Oriol Juan-Babot

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.

Hypoxia Stimulates Low-Density Lipoprotein Receptor–Related Protein-1 Expression Through Hypoxia-Inducible Factor-1α in Human Vascular Smooth Muscle Cells

Objective—Hypoxia is considered a key factor in the progression of atherosclerotic lesions. Low-density lipoprotein receptor–related protein (LRP1) plays a pivotal role in the vasculature. The aim of this study was to investigate the effect of hypoxia on LRP1 expression and function in vascular smooth muscle cells (VSMC) and the role of hypoxia-inducible factor-&agr; (HIF-1&agr;). Methods and Results—Real-time polymerase chain reaction and Western blot analysis demonstrated that hypoxia (1% O2) time-dependently induced LRP1 mRNA (maximum levels at 1 to 2 hours) and protein expression (maximum levels at 12 to 24 hours). The delayed hypoxic upregulation of LRP1 protein versus mRNA may be explained by the long half-life of LRP1 protein. Luciferase assays demonstrated that hypoxia and HIF-1&agr; overaccumulation induced LRP1 promoter activity and that 2 consensus hypoxia response element sites located at −1072/−1069 and −695/−692 participate in the induction. Chromatin immunoprecipitation showed the in vivo binding of HIF-1&agr; to LRP1 promoter in hypoxic VSMC. Hypoxia effects on LRP1 protein expression were functionally translated into an increased cholesteryl ester (CE) accumulation from aggregated low-density lipoprotein (agLDL) uptake. The blockade of HIF-1&agr; expression inhibited the upregulatory effect of hypoxia on LRP1 expression and agLDL-derived intracellular CE overaccumulation, suggesting that both LRP1 overexpression and CE overaccumulation in hypoxic vascular cells are dependent on HIF-1&agr;. Immunohistochemical analysis showed the colocalization of LRP1 and HIF-1&agr; in vascular cells of human advanced atherosclerotic plaques. Conclusion—Hypoxia upregulates LRP1 expression and agLDL-derived intracellular CE accumulation in human VSMC through HIF-1&agr; induction.

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.

Expression of cyclin-dependent kinase 5 mRNA and protein in the human brain following acute ischemic stroke

Neuronal cell death after brain ischemia may be regulated by activation of cyclin‐dependent kinase 5 (Cdk5). In this study, expression of Cdk5 and its activator p35/p25 was examined in human post‐mortem stroke tissue and in human cerebral cortical fetal neurons and human brain microvascular endothelial cells exposed to oxygen‐glucose deficiency and reperfusion. The majority of patients demonstrated increased expression of Cdk5 and p‐Cdk5 in stroke‐affected tissue, with about a third showing increased p35 and p25 cleaved fragment as determined by Western blotting. An increase in Cdk5‐, p‐Cdk5‐ and p35‐positive neurons and microvessels occurred in stroke‐affected regions of patients. Staining of neurons became irregular and clumped in the cytoplasm, and nuclear translocation occurred, with colocalization of p35 and Cdk5. Association of Cdk5 with nuclear damage was demonstrated by coexpression of nuclear Cdk5 in TUNEL‐positive neurons and microvessels in peri‐infarcted regions. In vitro studies showed up‐regulation and/or nuclear translocation of Cdk5, p‐Cdk5 and p35 in neurons and endothelial cells subjected to oxygen‐glucose deficiency, and strong staining was associated with propidium iodide positive nuclei, an indicator of cellular damage. These results provide new evidence for a role of Cdk5 in the events associated with response to ischemic injury in humans.

Changes in thrombus composition and profilin-1 release in acute myocardial infarction

AIM Thrombus formation is a dynamic process regulated by flow, blood cells, and plasma proteins. The present study was performed to investigate the characteristics of human coronary thrombus in ST-segment elevation myocardial infarction (STEMI). METHODS AND RESULTS Patients admitted with ST-elevation myocardial infarction, in which thrombectomy was performed, were included (n = 86). Intracoronary thrombi and blood from the culprit coronary site and the systemic circulation were obtained during percutaneous coronary intervention (PCI). Thrombi were categorized by onset-of-pain-to-PCI elapsed time in thrombus of <3 (T3) and more than 6 h of evolution (T6). Clinical, morphological, and proteomic variables were investigated. While T3 were mainly composed by platelets and fibrin(ogen), T6 were characterized by a reduced platelet content, increased leucocytes infiltration (including monocytes, neutrophils, T-cells, and B-cells), and appearance of undifferentiated progenitor cells. Significant differences between T3 and T6 were found in the cell cytoskeleton-associated proteome (beta-actin and tropomyosin 3 and 4). By discovery proteomics, we have identified profilin-1 (Pfn-1) in the coronary thrombi and detected higher levels in T3 than in T6. While plasma Pfn-1 levels were low in T3 patients, levels significantly increased in both coronary and peripheral circulation in T6 patients indicating release. In vitro platelet aggregation studies showed that platelets secrete Pfn-1 upon complete activation. CONCLUSION Coronary thrombi show rapid dynamic changes both in structure and cell composition as a function of elapsed onset-of-pain-to-PCI time. Aged ischaemic thrombi were more likely to have reduced Pfn-1 content releasing Pfn-1 to the circulation. Onset-of-pain-to-PCI elapsed time in STEMI patients and hence age of occlusive thrombus can be profiled by Pfn-1 levels found in the peripheral circulation.

Wnt pathway activation, cell migration, and lipid uptake is regulated by low-density lipoprotein receptor-related protein 5 in human macrophages

AIMS Atherosclerosis plaque development includes infiltration of inflammatory cells, accumulation of lipids and fibrous cap formation. Low-density lipoprotein receptor-related protein 1 (LRP1) is expressed on atherosclerotic lesions associated with macrophages and vascular smooth muscle cells. The aim of this work is to analyse the role in atherosclerosis lesion progression of another member of the LDL receptor protein family, low-density lipoprotein receptor-related protein 5 (LRP5), a co-receptor with Frizzled known to activate the Wnt signalling pathway in several cell types. METHODS AND RESULTS LRP5 is expressed in human vascular and innate inflammatory cells. LRP5 is transcriptionally regulated by aggregated LDL (agLDL), participating in the lipid uptake and transformation of macrophages into foam cells, a critical step in atherosclerosis progression. AgLDL-treated macrophages show up-regulated expression of β-catenin, LEF1, c-jun, cyclinD1, bone morphogenetic protein 2 (BMP2), and osteopontin (OPN), proteins and targets of the Wnt signalling pathway, whereas LRP5-silenced macrophages show a significant down-regulation of OPN and BMP2 expression. Furthermore, LRP5-deficient macrophages exhibit an impaired migration both in wound-repair and modified Boyden chambers models. CONCLUSION These results demonstrate the involvement of LRP5 in the innate inflammatory reaction to lipid infiltration in atherosclerosis.

Overexpression of hypoxia/inflammatory markers in atherosclerotic carotid plaques.

Hypoxia, angiogenesis and inflammation leads to plaque progression and remodelling and may significantly contribute towards plaque rupture and subsequent cerebrovascular events. Our aim was to study, markers of hypoxia and inflammation previously identified by microarray analysis, in atherosclerotic carotid arteries with low to moderate stenosis. We hoped to describe different cellular populations expressing the studied markers. The location of selected inflammatory molecules obtained as vascular transplants from organ donors were analysed by immunohistochemistry with monoclonal and polyclonal antibodies. Paraffin-embedded sections were cut and probed with antibodies recognizing active B and T-lymphocytes (CD30), hypoxia-inducible factor-1alpha, endoglin (CD105), Interleukin-6 and C-reactive protein. We observed a notable overexpression of HIF-1alpha in inflammatory and hypoxic areas of carotid arteries in all types of lesions from type II-V taken from the patients with carotid stenosis less than 50%. This suggests that HIF-1alpha may have a putative role in atherosclerosis progression and angiogenesis. Dynamic changes in the non-occluding plaques may explain some of the clinical events in patients with low to moderate carotid stenosis.

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.

Atherothrombosis and Plaque Heterology: Different Location or a Unique Disease?

Formation of unstable plaques frequently results in atherothrombosis, the major cause for ischaemic stroke, myocardial infarction and peripheral arterial disease. Patients who have symptomatic thrombosis in one vascular bed are at increased risk of disease in other beds. However, the development of the disease in carotid, coronary and peripheral arteries may have different pathophysiology suggesting that more complex treatment protocols may have to be designed to reduce plaque development at different locations. In this review we describe the known risk factors, compare the developmental features of coronary and carotid plaque development and determine their association with end-point ischaemic events. Differences are also seen in the genetic contribution to plaque development as well as in the deregulation of gene and protein expression and cellular signal transduction activity of active cells in regions susceptible to thrombosis. Differences between carotid and coronary artery plaque development might help to explain the differences in anatomopathological appearance and risk of rupture.

Low density lipoprotein receptor-related protein 1 expression correlates with cholesteryl ester accumulation in the myocardium of ischemic cardiomyopathy patients

Our hypothesis was that overexpression of certain lipoprotein receptors might be related to lipid accumulation in the human ischemic myocardium. Intramyocardial lipid overload contributes to contractile dysfunction and arrhythmias in cardiomyopathy. Thus, the purpose of this study was to assess the effect of hypercholesterolemic LDL and hypertrigliceridemic VLDL dose on LRP1 expression in cardiomyocytes, as well as the potential correlation between LRP1 expression and neutral lipid accumulation in the left ventricle tissue from ischemic cardiomyopathy patients. Cell culture experiments include control and LRP1-deficient cardiomyocytes exposed to lipoproteins under normoxic and hypoxic conditions. Explanted hearts from 18 ICM patients and eight non-diseased hearts (CNT) were included. Low density lipoprotein receptor-related protein 1 (LRP1), very low density lipoprotein receptor (VLDLR) and low density lipoprotein receptor (LDLR) expression was analyzed by real time PCR and Western blotting. Cholesteryl ester (CE), triglyceride (TG) and free cholesterol (FC) content was assess by thin layer chromatography following lipid extraction. Western blotting experiments showed that protein levels of LRP1, VLDLR and HIF-1α were significantly upregulated in ischemic hearts. Immunohistochemistry and confocal microscopy analysis showed that LRP1 and HIF-1α were upregulated in cardiomyocytes of ICM patients. In vitro studies showed that VLDL, LDL and hypoxia exerted an upregulatory effect on LRP1 expression and that LRP1 played a major role in cholesteryl ester accumulation from lipoproteins in cardiomyocytes. Myocardial CE accumulation strongly correlated with LRP1 levels in ischemic hearts. Taken together, our results suggest that LRP1 upregulation is key for myocardial cholesterol ester accumulation in ischemic human hearts and that LRP1 may be a target to prevent the deleterious effects of myocardial cholesterol accumulation in ischemic cardiomyopathy.