Regulatory T-cells, FoxP3 and atherosclerosis

The significance of Agaricus blazei as an immunomodulator of the level of IL-17 in Balb/C mice with atherosclerosis

Atherosclerosis is a disease caused by an inflammatory response which involved the interaction between endothelial cells, macrophages and lymphocytes, and is closely related to IL-17 regulation. This study is important to investigate the activity of Agaricusblazei in modulating the immunological activity based on the profile of CD4⁺IL-17⁺, CD8⁺IL-17⁺, and CD11b⁺ IL-17⁺ in high-fat diet (HFD)-induced Balb/c mice. Mice in dietary groups were fed with HFD and then fed with A. blazei extract with three different doses including D1 (100 mg/kg BW), D2 (200 mg/kg BW), and D3 (400 mg/kg BW) once a day for 12 weeks. The cells were analyzed using flow cytometry and tested statistically with one-way ANOVA with α = 0.05 by using SPSS 16.00 software. The results showed that mice with HFD treatment had a higher level of Lp-PLA2 (atherosclerosis marker) compared with the control group (data not shown). The level of IL-17 in the atherosclerotic mice in the D1 group was significantly depleted compared to the control group. Of the three doses above, D1 may be an optimal dose to minimize or prevent the damage from atherosclerosis than the other doses.

Telomerase Mediates Lymphocyte Proliferation but Not the Atherosclerosis-Suppressive Potential of Regulatory T-Cells

Supplemental Digital Content is available in the text.

Objective—

Atherosclerosis is an age-related disease characterized by systemic oxidative stress and low-grade inflammation. The role of telomerase and telomere length in atherogenesis remains contentious. Short telomeres of peripheral leukocytes are predictive for coronary artery disease. Conversely, attenuated telomerase has been demonstrated to be protective for atherosclerosis. Hence, a potential causative role of telomerase in atherogenesis is critically debated.

Approach and Results—

In this study, we used multiple mouse models to investigate the regulation of telomerase under oxidative stress as well as its impact on atherogenesis in vitro and in vivo. Using primary lymphocytes and myeloid cell cultures, we demonstrate that cultivation under hyperoxic conditions induced oxidative stress resulting in chronic activation of CD4⁺ cells and significantly reduced CD4⁺ T-cell proliferation. The latter was telomerase dependent because oxidative stress had no effect on the proliferation of primary lymphocytes isolated from telomerase knockout mice. In contrast, myeloid cell proliferation was unaffected by oxidative stress nor reliant on telomerase. Telomerase reverse transcriptase deficiency had no effect on regulatory T-cell (T_reg) numbers in vivo or suppressive function ex vivo. Adoptive transfer of telomerase reverse transcriptase^–/– T_regs into Rag2^–/– ApoE^–/– (recombination activating gene 2/apolipoprotein E) double knockout mice demonstrated that telomerase function was not required for the ability of T_regs to protect against atherosclerosis. However, telomere length was critical for T_reg function.

Conclusions—

Telomerase contributes to lymphocyte proliferation but plays no major role in T_reg function, provided that telomere length is not critically short. We suggest that oxidative stress may contribute to atherosclerosis via suppression of telomerase and acceleration of telomere attrition in T_regs.

Changes in CD4+CD25+ Tregs in the pathogenesis of atherosclerosis in ApoE-/- mice

The goal of this study was to observe the pathological characteristics of atherosclerotic plaques in the aortic walls of ApoE^-/- and C57BL/6J mice and the changes of CD4⁺CD25⁺ regulatory T cells (Tregs) in atherosclerotic mice. Twenty ApoE^-/- mice were split into high-fat diet (AH) and normal diet (AN) groups and 10 C57BL/6J male mice were designated as the control group (BN). The serum concentrations of IL-10 and TGF-β1 were detected by enzyme-linked immunosorbent assay; paraffin sections of the aorta were stained with hematoxylin & eosin, and morphometric parameters were measured using the Image Pro Plus 6.0 system. Verhoeff stain was used to observe the distribution of elastic fibers, and immunohistochemical staining was performed to verify the phenotype of the forkhead box protein 3 (Foxp3⁺) CD25⁺ cells in the atherosclerotic tissue. The proportion of CD4⁺CD25⁺ Tregs in the spleen was calculated by flow cytometry. The thickness of the intima, the intima/media ratio, the plaque area, and the plaque/lumen ratio of mice in AN group were significantly larger than those of mice in BN group. The thickness of the intima, the plaque area, and the plaque/lumen ratio of the mice in AH group were significantly increased compared with those of the AN group mice. The serum concentrations of IL-10 and TGF-β1 and the percentage of splenic CD4⁺CD25⁺ Tregs in AN group mice were significantly decreased compared with the control group. The serum concentrations of IL-10 and TGF-β1 and the percentage of splenic CD4⁺CD25⁺ Tregs in the mice in AH group were significantly decreased compared with those in AN group. The proportions of Foxp3⁺ and CD25⁺ cells within the total lymphocyte population were significantly decreased in AH group mice compared with those in AN group mice. Atherosclerosis in an experimental mouse model was correlated with Treg depletion in the lymphoid tissues and plaques, indicating the important antiatherosclerotic role of CD4⁺CD25⁺ Tregs. Impact statement In this article, we conclude that Tregs decreased with atherosclerosis (AS) as determined in ApoE knockout mice fed a high fat diet. It is an important matter for understanding the AS pathology.

Mesenchymal stem cells alleviate atherosclerosis by elevating number and function of CD4(+)CD25 (+)FOXP3 (+) regulatory T-cells and inhibiting macrophage foam cell formation

Atherosclerosis is a chronic inflammatory disease characterized by the formation of plaques inside arteries, leading to narrowing and blockage. Potential therapeutic strategies include expanding the population of regulatory T-cells (Tregs) to enhance atheroprotective immunity, and inhibiting the formation of macrophage foam cells. Here, we studied the effect of bone marrow-derived mesenchymal stem cells (BM-MSCs) on atherosclerotic plaque formation in Apolipoprotein E(-/-) (ApoE-KO) mice, and elucidated the underlying mechanism. BM-MSCs isolated from 4 week-old ApoE-KO mice were evaluated by flow cytometry for expression of MSC-specific markers. Thirty eight week-old ApoE-KO mice were randomly divided into three experimental groups (n = 10 per group): 1. MSC group-received BM-MSCs intravenously; 2. Vehicle group-received DMEM; 3. Control group-did not receive any treatment. Administration of MSCs resulted in a marked decrease in the size of atherosclerotic plaques 3 months after treatment. In addition, the number and function of CD4(+)CD25(+)FOXP3(+) regulatory T-cells (Tregs) in cultured splenocytes, and the expression of FOXP3 at both mRNA and protein levels, was significantly increased in the MSC group. In vitro experiments further indicated that the formation of macrophage foam cells was inhibited by treatment with MSCs, accompanied by a significant downregulation in CD36 and scavenger receptor A (SRA). Our findings suggest that MSCs play an atheroprotective role by enhancing the number and function of Tregs and inhibiting the formation of macrophage foam cells. Hence, administration of MSCs to atherosclerotic patients might have significant clinical benefits.

The influence of innate and adaptive immune responses on atherosclerosis

Both the chronic development of atherosclerotic lesions and the acute changes in lesion phenotype that lead to clinical cardiovascular events are significantly influenced by the innate and adaptive immune responses to lipoprotein deposition and oxidation in the arterial wall. The rapid pace of discovery of mechanisms of immunologic recognition, effector functions, and regulation has significantly influenced the study of atherosclerosis, and our new knowledge is beginning to affect how we treat this ubiquitous disease. In this review, we discuss recent advances in our understanding of how innate and adaptive immunity contribute to atherosclerosis, as well as therapeutic opportunities that arise from this knowledge.

Telomere length in cardiovascular disease: new challenges in measuring this marker of cardiovascular aging

Atherosclerosis is an age-related systemic disease characterized by systemic oxidative stress and low grade chronic inflammation. Various types of leukocytes play an important role within this process. Telomeres, the ends of chromosomes, shorten during each and every cell division and have therefore been regarded as a cellular clock. Telomere dysfunction has been implicated in aging and senescence, and shorter leukocyte telomere length (LTL) has been demonstrated to predict cardiovascular disease and mortality. However, although LTL can predict cardiovascular events in population studies, a number of factors have prevented its broad use as a surrogate end point, such as serum levels of LDL cholesterol. In this article we will provide an overview of telomere biology and telomere dynamics of different leukocyte populations, and we will also discuss pitfalls in the methodology of LTL quantification, in context with landmark studies, which measured LTL in cardiovascular disease. Finally, we will attempt to critically assess and explain the shortcomings of LTL as a biomarker and identify further research avenues that require further investigation before telomere length can be implemented as an individual biomarker for cardiovascular aging. From this it becomes evident that LTL can be susceptible to methodological errors affecting longitudinal reproducibility. LTL is generally confounded at least by genetic factors, population variation and leukocyte composition.

Aspirin may do wonders by the induction of immunological self-tolerance against autoimmune atherosclerosis

Induction of immune tolerance is one of the recent novel immunomodulatory strategies to directly intervene the autoimmune-driven atherosclerosis. Aspirin is a prototypic non-steroidal anti-inflammatory drug, which is now being regarded as a life-saver in variety of atherosclerotic cardiovascular complications. Considerable amount of data emerged during last few years clearly suggests that aspirin can cause immunomodulation by several mechanisms, particularly, its ability to induce tolerogenic dendritic cells (DCs) and to upregulate T regulatory (Treg) cells is especially appealing with respect to induction of immunological self-tolerance. Based on this fact, we hypothesize that aspirin, in addition to its anti-inflammatory effect, may also specifically inhibit autoimmune response in atherosclerosis by actively increasing CD4+CD25+FOXP3+Treg cells as well as by inducing tolerogenic DCs which induce hyporesponsiveness in responder naïve T cells. If proved to be correct, this hypothesis will provide an opportunity to medical community with an already available aspirin-based immunotherapeutic approach for inducing immune tolerance against atherosclerosis.