Laura Casaní

Molecular and cellular mechanisms involved in cardiac remodeling after acute myocardial infarction

The extent of cardiac remodeling determines survival after acute MI. However, the mechanisms driving cardiac remodeling remain unknown. We examined the effect of ischemia and reperfusion (R) on myocardial changes up to 6 days post-MI. Pigs underwent 1.5h or 4h mid-LAD balloon occlusion and sacrificed or 1.5h occlusion followed by R and sacrificed at 2.5h, 1 day, 3 days, and 6 days. Ischemic- (IM) and non-ischemic myocardium (NIM) was obtained for molecular analysis of: 1) apoptosis (P-Bcl2, Bax, P-p53, active-caspase-3); 2) the TLR-4-MyD88-dependent and independent pathways; 3) Akt/mTOR/P70(S6K) axis activation; and, 4) fibrosis (TGF-β, collagen1-A1/A3). Histopathology for inflammation, collagen, and fibroblast content, TUNEL staining, and metalloproteinase activity was performed. Apoptosis is only detected upon R in IM cardiomyocytes and progresses up to 6 days post-R mainly associated with infiltrated macrophages. The Akt/mTOR/P70(s6K) pathway is also activated upon R (IM) and remains elevated up to 6 days-R (P<0.05). Ischemia activates the TLR-4-MyD88-dependent (cytokines/chemokines) and -independent (IRF-3) pathways in IM and NIM and remains high up to 6 days post-R (P<0.05). Accordingly, leukocytes and macrophages are progressively recruited to the IM (P<0.05). Ischemia up-regulates pro-fibrotic TGF-β that gradually rises collagen1-A1/-A3 mRNA with subsequent increase in total collagen fibrils and fibroblasts from 3 days-R onwards (P<0.005). MMP-2 activity increases from ischemia to 3 days post-R (P<0.05). We report that there is a timely coordinated cellular and molecular response to myocardial ischemia and R within the first 6 days after MI. In-depth understanding of the mechanisms involved in tissue repair is warranted to timely intervene and better define novel cardioprotective strategies.

A thromboxane A2/prostaglandin H2 receptor antagonist (S18886) shows high antithrombotic efficacy in an experimental model of stent-induced thrombosis

Acute thrombosis is a threat in patients undergoing percutaneous coronary intervention with stent implantation. Our objective was to determine if stent-induced thrombus formation could be inhibited by oral treatment with a thromboxane A(2)/prostaglandin H(2) receptor antagonist (TPr; S18886) as an alternative to standard therapy. Pigs were allocated in the following treatment (p.o) groups: I) clopidogrel (CLOP); II) ASA; III) S18886; IV) ASA+CLOP; and V) placebo-control. Damaged vessel was placed in the Badimon chamber containing a stent and perfused at 212/s. Antithrombotic effects were assessed as (111)In-platelet deposition (PD) in two series (60 and 180 min after drug intake). Fibrin(ogen) deposition, light transmittance aggregometry (LTA; collagen, U46619, and ADP), and bleeding time (BT) were also evaluated. After 60 min S18886 reduced PD < or =48%, 40%, and 35% vs placebo, CLOP-, and ASA-treated animals, respectively (P < 0.05), while ASA+CLOP showed a 58% reduction versus placebo (P < 0.01). After 3 hours, ASA+CLOP decreased PD by 55%, S18886 by 40%, CLOP alone by 28% (P < 0.05), and ASA showed no inhibition versus placebo. Similar effects were found in S18886- and ASA+CLOP-treated animals at both times. Fibrin(ogen) deposition followed the same pattern. Collagen-induced LTA was significantly reduced by ASA, ASA+CLOP, and S18886; S18886 abolished U46619-induced LTA; and, CLOP +/- ASA reduced ADP-induced LTA in a time-dependent manner. TPr blockade did not prolong BT, whereas CLOP +/- ASA significantly did (P < 0.0001). In conclusion, blockade of the TPr provided a fast and potent platelet inhibitory effect in a porcine model of in-stent thrombosis comparable to that of blocking both the ADP receptor and cyclooxygenase activation; in addition, TPr provided a more favorable bleeding risk profile.

Pravastatin reduces thrombogenicity by mechanisms beyond plasma cholesterol lowering

Inhibitors of 3-hydroxy-3-methylglutaryl coenzymeA reductase are widely used in the management and prevention of cardiovascular disease. In addition to its major activity, plasma lipid lowering, statins have shown a wide spectrum of additional effects that may contribute to their benefits in the prevention of cardiovascular disease. Our objective was to study whether treatment with a statin, pravastatin, could reduce thrombosis triggered by damaged vessels without changing plasma cholesterol levels. A cholesterol-clamp animal model was developed by feeding swine for 100 days on an hypercholesterolemic (HL) diet; in the last 50 days, they were randomly assigned to receive either placebo (HLC) or pravastatin (5 mg . kg(-1) . day(-1)) (HLP) in addition to the hypercholesterolemic diet. A normocholesterolemic control group (NLC) was simultaneously studied. There were no significant differences in total cholesterol, LDL and HDL plasma levels between the two groups; however, mural thrombosis triggered by both an eroded and disrupted vessel wall was significantly inhibited by pravastatin (P<0.05). Axial dependence analysis of platelet deposition revealed that pravastatin treatment reduced the increase in platelet deposition associated to the shear rate increase at the stenosis. Additionally, pravastatin treatment significantly reduced platelet membrane RhoA expression (P<0.05) and vascular wall tissue factor (TF) protein expression (P<0.05). In addition to its lipid lowering effects, pravastatin can reduce blood thrombogenicity by mechanisms independent of plasma cholesterol lowering.

Induction of RISK by HMG-CoA reductase inhibition affords cardioprotection after myocardial infarction

OBJECTIVES Coronary occlusion and revascularization leads to myocardial damage and heart function deterioration. Statins can regress atherosclerosis and modulate platelet function, but their effect on post-acute myocardial infarction (AMI) injury remains to be fully determined. We sought to examine whether rosuvastatin (R) exerts any effect on the RISK/apoptosis pathway when administered early after coronary reperfusion. METHODS Pigs were fed 10 days a hypercholesterolemic diet before AMI induction and thereafter for 7 days randomly distributed to receive R or placebo (C) with the same diet. At sacrifice, hearts were sliced and alternatively collected for MI size and molecular analysis (gene and protein expression) in the peri-infarcted and remote myocardium. The RISK components (PKC, Erk2, and Akt/PKB) and downstream targets (HIF-1alpha and VEGF), and cell survival/apoptosis markers (Bcl-2, Bax, and Caspase-3) were analyzed. Annexin-V, Mito-Tracker staining, and inflammatory infiltration were also evaluated. RESULTS R enhanced PKC, Erk2, Akt/PKB and its downstream effectors, and attenuated inflammation and cardiomyocyte apoptosis in the peri-infarcted zone (p<0.05). No changes were detected in the remote myocardium. Infarct size was smaller in R than in C pigs (7% absolute reduction; 36% relative reduction; p<0.05) and was associated with an absolute 12% recovery of LVEF (24% relative restoration; p<0.05 vs. post-AMI). CONCLUSIONS HMG-CoA inhibition early after reperfusion activates RISK kinases, reduces the extent of damaged myocardium, and improves heart function.

Short-term myocardial ischemia induces cardiac modified C-reactive protein expression and proinflammatory gene (cyclo-oxygenase-2, monocyte chemoattractant protein-1, and tissue factor) upregulation in peripheral blood mononuclear cells

Summary.  Background: Prompt coronary thrombus resolution, reducing time of ischemia, improves cardiac recovery. The factors triggered by ischemia that contribute to the clinical outcome are not fully known. We hypothesize that unabated inflammation due to cardiac ischemia may be a contributing factor. Aims: As a proof‐of‐concept, we evaluated the effect of short‐term myocardial ischemia on the local and systemic inflammatory response. Methods: Pigs underwent either 90‐min mid‐left anterior descending (LAD) coronary artery balloon occlusion (infarct size 25% ± 1% left ventricle; 29% heart function deterioration) or a sham‐operation procedure. Peri‐infarcted and non‐ischemic cardiac tissue was obtained for histopathologic, molecular and immunohistochemical analysis of inflammatory markers [interleukin‐6 (IL‐6), tumor necrosis factor‐α (TNF‐α), modified C‐reactive protein (mCRP), and human alveolar macrophage‐56 (HAM‐56)]. Blood (femoral vein) was withdrawn prior to myocardial infarction (MI) induction (t = 0) and at 30 and 90 min to evaluate: (i) systemic cytokine levels (IL‐6, TNF‐α, CRP); (ii) proinflammatory gene and protein expression in peripheral blood mononuclear cells (PBMCs) of tissue factor (TF), cyclo‐oxygenase‐2 (Cox‐2), monocyte chemoattractant protein‐1 (MCP‐1), and CRP; and (iii) platelet activation (assessed by perfusion studies and RhoA activation). Results: Short‐term ischemia triggered cardiac IL‐6 and TNF‐α expression, recruitment of inflammatory cells, and mCRP expression in infiltrated macrophages (P < 0.05 vs. t = 0 and sham). PBMC mRNA and protein expression of MCP‐1, Cox‐2 and TF was significantly increased by ischemia, whereas no differences were detected in CRP. Ischemia increased cardiac troponin‐I, IL‐6 and TNF‐α systemic levels, and was associated with higher platelet deposition and RhoA activation (P < 0.001 vs. t = 0 and sham). Conclusion: Short‐term myocardial ischemia, even without atherosclerosis, induces an inflammatory phenotype by inducing local recruitment of macrophages and systemic activation of mononuclear cells, and renders platelets more susceptible to activation.

Protective Effects of Ticagrelor on Myocardial Injury After Infarction

Background: The P2Y12 receptor antagonist ticagrelor has been shown to be clinically superior to clopidogrel. Although the underlying mechanisms remain elusive, ticagrelor may exert off-target effects through adenosine-related mechanisms. We aimed to investigate whether ticagrelor reduces myocardial injury to a greater extent than clopidogrel after myocardial infarction (MI) at a similar level of platelet inhibition and to determine the underlying mechanisms. Methods: Pigs received the following before MI induction: (1) placebo-control; (2) a loading dose of clopidogrel (600 mg); (3) a loading dose of ticagrelor (180 mg); or (4) a loading dose of ticagrelor followed by an adenosine A1/A2-receptor antagonist [8-(p-sulfophenyl)theophylline, 4 mg/kg intravenous] to determine the potential contribution of adenosine in ticagrelor-related cardioprotection. Animals received the corresponding maintenance doses of the antiplatelet agents during the following 24 hours and underwent 3T-cardiac MRI analysis. Platelet inhibition was monitored by ADP-induced platelet aggregation. In the myocardium, we assessed the expression and activation of proteins known to modulate edema formation, including aquaporin-4 and AMP-activated protein kinase and its downstream effectors CD36 and endothelial nitric oxide synthase and cyclooxygenase-2 activity. Results: Clopidogrel and ticagrelor exerted a high and consistent antiplatelet effect (68.2% and 62.2% of platelet inhibition, respectively, on challenge with 20 &mgr;mol/L ADP) that persisted up to 24 hours post-MI (P<0.05). All groups showed comparable myocardial area-at-risk and cardiac worsening after MI induction. 3T-Cardiac MRI analysis revealed that clopidogrel- and ticagrelor-treated animals had a significantly smaller extent of MI than placebo-control animals (15.7 g left ventricle and 12.0 g left ventricle versus 22.8 g left ventricle, respectively). Yet, ticagrelor reduced infarct size to a significantly greater extent than clopidogrel (further 23.5% reduction; P=0.0026), an effect supported by troponin-I assessment and histopathologic analysis (P=0.0021). Furthermore, in comparison with clopidogrel, ticagrelor significantly diminished myocardial edema by 24.5% (P=0.004), which correlated with infarct mass (r=0.73; P<0.001). 8-(p-Sulfophenyl)theophylline administration abolished the cardioprotective effects of ticagrelor over clopidogrel. At a molecular level, aquaporin-4 expression decreased and the expression and activation of AMP-activated protein kinase signaling and cyclooxygenase-2 increased in the ischemic myocardium of ticagrelor- versus clopidogrel-treated animals (P<0.05). These protein changes were not observed in those animals administered the adenosine receptor blocker 8-(p-sulfophenyl)theophylline. Conclusions: Ticagrelor, beyond its antiplatelet efficacy, exerts cardioprotective effects by reducing necrotic injury and edema formation via adenosine-dependent mechanisms.

Antithrombotic effects of saratin on human atherosclerotic plaques

Platelets play a primary role in thrombus formation after plaque rupture. Platelets recognize the exposed collagen via Von Willebrand factor (VWF) and become activated. Saratin, an inhibitor of the VWF-dependent binding of platelets to collagen, may reduce the thrombotic risk associated to atherosclerosis. Our objective was to evaluate the antithrombotic effects of local treatment with saratin on human atherosclerotic lesions. Thrombus formation was assessed by the deposition of (111)In-platelets on different human atherosclerotic lesions under three local shear conditions (800,1700 and 3400/s) with blood derived from catheterized pigs. Human atherosclerotic lesions were locally treated with saratin (30 microg/ml) at 37 degrees C for 5 min and placed in the chamber. Under stenotic shear conditions of 800/s, saratin significantly (p<0.05) reduced platelet deposition triggered by human denuded vessel wall (44%), fatty streaks (47%), severely damaged vessel (50%) and atherosclerotic plaque (57%). Thrombus characterization by immunohistochemistry showed also a reduction in fibrin deposition in treat-ed vessels. These results suggest that the local site-specific treatment with saratin inhibits atherosclerotic plaque thrombogenicity at haemodynamic conditions typical of moderately stenotic coronary arteries.

Glucose-Regulated Protein 78 and Platelet Deposition: Effect of Rosuvastatin

Objective—To investigate the effect of rosuvastatin on platelet deposition under controlled shear rate conditions and to identify new platelet proteins involved in the interaction with the activating substrate. Methods and Results—Platelet-vessel wall interaction and thrombosis take place under dynamic conditions involving the interaction of the exposed damaged vascular wall with the circulating blood cells and proteins. Blood was perfused over type I collagen at different wall shear rates, and platelet deposition was measured by confocal microscopy. Perfused effluent blood was collected, platelets were sequentially extracted based on differential protein solubility, and proteins were separated by 2D gel electrophoresis. Blockade of 3-hydroxy-3-methylglutaryl–coenzyme A reductase significantly reduced platelet deposition and modulated the expression pattern of 18 proteins in the platelet subproteome. Among them, an increase in platelet surface 78-kDa glucose-regulated protein (GRP78), a stress-inducible multifunctional endoplasmic reticulum protein, was clearly apparent. Immunoprecipitation of platelet GRP78 revealed its interaction with tissue factor. Moreover, blockade of surface GRP78 resulted in a substantial increase in platelet deposition and tissue factor procoagulant activity and in a decrease in clotting time. Conclusion—These findings demonstrate that blockade of 3-hydroxy-3-methylglutaryl–coenzyme A reductase reduces platelet deposition and inhibits GRP78 translocation from the platelet surface after shear and collagen activation. For the first time to our knowledge, this study reports on the presence and functional role of GRP78 in platelets and indicates that GRP78 has additional functions beyond those of a molecular chaperone.

A novel anti-ischemic nitric oxide donor inhibits thrombosis without modifying haemodynamic parameters

Platelets are involved in the clinical presentations of ischemic heart disease. Our objective was to study the antithrombotic effects of a new nitric oxide donor (LA419), a neutral sugar organic nitrate with a protected thiol group in its molecular structure. Animals were randomly distributed in three groups: I) oral administration of LA419 (0.9-1.8-3.6-5 mg/kg/d, 10 days); II) oral administration of standard IS-5-MN (0.9-1.8 mg/kg/d, 10 days); III) non-treated group (control). In catheterized pigs, thrombosis was studied under controlled rheological conditions by radioisotopic evaluation of deposited platelets on damaged vessel wall, placed in an extracorporeal perfusion chamber. Changes in blood pressure, heart rate, and platelet aggregation were evaluated. Results have shown that LA419 significantly decreased thrombus formation according to the degree of vascular damage, and shear rate conditions in a dose-dependent manner (p<0.005), without significant modifications on blood pressure and/or elevation of liver enzymes. In contrast, IS-5-MN only showed a significant reduction on platelet deposition at the high dose, that was associated to hypotension and elevation of liver enzymes. Therefore, we conclude that this new anti-ischemic NO-donor (NOd) LA419 that inhibits platelet function without modifying blood pressure may be a highly efficacious strategy to passivate platelet activation induced by a damaged vessel wall.

Bioluminescence imaging of cardiomyogenic and vascular differentiation of cardiac and subcutaneous adipose tissue-derived progenitor cells in fibrin patches in a myocardium infarct model

BACKGROUND Adipose tissue-derived progenitor cells (ATDPCs) isolated from human cardiac adipose tissue are useful for cardiac regeneration in rodent models. These cells do not express cardiac troponin I (cTnI) and only express low levels of PECAM-1 when cultured under standard conditions. The purpose of the present study was to evaluate changes in cTnI and PECAM-1 gene expression in cardiac ATDPCs following their delivery through a fibrin patch to a murine model of myocardial infarction using a non-invasive bioluminescence imaging procedure. METHODS AND RESULTS Cardiac and subcutaneous ATDPCs were doubly transduced with lentiviral vectors for the expression of chimerical bioluminescent-fluorescent reporters driven by constitutively active and tissue-specific promoters (cardiac and endothelial for cTnI and PECAM-1, respectively). Labeled cells mixed with fibrin were applied as a 3-D fibrin patch over the infarcted tissue. Both cell types exhibited de novo expression of cTnI, though the levels were remarkably higher in cardiac ATDPCs. Endothelial differentiation was similar in both ATDPCs, though cardiac cells induced vascularization more effectively. The imaging results were corroborated by standard techniques, validating the use of bioluminescence imaging for in vivo analysis of tissue repair strategies. Accordingly, ATDPC treatment translated into detectable functional and morphological improvements in heart function. CONCLUSIONS Both ATDPCs differentiate to the endothelial lineage at a similar level, cardiac ATDPCs differentiated more readily to the cardiomyogenic lineage than subcutaneous ATDPCs. Non-invasive bioluminescence imaging was a useful tool for real time monitoring of gene expression changes in implanted ATDPCs that could facilitate the development of procedures for tissue repair.