Long pentraxin 3, a key component of innate immunity, is modulated by high-density lipoproteins in endothelial cells

Role of sphingosine 1-phosphate in anti-atherogenic actions of high-density lipoprotein

The reverse cholesterol transport mediated by high-density lipoprotein (HDL) is an important mechanism for maintaining body cholesterol, and hence, the crucial anti-atherogenic action of the lipoprotein. Recent studies, however, have shown that HDL exerts a variety of anti-inflammatory and anti-atherogenic actions independently of cholesterol metabolism. The present review provides an overview of the roles of sphingosine 1-phosphate (S1P)/S1P receptor and apolipoprotein A-I/scavenger receptor class B type I systems in the anti-atherogenic HDL actions. In addition, the physiological significance of the existence of S1P in the HDL particles is discussed.

Dual effect of hypochlorite in the modification of high density lipoproteins

HDL-cholesterol levels are inversely correlated to the risk of cardiovascular disease. In recent years the concept that not only the quantity, but also the quality of HDL is related to their atheroprotective function has gained momentum. In fact several studies have showed that HDL can shift their properties from anti-atherogenic to pro-atherogenic upon chemical or enzymatic "modification". However, not all kind of modifications affect the antiatherogenic properties of HDL. For example, tyrosylation of HDL improves its ability to remove cholesterol from cultured cells and inhibits mice atherosclerotic lesion formation; oxidation of HDL(3) with 15-lipoxygenase or with copper ions for short time induce the formation of pre-β-migrating particles that are highly effective as cholesterol acceptors from lipid laden cells. Myeloperoxidase modifies HDL and apoA-I and reduces their ability to promote ABCA1-mediated cholesterol efflux. In the present study we show that modification with low concentration HOCl (a myeloperoxidase product) induces the formation of pre-β-migrating particles, thus improving the function of HDL in the reverse cholesterol transport, without affecting the anti-inflammatory activity. At higher HOCl concentration, pre-β-migrating particles were not detectable and the anti-inflammatory properties of HDL were lost. These findings suggest that during early phases of inflammation, when a low HOCl concentration is generated, changes in HDL occur that increase their ability to remove cholesterol and sparing anti-inflammatory properties; later during acute inflammation, when higher HOCl concentration are present changes in HDL occur that severely decrease their ability to remove cholesterol from macrophages and to protect endothelial cells from pro-inflammatory stimuli.

Reciprocal contribution of pentraxin 3 and C-reactive protein to obesity and metabolic syndrome

Pentraxin 3 (PTX3) is an acute-phase protein that shares structural homology with C-reactive protein (CRP). PTX3 is produced in macrophages, endothelial cells, and adipocytes in response to inflammatory stimuli, whereas hepatocytes are the main source of CRP. Because obesity and metabolic syndrome (MetS) are considered chronic inflammatory states, PTX3 might be involved in the pathogenesis of obesity and MetS as well as CRP. Levels of CRP correlated positively with body weight, BMI, waist circumference (WC), fasting plasma glucose and interleukin (IL)-6, and negatively with high-density lipoprotein cholesterol and adiponectin in healthy males. In contrast, PTX3 correlated positively with adiponectin, and negatively with body weight, BMI, WC, and triglyceride. Plasma CRP significantly increased, whereas plasma PTX3 significantly decreased with increasing BMI. Plasma CRP and PTX3 levels were significantly higher and lower, respectively, in individuals who had more than one MetS component compared with those who had none. In conclusion, PTX3 and CRP antagonistically participate in the development of obesity or MetS.

Circulating CD4+CD25hiCD127lo regulatory T-Cell levels do not reflect the extent or severity of carotid and coronary atherosclerosis

OBJECTIVE

Regulatory T (Treg) cells play a protective role in experimental atherosclerosis. In the present study, we investigated whether the levels of circulating Treg cells relate to the degree of atherosclerosis in carotid and coronary arteries.

METHODS AND RESULTS

We studied 2 distinct populations: (1) 113 subjects, selected from a free-living population (carotid study), in which we measured the intima-media thickness of the common carotid artery, as a surrogate marker of initial atherosclerosis; and (2) 75 controls and 125 patients with coronary artery disease (coronary study): 36 with chronic stable angina, 50 with non-ST-elevation acute coronary syndrome, 39 with ST-elevation acute myocardial infarction. Treg-cell levels were evaluated by flow cytometry (Treg cells identified as CD3(+)CD4(+)CD25(high)CD127(low)) and by mRNA expression of forkhead box P3 or of Treg-associated cytokine interleukin 10. In the carotid study, no correlation was observed between Treg-cell levels and intima-media thickness. No differences in Treg-cell levels were observed comparing rapid versus slow intima-media thickness progressors from a subgroup of patients (n=65), in which prospective data on 6-year intima-media thickness progression were available. In the coronary group, Treg-cell levels were not altered in chronic stable angina patients. In contrast, nonunivocal variations were observed in patients suffering an acute coronary syndrome (with a Treg-cell increase in ST-elevation acute myocardial infarction and a Treg-cell decrease in non-ST-elevation acute coronary syndrome patients).

CONCLUSIONS

The results suggest that determination of circulating Treg-cell levels based on flow cytometry or mRNA assessment is not a useful indicator of the extent or severity of atherosclerosis.

The androgen derivative 5alpha-androstane-3beta,17beta-diol inhibits tumor necrosis factor alpha and lipopolysaccharide induced inflammatory response in human endothelial cells and in mice aorta

BACKGROUND

An increasing body of evidence suggests that testosterone may exert beneficial effects against the development of atherosclerosis. These effects are thought to be the consequence of its conversion into estradiol and the activation of the estrogen receptors; however a direct role of androgens, such as dihydrotestosterone, has also been proposed. More recently, it has been shown that the transformation of the dihydrotestosterone to 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) and 5alpha-androstane-3beta,17beta-diol (3beta-Adiol), generates two molecules unable to bind the androgen receptor, but with a high affinity for the estrogen receptors (ERs) in particular the beta isoform. As the actions of testosterone may result from the balance between androgenic and estrogenic molecules originating from its catabolism, we investigated the effects of the 3beta-Adiol on inflammatory responses in vitro in human endothelial cells and ex vivo in mice aortas.

METHODS AND RESULTS

3beta-Adiol reverts the pro-inflammatory gene expression pattern induced by TNF-alpha in HUVECs as determined by a cDNA microrray approach. Q-real-time PCR and protein array approaches confirmed that TNF-alpha-induced ICAM-1, VCAM-1 and ELAM-1 as well as MCP-1 and IL-6 induction was affected upon 3beta-Adiol pre-incubation. ICI 182780, an estrogen receptor antagonist and R,R-THC, an estrogen receptor beta antagonist, counteracted the effect of 3beta-Adiol while bicalutamide, an androgen receptor antagonist, had minor effects. 3beta-Adiol exerted a similar action on macrophages. Finally in castrated male mice, 3beta-Adiol significantly counteracted the LPS mediated mRNA induction of IL-6, ELAM-1and PECAM-1 in the aortas.

CONCLUSION

3beta-Adiol reverts in vitro the TNF-alpha and LPS induced pro-inflammatory activation of endothelial cells and macrophages. 3beta-Adiol in vivo modulates the inflammatory response induced by LPS in the arterial vascular wall.

An integrated view of humoral innate immunity: pentraxins as a paradigm

The innate immune system consists of a cellular and a humoral arm. Pentraxins (e.g., the short pentraxin C reactive protein and the long pentraxin PTX3) are key components of the humoral arm of innate immunity which also includes complement components, collectins, and ficolins. In response to microorganisms and tissue damage, neutrophils, macrophages, and dendritic cells are major sources of fluid-phase pattern-recognition molecules (PRMs) belonging to different molecular classes. Humoral PRMs in turn interact with and regulate cellular effectors. Effector mechanisms of the humoral innate immune system include activation and regulation of the complement cascade; agglutination and neutralization; facilitation of recognition via cellular receptors (opsonization); and regulation of inflammation. Thus, the humoral arm of innate immunity is an integrated system consisting of different molecules and sharing functional outputs with antibodies.

HDL and immunomodulation: an emerging role of HDL against atherosclerosis

Changes in plasma lipoprotein profiles, particularly low levels of high-density lipoprotein (HDL) cholesterol, are associated with several inflammatory and immune diseases, including atherosclerosis and rheumatoid arthritis, implying the potential link between HDL and immunity. Accumulating evidence suggests that HDL possesses anti-inflammatory effects and has an important function in host defense as part of the innate immune system. In addition, HDL inhibits the ability of antigen-presenting cells (APCs) to stimulate T cells. It is subsequently discovered that HDL or HDL-associated platelet-activating factor-acetylhydrolase can restore the emigratory process of monocyte-derived dendritic cells and thus result in resolution of inflammatory reactions in atherosclerotic plaques. Lipid rafts in plasma membrane are the key structure responsible for the immunomodulation effects of HDL, the remarkable ability of HDL to regulate innate and adaptive immune responses extends our understanding of its atheroprotective role, and provides new therapeutic approaches to atherosclerosis and other inflammatory conditions.

Plasma adiponectin levels in chronic kidney disease patients: relation with molecular inflammatory profile and metabolic status

BACKGROUND AND AIM

Adiponectin (ADPN) exerts anti-inflammatory and cardio protective effects and is associated with decreased cardiovascular risk, however its role in patients with chronic kidney disease is unclear.

METHODS AND RESULTS

We investigated the correlation between plasma ADPN levels, the progression of CVD and CKD and the inflammatory gene expression profile of peripheral blood mononuclear cells in patients from the NephroPLIC study (a prospective study aimed at addressing the progression of cardiovascular damage in relation to kidney dysfunction). Plasma ADPN levels were directly correlated with age, HDL-C and creatinine, and inversely with BMI, triglycerides and glomerular filtration rate (GFR). Multiple regression analysis identified plasma creatinine and HDL as the independent factors associated with ADPN plasma levels. In peripheral blood mononuclear cells (PBMC), the mRNA expression of MCP-1, CD40, Cox-2, TLR4, PAI-1, TNF alpha, resistin and RAGE was up-regulated in the group with higher GFR and higher ADPN plasma levels compared to that with low GFR and ADPN plasma levels. Patients with similar GFR values showed no differences in the gene expression profile of PBMC although ADPN levels were associated with decreased CRP and IL-6 plasma levels and decreased IMT and heart left ventricular mass.

CONCLUSION

In CKD patients who are not in dialysis ADPN plasma levels are associated with a reduced renal excretory function, but correlate inversely with the determinants of the metabolic syndrome such as glucose, triglycerides and BMI, and directly with HDL. Furthermore, in patients with a similar degree of renal impairment, ADPN plasma levels are associated with a better cardiometabolic profile, despite no significant difference being observed in the gene expression pattern of PBMC.

Deficiency of the long pentraxin PTX3 promotes vascular inflammation and atherosclerosis

BACKGROUND

Immune responses participate in several phases of atherosclerosis; there is, in fact, increasing evidence that both adaptive immunity and innate immunity tightly regulate atherogenesis. Pentraxins are a superfamily of acute-phase proteins that includes short pentraxins such as C-reactive protein or long pentraxins such as PTX3, a molecule acting as the humoral arm of innate immunity. To address the potential role of PTX3 in atherogenesis, we first investigated the expression of PTX3 during atherogenesis, generated double-knockout mice lacking PTX3 and apolipoprotein E, and then studied the effect of murine PTX3 deficiency on plasma lipids, atherosclerosis development, and gene expression pattern in the vascular wall.

METHODS AND RESULTS

PTX3 expression increases in the vascular wall of apolipoprotein E-knockout mice from 3 up to 18 months of age. Double-knockout mice lacking PTX3 and apolipoprotein E were fed an atherogenic diet for 16 weeks. Aortic lesions were significantly increased in double-knockout mice and mice heterozygous for PTX3 compared with apolipoprotein E-knockout mice. Mice lacking PTX3 showed a more pronounced inflammatory profile in the vascular wall as detected by cDNA microarray and quantitative polymerase chain reaction analysis and an increased macrophage accumulation within the plaque. Finally, lesion size correlated with the number of bone marrow monocytes.

CONCLUSIONS

PTX3 has atheroprotective effects in mice, which, in light of the cardioprotective effects recently reported, suggests a cardiovascular protective function of the long pentraxin 3 through the modulation of the immunoinflammatory balance in the cardiovascular system.

Translational mini-review series on immunology of vascular disease: mechanisms of vascular inflammation and remodelling in systemic vasculitis

Vessel walls are the primary inflammatory sites in systemic vasculitides. In most cases the initiating event is unknown, and a self-sustaining circuit attracts and activates inflammatory leucocytes in the wall of vessels of various size and anatomical characteristics. Recent studies have revealed homeostatic roles of vascular inflammation and have identified the action of humoral innate immunity, in particular injury-associated signals and acute phase proteins, on the activation of circulating leucocytes, platelets and endothelial cells. These advances have provided clues to the molecular mechanisms underlying the vicious circle that maintains and amplifies vessel and tissue injury.

Anti-atherogenic actions of high-density lipoprotein through sphingosine 1-phosphate receptors and scavenger receptor class B type I

Plasma high-density lipoprotein (HDL) is a potent anti-atherogenic factor, a critical role of which is thought to be reverse cholesterol transport through the lipoprotein-associated apolipoprotein A-I (apoA-I). HDL also carries a potent bioactive lipid mediator, sphingosine 1-phophate (S1P), which exerts diverse physiological and pathophysiological actions in a variety of biological systems, including the cardiovascular system. In addition, HDL-associated apoA-I is known to stimulate intracellular signaling pathways unrelated to transporter activity. Mounting evidence indicates that multiple antiatherogenic or anti-inflammatory actions of HDL independent of cholesterol metabolism are mediated by the lipoprotein-associated S1P through S1P receptors and by apoA-I through scavenger receptor class B type I.

Pentraxins, humoral innate immunity and tissue injury

Tissue damage elicits an inflammatory response, which comprises the rapid synthesis of acute phase molecules. The early local response shapes the resolution of inflammation. Pentraxins are evolutionary conserved soluble pattern recognition receptors, produced in the liver (e.g. C-reactive protein) or at sites of inflammation (the long pentraxin PTX3). Pentraxins behave as flexible adaptors of innate cell functions, complement activation and clearance of cell and matrix debris, regulating tissue hyperplasia and scarring and limiting the risk of autoimmunity associated to unscheduled cell death in vivo.

Three-dimensional models of HDL apoA-I: implications for its assembly and function

The purpose of this review is to highlight recent advances toward the refinement of a three-dimensional structure for lipid-bound apolipoprotein A-I (apoA-I) on recombinant HDL. Recently, X-ray crystallography has yielded a new structure for full-length, lipid-free apoA-I. Although this approach has not yet been successful in solving the three-dimensional structure of lipid-bound apoA-I, analysis of the X-ray structures has been of immense help in the interpretation of structural data obtained from other methods that yield structural information. Recent studies emphasize the use of mass spectrometry to unambiguously identify cross-linked peptides or to quantify solvent accessibility using hydrogen-deuterium exchange. The combination of mass spectrometry, molecular modeling, molecular dynamic analysis, and small-angle X-ray diffraction has provided additional structural information on apoA-I folding that complements previous approaches.