Matrix Gla Protein, Plaque Stability, and Cardiovascular Events in Patients with Severe Atherosclerotic Disease

OBJECTIVE

This study aims to investigate whether plasma matrix Gla protein (MGP) species, desphospho-uncarboxylated (dp-uc) MGP, and total uncarboxylated (t-uc) MGP are associated with plaque levels of uncarboxylated (uc) MGP, markers of plaque stability, and cardiovascular disease (CVD) risk.

METHODS

From the Athero-Express biobank, we selected carotid plaque samples of 100 patients who underwent carotid endarterectomy. The level of agreement between plasma MGP species and plaque ucMGP levels was assessed using weighted kappa (κ). We analyzed histological characteristics of plaque composition (plaque hemorrhage, lipid and calcification content). Logistic regression analyses were used to assess the association between plasma MGP and plaque characteristics. Furthermore, CVD endpoints (n = 20) were collected over a mean follow-up of 2.6 years.

RESULTS

Weighted κ statistics of plasma dp-ucMGP and t-ucMGP and plaque ucMGP were 0.10 (95% CI -0.31 to 0.52) and 0.14 (95% CI -0.20 to 0.48). Higher dp-ucMGP levels tended to be associated with less plaque hemorrhage (ORper 500 nM 0.96; 95% CI 0.92-1.00). No association was found for lipid and calcification content. Cox proportional hazards models showed no association between dp-ucMGP (HRper 200 pM 0.92; 95% CI 0.75-1.11) and an inverse association between t-ucMGP (HRper 500 nM 0.79; 95% CI 0.62-0.99) and cardiovascular events.

CONCLUSIONS

Plasma dp-ucMGP and t-ucMGP concentrations do not reflect plaque ucMGP levels. Elevated dp-ucMGP levels may be associated with less plaque hemorrhage, suggestive of more stable plaques. T-ucMGP was not related with markers of plaque stability; however, elevated plasma t-ucMGP levels were associated with a reduced CVD risk.

F2-isoprostanes affect macrophage migration and CSF-1 signalling

F₂-isoprostanes (F₂-IsoP) are formed in vivo via free radical peroxidation of arachidonic acid. Enhanced oxidative stress is implicated in the development of atherosclerosis in humans and F₂-IsoP have been detected in atherosclerotic plaque. Colony stimulating factor-1 (CSF-1) is essential to macrophage survival, proliferation and differentiation and has been detected in human atherosclerotic plaques. Accumulation of macrophages within the vascular wall is an important component of atherosclerosis but little is known about the effect of F₂-IsoP on the migration of these cells. Our aim was to examine the effect of free and lipid-bound 15-F_2t-isoprostane (15-F_2t-IsoP) on macrophage migration and investigate the signalling pathways involved. Mouse macrophages (cell line BAC1.2F5) were pre-incubated with 15-F_2t-IsoP (free, bound to cholesterol or monoacylglycerol or within oxidized phospholipid) and cell migration was assessed using chemotaxis towards CSF-1 in Boyden chambers. Migration was also measured using the wound healing assay with primary mouse bone marrow derived macrophages. We showed that 15-F_2t-IsoP dose-dependently inhibited BAC1.2F5 macrophage spreading and adhesion but stimulated their migration towards CSF-1, with maximum effect at 10 µM. Analysis of CSF-1 stimulated signalling pathways in BAC1.2F5 macrophages showed that phosphorylation of Akt, a key mediator of cell migration, and one of its regulators, the mTORC2 component, Rictor, was significantly decreased. In contrast, phosphorylation of the adhesion kinases, FAK and Pyk2, and the adhesion scaffold protein, paxillin, was enhanced after treatment with 15-F_2t-IsoP. Mouse bone marrow macrophages were transfected with FAK or Pyk2 small interfering RNA (siRNA) to examine the role of FAK and Pyk2 in 15-F_2t-IsoP signalling. Pyk2 silencing inhibited 15-F_2t-IsoP-induced reduction in cell area and phospho-paxillin adhesion numbers. The size distribution of adhesions in the presence of 15-F_2t-IsoP was also affected by Pyk2 silencing and there was a trend for Pyk2 silencing to reduce 15-F_2t-IsoP-stimulated macrophage migration. These results demonstrate that 15-F_2t-IsoP affects macrophage adhesions and migration, which are integral components of macrophage involvement in atherosclerosis.

Human Aldose Reductase Expression Prevents Atherosclerosis Regression in Diabetic Mice

Guidelines to reduce cardiovascular risk in diabetes include aggressive LDL lowering, but benefits are attenuated compared with those in patients without diabetes. Consistent with this, we have reported in mice that hyperglycemia impaired atherosclerosis regression. Aldose reductase (AR) is thought to contribute to clinical complications of diabetes by directing glucose into pathways producing inflammatory metabolites. Mice have low levels of AR, thus raising them to human levels would be a more clinically relevant model to study changes in diabetes under atherosclerosis regression conditions. Donor aortae from Western diet-fed Ldlr^-/- mice were transplanted into normolipidemic wild-type, Ins2Akita (Akita^+/- , insulin deficient), human AR (hAR) transgenic, or Akita^+/- /hAR mice. Akita^+/- mice had impaired plaque regression as measured by changes in plaque size and the contents of CD68⁺ cells (macrophages), lipids, and collagen. Supporting synergy between hyperglycemia and hAR were the even more pronounced changes in these parameters in Akita^+/- /hAR mice, which had atherosclerosis progression in spite of normolipidemia. Plaque CD68⁺ cells from the Akita^+/- /hAR mice had increased oxidant stress and expression of inflammation-associated genes but decreased expression of anti-inflammatory genes. In summary, hAR expression amplifies impaired atherosclerosis regression in diabetic mice, likely by interfering with the expected reduction in plaque macrophage inflammation.

Matrix metalloproteinases in pro-atherosclerotic arterial remodeling

Matrix metalloproteinases (MMPs) is a family of Zn²⁺ endopeptidases that process various components of the extracellular matrix. These enzymes are also involved in activation and inhibition of signaling cascades through proteolytic cleavage of surface receptors. Moreover, MMPs play a key role in tissue remodeling and and repair. Dysregulation of MMPs is observed in patholofgical conditions, including atherosclerosis, which is associated with hyperactivation of MMPs, aberrant tissue remodeling and neovascularization of the growing atherosclerotic plaques. This makes MMPs interesting therapeutic targets that can be employed for developing novel therapies to treat atherosclerosis and its complications. Currently, a growing number of synthetic MMP inhibitors is available. In this review, we will discuss the role of these enzymes in atherosclerosis pathology and the ways of their pothential therapeutic use.

A Novel Mechanism for Atherosclerotic Calcification: Potential Resolution of the Oxidation Paradox

AIM

In this study, we tested the hypothesis that lipid peroxide-derived dicarboxylic acids (DCAs), by virtue of their ability to bind to calcium (Ca), might be involved in atherosclerotic calcification. We determined the ability of azelaic acid (AzA) to promote calcification in human aortic smooth muscle cells (HASMCs), identified AzA in human calcified atherosclerotic lesions, and compared its levels with control and noncalcified atherosclerotic lesions.

RESULTS

HASMCs efficiently converted 9-oxononanoic acid (ONA), a lipid peroxide-derived monocarboxylic aldehyde, to AzA. In vitro incubations of AzA micelles with HASMC resulted in the formation of Ca deposits, which contained AzA. Liquid chromatography-mass spectrometry analysis of human control uninvolved artery, noncalcified, and calcified lesions showed significant increase of AzA in calcified lesions compared with noncalcified and control tissues. Calcified mouse atherosclerotic lesions also showed substantial presence of AzA in Ca complexes.

INNOVATION

This study identifies a DCA, AzA, as an integral part of the Ca complex. The study also demonstrates the conversion of a lipid peroxidation product, ONA, as a potential source of AzA, and establishes the presence of AzA in calcified materials isolated from human and mouse lesions.

CONCLUSION

The presence of AzA as a Ca sequestering agent in atherosclerotic lesions (i) might indicate participation of oxidized low-density lipoprotein (Ox-LDL) derived products in calcification, (ii) explain the potential correlation between calcification and overall plaque burden (as Ox-LDL has been suggested to be involved in atherogenesis), (iii) could contribute to plaque stabilization via its anti-inflammatory actions, and (iv) might explain why antioxidants failed to affect atherosclerosis in clinical studies. Antioxid. Redox Signal. 29, 471-483.

Role of AGEs in the progression and regression of atherosclerotic plaques

The formation of advanced glycation end-products(AGEs) is an important cause of metabolic memory in diabetic patients and a key factor in the formation of atherosclerosis(AS) plaques in patients with diabetes mellitus. Related studies showed that AGEs could disrupt hemodynamic steady-state and destroy vascular wall integrity through the endothelial barrier damage, foam cell(FC) formation, apoptosis, calcium deposition and other aspects. At the same time, AGEs could initiate oxidative stress and inflammatory response cascade via receptor-depended and non-receptor-dependent pathways, promoting plaques to develop from a steady state to a vulnerable state and eventually tend to rupture and thrombosis. Numerous studies have confirmed that these pathological processes mentioned above could lead to acute coronary heart disease(CHD) and other acute cardiovascular and cerebrovascular events. However, the specific role of AGEs in the progression and regression of AS plaques has not yet been fully elucidated. In this paper, the formation, source, metabolism, physical and chemical properties of AGEs and their role in the migration of FCs and plaque calcification are briefly described, we hope to provide new ideas for the researchers that struggling in this field.

Senescent Microvesicles: A Novel Advance in Molecular Mechanisms of Atherosclerotic Calcification

Atherosclerosis, a chronic inflammatory disease that causes the most heart attacks and strokes in humans, is the leading cause of death in the developing world; its principal clinical manifestation is coronary artery disease. The development of atherosclerosis is attributed to the aging process itself (biological aging) and is also associated with the development of chronic diseases (premature aging). Both aging processes produce an increase in risk factors such as oxidative stress, endothelial dysfunction and proinflammatory cytokines (oxi-inflamm-aging) that might generate endothelial senescence associated with damage in the vascular system. Cellular senescence increases microvesicle release as carriers of molecular information, which contributes to the development and calcification of atherosclerotic plaque, as a final step in advanced atherosclerotic plaque formation. Consequently, this review aims to summarize the information gleaned to date from studies investigating how the senescent extracellular vesicles, by delivering biological signalling, contribute to atherosclerotic calcification.

Imaging of chemokine receptor CXCR4 expression in culprit and nonculprit coronary atherosclerotic plaque using motion-corrected [68Ga]pentixafor PET/CT

Purpose

The chemokine receptor CXCR4 is a promising target for molecular imaging of CXCR4⁺ cell types, e.g. inflammatory cells, in cardiovascular diseases. We speculated that a specific CXCR4 ligand, [⁶⁸Ga]pentixafor, along with novel techniques for motion correction, would facilitate the in vivo characterization of CXCR4 expression in small culprit and nonculprit coronary atherosclerotic lesions after acute myocardial infarction by motion-corrected targeted PET/CT.

Methods

CXCR4 expression was analysed ex vivo in separately obtained arterial wall specimens. [⁶⁸Ga]Pentixafor PET/CT was performed in 37 patients after stent-based reperfusion for a first acute ST-segment elevation myocardial infarction. List-mode PET data were reconstructed to five different datasets using cardiac and/or respiratory gating. Guided by CT for localization, the PET signals of culprit and various groups of nonculprit coronary lesions were analysed and compared.

Results

Ex vivo, CXCR4 was upregulated in atherosclerotic lesions, and mainly colocalized with CD68⁺ inflammatory cells. In vivo, elevated CXCR4 expression was detected in culprit and nonculprit lesions, and the strongest CXCR4 PET signal (median SUV_max 1.96; interquartile range, IQR, 1.55–2.31) was observed in culprit coronary artery lesions. Stented nonculprit lesions (median SUV_max 1.45, IQR 1.23–1.88; P = 0.048) and hot spots in naive remote coronary segments (median SUV_max 1.34, IQR 1.23–1.74; P = 0.0005) showed significantly lower levels of CXCR4 expression. Dual cardiac/respiratory gating provided the strongest CXCR4 PET signal and the highest lesion detectability.

Conclusion

We demonstrated the basic feasibility of motion-corrected targeted PET/CT imaging of CXCR4 expression in coronary artery lesions, which was triggered by vessel wall inflammation but also by stent-induced injury. This novel methodology may serve as a platform for future diagnostic and therapeutic clinical studies targeting the biology of coronary atherosclerotic plaque.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4076-2) contains supplementary material, which is available to authorized users.

The role of non-resolving inflammation in atherosclerosis

Non-resolving inflammation drives the development of clinically dangerous atherosclerotic lesions by promoting sustained plaque inflammation, large necrotic cores, thin fibrous caps, and thrombosis. Resolution of inflammation is not merely a passive return to homeostasis, but rather an active process mediated by specific molecules, including fatty acid-derived specialized pro-resolving mediators (SPMs). In advanced atherosclerosis, there is an imbalance between levels of SPMs and proinflammatory lipid mediators, which results in sustained leukocyte influx into lesions, inflammatory macrophage polarization, and impaired efferocytosis. In animal models of advanced atherosclerosis, restoration of SPMs limits plaque progression by suppressing inflammation, enhancing efferocytosis, and promoting an increase in collagen cap thickness. This Review discusses the roles of non-resolving inflammation in atherosclerosis and highlights the unique therapeutic potential of SPMs in blocking the progression of clinically dangerous plaques.

Wenyang Huoxue Jiedu formula inhibits thin-cap fibroatheroma plaque formation via the VEGF/VEGFR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

For many years, Guangzhou University of Chinese Medicine has been successfully using the empirical Wenyang Huoxue Jiedu formula (WHJF) to treat coronary heart disease. Modern theories of acute coronary syndrome mainly focus on rupture of thin-cap fibroatheromas (TCFAs), which is closely related to the release of vascular endothelial growth factor and its receptor (VEGF/VEGFR).

AIM OF STUDY

We investigated the effects of WHJF on the formation of TCFA plaques and the potential mechanism (VEGF/VEGFR signaling pathway).

MATERIALS AND METHODS

For the in vivo experiments, WHJF was administered to ApoE^-/- mice, as a model of TCFA plaque formation. Aortic sections of the mice were obtained, and the vulnerability index and new vessel density of plaques were calculated by the Movat staining assay and immunohistochemistry kit, respectively. Protein and mRNA expression levels of VEGF/VEGFR in aortas were assayed by capillary electrophoresis immunoassay and quantitative real-time polymerase chain reaction analyses. In vitro, WHJF serum was produced in rats on the fourth day 2 h after the first administration of different concentrations of WHJF. Proliferation, migration, and lumen formation ability of human umbilical vein endothelial cells (HUVECs) treated with sera from these rats were assayed by the CKK-8 kit, Transwell plates, and Matrigel assay, respectively. Protein and mRNA expression levels of signaling molecules in the VEGF/VEGFR pathways were also examined.

RESULTS

In vivo, the vulnerability index and new vessel density of plaques in the WHJF group were lower than those values in the blank control group (P < 0.05). No differences were found between the groups in the expression levels of VEGF/VEGFR (P > 0.05). In vitro, the proliferation, migration, and tube formation of HUVECs in the high-dose WHJF group were reduced compared to the control group (P < 0.05). This finding was in agreement with the downregulation of VEGFR-2 and pERK (P < 0.05). The mRNA expression of signaling molecules showed no difference between the groups (P > 0.05).

CONCLUSIONS

WHJF inhibits TCFA formation by influencing the VEGF/VEGFR signaling pathway.

[18F]-Fluorodeoxyglucose PET/CT imaging as a marker of carotid plaque inflammation: Comparison to immunohistology and relationship to acuity of events

BACKGROUND

[18F]-fluorodeoxyglucose (¹⁸FDG) uptake imaged with positron emission tomography (PET) and computed tomography (CT) may serve as a biomarker of plaque inflammation. This study evaluated the relationship between carotid plaque ¹⁸FDG uptake and a) intraplaque expression of macrophage and macrophage-like cellular CD68 immunohistology; b) intraplaque inflammatory burden using leukocyte-sensitive CD45 immunohistology; c) symptomatic patient presentation; d) time from last cerebrovascular event.

METHODS

54 patients scheduled for carotid endarterectomy underwent ¹⁸FDG PET/CT imaging. Maximum 18FDG uptake (SUV_max) and tissue-to-blood ratio (TBR_max) was measured for carotid plaques. Quantitative immunohistological analysis of macrophage-like cell expression (CD68) and leukocyte content (CD45) was performed.

RESULTS

¹⁸FDG uptake was related to CD68 macrophage expression (TBR_max: r = 0.51, p < 0.001), and total-plaque leukocyte CD45 expression (TBR_max: r = 0.632, p = 0.009, p < 0.001). ¹⁸FDG TBR_max uptake in carotid plaque associated with patient symptoms was greater than asymptomatic plaque (3.58 ± 1.01 vs. 3.13 ± 1.10, p = 0.008). ¹⁸FDG uptake differed between an acuity threshold of <90 days and >90 days (SUV_max:3.15 ± 0.87 vs. 2.52 ± 0.45, p = 0.015).

CONCLUSIONS

In this CAIN cohort, ¹⁸FDG uptake imaged with PET/CT serves a surrogate marker of intraplaque inflammatory macrophage, macrophage-like cell and leukocyte burden. 18FDG uptake is greater in plaque associated with patient symptoms and those with recent cerebrovascular events. Future studies are needed to relate ¹⁸FDG uptake and disease progression.

Comparison of 125I- and 111In-labeled peptide probes for in vivo detection of oxidized low-density lipoprotein in atherosclerotic plaques

OBJECTIVE

Oxidized low-density lipoprotein (OxLDL) plays a pivotal role in atherosclerotic plaque destabilization, which suggests its potential as a nuclear medical imaging target. We previously developed radioiodinated ¹²⁵I-AHP7, a peptide probe carrying a 7-residue sequence from the OxLDL-binding protein Asp-hemolysin, for specific OxLDL imaging. Although ¹²⁵I-AHP7 recognized OxLDL, it had low stability. Thus, to improve stability, we designed radiolabeled 22-residue peptide probes, ¹²⁵I-AHP22 and ¹¹¹In-AHP22, which include the entire AHP7 sequence, and evaluated the stability, activity, and applications of these probes in vitro and in vivo.

METHODS

Probes consisting of a 21-residue peptide derived from the Asp-hemolysin sequence and an N-terminal Cys or aminohexanoic acid for labeling with ¹²⁵I-N-(3-iodophenyl)maleimide or ¹¹¹In diethylene triamine pentaacetic acid were termed ¹²⁵I-AHP22 and ¹¹¹In-AHP22. An in vitro-binding inhibition assay with OxLDL was performed using ¹²⁵I-AHP7 as a radiotracer. Radioactivity accumulation in the atherosclerotic aorta and plasma intact fraction was evaluated 30 min after intravenous administration of probes in myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits.

RESULTS

¹²⁵I-AHP22 and ¹¹¹In-AHP22 were synthesized in ~ 360 and 60 min, respectively, with > 98% radiochemical purities after RP-HPLC purification. An in vitro-binding assay revealed similar or greater inhibition of OxLDL binding by both In-AHP22 and I-AHP22 compared to I-AHP7. The fraction of intact ¹²⁵I-AHP22 and ¹¹¹In-AHP22 in plasma was estimated to be approximately tenfold higher than that of ¹²⁵I-AHP7. Both probes were rapidly cleared from the blood. ¹¹¹In-AHP22 had a 2.3-fold higher accumulation in WHHLMI rabbit aortas compared to control rabbits, which was similar to ¹²⁵I-AHP7. However, ¹²⁵I-AHP22 accumulated to similar levels in aortas of WHHLMI and control rabbits due to high nonspecific accumulation in normal aortas that could be due to high lipophilicity.

CONCLUSIONS

¹¹¹In-AHP22, easily prepared within 1 h, showed moderate affinity for OxLDL, high stability in vivo, and high accumulation in atherosclerotic aortas. ¹¹¹In-AHP22 could be a potential lead compound to develop future effective OxLDL imaging probes.

Silencing of Non-POU-domain-containing octamer-binding protein stabilizes atherosclerotic plaque in apolipoprotein E-knockout mice via NF-κB signaling pathway

BACKGROUND

It remains unknown whether Non-POU-domain-containing octamer-binding protein (NonO) plays a causative role in plaque destabilization. We hypothesized that NonO gene silencing may stabilize atherosclerotic plaque by increasing P4Hα1 expression and inhibiting the inflammation.

METHODS AND RESULTS

Vulnerable atherosclerotic plaques were induced in ApoE-/- mice by high fat diet, perivascular collar placement and mental stress. Compared with normal carotid arteries, those contained vulnerable plaques had high NonO expression. In another in vivo experiment, mice contained vulnerable plaques were randomly divided into 5 groups to receive physiological saline, si-N.C-lentivirus (LV), si-NonO-LV, pGC-GFP-LV and NonO-LV, respectively. NonO overexpression increased while NonO silencing decreased the incidence of carotid plaque disruption. NonO overexpression enhanced macrophage infiltration and lipid deposition but reduced the content of vascular smooth muscle cells and collagen in plaques, leading to an increased plaque vulnerability index, whereas NonO silencing exhibited the opposite effect. In addition, NonO overexpression increased the expression of proinflammatory cytokines and matrix metalloproteinases and decreased the expression of P4Hα1 both in vivo and in vitro, whereas NonO silencing showed the contrary effect. NonO co-immunoprecipitated with NF-κB p65, and promoted its nuclear translocation and phosphorylation, and these effects were reversed by NonO silencing.

CONCLUSION

NonO may promote plaque destabilization and increase the incidence of plaque disruption in ApoE-/- mice by inducing the expression of inflammatory cytokines and matrix metalloproteinases and suppressing that of P4Hα1. The mechanism may involve the interaction of NonO with NF-κB leading to enhanced NF-κB nuclear translocation and phosphorylation.

Macrophage polarization and acceleration of atherosclerotic plaques in a swine model

Aims

Atherosclerosis is a well-known cause of cardiovascular disease and is associated with a variety of inflammatory reactions. However, an adequate large-animal model of advanced plaques to investigate the pathophysiology of atherosclerosis is lacking. Therefore, we developed and assessed a swine model of advanced atherosclerotic plaques with macrophage polarization.

Methods

Mini-pigs were fed a 2% high-cholesterol diet for 7 weeks followed by withdrawal periods of 4 weeks. Endothelial denudation was performed using a balloon catheter on 32 coronary and femoral arteries of 8 mini-pigs. Inflammatory proteins (high-mobility group box 1 [HMGB1] or tumor necrosis factor alpha (TNF-α) were injected via a micro-infusion catheter into the vessel wall. All lesions were assessed with angiography and optical coherence tomography and all tissues were harvested for histological evaluation.

Results

Intima/plaque area was significantly higher in the HMGB1- and TNF-α-injected groups compared to the saline-injected group (p = 0.002). CD68 antibody detection and polarization of M1 macrophages significantly increased in the inflammatory protein-injected groups (p<0.001). In addition, advanced atherosclerotic plaques were observed more in the inflammatory protein-injected groups compared with the control upon histologic evaluation.

Conclusion

Direct injection of inflammatory proteins was associated with acceleration of atherosclerotic plaque formation with M1 macrophage polarization. Therefore, direct delivery of inflammatory proteins may induce a pro-inflammatory response, providing a possible strategy for development of an advanced atherosclerotic large-animal model in a relatively short time period.

Localization of lipopolysaccharide from Escherichia Coli into human atherosclerotic plaque

Experimental studies showed that gut-derived lipopolysaccharide (LPS) is pro-atherogenic, however, its relationship with human atherosclerosis is still to be defined. We investigate if gut-derived LPS from Escherichia Coli localizes in human carotid plaque and its potential role as pro-inflammatory molecule in the atherosclerotic lesion. LPS from Escherichia Coli and Toll-like receptor 4 (TLR4) were studied in specimens from carotid and thyroid arteries of 10 patients undergoing endarterectomy and 15 controls matched for demographic and clinical characteristics. Blood LPS were significantly higher in patients compared to controls. Immunochemistry analysis revealed positivity for antibodies against LPS and TLR4 coincidentally with positivity for CD68 only in the atherosclerotic plaque of carotid arteries but not in thyroid arteries; the positivity for LPS and TLR4 was greater in the area with activated macrophages. LPS concentration similar to that detected in atherosclerotic plaque resulted in a dose-dependent TLR4-mediated Nox2 up-regulation by human monocytes. These data provide the first evidence that LPS from Escherichia Coli localizes in human plaque and may contribute to atherosclerotic damage via TLR4-mediated oxidative stress.

Legumain suppresses OxLDL-induced macrophage apoptosis through enhancement of the autophagy pathway

OBJECTIVE

Autophagy plays a prominent role in the pathogenesis of plaques formation and progression of atherosclerosis (AS). The cysteine protease legumain is known to participate in atherogenesis, but its function and underlying mechanism in AS macrophages remain unclear.

METHODS

The expressions of legumain in plaques isolated from AS patients and in macrophages stimulated with oxLDL were examined. Moreover, we effectively altered legumain expression in macrophages to characterize the effect of legumain on oxLDL-induced macrophage apoptosis. The expression of apoptotic and autophagic factors was analysed.

RESULTS

Legumain was present in plaques, and its expression was upregulated in macrophages treated with oxLDL. Suppressing legumain significantly increased oxLDL-induced macrophage apoptosis and the expression of caspase 3, caspase 9 and Bax. However, legumain overexpression decreased macrophage apoptosis upon oxLDL exposure and the levels of caspase 3, caspase 9 and Bax. In addition, recombinant legumain protein suppressed macrophage apoptosis. Biochemical experiments revealed that legumain deficiency decreased the levels of Beclin1 and LC3, whereas increased legumain expression increased the levels of Beclin1 and LC3 significantly.

CONCLUSION

Legumain regulates oxLDL-induced macrophage apoptosis by enhancing the autophagy pathway, which may also influence the vulnerability of atherosclerotic plaques.

Ca2+-dependent potassium channels and cannabinoid signaling in the endothelium of apolipoprotein E knockout mice before plaque formation

Endothelial Ca2+-dependent K+ channels (KCa) regulate endothelial function. We also know that stimulation of type 2 cannabinoid (CB2) receptors ameliorates atherosclerosis. However, whether atherosclerosis is accompanied by altered endothelial KCa- and CB2 receptor-dependent signaling is unknown. By utilizing an in situ patch-clamp approach, we directly evaluated the KCa channel function and the CB2 receptor-dependent electrical responses in the endothelium of aortic strips from young ApoE-/- and C57Bl/6 mice. In the ApoE-/- group, the resting membrane potential (-30.1±1.1mV) was less negative (p<0.05) compared to WT (-38.9±1.4mV) and voltage ramps generated an overall KCa current of reduced amplitude. The peak hyperpolarization to 2μM Ach was not different between the groups. However, the sustained component was significantly reduced in ApoE-/- strips. In contrast, the peak hyperpolarization to 0.2μM Ach was increased in the ApoE-/- group, and SKA-31, a direct IKCa/SKCa channel opener, produced a hyperpolarization and whole-cell current of greater amplitude. The BKCa opener NS1619 produced hyperpolarization that was enhanced in ApoE-/- group. N-arachidonoyl glycine, a BKCa opener, produced a hyperpolarization of enhanced amplitude in ApoE-/- arteries. Selective CB2 receptor agonist AM1241 (5μM) had no effect on endothelial membrane potential in WT group; however, in ApoE-/- group, it elicited hyperpolarization that was inhibited by a selective CB2 receptor antagonist AM630. Conclusively, our data point to functional down-regulation of basal IKCa activity in unstimulated endothelium of ApoE-/- mice. Direct and indirect IKCa stimulation resulted in increased recruitment of the channels. In addition, our data point to up-regulation of endothelial BKCa channels and CB2 receptors in ApoE-/- arteries.

Nanoparticle Functionalization with Platelet Membrane Enables Multifactored Biological Targeting and Detection of Atherosclerosis

Cardiovascular disease represents one of the major causes of death across the global population. Atherosclerosis, one of its most common drivers, is characterized by the gradual buildup of arterial plaque over time, which can ultimately lead to life-threatening conditions. Given the impact of the disease on public health, there is a great need for effective and noninvasive imaging modalities that can provide valuable information on its biological underpinnings during development. Here, we leverage the role of platelets in atherogenesis to design nanocarriers capable of targeting multiple biological elements relevant to plaque development. Biomimetic nanoparticles are prepared by coating platelet membrane around a synthetic nanoparticulate core, the product of which is capable of interacting with activated endothelium, foam cells, and collagen. The effects are shown to be exclusive to platelet membrane-coated nanoparticles. These biomimetic nanocarriers are not only capable of efficiently localizing to well-developed atherosclerotic plaque, but can also target subclinical regions of arteries susceptible to plaque formation. Using a commonly employed magnetic resonance imaging contrast agent, live detection is demonstrated using an animal model of atherosclerosis. Ultimately, this strategy may be leveraged to better assess the development of atherosclerosis, offering additional information to help clinicians better manage the disease.

Improving myocardial fractional flow reserve in coronary atherosclerosis via CX37 gene silence: a preclinical validation study in pigs

OBJECTIVES

The purpose of this study was to evaluate the effect of CX37 gene silence on myocardial fractional flow reserve (FFR).

METHODS

A total of 90 male pigs were randomly divided into saline, mock and 3 different doses (5, 10 and 20 µl) of CX37 viral suspension groups that could induce coronary plaque formation with high-fat diet. After performing myocardial FFR by intravascular ultrasound, different doses of CX37 viral suspension, saline and mock small interfering RNA (siRNA) were transfected into the related coronary. The FFR, the myocardial enzymes and the cardiac structures and functions of the pigs were detected at baseline, 4th, 8th and 12th week after transfection, respectively.

RESULTS

Repeated measures analysis of variance comparison showed that the difference in the FFR among the 5 groups was statistically significant (F = 27.0, P < 0.01). Post hoc analysis showed that FFR were highest in the siRNA CX37 group (20 µl), followed by the siRNA CX37 group (10 µl) and the siRNA CX37 group (5 µl), and lowest in the mock and saline groups. Left ventricular end-diastolic diameter was significantly smaller and ejection fraction was obviously higher in the 3 siRNA CX37 groups compared with the untreated groups.

CONCLUSIONS

Our study showed that FFR levels increased along with decreased doses of siRNA CX37 lentivirus, indicating that siRNA CX37 lentivirus may reduce the risk of coronary atherosclerosis and provide a potential approach to treat coronary heart disease.

[The (un)predictability of coronary atherosclerosis]

Coronary atherosclerosis is a common disease. The plaques developing inside coronary vessels may have serious consequences such as myocardial infarction. However, the course of this multifactorial and heterogeneous disease is difficult to predict and is different for each patient. Atherosclerosis is often described as a gradually progressive disease, but in addition to slow progression, a certain periodicity is often seen. There may be periods with more stability and periods of regression. Several processes are known to be involved in plaque development and their increasing vulnerability. We describe some of these processes in this article. Despite existing knowledge about these processes, atherosclerosis periodicity remains largely unexplained. More insight into this periodicity may potentially be relevant to the development of new therapies. Drug therapy to lower LDL-cholesterol is currently the cornerstone of treatment, in addition to lifestyle advice.

microRNA let-7g suppresses PDGF-induced conversion of vascular smooth muscle cell into the synthetic phenotype

Platelet-derived growth factor (PDGF) can promote vascular smooth muscle cells (VSMCs) to switch from the quiescent contractile phenotype to synthetic phenotype, which contributes to atherosclerosis. We aimed to investigate the role of microRNA let-7g in phenotypic switching. Bioinformatics prediction was used to find let-7g target genes in the PDGF/mitogen-activated protein kinase kinase kinase 1 (MEKK1)/extracellular signal-regulated kinase (ERK)/Krüppel-like factor-4 (KLF4) signalling pathway that affects VSMC phenotypic switching. The luciferase reporter assay and let-7g transfection were used to confirm let-7g target genes. Two contractile proteins alpha-smooth muscle actin (α-SMA) and calponin were VSMC-specific genes and were measured as the indicators for VSMC phenotype. Lentivirus carrying the let-7g gene was injected to apolipoprotein E knockout (apoE-/- ) mice to confirm let-7g's effect on preventing atherosclerosis. Through the PDGF/MEKK1/ERK/KLF4 signalling pathway, PDGF-BB can inhibit α-SMA and calponin. The PDGFB and MEKK1 genes were predicted to harbour let-7g binding sites, which were confirmed by our reporter assays. Transfection of let-7g to VSMC also reduced PDGFB and MEKK1 levels. Moreover, we showed that let-7g decreased phosphorylated-ERK1/2 while had no effect on total ERK1/2. KLF4 can reduce VSMC-specific gene expression by preventing myocardin-serum response factor (SRF) complex from associating with these gene promoters. The immunoprecipitation assay showed that let-7g decreased the interaction between KLF4 and SRF. Further experiments demonstrated that let-7g can increase α-SMA and calponin levels to maintain VSMC in the contractile status. Injection of lentivirus carrying let-7g gene increased let-7g's levels in aorta and significantly decreased atherosclerotic plaques in the apoE-/- mice. We demonstrated that let-7g reduces the PDGF/MEKK1/ERK/KLF4 signalling to maintain VSMC in the contractile status, which further reduce VSMC atherosclerotic change.

Interleukin 27 is increased in carotid atherosclerosis and promotes NLRP3 inflammasome activation

Aim

Interleukin-27 (IL-27) is involved in different inflammatory diseases; however, its role in atherosclerosis is unclear. In this study we investigated the expression of IL-27 and its receptor in patients with carotid atherosclerosis and if IL-27 could modulate the inflammatory effects of the NLRP3 inflammasome in vitro.

Methods

Plasma IL-27 was measured by enzyme immunoassay in patients with carotid stenosis (n = 140) and in healthy controls (n = 19). Expression of IL-27 and IL-27R was analyzed by quantitative PCR and immunohistochemistry in plaques from patients and in non-atherosclerotic vessels. THP-1 monocytes, primary monocytes and peripheral blood mononuclear cells (PBMCs) were used to study effects of IL-27 in vitro.

Results

Our main findings were: (i) Plasma levels of IL-27 were significantly elevated in patients with carotid atherosclerotic disease compared to healthy controls. (ii) Gene expression of IL-27 and IL-27R was significantly elevated in plaques compared to control vessels, and co-localized to macrophages. (iii) In vitro, IL-27 increased NLRP3 inflammasome activation in monocytes with enhanced release of IL-1 β.

Conclusions

We demonstrate increased levels of IL-27 and IL-27R in patients with carotid atherosclerosis. Our in vitro findings suggest an inflammatory role for IL-27, which can possibly be linked to atherosclerotic disease development.

Nonlinear dynamics of early atherosclerotic plaque formation may determine the efficacy of high density lipoproteins (HDL) in plaque regression

We use a computational model to explore the effect of foam cell accumulation on plaque regression following an increase in high density lipoprotein (HDL) influx into the plaque. Atherosclerotic plaque formation is the outcome of cellular and cytokine responses to low density lipoproteins (LDL) that penetrate the artery wall following an injury to the endothelium and become modified. We modelled the cells and cytokines that are most important in plaque formation using partial differential equations. The model includes monocytes and macrophages, foam cells, macrophage chemoattractants, endothelium-stimulating cytokines, modified low density lipoproteins (mod LDL) and HDL. We included interactions both at the endothelium surface and inside the artery wall. The model predicts that when HDL influx into a well-established plaque with large numbers of foam cells is increased, the plaque may not regress but may continue to grow at a slower rate. If HDL influx is increased when a model plaque is recently established and has fewer foam cells, then the plaque does regress. If modLDL influx into the plaque is lowered at the same time that HDL influx increased or the capacity of the HDL to remove cholesterol from foam cells is increased, then the plaque is more likely to regress. The predictions of the model are in qualitative agreement with experimental studies in mice and rabbits. The results suggest that the intrinsic dynamics of reverse cholesterol transport by HDL are important in determining the success of HDL raising in promoting plaque regression.

Frequency of Cholesterol Crystals in Culprit Coronary Artery Aspirate During Acute Myocardial Infarction and Their Relation to Inflammation and Myocardial Injury

Cholesterol crystals (CCs) have been associated with plaque rupture through mechanical injury and inflammation. This study evaluated the presence of CCs during acute myocardial infarction (AMI) and associated myocardial injury, inflammation, and arterial blood flow before and after percutaneous coronary intervention. Patients presenting with AMI (n = 286) had aspiration of culprit coronary artery obstruction. Aspirates were evaluated for crystal content, size, composition, and morphology by scanning electron microscopy, crystallography, and infrared spectroscopy. These were correlated with inflammatory biomarkers, cardiac enzymes, % coronary stenosis, and Thrombolysis in Myocardial Infarction (TIMI) blush and flow grades. Crystals were detected in 254 patients (89%) and confirmed to be cholesterol by spectroscopy. Of 286 patients 240 (84%) had CCs compacted into clusters that were large enough to be measured and analyzed. Moderate to extensive CC content was present in 172 cases (60%). Totally occluded arteries had significantly larger CC clusters than partially occluded arteries (p <0.05). Patients with CC cluster area >12,000 µm² had significantly elevated interleukin-1 beta (IL-1β) levels (p <0.01), were less likely to have TIMI blush grade of 3 (p <0.01), and more likely to have TIMI flow grade of 1 (p <0.01). Patients with recurrent AMI had smaller CC cluster area (p <0.04), lower troponin (p <0.02), and IL-1β levels (p <0.04). Women had smaller CC clusters (p <0.04). Macrophages in the aspirates were found to be attached to CCs. Coronary artery aspirates had extensive deposits of CCs during AMI. In conclusion, presence of large CC clusters was associated with increased inflammation (IL-1β), increased arterial narrowing, and diminished reflow following percutaneous coronary intervention.

The feedback loop of "EMMPRIN/NF-κB" worsens atherosclerotic plaque via suppressing autophagy in macrophage

This study examined the significance of macrophage autophagy in extracellular matrix metalloproteinase inducer (EMMPRIN)-mediated atherosclerosis (AS). Apolipoprotein E-deficient (ApoE-/-) mice were fed a western diet to establish an AS model. EMMPRIN and p62/Sequestosome-1(SQSTM1) expression were evaluated in plaque macrophages from the AS mice using immunofluorescence. The EMMPRIN and p62/SQSTM1 protein expression levels in macrophages increased with the increasing vulnerability of the atherosclerotic plaques. RAW264.7 cells and ApoE-/- mice Bone Marrow-derived macrophages were transfected with different small interfering RNAs (siRNAs) or plasmids, or treated with different drugs in the presence or absence of oxidized low-density lipoprotein (oxLDL). The protein levels of the targets were evaluated using western blotting (WB), and the autophagosomes were observed under a transmission electron microscope (TEM). Over-expressed EMMPRIN dramatically inhibited oxLDL-mediated autophagy. EMMPRIN also negatively regulated autophagy primarily through the nuclear factor-kappa B (NF-κB) signalling pathway. In turn, activated NF-κB up-regulated EMMPRIN expression. Inhibition of EMMPRIN decreased cell apoptosis and the release of inflammatory cytokines via the promotion of macrophage autophagy. Infection with an adenovirus delivering the EMMPRIN-siRNA ameliorated AS, promoted macrophage autophagy in plaques and reduced the serum TNF-α, IL-6, MCP-1 and NF-κB expression levels in the AS mice. Chloroquine (CQ) reversed these effects. This study revealed for the first time that the feedback loop of the "EMMPRIN/NF-κB" pathway plays an important role in atherosclerotic plaques via modulation of autophagy in macrophages, which might provide a potential strategy for the clinical treatment of AS.