LRP5/canonical Wnt signalling and healing of ischemic myocardium.

LRP5 (low-density lipoprotein receptor-related protein 5) activates canonical Wnt signalling. LRP5 plays multiple roles including regulation of lipoprotein and cholesterol homeostasis as well as innate immunity cell function. However, it is not known whether LRP5 has a role in the myocardium. The aim of this study was to investigate LRP5 and Wnt signalling in myocardial remodelling after acute myocardial infarction (MI). Wnt protein levels were determined in a hypercholesterolemic porcine model of MI, in Lrp5 -/- C57Bl6 mice, in cultured cardiomyocytes and in human explanted hearts with previous MI episodes. 21 days post-MI, there was upregulation of LRP5 in the ischemic myocardium of hypercholesterolemic pigs as well as an upregulated expression of proteins of the Wnt pathway. We demonstrate via overexpression and silencing experiments that LRP5 induces Wnt pathway activation in isolated cardiomyocytes. Hypoxia and lipid-loading induced the expression of Wnt proteins, whereas this effect is blocked in LRP5-silenced cardiomyocytes. To characterize the function of the LRP5-Wnt axis upregulation in the heart, we induced MI in wild-type and Lrp5 -/- mice. Lrp5 -/- mice had significantly larger infarcts than Wt mice, indicating a protective role of LRP5 in injured myocardium. The LRP5 upregulation in post-MI hearts seen in pigs and mice was also evident in human hearts as dyslipidemic patients with previous episodes of ischemia have higher expression of LRP5 and Wnt-signalling genes than non-ischemic dilated hearts. We demonstrate an upregulation of LRP5 and the Wnt signalling pathway that it is a prosurvival healing response of cardiomyocytes upon injury.

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.

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-alpha (TNF-alpha), 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-alpha, 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-alpha 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-alpha 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.

Moderate daily intake of red wine inhibits mural thrombosis and monocyte tissue factor expression in an experimental porcine model.

BACKGROUND: Moderate consumption of red wine has been epidemiologically associated with a reduction in cardiovascular disease, but its mechanism of action is not fully understood. The objective was to study whether the protective effects of a daily intake of red wine (Tempranillo, 12.8% alcohol vol/vol) could be related to inhibition of thrombosis in an experimental model of diet-induced hyperlipemia. METHODS AND RESULTS: For 100 days, animals were fed a western-type proatherogenic diet containing 2% cholesterol and 20% saturated fat. Three doses of red wine were studied (20, 30, and 40 g wine-ethanol/d) and compared with placebo-control animals not taking any wine. Thrombosis under flow conditions was evaluated by radioisotopic quantification of deposited platelets on damaged arteries. Changes in RhoA translocation in platelets and monocyte tissue factor expression were also analyzed. Mural platelet deposition was significantly reduced in animals ingesting red wine with their food. Expression of RhoA in the platelet cytoplasm (inactive form) was increased in wine-fed animals. Tissue factor mRNA expression in lipopolysaccharide-stimulated monocytes was reduced in wine-fed animals. Total cholesterol levels were not significantly different among groups. CONCLUSIONS: Moderate red wine intake significantly reduces platelet deposition triggered by damaged vessel wall, partially explained by inhibition of RhoA translocation to the platelet membrane. Hence, a daily moderate intake of wine seems to inhibit different pathways that converge in a reduced thrombotic risk on vessel wall injury.