Pioglitazone modulates the balance of effector and regulatory T cells in apolipoprotein E deficient mice

Overview of multifunctional Tregs in cardiovascular disease: From insights into cellular functions to clinical implications

Regulatory T cells (Tregs) are crucial in regulating T-cell-mediated immune responses. Numerous studies have shown that dysfunction or decreased numbers of Tregs may be involved in inflammatory cardiovascular diseases (CVDs) such as atherosclerosis, hypertension, myocardial infarction, myocarditis, cardiomyopathy, valvular heart diseases, heart failure, and abdominal aortic aneurysm. Tregs can help to ameliorate CVDs by suppressing excessive inflammation through various mechanisms, including inhibition of T cells and B cells, inhibition of macrophage-induced inflammation, inhibition of dendritic cells and foam cell formation, and induction of anti-inflammatory macrophages. Enhancing or restoring the immunosuppressive activity of Tregs may thus serve as a fundamental immunotherapy to treat hypertension and CVDs. However, the precise molecular mechanisms underlying the Tregs-induced protection against hypertension and CVDs remain to be investigated. This review focuses on recent advances in our understanding of Tregs subsets and function in CVDs. In addition, we discuss promising strategies for using Tregs through various pharmacological approaches to treat hypertension and CVDs.

Regulatory T Cells in Atherosclerosis: Is Adoptive Cell Therapy Possible?

Atherosclerosis is an insidious vascular disease with an asymptomatic debut and development over decades. The aetiology and pathogenesis of atherosclerosis are not completely clear. However, chronic inflammation and autoimmune reactions play a significant role in the natural course of atherosclerosis. The pathogenesis of atherosclerosis involves damage to the intima, immune cell recruitment and infiltration of cells such as monocytes/macrophages, neutrophils, and lymphocytes into the inner layer of vessel walls, and the accumulation of lipids, leading to vascular inflammation. The recruited immune cells mainly have a pro-atherogenic effect, whereas CD4+ regulatory T (Treg) cells are another heterogeneous group of cells with opposite functions that suppress the pathogenic immune responses. Present in low numbers in atherosclerotic plaques, Tregs serve a protective role, maintaining immune homeostasis and tolerance by suppressing pro-inflammatory immune cell subsets. Compelling experimental data suggest that various Treg cell-based approaches may be important in the treatment of atherosclerosis. Here we highlight the most recent advances in our understanding of the roles of FOXP3-expressing CD4+ Treg cells in the atherogenic process and discuss potential translational strategies for the treatment of atherosclerosis by Treg manipulation.

Immunity in Atherosclerosis: Focusing on T and B Cells

Atherosclerosis is the major cause of the development of cardiovascular disease, which, in turn, is one of the leading causes of mortality worldwide. From the point of view of pathogenesis, atherosclerosis is an extremely complex disease. A huge variety of processes, such as violation of mitophagy, oxidative stress, damage to the endothelium, and others, are involved in atherogenesis; however, the main components of atherogenesis are considered to be inflammation and alterations of lipid metabolism. In this review, we want to focus on inflammation, and more specifically on the cellular elements of adaptive immunity, T and B cells. It is known that various T cells are widely represented directly in atherosclerotic plaques, while B cells can be found, for example, in the adventitia layer. Of course, such widespread and well-studied cells have attracted attention as potential therapeutic targets for the treatment of atherosclerosis. Various approaches have been developed and tested for their efficacy.

Effect of pioglitazone in acute ischemic stroke patients with diabetes mellitus: a nested case-control study

Background

Pioglitazone is an oral antidiabetic drug with multiple pleiotropic actions. Recent clinical trials have demonstrated that treatment with pioglitazone reduces cardiovascular risk in patients who have had an ischemic stroke. We examined the secondary preventive effects of pioglitazone in acute ischemic stroke patients with diabetes mellitus (DM) based on nationwide real-world data.

Methods

A nested case–control study was conducted with data from the National Health Insurance Service-National Sample Cohort in Korea. Study subjects were diabetic patients admitted for acute ischemic stroke (ICD-10 code; I63) between 2002 and 2013. Cases were defined as patients who suffered from composites of recurrent stroke (I60–63), myocardial infarction (I21), or all-cause mortality after ischemic stroke. Controls were selected by incidence density sampling. Three controls were matched to each case for sex, age, treatment with insulin, and oral antidiabetic medications, with the exception of pioglitazone. Medication history after ischemic stroke was obtained by accessing the prescription records. In the matched dataset, conditional logistic regression analysis was performed with adjustments for hypertension, atrial fibrillation, prior myocardial infarction, and treatment with oral antithrombotics and statins.

Results

From the patients with acute ischemic stroke and DM, 1150 cases with primary outcomes were matched to 3450 controls. In the matched analysis, treatment with pioglitazone was significantly associated with a lower cardiovascular risk (adjusted OR [95% CI], 0.43 [0.23–0.83]).

Conclusions

In this nested case–control study using real-world data, treatment with pioglitazone exhibited significant cardiovascular preventive effect in diabetic patients with acute ischemic stroke.

Pioglitazone suppresses macrophage proliferation in apolipoprotein-E deficient mice by activating PPARγ

BACKGROUND AND AIMS

Local macrophage proliferation is linked to enhanced atherosclerosis progression. Our previous study found that troglitazone, a thiazolidinedione (TZD), suppressed oxidized low-density lipoprotein (Ox-LDL)-induced macrophage proliferation. However, its effects and mechanisms are unclear. Therefore, we investigated the effects of pioglitazone, another TZD, on macrophage proliferation.

METHODS

Normal chow (NC)- or high-fat diet (HFD)-fed apolipoprotein E-deficient (Apoe^-/-) mice were treated orally with pioglitazone (10 mg/kg/day) or vehicle (water) as a control. Mouse peritoneal macrophages were used in in vitro assays.

RESULTS

Atherosclerosis progression was suppressed in aortic sinuses of pioglitazone-treated Apoe^-/- mice, which showed fewer proliferating macrophages in plaques. Pioglitazone suppressed Ox-LDL-induced macrophage proliferation in a dose-dependent manner. However, treatment with peroxisome proliferator-activated receptor-γ (PPARγ) siRNA ameliorated pioglitazone-induced suppression of macrophage proliferation. Low concentrations (less than 100 μmol/L) of pioglitazone, which can suppress macrophage proliferation, activated PPARγ in macrophages, but did not induce macrophage apoptosis. Pioglitazone treatment did not induce TUNEL-positive cells in atherosclerotic plaques of aortic sinuses in Apoe^-/- mice.

CONCLUSIONS

Pioglitazone suppressed macrophage proliferation through PPARγ without inducing macrophage apoptosis. These findings imply that pioglitazone could prevent macrovascular complications in diabetic individuals.

Pu-erh Tea Ameliorates Atherosclerosis Associated with Promoting Macrophage Apoptosis by Reducing NF-κB Activation in ApoE Knockout Mice

We explored whether pu-erh tea consumption ameliorates atherosclerosis and the possible mechanism for its effects in apolipoprotein E-deficient (ApoE^−/−) mice. Our data showed that pu-erh tea consumption markedly reduced early fatty streak formation and the advanced fibrofatty plaque sizes. Additionally, the mean proportion of inflammatory macrophages in the plaque decreased, and the number of apoptotic macrophages increased significantly. NF-κB activity in peritoneal macrophages decreased by 75.6% compared to the controls, similar with the levels of IL-6, IL-12, and TNF-α expression. The tea extract increased the apoptosis of RAW264.7 cells by decreasing NF-κB activation and reducing the inflammatory cytokine expression. In conclusion, pu-erh tea ameliorates atherosclerosis progress by alleviating the chronic inflammatory state by reducing NF-κB activation and promoting macrophage apoptosis in atherosclerotic plaques.

Regulatory T cells as a new therapeutic target for atherosclerosis

Atherosclerosis is an autoimmune disease caused by self- and non-self-antigens contributing to excessive activation of T and B cell immune responses. These responses further aggravate vascular infiammation and promote progression of atherosclerosis and vulnerability to plaques via releasing pro-infiammatory cytokines. Regulatory T cells (Tregs) as the major immunoregulatory cells, in particular, induce and maintain immune homeostasis and tolerance by suppressing the immune responses of various cells such as T and B cells, natural killer (NK) cells, monocytes, and dendritic cells (DCs), as well as by secreting inhibitory cytokines interleukin (IL)-10, IL-35 and transcription growth factor β (TGF-β) in both physiological and pathological states. Numerous evidence demonstrates that reduced numbers and dysfunction of Treg may be involveved in atherosclerosis pathogenesis. Increasing or restoring the numbers and improving the immunosuppressive capacity of Tregs may serve as a fundamental immunotherapy to treat atherosclerotic cardiovascular diseases. In this article, we briefiy present current knowledge of Treg subsets, summarize the relationship between Tregs and atherosclerosis development, and discuss the possibilities of regulating Tregs for prevention of atherosclerosis pathogenesis and enhancement of plaque stability. Although the exact molecular mechanisms of Treg-mediated protection against atherosclerosis remain to be elucidated, the strategies for targeting the regulation of Tregs may provide specific and significant approaches for the prevention and treatment of atherosclerotic cardiovascular diseases.

Allergic asthma accelerates atherosclerosis dependent on Th2 and Th17 in apolipoprotein E deficient mice

AIMS

The chronic inflammation of atherosclerosis is regulated by Th1, while allergic asthma is controlled by Th2. The direct relationship between atherosclerosis and asthma is contradictory. The aim of this study was to investigate the role of allergic asthma in atherosclerotic plaque formation and the change of CD4(+) T cells subsets.

METHODS AND RESULTS

Six-week C57BL/6J or apoE(-/-) mice were sensitized on day 0, 7 and 14, then exposed to aerosolized 1% Ovalbumin (OVA) or PBS 30min/day, 3 times/week for 8 or 16weeks from day 14 onward. The results showed that allergic asthma mice models were successfully established and the accelerated atherosclerosis induced by allergic asthma accompanied with increased Th2 and Th17 cells but not Th1 cells in spleen. Moreover, the expression and production of Th2 and Th17 biomarkers including IL-4 and IL-17A were significantly elevated in asthmatic apoE(-/-) mice. After 8-week treated with the neutralizing antibody of IL-4 or IL-17A, the lesion area in the aortic root of asthmatic apoE(-/-) mice was markedly decreased, and more dramatical result was observed after the combined treatment with IL-4 and IL-17A mAbs. The expression of IgE and FcεRIα in the aortic root of apoE(-/-) mice was markedly increased but was significantly reduced after 8-week treatment with IL-4 mAb.

CONCLUSION

Allergic asthma accelerates atherosclerosis by modulating the balance of Teff/Treg cells in apoE(-/-) mice, which is associated with increased Th2 and Th17 cells but not Th1 cells.

Multiple roles of SOCS proteins: differential expression of SOCS1 and SOCS3 in atherosclerosis

Pro-inflammatory cytokines play a key pathogenic role in atherosclerosis, which are induced by the Janus kinase/signal transducer and activator of transduction (JAK/STAT) pathway. Furthermore, the JAK/STAT pathway is negatively regulated by the suppressor of cytokine signaling (SOCS) proteins. However, the change in SOCS expression levels and the correlation between SOCS expression and cholesterol levels in atherosclerosis is not yet well understood. To this end, a mouse model of atherosclerosis was established using apolipoprotein-deficient (ApoE(-/-)) mice. The mice were fed either a chow or high-fat diet. The mRNA and protein expression of SOCS1 and SOCS3 in plaque and vessels were determined at different time points. Furthermore, SOCS1 and SOCS3 mRNA expression was detected in the peripheral blood mononuclear cells (PBMCs) obtained from 18 male subjects with no coronary heart disease (non-CHD) population. The expression of SOCS1 in the ApoE(-/-) mice first increased and then decreased and the high-fat diet accelerated the appearance of the peak; the expression of SOCS3 increased with the increased feeding duration, and this trend was more pronounced in the mice fed the high-fat diet. SOCS1/CD68 and SOCS3/CD68 showed opposite trends in expression with the increased duration of the high-fat diet. Interleukin-6 (IL-6) expression in the main aorta of the ApoE(-/-) mice fed the high-fat diet also increased with the increased feeding duration. In the non-CHD population, the total serum cholesterol levels positively correlated with SOCS3 mRNA expression in the PBMCs (r=0.433, P=0.012). These results demonstrate the differential expression of SOCS1 and SOCS3 in atherosclerosis and suggest that SOCS3, together with IL-6 may promote the formation and development of atherosclerosis.