells. In contrast, TF pathway inhibitor (TFPI) remained unaffected by both dugs. CONCLUSION: Ticagrelor, but not CAM, reduces expression and activity of TF and PAI-1 in LAA endocardial cells isolated from patients with AF, indicating possible local antithrombotic effects. Such pleiotropic properties of ticagrelor may contribute to a reduction in thromboembolic complications in patients with AF.

Ticagrelor, but not clopidogrel, reduces arterial thrombosis via endothelial tissue factor suppression.

AIMS: The P2Y12 antagonist ticagrelor reduces mortality in patients with acute coronary syndrome (ACS), compared with clopidogrel, and the mechanisms underlying this effect are not clearly understood. Arterial thrombosis is the key event in ACS; however, direct vascular effects of either ticagrelor or clopidogrel with focus on arterial thrombosis and its key trigger tissue factor have not been previously investigated. METHODS AND RESULTS: Human aortic endothelial cells were treated with ticagrelor or clopidogrel active metabolite (CAM) and stimulated with tumour necrosis factor-alpha (TNF-α); effects on procoagulant tissue factor (TF) expression and activity, its counter-player TF pathway inhibitor (TFPI) and the underlying mechanisms were determined. Further, arterial thrombosis by photochemical injury of the common carotid artery, and TF expression in the murine endothelium were examined in C57BL/6 mice treated with ticagrelor or clopidogrel. Ticagrelor, but not CAM, reduced TNF-α-induced TF expression via proteasomal degradation and TF activity, independently of the P2Y12 receptor and the equilibrative nucleoside transporter 1 (ENT1), an additional target of ticagrelor. In C57BL/6 mice, ticagrelor prolonged time to arterial occlusion, compared with clopidogrel, despite comparable antiplatelet effects. In line with our in vitro results, ticagrelor, but not clopidogrel, reduced TF expression in the endothelium of murine arteries. CONCLUSION: Ticagrelor, unlike clopidogrel, exhibits endothelial-specific antithrombotic properties and blunts arterial thrombus formation. The additional antithrombotic properties displayed by ticagrelor may explain its greater efficacy in reducing thrombotic events in clinical trials. These findings may provide the basis for new indications for ticagrelor.