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

Systemic GDF11 replenishment ignites myocardial injury through diminishing anti-apoptotic activity of cardiac progenitor cells

Background

Tissue damage due to acute myocardial infarction is caused by both the ischemic insult and subsequent reperfusion injury (I/R). Restoration of coronary blood flow accelerates cardiomyocyte death, a phenomenon referred to as reperfusion injury, the extent of which is partly modulated by cardiac progenitor cells (CPC). Development of novel therapies to reduce infarct size, the main determinant of outcome, represent a huge unmet medical need (1). Systemic levels of growth differentiation factor 11 (GDF11), a TGF-β superfamily member that shares 90% homology with myostatin, decline with age, and GDF11 replenishment by heterochronic parabiosis or systemic recombinant GDF11 (rGDF11) delivery was postulated to have rejuvenating effects (2).

Purpose

We aimed to probe the effects of systemic GDF11 replenishment on I/R injury and deepen insights into the molecular mechanisms involved.

Methods

We designed a vehicle-controlled study in which young (3–4 months) and old (22–24 months) C57Bl/6 mice were randomly assigned to either daily systemic rGDF11 or control treatment over 30 days before myocardial I/R injury was induced. Dissected hearts were subjected to in-depth profiling followed by IPA-guided -omics to identify key regulatory mechanisms. Finally, in vitro experiments on human CPCs and HL-1 cardiomyocytes were performed.

Results

Myocardial Gdf11 expression declined with age, whereas myostatin (Mstn) showed an opposing expression pattern (Fig. 1A), a trend similarly observed upon I/R (Fig. 1B). Surprisingly, after the 30-day study period (Fig. 1C), young and aged rGDF11-treated mice showed higher I/R-induced infarct size and serum cardiac troponin I levels than controls, despite comparable areas at risk (Fig. 1D). Importantly, while proxies of necroptosis/pyroptosis remained unchanged, rGDF11-treated animals showed reduced cardiomyocyte viability irrespective of their age (Fig. 2A). Targeted transcriptomics applied on cardiac tissues of both groups identified the CPC-marker Nkx2–5 to be differentially regulated (Fig. 2B-C), an expression pattern validated in an independent cohort at both mRNA and protein levels (Fig. 2D). In the adult myocardium, the expression of both Nkx2–5 and its cofactor Gata4 is mainly confined to CPCs; indeed, similar reductions in Nkx2–5 and Gata4 expression were observed in CPCs exposed to rGDF11 (Fig. 2E) which coincided with accelerated cardiomyocyte death if cultured in conditioned media obtained from CPCs treated with rGDF11 (Fig. 2F), pointing toward a paracrine signalling pathway.

Conclusions

Myocardial expression of GDF11 declines with age, and is blunted upon I/R injury, thereby opposing the expression pattern of myostatin. Surprisingly, however, systemic GDF11 replenishment by rGDF11 supplementation enhances rather than reduces myocardial infarct size through augmented apoptosis, a phenomenon mediated by diminished cardioprotective function of CPCs.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Foundation for Cardiovascular Research – Zurich Heart House

SGLT-2 inhibition by empagliflozin exerts neutral effects on experimental arterial thrombosis in a murine model of low-grade inflammation

Introduction

Low-grade inflammation couples dysmetabolic states to insulin resistance and atherosclerotic cardiovascular disease (ASCVD). Selective sodium-glucose co-transporter 2 (SGLT-2) inhibition by empagliflozin improves clinical outcomes in patients with ASCVD independently of glucose-lowering. Yet, its mechanism of action remains largely undetermined.

Purpose

We aimed to test whether empagliflozin affects arterial thrombus formation in baseline conditions or low-grade inflammation, a systemic milieu shared among patients with ASCVD.

Methods

Sixteen-week-old C57BL/6 mice were randomly assigned to acute administration of empagliflozin (25 mg/kg BW) or vehicle, of which a subgroup was pre-treated biweekly over 4 weeks with super-low-dose lipopolysaccharide (LPS; 5 ng/kg BW), before carotid thrombosis was induced by photochemical injury. The translational value of these findings was investigated in primary human aortic endothelial cells (HAECs) and plasma samples of patients randomized to empagliflozin therapy.

Results

The between-group difference in doppler-flow probe detected time-to-occlusion (TTO) remained within the predefined equivalence margin (Δ=|10.50|), irrespective of low-grade inflammation (95% confidence interval [CI], −9.82 to 8.85 and −9.20 to 9.69), while glucose dropped by 1.64 and 4.84 mmol/l, respectively (Fig. 1). Ex vivo platelet aggregometry suggests similar platelet activation status, corroborated by unchanged circulating platelet-factor 4 (PF4) plasma levels. In concert, carotid PAI-1 expression and TF activity remained unaltered upon SGLT-2 inhibition, and no difference in plasma D-dimer levels was detected, suggesting comparable coagulation cascade activation and fibrinolytic activity (Fig. 1). In HAECs pre-treated with LPS, empagliflozin neither changed TF activity nor PAI-1 expression (Fig. 2). Accordingly, among patients with established ASCVD or at high cardiovascular (CV) risk randomized to 10 mg empagliflozin daily signatures of thrombotic (i.e., TF) and fibrinolytic activity (i.e., PAI-1) remained unchanged, while plasma glucose declined significantly during 3 months of follow-up (Fig. 2).

Conclusion

SGLT-2 inhibition by empagliflozin does not impact experimental arterial thrombus formation, neither under baseline conditions nor during sustained low-grade inflammation, and has no impact on proxies of thrombotic/fibrinolytic activity in patients with ASCVD. The beneficial pleiotropic effects of empagliflozin are likely independent of pathways mediating thrombosis.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science FoundationSwiss Heart FoundationFoundation for Cardiovascular Research–Zurich Heart House

In vitro fertilization exacerbates stroke size and neurological disability in wildtype mice

BACKGROUND AND PURPOSE

Assisted reproductive technologies (ART) induce premature vascular aging in human offspring. The related alterations are well-established risk factors for stroke and predictors of adverse stroke outcome. However, given the young age of the human ART population there is no information on the incidence and outcome of cerebrovascular complications in humans. In mice, ART alters the cardiovascular phenotype similarly to humans, thereby offering the possibility to study this problem.

METHODS

We investigated the morphological and clinical outcome after ischemia/reperfusion brain injury induced by transient (45 min) middle cerebral artery occlusion in ART and control mice.

RESULTS

We found that stroke volumes were almost 3-fold larger in ART than in control mice (P < 0.001). In line with these morphological differences, neurological performance assessed by the Bederson and RotaRod tests 24 and 48 h after artery occlusion was significantly worse in ART compared with control mice. Plasma levels of TNF-alpha, were also significantly increased in ART vs. control mice after stroke (P < 0.05). As potential underlying mechanisms, we identified increased blood-brain barrier permeability evidenced by increased IgG extravasation associated with decreased tight junctional protein claudin-5 and occludin expression, increased oxidative stress and decreased NO-bioactivity in ART compared with control mice.

CONCLUSIONS

In wildtype mice, ART predisposes to significantly worse morphological and functional stroke outcomes, related at least in part to altered blood-brain barrier permeability. These findings demonstrate that ART, by inducing premature vascular aging, not only is a likely risk factor for stroke-occurrence, but also a mediator of adverse stroke-outcome.

TRANSLATIONAL PERSPECTIVE

This study highlights that ART not only is a likely risk factor for stroke-occurrence, but also a mediator of adverse stroke-outcome. The findings should raise awareness in the ever-growing human ART population in whom these techniques cause similar alterations of the cardiovascular phenotype and encourage early preventive and diagnostic efforts.

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

Lifelong dietary omega-3 fatty acid reverses cardiac and vascular dysfunction via MMP-2 modulation in aged mice

Background

Aging has a remarkable effect on the cardiovascular system, and negatively causes structural and functional changes in the heart including diastolic/systolic dysfunction and left ventricular (LV) dyssynchrony, as well as, arterial stiffness which may develop to heart failure with preserved ejection fraction (HFpEF) in aged adults. We recently showed that the plant-derived omega-3-fatty-acid α-linolenic-acid (ALA) has emerged to confer potential protective effects against cardiovascular disease. Since cardiovascular aging is a chronic process, we hypothesized that a lifelong effective dietary supplementation with ALA will reverse or prevent age-related diastolic and arterial dysfunction during aging.

Purpose

Here, we test the hypotheses that (1) lifelong dietary ALA will prevent LV diastolic and arterial dysfunction in aged mice and that (2) lifelong dietary ALA will prevent the age-related cardiovascular dysfunction through modiulation of matrix-metalloproteinase-2 (MMP-2) in the heart and arteries.

Methods and results

6-month-old (young) wild-type C57BL/6J mice were fed a low (0.03%), as control, or high ALA (7.3%) diet for more than 12 months. Our results show that aged (&gt;18 months) mice on low ALA diet recapitulate major hallmarks of HFpEF, including diastolic dysfunction with preserved left ventricular ejection fraction, cardiac interstitial fibrosis, impaired acetylcholine-induced relaxation of aortic segments, and arterial stiffness. Intriguingly, we revealed that lifelong ALA-rich diet prevents diastolic dysfunction, vascular relaxation capacity, reduced pulse wave velocity, interstitial fibrosis, and coincident hemodynamic abnormalities in aged mice. Lifelong dietary ALA-in the prevention strategy-was associated with remarkably reduced cardiac and aortic MMP-2 and COX-2 expression, lower levels of pro-inflammatory cytokine TNF-α, and increased isocitrate dehydrogenase 2 (Idh2) expression, decreased function of which has previously been associated with cardiac dysfunction.

Conclusions

Our data support that lifelong ALA-rich diet restores normal cardiac and vascular function in aged mice with LV diastolic and arterial dysfunction and prevents development of age-related cardiovascular dysfunction through the modulation of MMP-2 signaling.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): 1. Swiss National Science Foundation (number 324730_182328)2. the Kardio Stiftung, Baden, Switzerland

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

High plasma levels of soluble LOX-1 portends poor survival in acute coronary syndromes beyond GRACE 2.0: a multicentre prospective cohort study

Background

While inflammatory states and dyslipidemias confer a dismal prognosis following myocardial ischaemia, the role of the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) which sits at the confluence of these conditions remains elusive. Given soluble LOX-1' (sLOX-1) pivotal role in inflammatory processes underlying atherosclerotic plaque progression, we sought to study its prognostic utility on the risk of adverse events in acute coronary syndromes (ACS).

Purpose

Hence, we aimed to investigate whether sLOX-1 is an independent predictor of all-cause death at one year beyond traditional and emerging risk factors for poor survival following ACS.

Methods

2678 ACS patients were recruited in the prospective, multicentre SPUM-ACS trial, of which 2525 completed follow-up at one year. Major adverse cardiovascular events, including death from any cause, were adjudicated by an independent clinical endpoint committee. By employing high-sensitive enzyme-linked immunosorbent assay, sLOX-1 was assessed in the plasma at the time of presentation in ACS and age-matched chronic coronary syndrome (CCS) patients. Kaplan-Meier survival analysis and Cox proportional hazard regression models, adjusted for baseline variables and the GRACE 2.0 score, were used to study the predictive utility of sLOX-1.

Results

At the time of presentation, ACS patients, specifically those with ST-segment elevation ACS, had significantly elevated sLOX-1 levels as compared to patients with CCS (median, 35.40 vs. 2.00 pg/ml, P&lt;0.0001). Patients in the upper sLOX-1 tertile were at heightened risk for both death from any cause (crude HR 1.785, 95% CI 1.083–2.941, P&lt;0.05; adjusted HR 2.035, 95% CI 1.176–3.519, P&lt;0.05) and CV death (crude HR 2.447, 95% CI 1.285–4.663, P&lt;0.01; adjusted HR 2.383, 95% CI 1.206–4.710, P&lt;0.05) compared to those in the first tertile. Importantly, sLOX-1 remained an independent predictor of all-cause death after adjustment for known risk factors of adverse outcome and the GRACE 2.0 score (adjusted + GRACE 2.0 HR 1.896, 95% CI 1.034–3.476, P&lt;0.05).

Conclusions

Plasma sLOX-1 is elevated in ACS patients and predicts poor survival independent of both traditional and emerging risk factors and provides prognostic information beyond GRACE 2.0.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Swiss National Science FoundationFoundation for Cardiovascular Research - Zurich Heart House

The role of matrix metalloproteinase-2 on age-dependent arterial stiffness

Introduction

Arterial stiffness is a well-characterized sign of vascular aging. It strongly predicts the development of several cardiovascular diseases (CVD), such as hypertension, stroke and heart failure. The age-dependent stiffening of elastic arteries is primarily attributed to the loss of interlaminar elastic fibers and the increase of collagen fibers. This process is regulated by matrix metalloproteinases (MMPs), including MMP-2. A strong correlation between MMP-2 levels and arterial stiffness has been previously described. However, the causative link between age-dependent arterial stiffness and MMP-2 remains unclear.

Purpose

In this study, we aimed to prospectively investigate the effect of MMP-2 gene silencing on the development of age-dependent carotid stiffness in wild type (WT) mice.

Methods

Pulse Wave Velocity (PWV), as the gold standard technique to assess arterial stiffness, was assessed in the right common carotid artery (RCCA) of C57BL/6 WT mice of various ages ranging between 3 and 25 months. Plasma and vascular levels of MMP-2 on RCCA were also measured and correlate with PWV. Moreover, aged WT male mice (18–21-month-old) were treated for 4 weeks with either MMP-2 siRNA or Scr siRNA via tail vein injection every 4 days and PWV was assessed at baseline, 2 and 4 weeks.

Results

Mouse carotid PWV increased and was positively correlated with age in our in vivo longitudinal study. Increases of vascular and circulating MMP-2 levels were also observed in this study. MMP-2 knockdown by siRNA treatment reduced vascular MMP-2 level (Fig. 1), which in turn attenuated age-dependent carotid stiffening (data not shown). siMMP-2 treated animals also showed an increase of elastin to collagen ratio. Furthermore, enhanced phosphorylation of the activatory eNOS Ser1177 was observed in the siMMP-2 group without affecting the level of total eNOS and Akt phosphorylation. Interestingly, co-immunoprecipitation experiments demonstrated that MMP-2 directly interacts with eNOS and this interaction is augmented with age.

Conclusion

The silencing of MMP-2 attenuates age-dependent carotid stiffness by affecting elastin to collagen ratio and interfering with eNOS activation. Thus, MMP-2 may mediate ECM remodeling and endothelial-dependent vasorelaxation in the development of age-dependent vascular stiffness.

Funding Acknowledgement

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

P6286Old age significantly worsens stroke outcome in old mice through a mechanism of inflamm-aging successfully countered by the tumour necrosis factor alpha antibody infliximab

Background

Stroke is the second leading cause of death and the number one cause of adult disability worldwide. As a strongly age-dependant disease, its prevalence is expected to rise along with the average age in western populations. While the epidemiological evidence linking stroke to age is non-refutable, the specific and independent effects of age on stroke remain elusive.

This presents an important missing link for developing targeted treatments tailored to the growing elderly population.

A potential mechanism pertinent to stroke outcome in the elderly is a chronic low-grade inflammatory state, coined “inflamm-aging”. Such a phenomenon could not only increase the risk for stroke, but also negatively affect its outcome and thus offers both preventive and therapeutic value.

Purpose

To determine the specific effects of age on the outcome after stroke in mice and delineate culprit molecular pathways with a focus on inflammatory mediators and to assess the efficacy of specific anti-inflammatory treatment with the TNF-α antibody Infliximab in this setting.

Methods

Old (18–20 months) C57BL/6 wildtype mice were compared to young (12 weeks) controls. Baseline levels of inflammatory cytokines were assayed in plasma and brain homogenates by ELISA. Ischemic stroke was induced by transient middle cerebral artery occlusion (30 minutes/48 h). Neurological function was assessed by a Bederson based score and the RotaRod test. Anti-inflammatory treatment with Infliximab was administered to a subset of old mice via weekly intraperitoneal injections (10 mg/kg) for 4 weeks prior to stroke induction. Young and old control animals received vehicle.

Results

At baseline (prior to stroke), old animals showed significantly higher plasma levels of TNF-α compared to young (Fig. 1A), while IL-6 and IL-1β remained below detection level in both groups. In brain homogenates of healthy old and young animals, TNF-α and IL-1β did not differ, while IL-6 was below detection level.

Old mice showed significantly larger stroke sizes (Fig.1B), performed worse neurologically (Fig. 1C) and suffered from higher post-stroke mortality compared to young (Fig. 1D). Pre-treatment with the TNF-α inhibitor Infliximab significantly decreased stroke size, neurological impairment and mortality in old animals (Fig1B-D).

Figure 1

Conclusions

In a model lacking additional confounding factors, we demonstrate a direct adverse effect of age per se on stroke outcome and mortality. Elevated TNF-α plasma levels in old mice outline the mechanism of “inflamm-aging” as a possible culprit. This concept is strongly supported by the beneficial effect of Infliximab on stroke outcome in old animals. Further investigation of the downstream mediators of the observed effect could help in tailoring treatments to the particularly vulnerable and growing elderly population.

2182Sirtuin 5 regulates arterial thrombosis by modulating endothelial plasminogen activator inhibitor-1

Introduction

Arterial thrombosis as a result of plaque rupture or erosion is a crucial event in myocardial infarction and stroke. Oxidative stress and inflammation promote endothelial dysfunction and play a pivotal role in destabilization of the atherosclerotic plaque. Sirtuin 5 (SIRT5) is a member of the sirtuin protein family with function as a NAD+-dependent protein desuccinylase and demalonylase. Being implicated in the regulation of different pathophysiological processes among which production of reactive oxygen species and transcription of inflammatory mediators, SIRT5 plays a role in the development of several cardiovascular diseases such as myocardial infarction and stroke. To date, the possible involvement of SIRT5 as a mediator of arterial thrombosis remains to be investigated.

Purpose

In this study we investigate the putative role of this protein in arterial thrombosis by using an established in vivo mouse model. The translational value of animal findings as well as the molecular mechanism underlying the observed effect will be investigated also in primary human aortic endothelial cells (HAECs).

Methods

SIRT5 knockout (KO) as well as SIRT5 transgenic (TG) animals were used for in vivo experiments. HAECs treated with SIRT5 silencing RNA (si-SIRT5) and stimulated with tumor necrosis factor (TNF)-α were used for in vitro assays.

Results

When compared to WT animals, SIRT5 KO mice display blunted carotid artery thrombus formation as underlined by delayed time to occlusion in a photochemical injury model. Oppositely, in SIRT5 TG mice the formation of an occlusive thrombus is accelerated (Fig 1). Mechanistically, SIRT5 KO and WT animals show no difference in terms of vascular tissue factor (TF) activity, TF concentration in plasma and expression of TF pathway inhibitor (TFPI) in the aorta. In line with the observed reduced thrombogenicity, SIRT5 KO animal express reduced level of the pro-thrombotic plasminogen activator-1 (PAI-1), as assessed by western blot in aorta lysate. Of interest, SIRT5 genetic deletion does not affect platelet aggregation, as assessed by ex-vivo collagen-induced aggregometry. In HAECs, SIRT5-silencing inhibits PAI-1 expression in response to TNF-α. Real-time polymerase chain reaction revealed that inhibition of PAI-1 expression occurs at the mRNA level. This effect is mediated by reduced activation of the MAP kinase Erk 1/2, but not JNK (Fig 1).

Conclusions

SIRT5 mediates arterial thrombosis by increasing endothelial PAI-1 expression. Hence, SIRT5 may be an effective therapeutic target in the context of atherothrombosis.

2287Endothelial SIRT6 exerts a beneficial role in cerebral ischemia/reperfusion injury by preserving blood-brain barrier integrity

Introduction

Stroke is a major cause of mortality and morbidity worldwide. Yet, therapeutic strategies are limited to the early reperfusion which can, on the other hand, worsen the brain damage trough ischemia/reperfusion (I/R) injury. Post-stroke blood-brain barrier (BBB) impairment is associated with worsened outcome. Aging is a major risk factor for stroke and genes regulating lifespan also contribute to the determination of cerebral damage during I/R injury.

Purpose

Given the pivotal role of endothelial cells in BBB, we hypothesized that the endothelial-specific expression of the longevity gene SIRT6 may protect the BBB from ischemia/reperfusion damage thus having a beneficial role on stroke outcome.

Methods

Endothelial-specific SIRT6 knockout (eSIRT6−/−) mice and control littermates (CTRL) underwent transient middle cerebral artery occlusion (tMCAO) for 45 min followed by 48 hours of reperfusion. Immunohistochemistry (IHC) was used to investigate BBB permeability by IgG extravasation and molecular mechanisms. Primary human brain microvascular endothelial cells (HBMVECs) transfected with either SIRT6 (siSIRT6) or scrambled (siSCR) small interfering RNA were subjected to hypoxia/reoxygenation (H/R). An in vitro BBB model consisting of a monolayer of siRNA-treated HBMVECs was established and barrier function was assessed by 48 h-lasting transendothelial electrical resistance measurement. SIRT6 expression in monocytes from stroke patients was correlated with the short-term neurological outcome [ΔNIHSS% = (NIHSS discharge-NIHSS admission)/ NIHSS admission*100].

Results

eSIRT6−/− displayed higher infarct volumes and lower survival rate compared to WT mice 48 h after tMCAO. The increased infarct volume was functionally relevant as eSIRT6−/− also showed worse post-stroke neurological impairment. Analysis of brain sections revealed increased BBB damage and increased endothelial expression of cleaved caspase-3 in eSIRT6−/− as compared to control littermates. In vitro, H/R reduced SIRT6 expression in HBMVECs. Mirroring the animal results, SIRT6 silencing impaired the barrier function of HBMVECs 48 h after exposure to H/R. In line with this, SIRT6-silenced HBMVECs showed reduced viability, increased cleaved caspase-3 expression and reduced activation of the anti-apoptotic survival pathway Akt as compared to control cells after H/R. The direct interaction between SIRT6 and Akt was confirmed by co-immunoprecipitation. In ischemic stroke patients, SIRT6 expression was higher in those with short-term neurological improvement (ΔNIHSS% >0) and negatively correlated with ΔNIHSS%.

Conclusion

Endothelial SIRT6 exerts a beneficial role in ischemic stroke by blunting I/R-mediated BBB damage. Specifically, SIRT6 reduces endothelial I/R-induced apoptotic death through activation of the protective Akt pathway. The longevity gene SIRT6 may represent a novel therapeutic target for the treatment of ischemic stroke.

Acknowledgement/Funding

Swiss National Science Foundation

P4468Dietary plant derived omega-3 fatty acid alpha linolenic acid prevents age-dependent arterial stiffness and improves outcome after stroke in mice

Background

A fundamental determinant of cardio- and cerebrovascular diseases is vascular aging, characterized by arterial stiffness. Arterial stiffness is an independent predictor of adverse cardio- and cerebrovascular events and mortality.

Fish-derived omega-3 fatty acids (n3-FA) have been described to decrease cardiovascular events in high risk populations. Little is known on the effects of the plant-derived n3 FA alpha-linolenic acid (ALA). More insight is urgently needed, because of the low costs and abundant global supply of ALA. Thus, we aimed to investigate the effects of a long-term dietary intervention with ALA on age-dependent arterial stiffness and the magnitude of these effects on a specific vascular endpoint – ischemic stroke – in a mouse model of aging.

Methods

C57BL/6 wildtype males were either fed an ALA-rich (high ALA, 7.3 g%) or a respective control (0.3 g%) diet for 12 months, starting from 6 months of age.

At 9, 15 and 18 months, arterial stiffness was assessed by measuring pulse wave velocity (PWV) in the right common carotid artery using a Vevo 3100 system (VisualSonics, Fig. 1A).

At 18 months, ischemic stroke was induced by transient middle cerebral artery occlusion (30 mins/48 h). Stroke size was assessed by triphenyl tetrazolium chloride staining and neurological function by a Bederson based score.

Results

Arterial stiffness steadily and significantly increased in controls over time, while ALA clearly and effectively prevented it (PWV at 9 vs. 18 months: controls + 95%; p<0,0001 vs. High ALA + 15%; ns) (Fig 1A).

Stroke size at 18 months was significantly decreased in ALA-fed animals compared to controls (28.39 mm3 vs. 51.77 mm3 p=0.0017) (Fig. 1B). In line with the morphological changes, controls performed significantly worse neurologically (Fig. 1C). Additionally, post-stroke survival at 48 h was improved in ALA-fed animals compared to controls, with 85% survival compared to 57% (Fig. 1D).

Figure 1

Conclusion

We demonstrate that long-term dietary supplementation with the plant-derived ALA fully prevents the development of age-dependent arterial stiffness.

The magnitude of this effect is clearly reflected in biologically relevant decreased stroke size, improved neurological performance and even post-stroke survival.

This study not only demonstrates vasoprotective effects of ALA, but also links them to improved outcome of a specific clinical endpoint. Future analyses will aim at delineating the molecular basis of the observed benefits. This will result in a better understanding of some ambiguous results from clinical trials and likely define the population which benefits from ALA.

Tumour Necrosis Factor-α Inhibition Improves Stroke Outcome in a Mouse Model of Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is a chronic inflammatory disorder where incidence and severity of myocardial infarction are increased. Data on the incidence and outcome of stroke are conflicting. Thus, we investigated outcome after Ischemia/Reperfusion (I/R) brain injury in a mouse model of RA and assessed for the role of the tumour necrosis factor-α (TNF-α) inhibitor Infliximab herein. We used a TNF-α reliant mouse model of RA. RA and wildtype (WT) animals were treated with vehicle (RA/WT) or Infliximab (RA Infliximab) for 4 weeks, before undergoing I/R brain injury. RA-animals displayed larger strokes and poorer neurological performance. Immunohistochemistry on brain sections revealed increased numbers of resident and peripheral innate immune cells (microglia and macrophages); increased Blood-Brain-Barrier (BBB)-disruption; decreased levels of the tight junction proteins (TJPs) claudin-5 and occludin; increased expression of matrix-metalloproteinases (MMP)-3 and -9 and enhanced lipid peroxidation. Treatment with Infliximab corrected these alterations. We show that RA associates to worse stroke-outcome via exacerbated BBB degradation by decrease of the TJPs claudin-5 and occludin. We identified MMPs-3 and -9 and increased oxidative stress as potential mediators thereof. Increased numbers of resident and peripheral innate immune cells (microglia and macrophages) may in turn contribute to all these effects. Infliximab-treatment restored the phenotype of RA-mice to baseline. Our data provide evidence clearly linking RA to adverse stroke-outcome in mice and indicate an approved TNF-α inhibitor as a potential strategy to reduce stroke-burden in this setting.

Serum levels of osteopontin predict diabetes remission after bariatric surgery

AIM

Bariatric surgery has been shown to effectively improve glycaemic control in morbidly obese subjects. However, the molecular bases of this association are still elusive and may act independently of weight loss. Here, our retrospective study has investigated the inflammatory molecule osteopontin (OPN) as a potential predictor of type 2 diabetes mellitus (T2DM) remission.

METHODS

Baseline serum levels of OPN were analyzed in 41 T2DM patients who underwent bariatric surgery. Anthropometric measures and biochemical variables, including insulin sensitivity indices (HOMA2), were assessed at baseline and at 1 and 3 years after surgery.

RESULTS

At baseline, patients who experienced T2DM remission had increased waist circumference, body weight and BMI, and higher serum OPN, compared with non-remitters. Patients with and without T2DM remission improved their lipid and glucose profiles, although insulin resistance indices were only improved in the T2DM remission group. In the overall cohort of both T2DM remission and non-remission patients, baseline circulating levels of OPN significantly correlated with reductions of body weight and BMI over time, and insulin sensitivity improved as well. However, only the HOMA2-%S remained independently associated with serum OPN on multivariate linear regression analysis (B: 0.227, 95% CI: 0.067-0.387, β = 0.831; P = 0.010). Baseline values of OPN predicted 3-year T2DM remission independently of body weight loss, lower BMI and duration of diabetes (OR: 1.046, 95% CI: 1.004-1.090; P = 0.033).

CONCLUSION

Although larger studies are still needed to confirm our preliminary results, pre-operative OPN serum levels might be useful for predicting 3-year T2DM remission independently of weight loss in patients undergoing bariatric surgery.

High baseline C-reactive protein levels predict partial type 2 diabetes mellitus remission after biliopancreatic diversion

BACKGROUND AND AIMS

Several studies demonstrated that surgery can improve inflammation parameters, such as C-reactive protein (CRP). Few biomarkers have been investigated to potentially predict type 2 diabetes mellitus (T2DM) remission. We aimed at determining whether pre-surgery serum CRP levels could predict T2DM remission after 3 years in patients undergoing bariatric surgery, especially biliopancreatic diversion (BPD).

METHODS AND RESULTS

This study was conducted from 2007 to 2009 at the Surgical Department of the University of Genoa, Italy. Forty-four patients with T2DM undergoing BPD (n = 38) or Roux-en-Y gastric bypass (n = 6) were enrolled. The primary endpoint was to evaluate whether pre-surgery CRP levels could predict T2DM partial remission at 3-year follow-up. Secondary endpoints were to assess whether glycaemic, lipid, and inflammatory parameters modified during the follow-up. At baseline, patients with T2DM ranged from overweight to morbid obesity, had mild dyslipidaemia, and a low-grade inflammation. Bariatric surgery improved body weight, lipid and glycaemic profile both at 1- and 3-year follow-up. Pre-surgery CRP levels progressively decreased at 1- and 3-year follow-up. Among inflammatory pre-surgery parameters, only high CRP levels were shown to predict T2DM partial remission after 3 years. Multivariate analysis confirmed the predictive value of pre-surgery CRP levels independently of age, gender, type of surgery, and body mass index.

CONCLUSION

Bariatric surgery, in particular BPD, improved both metabolic and inflammatory biomarkers at 1- and 3-year follow-up. Pre-surgery high CRP levels predicted 3-year T2DM partial remission, indicating a promising target population to be especially treated with BPD.

Gonadotropin levels in women with polycystic ovary syndrome: their relationship to body weight and insulin levels

The purpose of this work was to investigate the relationship of gonadotropin levels to body weight and insulin levels in woman with polycystic ovary syndrome (PCOS). Specifically, we wished to test the hypothesis that circulating luteinizing hormone (LH) and insulin levels are different in obese and normal weight patients with PCOS. The basal plasma levels of gonadotropins, estrogens, androgens and sex hormone-binding globulin, the gonadotropin responses to gonadotropin releasing hormone (GnRH) and the insulin and C-peptide responses to a 3-hour oral glucose tolerance test (OGTT) were measured in 19 obese and 19 normal weight patients with PCOS and 7 obese and 8 normal weight ovulatory controls. Data of the patients were evaluated according to body weight (obese vs normal weight) and basal LH (high vs normal). There was no significant difference in basal LH and androgen levels and in the insulin response to oral glucose between obese and normal weight patients with PCOS. Compared to the weight matched controls, both obese and non obese patients showed significantly higher LH responses to GnRH and C-peptide responses to OGTT. When the high LH patients (no = 18) were compared those with normal LH (no = 20), the high LH subjects exhibited significantly higher androstenedione levels. Both obese (no = 10) and normal weight (no = 8) patients with high LH showed significantly greater C-peptide responses to OGTT than obese (no = 9) and non obese (no = 11) patients with normal LH. However, as compared with the weight matched controls, both the high LH and normal LH patients had significantly greater C-peptide responses to OGTT. We conclude that obese and non obese patients with PCOS do not seem to differ in the prevalence of elevated LH levels or in the LH secretory pattern. Insulin resistance, expressed by an enhanced pancreatic sensitivity to oral glucose, is present in both the high LH and the normal LH subjects, even though the PCOS patients with elevated LH tend to be more insulin resistant and hyperandrogenic than the normal LH patients.