Paraoxonase 1 and atherosclerosis

Paraoxonase 1 (PON1), residing almost exclusively on HDL, was discovered because of its hydrolytic activity towards organophosphates. Subsequently, it was also found to hydrolyse a wide range of substrates, including lactones and lipid hydroperoxides. PON1 is critical for the capacity of HDL to protect LDL and outer cell membranes against harmful oxidative modification, but this activity depends on its location within the hydrophobic lipid domains of HDL. It does not prevent conjugated diene formation, but directs lipid peroxidation products derived from these to become harmless carboxylic acids rather than aldehydes which might adduct to apolipoprotein B. Serum PON1 is inversely related to the incidence of new atherosclerotic cardiovascular disease (ASCVD) events, particularly in diabetes and established ASCVD. Its serum activity is frequently discordant with that of HDL cholesterol. PON1 activity is diminished in dyslipidaemia, diabetes, and inflammatory disease. Polymorphisms, most notably Q192R, can affect activity towards some substrates, but not towards phenyl acetate. Gene ablation or over-expression of human PON1 in rodent models is associated with increased and decreased atherosclerosis susceptibility respectively. PON1 antioxidant activity is enhanced by apolipoprotein AI and lecithin:cholesterol acyl transferase and diminished by apolipoprotein AII, serum amyloid A, and myeloperoxidase. PON1 loses this activity when separated from its lipid environment. Information about its structure has been obtained from water soluble mutants created by directed evolution. Such recombinant PON1 may, however, lose the capacity to hydrolyse non-polar substrates. Whilst nutrition and pre-existing lipid modifying drugs can influence PON1 activity there is a cogent need for more specific PON1-raising medication to be developed.

Treatment of atherosclerosis through transplantation of endothelial progenitor cells overexpressing dimethylarginine dimethylaminohydrolase (DDAH) in rabbits

BACKGROUND

Endothelial dysfunction is a key event in the development of vascular diseases, including atherosclerosis. Endothelial progenitor cells (EPCs) play an important role in vascular repair. Decreased dimethylarginine dimethylaminohydrolase (DDAH) activity is observed in several pathological conditions, and it is associated with an increased risk of vascular disease. We hypothesized that bone marrow-derived EPCs and combination therapy with DDAH2-EPCs could reduce plaque size and ameliorate endothelial dysfunction in an atherosclerosis rabbit model.

METHOD

Four groups of rabbits (n = 8 per group) were subjected to a hyperlipidemic diet for a month. After establishing the atherosclerosis model, rabbits received 4 × 10⁶ EPC, EPCs expressing DDAH2, through femoral vein injection, or saline (the control group with basic food and the untreated group). One month after transplantation, plaque thickness, endothelial function, oxidative stress, and inflammatory mRNAs, DDAH, and eNOS function were assessed.

RESULTS

DDAH2-EPCs transplantation (p < 0.05) and EPCs transplantation (p < 0.05) were both associated with a reduction in plaque size compared to the control saline injection. The antiproliferative and antiatherogenic effects of EPCs were further enhanced by the overexpression of DDAH2 (p < 0.05, DDAH2-EPCs vs. EPCs). Furthermore, DDAH2-EPCs transplantation significantly increased endothelium integrity compared to the EPCs transplantation.

CONCLUSION

Transplantation of EPCs overexpressing DDAH2 may enhance the repair of injured endothelium by reducing inflammation and restoring endothelial function. Therefore, pCMV6-mediated DDAH2 gene-transfected EPCs are a potentially valuable tool for the treatment of atherosclerosis.

The antiatherogenic function of kallistatin and its potential mechanism

Atherosclerosis is the pathological basis of most cardiovascular diseases, the leading cause of morbidity and mortality worldwide. Kallistatin, originally discovered in human serum, is a tissue-kallikrein-binding protein and a unique serine proteinase inhibitor. Upon binding to its receptor integrin β3, lipoprotein receptor-related protein 6, nucleolin, or Krüppel-like factor 4, kallistatin can modulate various signaling pathways and affect multiple biological processes, including angiogenesis, inflammatory response, oxidative stress, and tumor growth. Circulating kallistatin levels are significantly decreased in patients with coronary artery disease and show an inverse correlation with its severity. Importantly, both in vitro and in vivo experiments have demonstrated that kallistatin reduces atherosclerosis by inhibiting vascular inflammation, antagonizing endothelial dysfunction, and improving lipid metabolism. Thus, kallistatin may be a novel biomarker and a promising therapeutic target for atherosclerosis-related diseases. In this review, we focus on the antiatherogenic function of kallistatin and its potential mechanism.

MeCP2 inhibits cell functionality through FoxO3a and autophagy in endothelial progenitor cells

Objectives: Autophagy is an evolutionarily conserved intracellular degradation mechanism in which cell constituents are phagocytosed to maintain cellular homeostasis. Forkhead box O 3a (FoxO3a) promotes autophagy to protect cells from environmental stress. Methylated CpG binding protein 2 (MeCP2) is a nuclear protein that binds DNA and represses transcription. However, the mechanism and interplay between FoxO3a and MeCP2 underlying endothelial progenitor cell (EPC) function are not fully understood.

Results: In EPCs, MeCP2 overexpression attenuated autophagy and cell functionality, which were reversed by the autophagy activator rapamycin or co-transfection with FoxO3a. FoxO3a promoted cell function, which was reversed by the autophagy inhibitor chloroquine. Following MeCP2 overexpression, MeCP2 was found enriched on the FoxO3a promoter, resulting in promoter hypermethylation and enhanced H3K9 histone modification in nucleosomes of the FoxO3a promoter.

Conclusions: MeCP2 attenuated cell functionality via DNA hypermethylation and histone modification of the FoxO3a promoter to inhibit FoxO3a transcription and autophagy.

Materials and Methods: EPCs were isolated from human umbilical cord blood and treated with adenoviral vectors containing interference sequences. The effects and mechanism of MeCP2 and FoxO3a were analyzed by utilizing western blotting, cell counting kit-8, transwell plates, Matrigel, matrix adhesion, transmission electron microscopy, and chromatin immunoprecipitation.

PJ34, a PARP1 inhibitor, promotes endothelial repair in a rabbit model of high fat diet-induced atherosclerosis

Objective: Atherosclerosis involves endothelial injury caused by oxidative stress. Endothelial progenitor cells (EPCs) play important roles in preventing the early stages of atherosclerosis. Meanwhile, poly (ADP-ribose) polymerase 1 (PARP1) utilizes nicotinamide adenine dinucleotide (NAD⁺) to repair DNA damage. PARP1 overactivation results in excessive NAD⁺ consumption in the presence of pathological DNA damage. PJ34 is a PARP1 inhibitor that attenuates cellular NAD+ depletion and can prevent endothelial dysfunction. However, few studies have been conducted on its effects on EPCs. In this study, we tried to elucidate the action of PJ34 in rabbit EPCs and tested its effectiveness in rabbit atherosclerosis. Methods: We analyzed the effect of PJ34 supplementation by inducing oxidative damage by H₂O₂ in vitro and using a rabbit atherosclerosis model induced by a high-fat-diet in vivo. Transwell, immunofluorescence, Matrigel, and western blot analyses, as well as adenoviral vector transfection were used to quantify the levels of reactive oxygen species, proteins, and NAD⁺. Results: The effects of PJ34 were dependent on SIRT1 levels. In vitro results showed that when oxidative damage attenuated cellular function, PJ34 treatment restored partial functionality. In vivo results confirmed that PJ34 can prevent atherosclerosis in a rabbit model.

PARP1 inhibitor (PJ34) improves the function of aging-induced endothelial progenitor cells by preserving intracellular NAD+ levels and increasing SIRT1 activity

Background

Nicotinamide adenine dinucleotide (NAD⁺) is a critical molecule involved in various biological functions. Poly (ADP-ribose) polymerase 1 (PARP1) and sirtuin 1 (SIRT1) affect cellular NAD⁺ levels and play essential roles in regulating metabolism. However, there has been little research on the effects of PARP1 and SIRT1 crosstalk during senescence.

Methods

We isolated endothelial progenitor cells (EPCs) from human umbilical cord blood and treated them with a PARP1 inhibitor (PJ34).

Results

Using a stress-induced premature aging model built by H₂O₂, transfection with adenoviral vectors, and Western blot analysis, we observed that PJ34 treatment preserved intracellular NAD⁺ levels, increased SIRT1 activity, decreased p53 acetylation, and improved the function of stress-induced premature aging EPCs.

Conclusions

Our results suggest that PJ34 improves the function of aging-induced EPCs and may contribute to cellular therapies for atherosclerosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0961-7) contains supplementary material, which is available to authorized users.

Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model

AIM

In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms.

METHODS

Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive-hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group.

RESULTS

The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein and Ulex europaeus agglutinin lectin-1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie-2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR-10a, miR-21, miR-126, miR-146a, miR-223 transfer and IGF-1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer.

CONCLUSION

The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.

Injection of hTERT-Transduced Endothelial Progenitor Cells Promotes Beneficial Aortic Changes in a High-Fat Dietary Model of Early Atherosclerosis

Objectives: Cultured endothelial progenitor cells (EPCs) display troubling issues that adversely affect their applicability to endothelial regeneration. We hypothesized that transduction of the human telomerase catalytic subunit (hTERT) gene would enhance EPC function in treating dietary-induced early atherosclerosis (AS). Methods: A dietary-induced early AS model was successfully constructed in 90 healthy male rats, while 30 healthy control (HC) rats were normally fed. Four experimental groups were constructed: an untreated HC group; an untreated AS group injected with PBS; a null EPC AS group injected with null vector-transduced EPCs, and an hTERT EPC AS group injected with hTERT-transduced EPCs. Two months postinjection, abdominal aortas were extracted to validate EPC integration and comparatively assess mRNA and protein expression of the early atherosclerotic markers VCAM-1, ICAM-1, LFA-1, Mac-1, CD44, MCP-1, endothelial nitric oxide synthase (eNOS), and apolipoprotein E. Results: In vitro, hTERT transduction of EPCs resulted in a significantly superior proliferative capacity as well as significantly higher NO, iNOS, and LDH secretory capacity. In vivo injection of hTERT-transduced EPCs produced significant reductions in CD44 and MCP-1 expression as well as a significant increase in eNOS expression relative to injection with null vector-transduced EPCs (all p < 0.05). Conclusion: hTERT-transduced human EPCs may be useful in treating dietary-induced early AS.

Hyperglycaemia exerts deleterious effects on late endothelial progenitor cell secretion actions

Endothelial progenitor cells (EPCs) play a fundamental role in tissue regeneration and vascular repair both by differentiating into endothelial cells and by secretion of vasoactive substances that promote angiogenesis and maintain vascular homeostasis. It has previously been shown that hyperglycaemia impairs early and late EPC functions, such as differentiation, proliferation and adhesion. However, its role in the regulation of the production of vasoactive substances in EPCs, especially in late EPCs, is less well defined. We investigated the effects of hyperglycaemia on the production of vasodilator, fibrinolytic and angiogenic growth factors, and also on the activity of superoxide dismutase (SOD) in late EPCs. For this purpose, late EPCs were incubated with different concentrations of D-glucose (5-40 mmol/L) for 24 hr. Levels of nitric oxide (NO), tissue plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), prostaglandin I(2) (PGI(2)), vascular endothelial growth factor (VEGF) and the activity of SOD were measured by enzyme-linked immunosorbent assay (ELISA). Under high glucose stress conditions, late EPCs exhibited lower levels of NO, t-PA, PAI-1, PGI(2) and VEGF compared to control medium (5 mmol/L glucose). Moreover, high glucose was also observed to decrease the activity of SOD in late EPCs. These results suggest that hyperglycaemia-induced impairment of late EPC secretion functions could contribute to the development of vascular disease in diabetes.