Immune regulation by oral tolerance induces alternate activation of macrophages and reduces markers of plaque destabilization in Apobtm2Sgy/Ldlrtm1Her/J mice.

Atherosclerosis is the leading cause for cardiovascular mortality. We determined the effect of multi-antigenic construct expressing three peptides AHC (ApoB100, HSP60 and outer membrane protein of chlamydia pneumonia) in stabilizing advanced atherosclerosis in Apobtm2Sgy/Ldlrtm1Her/J mice. Atherosclerosis was induced by feeding high fat diet (HFD) to mice for 10 weeks, followed by five oral dosing with purified AHC or ovalbumin on alternate days and continued on HFD for another 10 weeks. Tolerance was associated with significantly higher numbers of regulatory T cells both in aortic sinus and spleen with higher mRNA expression of CTLA4 (3 fold), Foxp3 (1.4 folds) and TGF-ß (1.62) in aorta. Tregs cells were found to induce alternate activation of macrophages to M2 phenotype, with a reduction in plaque inflammation. AHC treatment showed evidence of plaque stabilization as observed by reduction in plaque necrosis in aortic sinus (35.8%) and in brachiocephalic artery (26%), with reduced expression of Tissue factor and MMP9. Macrophage apoptosis was reduced and collagen content was enhanced by treatment. Our results suggest that tolerance to atherogenic peptides increases regulatory T cells which activate M2 macrophages, prevent T cell proliferation and reduce plaque destabilization and inflammatory markers thus providing evidences for plaque stabilization in mice with advanced atherosclerosis.

Differential effects of NOX4 and NOX1 on immune cell-mediated inflammation in the aortic sinus of diabetic ApoE-/- mice.

Oxidative stress and inflammation are central mediators of atherosclerosis particularly in the context of diabetes. The potential interactions between the major producers of vascular reactive oxygen species (ROS), NADPH oxidase (NOX) enzymes and immune-inflammatory processes remain to be fully elucidated. In the present study we investigated the roles of the NADPH oxidase subunit isoforms, NOX4 and NOX1, in immune cell activation and recruitment to the aortic sinus atherosclerotic plaque in diabetic ApoE(-/-) mice. Plaque area analysis showed that NOX4- and NOX1-derived ROS contribute to atherosclerosis in the aortic sinus following 10 weeks of diabetes. Immunohistochemical staining of the plaques revealed that NOX4-derived ROS regulate T-cell recruitment. In addition, NOX4-deficient mice showed a reduction in activated CD4(+) T-cells in the draining lymph nodes of the aortic sinus coupled with reduced pro-inflammatory gene expression in the aortic sinus. Conversely, NOX1-derived ROS appeared to play a more important role in macrophage accumulation. These findings demonstrate distinct roles for NOX4 and NOX1 in immune-inflammatory responses that drive atherosclerosis in the aortic sinus of diabetic mice.

Modulation of recombinant antigenic constructs containing multi-epitopes towards effective reduction of atherosclerotic lesion in B6;129S-Ldlr(tm1Her)Apob(tm2Sgy)/J mice.

Atherosclerosis is increasingly recognized as a complex chronic inflammatory disease. Many more studies have extended vaccination against atherosclerosis by using epitopes from self-antigens or beyond and demonstrated that vaccination with antigens or derivatives could reduce the extent of the lesions in atherosclerosis-prone mice. Our previous study has demonstrated that construct AHHC [ApoB100688-707 + hHSP60303-312 + hHSP60153-163 + Cpn derived peptide (C)] significantly reduced atherosclerotic lesion. The aim of this study was to investigate whether AHHC can be modulated towards increased lesion reduction in mice by creating two other derivatives with a sequential epitope-substitution named RHHC in which A was replaced by an "R" (C5aR1-31) and RPHC with a further "H" (hHSP60303-312) conversion into "P" (protease-activated receptor-142-55) in mice. Antigenic epitopes were incorporated into a dendroaspin scaffold. Immunization of B6;129S-Ldlrtm1HerApobtm2Sgy/J mice with three constructs elicited production of high levels of antibodies against each epitope (apart from hHSP60153-163 and P which induced a low antibody response). Histological analyses demonstrated that the mice immunized with either RPHC or RHHC showed significant reductions in the size of atherosclerostic lesions compared to those with AHHC (69.5±1.1% versus 55.7±3.4%, P<0.01 or 65.6±1.3% versus 55.7±3.4%, P<0.01). Reduction of plaque size in the aortic sinus and descending aorta correlated with alterations in cellular immune responses when compared with controls. We conclude that a recombinant construct RPHC may provide new antigenic and structural features which are favorable for significant reduction in atherosclerotic lesion formation. This approach offers a novel strategy for developing anti-atherosclerotic agents.

CD4+ natural killer T cells potently augment aortic root atherosclerosis by perforin- and granzyme B-dependent cytotoxicity.

RATIONALE: CD4(+) natural killer T (NKT) cells augment atherosclerosis in apolipoprotein E-deficient (ApoE)(-/-) mice but their mechanisms of action are unknown. OBJECTIVES: We investigated the roles of bystander T, B, and NK cells; NKT cell-derived interferon-γ, interleukin (IL)-4, and IL-21 cytokines; and NKT cell-derived perforin and granzyme B cytotoxins in promoting CD4(+) NKT cell atherogenicity. METHODS AND RESULTS: Transfer of CD4(+) NKT cells into T- and B-cell-deficient ApoE(-/-)Rag2(-/-) mice augmented aortic root atherosclerosis by ≈75% that was ≈30% of lesions in ApoE(-/-) mice; macrophage accumulation similarly increased. Transferred NKT cells were identified in the liver and atherosclerotic lesions of recipient mice. Transfer of CD4(+) NKT cells into T-, B-cell-deficient, and NK cell-deficient ApoE(-/-)Rag2(-/-)γC(-/-) mice also augmented atherosclerosis. These data indicate that CD4(+) NKT cells can exert proatherogenic effects independent of other lymphocytes. To investigate the role of NKT cell-derived interferon-γ, IL-4, and IL-21 cytokines and perforin and granzyme B cytotoxins, CD4(+) NKT cells from mice deficient in these molecules were transferred into NKT cell-deficient ApoE(-/-)Jα18(-/-) mice. CD4(+) NKT cells deficient in IL-4, interferon-γ, or IL-21 augmented atherosclerosis in ApoE(-/-)Jα18(-/-) mice by ≈95%, ≈80%, and ≈70%, respectively. Transfer of CD4(+) NKT cells deficient in perforin or granzyme B failed to augment atherosclerosis. Apoptotic cells, necrotic cores, and proinflammatory VCAM-1 (vascular cell adhesion molecule) and MCP-1 (monocyte chemotactic protein) were reduced in mice receiving perforin-deficient NKT cells. CD4(+) NKT cells are twice as potent as CD4(+) T cells in promoting atherosclerosis. CONCLUSIONS: CD4(+) NKT cells potently promote atherosclerosis by perforin and granzyme B-dependent apoptosis that increases postapoptotic necrosis and inflammation.

Role of toll-like receptor 4 on lupus lung injury and atherosclerosis in LPS-challenge ApoE⁻/⁻ mice.

To investigate the pathologic mechanisms of toll-like receptor 4 (TLR4) in lung injury and atherosclerosis, ApoE⁻/⁻ or wild-type mice were intraperitoneally administered saline, lipopolysaccharides (LPS), or LPS plus TAK-242 (TLR4 inhibitor), respectively, twice a week for 4 weeks. Serum autoantibody of antinuclear antibody (ANA), anti-double-stranded DNA (anti-dsDNA), and cytokines of interferon-gamma (IFN-γ), tumor necrosis factor (TNF-α ), and interleukin-1 (IL-1ß) were assessed by ELISA. Hematoxylin and eosin (HE) and Perl's stains for lung pathomorphology as well as HE staining for atherosclerosis were employed. TLR4 in macrophages was detected by double immunofluorescent staining. While protein expressions of TLR4, nuclear factor-kappa B p65 (NF-κB p65), and B cell activating factor belonging to the TNF family (BAFF) were examined by immunohistochemistry. We found that serum autoantibody (ANA and anti-dsDNA), cytokines (IFN-γ, TNF-α, IL-1ß), lung inflammation, and intima-media thickness in brachiocephalic artery were obviously increased after LPS challenge in both genotypes, but to a lesser extent in wild-type strains. And those alterations were alleviated by coadministration of LPS and TAK-242. Mechanistically, upregulation of TLR4, NF-κb, and BAFF was involved. We concluded that TLR4/NF-κb/BAFF in macrophages might be a possible common autoimmune pathway that caused lung injury and atherosclerosis. TLR4 signal will be a therapeutic target in atherosclerosis and immune-mediated lung injury.

Recurrent giant sinus of Valsalva aneurysm and ankylosing spondylitis.

A 48-year-old woman underwent aneurysmectomy and primary suture repair with a pericardial patch for sinus of Valsalva aneurysm secondary to ankylosing spondylitis. The sinus of Valsalva aneurysm recurred one year after surgery, and reached a diameter of 53 mm. Special attention must be paid to the potential relapse of aortic aneurysms that develop secondary to autoimmune disorders, when using primary suture or patch repair.

Identification of antigen-presenting dendritic cells in mouse aorta and cardiac valves.

Presumptive dendritic cells (DCs) bearing the CD11c integrin and other markers have previously been identified in normal mouse and human aorta. We used CD11c promoter-enhanced yellow fluorescent protein (EYFP) transgenic mice to visualize aortic DCs and study their antigen-presenting capacity. Stellate EYFP(+) cells were readily identified in the aorta and could be double labeled with antibodies to CD11c and antigen-presenting major histocompatability complex (MHC) II products. The DCs proved to be particularly abundant in the cardiac valves and aortic sinus. In all aortic locations, the CD11c(+) cells localized to the subintimal space with occasional processes probing the vascular lumen. Aortic DCs expressed little CD40 but expressed low levels of CD1d, CD80, and CD86. In studies of antigen presentation, DCs selected on the basis of EYFP expression or binding of anti-CD11c antibody were as effective as DCs similarly selected from the spleen. In particular, the aortic DCs could cross-present two different protein antigens on MHC class I to CD8(+) TCR transgenic T cells. In addition, after intravenous injection, aortic DCs could capture anti-CD11c antibody and cross-present ovalbumin to T cells. These results indicate that bona fide DCs are a constituent of the normal aorta and cardiac valves.

Pro-atherogenic lung and oral pathogens induce an inflammatory response in human and mouse mast cells.

A broad variety of microbes are present in atherosclerotic plaques and chronic bacterial infection increases the risk of atherosclerosis by mechanisms that have remained vague. One possible mechanism is that bacteria or bacterial products activate plaque mast cells that are known to participate in the pathogenesis of atherosclerosis. Here, we show by real-time PCR analysis and ELISA that Chlamydia pneumoniae (Cpn) and a periodontal pathogen, Aggregatibacter actinomycetemcomitans (Aa), both induce a time and concentration-dependent expression and secretion of interleukin 8 (IL-8), tumour necrosis factor-alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1) by cultured human peripheral blood-derived mast cells, but not anti-inflammatory molecules, such as IL-10 or transforming growth factor beta 1 (TGF-beta 1). The IL-8 and MCP-1 responses were immediate, whereas the onset of TNF-alpha secretion was delayed. The Cpn-mediated pro-inflammatory effect was attenuated when the bacteria were inactivated by UV-treatment. Human monocyte-derived macrophages that were pre-infected with Cpn also induced a significant pro-inflammatory response in human mast cells, both in cocultures and when preconditioned media from Cpn-infected macrophages were used. Intranasal and intravenous administration of live Cpn and Aa, respectively induced an accumulation of activated mast cells in the aortic sinus of apolipoprotein E-deficient mice, however, with varying responses in the systemic levels of lipopolysaccharide (LPS) and TNF-alpha. Pro-atherogenic Cpn and Aa induce a pro-inflammatory response in cultured human connective tissue-type mast cells and activation of mouse aortic mast cells in vivo.

Chlamydia pneumoniae infections augment atherosclerotic lesion formation: a role for serum amyloid P.

Multiple reports have demonstrated an association between Chlamydia pneumoniae (Cpn) and cardiovascular disease. In this study we evaluated the effect of Cpn infections on early lesion progression in C57BL/6J mice. Since plaque formation in these mice does not develop past the initial stage, we thought these mice might be a better model for unravelling the effect of Cpn infection on early lesion type progression. C57BL/6J mice were fed an atherogenic diet and injected 10 times with 5 x 10(7) IFU Cpn or mock. At sacrifice, lesion number, size and type were analysed. To study the role of Cpn in inflammation, serum amyloid P (SAP) in plasma was determined as well as T-cells, macrophages and SAP in the lesions. In the aortic sinus of both groups, type 2 lesions were found. Cpn infection resulted in a 2.2-fold increase in total lesion size (Cpn: 10821+/-2429 microm(2)vs mock: 5022+/-1348 microm(2); p=0.04). No difference in lesion number was observed. Also, Cpn infection increased SAP in the lesions from 1.10(-4)+/-0.1.10(-4) SAP-positive cells/lesion area to 10.10(-4)+/-1.10(-4) SAP-positive cells/lesion area (p=0.05). The influx of T-lymphocytes and macrophages in the lesions as well as SAP plasma levels were not different between groups. Multiple Cpn infections resulted in a significant increase in total lesion size of C57BL/6J mice. Increase in total SAP-positive area in infected mice suggests a role for this acute-phase protein in lesion enlargement.

Anti-heat shock protein 60 autoantibodies induce atherosclerosis in apolipoprotein E-deficient mice via endothelial damage.

BACKGROUND: Accumulating evidence established a positive association of anti-heat shock protein 60 (HSP60) autoantibodies and the presence of atherosclerosis in humans. However, whether these autoantibodies play a causal role in the development of atherosclerosis is unknown. METHODS AND RESULTS: In the present study, anti-HSP60 autoantibodies from blood of patients with coronary heart disease were isolated by affinity chromatography and injected into the tail vein of apolipoprotein E-deficient mice. Atherosclerotic lesions in aortas were significantly increased 8 weeks after injection. Furthermore, administration of a specific mouse monoclonal antibody (II-13) recognizing amino acid residues 288 to 366 of HSP60 effectively induced atherosclerotic lesions in apolipoprotein E-deficient mice. II-13 injection resulted in endothelial cell damage, followed by increased leukocyte attachment and accumulation of macrophages and smooth muscle cells in lesions. Interestingly, II-13-induced atherosclerosis was blocked by pretreatment of animals with F(ab)2 segments derived from the antibody, but not mouse IgG F(ab)2. CONCLUSIONS: Autoantibodies recognizing amino acid residues 288 to 366 of HSP60 induce atherosclerosis via the mechanisms of autoimmune reactions to HSP60 expressed on arterial endothelial cells, which can be prevented by F(ab)2 segments derived from these antibodies.

Processes involved in the site-specific effect of probucol on atherosclerosis in apolipoprotein E gene knockout mice.

OBJECTIVE: To elucidate processes by which the antioxidant probucol increases lesion size at the aortic sinus and decreases atherosclerosis at more distal sites in apolipoprotein E-deficient (apoE(-/-)) mice. METHODS AND RESULTS: Male apoE(-/-) mice were fed high-fat chow with 1% (w/w) probucol or without (controls) for 6 months, before aortic sinus, arch, and descending aorta were analyzed separately for lesion size and composition. Compared with control, probucol significantly increased lesion size by 33% at the sinus, but it inhibited atherosclerosis at the descending aorta by 94%. Sites where atherosclerosis was inhibited contained substantially fewer macrophages, less lipids (cholesterol and cholesteryl esters), and endogenous antioxidant (alpha-tocopherol), but not oxidized lipids, and the extent to which probucol metabolism occurred was increased. Compared with control, aortic sinus lesions of probucol mice contained a substantially increased content of extracellular matrix, but decreased total cell and macrophage density, comparable levels of lipids and alpha-tocopherol, and decreased concentrations of oxidized lipids (cholesteryl ester hydroperoxides, F2-isoprostanes, and 7-ketocholesterol). CONCLUSIONS: Probucol affects atherosclerosis in apoE(-/-) mice independent of the accumulation of arterial lipid oxidation products, thereby dissociating the 2 processes. Rather, probucol exerts antiinflammatory activity by decreasing accumulation of macrophages in lesions, and it promotes a more stable lesion composition at the aortic sinus.

Complement activation in patients with congestive heart failure: effect of high-dose intravenous immunoglobulin treatment.

BACKGROUND: Increasing evidence implicates innate immunity in the pathogenesis of congestive heart failure (CHF). In the present study, we examined the possible role of complement, an important part of innate immunity, in CHF. METHODS AND RESULTS: Complement activation was analyzed in systemic and coronary circulation in 39 patients with CHF and 20 healthy control subjects. In a double-blind, placebo-controlled study, we have recently reported that high-dose intravenous immunoglobulin (IVIG) improves left ventricular ejection fraction (LVEF) in these patients. To examine if this improvement was related to IVIG-induced effects on complement, we also examined complement activation during induction (first week) and maintenance therapy (6 months) with IVIG or placebo. Our main findings were: (1) We found enhanced systemic complement activation involving classic, alternative, as well as terminal pathway in patients with CHF compared with healthy control subjects. (2) Particularly enhanced complement activation was found in coronary sinus, representing venous drainage from the heart. (3) The systemic complement activation was further enhanced during IVIG but not during placebo therapy, particularly during induction therapy. (4) Although IVIG improved LVEF in patients with CHF, the degree of IVIG-mediated complement activation was negatively correlated with this improvement of LVEF. CONCLUSIONS: This study further supports the involvement of innate immunity in the pathogenesis of CHF. Our findings suggest that complement may be added to the list of possible therapeutic targets in CHF and that future studies with specific complement inhibitors may be of interest in this disorder.

Correlation between CD11b/CD18 and increase of aggregability of granulocytes in coronary artery disease.

Recent studies suggest that granulocytes (PMNs) play a role in the pathogenesis of acute and chronic myocardial ischemia and extension of myocardial injury. Rabbit-derived antiserum-dependent reduction of circulating PMNs in the dog or using monoclonal antibody anti-CD11b/CD18 of PMNs resulted in smaller myocardial infarcts. Experience in humans shows the modification of PMN function in angina and during myocardial ischemia. In our studies, patients affected by coronary artery disease presented an increase in granulocyte aggregability in coronary sinus and showed a related higher expression of CD11b/CD18 in coronary sinus with respect to aorta leukocytes. The potential role of this modification of PMNs was analyzed.