Disrupted Binding of Cystathionine γ-Lyase to p53 Promotes Endothelial Senescence.

BACKGROUND: Advanced age is unequivocally linked to the development of cardiovascular disease; however, the mechanisms resulting in reduced endothelial cell regeneration remain poorly understood. Here, we investigated novel mechanisms involved in endothelial cell senescence that impact endothelial cell transcription and vascular repair after injury. METHODS: Native endothelial cells were isolated from young (20±3.4 years) and aged (80±2.3 years) individuals and subjected to molecular analyses to assess global transcriptional and metabolic changes. In vitro studies were conducted using primary human and murine endothelial cells. A murine aortic re-endothelialization model was used to examine endothelial cell regenerative capacity in vivo. RESULTS: RNA sequencing of native endothelial cells revealed that aging resulted in p53-mediated reprogramming to express senescence-associated genes and suppress glycolysis. Reduced glucose uptake and ATP contributed to attenuated assembly of the telomerase complex, which was required for endothelial cell proliferation. Enhanced p53 activity in aging was linked to its acetylation on K120 due to enhanced activity of the acetyltransferase MOZ (monocytic leukemic zinc finger). Mechanistically, p53 acetylation and translocation were, at least partially, attributed to the loss of the vasoprotective enzyme, CSE (cystathionine γ-lyase). CSE physically anchored p53 in the cytosol to prevent its nuclear translocation and CSE absence inhibited AKT (Protein kinase B)-mediated MOZ phosphorylation, which in turn increased MOZ activity and subsequently p53 acetylation. In mice, the endothelial cell-specific deletion of CSE activated p53, induced premature endothelial senescence, and arrested vascular repair after injury. In contrast, the adeno-associated virus 9-mediated re-expression of an active CSE mutant retained p53 in the cytosol, maintained endothelial glucose metabolism and proliferation, and prevented endothelial cell senescence. Adenoviral overexpression of CSE in native endothelial cells from aged individuals maintained low p53 activity and reactivated telomerase to revert endothelial cell senescence. CONCLUSIONS: Aging-associated impairment of vascular repair is partly determined by the vasoprotective enzyme CSE.

Nitric oxide maintains endothelial redox homeostasis through PKM2 inhibition.

Decreased nitric oxide (NO) bioavailability and oxidative stress are hallmarks of endothelial dysfunction and cardiovascular diseases. Although numerous proteins are S-nitrosated, whether and how changes in protein S-nitrosation influence endothelial function under pathophysiological conditions remains unknown. We report that active endothelial NO synthase (eNOS) interacts with and S-nitrosates pyruvate kinase M2 (PKM2), which reduces PKM2 activity. PKM2 inhibition increases substrate flux through the pentose phosphate pathway to generate reducing equivalents (NADPH and GSH) and protect against oxidative stress. In mice, the Tyr656 to Phe mutation renders eNOS insensitive to inactivation by oxidative stress and prevents the decrease in PKM2 S-nitrosation and reducing equivalents, thereby delaying cardiovascular disease development. These findings highlight a novel mechanism linking NO bioavailability to antioxidant responses in endothelial cells through S-nitrosation and inhibition of PKM2.

The endothelial-enriched lncRNA LINC00607 mediates angiogenic function.

Long non-coding RNAs (lncRNAs) can act as regulatory RNAs which, by altering the expression of target genes, impact on the cellular phenotype and cardiovascular disease development. Endothelial lncRNAs and their vascular functions are largely undefined. Deep RNA-Seq and FANTOM5 CAGE analysis revealed the lncRNA LINC00607 to be highly enriched in human endothelial cells. LINC00607 was induced in response to hypoxia, arteriosclerosis regression in non-human primates, post-atherosclerotic cultured endothelial cells from patients and also in response to propranolol used to induce regression of human arteriovenous malformations. siRNA knockdown or CRISPR/Cas9 knockout of LINC00607 attenuated VEGF-A-induced angiogenic sprouting. LINC00607 knockout in endothelial cells also integrated less into newly formed vascular networks in an in vivo assay in SCID mice. Overexpression of LINC00607 in CRISPR knockout cells restored normal endothelial function. RNA- and ATAC-Seq after LINC00607 knockout revealed changes in the transcription of endothelial gene sets linked to the endothelial phenotype and in chromatin accessibility around ERG-binding sites. Mechanistically, LINC00607 interacted with the SWI/SNF chromatin remodeling protein BRG1. CRISPR/Cas9-mediated knockout of BRG1 in HUVEC followed by CUT&RUN revealed that BRG1 is required to secure a stable chromatin state, mainly on ERG-binding sites. In conclusion, LINC00607 is an endothelial-enriched lncRNA that maintains ERG target gene transcription by interacting with the chromatin remodeler BRG1 to ultimately mediate angiogenesis.

Inhibition of soluble epoxide hydrolase prevents diabetic retinopathy.

Diabetic retinopathy is an important cause of blindness in adults, and is characterized by progressive loss of vascular cells and slow dissolution of inter-vascular junctions, which result in vascular leakage and retinal oedema. Later stages of the disease are characterized by inflammatory cell infiltration, tissue destruction and neovascularization. Here we identify soluble epoxide hydrolase (sEH) as a key enzyme that initiates pericyte loss and breakdown of endothelial barrier function by generating the diol 19,20-dihydroxydocosapentaenoic acid, derived from docosahexaenoic acid. The expression of sEH and the accumulation of 19,20-dihydroxydocosapentaenoic acid were increased in diabetic mouse retinas and in the retinas and vitreous humour of patients with diabetes. Mechanistically, the diol targeted the cell membrane to alter the localization of cholesterol-binding proteins, and prevented the association of presenilin 1 with N-cadherin and VE-cadherin, thereby compromising pericyte-endothelial cell interactions and inter-endothelial cell junctions. Treating diabetic mice with a specific sEH inhibitor prevented the pericyte loss and vascular permeability that are characteristic of non-proliferative diabetic retinopathy. Conversely, overexpression of sEH in the retinal Müller glial cells of non-diabetic mice resulted in similar vessel abnormalities to those seen in diabetic mice with retinopathy. Thus, increased expression of sEH is a key determinant in the pathogenesis of diabetic retinopathy, and inhibition of sEH can prevent progression of the disease.

Mapping the Endothelial Cell S-Sulfhydrome Highlights the Crucial Role of Integrin Sulfhydration in Vascular Function.

BACKGROUND: In vascular endothelial cells, cysteine metabolism by the cystathionine γ lyase (CSE), generates hydrogen sulfide-related sulfane sulfur compounds (H2Sn), that exert their biological actions via cysteine S-sulfhydration of target proteins. This study set out to map the "S-sulfhydrome" (ie, the spectrum of proteins targeted by H2Sn) in human endothelial cells. METHODS: Liquid chromatography with tandem mass spectrometry was used to identify S-sulfhydrated cysteines in endothelial cell proteins and ß3 integrin intraprotein disulfide bond rearrangement. Functional studies included endothelial cell adhesion, shear stress-induced cell alignment, blood pressure measurements, and flow-induced vasodilatation in endothelial cell-specific CSE knockout mice and in a small collective of patients with endothelial dysfunction. RESULTS: Three paired sample sets were compared: (1) native human endothelial cells isolated from plaque-free mesenteric arteries (CSE activity high) and plaque-containing carotid arteries (CSE activity low); (2) cultured human endothelial cells kept under static conditions or exposed to fluid shear stress to decrease CSE expression; and (3) cultured endothelial cells exposed to shear stress to decrease CSE expression and treated with solvent or the slow-releasing H2Sn donor, SG1002. The endothelial cell "S-sulfhydrome" consisted of 3446 individual cysteine residues in 1591 proteins. The most altered family of proteins were the integrins and focusing on ß3 integrin in detail we found that S-sulfhydration affected intraprotein disulfide bond formation and was required for the maintenance of an extended-open conformation of the ß leg. ß3 integrin S-sulfhydration was required for endothelial cell mechanotransduction in vitro as well as flow-induced dilatation in murine mesenteric arteries. In cultured cells, the loss of S-sulfhydration impaired interactions between ß3 integrin and Gα13 (guanine nucleotide-binding protein subunit α 13), resulting in the constitutive activation of RhoA (ras homolog family member A) and impaired flow-induced endothelial cell realignment. In humans with atherosclerosis, endothelial function correlated with low H2Sn generation, impaired flow-induced dilatation, and failure to detect ß3 integrin S-sulfhydration, all of which were rescued after the administration of an H2Sn supplement. CONCLUSIONS: Vascular disease is associated with marked changes in the S-sulfhydration of endothelial cell proteins involved in mediating responses to flow. Short-term H2Sn supplementation improved vascular reactivity in humans highlighting the potential of interfering with this pathway to treat vascular disease.

Phosphodiesterases S-sulfhydration contributes to human skeletal muscle function.

The increase in intracellular calcium is influenced by cyclic nucleotides (cAMP and cGMP) content, which rating is governed by phosphodiesterases (PDEs) activity.Despite it has been demonstrated a beneficial effect of PDEs inhibitors in different pathological conditions involving SKM, not much is known on the role exerted by cAMP-cGMP/PDEs axis in human SKM contractility. Here, we show that Ssulfhydration of PDEs modulates human SKM contractility in physiological and pathological conditions. Having previously demonstrated that, in the rare human syndrome Malignant Hyperthermia (MH), there is an overproduction of hydrogen sulfide (H2S) within SKM contributing to hyper-contractility, here we have used MH negative diagnosed biopsies (MHN) as healthy SKM, and MH susceptible diagnosed biopsies (MHS) as a pathological model of SKM hypercontractility. The study has been performed on MHS and MHN human biopsies after diagnosis has been made and on primary SKM cells derived from both MHN and MHS biopsies. Our data demonstrate that in normal conditions PDEs are S-sulfhydrated in both quadriceps' biopsies and primary SKM cells. This post translational modification (PTM) negatively regulates PDEs activity with consequent increase of both cAMP and cGMP levels. In hypercontractile biopsies, due to an excessive H2S content, there is an enhanced Ssulfhydration of PDEs that further increases cyclic nucleotides levels contributing to SKM hyper-contractility. Thus, the identification of a new endogenous PTM modulating PDEs activity represents an advancement in SKM physiopathology understanding.

Increased susceptibility of human endothelial cells to infections by SARS-CoV-2 variants.

Coronavirus disease 2019 (COVID-19) spawned a global health crisis in late 2019 and is caused by the novel coronavirus SARS-CoV-2. SARS-CoV-2 infection can lead to elevated markers of endothelial dysfunction associated with higher risk of mortality. It is unclear whether endothelial dysfunction is caused by direct infection of endothelial cells or is mainly secondary to inflammation. Here, we investigate whether different types of endothelial cells are susceptible to SARS-CoV-2. Human endothelial cells from different vascular beds including umbilical vein endothelial cells, coronary artery endothelial cells (HCAEC), cardiac and lung microvascular endothelial cells, or pulmonary arterial cells were inoculated in vitro with SARS-CoV-2. Viral spike protein was only detected in HCAECs after SARS-CoV-2 infection but not in the other endothelial cells tested. Consistently, only HCAEC expressed the SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2), required for virus infection. Infection with the SARS-CoV-2 variants B.1.1.7, B.1.351, and P.2 resulted in significantly higher levels of viral spike protein. Despite this, no intracellular double-stranded viral RNA was detected and the supernatant did not contain infectious virus. Analysis of the cellular distribution of the spike protein revealed that it co-localized with endosomal calnexin. SARS-CoV-2 infection did induce the ER stress gene EDEM1, which is responsible for clearance of misfolded proteins from the ER. Whereas the wild type of SARS-CoV-2 did not induce cytotoxic or pro-inflammatory effects, the variant B.1.1.7 reduced the HCAEC cell number. Of the different tested endothelial cells, HCAECs showed highest viral uptake but did not promote virus replication. Effects on cell number were only observed after infection with the variant B.1.1.7, suggesting that endothelial protection may be particularly important in patients infected with this variant.

Cystathionine γ Lyase Sulfhydrates the RNA Binding Protein Human Antigen R to Preserve Endothelial Cell Function and Delay Atherogenesis.

BACKGROUND: Hydrogen sulfide (H2S), generated by cystathionine γ lyase (CSE), is an important endogenous regulator of vascular function. The aim of the present study was to investigate the control and consequences of CSE activity in endothelial cells under physiological and proatherogenic conditions. METHODS: Endothelial cell CSE knockout mice were generated, and lung endothelial cells were studied in vitro (gene expression, protein sulfhydration, and monocyte adhesion). Mice were crossed onto the apolipoprotein E-deficient background, and atherogenesis (partial carotid artery ligation) was monitored over 21 days. CSE expression, H2S bioavailability, and amino acid profiling were also performed with human material. RESULTS: The endothelial cell-specific deletion of CSE selectively increased the expression of CD62E and elevated monocyte adherence in the absence of an inflammatory stimulus. Mechanistically, CD62E mRNA was more stable in endothelial cells from CSE-deficient mice, an effect attributed to the attenuated sulfhydration and dimerization of the RNA-binding protein human antigen R. CSE expression was upregulated in mice after partial carotid artery ligation and in atheromas from human subjects. Despite the increase in CSE protein, circulating and intraplaque H2S levels were reduced, a phenomenon that could be attributed to the serine phosphorylation (on Ser377) and inhibition of the enzyme, most likely resulting from increased interleukin-1ß. Consistent with the loss of H2S, human antigen R sulfhydration was attenuated in atherosclerosis and resulted in the stabilization of human antigen R-target mRNAs, for example, CD62E and cathepsin S, both of which are linked to endothelial cell activation and atherosclerosis. The deletion of CSE from endothelial cells was associated with the accelerated development of endothelial dysfunction and atherosclerosis, effects that were reversed on treatment with a polysulfide donor. Finally, in mice and humans, plasma levels of the CSE substrate l-cystathionine negatively correlated with vascular reactivity and H2S levels, indicating its potential use as a biomarker for vascular disease. CONCLUSIONS: The constitutive S-sulfhydration of human antigen R (on Cys13) by CSE-derived H2S prevents its homodimerization and activity, which attenuates the expression of target proteins such as CD62E and cathepsin S. However, as a consequence of vascular inflammation, the beneficial actions of CSE-derived H2S are lost owing to the phosphorylation and inhibition of the enzyme.

Pleiotropic effects of laminar flow and statins depend on the Krüppel-like factor-induced lncRNA MANTIS.

AIMS: To assess the functional relevance and therapeutic potential of the pro-angiogenic long non-coding RNA MANTIS in vascular disease development. METHODS AND RESULTS: RNA sequencing, CRISPR activation, overexpression, and RNAi demonstrated that MANTIS, especially its Alu-element, limits endothelial ICAM-1 expression in different types of endothelial cells. Loss of MANTIS increased endothelial monocyte adhesion in an ICAM-1-dependent manner. MANTIS reduced the binding of the SWI/SNF chromatin remodelling factor BRG1 at the ICAM-1 promoter. The expression of MANTIS was induced by laminar flow and HMG-CoA-reductase inhibitors (statins) through mechanisms involving epigenetic rearrangements and the transcription factors KLF2 and KLF4. Mutation of the KLF binding motifs in the MANTIS promoter blocked the flow-induced MANTIS expression. Importantly, the expression of MANTIS in human carotid artery endarterectomy material was lower compared with healthy vessels and this effect was prevented by statin therapy. Interestingly, the protective effects of statins were mediated in part through MANTIS, which was required to facilitate the atorvastatin-induced changes in endothelial gene expression. Moreover, the beneficial endothelial effects of statins in culture models (spheroid outgrowth, proliferation, telomerase activity, and vascular organ culture) were lost upon knockdown of MANTIS. CONCLUSION: MANTIS is tightly regulated by the transcription factors KLF2 and KLF4 and limits the ICAM-1 mediated monocyte adhesion to endothelial cells and thus potentially atherosclerosis development in humans. The beneficial effects of statin treatment and laminar flow are dependent on MANTIS.

Comparison of the effects of e-cigarette vapor with cigarette smoke on lung function and inflammation in mice.

Electronic cigarettes (e-cigs) are advertised as a less harmful nicotine delivery system or as a new smoking cessation tool. We aimed to assess the in vivo effects of e-cig vapor in the lung and to compare them to those of cigarette smoke (CS). We exposed C57BL/6 mice for either 3 days or 4 wk to ambient air, CS, or e-cig vapor containing 1) propylene glycol/vegetable glycerol (PG:VG-Sol; 1:1), 2) PG:VG with nicotine (G:VG-N), or 3) PG:VG with nicotine and flavor (PG:VG-N+F) and determined oxidative stress, inflammation, and pulmonary mechanics. E-cig vapors, especially PG:VG-N+F, increased bronchoalveolar lavage fluid (BALF) cellularity, Muc5ac production, as well as BALF and lung oxidative stress markers at least comparably and in many cases more than CS. BALF protein content at both time points studied was only elevated in the PG:VG-N+F group. After 3 days, PG:VG-Sol altered tissue elasticity, static compliance, and airway resistance, whereas after 4 wk CS was the only treatment adversely affecting these parameters. Airway hyperresponsiveness in response to methacholine was increased similarly in the CS and PG:VG-N+F groups. Our findings suggest that exposure to e-cig vapor can trigger inflammatory responses and adversely affect respiratory system mechanics. In many cases, the added flavor in e-cigs exacerbated the detrimental effects of e-cig vapor. We conclude that both e-cig vaping and conventional cigarette smoking negatively impact lung biology.

Phosphorylation of vasodilator-stimulated phosphoprotein contributes to myocardial ischemic preconditioning.

Ischemic preconditioning (IP) is a well-known strategy to protect organs against cell death following ischemia. The previous work has shown that vasodilator-stimulated phosphoprotein (VASP) is involved in cytoskeletal reorganization and that it holds significant importance for the extent of myocardial ischemia reperfusion injury. Yet, the role of VASP during myocardial IP is, to date, not known. We report here that VASP phosphorylation at serine157 and serine239 is induced during hypoxia in vitro and during IP in vivo. The preconditioning-induced VASP phosphorylation inactivates the GP IIb/IIIa integrin receptor on platelets, which results in the reduced formation of organ compromising platelet neutrophil complexes. Experiments in chimeric mice confirmed the importance of VASP phosphorylation during myocardial IP. When studying this in VASP-/- animals and in an isolated heart model, we were able to confirm the important role of VASP on myocardial IP. In conclusion, we were able to show that IP-induced VASP phosphorylation in platelets is a protective mechanism against the deleterious effects of ischemia.

Hydrogen Sulfide Preserves Endothelial Nitric Oxide Synthase Function by Inhibiting Proline-Rich Kinase 2: Implications for Cardiomyocyte Survival and Cardioprotection.

Hydrogen sulfide (H2S) exhibits beneficial effects in the cardiovascular system, many of which depend on nitric oxide (NO). Proline-rich tyrosine kinase 2 (PYK2), a redox-sensitive tyrosine kinase, directly phosphorylates and inhibits endothelial NO synthase (eNOS). We investigated the ability of H2S to relieve PYK2-mediated eNOS inhibition and evaluated the importance of the H2S/PYK2/eNOS axis on cardiomyocyte injury in vitro and in vivo. Exposure of H9c2 cardiomyocytes to H2O2 or pharmacologic inhibition of H2S production increased PYK2 (Y402) and eNOS (Y656) phosphorylation. These effects were blocked by treatment with Na2S or by overexpression of cystathionine γ-lyase (CSE). In addition, PYK2 overexpression reduced eNOS activity in a H2S-reversible manner. The viability of cardiomyocytes exposed to Η2Ο2 was reduced and declined further after the inhibition of H2S production. PYK2 downregulation, l-cysteine supplementation, or CSE overexpression alleviated the effects of H2O2 on H9c2 cardiomyocyte survival. Moreover, H2S promoted PYK2 sulfhydration and inhibited its activity. In vivo, H2S administration reduced reactive oxygen species levels, as well as PYK2 (Y402) and eNOS (Y656) phosphorylation. Pharmacologic blockade of PYK2 or inhibition of PYK2 activation by Na2S reduced myocardial infarct size in mice. Coadministration of a PYK2 inhibitor and Na2S did not result in additive effects on infarct size. We conclude that H2S relieves the inhibitory effect of PYK2 on eNOS, allowing the latter to produce greater amounts of NO, thereby affording cardioprotection. Our results unravel the existence of a novel H2S-NO interaction and identify PYK2 as a crucial target for the protective effects of H2S under conditions of oxidative stress.

Exposure to cigarette smoke abrogates the beneficial effect of ischemic postconditioning.

Cigarette smoking is one of the risk factors for coronary artery disease. Although conditioning decreases infarct size in hearts from healthy animals, comorbidities may render it ineffective. We investigated the effects of cigarette smoke (CS) exposure on intracellular myocardial signaling, infarct size after ischemia-reperfusion, and the potential interference with ischemic conditioning. Exposure of mice to CS increased blood pressure, caused cardiac hypertrophy, and upregulated the nitric oxide synthatse (NOS)/soluble guanylate cyclase (sGC)/cGMP pathway. To test the effect of CS exposure on the endogenous cardioprotective mechanisms, mice were subjected to regional myocardial ischemia and reperfusion with no further intervention or application of preconditioning (PreC) or postconditioning (PostC). Exposure to CS did not increase the infarction compared with the room air (RA)-exposed group. PreC was beneficial for both CS and RA vs. nonconditioned animals. PostC was effective only in RA animals, while the infarct size-limiting effect was not preserved in the CS group. Differences in oxidative stress markers, Akt, and endothelial NOS phosphorylation and cGMP levels were observed between RA and CS groups subjected to PostC. In conclusion, exposure to CS does not per se increase infarct size. The beneficial effect of ischemic PreC is preserved in mice exposed to CS, as it does not affect the cardioprotective signaling; in contrast, PostC fails to protect CS-exposed mice due to impaired activation of the Akt/eNOS/cGMP axis that occurs in parallel to enhanced oxidative stress.

Cardioprotection by H2S Donors: Nitric Oxide-Dependent and ­Independent Mechanisms.

Hydrogen sulfide (H2S) is a signaling molecule with protective effects in the cardiovascular system. To harness the therapeutic potential of H2S, a number of donors have been developed. The present study compares the cardioprotective actions of representative H2S donors from different classes and studies their mechanisms of action in myocardial injury in vitro and in vivo. Exposure of cardiomyocytes to H2O2 led to significant cytotoxicity, which was inhibited by sodium sulfide (Na2S), thiovaline (TV), GYY4137 [morpholin-4-ium 4 methoxyphenyl(morpholino) phosphinodithioate], and AP39 [(10-oxo-10-(4-(3-thioxo-3H-1,2-dithiol5yl)phenoxy)decyl) triphenylphospho-nium bromide]. Inhibition of nitric oxide (NO) synthesis prevented the cytoprotective effects of Na2S and TV, but not GYY4137 and AP39, against H2O2-induced cardiomyocyte injury. Mice subjected to left anterior descending coronary ligation were protected from ischemia-reperfusion injury by the H2S donors tested. Inhibition of nitric oxide synthase (NOS) in vivo blocked only the beneficial effect of Na2S. Moreover, Na2S, but not AP39, administration enhanced the phosphorylation of endothelial NOS and vasodilator-associated phosphoprotein. Both Na2S and AP39 reduced infarct size in mice lacking cyclophilin-D (CypD), a modulator of the mitochondrial permeability transition pore (PTP). Nevertheless, only AP39 displayed a direct effect on mitochondria by increasing the mitochondrial Ca(2+) retention capacity, which is evidence of decreased propensity to undergo permeability transition. We conclude that although all the H2S donors we tested limited infarct size, the pathways involved were not conserved. Na2S had no direct effects on PTP opening, and its action was nitric oxide dependent. In contrast, the cardioprotection exhibited by AP39 could result from a direct inhibitory effect on PTP acting at a site different than CypD.

Regulation and role of endogenously produced hydrogen sulfide in angiogenesis.

Recent studies have implicated endogenously produced H2S in the angiogenic process. On one hand, pharmacological inhibition and silencing of the enzymes involved in H2S synthesis attenuate the angiogenic properties of endothelial cells, including proliferation, migration and tube-like structure network formation. On the other hand, enhanced production of H2S by substrate supplementation or over-expression of H2S-producing enzymes leads to enhanced angiogenic responses in cultured endothelial cells. Importantly, H2S up-regulates expression of the key angiogenic factor vascular endothelial growth factor (VEGF) and contributes to the angiogenic signaling in response to VEGF. The signaling pathways mediating H2S-induced angiogenesis include mitogen-activated protein kinases, phosphoinositide-3 kinase, nitric oxide/cGMP-regulated cascades and ATP-sensitive potassium channels. Endogenously produced H2S has also been shown to facilitate neovascularization in prototypical model systems in vivo, and to contribute to wound healing, post-ischemic angiogenesis in the heart and other tissues, as well as in tumor angiogenesis. Targeting of H2S synthesizing enzymes might offer novel therapeutic opportunities for angiogenesis-related diseases.

Role of cGMP in hydrogen sulfide signaling.

The importance of hydrogen sulfide (H2S) in physiology and disease is being increasingly recognized in recent years. Unlike nitric oxide (NO) that signals mainly through soluble guanyl cyclase (sGC)/cGMP, H2S is more promiscuous, affecting multiple pathways. It interacts with ion channels, enzymes, transcription factors and receptors. It was originally reported that H2S does not alter the levels of cyclic nucleotides. More recent publications, however, have shown increases in intracellular cGMP following exposure of cells or tissues to exogenously administered or endogenously produced H2S. Herein, we discuss the evidence for the participation of cGMP in H2S signaling and reconcile the seemingly divergent results presented in the literature on the role of this cyclic nucleotide in the biological actions of H2S.

The natural olive constituent oleuropein induces nutritional cardioprotection in normal and cholesterol-fed rabbits: comparison with preconditioning.

Ischemic preconditioning, which is mediated by cell signaling molecules, protects the heart from ischemia-reperfusion injury by limiting the infarct size. Oleuropein, the main polyphenolic constituent of olives, reduced the infarct size in normal and cholesterol-fed rabbits when it was administered at a nutritional dose. The aim of the present study was to compare the effects of oleuropein and preconditioning in terms of the cell signaling and metabolism pathways underlying myocardial protection. Rabbits were randomly divided into six groups: the control group received 5 % dextrose for six weeks, the preconditioning group was subjected to two cycles of preconditioning with 5 min ischemia/10 min reperfusion, the O6 group was treated with oleuropein for six weeks, the Chol group was fed a cholesterol-enriched diet and 5 % dextrose for six weeks, and the CholO6 and CholO3 groups were treated with cholesterol and oleuropein for six and three weeks, respectively; oleuropein was dissolved in 5 % dextrose solution and was administered orally at a dose of 20 mg × kg(-1) × day(-1). All animals were subsequently subjected to 30 min myocardial ischemia followed by 10 min of reperfusion. At that time, myocardial biopsies were taken from the ischemic areas for the assessment of oxidative and nitrosative stress biomarkers (malondialdehyde and nitrotyrosine), and determination of phosphorylation of signaling molecules involved in the mechanism of preconditioning (PI3K, Akt, eNOS, AMPK, STAT3). The tissue extracts NMR metabolic profile was recorded and further analyzed by multivariate statistics. Oxidative biomarkers were significantly reduced in the O6, CholO6, and CholO3 groups compared to the control, preconditioning, and Chol groups. Considering the underlying signaling cascade, the phosphorylation of PI3K, Akt, eNOS, AMPK, and STAT-3 was significantly higher in the preconditioning and all oleuropein-treated groups compared to the control and Chol groups. The NMR-based metabonomic study, performed through the analysis of spectroscopic data, depicted differences in the metabolome of the various groups with significant alterations in purine metabolism. In conclusion, the addition of oleuropein to a normal or hypercholesterolemic diet results in a preconditioning-like intracellular effect, eliminating the deleterious consequences of ischemia and hypercholesterolemia, followed by a decrease of oxidative stress biomarkers. This effect is exerted through inducing preconditioning-involved signaling transduction. Nutritional preconditioning may support the low cardiovascular morbidity and mortality associated with the consumption of olive products.

Oleuropein prevents doxorubicin-induced cardiomyopathy interfering with signaling molecules and cardiomyocyte metabolism.

Oleuropein, a natural phenolic compound, prevents acute doxorubicin (DXR)-induced cardiotoxicity but there is no evidence regarding its role in chronic DXR-induced cardiomyopathy (DXR-CM). In the present study, we investigated the role of oleuropein in DXR-CM by addressing cardiac geometry and function (transthoracic echocardiography), cardiac histopathology, nitro-oxidative stress (MDA, PCs, NT), inflammatory cytokines (IL-6, Big ET-1), NO homeostasis (iNOS and eNOS expressions), kinases involved in apoptosis and metabolism (Akt, AMPK) and myocardial metabonomics. Rats were randomly divided into 6 groups: Control, OLEU-1 and OLEU-2 [oleuropein at 1000 and 2000 mg/kg in total, respectively, intraperitoneally (i.p.) for 14 days], DXR (18 mg/kg, i.p. divided into 6 equal doses for 2 weeks), DXR-OLEU-1 and DXR-OLEU-2 (both oleuropein and DXR as previously described). Impaired left ventricular contractility and inflammatory and degenerative pathology lesions were encountered only in the DXR group. The DXR group also had higher MDA, PCs, NT, IL-6 and Big ET-1 levels, higher iNOS and lower eNOS, Akt and AMPK activation compared to controls and the oleuropein-treated groups. Metabonomics depicted significant metabolite alterations in the DXR group suggesting perturbed energy metabolism and protein biosynthesis. The effectiveness of DXR in inhibiting cell proliferation is not compromised when oleuropein is present. We documented an imbalance between iNOS and eNOS expressions and a disturbed protein biosynthesis and metabolism in DXR-CM; these newly recognized pathways in DXR cardiotoxicity may help identifying novel therapeutic targets. Activation of AMPK and suppression of iNOS by oleuropein seem to prevent the structural, functional and histopathological cardiac effects of chronic DXR toxicity.

Monitoring Mitophagy Dynamics in Live Cells.

The purpose of this protocol is to provide a comprehensive, stepwise guide for assessing mitophagy flux utilizing a live-cell mt-KEIMA approach. The proposed protocol is sensitive, reproducible, quantitative, and easy to perform. While mitophagy has been extensively studied, current methodologies primarily focus on terminal measurements, neglecting the dynamic aspect of this process. Hence, the introduction of this straightforward live-cell mitophagy tracing protocol enables real-time monitoring of the dynamics of mitochondrial selective autophagy, thereby enhancing the ability to draw conclusions regarding key regulators and the reversibility of the process. The assay employs a lentiviral approach to induce mt-KEIMA expression in primary or immortalized cell lines. Subsequently, the respective mitophagy reporter cells are observed using a live-cell imaging system at specific time intervals, and further quantification allows the detection of mitophagy flux. This protocol has proven efficacious in investigating mitophagy flux, including responses to chemical inducers or genetically modified cells over time. Notably, this approach is well-suited for large throughput screening of chemicals or appropriate gene-editing libraries that may influence mitophagy responses in cells.

Loss of cardiac mitochondrial complex I persulfidation impairs NAD+ homeostasis in aging.

Protein persulfidation is a significant post-translational modification that involves addition of a sulfur atom to the cysteine thiol group and is facilitated by sulfide species. Persulfidation targets reactive cysteine residues within proteins, influencing their structure and/or function across various biological systems. This modification is evolutionarily conserved and plays a crucial role in preventing irreversible cysteine overoxidation, a process that becomes prominent with aging. While, persulfidation decreases with age, its levels in the aged heart and the functional implications of such a reduction in cardiac metabolism remain unknown. Here we interrogated the cardiac persulfydome in wild-type adult mice and age-matched mice lacking the two sulfide generating enzymes, namely cystathionine gamma lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3MST). Our findings revealed that cardiac persulfidated proteins in wild type hearts are less abundant compared to those in other organs, with a primary involvement in mitochondrial metabolic processes. We further focused on one specific target, NDUFB7, which undergoes persulfidation by both CSE and 3MST derived sulfide species. In particular, persulfidation of cysteines C80 and C90 in NDUFB7 protects the protein from overoxidation and maintains the complex I activity in cardiomyocytes. As the heart ages, the levels of CSE and 3MST in cardiomyocytes decline, leading to reduced NDUFB7 persulfidation and increased cardiac NADH/NAD+ ratio. Collectively, our data provide compelling evidence for a direct link between cardiac persulfidation and mitochondrial complex I activity, which is compromised in aging.