Loss of Y Chromosome in Blood Is Associated With Major Cardiovascular Events During Follow-Up in Men After Carotid Endarterectomy

Background: Recent studies found an immune regulatory role for Y chromosome and a relationship between loss of Y chromosome (LOY) in blood cells and a higher risk of cancer and mortality. Given involvement of immune cells in atherosclerosis, we hypothesized that LOY is associated with the severity of atherosclerotic plaque characteristics and outcome in men undergoing carotid endarterectomy. // Methods and Results: LOY was quantified in blood and plaque from raw intensity genotyping data in men within the Athero-Express biobank study. Plaques were dissected, and the culprit lesions used for histology and the measurement of inflammatory proteins. We tested LOY for association with (inflammatory) atherosclerotic plaque phenotypes and cytokines and assessed the association of LOY with secondary events during 3-year follow-up. Of 366 patients with carotid endarterectomy, 61 exhibited some degree of LOY in blood. LOY was also present in atherosclerotic plaque lesions (n=8/242, 3%). LOY in blood was negatively associated with age (β=−0.03/10 y; r2=0.07; P=1.6×10–7) but not with cardiovascular disease severity at baseline. LOY in blood was associated with a larger atheroma size (odds ratio, 2.15; 95% confidence interval, 1.06–4.76; P=0.04); however, this association was not significant after correction for multiple testing. LOY was independently associated with secondary major cardiovascular events (hazard ratio=2.28; 95% confidence interval, 1.11–4.67; P=0.02) in blood when corrected for confounders. // Conclusions: In this hypothesis-generating study, LOY in blood is independently associated with secondary major cardiovascular events in a severely atherosclerotic population. Our data could indicate that LOY affects secondary outcome via other mechanisms than inflammation in the atherosclerotic plaque

Enhanced Neointima Formation Following Arterial Injury in Immune Deficient Rag-1−/− Mice Is Attenuated by Adoptive Transfer of CD8+ T cells

T cells modulate neointima formation after arterial injury but the specific T cell population that is activated in response to arterial injury remains unknown. The objective of the study was to identify the T cell populations that are activated and modulate neointimal thickening after arterial injury in mice. Arterial injury in wild type C57Bl6 mice resulted in T cell activation characterized by increased CD4+CD44hi and CD8+CD44hi T cells in the lymph nodes and spleens. Splenic CD8+CD25+ T cells and CD8+CD28+ T cells, but not CD4+CD25+ and CD4+CD28+ T cells, were also significantly increased. Adoptive cell transfer of CD4+ or CD8+ T cells from donor CD8−/− or CD4−/− mice, respectively, to immune-deficient Rag-1−/− mice was performed to determine the T cell subtype that inhibits neointima formation after arterial injury. Rag-1−/− mice that received CD8+ T cells had significantly reduced neointima formation compared with Rag-1−/− mice without cell transfer. CD4+ T cell transfer did not reduce neointima formation. CD8+ T cells from CD4−/− mice had cytotoxic activity against syngeneic smooth muscle cells in vitro. The study shows that although both CD8+ T cells and CD4+ T cells are activated in response to arterial injury, adoptive cell transfer identifies CD8+ T cells as the specific and selective cell type involved in inhibiting neointima formation

Cholesterol Crystals Activate the NLRP3 Inflammasome in Human Macrophages: A Novel Link between Cholesterol Metabolism and Inflammation

Chronic inflammation of the arterial wall is a key element in the pathogenesis of atherosclerosis, yet the factors that trigger and sustain the inflammation remain elusive. Inflammasomes are cytoplasmic caspase-1-activating protein complexes that promote maturation and secretion of the proinflammatory cytokines interleukin(IL)-1beta and IL-18. The most intensively studied inflammasome, NLRP3 inflammasome, is activated by diverse substances, including crystalline and particulate materials. As cholesterol crystals are abundant in atherosclerotic lesions, and IL-1beta has been linked to atherogenesis, we explored the possibility that cholesterol crystals promote inflammation by activating the inflammasome pathway.Here we show that human macrophages avidly phagocytose cholesterol crystals and store the ingested cholesterol as cholesteryl esters. Importantly, cholesterol crystals induced dose-dependent secretion of mature IL-1beta from human monocytes and macrophages. The cholesterol crystal-induced secretion of IL-1beta was caspase-1-dependent, suggesting the involvement of an inflammasome-mediated pathway. Silencing of the NLRP3 receptor, the crucial component in NLRP3 inflammasome, completely abolished crystal-induced IL-1beta secretion, thus identifying NLRP3 inflammasome as the cholesterol crystal-responsive element in macrophages. The crystals were shown to induce leakage of the lysosomal protease cathepsin B into the cytoplasm and inhibition of this enzyme reduced cholesterol crystal-induced IL-1beta secretion, suggesting that NLRP3 inflammasome activation occurred via lysosomal destabilization.The cholesterol crystal-induced inflammasome activation in macrophages may represent an important link between cholesterol metabolism and inflammation in atherosclerotic lesions

Temporal Network Based Analysis of Cell Specific Vein Graft Transcriptome Defines Key Pathways and Hub Genes in Implantation Injury

Vein graft failure occurs between 1 and 6 months after implantation due to obstructive intimal hyperplasia, related in part to implantation injury. The cell-specific and temporal response of the transcriptome to vein graft implantation injury was determined by transcriptional profiling of laser capture microdissected endothelial cells (EC) and medial smooth muscle cells (SMC) from canine vein grafts, 2 hours (H) to 30 days (D) following surgery. Our results demonstrate a robust genomic response beginning at 2 H, peaking at 12–24 H, declining by 7 D, and resolving by 30 D. Gene ontology and pathway analyses of differentially expressed genes indicated that implantation injury affects inflammatory and immune responses, apoptosis, mitosis, and extracellular matrix reorganization in both cell types. Through backpropagation an integrated network was built, starting with genes differentially expressed at 30 D, followed by adding upstream interactive genes from each prior time-point. This identified significant enrichment of IL-6, IL-8, NF-κB, dendritic cell maturation, glucocorticoid receptor, and Triggering Receptor Expressed on Myeloid Cells (TREM-1) signaling, as well as PPARα activation pathways in graft EC and SMC. Interactive network-based analyses identified IL-6, IL-8, IL-1α, and Insulin Receptor (INSR) as focus hub genes within these pathways. Real-time PCR was used for the validation of two of these genes: IL-6 and IL-8, in addition to Collagen 11A1 (COL11A1), a cornerstone of the backpropagation. In conclusion, these results establish causality relationships clarifying the pathogenesis of vein graft implantation injury, and identifying novel targets for its prevention

Atherosclerotic lesion development and Toll like receptor 2 and 4 responsiveness

Background: Toll like receptors (TLR) have been recognized for their role in atherosclerotic lesion development and progression. Endogenous TLR ligands that are also expressed in atherosclerotic tissues have been shown to promote atherosclerosis in mice. Since repetitive stimulation of TLR induces an attenuated inflammatory response, we hypothesized that the TLR response is altered during atherosclerosis development, due to chronic exposure to endogenous ligands. Methods and Results: We examined five groups of both ApoE-/- and C57B1/6 mice aged 5, 10, 15, 25 and 40 weeks. In ApoE-/- mice with advanced stages of atherosclerosis, levels of mRNA encoding TLR2 and TLR4, the endogenous TLR ligands EDA and hsp60 as well as intracellular TLR-regulating mediators, like IRAK-M, were increased. Systemic TLR cell surface expression on circulating monocytes and EDA plasma levels were significantly increased in ApoE-/- mice with advanced atherosclerosis. We also observed that the endogenous TLR ligand EDA was capable of activating the TLR-signaling pathway in white blood cells. During the plaque progression stage however, stimulation of TLR2 and TLR4 in blood samples attenuated MIP-1 alpha and RANTES release in atherosclerotic mice. Conclusion: During atherosclerotic lesion development, TLR2 and TLR4 expression increases in atherosclerotic plaques and on circulating blood cells. However, with advanced stages of atherosclerotic disease, circulating blood cells become less responsive to TLR ligation, which may be due to chronic TLR engagement by endogenous EDA. (c) 2007 Elsevier Ireland Ltd. All rights reserved