Cardiovascular phenotype of mice lacking 3-mercaptopyruvate sulfurtransferase

Rationale: Hydrogen sulfide (H2S) is a physiological mediator that regulates cardiovascular homeostasis. Three major enzymes contribute to the generation of endogenously produced H2S, namely cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). Although the biological roles of CSE and CBS have been extensively investigated in the cardiovascular system, very little is known about that of 3-MST. In the present study we determined the importance of 3-MST in the heart and blood vessels, using a genetic model with a global 3-MST deletion. Results: 3-MST is the most abundant transcript in the mouse heart, compared to CSE and CBS. 3-MST was mainly localized in smooth muscle cells and cardiomyocytes, where it was present in both the mitochondria and the cytosol. Levels of serum and cardiac H2S species were not altered in adult young (2–3 months old) 3-MST−/− mice compared to WT animals. No significant changes in the expression of CSE and CBS were observed. Additionally, 3-MST−/− mice had normal left ventricular structure and function, blood pressure and vascular reactivity. Interestingly, genetic ablation of 3-MST protected mice against myocardial ischemia reperfusion injury, and abolished the protection offered by ischemic pre- and post-conditioning. 3-MST−/− mice showed lower expression levels of thiosulfate sulfurtransferase, lower levels of cellular antioxidants and elevated basal levels of cardiac reactive oxygen species. In parallel, 3-MST−/− mice showed no significant alterations in endothelial NO synthase or downstream targets. Finally, in a separate cohort of older 3-MST−/− mice (18 months old), a hypertensive phenotype associated with cardiac hypertrophy and NO insufficiency was observed. Conclusions: Overall, genetic ablation of 3-MST impacts on the mouse cardiovascular system in an age-dependent manner. Loss of 3-MST exerts a cardioprotective role in young adult mice, while with aging it predisposes them to hypertension and cardiac hypertrophy

The role of polycystin 1 and 2 in atherosclerosis: investigation of intracellular molecular pathways

The molecular events through which mechanical forces, in the form of wall shear stress (WSS), trigger intracellular signaling cascades on vascular endothelium remain elusive. Previous studies have suggested a role in cell proliferation and apoptosis for the mechanosensitive protein complex of Polycystin 1 (PC-1) and 2 (PC-2) in endothelial WSS responses. The aim of our study is to explore the role of PC1/PC2 protein mechanosensitive complex on cell proliferation and apoptosis, in vitro and in vivo under different hemodynamic conditions. Our findings will provide hints for further investigation considering molecular biomarkers on atherosclerosis since it is a progressive disease that may start early in life and affect a significant part of general population.Το αγγειακό ενδοθήλιο υπόκειται στην επίδραση μηχανικών δυνάμεων όπως η διατμητική τάση. Ο μηχανισμός μέσω του οποίου η μηχανική διέγερση μπορεί να συμβάλει στην ανάπτυξη αθηρωματικών αλλοιώσεων παραμένει υπό διερεύνηση. Την τελευταία δεκαετία έχει δοθεί μεγάλη βαρύτητα στο ρόλο μηχανοευαίσθητων μορίων όπως οι διαμεμβρανικές πρωτεΐνες, Πολυκυστίνες 1 (PC-1) και 2 (PC-2) στην ενδοκυττάρια μεταγωγή σήματος και στην επαγόμενη ρύθμιση κυτταρικών λειτουργιών όπως ο πολλαπλασιασμός και η απόπτωση. Στόχος της μελέτης είναι η διερεύνηση του ρόλου του πρωτεϊνικού συμπλόκου PC1/PC2 in vitro και in vivo σε σχέση με τη διατμητική τάση και τη ρύθμιση του πολλαπλασιασμού και της απόπτωσης. Η πιθανή συσχέτιση θα προσθέσει νέα ερευνητικά δεδομένα και θα συμβάλει στην ανάπτυξη νέων μοριακών δεικτών για την αποτελεσματικότερη αντιμετώπιση της αθηρωματικής νόσου, η οποία εδραιώνεται σε πρώιμη ηλικία και αφορά πλέον ένα σημαντικό ποσοστό του γενικού πληθυσμού

Amelioration of desmin network defects by αB-crystallin overexpression confers cardioprotection in a mouse model of dilated cardiomyopathy caused by LMNA gene mutation

International audienceThe link between the cytoplasmic desmin intermediate filaments and those of nuclear lamins serves as a major integrator point for the intracellular communication between the nucleus and the cytoplasm in cardiac muscle. We investigated the involvement of desmin in the cardiomyopathy caused by the lamin A/C gene mutation using the LmnaH222P/H222P mouse model of the disease. We demonstrate that in these mouse hearts desmin loses its normal Z disk and intercalated disc localization and presents aggregate formation along with mislocalization of basic intercalated disc protein components, as well as severe structural abnormalities of the intercalated discs and mitochondria. To address the extent by which the observed desmin network defects contribute to the progression of LmnaH222P/H222P cardiomyopathy, we investigated the consequences of desmin-targeted approaches for the disease treatment. We showed that cardiac-specific overexpression of the small heat shock protein αΒ-Crystallin confers cardioprotection in LmnaH222P/H222P mice by ameliorating desmin network defects and by attenuating the desmin-dependent mislocalization of basic intercalated disc protein components. In addition, αΒ-Crystallin overexpression rescues the intercalated disc, mitochondrial and nuclear defects of LmnaH222P/H222P hearts, as well as the abnormal activation of ERK1/2. Consistent with that, by generating the LmnaH222P/H222PDes+/- mice, we showed that the genetically decreased endogenous desmin levels have cardioprotective effects in LmnaH222P/H222P hearts since less desmin is available to form dysfunctional aggregates. In conclusion, our results demonstrate that desmin network disruption, disorganization of intercalated discs and mitochondrial defects are a major mechanism contributing to the progression of this LMNA cardiomyopathy and can be ameliorated by αΒ-Crystallin overexpression

Peptide-Drug conjugate gnrh-sunitinib targets angiogenesis selectively at the site of action to inhibit tumor growth

The potential to heighten the efficacy of antiangiogenic agents was explored in this study based on active targeting of tumor cells overexpressing the gonadotropin-releasing hormone receptor (GnRH-R). The rational design pursued focused on five analogues of a clinically established antiangiogenic compound (sunitinib), from which a lead candidate (SAN1) was conjugated to the targeting peptide [D-Lys6]-GnRH, generating SAN1GSC. Conjugation of SAN1 did not disrupt any of its antiangiogenic or cytotoxic properties in GnRH-R-expressing prostate and breast tumor cells. Daily SAN1GSC treatments in mouse xenograft models of castration-resistant prostate cancer resulted in significant tumor growth delay compared with equimolar SAN1 or sunitinib alone. This efficacy correlated with inhibited phosphor-ylation of AKT and S6, together with reduced Ki-67 and CD31 expression. The superior efficacy of the peptide-drug conjugate was also attributed to the finding that higher amounts of SAN1 were delivered to the tumor site (∼4-fold) following dosing of SAN1GSC compared with equimolar amounts of nonconjugated SAN1. Importantly, treatment with SAN1GSC was associated with minimal hematotoxicity and cardiotoxicity based on measurements of the left ventricular systolic function in treated mice. Our results offer preclinical proof-of-concept for SAN1GSC as a novel molecule that selectively reaches the tumor site and downregulates angiogenesis with negligible cardiotoxicity, thus encouraging its further clinical development and evaluation.</p

Impaired calcium homeostasis is associated with sudden cardiac death and arrhythmias in a genetic equivalent mouse model of the human HRC-Ser96Ala variant

Aims The histidine-rich calcium-binding protein (HRC) Ser96Ala variant has previously been identified as a potential biomarker for ventricular arrhythmias and sudden cardiac death in patients with idiopathic dilated cardiomyopathy. Herein, the role of this variant in cardiac pathophysiology is delineated through a novel mouse model, carrying the human mutation in the homologous mouse position. Methods and results The mouse HRC serine 81, homologous to human HRC serine 96, was mutated to alanine, using knock-in gene targeting. The HRC-Ser81Ala mice presented increased mortality in the absence of structural or histological abnormalities, indicating that early death may be arrhythmia-related. Indeed, under stress-but not baseline-conditions, the HRC-Ser81Ala mice developed ventricular arrhythmias, whilst at the cardiomyocyte level they exhibited increased occurrence of triggered activity. Cardiac contraction was decreased in vivo, ex vivo, and in vitro. Additionally, Ca2+ transients and SR Ca2+ load were both reduced suggesting that cytosolic Ca2+ overload is not the underlying proarrhythmic mechanism. Interestingly, total SR Ca2+ leak was increased in HRC-Ser81Ala cardiomyocytes, without an increase in Ca2+ spark and wave frequency. However, Ca2+ wave propagation was significantly slower and the duration of the associated Na/Ca exchange current was increased. Moreover, action potential duration was also increased. Notably, Ca2+/Calmodulin kinase II (CaMKII) phosphorylation of the ryanodine receptor was increased, whilst KN-93, an inhibitor of CaMKII, reduced the occurrence of arrhythmias. Conclusions The homologous mutation Ser81Ala in HRC in mice, corresponding to Ser96Ala in humans, is associated with sudden death and depressed cardiac function. Ventricular arrhythmias are related to abnormal Ca2+ cycling across the SR. The data further support a role for CaMKII with the perspective to treat arrhythmias through CaMKII inhibition