Anton Baysa

Retinoic acid signalling is activated in the postischemic heart and may influence remodelling

Background All-trans retinoic acid (atRA), an active derivative of vitamin A, regulates cell differentiation, proliferation and cardiac morphogenesis via transcriptional activation of retinoic acid receptors (RARs) acting on retinoic acid response elements (RARE).We hypothesized that the retinoic acid (RA) signalling pathway is activated in myocardial ischemia and postischemic remodelling. Methods and Findings Myocardial infarction was induced through ligating the left coronary artery in mice. In vivo cardiac activation of the RARs was measured by imaging RARE-luciferase reporter mice, and analysing expression of RAR target genes and proteins by real time RT-PCR and western blot. Endogenous retinoids in postinfarcted hearts were analysed by triple-stage liquid chromatography/tandem mass spectrometry. Cardiomyocytes (CM) and cardiofibroblasts (CF) were isolated from infarcted and sham operated RARE luciferase reporter hearts and monitored for RAR activity and expression of target genes. The effect of atRA on CF proliferation was evaluated by EdU incorporation. Myocardial infarction increased thoracic RAR activity in vivo (p<0.001), which was ascribed to the heart through ex vivo imaging (p = 0.002) with the largest signal 1 week postinfarct. This was accompanied by increased cardiac gene and protein expression of the RAR target genes retinol binding protein 1 (p = 0.01 for RNA, p = 0,006 for protein) and aldehyde dehydrogenase 1A2 (p = 0.04 for RNA, p = 0,014 for protein), while gene expression of cytochrome P450 26B1 was downregulated (p = 0.007). Concomitantly, retinol accumulated in the infarcted zone (p = 0.02). CM and CF isolated from infarcted hearts had higher luminescence than those from sham operated hearts (p = 0.02 and p = 0.008). AtRA inhibited CF proliferation in vitro (p = 0.02). Conclusion The RA signalling pathway is activated in postischemic hearts and may play a role in regulation of damage and repair during remodelling.

Expression of bone morphogenetic protein 4 and its receptors in the remodeling heart.

AIMS Heart failure is associated with activation of fetal gene programs. Bone morphogenetic proteins (BMPs) regulate embryonic development through interaction with BMP receptors (BMPRs) on the cell surface. We investigated if the expression of BMP4 and its receptors BMPR1a and BMPR2 were activated in post-infarction remodeling and heart failure. MAIN METHODS Left ventricular biopsies were taken from explanted hearts of patients with end-stage heart failure due to dilated cardiomyopathy (CMP; n=15) or ischemic heart disease (CAD; n=9), and compared with homograft control preparations from organ donors deceased due to non-cardiac causes (n=7). Other samples were taken from patients undergoing coronary artery bypass grafting (CABG; n=11). Mice were subjected to induced infarction by permanent coronary artery ligation or sham operation, and hearts were sampled serially thereafter (n=7 at each time point). KEY FINDINGS Human and mouse hearts expressed BMP4 and both receptor subtypes. CABG and CMP patients had increased expression of mRNA encoding for BMP4, but unchanged protein. Mouse hearts had increased BMP4 precursor protein 24h after infarction. BMPR1a protein decreased in CAD patients and initially in postinfarcted mouse hearts, but increased again in the latter after two weeks. Human recombinant BMP4 promoted survival after H2O2 injury in HL-1 cells, and also protected adult mouse cardiomyocytes against hypoxia-reoxygenation injury. SIGNIFICANCE Adult hearts express BMP4, the mRNA increasingly so in patients with coronary artery disease with good cardiac function. BMPRs are downregulated in cardiac remodeling and failure. Recombinant BMP4 has protective effects on cultured cardiomyocytes.

The cellular prion protein counteracts cardiac oxidative stress

AIMS The cellular prion protein, PrP(C), whose aberrant isoforms are related to prion diseases of humans and animals, has a still obscure physiological function. Having observed an increased expression of PrP(C) in two in vivo paradigms of heart remodelling, we focused on isolated mouse hearts to ascertain the capacity of PrP(C) to antagonize oxidative damage induced by ischaemic and non-ischaemic protocols. METHODS AND RESULTS Hearts isolated from mice expressing PrP(C) in variable amounts were subjected to different and complementary oxidative perfusion protocols. Accumulation of reactive oxygen species, oxidation of myofibrillar proteins, and cell death were evaluated. We found that overexpressed PrP(C) reduced oxidative stress and cell death caused by post-ischaemic reperfusion. Conversely, deletion of PrP(C) increased oxidative stress during both ischaemic preconditioning and perfusion (15 min) with H2O2. Supporting its relation with intracellular systems involved in oxidative stress, PrP(C) was found to influence the activity of catalase and, for the first time, the expression of p66(Shc), a protein implicated in oxidative stress-mediated cell death. CONCLUSIONS Our data demonstrate that PrP(C) contributes to the cardiac mechanisms antagonizing oxidative insults.

Interleukin-17 (IL-17) Expression Is Reduced during Acute Myocardial Infarction: Role on Chemokine Receptor Expression in Monocytes and Their in Vitro Chemotaxis towards Chemokines

The roles of immune cells and their soluble products during myocardial infarction (MI) are not completely understood. Here, we observed that the percentages of IL-17, but not IL-22, producing cells are reduced in mice splenocytes after developing MI. To correlate this finding with the functional activity of IL-17, we sought to determine its effect on monocytes. In particular, we presumed that this cytokine might affect the chemotaxis of monocytes important for cardiac inflammation and remodeling. We observed that IL-17 tends to reduce the expression of two major chemokine receptors involved in monocyte chemotaxis, namely CCR2 and CXCR4. Further analysis showed that monocytes pretreated with IL-17 have reduced in vitro chemotaxis towards the ligand for CCR2, i.e., MCP-1/CCL2, and the ligand for CXCR4, i.e., SDF-1α/CXCL12. Our results support the possibility that IL-17 may be beneficial in MI, and this could be due to its ability to inhibit the migration of monocytes.

Connective tissue growth factor and bone morphogenetic protein 2 are induced following myocardial ischemia in mice and humans

Abstract We aimed to study the cardiac expression of bone morphogenetic protein 2, its receptor 1 b, and connective tissue growth factor, factors implicated in cardiac embryogenesis, following ischemia/hypoxia, heart failure, and in remodeling hearts from humans and mice. Biopsies from the left ventricle of patients with end-stage heart failure due to dilated cardiomyopathy or coronary artery disease were compared with donor hearts and biopsies from patients with normal heart function undergoing coronary artery bypass grafting. Mouse model of post-infarction remodeling was made by permanent ligation of the left coronary artery. Hearts were analyzed by real-time polymerase chain reaction and Western blotting after 24 hours and after 2 and 4 weeks. Patients with dilated cardiomyopathy and mice post-infarction had increased cardiac expression of connective tissue growth factor. Bone morphogenetic protein 2 was increased in human hearts failing due to coronary artery disease and in mice post-infarction. Gene expression of bone morphogenetic protein receptor 1 beta was reduced in hearts of patients with failure, but increased two weeks following permanent ligation of the left coronary artery in mice. In conclusion, connective tissue growth factor is upregulated in hearts of humans with dilated cardiomyopathy, bone morphogenetic protein 2 is upregulated in remodeling due to myocardial infarction while its receptor 1 b in human failing hearts is downregulated. A potential explanation might be an attempt to engage regenerative processes, which should be addressed by further, mechanistic studies.