PARP1 is required for adhesion molecule expression in atherogenesis

NAD+ metabolism and therapeutic strategies in cardiovascular diseases

Nicotinamide adenine dinucleotide (NAD+) is a central and pleiotropic metabolite involved in cellular energy metabolism, cell signaling, DNA repair, and protein modifications. Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Metabolic stress and aging directly affect the cardiovascular system. Compelling data suggest that NAD + levels decrease with age, obesity, and hypertension, which are all notable risk factors for CVD. In addition, the therapeutic elevation of NAD + levels reduces chronic low-grade inflammation, reactivates autophagy and mitochondrial biogenesis, and enhances oxidative metabolism in vascular cells of humans and rodents with vascular disorders. In preclinical models, NAD + boosting can also expand the health span, prevent metabolic syndrome, and decrease blood pressure. Moreover, NAD + storage by genetic, pharmacological, or natural dietary NAD + -increasing strategies has recently been shown to be effective in improving the pathophysiology of cardiac and vascular health in different animal models, and human health. Here, we review and discuss NAD + -related mechanisms pivotal for vascular health and summarize recent experimental evidence in NAD + research directly related to vascular disease, including atherosclerosis, and coronary artery disease. Finally, we comparatively assess distinct NAD + precursors for their clinical efficacy and the efficiency of NAD + elevation in the treatment of major CVD. These findings may provide ideas for new therapeutic strategies to prevent and treat CVD in the clinic.

Poly (ADP-ribose) Polymerase-1 modulations in the genesis of thrombosis

Thrombosis, a coagulation disorder, occurs due to altered levels of coagulation, fibrinolytic and immune factors, which are otherwise known to maintain hemostasis in normal physiological conditions. Here, we review the direct and indirect participation of a multifunctional nuclear enzyme poly (ADP-ribose) polymerase-1 (PARP1) in the expression of key genes and cellular processes involved in thrombotic pathogenesis. PARP1 biological activities range from maintenance of genomic integrity, chromatin remodeling, base excision DNA repair, stress responses to cell death, angiogenesis and cell cycle pathways. However, under homeostatic imbalances, PARP1 activities are linked with the pathogenesis of diseases, including cancer, aging, neurological disorders, and cardiovascular diseases. Disease-associated distressed cells employ a variety of PARP-1 functions such as oxidative damage exacerbations, cellular energetics and apoptosis pathways, regulation of inflammatory mediators, promotion of endothelial dysfunction, and ERK-mediated signaling in pathogenesis. Thrombosis is one such pathogenesis that comprises exacerbation of coagulation cascade due to biochemical alterations in endothelial cells, platelet activation, overexpression of adhesion molecules, cytokines release, and leukocyte adherence. Thus, the activation of endothelial and inflammatory cells in thrombosis implicates a potential role of PARP1 activation in thrombogenesis. This review article explores the direct impact of PARP1 activation in the etiology of thrombosis and discusses PARP1-mediated endothelial dysfunction, inflammation, and epigenetic regulations in the disease manifestation. Understanding PARP1 functions associated with thrombosis may elucidate novel pathogenetic mechanisms and help in better disease management through newer therapeutic interventions targeting PARP1 activity.

PARPs and ADP-Ribosylation in Chronic Inflammation: A Focus on Macrophages

Aberrant adenosine diphosphate-ribose (ADP)-ribosylation of proteins and nucleic acids is associated with multiple disease processes such as infections and chronic inflammatory diseases. The poly(ADP-ribose) polymerase (PARP)/ADP-ribosyltransferase (ART) family members promote mono- or poly-ADP-ribosylation. Although evidence has linked PARPs/ARTs and macrophages in the context of chronic inflammation, the underlying mechanisms remain incompletely understood. This review provides an overview of literature focusing on the roles of PARP1/ARTD1, PARP7/ARTD14, PARP9/ARTD9, and PARP14/ARTD8 in macrophages. PARPs/ARTs regulate changes in macrophages during chronic inflammatory processes not only via catalytic modifications but also via non-catalytic mechanisms. Untangling complex mechanisms, by which PARPs/ARTs modulate macrophage phenotype, and providing molecular bases for the development of new therapeutics require the development and implementation of innovative technologies.

Targeting protein modifications in metabolic diseases: molecular mechanisms and targeted therapies

The ever-increasing prevalence of noncommunicable diseases (NCDs) represents a major public health burden worldwide. The most common form of NCD is metabolic diseases, which affect people of all ages and usually manifest their pathobiology through life-threatening cardiovascular complications. A comprehensive understanding of the pathobiology of metabolic diseases will generate novel targets for improved therapies across the common metabolic spectrum. Protein posttranslational modification (PTM) is an important term that refers to biochemical modification of specific amino acid residues in target proteins, which immensely increases the functional diversity of the proteome. The range of PTMs includes phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, glycosylation, palmitoylation, myristoylation, prenylation, cholesterylation, glutathionylation, S-nitrosylation, sulfhydration, citrullination, ADP ribosylation, and several novel PTMs. Here, we offer a comprehensive review of PTMs and their roles in common metabolic diseases and pathological consequences, including diabetes, obesity, fatty liver diseases, hyperlipidemia, and atherosclerosis. Building upon this framework, we afford a through description of proteins and pathways involved in metabolic diseases by focusing on PTM-based protein modifications, showcase the pharmaceutical intervention of PTMs in preclinical studies and clinical trials, and offer future perspectives. Fundamental research defining the mechanisms whereby PTMs of proteins regulate metabolic diseases will open new avenues for therapeutic intervention.

Endothelial SIRT6 deficiency promotes arterial thrombosis in mice

OBJECTIVE

Arterial thrombosis may be initiated by endothelial inflammation or denudation, activation of blood-borne elements or the coagulation system. Tissue factor (TF), a central trigger of the coagulation cascade, is regulated by the pro-inflammatory NF-κB-dependent pathways. Sirtuin 6 (SIRT6) is a nuclear member of the sirtuin family of NAD⁺-dependent deacetylases and is known to inhibit NF-κB signaling. Its constitutive deletion in mice shows early lethality with hypoglycemia and accelerated aging. Of note, the role of SIRT6 in arterial thrombosis remains unknown. Thus, we hypothesized that endothelial SIRT6 protects from arterial thrombosis by modulating inhibition of NF-κB-associated pathways.

APPROACH AND RESULTS

Using a laser-induced carotid thrombosis model, in vivo arterial occlusion occurred 45% faster in 12-week-old male endothelial-specific Sirt6^-/- mice as compared to Sirt6^fl/fl controls (n ≥ 9 per group; p = 0.0012). Levels of procoagulant TF were increased in animals lacking endothelial SIRT6 as compared to control littermates. Similarly, in cultured human aortic endothelial cells, SIRT6 knockdown increased TF mRNA, protein and activity. Moreover, SIRT6 knockdown increased mRNA levels of NF-κB-associated genes tumor necrosis factor alpha (TNF-α), poly [ADP-ribose] polymerase 1 (PARP-1), vascular cell adhesion molecule 1 (VCAM-1), and cyclooxygenase-2 (COX-2); at the protein level, COX-2, VCAM-1, TNF-α, and cleaved PARP-1 remained increased after Sirt6 knockdown.

CONCLUSIONS

Endothelium-specific Sirt6 deletion promotes arterial thrombosis in mice. In cultured human aortic endothelial cells, SIRT6 silencing enhances TF expression and activates pro-inflammatory pathways including TNF-α, cleaved PARP-1, VCAM-1 and COX-2. Hence, endogenous endothelial SIRT6 exerts a protective role in experimental arterial thrombosis.

Dipotassium Glycyrrhizinate on Melanoma Cell Line: Inhibition of Cerebral Metastases Formation by Targeting NF-kB Genes-Mediating MicroRNA-4443 and MicroRNA-3620-Dipotassium Glycyrrhizinate Effect on Melanoma

Glycyrrhizic acid (GA), a natural compound isolated from licorice (Glycyrrhiza glabra), has exhibited anti-inflammatory and anti-tumor effects in vitro. Dipotassium glycyrrhizinate (DPG), a dipotassium salt of GA, also has shown an anti-tumor effect on glioblastoma cell lines, U87MG and T98G. The study investigated the DPG effects in the melanoma cell line (SK-MEL-28). MTT assay demonstrated that the viability of the cells was significantly decreased in a time- and dose-dependent manner after DPG (IC50 = 36 mM; 24 h). DNA fragmentation suggested that DPG (IC50) induced cellular apoptosis, which was confirmed by a significant number of TUNEL-positive cells (p-value = 0.048) and by PARP-1 [0.55 vs. 1.02 arbitrary units (AUs), p-value = 0.001], BAX (1.91 vs. 1.05 AUs, p-value = 0.09), and BCL-2 (0.51 vs. 1.07 AUs, p-value = 0.0018) mRNA compared to control cells. The proliferation and wound-healing assays showed an anti-proliferative effect on DPG-IC50-treated cells, also indicating an inhibitory effect on cell migration (p-values < 0.001). Moreover, it was observed that DPG promoted a 100% reduction in melanospheres formation (p-value = 0.008). Our previous microRNAs (miRs) global analysis has revealed that DPG might increase miR-4443 and miR-3620 expression levels. Thus, qPCR showed that after DPG treatment, SK-MEL-28 cells presented significantly high miR-4443 (1.77 vs. 1.04 AUs, p-value = 0.02) and miR-3620 (2.30 vs. 1.00 AUs, p-value = 0.01) expression compared to control cells, which are predicted to target the NF-kB, CD209 and TNC genes, respectively. Both genes are responsible for cell attachment and migration, and qPCR revealed significantly decreased CD209 (1.01 vs. 0.54 AUs, p-value = 0.018) and TNC (1.00 vs. 0.31 AUs, p-value = 2.38 × 10−6) mRNA expression levels after DPG compared to untreated cells. Furthermore, the migration of SK-MEL-28 cells stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) was attenuated by adding DPG by wound-healing assay (48 h: p-value = 0.004; 72 h: p-value = 7.0 × 10−4). In addition, the MMP-9 expression level was inhibited by DPG in melanoma cells stimulated by TPA and compared to TPA-treated cells (3.56 vs. 0.99 AUs, p-value = 0.0016) after 24 h of treatment. Our results suggested that DPG has an apoptotic, anti-proliferative, and anti-migratory effect on SK-MEL-28 cells. DPG was also able to inhibit cancer stem-like cells that may cause cerebral tumor formation.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

PARPs in lipid metabolism and related diseases

PARPs and tankyrases (TNKS) represent a family of 17 proteins. PARPs and tankyrases were originally identified as DNA repair factors, nevertheless, recent advances have shed light on their role in lipid metabolism. To date, PARP1, PARP2, PARP3, tankyrases, PARP9, PARP10, PARP14 were reported to have multi-pronged connections to lipid metabolism. The activity of PARP enzymes is fine-tuned by a set of cholesterol-based compounds as oxidized cholesterol derivatives, steroid hormones or bile acids. In turn, PARPs modulate several key processes of lipid homeostasis (lipotoxicity, fatty acid and steroid biosynthesis, lipoprotein homeostasis, fatty acid oxidation, etc.). PARPs are also cofactors of lipid-responsive nuclear receptors and transcription factors through which PARPs regulate lipid metabolism and lipid homeostasis. PARP activation often represents a disruptive signal to (lipid) metabolism, and PARP-dependent changes to lipid metabolism have pathophysiological role in the development of hyperlipidemia, obesity, alcoholic and non-alcoholic fatty liver disease, type II diabetes and its complications, atherosclerosis, cardiovascular aging and skin pathologies, just to name a few. In this synopsis we will review the evidence supporting the beneficial effects of pharmacological PARP inhibitors in these diseases/pathologies and propose repurposing PARP inhibitors already available for the treatment of various malignancies.

Yin and Yang Regulation of Liver X Receptor α Signaling Control of Cholesterol Metabolism by Poly(ADP-ribose) polymerase 1

Liver X receptor α (LXRα) controls a set of key genes involved in cholesterol metabolism. However, the molecular mechanism of this regulation remains unknown. The regulatory role of poly(ADP-ribose) polymerase 1 (PARP1) in cholesterol metabolism in the liver was examined. Activation of PARP1 in the liver suppressed LXRα sensing and prevented upregulation of genes involved in HCD-induced cholesterol disposal. Mechanistically, LXRα was poly(ADP-ribosyl)ated by activated PARP1, which decreased DNA binding capacity of LXRα, thus preventing its recruitment to the target promoter. Intriguingly, we found that unactivated PARP1 was indispensable for LXRα transactivation and target expression. Further exploration identified unactivated PARP1 as an essential component of the LXRα-promoter complex. Taken together, the results indicate that activated PARP1 suppresses LXRα activation through poly(ADP-ribosyl)ation, while unactivated PARP1 promotes LXRα activation through physical interaction. PARP1 is a pivotal regulator of LXRα signaling and cholesterol metabolism in the liver.

The role of ADP-ribose metabolism in metabolic regulation, adipose tissue differentiation, and metabolism

In this review, Szanto et al. summarize the metabolic regulatory roles of PARP enzymes and their associated pathologies.

Poly(ADP-ribose) polymerases (PARPs or ARTDs), originally described as DNA repair factors, have metabolic regulatory roles. PARP1, PARP2, PARP7, PARP10, and PARP14 regulate central and peripheral carbohydrate and lipid metabolism and often channel pathological disruptive metabolic signals. PARP1 and PARP2 are crucial for adipocyte differentiation, including the commitment toward white, brown, or beige adipose tissue lineages, as well as the regulation of lipid accumulation. Through regulating adipocyte function and organismal energy balance, PARPs play a role in obesity and the consequences of obesity. These findings can be translated into humans, as evidenced by studies on identical twins and SNPs affecting PARP activity.

The impact of PARPs and ADP-ribosylation on inflammation and host-pathogen interactions

Poly-adenosine diphosphate-ribose polymerases (PARPs) promote ADP-ribosylation, a highly conserved, fundamental posttranslational modification (PTM). PARP catalytic domains transfer the ADP-ribose moiety from NAD⁺ to amino acid residues of target proteins, leading to mono- or poly-ADP-ribosylation (MARylation or PARylation). This PTM regulates various key biological and pathological processes. In this review, we focus on the roles of the PARP family members in inflammation and host-pathogen interactions. Here we give an overview the current understanding of the mechanisms by which PARPs promote or suppress proinflammatory activation of macrophages, and various roles PARPs play in virus infections. We also demonstrate how innovative technologies, such as proteomics and systems biology, help to advance this research field and describe unanswered questions.

Inflammation-induced DNA damage, mutations and cancer

The relationships between inflammation and cancer are varied and complex. An important connection linking inflammation to cancer development is DNA damage. During inflammation reactive oxygen and nitrogen species (RONS) are created to combat pathogens and to stimulate tissue repair and regeneration, but these chemicals can also damage DNA, which in turn can promote mutations that initiate and promote cancer. DNA repair pathways are essential for preventing DNA damage from causing mutations and cytotoxicity, but RONS can interfere with repair mechanisms, reducing their efficacy. Further, cellular responses to DNA damage, such as damage signaling and cytotoxicity, can promote inflammation, creating a positive feedback loop. Despite coordination of DNA repair and oxidative stress responses, there are nevertheless examples whereby inflammation has been shown to promote mutagenesis, tissue damage, and ultimately carcinogenesis. Here, we discuss the DNA damage-mediated associations between inflammation, mutagenesis and cancer.

Poly(ADP-ribose) Polymerase (PARP) and PARP Inhibitors: Mechanisms of Action and Role in Cardiovascular Disorders

Poly(ADP-ribosyl)ation is an immediate cellular repair response to DNA damage and is catalyzed primarily by poly(ADP-ribose)polymerase-1 (PARP1), which is the most abundant of the 18 different PARP isoforms and accounts for more than 90% of the catalytic activity of PARP in the cell nucleus. Upon detection of a DNA strand break, PARP1 binds to the DNA, cleaves nicotinamide adenine dinucleotide between nicotinamide and ribose and then modifies the DNA nuclear acceptor proteins by formation of a bond between the protein and the ADP-ribose residue. This generates ribosyl-ribosyl linkages that act as a signal for other DNA-repairing enzymes and DNA base repair. Extensive DNA breakage in cells results in excessive activation of PARP with resultant depletion of the cellular stores of nicotinamide adenine dinucleotide (NAD+) which slows the rate of glycolysis, mitochondrial electron transport, and ultimately ATP formation in these cells. This paper focuses on PARP in DNA repair in atherosclerosis, acute myocardial infarction/reperfusion injury, and congestive heart failure and the role of PARP inhibitors in combating the effects of excessive PARP activation in these diseases. Free oxygen radicals and nitrogen radicals in arteries contribute to disruption of the vascular endothelial glycocalyx, which increase the permeability of the endothelium to inflammatory cells and also low-density lipoproteins and the accumulation of lipid in the vascular intima. Mild inflammation and DNA damage within vascular cells promote PARP1 activation and DNA repair. Moderate DNA damage induces caspase-dependent PARP cleavage and vascular cell apoptosis. Severe DNA damage due to vascular inflammation causes excessive activation of PARP1. This causes endothelial cell depletion of NAD+ and ATP, downregulation of atheroprotective SIRT1, necrotic cell death, and ultimately atherosclerotic plaque disruption. Inhibition of PARP decreases vascular endothelial cell adhesion P-selectin and ICAM-1 molecules, inflammatory cells, pro-death caspase-3, and c-Jun N-terminal kinase (JNK) activation and upregulates prosurvival extracellular signal-regulated kinases and AKT, which decrease vascular cell apoptosis and necrosis and limit atherosclerosis and plaque disruption. In myocardial infarction with coronary occlusion then reperfusion, which occurs with coronary angioplasty or thrombolytic therapy, reperfusion injury occurs in as many as 31% of patients and is caused by inflammatory cells, free oxygen and nitrogen radicals, the rapid transcriptional activation of inflammatory cytokines, and the activation of PARP1. Inhibition of PARP attenuates neutrophil infiltration and inflammatory cytokine expression in the reperfused myocardium and preserves myocardial NAD+ and ATP. In addition, PARP inhibition increases the activation of myocyte survival enzymes protein kinase B (Akt) and protein kinase C epsilon (PKCε), and decreases the activity of myocardial ventricular remodeling enzymes PKCα/β, PKCζ/λ, and PKCδ. As a consequence, cardiomyocyte and vascular endothelial cell necrosis is decreased and myocardial contractility is preserved. In heart failure and circulatory shock in animal models, PARP inhibition significantly attenuates decreases in left ventricular systolic pressure, ventricular contractility and relaxation, stroke volume, and increases survival by limiting or preventing upregulation of adhesion molecules, proinflammatory cytokines, myocardial mononuclear cell infiltration, and PKCα/β and PKC λ/ζ. In this manner, PARP inhibition partially restores the myocardial concentrations of NAD+, limits ventricular remodeling and fibrosis, and prevents significant decreases in myocardial contractility. Based primarily on investigations in preclinical models of atherosclerosis, myocardial infarction, and heart failure, PARP inhibition appears to be beneficial in limiting or inhibiting cardiovascular dysfunction. These studies indicate that investigations of acute and chronic PARP inhibition are warranted in patients with atherosclerotic coronary artery disease.

Cancer Etiology: A Metabolic Disease Originating from Life's Major Evolutionary Transition?

A clear understanding of the origins of cancer is the basis of successful strategies for effective cancer prevention and management. The origin of cancer at the molecular and cellular levels is not well understood. Is the primary cause of the origin of cancer the genomic instability or impaired energy metabolism? An attempt was made to present cancer etiology originating from life's major evolutionary transition. The first evolutionary transition went from simple to complex cells when eukaryotic cells with glycolytic energy production merged with the oxidative mitochondrion (The Endosymbiosis Theory first proposed by Lynn Margulis in the 1960s). The second transition went from single-celled to multicellular organisms once the cells obtained mitochondria, which enabled them to obtain a higher amount of energy. Evidence will be presented that these two transitions, as well as the decline of NAD+ and ATP levels, are the root of cancer diseases. Restoring redox homeostasis and reactivation of mitochondrial oxidative metabolism are important factors in cancer prevention.

Poly(ADP-Ribose) Polymerases in Host-Pathogen Interactions, Inflammation, and Immunity

The literature review presented here details recent research involving members of the poly(ADP-ribose) polymerase (PARP) family of proteins. Among the 17 recognized members of the family, the human enzyme PARP1 is the most extensively studied, resulting in a number of known biological and metabolic roles. This review is focused on the roles played by PARP enzymes in host-pathogen interactions and in diseases with an associated inflammatory response. In mammalian cells, several PARPs have specific roles in the antiviral response; this is perhaps best illustrated by PARP13, also termed the zinc finger antiviral protein (ZAP). Plant stress responses and immunity are also regulated by poly(ADP-ribosyl)ation. PARPs promote inflammatory responses by stimulating proinflammatory signal transduction pathways that lead to the expression of cytokines and cell adhesion molecules. Hence, PARP inhibitors show promise in the treatment of inflammatory disorders and conditions with an inflammatory component, such as diabetes, arthritis, and stroke. These functions are correlated with the biophysical characteristics of PARP family enzymes. This work is important in providing a comprehensive understanding of the molecular basis of pathogenesis and host responses, as well as in the identification of inhibitors. This is important because the identification of inhibitors has been shown to be effective in arresting the progression of disease.

PARP-1 inhibition ameliorates elastase induced lung inflammation and emphysema in mice

COPD is associated with high morbidity and mortality and no effective treatment is available till date. We have previously reported that PARP-1 plays an important role in the establishment of airway inflammation associated with asthma and ALI. In the present work, we have evaluated the beneficial effects of PARP-1 inhibition on COPD pathogenesis utilizing elastase induced mouse model of the disease. Our data show that PARP-1 inhibition by olaparib significantly reduced the elastase-induced recruitment of inflammatory cells particularly neutrophils in the lungs of mice when administered at a dose of 5 mg/kg b.wt (i.p.). Reduction in the lung inflammation was associated with suppressed myeloperoxidase activity. Further, the drug restored the redox status in the lung tissues towards normal as reflected by the levels of ROS, GSH and MDA. Olaparib administration prior to elastase instillation blunted the phosphorylation of P65-NF-κB at Ser 536 without altering phosphorylation of its inhibitor IκBα in the lungs. Furthermore, olaparib down regulated the elastase-induced expression of NF-κB dependent pro-inflammatory cytokines (TNF-A, IL-6), chemokine (MIP-2) and growth factor (GCSF) severely both at the mRNA and protein levels. Additionally, PARP-1 heterozygosity suppressed the recruitment of inflammatory cells and production of TNF-A, IL-6, MIP-2 and GCSF in the BALF to the similar extent as exhibited by olaparib administration. Finally, PARP-1 inhibition by olaparib or gene deletion protected against elastase-induced emphysema markedly. Overall, our data strongly suggest that PARP-1 plays a critical role in elastase induced lung inflammation and emphysema, and thus may be a new drug target candidate in COPD.

PARP-1 Variant Rs1136410 Confers Protection against Coronary Artery Disease in a Chinese Han Population: A Two-Stage Case-Control Study Involving 5643 Subjects

Inhibition of poly(ADP-ribose) polymerase (PARP) may protect against coronary artery disease (CAD) in animal models, and rs1136410, a non-synonymous single nucleotide polymorphism (SNP) in PARP-1, has a potential impact on PARP activities in vitro. This two-stage case-control study, involving 2803 CAD patients and 2840 controls, aimed to investigate the associations of PARP-1 rs1136410 with CAD development, lipid levels, PARP activities, 8-hydroxy-2'-dexyguanosine (8-OHdG), and interleukin (IL)-6 levels in a Chinese Han population. Assuming a recessive model, the variant genotype GG of SNP rs1136410 showed a significantly inverse association with CAD risk (adjusted odds ratio (OR) = 0.73, P < 0.001), left main coronary artery (LMCA) lesions (P = 0.003), vessel scores (P = 0.003), and modified Gensini scores (P < 0.001). There were significant correlations of SNP rs1136410 with higher levels of total cholesterol (TC) and lower levels of high-density lipoprotein cholesterol (HDL-c). In gene-environment interaction analyses, participants with the variant genotype GG, but without smoking habit, type 2 diabetes mellitus, and hyperlipidemia, conferred an 84% (P < 0.001) decreased risk of CAD. The genotype-phenotype correlation analyses further supported the functional roles of SNP rs1136410 in decreasing PARP activities and 8-OHdG levels. Taken together, our data suggest that SNP rs1136410 may confer protection against CAD through modulation of PARP activities and gene-environment interactions in a Chinese Han population.

Poly(ADP-Ribose)Polymerase-1 in Lung Inflammatory Disorders: A Review

Asthma, acute lung injury (ALI), and chronic obstructive pulmonary disease (COPD) are lung inflammatory disorders with a common outcome, that is, difficulty in breathing. Corticosteroids, a class of potent anti-inflammatory drugs, have shown less success in the treatment/management of these disorders, particularly ALI and COPD; thus, alternative therapies are needed. Poly(ADP-ribose)polymerases (PARPs) are the post-translational modifying enzymes with a primary role in DNA repair. During the last two decades, several studies have reported the critical role played by PARPs in a good of inflammatory disorders. In the current review, the studies that address the role of PARPs in asthma, ALI, and COPD have been discussed. Among the different members of the family, PARP-1 emerges as a key player in the orchestration of lung inflammation in asthma and ALI. In addition, PARP activation seems to be associated with the progression of COPD. Furthermore, PARP-14 seems to play a crucial role in asthma. STAT-6 and GATA-3 are reported to be central players in PARP-1-mediated eosinophilic inflammation in asthma. Interestingly, oxidative stress-PARP-1-NF-κB axis appears to be tightly linked with inflammatory response in all three-lung diseases despite their distinct pathophysiologies. The present review sheds light on PARP-1-regulated factors, which may be common or differential players in asthma/ALI/COPD and put forward our prospective for future studies.

Poly(ADP-ribose) polymerase 1 deficiency increases nitric oxide production and attenuates aortic atherogenesis through downregulation of arginase II

Poly (ADP-ribose) polymerase (PARP) plays an important role in endothelial dysfunction, leading to atherogenesis and vascular-related diseases. However, whether PARP regulates nitric oxide (NO), a key regulator of endothelial function, is unclear so far. We investigated whether inhibition of PARP-1, the most abundant PARP isoform, prevents atherogenesis by regulating NO production and tried to elucidate the possible mechanisms involved in this phenomenon. In apolipoprotein E-deficient (apoE^-/- ) mice fed a high-cholesterol diet for 12 weeks, PARP-1 inhibition via treatment with 3,4-dihydro-54-(1-piperindinyl) butoxy-1(2H)-isoquinoline (DPQ) or PARP-1 gene knockout reduced aortic atherosclerotic plaque areas (49% and 46%, respectively). Both the groups showed restored NO production in mouse aortas with reduced arginase II (Arg II) expression compared to that in the controls. In mouse peritoneal macrophages and aortic endothelial cells (MAECs), PARP-1 knockout resulted in lowered Arg II expression. Moreover, phosphorylation of endothelial NO synthase (eNOS) was preserved in the aortas and MAECs when PARP-1 was inhibited. Reduced NO production in vitro due to PARP-1 deficiency could be restored by treating the MAECs with oxidized low-density lipoprotein treatment, but this effect could not be achieved with peritoneal macrophages, which was likely due to a reduction in the expression of induced NOS expression. Our findings indicate that PARP-1 inhibition may attenuate atherogenesis by restoring NO production in endothelial cells and thus by reducing Arg II expression and consequently arginase the activity.

Chronic PARP-1 inhibition reduces carotid vessel remodeling and oxidative damage of the dorsal hippocampus in spontaneously hypertensive rats

Vascular remodeling during chronic hypertension may impair the supply of tissues with oxygen, glucose and other compounds, potentially unleashing deleterious effects. In this study, we used Spontaneously Hypertensive Rats and normotensive Wistar-Kyoto rats with or without pharmacological inhibition of poly(ADP-ribose)polymerase-1 by an experimental compound L-2286, to evaluate carotid artery remodeling and consequent damage of neuronal tissue during hypertension. We observed elevated oxidative stress and profound thickening of the vascular wall with fibrotic tissue accumulation induced by elevated blood pressure. 32 weeks of L-2286 treatment attenuated these processes by modulating mitogen activated protein kinase phosphatase-1 cellular levels in carotid arteries. In hypertensive animals, vascular inflammation and endothelial dysfunction was observed by NF-κB nuclear accumulation and impaired vasodilation to acetylcholine, respectively. Pharmacological poly(ADP-ribose)polymerase-1 inhibition interfered in these processes and mitigated Apoptosis Inducing Factor dependent cell death events, thus improved structural and functional alterations of carotid arteries, without affecting blood pressure. Chronic poly(ADP-ribose)polymerase-1 inhibition protected neuronal tissue against oxidative damage, assessed by nitrotyrosine, 4-hydroxinonenal and 8-oxoguanosine immunohistochemistry in the area of Cornu ammonis 1 of the dorsal hippocampus in hypertensive rats. In this area, extensive pyramidal cell loss was also attenuated by treatment with lowered poly(ADP-ribose)polymer formation. It also preserved the structure of fissural arteries and attenuated perivascular white matter lesions and reactive astrogliosis in hypertensive rats. These data support the premise in which chronic poly(ADP-ribose)polymerase-1 inhibition has beneficial effects on hypertension related tissue damage both in vascular tissue and in the hippocampus by altering signaling events, reducing oxidative/nitrosative stress and inflammatory status, without lowering blood pressure.

SIRT1 improves VSMC functions in atherosclerosis

Despite advancements in diagnosis and treatment of cardiovascular diseases (CVDs), the morbidity and mortality of CVDs are still rising. Atherosclerosis is a chronic inflammatory disease contributing to multiple CVDs. Considering the complexity and severity of atherosclerosis, it is apparent that exploring the mechanisms of atherosclerotic formation and seeking new therapies for patients with atherosclerosis are required to overcome the heavy burden of CVDs on the quality and length of life of the global population. Vascular smooth muscle cells (VSMCs) play a dominant role in functional and structural changes of the arterial walls in response to atherogenic factors. Therefore, improvement of VSMC functions will slow down the development of atherosclerosis to a large extent. Given its protective performances on regulation of cholesterol metabolism and inflammatory responses, SIRT1 has long been known as an anti-atherosclerosis factor. In this review, we focus on the effects of SIRT1 on VSMC functions and thereby the development of atherosclerosis.

Cardiovascular Protective Effect of Metformin and Telmisartan: Reduction of PARP1 Activity via the AMPK-PARP1 Cascade

Hyperglycemia and hypertension impair endothelial function in part through oxidative stress-activated poly (ADP-ribose) polymerase 1 (PARP1). Biguanides and angiotensin II receptor blockers (ARBs) such as metformin and telmisartan have a vascular protective effect. We used cultured vascular endothelial cells (ECs), diabetic and hypertensive rodent models, and AMPKα2-knockout mice to investigate whether metformin and telmisartan have a beneficial effect on the endothelium via AMP-activated protein kinase (AMPK) phosphorylation of PARP1 and thus inhibition of PARP1 activity. The results showed that metformin and telmisartan, but not glipizide and metoprolol, activated AMPK, which phosphorylated PARP1 Ser-177 in cultured ECs and the vascular wall of rodent models. Experiments using phosphorylated/de-phosphorylated PARP1 mutants show that AMPK phosphorylation of PARP1 leads to decreased PARP1 activity and attenuated protein poly(ADP-ribosyl)ation (PARylation), but increased endothelial nitric oxide synthase (eNOS) activity and silent mating type information regulation 2 homolog 1 (SIRT1) expression. Taken together, the data presented here suggest biguanides and ARBs have a beneficial effect on the vasculature by the cascade of AMPK phosphorylation of PARP1 to inhibit PARP1 activity and protein PARylation in ECs, thereby mitigating endothelial dysfunction.

NAD+ as the Link Between Oxidative Stress, Inflammation, Caloric Restriction, Exercise, DNA Repair, Longevity, and Health Span

Oxidative stress and decreased DNA damage repair in vertebrates increase with age also due to lowered cellular NAD+. NAD+ depletion may play a major role in the aging process at the cellular level by limiting (1) energy production, (2) DNA repair, and (3) genomic signaling. In this study, we hypothesize that it is not NAD+ as a cofactor in redox reactions and coenzyme in metabolic processes that has the ultimate role in aging, but rather the role of NAD+ in cellular signaling when used as substrate for sirtuins (SIRT1-7 in mammals) and PARPs [Poly(ADP-ribose) polymerases]. Both sirtuins and PARPs influence many transcription factors and can affect gene expression. As a signaling molecule, NAD+ is consumed in the reaction donating ADP-ribose and releasing nicotinamide (NAM) as a by-product. It seems that aging at the cellular level is associated with a decline of NAD+ and that NAD+ restoration can reverse phenotypes of aging by inducing cellular repair and stress resistance. Adequate intracellular NAD+ concentrations may be an important longevity assurance factor, while lowered cellular NAD+ concentration may negatively influence the life span.

ARTD1 Suppresses Interleukin 6 Expression by Repressing MLL1-Dependent Histone H3 Trimethylation

ADP-ribosyltransferase diphtheria-toxin like 1/poly(ADP-ribose) polymerase 1 (ARTD1/PARP1) is a chromatin-associated protein in the nucleus and plays an important role in different cellular processes such as regulation of gene transcription. ARTD1 has been shown to coregulate the inflammatory response by modulating the activity of the transcription factor nuclear factor κB (NF-κB), the principal regulator of interleukin 6 (IL-6), an important inflammatory cytokine implicated in a variety of diseases such as cancer. However, to what extent and how ARTD1 regulates IL-6 transcription has not been clear. Here, we show that ARTD1 suppresses lipopolysaccharide (LPS)-induced IL-6 expression in macrophages, without affecting the recruitment of the NF-κB subunit RelA to the IL-6 promoter and independent of its enzymatic activity. Interestingly, knockdown of ARTD1 did not alter H3 occupancy but increased LPS-induced trimethylation of histone 3 at lysine 4 (H3K4me3), a hallmark of transcriptionally active genes. We found that ARTD1 mediates its effect through the methyltransferase MLL1, by catalyzing H3K4me3 at the IL-6 promoter and forming a complex with NF-κB. These results demonstrate that ARTD1 modulates IL-6 expression by regulating the function of an NF-κB enhanceosome complex, which involves MLL1 and does not require ADP-ribosylation.

Protective effects of sirtuins in cardiovascular diseases: from bench to bedside

Sirtuins (Sirt1–Sirt7) comprise a family of nicotinamide adenine dinucleotide (NAD⁺)-dependent enzymes. While deacetylation reflects their main task, some of them have deacylase, adenosine diphosphate-ribosylase, demalonylase, glutarylase, and desuccinylase properties. Activated upon caloric restriction and exercise, they control critical cellular processes in the nucleus, cytoplasm, and mitochondria to maintain metabolic homeostasis, reduce cellular damage and dampen inflammation—all of which serve to protect against a variety of age-related diseases, including cardiovascular pathologies. This review focuses on the cardiovascular effects of Sirt1, Sirt3, Sirt6, and Sirt7. Most is known about Sirt1. This deacetylase protects from endothelial dysfunction, atherothrombosis, diet-induced obesity, type 2 diabetes, liver steatosis, and myocardial infarction. Sirt3 provides beneficial effects in the context of left ventricular hypertrophy, cardiomyopathy, oxidative stress, metabolic homeostasis, and dyslipidaemia. Sirt6 is implicated in ameliorating dyslipidaemia, cellular senescence, and left ventricular hypertrophy. Sirt7 plays a role in lipid metabolism and cardiomyopathies. Most of these data were derived from experimental findings in genetically modified mice, where NFκB, Pcsk9, low-density lipoprotein-receptor, PPARγ, superoxide dismutase 2, poly[adenosine diphosphate-ribose] polymerase 1, and endothelial nitric oxide synthase were identified among others as crucial molecular targets and/or partners of sirtuins. Of note, there is translational evidence for a role of sirtuins in patients with endothelial dysfunction, type 1 or type 2 diabetes and longevity. Given the availability of specific Sirt1 activators or pan-sirtuin activators that boost levels of the sirtuin cofactor NAD⁺, we anticipate that this field will move quickly from bench to bedside.

Nuclear ADP-Ribosylation and Its Role in Chromatin Plasticity, Cell Differentiation, and Epigenetics

Protein ADP-ribosylation is an ancient posttranslational modification with high biochemical complexity. It alters the function of modified proteins or provides a scaffold for the recruitment of other proteins and thus regulates several cellular processes. ADP-ribosylation is governed by ADP-ribosyltransferases and a subclass of sirtuins (writers), is sensed by proteins that contain binding modules (readers) that recognize specific parts of the ADP-ribosyl posttranslational modification, and is removed by ADP-ribosylhydrolases (erasers). The large amount of experimental data generated and technical progress made in the last decade have significantly advanced our knowledge of the function of ADP-ribosylation at the molecular level. This review summarizes the current knowledge of nuclear ADP-ribosylation reactions and their role in chromatin plasticity, cell differentiation, and epigenetics and discusses current progress and future perspectives.

PARP1 during embryo implantation and its upregulation by oestradiol in mice

Pregnancy requires successful implantation of an embryo, which occurs during a restricted period defined as ‘receptivity of the endometrium’ and is influenced by the ovarian steroids progesterone and oestradiol. The role of poly(ADP-ribose)polymerase-1 (PARP1) in apoptosis is well established. However, it is also involved in cell differentiation, proliferation and tissue remodelling. Previous studies have described the presence of PARP in the uterus, but its exact role in embryo implantation is not yet elucidated. Hence, in this study, we studied the expression of PARP1 in the uterus during embryo implantation and decidualisation, and its regulation by ovarian steroids. Our results show upregulation of the native form of PARP1 (∼116 kDa) in the cytosolic and nuclear compartments of implantation and non-implantation sites at day 5 (0500 h), followed by downregulation at day 5 (1000 h), during the embryo implantation period. The transcript level of Parp1 was also augmented during day 5 (0500 h). Inhibition of PARP1 activity by the drug EB-47 decreased the number of embryo implantation sites and blastocysts at day 5 (1000 h). Further, cleavage of native PARP1 was due to the activity of caspase-3 during the peri-implantation stage (day 5 (0500 h)), and is also required for embryo implantation, as inhibition of its activity compromised blastocyst implantation. The native (∼116 kDa) and cleaved (∼89 kDa) forms of PARP1 were both elevated during decidualisation of the uterus. Furthermore, the expression level of PARP1 in the uterus was found to be under the control of the hormone oestrogen. Our results clearly demonstrate that PARP1 participates in the process of embryo implantation.

Daidzein suppresses pro-inflammatory chemokine Cxcl2 transcription in TNF-α-stimulated murine lung epithelial cells via depressing PARP-1 activity

AIM

Daidzein (4',7-dihydroxyisoflavone) is an isoflavone exiting in many herbs that has shown anti-inflammation activity. The aim of this study was to investigate the mechanism underlying its anti-inflammatory action in murine lung epithelial cells.

METHODS

C57BL/6 mice were intranasally exposed to TNF-α to induce lung inflammation. The mice were injected with daidzein (400 mg/kg, ip) before TNF-α challenge, and sacrificed 12 h after TNF-α challenge, and lung tissues were collected for analyisis. In in vitro studies, murine MLE-12 epithelial cells were treated with TNF-α (20 ng/mL). The expression of pro-inflammatory chemokine Cxcl2 mRNA and NF-κB transcriptional activity were examined using real-time PCR and a dual reporter assay. Protein poly-adenosine diphosphate-ribosylation (PARylation) was detecyed using Western blotting and immunoprecipitation assays.

RESULTS

Pretreatment of the mice with daidzein markedly attenuated TNF-α-induced lung inflammation, and inhibited Cxcl2 expression in lung tissues. Furthermore, daidzein (10 μmol/L) prevented TNF-α-induced increases in Cxcl2 expression and activity and NF-κB transcriptional activity, and markedly inhibited TNF-α-induced protein PARylation in MLE-12 cells in vitro. In MLE-12 cells co-transfected with the PARP-1 expression plasmid and NF-κB-luc (or Cxcl2-luc) reporter plasmid, TNF-α markedly increased NF-κB (or Cxcl2) activation, which were significantly attenuated in the presence of daidzein (or the protein PARylation inhibitor PJ 34). PARP-1 activity assay showed that daidzein (10 μmol/L) reduced the activity of PARP-1 by ∼75%.

CONCLUSION

The anti-inflammatory action of daidzein in murine lung epithelial cells seems to be mediated via a direct interaction with PARP-1, which inhibits RelA/p65 protein PARylation required for the transcriptional modulation of pro-inflammatory chemokines such as Cxcl2.

Endothelial overexpression of LOX-1 increases plaque formation and promotes atherosclerosis in vivo

AIMS

Lectin-like oxLDL receptor-1 (LOX-1) mediates the uptake of oxidized low-density lipoprotein (oxLDL) in endothelial cells and macrophages. However, the different atherogenic potential of LOX-1-mediated endothelial and macrophage oxLDL uptake remains unclear. The present study was designed to investigate the in vivo role of endothelial LOX-1 in atherogenesis.

METHODS AND RESULTS

Endothelial-specific LOX-1 transgenic mice were generated using the Tie2 promoter (LOX-1TG). Oxidized low-density lipoprotein uptake was enhanced in cultured endothelial cells, but not in macrophages of LOX-1TG mice. Six-week-old male LOX-1TG and wild-type (WT) mice were fed a high-cholesterol diet (HCD) for 30 weeks. Increased reactive oxygen species production, impaired endothelial nitric oxide synthase activity and endothelial dysfunction were observed in LOX-1TG mice as compared with WT littermates. LOX-1 overexpression led to p38 phosphorylation, increased nuclear factor κB activity and subsequent up-regulation of vascular cell adhesion molecule-1, thereby favouring macrophage accumulation and aortic fatty streaks. Consistently, HCD-fed double-mutant LOX-1TG/ApoE(-/-) displayed oxidative stress and vascular inflammation with higher aortic plaques than ApoE(-/-) controls. Finally, bone marrow transplantation experiments showed that endothelial LOX-1 was sufficient for atherosclerosis development in vivo.

CONCLUSIONS

Endothelial-specific LOX-1 overexpression enhanced aortic oxLDL levels, thereby favouring endothelial dysfunction, vascular inflammation and plaque formation. Thus, LOX-1 may serve as a novel therapeutic target for atherosclerosis.

Deletion of Sirt3 does not affect atherosclerosis but accelerates weight gain and impairs rapid metabolic adaptation in LDL receptor knockout mice: implications for cardiovascular risk factor development

Sirt3 is a mitochondrial NAD(+)-dependent deacetylase that governs mitochondrial metabolism and reactive oxygen species homeostasis. Sirt3 deficiency has been reported to accelerate the development of the metabolic syndrome. However, the role of Sirt3 in atherosclerosis remains enigmatic. We aimed to investigate whether Sirt3 deficiency affects atherosclerosis, plaque vulnerability, and metabolic homeostasis. Low-density lipoprotein receptor knockout (LDLR(-/-)) and LDLR/Sirt3 double-knockout (Sirt3(-/-)LDLR(-/-)) mice were fed a high-cholesterol diet (1.25 % w/w) for 12 weeks. Atherosclerosis was assessed en face in thoraco-abdominal aortae and in cross sections of aortic roots. Sirt3 deletion led to hepatic mitochondrial protein hyperacetylation. Unexpectedly, though plasma malondialdehyde levels were elevated in Sirt3-deficient mice, Sirt3 deletion affected neither plaque burden nor features of plaque vulnerability (i.e., fibrous cap thickness and necrotic core diameter). Likewise, plaque macrophage and T cell infiltration as well as endothelial activation remained unaltered. Electron microscopy of aortic walls revealed no difference in mitochondrial microarchitecture between both groups. Interestingly, loss of Sirt3 was associated with accelerated weight gain and an impaired capacity to cope with rapid changes in nutrient supply as assessed by indirect calorimetry. Serum lipid levels and glucose tolerance were unaffected by Sirt3 deletion in LDLR(-/-) mice. Sirt3 deficiency does not affect atherosclerosis in LDLR(-/-) mice. However, Sirt3 controls systemic levels of oxidative stress, limits expedited weight gain, and allows rapid metabolic adaptation. Thus, Sirt3 may contribute to postponing cardiovascular risk factor development.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

Poly(ADP-ribose) polymerase 1 (PARP1) in atherosclerosis: from molecular mechanisms to therapeutic implications

Poly(ADP-ribosyl)ation reactions, carried out by poly(ADP-ribose) polymerases (PARPs/ARTDs), are reversible posttranslational modifications impacting on numerous cellular processes (e.g., DNA repair, transcription, metabolism, or immune functions). PARP1 (EC 2.4.2.30), the founding member of PARPs, is particularly important for drug development for its role in DNA repair, cell death, and transcription of proinflammatory genes. Recent studies have established a novel concept that PARP1 is critically involved in the formation and destabilization of atherosclerotic plaques in experimental animal models and in humans. Reduction of PARP1 activity by pharmacological or molecular approaches attenuates atherosclerotic plaque development and enhances plaque stability as well as promotes the regression of pre-established atherosclerotic plaques. Mechanistically, PARP1 inhibition significantly reduces monocyte differentiation, macrophage recruitment, Sirtuin 1 (SIRT1) inactivation, endothelial dysfunction, neointima formation, foam cell death, and inflammatory responses within plaques, all of which are central to the pathogenesis of atherosclerosis. This article presents an overview of the multiple roles and underlying mechanisms of PARP1 activation (poly(ADP-ribose) accumulation) in atherosclerosis and emphasizes the therapeutic potential of PARP1 inhibition in preventing or reversing atherosclerosis and its cardiovascular clinical sequalae.

Systemic VEGF inhibition accelerates experimental atherosclerosis and disrupts endothelial homeostasis--implications for cardiovascular safety

OBJECTIVES

This study sought to examine the effects and underlying mechanisms of systemic VEGF inhibition in experimental atherosclerosis and aortic endothelial cells.

BACKGROUND

Pharmacological inhibition of vascular endothelial growth factor (VEGF), a major mediator of angiogenesis, has become a widely applied treatment of certain cancers and multiple ocular diseases including age-related macular degeneration. However, recent clinical trials raise concern for systemic vascular adverse effects, prompting the Food and Drug Administration to revoke the approval of bevacizumab for metastatic breast cancer.

METHODS

Eight-week old apolipoprotein E knockout mice received a high-cholesterol diet (1.25% cholesterol) for 24 weeks and were exposed to a systemic pan-VEGF receptor inhibitor (PTK787/ZK222584, 50mg/kg/d) or placebo (gavage) for the last 10 weeks. Atherosclerotic lesions were characterized in thoraco-abdominal aortae and aortic arches. Mechanistic analyses were performed in cultured human aortic endothelial cells.

RESULTS

Systemic VEGF inhibition increased atherosclerotic lesions by 33% whereas features of plaque vulnerability (i.e. necrotic core size, fibrous cap thickness) remained unchanged compared with controls. Aortic eNOS expression was decreased (trend). In human endothelial cells VEGF inhibition induced a dose-dependent increase in mitochondrial superoxide generation with an uncoupling of eNOS, resulting in reduced NO availability and decreased proliferation.

CONCLUSION

Systemic VEGF inhibition disrupts endothelial homeostasis and accelerates atherogenesis, suggesting that these events contribute to the clinical cardiovascular adverse events of VEGF-inhibiting therapies. Cardiovascular safety profiles of currently applied anti-angiogenic regimens should be determined to improve patient selection for therapy and allow close monitoring of patients at increased cardiovascular risk.

AMPKα2 exerts its anti-inflammatory effects through PARP-1 and Bcl-6

B-cell lymphoma-6 protein (Bcl-6) is a corepressor for inflammatory mediators such as vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 and -3, which function to recruit monocytes to vascular endothelial cells upon inflammation. Poly [ADP ribose] polymerase 1 (PARP-1) is proinflammatory, in part through its binding at the Bcl-6 intron 1 to suppress Bcl-6 expression. We investigated the mechanisms by which PARP-1 dissociates from the Bcl-6 intron 1, ultimately leading to attenuation of endothelial inflammation. Analysis of the PARP-1 primary sequence suggested that phosphorylation of PARP-1 Serine 177 (Ser-177) by AMP-activated protein kinase (AMPK) is responsible for the induction of Bcl-6. Our results show that AMPK activation with treatment of 5-aminoimidazole-4-carboxamide ribonucleotide, metformin, or pulsatile shear stress induces PARP-1 dissociation from the Bcl-6 intron 1, increases Bcl-6 expression, and inhibits expression of inflammatory mediators. Conversely, AMPKα suppression or knockdown produces the opposite effects. The results demonstrate an anti-infamatory pathway linking AMPK, PARP-1, and Bcl-6 in endothelial cells.

PARP-1 and gene regulation: progress and puzzles

Poly(ADP-ribose) polymerase-1 (PARP-1), also referred to as ADP-ribosyltransferase Diphtheria toxin-like 1 (ARTD1), is an abundant nuclear protein that plays key roles in a variety of nuclear processes, including the regulation of transcription. PARP-1 possesses an intrinsic enzymatic activity that catalyzes the transfer of ADP-ribose (ADPR) units from nicotinamide adenine dinucleotide (NAD(+)) onto target gene regulatory proteins, thereby modulating their activities. Although great strides have been made in the past decade in deciphering the seemingly opposing and varied roles of PARP-1 in gene regulation, many puzzles remain. In this review, we discuss the current state of understanding in this area, especially how PARP-1 interfaces with various components of gene regulatory pathways (e.g., the basal transcription machinery, DNA-binding transcription factors, coregulators, chromatin remodeling, histone modifications, and DNA methylation). In addition, we discuss some gene-specific, cell type-specific, and cell state-specific effects of PARP-1 on gene regulation, which might contribute to its biological functions. Finally, we review some of the recent progress targeting PARPs using chemical inhibitors, some of which may alter PARP-1-dependent gene regulatory programs to promote therapeutic outcomes.

Racial and tissue-specific cancer risk associated with PARP1 (ADPRT) Val762Ala polymorphism: a meta-analysis

The Val762Ala polymorphism poly [ADP-ribose] polymerase 1 (PARP1) gene [ADPRT (adenosine diphosphate ribosyltransferase) gene] affects enzymatic activity, which modulates cancer susceptibility among human populations. Individual data on 13,745 cases and 16,947 controls from 28 published case-control studies were re-evaluated. Odds ratios (OR) were estimated for ethnic group, cancer type, smoking joint effects and studies confined to the Hardy-Weinberg equilibrium. We applied subgroup, sensitivity and outlier analyses as well as the Bonferroni correction for multiple testing. The results show strong evidence that the variant (C) allele confers significant increased risk in the Chinese (OR 1.20-1.44, P < 0.0001-0.002), exacerbated by smoking (OR 1.66-2.53, P < 0.0001) and joint interaction with XRCC1 Arg399Gln (OR 1.39, P < 0.0001) as well as adjustment for tumor type (gastric carcinoma ORs 1.39-2.01, P < 0.0001). These significant effects were unaltered following conservative correction for multiple tests. By contrast, this procedure erased the protective significance in Caucasians, but not in two American subgroups, (i) those in the brain tumor category (0.77-0.79, P < 0.0001) and (ii) smokers in the dominant model (OR 0.86, P < 0.0001). These differential findings between the two ethnicities maybe correlated with significantly (P < 0.0001) greater allele frequency of the variant allele (C) among the Chinese compared to Caucasians. Our racial and tissue-specific summary estimates imply consideration of the Val762Ala polymorphism as candidate gene marker for screening cancer patients' best suited for PARP inhibitor therapy.

Pleiotropic cellular functions of PARP1 in longevity and aging: genome maintenance meets inflammation

Aging is a multifactorial process that depends on diverse molecular and cellular mechanisms, such as genome maintenance and inflammation. The nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP1), which catalyzes the synthesis of the biopolymer poly(ADP-ribose), exhibits an essential role in both processes. On the one hand, PARP1 serves as a genomic caretaker as it participates in chromatin remodelling, DNA repair, telomere maintenance, resolution of replicative stress, and cell cycle control. On the other hand, PARP1 acts as a mediator of inflammation due to its function as a regulator of NF-κB and other transcription factors and its potential to induce cell death. Consequently, PARP1 represents an interesting player in several aging mechanisms and is discussed as a longevity assurance factor on the one hand and an aging-promoting factor on the other hand. Here, we review the molecular mechanisms underlying the various roles of PARP1 in longevity and aging with special emphasis on cellular studies and we briefly discuss the results in the context of in vivo studies in mice and humans.

Neutrophil recruitment is inhibited by nicotinamide in experimental pleurisy in mice

Several emerging lines of evidence support an anti-inflammatory role for nicotinamide and other vitamin B components. However, the mechanisms underlying their activity remain unclear. In the present study, we investigated the ability of nicotinamide to inhibit both neutrophil recruitment in IL-8-, LTB(4)- or carrageenan-induced pleurisy in mice and the rolling and adherence of neutrophils. Nicotinamide inhibited IL-8-, LTB(4)- and carrageenan-induced neutrophil migration, KC production and carrageenan-induced neutrophil rolling and adherence. We propose that the effects of nicotinamide in inhibiting neutrophil recruitment in carrageenan-induced pleurisy may be due to the ability of nicotinamide to inhibit the action of IL-8 and LTB(4), decrease KC production, and inhibit early events that regulate leukocyte migration from blood vessels into tissue.

Lipopolysaccharide activates ERK-PARP-1-RelA pathway and promotes nuclear factor-κB transcription in murine macrophages

Poly(ADP-ribosyl)ation, like acetylation, methylation and phosphorylation, is one of the essential post-translational protein modifications. Poly(ADP-ribose) polymerase 1 (PARP-1), the best characterized member of the PARP family, catalyzes PAR formation, and has been implemented in the in vivo and in vitro inflammatory disease models. However, the exact signaling pathways leading to PARP-1 activation and the molecular mechanisms of activated PARP-1 signaling of inflammatory genes' expression remains to be further elucidated. In the present study, murine macrophages, in vitro stimulated with lipopolysaccharide (LPS), showed a profound activation of PARP-1, and PARP-1-dependent expression of mRNA for interleukin (IL)-1β and IL-18 inflammatory cytokines. Immunoprecipitation assays showed that LPS stimulation enhanced the binding of PARP-1 with p65 (RelA) and poly(ADP-ribosyl)ation of p65, which might account for the upregulated transcription activity of nuclear factor (NF)-κB and the increased expression of proinflammatory genes. The application of various signal pathway inhibitors revealed that besides the canonical ROS-DNA damage signal, ERK pathway modulated the activation of PARP-1. ERK inhibitor blocked the interaction of PARP-1 with ERK1/2, phosphorylation of PARP-1, and poly(ADP-ribosyl)ation of p65, suggesting that ERK-dependent phosphorylation of PARP-1 regulates PARP-1 activity and NF-κB activation. Taken together, our results suggest that an ERK-PARP-1-RelA pathway in macrophages promote inflammatory progression in septic diseases.

Cardiac and vascular phenotypes in the apolipoprotein E-deficient mouse

Cardiovascular death is frequently associated with atherosclerosis, a chronic multifactorial disease and a leading cause of death worldwide. Genetically engineered mouse models have proven useful for the study of the mechanisms underlying cardiovascular diseases. The apolipoprotein E-deficient mouse has been the most widely used animal model of atherosclerosis because it rapidly develops severe hypercholesterolemia and spontaneous atherosclerotic lesions similar to those observed in humans. In this review, we provide an overview of the cardiac and vascular phenotypes and discuss the interplay among nitric oxide, reactive oxygen species, aging and diet in the impairment of cardiovascular function in this mouse model.

PARP inhibition in atherosclerosis and its effects on dendritic cells, T cells and auto-antibody levels

Objective

Atherosclerosis is a chronic inflammatory process. Poly(ADP-ribose) polymerase-1 (PARP), a nuclear enzyme linked to DNA repair, has been shown to be involved in atherogenesis; however, the effects on dendritic cells, T cells and serum auto-antibody levels are not fully understood.

Methods

Male Apoe^-/- mice on a western diet were treated with the PARP inhibitor 1NO-1001 (n = 15), while the control group (n = 15) received 5% glucose solution for 10 weeks.

Results

Inhibition of PARP markedly reduced atherosclerotic lesion development (p = 0.001). Immunohistochemistry and mRNA analysis revealed a reduced inflammatory compound inside the lesion. Focusing on dendritic cells, INO-1001 reduced number of cells (p = 0.04), grade of activation, represented by I/12 (p = 0.04) and Cd83 (p = 0.03), and grade of attraction, represented by Mip3α (p = 0.02) in the plaque. Furthermore, INO-1001 decreased number of T lymphocyte (p = 0.003) in the lesion and grade of activation after stimulation with oxLDL in vitro. Moreover, serum IgM antibody levels to oxLDL were significantly lower in INO-1001 treated mice (p = 0.03).

Conclusions

Functional blockade of PARP by INO-1001 reduces atherosclerotic lesion development. The anti-atherogenic effect is beside already known mechanisms also moderated due to modulation of DC and T cell invasion and activation, DC attraction as well as IgM antibody levels to oxLDL.

Signaling mechanism of poly(ADP-ribose) polymerase-1 (PARP-1) in inflammatory diseases

Poly(ADP-ribosyl)ation, attaching the ADP-ribose polymer chain to the receptor protein, is a unique posttranslational modification. Poly(ADP-ribose) polymerase-1 (PARP-1) is a well-characterized member of the PARP family. In this review, we provide a general update on molecular structure and structure-based activity of this enzyme. However, we mainly focus on the roles of PARP-1 in inflammatory diseases. Specifically, we discuss the signaling pathway context that PARP-1 is involved in to regulate the pathogenesis of inflammation. PARP-1 facilitates diverse inflammatory responses by promoting inflammation-relevant gene expression, such as cytokines, oxidation-reduction-related enzymes, and adhesion molecules. Excessive activation of PARP-1 induces mitochondria-associated cell death in injured tissues and constitutes another mechanism for exacerbating inflammation.

Age related changes in NAD+ metabolism oxidative stress and Sirt1 activity in wistar rats

The cofactor nicotinamide adenine dinucleotide (NAD+) has emerged as a key regulator of metabolism, stress resistance and longevity. Apart from its role as an important redox carrier, NAD+ also serves as the sole substrate for NAD-dependent enzymes, including poly(ADP-ribose) polymerase (PARP), an important DNA nick sensor, and NAD-dependent histone deacetylases, Sirtuins which play an important role in a wide variety of processes, including senescence, apoptosis, differentiation, and aging. We examined the effect of aging on intracellular NAD+ metabolism in the whole heart, lung, liver and kidney of female wistar rats. Our results are the first to show a significant decline in intracellular NAD+ levels and NAD:NADH ratio in all organs by middle age (i.e.12 months) compared to young (i.e. 3 month old) rats. These changes in [NAD(H)] occurred in parallel with an increase in lipid peroxidation and protein carbonyls (o- and m- tyrosine) formation and decline in total antioxidant capacity in these organs. An age dependent increase in DNA damage (phosphorylated H2AX) was also observed in these same organs. Decreased Sirt1 activity and increased acetylated p53 were observed in organ tissues in parallel with the drop in NAD+ and moderate over-expression of Sirt1 protein. Reduced mitochondrial activity of complex I-IV was also observed in aging animals, impacting both redox status and ATP production. The strong positive correlation observed between DNA damage associated NAD+ depletion and Sirt1 activity suggests that adequate NAD+ concentrations may be an important longevity assurance factor.

Dietary α-linolenic acid diminishes experimental atherogenesis and restricts T cell-driven inflammation

Aims

Epidemiological studies report an inverse association between plant-derived dietary α-linolenic acid (ALA) and cardiovascular events. However, little is known about the mechanism of this protection. We assessed the cellular and molecular mechanisms of dietary ALA (flaxseed) on atherosclerosis in a mouse model.

Methods and results

Eight-week-old male apolipoprotein E knockout (ApoE^−/−) mice were fed a 0.21 % (w/w) cholesterol diet for 16 weeks containing either a high ALA [7.3 % (w/w); n = 10] or low ALA content [0.03 % (w/w); n = 10]. Bioavailability, chain elongation, and fatty acid metabolism were measured by gas chromatography of tissue lysates and urine. Plaques were assessed using immunohistochemistry. T cell proliferation was investigated in primary murine CD3-positive lymphocytes. T cell differentiation and activation was assessed by expression analyses of interferon-γ, interleukin-4, and tumour necrosis factor α (TNFα) using quantitative PCR and ELISA. Dietary ALA increased aortic tissue levels of ALA as well as of the n−3 long chain fatty acids (LC n−3 FA) eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid. The high ALA diet reduced plaque area by 50% and decreased plaque T cell content as well as expression of vascular cell adhesion molecule-1 and TNFα. Both dietary ALA and direct ALA exposure restricted T cell proliferation, differentiation, and inflammatory activity. Dietary ALA shifted prostaglandin and isoprostane formation towards 3-series compounds, potentially contributing to the atheroprotective effects of ALA.

Conclusion

Dietary ALA diminishes experimental atherogenesis and restricts T cell-driven inflammation, thus providing the proof-of-principle that plant-derived ALA may provide a valuable alternative to marine LC n−3 FA.

PARP-1 cleavage fragments: signatures of cell-death proteases in neurodegeneration

The normal function of poly (ADP-ribose) polymerase-1 (PARP-1) is the routine repair of DNA damage by adding poly (ADP ribose) polymers in response to a variety of cellular stresses. Recently, it has become widely appreciated that PARP-1 also participates in diverse physiological and pathological functions from cell survival to several forms of cell death and has been implicated in gene transcription, immune responses, inflammation, learning, memory, synaptic functions, angiogenesis and aging. In the CNS, PARP inhibition attenuates injury in pathologies like cerebral ischemia, trauma and excitotoxicity demonstrating a central role of PARP-1 in these pathologies. PARP-1 is also a preferred substrate for several 'suicidal' proteases and the proteolytic action of suicidal proteases (caspases, calpains, cathepsins, granzymes and matrix metalloproteinases (MMPs)) on PARP-1 produces several specific proteolytic cleavage fragments with different molecular weights. These PARP-1 signature fragments are recognized biomarkers for specific patterns of protease activity in unique cell death programs. This review focuses on specific suicidal proteases active towards PARP-1 to generate signature PARP-1 fragments that can identify key proteases and particular forms of cell death involved in pathophysiology. The roles played by some of the PARP-1 fragments and their associated binding partners in the control of different forms of cell death are also discussed.

Helicobacter pylori activation of PARP-1: usurping a versatile regulator of host cellular health

Chronic infection of the human stomach by Helicobacter pylori is an important risk factor for gastric cancer. H. pylori produces a cache of virulence factors that promote colonization and persistence, which, in turn, contributes to a robust inflammatory response at the host-pathogen interface. Recently, we reported that H. pylori activates the abundant nuclear regulator poly(ADP-ribose) polymerase (PARP)-1, resulting in the production of the catabolite poly(ADP-ribose) (PAR). PARP-1 is emerging as a key player in establishing homeostasis at the host-pathogen interface. In this article, we summarize the discovery of H. pylori-dependent PARP-1 activation, and discuss potential roles for PARP-1 in H. pylori-mediated gastric disease. In light of the remarkable successes that have reported for treating inflammatory disorders and cancers with PARP-1 inhibitors, we discuss the prospects of targeting PARP-1 for treatment of H. pylori-associated gastric disease.

Correction of CNS defects in the MPSII mouse model via systemic enzyme replacement therapy

Mucopolysaccharidosis type II (MPSII), or Hunter syndrome, is a devastating disorder associated with a shortened life expectancy. Patients affected by MPSII have a variety of symptoms that affect all organs of the body and may include progressive cognitive impairment. MPSII is due to inactivity of the enzyme iduronate-2-sulfatase (IDS), which results in the accumulation of storage material in the lysosomes, such as dermatan and heparan sulfates, with consequent cell degeneration in all tissues including, in the severe phenotype, neurodegeneration in the central nervous system (CNS). To date, the only treatment available is systemic infusion of IDS, which ameliorates exclusively certain visceral defects. Therefore, it is important to simultaneously treat the visceral and CNS defects of the MPSII patients. Here, we have developed enzyme replacement therapy (ERT) protocols in a mouse model that allow the IDS to reach the brain, with the substantial correction of the CNS phenotype and of the neurobehavioral features. Treatments were beneficial even in adult and old MPSII mice, using relatively low doses of infused IDS over long intervals. This study demonstrates that CNS defects of MPSII mice can be treated by systemic ERT, providing the potential for development of an effective treatment for MPSII patients.

Regulatory role of mitochondria in oxidative stress and atherosclerosis

Mitochondrial physiology and biogenesis play a crucial role in the initiation and progression of cardiovascular disease following oxidative stress-induced damage such as atherosclerosis (AST). Dysfunctional mitochondria caused by an increase in mitochondrial reactive oxygen species (ROS) production, accumulation of mitochondrial DNA damage, and respiratory chain deficiency induces death of endothelial/smooth muscle cells and favors plaque formation/rupture via the regulation of mitochondrial biogenesis-related genes such as peroxisome proliferator-activated receptor γ coactivator (PGC-1), although more detailed mechanisms still need further study. Based on the effect of healthy mitochondria produced by mitochondrial biogenesis on decreasing ROS-mediated cell death and the recent finding that the regulation of PGC-1 involves mitochondrial fusion-related protein (mitofusin), we thus infer the regulatory role of mitochondrial fusion/fission balance in AST pathophysiology. In this review, the first section discusses the possible association between AST-inducing factors and the molecular regulatory mechanisms of mitochondrial biogenesis and dynamics, and explains the role of mitochondria-dependent regulation in cell apoptosis during AST development. Furthermore, nitric oxide has the Janus-faced effect by protecting vascular damage caused by AST while being a reactive nitrogen species (RNS) which act together with ROS to damage cells. Therefore, in the second section we discuss mitochondrial ATP-sensitive K(+) channels, which regulate mitochondrial ion transport to maintain mitochondrial physiology, involved in the regulation of ROS/RNS production and their influence on AST/cardiovascular diseases (CVD). Through this review, we can further appreciate the multi-regulatory functions of the mitochondria involved in AST development. The understanding of these related mechanisms will benefit drug development in treating AST/CVD through targeted biofunctions of mitochondria.

Opposing roles of PARP-1 in MMP-9 and TIMP-2 expression and mast cell degranulation in dyslipidemic dilated cardiomyopathy

INTRODUCTION

Previously, we demonstrated that inhibition of poly(ADP-ribose) polymerase (PARP) exerts protective effects against high-fat (HF) diet-induced atherogenesis in part by increasing tissue inhibitor of metalloproteinase (TIMP)-2 expression. Given that characteristics of dilated cardiomyopathy closely associate with atherosclerosis and are mediated by an imbalance between matrix metalloproteinases (MMPs) and TIMPs, we hypothesized that PARP-1 gene deletion may protect against HF-induced cardiac hypertrophy and dilatations by altering TIMP-2/MMPs balance in favor of a maintenance of tissue homeostasis.

METHODS AND RESULTS

Hemodynamic parameters determined by echocardiography were similar in ApoE(-/-) mice and PARP-1-deficient ApoE(-/-) mice (DKO) fed a regular diet (RD). However, histological analysis revealed that cardiomyocytes of ApoE(-/-) mice on RD were hypertrophied, displaying an enlarged cell body and nucleus, traits that were absent in DKO animals. HF diet-fed ApoE(-/-) mice exhibited increased interventricular septum, left ventricular (LV) internal dimension, LV volume, and LV mass in addition to a separation of myocardial fibers suggestive of dilated cardiomyopathy. PARP-1 gene deletion protected against these degenerative changes. MMP activity was dramatically increased in hearts of ApoE(-/-) mice on HF diet and was accompanied by increased collagen degradation, mast cell degranulation, and increased myocyte cell death. PARP-1 gene knockout was associated with increased TIMP-2 expression antagonizing, as a result, the damaging effects of active MMPs.

CONCLUSIONS

The present study demonstrates that PARP-1 gene deletion exerts protective effects against HF diet-induced dilated cardiomyopathy by maintaining increased expression of TIMP-2. With additional protective effects against cell death and inflammation, PARP-1 deficiency preserves cardiac tissue homeostasis.