Plaque Homogenates Research Articles

CCL3 and CCL5 as potential markers of carotid atherosclerotic plaque stability – preliminary research

Introduction: Carotid atherosclerosis is one of the main causes of ischaemic stroke. The study verified the hypothesis on the relationship between the expression of selected inflammatory markers and the stability of atherosclerotic plaque in stroke patients. Aim: The aim of the study was to determine CCL3 and CCL5 levels in both plasma and carotid atherosclerotic plaques in relation to the history of ischaemic stroke, as well as to assess plaque morphology and stability. Materials and methods: The levels of CCL3 and CCL5 chemokines were determined by ELISA for both plasma and supernatants of atherosclerotic plaque homogenates from patients undergoing endarterectomy due to at least 70% carotid artery stenosis. Results: Both chemokines were found in atherosclerotic plaques, with elevated CCL3 in unstable plaques. Furthermore, patients with atherosclerosis showed significantly higher plasma CCL5 compared to healthy individuals. Conclusions: The chemokines CCL3 and CCL5 are likely to be involved in the inflammatory processes contributing to the development of atherosclerotic plaque, but this needs to be confirmed in further studies.

Antithrombotic Effects of Fostamatinib in Combination with Conventional Antiplatelet Drugs.

New antithrombotic medications with less effect on haemostasis are needed for the long-term treatment of acute coronary syndromes (ACS). The platelet receptor glycoprotein VI (GPVI) is critical in atherothrombosis, mediating platelet activation at atherosclerotic plaque. The inhibition of spleen tyrosine kinase (Syk) has been shown to block GPVI-mediated platelet function. The aim of our study was to investigate if the Syk inhibitor fostamatinib could be repurposed as an antiplatelet drug, either alone or in combination with conventional antiplatelet therapy. The effect of the active metabolite of fostamatinib (R406) was assessed on platelet activation and function induced by atherosclerotic plaque and a range of agonists in the presence and absence of the commonly used antiplatelet agents aspirin and ticagrelor. The effects were determined ex vivo using blood from healthy volunteers and aspirin- and ticagrelor-treated patients with ACS. Fostamatinib was also assessed in murine models of thrombosis. R406 mildly inhibited platelet responses induced by atherosclerotic plaque homogenate, likely due to GPVI inhibition. The anti-GPVI effects of R406 were amplified by the commonly-used antiplatelet medications aspirin and ticagrelor; however, the effects of R406 were concentration-dependent and diminished in the presence of plasma proteins, which may explain why fostamatinib did not significantly inhibit thrombosis in murine models. For the first time, we demonstrate that the Syk inhibitor R406 provides mild inhibition of platelet responses induced by atherosclerotic plaque and that this is mildly amplified by aspirin and ticagrelor.

Targeting platelet-derived CXCL12 impedes arterial thrombosis

AbstractThe prevention and treatment of arterial thrombosis continue to be clinically challenging, and understanding the relevant molecular mechanisms in detail may facilitate the quest to identify novel targets and therapeutic approaches that improve protection from ischemic and bleeding events. The chemokine CXCL12 augments collagen-induced platelet aggregation by activating its receptor CXCR4. Here we show that inhibition of CXCR4 attenuates platelet aggregation induced by collagen or human plaque homogenate under static and arterial flow conditions by antagonizing the action of platelet-secreted CXCL12. We further show that platelet-specific CXCL12 deficiency in mice limits arterial thrombosis by affecting thrombus growth and stability without increasing tail bleeding time. Accordingly, neointimal lesion formation after carotid artery injury was attenuated in these mice. Mechanistically, CXCL12 activated via CXCR4 a signaling cascade involving Bruton's tyrosine kinase (Btk) that led to integrin αIIbβ3 activation, platelet aggregation, and granule release. The heterodimeric interaction between CXCL12 and CCL5 can inhibit CXCL12-mediated effects as mimicked by CCL5-derived peptides such as [VREY]4. An improved variant of this peptide, i[VREY]4, binds to CXCL12 in a complex with CXCR4 on the surface of activated platelets, thereby inhibiting Btk activation and preventing platelet CXCL12-dependent arterial thrombosis. In contrast to standard antiplatelet therapies such as aspirin or P2Y12 inhibition, i[VREY]4 reduced CXCL12-induced platelet aggregation and yet did not prolong in vitro bleeding time. We provide evidence that platelet-derived CXCL12 is involved in arterial thrombosis and can be specifically targeted by peptides that harbor potential therapeutic value against atherothrombosis.

The effect of Bruton's tyrosine kinase inhibitor ibrutinib on atherothrombus formation under stenotic flow conditions

BackgroundBruton's kinase (Btk) is critical for collagen-triggered platelet signal transduction. The Btk inhibitor ibrutinib has been shown to selectively block platelet adhesion to atherosclerotic plaque material under laminar arterial flow. However, this has not been studied under a shear gradient, which is characteristic for atherothrombosis. ObjectiveTo determine the effect of ibrutinib treatment on in vitro thrombus formation on collagen and atherosclerotic plaque material in the absence or presence of a shear gradient. MethodsBlood was obtained from patients with chronic lymphocytic leukemia, mantle-cell lymphoma and Waldenström macroglobulinemia with and without ibrutinib treatment and perfused through a microfluidic channel with(out) 60% stenosis over Horm type I collagen or human atherosclerotic plaque homogenate. ResultsAt a constant shear rate of 1500 s−1, platelet deposition was significantly decreased in blood from haematological malignancy patients treated with ibrutinib as compared to untreated patients, on atherosclerotic plaque material but not on collagen. However, thrombus size, stability, and height, were reduced on both plaque material and collagen. An increase in shear rate up to 3900 s−1, as induced by 60% stenosis, resulted in decreased platelet deposition and thrombus parameters on plaque material but not on collagen when compared to a laminar shear of 1500 s−1. Ibrutinib treatment decreased platelet deposition and thrombus parameters even further around the stenosis. ConclusionTreatment of patients with haematological disorders with the Btk inhibitor ibrutinib reduces in vitro platelet deposition, thrombus size and contraction on human atherosclerotic plaque around a stenosis when compared to patients not receiving ibrutinib.

Role of Tyrosine Kinase Syk in Thrombus Stabilisation at High Shear.

Understanding the pathways involved in the formation and stability of the core and shell regions of a platelet-rich arterial thrombus may result in new ways to treat arterial thrombosis. The distinguishing feature between these two regions is the absence of fibrin in the shell which indicates that in vitro flow-based assays over thrombogenic surfaces, in the absence of coagulation, can be used to resemble this region. In this study, we have investigated the contribution of Syk tyrosine kinase in the stability of platelet aggregates (or thrombi) formed on collagen or atherosclerotic plaque homogenate at arterial shear (1000 s−1). We show that post-perfusion of the Syk inhibitor PRT-060318 over preformed thrombi on both surfaces enhances thrombus breakdown and platelet detachment. The resulting loss of thrombus stability led to a reduction in thrombus contractile score which could be detected as early as 3 min after perfusion of the Syk inhibitor. A similar loss of thrombus stability was observed with ticagrelor and indomethacin, inhibitors of platelet adenosine diphosphate (ADP) receptor and thromboxane A2 (TxA2), respectively, and in the presence of the Src inhibitor, dasatinib. In contrast, the Btk inhibitor, ibrutinib, causes only a minor decrease in thrombus contractile score. Weak thrombus breakdown is also seen with the blocking GPVI nanobody, Nb21, which indicates, at best, a minor contribution of collagen to the stability of the platelet aggregate. These results show that Syk regulates thrombus stability in the absence of fibrin in human platelets under flow and provide evidence that this involves pathways additional to activation of GPVI by collagen.

Soluble CD40 Levels in Plasma Are Associated with Cardiovascular Disease and in Carotid Plaques with a Vulnerable Phenotype.

Background and PurposeCD40 and CD40 ligand (CD40L) are costimulatory molecules of the tumor necrosis factor receptor superfamily and well known for their involvement in inflammatory diseases: atherosclerotic mouse models with disrupted CD40 signalling develop lesions of reduced size with a more stable plaque profile. This study investigated the potential of plasma and intraplaque levels of CD40 and CD40L as markers for cardiovascular disease (CVD) in humans and their association with plaque stability. MethodsSoluble CD40 and CD40L (sCD40L) were measured in plasma in 1,437 subjects from The SUrrogate markers for Micro- and Macro-vascular hard endpoints for Innovative diabetes Tools (SUMMIT) cohort. Intra-plaque levels of sCD40 and sCD40L were measured in atherosclerotic plaque homogenates from 199 subjects of the Carotid Plaque Imaging Project (CPIP) cohort. ResultsBoth plasma sCD40 and sCD40L levels were elevated in individuals with prevalent stroke, while sCD40 levels also were higher in individuals with a prior acute myocardial infarction. Plasma levels of sCD40 correlated with carotid intima-media thickness and total carotid plaque area and were associated with risk of cardiovascular events over a 3-year follow-up period. Intra-plaque levels of sCD40 and sCD40L were associated with plaque components characteristic for plaque vulnerability and extracellular matrix remodelling. ConclusionsHigher plasma sCD40 and sCD40L levels are associated with prevalent CVD. Plasma sCD40 levels also correlate with the severity of carotid atherosclerosis and predict future cardiovascular events, while intra-plaque levels correlate with a vulnerable plaque phenotype. Our findings thus demonstrate that elevated levels of sCD40 and sCD40L are markers of CVD.

Features of interleukin-19 production in patients with atherosclerosis

Objective. To study the features of local and systemic production of interleukin-19 in patients with atherosclerosis.Material and Methods. The study comprised a total of 46 patients (26 women and 20 men) treated for arterial hypertension in the therapeutic department of Republican Clinical Hospital named after G.Y. Remishevskaya. The mean age of subjects was 63.4 ± 3.2 years. The control group included 40 patients (23 women and 17 men aged 44.7 ± 5.5 years) who did not have atherosclerosis. Samples of atherosclerotic plaques and venous blood were examined. Atherosclerotic plaques were obtained by endarterectomy and then subjected to homogenization followed by enzymatic hydrolysis for 1 h at 37 °C with collagenase IV in the presence of proteinase III inhibitors. The serum levels of cytokines (in the control group and in patients with atherosclerosis) and in the atherosclerotic plaque homogenate (in patients with atherosclerosis) were determined by ELISA. To assess the cytokine-producing capacity of blood leukocytes and white blood cells isolated from atherosclerotic plaques, spontaneous and phytohemagglutinin (PHA)-induced cytokine production was determined when the cells were cultured in RPMI-1640.Results. The serum levels of IL-19 did not significantly differ between the patients with atherosclerosis and the control group. A statistically significant two-fold increase in the spontaneous expression of IL-19 by blood leukocytes was observed in the group of patients with atherosclerosis in comparison with the control group. When comparing the contents of IL-19 in blood serum and atherosclerotic plaque homogenate in patients with atherosclerosis, no statistically significant differences were found (p = 0.182). The level of PHA-induced IL-19 production by the atherosclerotic plaque white blood cells was significantly lower than that of blood leucocytes.Conclusion. The study showed that the reserve capacity for IL-19 synthesis in the atherosclerotic plaque white blood cells decreases leading to the progression of inflammation. The obtained results suggest that IL-19 plays the anti-atherogenic role and its production is involved in the maintaining the mechanisms for down-regulation of inflammation in atherosclerotic plaques.

Regulation of glycolytic genes in human macrophages by oxysterols: a potential role for liver X receptors.

Subset of macrophages within the atheroma plaque displays a high glucose uptake activity. Nevertheless, the molecular mechanisms and the pathophysiological significance of this high glucose need remain unclear. While the role for hypoxia and hypoxia inducible factor 1α has been demonstrated, the contribution of lipid micro-environment and more specifically oxysterols is yet to be explored. Human macrophages were conditioned in the presence of homogenates from human carotid plaques, and expression of genes involved in glucose metabolism was quantified. Correlative analyses between gene expression and the oxysterol composition of plaques were performed. Conditioning of human macrophages by plaque homogenates induces expression of several genes involved in glucose uptake and glycolysis including glucose transporter 1 (SLC2A1) and hexokinases 2 and 3 (HK2 and HK3). This activation is significantly correlated to the oxysterol content of the plaque samples and is associated with a significant increase in the glycolytic activity of the cells. Pharmacological inverse agonist of the oxysterol receptor liver X receptor (LXR) partially reverses the induction of glycolysis genes without affecting macrophage glycolytic activity. Chromatin immunoprecipitation analysis confirms the implication of LXR in the regulation of SLC2A1 and HK2 genes. While our work supports the role of oxysterols and the LXR in the modulation of macrophage metabolism in atheroma plaques, it also highlights some LXR-independent effects of plaques samples. Finally, this study identifies hexokinase 3 as a promising target in the context of atherosclerosis. This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.

CD40 levels in plasma are associated with cardiovascular disease and in carotid plaques with a vulnerable plaque phenotype and remodelling

Abstract Background and purpose CD40 and CD40 ligand (CD40L) are costimulatory molecules and members of the TNF receptor superfamily well known for their involvement in inflammatory and autoimmune diseases. This study uses two large human cohorts – the SUrrogate markers for Micro- and Macro-vascular hard endpoints for Innovative diabetes Tools (SUMMIT) and the Carotid Plaque Imaging Project (CPIP) – to explore the potential of plasma or intra-plaque expression of CD40 and CD40L as biomarkers and to locally affect plaque stability. Methods Proximity Extension Assay (PEA) technique was used to measure soluble CD40 and CD40L (sCD40 and sCD40L) in plasma from 1437 subjects from the SUMMIT cohort, the majority of which (80%) with pre-existing cardiovascular disease, and in atherosclerotic plaque homogenates from 199 subjects of the CPIP cohort undergoing carotid endarterectomy. The Mann-Whitney U test was used to compare groups and Spearman's rank correlation/the Chi-square test was used to assess correlations. Multiple comparisons were corrected for using the Holm-Šídák test. A logistic regression model was used to test for associations with future cardiovascular events and mortality. Results In the SUMMIT cohort both plasma CD40 and CD40L levels were elevated in individuals with a history of stroke (p=0.000030 and p=0.020, respectively), while sCD40 levels also were higher in individuals with a prior acute myocardial infarction (p=0.016). Plasma levels of sCD40 correlated with carotid plaque burden (as measured by ultrasound imaging, r=0.355, p<1x10–16) and were associated with future cardiovascular events over a three year-follow up period (p=0.02, hazard ratio 1.3, 95% C.I: 1.042–1.625). sCD40 and sCD40L were associated with a plaque phenotype characterized by the strong presence of features both of vulnerability such as high content oxidized low-density lipoprotein (LDL; r=0.236, p=0.004 and r=0.259, p=0.0037, respectively) and pro-inflammatory cytokines (e.g. tumour necrosis factor-α: p=3.1x10–7 and p=0.0006, respectively) and low calcium content (r=−0.208, p=0.012 and r=0.268, p=0.00034, respectively). Conclusion High plasma CD40 and CD40L levels are associated with symptomatic cardiovascular disease. Plasma CD40 levels correlate with the severity of carotid atherosclerosis and are associated with an increased risk for future cardiovascular events. Additionally, intra-plaque levels are associated with a vulnerable plaque phenotype. Our findings thus support the value of sCD40 and sCD40L both as biomarkers and therapeutic targets for cardiovascular disease. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): The Swedish Heart and Lung Foundation (1) and the Swedish Research Council (2)

The proteoglycan mimecan is associated with carotid plaque vulnerability and increased risk of future cardiovascular death

Background and aimsA vulnerable plaque is an atherosclerotic plaque that is rupture-prone with a higher risk to cause cardiovascular symptoms such as myocardial infarction or stroke. Mimecan or osteoglycin is a small leucine-rich proteoglycan, important for collagen fibrillogenesis, that has been implicated in atherosclerotic disease, yet the role of mimecan in human atherosclerotic disease remains unknown. Methods196 human atherosclerotic carotid plaques were immunostained for mimecan. Smooth muscle cells, macrophages and intraplaque haemorrhage were also measured with immunohistochemistry. Neutral lipids were stained with Oil Red O and calcium deposits were quantified. Plaque homogenate levels of MCP-1, IL-6 and MIP-1β were measured using a Proximity Extension Assay and MMP-9 levels were measured using Mesoscale. Glycosaminoglycans, collagen and elastin were assessed by colorimetric assays and TGF-β1, β2 and β3 were measured using a multiplex assay. Mimecan gene expression in THP-1 derived macrophages was quantified by qPCR and protein expression in vitro was visualized with immunofluorescence. Cardiovascular events were registered using medical charts and national registers during follow-up. ResultsMimecan correlated positively with plaque area of lipids, macrophages, intraplaque haemorrhage and inversely with smooth muscle cell staining. Mimecan also correlated positively with plaque levels of MMP-9 and MCP-1. Mimecan was upregulated in THP-1 derived macrophages upon stimulation with MCP-1. Patients with high levels of mimecan (above median) had higher risk for cardiovascular death. ConclusionsThis study indicates that mimecan is associated with a vulnerable plaque phenotype, possibly regulated by plaque inflammation. In line, plaque levels of mimecan independently predict future cardiovascular death.

Interplay between Liver X Receptor and Hypoxia Inducible Factor 1α Potentiates Interleukin-1β Production in Human Macrophages

Low-grade inflammation is constitutive of atherosclerosis, and anti-inflammatory therapy inhibiting interleukin-1β (IL-1β) reduces the rate of cardiovascular events. While cholesterol accumulation in atheroma plaque and macrophages is a major driver of the inflammatory process, the role of the LXR cholesterol sensors remains to be clarified. Murine and human macrophages were treated with LXR agonists for 48h before Toll-like receptor (TLR) stimulation. Unexpectedly, we observe that, among other cytokines, LXR agonists selectively increase IL1B mRNA levels independently of TLR activation. This effect, restricted to human macrophages, is mediated by activation of HIF-1α through LXR. Accordingly, LXR agonists also potentiate other HIF-1α-dependent pathways, such as glycolysis. Treatment of human macrophages with carotid plaque homogenates also leads to induction of IL1B in an LXR-dependent manner. Thus, our work discloses a mechanism by which cholesterol and oxysterols trigger inflammation in atherosclerosis. This suggests perspectives to target IL-1β production in atherosclerotic patients.

Is Neovascularization a Leading Mechanism of Intra-plaque Hemorrhage and Carotid Plaque Destabilization?

Introduction: The accelerating carotid plaque growth can cause fibrous cap rupture followed by embolization to brain vessels. Important role in this process is ascribed to thrombotic factors and their inhibitors although another mechanism based on rupture of deficient vessels formed inside the plaque within the neovascularization process is also proposed. Interestingly, the second sequence of events provoke intra-plaque hemorrhage without a fibrous cap rupture. To determine whether the neovascularization is a main process responsible for carotid plaque destabilization the current study was conducted in asymptomatic and symptomatic patients with carotid stenosis. Methods: There were 121 individuals included to the study. Among them, study group consisted of 86 consecutive patients undergoing carotid endarterectomy (23 symptomatic, 63 asymptomatic, mean age 68±7,4 years) and 35 individuals without any symptoms and signs of atherosclerosis served as a control group. The concentration of vascular endothelial growth factor (VEGF) and its receptors, sVEGFR1, sVEGFR2, and tissue factor (TF) and tissue factor pathway inhibitor (TFPI) (ELISA immunoassay) in plaque homogenates and blood plasma was measured. In addition, activity of TF and TFPI (actichrome assay) were also measured. Concentration and activity results of all tested parameters were recounted for the milligram of protein contained in the plasma and plaques homogenates. Results: Analyzing patients with symptomatic and asymptomatic carotid stenosis the only statistically significant difference was found in the concentration of VEGF in plaque homogenates which was significantly higher in symptomatic plaques (302,9 vs 182,1 pg/ml; p=0,005 and 88,0 vs 67,9 pg/mg protein; p=0,05). The plaques homogenate’s TF level recounted for the milligram of protein was nearly 300-fold higher and TF activity was 5-fold higher in comparison with their plasma concertation and activity in the study group. The concentration and activity of TFPI was also higher in the plaque homogenates then in the plasma. The activity of TFPI in plaque homogenates recounted for the milligram of protein was 25-fold higher than in the plasma of the study patients. The VEGF concentration in plaque homogenates was significantly higher than in the plasma of study patients. There was no difference in VEGF concentration in the plasma of the study group and the control group. The lowest concentration of VEGF-R1 recounted for the milligram of protein was observed in the plasma of the control group. Higher concentration of VEGF-R1 recounted for the milligram protein was found in the plasma of the study group, but the distinctly highest concentration of VEGF-R1 (more than 10-fold higher) was observed in the study group plaque homogenates. Reverse characteristic showed the concentration of VEGF-R2, the lowest level was observed in the plaque homogenates and the highest in the plasma of the control group. Conclusion: The neovascularization process might be a leading mechanism of intra-plaque hemorrhage and carotid plaque destabilization. The plaque homogenates and blood plasma of patients with severe carotid stenosis have a strong prothrombotic profile. The plaque homogenates of patients with carotid stenosis in contrary to plasma possess signs of outspread angiogenetic activity.

A Proteomic Study of Atherosclerotic Plaques in Men with Coronary Atherosclerosis.

Background: To study the changes in protein composition of atherosclerotic plaques at different stages of their development in coronary atherosclerosis using proteomics. Methods: The object of research consisted of homogenates of atherosclerotic plaques from coronary arteries at different stages of development, obtained from 15 patients. Plaque proteins were separated by two-dimensional electrophoresis. The resultant protein spots were identified by the matrix-assisted laser desorption ionization method with peptide mass mapping. Results: Groups of differentially expressed proteins, in which the amounts of proteins differed more than twofold (p < 0.05), were identified in pools of homogenates of atherosclerotic plaques at three stages of development. The amounts of the following proteins were increased in stable atherosclerotic plaques at the stage of lipidosis and fibrosis: vimentin, tropomyosin β-chain, actin, keratin, tubulin β-chain, microfibril-associated glycoprotein 4, serum amyloid P-component, and annexin 5. In plaques at the stage of fibrosis and calcification, the amounts of mimecan and fibrinogen were increased. In unstable atherosclerotic plaque of the necrotic–dystrophic type, the amounts of human serum albumin, mimecan, fibrinogen, serum amyloid P-component and annexin were increased. Conclusion: This proteomic study identifies the proteins present in atherosclerotic plaques of coronary arteries by comparing their proteomes at three different stages of plaque development during coronary atherosclerosis.

High Levels of Soluble Lectinlike Oxidized Low-Density Lipoprotein Receptor-1 Are Associated With Carotid Plaque Inflammation and Increased Risk of Ischemic Stroke.

BackgroundWhen the lectinlike oxidized low‐density lipoprotein (oxLDL) receptor‐1 (LOX‐1), a scavenger receptor for oxLDL, binds oxLDL, processes leading to endothelial dysfunction and inflammation are promoted. We aimed to study release mechanisms of LOX‐1 and how circulating levels of soluble LOX‐1 (sLOX‐1) relate to plaque inflammation and future risk for ischemic stroke.Methods and ResultsEndothelial cells and leukocytes were used to study release of sLOX‐1. Plasma levels of sLOX‐1 were determined in 4703 participants in the Malmö Diet and Cancer cohort. Incidence of ischemic stroke was monitored. For 202 patients undergoing carotid endarterectomy, levels of sLOX‐1 were analyzed in plasma and plaque homogenates and related to plaque inflammation factors. Endothelial cells released sLOX‐1 when exposed to oxLDL. A total of 257 subjects experienced stroke during a mean follow‐up of 16.5 years. Subjects in the highest tertile of sLOX‐1 had a stroke hazard ratio of 1.75 (95% CI, 1.28–2.39) compared with those in the lowest tertile after adjusting for age and sex. The patients undergoing carotid endarterectomy had a significant association between plasma sLOX‐1 and the plaque content of sLOX‐1 (r=0.209, P=0.004). Plaques with high levels of sLOX‐1 had more oxLDL, proinflammatory cytokines, and matrix metalloproteinases.ConclusionsOur findings demonstrate that oxLDL induces the release of sLOX‐1 from endothelial cells and that circulating levels of sLOX‐1 correlate with carotid plaque inflammation and risk for ischemic stroke. These observations provide clinical support to experimental studies implicating LOX‐1 in atherosclerosis and its possible role as target for cardiovascular intervention.

ANALYSIS OF DIFFERENTIAL ExPRESSION OF MATRIx METALLOPROTEASES IN STABLE AND UNSTABLE ATHEROSCLEROTIC LESIONS BY A METHOD OF FULL GENOME SEQUENCING OF RNA: PILOT STUDY

Aim. To analyze differential expression of metalloproteases genes, involved into the processes of stabilization/destabilization of atherosclerotic plaque, with the method of full genome sequencing of RNA, and to evaluate the level of metalloproteases in homogenates of plaques of various types by immune enzyme assay method (IEA).Material and methods. The study has been conducted on the specimens of atherosclerotic plaques of patients aged 45-65 y.o., inhabitants of Western Siberia with angiographically proven coronary atherosclerosis and no acute coronary syndrome, with stable angina II-IV functional class. Specimens collection from the plaques was done during an operation if there were intraoperational indications. Histology performed. In intima/media homogenates by IEA method, with BCM Diagnostics assays the levels of destructive markers were measured: MMP-1, MMP3, MMP-7, MMP-9, TIMP-1 on the Multiscan EX (Thermo Fisher Scientific, USA). Libraries preparation for full genomic sequencing of RNA was done with Illumina’s TruSeq RNA Sample Preparation Kit (Illumina, USA). Expression profile in tissues was done on HiSeq 1500 (Illumina, USA).Results. There are differences in expression of the genes MMP2, MMP7, MMP8, MMP9, MMP12, и MMP14 in different types of plaques. There was 8 times higher significant raise in increase of the expression level of ММР9 (p&lt;0,001) in unstable plaque of dystrophic-necrotic type. Study by IEA of MMP-7 content, which is an activator of pro-MMP-9, as well as the content of MMP-9 itself, showed their increased levels in unstable plaques comparing to fatty streaks (1,5 and 2,4 times) and young stable plaques (1,4 and 2,1 times).Conclusion. For the gene ММР9 there were significant differences obtained, of expression levels in stable atherosclerotic fibrous plaque and unstable plaque of dystrophic-necrotic type. With the IEA it was found that fatty streaks and young stable atheromas of coronary arteries have an increased concentration of MMP-3 and decreased activity of tissue inhibitor of metalloproteases. In unstable plaques with the tendency to rupture/ulceration there are increased levels of MMP-1, MMP-7, MMP-9.

Oral Bruton tyrosine kinase inhibitors selectively block atherosclerotic plaque–triggered thrombus formation in humans

AbstractInteraction of von Willebrand factor (VWF) with platelet glycoprotein Ib (GPIb) and interaction of collagen with GPVI are essential for thrombus formation on ruptured or eroded atherosclerotic plaques (atherothrombosis). GPIb and GPVI signal through Bruton tyrosine kinase (Btk), which can be blocked irreversibly by oral application of ibrutinib, an established therapy for chronic lymphocytic leukemia (CLL) with long-term safety. We found that ibrutinib and the novel Btk inhibitors acalabrutinib and ONO/GS-4059 block GPVI-dependent static platelet aggregation in blood exposed to human plaque homogenate and collagen but not to ADP or arachidonic acid. Moreover, Btk inhibitors prevented platelet thrombus formation on human atherosclerotic plaque homogenate and plaque tissue sections from arterially flowing blood, whereas integrin α2β1 and VWF-dependent platelet adhesion to collagen, which is important for physiologic hemostasis, was not affected. This plaque-selective platelet inhibition was also observed in CLL patients taking 450 mg of ibrutinib and in volunteers after much lower and intermittent dosing of the drug. We conclude that Btk inhibitors, by targeting GPIb and GPVI signal transduction, suppress platelet thrombus accretion from flowing blood on atherosclerotic plaque but spare hemostatic platelet function. Btk inhibitors hold promise as the first culprit lesion–focused oral antiplatelet drugs and are effective at low doses.

Vaccination against T-cell epitopes of native ApoB100 reduces vascular inflammation and disease in a humanized mouse model of atherosclerosis.

The T-cell response to low-density lipoprotein (LDL) in the vessel wall plays a critical role in atherosclerotic plaque formation and stability. In this study, we used a new translational approach to investigate epitopes from human apolipoprotein B100 (ApoB100), the protein component of LDL, which triggers T-cell activation. We also evaluated the potential of two selected native ApoB100 epitopes to modulate atherosclerosis in human ApoB100-transgenic Ldlr-/- (HuBL) mice. HuBL mice were immunized with human atherosclerotic plaque homogenate to boost cellular autoimmune response to tissue-derived ApoB100 epitopes. In vitro challenge of splenocytes from immunized mice with a library of overlapping native peptides covering human ApoB100 revealed several sequences eliciting T-cell proliferation. Of these sequences, peptide (P) 265 and P295 were predicted to bind several human leucocyte antigen (HLA) haplotypes and induced high levels of interferon (IFN)-γ. Vaccination of HuBL mice with these peptides mounted a strong adaptive immune response to native ApoB100, including high levels of epitope-specific plasma IgGs. Interestingly, P265 and P295 vaccines significantly decreased plaque size, reduced macrophage infiltration and increased IgG1 deposition in the plaques. Purified IgGs from vaccinated mice displayed anti-inflammatory properties against macrophages invitro, reducing their response to LPS in a dose-dependent manner. We identified two specific epitopes from human native ApoB100 that trigger T-cell activation and protect HuBL mice against atherosclerosis when used in a vaccine. Our data suggest that vaccination-induced protective mechanisms may be mediated at least in part through specific antibody responses to LDL that inhibit macrophage activation.

Oral thrombin inhibitor aggravates platelet adhesion and aggregation during arterial thrombosis.

In patients with atrial fibrillation, oral anticoagulation with oral thrombin inhibitors (OTIs), in contrast to vitamin K antagonists (VKAs), associates with a modest increase in acute coronary syndromes (ACSs). Whether this observation is causatively linked to OTI treatment and, if so, whether OTI action is the result of a lower antithrombotic efficacy of OTI compared to VKA or reflects a yet undefined prothrombotic activity of OTI remain unclear. We analyzed platelet function in patients receiving OTI or dose-adapted VKA under static and flow conditions. In vivo, we studied arterial thrombosis in OTI-, VKA-, and vehicle-treated mice using carotid ligation and wire injury models. Further, we examined thrombus formation on human atherosclerotic plaque homogenates under arterial shear to address the relevance to human pathology. Under static conditions, aggregation in the presence of ristocetin was increased in OTI-treated blood, whereas platelet reactivity and aggregation to other agonists were only marginally affected. Under flow conditions, firm platelet adhesion and thrombus formation on von Willebrand factor, collagen, and human atherosclerotic plaque were increased in the presence of OTI in comparison to VKA. OTI treatment was associated with increased thrombus formation in injured carotid arteries of mice. Inhibition or ablation of GPIbα-thrombin interactions abolished the effect of OTI on thrombus formation, suggesting a mechanistic role of the platelet receptor GPIbα and its thrombin-binding site. The effect of OTI was also abrogated in the presence of aspirin. In summary, OTI treatment has prothrombotic activity that might contribute to the increase in ACS observed clinically in patients.

Human Carotid Plaques With High Levels of Interleukin-16 Are Associated With Reduced Risk for Cardiovascular Events.

Interleukin-16 (IL-16) functions as a regulator of T-cell growth and acts as an inducer of cell migration. The aim of this study was to determine whether IL-16 measured in human carotid plaques was associated with symptoms (eg, stroke, transient ischemic attack, or amaurosis fugax), markers of plaque stability, and postoperative cardiovascular events. Plaques obtained from patients who had ≥1 cerebrovascular ischemic events within 1 month before endarterectomy (n=111) were compared with plaques from patients without symptoms (n=95). Neutral lipids, smooth muscle cell, and macrophage contents were evaluated histologically, and collagen, elastin, and caspase-3 activity were measured biochemically. IL-16, matrix metalloproteinases, and tissue inhibitors of metalloproteinases were measured in plaque homogenates using a multiplex immunoassay. IL-16, CD3, CD4, and FoxP3 mRNA expressions in carotid plaques were analyzed with quantitative real-time polymerase chain reaction. Carotid plaques from asymptomatic patients had higher levels of IL-16 mRNA. High plaque IL-16 protein levels (above median) were associated with reduced incidence of postoperative cardiovascular events during a mean follow-up of 21 months (hazard ratio, 0.47; 95% confidence interval, 0.22-0.99; P=0.047). IL-16 levels correlated with the plaque-stabilizing components: elastin, collagen, matrix metalloproteinase-2, tissue inhibitors of metalloproteinase-1, tissue inhibitors of metalloproteinase-2 and FoxP3 mRNA. This study shows that high levels of IL-16 are associated with asymptomatic carotid plaques, expression of factors contributing to plaque stability, and decreased risk of new cardiovascular events during a 2-year period after surgery, suggesting that IL-16 might have a protective role in human atherosclerotic disease.

Human carotid atherosclerotic lesion protein components decrease cholesterol biosynthesis rate in macrophages through 3-hydroxy-3-methylglutaryl-CoA reductase regulation.

Atherosclerosis is characterized by the formation of cholesterol-loaded macrophages, which are turned into foam cells, the hallmark of early atherogenesis. As part of ongoing research on the interactions among human carotid lesion components and blood elements, the effect of plaque homogenate on macrophage cholesterol biosynthesis rate was examined. Human carotid plaques were ground, extracted with phosphate-buffered saline (homogenate), and then added to the macrophage medium. This extract decreased macrophage cholesterol biosynthesis rate up to 50% in a dose-dependent manner. Cholesterol or lipoproteins were separated from the homogenate and added to the MQ medium. Unlike the homogenate, neither free cholesterol nor the lipoproteins were able to inhibit cholesterol biosynthesis rate under the above experimental concentration, suggesting that the homogenate-induced cholesterol biosynthesis inhibition in our experimental system was not owing to the feedback inhibition of cholesterol. Furthermore, the homogenate remaining after lipoprotein removal (lipoprotein-deficient homogenate) also decreased cholesterol biosynthesis rate, whereas boiled homogenate or phospholipids extracted from the homogenate decreased macrophage cholesterol biosynthesis rate only partially. Finally, cholesterol biosynthesis inhibition was achieved only upon using the precursor [(3)H]acetate, but not [(14)C]mevalonate, suggesting that 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCoA Reductase), the rate-limiting enzyme in the cholesterol biosynthesis pathway, is involved in the above antiatherogenic effect of the homogenate, whereas the treatment with homogenate decreased HMGCoA Reductase mRNA. Proteins and phospholipids from human carotid lesion homogenate decrease cholesterol biosynthesis rate in macrophages secondary to HMGCoA Reductase feedback regulation. Such an effect may delay foam cell formation and atherosclerosis progression.