SIRT1, heme oxygenase-1 and NO-mediated vasodilation in a human model of endogenous angiotensin II type 1 receptor antagonism: implications for hypertension

Sirtuin 1 aggravates hypertrophic heart failure caused by pressure overload via shifting energy metabolism

Sirtuin1 (SIRT1) is involved in regulating substrate metabolism in the cardiovascular system. Metabolic homeostasis plays a critical role in hypertrophic heart failure. We hypothesize that cardiac SIRT1 can modulate substrate metabolism during pressure overload-induced heart failure. The inducible cardiomyocyte Sirt1 knockout (icSirt1-/-) and its wild type littermates (Sirt1f/f) C57BL/6J mice were subjected to transverse aortic constriction (TAC) surgery to induce pressure overload. The pressure overload induces upregulation of cardiac SIRT1 in Sirt1f/f but not icSirt1-/- mice. The cardiac contractile dysfunctions caused by TAC-induced pressure overload occurred in Sirt1f/f but not in icSirt1-/- mice. Intriguingly, Sirt1f/f heart showed a drastic reduction in systolic contractility and electric signals during post-TAC surgery, whereas icSirt1-/- heart demonstrated significant resistance to pathological stress by TAC-induced pressure overload as evidenced by no significant changes in systolic contractile functions and electric properties. The targeted proteomics showed that the pressure overload triggered downregulation of the SIRT1-associated IDH2 (isocitrate dehydrogenase 2) that resulted in increased oxidative stress in mitochondria. Moreover, metabolic alterations were observed in Sirt1f/f but not in icSirt1-/- heart in response to TAC-induced pressure overload. Thus, SIRT1 interferes with metabolic homeostasis through mitochondrial IDH2 during pressure overload. Inhibition of SIRT1 activity benefits cardiac functions under pressure overload-related pathological conditions.

5-Aminolevulinic acid combined with sodium ferrous citrate (5-ALA/SFC) ameliorated liver injury in a murine acute graft-versus-host disease model by reducing inflammation responses through PGC1-α activation

Acute graft-versus-host disease (aGvHD) remains lethal as a life-threatening complication after allogeneic hematopoietic stem cell transplantation (HSCT). Inflammatory responses play an important role in aGvHD. 5-Aminolevulinic acid combined with sodium ferrous citrate (5-ALA/SFC) has been widely reported to have a major effect on the anti-inflammatory response; however, these effects in aGvHD models have never been reported. In this study, a murine aGvHD model was developed by transferring spleen cells from donor B6/N (H-2kb) mice into recipient B6D2F1 (H-2kb/d) mice. In addition to evaluating manifestations in aGvHD mice, we analyzed the serum ALT/AST levels, liver pathological changes, infiltrating cells and mRNA expression of inflammation-related cytokines and chemokines. 5-ALA/SFC treatment significantly ameliorated liver injury due to aGvHD and decreased the population of liver-infiltrating T cells, resulting in a reduced expression of pro-inflammatory cytokines and chemokines. Furthermore, the mRNA expression proliferator-activated receptor-γcoactivator (PGC-1α) was enhanced, which might explain why 5-ALA/SFC treatment downregulates inflammatory signaling pathways. Our results indicated that 5-ALA/SFC can ameliorate liver injury induced by aGvHD through the activation of PGC-1α and modulation of the liver mRNA expression of inflammatory-related cytokines and chemokines. This may be a novel strategy for treating this disease.

Sirt1 Activity in PBMCs as a Biomarker of Different Heart Failure Phenotypes

Heart Failure (HF) is a syndrome, which implies the existence of different phenotypes. The new categorization includes patients with preserved ejection fraction (HFpEF), mid-range EF (HFmrEF), and reduced EF (HFrEF) but the molecular mechanisms involved in these HF phenotypes have not yet been exhaustively investigated. Sirt1 plays a crucial role in biological processes strongly related to HF. This study aimed to evaluate whether Sirt1 activity was correlated with EF and other parameters in HFpEF, HFmrEF, and HFrEF. Seventy patients, HFpEF (n = 23), HFmrEF (n = 23) and HFrEF (n = 24), were enrolled at the Cardiology Unit of the University Hospital of Salerno. Sirt1 activity was measured in peripheral blood mononuclear cells (PBMCs). Angiotensin-Converting Enzyme 2 (ACE2) activity, Tumor Necrosis Factor-alpha (TNF-α) and Brain Natriuretic Peptide (BNP) levels were quantified in plasma. HFpEF showed lower Sirt1 and ACE2 activities than both HFmrEF and HFrEF (p < 0.0001), without difference compared to No HF controls. In HFmrEF and HFrEF a very strong correlation was found between Sirt1 activity and EF (r² = 0.899 and r² = 0.909, respectively), and between ACE2 activity and Sirt1 (r² = 0.801 and r² = 0.802, respectively). HFrEF showed the highest TNF-α levels without reaching statistical significance. Significant differences in BNP were found among the groups, with the highest levels in the HFrEF. Determining Sirt1 activity in PBMCs is useful to distinguish the HF patients’ phenotypes from each other, especially HFmrEF/HFrEF from HFpEF.

The Role of Sirtuin-1 in the Vasculature: Focus on Aortic Aneurysm

Sirtuin-1 (SirT1) is a nicotinamide adenine dinucleotide-dependent deacetylase and the best characterized member of the sirtuins family in mammalians. Sirtuin-1 shuttles between the cytoplasm and the nucleus, where it deacetylates histones and non-histone proteins involved in a plethora of cellular processes, including survival, growth, metabolism, senescence, and stress resistance. In this brief review, we summarize the current knowledge on the anti-oxidant, anti-inflammatory, anti-apoptotic, and anti-senescence effects of SirT1 with an emphasis on vascular diseases. Specifically, we describe recent research advances on SirT1-mediated molecular mechanisms in aortic aneurysm (AA), and how these processes relate to oxidant stress and the heme-oxygenase (HO) system. HO-1 and HO-2 catalyze the rate-limiting step of cellular heme degradation and, similar to SirT1, HO-1 exerts beneficial effects in the vasculature through the activation of anti-oxidant, anti-inflammatory, anti-apoptotic, and anti-proliferative signaling pathways. SirT1 and HO-1 are part of an integrated system for cellular stress tolerance, and may positively interact to regulate vascular function. We further discuss sex differences in HO-1 and SirT1 activity or expression, and the potential interactions between the two proteins, in relation to the progression and severity of AA, as well as the ongoing efforts for translational applications of SirT1 activation and HO-1 induction in the treatment of cardiovascular diseases including AA.

The Peroxisome Proliferator-Activated Receptor-Gamma Coactivator-1α-Heme Oxygenase 1 Axis, a Powerful Antioxidative Pathway with Potential to Attenuate Diabetic Cardiomyopathy

Significance: From studies of diabetic animal models, the downregulation of peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α)-heme oxygenase 1 (HO-1) axis appears to be a crucial event in the development of obesity and diabetic cardiomyopathy (DCM). In this review, we discuss the role of metabolic and biochemical stressors in the rodent and human pathophysiology of DCM. A crucial contributor for many cardiac pathologies is excessive production of reactive oxygen species (ROS) pathologies, which lead to extensive cellular damage by impairing mitochondrial function and directly oxidizing DNA, proteins, and lipid membranes. We discuss the role of ROS production and inflammatory pathways with multiple contributing and confounding factors leading to DCM. Recent Advances: The relevant biochemical pathways that are critical to a therapeutic approach to treat DCM, specifically caloric restriction and its relation to the PGC-1α-HO-1 axis in the attenuation of DCM, are elucidated. Critical Issues: The increased prevalence of diabetes mellitus type 2, a major contributor to unique cardiomyopathy characterized by cardiomyocyte hypertrophy with no effective clinical treatment. This review highlights the role of mitochondrial dysfunction in the development of DCM and potential oxidative targets to attenuate oxidative stress and attenuate DCM. Future Directions: Targeting the PGC-1α-HO-1 axis is a promising approach to ameliorate DCM through improvement in mitochondrial function and antioxidant defenses. A pharmacological inducer to activate PGC-1α and HO-1 described in this review may be a promising therapeutic approach in the clinical setting.

Effect of heme oxygenase 1 and renin/prorenin receptor on oxidized low-density lipoprotein-induced human umbilical vein endothelial cells

The incidence of depression has previously been correlated to hypertension. The aim of the present study was to explore the mechanisms of depression and hypertension by examining the expression and interaction of renin/prorenin receptor (PRR) and heme oxygenase 1 (HO-1) in vascular endothelial cells. A case-control study was conducted, and general data and serum factors were compared between hypertension patients complicated with depression and patients with hypertension alone. Logistic regression analysis was used to detect risk factors associated with hypertension complicated with depression. In addition, human umbilical vein endothelial cells (HUVECs) were treated with oxidized low-density lipoprotein (ox-LDL) and/or PRR gene silencing, and a Cell Counting Kit-8 (CCK-8) assay was performed to test their proliferation. The concentrations of inflammatory factors and oxidative stress factor were also detected using enzyme-linked immunosorbent assay and chemical colorimetry. Western blot analysis and reverse transcription-quantitative polymerase chain reaction were applied to detect protein and mRNA expression levels, respectively. The results revealed that HO-1 and renin precursor (Rep) were independent factors that affected hypertension complicated with depression. Serum HO-1 levels in patients with hypertension complicated with depression were significantly lower than that in hypertensive patients without depression, while Rep levels in patients with hypertension complicated with depression were significantly higher than that in hypertensive patients without depression. In HUVECs, ox-LDL reduced the cell proliferation in a dose-dependent manner, upregulated the expression of PRR gene and downregulated the expression of HO-1 gene. It was also observed that silencing of the PRR gene promoted the expression of the HO-1 gene. Furthermore, ox-LDL upregulated the inflammatory response and oxidative stress levels, while PRR gene silencing inhibited the ox-LDL-induced inflammatory factor and oxidative stress levels in HUVECs. Thus, regulating the expression levels of HO-1 and PRR to inhibit the oxidative stress and pro-inflammatory effect of ox-LDL may provide new insight for the treatment of hypertension patients with depression.

Regulation of diabetic cardiomyopathy by caloric restriction is mediated by intracellular signaling pathways involving 'SIRT1 and PGC-1α'

Background

Metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus (DM2) are all linked to diabetic cardiomyopathy that lead to heart failure. Cardiomyopathy is initially characterized by cardiomyocyte hypertrophy, followed by mitochondrial dysfunction and fibrosis, both of which are aggravated by angiotensin. Caloric restriction (CR) is cardioprotective in animal models of heart disease through its catabolic activity and activation of the expression of adaptive genes. We hypothesized that in the diabetic heart; this effect involves antioxidant defenses and is mediated by SIRT1 and the transcriptional coactivator PGC-1α (Peroxisome proliferator-activated receptor-γ coactivator).

Methods

Obese Leptin resistant (db/db) mice characterized by DM2 were treated with angiotensin II (AT) for 4 weeks to enhance the development of cardiomyopathy. Mice were concomitantly either on a CR diet or fed ad libitum. Cardiomyocytes were exposed to high levels of glucose and were treated with EX-527 (SIRT1 inhibitor). Cardiac structure and function, gene and protein expression and oxidative stress parameters were analyzed.

Results

AT treated db/db mice developed cardiomyopathy manifested by elevated levels of serum glucose, cholesterol and cardiac hypertrophy. Leukocyte infiltration, fibrosis and an increase in an inflammatory marker (TNFα) and natriuretic peptides (ANP, BNP) gene expression were also observed. Oxidative stress was manifested by low SOD and PGC-1α levels and an increase in ROS and MDA. DM2 resulted in ERK1/2 activation. CR attenuated all these deleterious perturbations and prevented the development of cardiomyopathy. ERK1/2 phosphorylation was reduced in CR mice (p = 0.008). Concomitantly CR prevented the reduction in SIRT activity and PGC-1α (p < 0.04). Inhibition of SIRT1 activity in cardiomyocytes led to a marked reduction in both SIRT1 and PGC-1α. ROS levels were significantly (p < 0.03) increased by glucose and SIRT1 inhibition.

Conclusion

In the current study we present evidence of the cardioprotective effects of CR operating through SIRT1 and PGC-1 α, thereby decreasing oxidative stress, fibrosis and inflammation. Our results suggest that increasing SIRT1 and PGC-1α levels offer new therapeutic approaches for the protection of the diabetic heart.

Endothelial Function Is Impaired in Patients Receiving Antihypertensive Drug Treatment Regardless of Blood Pressure Level: FMD-J Study (Flow-Mediated Dilation Japan)

Hypertension is associated with endothelial dysfunction. Blood pressure significantly correlates with endothelial function in antihypertensive drug-naive subjects. The purpose of this study was to determine whether treatment status affects the relationship between blood pressure and endothelial function. We measured flow-mediated vasodilation (FMD) in 2297 subjects, including 1822 antihypertensive drug-naive subjects and 475 treated hypertensive patients. FMD significantly decreased in relation to increase in systolic blood pressure (8.2±3.1% in subjects with systolic blood pressure of <120 mm Hg, 7.5±2.8% for 120-129 mm Hg, 7.1±2.8% for 130-139 mm Hg, and 6.7±2.6% for ≥140 mm Hg; P<0.001). Systolic blood pressure was independently associated with FMD in untreated subjects. In contrast, there was no significant relationship between systolic blood pressure and FMD in treated hypertensive patients (4.6±3.1% in treated hypertensives with systolic blood pressure of <120 mm Hg, 4.8±2.7% for 120-129 mm Hg, 4.9±2.8% for 130-139 mm Hg, and 4.5±2.3% for ≥140 mm Hg; P=0.77). Propensity score matching analysis revealed that the prevalence of endothelial dysfunction defined as FMD of less than the division point for the lowest tertile, and the middle tertile of FMD was significantly higher in treated hypertensive patients than in untreated subjects in all systolic blood pressure categories. Endothelial function assessed by FMD was impaired regardless of the level of blood pressure achieved by antihypertensive drug treatment in hypertensive patients.

Enrichment of in vivo transcription data from dietary intervention studies with in vitro data provides improved insight into gene regulation mechanisms in the intestinal mucosa

Background

Gene expression profiles of intestinal mucosa of chickens and pigs fed over long-term periods (days/weeks) with a diet rich in rye and a diet supplemented with zinc, respectively, or of chickens after a one-day amoxicillin treatment of chickens, were recorded recently. Such dietary interventions are frequently used to modulate animal performance or therapeutically for monogastric livestock. In this study, changes in gene expression induced by these three interventions in cultured “Intestinal Porcine Epithelial Cells” (IPEC-J2) recorded after a short-term period of 2 and 6 hours, were compared to the in vivo gene expression profiles in order to evaluate the capability of this in vitro bioassay in predicting in vivo responses.

Methods

Lists of response genes were analysed with bioinformatics programs to identify common biological pathways induced in vivo as well as in vitro. Furthermore, overlapping genes and pathways were evaluated for possible involvement in the biological processes induced in vivo by datamining and consulting literature.

Results

For all three interventions, only a limited number of identical genes and a few common biological processes/pathways were found to be affected by the respective interventions. However, several enterocyte-specific regulatory and secreted effector proteins that responded in vitro could be related to processes regulated in vivo, i.e. processes related to mineral absorption, (epithelial) cell adherence and tight junction formation for zinc, microtubule and cytoskeleton integrity for amoxicillin, and cell-cycle progression and mucus production for rye.

Conclusions

Short-term gene expression responses to dietary interventions as measured in the in vitro bioassay have a low predictability for long-term responses as measured in the intestinal mucosa in vivo. The short-term responses of a set regulatory and effector genes, as measured in this bioassay, however, provided additional insight into how specific processes in piglets and broilers may be modulated by “early” signalling molecules produced by enterocytes. The relevance of this set of regulatory/effector genes and cognate biological processes for zinc deficiency and supplementation, gluten allergy (rye), and amoxicillin administration in humans is discussed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-017-0559-1) contains supplementary material, which is available to authorized users.

Mesenchymal stem cell-conditioned media ameliorate diabetic endothelial dysfunction by improving mitochondrial bioenergetics via the Sirt1/AMPK/PGC-1α pathway

Vasculopathy is a major complication of diabetes. Impaired mitochondrial bioenergetics and biogenesis due to oxidative stress are a critical causal factor for diabetic endothelial dysfunction. Sirt1, an NAD⁺-dependent enzyme, is known to play an important protective role through deacetylation of many substrates involved in oxidative phosphorylation and reactive oxygen species generation. Mesenchymal stem cell-conditioned medium (MSC-CM) has emerged as a promising cell-free therapy due to the trophic actions of mesenchymal stem cell (MSC)-secreted molecules. In the present study, we investigated the therapeutic potential of MSC-CMs in diabetic endothelial dysfunction, focusing on the Sirt1 signalling pathway and the relevance to mitochondrial function. We found that high glucose-stimulated MSC-CM attenuated several glucotoxicity-induced processes, oxidative stress and apoptosis of endothelial cells of the human umbilical vein. MSC-CM perfusion in diabetic rats ameliorated compromised aortic vasodilatation and alleviated oxidative stress in aortas. We further demonstrated that these effects were dependent on improved mitochondrial function and up-regulation of Sirt1 expression. MSC-CMs activated the phosphorylation of phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt), leading to direct interaction between Akt and Sirt1, and subsequently enhanced Sirt1 expression. In addition, both MSC-CM and Sirt1 activation could increase the expression of peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1α), as well as increase the mRNA expression of its downstream, mitochondrial, biogenesis-related genes. This indirect regulation was mediated by activation of AMP-activated protein kinase (AMPK). Overall our findings indicated that MSC-CM had protective effects on endothelial cells, with respect to glucotoxicity, by ameliorating mitochondrial dysfunction via the PI3K/Akt/Sirt1 pathway, and Sirt1 potentiated mitochondrial biogenesis, through the Sirt1/AMPK/PGC-1α pathway.

Bartter/Gitelman syndromes as a model to study systemic oxidative stress in humans

Reactive oxygen species (ROS) are intermediates in reduction-oxidation reactions that begin with the addition of one electron to molecular oxygen, generating the primary ROS superoxide, which in turn interacts with other molecules to produce secondary ROS, such as hydrogen peroxide, hydroxyl radical, and peroxynitrite. ROS are continuously produced during metabolic processes and are deemed to play an important role in cardiovascular diseases, namely, myocardial hypertrophy and fibrosis and atherosclerosis, via oxidative damage of lipids, proteins, and deoxyribonucleic acid. Angiotensin II (Ang II) is a potent vasoactive agent that also exerts mitogenic, proinflammatory, and profibrotic effects through several signaling pathways, in part involving ROS, particularly superoxide and hydrogen peroxide. Moreover, Ang II stimulates NADPH oxidases, leading to higher ROS generation and oxidative stress. Bartter/Gitelman syndrome patients, despite elevated plasma renin activity, Ang II, and aldosterone levels, exhibit reduced peripheral resistance, normal/low blood pressure, and blunted pressor effect of vasoconstrictors. In addition, notwithstanding the activation of the renin-angiotensin system and the increased plasma levels of Ang II, these patients display decreased production of ROS, reduced oxidative stress, and increased antioxidant defenses. In fact, Bartter/Gitelman syndrome patients are characterized by reduced levels of p22(phox) gene expression and undetectable plasma peroxynitrite levels, while showing increased plasma antioxidant power and expression of antioxidant enzymes, such as heme oxygenase-1. In conclusion, multifarious data suggest that Bartter and Gitelman syndrome patients are a model of low oxidative stress and high antioxidant defenses. The contribution offered by the study of these syndromes in elucidating the molecular mechanisms underlying this favorable status could offer chances for new therapeutic targets in disease characterized by high levels of reactive oxygen species.

Bilirubin exerts pro-angiogenic property through Akt-eNOS-dependent pathway

Low serum bilirubin levels are associated with the risk of cardiovascular diseases including peripheral artery disease. Bilirubin is known to exert its property such as antioxidant effect or the enhancement of flow-mediated vasodilation, however, bilirubin action on angiogenesis remains unclear. To investigate the molecular mechanism of bilirubin on angiogenic effect, we first employed C57BL/6J mice with unilateral hindlimb ischemia surgery and divided the mice into two groups (vehicle-treated group and bilirubin-treated group). The analysis of laser speckle blood flow demonstrated the enhancement of blood flow recovery in response to ischemia of mice with bilirubin treatment. The density of capillaries was significantly higher in ischemic-adductor muscles of bilirubin-treated mice. The phosphorylated levels of endothelial nitric oxide synthase (eNOS) and Akt were increased in ischemic skeletal muscles of mice with bilirubin treatment compared with vehicle treatment. In in vitro experiments by using human aortic endothelial cells, bilirubin augmented eNOS and Akt phosphorylation, cell proliferation, cell migration and tube formation. These bilirubin actions on endothelial cell activation were inhibited by LY294002, a phosphatidylinositol 3-kinase inhibitor. In conclusion, bilirubin promotes angiogenesis through endothelial cells activation via Akt-eNOS-dependent manner.

Angiotensin II blockade: how its molecular targets may signal to mitochondria and slow aging. Coincidences with calorie restriction and mTOR inhibition

Caloric restriction (CR), renin angiotensin system blockade (RAS-bl), and rapamycin-mediated mechanistic target of rapamycin (mTOR) inhibition increase survival and retard aging across species. Previously, we have summarized CR and RAS-bl's converging effects, and the mitochondrial function changes associated with their physiological benefits. mTOR inhibition and enhanced sirtuin and KLOTHO signaling contribute to the benefits of CR in aging. mTORC1/mTORC2 complexes contribute to cell growth and metabolic regulation. Prolonged mTORC1 activation may lead to age-related disease progression; thus, rapamycin-mediated mTOR inhibition and CR may extend lifespan and retard aging through mTORC1 interference. Sirtuins by deacetylating histone and transcription-related proteins modulate signaling and survival pathways and mitochondrial functioning. CR regulates several mammalian sirtuins favoring their role in aging regulation. KLOTHO/fibroblast growth factor 23 (FGF23) contribute to control Ca(2+), phosphate, and vitamin D metabolism, and their dysregulation may participate in age-related disease. Here we review how mTOR inhibition extends lifespan, how KLOTHO functions as an aging suppressor, how sirtuins mediate longevity, how vitamin D loss may contribute to age-related disease, and how they relate to mitochondrial function. Also, we discuss how RAS-bl downregulates mTOR and upregulates KLOTHO, sirtuin, and vitamin D receptor expression, suggesting that at least some of RAS-bl benefits in aging are mediated through the modulation of mTOR, KLOTHO, and sirtuin expression and vitamin D signaling, paralleling CR actions in age retardation. Concluding, the available evidence endorses the idea that RAS-bl is among the interventions that may turn out to provide relief to the spreading issue of age-associated chronic disease.

SIRT1: role in cardiovascular biology

SIRT1 (silent information regulator two protein) is a type III protein deacetylase that regulates a variety of important metabolic and physiologic processes including stress resistance, metabolism, apoptosis and energy balance. It reverses cholesterol transport and reduces risk for development of atherosclerosis and cardiovascular disease. The following review highlights the potential role of SIRT1 on cardiovascular biology and function.