Paraoxonase 2 prevents the development of heart failure

Pleiotropic functions and clinical importance of circulating HDL-PON1 complex

High density lipoprotein (HDL) functions are mostly mediated through a complex proteome, particularly its enzymes. HDL can provide a scaffold for the assembly of several proteins that affect each other's function. HDL particles, particularly small, dense HDL3, are rich in paraoxonase 1 (PON1), which is an important enzyme in the functionality of HDL, so the antioxidant and antiatherogenic properties of HDL are largely attributed to this enzyme. There is an increasing need to represent a valid, reproducible, and reliable method to assay HDL function in routine clinical laboratories. In this context, HDL-associated proteins may be key players; notably PON1 activity (its arylesterase activity) may be a proper candidate because its decreased activity can be considered an important risk factor for HDL dysfunctionality. Of note, automated methods have been developed for the measurement of serum PON1 activity that facilitates its assay in large sample numbers. Arylesterase activity is proposed as a preferred activity among the different activities of PON1 for its assay in epidemiological studies. The binding of PON1 to HDL is critical for the maintenance of its activity and it appears apolipoprotein A-I plays an important role in HDL-PON1 interaction as well as in the biochemical and enzymatic properties of PON1. The interrelationships between HDL, PON1, and HDL's other components are complex and incompletely understood. The purpose of this review is to discuss biochemical and clinical evidence considering the interactions of PON1 with HDL and the role of this enzyme as an appropriate biomarker for HDL function as well as a potential therapeutic target.

Paraoxonase 2 Deficiency Causes Mitochondrial Dysfunction in Retinal Pigment Epithelial Cells and Retinal Degeneration in Mice

Although AMD is a complex disease, oxidative stress is a crucial contributor to its development, especially in view of the higher oxygen demand of the retina. Paraoxonase 2 (PON2) is a ubiquitously and constitutively expressed antioxidant protein that is found intracellularly associated with mitochondrial membranes and modulates mitochondrial ROS production and function. The contribution of PON2 to AMD has not been studied to date. In this study, we examined the role of PON2 in AMD utilizing both in vitro and in vivo models of AMD with emphasis on mitochondrial function. Mitochondrial localization and regulation of PON2 following oxidative stress were determined in human primary cultured retinal pigment epithelium (hRPE) cells. PON2 was knocked down in RPE cells using siRNA and mitochondrial bioenergetics were measured. To investigate the function of PON2 in the retina, WT and PON2-deficient mice were administered NaIO3 (20 mg/kg) intravenously; fundus imaging, optical coherence tomography (OCT), electroretinography (ERG) were conducted; and retinal thickness and cell death were measured and quantified. In hRPE, mitochondrial localization of PON2 increased markedly with stress. Moreover, a time-dependent regulation of PON2 was observed following oxidative stress, with an initial significant increase in expression followed by a significant decrease. Mitochondrial bioenergetic parameters (basal respiration, ATP production, spare respiratory capacity, and maximal respiration) showed a significant decrease with oxidative stress, which was further exacerbated in the absence of PON2. NaIO3 treatment caused significant retinal degeneration, retinal thinning, and reduced rod and cone function in PON2-deficient mice when compared to WT mice. The apoptotic cells and active caspase 3 significantly increased in PON2-deficient mice treated with NaIO3, when compared to WT mice. Our investigation demonstrates that deficiency of PON2 results in RPE mitochondrial dysfunction and a decline in retinal function. These findings imply that PON2 may have a beneficial role in retinal pathophysiology and is worthy of further investigation.

Paraoxonases at the Heart of Neurological Disorders

Paraoxonase enzymes serve as an important physiological redox system that participates in the protection against cellular injury caused by oxidative stress. The PON enzymes family consists of three members (PON-1, PON-2, and PON-3) that share a similar structure and location as a cluster on human chromosome 7. These enzymes exhibit anti-inflammatory and antioxidant properties with well-described roles in preventing cardiovascular disease. Perturbations in PON enzyme levels and their activity have also been linked with the development and progression of many neurological disorders and neurodegenerative diseases. The current review summarizes the available evidence on the role of PONs in these diseases and their ability to modify risk factors for neurological disorders. We present the current findings on the role of PONs in Alzheimer's disease, Parkinson's disease, and other neurodegenerative and neurological diseases.

Thymidine Phosphorylase Deficiency or Inhibition Preserves Cardiac Function in Mice With Acute Myocardial Infarction

Background Ischemic cardiovascular disease is the leading cause of death worldwide. Current pharmacologic therapy has multiple limitations, and patients remain symptomatic despite maximal medical therapies. Deficiency or inhibition of thymidine phosphorylase (TYMP) in mice reduces thrombosis, suggesting that TYMP could be a novel therapeutic target for patients with acute myocardial infarction (AMI). Methods and Results A mouse AMI model was established by ligation of the left anterior descending coronary artery in C57BL/6J wild-type and TYMP-deficient (Tymp-/-) mice. Cardiac function was monitored by echocardiography or Langendorff assay. TYMP-deficient hearts had lower baseline contractility. However, cardiac function, systolic left ventricle anterior wall thickness, and diastolic wall strain were significantly greater 4 weeks after AMI compared with wild-type hearts. TYMP deficiency reduced microthrombus formation after AMI. TYMP deficiency did not affect angiogenesis in either normal or infarcted myocardium but increased arteriogenesis post-AMI. TYMP deficiency enhanced the mobilization of bone marrow stem cells and promoted mesenchymal stem cell (MSC) proliferation, migration, and resistance to inflammation and hypoxia. TYMP deficiency increased the number of larger MSCs and decreased matrix metalloproteinase-2 expression, resulting in a high homing capability. TYMP deficiency induced constitutive AKT phosphorylation in MSCs but reduced expression of genes associated with retinoid-interferon-induced mortality-19, a molecule that enhances cell death. Inhibition of TYMP with its selective inhibitor, tipiracil, phenocopied TYMP deficiency, improved post-AMI cardiac function and systolic left ventricle anterior wall thickness, attenuated diastolic stiffness, and reduced infarct size. Conclusions This study demonstrated that TYMP plays an adverse role after AMI. Targeting TYMP may be a novel therapy for patients with AMI.

PON2 ameliorates Ang II-induced cardiomyocyte injury by targeting the CANX/NOX4 signaling pathway

BACKGROUND

The incidence of heart failure (HF) presents an escalating trend annually, second only to cancer. Few literatures are available regarding on the role of paraoxonase 2 (PON2) in HF so far despite the protective role of PON2 in cardiovascular diseases.

METHODS

PON2 expression in AC16 cells was examined with reverse transcriptase-quantitative polymerase chain reaction and western blot following angiotensin II (Ang II) challenging. After PON2 elevation, 2, 7-dichlorofluorescein diacetate assay estimated reactive oxygen species content, related kits appraised oxidative stress, enzyme-linked immunosorbent assay evaluated inflammatory levels, and Western blot was applied to the analysis of apoptosis levels. Research on cytoskeleton was conducted by immunofluorescence (IF), and Western blot analysis of the expressions of hypertrophy-related proteins was performed. BioGRID and GeneMania databases were used to analyze the relationship between PON2 and Calnexin (CANX), which was corroborated by co-immunoprecipitation experiment. Subsequently, PON2 and CANX were simultaneously overexpressed in AC16 cells induced by Ang II to further figure out the mechanism.

RESULTS

PON2 expression was depleted in Ang II-induced AC16 cells. PON2 might mediate CANX/NOX4 signaling to inhibit oxidation, inflammatory, hypertrophy, and damage in Ang II-induced AC16 cells.

CONCLUSION

PON2 can ease Ang II-induced cardiomyocyte injury via targeting CANX/NOX4 signaling.

Highly Dynamic Gene Family Evolution Suggests Changing Roles for PON Genes Within Metazoa

Change in gene family size has been shown to facilitate adaptation to different selective pressures. This includes gene duplication to increase dosage or diversification of enzymatic substrates and gene deletion due to relaxed selection. We recently found that the PON1 gene, an enzyme with arylesterase and lactonase activity, was lost repeatedly in different aquatic mammalian lineages, suggesting that the PON gene family is responsive to environmental change. We further investigated if these fluctuations in gene family size were restricted to mammals and approximately when this gene family was expanded within mammals. Using 112 metazoan protein models, we explored the evolutionary history of the PON family to characterize the dynamic evolution of this gene family. We found that there have been multiple, independent expansion events in tardigrades, cephalochordates, and echinoderms. In addition, there have been partial gene loss events in monotremes and sea cucumbers and what appears to be complete loss in arthropods, urochordates, platyhelminths, ctenophores, and placozoans. In addition, we show the mammalian expansion to three PON paralogs occurred in the ancestor of all mammals after the divergence of sauropsida but before the divergence of monotremes from therians. We also provide evidence of a novel PON expansion within the brushtail possum. In the face of repeated expansions and deletions in the context of changing environments, we suggest a range of selective pressures, including pathogen infection and mitigation of oxidative damage, are likely influencing the diversification of this dynamic gene family across metazoa.

Examining the role of paraoxonase 2 in the dopaminergic system of the mouse brain

BACKGROUND

Paraoxonase 2 (PON2) is an intracellular antioxidant enzyme located at the inner mitochondrial membrane. Previous studies have found PON2 to be an important antioxidant in a variety of cellular systems, such as the cardiovascular and renal system. Recent work has also suggested that PON2 plays an important role in the central nervous system (CNS), as decreased PON2 expression in the CNS leads to higher oxidative stress and subsequent cell toxicity. However, the precise role of PON2 in the CNS is still largely unknown, and what role it may play in specific regions of the brain remains unexamined. Dopamine metabolism generates considerable oxidative stress and antioxidant function is critical to the survival of dopaminergic neurons, providing a potential mechanism for PON2 in the dopaminergic system.

METHODS

In this study, we investigated the role of PON2 in the dopaminergic system of the mouse brain by comparing transcript and protein expression of dopaminergic-related genes in wildtype (WT) and PON2 deficient (PON2-def) mouse striatum, and exposing WT cultured primary neurons to dopamine receptor agonists.

RESULTS

We found alterations in multiple key dopaminergic genes at the transcript level, however many of these changes were not observed at the protein level. In cultured neurons, PON2 mRNA and protein were increased upon exposure to quinpirole, a dopamine receptor 2/3 (DRD2/3) agonist, but not fenoldopam, a dopamine receptor 1/5 (DRD1/5) agonist, suggesting a receptor-specific role in dopamine signaling.

CONCLUSIONS

Our findings suggest PON2 deficiency significantly impacts the dopaminergic system at the transcript level and may play a role in mitigating oxidative stress in this system further downstream through dopamine receptor signaling.

The role of sex and ovarian hormones in hippocampal damage and cognitive deficits induced by chronic exposure to hypobaric hypoxia

Purpose

This study aims to investigate the role of sex and ovarian hormones in hippocampal damage and cognitive deficits and behavioral dysfunction in rats induced by chronic exposure to hypobaric hypoxia.

Methods

Six-week-old male and female SD rats were housed for 3 months either in a real altitude (4,250 m) environment as the model of chronic hypobaric-hypoxia (CHH) or in a plain as controls. The animal behavioral and hippocampal neurons at subcellular, molecular, and ultrastructural levels were characterized after CHH exposure.

Results

After 3 months of CHH exposure, (1) male CHH rats’ serum testosterone level was lower than male controls’ whereas female CHH rats’ serum estradiol level was higher than female controls’; (2) Morris water maze test finds that male rats showed more learning and spatial memory deficits than female rats; (3) male rats showed more severe hippocampal damage, hippocampal inflammation, oxidative stress and decreased hippocampal integrity (neurogenesis and dendritic spine density) than female rats; (4) Western blot analysis shows that, compared with the male control group, in male CHH group’s hippocampus, expression of nNOS, HO-1, and Bax protein increased whereas that of Bcl-2 protein decreased; (5) Expression of PON2 protein in male rats (CHH and controls) was lower than female rats (CHH and controls). In addition, CHH exposure decreased the expression of PON2 protein in both male and female rats; (6) qPCR analysis reveals that CHH exposure reduced the gene expression of N-methyl-D-aspartate receptor NR2A and NR2B subunits in male rats’ hippocampus. In addition, compared with the sham CHH group, the expression level of PON2 protein decreased in the OVX-CHH group’s hippocampus whereas oxidative stress, neuroinflammation, and degeneration of hippocampal neurons increased in the OVX-CHH group’s hippocampus.

Conclusion

After CHH exposure, male rats were significantly more likely than female rats to develop hippocampal damage, hippocampal neuroinflammation, and cognitive decline and deficits, suggesting that sex and ovarian hormones were significantly involved in regulating the rats’ susceptibility to CHH exposure-induced hippocampal damage.

Airway epithelial Paraoxonase-2 in obese asthma

Background

Obesity in asthmatics has been associated with higher airway oxidative stress in which dysfunctional mitochondria are a potential contributing source of excess free radicals. Paraoxonase 2 (PON2) plays an important role in reducing mitochondrial-derived oxidative stress and could, therefore, have therapeutic potential in these patients.

Objectives

We used primary human bronchial epithelial cells (HBECs) from asthmatics and healthy controls to evaluate: a) protein levels of Paraoxonase 2 and b) to test the potential protective effect of quercetin supplementation in cells under oxidative stress conditions.

Results

Compared to lean controls, obese asthmatics had significantly lower PON2 airway epithelial levels (respectively, 1.08 vs. 0.47 relative units normalized by GAPDH) (p-value < 0.006). Treating HBECs in vitro for 24 hrs. with 25μM quercetin significantly increased PON2 protein levels: 15.5 treated cells vs. 9.8 untreated cells (relative units normalized by GAPDH) (p value = 0.004). Notably, compared to untreated cells, quercetin supplementation reduces mitochondrial superoxide and hydrogen peroxide production on HBECs cells exposed to different oxidative stress triggers such as 1–2 Naphthoquinone (1–2 NQ) and hydrogen peroxide, suggesting that PON2 might play a protective role ameliorating oxidative injury on human airway epithelium.

Conclusion

Compared to lean controls, obese asthmatics have significantly reduced PON2 levels in airway epithelial cells. Treatment with quercetin in vitro increased PON2 protein levels and prevented oxidative stress from different types of stimuli. Hence, quercetin supplementation may be a potential therapeutic strategy to prevent obesity-mediated airway oxidative stress in obese asthmatics.

Insights into the role of paraoxonase 2 in human pathophysiology

Paraoxonase 2 (PON2) is a ubiquitously expressed intracellular enzyme that is known to have a protective role from oxidative stress. Clinical studies have also demonstrated the significance of PON2 in the manifestation of cardiovascular and several other diseases, and hence, it is considered an important biomarker. Recent findings of its expression in brain tissue suggest its potential protective effect on oxidative stress and neuroinflammation. Polymorphisms of PON2 in humans are a risk factor in many pathological conditions, suggesting a possible mechanism of its anti-oxidative property probably through lactonase activity. However, exogenous factors may also modulate the expression and activity of PON2. Hence, this review aims to report the mechanism by which PON2 expression is regulated and its role in oxidative stress disorders such as neurodegeneration and tumor formation. The role of PON2 owing to its lactonase activity in bacterial infectious diseases and association of PON2 polymorphism with pathological conditions are also highlighted.

Insights into the role of paraoxonase 2 in human pathophysiology

Paraoxonase 2 (PON2) is a ubiquitously expressed intracellular enzyme that is known to have a protective role from oxidative stress. Clinical studies have also demonstrated the significance of PON2 in the manifestation of cardiovascular and several other diseases, and hence, it is considered an important biomarker. Recent findings of its expression in brain tissue suggest its potential protective effect on oxidative stress and neuroinflammation. Polymorphisms of PON2 in humans are a risk factor in many pathological conditions, suggesting a possible mechanism of its anti-oxidative property probably through lactonase activity. However, exogenous factors may also modulate the expression and activity of PON2. Hence, this review aims to report the mechanism by which PON2 expression is regulated and its role in oxidative stress disorders such as neurodegeneration and tumor formation. The role of PON2 owing to its lactonase activity in bacterial infectious diseases and association of PON2 polymorphism with pathological conditions are also highlighted.

MiR-125b inhibits cardiomyocyte apoptosis by targeting BAK1 in heart failure

Background

Although miR-125b plays a crucial role in many human cancers. However, its function in heart failure (HF) remains unclear. Our study aimed to investigate its involvement in heart failure.

Methods

In this study, the mouse HF model was successfully constructed through transverse aortic constriction (TAC) operation. Changes in mRNA and protein levels in isolated myocytes and heart tissues were examined using qRT-PCR, Western blot and Immunohistochemical staining and immunofluorescent staining. Changes in cardiac functions were examined using ultrasound. Interactions between miR-125b and BAK1 was analyzed using the luciferase reporter assay. Cardiomyocyte apoptosis was evaluated using the TUNEL staining.

Results

We found that miR-125b expression was significantly downregulated in myocardial tissues of HF mice. Moreover, miR-125b upregulation in HF mice injected with agomir-125b efficiently ameliorated cardiac function. Further, miR-125b upregulation significantly decreased the protein levels of apoptosis-related makers c-caspase 3 and Bax, while increased Bcl-2 expression. In addition, BAK1 was identified as a direct target of miR-125b. As expected, BAK1 overexpression observably reversed the effect of agomir-125b on cardiac function and on the expression of apoptosis-related makers in the heart tissues of HF mice.

Conclusions

Taken together, miR-125b overexpression efficiently attenuated cardiac function injury of HF mice by targeting BAK1 through inhibiting cardiomyocyte apoptosis, suggesting that miR-125b/BAK1 axis might be a potential target for the diagnosis or treatment of HF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00328-w.

Dexmedetomidine Protects Human Cardiomyocytes Against Ischemia-Reperfusion Injury Through α2-Adrenergic Receptor/AMPK-Dependent Autophagy

Background: Ischemia-reperfusion injury (I/R) strongly affects the prognosis of children with complicated congenital heart diseases (CHDs) who undergo long-term cardiac surgical processes. Recently, the α2-adrenergic receptor agonist Dexmedetomidine (Dex) has been reported to protect cardiomyocytes (CMs) from I/R in cellular models and adult rodent models. However, whether and how Dex may protect human CMs in young children remains largely unknown. Methods and Results: Human ventricular tissue from tetralogy of Fallot (TOF) patients and CMs derived from human-induced pluripotent stem cells (iPSC-CMs) were used to assess whether and how Dex protects human CMs from I/R. The results showed that when pretreated with Dex, the apoptosis marker-TUNEL and cleaved caspase 3 in the ventricular tissue were significantly reduced. In addition, the autophagy marker LC3II was significantly increased compared with that of the control group. When exposed to the hypoxia/reoxygenation process, iPSC-CMs pretreated with Dex also showed reduced TUNEL and cleaved caspase 3 and increased LC3II. When the autophagy inhibitor (3-methyladenine, 3-MA) was applied to the iPSC-CMs, the protective effect of Dex on the CMs was largely blocked. In addition, when the fusion of autophagosomes with lysosomes was blocked by Bafilomycin A1, the degradation of p62 induced by Dex during the autophagy process was suspended. Moreover, when pretreated with Dex, both the human ventricle and the iPSC-CMs expressed more AMP-activated protein kinase (AMPK) and phospho AMPK (pAMPK) during the I/R process. After AMPK knockout or the use of an α2-adrenergic receptor antagonist-yohimbine, the protection of Dex and its enhancement of autophagy were inhibited. Conclusion: Dex protects young human CMs from I/R injury, and α2-adrenergic receptor/AMPK-dependent autophagy plays an important role during this process. Dex may have a therapeutic effect for children with CHD who undergo long-term cardiac surgical processes.

Functional States in Tumor-Initiating Cell Differentiation in Human Colorectal Cancer

Simple Summary

Different types of cells with tumor-initiating cell (TIC) activity contribute to colorectal cancer (CRC) progression and resistance to anti-cancer treatment. In this study, we aimed to understand whether different cell types exist within a patient-derived tumor culture, distinguishable by different patterns of their gene expression. By mRNA sequencing of patient-derived CRC cultures at the single-cell level, we defined expression programs that closely resemble differentiated cell populations of the normal intestine. Here, cell type-associated subpopulations showed differences in functional properties such as cell growth and energy metabolism. Subsequent functional analyses in vitro and in vivo demonstrated that metabolic states are linked to TIC activity in primary CRC cultures. We also show that TIC activity is dependent on oxidative phosphorylation, which may therefore represent a target for novel therapies.

Abstract

Intra-tumor heterogeneity of tumor-initiating cell (TIC) activity drives colorectal cancer (CRC) progression and therapy resistance. Here, we used single-cell RNA-sequencing of patient-derived CRC models to decipher distinct cell subpopulations based on their transcriptional profiles. Cell type-specific expression modules of stem-like, transit amplifying-like, and differentiated CRC cells resemble differentiation states of normal intestinal epithelial cells. Strikingly, identified subpopulations differ in proliferative activity and metabolic state. In summary, we here show at single-cell resolution that transcriptional heterogeneity identifies functional states during TIC differentiation. Furthermore, identified expression signatures are linked to patient prognosis. Targeting transcriptional states associated to cancer cell differentiation might unravel novel vulnerabilities in human CRC.

Human Paraoxonase-2 (PON2): Protein Functions and Modulation

PON1, PON2, and PON3 belong to a family of lactone hydrolyzing enzymes endowed with various substrate specificities. Among PONs, PON2 shows the highest hydrolytic activity toward many acyl-homoserine lactones (acyl-HL) involved in bacterial quorum-sensing signaling. Accordingly, defense against pathogens, such as Brevundimonas aeruginosa (B. aeruginosa), was postulated to be the principal function of PON2. However, recent findings have highlighted the importance of PON2 in oxidative stress control, inhibition of apoptosis, and the progression of various types of malignancies. This review focuses on all of these aspects of PON2.

The Structure and Function of Paraoxonase-1 and Its Comparison to Paraoxonase-2 and -3

Serum paraoxonase-1 (PON1) is the most studied member of the group of paraoxonases (PONs). This enzyme possesses three enzymatic activities: lactonase, arylesterase, and paraoxonase activity. PON1 and its isoforms play an important role in drug metabolism as well as in the prevention of cardiovascular and neurodegenerative diseases. Although all three members of the PON family have the same origin and very similar amino acid sequences, they have different functions and are found in different locations. PONs exhibit substrate promiscuity, and their true physiological substrates are still not known. However, possible substrates include homocysteine thiolactone, an analogue of natural quorum-sensing molecules, and the recently discovered derivatives of arachidonic acid—bioactive δ-lactones. Directed evolution, site-directed mutagenesis, and kinetic studies provide comprehensive insights into the active site and catalytic mechanism of PON1. However, there is still a whole world of mystery waiting to be discovered, which would elucidate the substrate promiscuity of a group of enzymes that are so similar in their evolution and sequence yet so distinct in their function.

Progression of heart failure is attenuated by antioxidant therapy with N-acetylcysteine in myocardial infarcted female rats

This study investigated the therapeutic potential of N-acetylcysteine (NAC) in the treatment of heart failure in female rats. Myocardial infarcted (MI) rats were given NAC (250 mg/kg/day p.o.) during 28 days after surgery (MI + NAC) or vehicle (MI + Placebo), and sham-operated rats received the same treatments (Sham + NAC and Sham + Placebo). Electrocardiographic and echocardiographic analyses were performed in the last week of treatment. Cardiac mRNA levels of types I and II superoxide dismutase (SOD), catalase, types I and III glutathione peroxidase (GPX), nerve growth factor (NGF), β1-adrenergic receptor (β1ADR), and type 2 muscarinic receptor (M2R) were assessed. Cardiac levels NADPH oxidase (NOX) activity_, total content of reduced thiols, and SOD, GPX, and catalase activity were assessed. Compared to MI + Placebo group, MI + NAC group exhibited decreased NOX activity, increased content of reduced thiols, increased GPX activity, and normalized GPX III mRNA levels (p < 0.05). Heart and lung weights, left ventricular (LV) end-diastolic volume and left atrium/aorta ratio were decreased, while LV posterior wall thickness and ejection fraction were increased in MI + NAC group versus MI + Placebo rats (p < 0.05). Power density of low frequency band was decreased, while power density of high frequency and the root mean square of the successive differences were increased in MI + NAC rats versus MI + Placebo (p < 0.05). These findings indicate that NAC promotes therapeutic effects in the progression of MI-induced heart failure in female rats.

PON1 Hypermethylation and PON3 Hypomethylation are Associated with Risk of Cerebral Infarction

OBJECTIVE

Paraoxonase (PON) family genes are closely related to the etiology and prognosis of cerebral infarction. This study explored the association of the promoter methylation of PON family genes (PON1, PON2 and PON3) with the risk of cerebral infarction.

MATERIALS AND METHODS

In this study, 152 patients with confirmed cerebral infarction were selected as the case group, and 152 healthy controls were selected as the control group. The quantitative methylation-specific PCR (qMSP) was used to determine the promoter methylation levels of PON1, PON2 and PON3 genes. The methylation level was expressed as a methylation reference percentage (PMR).

RESULTS

Our results indicated that PON1 methylation was significantly higher in the case group than in the control group (P = 0.0001). On the contrary, PON3 methylation was significantly lower in the case group than in the control group (P = 0.002). In addition, we found that PON2 gene had a very low level of methylation in both case and control groups (PMR = 0). Subgroup analysis showed that PON1 and PON3 methylation were associated with cerebral infarction only in males (PON1, P = 0.0002; PON3, P = 0.007). Interestingly, the methylation levels of PON1 and PON3 were correlated with each other (case: r = 0.418, P = 0.0001; control: r = 0.3, P = 0.0002). Further multiple regression analysis suggested that elevated methylation levels of PON3 were a protective factor for cerebral infarction [OR (95%CI) = 0.979 (0.96, 0.999), β = -0.021, P = 0.035)], highdensity lipoprotein (HDL) and uric acid (UA) also were protective factors for cerebral infarction [HDL, OR (95% CI) = 0.01 (0.003, 0.033), P < 0.0001); UA, OR (95% CI) = 0.995 (0.991, 0.998), P = 0.003)]. The ROC curve analysis found that the combination of PON3, HDL, and UA had a good predictive power for cerebral infarction (AUC=0.878, 95% CI=0.839-0.918, sensitivity 73.7%, specificity 89.7%, P < 0.0001).

CONCLUSION

PON1 and PON3 promoter methylation levels in peripheral blood were closely related. PON1 and PON3 methylation were associated with the risk of cerebral infarction in men. PON3 promoter methylation combined with HDL and UA could be used as potential biomarkers for the diagnosis of cerebral infarction.

Global analysis of histone modifications and long-range chromatin interactions revealed the differential cistrome changes and novel transcriptional players in human dilated cardiomyopathy

BACKGROUND

Acetylation and methylation of histones alter the chromatin structure and accessibility that affect transcriptional regulators binding to enhancers and promoters. The binding of transcriptional regulators enables the interaction between enhancers and promoters, thus affecting gene expression. However, our knowledge of these epigenetic alternations in patients with heart failure remains limited.

METHODS AND RESULTS

From the comprehensive analysis of major histone modifications, 3-dimensional chromatin interactions, and transcriptome in left ventricular (LV) tissues from dilated cardiomyopathy (DCM) patients and non-heart failure (NF) donors, differential active enhancer and promoter regions were identified between NF and DCM. Moreover, the genome-wide average promoter signal is significantly lower in DCM than in NF. Super-enhancer (SE) analysis revealed that fewer SEs were found in DCM LVs than in NF ones, and three unique SE-associated genes between NF and DCM were identified. Moreover, SEs are enriched within the genomic region associated with long-range chromatin interactions. The differential enhancer-promoter interactions were observed in the known heart failure gene loci and are correlated with the gene expression levels. Motif analysis identified known cardiac factors and possible novel players for DCM.

CONCLUSIONS

We have established the cistrome of four histone modifications and chromatin interactome for enhancers and promoters in NF and DCM tissues. Differential histone modifications and enhancer-promoter interactions were found in DCM, which were associated with gene expression levels of a subset of disease-associated genes in human heart failure.

RNA Sequence Analyses throughout the Course of Mouse Cardiac Laminopathy Identify Differentially Expressed Genes for Cell Cycle Control and Mitochondrial Function

Lamin A/C (LMNA) gene mutations are a known cause of familial dilated cardiomyopathy, but the precise mechanisms triggering disease progression remain unknown. We hypothesize that analysis of differentially expressed genes (DEGs) throughout the course of Lmna knockout (Lmna-/-)-induced cardiomyopathy may reveal novel Lmna-mediated alterations of signaling pathways leading to dilated cardiomyopathy. Although Lmna was the only DEG down-regulated at 1 week of age, we identified 730 and 1004 DEGs in Lmna-/- mice at 2 weeks and 1 month of age, respectively. At 2 weeks, Lmna-/- mice demonstrated both down- and up-regulation of the key genes involving cell cycle control, mitochondrial dysfunction, and oxidative phosphorylation, as well as down-regulated genes governing DNA damage repair and up-regulated genes involved in oxidative stress response, cell survival, and cardiac hypertrophy. At 1 month, the down-regulated genes included those involved in oxidative phosphorylation, mitochondrial dysfunction, nutrient metabolism, cardiac β-adrenergic signaling, action potential generation, and cell survival. We also found 96 overlapping DEGs at both ages involved in oxidative phosphorylation, mitochondrial function, and calcium signaling. Impaired oxidative phosphorylation was observed at early disease stage, even before the appearance of disease phenotypes, and worsened with disease progression, suggesting its importance in the pathogenesis and progression of LMNA cardiomyopathy. Reduction of oxidative stress might therefore prevent or delay the development from Lmna mutation to LMNA cardiomyopathy.

Paraoxonase 2 protects against acute myocardial ischemia-reperfusion injury by modulating mitochondrial function and oxidative stress via the PI3K/Akt/GSK-3β RISK pathway

OBJECTIVE

To investigate the novel role of Paraoxonase 2 (PON2) in modulating acute myocardial ischemia-reperfusion injury (IRI).

APPROACH

IRI was induced both in vivo and ex vivo in male, C57BL6/J (WT) and PON2-deficient (PON-def) mice. In addition, in vitro hypoxia-reoxygenation injury (HRI) was induced in H9c2 cells expressing empty vector (H9c2-EV) or human PON2 (H9c2-hPON2) ± LY294002 (a potent PI3K inhibitor). Infarct size, PON2 gene expression, mitochondrial calcium retention capacity (CRC), reactive oxygen species (ROS) generation, mitochondrial membrane potential, CHOP and pGSK-3β protein levels, and cell apoptosis were evaluated.

RESULTS

PON2 gene expression is upregulated in WT mice following in vivo IRI. PON2-def mice exhibit a 2-fold larger infarct, increased CHOP levels, and reduced pGSK-3β levels compared to WT controls. Global cardiac mitochondria isolated from PON2-def mice exhibit reduced CRC and increased ROS production. Cardiomyocytes isolated from PON2-def mice subjected to ex vivo IRI have mitochondria with reduced CRC (also seen under non-IRI conditions), and increased ROS generation and apoptosis compared to WT controls. PON2 knockdown in H9c2 cells subjected to HRI leads to an increase in mitochondrial membrane depolarization. H9c2-hPON2 cells exhibit i) improvement in mitochondrial membrane potential, pGSK-3β levels and mitochondrial CRC, and ii) decrease in CHOP levels, mitochondrial ROS generation and cell apoptosis, when compared to H9c2-EV controls. Treatment with LY294002 resulted in a decrease of mitochondrial CRC and increase in mitochondrial ROS production and cell apoptosis in the H9c2-hPON2 group versus H9c2-EV controls.

CONCLUSION

PON2 protects against acute myocardial IRI by reducing mitochondrial dysfunction and oxidative stress in cardiomyocytes via activation of the PI3K/Akt/GSK-3β RISK pathway.

Exogenous (Pomegranate Juice) or Endogenous (Paraoxonase1) Antioxidants Decrease Triacylglycerol Accumulation in Mouse Cardiovascular Disease-Related Tissues

The polyphenol-rich pomegranate juice (PJ) and the high-density lipoprotein (HDL)-associated paraoxonase1 (PON1) are known as potent atheroprotective antioxidants, but their effects on other tissues related to cardiovascular disease (CVD) remain unknown. The current study aimed to investigate the effects of treating mice with PJ or recombinant PON1 (rePON1) on the oxidation and lipid status of CVD-related tissues: serum, aorta, heart, liver, kidney, visceral, and subcutaneous adipose tissues (VAT and SAT). Both PJ consumption and rePON1 injection decreased the serum levels of thiobarbituric acid-reactive substances (16% and 19%) and triacylglycerols (TAG, 24% and 27%), while only rePON1 increased the levels of thiol groups (35%) and decreased serum cholesterol (15%). Both PJ and rePON1 significantly decreased aortic cholesterol (38% and 32%) and TAG (62% and 58%) contents in association with downregulation of the key TAG biosynthetic enzyme diacylglycerol O-acyltransferase 1 (DGAT1, 71% and 65%), while only PJ decreased aortic lipid peroxides (47%). Substantial TAG-lowering effects of both PJ and rePON1 were observed also in the heart (31% and 42%), liver (34% and 42%), and kidney (42% and 57%). In both VAT and SAT, rePON1 decreased the levels of lipid peroxides (28% and 25%), while PJ decreased the TAG content (22% and 18%). Ex vivo incubation of SAT with serum derived from mice that consumed PJ or injected with rePON1 decreased SAT lipid peroxides (35% or 28%) and TAG mass (12% or 10%). These novel findings highlight potent TAG-lowering properties of exogenous (PJ) and endogenous (PON1) antioxidants in tissues associated with CVD.