Haematopoietic and cardiac GPR55 synchronize post-myocardial infarction remodelling

While classical cannabinoid receptors are known to crucially impact on myocardial infarction (MI) repair, a function of the cannabinoid-sensitive receptor GPR55 herein is poorly understood. We investigated the role of GPR55 in cardiac physiology and post-MI inflammation and remodelling. Global GPR55−/− and wildtype (WT) mice were basally characterized or assigned to 1, 3 or 28 days permanent MI and subsequently analysed via pro-inflammatory and pro-hypertrophic parameters. GPR55−/− deficiency was basally associated with bradycardia, increased diastolic LV volume and sarcomere length and a subtle inflammatory phenotype. While infarct size and myeloid cell infiltration were unaffected by GPR55 depletion, acute cardiac chemokine production was prolonged post-MI. Concurrently, GPR55−/− hearts exhibited a premature expansion of pro-reparative and phagocytic macrophages paralleled by early up-regulation of extracellular matrix (ECM) factors 3 days post-MI, which could be mimicked by sole haematopoietic GPR55 depletion. Moreover, global GPR55 deficiency mitigated MI-induced foetal gene re-programming and cardiomyocyte hypertrophy, culminating in aggravated LV dilatation and infarct expansion. GPR55 regulates cardiac homeostasis and ischaemia responses by maintaining adequate LV filling and modulating three crucial processes post-MI: wound healing kinetics, cardiomyocyte hypertrophy and maladaptive remodelling.

Haematopoietic and Cardiac GPR55 Synchronize Post-myocardial Infarction Remodelling

Background and purpose: While classical cannabinoid receptors are known to crucially impact on myocardial infarction (MI) repair, a function of the cannabinoid-sensitive receptor GPR55 herein is poorly understood. We investigated the role of GPR55 in cardiac physiology and post-MI inflammation and remodelling. Methods and results: Global GPR55-/- and wildtype (WT) mice were basally characterized or assigned to 1, 3 or 28 days permanent MI and subsequently analysed via pro-inflammatory and pro-hypertrophic parameters. GPR55-/- deficiency was basally associated with bradycardia, increased diastolic LV volume and sarcomere length and a subtle inflammatory phenotype. While infarct size and myeloid cell infiltration were unaffected by GPR55 depletion, acute cardiac chemokine production was prolonged post-MI. Concurrently, GPR55-/- hearts exhibited a premature expansion of pro-reparative and phagocytic macrophages paralleled by early up regulation of extracellular matrix (ECM) factors 3 days post-MI, which could be mimicked by sole haematopoietic GPR55 depletion. Moreover, global GPR55 deficiency mitigated MI-induced foetal gene re-programming and cardiomyocyte hypertrophy, culminating in aggravated LV dilatation and infarct expansion. Conclusions: GPR55 regulates cardiac homeostasis and ischaemia responses by maintaining adequate LV filling and modulating three crucial processes post-MI: wound healing kinetics, cardiomyocyte hypertrophy and maladaptive remodelling.

Human Mesenchymal Stem Cells being Encapsulated in Alginate/reduced Geraphen Oxide Improving Infarct Expansion, and Inducing Neovasculariziation Formation in Ischemic Myocardium

Currently, one of the new therapeutic strategies is injection of hydrogel and cells to myocardial infarction (MI) patients, which has some limitations such as lack of electromechanical properties and neovascularization. In this study, we investigated the therapeutic potential of new electroactive hydrogel [Reduced graphene oxide (rGO)/Alginate (ALG)] encapsulated human bone marrow mesenchymal stem cell (BMSC) in different experimental groups. The study was done in rat model of chronic ischemic cardiomyopathy by ligating the left anterior descending coronary artery (LAD). Echocardiograms were analyzed at 4 and 8 weeks after MI induction. Experimental groups particularly (BMSC) encapsulated in rGO-ALG increased significantly improvement of fractional shortening (FS) and ejection fraction (EF) compared to the control group. Eighth week after injection, Eosin (H&E) staining was performed. MSC-ALG-rGO demonstrated that significantly increasing vascularization and connective tissue in comparison with control. Masson's trichrome staining indicated reduced scarring/collagen deposition and improved remodeling LV thickness in the MSC-ALG-rGo group. Anti-CD31 antibody applied to detect neovascularization in the experimental groups. Microvessel density was significantly higher in MSC-ALG-rGO treatment than other groups (MSC-ALG and control) (p<0.01).This study demonstrates, use of rGO/ALG a bio-electroactive hydrogel appears safe for intramyocardial injection, improving (LV) function, neovascularization, adjust the electrical properties following MI.

PCSK9 (Proprotein Convertase Subtilisin/Kexin 9) Enhances Platelet Activation, Thrombosis, and Myocardial Infarct Expansion by Binding to Platelet CD36

Background: PCSK9 (proprotein convertase subtilisin/kexin 9), mainly secreted by the liver and released into the blood, elevates plasma low-density lipoprotein cholesterol by degrading low-density lipoprotein receptor. Pleiotropic effects of PCSK9 beyond lipid metabolism have been shown. However, the direct effects of PCSK9 on platelet activation and thrombosis, and the underlying mechanisms, as well, still remain unclear. Methods: We detected the direct effects of PCSK9 on agonist-induced platelet aggregation, dense granule ATP release, integrin αIIbβ3 activation, α-granule release, spreading, and clot retraction. These studies were complemented by in vivo analysis of FeCl 3 -injured mouse mesenteric arteriole thrombosis. We also investigated the underlying mechanisms. Using the myocardial infarction (MI) model, we explored the effects of PCSK9 on microvascular obstruction and infarct expansion post-MI. Results: PCSK9 directly enhances agonist-induced platelet aggregation, dense granule ATP release, integrin αIIbβ3 activation, P-selectin release from α-granules, spreading, and clot retraction. In line, PCSK9 enhances in vivo thrombosis in a FeCl 3 -injured mesenteric arteriole thrombosis mouse model, whereas PCSK9 inhibitor evolocumab ameliorates its enhancing effects. Mechanism studies revealed that PCSK9 binds to platelet CD36 and thus activates Src kinase and MAPK (mitogen-activated protein kinase)–extracellular signal-regulated kinase 5 and c-Jun N-terminal kinase, increases the generation of reactive oxygen species, and activates the p38MAPK/cytosolic phospholipase A2/cyclooxygenase-1/thromboxane A 2 signaling pathways downstream of CD36 to enhance platelet activation, as well. Using CD36 knockout mice, we showed that the enhancing effects of PCSK9 on platelet activation are CD36 dependent. It is important to note that aspirin consistently abolishes the enhancing effects of PCSK9 on platelet activation and in vivo thrombosis. Last, we showed that PCSK9 activating platelet CD36 aggravates microvascular obstruction and promotes MI expansion post-MI. Conclusions: PCSK9 in plasma directly enhances platelet activation and in vivo thrombosis, and MI expansion post-MI, as well, by binding to platelet CD36 and thus activating the downstream signaling pathways. PCSK9 inhibitors or aspirin abolish the enhancing effects of PCSK9, supporting the use of aspirin in patients with high plasma PCSK9 levels in addition to PCSK9 inhibitors to prevent thrombotic complications.

Endothelial S1P 1 Signaling Counteracts Infarct Expansion in Ischemic Stroke

Rationale: Cerebrovascular function is critical for brain health, and endogenous vascular-protective pathways may provide therapeutic targets for neurological disorders. Sphingosine 1-phosphate (S1P) signaling coordinates vascular functions in other organs, and S1P receptor-1 (S1P 1 ) modulators including fingolimod show promise for the treatment of ischemic and hemorrhagic stroke. However, S1P 1 also coordinates lymphocyte trafficking, and lymphocytes are currently viewed as the principal therapeutic target for S1P 1 modulation in stroke. Objective: To address roles and mechanisms of engagement of endothelial cell (EC) S1P 1 in the naïve and ischemic brain and its potential as a target for cerebrovascular therapy. Methods and Results: Using spatial modulation of S1P provision and signaling, we demonstrate a critical vascular protective role for endothelial S1P 1 in the mouse brain. With an S1P 1 signaling reporter, we reveal that abluminal polarization shields S1P 1 from circulating endogenous and synthetic ligands after maturation of the blood-neural barrier, restricting homeostatic signaling to a subset of arteriolar ECs. S1P 1 signaling sustains hallmark endothelial functions in the naïve brain, and expands during ischemia by engagement of cell-autonomous S1P provision. Disrupting this pathway by EC-selective deficiency in S1P production, export, or the S1P 1 receptor substantially exacerbates brain injury in permanent and transient models of ischemic stroke. By contrast, profound lymphopenia induced by loss of lymphocyte S1P 1 provides modest protection only in the context of reperfusion. In the ischemic brain, EC S1P 1 supports blood-brain barrier (BBB) function, microvascular patency, and the rerouting of blood to hypo-perfused brain tissue through collateral anastomoses. Selective S1P 1 agonism counteracts cortical infarct expansion after middle cerebral artery occlusion by engaging the endothelial receptor pool after BBB penetration. Conclusions: This study provides genetic evidence to support a pivotal role for the endothelium in maintaining perfusion and microvascular patency in the ischemic penumbra that is coordinated by S1P signaling and can be harnessed for neuroprotection with BBB-penetrating S1P 1 agonists.

Spinal cerebrospinal fluid flow is increased in rats with elevated intracranial pressure 18 hours after cortical ischaemic stroke

Background A dramatic oedema-independent intracranial pressure (ICP) rise occurs 24 hours post-stroke in rats and may explain infarct expansion. Underlying mechanisms of this rise are unknown but evidence suggests cerebrospinal fluid (CSF) dynamics are involved. Methods We investigated how CSF flow changes post-stroke and how this relates to ICP by infusing CSF tracer into the lateral ventricles of rats and assessing transport time and total tracer transport to the spinal subarachnoid space over a 90 minute period. Results Stroke animals with ICP rise had faster tracer transit when compared with stroke animals without ICP rise (27.6 ± 4, n = 6, vs 48.6 ± 4.5 mins, n = 6) or animals subjected to a sham procedure (47.9 ± 4 mins, n = 8), F(2,17) = 0.1, p≤0.01. There was a correlation between tracer transit time and ΔICP (R = -0.52, p=0.02) and infarct volume (R = -0.6, p=0.04). There was no difference in total tracer observed. Conclusions Faster tracer transit in stroke animals may be explained by impairment of other CSF outflow pathways, whereby, spinal drainage acts as a compensatory mechanism. Investigation into the disruption of other CSF drainage routes post-stroke may offer insight into the underlying mechanisms of infarct expansion post-stroke.

The Chemical Optimization of Cerebral Embolectomy trial: Study protocol

Rationale The potential value of rescue intraarterial thrombolysis in patients with large vessel occlusion stroke treated with mechanical thrombectomy has not been assessed in randomized trials. Aim The CHemical OptImization of Cerebral Embolectomy trial aims to establish whether rescue intraarterial thrombolysis is more effective than placebo in improving suboptimal reperfusion scores in patients with large vessel occlusion stroke treated with mechanical thrombectomy. Sample size estimates A sample size of 200 patients allocated 1:1 to intraarterial thrombolysis or intraarterial placebo will have >95% statistical power for achieving the primary outcome (5% in the control versus 60% in the treatment group) for a two-sided (5% alpha, and 5% lost to follow-up). Methods and design We conducted a multicenter, randomized, placebo-controlled, double blind, phase 2b trial. Eligible patients are 18 or older with symptomatic large vessel occlusion treated with mechanical thrombectomy resulting in a modified treatment in cerebral ischemia score 2b at end of the procedure. Patients will receive 20–30 min intraarterial infusion of recombinant tissue plasminogen activator or placebo (0.5 mg/ml, maximum dose limit 22.5 mg). Study outcome(s) The primary outcome is the proportion of patients with an improved modified treatment in cerebral ischemia score 10 min after the end of the study treatment. Secondary outcomes include the shift analysis of the modified Rankin Scale, the infarct expansion ratio, the proportion of excellent outcome (modified Rankin Scale 0–1), the proportion of infarct expansion, and the infarction volume. Mortality and symptomatic intracerebral bleeding will be assessed. Discussion The study will provide evidence whether rescue intraarterial thrombolysis improves brain reperfusion in patients with large vessel occlusion stroke and incomplete reperfusion (modified treatment in cerebral ischemia 2b) at the end of mechanical thrombectomy.