The immunology of atherosclerosis

VEGF-A/VEGFR-2 and FGF-2/FGFR-1 but not PDGF-BB/PDGFR-β play important roles in promoting immature and inflammatory intraplaque angiogenesis

Various angiogenic factors have been shown to play important roles in intraplaque angiogenesis, while little is known about the dynamic expression change and interplay between various angiogenic factors and intraplaque angiogenesis under high cholesterol conditions. New Zealand rabbits underwent balloon injury of the abdominal artery and then were assigned to a control group (n = 15, normal chow) or high cholesterol group (n = 25, 1% high cholesterol diet). At weeks 4, 6, 8, 10, and 12 after acclimation, rabbits (high cholesterol group, n = 5; control group, n = 3) were euthanized. No lesions were observed in the control group. From week 4 to week 12, the expression of vascular endothelial growth factor A (VEGF-A), VEGF receptor 2 (VEGFR-2), fibroblast growth factor 2 (FGF-2), FGF receptor 1 (FGFR-1), platelet-derived growth factor-BB (PDGF-BB), and tumor necrosis factor alpha (TNF-α), the vulnerability index (VI) and the microvessel density (MVD) were significantly elevated in the high cholesterol group; however, PDGF receptor β (PDGFR-β) expression showed little change. Analysis by double-label immunofluorescence (CD31 and Ng2) and FITC-dextran indicated that the neovessels within the plaque were leaky due to a lack of pericytes. As indicated by Pearson’s correlation analysis, there was a highly positive correlation between the VI, MVD, macrophage content, and TNF-α level, and the levels of VEGF-A/VEGFR-2 and FGF-2/FGFR-1. However, no correlations were observed between PDGFR-β levels and the VI or MVD. High expression of VEGF-A/VEGFR-2 and FGF-2/FGFR-1 but not of PDGF-BB/PDGFR-β may contribute to immature and inflammatory intraplaque angiogenesis and plaque instability in a rabbit model of atherosclerosis.

Foam cell formation: A new target for fighting atherosclerosis and cardiovascular disease

During atherosclerosis, the gradual accumulation of lipids into the subendothelial space of damaged arteries results in several lipid modification processes followed by macrophage uptake in the arterial wall. The way in which these modified lipoproteins are dealt with determines the likelihood of cholesterol accumulation within the monocyte-derived macrophage and thus its transformation into the foam cell that makes up the characteristic fatty streak observed in the early stages of atherosclerosis. The unique expression of chemokine receptors and cellular adhesion molecules expressed on the cell surface of monocytes points to a particular extravasation route that they can take to gain entry into atherosclerotic site, in order to undergo differentiation into the phagocytic macrophage. Indeed several GWAS and animal studies have identified key genes and proteins required for monocyte recruitment as well cholesterol handling involving lipid uptake, cholesterol esterification and cholesterol efflux. A re-examination of the previously accepted paradigm of macrophage foam cell origin has been called into question by recent studies demonstrating shared expression of scavenger receptors, cholesterol transporters and pro-inflammatory cytokine release by alternative cell types present in the neointima, namely; endothelial cells, vascular smooth muscle cells and stem/progenitor cells. Thus, therapeutic targets aimed at a more heterogeneous foam cell population with shared functions, such as enhanced protease activity, and signalling pathways, mediated by non-coding RNA molecules, may provide greater therapeutic outcome in patients. Finally, studies targeting each aspect of foam cell formation and death using both genetic knock down and pharmacological inhibition have provided researchers with a clearer understanding of the cellular processes at play, as well as helped researchers to identify key molecular targets, which may hold significant therapeutic potential in the future.

Healthy Adult LDL-C Bears Reverse Association with Serum IL-17A Levels

Background:

Hypercholesterolemia is a modifiable risk factor in atherosclerosis with a complex association with inflammation.

Objective:

In the present study, the association between low-density lipoprotein cholesterol (LDL-C) and interleukin 17A (IL-17A), as an inflammatory cytokine, was investigated. In addition to IL-17A, serum levels of interleukin 23 (IL-23) and transforming growth factor β (TGF-β), as effective cytokines in T helper 17 cell (Th17) development, were also determined.

Method:

Cytokine levels were measured using enzyme-linked immunosorbent assay (ELISA) in healthy subjects with LDL-C<130 versus LDL-C=>130 mg/dL.

Results:

Although IL-17A is an inflammatory cytokine and a positive association between its levels and LDL-C is expected, the data obtained in this study provide support for a reverse association (p<0.05).

Conclusion:

Inflammation plays a major role in atherosclerosis development; however, various inflammatory components involved in atherosclerosis assert their own unique association with hypercholesterolemia.

The pleiotropic role of interleukin-17 in atherosclerosis

Atherosclerosis is the main cause of cardiovascular diseases (CVDs), which considers the leading cause of mortality worldwide. Atherosclerosis is a chronic inflammatory condition of arterials' wall in which the development and the destabilization of plaque occur. Both innate and adaptive immunity play a significant role in modifying lipoproteins in arterials' wall. Recent investigations have demonstrated the opposing roles of CD4⁺ T cells subtypes in atherosclerosis. T helper-1 (Th1) response and pro-inflammatory cytokines possess proatherogenic effects, whereas T regulatory (Treg) cells have an atheroprotective role. Th17 cells have emerged as a new CD4⁺ T-cell subtype, which produce IL-17 that plays a crucial role in numerous inflammatory and autoimmune diseases. Recently, several studies have investigated the potential role of IL-17 in atherosclerosis. Some investigations have suggested a proatherogenic effect, however the others proposed an atheroprotective role. Hence, the exact role of IL-17 in the disease development and plaque stability is still debatable. In this review, we summarize the current knowledge on both atherogenesis and atheroprotective roles of IL-17. In addition, the synergistic and antagonistic effects of IL-17 with other cytokines in atherosclerosis will be discussed. On the basis of the current understanding of these roles, the possibility of developing novel therapeutic strategies against atherosclerosis may be evolved.

Physical Activity, Immune System, and the Microbiome in Cardiovascular Disease

Cardiovascular health is a primary research focus, as it is a leading contributor to mortality and morbidity worldwide, and is prohibitively costly for healthcare. Atherosclerosis, the main driver of cardiovascular disease, is now recognized as an inflammatory disorder. Physical activity (PA) may have a more important role in cardiovascular health than previously expected. This review overviews the contribution of PA to cardiovascular health, the inflammatory role of atherosclerosis, and the emerging evidence of the microbiome as a regulator of inflammation.

CD19+ B-Cells, a New Biomarker of Mortality in Hemodialysis Patients

Background and objectives

Mortality of patients on hemodialysis (HD) remains very high despite recent improvements in HD techniques. Cardiovascular (CV) complications and infections are the main causes of death. Some studies suggest that disturbances in the immune system could play a role in this disproportionate mortality, through the links of immunity with inflammation and propensity to infections. However, few studies have addressed the role of lymphocyte populations and the global and CV mortality of HD patients.

Aim

To analyze the relationship of peripheral blood lymphocyte populations (PBLP) and all-cause and CV mortality of HD patients.

Design, setting, participants, and measurements

We design a prospective observational single center study in a cohort of HD prevalent patients. PBLP were analyzed at baseline and after 1 year and patients were followed for a 5-year period. Main outcomes were all-cause and CV mortality.

Results

One hundred and four patients (51% male, mean age 64.8 ± 15 years) were included. Follow-up was 18 (7–47) months. Fifty-five patients (52.8%) died, main causes of death being CVD (40%) and infections (29.1%). Low total lymphocyte counts were found in 47 patients (45.2%), and the most frequency lymphopenias were CD19⁺ B-cell (57.7%), CD3⁺ (40.4%), and CD4⁺ (36.5%). After 1 year, all determinations were lower except CD56⁺CD16⁺CD3⁻ natural killer. Patient survival was significantly lower in patients with a CD19⁺ B-cell count < 100 cells/μL at baseline as compared to patients with CD19⁺ B-cell ≥ 100 cells/μL counts at the end of follow-up (16.5 vs 54%, p = 0.003). By multivariable analysis, age, history of CV disease, Charlson index, a KT/V < 1.2, and a CD19⁺ B-cell count < 100 cells/μL at baseline and after 1-year were factors associated with of all-cause mortality. A CD19⁺ B-cell count < 100 cells/μL at baseline was associated with CV mortality.

Conclusion

CD19⁺ B-cell lymphopenia is very common among HD patients, and it could be an independent predictor of all-cause and CV mortality. More studies are needed to confirm these findings.

The Signaling Pathways Involved in the Antiatherosclerotic Effects Produced by Chinese Herbal Medicines

Cardiovascular diseases (CVDs) are considered to be the predominant cause of death in the world. Chinese herb medicines (CHMs) have been widely used for the treatment of CVDs in Asian countries for thousands of years. One reason of high efficacy of CHMs in treating CVDs is attributed to their inhibition in atherosclerosis (AS) development, a critical contributor to CVDs occurrence. Cumulative studies have demonstrated that CHMs alleviate atherogenesis via mediating pathophysiologic events involved in AS. However, there is deficiency in the summaries regarding antiatherogenic signal pathways regulated by CHMs. In this review, we focus on the signal cascades by which herb medicines and relevant extractives, derivatives, and patents improve proatherogenic processes including endothelium dysfunction, lipid accumulation, and inflammation. We mainly elaborate the CHMs-mediated signaling pathways in endothelial cells, macrophages, and vascular smooth muscle cells of each pathogenic event. Moreover, we briefly describe the other AS-related factors such as thrombosis, autophagy, immune response, and noncoding RNAs and effects of CHMs on them in the way of cascade regulation, which is helpful to further illustrate the molecular mechanisms of AS initiation and progression and discover newly effective agents for AS management.

Aging-Induced Biological Changes and Cardiovascular Diseases

Aging is characterized by functional decline in homeostatic regulation and vital cellular events. This process can be linked with the development of cardiovascular diseases (CVDs). In this review, we discussed aging-induced biological alterations that are associated with CVDs through the following aspects: (i) structural, biochemical, and functional modifications; (ii) autonomic nervous system (ANS) dysregulation; (iii) epigenetic alterations; and (iv) atherosclerosis and stroke development. Aging-mediated structural and biochemical modifications coupled with gradual loss of ANS regulation, vascular stiffening, and deposition of collagen and calcium often disrupt cardiovascular system homeostasis. The structural and biochemical adjustments have been consistently implicated in the progressive increase in mechanical burden and functional breakdown of the heart and vessels. In addition, cardiomyocyte loss in this process often reduces adaptive capacity and cardiovascular function. The accumulation of epigenetic changes also plays important roles in the development of CVDs. In summary, the understanding of the aging-mediated changes remains promising towards effective diagnosis, discovery of new drug targets, and development of new therapies for the treatment of CVDs.

PKM2-dependent metabolic reprogramming in CD4+ T cells is crucial for hyperhomocysteinemia-accelerated atherosclerosis

Inflammation mediated by activated T cells plays an important role in the initiation and progression of hyperhomocysteinemia (HHcy)-accelerated atherosclerosis in ApoE^-/- mice. Homocysteine (Hcy) activates T cells to secrete proinflammatory cytokines, especially interferon (IFN)-γ; however, the precise mechanisms remain unclear. Metabolic reprogramming is critical for T cell inflammatory activation and effector functions. Our previous study demonstrated that Hcy regulates T cell mitochondrial reprogramming by enhancing endoplasmic reticulum (ER)-mitochondria coupling. In this study, we further explored the important role of glycolysis-mediated metabolic reprogramming in Hcy-activated CD4⁺ T cells. Mechanistically, Hcy-activated CD4⁺ T cell increased the protein expression and activity of pyruvate kinase muscle isozyme 2 (PKM2), the final rate-limiting enzyme in glycolysis, via the phosphatidylinositol 3-kinase/AKT/mechanistic target of rapamycin signaling pathway. Knockdown of PKM2 by small interfering RNA reduced Hcy-induced CD4⁺ T cell IFN-γ secretion. Furthermore, we generated T cell-specific PKM2 knockout mice by crossing LckCre transgenic mice with PKM2^fl/fl mice and observed that Hcy-induced glycolysis and oxidative phosphorylation were both diminished in PKM2-deficient CD4⁺ T cells with reduced glucose and lipid metabolites, and subsequently reduced IFN-γ secretion. T cell-depleted apolipoprotein E-deficient (ApoE^-/-) mice adoptively transferred with PKM2-deficient CD4⁺ T cells, compared to mice transferred with control cells, showed significantly decreased HHcy-accelerated early atherosclerotic lesion formation. In conclusion, this work indicates that the PKM2-dependent glycolytic-lipogenic axis, a novel mechanism of metabolic regulation, is crucial for HHcy-induced CD4⁺ T cell activation to accelerate early atherosclerosis in ApoE^-/- mice.

KEY MESSAGES

Metabolic reprogramming is crucial for Hcy-induced CD4⁺ T cell inflammatory activation. Hcy activates the glycolytic-lipogenic pathway in CD4⁺ T cells via PKM2. Targeting PKM2 attenuated HHcy-accelerated early atherosclerosis in ApoE^-/- mice in vivo.

A new perspective on lipid research in age-related macular degeneration

There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.

Cardiovascular disease after transplantation: an emerging role of the immune system

Cardiovascular disease (CVD) after transplantation remains a major concern. Little is known about what drives the increased cardiovascular risk in transplant recipients apart from traditional risk factors. The immune system is involved in the pathogenesis of hypertension, atherosclerosis, and coronary artery disease in the general population. Recently, inhibition of interleukin 1 - β by canakinumab versus placebo decreased the incidence of cardiovascular events. Emerging evidence points to a role of adaptive cellular immunity in the development of CVD. Especially, expansion of pro-inflammatory and antiapoptotic cytotoxic CD4⁺ CD28^null T cells is closely associated with incident CVD in various study populations including transplant recipients. The association of cytomegalovirus exposure with increased cardiovascular mortality might be explained by its capacity to upregulate these cytotoxic cells. Also, humoral immunity seems to be relevant for cardiovascular outcome in transplant recipients. Panel-reactive antibodies at baseline and donor-specific antibodies are independently associated with poor cardiovascular outcome after kidney transplantation. Cardiovascular effects of immunosuppressive drugs and statins do not only imply indirect positive or negative effects on traditional cardiovascular risk factors but also intrinsic immunological effects. How immunosuppressive drugs modify atherosclerosis largely remains elusive.

Association of Total and Differential Leukocyte Counts With Cardiovascular Disease and Mortality in the UK Biobank

OBJECTIVE

Elevated white blood cell count is associated with a higher risk of cardiovascular disease (CVD). We aimed to investigate whether specific leukocyte subpopulations, which may more closely indicate a specific inflammatory pathway, are specifically associated with CVD.

APPROACH AND RESULTS

Participants (478 259) from UK Biobank with data for white blood cell count were included. Death because of CVD (n=1377) and non-CVD causes (n=8987) occurred during median follow-up time of 7.0 years (interquartile range, 6.3-7.6). In Cox models, deciles of leukocyte counts (lymphocytes, monocytes, neutrophils, eosinophils, and basophils) were examined using the fifth decile as the referent group. Models were stratified by sex and adjusted for a range of classical risk factors. A sensitivity analysis excluded participants with baseline comorbidites and the first 2 years of follow-up. Men (hazard ratio [HR], 1.59; 95% confidence interval, 1.22-2.08) and women (HR, 2.15; 95% confidence interval, 1.38-3.35) in the highest decile of neutrophil count were at higher risk of CVD mortality and nonfatal CVD (men HR, 1.28; 95% confidence interval, 1.16-1.42 and women HR, 1.21; 95% confidence interval, 1.06-1.38). In the sensitivity analysis, the power to investigate CVD mortality was limited, but for both sexes combined, the linear HRs for a 1×10⁹/L cell count increase in white blood cell count and neutrophils, respectively, was 1.05 (1.03-1.07) and 1.07 (1.04-1.11).

CONCLUSIONS

Among circulating leukocyte subpopulations, neutrophil count in men was most consistently associated with fatal and nonfatal CVD. Further studies of interventions that lower circulating neutrophils, such as canakinumab, are required to investigate causality.

Effects of different doses of granulocyte colony-stimulating factor mobilization therapy on ischemic cardiomyopathy

G-CSF mobilization might be beneficial to ICM, but the relationship between effect/safety and the dosage of G-CSF remains unclear. In this study, 24 pigs were used to build ICM models and were randomized into four groups. Four weeks later, different dosages of G-CSF were given daily by subcutaneous injection for 5 days. Another 4 weeks later, all the animals were sacrificed. Electrocardiography, coronary arteriography, left ventriculography, transthoracic echocardiography, cardiac MRI, and SPECT, histopathologic analysis, and immunohistochemistry techniques were used to evaluate left ventricular function and myocardial infarct size. Four weeks after G-CSF treatment, pigs in middle-dose G-CSF group exhibited obvious improvements of left ventricular remodeling and function. Moderate G-CSF mobilization ameliorated the regional contractility of ICM, preserved myocardial viability, and reduced myocardial infarct size. More neovascularization and fewer apoptotic myocardial cells were observed in the ischemic region of the heart in middle-dose group. Expression of vWF, VEGF and MCP-1 were up-regulated, and Akt1 was activated in high- and middle-dose groups. Moreover, CRP, TNF-α and S-100 were elevated after high-dose G-CSF mobilization. Middle-dose G-CSF mobilization therapy is an effective and safe treatment for ICM, and probably acts via a mechanism involving promoting neovascularization, inhibiting cardiac fibrosis and anti-apoptosis.

Systemic Inflammation and Cardiovascular Comorbidity in Psoriasis Patients: Causes and Consequences

Psoriasis is a common inflammatory skin disease characterized by the appearance of red scaly plaques that can affect any part of the body. High prevalence, chronicity, disfiguration, disability, and associated comorbidity make it a challenge for clinicians of multiple specialties. Likewise, its complex pathogenesis, comprising inflammation, hyperproliferation, and angioneogenesis, intrigues numerous scientific disciplines, namely, immunology. From a clinical perspective, the severity of psoriasis is highlighted by its increased mortality, with cardiovascular diseases contributing the highest excess risk. From a scientific point of view, psoriasis has to be considered a systemic inflammatory condition, as blood biomarkers of inflammation are elevated and imaging techniques document sites of inflammation beyond the skin. While the association of psoriasis with cardiovascular diseases is now widely accepted, causes and consequences of this association are controversially discussed. This review comments on epidemiologic, genetic, and mechanistic studies that analyzed the relation between psoriasis and cardiovascular comorbidity. The hypothesis of psoriasis potentially being an independent cardiovascular risk factor, driving atherosclerosis via inflammation-induced endothelial dysfunction, will be discussed. Finally, consequences for the management of psoriasis with the objective to reduce the patients’ excess cardiovascular risk will be pointed out.

CD6 expression has no effect on atherosclerosis in apolipoprotein E-deficient mice

OBJECTIVE

To determine if deficiency of CD6, a cell surface protein on lymphocytes that alters natural antibody production, increases atherosclerosis in ApoE-deficient mice fed a chow or a western-type diet.

RESULTS

We compared cholesterol levels, IgM, B1a cells, and aortic root lesion areas in ApoE-deficient vs. CD6/ApoE double deficient mice. Feeding the high-fat western type diet increased all parameters, except for B1a cell numbers decreased. Sex also had an effect on many parameters with males having increased body weights, higher high density lipoprotein cholesterol, higher B1a cells, but smaller atherosclerotic lesions if chow fed mice; however, this sex effect on atherosclerosis was absent in mice fed the western-type diet. CD6 deficiency had no effect on atherosclerosis in both male and female mice on either diet. Thus, loss of CD6 on lymphocytes did not lead to expected reductions in B1a cells and protective IgM levels, and in turn did not alter atherosclerosis in mice.

Transcriptional programming of tissue-resident memory CD8+ T cells

Tissue-resident memory CD8⁺ T cells (T_RM) are localized in non-lymphoid tissues throughout the body where they mediate long-lived protective immunity at common sites of pathogen exposure. As the signals controlling T_RM differentiation are uncovered, it is becoming apparent that the dynamic activities of numerous transcription factors are intricately involved in T_RM formation. Here, we highlight known transcriptional regulators of T_RM differentiation and discuss how understanding the transcriptional programming of CD8⁺ T cell residency in non-lymphoid tissues can be leveraged to prevent or treat disease.

Role of hyaluronan in atherosclerosis: Current knowledge and open questions

Hyaluronan (HA), HA synthases (HAS) and HA receptors are expressed during the progression of atherosclerotic plaques. HA is thought to promote the activated phenotype of local vascular smooth muscle cells characterized by increased migration, proliferation and matrix synthesis. Furthermore, HA may modulate the immune response by increasing macrophage retention and by promoting the polarization of Th1 cells that enhance macrophage driven inflammation as well. The pro-atherosclerotic functions of HA are opposed by the presence of HA in the glycocalyx where it critically contributes to anti-thrombotic and anti-inflammatory function of the glycocalyx. Patients with atherosclerosis often are affected by comorbidities among them diabetes mellitus type 2 and inflammatory comorbidities. Diabetes mellitus type 2 likely has close interrelations to HA synthesis in atherosclerosis because the activity and transcription of HA synthases are sensitive to the intracellular glucose metabolism, which determines the substrate availability and the posttranslational modifications of HA synthases. The pro-inflammatory comorbidities aggravate the course of atherosclerosis and will affect the expression of the genes related to HA biosynthesis, -degradation, HA-matrix assembly or signaling. One example being the induction of HAS3 by interleukin-1β and other cytokines. Furthermore complications of atherosclerosis such as the healing after myocardial infarction also involve HA responses.

Neutrophil: A Cell with Many Roles in Inflammation or Several Cell Types?

Neutrophils are the most abundant leukocytes in the circulation, and have been regarded as first line of defense in the innate arm of the immune system. They capture and destroy invading microorganisms, through phagocytosis and intracellular degradation, release of granules, and formation of neutrophil extracellular traps after detecting pathogens. Neutrophils also participate as mediators of inflammation. The classical view for these leukocytes is that neutrophils constitute a homogenous population of terminally differentiated cells with a unique function. However, evidence accumulated in recent years, has revealed that neutrophils present a large phenotypic heterogeneity and functional versatility, which place neutrophils as important modulators of both inflammation and immune responses. Indeed, the roles played by neutrophils in homeostatic conditions as well as in pathological inflammation and immune processes are the focus of a renovated interest in neutrophil biology. In this review, I present the concept of neutrophil phenotypic and functional heterogeneity and describe several neutrophil subpopulations reported to date. I also discuss the role these subpopulations seem to play in homeostasis and disease.

Increased risk of coronary heart disease among patients with primary Sjögren's syndrome: a nationwide population-based cohort study

To investigate the association between primary Sjögren’s syndrome (pSS) and coronary heart disease (CHD), and the influence of medications for pSS patients on risk of CHD. The authors identified 4175 patients with a new diagnosis of pSS between 2002 and 2013 from the National Health Insurance Research database. The control-to-case ratio was 4:1. The risk and cumulative incidences of CHD were calculated. The adjusted hazard ratio (HR) of CHD for pSS patients was 1.17 (1.03–1.34) after adjusting for age, sex, comorbidities, and medications. The cumulative incidence for CHD in the pSS group was significantly higher than that in the control group (log-rank p < 0.0001). The risk of CHD in pSS patients was increased with age by 4% per year, and 45- to 59-year-olds were at the highest risk (HR = 1.464, 1.195–1.794). The application of corticosteroids (HR = 1.45, 1.07–1.97) as well as NSAIDs (HR = 1.31, 1.05–1.65) both increased the risk of CHD among pSS patients. pSS is associated with an increased risk of subsequent CHD in Taiwan. Primary Sjögren’s syndrome might be an independent risk factor for CHD. Use of corticosteroids and NSAIDs in the treatment of pSS patients increased the risk of developing CHD.

Krüppel-like factors: Crippling and un-crippling metabolic pathways

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors that regulate various pathways that control metabolism and other cellular mechanisms. Various KLF isoforms have been associated with cellular, organ or systemic metabolism. Altered expression or activation of KLFs has been linked to metabolic abnormalities, such as obesity and diabetes, as well as with heart failure. In this review article we summarize the metabolic functions of KLFs, as well as the networks of different KLF isoforms that jointly regulate metabolism in health and disease.

Yirui Capsules Alleviate Atherosclerosis by Improving the Lipid Profile and Reducing Inflammation in Apolipoprotein E-Deficient Mice

Atherosclerosis (AS) is the main cause of cardiovascular diseases. This study investigated Yirui (YR) capsules, whose ingredients are available in health food stores, against AS and the underlying mechanisms. Male apolipoprotein E-deficient mice fed a high-fat diet for 10 weeks developed severe aortic lesions, but YR significantly decreased the plaque area in the total aorta and aortic root. YR affected the serum lipid profile by significantly reducing total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and oxidative modification of LDL-C (Ox-LDL) levels. In addition, multi-cytokine analysis revealed that higher serum levels of interleukin-1 alpha (IL-1α), interleukin-1 beta (IL-1β), interleukin-3 (IL-3), interleukin-6 (IL-6), interleukin-27 (IL-27), tumor necrosis factor alpha, interferon gamma, and regulated on activation, normal T cell expressed and secreted (RANTES), which were induced by a high-fat diet, declined with YR treatment. These results suggest that YR reduces the atherosclerotic plaque burden, thereby alleviating AS by modulating the lipid profile and inhibiting inflammation.

GATA3, HDAC6, and BCL6 Regulate FOXP3+ Treg Plasticity and Determine Treg Conversion into Either Novel Antigen-Presenting Cell-Like Treg or Th1-Treg

We conducted an experimental database analysis to determine the expression of 61 CD4+ Th subset regulators in human and murine tissues, cells, and in T-regulatory cells (Treg) in physiological and pathological conditions. We made the following significant findings: (1) adipose tissues of diabetic patients with insulin resistance upregulated various Th effector subset regulators; (2) in skin biopsy from patients with psoriasis, and in blood cells from patients with lupus, effector Th subset regulators were more upregulated than downregulated; (3) in rosiglitazone induced failing hearts in ApoE-deficient (KO) mice, various Th subset regulators were upregulated rather than downregulated; (4) aortic endothelial cells activated by proatherogenic stimuli secrete several Th subset-promoting cytokines; (5) in Treg from follicular Th (Tfh)-transcription factor (TF) Bcl6 KO mice, various Th subset regulators were upregulated; whereas in Treg from Th2-TF GATA3 KO mice and HDAC6 KO mice, various Th subset regulators were downregulated, suggesting that Bcl6 inhibits, GATA3 and HDAC6 promote, Treg plasticity; and (6) GATA3 KO, and Bcl6 KO Treg upregulated MHC II molecules and T cell co-stimulation receptors, suggesting that GATA3 and BCL6 inhibit Treg from becoming novel APC-Treg. Our data implies that while HDAC6 and Bcl6 are important regulators of Treg plasticity, GATA3 determine the fate of plastic Tregby controlling whether it will convert in to either Th1-Treg or APC-T-reg. Our results have provided novel insights on Treg plasticity into APC-Treg and Th1-Treg, and new therapeutic targets in metabolic diseases, autoimmune diseases, and inflammatory disorders.

β-glucans and cholesterol (Review)

Hypercholesterolemia is one of primary risk factors of cardiovascular disease, together with metabolic syndrome, hypertension and diabetes. Although progress has been made, the search for novel methods of preventing and treating dyslipidemia is ongoing and current therapies for cardiovascular disease induce various side effects. β-glucans are linear unbranched polysaccharides found in various natural sources, such as mushrooms. Due to their structure they are able to interact with innate immunity receptors, however they also act as dietary fibers in the digestive tract. As there are two forms of β-glucans, insoluble and soluble forms, they are able to interact with lipids and biliary salts in the bowel and consequently reduce cholesterol levels. Therefore, they may be developed as a suitable therapeutic option to treat patients with dyslipidemia, as they are natural molecules that do not induce any significant side effects. The current review discusses the evidence supporting the effects of β-glucans on cholesterol levels.

Curcumin Protects against Atherosclerosis in Apolipoprotein E-Knockout Mice by Inhibiting Toll-like Receptor 4 Expression

Toll-like receptor 4 (TLR4) has been reported to play a critical role in the pathogenesis of atherosclerosis, the current study aimed to investigate whether curcumin suppresses atherosclerosis development in ApoE-knockout (ApoE^-/-) mice by inhibiting TLR4 expression. ApoE^-/- mice were fed a high-fat diet supplemented with or without curcumin (0.1% w/w) for 16 weeks. Curcumin supplementation significantly reduced TLR4 expression and macrophage infiltration in atherosclerotic plaques. Curcumin also reduced aortic interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression, nuclear factor-κB (NF-κB) activity, and plasma IL-1β, TNF-α, soluble VCAM-1 and ICAM-1 levels. In addition, aortic sinus sections revealed that curcumin treatment reduced the extent of atherosclerotic lesions and inhibited atherosclerosis development. In vitro, curcumin inhibited NF-κB activation in macrophages and reduced TLR4 expression induced by lipopolysaccharide. Our results indicate that curcumin protects against atherosclerosis at least partially by inhibiting TLR4 expression and its related inflammatory reaction.

Metabolomics in Immunology Research

There is a growing appreciation that metabolic processes and individual metabolites can shape the function of immune cells and thereby play important roles in the outcome of immune responses. In this respect, the use of MS- and NMR spectroscopy-based platforms to characterize and quantify metabolites in biological samples has recently yielded important novel insights into how our immune system functions and has contributed to the identification of biomarkers for immune-mediated diseases. Here, these recent immunological studies in which metabolomics has been used and made significant contributions to these fields will be discussed. In particular the role of metabolomics to the rapidly advancing field of cellular immunometabolism will be highlighted as well as the future prospects of such metabolomic tools in immunology.

The Inflammasomes in Cardiovascular Disease

Cardiovascular disease (CVD) is the number one cause of death worldwide. The pathogenesis of various disease entities that comprise the area of CVD is complex and multifactorial. Inflammation serves a central role in these complex aetiologies. The inflammasomes are intracellular protein complexes activated by danger-associated molecular patterns (DAMPs) present in CVD such as atherosclerosis and myocardial infarction (MI). After a two-step process of priming and activation, inflammasomes are responsible for the formation of pro-inflammatory cytokines interleukin-1β and interleukin-18, inducing a signal transduction cascade resulting in a strong immune response that culminates in disease progression. In the past few years, increased interest has been raised regarding the inflammasomes in CVD. Inflammasome activation is thought to be involved in the pathogenesis of various disease entities such as atherosclerosis, MI and heart failure (HF). Interference with inflammasome-mediated signalling could reduce inflammation and attenuate the severity of disease. In this chapter we provide an overview of the current literature available on the role of inflammasome inhibition as a therapeutic intervention and the possible clinical implications for CVD.

The immunoinhibitory PD-1/PD-L1 pathway in inflammatory blood vessel disease

Because of their vital function, the wall structures of medium and large arteries are immunoprivileged and protected from inflammatory attack. That vascular immunoprivilege is broken in atherosclerosis and in vasculitis, when wall-invading T cells and macrophages (Mϕ) promote tissue injury and maladaptive repair. Historically, tissue-residing T cells were studied for their antigen specificity, but recent progress has refocused attention to antigen-nonspecific regulation, which determines tissue access, persistence, and functional differentiation of T cells. The coinhibitory receptor PD-1, expressed on T cells, delivers negative signals when engaged by its ligand PD-L1, expressed on dendritic cells, Mϕ, and endothelial cells to attenuate T cell activation, effector functions, and survival. Through mitigating signals, the PD-1 immune checkpoint maintains tissue tolerance. In line with this concept, dendritic cells and Mϕs from patients with the vasculitic syndrome giant cell arteritis (GCA) are PD-L1^lo ; including vessel-wall-embedded DCs that guard the vascular immunoprivilege. GCA infiltrates in the arterial walls are filled with PD-1⁺ T cells that secrete IFN-γ, IL-17, and IL-21; drive inflammation-associated angiogenesis; and facilitate intimal hyperplasia. Conversely, chronic tissue inflammation in the atherosclerotic plaque is associated with an overreactive PD-1 checkpoint. Plaque-residing Mϕs are PD-L1^hi , a defect induced by their addiction to glucose and glycolytic breakdown. PD-L1^hi Mϕs render patients with coronary artery disease immunocompromised and suppress antiviral immunity, including protective anti-varicella zoster virus T cells. Thus, immunoinhibitory signals affect several domains of vascular inflammation; failing PD-L1 in vasculitis enables unopposed immunostimulation and opens the flood gates for polyfunctional inflammatory T cells, and excess PD-L1 in the atherosclerotic plaque disables tissue-protective T cell immunity.

Annexin A5 reduces early plaque formation in ApoE -/- mice

Annexin A5 (AnxA5) exerts anti-inflammatory, anticoagulant and anti-apoptotic effects through its binding to cell surface expressed phosphatidylserine. We previously showed that AnxA5 can stabilize advanced atherosclerotic plaques by reducing macrophage infiltration. We now investigated the effects of AnxA5 administration on the onset of atherosclerosis development. Eight-week-old ApoE-/-mice were fed a western diet while being administered AnxA5 or control (M1234) for a total of 6 weeks. AnxA5 administration reduced plaque size in the aortic root as well as the aortic arch by 36% and 55% respectively. As determined by immunohistochemistry, administration of AnxA5 further stabilized plaque by reducing macrophage content and increasing smooth muscle cell content. Furthermore, the pre-treatment of HUVEC's with AnxA5 reduced monocyte adhesion under flow-conditions. Finally, AnxA5 administration results in a trend to reduced cell death more pronounced in the aortic arch than the aortic root. In conclusion, treatment with AnxA5 before the onset of atherosclerosis reduces plaque formation in a murine model of atherosclerosis in part by reducing apoptotic rates further to its beneficial effect on macrophage infiltration and activation.

Relationship Between Total Serum Bilirubin Levels and Carotid and Femoral Atherosclerosis in Familial Dyslipidemia

Objective—

Bilirubin is a potent antioxidant that has been inversely related to cardiovascular disease. There is little information on serum total bilirubin (TB) in relation to atherosclerosis in familial dyslipidemia. We assessed the association between TB and carotid and femoral atherosclerosis in this high-risk group.

Approach and Results—

We evaluated 464 individuals with familial dyslipidemia (56% men; median age, 48 years), 322 with familial hypercholesterolemia, and 142 with familial combined hyperlipidemia. Carotid and femoral arteries were imaged bilaterally with a standardized ultrasonographic protocol. Mean and maximum intima-media thickness and plaque presence (≥1.2 mm) and height were recorded. Cross-sectional associations between TB and atherosclerosis variables were investigated in multivariable-adjusted models, including lipid values and hypolipidemic drug use. Inflammatory markers (C-reactive protein, total leukocyte count, and lipoprotein[a]) were also determined. Increasing TB levels were associated with decreasing intima-media thickness of all carotid segments ( P <0.05, all). TB also related to carotid plaque, present in 78% of individuals, and to plaque burden (≥3 plaques), with odds ratios (95% confidence interval) 0.59 (0.36–0.98) and 0.57 (0.34–0.96) for each increase of 0.5 mg in TB, respectively. Findings were confirmed in a validation cohort of 177 subjects with nonfamilial dyslipidemia. Only the familial combined hyperlipidemia group, with higher inflammation-related markers, showed an inverse association between TB and femoral plaque height (β=−0.183; P =0.030).

Conclusions—

TB was inversely and independently associated with carotid plaque burden in familial and nonfamilial dyslipidemia. These findings support the use of TB as a biomarker of atherosclerosis in this high-risk group.

Platelet-neutrophil interactions as drivers of inflammatory and thrombotic disease

Neutrophils are well known for their role in infection and inflammatory disease and are first responders at sites of infection or injury. Platelets have an established role in hemostasis and thrombosis and are first responders at sites of vascular damage. However, neutrophils are increasingly recognized for their role in thrombosis, while the immunemodulatory properties of platelets are being increasingly studied. Platelets and neutrophils interact during infection, inflammation and thrombosis and modulate each other’s functions. This review will discuss the consequences of platelet–neutrophil interactions in infection, thrombosis, atherosclerosis and tissue injury and repair.

Lunasin abrogates monocytes to endothelial cells

The adherence of monocytes to endothelial cells plays a causal role in the early development of atherosclerosis and is driven by several inflammatory stimuli, which includes oxidized low-density lipoprotein (ox-LDL). Lunasin, a natural peptide identified in soybean seeds, soy-derived food products, other grains and herbal plants, has been found to exert numerous biological activities, including anti-inflammatory and antioxidant properties. However, little is known regarding the mechanism of action of lunasin in ox-LDL-induced endothelial inflammation. The results of the present study indicate that lunasin significantly ameliorated ox-LDL-induced adhesion of THP-1 monocytes to the surface of human umbilical vein endothelial cells (HUVECs). Lunasin also suppressed expression of the adhesion molecules VCAM-1 and E-selectin, but not ICAM-1. Notably, the inhibitory mechanism of lunasin is associated with its stimulatory effects on expression of the KLF2 transcriptional factor. In addition, lunasin treatment could reverse the effects of ox-LDL on the expression of eNOS and PAI-1, the direct target genes of KLF2. Mechanistically, it was proven that the MEK5/ERK5 pathway mediates the effects of lunasin on KLF2 expression. Taken together, the results of this study suggest that dietary or supplementary intake of lunasin may have a prophylactic or therapeutic capacity in cardiovascular diseases such as atherosclerosis.

Identification of Key Pathways and Genes in Advanced Coronary Atherosclerosis Using Bioinformatics Analysis

Background

Coronary artery atherosclerosis is a chronic inflammatory disease. This study aimed to identify the key changes of gene expression between early and advanced carotid atherosclerotic plaque in human.

Methods

Gene expression dataset GSE28829 was downloaded from Gene Expression Omnibus (GEO), including 16 advanced and 13 early stage atherosclerotic plaque samples from human carotid. Differentially expressed genes (DEGs) were analyzed.

Results

42,450 genes were obtained from the dataset. Top 100 up- and downregulated DEGs were listed. Functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) identification were performed. The result of functional and pathway enrichment analysis indicted that the immune system process played a critical role in the progression of carotid atherosclerotic plaque. Protein-protein interaction (PPI) networks were performed either. Top 10 hub genes were identified from PPI network and top 6 modules were inferred. These genes were mainly involved in chemokine signaling pathway, cell cycle, B cell receptor signaling pathway, focal adhesion, and regulation of actin cytoskeleton.

Conclusion

The present study indicated that analysis of DEGs would make a deeper understanding of the molecular mechanisms of atherosclerosis development and they might be used as molecular targets and diagnostic biomarkers for the treatment of atherosclerosis.

Collectins in urinary tract and kidney diseases

The innate immune system serves as the frontline defense against invading pathogens and initiates an inflammatory response to microorganisms. Collectins are C-type lectins that are structurally characterized by a collagen-like sequence and a carbohydrate recognition domain. Moreover, they are widely expressed throughout the body and are involved in the innate immunity against a variety of pathogens, regulating inflammation, and protecting the lungs from pathogens. Recently, two classical collectins, surfactant protein A (SP-A) and surfactant protein D (SP-D), as well as novel collectin 11, were found present in urinary tract tissues. They are increasingly recognized as key players in activating the humoral arm of innate immunity and host defense in urinary tract and kidney diseases, although their biological features, functions, and mechanisms in this regard remain largely unclear. In this review, we aim to integrate results reported by ourselves and others to summarize and gain a better understanding of the functions of collectins (SP-A, SP-D, and collectin 11) in urinary tract and kidney diseases.

The Role of Hydrogen Sulfide on Cardiovascular Homeostasis: An Overview with Update on Immunomodulation

Hydrogen sulfide (H₂S), the third endogenous gaseous signaling molecule alongside nitric oxide (NO) and carbon monoxide, is synthesized by multiple enzymes in cardiovascular system. Similar to other gaseous mediators, H₂S has demonstrated a variety of biological activities, including anti-oxidative, anti-apoptotic, pro-angiogenic, vasodilating capacities and endothelial NO synthase modulating activity, and regulates a wide range of pathophysiological processes in cardiovascular disorders. However, the underlying mechanisms by which H₂S mediates cardiovascular homeostasis are not fully understood. This review focuses on the recent progress on functional and mechanistic aspects of H₂S in the inflammatory and immunoregulatory processes of cardiovascular disorders, importantly myocardial ischemia, heart failure, and atherosclerosis. Moreover, we highlight the challenges for developing H₂S-based therapy to modulate the pathological processes in cardiovascular diseases. A better understanding of the immunomodulatory and biochemical functions of H₂S might provide new therapeutic strategies for these cardiovascular diseases.

RGS3 inhibits TGF-β1/Smad signalling in adventitial fibroblasts

Recent evidence suggests that adventitial fibroblasts (AFs) are crucially implicated in atherosclerosis. However, the mechanisms by which AFs are dysfunctional and contribute to atherosclerosis remain unclear. This study aimed to investigate the role of regulator of G-protein signalling 3 (RGS3) in the regulation of AFs using apoE knockout mouse as the model. Pathological changes in aortic arteries of apoE knockout mice fed with hyperlipid diet were examined by Movat staining. The expression of RGS3, α-SMA, TGF-β1, Smad2, and Smad3 in the adventitia was detected by immunohistochemistry. Adventitial fibroblasts were isolated from aortic arteries of apoE knockout mice and infected with RGS3 overexpression lentivirus or empty lentivirus. The expression of RGS3, α-SMA, TGF-β1, Smad2, and Smad3 in AFs was detected by real-time polymerase chain reaction and Western blot analysis. We found that hyperlipidic diet caused significant aortic intima thickening and atherosclerotic plaques in 15-week-old apoE knockout mice. Compared to wild-type mice, RGS3 expression was lower while α-SMA, TGF-β1, Smad2, and Smad3 expression was higher in the adventitia of apoE knockout mice. In addition, lentivirus mediated overexpression of RGS3 caused decreased expression of α-SMA, TGF-β1, Smad2, and Smad3 in AFs derived from apoE(-/-) mice. In conclusion, these results suggest that RGS3 may provide protection against pathological changes of AFs and the development of atherosclerosis by inhibiting TGF-β1/Smad signalling. RGS3 may be a potential therapeutic target for atherosclerosis.

TSPO PET Imaging: From Microglial Activation to Peripheral Sterile Inflammatory Diseases?

Peripheral sterile inflammatory diseases (PSIDs) are a heterogeneous group of disorders that gathers several chronic insults involving the cardiovascular, respiratory, gastrointestinal, or musculoskeletal system and wherein inflammation is the cornerstone of the pathophysiology. In PSID, timely characterization and localization of inflammatory foci are crucial for an adequate care for patients. In brain diseases, in vivo positron emission tomography (PET) exploration of inflammation has matured over the last 20 years, through the development of radiopharmaceuticals targeting the translocator protein-18 kDa (TSPO) as molecular biomarkers of activated microglia. Recently, TSPO has been introduced as a possible molecular target for PSIDs PET imaging, making this protein a potential biomarker to address disease heterogeneity, to assist in patient stratification, and to contribute to predicting treatment response. In this review, we summarized the major research advances recently made in the field of TSPO PET imaging in PSIDs. Promising preliminary results have been reported in bowel, cardiovascular, and rheumatic inflammatory diseases, consolidated by preclinical studies. Limitations of TSPO PET imaging in PSIDs, regarding both its large expression in healthy peripheral tissues, unlike in central nervous system, and the production of peripheral radiolabeled metabolites, are also discussed, regarding their possible consequences on TSPO PET signal's quantification.