CTACK a new pro-angiogenic factor for dermal endothelial cells

International audienc

Phosphorylation of cyclophilin D at serine 191 regulates mitochondrial permeability transition pore opening and cell death after ischemia-reperfusion

International audienceThe mitochondrial permeability transition pore (mPTP) plays a critical role in the pathogenesis of cardiovascular diseases, including ischemia/reperfusion injury. Although the pore structure is still unresolved, the mechanism through which cyclophilin D (CypD) regulates mPTP opening is the subject of intensive studies. While post-translational modifications of CypD have been shown to modulate pore opening, specific phosphorylation sites of CypD have not yet been identified. We hypothesized here that phosphorylation of CypD on a serine residue controls mPTP opening and subsequent cell death at reperfusion. We combined in silico analysis with in vitro and genetic manipulations to determine potential CypD phosphorylation sites and their effect on mitochondrial function and cell death. Importantly, we developed an in vivo intramyocardial adenoviral strategy to assess the effect of the CypD phosphorylation event on infarct size. Our results show that although CypD can potentially be phosphorylated at multiple serine residues, only the phosphorylation status at S191 directly impacts the ability of CypD to regulate the mPTP. Protein-protein interaction strategies showed that the interaction between CypD and oligomycin sensitivity-conferring protein (OSCP) was reduced by 45% in the phosphoresistant S191A mutant, whereas it was increased by 48% in the phosphomimetic S191E mutant cells. As a result, the phosphoresistant CypD S191A mutant was protected against 18 h starvation whereas cell death was significantly increased in phosphomimetic S191E group, associated with mitochondrial respiration alteration and ROS production. As in vivo proof of concept, in S191A phosphoresistant rescued CypD-KO mice developed significantly smaller infarct as compared to WT whereas infarct size was drastically increased in S191E phosphomimetic rescued mice. We conclude that CypD phosphorylation at S191 residue leads to its binding to OSCP and thus sensitizes mPTP opening for the subsequent cell death

CTACK a new pro-angiogenic factor for dermal endothelial cells

International audienc

Suppression of hypoxia-induced HIF-1α and of angiogenesis in endothelial cells by myo-inositol trispyrophosphate-treated erythrocytes

Allosteric regulation of oxygen delivery by RBCs may have significant effects on tumor growth. Indeed, angiogenesis, the formation of new blood vessels, is induced in growing tumors by low oxygen partial pressure. Hypoxia-inducible genes are switched on, among which are the VEGF gene and its receptors. Most important, under hypoxia, hypoxia-inducible factor 1α has a significantly prolonged half-life and up-regulates a number of hypoxia genes. Human microvascular endothelial cells (MECs), when subjected in vitro to hypoxia, align to form vessel-like structures as in the angiogenic process. We report here that, when cultured in hypoxic conditions in the presence of human RBCs loaded with a new membrane-permeant allosteric effector of Hb, myo-inositol trispyrophosphate (ITPP), endothelial cells (ECs) do not align, i.e., do not form “vessel”-like structures, because the “loaded” RBCs are capable of releasing under hypoxia more oxygen than their “normal” counterparts. Levels of VEGF and of hypoxia-inducible factor 1α, elevated in the human MECs under hypoxia, were dramatically reduced or even suppressed in the presence of the ITPP-loaded RBCs. Treatment of these ECs directly with free ITPP at different concentrations had no effect on their ability to undertake angiogenesis. Incubation with ITPP enhances the capacity of Hb to release bound oxygen, leading to higher oxygen tension in the hypoxic environment, thus inhibiting hypoxia-induced angiogenesis. These observations are suggestive of a potential in vivo role of ITPP-loaded, “low-O(2)-affinity” RBCs in cancer therapy

Treatment of hypoxia-dependent cardiovascular diseases by myo-inositol trispyrophosphate (ITPP)-enhancement of oxygen delivery by red blood cells

International audienceHeart failure is a consequence of progression hypoxia-dependent tissue damages. Therapeutic approaches to restore and/or protect the healthy cardiac tissue have largely failed and remain a major challenge of regenerative medicine. The myo-inositol trispyrophosphate (ITPP) is a modifier of haemoglobin which enters the red blood cells and modifies the haemoglobin properties, allowing for easier and better delivery of oxygen by the blood. Here, we show that this treatment approach in an in vivo model of myocardial infarction (MI) results in an efficient protection from heart failure, and we demonstrate the recovery effect on post-MI left ventricular remodelling in the rat model. Cultured cardiomyocytes used to study the molecular mechanism of action of ITPP in vitro displayed the fast stimulation of HIF-1 upon hypoxic conditions. HIF-1 overexpression was prevented by ITPP when incorporated into red blood cells applied in a model of blood-perfused cardiomyocytes coupling the dynamic shear stress effect to the enhanced O(2) supply by modification of haemoglobin ability to release O(2) in hypoxia. ITPP treatment appears a breakthrough strategy for the efficient and safe treatment of hypoxia- or ischaemia-induced injury of cardiac tissue

Heat Shock Protein 70 as a Biomarker of Clinical Outcomes After STEMI

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Inhibition of myocardial reperfusion injury by ischemic postconditioning requires sirtuin 3-mediated deacetylation of cyclophilin D

International audienceRATIONALE: How ischemic postconditioning can inhibit opening of the mitochondrial permeability transition pore (PTP) and subsequent cardiac myocytes death at reperfusion remains unknown. Recent studies have suggested that de-acetylation of cyclophilin D (CyPD) by sirtuin 3 (SIRT3) can modulate its binding to the PTP. OBJECTIVE: The aim of the present study was to examine whether ischemic postconditioning (PostC) might activate SIRT3 and consequently prevent lethal myocardial reperfusion injury through a deacetylation of CyPD. METHODS AND RESULTS: Using hypoxia-reoxygenation (H/R) in H9C2 cells, we showed that SIRT3 overexpression prevented CyPD acetylation, limited PTP opening and reduced cell death by 24%. In vitro modification of the CyPD acetylation status in MEFs by site-directed mutagenesis altered capacity of PTP opening by calcium. Calcium Retention Capacity (CRC) was significantly decreased with CyPD-KQ that mimics acetylated protein compared with CyPD WT (871 +/- 266 vs 1193 +/- 263 nmoles Ca(2+)/mg protein respectively). Cells expressing non-acetylable CyPD mutant (CyPD-KR) displayed 20% decrease in cell death compared to cells expressing CyPD WT after H/R. Correspondingly, in mice we showed that cardiac ischemic postconditioning could not reduce infarct size and CyPD acetylation in SIRT3 KO mice, and was unable to restore CRC in mitochondria as it is observed in WT mice. CONCLUSIONS: Our study suggests that the increased acetylation of CyPD following myocardial ischemia-reperfusion facilitates PTP opening and subsequent cell death. Therefore ischemic postconditioning might prevent lethal reperfusion injury through an increased SIRT3 activity and subsequent attenuation of CyPD acetylation at reperfusion

An innovative sequence of hypoxia-reoxygenation on adult mouse cardiomyocytes in suspension to perform multilabeling analysis by flow cytometry

International audienceCardiovascular diseases still represent the leading cause of death worldwide, a better understanding of the underlying physiopathological mechanisms is therefore needed. In vitro cellular models participate to decipher the molecular mechanisms, especially adult mouse cardiomyocytes. Unfortunately, due to their high fragilitity as well as their size (150 mum), flow cytometry is usually not performed and mainly conventional techniques are used like cell imaging, which is time and animal-consuming and causes low statistical power. Here, we described a new, simple and rapid one-day protocol in living adult mouse cardiomyocytes submitted to in suspension hypoxia-reoxygenation to allow multilabeling analysis by flow cytometry. Our method enables the measurement of several physiological parameters thanks to fluorescent probes labeling, assessing notably cell viability (Propidium Iodide, Calcein-AM and Sytox Green), mitochondrial membrane potential (DilC1(5), TMRM), reactive oxygen species (ROS) production (MitoSOX Red) and mitochondrial mass (MitoTracker Deep Red). Additionally, we validate our model by using the protective treatment : cyclosporine A (CsA) to illustrate robustness and sensitivity of the utilized methods for pharmacological screening. In summary, our new hypoxia-reoxygenation sequence in suspension will offer a high-speed quantitative multilabeling analysis of adult mouse cardiomyocytes which can be extended to various cellular stress challenges (oxidative, inflammation) or pharmacological screening