Enhanced neointima formation following arterial injury in immune deficient Rag-1-/- mice is attenuated by adoptive transfer of CD8 T cells

Vascular Inflammation in Cardiovascular Disease: Is Immune System Protective or Bystander?

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. Chronic atherosclerosis induced vascular inflammation and perturbation of lipid metabolism is believed to be a major cause of CVD. Interplay of innate and adaptive Immune system has been interwined with various risk factors associated with the initiation and progression of atherosclerosis in CVD. A large body of evidence indicates a correlation between immunity and atherosclerosis. Retention of plasma lipoproteins in arterial subendothelial wall triggers the T helper type 1 (Th1) cells and monocyte-derived macrophages to form atherosclerotic plaques. In the present review, we will discuss the pathogenesis of CVD in relation to atherosclerosis with a particular focus on pro-atherogenic role of immune cells. Recent findings have also suggested anti-atherogenic roles of different B cell subsets. Therapeutic approaches to target atherosclerosis risk factors have reduced the mortality, but a need exists for the novel therapies to treat arterial vascular inflammation. These insights into the immune pathogenesis of atherosclerosis can lead to new targeted therapeutics to abate cardiovascular mortality and morbidity.

The Role of Immunomodulation in Vein Graft Remodeling and Failure

Obstructive arterial disease is a major cause of morbidity and mortality in the developed world. Venous bypass graft surgery is one of the most frequently used revascularization strategies despite its considerable short and long time failure rate. Due to vessel wall remodeling, inflammation, intimal hyperplasia, and accelerated atherosclerosis, vein grafts may (ultimately) fail to revascularize tissues downstream to occlusive atherosclerotic lesions. In the past decades, little has changed in the prevention of vein graft failure (VGF) although new insights in the role of innate and adaptive immunity in VGF have emerged. In this review, we discuss the pathophysiological mechanisms underlying the development of VGF, emphasizing the role of immune response and associated factors related to VG remodeling and failure. Moreover, we discuss potential therapeutic options that can improve patency based on data from both preclinical studies and the latest clinical trials. This review contributes to the insights in the role of immunomodulation in vein graft failure in humans. We describe the effects of immune cells and related factors in early (thrombosis), intermediate (inward remodeling and intimal hyperplasia), and late (intimal hyperplasia and accelerated atherosclerosis) failure based on both preclinical (mouse) models and clinical data.

CD4+/CD8+ ratio positively correlates with coronary plaque instability in unstable angina pectoris patients but fails to predict major adverse cardiovascular events

Background:

The association between CD4+/CD8+ ratio and coronary plaque instability in patients with unstable angina pectoris (UAP) has not been investigated. We sought to elucidate the correlation between CD4+/CD8+ ratio and plaque instability in this patient population.

Methods:

We enrolled 266 UAP patients who underwent pre-intervention optical coherence tomography (OCT) examination and percutaneous coronary intervention in our center from January 2016 to January 2018. Features of coronary plaques in the culprit arteries were classified as unstable plaque and stable plaque. Primary endpoint was occurrence of a major adverse cardiovascular event (MACE). Receiver operating characteristic (ROC) analyses were used to determine the predictive efficacy of the CD4+/CD8+ ratio for a group of unstable plaque patients, and binary logistic regression analysis was performed to evaluate potential independent predictors of plaque instability. All-cause mortality and MACE between the two groups were analyzed.

Results:

UAP patients with unstable plaque had a higher CD4/CD8 ratio compared with stable plaque patients (p < 0.05). Results of binary logistic regression analyses showed that CD4+/CD8+ ratio ⩾1.725 and prior stroke were predictors and risk factors of plaque instability (p < 0.05). ROC analyses showed that CD4+/CD8+ ratio ⩾1.725 was predictive of plaque instability in UAP patients. However, the Kaplan–Meier estimate for MACE and all-cause mortality showed no statistical significance.

Conclusions:

Higher CD4+/CD8+ ratio is associated with higher risk of plaque instability in our cohort of UAP patients. However, CD4+/CD8+ ratio was not an independent predictor of 1-year MACE or all-cause mortality.

Depletion of CD4 and CD8 Positive T Cells Impairs Venous Thrombus Resolution in Mice

Resolution of deep venous thrombosis involves coordinated inflammatory processes. T cells regulate inflammation in vivo and modulate vascular remodeling in other settings, but their role in venous thrombus resolution remains undefined. To determine the role of T cells in venous thrombus resolution in vivo, stasis induced thrombi were created by vena cava ligation in outbred CD-1 mice. CD4 and CD8 positive T cells, as determined by flow cytometry, were present in thrombi both during thrombus formation and resolution. Depletion of the CD4 and CD8 positive T cells by antibody treatment selectively impaired thrombus resolution compared to animals treated with isotype control antibodies, without an effect on venous thrombus formation. Quantitation of intra-thrombus macrophage numbers, fibrinolytic marker expression, and gelatinolytic activity by zymography revealed that T cell depletion decreased the number of macrophages, reduced the expression of fibrinolytic marker urokinase plasminogen activator (uPA), and decreased the activity of matrix metalloprotinease-9 (MMP-9). These data implicate CD4 and CD8 positive T cells in functionally contributing to venous thrombus resolution, thus representing a potential therapeutic target, but also underscoring potential risks involved in T cell depletion used clinically for solid organ and hematopoietic transplantation procedures.

Fimasartan reduces neointimal formation and inflammation after carotid arterial injury in apolipoprotein E knockout mice

BACKGROUND

The beneficial effects of angiotensin II type 1 receptor blockers (ARBs) on atherosclerosis have been demonstrated in numerous studies. We investigated the effects of fimasartan on reducing neointimal formation and systemic inflammation after carotid artery (CA) injury in Apolipoprotein E knockout (ApoE KO) mice.

METHODS

ApoE KO mice were randomly allocated to Group I (without CA injury), Group II (without CA injury + Fimasartan), Group III (CA injury), and Group IV (CA injury + Fimasartan). Fimasartan was orally administered everyday starting 3 days before iatrogenic left CA injury.

RESULTS

At 28 days, neointimal hyperplasia and the inflammatory cytokines including TNFα, IL-6, ICAM, and MMP-9 in the peripheral blood were significantly reduced in Groups II and IV compared to Groups I and III, respectively. All fimasartan-administered groups revealed significant increases of CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cells with increased plasma levels of IL-10 and TGFβ. In addition, increased CD8⁺ T cells by fimasartan were correlated with reduced smooth muscle cell (SMC) proliferation in the neointima in Groups II and IV. Furthermore, the populations of Treg and CD8⁺ T cells in total splenocytes were increased in Groups II and IV compared to Groups I and III, respectively. The enlargement of spleens due to CA injury in the Group III was attenuated by fimasartan, as shown in the Group IV. These data indicate that fimasartan significantly reduced SMC proliferation in neointima and increased Treg cells in ApoE KO CA injury mice.

CONCLUSIONS

This study suggests fimasartan could be an efficient strategy for reduction of atherosclerotic progression, with a decrease in immune response and systemic inflammation.

CD8+ T Cells Protect During Vein Graft Disease Development

Aims: Vein grafts are frequently used conduits for arterial reconstruction in patients with cardiovascular disease. Unfortunately, vein graft disease (VGD) causes diminished patency rates. Innate immune system components are known to contribute to VGD. However, the role of T cells has yet to be established. The purpose of this study was to investigate the role of T cells and T cell activation pathways via the T cell receptor (TCR), co-stimulation and bystander effect in VGD.

Methods and results: Here, we show upon vein graft surgery in mice depleted of CD4+ T cells or CD8+ T cells, that CD8+ T cells are locally activated and have a major protective role for vein graft patency. In presence of CD8+ T cells vein grafts appear patent while CD8+ T cell depletion results in occluded vein grafts with increases apoptosis. Importantly, the protective effect of CD8+ T cells in VGD development was TCR and co-stimulation independent. This was demonstrated in vein grafts of OT-I mice, CD70^−/−, CD80/86^−/−, and CD70/80/86^−/− mice compared to C57BL/6 mice. Interestingly, cytokines including IL-15, IL-18, IL-33, and TNF are up-regulated in vein grafts. These cytokines are co-operatively capable to activate CD8+ T cells in a bystander-mediated fashion, in contrast to CD4+ T cells.

Conclusions: T cells are modulators of VGD with a specific protective role of CD8+ T cells, which are locally activated in vein grafts. CD8+ T cells may protect against occlusive lesions by providing survival signals, and concert their protection independent of TCR and co-stimulation signaling.

The many faces of CD8+ T cells in atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis and the clinical consequence of cardiovascular disease remain the leading cause of death worldwide. Both an increase in cholesterol levels, as well as immune responses drive the pathogenesis of this disease. Although much is known about the role of many immune cell subsets in atherogenesis, research into the role of CD8 T cells is limited.

RECENT FINDINGS

Both atheroprotective and atherogenic functions of CD8 T cells have been reported. On the one hand, the inflammatory cytokines produced by CD8 T cells exacerbate inflammatory responses, and the cytotoxic activity of these cells toward lesion-stabilizing cells such as endothelial cells drives the progression and instability of atherosclerotic lesions. On the other hand, cytotoxic activity toward antigen presenting cells and the presence of regulatory CD8 T-cell subsets dampen immunity and can limit atherosclerosis.

SUMMARY

Here we review the different roles of CD8 T cells in atherosclerosis and discuss possible treatment strategies targeting these cells to reduce atherosclerotic lesion burden.

Novel Adipokine, FAM19A5, Inhibits Neointima Formation After Injury Through Sphingosine-1-Phosphate Receptor 2

Background:

Obesity plays crucial roles in the development of cardiovascular diseases. However, the mechanisms that link obesity and cardiovascular diseases remain elusive. Compelling evidence indicates that adipokines play an important role in obesity-related cardiovascular diseases. Here, we found a new adipokine-named family with sequence similarity 19, member A5 (FAM19A5), a protein with unknown function that was predicted to be distantly related to the CC-chemokine family. We aimed to test whether adipose-derived FAM19A5 regulates vascular pathology on injury.

Methods:

DNA cloning, protein expression, purification, and N-terminal sequencing were applied to characterize FAM19A5. Adenovirus infection and siRNA transfection were performed to regulate FAM19A5 expression. Balloon and wire injury were performed in vivo on the rat carotid arteries and mouse femoral arteries, respectively. Bioinformatics analysis, radioactive ligand-receptor binding assays, receptor internalization, and calcium mobilization assays were used to identify the functional receptor for FAM19A5.

Results:

We first characterized FAM19A5 as a secreted protein, and the first 43 N-terminal amino acids were the signal peptides. Both FAM19A5 mRNA and protein were abundantly expressed in the adipose tissue but were downregulated in obese mice. Overexpression of FAM19A5 markedly inhibited vascular smooth muscle cell proliferation and migration and neointima formation in the carotid arteries of balloon-injured rats. Accordingly, FAM19A5 silencing in adipocytes significantly promoted vascular smooth muscle cell activation. Adipose-specific FAM19A5 transgenic mice showed greater attenuation of neointima formation compared with wild-type littermates fed with or without Western-style diet. We further revealed that sphingosine-1-phosphate receptor 2 was the functional receptor for FAM19A5, with a dissociation constant ( K d ) of 0.634 nmol/L. Inhibition of sphingosine-1-phosphate receptor 2 or its downstream G12/13-RhoA signaling circumvented the suppressive effects of FAM19A5 on vascular smooth muscle cell proliferation and migration.

Conclusions:

We revealed that a novel adipokine, FAM19A5, was capable of inhibiting postinjury neointima formation via sphingosine-1-phosphate receptor 2-G12/13-RhoA signaling. Downregulation of FAM19A5 during obesity may trigger cardiometabolic diseases.

Identification of apoB-100 Peptide-Specific CD8+ T Cells in Atherosclerosis

Background

T cells are found in atherosclerotic plaques, with evidence supporting a potential role for CD8+ T cells in atherogenesis. Prior studies provide evidence of low‐density lipoprotein and apoB‐100 reactive T cells, yet specific epitopes relevant to the disease remain to be defined. The current study was undertaken to identify and characterize endogenous, antigen‐specific CD8+ T cells in atherosclerosis.

Methods and Results

A peptide fragment of apoB‐100 that tested positive for binding to the mouse MHC‐I allele H2K^b was used to generate a fluorescent‐labeled H2K^b pentamer and tested in apoE^−/− mice. H2K^b pentamer(+)CD8+ T cells were higher in apoE^−/− mice fed an atherogenic diet compared with those fed a normal chow. H2K^b pentamer (+)CD8+ T cells in atherogenic diet–fed mice had significantly increased effector memory phenotype with a shift in Vβ profile. H2K^b pentamer blocked lytic activity of CD8+ T cells from atherogenic diet–fed mice. Immunization of age‐matched apoE^−/− mice with the apoB‐100 peptide altered the immune‐dominant epitope of CD8+ T cells and reduced atherosclerosis.

Conclusions

Our study provides evidence of a self‐reactive, antigen‐specific CD8+ T‐cell population in apoE^−/− mice. Immune modulation using the peptide antigen reduced atherosclerosis in apoE^−/− mice.

Impact of Immune Deficiency on Remodeling of Maternal Resistance Vasculature 4 Weeks Postpartum in Mice

Pregnancy manifests changes in the vascular and immune systems that persist postpartum (PP), have important implications for future pregnancies, and may modify responses to cardiovascular stress in late life. The association between immune and vascular function and the generation or progression of cardiovascular disease beg the question of whether altered immunity modifies pregnancy-induced changes in the vasculature. Our objective was to compare changes in the function and remodeling of systemic resistance vessels 4 weeks PP in normal C57BL/6 (B6), and immunodeficient mice recombinase 1-deficient/B6 ( Rag1^-/-). Immune deficiency did not change the responsiveness to acetylcholine (ACh) and phenylephrine at baseline but decreased arterial distensibility and increased stiffness PP. Adoptive transfer of CD8 T cells into Rag1^-/- mice decreased the response to ACh while increasing distensibility and wall thickness. When compared to PP Rag1^-/-, vessels from PP CD4-deficient mice, which have B cells and CD8 T cells, but no CD4 cells, show increased distensibility and decreased responsiveness to ACh in a pattern similar to that seen in Rag1^-/- given CD8 T cells prior to mating. These studies suggest a key role for T cell, particularly CD8 T cell, associated factors in the PP remodeling of maternal resistance vessels.

Distinct Differences on Neointima Formation in Immunodeficient and Humanized Mice after Carotid or Femoral Arterial Injury

Percutaneous coronary intervention is widely adopted to treat patients with coronary artery disease. However, restenosis remains an unsolved clinical problem after vascular interventions. The role of the systemic and local immune response in the development of restenosis is not fully understood. Hence, the aim of the current study was to investigate the role of the human immune system on subsequent neointima formation elicited by vascular injury in a humanized mouse model. Immunodeficient NOD.Cg-Prkdc^scidIL2rg^tm1Wjl(NSG) mice were reconstituted with human (h)PBMCs immediately after both carotid wire and femoral cuff injury were induced in order to identify how differences in the severity of injury influenced endothelial regeneration, neointima formation, and homing of human inflammatory and progenitor cells. In contrast to non-reconstituted mice, hPBMC reconstitution reduced neointima formation after femoral cuff injury whereas hPBMCs promoted neointima formation after carotid wire injury 4 weeks after induction of injury. Neointimal endothelium and smooth muscle cells in the injured arteries were of mouse origin. Our results indicate that the immune system may differentially respond to arterial injury depending on the severity of injury, which may also be influenced by the intrinsic properties of the arteries themselves, resulting in either minimal or aggravated neointima formation.

[Adhesion molecules and mononuclear cell subpopulations in the coronary and pulmonary arteries of patients with coronary heart disease]

Atherosclerosis is a multifactor disease, in which dysfunction of the endothelium leads to the emergence of its adhesion molecules.

OBJECTIVE

to investigate the expression of the endothelial adhesion molecules PECAM (CD31), ICAM, and VCAM, as well as adherent endothelial T cells and monocytes. The material examined was en face pulmonary and coronary artery samples taken during autopsies (10 men), and en face specimens obtained from the coronary artery fragments taken from coronary heart disease patients during endarterectomy (37 men). This investigation used antibodies to the adhesion molecules ICAM-1, VCAM-1, and PECAM and those to CD3, CD4, CD8 T-cells and CD68 monocytes.

RESULTS

The endothelial cells in the atherosclerotically intact coronary arteries had an elongated shape and were aligned along the blood flow. Those located above atheromas and fibroatheromas changed their shape from elongated to polygonal. Above the fatty streaks and atheromas, the reaction with antibodies to CD31 antigens became weaker at the edge of endothelial cells and disappeared in places. While the atherosclerotic process progressed, the reaction with the CD31 antigen at the edge of endothelial cells was similar in intensity to that on the surface of the endothelium. Adhesion of T cells and monocytes to the endothelium of coronary arteries increased as the atherosclerotic vascular process progressed. T cells and monocytes more often adhered to the endothelium at the sites where the endothelial cells contacted each other.

CONCLUSION

Heterogeneity was found in the endothelial cells: their shape, the expression of adhesion molecules, and the adhesion of lymphocytes and monocytes to them changed during the progression of the atherosclerotic process.

Cuff-Induced Neointimal Formation in Mouse Models

Ischemic heart failure caused by atherosclerosis is a major cause of death worldwide. Although remarkable technological advances have been made in the treatment of coronary heart disease, there is as yet no treatment that can sufficiently suppress the progression of atherosclerosis, including neointimal thickening. Therefore, a precise understanding of the mechanism of neointimal hyperplasia will provide the development of new technologies. Both ApoE-KO and LDLR-KO mice have been employed to generate other relevant mouse models of cardiovascular disease through breeding strategies. Although these mice are effective tools for the investigation of atherosclerosis, development of a progressive atherosclerotic lesion takes a long time, resulting in increase of both the costs and the space needed for the research. Thus, it is necessary to develop simpler tools that would allow easy evaluation of atherosclerosis in mouse models. In this review, we discuss our experience in generating mouse models of cuff-induced injury of the femoral artery and attempt to provide a better understanding of cuff-induced neointimal formation.

PD-1 and Tim-3 Pathways Regulate CD8+ T Cells Function in Atherosclerosis

T cell-mediated immunity plays a significant role in the development of atherosclerosis (AS). There is increasing evidence that CD8+ T cells are also involved in AS but their exact roles remain unclear. The inhibitory receptors programmed cell death-1 (PD-1) and T cell immunoglobulin and mucin domain 3 (Tim-3) are well known inhibitory molecules that play a crucial role in regulating CD8+ T cell activation or tolerance. Here, we demonstrate that the co-expression of PD-1 and Tim-3 on CD8+ T cells is up-regulated in AS patients. PD-1+ Tim-3+ CD8+ T cells are enriched for within the central T (TCM) cell subset, with high proliferative activity and CD127 expression. Co-expression of PD-1 and Tim-3 on CD8+ T cells is associated with increased anti-atherogenic cytokine production as well as decreased pro-atherogenic cytokine production. Blockade of PD-1 and Tim-3 results in a decrease of anti-atherogenic cytokine production by PD-1+ Tim-3+ CD8+ T cells and in an augmentation of TNF-α and IFN-γ production. These findings highlight the important role of the PD-1 and Tim-3 pathways in regulating CD8+ T cells function in human AS.

CD4(+) lymphocytes improve venous blood flow in experimental arteriovenous fistulae

BACKGROUND

The role of immune cells in arteriovenous fistulae (AVF) maturation is poorly understood and has received, until quite recently, little attention. This study examines the function of T lymphocytes in AVF vascular remodeling.

METHODS

Experimental fistulae were created in athymic rnu nude rats lacking mature T lymphocytes and euthymic control animals by anastomosing the left superior epigastric vein to the nearby femoral artery. Blood flow rates, wall morphology, and histologic changes were assessed in AVF 21 days after creation. The effect of CD4(+) lymphocytes on AVF maturation in athymic animals was analyzed by adoptive transfer of cells after fistula creation.

RESULTS

The absence of T lymphocytes compromised blood flow in experimental fistulae. Histopathologic inspection of AVF from athymic rats revealed that T-cell immunodeficiency negatively affected venous vascular remodeling, as evidenced by a reduced lumen, a thick muscular layer, and a low number of inflammatory cells compared with control animals. Adoptive transfer of CD4(+) lymphocytes from euthymic rats into athymic animals after fistula creation improved blood flow and reduced intima-media thickness.

CONCLUSION

These results point at the protective role of CD4(+) lymphocytes in the remodeling of the AVF vascular wall.

Rosuvastatin reduces vascular inflammation and T-cell and monocyte activation in HIV-infected subjects on antiretroviral therapy

BACKGROUND

Despite suppressive antiretroviral therapy (ART), increased levels of immune activation persist in HIV-infected subjects. Statins have anti-inflammatory effects and may reduce immune activation in HIV disease.

METHODS

Stopping Atherosclerosis and Treating Unhealthy bone with RosuvastatiN in HIV (SATURN-HIV) is a randomized, double-blind placebo-controlled trial assessing the effect of rosuvastatin (10 mg daily) on markers of cardiovascular risk and immune activation in ART-treated patients. T-cell activation was measured by expression of CD38, HLA-DR, and PD1. Monocyte activation was measured with soluble markers (sCD14 and sCD163) and by enumeration of monocyte subpopulations and tissue factor expression. Markers of systemic and vascular inflammation and coagulation were also measured. SATURN-HIV is registered on clinicaltrials.gov (identifier: NCT01218802).

RESULTS

Rosuvastatin, compared with placebo, reduced sCD14 (-10.4% vs 0.5%, P = 0.006), lipoprotein-associated phospholipase A2 (-12.2% vs -1.7%, P = 0.0007), and IP-10 (-27.5 vs -8.2%, P = 0.03) levels after 48 weeks. The proportion of tissue factor-positive patrolling (CD14CD16) monocytes was also reduced by rosuvastatin (-41.6%) compared with placebo (-18.8%, P = 0.005). There was also a greater decrease in the proportions of activated (CD38HLA-DR) T cells between the arms (-38.1% vs -17.8%, P = 0.009 for CD4 cells, and -44.8% vs -27.4%, P = 0.003 for CD8 cells).

CONCLUSIONS

Forty-eight weeks of rosuvastatin treatment reduced significantly several markers of inflammation and lymphocyte and monocyte activation in ART-treated subjects.

Targeting PI3Kγ activity decreases vascular trauma-induced intimal hyperplasia through modulation of the Th1 response

Interventional strategies to treat atherosclerosis, such as transluminal angioplasty and stent implantation, often cause vascular injury. This leads to intimal hyperplasia (IH) formation that induces inflammatory and fibroproliferative processes and ultimately restenosis. We show that phosphoinositide 3-kinase γ (PI3Kγ) is a key player in IH formation and is a valid therapeutic target in its prevention/treatment. PI3Kγ-deficient mice and mice expressing catalytically inactive PI3Kγ (PI3Kγ KD) showed reduced arterial occlusion and accumulation of monocytes and T cells around sites of vascular lesion. The transfer of PI3Kγ KD CD4(+) T cells into Rag2-deficient mice greatly reduced vascular occlusion compared with WT cells, clearly demonstrating the involvement of PI3Kγ in CD4(+) T cells during IH formation. In addition we found that IH is associated with increased levels of Th1 and Th17 cytokines. A specific decrease in the Th1 response was observed in the absence of PI3Kγ activity, leading to decreased CXCL10 and RANTES production by smooth muscle cells. Finally, we show that treatment with the PI3Kγ inhibitor AS-605240 is sufficient to decrease IH in both mouse and rat models, reinforcing the therapeutic potential of PI3Kγ inhibition. Altogether, these findings demonstrate a new role for PI3Kγ activity in Th1-controlled IH development.

Macrophage-derived IL-18 and increased fibrinogen deposition are age-related inflammatory signatures of vascular remodeling

Aging has been associated with pathological vascular remodeling and increased neointimal hyperplasia. The understanding of how aging exacerbates this process is fundamental to prevent cardiovascular complications in the elderly. This study proposes a mechanism by which aging sustains leukocyte adhesion, vascular inflammation, and increased neointimal thickness after injury. The effect of aging on vascular remodeling was assessed in the rat balloon injury model using microarray analysis, immunohistochemistry, and LINCOplex assays. The injured arteries in aging rats developed thicker neointimas than those in younger animals, and this significantly correlated with a higher number of tissue macrophages and increased vascular IL-18. Indeed, IL-18 was 23-fold more abundant in the injured vasculature of aged animals compared with young rats, while circulating levels were similar in both groups of animals. The depletion of macrophages in aged rats with clodronate liposomes ameliorated vascular accumulation of IL-18 and significantly decreased neointimal formation. IL-18 was found to inhibit apoptosis of vascular smooth muscle cells (VSMC) and macrophages, thus favoring both the formation and inflammation of the neointima. In addition, injured arteries of aged rats accumulated 18-fold more fibrinogen-γ than those of young animals. Incubation of rat peritoneal macrophages with immobilized IL-18 increased leukocyte adhesion to fibrinogen and suggested a proinflammatory positive feedback loop among macrophages, VSMC, and the deposition of fibrinogen during neointimal hyperplasia. In conclusion, our data reveal that concentration changes in vascular cytokine and fibrinogen following injury in aging rats contribute to local inflammation and postinjury neointima formation.

CD8(+)CD25(+) T cells reduce atherosclerosis in apoE(-/-) mice

BACKGROUND

It is increasingly evident that CD8(+) T cells are involved in atherosclerosis but the specific subtypes have yet to be defined. CD8(+)CD25(+) T cells exert suppressive effects on immune signaling and modulate experimental autoimmune disorders but their role in atherosclerosis remains to be determined. The phenotype and functional role of CD8(+)CD25(+) T cells in experimental atherosclerosis were investigated in this study.

METHODS AND RESULTS

CD8(+)CD25(+) T cells were observed in atherosclerotic plaques of apoE(-/-) mice fed hypercholesterolemic diet. Characterization by flow cytometric analysis and functional evaluation using a CFSE-based proliferation assays revealed a suppressive phenotype and function of splenic CD8(+)CD25(+) T cells from apoE(-/-) mice. Depletion of CD8(+)CD25(+) from total CD8(+) T cells rendered higher cytolytic activity of the remaining CD8(+)CD25(-) T cells. Adoptive transfer of CD8(+)CD25(+) T cells into apoE(-/-) mice suppressed the proliferation of splenic CD4(+) T cells and significantly reduced atherosclerosis in recipient mice.

CONCLUSIONS

Our study has identified an athero-protective role for CD8(+)CD25(+) T cells in experimental atherosclerosis.

Association between CD8+ T-cell subsets and cardiovascular disease

BACKGROUND

The findings of experimental studies suggest that the immune system plays a key role in atherosclerosis, but the clinical importance of different immune cells in cardiovascular disease remains poorly characterized. In this study we investigated the association between CD8(+) T cells and carotid disease as well as development of cardiovascular disease events.

METHODS

The study cohort comprised 700 subjects from the cardiovascular arm of the Malmö Diet and Cancer Study. Peripheral blood mononuclear cells, obtained at the 1991-1994 baseline investigation and stored at -140 °C, were thawed and the different CD8(+) T-cell populations analysed by flow cytometry. Baseline carotid intima-media thickness and stenosis were assessed by ultrasonography and clinical events were monitored through validated national registers.

RESULTS

Subjects with a high fraction of CD8(+) T cells were characterized by decreased cytokine release from activated leucocytes, metabolic signs of insulin resistance and increased incidence of coronary events; hazard ratios (95% confidence intervals) for the second and third tertiles of CD8(+) T cells were 2.57 (1.16, 5.67) and 2.61 (1.19, 5,71), respectively, in a Cox proportional hazards regression model. Correlations were found between the fraction of CD8(+) CD25(+) T cells and the degree of carotid stenosis (r = 0.11, P < 0.01), and between the CD8(+) CD56(-) IFN-γ(+) T-cell fraction and the degree of stenosis (r = -0.18, P < 0.005). The association between CD8(+) CD56(-) IFN-γ(+) T cells and carotid stenosis remained significant after controlling for major cardiovascular disease risk factors.

CONCLUSION

This study provides prospective clinical evidence for a role of CD8(+) T cells in cardiovascular disease and suggests the existence of CD8(+) T-cell subsets with different pathological functions.

Reduced neointima formation after arterial injury in CD4-/- mice is mediated by CD8+CD28hi T cells

Background

CD8⁺ T‐cell activation, characterized by increased CD28 expression, reduces neointima formation after arterial injury in mice. The CD8⁺CD28^hi phenotype is associated with increased effector function. In this study, we used a mouse model that has CD8⁺ but no CD4⁺ T cells (CD4−/−) to assess the role of CD8⁺ T cells and test the function of CD8⁺CD28^hi T cells in modulating neointima formation after arterial injury.

Methods and Results

Neointima formation after pericarotid arterial cuff injury was significantly less in CD4−/− mice compared with wild‐type (WT) mice. Negligible baseline lytic activity by splenic CD8⁺ T cells from uninjured WT mice against target syngeneic smooth muscle cells was significantly increased 7 days after injury. Interestingly, CD8⁺ T cells from uninjured CD4−/− mice had significant lytic activity at baseline that remained elevated 7 days after injury. CD8⁺ T‐cell lytic activity was significantly reduced by depletion of CD28^hi cells. CD8⁺CD28^hi T cells adoptively transferred into recipient Rag‐1−/− mice significantly reduced neointima formation compared with CD8⁺CD28⁺ T‐cell recipient mice.

Conclusions

CD8⁺ T cells reduced neointima formation after arterial injury, attributed in part to increased function of the CD8⁺CD28^hi phenotype.

Knockout of CD8 delays reendothelialization and accelerates neointima formation in injured arteries of mouse via TNF-α inhibiting the endothelial cells migration

Objective

Delayed or impaired reendothelialization is a major cause of stent thrombosis in the interventional treatment of coronary heart disease. T cells are involved in neointima formation of injured arteries. However, the regulated mechanism of reendothelialization and the role of CD8 T cell in reendothelialization are unclear.

Methods and Results

Immunofluorescence staining showed that CD8 positive cells were increased in wire injured femoral artery of mice. On day 21 after injury, elastin staining showed that knockout of CD8 (CD8^−/−) significantly increased intimal thickness and a ratio of intima to media by 1.8 folds and 1.9 folds respectively in injured arteries. Evans blue staining showed that knockout of CD8 delayed the reendothelialization area on day 7 after injury (18.8±0.5% versus 42.1±5.6%, p<0.05). In vitro, a migration assay revealed that CD8^−/− T cells co-cultured with WT macrophages significantly inhibited the migration of the endothelial cells (ECs); compared to CD4⁺ T cells, and CD8⁺ T cells could promote the ECs migration. Furthermore, real-time PCR analysis showed that knockout of CD8 increased the level of tumor necrosis factor α (TNF-α) in injured arteries and cytometric bead cytokine array showed that TNF-α was elevated in cultured CD8^−/− T cells. Finally, a wound-healing assay showed that recombinant TNF-α significantly inhibited the migration of ECs.

Conclusion

Our study suggested that CD8⁺ T cells could promote the reendothelialization and inhibit the neointima formation after the artery wire injury, and this effect is at least partly dependent on decreasing TNF-α production promoting ECs migration.

Cytotoxic and proinflammatory CD8+ T lymphocytes promote development of vulnerable atherosclerotic plaques in apoE-deficient mice

BACKGROUND

Heart attacks and strokes, leading causes of deaths globally, arise from thrombotic occlusion of ruptured vulnerable atherosclerotic plaques characterized by abundant apoptosis, large necrotic cores derived from inefficient apoptotic cell clearance, thin fibrous caps, and focal inflammation. The genesis of apoptosis and necrotic cores in these vulnerable atherosclerotic plaques remains unknown. Cytotoxic CD8(+) T lymphocytes represent up to 50% of leukocytes in advanced human plaques and dominate early immune responses in mouse lesions, yet their role in atherosclerosis also remains unresolved.

METHODS AND RESULTS

CD8(+) T-lymphocyte depletion by CD8α or CD8β monoclonal antibody in apolipoprotein E-deficient mice fed a high-fat diet ameliorated atherosclerosis by reducing lipid and macrophage accumulation, apoptosis, necrotic cores, and monocyte chemoattractant protein 1, interleukin 1β, interferon γ, and vascular cell adhesion molecule 1. Transfer of CD8(+) T cells into lymphocyte-deficient, apolipoprotein E-deficient mice partially reconstituted CD8(+) T cells in lymphoid compartments and was associated with CD8(+) T-cell infiltration in lesions, increased lipid and macrophage accumulation, apoptotic cells, necrotic cores, and interleukin 1β in atherosclerotic lesions. Transfer of CD8(+) T cells deficient in perforin, granzyme B, or tumor necrosis factor α but not interferon γ failed to increase atherosclerotic lesions despite partial reconstitution in the lymphoid system and the presence in atherosclerotic lesions. Macrophages, smooth muscle cells, and endothelial cells were identified as apoptotic targets.

CONCLUSIONS

We conclude that CD8(+) T lymphocytes promote the development of vulnerable atherosclerotic plaques by perforin- and granzyme B-mediated apoptosis of macrophages, smooth muscle cells, and endothelial cells that, in turn, leads to necrotic core formation and further augments inflammation by tumor necrosis factor α secretion.

Mobilization of regulatory T cells in response to carotid injury does not influence subsequent neointima formation

AIM

T cells have been attributed an important role in modulating repair responses following vascular injury. The aim of this study was to investigate the role of different T cell subsets in this context.

METHODS AND RESULTS

A non-obstructive collar was introduced to inflict carotid artery injury in mice and subsequent activation of immune cells in draining lymph nodes and spleen were studied by flow cytometry. Carotid artery injury of wild type mice was associated with mobilization of both Th1 type CD4(+)IFNγ(+) and regulatory CD4(+)CD25(+)FoxP3(+) T cells in draining lymph nodes. Studies using FoxP3-green fluorescent protein (GFP) transgenic C57/Bl6 mice demonstrated scattered presence of regulatory T cells in the adventitial tissue of injured arteries as well as a massive emigration of regulatory T cells from the spleen in response to carotid injury. However, deletion of antigen presentation to CD4+ T cells (H2(0) mice), as well as deletion of regulatory T cells (through treatment with blocking anti-CD25 antibodies), did not affect neointima formation. Also deletion of antigen presentation to CD8(+) T cells (Tap1(0) mice) was without effect on carotid collar-induced neointima formation.

CONCLUSION

The results demonstrate that carotid artery injury is associated with mobilization of regulatory T cells. Depletion of regulatory T cells does not, however, influence the subsequent repair processes leading to the formation of a neointima. The results also demonstrate that lack of CD8(+) T cells does not influence neointima formation in presence of functional CD4(+) T cells and B cells.

Increased inflammation in atherosclerotic lesions of diabetic Akita-LDLr⁻/⁻ mice compared to nondiabetic LDLr⁻/⁻ mice

Background. Diabetes is associated with increased cardiovascular disease, but the underlying cellular and molecular mechanisms are poorly understood. One proposed mechanism is that diabetes aggravates atherosclerosis by enhancing plaque inflammation. The Akita mouse has recently been adopted as a relevant model for microvascular complications of diabetes. Here we investigate the development of atherosclerosis and inflammation in vessels of Akita mice on LDLr^−/− background. Methods and Results. Akita-LDLr^−/− and LDLr^−/− mice were fed high-fat diet from 6 to 24 weeks of age. Blood glucose levels were higher in both male and female Akita-LDLr^−/− mice (137% and 70%, resp.). Male Akita-LDLr^−/− mice had markedly increased plasma cholesterol and triglyceride levels, a three-fold increase in atherosclerosis, and enhanced accumulation of macrophages and T-cells in plaques. In contrast, female Akita-LDLr^−/− mice demonstrated a modest 29% increase in plasma cholesterol and no significant increase in triglycerides, atherosclerosis, or inflammatory cells in lesions. Male Akita-LDLr^−/− mice had increased levels of plasma IL-1β compared to nondiabetic mice, whereas no such difference was seen between female diabetic and nondiabetic mice. Conclusion. Akita-LDLr^−/− mice display considerable gender differences in the development of diabetic atherosclerosis. In addition, the increased atherosclerosis in male Akita-LDLr^−/− mice is associated with an increase in inflammatory cells in lesions.

Intimal hyperplasia: slow but deadly

Intimal hyperplasia is the leading cause of long-term failure in coronary artery bypass vein grafting, coronary artery stenting, angioplasty, arteriovenous fistula for dialysis, and allograft transplantation. Intimal hyperplasia is a product of vascular smooth muscle cell proliferation, migration through the internal elastic lamina, and deposition of extracellular matrix proteins driven by growth factors in the vasculature. This vascular pathology results in a progressive diminution of the vessel lumen and serves as a site for thrombosis and atherosclerotic lesions. A key cell type in the initiation of intimal hyperplasia is the vascular endothelial cell, which appears to have down-stream effects on the vascular smooth muscle proliferation and migration. Currently, the only means available for prevention of intimal hyperplasia is through inhibition of mammalian target of rapamycin (mTOR) with the immunosuppressant rapamycin. mTOR integrates up-stream signals from growth factors such as IL-2 and senses the cellular nutrient and energy levels and redox status. This presentation will discuss the potential means of preserving the vascular endothelial cell and, thereby, reducing the development of intimal hyperplasia in our open-heart surgical patients.

CD8+ T cells mediate the athero-protective effect of immunization with an ApoB-100 peptide

Immunization of hypercholesterolemic mice with selected apoB-100 peptide antigens reduces atherosclerosis but the precise immune mediators of athero-protection remain unclear. In this study we show that immunization of apoE (-/-) mice with p210, a 20 amino acid apoB-100 related peptide, reduced aortic atherosclerosis compared with PBS or adjuvant/carrier controls. Immunization with p210 activated CD8⁺ T cells, reduced dendritic cells (DC) at the site of immunization and within the plaque with an associated reduction in plaque macrophage immunoreactivity. Adoptive transfer of CD8⁺ T cells from p210 immunized mice recapitulated the athero-protective effect of p210 immunization in naïve, non-immunized mice. CD8⁺ T cells from p210 immunized mice developed a preferentially higher cytolytic response against p210-loaded dendritic cells in vitro. Although p210 immunization profoundly modulated DCs and cellular immune responses, it did not alter the efficacy of subsequent T cell dependent or independent immune response to other irrelevant antigens. Our data define, for the first time, a role for CD8⁺ T cells in mediating the athero-protective effects of apoB-100 related peptide immunization in apoE (-/-) mice.