Regulating Protective Immunity in Atherosclerosis

β-Glucans as a panacea for a healthy heart? Their roles in preventing and treating cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Factors increasing the risks for CVD development are related to obesity, diabetes, high blood cholesterol, high blood pressure and lifestyle. CVD risk factors may be treated with appropriate drugs, but prolonged can use cause undesirable side-effects. Among the natural products used in complementary and alternative medicines, are the β-ᴅ-glucans; biopolymers found in foods (cereals, mushrooms), and can easily be produced by microbial fermentation. Independent of source, β-glucans of the mixed-linked types [(1 → 3)(1 → 6)-β-ᴅ-glucans - fungal, and (1 → 3)(1 → 4)-β-ᴅ-glucans - cereal] have widely been studied because of their biological activities, and have demonstrated cardiovascular protective effects. In this review, we discuss the roles of β-ᴅ-glucans in various pathophysiological conditions that lead to CVDs including obesity, dyslipidemia, hyperglycemia, oxidative stress, hypertension, atherosclerosis and stroke. The β-glucans from all of the sources cited demonstrated potential hypoglycemic, hypocholesterolemic and anti-obesogenicity activities, reduced hypertension and ameliorated the atherosclerosis condition. More recently, β-glucans are recognized as possessing prebiotic properties that modulate the gut microbiome and impact on the health benefits including cardiovascular. Overall, all the studies investigated unequivocally demonstrated the dietary benefits of consuming β-glucans regardless of source, thus constituting a promising panaceutical approach to reduce CVD risk factors.

Disruption of the TSLP-TSLPR-LAP signaling between epithelial and dendritic cells through hyperlipidemia contributes to regulatory T-Cell defects in atherosclerotic mice

Regulatory T-Cells (Tregs) play a protective role against the development of atherosclerosis. Moreover, thymic stromal lymphopoietin (TSLP)/thymic stromal lymphopoietin receptor (TSLPR) signaling in myeloid dendritic cells (DCs) promote Treg differentiation. Here, we examined the potential role of TSLP/TSLPR on Treg homeostasis in atherosclerosis. The frequencies of both latency-associated peptide (LAP)(+) and Foxp3(+) Tregs were reduced in the thymus and spleen of ApoE(-/-) mice compared with C57BL/6 mice, and this effect was associated with decreased thymic output. The tolerogenic function of DCs obtained from ApoE(-/-) mice was compromised compared with those from C57BL/6 mice. The expression of TSLP and TSLPR was also inhibited in ApoE(-/-) mice. In addition, we found that ox-LDL attenuated TSLP expression in cultured thymic epithelial cells (TECs) through the activation of retinoid X receptor alpha (RXRA) and IL-1β and decreased LAP and PD-L1 expression in oxLDL-activated DCs while both were up-regulated in TSLP-activated DCs. We also observed that the TSLP-DCs mediated differentiation of Tregs was abrogated through LAP neutralization. Furthermore, TSLP injection rescued Treg defects in ApoE(-/-) mice. These findings suggest that Treg defects in ApoE(-/-) mice might partially be attributed to the disruption of TSLP-TSLPR-LAP signaling in epithelial cells (ECs) and DCs.

Antigen-induced immunomodulation in the pathogenesis of atherosclerosis

Atherosclerosis is a chronic inflammatory disorder characterised by the accumulation of monocytes/macrophages, smooth muscle cells, and lymphocytes within the arterial wall in response to the release of proinflammatory molecules. Such accumulation results in the formation of the atherosclerotic plaque, which would eventually evolve to complications such as total artery occlusion, rupture, calcification, or aneurysm. Although the molecular mechanism responsible for the development of atherosclerosis is not completely understood, it is clear that the immune system plays a key role in the development of the atherosclerotic plaque and in its complications. There are multiple antigenic stimuli that have been associated with the pathogenesis of atherosclerosis. Most of these stimuli come from modified self-molecules such as oxidised low-density lipoproteins (oxLDLs), beta2glycoprotein1 (β2GP1), lipoprotein a (LP(a)), heat shock proteins (HSPs), and protein components of the extracellular matrix such as collagen and fibrinogen in the form of advanced glycation-end (AGE) products. In addition, several foreign antigens including bacteria such as Porphyromonas gingivalis and Chlamydia pneumoniae and viruses such as enterovirus and cytomegalovirus have been associated with atherosclerosis as potentially causative or bystander participants, adding another level of complexity to the analysis of the pathophysiology of atherosclerosis. The present review summarises the most important scientific findings published within the last two decades on the importance of antigens, antigen stimulation, and adaptive immune responses in the development of atherosclerotic plaques.

Autoimmunity and atherosclerosis: functional polymorphism of PTPN22 is associated with phenotypes related to the risk of atherosclerosis. The Cardiovascular Risk in Young Finns Study

There is a growing body of evidence attesting the significance of inflammation in the pathogenesis of atherosclerosis. Protein tyrosine phosphate PTPN22 C/T single nucleotide polymorphism (SNP) at + 1858 has been identified recently as a susceptibility factor for various inflammatory autoimmune diseases. We hypothesized that data on the genetic polymorphism of the PTPN22 enzyme associated with an increased risk of autoimmunity could also provide insight into the possible role of autoimmunity in the pathogenesis of atherosclerosis. Therefore we analysed the PTPN22 + 1858 C/T polymorphism in a population of young Finnish adults (n = 2268) for whom data on carotid artery intima-media thickness (IMT), a presymptomatic predictor of atherosclerosis, and risk factors for atherosclerosis were available. In males carriage of the T allele of PTPN22 + 1858 was associated significantly with IMT in univariate and multivariate analyses, while in females it was associated with several risk factors for atherosclerosis (BMI, waist circumference, waist-to-hip ratio, serum concentrations of C-reactive protein and triglycerides) but not with IMT. Our results indicate that the genetic polymorphism of PTPN22 + 1858 known to predispose to autoimmunity also enhances the development of atherosclerosis and thereby links the genetics of autoimmunity and atherosclerosis.

Pro-Atherogenic Alterations in T-Lymphocyte Subpopulations Related to Acute Hyperglycaemia in Type 2 Diabetic Patients

BACKGROUND

T cells are among the earliest cells to infiltrate the arterial intima during the initial stages of atherosclerosis. Alterations in the peripheral blood lymphocyte distribution might be associated with intensive lymphocytes extravasation and stimulation of atherosclerotic plaque development. Epidemiological data reveal that short-term postprandial hyperglycemia is a significant risk factor for coronary heart disease. Using a parameter that indicates recently-past acute hyperglycemia, 1,5-anhydro-D-glucitol (1,5-AG), the aim of the present study was to elucidate which alterations in peripheral blood T-lymphocytes, if any, are associated with acute hyperglycemia in patients with type 2 diabetes mellitus (DM) and, thus, might be involved in the progression of atherosclerosis.

METHODS AND RESULTS

Measurement of fasting glucose level, glycated hemoglobin A(1c), 1,5-AG, lipid profile and lymphocyte receptors expression (CD3+, CD4+, CD8+, CD8+28+, CD+28 -) was performed in 97 patients with type 2 DM, 23 patients with coronary heart disease, and 15 healthy controls. The mean CD3+, CD4+, CD8+28 - and CD8+28+ lymphocyte counts were significantly higher in the DM patients than in both control groups. Multiple regression analysis revealed that CD4+ and CD8+28- lymphocyte counts primarily were dependent on 1,5-anhydro-D-glucitol plasma levels.

CONCLUSIONS

These results suggest that acute hyperglycemia results in the progression of atherosclerosis in type 2 DM, at least in part through changes in CD4+ and CD8+28- lymphocyte subsets.