Arterial thrombosis in Hutchinson-Gilford Progeria Syndrome

Introduction

Arterial thrombosis is the most common age-associated event underlying major adverse cardiovascular (CV) events. The interplay between the vascular endothelium, platelets, and the coagulation cascade leads to thrombus formation, which results in the cessation of blood supply to the downstream tissues. Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare genetic condition with striking features of premature aging. It is caused by defects in the nuclear A-type lamin gene, leading to intracellular accumulation of progerin. This genetic disorder is characterized by shortened lifespan, primarily due to an increased incidence of myocardial infarction and ischemic stroke. Declined vascular function and compliance have been reported in HGPS patients. Nevertheless, the effect of the specific A-type lamin gene mutation on coagulation and thrombus formation has not been investigated previously.

Methods

28- to 30-week-old male and female transgenic heterozygous LmnaG609G knock-in (HGPS) mice and corresponding wild-type (WT) littermate controls were exposed to photochemically-induced carotid artery endothelial injury to trigger arterial thrombosis. Vascular and circulating levels of tissue factor (TF), plasminogen activator inhibitor (PAI)-1, and von Willebrand factor (vWF) were measured using enzyme-linked immunosorbent assay (ELISA). TF activity assay was also performed on carotid artery homogenates of WT and HGPS animals.

Results

HGPS mice displayed accelerated thrombus formation compared to the WT animals as underlined by a shortened time to occlusion. Although this finding suggests an increased activation of the extrinsic coagulation cascade, no significant differences were found in TF expression and activity in carotid artery lysates. Circulating and vascular expression of the fibrinolytic factor PAI-1 was also found to be similar between WT and HGPS animals. Furthermore, no significant difference in plasma vWF between the two groups was observed.

Conclusions

Our results show an increased arterial thrombotic response in HGPS mice as compared to WT littermates. This novel observation could provide a mechanistic explanation for the increased incidence of acute cardiovascular events observed in HGPS patients. Further studies will be conducted to investigate the molecular mechanism underlying the observed effects, in particular, on the potential involvement of platelets.

Funding Acknowledgement

Type of funding sources: None.

Endothelial expression of JCAD worsens outcome after acute ischemic stroke: a translational study

Introduction

Despite the increasing availability of early reperfusion, acute ischemic stroke (AIS) is still burdened by high mortality and long-time disability. Junctional protein associated with Coronary Artery Disease (JCAD) was associated to multiple cardiovascular disorders, but its role in AIS has not been investigated so far.

Purpose

To investigate the role of endothelial JCAD in the pathogenesis of AIS and its potential as a therapeutic target.

Methods

Cerebral ischemia was induced by transient Middle Cerebral Artery Occlusion (tMCAO) in mice with either global or endothelial-specific JCAD genetic deletion, and littermate controls. Stroke size was assessed ex-vivo by tetrazolium chloride staining 48 hours after reperfusion. For neurological assessment, RotaRod Test and Bederson score were recorded 24 and 48 hours after reperfusion. In vivo silencing of JCAD was achieved by intravenous injection of a JCAD small interfering RNA (siRNA) after tMCAO.

In parallel, JCAD silencing was performed in vitro in human brain microvascular endothelial cells (HBMVECs) using siRNA transfection, followed by hypoxia/reoxygenation (H/R) injury. Cell death and trans-endothelial electrical resistance (TEER) were measured by LDH assay and electrical cell-substrate impedance sensing, respectively. Molecular mechanisms were investigated in vivo by immunohistochemistry and in vitro by Western blot, respectively.

Lastly, JCAD plasma levels were measured by ELISA in two independent cohorts of patients with AIS.

Results

The expression of JCAD was up-regulated in the ipsilateral hemisphere of stroke in wild-type mice. Both global and endothelial-specific JCAD knockout mice displayed reduced stroke size after tMCAO and a significantly improved Bederson score. Similarly, mice with post-ischemic JCAD silencing had a reduced stroke size and a better motor performance at the RotaRod test (Figure 1).

In vitro, JCAD-silenced HBMVECs showed a reduced cell death rate and a higher TEER after H/R injury, compared to controls. JCAD-silenced HBMVECs also had an increased phosphorylation of Akt. After treatment with the Akt/PI3K inhibitor Wortmannin, JCAD-silenced HBMVECs showed similar TEER and cell death rates to non-silenced cells, following H/R (Figure 2).

Lastly, an increase of circulating levels of JCAD was observed in patients with AIS within 24 hours from symptoms onset. Furthermore, higher levels of JCAD at the time of hospitalization were associated with a higher risk of death within 90 days after the event.

Conclusions

JCAD expression is associated with a larger brain damage in mice in vivo and with a higher mortality in patients. In vitro results suggest that JCAD plays a pivotal role in regulating the integrity of endothelium after a H/R injury, inducing cellular death through the inhibition of the Akt/PI3K pathway. Thus, post-ischemic silencing of JCAD may represent a therapeutic strategy to improve the prognosis of patients with acute ischemic stroke.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation

JCAD enhances arterial thrombosis by regulating endothelial plasminogen activator inhibitor-1 and tissue factor expression

Introduction

Arterial thrombosis underlies most acute CV events. Variants of the Junctional cadherin 5 associated (JCAD) locus were consistently shown to associate with increased risk of acute coronary syndrome. Being a component of cell junctions, JCAD protein is highly expressed in endothelial cells and was shown to promote atherosclerosis by acting on the Hippo pathway through LATS2 kinase.

Purpose

This project investigated the effect of JCAD in arterial thrombosis by using an established in vivo mouse model of carotid injury. The translational value of animal findings was assessed in primary human aortic endothelial cells (HAECs) as well as in CV patients.

Methods

JCAD knock-out (Jcad−/−) mice were exposed to photochemically-induced carotid artery endothelial injury to trigger thrombosis. Primary HAECs treated with JCAD small-interfering RNA (si-JCAD), LATS2-silencing RNA (si-LATS2) or control siRNA (si-SCR) were employed for in vitro assays. Plasma JCAD was measured in patients with chronic coronary syndrome (CCS) or ST-elevation myocardial infarction (STEMI).

Results

Compared to wild-type, Jcad−/− mice displayed reduced thrombus formation as underlined by delayed time to occlusion following endothelial-specific carotid damage. Suggesting a blunted activation of the extrinsic coagulation cascade, Jcad−/− animals showed reduced tissue factor (TF) protein expression and activity in carotid artery lysates (Fig. 1). Increased thrombus embolization episodes and D-dimer further suggested an increased activation of the fibrinolytic system in Jcad−/− mice. Indeed, Jcad−/− mice displayed reduced vascular expression of the fibrinolysis inhibitor plasminogen activator inhibitor (PAI)-1. In contrast, platelets aggregation in response to collagen and thrombin was similar in Jcad−/− and Jcad+/+ mice (Fig. 1). In line with the in vivo data, JCAD-silencing of HAECs inhibited TF and PAI-1 gene and protein expression. In accordance with previous literature, JCAD-silenced HAECs displayed increased levels of LATS2 Kinase, which blunts the Hippo pathway by increasing YAP phosphorylation. Yet, double JCAD and LATS2 silencing did not retrieve the phenotype of control HAECs. Of interest, si-JCAD HAECs showed increased levels of Akt phosphorylation, known to downregulate procoagulant expression and to directly phosphorylate YAP. Treatment with the Akt inhibitor Wortmannin prevented the effect of JCAD silencing on TF and PAI-1 indicating a causative role for this pathway (Fig. 2). Recapitulating in vitro findings, p-Akt and p-YAP levels were higher in arterial tissue of Jcad−/− animals as compared to WT (Fig. 1). Patients with STEMI showed significantly higher plasma levels of JCAD as compared to CCS (Fig. 2).

Conclusions

JCAD promotes arterial thrombosis by selectively modulating coagulation and fibrinolysis, but not platelet aggregation through endothelial TF and PAI-1. Our findings support the importance of JCAD as a novel therapeutic target for CV prevention.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation

MMP-2 gene silencing attenuates age-dependent carotid stiffness via reduction of elastin degradation and increased eNOS activation

Background and aims

Arterial stiffness is a hallmark of vascular aging. Being characterized by a loss of elasticity of large arterial walls, arterial stiffness is associated with an increased risk of cardiovascular disease (CVD). The age-dependent arterial stiffness is primarily attributed to alterations in the elastic and collagen deposition that is regulated by a number of enzymes, including matrix metalloproteinase-2 (MMP-2). Nevertheless, the mechanistic link between age-dependent arterial stiffness and MMP-2 remains unclear.

In this study, we investigated the effect and efficacy of therapeutic MMP-2 knockdown using small interfering RNA (siRNA) on age-dependent arterial stiffness.

Methods

Pulse wave velocity (PWV) was assessed in the right carotid artery of wild-type (WT) mice of different age groups. MMP-2 levels and activity in the carotid artery and plasma of young (3 months) and aged (20–25 months) WT mice were determined. Old WT mice (18–21 months) were treated for 4 weeks with either MMP-2 or scrambled siRNA, in which carotid PWV was assessed at baseline, 2 and 4 weeks after the start of the treatment. Elastin to collagen ratio, desmosin (DES) level, and endothelial nitric oxide synthase (eNOS) pathways were also evaluated and compared. Lastly, levels of circulating MMP-2 and DES, the breakdown product of elastin, were measured in a human cohort (23–86 years old), in whom carotid-femoral PWV was assessed.

Results

Carotid PWV, as well as both vascular and circulating MMP-2 levels, were elevated with increasing age in WT mice (Figure 1). Therapeutic MMP-2 knockdown in aged WT mice reduced the vascular MMP-2 expression and attenuated age-dependent carotid stiffness. Increased elastin to collagen ratio and a lower plasma DES level were observed on MMP-2 silenced treated animals (Figure 2). Moreover, siMMP-2 treated mice showed enhanced eNOS phosphorylation on Ser1177. A direct interaction between MMP-2 and eNOS was also observed, which, interestingly, is augmented with age. Finally, collected human data showed a higher level of circulating MMP-2 levels on the elderly subjects. In addition, plasma DES level is positively correlated with age and aortic PWV, indicating the involvement of vascular elastin catabolism on arterial stiffness.

Conclusions

Therapeutic MMP-2 gene silencing, specifically targeting vascular MMP-2, attenuates age-dependent carotid stiffness. This effect is mediated by augmenting eNOS activation and reducing elastin degradation. Thus, our findings indicate MMP-2 as a potential therapeutic target to mitigate age-dependent arterial stiffness and CVD.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Swiss National Science Foundation,Foundation for Cardiovascular Research–Zurich Heart House Figure 1